Document transport device

Abstract

To provide a document transport device that can suppress the generation of abnormal noises in the separation nip. [Solution] The document transport device comprises a paper feed tray, a pickup roller 37, a drive shaft 33, a paper feed roller 35 supported by the drive shaft 33, a separation pad 61 that forms a separation nip between itself and the paper feed roller 35, a frame 65 that supports the separation pad 61 so that it can move between an upstream position and a downstream position in the transport direction, and a biasing means that biases the separation pad 61 toward the upstream position. During the paper feeding operation of documents on the paper feed tray, the separation pad 61 remains in the upstream position and the paper feed roller 35 rotates in one direction. After the last document on the paper feed tray passes through the separation nip, the separation pad 61 moves to the downstream position due to the rotation of the paper feed roller 35 in one direction, and then the separation pad 61 moves to the upstream position due to the rotation of the drive shaft 33 in the opposite direction.

Description

Technical Field

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[0001] The present invention relates to a document conveying apparatus that separates and conveys a document at a separation nip.

Background Art

[0002] In a document conveying apparatus, a separation nip is provided to separate and convey the topmost document from other documents when a plurality of documents are fed. In the document conveying apparatus described in Patent Document 1, the separation nip is formed between a paper feed roller that rotates in a predetermined direction and a separation pad that is pressed against the paper feed roller.

[0003]

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In the above-described document conveying apparatus, after a single document passes through the separation nip, the paper feed roller rotates while sliding on the separation pad until the next document reaches the separation nip. Further, even until the last document passes through the separation nip and is discharged, the paper feed roller rotates while sliding on the separation pad.

[0006] When the time during which the paper feed roller rotates while sliding on the separation pad becomes long, abnormal noise may occur at the separation nip. This is presumably due to dirt on the paper feed roller and the separation pad, or changes in the surface state of the separation pad due to friction between the two.

[0007] [[ID=​​

[0008] To solve the above problems, the present invention provides a document transport device comprising: a paper feed tray on which a document is placed; a pickup roller that contacts the document placed on the paper feed tray and rotates to feed the document in the transport direction; a paper feed roller positioned downstream of the pickup roller in the transport direction and rotating in one direction to transport the document fed by the pickup roller; a drive shaft that supports the paper feed roller and transmits rotation from a drive source to the paper feed roller; and a separation pad that is pressed against the paper feed roller and forms a separation nip between itself and the paper feed roller. The separation pad is supported by a frame that allows it to move between an upstream position and a downstream position in the transport direction, and by a biasing means that biases the separation pad toward the upstream position. During the paper feeding operation of documents on the paper tray, the separation pad remains in the upstream position and the paper feed roller rotates in one direction. After the last document on the paper tray passes the separation nip, the separation pad moves to the downstream position due to the rotation of the paper feed roller in one direction, and then the separation pad moves to the upstream position due to the rotation of the drive shaft in the opposite direction.

[0009] In the present invention, the present invention may further include a holder that supports the pickup roller and rotates between a paper-feed position in which the pickup roller is in contact with the document and a separated position in which it is separated upward from the document, wherein during the paper-feed operation, the paper-feed roller rotates in one direction and the holder rotates to the paper-feed position, and after the last document on the paper tray has passed the separation nip, the drive shaft rotates in the opposite direction and the holder rotates to the separated position.

[0010] The present invention further comprises a fixing mechanism for fixing the separation pad to the upstream position, the fixing mechanism comprising an actuator that rotates from an upright position to a reclined position when a document is placed on the paper feed tray, and a link member disposed between the actuator and the separation pad and performing a seesaw motion in conjunction with the rotation of the actuator, wherein when a document is placed on the paper feed tray, the actuator rotates to the reclined position, causing the link member to perform a seesaw motion and engage with the separation pad, thereby restricting the movement of the separation pad from the upstream position, and when the last document is fed out of the paper feed tray, the actuator rotates to the upright position, causing the link member to perform a seesaw motion and separate from the separation pad, thereby allowing the separation pad to move.

[0011] In the present invention, the actuator has a pivot shaft, an actuator piece extending radially from the pivot shaft and being pressed down by a document, and a projection extending radially from the pivot shaft, and the link member has a pivot shaft, an engaging piece extending radially from the pivot shaft toward the separation pad, and a pressed piece extending radially from the pivot shaft toward the actuator, wherein when the actuator rotates to the tilted position, the pressed piece of the link member is pressed down by the projection, causing the link member to move like a seesaw around the pivot shaft, the engaging piece engages with the separation pad and restricts the movement of the separation pad, and when the actuator rotates to the upright position, the projection separates from the pressed piece of the link member, causing the link member to move like a seesaw around the pivot shaft, the engaging piece separates from the separation pad and allows the movement of the separation pad. [Effects of the Invention]

