PRINTING APPARATUS AND PRINTING METHOD

Abstract

By effectively using a sheet feeding mechanism used for feeding a printing medium in a single transporting path for the purpose of another transporting path, a printing apparatus and a printing method that can simplify a configuration and reduce a size are provided. A first transporting path and a second transporting path are selectively used when an image is to be printed on a printing sheet. The first transporting path transports the printing sheet supplied by a sheet feeding roller from a printing sheet loading portion to a printing position. The second transporting path transports the printing sheet located at a position different from the printing sheet loading portion to the printing position. When the printing sheet is to be transported by the second transporting path, the sheet feeding roller is moved onto the second transporting path so as to transport the printing sheet in the second transporting path.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a printing apparatus that can print an image on a printing medium selectively using a plurality of transporting paths and a printing method.

2. Description of the Related Art

Printing apparatuses include those in which a plurality of transporting paths for a printing medium are formed.

Japanese Patent Laid-Open No. 2002-249241 describes a printing apparatus provided with a transport path that transports a printing medium supplied from a sheet feeding cassette and a transport path that transports a manually fed printing medium. The printing medium loaded on the sheet feeding cassette is supplied by a sheet feeding roller and then, transported by a transporting roller (intermediate roller). The transporting roller also transports the manually fed printing medium. When the manually fed printing medium is to be transported, the sheet feeding roller is idly rotated.

Japanese Patent Laid-Open No. 2005-161839 describes a printing apparatus that can print images on both sides of a printing medium. The printing apparatus is provided with a transport path that transports the printing medium so that an image is printed on the front face of the printing medium and a transport path that transports the printing medium so that an image is printed on the back face of the printing medium. The former transport path supplies the printing medium loaded on a sheet feeding cassette by a sheet feeding roller and then, transports the printing medium by a transporting roller so as to oppose the front face of the printing medium to a print head. As a result, an image is printed on the front face of the printing medium. The latter transport path reverses the printing medium printed on the front face so as to make the front and back faces upside down and then, transports the printing medium again by the transporting roller so as to oppose the back face of the printing medium to the print head. As a result, an image is printed on the back face of the printing medium.

In this type of printing apparatus described in Japanese Patent Laid-Open No. 2005-161839, the same transporting roller is located in the both transport paths, and the both transport paths are partially made common. When the printing medium whose front and back faces are made upside down is to be transported by the latter transport path, the sheet feeding roller located in the former transport path does not function.

In Japanese Patent Laid-Open No. 2002-249241 and Japanese Patent Laid-Open No. 2005-161839, the transporting roller is commonly used in the two transport paths, but the sheet feeding roller is used only for feeding the printing medium in one transport path and not used for the purpose other than the sheet feeding.

SUMMARY OF THE INVENTION

The present invention provides a printing apparatus and a printing method which can simplify a configuration and reduce a size by effectively using a mechanism that feeds a printing medium in one transport path for another transport path.

In the first aspect of the present invention, there is provided a printing apparatus in which a printing medium is transported to a printing position of a printing unit and an image is printed on the printing medium, comprising: a first transporting path that transports the printing medium supplied by a supplying unit from a first position where the printing medium is loaded to the printing position; and a second transporting path that transports the printing medium located at a second position different from the first position to the printing position, wherein the supplying unit can move onto the second transporting path so that the printing medium in the second transporting path is transported along the second transporting path.

In the second aspect of the present invention, there is provided a printing method in which a printing medium is transported to a printing position of a printing unit and an image is printed on the printing medium, wherein using: a first transporting path that transports the printing medium supplied by a supplying unit from a first position where the printing medium is loaded to the printing position; and a second transporting path that transports the printing medium located at a second position different from the first position to the printing position, when the printing medium is transported by the second transporting path, the supplying unit is moved onto the second transporting path, and the printing medium in the second transporting path is transported by the supplying unit.

According to the present invention, an image is printed on the printing medium by selectively using the first transport path that transports the printing medium supplied by the supplying unit to the printing position and the second transport path that transports the printing medium located at a position different from the supply destination of the printing medium by the supplying unit to the printing position. When the printing medium is to be transported by the second transport path, the supplying unit is moved onto the second transport path so as to transport the printing medium in the second transport path by the supplying unit so that the supplying unit of the first transport path can also perform a function as a transport unit of the second transport path. As a result, the supplying unit of the first transport path can be effectively used in the second transport path, and simplification of the configuration and size reduction of the printing apparatus can be realized.

The first transport path can be a transport path that transports the printing medium so that an image is printed on one of the faces of the printing medium, for example. Further, the second transport path can be a transport path that transports the printing medium so that an image is printed on the other face of the printing medium in which an image has been printed on one face, for example.

