JP2019089627A - Image forming apparatus - Google Patents

Abstract

To provide an image forming apparatus capable of avoiding collision between a sheet stacking plate and a pickup roller when a sheet loading plate is unlocked.SOLUTION: The image forming apparatus includes: a sheet storage cassette having a cassette base, a sheet stacking plate, an urging member, and a lock mechanism; and a cassette insertion portion having guide members, an unlock member, and a pickup roller. The guide member has a first tapered surface inclined downward along an insertion direction of the sheet storage cassette, and a second tapered surface provided on the downstream from the first tapered surface and inclined upward along the insertion direction of the sheet storage cassette. The unlock member unlocks the sheet stacking plate having been locked by the lock mechanism, while the lever portion of the sheet storage cassette passes below the second tapered surface before the end portion on the downstream from the sheet stacking plate in the sheet feeding direction reaches a position below the pickup roller.SELECTED DRAWING: Figure 10

Description

  The present invention relates to an image forming apparatus including a sheet storage cassette for storing a sheet-like recording medium such as a sheet, which is used for a copying machine, a printer, a facsimile machine, and a multifunction peripheral thereof.

  2. Description of the Related Art Conventionally, an image forming apparatus is widely used, in which a sheet feeding cassette in which a plurality of sheets of paper (sheets) are stored is provided at a bottom portion of the apparatus main body so as to be extractable. In this image forming apparatus, the sheets stored in the sheet feeding cassette are sequentially fed one by one by a separation feeding unit configured by a pickup roller and the like disposed above the sheet feeding cassette, and the image forming unit is And an image is formed on the sheet by being conveyed to the fixing unit.

  Further, there is a sheet feeding cassette provided with a sheet stacking plate on which a sheet is placed on the upper surface. The sheet stacking plate has an upstream end supported in the bottom surface of the cassette main body in the sheet feeding direction, and is rotatable with an end on the downstream side in the sheet feeding direction as a pivoting end. Then, in order to smoothly insert the sheet feeding cassette into the main body of the image forming apparatus, as disclosed in Patent Document 1, locking is performed in a state where the sheet stacking plate is pressed down by a lock mechanism provided on the bottom surface of the sheet feeding cassette. Was done.

  However, the user may insert the sheet feeding cassette into the image forming apparatus main body in a state where the rotating end of the sheet stacking plate is lifted without locking the sheet stacking plate. In this case, there is a possibility that the rotating end of the sheet stacking plate may collide with the cassette insertion slot on the image forming apparatus main body side to damage the sheet stacking plate or the cassette insertion slot.

  Therefore, Patent Document 2 discloses a sheet feeding device in which an entrance side cam surface is provided in a cassette insertion slot on the image forming apparatus main body side. According to this configuration, when the sheet stacking plate of the sheet feeding cassette is not locked but inserted into the cassette insertion slot, the lock lever provided at the rotational end of the sheet stacking plate is along the inlet cam surface of the guide plate Push down the paper loading plate.

JP 2004-323125 A JP, 2009-23754, A

  As described above, in the configuration provided with the lock mechanism for locking the sheet stacking plate of the sheet feed cassette, the release mechanism is provided for automatically releasing the lock when the sheet feed cassette is inserted into the image forming apparatus main body. However, if the lock of the sheet stacking plate is released immediately before the insertion of the sheet feeding cassette into the insertion position (sheet feeding position) is completed, the sheet stacking plate acts as a pickup roller by a spring urging the sheet stacking plate upward. collide. When the sheets are fully loaded on the sheet stacking plate, the biasing force of the spring is alleviated by the weight of the sheets, but when the number of sheets on the sheet stacking plate is small, the impact on the pickup roller becomes large, and the conveyance performance of the pickup roller is achieved. There was a risk of affecting.

  Further, in the configuration of Patent Document 2, a collision between the sheet stacking plate and the cassette insertion portion at the time of insertion and withdrawal of the sheet feeding cassette into the image forming apparatus main body can be avoided, but the sheet at the time of insertion of the sheet feeding cassette The timing of unlocking the loading plate was not considered.

  SUMMARY OF THE INVENTION An object of the present invention is to provide an image forming apparatus capable of avoiding a collision between a sheet stacking plate and a pickup roller when the locking of the sheet stacking plate is released.