[0012] According to the present invention, since the position in which the separation pad is pressed against the paper feed roller is distributed to two locations, changes in the surface condition of the separation pad due to friction with the paper feed roller can be suppressed, and the generation of abnormal noise at the separation nip can be suppressed. [Brief explanation of the drawing]

[0013] [Figure 1] This is a perspective view showing a document transport device according to one embodiment of the present invention. [Figure 2] This is a cross-sectional view showing the transport section of a document transport device according to one embodiment of the present invention. [Figure 3] This is a view of the paper feeding unit from above in a document transport device according to one embodiment of the present invention. [Figure 4] This is a view of the paper feeding unit from below in a document transport device according to one embodiment of the present invention. [Figure 5] This is an exploded perspective view showing a separation pad assembly in a document transport device according to one embodiment of the present invention. [Figure 6] This is a side view showing a separation pad assembly in a document transport device according to one embodiment of the present invention. [Figure 7] This diagram illustrates the process of supporting the pad holder of a separation pad assembly on a frame in a document transport device according to one embodiment of the present invention. [Figure 8] This is a side view showing the frame and actuator of a separation pad assembly in a document transport device according to one embodiment of the present invention. [Figure 9] This is a side view showing the frame and link member of a separation pad assembly in a document transport device according to one embodiment of the present invention. [Figure 10] This is a side view showing the paper feed unit and separation pad assembly before the document is placed in a document transport device according to one embodiment of the present invention. [Figure 11] This is a side view showing the paper feeding unit and separation pad assembly after the document has been placed in a document transport device according to one embodiment of the present invention. [Figure 12] This is a side view showing the paper feeding unit and separation pad assembly during paper feeding operation in a document transport device according to one embodiment of the present invention. [Figure 13] This is a side view of the paper feeding unit and the separation pad assembly in a document transport device according to one embodiment of the present invention, after the last document has passed through the separation nip (before the separation pad moves). [Figure 14] In a document transport device according to an embodiment of the present invention, it is a side view showing a paper feed unit and a separation pad assembly after the last document has passed through the separation nip (after the separation pad has moved). [Figure 15] In a document transport device according to an embodiment of the present invention, it is a side view showing the paper feed unit and the separation pad assembly in a state where the paper feed unit is rotated upward.

Mode for Carrying Out the Invention

[0014] Hereinafter, a document transport device according to an embodiment of the present invention will be described with reference to the drawings.

[0015] First, referring to FIGS. 1 and 2, the overall configuration of the document transport device 1 will be described. FIG. 1 is a perspective view showing the document transport device 1, and FIG. 2 is a cross-sectional view showing the document transport device 1. Fr, Rr, L, and R shown in each figure indicate the front, rear, left, and right of the document transport device 1, respectively.

[0016] As shown in FIG. 1, the document transport device 1 includes a transport unit 3, a paper feed tray 5, and a discharge tray 7.

[0017] First, the transport unit 3 will be described. As shown in FIG. 2, a paper feed port 11 and a discharge port 13 are formed on the right side surface of the transport unit 3. The discharge port 13 is arranged below the paper feed port 11. Further, a horizontal U-shaped transport path 15 extending from the paper feed port 11 toward the discharge port 13 is formed in the transport unit 3. The direction in which the document is transported along the transport path 15 is defined as the transport direction. An opening is formed at the left end of the lower surface of the transport unit 3 along the width direction of the document. A transparent glass plate 17 is fitted into the opening. An image reading sensor 19 is arranged above the glass plate 17. When the document is transported below the glass plate 17, an image of one surface (back surface) of the document is read by the image reading sensor 19.

[0018] The transport path 15 is equipped with, in order from the upstream side in the transport direction, a paper feeding unit 21, a separation pad assembly 23, a first transport roller pair 25, a second transport roller pair 27, and a discharge roller pair 29.

[0019] First, the paper feeding unit 21 will be described with reference to Figures 2, 3, and 4. Figure 3 is a view of the paper feeding unit 21 from above, and Figure 4 is a view of the paper feeding unit 21 from below. The paper feeding unit 21 includes a holder 31, a drive shaft 33 that supports the holder 31, a paper feeding roller 35 supported by the drive shaft 33 (see Figures 2 and 4), and a pickup roller 37 supported by the holder 31 upstream of the paper feeding roller 35 in the transport direction (right side of the figure). In the following description, upstream and downstream refer to the upstream side (right side of the figure) and downstream side (left side of the figure) in the transport direction, respectively.

[0020] First, the holder 31 will be described with reference to Figures 3 and 4. The holder 31 has a top plate 31a, front and rear side plates 31b facing each other in the front-rear direction, and an inner plate 31c positioned between the front and rear side plates 31b, and has a box-like shape with an open bottom. Downstream shaft holes are coaxially drilled at the downstream ends of the front and rear side plates 31b. Upstream shaft holes are coaxially drilled at the upstream ends of the rear side plate 31b and the inner plate 31c. The pickup roller shaft 39 is inserted through the upstream shaft holes.

