Image forming apparatus

Abstract

To provide an image forming apparatus with sheet loading means and a metal tray grounded in an inexpensive and lightweight configuration.SOLUTION: A color laser printer A includes a grounded storage section 30, a feeder cassette 100 that is stored in the storage section in a drawable manner and can store sheets S, an image forming section 90 that forms images on the sheets, and a feed roller 14 that feeds the sheets from the feeder cassette to the image forming section. The feeder cassette includes a first tray 50, a metal intermediate plate 51 that is arranged to be able to rise and fall in the first tray and on which the leading end portions of sheets fed by the feeder roller in a feeding direction FD are loaded, a metal second tray 60 that is connected to the first tray 50 and on which the trailing end portions of sheets in the feeding direction are loaded, and an earthing arrangement 550 that grounds the intermediate plate and the second tray when the feeder cassette is stored in the storage section.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to an image forming apparatus having a sheet tray.

Background Art

[0002] In image forming apparatuses employing electrophotographic methods, electrostatic recording methods, inkjet methods, etc., such as copiers, printers, and facsimiles, paper is widely used as an image transfer medium. Image forming apparatuses that can handle not only general office standard paper such as A4 size but also long paper are widely known. As a means for storing long paper, as described in Patent Document 1, a sheet tray made of metal that can be extended or connected has been proposed in order to increase the rigidity of the sheet tray.

[0003] On the other hand, the sheet tray is likely to be triboelectrically charged during feeding, and sometimes the discharge of the charged electric charge becomes a source of radio wave noise and affects the control means. In addition, the electrostatic force due to the charged electric charge may cause the sheets to adsorb to each other, and when a plurality of adsorbed sheets are fed, jams (such as paper jams) may occur. To prevent these, it is known to electrically ground the sheet tray.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, conventionally, an image forming apparatus having a feeding cassette that adds a metal tray to accommodate long sheets has provided a metal bottom plate that bridges the side frames of the image forming apparatus main body, and has made an earth connection by bringing the metal tray into contact with the metal bottom plate. Therefore, the conventional image forming apparatus has suffered from problems of cost increase and weight increase due to the addition of the metal bottom plate to the image forming apparatus main body. Accordingly, the present invention provides an image forming apparatus capable of grounding a sheet loading means and a metallic tray with an inexpensive and lightweight configuration.

Means for Solving the Problems

[0006] An image forming apparatus according to an embodiment of the present invention includes: a storage means in a grounded state; a sheet tray that is removably stored in the storage means and is capable of storing sheets; an image forming unit that forms an image on the sheet; a sheet feeding means that feeds the sheet from the sheet tray to the image forming unit; and the sheet tray includes: a first tray; a metallic sheet loading means that is disposed to be movable up and down on the first tray and on which a front end side portion in a feeding direction of the sheet fed by the sheet feeding means is loaded; a metallic second tray that is connected to the first tray and on which a rear end side portion of the sheet in the feeding direction is loaded; a grounding means that grounds the sheet loading means and the second tray when the sheet tray is stored in the storage means; and is characterized by having the above.

Advantages of the Invention

[0007] According to the present invention, it is possible to ground a sheet loading means and a metallic tray with an inexpensive and lightweight configuration.

Brief Description of the Drawings

[0008]

Figure 1

Figure 2

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Figure 6

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Figure 8

Figure 9

Figure 10

Best Mode for Carrying Out the Invention

[0009] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

Examples

[0010] [Overall Configuration of Image Forming Apparatus] Referring to FIG. 1, a color laser printer A as an example of an image forming apparatus according to the first embodiment will be described. FIG. 1 is a cross-sectional view of the color laser printer A. The color laser printer A is an electrophotographic color image forming apparatus, but the image forming apparatus may be an electrophotographic copier or facsimile, or may be a copier, printer, or facsimile using an electrostatic recording method or an inkjet method. The color laser printer A includes an image forming unit 90 that forms an image on a recording medium, and a feeding unit 92 that is provided below the image forming unit 90 and feeds the recording medium to the image forming unit 90. The recording medium includes not only paper such as plain paper and thick paper, but also special paper such as coated paper, materials made of any material such as plastic films for overhead projectors and cloth, and those having any shape such as envelopes and index sheets. In the following description, the recording medium is referred to as a sheet.