  In order to achieve the above object, a first configuration of the present invention is an image forming apparatus provided with a sheet storage cassette and a cassette insertion unit. The sheet storage cassette has a cassette base, a sheet stacking plate, a biasing member, and a lock mechanism, and is inserted into the apparatus main body along the sheet feeding direction. The cassette base can be inserted into and withdrawn from the apparatus body to store the sheet. The sheet stacking plate has a bottom surface of the cassette base rotatably supported at an end on the upstream side in the sheet feeding direction, and the sheet is placed on the upper surface. The biasing member biases the downstream end of the sheet stacking plate in the sheet feeding direction upward. The locking mechanism locks the sheet stacking plate in a collapsed state along the bottom surface of the cassette base. The cassette insertion portion has a guide member, a lock release member, and a pickup roller, and is provided on the apparatus main body side. The guide member swings the end of the sheet stacking plate on the downstream side in the sheet feeding direction up and down as the sheet storage cassette is inserted or pulled out. The lock release member releases the locked state of the sheet stacking plate by the lock mechanism along with the insertion operation of the sheet storage cassette. When the sheet storage cassette is inserted to a predetermined position, the pickup roller abuts on the downstream end of the sheet stacking plate in the sheet feeding direction, or the sheet placed on the upper surface of the sheet stacking plate, and feeds the sheet Send to The sheet stacking plate has a lever portion that protrudes from the side edge orthogonal to the insertion direction of the sheet storage cassette to the outside of the cassette base. The guide member is provided on the downstream side of the first tapered surface with respect to the insertion direction of the sheet storage cassette, and the first tapered surface that inclines downward along the insertion direction of the sheet storage cassette, along the insertion direction of the sheet storage cassette And a second tapered surface inclined upward. When the lever portion contacts the first tapered surface and the second tapered surface as the sheet storage cassette is inserted or pulled out, the downstream end of the sheet stacking plate in the sheet feeding direction swings. The lock releasing member is a sheet stacking plate by the locking mechanism while the lever portion passes below the second tapered surface before the downstream end of the sheet stacking direction of the sheet stacking plate reaches the lower side of the pickup roller. Release the lock state of.

  According to the first configuration of the present invention, the locked state of the sheet stacking plate is released by the unlocking member, and the lever portion contacts the second tapered surface when the sheet stacking plate is lifted by the biasing force of the biasing member. Therefore, it is possible to prevent the sheet stacking plate from rising at once to the highest position. Therefore, the collision between the sheet stacking plate and the pickup roller can be effectively suppressed.

Side surface sectional view showing an internal structure of an image forming apparatus 100 according to an embodiment of the present invention A perspective view showing a state in which the sheet feeding cassette 10 is pulled out of the main body of the image forming apparatus 100 Side cross-sectional view of the sheet feeding cassette 10 cut along the sheet feeding direction Side view of the lock mechanism 55 viewed from the downstream side in the sheet feeding direction A side view of a state in which the engaged portion 57 of the sheet stacking plate 28 abuts on the hook portion 63 of the lock mechanism 55 as viewed from the downstream side in the sheet feeding direction Side view of the sheet stacking plate 28 locked along the bottom surface of the cassette base 25 using the locking mechanism 55 as viewed from the downstream side in the sheet feeding direction A perspective view of the cassette storage unit 65 of the image forming apparatus 100 main body A plan sectional view as viewed from above the state immediately before the sheet feeding cassette 10 is inserted to the insertion position of the cassette insertion portion 65 An enlarged view showing a configuration of the guide frame 70a side in FIG. 8 The partial perspective view which looked at the cassette insertion port 65a vicinity of the guide frame 70a from inner side Partial perspective view of the right side of the sheet feeding cassette 10 when the sheet feeding cassette 10 is inserted into the cassette insertion portion 65 without locking the sheet stacking plate 28

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a side sectional view showing an internal structure of an image forming apparatus 100 in which a sheet feeding cassette 10 according to an embodiment of the present invention is mounted. In the image forming apparatus (for example, a monochrome printer) 100, an image forming portion P for forming a monochrome image by each process of charging, exposure, development and transfer is disposed. In the image forming portion P, the charging unit 4, the exposure unit (laser scanning unit etc.) 7, the developing unit 8, the transfer roller 14, the cleaning device along the rotational direction of the photosensitive drum 5 (clockwise direction in FIG. 1). 19, and a charge removing device (not shown).