[0021] Next, the drive shaft 33 will be described. As shown in Figure 2, the drive shaft 33 is rotatably supported at its front and rear ends by the front and rear side plates of the transport unit 3 downstream of the paper feed opening 11. As shown in Figures 3 and 4, the rear end of the drive shaft 33 is connected to the motor 41. The drive shaft 33 is driven by the motor 41 (drive source) and rotates in the forward direction (clockwise direction in Figure 2, see arrow R1 in Figures 3 and 4) and the reverse direction (see arrow R2 in Figures 3 and 4).

[0022] The drive shaft 33 passes through the downstream shaft holes of the front and rear side plates 31b of the holder 31. This allows the holder 31 to rotate vertically around the drive shaft 33. A torque limiter 43 (see Figure 4) is interposed between the holder 31 and the drive shaft 33. When the rotation of the holder 31 is not restricted, the torque limiter 43 transmits the rotation of the drive shaft 33 to the holder 31, causing the holder 31 to rotate together with the drive shaft 33. On the other hand, when the rotation of the holder 31 is restricted, the drive shaft 33 rotates freely relative to the holder 31. In addition, a cylindrical belt support 45 (see Figure 4) is fixed coaxially to the drive shaft 33 inside the rear side plate 31b.

[0023] Next, the paper feed roller 35 will be described. As shown in Figure 4, the paper feed roller 35 is pivotally supported on the drive shaft 33 via a one-way clutch 47 between the belt support 45 and the torque limiter 43. When the paper feed roller 35 rotates during paper feeding, the one-way clutch 47 transmits the rotation of the drive shaft 33 to the paper feed roller 35. Also, when the paper feed roller 35 rotates in conjunction with the document being transported, the one-way clutch 47 allows the paper feed roller 35 to rotate freely relative to the drive shaft 33.

[0024] Next, the pickup roller 37 will be described. The pickup roller 37 is rotatably supported integrally with the pickup roller shaft 39, which is inserted through the upstream shaft hole of the holder 31. A ratchet portion 37a is formed on one end face (the rear end face) of the pickup roller 37. The ratchet portion 37a has ratchet teeth that are inclined in the opposite direction to the rotation direction of the pickup roller 37 during paper feeding (see arrow R1 in the figure).

[0025] The pickup roller shaft 39 is pivotally supported between the rear plate 31b and the pickup roller 37 by an input engaging body 51 and a transmission engaging body 53.

[0026] The input engaging body 51 has a disc-shaped main body 51a, a belt support portion 51b formed on one side of the main body 51a, and an engaging portion 51c formed on the other side of the main body 51a. The belt support portion 51b has a cylindrical shape coaxial with the pickup roller shaft 39. The engaging portion 51c protrudes in the axial direction of the pickup roller shaft 39 along a part of the circumferential direction of the main body 51a. The input engaging body 51 is pivotally supported on the pickup roller shaft 39 in a position where the engaging portion 51c faces the pickup roller 37.

[0027] A belt 55 is wrapped around the belt support portion 51b and the belt support 45 fixed to the drive shaft 33. As a result, the rotation of the drive shaft 33 is transmitted to the input engaging body 51 via the belt 55.

[0028] The transmission engaging body 53 comprises a disc-shaped main body 53a, an engaging portion 53b formed on one surface of the main body 53a, and a ratchet portion 53c formed on the other surface of the main body 53a. The engaging portion 53b protrudes in the axial direction of the pickup roller shaft 39 along a part of the circumferential direction of the main body 53a. The ratchet portion 53c has ratchet teeth inclined toward the pickup roller 37 in the rotational direction of the pickup roller 37 during paper feeding (see arrow R1 in the figure). The transmission engaging body 53 is pivotally supported on the pickup roller shaft 39 between the input engaging body 51 and the pickup roller 37, with the ratchet portion 53c facing the pickup roller 37. The engaging portion 53b of the transmission engaging body 53 and the engaging portion 51c of the input engaging body 51 partially overlap in the axial direction of the pickup roller shaft 39.

[0029] Next, the paper feeding operation of the paper feeding unit 21 will be briefly explained. When no paper feeding operation is being performed, the holder 31 rotates upward and the pickup roller 37 moves upward away from the paper tray 5 (separated position, see the dashed line in Figure 2). When a document is placed on the paper tray 5, the motor 41 is driven and the drive shaft 33 rotates clockwise in Figure 2 (see arrow R1 in Figures 3 and 4). The rotation of the drive shaft 33 is transmitted to the paper feeding roller 35 via the one-way clutch 47, and the paper feeding roller 35 rotates in the paper feeding direction (see arrow R1 in the figure).