[0011] The feeding unit 92 includes a feeding cassette (sheet tray) 100 that can store the sheet S, and a feeding roller (sheet feeding means) 14 that feeds the sheet S toward the registration roller unit 16 from the feeding cassette 100 in the feeding direction FD. The feeding cassette 100 is detachably mounted on a storage unit (storage means) 30 provided at the lower part of the color laser printer A. The feeding cassette 100 is stored in the storage unit 30 so as to be pullable out, and the user can pull out the feeding cassette 100 from the storage unit 30 to replenish the sheet S in the feeding cassette 100 or replace the sheet S. The feeding roller 14 feeds the sheet S from the feeding cassette 100 toward the registration roller unit 16 in the feeding direction FD. The registration roller unit 16 corrects the skew of the sheet S and adjusts the conveyance timing of the sheet S.

[0012] The image forming unit 90 is detachably attached with process cartridges 1Y, 1M, 1C, and 1Bk. The process cartridges 1Y, 1M, 1C, and 1Bk rotatably hold photosensitive drums 2Y, 2M, 2C, and 2Bk respectively. Below the process cartridges 1Y, 1M, 1C, and 1Bk, an exposure device 7 is arranged to emit laser light toward the photosensitive drums 2Y, 2M, 2C, and 2Bk according to the yellow (Y), magenta (M), cyan (C), and black (Bk) image signals. Toner images of yellow, magenta, cyan, and black are respectively formed on the surfaces of the photosensitive drums 2Y, 2M, 2C, and 2Bk.

[0013] Above the process cartridges 1Y, 1M, 1C, and 1Bk arranged linearly, an intermediate transfer unit 40 is arranged. The intermediate transfer unit 40 includes an intermediate transfer belt 8. Inside the intermediate transfer belt 8, primary transfer rollers 5Y, 5M, 5C, and 5Bk are arranged. The intermediate transfer belt 8 is rotatably stretched by the primary transfer rollers 5Y, 5M, 5C, and 5Bk, a secondary transfer opposing roller 10, and a tension roller 11. The primary transfer rollers 5Y, 5M, 5C, and 5Bk are arranged to face the photosensitive drums 2Y, 2M, 2C, and 2Bk, and form primary transfer portions respectively between the photosensitive drums 2Y, 2M, 2C, and 2Bk and the intermediate transfer belt 8. The primary transfer rollers 5Y, 5M, 5C, and 5Bk have a transfer voltage applied thereto, and transfer the yellow, magenta, cyan, and black toner images on the photosensitive drums 2Y, 2M, 2C, and 2Bk to the intermediate transfer belt 8.

[0014] The secondary transfer roller 12 is disposed opposite to the secondary transfer opposing roller 10, and a secondary transfer portion is formed between the secondary transfer roller 12 and the intermediate transfer belt 8. A transfer voltage is applied to the secondary transfer roller 12 to transfer the toner image on the intermediate transfer belt 8 onto the sheet S. The intermediate transfer unit 40 is provided with an intermediate transfer belt cleaning means 17 for removing the toner remaining on the intermediate transfer belt 8 after secondary transfer. Downstream of the secondary transfer portion in the conveyance direction of the sheet S, a fixing unit 20 is disposed. The fixing unit 20 heats and presses the toner image transferred onto the sheet S to fix the toner image onto the sheet S. Thereby, a full-color image is formed on the sheet S.

[0015] The sheet S on which the image is formed is conveyed to the discharge roller pair 22 by switching the conveyance path by a flapper 21 which is a branching means, and is discharged onto a discharge tray provided above the color laser printer A by the discharge roller pair 22. In the case of double-sided printing, the sheet S with an image formed on the front surface is conveyed to the reverse roller pair 23 by switching the conveyance path by the flapper 21. The reverse roller pair 23 reversely rotates to convey the sheet S to the double-sided conveyance unit 24, and the image is transferred onto the back surface of the sheet S again at the secondary transfer portion. The sheet S with images formed on both sides is discharged onto the discharge tray by the discharge roller pair 22.