  When the image forming operation is performed, the photosensitive drum 5 rotating in the clockwise direction is uniformly charged by the charging unit 4, and electrostatic latent latent on the photosensitive drum 5 is generated by the laser beam from the exposure unit 7 based on the document image data. An image is formed, and a developer (hereinafter referred to as toner) is attached to the electrostatic latent image by the developing unit 8 to form a toner image.

  The supply of toner to the developing unit 8 is performed from the toner container 9. The image data is transmitted from a personal computer (not shown) or the like. Further, a charge removing device (not shown) for removing residual charge on the surface of the photosensitive drum 5 is provided on the downstream side of the cleaning device 19.

  The sheet is conveyed from the sheet feeding cassette 10 or the manual sheet feeding device 11 through the sheet conveyance path 12 and the registration roller pair 13 toward the photosensitive drum 5 on which the toner image is formed as described above, and the transfer roller 14 is The toner image formed on the surface of the photosensitive drum 5 is transferred onto the sheet by (image transfer portion). The sheet on which the toner image has been transferred is separated from the photosensitive drum 5 and conveyed to the fixing device 15 to fix the toner image. The sheet having passed through the fixing device 15 is conveyed to the upper portion of the apparatus by the sheet conveyance path 16, and is discharged to the discharge tray 18 by the discharge roller pair 17 when forming an image on only one side of the sheet (in single-sided printing).

  On the other hand, in the case of forming an image on both sides of a sheet (during double-sided printing), the transport direction is reversed after the rear end of the sheet passes through the branch portion 20 of the sheet transport path 16. As a result, the sheet is distributed to the reverse conveyance path 21 branched from the branch unit 20, and is re-conveyed to the registration roller pair 13 in a state where the image surface is reversed. Then, the next toner image formed on the photosensitive drum 5 is transferred by the transfer roller 14 to the surface of the sheet on which the image is not formed. The sheet on which the toner image has been transferred is conveyed to the fixing device 15 and the toner image is fixed, and then the sheet is discharged to the discharge tray 18 by the discharge roller pair 17.

  Next, the configuration of the sheet feeding cassette 10 will be described. FIG. 2 is a perspective view showing a state in which the sheet feeding cassette 10 is pulled out of the main body of the image forming apparatus 100. FIG. 3 is a side sectional view of the sheet feeding cassette 10 cut along the sheet feeding direction. In FIG. 2, the insertion direction of the sheet feeding cassette 10 with respect to the main body of the image forming apparatus 100 is indicated by arrow A, the pulling out direction is indicated by arrow A ′, and the sheet feeding direction of the sheet feeding cassette 10 is indicated by arrow B.

  The cassette base 25 constitutes a housing (casing) of the sheet feeding cassette 10, and has a tray shape in which sidewalls 25a to 25d are formed on four sides of a rectangular bottom surface. A cassette cover 33 is attached to the side wall 25 a on the downstream side with respect to the insertion direction of the sheet feeding cassette 10. The front surface side (the rear right side in FIG. 2) of the cassette cover 33 is exposed to the outside to form a part of the exterior surface of the main body of the image forming apparatus 100 (see FIG. 1).

  The sheet stacking plate 28 on which the sheets are stacked has a cassette base on the downstream side (right side in FIG. 3) of the sheet feeding direction upstream side (right side in FIG. 2) with the swing shaft 28a as the fulcrum It is provided to be able to move up and down with respect to the bottom surface of 25. Further, the end (rotational end) on the downstream side of the sheet stacking plate 28 in the sheet feeding direction is urged upward by the push-up spring 50. As shown in FIG. 3, when the sheet feeding cassette 10 is inserted into the main body of the image forming apparatus 100, the downstream end of the sheet bundle stacked on the sheet stacking plate 28 is pressed by the pickup roller 51. Note that FIG. 3 shows a state in which the sheet bundle is not stacked, and the downstream end of the sheet stacking plate 28 in the sheet feeding direction is in contact with the pickup roller 51.

  Further, on both sides in the width direction of the sheet stacking plate 28, a pair of width alignment cursors 37 a and 37 b for positioning in the width direction of the sheets stacked on the sheet stacking plate 28 are along the guide grooves formed in the cassette base 25. They are provided so as to be reciprocally movable in the sheet width direction (direction orthogonal to the arrow B direction in FIG. 2).