Further features of the present invention will become apparent from the following description of exemplary embodiments (with reference to the attached drawings).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an appearance view of an inkjet printing apparatus of a first embodiment of the present invention;

FIG. 2 is a perspective view of an engine portion in the printing apparatus in FIG. 1;

FIG. 3 is a perspective view of a transport portion and a sheet discharging portion in the printing apparatus in FIG. 1;

FIG. 4 is a schematic configuration diagram of the engine portion in the printing apparatus in FIG. 1;

FIG. 5 is a schematic diagram of an essential part during sheet feeding of the printing apparatus in FIG. 1;

FIG. 6 is a perspective view of a U-turn sheet feeding roller portion in the printing apparatus in FIG. 1;

FIG. 7 is a schematic diagram for explaining a transport state of a printing sheet in the printing apparatus in FIG. 1;

FIG. 8 is a schematic diagram for explaining a reversing state of the printing sheet in the printing apparatus in FIG. 1.

FIG. 9 is a schematic diagram of the essential part during reversing of the printing sheet in the printing apparatus in FIG. 1;

FIG. 10 is a schematic diagram for explaining the reversing state of the printing sheet in an inkjet printing apparatus of a second embodiment of the present invention; and

FIG. 11 is a schematic diagram of the essential part during reversing of the printing sheet in the printing apparatus in FIG. 10.

DESCRIPTION OF THE EMBODIMENTS

Modes for carrying out the present invention will be described referring to the attached drawings.

First Embodiment

A first embodiment of the present invention will be described based on FIGS. 1 to 9.

FIG. 1 is an appearance view of an inkjet printing apparatus of this embodiment, and FIG. 2 is a perspective view of an engine portion in the printing apparatus. FIG. 3 is a perspective view of a transport portion and a sheet discharging portion in the printing apparatus, and FIG. 4 is a schematic sectional diagram illustrating a transport state of a printing sheet (printing medium) P of the printing apparatus.

A printing apparatus 900 of this example includes an engine portion 100, an exterior portion 200, a sheet feeding portion 1, a transport portion 2, a carriage portion 3, a sheet discharging portion 4, a recovery device portion 5, a print head 30, a U-turn sheet feeding portion 7, a transport portion 8 for double-sided printing, and a control portion. In this example, as the sheet feeding portion for the printing sheet P, the sheet feeding portion 1 that supplies the printing sheet P from an upper-side position of the printing apparatus, and the U-turn sheet feeding portion 7 that supplies the printing sheet P so as to turn in a U-turn from a lower-side position of the printing apparatus. However, the sheet feeding portion may be constituted only by the U-turn sheet feeding portion 7.

(A) Sheet Feeding Portion

On an ASF (Automatic Sheet Feeding) base 15 of the sheet feeding portion 1, a pressure plate 11 on which the printing sheets P are loaded, a sheet feeding roller 12 that feeds the printing sheet P, a separation roller 13a that separates the printing sheets P one by one, and a return lever 14 are mounted. The return lever 14 is a lever that returns the printing sheet P to a loading position. A sheet feeding tray 16 that holds the loaded printing sheets P is mounted on the ASF base 15 or the exterior 200.

The sheet feeding roller 12 forms a rod-state having an arc section. One sheet feeding roller 12 is provided close to a reference position of the printing sheet P, by which the printing sheet P is fed. A driving force of the sheet feeding roller 12 is transmitted from a motor (hereinafter referred to as an LF motor) 30 commonly used by the transport portion 2 through a gear train.

A movable side guide 17 is movably provided on the pressure plate 11, by which a loading position of the printing sheet P is regulated. The pressure plate 11 is rotatable around a rotation shaft connected to the ASP base 15 and is urged by a pressure-plate spring 11a (See FIG. 4) in a direction of the sheet feeding roller 12. At a portion of the pressure plate 11 opposing the sheet feeding roller 12, a separation sheet 13b made of a material with a large friction coefficient such as artificial leather is provided in order to prevent double-feeding of the printing sheet P loaded below. The pressure plate 11 is constituted so as to be brought into contact with and separated from the sheet feeding roller 12 by a pressure plate cam (not shown).

A separation roller holder 13 to which the separation roller 13a that separates the printing sheets P one by one is rotatable around the rotation shaft provided on the ASF base 15 and is urged by a separation roller spring (not shown) in a direction of the sheet feeding roller 12. On the separation roller 13a, a clutch spring (not shown) is mounted, and if a load more than predetermined is applied, a portion to which the separation roller 13a is mounted can rotate. The separation roller 13a is constituted so as to be brought into contact with and separated from the sheet feeding roller 12 by a separation roller release shaft (not shown) and a control cam (not shown).

The return lever 14 that returns the printing sheet P to the loading position is rotatably mounted on the ASF base 15 and is urged by a return lever spring (not shown) in a releasing direction. When the printing sheet P is to be returned to the loading position, the return lever 14 is rotated by the control cam (not shown).

In a usual stand-by state, the pressure plate 11 is released by the pressure plate cam (not shown), and the separation roller 13a is released by the control cam (not shown). The return lever 14 returns the printing sheet P and is provided at a position blocking a loading port so that the printing sheet P does not enter the depth at loading. Sheet feed is started in this stand-by state, and first, the separation roller 13a is brought into contact with the sheet feeding roller 12 by driving of the motor. Then, the return lever 14 is released, and the pressure plate 11 is brought into contact with the sheet feeding roller 12 through the printing sheet P.