[0016] [Configuration of the Feeding Cassette] The feeding cassette 100 will be described with reference to FIGS. 2 to 5. FIG. 2 is a perspective view of the feeding cassette 100 in the first state U1. The feeding cassette 100 in the first embodiment is composed of two trays, namely, a first tray 50 made of resin and a second tray 60 made of metal. The first tray 50 is mainly made of a material such as PC + ABS (polycarbonate + acrylonitrile-butadiene-styrene copolymer) or ABS (acrylonitrile-butadiene-styrene terpolymer). The second tray 60 is made of metal. On the second tray 60, a portion on the rear end side in the feeding direction FD of the sheet S fed by the feeding roller 14 is loaded. The second tray 60 is provided so as to be slidable along the feeding direction (the X direction in FIG. 2) with respect to the first tray 50. The first tray 50 is provided with a handle portion 56 on which a user can place a hand when attaching and detaching the feeding cassette 100 to and from the storage portion 30 of the main body of the color laser printer A. In the first state U1 shown in FIG. 2, the metal second tray 60 is set at a position for storing the shortest-size sheet in the feeding cassette 100. FIG. 3 is a perspective view of the feeding cassette 100 in the second state U2. In the second state U2 shown in FIG. 3, the second tray 60 is slid in the X direction and set at a position for storing the longest-size sheet in the feeding cassette 100. FIG. 4(a) is an exploded perspective view of the feeding cassette 100. FIG. 4(b) is an enlarged view of the portion IVB surrounded by a circle in FIG. 4(a). FIG. 5(a) is a perspective view of the lock lever 61. FIG. 5(b) is an enlarged view of the portion VB surrounded by a circle in FIG. 5(a).

[0017] [Slide mechanism of the second tray] The second tray 60 is provided with arm portions 60a extending in the feeding direction FD from both side portions. Inside both side portions of the first tray 50, an upper guide portion 50a and a lower guide portion 50b are provided (Fig. 4(a)). The arm portions 60a of the second tray 60 engage with the upper guide portion 50a and the lower guide portion 50b of the first tray 50. The L-shaped bending-up guide 60b of the second tray 60 is configured to engage with the L-shaped guide portion 50c of the first tray 50 (Fig. 4(b)). A groove portion 60c extending in the feeding direction FD is provided at the central portion of the second tray 60. The lock lever 61 is disposed in the groove portion 60c of the second tray 60. Shaft portions 61P are respectively provided at both side portions of the lock lever 61. The shaft portions 61P at both side portions of the lock lever 61 are respectively supported by both side surfaces of the groove portion 60c, and the lock lever 61 is rotatable. The lock lever 61 is biased in the direction of arrow B in Fig. 2 by a lever spring (not shown) provided below the rear end portion of the lock lever 61 at the rear end portion of the groove portion 60c of the second tray 60. A rack 61a is provided on the lower surface of the tip end portion of the lock lever 61 (Fig. 5(a)). The rack 61a passes through a square hole 60d (Fig. 4(b)) of the second tray 60 and engages with a rack 50d (Fig. 4(b)) of the first tray 50. So that the second tray 60 does not easily move in the front-rear direction FR with respect to the first tray 50, the rack 61a of the lock lever 61 and the rack 50d of the first tray 50 have two types of shapes that are less likely to have tooth gaps in the front-rear direction FR (Fig. 5(b)).

