DOCUMENT TRANSPORT DEVICE INCLUDING SLIDER THAT MOVES BETWEEN CONNECTED POSITION FOR TRANSMITTING ROTATIONAL FORCE TO SHEET FEEDING ROLLER, AND SEPARATED POSITION FOR DISCONNECTING TRANSMISSION OF ROTATIONAL FORCE TO SHEET FEEDING ROLLER

Abstract

A document transport device includes a document tray, an actuator, a delivery roller, a rotary shaft, a sheet feeding roller, a separation member, a slider movable along the rotary shaft, between a connected position where the slider is linked with the sheet feeding roller to transmit rotational force thereto, and a separated position where the slider is spaced from the sheet feeding roller, thereby disconnecting transmission of the rotational force to the sheet feeding roller, and an operation lever rotatably supporting the slider, and configured to move parallel to an axial direction of the rotary shaft, when the actuator rotates. When no document is on the document tray and the actuator is not rotating, the operation lever moves the slider to the separated position, and when the document is placed on the document tray and the actuator rotates, the operation lever moves, thereby moving the slider to the connected position.

Description

INCORPORATION BY REFERENCE

This application claims priority to Japanese Patent Application No. 2022-172443 filed on Oct. 27, 2022, the entire contents of which are incorporated by reference herein.

BACKGROUND

The present disclosure relates to a document transport device that transports documents one by one from a sheaf of documents.

The document transport device includes a document tray on which the sheaf of documents is placed, a delivery roller that delivers the documents by rotating in contact with the uppermost one of the sheaf of documents, and a sheet feeding roller that transports the delivered documents to a transport route. The sheet feeding roller is in contact with a pad, thereby defining a separation nip therebetween. The delivered documents are released from each other in the separation nip, and transported one by one to the transport route.

For example, some existing document transport devices are provided with an electromagnetic clutch, configured to switch between a transmitting state in which driving force from a drive source is transmitted to a separation roller (corresponding to the sheet feeding roller), and a non-transmitting state in which the separation roller is disconnected from the driving force. The separation roller can be made to rotate at a predetermined timing, by switching the electromagnetic clutch.

SUMMARY

The disclosure proposes further improvement of the foregoing techniques.

In an aspect, the disclosure provides a document transport device including a document tray, an actuator, a delivery roller, a rotary shaft, a sheet feeding roller, a separation member, a slider, and an operation lever. The actuator is made to rotate when a document is placed on the document tray. The delivery roller delivers the document. The rotary shaft rotates by being driven. The sheet feeding roller transports the document delivered by the delivery roller, upon being made to rotate by rotational force of the rotary shaft. The separation member defines a separation nip by abutting against the sheet feeding roller. The slider is supported so as to move along the rotary shaft, between a connected position where the slider is connected to the sheet feeding roller, to transmit rotational force to the sheet feeding roller, and a separated position where the slider is separated from the sheet feeding roller, to disconnect transmission of the rotational force from the rotary shaft to the sheet feeding roller. The operation lever rotatably supports the slider, and moves parallel to an axial direction of the rotary shaft, when the actuator rotates. When no document is on the document tray and the actuator is not rotating, the operation lever moves the slider to the separated position, and when the document is placed on the document tray and the actuator rotates, the operation lever moves, thereby moving the slider to the connected position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic front view showing an internal structure of a document transport device;

FIG. 2 is a perspective view showing a sheet feeding unit;

FIG. 3A to FIG. 3C are perspective views each showing a link mechanism between a sheet feeding roller and a transmission gear;

FIG. 4 is a cross-sectional view showing a slider and an operation lever;

FIG. 5A is a perspective view showing respective end portions of the operation lever and a link lever;

FIG. 5B and FIG. 5C are perspective views each showing a joint portion between the operation lever and the link lever;

FIG. 6 is a perspective view showing the operation lever, the link lever, and an actuator;

FIG. 7A is a front view showing the actuator, the link lever, and the operation lever, in the state where a sheaf of documents is not placed on a sheet tray;

FIG. 7B is a front view showing the actuator, the link lever, and the operation lever, in the state where the sheaf of documents is placed on the sheet tray;

FIG. 8A is a front view showing the sheet feeding unit, in the state where the sheaf of documents is not placed on the sheet tray;