Movement of the printing sheet P is restricted by a front-stage separation portion (not shown) provided on the separation roller holder 13, and only the predetermined number of printing sheets P are fed to a nip between the sheet feeding roller 12 and the separation roller 13a. The predetermined number of printing sheets P are separated at this nip, and only the uppermost printing sheet P is transported.

As will be described later, when a front end Pa of the printing sheet P reaches position between a main transporting roller 21 and a pinch roller 22a, the pressure plate 11 is released by the pressure plate cam (not shown), and the separation roller 13a is released by the control cam (not shown). The return lever 14 is returned by the control cam (not shown) to the loading position. At this time, the printing sheet P having reached the nip between the sheet feeding roller 12 and the separation roller 13a can be returned to the loading position.

(B) Transport Portion

The transport portion 2 is mounted on a chassis 101 made of a bent and raised sheet metal. The transport portion 2 is provided with the main transporting roller 21 that transports the printing sheet P and a PB sensor (not shown). The main transporting roller 21 is constituted such that a surface of a metal shaft is coated with ceramic fine particles and is mounted on the chassis 101 by bearings 21d receiving metal portions on both ends thereof. Between the bearing 21d and the main transporting roller 21, a transporting roller tension spring (not shown) is provided, and by urging the main transporting roller 21 so as to apply a predetermined load. The load is given during rotation of the main transporting roller 21 and stable transporting can be performed.

With the main transporting roller 21, a plurality of driven pinch rollers 22a are brought into contact. The pinch roller 22a is held by a pinch roller holder 22, and by urging the roller by a pinch roller spring 22b, the roller is pressed into contact with the main transporting roller 21 and generates a transporting force for the printing sheet P. The pinch roller holder 22 has its rotation shaft mounted in the bearing of the chassis 101 and is rotated around it. Further, on the pinch roller holder 22, a PE sensor lever 23 rotated by a front end Pa and a rear end Pb of the printing sheet P is provided, and the rotational movement is transmitted to the PE sensor (not shown). By means of the PE sensor, the front end Pa and the rear end Pb of the printing sheet P are detected. A platen 25 is mounted on the chassis 101.

In the above configuration, the printing sheet P fed to the transport portion 2 is guided by the pinch roller holder 22 and sent to a roller pair of the main transporting roller 21 and the pinch roller 22a. At this time, a guide flapper 83 has been rotated in an arrow direction E1 in FIG. 4, and the printing sheet P is transported above it. Further, the front end Pa of the printing sheet P is detected by the PE sensor, by which a position to be printed on the printing sheet P is acquired. In addition, the printing sheet P is transported on the platen 25 by the roller pair 21 and 22a rotated by an LF motor 26. On the platen 25, a rib forming a transporting reference face of the printing sheet P is formed so that an opposing interval between the printing sheet P and the print head 30 is managed and occurrence of a ruffling phenomenon of the printing sheet P is suppressed together with the sheet discharging portion 4, which will be described later.

In order to drive the main transporting roller 21, rotation of the LF motor (DC motor, for example) 26 is, as shown in FIG. 3, transmitted by an LF timing belt 26a to an LF pulley 21c provided on the shaft of the main transporting roller 21. On the shaft of the main transporting roller 21, an LF code wheel 21a that detects a transporting amount of the printing sheet P transported by the main transporting roller 21 is provided. On the LF code wheel 21a, marking is applied with a pitch of 150 to 300 lpi (line/inch), and an LF encoder 21b that reads the marking is mounted on the chassis 101 at a position adjacent to the LF code wheel 21a.

At a position on the downstream side in the transporting direction of the printing sheet from the main transporting roller 21, an inkjet print head 30 that prints an image on the basis of image information is provided. The print head 30 in this example is configured such that a replaceable ink tank 500 is mounted, and four tanks are provided so that different types of ink are ejected. The print head 30 can eject ink from a nozzle by using an ejection energy generating element such as an electrothermal conversion element (heater) or a piezoelectric element. If the electrothermal conversion element is used, for example, heat is applied to ink so as to generate foam and the ink can be ejected from the nozzle using the foaming energy. By means of the ink ejected from the nozzle, an image is printed on the printing sheet P.

(C) Carriage Portion

The carriage portion 3 is provided with a carriage 31 on which the print head 30 can be mounted. The carriage 31 is reciprocally moved in a primary scanning direction of an arrow X crossing (orthogonal in this example) a transporting direction (secondary scanning direction) of an arrow Y of the printing sheet P. Thus, a guide sheet-metal rail 32b that guides the carriage 31 and a carriage unit of the chassis 101 that holds an upper end portion of the carriage 31 are provided. The guide sheet-metal rail 32b has an L-shaped section. In order to stabilize an attitude of the carriage 31 in the secondary scanning direction of the arrow Y with respect to the guide sheet-metal rail 32b, a bearing plate 37 is mounted on the carriage 31. In order to urge the bearing plate 37 on the downstream side in the feeding direction of the printing sheet P, a bearing plate spring (not shown) is provided. By sandwiching the guide sheet-metal rail 32b between the carriage 31 and the bearing plate 37 using this urging force, the attitude of the carriage 31 in the secondary scanning direction of the arrow Y is stabilized.