[0018] The first tray 50 is provided with a groove portion 50m extending in the feeding direction FD. In the groove portion 50m, a groove tip wall portion 50mf is provided on the downstream side in the feeding direction FD, and a groove rear end wall portion 50mb is provided on the upstream side. When the second tray 60 is slid and the stopper portion 60e bent downward of the second tray 60 abuts against the groove tip wall portion 50mf of the first tray 50, the second tray 60 stops at a position for storing the sheet of the shortest size and enters the first state U1. When the second tray 60 is slid and the stopper portion 60e abuts against the groove rear end wall portion 50mb, the second tray 60 stops at a position for storing the sheet of the longest size and enters the second state U2. In either the first state U1 or the second state U2, the rack 61a of the lock lever 61 meshes with the rack 50d of the first tray 50, restricting the movement of the second tray 60. Also, the second tray 60 can be slid to any position between the first state U1 and the second state U2 by releasing the lock of the lock lever 61. By locking the lock lever 61 between the first state U1 and the second state U2, the second tray 60 can be fixed to the first tray 50 corresponding to the size of the sheet S in pitch increments of the teeth of the rack 61a.

[0019] [Configuration of the middle plate] On the downstream side in the feeding direction FD within the feeding cassette 100, a metal middle plate 51 as a sheet loading plate (sheet loading means) is disposed so as to be movable up and down. The leading end side portion of the sheet S fed by the feeding roller 14 in the feeding direction FD is loaded on the middle plate 51. The middle plate 51 is provided with hook portions 51a on the left and right side portions in the left-right direction (Y direction in FIG. 2), respectively. The first tray 50 is provided with a shaft portion 50P and a claw portion 50Q on the left inner wall portion and the right inner wall portion in the left-right direction, respectively (FIG. 4(a)). The hook portion 51a of the middle plate 51 is hung on the shaft portion 50P of the first tray 50, and the claw portion 50Q prevents it from coming off the shaft portion 50P. Thereby, the middle plate 51 is rotatably supported by the first tray 50. The leading end portion 51L of the middle plate 51 is urged upward by a compression spring 52 from below, and abuts the loaded sheet S against the feeding roller 14 as shown in FIG. 1.

[0020] [Grounding Configuration of the Middle Plate and the Second Tray] Next, with reference to FIGS. 6 and 7, the grounding configuration of the middle plate 51 and the metal second tray 60 will be described. FIG. 6 is a perspective view of the feeding cassette 100 as seen from below with a part of the first tray 50 removed. FIG. 7 is a perspective view of the grounding configuration (grounding means) 550. The grounding configuration 550 includes a grounding spring (conductive member) 55 that is a conductive elastic member, spring support shafts (spring support portions) 50h1, 50h2, 50h3 provided on the first tray 50, and a guide portion 50g that guides the grounding spring 55.

[0021] In the first embodiment, the grounding spring 55 is formed of a wire spring. A downstream portion of the grounding spring 55 is formed into a first torsion coil spring portion 55S1. The first torsion coil spring portion 55S1 is supported by a spring support shaft 50h1 formed on the first tray 50. One end portion (first contact portion) 55f of the grounding spring 55 on the downstream side of the first torsion coil spring portion 55S1 is bent in an L shape. Here, the downstream side is the downstream side in the feeding direction FD of the sheet S. The feeding direction FD is the direction opposite to the X direction shown in FIG. 7. The one end portion 55f is configured to always elastically contact the lower surface 51d (FIG. 6) of the middle plate 51 following the vertical movement of the middle plate 51. An upstream portion of the grounding spring 55 is formed into a second torsion coil spring portion 55S2. The second torsion coil spring portion 55S2 is supported by a spring support shaft 50h2 formed on the first tray 50.

[0022] The ground spring 55 has a part of the straight portion between the first torsion coil spring portion 55S1 and the second torsion coil spring portion 55S2 bent in a convex shape upward (the direction indicated by the arrow Z) to form a first convex portion (third contact portion) 55T1. The first convex portion 55T1 is set to a convex shape that penetrates about 2 to 5 mm into the lower surface 60f of the second tray 60. When the first convex portion 55T1 abuts against the lower surface 60f which is a part of the second tray 60, the ground spring 55 is deformable. The ground spring 55 penetrates the left side surface of the first tray 50, and a part of the outer ground spring 55 is formed in the third torsion coil spring portion 55S3. The third torsion coil spring portion 55S3 is supported by the third spring support shaft 50h3. The other end of the ground spring 55 on the upstream side of the third torsion coil spring portion 55S3 is bent in a convex shape outward in the horizontal direction from the third spring support shaft 50h3 to form a second convex portion (second contact portion) 55T2. The storage portion 30 of the main body of the color laser printer A includes metal parts that are already grounded, such as a main body frame (not shown) or a feed cassette rail (not shown), and is in a grounded state. The second convex portion 55T2 abuts against the metal parts that are already grounded in the storage portion 30 when the feed cassette 100 is inserted into the storage portion 30. The ground spring 55 electrically connects the middle plate 51 and the storage portion 30, and by contacting a part of the second tray 60, grounds the middle plate 51 and the second tray 60.

[0023] With the above configuration, since there is no need to newly provide new functional components such as a bottom stay for the second tray 60 made of metal, the cost can be reduced. In this embodiment, the second tray 60 made of metal is slidably provided with respect to the main resin-made first tray 50. However, a structure in which the second tray 60 made of metal is fixed to the first tray 50 made of resin may be used. In that case, the second tray 60 made of metal may be used for the long-sized sheet, and may be replaced with another slidable resin-made second tray for the non-long-sized sheet. Also, a configuration may be adopted in which a slidable or fixed third tray can be added between the resin-made first tray and the fixed metal-made second tray. That is, the second tray 60 may be fixedly connected to the first tray 50, or may be connected to the first tray 50 via the third tray. According to the first embodiment, the intermediate plate 51 and the metal-made second tray can be grounded with an inexpensive and lightweight configuration. Thereby, it is possible to prevent the sheet S stored in the feed cassette 100 from being charged.

Embodiment

[0024] Next, with reference to FIGS. 8, 9, and 10, a second embodiment will be described below. In the second embodiment, the same reference numerals are given to the same structures as those in the first embodiment, and the description thereof will be omitted. The color laser printer A of the second embodiment is the same as that of the first embodiment. FIG. 8(a) is a perspective view of the feed cassette 101 of the second embodiment. FIG. 8(b) is an enlarged view of the portion VIIIB circled in FIG. 8(a). The feed cassette 101 in the second embodiment is composed of two trays, that is, a resin-made first tray 70 and a metal-made second tray 80, in the same manner as in the first embodiment. FIG. 9 is a perspective view of the feed cassette 101 with the second tray 80 separated from the first tray 70. FIG. 10 is a perspective view of the grounding configuration (grounding means) 720 of the second embodiment. The grounding configuration 720 includes a grounding spring (conductive member) 72 that is a conductive elastic member, a spring support shaft (spring support portion) 70f provided on the first tray 70, a guide portion 70g that guides the grounding spring 72, and a bent portion 82b provided on the second tray 80. Hereinafter, the differences from the first embodiment will be mainly described, and the description of the same structure as that of the first embodiment will be omitted.

[0025] [Configuration of the Feeding Cassette] In the feeding cassette 101 of the second embodiment, the movement of the metal second tray 80 relative to the first tray 70 is restricted. The two stopper claws 80b of the second tray 80 abut against the two abutting portions 70c provided in the groove portion 70b of the first tray 70, and the movement of the second tray 80 in the direction approaching the middle plate 71 is restricted. Similarly, the two stopper claws 80c of the second tray 80 abut against the two abutting portions 70d provided in the groove portion 70b of the first tray 70, and the movement of the second tray 80 in the opposite direction away from the middle plate 71 is restricted. In this way, the second tray 80 is fixedly connected to the first tray 70.

[0026] [Grounding Configuration of the Middle Plate and the Second Tray] As shown in FIG. 10, an arm portion 71a is provided on the middle plate 71, and the arm portion 71a is rotatably supported by a middle plate support rotating shaft 70e provided on the first tray 70. A U-shaped bending portion 82b with a narrow width and an open tip is provided on the arm portion 80a of the second tray 80 so that a part of it penetrates into the middle plate 71. The bending portion 82b having such a shape is an elastic contact portion that elastically contacts the middle plate 71. Since the bending portion 82b has elasticity, even if there is a variation in the dimension of the arm portion 80a with respect to the middle plate 71, the bending portion 82b reliably contacts the middle plate 71 without interfering with the rotation operation of the middle plate 71. Further, the position where the bending portion 82b contacts the middle plate 71 is set so that the bending portion 82b always contacts the middle plate 71 regardless of the number of sheets stacked on the middle plate 71, that is, even if the middle plate 71 rotates.

[0027] A part of the ground spring (coil spring) 72 is formed in the torsion coil spring part 72b. The torsion coil spring part 72b is supported by the middle plate support rotating shaft 70e provided on the first tray 70. One end 72a of the ground spring 72 is hooked on the hook hole 71b provided on the arm part 71a of the middle plate 71. Another part of the ground spring 72 is formed in the torsion coil spring part 72c. The torsion coil spring part 72c is supported by the spring support shaft 70f of the guide part 70g provided on the first tray 70. The other end of the ground spring 72 is formed in the convex part 72d protruding outside the first tray 70. The convex part 72d contacts a metal part in a grounded state such as the main body frame (not shown) or the feed cassette rail (not shown) when the feed cassette 101 is inserted into the storage part 30 of the main body of the color laser printer A.

[0028] With the above configuration, the ground spring 72 of the second embodiment only needs to conduct between the middle plate 71 and the main body frame (not shown). Therefore, compared with the ground spring 55 of the first embodiment that also contacts the second tray 60, the required length can be shortened and the shape can be simplified. Thus, further cost reduction can be achieved. In the second embodiment as well, similar to the first embodiment, a slidable or fixed third tray can be added between the resin-made first tray 70 and the fixed metal-made second tray 80. That is, the second tray 80 may be connected to the first tray 70 so as to be slidable, or may be connected to the first tray 70 via the third tray. According to the second embodiment, the middle plate 71 and the metal-made second tray can be grounded with an inexpensive and lightweight configuration. Thereby, the charging of the sheet S stored in the feed cassette 101 can be prevented.

Explanation of Reference Numerals

[0029] 14: Feed roller 50, 70: First tray 51, 71: Middle plate 60, 80: Second tray 30: Storage part 90: Image forming part 100, 101: Feed cassette 550, 720: Ground configuration A: Color laser printer S: Sheet FD: Feeding direction

Claims

1. A storage means in a grounded state, A sheet tray that is removably stored in the storage means and can store sheets, An image forming unit that forms an image on the sheet, Sheet feeding means for feeding the sheet from the sheet tray to the image forming unit, Comprising, The sheet tray, A first tray, A metal sheet loading means that is disposed movably up and down on the first tray and on which the front end side portion of the sheet fed by the sheet feeding means is loaded, A second metal tray that is connected to the first tray and on which the rear end side portion of the sheet in the feeding direction is loaded, Grounding means for grounding the sheet loading means and the second tray when the sheet tray is stored in the storage means, An image forming apparatus characterized by having the above.

2. The grounding means has a conductive member that electrically connects the sheet loading means and the storage means, and the image forming apparatus according to claim 1, characterized in that a part of the second tray is brought into contact with the conductive member.

3. The conductive member has a first contact portion that contacts the sheet loading means, a second contact portion that contacts the storage means, and a third contact portion that contacts the second tray, and the image forming apparatus according to claim 2, characterized by having the above.

4. The conductive member is formed of a wire spring, and the image forming apparatus according to claim 2, characterized by having the above.

5. A part of the second tray contacts the sheet loading means, and the image forming apparatus according to claim 1, characterized by having the above.

6. The part of the second tray is an elastic contact portion that elastically contacts the sheet loading means, and the image forming apparatus according to claim 5, characterized by having the above.

7. The elastic contact portion is a bent portion, and the image forming apparatus according to claim 6, characterized by having the above.

8. The second tray is connected to the first tray so as to be slidable relative to the first tray, and the image forming apparatus according to claim 1, characterized by having the above.

9. The second tray is fixedly connected to the first tray, and the image forming apparatus according to claim 1, characterized by having the above.

10. The second tray is connected to the first tray via a third tray, and the image forming apparatus according to claim 1, characterized by having the above.

11. The sheet loading means is made of metal, and the image forming apparatus according to claim 1, characterized by having the above.

Images