SCREEN UNIT

Abstract

A screen unit includes: a screen which has a first side and a second side opposing to each other in a first direction and extending substantially in parallel with each other; a first supporting portion extending along the first side to support the first side; a second supporting portion extending along the second side to support the second side; and a plurality of connecting mechanisms each of which extends between the first supporting portion and the second supporting portion, and expands and contracts in the first direction to move the second supporting portion close to and away from the first supporting portion, wherein the plurality of connecting mechanisms are disposed in parallel with the first supporting portion, and are located almost linearly symmetric with respect to a center line connecting approximately the center of the first side and approximately the center of the second side.

Description

BACKGROUND

1. Technical Field

The present invention relates to a screen unit.

2. Related Art

A screen unit of a type currently known expands a screen on which an image is projected from a projection type display apparatus such as a projector when the screen is used, and stores the screen when the screen is not used. This type of screen unit uses a pantograph-shaped connecting mechanism in many cases which has a plurality of arms connected with each other as a mechanism for shifting the screen upward and downward at the time of expansion and storage of the screen and for supporting the screen in an expanded condition.

An example known as a structure of this connecting mechanism has arms connected in a rhomboidal shape and supporting the upper end portion of the screen at one point around the center of the screen. Also, such a structure which has arms crossing each other substantially in an X shape for connection with each other and supporting two points of the upper end portion of the screen has been disclosed (For example, see JP-A-5-34826). According to the screen unit shown in JP-A-5-34826, one of the arms of the connecting mechanism is supported by a fixed support on the upper end portion, and the other is supported by a movable support movable in the horizontal direction, in such a manner that the respective arms can freely rotate.

According to the structure which supports the upper end portion of the screen at one point around the center of the screen, the left and right ends of the upper end portion of the screen easily bend in the downward direction, and the support for the screen easily becomes unstable. According to the structure of the screen unit shown in JP-A-5-34826 which supports the upper end portion of the screen at the two points of the fixed support and the movable support, the supporting conditions at the fixed support and the movable support differ from each other on the left side and the right side. In this case, the movable support side more easily bends in the downward direction than the fixed support side, and the upper end portion of the screen easily shifts toward the fixed support side in the left-right direction.

According to this type of connecting mechanism, in most cases, the connected arms cross each other while overlapping with each other at front and rear positions in the normal line direction of the projection surface of the screen, and thus the arms constituting the connecting mechanism are not located on the same plane. In this arrangement, the connecting mechanism is easily twisted by the load or the like generated by the support of the upper end portion of the screen. As a result, relative twisting between the upper end portion and the lower end portion of the screen is easily produced.

The bend of the upper end portion of the screen, the shift of the upper end portion in the left-right direction, and the twist between the upper end portion and the lower end portion are more easily produced as the size of the screen increases. These conditions decrease uniformity of the tension applied to the screen, and thus lowers the flatness of the screen. Therefore, such a screen unit which can reduce lowering of the flatness of the screen even when the size of the screen enlarges has been demanded.

SUMMARY

It is an advantage of some aspects of the invention to provide a technology capable of solving at least a part of the problems described above and the invention can be embodied as the following forms or application examples.

Application Example 1

A screen unit according to this application example includes: a screen which has a first side and a second side disposed opposed to each other and extending substantially in parallel with each other; a first supporting portion extending along the first side of the screen to support the first side; a second supporting portion extending along the second side of the screen to support the second side; and a plurality of connecting mechanisms each of which extends between the first supporting portion and the second supporting portion, and expands and contracts in the direction in which the first supporting portion and the second supporting portion are opposed to move the second supporting portion close to and away from the first supporting portion. The plurality of connecting mechanisms are disposed in parallel in the direction in which the first supporting portion and the second supporting portion extend, and are located almost linearly symmetric with respect to a center line connecting approximately the center of the first side in the extending direction of the first side and approximately the center of the second side in the extending direction of the second side.

According to this structure, the screen is expanded when the second supporting portion is moved away from the first supporting portion in the upward direction, for example, by using the plural connecting mechanisms. In the expanded condition of the screen, each of the first supporting portion and the second supporting portion is supported at plural points in its extending direction by the plural connecting mechanisms. Thus, bending of the second supporting portion positioned above can be reduced. Moreover, since the plural connecting mechanisms are disposed almost linearly symmetric with respect to the center line, the first supporting portion and the second supporting portion are supported approximately at symmetric positions in the left-right direction. Accordingly, in the expanded condition of the screen, a tension applied to a left part of the screen and a tension applied to a right part of the screen become more uniform, and thus the flatness of the screen increases. Accordingly, the flatness of the screen does not lower even when the size of the screen enlarges.

Application Example 2

In the screen unit of the above application example, it is preferable that the plural connecting mechanisms include a plurality of first connecting mechanisms disposed as a pair or pairs on both parts of the screen unit with the center line interposed therebetween.

According to this structure, the plural first connecting mechanisms are disposed as a pair or pairs on both parts of the screen unit with the center line interposed between the parts of the screen unit. Thus, the strengths for supporting the first supporting portion and the second supporting portion become more uniform on the left and right parts in the expanded condition of the screen. Thus, the flatness of the screen further increases.

Application Example 3

In the screen unit of the above application example, it is preferable that the plural connecting mechanisms include a pair of the first connecting mechanisms, and that the pair of the first connecting mechanisms have almost linearly symmetric structures with respect to the center line as viewed in the normal line direction of a projection surface of the screen.

According to this structure, the pair of the first connecting mechanisms has almost linearly symmetric structures with respect to the center line. Thus, even when twisting is produced on each of the first connecting mechanisms, the twisting can be cancelled by the first connecting mechanism as a paired unit. Accordingly, relative twisting between the first supporting portion and the second supporting portion can be reduced, which further increases the flatness of the screen.

Application Example 4

It is preferable that the screen unit of the above application example is configured such that the first supporting portion includes a pair of fixed supports provided at predetermined positions and a pair of movable supports movable in the extending direction of the first supporting portion in correspondence with the pair of the first connecting mechanisms; the second supporting portion includes a pair of fixed supports provided at predetermined positions and a pair of movable supports movable in the extending direction of the second supporting portion in correspondence with the pair of the first connecting mechanisms; the respective first connecting mechanisms are connected with the respective fixed supports and the respective movable supports of the first supporting portion and with the respective fixed supports and the respective movable supports of the second supporting portion; and each pair of the fixed supports of the first supporting portion, each pair of the movable supports of the first supporting portion, each pair of the fixed supports of the second supporting portion and each pair of the movable supports of the second supporting portion are disposed almost linearly symmetric with respect to the center line.

According to this structure, each pair of the fixed supports of the first supporting portion, each pair of the movable supports of the first supporting portion, each pair of the fixed supports of the second supporting portion and each pair of the movable supports of the second supporting portion are disposed almost linearly symmetric with respect to the center line. Thus, the restricting condition for each of the pair of the first connecting mechanisms becomes approximately the same on the left and right parts. Accordingly, the supporting condition for each of the first supporting portion and the second supporting portion becomes substantially equivalent to each other in the left part and in the right part, and thus bending and shift of the second supporting portion can be reduced.

Application Example 5

In the screen unit of the above application example, it is preferable that the pair of the fixed supports of each of the first supporting portion and the second supporting portion are disposed outside the pair of the movable supports of the corresponding supporting portion with respect to the center line.

