Document transport device

Abstract

To provide a document transport device which can be made lower in height and which makes it easy to remove paper jammed in a separation nip. [Solution] The document transport device is a document transport device that separates and feeds paper at a separation nip formed between a paper feed roller and a separation pad, and includes a pad holder that holds the separation pad and is rotatable in the vertical direction around a pivot axis (53), and a tension spring (55) that urges the pad holder upward to press the separation pad against the paper feed roller, and a separation pad support mechanism (45) that, when a paper jam occurs in the separation nip, rotates the pad holder in a direction that moves the separation pad away from the paper feed roller against the urging force of the tension spring (55).

Description

[Technical Field]

[0001] The present invention relates to a document transport device that separates and transports documents at a separation nip. [Background technology]

[0002] The document transport device is provided with a separation nip that separates the top document from the other documents when multiple documents are fed. The separation nip is formed between a paper feed roller and a separation pad that is pressed against the paper feed roller.

[0003] To reliably separate the top sheet at the separation nip, the separation pad needs to be pressed against the paper feed roller with a certain amount of force. Therefore, as in the automatic document feeder described in Patent Document 1, the separation pad is often pressed against the paper feed roller with a predetermined pressure by an elastic member (spring member). In this automatic document feeder, a compression coil spring is used as the elastic member. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-145472 Summary of the Invention [Problem to be solved by the invention]

[0005] However, as described in Patent Document 1, if a compression coil spring is used as the elastic member that presses the separation pad against the paper feed roller, the compression coil spring must be located below the paper feed roller. This increases the height of the document transport device by the height of the compression coil spring. Furthermore, when paper jams at the separation nip, the paper held in the separation nip must be pulled out, which requires a large amount of force and can cause the paper to tear.

[0006] SUMMARY OF THE INVENTION In consideration of the above circumstances, it is an object of the present invention to provide a document transport device that can be made low in height and that makes it easy to remove paper jammed in the separation nip. [Means for solving the problem]

[0007] In order to solve the above problem, the document transport device of the present invention is a document transport device that separates and feeds paper at a separation nip formed between a paper feed roller and a separation pad, and is characterized by comprising: a pad holder that holds the separation pad and is rotatable in the vertical direction around a rotation axis; a tension spring that urges the pad holder upward to press the separation pad against the paper feed roller; and a separation pad support mechanism that rotates the pad holder in a direction that moves the separation pad away from the paper feed roller against the urging force of the tension spring.

[0008] In the present invention, the separation pad support mechanism may include a rotating member rotatably supported about an axis parallel to the rotation axis of the pad holder, and to which one end of the tension spring is connected; a link bar connecting the rotating member and the rotation axis of the pad holder; and a drive member for rotating the rotating member, wherein during normal paper feeding, the rotating member is pulled by the tension spring and rotates in one direction, rotating the pad holder upward via the link bar and pressing the separation pad against the paper feed roller, and when a paper jam occurs in the separation nip, the drive member rotates the rotating member in the opposite direction against the biasing force of the tension spring and rotating the pad holder downward via the link bar to separate the separation pad from the paper feed roller.

[0009] In the present invention, the device may further include a transport roller arranged downstream of the separation nip in the paper transport direction, and a transport gear that can rotate integrally with the transport roller and can rotate relative to the transport roller within a certain angle, and the drive member may include a drive gear that meshes with the transport gear.

[0010] In the present invention, the separation pad support mechanism may further include a ratchet mechanism that transmits the rotation of the drive gear to the rotating member when the drive gear rotates in one direction, and does not transmit the rotation of the drive gear to the rotating member when the drive gear rotates in the other direction, so that when the transport gear rotates so that the transport roller rotates in the direction in which the paper is transported, the drive gear rotates in the other direction, and the rotation of the drive gear is not transmitted to the rotating member by the ratchet mechanism, and when the transport gear rotates in the opposite direction, the drive gear rotates in the one direction, and the rotation of the drive gear is transmitted to the rotating member by the ratchet mechanism, causing the rotating member to rotate in the opposite direction.

[0011] In the present invention, the transport gear may rotate within the angle in the opposite direction relative to the transport roller.

[0012] In the present invention, the tension spring and the separation pad support mechanism may be disposed outside a paper passing area. [Effects of the Invention]

[0013] According to the present invention, a tension coil spring is used as the biasing member that presses the separation pad against the paper feed roller, so the height of the document transport device can be made lower than when a compression coil spring is used as the biasing member. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing a document transport device according to an embodiment of the present invention; [Figure 2] 1 is a cross-sectional view showing a paper feed unit of a document transport device according to an embodiment of the present invention. [Figure 3] FIG. 2 is a plan view showing an inner frame in the document transport device according to the embodiment of the present invention. [Figure 4] 3 is a rear view of a separation pad support mechanism (holder rotation shaft, rotating member, and driving member) in a document transport device according to an embodiment of the present invention. FIG. [Figure 5] 3 is a cross-sectional view showing a separation pad support mechanism (pad holder, holder rotation shaft) in the document transport device according to one embodiment of the present invention. FIG. [Figure 6] 2 is a perspective view showing a separation pad support mechanism (holder rotation shaft, rotating member, and driving member) in the document transport device according to the embodiment of the present invention. FIG. [Figure 7] 2 is a cross-sectional view showing a separation pad support mechanism (rotating member, driving member) in the document transport device according to the embodiment of the present invention. FIG. [Figure 8] 3 is a cross-sectional view showing a separation pad support mechanism (driving member) in the document transport device according to one embodiment of the present invention. FIG. [Figure 9] 1 is a perspective view showing a separation pad support mechanism (in a state where the ratchet cylinder is separated from the rotating member) in a document transport device according to an embodiment of the present invention. FIG. [Figure 10] 1 is a perspective view showing a separation pad support mechanism (in a state where a ratchet cylinder is engaged with a rotating member) in a document transport device according to an embodiment of the present invention. FIG. [Figure 11] 1 is a rear view of a separation pad support mechanism (when a separation nip is formed) in a document transport device according to an embodiment of the present invention. FIG. [Figure 12] 1 is a rear view of a separation pad support mechanism (when the separation nip is released) in a document transport device according to an embodiment of the present invention. FIG. [Figure 13] FIG. 2 is a side view showing a transport roller in the document transport device according to the embodiment of the present invention. [Figure 14] 2 is a cross-sectional view showing a transport roller in the document transport device according to the embodiment of the present invention. FIG. [Figure 15] 10 is a rear view of the separation pad support mechanism and the conveying gear (when the separation nip is released) in the document conveying device according to the embodiment of the present invention. FIG. [Figure 16] 10 is a rear view of the separation pad support mechanism and the conveying gear (when the separation nip is formed) in the document conveying device according to the embodiment of the present invention. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0015] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A document transport device according to an embodiment of the present invention will now be described with reference to the accompanying drawings.

[0016] First, the overall configuration of the document transport device 1 will be described with reference to Fig. 1. Fig. 1 is a perspective 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, respectively.

[0017] The document transport device 1 includes a transport section 3 through which documents are transported and an image on one side of the document is read, a paper feed tray 5 on which the documents are placed, and a discharge tray 7 on which the documents after the images have been read are stacked. The document transport device 1 is disposed above an image reading device (not shown) that reads the image on the other side of the document using a reading sensor.

[0018] First, the conveying unit 3 will be described with reference to Fig. 2. Fig. 2 is a cross-sectional view showing the conveying unit 3. A paper feed opening 11 and a paper discharge opening 13 are formed on the right side of the conveying unit 3. The paper discharge opening 13 is located below the paper feed opening 11.

[0019] The transport unit 3 has an inner frame 15 and an outer frame 17. A horizontally U-shaped transport path 19 is formed between the two frames 15, 17, running from the paper feed port 11 through a document reading position P toward the document discharge port 13. The direction in which the document is transported along the transport path 19 is referred to as the transport direction X. An opening 21 is formed in the left end of the lower surface of the inner frame 15, extending along the width direction of the document. A transparent glass plate 23 is disposed in the opening 21. A reading sensor 25 is disposed above the glass plate 23. A reading sensor of an image reading device is disposed below the glass plate 23. As the document is transported below the glass plate 23, images on both sides of the document are read by the reading sensor 25 and the reading sensor of the image reading device. A predetermined position below the glass plate 23 is referred to as the reading position P.

[0020] The conveying path 19 is provided with, in order from the upstream side in the conveying direction X, a pickup roller 31, a paper feed roller 33, a separation pad 35, a first conveying roller pair 37, a second conveying roller pair 39, and a discharge roller pair 41.

[0021] The pickup roller 31 is rotatably supported by the outer frame 17 inside the paper feed opening 11. The paper feed roller 33 is rotatably supported by the outer frame 17. The separation pad 35 is supported by the inner frame 15 and is pressed against the paper feed roller 33 as described below. This forms a separation nip N between the paper feed roller 33 and the separation pad 35. The first transport roller pair 37 includes a transport roller 101 and a driven roller. The transport roller 101 is rotatably supported by the inner frame 15, and the driven roller is rotatably supported by the outer frame 17. The second transport roller pair 39 is disposed between the first transport roller pair 37 and the reading position P and includes a drive roller and a driven roller. The drive roller is rotatably supported by the inner frame 15, and the driven roller is rotatably supported by the outer frame 17. The discharge roller pair 41 is disposed inside the discharge opening 13 and includes a transport roller 101 and a driven roller rotatably supported by the inner frame 15. The transport roller 101 also serves as the transport roller 101 of the first transport roller pair 37 .

[0022] Next, the paper feed tray 5 and the discharge tray 7 will be described. As shown in Fig. 1, the paper feed tray 5 is supported below the paper feed opening 11 of the conveying unit 3 in a position inclined downward toward the paper feed opening 11. As shown in Fig. 1, the discharge tray 7 is provided below the paper feed tray 5, below the discharge opening 13 of the conveying unit 3.

[0023] Next, a brief description of the image reading operation will be given. A document placed on the paper feed tray 5 is fed from the paper feed tray 5 to the conveyance path 19 by the pickup roller 31. If the fed document is a single document, the document is conveyed through the separation nip N. If the fed document is a multiple-sheet document, only the topmost document is separated from the other documents at the separation nip N and conveyed from the separation nip N. The document is conveyed to the reading position P by the first conveyance roller pair 37 and the second conveyance roller pair 39. At the reading position P, images on one or both sides of the document are read by the reading sensor 25. The document is then conveyed by the discharge roller pair 41 and discharged to the discharge tray 7 through the discharge port 14.

[0024] As described above, the separation pad 35 is pressed against the paper feed roller 33, forming a separation nip N therebetween. Hereinafter, the separation pad support mechanism 45 that presses the separation pad 35 against the paper feed roller 33 and separates the separation pad 35 from the paper feed roller 33 will be described with reference to Figures 3 and 4. Figure 3 is a plan view showing the inner frame 15 on which the separation pad support mechanism 45 is supported, and Figure 4 is a view of the separation pad support mechanism 45 as seen from the rear side.

[0025] The separation pad support mechanism 45 includes a pad holder 51 that holds the separation pad 35, a holder rotation shaft 53 connected to the pad holder 51, a tension spring 55 that biases the holder rotation shaft 53, a rotating member 57 arranged between the holder rotation shaft 53 and the tension spring 55, and a drive member 59 that rotates the rotating member 57 in only one direction.

[0026] First, the inner frame 15 that supports these components will be described with reference to FIGS. 3 and 5. FIG. 5 is a side view showing the pad holder 51. The inner frame 15 guides the underside of the document transported through the transport path 19 along the transport direction X. As shown in FIG. 3, the inner frame 15 has a horizontal wall 15a and a vertical wall 15b formed below the paper feed roller 33 (see FIG. 3). The horizontal wall 15a is formed between two grooves that are parallel to the transport direction X. A rotation shaft 15c is provided on both side surfaces of the horizontal wall 15a and extends along the width direction that intersects with the transport direction X (see FIG. 5). The vertical wall 15b is located downstream of the horizontal wall 15a in the transport direction X, with a gap between them.

[0027] Furthermore, as shown in FIG. 3, an outer cover plate 16 is fixed to the outside of the rear plate of the inner frame 15 with a predetermined gap therebetween.

[0028] Next, the pad holder 51 will be described with reference to Figures 3 and 5. As shown in Figure 5, the pad holder 51 has a rectangular plate-shaped holding portion 61 on which the separation pad 35 is supported, two legs 63 formed on one short side surface of the holding portion 61, and a hook portion 65 bent downward from the other short side surface of the holding portion 61.

[0029] As shown in Fig. 5, the two legs 63 are rotatably supported on pivots 15c erected on both side surfaces of the horizontal wall 15a of the inner frame 15. The hook portion 65 fits into the gap between the horizontal wall 15a and the vertical wall 15b. The pad holder 51 is rotatable up and down about the pivots 15c between an upper position (see solid lines in Fig. 5) where the hook portion 65 is engaged with the vertical wall 15b, and a lower position (see chain double-dashed lines in Fig. 5) where the holding portion 61 is engaged with the horizontal wall 15a.

[0030] Next, the holder rotation shaft 53 will be described. As shown in FIG. 3, one end (front end) of the holder rotation shaft 53 is connected to one leg 63 of the pad holder 51 by a coupling so as to be rotatable integrally therewith (see also FIG. 5). The other end (rear end) of the holder rotation shaft 53 penetrates the rear plate of the inner frame 15 and protrudes between the rear plate and the outer cover plate 16. An arm portion 71 extending in the radial direction of the holder rotation shaft 53 is formed at the protruding end (see FIGS. 3 and 4). Rotation of the holder rotation shaft 53 causes the pad holder 51 to rotate vertically between an upper position and a lower position. Movement of the holder rotation shaft 53 in the width direction is restricted by the outer cover plate 16.

[0031] Next, a description will be given of the tension spring 55. As shown in Fig. 4, the fixed end of the tension spring 55 is fixed to the outer surface of the rear plate of the inner frame 15, above the holder rotation shaft 53.

[0032] Next, the rotating member 57 will be described with reference to Fig. 4, Fig. 6, Fig. 7, and Fig. 8. Fig. 6 is a perspective view showing the separation pad support mechanism 45 (holder rotation shaft 53, rotating member 57, driving member 59), Fig. 7 is a cross-sectional view showing the separation pad support mechanism 45 (rotating member 57, driving member 59), and Fig. 8 is a cross-sectional view showing the separation pad support mechanism 45 (driving member 59).

[0033] As shown in FIG. 4, the rotating member 57 has a cylindrical portion 81, and a long arm portion 83 and a short arm portion 85 extending radially from the side surface of the cylindrical portion 81. The long arm portion 83 and the short arm portion 85 are arranged at a predetermined interval in the circumferential direction of the cylindrical portion 81. As shown in FIG. 6, ratchet teeth 81a are formed on one end surface of the cylindrical portion 81. The ratchet teeth 81a are inclined counterclockwise when viewed from the rear side. In addition, as shown in FIG. 7, a protrusion 81b is formed on the inner peripheral surface of the cylindrical portion 81 along the circumferential direction. The rotating member 57 is supported by a driving member 59, as described below.

[0034] Next, the drive member 59 will be described with reference to Figures 4 and 6 to 8. The drive member 59 includes a drive shaft 91, a drive gear 93 provided coaxially with the drive shaft 91, and a ratchet cylinder 95 rotatably supported on the drive shaft 91.

[0035] First, the drive shaft 91 will be described. As shown in Fig. 7, a step 91a is formed in the circumferential direction on the outer peripheral surface of one end of the drive shaft 91. As shown in Fig. 4, the drive shaft 91 is disposed downstream of the holder rotation shaft 53 in the conveying direction X (to the left in Fig. 4). Both ends of the drive shaft 91 are rotatably supported by the rear plate of the inner frame 15 and the outer cover plate 16. In detail, as shown in Fig. 7, one end (rear end) of the drive shaft 91 is rotatably inserted into an opening formed in the outer cover plate 16, and the other end (front end) of the drive shaft 91 is rotatably supported in a recess formed in the rear plate.

[0036] Next, the drive gear 93 will be described. The drive gear 93 is fixed to approximately the center of the drive shaft 91. As shown in Fig. 8, a protrusion 93a is formed on the outer surface of the drive gear 93 (the surface facing the outer cover plate 16) along a part of the circumferential direction around the drive shaft 91.

[0037] Next, the ratchet tube 95 will be described. As shown in FIG. 6, ratchet teeth 95a that can mesh with ratchet teeth 81a formed on the cylindrical portion 81 of the rotating member 57 are formed on one end face (rear end face) of the ratchet tube 95. The ratchet teeth 95a are inclined in a clockwise direction when viewed from the rear. Two protrusions 95b that extend in the axial direction of the ratchet tube 95 are formed spaced apart in the circumferential direction on the other end face (front end face) of the ratchet tube 95. Furthermore, as shown in FIG. 6, an inclined surface 95c that is inclined in the axial direction of the ratchet tube 95 is formed between the two protrusions 95b on the other end face (front end face) of the ratchet tube 95. The inclined surface 95c is inclined clockwise when viewed from the rear so as to move away from the ratchet teeth 95a.

[0038] As shown in Figure 7, the ratchet tube 95 is fitted onto the drive shaft 91 between the drive gear 93 and the outer cover plate 16. The ratchet teeth 95a face away from the drive gear 93, and the two protrusions 95b face the drive gear 93. The ratchet tube 95 is movable along the drive shaft 91 and rotatable around the drive shaft 91. When the drive gear 93 rotates in either direction and the protrusion 93a (see Figure 8) of the drive gear 93 comes into contact with and presses the protrusion 95b of the ratchet tube 95, the ratchet tube 95 rotates in the same direction as the drive gear 93.

[0039] As described above, the rotating member 57 is supported by the driving member 59. More specifically, as shown in Figures 6 and 7, the cylindrical portion 81 of the rotating member 57 is fitted onto the drive shaft 91 of the driving member 59. The ratchet teeth 81a of the cylindrical portion 81 face the ratchet teeth 95a of the ratchet tube 95. As shown in Figure 7, the tip surface of the cylindrical portion 81 abuts against the outer cover plate 16, and the protrusion 81b formed on the inner peripheral surface abuts against the step 91a of the drive shaft 91. This allows the rotating member 57 to rotate around the drive shaft 91 but not to move in the axial direction of the drive shaft 91.

[0040] Next, the operation of the drive member 59 to rotate the rotation member 57 in only one direction will be described with reference to Figures 9 and 10. Figures 9 and 10 are perspective views showing the separation pad support mechanism 45 (rotation member 57, drive member 59).

[0041] When the drive shaft 91 is driven with the ratchet teeth 81a of the cylindrical portion 81 of the rotating member 57 and the ratchet teeth 95a of the ratchet tube 95 meshing (see FIG. 6), the drive gear 93 rotates counterclockwise (as viewed from the rear) (see arrow A1 in FIG. 6), and the protrusion 93a of the drive gear 93 comes into contact with the protrusion 95b of the ratchet tube 95 (see FIG. 8) and pushes the protrusion 95b counterclockwise. This causes the ratchet tube 95 to rotate counterclockwise (see arrow A2 in FIG. 6).

[0042] As described above, the rotating member 57 is immovable in the axial direction, and therefore, when the ratchet tube 95 rotates counterclockwise (see arrow A2 in FIG. 6), the ratchet teeth 95a of the ratchet tube 95 are guided counterclockwise by the ratchet teeth 81a of the cylindrical portion 81 of the rotating member 57. As a result, the ratchet tube 95 moves in a direction (forward) away from the rotating member 57 while rotating counterclockwise around the drive shaft 91 (see arrow A3 in FIG. 6). As a result, as shown in FIG. 9, the ratchet tube 95 moves away from the cylindrical portion 81 of the rotating member 57, and the rotation of the ratchet tube 95, i.e., the drive shaft 91, is not transmitted to the cylindrical portion 81, i.e., the rotating member 57.

[0043] On the other hand, when the drive shaft 91 is driven and the drive gear 93 rotates clockwise (as viewed from the rear) (see arrow B1 in FIG. 9) while the ratchet tube 95 is spaced apart from the cylindrical portion 81 of the rotating member 57 (see FIG. 9), as shown in FIG. 10, the edge of the protrusion 93a of the drive gear 93 presses against the inclined surface 95c of the ratchet tube 95, and the ratchet tube 95 moves in a direction away from the drive gear 93 (see arrow B2 in FIG. 10) while rotating in the same direction as the drive gear 93 (see arrow B2 in FIG. 10). As a result, the ratchet teeth 95a of the ratchet tube 95 mesh with the ratchet teeth 81a of the cylindrical portion 81 of the rotating member 57. As a result, the rotating member 57 rotates in the same direction as the drive gear 93, i.e., the drive shaft 91, via the ratchet tube 95. In this way, the ratchet teeth 81a on the cylindrical portion 81 of the rotating member 57 and the ratchet teeth 95a on the ratchet tube 95 of the driving member are an example of a ratchet mechanism in the present invention that transmits the rotation of the driving gear 93 in one direction to the rotating member 57, and does not transmit the rotation of the driving gear 93 to the rotating member 57 when the driving gear 93 rotates in the other direction.

[0044] Therefore, when the drive shaft 91 rotates clockwise (as viewed from the rear) (see arrow B1 in FIGS. 9 and 10), the rotation member 57 rotates clockwise via the ratchet tube 95. On the other hand, when the drive shaft 91 rotates counterclockwise (see arrow A1 in FIG. 6), the counterclockwise rotation is not transmitted to the rotation member 57 by the ratchet tube 95. In other words, the rotation member 57 is rotated only clockwise by the drive member 59.

[0045] 4, in the rotating member 57 supported by the drive member 59 in this manner, the arm portion 71 of the holder rotation shaft 53 is connected to the short arm portion 85 via a link bar 89, and the free end of the tension spring 55 is connected to the long arm portion 83. In detail, the long arm portion 83 and the free end of the tension spring 55 are connected to the right of and above the center of the drive shaft 91 of the drive member 59 (the opposite side to the holder rotation shaft 53).

[0046] The operation of forming and releasing the separation nip by the separation pad support mechanism 45 described above will be described with reference to Figures 11 and 12. Figures 11 and 12 are views of the separation pad support mechanism 45 as seen from the rear side.

[0047] First, the operation of forming the separation nip N will be described with reference to FIG. 11. When the separation nip N is formed, the drive gear 93 of the drive member 59 stops rotating. As described above, the rotation member 57 is rotatable about the drive shaft 91 of the drive member 59. Therefore, when the long arm portion 83 is pulled by the tension spring 55 (see arrow F1), the rotation member 57 rotates counterclockwise in FIG. 11 (see arrow A1). The rotation of the rotation member 57 is restricted by the long arm portion 83 abutting against the locking piece 15d formed on the rear side plate of the inner frame 15. When the rotation member 57 rotates in this manner, the arm portion 71 of the holder rotation shaft 53 is pulled leftward via the link bar 89 (see arrow A2), causing the holder rotation shaft 53 to rotate counterclockwise (see arrow A3).

[0048] 5, the pad holder 51 rotates upward, and the separation pad 35 is pressed against the paper feed roller 33 (see FIG. 2). Note that the pad holder 51 does not necessarily have to rotate to the upper position. By pressing the separation pad 35 against the paper feed roller 33 in this manner, a separation nip N is formed.

[0049] To release the separation nip N, as shown in FIG. 12, the drive shaft 91 of the drive member 59 is rotated clockwise by a predetermined angle (see arrow B1). The drive gear 93 rotates clockwise together with the drive shaft 91. As described above, the rotation member 57 is rotated only clockwise by the drive member 59. Therefore, when the drive gear 93 rotates clockwise, the rotation member 57 rotates clockwise via the ratchet tube 95 (see arrow B2). As a result, the tension spring 55 is pulled by the long arm portion 83 (see arrow F2). Furthermore, the short arm portion 85 pushes the arm portion 71 of the holder rotation shaft 53 to the left via the link bar 89 (see arrow B3). As a result, the holder rotation shaft 53 rotates clockwise (see arrow B4).

[0050] 5, the pad holder 51 rotates downward, and the separation pad 35 moves downward away from the paper feed roller 33. At this time, the separation pad 35 does not need to move completely away from the paper feed roller 33; it is sufficient if the nip pressure at the separation nip N is low enough that the document can be pulled out with a light force.

[0051] As is clear from the above description, according to the present invention, the separation nip N can be released (the nip pressure can be reduced) by the separation pad support mechanism 45, so that paper jammed in the separation nip can be removed with little force. Furthermore, the separation pad 35 is pressed against the paper feed roller 33 by the tension spring 55. The tension spring 55 is located on the rear side plate of the inner frame 15, i.e., outside the paper passage area. In other words, unlike when a compression coil spring is used as a biasing member that presses the separation pad 35 against the paper feed roller 33, the tension spring 55 does not need to be located below the separation pad 35. This allows the height of the document transport device 1 to be lower than when a compression coil spring is used as a biasing member. As an example, the height can be reduced by approximately 8% compared to when a compression coil spring is used.

[0052] Next, an example of a mechanism for rotating the drive shaft 91 of the drive member 59 will be described with reference to Figures 3 and 4, 13 and 14. Figure 13 is a perspective view showing the transport roller 101, and Figure 14 is a cross-sectional view showing the transport roller 101.

[0053] In this example, the drive shaft 91 of the drive member 59 is rotated by the transport roller 101 of the first transport roller pair 37 (discharge roller pair 41) (see FIG. 2). As shown in FIG. 3, the transport roller 101 is disposed downstream of the separation pad 35 in the transport direction X. The transport roller 101 protrudes into the transport path 19 through an opening formed in the inner frame 15.

[0054] 3, the rear end of the drive shaft of the transport roller 101 passes through the rear plate of the inner frame 15 and is rotatably supported by the outer cover plate 16. A transport gear 103 is supported on the transport roller 101 between the rear plate of the inner frame 15 and the outer cover plate 16 so as to be rotatable relative to the transport roller 101 but immovable in the axial direction of the transport roller 101. As shown in FIG. 4, the transport gear 103 meshes with the drive gear 93 of the drive member 59 of the separation pad support mechanism 45.

[0055] 13 and 14, two protrusions 103a are formed on the inner surface (rear surface) of the conveying gear 103 at a predetermined interval in the circumferential direction of the conveying roller 101. The conveying gear 103 is engaged with an output gear (not shown) connected to a motor (not shown). When the motor is driven, the conveying gear 103 rotates via the output gear.

[0056] Furthermore, a connecting member 105 is fixed to the transport roller 101, on the inner side (front side) of the transport gear 103. The connecting member 105 is a disk-shaped member, and as shown in FIG. 14 , two protrusions 105a are formed on the outer surface (rear surface) of the transport roller 101 at a predetermined interval in the circumferential direction of the transport roller 101. The two protrusions 103a of the transport gear 103 and the two protrusions 105a of the connecting member 105 overlap with each other in the axial direction of the transport roller 101. Therefore, when the transport gear 103 rotates, the protrusions 103a of the transport gear 103 push the protrusions 105a of the connecting member 105, and the transport roller 101 rotates in the same direction as the transport gear 103.

[0057] On the other hand, the conveying gear 103 is rotatable relative to the conveying roller 101 until the protrusion 103a of the conveying gear 103 separates from one protrusion 105a of the connecting member 105 and abuts against the other protrusion 105a (see arrow R in FIG. 14).

[0058] The formation and release operations of the separation nip N in this example will be described with reference to Figures 11 and 12, as well as Figures 15 and 16. Figures 15 and 16 are views of the separation pad support mechanism 45 as seen from the rear side.

[0059] When the document transport operation is not being performed, the first transport roller pair 37 and the discharge roller pair 41 are not driven, so the transport roller 101 does not rotate, and the transport gear 103 does not rotate either. That is, the drive gear 93 that meshes with the transport gear 103 does not rotate either. In this case, as described with reference to FIG. 11 , the long arm portion 83 of the rotating member 57 is pulled by the tension spring 55, causing the rotating member 57 to rotate counterclockwise in FIG. 11 . Then, the arm portion 71 of the holder rotation shaft 53 is pulled rightward via the link bar 89, causing the holder rotation shaft 53 to rotate counterclockwise. As a result, the pad holder 51 rotates upward, and the separation pad 35 is pressed against the paper feed roller 33, forming the separation nip N.

[0060] Next, a case where a document transport operation is performed will be described with reference to FIG. 15. In this case, the first transport roller pair 37 and the discharge roller pair 41 rotate in the direction in which the document is transported. That is, the motor is driven, and the transport gear 103 rotates clockwise as viewed from the rear side via the output gear (see arrow C1). When the transport gear 103 rotates, the protrusion 103a of the transport gear 103 presses the protrusion 105a of the connecting member 105, causing the connecting member 105 to rotate in the same direction as the transport gear 103. This rotation of the connecting member 105 causes the transport roller 101 to rotate clockwise as viewed from the rear side (see arrow C2 in FIG. 15), transporting the document in the transport direction X.

[0061] In this way, when the conveying gear 103 rotates clockwise, the drive gear 93, which meshes with the conveying gear 103, rotates counterclockwise as viewed from the rear (see arrow C3). As described above, when the drive gear 93 rotates counterclockwise, the ratchet cylinder 95 does not transmit the rotation of the drive gear 93 to the rotating member 57. In other words, the separation nip N remains formed, just as when no document conveying operation is being performed. Therefore, when the document fed by the pickup roller 31 reaches the separation nip N, only the top document in the separation nip N is fed by the feed roller 33. The document is then conveyed along the conveying path 19 by the first conveying roller pair 37.

[0062] Next, a case where a paper jam occurs at the separation nip N will be described with reference to FIG. 16. In this case, the motor is driven to rotate the conveying gear 103 counterclockwise by a predetermined angle via the output gear (see arrow D1). The predetermined angle is the angle at which the protrusion 103a of the conveying gear 103 separates from one protrusion 105a of the connecting member 105 and abuts against the other protrusion 105a (see arrow R in FIG. 14). As described above, in this case, the conveying gear 103 rotates relative to the conveying roller 101, but the conveying roller 101 does not rotate.

[0063] When the conveying gear 103 rotates in this manner, the drive gear 93, which meshes with the conveying gear 103, rotates a predetermined angle in the clockwise direction (see arrow D2). Then, as described above, the clockwise rotation is transmitted to the rotating member 97 via the ratchet tube 95 (see arrow D3). When the rotating member 97 rotates in this manner, the tension spring 55 is pulled by the long arm portion 83 (see arrow F2). Furthermore, the short arm portion 85 pushes the arm portion 71 of the holder rotation shaft 53 to the left via the link bar 89 (see arrow D4). Then, the holder rotation shaft 53 rotates in the clockwise direction (see arrow D5). As a result, the pad holder 51 rotates downward, and the separation pad 35 moves downward away from the paper feed roller 33. Since the separation nip N is thus opened, the jammed document can be easily removed.

[0064] As is clear from the above explanation, the drive member 59 of the separation pad support mechanism 45 can be driven by the motor that rotates the transport roller 101 of the first transport roller pair 37 (discharge roller pair 41), so there is no need to provide a separate drive source for forming and releasing the separation nip N. Furthermore, when releasing the separation nip N, the transport gear 103 rotates in the direction opposite to the rotation direction of the transport roller 101, but this rotation is not transmitted to the transport roller 101. Therefore, the document is not transported in the direction opposite to the transport direction X.

[0065] The drive gear 93 may be driven by a dedicated motor. In this case, when clearing a paper jam, the drive gear 93 is rotated clockwise as viewed from the rear by a predetermined angle. Alternatively, the holder rotation shaft 53 may be rotated by a dedicated motor without using the drive gear 93. In this case, for example, the free end of the tension spring 55 is connected to the arm portion 71 of the holder rotation shaft 53. When forming the separation nip N, the holder rotation shaft 53 is pulled by the tension spring 55 and rotates counterclockwise as viewed from the rear. This causes the pad holder 51 to rotate upward, and the separation pad 35 is pressed against the paper feed roller 33. When clearing a paper jam, the holder rotation shaft 53 is rotated clockwise by the motor. This causes the pad holder 51 to rotate downward, and the separation nip N is opened.

[0066] The above description of the embodiments of the present invention describes preferred embodiments of the document transport device and image forming device according to the present invention, and therefore may include various technically preferable limitations, but the technical scope of the present invention is not limited to these aspects unless there is a specific description that limits the present invention. [Explanation of symbols]

[0067] 1 Document transport device 33 Paper feed roller 35 Separation Pad 45 Separation pad support mechanism 51 Pad holder 55 Extension spring 57 Rotating members 59 Driving member 81 Cylindrical part (ratchet mechanism) 89 Link Bar 93 Drive Gear 95 Ratchet barrel (ratchet mechanism) 101 Transport roller 103 Conveyor gear

Claims

1. A document transport device that separates and feeds paper at a separation nip formed between a paper feed roller and a separation pad, a pad holder that holds the separation pad and is rotatable in the vertical direction around a rotation axis; a tension spring that urges the pad holder upward to press the separation pad against the paper feed roller; a separation pad support mechanism that rotates the pad holder in a direction that separates the separation pad from the paper feed roller against the biasing force of the tension spring.

2. The separation pad support mechanism includes: a rotary member that is supported rotatably about an axis parallel to the rotation axis of the pad holder and to which one end of the tension spring is connected; a link bar connecting the rotary member and the rotary shaft of the pad holder; a drive member that rotates the rotary member, During normal paper feeding, the rotary member is pulled by the tension spring and rotates in one direction, causing the pad holder to rotate upward via the link bar and pressing the separation pad against the paper feed roller. The document transport device of claim 1, characterized in that when a paper jam occurs in the separation nip, the drive member rotates the rotating member in the opposite direction against the biasing force of the tension spring, thereby rotating the pad holder downward via the link bar and separating the separation pad from the paper feed roller.

3. a conveyance roller disposed downstream of the separation nip in the sheet conveyance direction; a conveying gear that is rotatable integrally with the conveying roller and that is rotatable relative to the conveying roller within a certain angle; 3. The document transport device according to claim 2, wherein the driving member includes a driving gear that meshes with the transport gear.

4. The separation pad support mechanism includes: a ratchet mechanism that transmits the rotation of the drive gear to the rotating member when the drive gear rotates in one direction, and does not transmit the rotation of the drive gear to the rotating member when the drive gear rotates in the other direction, The document transport device described in claim 3, characterized in that when the transport gear rotates so that the transport roller rotates in the direction in which the paper is transported, the drive gear rotates in the other direction, and the rotation of the drive gear is not transmitted to the rotating member by the ratchet mechanism, and when the transport gear rotates in the opposite direction, the drive gear rotates in the one direction, and the rotation of the drive gear is transmitted to the rotating member by the ratchet mechanism, causing the rotating member to rotate in the opposite direction.

5. 5. The document transport device according to claim 4, wherein the transport gear rotates in the opposite direction to the transport roller within the angle range.

6. 2. The document transport device according to claim 1, wherein the tension spring and the separation pad support mechanism are disposed outside a paper passing area.

Images