  Further, since the sheet is sent in the direction of arrow B toward the sheet conveyance path 12 (see FIG. 1), the rear end cursor 31 for aligning the rear end of the sheet is fed along the guide groove formed in the cassette base 25. It is provided so as to be reciprocally movable in parallel with the paper direction (the arrow B direction in the figure). The sheet is stored at a predetermined position in the sheet feeding cassette 10 by moving the width alignment cursors 37 a and 37 b and the rear end cursor 31 in accordance with the size of the stacked sheets.

  A guide rail 40 is attached to the outside of the side walls 25b and 25c parallel to the insertion or withdrawal direction (arrow AA 'direction) of the sheet cassette 10. The cassette insertion portion 65 (see FIG. 7) on the main body side of the image forming apparatus 100 is provided with a rail support portion (not shown) for slidably supporting the guide rail 40, and the guide rail 40 is used as a rail support portion. By sliding along the sheet feed cassette 10, the sheet feed cassette 10 can be inserted into and withdrawn from the main body of the image forming apparatus 100.

  A retard roller 53 b is disposed in the vicinity of the downstream side of the rotational end of the sheet stacking plate 28 with respect to the sheet feeding direction. As shown in FIG. 3, when the sheet feeding cassette 10 is inserted into the main body of the image forming apparatus 100, the retard roller 53b abuts against the feed roller 53a provided on the main body side of the image forming apparatus 100. The feed roller 53 a and the retard roller 53 b constitute a sheet feed roller pair 53 that separates and conveys a plurality of sheets sent out by the pickup roller 51 one by one.

  Inside the bottom surface of the cassette base 25, there is provided a lock mechanism 55 which locks the sheet stacking plate 28 in a state of being laid down along the bottom surface of the cassette base 25.

  FIG. 4 is a view of the lock mechanism 55 as viewed from the downstream side (right side in FIG. 3) in the sheet feeding direction. The lock mechanism 55 has an arm member 60, a biasing spring 61 externally fitted to the arm member 60, and a hook portion 63 fixed to the arm member 60. The arm member 60 is a rod-like member supported so as to be reciprocally movable along the bottom surface of the cassette base 25 in the direction (the CC ′ direction in FIG. 4) orthogonal to the sheet feeding direction. The tip end portion 60 a of the arm member 60 penetrates the side wall 25 b of the cassette base 25 and protrudes to the outside.

  One end portion of the biasing spring 61 is fixed to the spring receiving portion 25 e of the cassette base 25, and the other end portion of the biasing spring 61 is fixed to the spring locking portion 60 b of the arm member 60. Thus, the arm member 60 is urged in the projecting direction (the direction of the arrow C) of the tip portion 60a.

  The hook portion 63 protrudes upward from a position facing the engaged portion 57 of the sheet stacking plate 28. The hook portion 63 is formed with an inclined portion 63 a at a portion in contact with the engaged portion 57 when the sheet stacking plate 28 is pivoted downward. The inclined portion 63 a is inclined downward in the projecting direction (arrow C direction) of the distal end portion 60 a of the arm member 60.

  FIG. 5 is a side view of a state in which the engaged portion 57 of the sheet stacking plate 28 abuts on the hook portion 63 of the lock mechanism 55 as viewed from the downstream side in the sheet feeding direction. When the rotating end of the sheet stacking plate 28 is pushed downward, an engaged portion 57 having an L-shaped cross section formed on the sheet stacking plate 28 is formed on the inclined surface 63 a of the hook portion 63 as shown in FIG. Abut.

  When the sheet stacking plate 28 is further pressed down from the state of FIG. 5, the inclined surface 63a is pressed by the engaged portion 57, whereby a component of force in the arrow C 'direction acts on the hook portion 63. As a result, the arm member 60 moves in the direction of the arrow C ′ against the biasing force of the biasing spring 61. That is, the engaged portion 57 moves downward while moving the arm member 60 (hook portion 63) in the direction of the arrow C '.

  FIG. 6 is a side view of the sheet stacking plate 28 locked along the bottom surface of the cassette base 25 using the lock mechanism 55 as viewed from the downstream side in the sheet feeding direction. When pressed by the engaged portion 57 and the arm member 60 moves in the direction of the arrow C ′, the engaged portion 57 drops out of the inclined surface 63 a of the hook portion 63. As a result, since the pressing force acting from the engaged portion 57 to the hook portion 63 does not act, the arm member 60 is moved in the arrow C direction by the restoring force of the biasing spring 61 as shown in FIG. The hook portion 63 engages with the engaged portion 57.