[0030] Furthermore, the rotation of the drive shaft 33 is transmitted to the holder 31 via the torque limiter 43, causing the holder 31 to rotate downward. When the holder 31 rotates downward and the pickup roller 37 contacts the uppermost document (paper feeding position, see solid line in Figure 2), the rotation of the holder 31 is restricted, and the drive shaft 33 rotates freely relative to the holder 31.

[0031] Furthermore, the belt support 45 rotates together with the drive shaft 33, and the input engaging body 51 rotates in the same direction as the drive shaft 33 via the belt 55. As the input engaging body 51 rotates, the engaging portion 51c of the input engaging body 51 eventually pushes the engaging portion 53b of the transmission engaging body 53, causing the transmission engaging body 53 to also rotate in the same direction as the drive shaft 33. As the transmission engaging body 53 rotates, the ratchet portion 53c engages with the ratchet portion 37a of the pickup roller 37, causing the pickup roller 37 to also rotate in the same direction as the drive shaft 33 (see arrow R1). As a result, the top document is fed in the transport direction.

[0032] When the paper feeding operation is complete, the motor 41 is driven and the drive shaft 33 rotates in the counterclockwise direction shown in Figure 2 (see arrow R2 in Figures 3 and 4), and the paper feed roller 35 does not rotate in the same direction as the drive shaft 33 due to the one-way clutch 47.

[0033] Furthermore, the rotation of the drive shaft 33 is transmitted to the holder 31 via the torque limiter 43, causing the holder 31 to rotate upward. That is, the pickup roller 37 moves upward away from the paper feed tray 5. When the holder 31 rotates upward until it contacts the stopper (not shown), the rotation of the holder 31 is restricted, and the drive shaft 33 rotates freely relative to the holder 31.

[0034] Furthermore, the belt support 45 rotates together with the drive shaft 33, and the input engaging body 51 rotates in the same direction as the drive shaft 33 via the belt 55. As the input engaging body 51 rotates, the engaging portion 51c of the input engaging body 51 eventually pushes the engaging portion 53b of the transmission engaging body 53, causing the transmission engaging body 53 to also rotate in the same direction as the drive shaft 33. As the transmission engaging body 53 rotates, the ratchet portion 53c separates from the ratchet portion 37a of the pickup roller 37. In this way, when the drive shaft 33 rotates in the opposite direction to the paper feeding direction (see arrow R1 in the figure) (see arrow R2 in the figure), the rotation of the drive shaft 33 is not transmitted to the pickup roller 37.

[0035] Next, the separation pad assembly 23 will be described with reference to Figures 2, 5, and 6. Figure 5 is an exploded perspective view showing the separation pad assembly 23, and Figure 6 is a side view showing the separation pad assembly 23 (the separation pad 61 and pad holder 63 are not shown). The separation pad assembly 23 comprises a separation pad 61, a pad holder 63 that holds the separation pad 61, a frame 65 that movably supports the pad holder 63, and a fixing mechanism 67 that fixes the pad holder 63 to the frame 65.

[0036] First, the separation pad 61 and the pad holder 63 will be described with reference to Figure 5. The separation pad 61 has a flat rectangular parallelepiped shape and is made of an elastic material such as rubber. The pad holder 63 has a recess for holding the separation pad. Locking protrusions 71 are erected on the lower surface of the pad holder 63 at both upstream corners. Furthermore, first protrusions 73 and second protrusions 75 are erected on the front and rear sides of the pad holder 63, running in the front-rear direction. The first protrusion 73 is located closer to the locking protrusions 71, and the second protrusion 75 is located downstream of the first protrusion 73. The lower parts of the first protrusion 73 and the second protrusion 75 protrude downward from the sides of the pad holder 63.

[0037] The first projection 73 is formed in an I-cut shape having two opposing arcuate surfaces and two opposing parallel planes. The two planes are parallel to the upper surface of the separation pad 61. The second projection 75 is cylindrical.

[0038] Next, the frame 65 will be described. The frame 65 comprises side plates 81 facing each other in the front-rear direction, and a mounting section 83 and a receiving recess 85 formed between the side plates. The leading edge (downstream end) of the document is placed on the mounting section 83. The pad holder 63 is supported in the receiving recess 85. The upper surface of the mounting section 83 is inclined upward along the transport direction. Two notches 91 (see Figure 5) are formed in the mounting section 83 at a predetermined distance from each other in the front-rear direction, along the transport direction. The two notches 91 communicate with the receiving recess 85.

[0039] On both sides of the plate 81, an upstream slit 93 and a downstream slit 95 are formed, extending upward from the lower edge at a predetermined distance in the conveying direction. The upstream slit 93 is formed at the same position as the upstream end of the notch 91 in the conveying direction. The downstream slit 95 is formed at the same position as the downstream end of the notch 91 in the conveying direction. The upper ends of both slits 93 and 95 are formed as circles with a diameter larger than the width of both slits 93 and 95. The actuator 111 and link member 113 of the fixing mechanism 67 are supported by the upstream slit 93 and the downstream slit 95, respectively, as will be described later (see Figure 6).

[0040] Furthermore, the side plates 81 have a first slit 101 and a second slit 103 formed on them, extending downward from the upper edge, starting from the upstream side. The first slit 101 and the second slit 103 are in communication with the receiving recess 85. The second slit 103 has a bent portion 103a (see Figure 6) that bends toward the side of the first slit 101 midway. The lower ends of the first slit 101 and the second slit 103 are connected by a rail portion 105 that is parallel to the conveying direction. The length of the rail portion 105 is wider than the distance between the first projection 73 and the second projection 75 that are erected on the front and rear sides of the pad holder 63.

[0041] Furthermore, guide walls 107 are formed in the receiving recess 85 on the inside of the front and rear side plates 81 (between the two notches 91 of the mounting section 83), and are inclined upward toward the downstream side.

[0042] Next, with reference to Figure 7, the process of supporting the pad holder 63 in the receiving recess 85 will be described. First, as shown in Figure 7(a), the pad holder 63 is held in a position where the separating pad 61 faces upstream, the first projection 73 is on the lower side, and the second projection 75 is on the upper side. Then, the first projection 73 is inserted into the first slit 101 of the side plate of the frame 65. The first projection 73 is inserted into the first slit 101 in a position where its parallel surfaces are aligned in the vertical direction.

[0043] As shown in Figure 7(b), when the first projection 73 reaches the lower end of the first slit 101, the pad holder 63 is moved downstream while maintaining the above posture. The first projection 73 moves along the rail portion 105.

[0044] Subsequently, as shown in Figure 7(c), when the first projection 73 reaches the front of the second slit 103, the pad holder 63 is rotated downstream around the first projection 73 to insert the second projection 75 into the second slit 103. Then, as the second projection 75 is lowered along the second slit 103, as shown in Figure 7(d), the first projection 73 moves the rail portion 105 upstream, and the second projection 75 reaches the bent portion 103a of the second slit 103.

[0045] As shown in Figure 2, after the frame 65 is positioned below the paper feed unit 21, as shown in Figure 7(e), when the paper feed roller 35 of the paper feed unit 21 is pressed against the separation pad 61 to form a separation nip N, the second projection 75 moves to the rail section 105 and the pad holder 63 is positioned. In this state, the separation pad 61 contacts the paper feed roller 35 in a nearly horizontal position. Also, as shown in Figure 7(e), the distance between the first projection 73 and the second projection 75 of the pad holder 63 is shorter than the length of the rail section 105, so the first projection 73 and the second projection 75 can move along the rail section 105 in the transport direction and the opposite direction, that is, the separation pad 61 can move in the transport direction and the opposite direction while remaining in contact with the paper feed roller 35. A nip coil spring 87 (see Figure 10) is positioned between the lower surface of the pad holder 63 and the bottom surface of the housing recess 85 of the frame 65. The nip coil spring 87 biases the pad holder 63 upward, pressing the separation pad 61 against the paper feed roller 35. In addition, a moving coil spring 89 (biasing means) (see Figure 10) is positioned in the housing recess 85, which contacts the downstream side of the pad holder 63 and moves the separation pad 61 toward the upstream side.

[0046] Next, the fixing mechanism 67 will be described. As shown in Figures 5 and 6, the fixing mechanism 67 comprises two actuators 111 that rotate due to the document placed on the mounting portion 83 of the frame 65, and two link members 113 that perform a seesaw motion in conjunction with the rotation of the two actuators 111.

[0047] First, the actuator 111 will be described with reference to Figure 8. Figure 8 shows the actuator 111 and the frame 65. The actuator 111 has a pivot shaft 121 and actuator pieces 123 and 125 extending radially from the pivot shaft 121. The pivot shaft 121 is formed in an I-cut shape having two opposing arcuate surfaces and two opposing parallel planes. The length of the actuator piece 123 is longer than the length of the 125. The central angle between the actuator piece 123 and the 125 with respect to the pivot shaft 121 is approximately 120 degrees.

[0048] The actuator 111 is supported by an upstream slit 93 formed in the side plate 81 of the frame 65. As shown in Figure 8, the pivot shaft 121 of the actuator 111 is inserted from below into the upstream slit 93 inside the side plate 81, with the parallel planes facing vertically and the actuator piece 123 facing downstream and the projection 125 facing downstream. After the pivot shaft 121 reaches the upper end of the upstream slit 93, when the pivot shaft 121 is rotated clockwise, the actuator piece 123 rotates through a notch 91 (see Figure 5) formed in the mounting portion 83 of the frame 65. The actuator 111 is biased by a torsion coil spring (not shown) into an upright position (see dashed line in Figure 8) in which the actuator piece 123 extends approximately perpendicularly from the upper surface of the mounting portion 83 and the projection 125 is inclined slightly downward toward the downstream side from the pivot shaft 121. When the actuator piece 123 is rotated downstream against the biasing force of the torsion coil spring, the actuator 111 rotates to a reclined position in which the actuator piece 123 is housed in the notch 91 (see the dashed line in Figure 8).

[0049] Next, the link member 113 will be described with reference to Figure 9. Figure 9 shows the link member 113 and the frame 65. The link member 113 has a pivot shaft 131 and an engaging piece 133 and a pressed piece 135 extending radially from the pivot shaft 131. The pivot shaft 131 is formed in an I-cut shape having two opposing arcuate surfaces and two opposing parallel planes. The engaging piece 133 and the pressed piece 135 are aligned in a direction parallel to the parallel planes of the pivot shaft 131. The engaging piece 133 has a curved tip. The central angle between the engaging piece 133 and the pressed piece 135 with respect to the pivot shaft 131 is approximately 180 degrees.

[0050] The link member 113 is supported by a downstream slit 95 formed in the side plate 81 of the frame 65. As shown in Figure 9, the pivot axis 131 of the link member 113 is inserted from below into the downstream slit 95 inside the side plate 81, with the parallel planes facing vertically and the engaging piece 133 facing upwards and the pressed piece 135 facing downwards. After the pivot axis 131 reaches the upper end of the downstream slit 95, when the pivot axis 131 is rotated counterclockwise, the engaging piece 133 is housed in the receiving recess 85 of the frame 65, and the pressed piece 135 is positioned across the upstream slit 93. The link member 113 moves in a seesaw motion around the pivot axis 131 (see the dashed line in Figure 9). The link member 113 is biased by a torsion coil spring (not shown) to an initial position in which the engaging piece 133 rotates downward and the pressed piece 135 moves upward.

[0051] As shown in Figure 2, the separation pad assembly 23 is positioned below the paper feed unit 21. More specifically, the mounting portion 83 of the frame 65 is positioned below the pickup roller 37 of the paper feed unit 21, and the separation pad 61 is pressed against the paper feed roller 35 from below. This forms a separation nip N between the paper feed roller 35 and the separation pad 61.

[0052] Next, the first transport roller pair 25, the second transport roller pair 27, and the discharge roller pair 29 will be described with reference to Figure 2. The first transport roller pair 25 is located downstream of the separation nip N and comprises a transport roller and a driven roller positioned on either side of the transport path 15. The second transport roller pair 27 is located between the first transport roller pair 25 and the reading sensor 19 and comprises a drive roller and a driven roller positioned on either side of the transport path 15. The discharge roller pair 29 is located inside the discharge port 13 and comprises a transport roller and a driven roller positioned on either side of the transport path 15. The drive roller of the discharge roller pair 29 also serves as the drive roller of the first transport roller pair 25.

[0053] Next, the paper feed tray 5 will be described with reference to Figure 1. The paper feed tray 5 is formed in the shape of a rectangular plate, having a fixed end that is fixed to the transport unit 3 and a free end opposite to the fixed end. The paper feed tray 5 is in a position that is inclined downward from the free end to the fixed end, with the fixed end supported below the paper feed opening 11 of the transport unit 3.

[0054] Next, the output tray 7 will be described with reference to Figures 1 and 2. The output tray 7 is formed in a rectangular shape along the direction of document output, extending from below the output port 13 of the transport unit 3 to below the paper feed tray 5.

[0055] The paper feeding operation of the document transport device 1 described above will be explained with reference to Figures 10 to 15. Figures 10 to 15 are front views of the paper feeding unit 21 and the separation pad assembly 23. The paper feeding operation of the paper feeding unit 21 is as described above. Note that the nip coil spring 87 and the moving coil spring 89 are omitted from the illustration in Figures 11 to 15.

[0056] As shown in Figure 10, when no document is placed on the paper tray 5, the holder 31 of the paper feed unit 21 rotates to a separated position, and the pickup roller 37 is separated upward from the mounting portion 83 of the frame 65 of the separation pad assembly 23. In the separation pad assembly 23, the biasing force of the moving coil spring 89 moves the pad holder 63 to the upstream side within the rail portion 105 (see Figure 6). A separation nip N is formed between the separation pad 61, which has moved to the upstream position P1, and the paper feed roller 35. Here, the biasing force of the moving coil spring 89 is set to be smaller than the frictional force between the separation pad 61 and the paper feed roller 35 at the separation nip N. Therefore, when the paper feed roller 35 is not rotating, the pad holder 63 will not move upstream due to the biasing force of the moving coil spring 89. Also, the actuator 111 rotates to the upright position, and the link member 113 rotates to the initial position. The projection 125 of the actuator 111 is located above the pressed piece 135 of the link member 113. The engaging piece 133 of the link member 113 is spaced lower than the locking projection 71 of the pad holder 63.

[0057] As shown in Figure 11, when the leading edge of the document D is placed on the mounting section 83, the actuator piece 123 of the actuator 111 is pushed down by the document, causing the actuator 111 to rotate counterclockwise in the figure. When the actuator 111 rotates to this reclined position, the projection 125 of the actuator 111 pushes down the pressed piece 135 of the link member 113. This causes the link member 113 to perform a seesaw motion, and the engaging piece 133 rotates upward. The engaging piece 133 rotates downstream of the locking projection 71 of the pad holder 63. This restricts the downstream movement of the pad holder 63. Therefore, the separation pad 61 is fixed in the upstream position P1.

[0058] Subsequently, when the document placed in the paper tray 5 is detected by the document detection unit (not shown), as shown in Figure 12, the drive shaft 33 of the paper feeding unit 21 rotates clockwise in the figure (see arrow A1), and the holder 31 rotates downward (see arrow A2), causing the pickup roller 37 to contact the topmost document. Furthermore, the paper feeding roller 35 and the pickup roller 37 rotate in the paper feeding direction (clockwise in the figure) (see arrow A3). As a result, the document D is fed out by the pickup roller 37. The fed-out document D is guided to the separation nip N by the guide wall 107 (see Figures 5 and 6), where it is separated, and the topmost document is transported in the transport direction.

[0059] The paper feed roller 35 rotates even between the time one document passes through the separation nip N and the time the next document reaches the separation nip N. As the separation pad 61 is fixed in the upstream position P1 as described above, during the paper feeding operation, the paper feed roller 35 rotates while sliding against the separation pad 61, which has moved to the upstream position P1.

[0060] As the last document is fed out by the pickup roller 37, the downward pressure on the actuator piece 123 of the actuator 111 by the document is released, as shown in Figure 13, causing the actuator 111 to rotate from a reclined position to an upright position. This causes the projection piece 125 of the actuator 111 to separate from the pressed piece 135 of the link member 113, causing the link member 113 to rotate back to its initial position. As a result, the engaging piece 133 of the link member 113 separates downward from the pad holder 63, allowing the pad holder 63, i.e., the separation pad 61, to move.

[0061] During this time, the paper feed roller 35 is rotating, and the friction between the paper feed roller 35 and the separation pad 61 causes the pad holder 63 to move downstream along the direction of rotation of the paper feed roller 35 (see arrow A4). As a result, as shown in Figure 14, a separation nip N is formed between the separation pad 61, which has moved to the downstream position P2, and the paper feed roller 35.

[0062] The paper feed roller 35 rotates until the last document is ejected from the output port 13. That is, from the time the last document passes through the separation nip N until it is ejected from the output port 13, the paper feed roller 35 rotates while sliding against the separation pad 61, which has moved to the downstream position P2.

[0063] After the last document is ejected from the output port 13, the drive shaft 33 of the paper feed unit 21 rotates counterclockwise in the figure, as shown in Figure 15 (see arrow A5). As a result, the holder 31 rotates upward (see arrow A6), and the pickup roller 37 moves upward away from the mounting portion 83 of the frame 65. Furthermore, while the drive shaft 33 is rotating counterclockwise, the paper feed roller 35 rotates counterclockwise in the figure (see arrow A7) when subjected to an external force, thus reducing the resistance to the movement of the separation pad 61 due to friction between the paper feed roller 35 and the separation pad 61. Then, due to the biasing force of the moving coil spring 89, the pad holder 63 moves upstream along the rotation direction of the paper feed roller 35 (see arrow A8). As a result, a separation nip N is formed between the separation pad 61, which has moved to the upstream position P1, and the paper feed roller 35.

[0064] Subsequently, as shown in Figure 11, the document D is placed on top, and as described above, the movement of the separation pad 61 from its upstream position P1 is restricted by the fixing mechanism 67.

[0065] As is clear from the above description, according to the present invention, during document transport in the paper feeding operation, a separation nip N is formed between the separation pad 61, which has moved to the upstream position P1, and the paper feed roller 35. From the time the last document passes through the separation nip N until it is discharged from the discharge port 13, a separation nip N is formed between the separation pad 61, which has moved to the downstream position P2, and the paper feed roller 35. In other words, the position in which the separation pad 61 is pressed against the paper feed roller 35 is distributed to two locations. Therefore, changes in the surface state of the separation pad 61 due to friction with the paper feed roller 35 can be suppressed, and the generation of abnormal noise at the separation nip N can be suppressed.

[0066] Furthermore, the separation pad 61 is moved in accordance with the rotation of the paper feed roller 35 during and after the paper feeding operation. Specifically, while the paper feed roller 35 is rotating in one direction during the paper feeding operation, the separation pad 61 moves to the upstream position P1. After the paper feeding operation, the drive shaft 33 is rotated in the opposite direction to rotate the holder 31 to the separated position, which allows the paper feed roller 35 to rotate in the opposite direction, and the biasing force of the moving coil spring 89 moves the separation pad 61 to the downstream position P2. Therefore, a dedicated mechanism for moving the separation pad 61 is not required.

[0067] Furthermore, since the device is equipped with a fixing mechanism 67 that secures the separation pad 61 to the upstream position P1, the separation pad 61 can be reliably fixed to the upstream position P1 even if the paper feed roller 35 rotates during the paper feeding operation.

[0068] Furthermore, since the fixing mechanism 67 includes an actuator 111 that is activated by the document placed on the mounting section 83, it is possible to reliably distinguish between the paper feeding operation and the completion of the paper feeding operation. Therefore, the separation pad 61 can be fixed by the fixing mechanism 67 at a reliable timing.

[0069] The actuator 111 of the fixing mechanism 67 may also be used as a document detection unit to detect a document placed on the placement section 83.

[0070] The above-described embodiments of the present invention describe preferred embodiments of the document transport apparatus and image forming apparatus according to the present invention, and may include various technically preferred limitations. However, the technical scope of the present invention is not limited to these embodiments unless otherwise specified. [Explanation of Symbols]

[0071] 1. Document transport device 5. Paper feed tray 31 Holder 33 Drive shaft 35 Paper feed roller 37 Pickup Roller 61 Separation Pad 65 frames 67 Fixing mechanism 89. Moving coil spring (biasing means) 111 Actuator 113 Link member 121 Rotary shaft 123 Actuator piece 125 Projection piece 131 Rotary shaft 133 Engaging piece 135 Pressed piece

Claims

1. The paper tray on which the document is placed, A pickup roller that contacts and rotates upon contact with the document placed in the paper feed tray, thereby feeding the document in the transport direction. A paper feed roller is positioned downstream of the pickup roller in the transport direction and rotates in one direction to transport the document fed out by the pickup roller. A drive shaft that supports the paper feed roller and transmits rotation from the drive source to the paper feed roller, A separation pad that is pressed against the paper feed roller and forms a separation nip between itself and the paper feed roller, A frame that supports the separation pad so as to be movable between an upstream position and a downstream position in the transport direction, The system includes a biasing means for biasing the separation pad toward the upstream position, During the paper feeding operation of the document on the paper tray, the separation pad remains in the upstream position and the paper feed roller rotates in one direction. After the last document on the paper tray has passed the separation nip, the separation pad moves to the downstream position due to the rotation of the paper feed roller in one direction. The document transport device is characterized in that the separation pad then moves to the upstream position by the rotation of the drive shaft in the opposite direction.

2. The holder further comprises a holder that supports the pickup roller and rotates between a paper feeding position in which the pickup roller contacts the document and a separated position in which it is separated upward from the document. During the aforementioned paper feeding operation, the paper feed roller rotates in one direction and the holder rotates to the aforementioned paper feeding position. The document transport device according to claim 1, characterized in that when the last document is fed out of the paper tray, the drive shaft rotates in the opposite direction and the holder rotates to the separated position.

3. The separation pad is further provided with a fixing mechanism for fixing it to the upstream position, The aforementioned fixing mechanism is An actuator that rotates from an upright position to a reclined position when a document is placed on the aforementioned paper feed tray, The system includes a link member positioned between the actuator and the separation pad, which moves in a seesaw motion in conjunction with the rotation of the actuator, When a document is placed on the paper feed tray, the actuator rotates to the tilted position, causing the link member to move in a seesaw motion and engage with the separation pad, thereby restricting the movement of the separation pad from its upstream position. The document transport device according to claim 1, characterized in that when the last document on the paper feed tray passes the separation nip, the actuator rotates to the upright position, causing the link member to move in a seesaw motion away from the separation pad, thereby allowing the separation pad to move.

4. The actuator comprises a pivot shaft, an actuator piece extending radially from the pivot shaft and being pressed down by the document, and a projection extending radially from the pivot shaft. The link member comprises a pivot shaft, an engaging piece extending radially from the pivot shaft toward the separation pad, and a pressed piece extending radially from the pivot shaft toward the actuator. When the actuator rotates to the tilted position, the projection pushes down the pressed piece of the link member, causing the link member to move like a seesaw around the pivot axis, and the engaging piece engages with the separation pad, restricting the movement of the separation pad. The document transport device according to claim 3, characterized in that when the actuator rotates to the upright position, the projection separates from the pressed piece of the link member, causing the link member to perform a seesaw motion around the rotation axis, and the engaging piece separates from the separation pad, allowing the separation pad to move.

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