The vertical direction of the carriage 31 is regulated by being brought into contact with the L-shaped guide sheet-metal rail 32b by its own weight of the carriage portion 3. With regard to the rotational direction of the carriage 31, the attitude is stabilized by a sliding portion between the carriage 31 and a carriage-unit upper part of the chassis 101 that holds an upper end portion of the carriage 31.

On the carriage 31, a carriage cover 38 is mounted, and the carriage cover 38 functions as a guiding member when a user attaches the print head 30 to the carriage 31 and also functions as a member that holds the ink tank 500. The guide sheet-metal rail 32b is mounted on the chassis 101, and the position of the carriage 31 is adjusted at factries by adjusting the position of the guide sheet-metal rail 32b.

The carriage 31 is driven by a CR motor 33 mounted on the chassis 101 through a CR timing belt 33a. The CR timing belt 33a is extended by an idler pulley 33b and connected to the carriage 31. A code strip 34 that detects a moving position of the carriage 31 is provided in parallel with the CR timing belt 33a, and the code strip 34 is marked with a pitch of 150 to 300 lpi (line/inch). On the carriage 31, an encoder (not shown) that reads the marking is provided.

In the above configuration, when an image is to be printed on the printing sheet P, the printing sheet P is transported by the roller pair 21 and 22a, and a position in a row direction on which the image is to be printed (position in the transporting direction of the printing sheet P) is positioned at a printing position of the print head 30. After that, while the carriage 31 is moved with the print head 30 in the primary scanning direction by a signal from the control portion, ink is ejected from the print head 30 so that the ink is landed at a position in a column direction where the image is to be printed (position in the primary scanning direction), and the image is printed. By repeating the transporting operation of the printing sheet P and the scanning by the print head 30, the image is sequentially printed on a front face (one face) or a back face (the other face) of the printing sheet P opposing the print head 30.

(D) Sheet Discharging Portion

The sheet discharging portion 4 is constituted by a first sheet discharging roller 41, a spur 41e that can be driven and rotated in contact with the first sheet discharging roller 41 with a predetermined pressure, a gear train that transmits rotational movement of the main transporting roller 21 to the first sheet discharging roller 41 and the like.

The first sheet discharging roller 41 is mounted on the platen 25 so as to be located on the downstream side in the feeding direction of the printing sheet P and is configured such that a plurality of rubber portions are provided on the metal shaft. The first sheet discharging roller 41 is driven by transmission of a driving force of the main transporting roller 21 through a sheet ejection idler gear 43.

The spur 41e is formed by molding a SUS thin plate with a plurality of projecting shapes provided on the periphery integrally into a resin portion and is mounted on a spur holder 44a. The spur 41e is mounted on the spur holder 44a by a spur spring (not shown) in which a coil spring is provided in a rod state and the spur is pressed onto the first sheet discharging roller 41 or the like. The plurality of spurs 41e include those with a function mainly to produce a transporting force of the printing sheet P opposite the rubber portion of the first sheet discharging roller 41 and those with a function to mainly suppress floating the printing sheet P during printing opposite a position without rubber portion of the first sheet discharging roller 41. Further, in order to suppress deformation of the spur holder 44a and deformation of the chassis 101, a spur stay 44b, which is a plate-shaped metal, is mounted.

With the above configuration, the printing sheet P with the image printed by the carriage portion 3 is transported while being sandwiched at the nip between the first sheet discharging roller 41 and the spur 41e and discharged onto a sheet discharge tray 49.

(E) U-Turn Sheet Feeding Portion

On a base 73 of the U-turn sheet feeding portion (supplying unit) 7, a printing sheet loading portion 9 on which the printing sheet P is loaded, a U-turn sheet feeding roller (supply roller) 71 that feeds the printing sheet P, a U-turn intermediate transporting roller 79, a U-turn separation member 72 and the like are mounted. The intermediate transporting roller 79 transports the printing sheet P, and the separation member 72 separates the printing sheets P. In this example, the intermediate transporting roller 79 is used but not limited to that, and the intermediate transporting roller 79 does not have to be provided depending on a size of a printing medium that can be loaded on the loading portion 9, that is, a specification of the loading portion 9.

On the base 73, a U-turn sheet feeding shaft 74 that transmits a driving force to the sheet feeding roller 71, a U-turn sheet feeding arm 75 and the like are mounted. The sheet feeding arm 75 is capable of pivotal rotation around the shaft 74, and the sheet feeding roller 71 is mounted thereon. A transporting path (first transporting path) that transports the printing sheet from the U-turn sheet feeding portion 7 is constituted mainly by a U-turn sheet-feeding rear guide 76, a lower face of the ASF base 15, the base 73, the guide flapper 83, and the pinch roller holder 22.

A driving force of the sheet feeding roller 71 may be supplied from the above-mentioned transport portion 2 through a belt or a gear train or may be supplied from an independent driving force. However, if the main transporting roller 21 is rotated backward in a direction of an arrow C2 in FIG. 4, it is necessary to switch the sheet feeding roller 71 to be rotated or not. In the case of this example, such switching is made using a PG motor (not shown) of a recovery device portion 5 in FIG. 2. However, the configuration is not limited to that, and such a configuration that a trigger is given to transmission of the driving force by movement of the carriage portion 3, for example, may be employed. The recovery device portion 5 performs recovery processing that maintains an ink ejection state of the print head 30 favorable. The recovery processing can include processing to eject or to suck and eject ink not contributing to printing of an image from the nozzle of the print head 30, processing to wipe a face of the print head 30 on which the nozzles are formed, and the like.

Subsequently, an ink supply method from the U-turn sheet feeding portion 7 will be described using FIGS. 4 and 5.

As shown in FIG. 4, when the printing sheet P is set on the loading portion 9 (hereinafter, the loaded printing sheet is also referred to as “printing sheet P0”) and a driving force of the LF motor 26 is transmitted to the sheet feeding roller 71, the LF motor 26 is rotated backward. The backward rotation direction of the LF motor 26 is a backward rotation direction (arrow C2 direction) when the printing sheet P is transported by the main transporting roller 21 to the upstream side in the transporting direction. The sheet feeding roller 71 is rotated in a direction that feeds the printing sheet P to the main transporting roller 21 and feeds the printing sheet P as shown by the arrow A in FIG. 4. The plurality of printing sheets P fed from the loading portion 9 hit the U-turn separation member 72 and are separated, and only the single sheet located on top is fed.

The separated single printing sheet P is transported to the arrow B direction in a transporting path L in FIG. 4. The front end Pa of the printing sheet P is detected when it hits the PE sensor lever 23, by which a printing position on the printing sheet P on which the image is to be printed is acquired. The printing sheet P is further transported and the front end Pa of the printing sheet P is pressed into the nip between the main transporting roller 21 rotated backward in the arrow C2 direction and the pinch roller 22a, and the position of the front end Pa is adjusted (skew correcting operation).

After that, by rotating the LF motor 26 forward and by rotating the main transporting roller 21 in the arrow C1 direction, the front end of the printing sheet P is bitten by the nip of the roller pair 21 and 22a. In the forward rotation of the LF motor 26, the U-turn sheet feeding roller 71 is not driven, but the U-turn sheet feeding roller 71 is brought into a free state and rotated along with the transporting of the printing sheet P.

After that, similarly to the above-mentioned case, the printing operation and the sheet-discharge operation are performed for the printing sheet P.

When the printing on the printing sheet P is finished, the sheet feeding arm 75 is pivotally rotated around the shaft 79 in a direction of an arrow D2 in FIG. 5, and the sheet feeding roller 71 is lifted up and retreated upward from the printing sheet P0 loaded on the loading portion 9. In this example, an operation to turn so as to lift up the sheet feeding arm 75 is triggered by the carriage portion 3. However, not limited to that, the sheet feeding arm 75 may be lifted up in conjunction with the forward-rotation driving of the main transporting roller 21.

(F) Transporting Portion for Double-Sided Printing

FIG. 6 is a perspective view of a transporting portion 8 for double-sided printing in this embodiment, and FIGS. 7 to 9 are schematic diagrams for explaining a transporting state of the printing sheet P in this embodiment.

FIG. 6 shows a transporting path 81 constituting the transporting portion 8 and the sheet feeding roller 71 in the above-mentioned U-turn sheet feeding portion 7. In a guide member forming the transporting path 81 located below the sheet feeding roller 71, a hole 81A is formed. During sheet feeding from the loading portion 9, as shown in FIG. 5, the sheet feeding roller 71 enters the hole 81A so as to feed the printing sheet P0 located below the transporting path 81.

FIG. 7 shows a state in which printing has been finished to the vicinity of the rear end Pb on the printing sheet P fed from the sheet feeding portion 1 or the U-turn sheet feeding portion 7. The rear end Pb of the printing sheet P is in a state bitten by the nip between the main transporting roller pair 21 and 22a as in the figure. The printing on the printing sheet P is finished in this state and then, an operation moves on to the reversing operation.

First, from this state, the guide flapper 83 is rotated in a direction of an arrow E2 in FIG. 8, and an inlet of the transporting path 81 is opened. When the carriage 31 is moved to a predetermined position in the primary scanning direction, the guide flapper 83 is capable of driving using the moving force of the carriage 31. For example, if the carriage 31 is moved from one direction to a position close to an end portion in the movement range, when the carriage 31 is brought into contact with a connecting member connected to the guide flapper 83, it can move the guide flapper 83 in a direction to open the inlet of the transporting path 81. After that, when the carriage 31 is moved to the other direction and separated from the connecting member, it can move the guide flapper 83 in a direction to close the inlet of the transporting path 81. However, a driving method of the guide flapper 83 is not limited to this type of method but a driving force may be obtained from a driving source different from the driving source of the carriage 31.

In a state in which the guide flapper 83 is opened in the arrow E2 direction as above, the LF motor 26 is rotated backward so as to rotate the main transporting roller 21 backward in the arrow C2 direction in FIG. 8, and the printing sheet P is reversed and transported to a direction of an arrow F. At that time, the PE sensor lever 23 is rotated in an arrow G direction by the front end (rear end before the reversing) Pb after the reversing of the printing sheet P. By detecting the rotation with the PE sensor (not shown), the front end Pb after reversing of the printing sheet P having been transported, and the position of the printing sheet P can be acquired.

After the fact that the printing sheet P has entered the transporting path (second transporting path) 81 is detected by the PE sensor (not shown), a guide member 82 housed in a lower part of the transporting path 81 is moved to a position blocking the hole 81A of the transporting path 81 as shown in FIG. 9. As a result, the guide member 82 forms a part of the transporting path 81. When the front end Pb after the reversing of the printing sheet P has reached under the sheet feeding roller 71, the shaft 74 is driven so as to pivotally rotate the sheet feeding arm 75 in an arrow D1 as shown in FIG. 9. As a result, the sheet feeding roller 71 is brought into contact with the printing sheet P having been transported. Since the guide member 82 blocks the hole 81A of the transporting path 81 at this time, the sheet feeding roller 71 is not lowered to a position for feeding the printing sheet P0 in the loading portion 9 but functions as a transporting roller for the printing sheet P.

In this example, the position of the printing sheet P is accurately detected by the PE sensor (not shown). The position of the printing sheet P during transporting in a direction passing through the transporting path 81 may be detected using another sensor without using the PE sensor lever 23 or the PE sensor (not shown).

FIG. 9 shows a state in which the front end Pb after the reversing of the printing sheet P has entered the transporting path L. By rotating the guide flapper 83 in the arrow E1 direction as shown in FIG. 4 while transporting the printing sheet P as it is, the printing sheet P passes over the guide flapper 83. Then, the front end Pb after the reversing of the printing sheet P is pressed into the nip between the main transporting roller 21 rotated backward in the arrow C2 direction and the pinch roller 22a, and the position of the front end Pb is adjusted (skew correcting operation). After that, the front end Pb after the reversing of the printing sheet P is bitten by the nip between the main transporting roller 21 rotated forward in the arrow C1 direction and the pinch roller 22a by rotating the LF motor 26 forward. The feeding roller 71 is not driven by the forward rotation of the LF motor 26 and brought into a free state and rotated along with the transporting of the printing sheet P.

Timing to shut off the driving of the feeding roller 71 is not limited to the timing when the front end Pb after the reversing of the printing sheet P is bitten by the nip between the roller pair 21 and 22a. For example, it may be the timing when the front end Pb is bitten by the nip between the intermediate transporting roller pair 79 and 79a.

After that, the operations of printing on the printing sheet P and sheet discharging are the same as the above-mentioned case. Since the printing sheet P after the reversing has its back face opposing the print head 30, the image is printed on the back face.

In the case of this example, when the printing sheet P after the reversing is to be transported, the timing to start rotation of the sheet feeding roller 71 should be after the front end Pb after the reversing of the printing sheet P has reached the sheet feeding roller 71, and then, the printing sheet P is transported by the main transporting roller 21 and the sheet feeding roller 71 in collaboration. In a case where a distance between the main transporting roller 21 and the sheet feeding roller 71 is large, if the distal end Pb after the reversing of the printing sheet P has reached the position of the sheet feeding roller 71, the rear end (front end before the reversing) Pa after the reversing of the printing sheet P may be removed from the nip of the main transporting roller 21. In that case, the subsequent transporting of the printing sheet P can be performed only by the sheet feeding roller 71, and a configuration that a relation of speed increase to speed reduction between the main transporting roller 21 and the sheet feeding roller 71 does not have to be considered can be employed. As a result, transporting of the printing sheet P with higher accuracy can be realized.

In this example, if the printing is to be performed on the back face of the printing sheet P in an automatic double-sided printing mode, the printing on the front face of the printing sheet P is performed till the rear end Pb of the printing sheet P is removed from the nip of the roller pair 21 and 22a. That is because if the rear end of the printing sheet P is removed from the nip of the roller pair 21 and 22a and transported to the downstream side in the transporting direction, there is a fear that the front end Pb after the reversing is not bitten by the roller pair 21 and 22a when the printing sheet P is reversed and fed back. However, by adding a configuration that the pinch roller holder 22 and the pinch roller 22a are released upward, the printing can be made to the full of the rear end Pb on the front face of the printing sheet P.

The transporting path (second transporting path) 81 forms a transporting path for transporting from a position (second position) on the transporting path where the printing sheet P after the image is printed on the front face is located to the printing position of the print head 30 after the printing sheet P is reversed. During the transporting of the printing sheet P after the reversing, the sheet feeding roller 71 functions as a transporting roller. In the printing apparatus of this example, the transporting path (second transporting path) formed by the transporting path 81 and the transporting path (first transporting path) for transporting the printing sheet P having been fed from the loading portion 9 to the printing position of the print head 30 are formed. These transporting paths include the transporting path L as a common path for the both.

Second Embodiment

FIGS. 10 and 11 are diagrams for explaining a second embodiment of the present invention. In this embodiment, a configuration of the transporting portion for double-sided printing is different from the above-mentioned first embodiment. The difference will be described below.

(F) Transporting Portion for Double-Sided Printing

FIG. 10 is an explanatory diagram of the printing sheet loading portion 9 in this embodiment, and FIG. 11 is an explanatory diagram of a feeding state of the printing sheet P in this embodiment. In this embodiment, instead of the guide member 82 in the first embodiment that blocks the hole 81A of the transporting path 81, the loading portion 9 is urged upward in the configuration.

In this example, the loading portion 9 located below the transporting path 81 is pressed downward by a cam (not shown) mounted on the base 73 in the occasions other than the double-sided printing. During the double-sided printing, as shown in FIG. 10, after it is detected by the PE sensor (not shown) that the reversed printing sheet P has entered the transporting path 81, the cam (not shown) is rotated and releases the pressing on the loading portion 9 downward. Therefore, as shown in FIG. 11, an urging spring 97 mounted at a lower part of the loading portion 9 urges the loading portion 9 upward. As a result, the printing sheet P0 loaded on the loading portion 9 blocks the hole 81A of the transporting path 81 and forms a part of the transporting path 81.

In this example, it is configured that the entire loading portion 9 is urged toward the transporting path 81. However, the present invention is not limited to that, and it may be so configured that the printing sheet P0 is urged using the pressure plate or the pressure plate spring provided at the front end of the loading portion 9, for example. In this case, too, the printing sheet P0 loaded on the loading portion 9 blocks the hole 81A of the transporting path 81 and forms a part of the transporting path 81.

When the front end (rear end before the reversing) Pb after the reversing of the printing sheet P has reached below the sheet feeding roller 71, the shaft 74 is driven so as to pivotally rotate the sheet feeding arm 75 in the arrow D1 direction. As a result, the sheet feeding roller 71 is brought into contact with the printing sheet P. At this time, since the hole 81A of the transporting path 81 is blocked by the printing sheet P0 of the loading portion 9, the sheet feeding roller 71 is not lowered to a position for feeding the printing sheet P0 in the loading portion 9 but functions as a transporting roller that transports the printing sheet P. A stopper portion 81B is provided below the transporting path 81 so that the printing sheet P0 loaded on the loading portion 9 is not fed at that time. Therefore, the printing sheet P0 loaded on the loading portion 9 is not fed. If there is no printing sheet P0 on the loading portion 9, the loading portion 9 is pressed against the lower part of the transporting path 81 by the urging spring 91, and the hole 81A of the transporting path 81 is blocked by an inner bottom face of the loading portion 9.

Other Embodiments

In the second embodiment, it is configured such that the sheet feeding roller 71 is moved by swing of the sheet feeding arm 75, and the printing sheets P0 are separated by the separation member 72. However, it may be so configured such that the sheet feeding roller 71 is moved vertically or the printing sheets P0 are separated without using the separation member 72. For example, the shaft 74 may be vertically movable and the sheet feeding roller may be supported by the shaft 74. Alternatively, without using the separation member 72, a configuration that the printing sheets P0 are separated by a separation roller (retard separation) similarly to the supply portion 1 may be employed.

The present invention can be widely applied to a printing apparatus provided at least with two transporting paths (first and second transporting paths) for transporting a printing medium in printing apparatuses that print an image on the printing medium by transporting the printing medium to a printing position of a printing unit. Therefore, as a printing method, various methods using a print head can be employed other than an inkjet print head. Further, in addition to the serial scanning type printing apparatus as in the above-mentioned embodiments, a full-line type printing apparatus using a lengthy print head extending in a width direction of a printing region in the printing medium may be used.

Further, it is only necessary that the first transporting path is a transporting path for transporting the printing medium supplied by a supplying unit from a first position on which the printing medium is loaded to a printing position. The first position is not limited to a printing sheet loading portion as in the above-mentioned embodiments, that is, not limited to a position on a supply tray on which a plurality of printing mediums can be loaded, but may be a position on which at least a single printing medium is loaded. Further, the first transporting path is not limited only to a configuration including a path for discharging the printing medium in which an image is printed on one face at the printing position through a second position as in the above-mentioned embodiment but it is only necessary that the transporting path can transport the printing medium supplied from the first position to the printing position.

Further, it is only necessary that the second transporting path is a second transporting path for transporting the printing medium located at the second position different from the first position to the printing position. The second position is not limited only to a transporting position of the printing medium in which an image is printed on one face as in the above-mentioned embodiments but may be a position for manually feeding of the printing medium. Essentially, it is only necessary that the second is different from the first position. In addition, the second transporting path is not limited only to a configuration in which the printing medium located at the second position is reversed and transported to the printing position so that an image is printed on the other face of the printing medium but it is only necessary that the second transporting path can transport the printing medium located at the second position to the printing position.

The first transporting path and the second transporting path can include a common path common to the both, and the common path can be provided with a transporting roller constituting a transporting unit as in the above-mentioned embodiments.

It is only necessary that the supplying unit can move on the second transporting path so that the printing medium in the second transporting path is transported along the second transporting path. In the above-mentioned embodiments, the sheet feeding roller (supply roller) constituting the supplying unit is moved to the position in FIG. 9. Further, the supplying unit can be configured to block the second transporting path when it is located on the first transporting path. In the above-mentioned embodiments, the sheet feeding roller (supply roller) constituting the supplying unit blocks the second transporting path as in FIG. 5.

The supply roller constituting the supplying unit can move to each of a position on the first transporting path and a position on the second transporting path by providing a rotatable arm as in the above-mentioned embodiments. In addition, the configuration to move the supply roller is not limited only to the above-mentioned embodiments.

It may be so configured that a part of the second transporting path is formed by an upper face of a guide member located above a supply tray, and the supply roller is opposed to the upper face of the guide member when moved onto the second transporting path and is opposed to the printing medium loaded on the supply tray when moved onto the first transporting path. In this case, the supply roller can move to each of the position on the first transporting path and the position on the second transporting path through a hole formed in the guide member. In addition, when the printing medium is to be transported by the second transporting path, a blocking unit that forms a part of the second transporting path by blocking the hole in the guide member can be provided. As the blocking unit, as in the above-mentioned first embodiment, a guide member as a blocking member located below the guide member and movable to the position to open and block the hole may be included. Further, as in the above-mentioned second embodiment, by urging the supply tray upward, the hole can be also blocked by the printing medium loaded on the supply tray or the inner bottom face of the supply tray. The configuration of the blocking unit is not limited only to these embodiments.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.

This application claims the benefit of Japanese Patent Application No. 2008-322164, filed Dec. 18, 2008, which is hereby incorporated by reference herein in its entirety.

Claims

1. A printing apparatus in which a printing medium is transported to a printing position of a printing unit and an image is printed on the printing medium, comprising:

a first transporting path that transports the printing medium supplied by a supplying unit from a first position where the printing medium is loaded to the printing position; and

a second transporting path that transports the printing medium located at a second position different from the first position to the printing position, wherein

the supplying unit can move onto the second transporting path so that the printing medium in the second transporting path is transported along the second transporting path.

2. The printing apparatus according to claim 1, wherein

the first transporting path and the second transporting path include a common path common to the both paths, and

the common path is provided with a feeding unit that transports the printing medium.

3. The printing apparatus according to claim 1, wherein

the first transporting path includes a path that discharges the printing medium in which an image is printed on one face at the printing position through the second position, and

the second transporting path reverses the printing medium at the second position and transports the printing medium to the printing position so that an image is printed on the other face of the printing medium.

4. The printing apparatus according to claim 1, wherein

the supplying unit blocks the second transporting path when the supplying unit is located on the first transporting path.

5. The printing apparatus according to claim 1, wherein

a supply tray on which a plurality of the printing mediums can be loaded is provided at the first position, and

the supplying unit includes a supply roller that supplies an uppermost one in the printing mediums loaded on the supply tray to the first transporting path.

6. The printing apparatus according to claim 5, wherein

the supply roller is movable to a position on the first transporting path and a position on the second transporting path, respectively.

7. The printing apparatus according to claim 6, wherein

the supply roller is provided at a rotatable arm.

8. The printing apparatus according to claim 6, wherein

a part of the second transporting path is formed by an upper face of a guide member located above the supply tray, and

the supply roller opposes the upper face of the guide member when the supply roller moves onto the second transporting path and opposes the printing medium loaded on the supply tray when the supply roller moves onto the first transporting path.

9. The printing apparatus according to claim 8, wherein

the supply roller is movable to a position on the first transporting path and a position on the second transporting path, respectively, through a hole formed in the guide member, and

a blocking unit is provided that forms a part of the second transporting path by blocking the hole when the printing medium is transported by the second transporting path.

10. The printing apparatus according to claim 9, wherein

the blocking unit includes a blocking member located below the guide member and movable to a position that opens and blocks the hole.

11. The printing apparatus according to claim 10, wherein

the blocking unit urges the supply tray upward so that the hole is blocked by the printing medium loaded on the supply tray or the inner bottom face of the supply tray.

12. The printing apparatus according to claim 1, wherein

the printing unit prints an image using an inkjet print head that can eject ink.

13. A printing method in which a printing medium is transported to a printing position of a printing unit and an image is printed on the printing medium, wherein using:

a first transporting path that transports the printing medium supplied by a supplying unit from a first position where the printing medium is loaded to the printing position; and

a second transporting path that transports the printing medium located at a second position different from the first position to the printing position,

when the printing medium is transported by the second transporting path, the supplying unit is moved onto the second transporting path, and the printing medium in the second transporting path is transported by the supplying unit.