  FIG. 7 is a perspective view of the cassette insertion portion 65 of the image forming apparatus 100 main body. As shown in FIG. 7, the cassette insertion portion 65 is formed in the shape of a rectangular frame which opens downward, and a cassette insertion port 65a into which the sheet feeding cassette 10 is inserted is formed at one end. The cassette insertion portion 65 has left and right guide frames 70a and 70b as viewed from the cassette insertion opening 65a, and a top plate frame 70c connecting upper surfaces of the guide frames 70a and 70b.

  A guide member 71 is provided on the inner surface of the guide frames 70a and 70b on the cassette insertion port 65a side. In FIG. 7, only the guide member 71 on the guide frame 70a side is shown. In the guide frame 70a, a lock release member 73 is provided on the downstream side of the guide member 71 in the insertion direction of the sheet feeding cassette 10.

  FIG. 8 is a plan sectional view as viewed from above the state immediately before the sheet feeding cassette 10 is inserted to the insertion position of the cassette insertion portion 65, and FIG. 9 is the guide frame 70a side in FIG. FIG. 6 is an enlarged view showing the configuration of FIG. FIG. 10 is a partial perspective view of the vicinity of the cassette insertion port 65a of the guide frame 70a as viewed from the inside. Hereinafter, the collision avoidance mechanism and the lock release mechanism of the sheet stacking plate 28 when the sheet feeding cassette 10 is inserted will be described.

  As shown in FIG. 9, the swing shaft 28a (see FIG. 3) is supported at the left and right side edges of the sheet stacking plate 28 orthogonal to the insertion direction of the sheet feeding cassette 10 when the sheet feeding cassette 10 is inserted. A lever portion 80 (only one of which is shown in FIG. 9) is provided to push downward the sheet stacking plate 28 which is swung as a mechanism. The lever portion 80 protrudes through the guide holes (not shown) formed in the side walls 25 a and 25 b of the cassette base 25 to the outside of the cassette base 25.

  As shown in FIG. 10, in the guide member 71, a first tapered surface 71a and a second tapered surface 71b are formed in this order from the cassette insertion port 65 side toward the insertion direction (arrow A direction). The first tapered surface 71 a is an inclined surface which inclines downward from the cassette insertion port 65 toward the insertion direction. The second tapered surface 71 b is an inclined surface that inclines upward from the cassette insertion port 65 toward the insertion direction. A flat portion 71c is formed between the first tapered surface 71a and the second tapered surface 71b. The first tapered surface 71 a and the second tapered surface 71 b are formed to a position higher than the upper limit position of the lever portion 80.

  The lock release member 73 is provided on the downstream side of the guide member 71 in the insertion direction (arrow A direction). The unlocking member 73 has an unlocking surface 73a that inclines inward in the insertion direction (arrow A direction).

  Next, the lifting and lowering operation of the sheet stacking plate 28 accompanying the insertion of the sheet feeding cassette 10 into the cassette insertion portion 65 will be described in detail. First, the case where the sheet feeding cassette 10 is inserted into the cassette insertion portion 65 in a state where the sheet stacking plate 28 is not locked will be described. In this case, the sheet stacking plate 28 is rotated to the uppermost position by the push-up spring 50, and the lever portions 80 provided on the left and right of the rotating end of the sheet stacking plate 28 are also raised to the upper limit.

  When the sheet feeding cassette 10 is inserted from the cassette insertion port 65 in this state, the lever portion 80 contacts the upper side of the first tapered surface 71a of the guide member 71 as shown in FIG. When the sheet feeding cassette 10 is further pushed in the insertion direction, the lever portion 80 moves in the insertion direction together with the sheet feeding cassette 10 while being pushed downward along the first tapered surface 71 a. As a result, the sheet stacking plate 28 rotates downward while compressing the push-up spring 50. Then, when the lever portion 80 reaches the lower end portion of the first tapered surface 71a, that is, the flat portion 71c, the sheet stacking plate 28 is locked by the lock mechanism 55 in a state of being inclined along the bottom surface of the cassette base 25.