FIG. 8B is a left side view showing the sheet feeding unit, in the state where the sheaf of documents is not placed on the sheet tray;

FIG. 9A is a front view showing the sheet feeding unit delivering the document;

FIG. 9B is a left side view showing the sheet feeding unit delivering the document;

FIG. 10A is a front view showing the sheet feeding unit, in the state where the document is passing a separation nip;

FIG. 10B is a left side view showing the sheet feeding unit, in the state where the document is passing a separation nip;

FIG. 11A is a front view showing the sheet feeding unit, in the state where the last document is being transported by a first transport roller pair;

FIG. 11B is a left side view showing the sheet feeding unit, in the state where the last document is being transported by the first transport roller pair; and

FIG. 12A and FIG. 12B are perspective views each showing the link mechanism between the sheet feeding roller and the transmission gear, in the state where the last document is being transported by the first transport roller pair.

DETAILED DESCRIPTION

Hereafter, a document transport device according to an embodiment of the disclosure will be described, with reference to the drawings.

Referring to FIG. 1, an overall configuration of the document transport device 1 according to the embodiment will be described. FIG. 1 is a schematic front view showing an internal structure of the document transport device 1. In the following description, the near side from the sheet face of FIG. 1 will be defined as the front side of the document transport device 1. Reference codes Fr, Rr, L, and R represent the front side, the rear side, the left side, and the right side of the document transport device, respectively.

The document transport device 1 is, for example, mounted on the upper face of a document reading device 3. The document transport device 1 automatically transports a source document, and reads the image on one face of the document being transported. The document reading device 3 reads the image on the other face of the document being transported by the document transport device 1. The image read as above is formed on a sheet, for example by an image forming device.

The document transport device 1 includes a transport device 5 that reads the image while transporting the document, a document tray 7 on which the document is placed, and a discharge tray 9 to which the document, the image of which has been read, is discharged.

A sheet inlet 11 and a sheet outlet 13 are formed in the right-side face of the transport device 5. The sheet outlet 13 is located on the lower side of the sheet inlet 11. A transport route 15 is formed between the sheet inlet 11 and the sheet outlet 13, in a horizontal U-shape in a view from the front side. The direction from the sheet inlet 11 and the sheet outlet 13 along the transport route 15 will hereinafter be referred to as transport direction of the document.

On the transport route 15, a sheet feeding device 17, a first transport roller pair 19, a second transport roller pair 21, a reader 23, and a delivery roller 25 are located in this order, from the upstream side in the transport direction. The sheet feeding device 17 is located at the sheet inlet 11, and the delivery roller 25 located at the sheet outlet 13.

Hereunder, the document transport operation will be briefly described. The sheet feeding device 17 delivers the uppermost one of a sheaf of documents placed on the document tray 7, from the sheet inlet 11 to the transport route 15. The first transport roller pair 19 and the second transport roller pair 21 each transport the document delivered as above, along the transport route 15. When the document is transported as far as the reader 23, the reader 23 reads the image on one face of the document. The delivery roller 25 discharges the document through the sheet outlet 13, thus to place the document, the image of which has been read as above, on the discharge tray 9.

Referring to FIG. 2, the sheet feeding device 17 will be described hereunder. FIG. 2 is a perspective view showing a sheet feeding unit 31 of the sheet feeding device 17. The sheet feeding device 17 includes a sheet feeding unit 31 and a separation pad 33 (see FIG. 1). The separation pad 33 exemplifies the separation member in the disclosure.

First, the sheet feeding unit 31 will be described. As shown in FIG. 2, the sheet feeding unit 31 includes a sheet feeding roller 43 and a delivery roller 45, supported by a sheet feeding holder 41 and configured to feed the documents from the sheaf of documents, and an actuator 47 driven by the sheaf of documents.

The sheet feeding holder 41 is formed in a cuboid box shape with an opening oriented downward, and includes a pair of side plates and a top plate. The sheet feeding holder 41 is rotatably supported by a free end portion of a rotary shaft 51, supported in a cantilever form by the rear plate of the transport device 5. To the fixed end portion of the rotary shaft 51, a drive gear 53 is fixed. The drive gear 53 is connected to the output gear of a motor, via a gear train. The motor can rotate in both directions. To deliver the document, the rotary shaft 51 is driven by the motor, so as to rotate clockwise in FIG. 2.

The free end portion of the rotary shaft 51 is penetrating through the end portion of the pair of side plates of the sheet feeding holder 41, on the downstream side in the transport direction. Accordingly, the sheet feeding holder 41 can pivot about the rotary shaft 51, in the up-down direction. A torque limiter is provided between one of the side plates of the sheet feeding holder 41 and the rotary shaft 51. The torque limiter allows the sheet feeding holder 41 to pivot together with the rotary shaft 51, when the torque applied by the rotary shaft 51 to the side plate, in other words to the sheet feeding holder 41, is smaller than a threshold. In contrast, when the torque applied to the sheet feeding holder 41 reaches the threshold, the torque limiter causes the rotary shaft 51 to slip with respect to the sheet feeding holder.

The sheet feeding roller 43 will now be described hereunder. The sheet feeding roller 43 is rotatably supported by the free end portion of the rotary shaft 51, between the pair of side plates of the sheet feeding holder 41. The sheet feeding roller 43 and the rotary shaft 51 can be connected to each other, via a link mechanism. When the sheet feeding roller 43 and the rotary shaft 51 are connected via the link mechanism, the rotational force of the rotary shaft 51 is transmitted to the sheet feeding roller 43. When the sheet feeding roller 43 and the rotary shaft 51 are separated from each other by the link mechanism, the transmission of the rotational force of the rotary shaft 51 to the sheet feeding roller 43 is disconnected.

The link mechanism between the sheet feeding roller 43 and the rotary shaft 51 will be described, with reference to FIG. 3A, FIG. 3B, and FIG. 3C. FIG. 3A, FIG. 3B, and FIG. 3C are perspective views each showing the link mechanism between the sheet feeding roller 43 and the rotary shaft 51. In the subsequent description, the term “axial direction” refers to the axial direction of the rotary shaft 51.

A plurality of projections 43A, protruding in the axial direction, are formed on the front end face of the sheet feeding roller 43, at predetermined intervals along the circumferential direction.

A transmission gear 55 is fixed to the free end portion of the rotary shaft 51. The transmission gear 55 rotates, interlocked with the rotary shaft 51. The transmission gear 55 is located on the front side of the sheet feeding roller 43. A projection 55A is formed on the rear end face of the transmission gear 55, so as to protrude in the axial direction.

The link mechanism includes a coupling 57 and a slider 59, both rotatably supported by the rotary shaft 51, between the transmission gear 55 and the sheet feeding roller 43. The coupling 57 is located on the side of the transmission gear 55, and the slider 59 is located on the side of the sheet feeding roller 43.

The coupling 57 includes a cylindrical portion 57A through which the rotary shaft 51 is inserted, a projection 57B protruding in the axial direction from the front end face 57D of the cylindrical portion 57A, and ratchet teeth 57C formed on the rear end face of the cylindrical portion 57A. The front end face 57D of the cylindrical portion 57A is inclined along the circumferential direction. To be more detailed, as shown in FIG. 3B, the front end face 57D is inclined toward the front side (toward the transmission gear 55), from the upstream side to the downstream side, in the rotating direction of the rotary shaft 51 at the time of delivering the document (direction of an arrow in FIGS. 3A to 3C). The ratchet teeth 57C each include a first face oriented along the axial direction, and a second face inclined so as to intersect the axial direction.

When the rotary shaft 51 (transmission gear 55) rotates in the mentioned rotating direction, and the rear end face of the projection 55A moves along the inclined front end face 57D of the coupling 57, in the state where the rear end face of the projection 55A of the transmission gear 55 is in contact with the front end face 57D of the coupling 57 (see FIG. 3A), the coupling 57 is pressed so as to move backward, in other words to the side of the slider 59, along the rotary shaft 51. Then when the side face of the projection 55A of the transmission gear 55 makes contact with the side face of the projection 57B of the coupling 57 as shown in FIG. 3B, the projection 57B of the coupling 57 is pressed by the projection 55A of the transmission gear 55, so that the coupling 57 rotates together with the transmission gear 55. The coupling 57 is movable along the axial direction, in a range in which the projection 57B and the projection 55A of the transmission gear 55 overlap with each other in the axial direction. Thus, the coupling 57, which is rotatable together with the transmission gear 55, is rotatable with respect to the rotary shaft 51 in a predetermined range along the circumferential direction, and also movable with respect to the rotary shaft 51, in a predetermined range along the axial direction.

The slider 59 includes a cylindrical portion 59A through which the rotary shaft 51 is inserted, ratchet teeth 59B formed on the front end face of the cylindrical portion 59A, and a plurality of projections 59C each protruding in the axial direction from the rear end face of the cylindrical portion 59A. The ratchet teeth 59B each include a first face oriented along the axial direction, and a second face inclined so as to intersect the axial direction. The ratchet teeth 59B are configured to mesh with the ratchet teeth 57C of the coupling 57.

When the ratchet teeth 59B of the slider 59 and the ratchet teeth 57C of the coupling 57 mesh with each other (see FIG. 3A and FIG. 3B), the slider 59 is enabled to rotate together with the coupling 57. When the projections 59C of the slider 59 mesh with the projections 43A of the sheet feeding roller 43 (see FIG. 3B and FIG. 3C), the sheet feeding roller 43 and the slider 59 are connected, so that the sheet feeding roller 43 is enabled to rotate together with the slider 59.

With the mentioned configuration, the slider 59 is movable along the rotary shaft 51, between a connected position where the sheet feeding roller 43 and the transmission gear 55 are connected via the coupling 57, and a separated position where the sheet feeding roller 43 and the transmission gear 55 are separated from each other. In the connected position shown in FIG. 3B, the slider 59 is meshed with the coupling 57, and located on the rear side to be connected to the sheet feeding roller 43. Accordingly, the rotation of the transmission gear 55 is transmitted to the sheet feeding roller 43, via the coupling 57 and the slider 59. However, when the slider 59 and the coupling 57 are separated from each other as shown in FIG. 3C, the rotation of the transmission gear 55 is not transmitted to the sheet feeding roller 43, despite the slider 59 being located at the connected position. On the other hand, in the separated position shown in FIG. 3A, the slider 59 is separated from the sheet feeding roller 43 to the front side. Therefore, the transmission of the rotation of the transmission gear 55 to the sheet feeding roller 43 is disconnected.

As shown in FIG. 2, the slider 59 is supported by the operation lever 61, so as to move between the connected position and the separated position. Referring to FIG. 2, FIG. 4, FIG. 5A, FIG. 5B, and FIG. 5C, the operation lever 61 will be described hereunder. FIG. 4 is a cross-sectional view showing the slider 59 and the operation lever 61. FIG. 5A, FIG. 5B, and FIG. 5C are perspective views each showing the end portion of the operation lever 61.

The operation lever 61 includes, as shown in FIG. 4, a frame 63 rotatably supporting the slider 59, and a rod 65 supporting the frame 63. As shown in FIG. 5A, the rear end face 65A of the rod 65 is inclined along the axial direction. At the center of the rear end face 65A, a minor-sized rod 69 is provided so as to project in the axial direction.

As shown in FIG. 2, the rod 65 is supported by a support member 17A supported by the sheet feeding device 17, so as to move in the axial direction, but not to rotate. The rod 65 biased toward the rear side, by a coil spring 67. Thus, the operation lever 61, in other words the slider 59, is biased toward the side of the sheet feeding roller 43, in other words toward the connected position.

Referring to FIG. 2, FIG. 6, FIG. 7A, and FIG. 7B, the actuator 47 will be described hereunder. FIG. 6 is a perspective view showing the actuator 47, a link lever 81, and the operation lever 61. FIG. 7A and FIG. 7B are front views each showing the actuator 47, the link lever 81, and the operation lever 61.

The actuator 47 is to be driven (made to rotate) by a sheaf of documents placed on the document tray 7. As shown in FIG. 6, the actuator 47 includes a rod 71, and an actuator arm 73 and a link arm 75, each radially projecting from the rod 71. The actuator arm 73 and the link arm 75 spaced from each other by a predetermined central angle with respect to the axial center of the rod 71. A pin 77 is provided at the distal end portion of the link arm 75, so as to protrude in the axial direction.

As shown in FIG. 2, the actuator 47 is located on the rear side of the sheet feeding holder 41. The rod 71 of the actuator 47 supported by the sheet feeding device 17, so as to rotate in a posture parallel to the axial direction. The actuator 47 is maintained, by a helical torsion spring 79 attached on the rod 71, in an initial posture such that the actuator arm 73 is suspended downward to a lower side of the sheet feeding holder 41, and the link arm 75 extends to the downstream side in the transport direction, with respect to the actuator arm 73 (see FIG. 7A). When the actuator arm 73 is pressed by the sheaf of documents in the initial posture, the rod 71 rotates clockwise in FIG. 2 (counterclockwise in FIG. 6, clockwise in FIG. 7A), against the biasing force of the helical torsion spring 79. When the sheaf of documents runs out, the rod 71 is biased by the helical torsion spring 79, so that the actuator 47 rotates to the initial posture (see FIG. 7A).

As shown in FIG. 2 and FIG. 6, the link lever 81 is located between the actuator 47 and the operation lever 61. The link lever 81 converts the rotating motion of the actuator 47 into the reciprocating motion of the operation lever 61 in the axial direction, in other words reciprocating motion of the slider 59 between the connected position and the separated position.

As shown in FIG. 6, the link lever 81 includes a rod 83, and a link arm 85 radially projecting from the rear end portion of the rod 83. The link arm 85 includes a slit 85A formed along the longitudinal direction. As also shown in FIG. 5A, the front end face 83A of the rod 83 is inclined along the axial direction. At the center of the front end face 83A, a shaft hole 87 is formed so as to extend in the axial direction (see FIG. 5A).

As shown in FIG. 2, the link lever 81 is located downstream of the actuator 47, in the transport direction. The rod 83 of the link lever 81 is supported by the support member 17A, so as to rotate aligned with the rod 65 of the operation lever 61 along the axial direction, but not to move in the axial direction. As shown in FIG. 6, the pin 77 of the link arm 75 of the actuator 47 is inserted in the slit 85A in the link arm 85 of the link lever 81. In addition, the minor-sized rod 69 on the rear end face 65A of the rod 65 of the operation lever 61 is inserted in the shaft hole 87 of the rod 83, so that the link lever 81 and the operation lever 61 are connected to each other (see FIG. 5A and FIG. 5B). The front end face 83A of the rod 83 of the link lever 81 is opposed to the rear end face 65A of the rod 65 of the operation lever 61.

Hereunder, description will be given regarding the action to convert the rotating motion of the actuator 47 into the reciprocating motion of the operation lever 61 in the axial direction, with the link lever 81. As shown in FIG. 7A, when the sheaf of documents is not placed on the document tray 7, the actuator 47 assumes the initial posture. The pin 77 of the link arm 75 of the actuator 47 is inserted in the slit 85A in the link arm 85 of the link lever 81, at a position close to the distal end portion.

As shown in FIG. 5B, the front end face 83A of the rod 83 of the link lever 81 and the rear end face 65A of the rod 65 of the operation lever 61 are shifted from each other in the circumferential direction, and are not completely in contact with each other. The operation lever 61 supported so as to move in the axial direction, while the link lever 81 is supported so as not to move in the axial direction. Accordingly, the rear end face 65A of the rod 65 of the operation lever 61 is pressed toward the front side by the front end face 83A of the rod 83 of the link lever 81, so that the operation lever 61 is moved to the front side, against the biasing force of the coil spring 67. Therefore, the minor-sized rod 69 is guided along the shaft hole 87, and the operation lever 61 moves along the axial direction. As result, the slider 59 moves to the separated position.

When the actuator arm 73 of the actuator 47 is pressed by the sheaf of documents D, the rod 71 is made to rotate clockwise, as shown in FIG. 7B. Accordingly, the link arm 75 is also made to rotate clockwise, so that the pin 77 presses one of the inner side faces of the slit 85A, while moving along the slit 85A, to thereby lift up the link arm 85 of the link lever 81. Therefore, the rod 83 of the link lever 81 rotates counterclockwise.

When the rod 83 of the link lever 81 rotates counterclockwise as shown in FIG. 5B, the front end face 83A of the rod 83 of the link lever 81 and the rear end face 65A of the rod 65 of the operation lever 61 are matched with each other in the circumferential direction, thus entering into contact with each other, as shown in FIG. 5C. Accordingly, the operation lever 61 is released from the pressure of the link lever 81, and the operation lever 61 is moved to the rear side by the biasing force of the coil spring 67. As result, the slider 59 moves to the connected position.

As described above, the rotating motion of the actuator 47 caused by the sheaf of documents is converted into the reciprocating motion of the operation lever 61 in the axial direction via the link lever 81, in other words the reciprocating motion of the slider 59 between the separated position and the connected position.

Referring again to FIG. 2, the delivery roller 45 will be described hereunder. The delivery roller 45 is located between the respective end portions of the pair of side plates of the sheet feeding holder 41, on the upstream side in the transport direction. The rotary shaft of the delivery roller 45 is rotatably supported by the pair of side plates. To the rotary shaft, the transmission gear is fixed. The transmission gear is meshed with the transmission gear 55 of the rotary shaft 51, via a plurality of idle gears 91 supported by the side plate (see FIG. 1). When the transmission gear 55 of the rotary shaft 51 rotates, the delivery roller 45 is made to rotate in the same direction as the transmission gear 55.

As described earlier, the sheet feeding holder 41 is pivotable in the up-down direction, about the rotary shaft 51. The sheet feeding holder 41 assumes, upon pivoting downward, a feeding posture such that the delivery roller 45 makes contact with the uppermost one of the sheaf of documents placed on the document tray 7. The sheet feeding holder 41 assumes, upon pivoting upward, a non-feeding posture such that the delivery roller 45 is spaced from the sheaf of documents to the upper side.

The sheet feeding holder 41 also supports a pair of stoppers 93 that delimit the position of the leading edge of the sheaf of documents. The stoppers 93 are rotatably attached to the outer face of the respective side plates. The distal end of each of the stoppers 93 is suspended downward, to a position lower than the lower end of the sheet feeding holder 41. When the sheet feeding holder 41 assumes the feeding posture, the pair of stoppers 93 become pivotable with respect to the sheet feeding holder 41, thereby allowing the document to be delivered. On the other hand, when the sheet feeding holder 41 assumes the non-feeding posture, the pair of stoppers 93 are restricted from pivoting with respect to the sheet feeding holder 41, thereby restricting the leading edge of the sheaf of documents from moving.

Hereunder, the separation pad 33 will be described with reference to FIG. 1. The separation pad 33 is supported by the sheet feeding device 17, so as to contact the sheet feeding roller 43 from the lower side. The separation pad 33 is in contact with the sheet feeding roller 43 with a predetermined pressure, by being biased by a coil spring 101. Accordingly, a separation nip N is defined between the separation pad 33 and the sheet feeding roller 43.

Referring to FIG. 8A to FIG. 12B, the document feeding operation, performed by the document transport device 1 configured as above, will be described hereunder. FIG. 8A, FIG. 9A, FIG. 10A, and FIG. 11A are front views of the sheet feeding unit 31. FIG. 8B, FIG. 9B, FIG. 10B, and FIG. 11B are left sides views of the sheet feeding unit 31. FIG. 12A and FIG. 12B are perspective views each showing the sheet feeding roller 43, the slider 59, the coupling 57, and the transmission gear 55.

As shown in FIG. 8A, the sheet feeding holder 41 assumes the non-feeding posture, when the sheaf of documents is not placed on the document tray 7. The actuator 47 is assuming the initial posture, and the actuator arm 73 is suspended downward, to the lower side of the sheet feeding holder 41. In addition, as shown in FIG. 8B, the rear end face 65A of the operation lever 61 is shifted from the front end face 83A of the link lever 81 in the circumferential direction, and these end faces are not completely in contact with each other. Thus, the operation lever 61 is pressed by the link lever 81 toward the front side, against the biasing force of the coil spring 67. Accordingly, the slider 59 is located at the separated position, and the transmission of the rotational force of the rotary shaft 51 to the sheet feeding roller 43 is disconnected. The ratchet teeth 59B of the slider 59 are meshed with the ratchet teeth 57C of the coupling 57, and the projection 55A of the transmission gear 55 is opposed to the front end face 57D of the coupling 57 (see FIG. 3A).

When the sheaf of documents D is placed on the document tray 7, and the leading edge of the sheaf of documents D is brought into contact with the stoppers 93, as shown in FIG. 9A, the actuator arm 73 of the actuator 47 is pressed by the sheaf of documents D, so that the rod 71 is made to rotate clockwise, as shown in FIG. 7B. Accordingly, as described above, the link lever 81 rotates such that the rear end face 65A of the operation lever 61 and the front end face 83A of the link lever 81 are matched with each other in the circumferential direction, thus entering into contact with each other. Therefore, the operation lever 61 is moved to the rear side by the biasing force of the coil spring 67, and resultantly the slider 59 is separated from the coupling 57 and reaches the connected position, as shown in FIG. 9B.

The rotation of the actuator 47 is transmitted to the rotary shaft 51, so that the rotary shaft 51 is made to rotate so as to make the sheet feeding holder 41 assume the feeding posture. When the delivery roller 45 makes contact with the uppermost one of the sheaf of documents D, the rotary shaft 51 slips with respect to the sheet feeding holder 41, with the effect of the torque limiter.

When the rotary shaft 51 rotates, the transmission gear 55 also rotates with the rotary shaft 51, and the delivery roller 45 is made to rotate, via the idle gears 91 (see FIG. 1). Since the sheet feeding holder 41 is in the feeding posture, the stoppers 93 are enabled to pivot with respect to the sheet feeding holder 41, and the uppermost document D1, with which the delivery roller 45 is in contact, is delivered toward the separation nip N, as shown in FIG. 10A.

Further, when the transmission gear 55 rotates, the rear end face of the projection 55A of the transmission gear 55 presses the inclined front end face 57D of the coupling 57 to the rear side, so that the ratchet teeth 57C of the coupling 57 mesh with the ratchet teeth 59B of the slider 59 (see FIG. 3B). As shown in FIG. 10B, when the rotary shaft 51 rotates further and the side face of the projection 55A of the transmission gear 55 makes contact with the side face of the projection 57B of the coupling 57, the coupling 57 rotates together with the transmission gear 55. Therefore, the rotation of the transmission gear 55 is transmitted to the sheet feeding roller 43, via the coupling 57 and the slider 59, so that the sheet feeding roller 43 is made to rotate. The documents thus delivered by the delivery roller 45 are released from each other in the separation nip N, and transported by the sheet feeding roller 43 toward the first transport roller pair 19.

The first transport roller pair 19 transports the document along the transport route 15, as described earlier. The first transport roller pair 19 transports the last document Dn from the sheaf of documents, which has passed the separation nip N as shown in FIG. 11A, along the transport route 15.

When the last document Dn passes the actuator 47, the actuator 47 assumes the initial posture, by being biased by the helical torsion spring 79 (see FIG. 8A). Accordingly, the link lever 81 rotates, so that the front end face 83A of the rod 83 presses the rear end face 65A of the rod 65 of the operation lever 61. Therefore, the operation lever 61 is moved to the front side, and the slider 59 attempts to move to the separated position. However, as shown in FIG. 10B, the slider 59 is meshed with the coupling 57. Therefore, resistance is applied against the movement of the slider 59 to the separated position.

Referring now to FIG. 12A and FIG. 12B, the document transport operation performed by the sheet feeding roller 43 and the first transport roller pair 19 will be described hereunder. A rotation speed (circumferential speed) V1 of the rotary shaft 51 is set to a level slightly slower than a rotation speed (circumferential speed) V2 of the first transport roller pair 19 (see FIG. 1). Accordingly, when the document is transported by the first transport roller pair 19, the document is transported at the speed corresponding to the circumferential speed V2 of the first transport roller pair 19. Since the sheet feeding roller 43 is in contact with the document, the sheet feeding roller 43, and the slider 59 connected thereto, also rotate at the speed corresponding to the circumferential speed V2 of the first transport roller pair 19, as shown in FIG. 12A. This speed is faster than the circumferential speed V1 of the rotary shaft 51 (transmission gear 55).

Then the respective second faces of the ratchet teeth 59B of the slider 59 press the opposing second faces of the ratchet teeth 57C of the coupling 57, to thereby move the coupling 57 to the front side, as shown in FIG. 12B. Therefore, the resistance against the movement of the slider 59 to the separated position is cancelled, and the slider 59 reaches the separated position, as shown in FIG. 11B.

As described above, after the last document Dn from the sheaf of documents has passed the separation nip N, the slider 59 moves to the separated position, so that the transmission of the rotational force to the sheet feeding roller 43 is disconnected. Accordingly, the sheet feeding roller 43 no longer rotates, after the last document Dn has been delivered. In other words, friction is not generated between the sheet feeding roller 43 and the separation pad 33.

Now, incorporating the electromagnetic clutch, as in the existing document transport device, incurs an increase in cost. Accordingly, it is preferable that the electromagnetic clutch is not introduced, in low-end models. However, without the electromagnetic clutch, it becomes difficult to properly control the rotation of the separation roller, and the separation roller and the pad wear out owing to the friction therebetween, which may disable the documents from being normally transported.

According to the foregoing embodiment, in contrast, the sheet feeding roller 43 can be made to properly rotate by employing the slider 59, without the need to depend on the electromagnetic clutch. The slider 59 is made to move between the connected position and the separated position, by the actuator 47 driven by the documents placed on the document tray 7. When the actuator 47 is made to pivot at the time of delivering the document, the slider 59 is moved to the connected position. Therefore, the rotational force of the rotary shaft 51 is transmitted to the sheet feeding roller 43, so that the sheet feeding roller 43 is made to rotate, and the document delivered by the delivery roller 45 is transported to the transport route 15. When the last document passes the separation nip N, the actuator 47 returns to the initial posture. Accordingly, the slider 59 moves to the separated position, thereby stopping the rotation of the sheet feeding roller 43. Therefore, friction is not generated between the sheet feeding roller 43 and the separation pad 33, and the wear of these components can be prevented. As result, the expected separation performance at the separation nip N can be secured, even in the low-end models which are without the electromagnetic clutch.

Employing the link lever 81 enables the rotating motion of the actuator 47, to be made to rotate by the document being delivered, to be easily converted to the reciprocating motion of the slider 59 between the connected position and the separated position.

In addition, since the coupling 57 is interposed between the slider 59 and the transmission gear 55, the movement of the slider 59 along the axial direction can be surely transmitted to the transmission gear 55, with the coupling 57.

Further, since the coupling 57 and the slider 59 are connected to each other via the ratchet mechanism, the rotational force of the transmission gear 55 can be surely transmitted from the coupling 57 to the sheet feeding roller 43, via the slider 59. Furthermore, the circumferential speed of the sheet feeding roller 43 is faster than the circumferential speed of the transmission gear 55. Therefore, the coupling 57 can be separated from the slider 59, after the last document has passed the separation nip N. As result, the slider 59 can be smoothly moved to the separated position.

Although a specific embodiment of the disclosure has been described as above, the disclosure is in no way limited to the foregoing embodiment. Persons skilled in the art may modify the embodiment as desired, without departing from the scope and spirit of the disclosure.

While the present disclosure has been described in detail with reference to the embodiments thereof, it would be apparent to those skilled in the art the various changes and modifications may be made therein within the scope defined by the appended claims.

Claims

1. A document transport device comprising:

a document tray;

an actuator to be made to rotate when a document is placed on the document tray;

a delivery roller that delivers the document;

a rotary shaft that rotates by being driven;

a sheet feeding roller that transports the document delivered by the delivery roller, upon being made to rotate by rotational force of the rotary shaft;

a separation member that defines a separation nip by abutting against the sheet feeding roller;

a slider supported so as to move along the rotary shaft, between a connected position where the slider is connected to the sheet feeding roller, to transmit rotational force to the sheet feeding roller, and a separated position where the slider is separated from the sheet feeding roller, to disconnect transmission of the rotational force from the rotary shaft to the sheet feeding roller;

an operation lever rotatably supporting the slider, and configured to move parallel to an axial direction of the rotary shaft, when the actuator rotates,

wherein, when no document is on the document tray and the actuator is not rotating, the operation lever moves the slider to the separated position, and

when the document is placed on the document tray and the actuator rotates, the operation lever moves, thereby moving the slider to the connected position.

2. The document transport device according to claim 1, further comprising a link lever provided between the actuator and the operation lever, and configured to convert a rotating motion of the actuator into a reciprocating motion of the operation lever along the parallel direction.

3. The document transport device according to claim 1, further comprising:

a transmission gear fixed to the rotary shaft; and

a coupling provided between the transmission gear and the slider, so as to move along the rotary shaft, and to rotate interlocked with the transmission gear,

wherein the slider is connected to the coupling, and connected to the sheet feeding roller, in the connected position.

4. The document transport device according to claim 1,

wherein the sheet feeding roller and the slider are connected to each other via a ratchet mechanism, in the connected position.

5. The document transport device according to claim 1,

wherein a circumferential speed of the sheet feeding roller is faster than a circumferential speed of the transmission gear.