According to this structure, the fixed supports are disposed outside the movable supports with respect to the center line. Thus, both outside areas of each of the first supporting portion and the second supporting portion are supported at fixed positions in the expanded condition of the screen. As a result, bending at both ends of the second supporting portion in the left-right direction can be further reduced. Moreover, since the pair of the movable supports is disposed inside at positions opposed to each other, a structure which moves the pair of the movable supports by a single mechanism can be easily provided.

Application Example 6

It is preferable that the screen unit of the above application example further includes a rotating mechanism which has a rotation shaft extending along the first supporting portion. In this case, each of the pair of the movable supports of the first supporting portion has a screw portion which has a female screw formed coaxially with each other. The rotation shaft is inserted through the screw portions of the pair of the movable supports of the first supporting portion and has a male screw engaging with the screw portions. One of the screw portions of the pair of the movable supports is a right-handed screw, and the other of the screw portions of the pair of the movable supports is a left-handed screw.

According to this structure, one of the screw portions of the pair of the movable supports is a right-handed screw, and the other of the screw portions of the pair of the movable supports is a left-handed screw. Thus, the pair of the movable supports shift in directions opposite to each other along the extending direction of the first supporting portion in accordance with the rotation direction of the rotation shaft which has the male screw engaging with the screw portions. Thus, the pair of the connecting mechanisms can be expanded and contracted for expansion and storage of the screen by increasing and decreasing each distance between the fixed supports and the movable supports achieved through the change of the rotation direction of the rotation shaft.

Application Example 7

It is preferable that the screen unit of the above application example further includes a rotating mechanism which has a rotation shaft disposed between the pair of the movable supports of the first supporting portion. In this case, one of the pair of the movable supports is connected with the rotation shaft via a first wire, and the other of the pair of the movable supports is connected with the rotation shaft via a second wire. The first wire and the second wire are wound or returned in accordance with the rotation direction of the rotation shaft to shift the pair of the movable supports in directions opposite to each other along the first supporting portion.

According to this structure, the pair of the movable supports are shifted in directions opposite to each other along the extending direction of the first supporting portion in accordance with the rotation direction of the rotation shaft by using the first wire and the second wire. Thus, the pair of the connecting mechanisms can be expanded and contracted for expansion and storage of the screen by increasing and decreasing each distance between the fixed supports and the movable supports achieved through the change of the rotation direction of the rotation shaft.

Application Example 8

In the screen unit of the above application example, it is preferable that the rotating mechanism has an electrically operated motor which rotates the rotation shaft.

According to this structure, the pair of the connecting mechanisms can be easily expanded and contracted by using the electrically operated system to expand and contract the screen.

Application Example 9

In the screen unit of the above application example, it is preferable that the plural connecting mechanisms further include a second connecting mechanism disposed on the center line.

According to this structure, the first supporting portion and the second supported portion are supported by the first connecting mechanisms and the second connecting mechanism. Thus, bending of the second supporting portion can be more effectively reduced.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described with reference to the accompanying drawings, wherein like numbers reference like elements.

FIG. 1 illustrates the general structure of a screen unit according to a first embodiment.

FIGS. 2A and 2B illustrate the general structure of the screen unit according to the first embodiment.

FIGS. 3A through 3C illustrate a rotating mechanism according to the first embodiment.

FIG. 4 illustrates the general structure of a screen unit according to a second embodiment.

FIG. 5 illustrates the general structure of a screen unit according to a third embodiment.

FIG. 6 illustrates the general structure of a screen unit according to a fourth embodiment.

FIG. 7 illustrates the general structure of a screen unit according to a fifth embodiment.

FIG. 8 illustrates the general structure of a screen unit according to a sixth embodiment.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Exemplary embodiments according to the invention are hereinafter described with reference to the drawings. In the figures to be referred to herein, the proportions, angles and the like of the sizes of the respective components and parts are varied as necessary for easy understanding of the structures.

First Embodiment

A screen unit according to a first embodiment is now described with reference to FIGS. 1, 2A and 2B, and 3A through 3C. FIGS. 1, 2A and 2B illustrate the general structure of the screen unit according to the first embodiment. More specifically, FIG. 1 schematically illustrates the screen unit in an expanded condition as viewed from the back. FIG. 2A schematically illustrates the screen unit in the expanded condition as viewed from above. FIG. 2B schematically illustrates the screen unit in a stored condition as viewed from the back. FIGS. 3A through 3C illustrate a rotating mechanism according to the first embodiment. More specifically, FIG. 3A is a perspective view showing the structure of a main part of the rotating mechanism, and FIGS. 3B and 3C illustrate the operation of the rotating mechanism.

As illustrated in FIG. 1, a screen unit 1 according to the first embodiment includes a screen 10, a storing portion 20 as a first supporting portion, a supporting portion 14 as a second supporting portion, a pair of connecting mechanisms 30a and 30b as first connecting mechanisms, and a rotating mechanism 40. The screen unit 1 is a screen unit including the screen 10 which is drawn out and expanded when the screen 10 is used, and is wound around a winding shaft 21 and stored in the storing portion 20 when the screen 10 is not used. In this embodiment, a case in which the screen unit 1 is installed on a floor surface shown as a crosshatched area in the figure will be discussed.

In the following explanation, the direction toward the floor surface on which the screen unit 1 is placed is referred to as the downward direction, and the direction toward the ceiling surface is referred to as the upward direction in some cases. In addition, the use condition of the screen unit 1 in which the screen 10 becomes substantially flat to form a projection surface is referred to as an expanded condition in some cases. In the expanded condition of the screen 10, the projection side and the side opposite to the projection side are referred to as the front side and the back side, respectively, in some cases. Also, the right side as viewed from the back and the left side as viewed from the back are referred to as the right and the left, respectively, in some cases. FIG. 1 shows the storing portion 20 in perspective.

The screen 10 is a reflection type screen having flexibility, and reflects image light projected from a projector or the like by a projection surface on the front side to display an image, for example. The screen 10 has a side 11 as a first side and a side 12 as a second side opposed to each other. The side 11 and the second side 12 extend substantially in parallel with each other. In the following explanation, the direction along the side 11 and the side 12 is referred to as an X direction in some cases. The side 11 is supported by the winding shaft 21 included in the storing portion 20, and the side 12 is supported by the supporting portion 14.

A center line CL indicated by an alternate long and short dash line is a line connecting the center of the side 11 in the X direction and the center of the side 12 in the X direction, and crosses the X direction approximately at right angles. In the following explanation, a direction extending along the center line CL is referred to as a Z direction, and a direction crossing the X direction and the Z direction approximately at right angles is referred to as a Y direction in some cases. The plane defined by the X direction and the Y direction corresponds to a plane substantially parallel with the floor surface as the installation surface of the screen unit 1 (storing portion 20). The plane defined by the X direction and the Z direction corresponds to a plane substantially parallel with the projection surface of the screen 10 in the expanded condition. The Y direction extends substantially in parallel with a normal line N direction of the projection surface of the screen 10 (see FIG. 2A).

The storing portion 20 is disposed on the floor surface side on which the screen unit 1 is installed, and extends in the X direction. The storing portion 20 has the winding shaft 21, a center shaft 22, a tensioning mechanism (not shown), and bearings 23. The winding shaft 21 is a cylindrical component extending in the X direction, and supports the side 11 of the screen 10. The winding shaft 21 is a shaft around which the screen 10 is wound. A pair of the bearings 23 are provided at both ends of the winding shaft 21 in the X direction to support the winding shaft 21 such that the winding shaft 21 can freely rotate.

The center shaft 22 is inserted into the winding shaft 21, and extends in the X direction similarly to the winding shaft 21. The center shaft 22 has the same rotation axis as that of the winding shaft 21, and rotates in accordance with the rotation of the winding shaft 21. The tensioning mechanism has a function of urging the center axis 22 in the direction of winding the screen 10, and has known parts such as a spring coil.

When the winding shaft 21 (center shaft 22) is rotated in the direction in which the screen 10 is drawn out, an urging force for rotating the center shaft 22 in the direction of winding the screen 10 is generated by the tensioning mechanism. Thus, when the screen 10 is expanded, the screen 10 is tensioned in the up-down direction (Z direction) by the urging force of the tensioning mechanism. When the screen 10 is stored, the screen 10 is wound around the winding shaft 21 by the urging force of the tensioning mechanism to be stored in the storing portion 20 (see FIG. 2B).

The supporting portion 14 extends in the X direction and supports the side 12. A guide member 16 extending in the X direction is provided on the supporting portion 14. The center line CL passes the center of the winding shaft 21 in the X direction and the center of the supporting portion 14 in the X direction. Thus, the center line CL corresponds to the center line of the screen unit 1.

The pair of the connecting mechanisms 30a and 30b extend between the storing portion 20 and the supporting portion 14, and are equipped on the back side of the screen 10. The connecting mechanisms 30a and 30b are so-called pantograph mechanisms. The connecting mechanism 30a is disposed on the right side with respect to the center line CL, and the connecting mechanism 30b is disposed on the left side with respect to the center line CL. The connecting mechanisms 30a and 30b are located almost linearly symmetrically with respect to the center line CL.

The connecting mechanism 30a has two pairs of (four) arms 31a, 32a, 33a, and 34a connected with each another. Each of the arms 31a, 32a, 33a, and 34a is a pillar-shaped hollow component having a rectangular cross section, and has an equal length. The arms 31a and 32a are disposed on the storing portion 20 side, and the arms 33a and 34a are disposed on the supporting portion 14 side. The arms 31a and 33a are positioned on the front side with respect to the arms 32a and 34a (see FIG. 2A).

The arms 31a and 32a are disposed in such a manner as to cross each other approximately in an X shape, and connected with each other by a connecting portion 35a positioned substantially at the centers of the arms 31a and 32a in such a manner as to be freely rotatable. The arms 33a and 34a are disposed in such a manner as to cross each other approximately in an X shape, and connected with each other by the connecting portion 35a positioned substantially at the centers of the arms 33a and 34a in such a manner as to be freely rotatable similarly to the arms 31a and 32a. The connected arms 31a and 32a and the connected arms 33a and 34a are stacked in the up-down direction (Z direction). The ends of the arm 31a and the arm 34a are connected by a connecting portion 36a, and the ends of the arm 32a and the arm 33a are similarly connected by the connecting portion 36a, in such a manner as to be freely rotatable.

Similarly to the connecting mechanism 30a, the connecting mechanism 30b has two pairs of (four) arms 31b, 32b, 33b, and 34b connected with each another in such a manner as to be freely rotatable. The arms 31b, 32b, 33b, and 34b and the arms 31a, 32a, 33a, and 34a are disposed almost linearly symmetrically with respect to the center line CL as viewed in the direction of the normal line N of the projection surface of the screen 10 (Y direction). Thus, the connecting mechanism 30a and the connecting mechanism 30b have almost linearly symmetric structures with respect to the center line CL as viewed in the direction of the normal line N of the projection surface of the screen 10.

The connecting mechanisms 30a and 30b expand and contract in the up-down direction (Z direction) by the stretch and bend of the arms connected with one another. The expansion and contraction of the connecting mechanisms 30a and 30b allows the supporting portion 14 to shift close to and away from the storing portion 20 (winding shaft 21) for expansion and storage of the screen 10. In the expanded condition of the screen 10, the connecting mechanisms 30a and 30b support the supporting portion 14 above the storing portion 20. In the stored condition of the screen 10, the connecting mechanisms 30a and 30b are folded to store the screen 10 (see FIG. 2B).

The storing portion 20 has a pair of fixed supports 24a and 24b and a pair of movable supports 26a and 26b in correspondence with the pair of the connecting mechanisms 30a and 30b. The fixed supports 24a and 24b are fixed to predetermined positions of the storing portion 20. The movable supports 26a and 26b are movable in the X direction. A screw portion having a female screw is formed on each of the movable supports 26a and 26b coaxially in the X direction. The screw portions of the movable supports 26a and 26b engage with a rotation shaft 44 of the rotating mechanism 40 described later.

The fixed support 24a and the movable support 26a associated with the connecting mechanism 30a are disposed on the right side with respect to the center line CL. The fixed support 24b and the movable support 26b associated with the connecting mechanism 30b are disposed on the left side with respect to the center line CL. The pair of the fixed support 24a and the movable support 26a, and the pair of the fixed support 24b and the movable support 26b are positioned almost linearly symmetrically with respect to the center line CL. The fixed supports 24a and 24b are located outside the movable supports 26a and 26b with respect to the center line CL.

The end of the arm 32a of the connecting mechanism 30a is supported by the fixed support 24a in such a manner as to be freely rotatable, and the end of the arm 31a is supported by the movable support 26a in such a manner as to be freely rotatable. The end of the arm 32b of the connecting mechanism 30b is supported by the fixed support 24b in such a manner as to be freely rotatable, and the end of the arm 31b is supported by the movable support 26b in such a manner as to be freely rotatable.

A pair of fixed supports 17a and 17b and a pair of movable supports 18a and 18b are provided on the supporting portion 14 in correspondence with the pair of the connecting mechanisms 30a and 30b. The fixed supports 17a and 17b are fixed to predetermined positions of the supporting portion 14. The movable supports 18a and 18b are movable in the X direction. More specifically, the guide member 16 has a guide hole extending in the X direction, and the movable supports 18a and 18b engage with the guide hole and freely slide within the guide hole in the X direction.

The fixed support 17a and the movable support 18a associated with the connecting mechanism 30a are disposed on the right side with respect to the center line CL, and the fixed support 17b and the movable support 18b associated with the connecting mechanism 30b are disposed on the left side with respect to the center line CL. The pair of the fixed support 17a and the movable support 18a, and the pair of the fixed support 17b and the movable support 18b are positioned almost linearly symmetrically with respect to the center line CL. The fixed supports 17a and 17b are disposed outside the movable supports 18a and 18b with respect to the center line CL.

The end of the arm 33a of the connecting mechanism 30a is supported by the fixed support 17a in such a manner as to be freely rotatable, and the end of the arm 34a is supported by the movable support 18a in such a manner as to be freely rotatable. The end of the arm 33b of the connecting mechanism 30b is supported by the fixed support 17b in such a manner as to be freely rotatable, and the end of the arm 34b is supported by the movable support 18b in such a manner as to be freely rotatable.

According to the screen unit 1 which includes the connecting mechanisms 30a and 30b connected with the storing portion 20 and the supporting portion 14, the storing portion 20 and the supporting portion 14 are supported at four points in the expanded condition of the screen 10. Thus, bending of the supporting portion 14 located on the upper side can be reduced. Moreover, since the connecting mechanisms 30a and 30b are disposed almost linearly symmetrically with respect to the center line CL, the storing portion 20 and the supporting portion 14 are supported approximately at the symmetric positions in the left-right direction. Accordingly, in the expanded condition of the screen 10, the strengths for supporting the storing portion 20 and the supporting portion 14 become almost uniform in the left-right direction, and thus a tension applied to a left part of the screen 10 and a tension applied to a right part of the screen 10 become more uniform.

In case of a structure which includes only the connecting mechanism 30a with the connecting portions 35a located on the center line CL in the expanded condition of the screen 10 as the screen unit disclosed in JP-A-5-34826, the supporting portion 14 is supported at the two points of the fixed support 17a and the movable support 18a. Since the movable support 18a freely slides in contrast with the fixed support 17a fixed to a predetermined position, the restricting conditions for the arms 33a and 34a of the connecting mechanism 30a differ from each other. Accordingly, the supporting conditions for the two points of the supporting portion 14 differ from each other.

In this case, the supporting portion 14 on the movable support 18a side more easily bends downward than on the fixed support 17a side, and the supporting portion 14 easily shifts toward the fixed support 17a in the left-right direction (X direction). The bend and shift produced on the supporting portion 14 causes the screen 10 to be tensioned non-uniformly and produces distortion and bend on the screen 10. In this case, problems such as deterioration of the quality of images projected on the projection surface of the screen 10, and shift of image projection from a desired projection position on the screen 10 arise.

According to the screen unit 1, however, the pair of the fixed support 17a and the movable support 18a and the pair of the fixed support 17b and the movable support 18b are disposed substantially symmetrically in the left-right direction. Thus, the restricting conditions for the connecting mechanisms 30a and 30b are approximately the same. Accordingly, the supporting condition for the supporting portion 14 in the left part and the supporting condition for the supporting portion 14 in the right part becomes approximately the same. Moreover, the fixed supports 17a and 17b are disposed outside the movable supports 18a and 18b with respect to the center line CL. Thus, both the outside areas of the supporting portion 14 in the left-right direction can be fixed and supported with stability. Accordingly, a tension applied to the left part of the screen 10 and a tension applied to the right part of the screen 10 become more uniform, and bending of the supporting portion 14 on one side and shift of the supporting portion 14 in the left-right direction (X direction) can be both reduced.

As illustrated in FIG. 2A, the respective arms 31a through 34a of the connecting mechanism 30a are disposed in such conditions that the arms 31a and 33a cross and overlap with the arms 32a and 34a in the front-rear direction, respectively, as viewed in the normal line N direction of the screen 10. The arms 31b and 33b and the arms 32b and 34b of the connecting mechanism 30b are disposed in a similar manner.

According to a typical connecting mechanism whose plural arms cross and connect with each other, the arms constituting the connecting mechanism are not located on the same plane. In this case, twisting is easily produced by the load or the like generated by the support of the upper end portion of the screen. In case of the structure of the screen unit which includes only the connecting mechanism 30a extending between the storing portion 20 and the supporting portion 14 as disclosed in JP-A-5-34826, the twist generated on the connecting mechanism 30a leads to relative twisting between the storing portion 20 and the supporting portion 14.

According to the screen unit 1, however, the connecting mechanisms 30a and 30b are provided as almost linearly symmetric structures with respect to the center line CL as viewed in the direction of the normal line N of the projection surface of the screen 10. Thus, even when twisting is generated on each of the connecting mechanisms 30a and 30b, the generated twists can be cancelled by each other due to the structure of the connecting mechanisms 30a and 30b substantially symmetric in the left-right direction. Accordingly, the relative twisting between the storing portion 20 and the supporting portion 14 can be reduced.

According to the screen unit 1, therefore, a tension applied to the left part of the screen 10 and a tension applied to the right part of the screen 10 become more uniform, and generation of bend and shift of the screen 10 can be reduced. Thus, the flatness of the screen 10 increases, and does not decrease even when the size of the screen 10 enlarges. Accordingly, deterioration of the quality of the images projected on the projection surface of the screen 10 can be avoided.

The rotating mechanism 40 is now explained. As illustrated in FIG. 1, the rotating mechanism 40 is disposed on the back side and on the storing portion 20 side of the screen 10. The rotating mechanism 40 includes an electrically operated motor 42, the rotation shaft 44, male screws 46a and 46b formed on the rotation shaft 44, and bearings 48. The electrically operated motor 42 is fixed to the storing portion 20. The electrically operated motor 42 rotates the rotation shaft 44.

The rotation shaft 44 extending in the X direction is threaded through the screw portion formed on the movable support 26a on the connecting mechanism 30a side, and the screw portion formed on the movable support 26b on the connecting mechanism 30b side. The bearings 48 are provided at both ends of the rotation shaft 44 in the extending direction of the rotation shaft 44 and approximately at the center of the rotation shaft 44 to support the rotation shaft 44 such that the rotation shaft 44 can freely rotate.

As illustrated in FIGS. 3A, 3B, and 3C, the screw portion formed on the movable support 26a associated with the connecting mechanism 30a engages with the male screw 46a formed on the rotation shaft 44. As illustrated in FIGS. 3B and 3C, the screw portion formed on the movable support 26b associated with the connecting mechanism 30b engages with the male screw 46b formed on the rotation shaft 44.

The screw portion formed on the movable support 26a is a left-handed screw, and the screw portion formed on the movable support 26b is a right-handed screw. The screw portions formed on the movable supports 26a and 26b have substantially the same pitch. The male screw 46a is formed on the rotation shaft 44 on the movable support 26a side with respect to the center line CL, and the male screw 46b is formed on the rotation shaft 44 on the movable support 26b side with respect to the center line CL. The male screw 46a is a left-handed screw, and the male screw 46b is a right-handed screw. The male screws 46a and 46b have approximately the same pitch. When the rotation shaft 44 is rotated in a predetermined rotation direction in this structure, the movable supports 26a and 26b are shifted in directions opposite to each other along the X direction in accordance with the rotation direction of the rotation shaft 44.

When the rotation shaft 44 is rotated anticlockwise as viewed from the electrically operated motor 42, for example, in the stored condition of the screen 10 (see FIG. 2B) as illustrated in FIG. 3B, each of the movable supports 26a and 26b shifts in a direction away from the center line CL. As a result, the end of the arm 31a supported by the movable support 26a and the end of the arm 31b supported by the movable support 26b shift outward on both sides with respect to the center line CL. In this condition, the distance between the end of the arm 31a (movable support 26a) and the end of the arm 32a (fixed support 24a) decreases on the connecting mechanism 30a side, and the distance between the end of the arm 31b (movable support 26b) and the end of the arm 32b (fixed support 24b) decreases on the connecting mechanism 30b side.

In accordance with this movement, the movable supports 18a and 18b on the supporting portion 14 side slide along the guide member 16 and shift in directions away from the center line CL. In this condition, the distance between the end of the arm 34a (movable support 18a) and the end of the arm 33a (fixed support 17a) decreases on the connecting mechanism 30a side, and the distance between the end of the arm 34b (movable support 18b) and the end of the arm 33b (fixed support 17b) decreases on the connecting mechanism 30b side. As a result, the connecting mechanisms 30a and 30b expand upward, thereby separating the supporting portion 14 from the storing portion 20 (winding shaft 21) for expansion of the screen 10 and tensioning the screen 10 in the up-down direction.

When the rotation of the rotation shaft 44 by using the electrically operated motor 42 is stopped in this condition, the movable supports 26a and 26b having the screw portions engaging with the male screws 46a and 46b stop moving at the positions at which the rotation of the rotation shaft 44 is suspended. Thus, the screen 10 (supporting portion 14) can be maintained at a desired height by controlling the positions of the movable supports 26a and 26b.

When the rotation shaft 44 is rotated clockwise as viewed from the electrically operated motor 42, for example, in the expanded condition of the screen 10 (see FIG. 1) as illustrated in FIG. 3C, each of the movable supports 26a and 26b shifts toward the center line CL. As a result, the distance between the end of the arm 31a (movable support 26a) and the end of arm 32a (fixed support 24a), and the distance between the end of the arm 34a (movable support 18a) and the end of the arm 33a (fixed support 17a) on the connecting mechanism 30a side increase as illustrated in FIG. 2B.

Similarly, the distance between the end of the arm 31b (movable support 26b) and the end of the arm 32b (fixed support 24b), and the distance between the end of the arm 34b (movable support 18b) and the end of the arm 33b (fixed support 17b) on the connecting mechanism 30b side increase. As a result, the connecting mechanisms 30a and 30b are folded downward, and the screen 10 is stored in the storing portion 20 by movement of the supporting portion 14 closer to the storing portion 20 (winding shaft 21).

Since the screw portions of the movable supports 26a and 26b have approximately the same pitch, the movement distances of the respective movable supports 26a and 26b for the number of revolutions of the rotation shaft 44 are substantially equivalent. In this case, the pair of the connecting mechanisms 30a and 30b can be expanded and contracted approximately with synchronization, and thus the screen 10 can be supported substantially in the symmetric condition in the left-right direction regardless of the expanding and contracting conditions of the connecting mechanisms 30a and 30b. Accordingly, a tension applied to the left part of the screen 10 and a tension applied to the right part of the screen 10 become more uniform, and can be expanded and stored in a stable condition.

According to the screen unit 1, the movable supports 26a and 26b of the storing portion 20 are positioned inside the fixed supports 24a and 24b. Thus, the structure which expands and contracts the pair of the connecting mechanisms 30a and 30b by using the one rotating mechanism 40 can be easily produced. Therefore, the screen 10 can be expanded and stored in a stable condition by a simple structure using electric power without requiring a large-scale mechanism.

The guide member 16 provided on the supporting portion 14 may be replaced with a rail member engaging with the movable supports 18a and 18b such that the movable supports 18a and 18b can freely slide within the rail member in the X direction. The guide member or rail member engaging with the movable supports 26a and 26b such that the movable supports 26a and 26b can freely slide within the guide member or rail member in the X direction may also be provided on the storing portion 20. In addition, a cover or the like for storing the respective components of the screen unit 1 in the storing portion 20 when the screen unit 1 is not used may be provided on the storing portion 20.

According to the structure of the screen unit 1 in the first embodiment, the following advantages can be offered.

(1) The storing portion 20 and the supporting portion are supported at plural positions by the connecting mechanisms 30a and 30b. Thus, bending of the supporting portion 14 can be reduced.

(2) The storing portion 20 and the supporting portion 14 are supported by the connecting mechanisms 30a and 30b substantially with symmetry in the left-right direction. Thus, the strengths for supporting the storing portion 20 and the supporting portion 14 become more uniform in the left-right direction.

(3) The supporting conditions for the storing portion 20 and the supporting portion 14 become substantially equivalent in the left-right direction. Thus, bend and shift of the supporting portion 14 can be reduced.

(4) The connecting mechanisms 30a and 30b have almost linearly symmetric structures with respect to the center line CL. In this case, twisting of the connecting mechanisms 30a and 30b can be cancelled by each other, and thus relative twisting between the storing portion 20 and the supporting portion 14 can be reduced.

As a result, a tension applied to the left part of the screen 10 and a tension applied to the right part of the screen 10 become more uniform, which increases the flatness of the screen 10. Accordingly, the flatness of the screen 10 does not lower even when the size of the screen 10 enlarges.

(5) The storing portion 20 and the supporting portion 14 are supported approximately with symmetry in the left-right direction regardless of the degree of expansion of the screen 10 (the height of the supporting portion 14 with respect to the storing portion 20). Thus, the screen 10 can be expanded and stored in a stable condition.

(6) The pair of the movable supports 26a and 26b are disposed inside at positions opposed to each other. Thus, the connecting mechanisms 30a and 30b can be expanded and contracted by using a simple structure including the rotating mechanism 40 such that the screen 10 can be expanded and stored by electrical power.

While the screen unit 1 placed on the floor surface has been discussed in this embodiment, the screen unit 1 may be installed on the ceiling surface. When the screen unit 1 is disposed on the ceiling surface, the storing portion 20 is positioned on the ceiling surface side. In this case, the positions of the connecting mechanisms 30a and 30b, the supporting portion 14 and others with respect to the storing portion 20 are reversed in the up-down direction. Also, the gravity acts in the direction of expanding the screen 10. Thus, the screen 10 can be expanded and stored by drawing the connecting mechanisms 30a and 30b downward from the storing portion 20 located on the ceiling surface side and contracting and folding the connecting mechanisms 30a and 30b upward toward the storing portion 20. When the screen unit 1 is installed on the ceiling surface for use, the screen 10 can be tensioned in the up-down direction by increasing the weight of the supporting portion 14.

Second Embodiment

A screen unit according to a second embodiment is now described with reference to the drawings. FIG. 4 illustrates the general structure of the screen unit in the second embodiment. More specifically, FIG. 4 schematically illustrates a main part of the screen unit as viewed from the back.

The screen unit in the second embodiment has a structure similar to that of the screen unit in the first embodiment except for the structure of the rotating mechanism. Common reference numbers are given to parts and components common to those in the first embodiment, and the same explanation of the common parts and components is not repeated.

The structure of a screen unit 2 according to the second embodiment is now explained with reference to FIG. 4. The screen unit 2 in the second embodiment is a screen unit installed on the floor surface. The screen unit 2 includes the screen 10 (see FIG. 1), the storing portion 20, the supporting portion 14 (see FIG. 1), a pair of the connecting mechanisms 30a and 30b, and a rotating mechanism 50A. The rotating mechanism 50A has a structure appropriate for installation on a floor surface.

The fixed supports 24a and 24b (see FIG. 1) and movable supports 28a and 28b are provided on the storing portion 20 in correspondence with the connecting mechanisms 30a and 30b. The end of the arm 31a is supported by the movable support 28a such that the arm 31a can freely rotate. The end of the arm 31b is supported by the movable support 28b such that the arm 31b can freely rotate. A guide member 27 extending in the X direction is further provided on the storing portion 20. The guide member 27 has a guide hole extending in the X direction, and the movable supports 28a and 28b engage with the guide hole in such a manner as to freely slide within the guide hole in the X direction.

The rotating mechanism 50A has the electrically operated motor 42 (see FIG. 1), the rotation shaft 44, a rotation shaft 54, a wire 58a as a first wire, a wire 58b as a second wire, and pulleys 59a and 59b. A worm gear 45 is equipped on the rotation shaft 44.

The rotation shaft 54 is supported by a supporting member 52 provided between the movable support 28a and the movable support 28b. The rotation shaft 54 extends in the Y direction. That is, the rotation shaft 54 crosses the rotation shaft 44 approximately at right angles. A spur gear 56 engaging with the worm gear 45 by screw engagement is provided on the rotation shaft 54. Thus, the rotation of the rotation shaft 44 is transmitted to the rotation shaft 54 via the worm gear 45 and the spur gear 56.

The pulley 59a is disposed outside (on the right side of) the movable support 28a with respect to the center line CL, and the pulley 59b is disposed outside (on the left side of) the movable support 28b with respect to the center line CL. The pulleys 59a and 59b are attached to corresponding shafts provided on the storing portion 20 and having axial directions extending in the Y direction.

One end of the wire 58a is connected with the movable support 28a, and the other end of the wire 58a is connected with the rotation shaft 54. One end of the wire 58b is connected with the movable support 28b, and the other end of the wire 58b is connected with the rotation shaft 54. Thus, the movable supports 28a and 28b are connected with the rotation shaft 54 via the wires 58a and 58b. The wire 58a is wound around the pulley 59a between the movable support 28a and the rotation shaft 54, and the wire 58b is wound around the pulley 59b between the movable support 28b and the rotation shaft 54.

When the rotation shaft 54 is rotated in a predetermined rotation direction in the stored condition of the screen 10 (see FIG. 2B), the ends of the wires 58a and 58b connected with the rotation shaft 54 are initially wound. The lengths of the wires 58a and 58b wound per one rotation of the rotation shaft 54 are equal to each other. By winding of the wires 58a and 58b around the rotation shaft 54, the movable support 28a (end of the arm 31a) connected with the wire 58a and the movable support 28b (end of the arm 31b) connected with the wire 58b shift toward the pulleys 59a and 59b, that is, outward on both sides with respect to the center line CL by pulling forces given from the wires 58a and 58b.

As a result, the distance between the ends of the arm 31a and the arm 32a of the connecting mechanism 30a and the distance between the ends of the arm 31b and the arm 32b of the connecting mechanism 30b (see FIG. 1) decrease, and thus the connecting mechanisms 30a and 30b stretch upward. Therefore, the screen 10 expands by separation of the supporting portion 14 from the storing portion 20.

According to the screen unit 2 installed on the floor surface, the gravity acts in the direction of moving the supporting portion 14 downward (toward the floor surface), that is, in the direction of folding the connecting mechanisms 30a and 30b. The screen 10 of the screen unit 2 is maintained in the expanded condition by the pulling forces given from the wires 58a and 58b by the engagement between the worm gear 45 and the spur gear 56 while resisting the gravity. Other components such as a mechanism for preventing reverse rotations of the worm gear 45 and the spur gear 56 in the expanded condition of the screen 10 may be added as necessary.

For storing the screen 10, the rotation shaft 54 around which the wires 58a and 58b are wound is rotated in the opposite direction to return the wires 58a and 58b wound around the rotation shaft 54 to the initial positions. In this case, the gravity acts in the direction of moving the supporting portion 14 downward, and thus the movable supports 28a and 28b shift toward the center line CL by the lengths of returning the wires 58a and 58b, allowing the connecting mechanisms 30a and 30b to be folded. As a result, the supporting portion 14 comes close to the storing portion 20, allowing the screen 10 to be stored in the storing portion 20.

According to the screen unit 2 in the second embodiment, therefore, the respective wires 58a and 58b are wound or returned in accordance with the rotation direction of the rotation shaft 54, and the ends of the arms 31a and 31b shift in directions opposite to each other along the X direction. By this method, the screen unit 2 can expand and store the screen 10 by expanding and contracting the connecting mechanisms 30a and 30b in the similar manner. The screen unit 2 in the second embodiment can provide advantages similar to those of the screen unit 1 in the first embodiment.

Each of the worm gear 45 provided on the rotation shaft 44 and the spur gear 56 provided on the rotation shaft 54 included in the screen unit 2 in the second embodiment may be replaced with a bevel gear.

Third Embodiment

A screen unit according to a third embodiment is now described with reference to the drawings. FIG. 5 illustrates the general structure of the screen unit in the third embodiment. More specifically, FIG. 5 schematically illustrates a main part of the screen unit as viewed from the back.

The screen unit in the third embodiment has substantially the same structure as that of the screen unit in the second embodiment except for a rotating mechanism suited for installation on the ceiling surface. Common reference numbers are given to parts and components common to those in the second embodiment, and the same explanation of the common parts and components is not repeated.

The structure of a screen unit 3 according to the third embodiment is now explained. The screen unit 3 in the third embodiment is a screen unit installed on the ceiling surface. The screen unit 3 includes the screen 10 (see FIG. 1), the storing portion 20, the supporting portion 14 (see FIG. 1), a pair of the connecting mechanisms 30a and 30b, and a rotating mechanism 50B. The rotating mechanism 50B has a structure appropriate for installation on the ceiling surface.

The rotating mechanism 50B includes the electrically operated motor 42 (see FIG. 1), the rotation shaft 44, the rotation shaft 54, and the wires 58a and 58b. The movable supports 28a and 28b are connected with the rotation shaft 54 via the wires 58a and 58b. When the wires 58a and 58b are wound around the rotation shaft 54, the movable support 28a (the end of the arm 31a) and the movable support 28b (the end of the arm 31b) shift toward the center line CL.

According to the screen unit 3 installed on the ceiling surface, the gravity acts in the direction of moving the supporting portion 14 downward from the ceiling surface, that is, in the direction of expanding the connecting mechanisms 30a and 30b. Thus, for storing the screen 10 in the storing portion 20, the connecting mechanisms 30a and 30b are contracted upward and folded against the gravity.

According to the screen unit 3, the distance between the arm 31a and the arm 32a of the connecting mechanism 30a and the distance between the arm 31b and the arm 32b of the connecting mechanism 30b (see FIG. 1) increase by winding the wires 58a and 58b around the rotation shaft 54. As a result, the connecting mechanisms 30a and 30b are folded upward, and thus the screen 10 is stored.

When the rotation shaft 54 around which the wires 58a and 58b are wound is rotated in the opposite direction, the wires 58a and 58b wound around the rotation shaft 54 return to the initial positions. In this case, the gravity acts in the direction of moving the supporting portion 14 downward, and thus the movable supports 28a and 28b shift outward on both sides with respect to the center line CL by the lengths of returning the wires 58a and 58b, allowing the connecting mechanisms 30a and 30b to expand downward. As a result, the screen 10 is expanded by the downward expansion of the connecting mechanisms 30a and 30b.

According to the screen unit 3 in the third embodiment, therefore, the respective wires 58a and 58b are wound or returned in accordance with the rotation direction of the rotation shaft 54, and the ends of the arms 31a and 31b shift in directions opposite to each other along the X direction similarly to the screen unit 2 in the second embodiment. Thus, the screen unit 3 can expand and store the screen 10 by expanding and contracting the connecting mechanisms 30a and 30b in the similar manner. The screen unit 3 in the third embodiment can provide advantages similar to those of the screen unit 2 in the second embodiment.

Fourth Embodiment

A screen unit according to a fourth embodiment is now described with reference to the drawings. FIG. 6 illustrates the general structure of the screen unit in the fourth embodiment. More specifically, FIG. 6 schematically illustrates the screen unit in the expanded condition as viewed from the back.

The screen unit in the fourth embodiment has substantially the same structure as that of the screen unit in the first embodiment except that the connecting mechanisms are manually expanded and contracted. Common reference numbers are given to parts and components common to those in the first embodiment, and the same explanation of the common parts and components is not repeated.

As illustrated in FIG. 6, the screen unit 4 in the fourth embodiment includes the screen 10, the storing portion 20, the supporting portion 14, and a pair of connecting mechanisms 60a and 60b as first connecting mechanisms. The connecting mechanisms 60a and 60b extend between the storing portion 20 and the supporting portion 14, and are disposed on the back side of the screen 10. The connecting mechanisms 60a and 60b are positioned almost linearly symmetrically with respect to the center line CL, and have almost linearly symmetric structures with respect to the center line CL.

The connecting mechanism 60a has three pairs of (six) arms 61a, 62a, 63a, 64a, 65a, and 66a connected with one another. The arms 63a and 64a are disposed in such a manner as to cross each other approximately in an X shape. The ends of the arms 63a and 64a on the storing portion 20 side are connected with the arms 61a and 62a, and the ends of the arms 63a and 64a on the supporting portion 14 side are connected with the arms 65a and 66a. The ends of the arms 61a and 62a on the storing portion 20 side are connected with each other and supported by a fixed support 29a provided on the storing portion 20 such that the arms 61a and 62a can freely rotate. The ends of the arms 65a and 66a on the supporting portion 14 side are connected with each other and supported by a fixed support 19a provided on the support portion 14 such that the arms 65a and 66a can freely rotate.

The connecting mechanism 60b has three pairs of (six) arms 61b, 62b, 63b, 64b, 65b, and 66b having similar structures as those of the arms 61a through 66a of the connecting mechanism 60a. The ends of the arms 61b and 62b on the storing portion 20 side are connected with each other and supported by a fixed support 29b provided on the storing portion 20 such that the arms 61b and 62b can freely rotate. The ends of the arms 65b and 66b on the supporting portion 14 side are connected with each other and supported by a fixed support 19b provided on the support portion 14 such that the arms 65b and 66b can freely rotate.

A pair of springs (gas springs or coil springs) 68a and 69a are provided between the arms 63a and 64a of the connecting mechanism 60a, and a pair of springs 68b and 69b are provided between the arms 63b and 64b of the connecting mechanism 60b. According to the screen unit 4, the connecting mechanisms 60a and 60b are manually expanded and contracted for expansion and storage of the screen 10, and the height of the supporting portion 14 of the screen 10 is maintained by using pressures or elastic forces of the springs 68a, 69a and 68b, 69b.

In case of a structure which has only the connecting mechanism 60a located on the center line CL, each of the storing portion 20 and the supporting portion 14 is supported at one point. In this case, bending is easily produced at both ends of the supporting portion 14 in the left-right direction, and also shift and twisting are easily generated.

According to the screen unit 4, however, the connecting mechanisms 60a and 60b are disposed almost linearly symmetrically with respect to the center line CL. Thus, each of the storing portion 20 and the supporting portion 14 is supported at two points substantially symmetric in the left-right direction. Moreover, the connecting mechanisms 60a and 60b have almost linearly symmetric structures with respect to the center line CL. Thus, respective twists of the connecting mechanisms 60a and 60b are canceled by each other. Accordingly, bend, shift, and twisting of the screen 10 decrease, which increases the flatness of the screen 10.

Fifth Embodiment

A screen unit according to a fifth embodiment is now described with reference to the drawings. FIG. 7 illustrates the general structure of the screen unit in the fifth embodiment. More specifically, FIG. 7 schematically illustrates the screen unit in the expanded condition as viewed from the back.

The screen unit in the fifth embodiment has substantially the same structure as that of the screen unit in the first embodiment except that a second connecting mechanism is provided in addition to the first connecting mechanisms. Common reference numbers are given to parts and components common to those in the first embodiment, and the same explanation of the common parts and components is not repeated.

As illustrated in FIG. 7, the screen unit 5 in the fifth embodiment includes the screen 10, the storing portion 20, the supporting portion 14, a pair of the connecting mechanisms 30a and 30b as the first connecting mechanisms, a connecting mechanism 60 as the second connecting mechanism, and the rotating mechanism 40.

The screen 10 of the screen unit 5 has a larger width in the left-right direction (X direction) than each width of the screen units 1, 2, 3, and 4 in the above embodiments. Thus, the lengths of the storing portion 20 and the supporting portion 14 in the left-right direction (X direction) are larger than those of the screen units 1, 2, 3, and 4 in the above embodiments. According to the screen unit 5, the connecting mechanisms 30a and 30b are main connecting mechanisms, and the connecting mechanism 60 is a supplementary connecting mechanism for the connecting mechanisms 30a and 30b.

The distance between the connecting mechanisms 30a and 30b is larger than that of the screen unit 1 in the first embodiment. The connecting mechanism 60 has a structure similar to that of the connecting mechanism 60a or the connecting mechanism 60b in the fourth embodiment, for example. The connecting mechanism 60 is disposed on the center line CL in the area between the connecting mechanisms 30a and 30b, and is connected with a fixed support 29 provided on the storing portion 20 and a fixed support 19 provided on the supporting portion 14.

The respective positions of the connecting mechanism 60, the fixed support 29, and the fixed support 19 in the X direction and the Y direction are determined in such positions as not to interfere with the connecting mechanisms 30a and 30b and the rotating mechanism 40. According to the screen unit 5, the connecting mechanisms 30a and 30b are expanded and contracted by electric power for expansion and storage of the screen 10, and the connecting mechanism 60 is also expanded and contracted in accordance with the movements of the connecting mechanisms 30a and 30b.

When the width of the screen 10 in the left-right direction (X direction) is increased without adding the connecting mechanism 60 and without changing the positions of the connecting mechanisms 30a and 30b from those of the screen unit 1 in the first embodiment, bending is easily produced at both ends of the supporting portion 14 in the left-right direction. When the distance between the connecting mechanisms 30a and 30b is enlarged, bending is easily produced at the center of the supporting portion 14.

According to the screen unit 5, both ends of each of the storing portion 20 and the supporting portion 14 in the left-right direction are supported substantially at symmetric positions in the left-right direction by the connecting mechanisms 30a and 30b, and the center of each of the storing portion 20 and the supporting portion 14 is supported by the connecting mechanism 60. Thus, even when the width of the screen 10 in the left-right direction (X direction) increases, bending at both ends of the supporting portion 14 in the left-right direction and the center of the supporting portion 14 decreases. Thus, the flatness of the screen 10 increases.

According to the screen unit 5 in the fifth embodiment, therefore, the flatness of the screen 10 does not lower even when the screen unit has a so-called wide projection surface whose ratio of the length in the horizontal direction (X direction) to the length in the vertical direction (Z direction) is larger.

In the screen unit 5, the rotating mechanism 40 may be replaced with the rotating mechanism 50A in the second embodiment or the rotating mechanism 50B in the third embodiment.

Sixth Embodiment

A screen unit according to a sixth embodiment is now described with reference to the drawings. FIG. 8 illustrates the general structure of the screen unit in the sixth embodiment. More specifically, FIG. 8 schematically illustrates the screen unit in the expanded condition as viewed from the back.

The screen unit in the sixth embodiment has substantially the same structure as that of the screen unit in the first embodiment except that two pairs of connecting mechanisms are provided as the first connecting mechanisms. Common reference numbers are given to parts and components common to those in the first embodiment, and the same explanation of the common parts and components is not repeated.

As illustrated in FIG. 8, the screen unit 6 in the sixth embodiment includes the screen 10, the storing portion 20, the supporting portion 14, two pairs of connecting mechanisms 30a, 30b, 30c and 30d as the first connecting mechanisms, and rotating mechanisms 40a and 40b. According to the screen unit 6, the width of the screen 10 in the left-right direction (X direction) is further larger than that of the screen 5 in the fifth embodiment.

The connecting mechanisms 30a and 30b are disposed on the right side with respect to the center line CL, and the connecting mechanisms 30c and 30d are disposed on the left side with respect to the center line CL. The connecting mechanisms 30a and 30b are located almost linearly symmetrically with respect to a center line CLa positioned approximately at the center between the connecting mechanisms 30a and 30b, and have almost linearly symmetric structures with respect to the center line CLa. The connecting mechanisms 30c and 30d are located almost linearly symmetrically with respect to a center line CLb positioned approximately at the center between the connecting mechanisms 30c and 30d, and have almost linearly symmetric structures with respect to the center line CLb.

Moreover, the connecting mechanisms 30a and 30d are located almost linearly symmetrically with respect to the center line CL, and have almost linearly symmetric structures with respect to the center line CL. The connecting mechanisms 30b and 30c are located almost linearly symmetrically with respect to the center line CL, and have almost linearly symmetric structures with respect to the center line CL. The center line CLa and the center line CLb are disposed almost linearly symmetrically with respect to the center line CL. The center line CLa may agree with a line connecting the center of the right part of the side 11 and the center of the right part of the side 12 with respect to the center line CL. Similarly, the center line CLb may agree with a line connecting the center of the left part of the side 11 and the center of the left part of the side 12 with respect to the center line CL.

According to the screen unit 6, therefore, the pair of the connecting mechanisms 30a and 30b are disposed as one of a pair on the right side, and the pair of the connecting mechanisms 30c and 30d are disposed as the other of the pair on the left side with the center line CL interposed therebetween. In another point of view, the pair of the connecting mechanisms 30a and 30d are disposed as a pair on the right side and the left side, and the pair of the connecting mechanisms 30b and 30c are disposed as a pair on the right side and the left side with the center line CL interposed between each pair.

According to the screen unit 6, both the right parts and the left parts of the storing portion 20 and the supporting portion 14 are supported by the connecting mechanisms 30a and 30b and the connecting mechanisms 30c and 30d substantially at the symmetric positions in the left-right direction and substantially in the same supporting conditions. Thus, even when the width of the screen 10 in the left-right direction (X direction) further increases, bending at both ends of the supporting portion 14 in the left-right direction and at the center of the supporting portion 14 can be reduced. Thus, the flatness of the screen 10 improves.

Each of the rotating mechanisms 40a and 40b has a structure similar to that of the rotating mechanism 40 in the first embodiment. The rotating mechanism 40a is disposed on the right side of the center line CL in correspondence with the positions of the connecting mechanisms 30a and 30b, and the rotating mechanism 40b are disposed on the left side of the center line CL in correspondence with the positions of the connecting mechanisms 30c and 30d. The rotating mechanisms 40a and 40b are disposed almost linearly symmetrically with respect to the center line CL, and have almost linearly symmetric structures with respect to the center line CL.

In addition, a guide member 16a is provided on the right part of the supporting portion 14 with respect to the center line CL in correspondence with the connecting mechanisms 30a and 30b, and a guide member 16b is provided on the left part of the supporting portion 14 with respect to the center line CL in correspondence with the connecting mechanisms 30c and 30d.

According to the screen unit 6, the connecting mechanisms 30a and 30b are expanded and contracted by the rotating mechanism 40a, and the connecting mechanisms 30c and 30d are expanded and contracted by the rotating mechanism 40b for expansion and storage of the screen 10. Thus, when the rotating mechanisms 40a and 40b are controlled such that they can rotate in synchronization with each other, the expansion and contract of the connecting mechanisms 30a and 30b and of the connecting mechanisms 30c and 30d can be synchronized with each other at the time of expansion and storage of the screen 10.

According to the structure of the screen unit 6 in the sixth embodiment, the flatness of the screen 10 does not lower even when the screen unit has a projection surface whose ratio of the length in the horizontal direction (X direction) to the length in the vertical direction (Z direction) is still larger.

In the screen unit 6, each of the rotating mechanisms 40a and 40b may be replaced with the rotating mechanism 50A in the second embodiment or the rotating mechanism 50B in the third embodiment.

The respective embodiments described herein may be modified in various ways without departing from the scope of the invention. For example, the following modifications may be made.

Modified Example 1

While each of the screen units in the respective embodiments except for the fourth embodiment expands and stores the screen by electric power using the electrically operated motor, the screen of the screen unit may be manually expanded and stored by rotating a handle or the like provided on the rotation shaft without using the electrically operated motor. In this structure, lowering of the flatness of the screen 10 can be prevented, and the screen can be expanded and stored in a stable condition.

Modified Example 2

While each of the screen units in the respective embodiments includes the connecting mechanisms each having two pairs of (four) or three pairs of (six) arms, the screen unit may include connecting mechanisms each having a pair of (two) or four pairs of (eight) or a larger number of arms. In these structures, advantages similar to those of the screen units in the respective embodiments can be provided.

Claims

1. A screen unit comprising:

a screen which has a first side and a second side disposed opposed to each other and extending substantially in parallel with each other;

a first supporting portion extending along the first side of the screen to support the first side;

a second supporting portion extending along the second side of the screen to support the second side; and

a plurality of connecting mechanisms each of which extends between the first supporting portion and the second supporting portion, and expands and contracts in the direction in which the first supporting portion and the second supporting portion are opposed to move the second supporting portion close to and away from the first supporting portion,

wherein the plurality of connecting mechanisms are disposed in parallel in the direction in which the first supporting portion and the second supporting portion extend, and are located almost linearly symmetric with respect to a center line connecting approximately the center of the first side in the extending direction of the first side and approximately the center of the second side in the extending direction of the second side.

2. The screen unit according to claim 1, wherein the plural connecting mechanisms include a plurality of first connecting mechanisms disposed as a pair or pairs on both parts of the screen unit with the center line interposed therebetween.

3. The screen unit according to claim 2, wherein

the plural connecting mechanisms include a pair of the first connecting mechanisms; and

the pair of the first connecting mechanisms have almost linearly symmetric structures with respect to the center line as viewed in the normal line direction of a projection surface of the screen.

4. The screen unit according to claim 3, wherein

the first supporting portion includes a pair of fixed supports provided at predetermined positions and a pair of movable supports movable in the extending direction of the first supporting portion in correspondence with the pair of the first connecting mechanisms;

the second supporting portion includes a pair of fixed supports provided at predetermined positions and a pair of movable supports movable in the extending direction of the second supporting portion in correspondence with the pair of the first connecting mechanisms;

the respective first connecting mechanisms are connected with the respective fixed supports and the respective movable supports of the first supporting portion and with the respective fixed supports and the respective movable supports of the second supporting portion; and

each pair of the fixed supports of the first supporting portion, each pair of the movable supports of the first supporting portion, each pair of the fixed supports of the second supporting portion and each pair of the movable supports of the second supporting portion are disposed almost linearly symmetric with respect to the center line.

5. The screen unit according to claim 4, wherein the pair of the fixed supports of each of the first supporting portion and the second supporting portion are disposed outside the pair of the movable supports of the corresponding supporting portion with respect to the center line.

6. The screen unit according to claim 5, further comprising:

a rotating mechanism which has a rotation shaft extending along the first supporting portion,

wherein

each of the pair of the movable supports of the first supporting portion has a screw portion which has a female screw formed coaxially with each other,

the rotation shaft is inserted through the screw portions of the pair of the movable supports of the first supporting portion and has a male screw engaging with the screw portions, and

one of the screw portions of the pair of the movable supports is a right-handed screw, and the other of the screw portions of the pair of the movable supports is a left-handed screw.

7. The screen unit according to claim 5, further comprising:

a rotating mechanism which has a rotation shaft disposed between the pair of the movable supports of the first supporting portion,

wherein

one of the pair of the movable supports is connected with the rotation shaft via a first wire, and the other of the pair of the movable supports is connected with the rotation shaft via a second wire, and

the first wire and the second wire are wound or returned in accordance with the rotation direction of the rotation shaft to shift the pair of the movable supports in directions opposite to each other along the first supporting portion.

8. The screen unit according to claim 6, wherein the rotating mechanism has an electrically operated motor which rotates the rotation shaft.

9. The screen unit according to claim 2, wherein the plural connecting mechanisms further include a second connecting mechanism disposed on the center line.