  When the sheet feeding cassette 10 is further pushed in the insertion direction, the lever portion 80 passes through the flat portion 71 c and moves to a position overlapping the second tapered surface 71 b. At this time, since the sheet stacking plate 28 is locked by the lock mechanism 55, the lever portion 80 does not rise from the height of the flat portion 71c.

  Thereafter, as shown in FIG. 9, when the leading end 60a of the arm member 60 reaches the unlocking surface 73a of the unlocking member 73, the leading end 60a rides on the unlocking surface 73a and is inside (direction of arrow C 'in FIG. 4). And the engagement between the hook portion 63 and the engaged portion 57 is released. As a result, the sheet stacking plate 28 is vigorously raised by the biasing force of the push-up spring 50.

  Further, when the engagement between the hook portion 63 and the engaged portion 57 is released, the lever portion 80 passes below the second tapered surface 71 b of the guide member 71. Thus, the lever portion 80 is pressed against the second tapered surface 71b by the elevation of the sheet stacking plate 28, and the lever portion 80 gradually rises along the inclination of the second tapered surface 71b as the sheet feeding cassette 10 is inserted. Do. Then, when the sheet feeding cassette 10 is inserted to the insertion position, the end on the downstream side in the sheet feeding direction of the sheet stacking plate 28 contacts the pickup roller 51. When the sheet is placed on the upper surface of the sheet stacking plate 28, the upper surface of the sheet contacts the pickup roller 51.

  Next, the case where the sheet feeding cassette 10 is inserted into the cassette insertion portion 65 in a state where the sheet stacking plate 28 is locked will be described. In this case, since the sheet stacking plate 28 is locked by the lock mechanism 55, the lever portion 80 passes through the flat portion 71c without contacting the first tapered surface 71a. Then, when the tip end portion 60 a of the arm member 60 reaches the lock release surface 73 a of the lock release member 73, the engagement between the hook portion 63 and the engaged portion 57 is released. The subsequent lifting operation of the sheet stacking plate 28 is as described above.

  When pulling out the sheet feeding cassette 10 from the cassette insertion portion 65, the lever portion 80 moves in the pulling direction along with the sheet feeding cassette 10 while being pushed downward along the second tapered surface 71b. As a result, the sheet stacking plate 28 rotates downward while compressing the push-up spring 50. When the lever portion 80 reaches the lower end portion of the second tapered surface 71b, that is, the flat portion 71c, the sheet stacking plate 28 is locked by the lock mechanism 55 in a state of being laid down along the bottom of the cassette base 25. Then, the sheet cassette 10 is pulled out from the cassette insertion port 65 in a state where the sheet stacking plate 28 is locked.

  In the present embodiment, the timing at which the engagement between the hook portion 63 and the engaged portion 57 is released by the contact between the lock release surface 73a and the tip end portion 60a of the arm member 60 is downstream of the sheet stacking plate 28 in the sheet feeding direction. It is set before the end on the side (rotational end) reaches the pickup roller 51. Specifically, the lock of the sheet stacking plate 28 is performed while the lever portion 80 passes below the second tapered surface 71 b of the guide member 71 before the rotational end of the sheet stacking plate 28 reaches the pickup roller 51. Release

  According to the above configuration, when the sheet loading plate 28 is lifted by the biasing force of the push-up spring 50, the lever portion 80 contacts the second tapered surface 71b, and therefore, the sheet loading plate 28 is rapidly raised to the uppermost position. It can prevent. Then, the lever portion 80 moves along the second tapered surface 71 b along with the insertion operation of the sheet feeding cassette 10, whereby the sheet loading plate 28 gradually rises to a position where it contacts the pickup roller 51. Therefore, the collision between the sheet loading plate 28 and the pickup roller 51 when the sheet loading plate 28 is released can be effectively suppressed.

  Further, the first tapered surface 71 a and the second tapered surface 71 b formed on the guide member 71 are formed to a position higher than the upper limit position of the lever portion 80. Thereby, when the sheet feeding cassette 10 is inserted into the cassette insertion portion 65 without locking the sheet stacking plate 28, the lever portion 80 is pushed downward along the first tapered surface 71a and the sheet stacking plate 28 is locked. Be done. Further, when pulling out the sheet feeding cassette 10, the lever portion 80 is pushed downward along the second tapered surface 71b, and the sheet stacking plate 28 is locked. Therefore, damage to the sheet stacking plate 28 due to a collision between the sheet stacking plate 28 and the cassette insertion opening 65a can be reliably prevented.

  Others The present invention is not limited to the above embodiment, and various modifications can be made without departing from the scope of the present invention. For example, the present invention is not limited to a monochrome printer as shown in FIG. 1 as long as it is an image forming apparatus in which a sheet feeding cassette which can be pulled out in a direction parallel to the sheet feeding direction is attached Of course, the present invention can also be applied to other types of image forming apparatuses such as monochrome and color copiers, digital multi-functional peripherals, or facsimiles.

  The present invention is applicable to an image forming apparatus provided with a sheet storage cassette which can be inserted into and withdrawn from the image forming apparatus main body. By using the present invention, an image forming apparatus can be provided with a simple configuration.

DESCRIPTION OF REFERENCE NUMERALS 10 paper cassette 25 cassette base 25a to 25d side wall 28 paper loading plate 50 push-up spring 55 lock mechanism 60 arm member 61 biasing spring 63 hook portion 65 cassette insertion portion 70a, 70b guide frame 71 guide member 71a first tapered surface 71b 2 Tapered surface 73 Lock release member 73 a Lock release surface 80 Lever portion 100 Image forming apparatus

Claims (4)

A cassette base that can be inserted into and withdrawn from the apparatus body and that accommodates a sheet;
A sheet stacking plate on which an end portion on the upstream side in the sheet feeding direction is rotatably supported by the bottom surface of the cassette base, and a sheet is mounted on the upper surface thereof;
An urging member for urging the end of the sheet stacking plate on the downstream side in the sheet feeding direction upward;
A lock mechanism which locks the sheet stacking plate in a state of being laid down along the bottom surface of the cassette base;
A sheet storage cassette inserted in the sheet feeding direction with respect to the apparatus main body;
A guide member that vertically swings an end of the sheet stacking plate on the downstream side in the sheet feeding direction with the insertion or withdrawal operation of the sheet storage cassette;
A lock release member that releases the locked state of the sheet stacking plate by the lock mechanism in accordance with the insertion operation of the sheet storage cassette;
When the sheet storage cassette is inserted to a predetermined position, the sheet storage plate abuts on the downstream end of the sheet stacking plate in the sheet feeding direction, or the sheet placed on the upper surface of the sheet stacking plate, Pickup roller to send out,
A cassette insertion unit provided on the apparatus body side,
In an image forming apparatus provided with
The sheet stacking plate has a lever portion that protrudes to the outside of the cassette base from a side edge orthogonal to the insertion direction of the sheet storage cassette,
The guide member is provided on a downstream side of the first tapered surface with respect to the insertion direction of the sheet storage cassette, and a first tapered surface that inclines downward along the insertion direction of the sheet storage cassette, and the sheet storage cassette And a second tapered surface inclined upward along the insertion direction of
When the lever portion contacts the first tapered surface and the second tapered surface as the sheet storage cassette is inserted or pulled out, the downstream end of the sheet stacking plate in the sheet feeding direction swings.
The lock release member is disposed before the end portion of the sheet stacking plate on the downstream side in the sheet feeding direction of the sheet stacking plate reaches the lower side of the pickup roller and the lever portion passes the lower side of the second tapered surface. An image forming apparatus characterized by releasing a locked state of the sheet stacking plate by a lock mechanism. When the locked state of the sheet stacking plate is released by the unlocking member and the sheet stacking plate is lifted and the lever portion contacts the second tapered surface, the upper surface of the sheet stacking plate and the pickup roller Facing each other at a predetermined interval,
By inserting the sheet storage cassette to the predetermined position, the lever portion moves upward along the second tapered surface, and the downstream end of the sheet stacking plate in the sheet feeding direction or the sheet The image forming apparatus according to claim 1, wherein the sheet placed on the upper surface of the stacking plate is in contact with the pickup roller.   The image forming apparatus according to claim 1, wherein the first tapered surface and the second tapered surface are formed to a position higher than the upper limit position of the lever portion.   The guide member has a flat portion between the first tapered surface and the second tapered surface, and the sheet stacking plate is locked by the lock mechanism when the lever portion passes the flat portion. The image forming apparatus according to any one of claims 1 to 3, characterized in that: