Paper discharge base of image forming apparatus

Abstract: A paper discharge base (10) is applied with a sponge sheet (84) as a damping plate (78) of an impact wall (70) provided at a paper discharge base (10). A protection sheet (16) is pasted on a surface of the sponge sheet (84). When the damping plate (78) is impacted by print sheet P, the impact force is transmitted from the protection sheet (86) to the sponge sheet (84) and is damped by the sponge sheet (84). Further, the sponge sheet (84) is protected by the protection sheet (86) and therefore, the sponge sheet (84) is not destructed by impact of the print sheet P.

Description: BACKGROUND OF THE INVENTION AND RELATED ART STATEMENT The present invention relates to a paper discharge base of an image forming apparatus such as a copying apparatus or a printing apparatus for containing print sheet discharged from a printing section of an image forming apparatus in a stacked state. With high speed formation of an image forming apparatus such as a copying apparatus or a printing apparatus in recent years, print sheet discharged from a printing section thereof is discharged at high speed toward a paper discharge base and is impacted to an impact wall of the paper discharge base with large momentum. In this case, when the impact wall is of a rigid structure, there is a drawback that large impact sound is emitted in impacting the print sheet. Hence, there is disclosed a paper discharge base for alleviating impact sound of print sheet in Japanese Patent Laid-Open No. 183553/1997. Such a paper discharge base is provided with a paper mounting floor and an impact wall. The main body of the impact wall is attached with an impact wall plate impacted by print sheet via an elastic film. Therefore, according to the paper discharge base, impact force when print sheet is impacted to the impact wall plate is damped by the elastic film and impact sound is alleviated. However, the impact wall plate impacted by print sheet is made of foamed styrene or foamed polyvinyl chloride. Since print sheet is directly impacted to the impact wall plate at high speed, there is a drawback that the impact wall plate is gradually impaired by the impact force after long hours of use. Further, since the impact wall of the paper discharge base needs a mechanism of expanding the elastic film, there also is a drawback that the structure of the impact wall becomes complicated. Further, depending on paper quality of print sheet, when print sheet is not impacted to an optimum position of the impact wall plate, print sheet loaded on the paper mounting floor does not align neatly. Further, the height of print sheet impacted to the impact wall plate differs by paper quality (weight) of print sheet, in the case of heavy print sheet, the height of impact is low and in the case of light print sheet, the height of impact becomes high. Therefore according to the paper discharge base disclosed in the publication, print sheet is not impacted to an optimum position of the impact wall plate depending on the paper quality of print sheet owing to a difference in the height of impact caused by the paper quality (weight) of print sheet as described above. Therefore, there is a drawback that the impact cannot be damped effectively. US-A-3,907,128 and DE-A-2,848,513 disclose apparatus for taking the impact of a moving sheet of material to bring it to rest for stacking. US-A-2,626,800 discloses an apparatus having the features of the preamble of claim 1. The present invention is characterized by the features of the characterizing portion of claim 1. Optional features are recited in the dependent claims. The present invention has been carried out in order to resolve the above-described drawbacks of the conventional technology. It is an object thereof to effectively damp impact of print sheet discharged from a printing section. Particularly, it is an object thereof to promote durability against impact of print sheet. Embodiments of the present invention may further promote strength of a surface of a damping member and damping operation of the damping member, to smoothly drop print sheet along the surface of the damping member in accordance with property of the surface, excellently align print sheet which is impacted to a damping member and drops, alleviate impact sound of print sheet and spring back of print sheet caused by impact, gradually reduce kinetic energy of print sheet impacted to a surface of a damping member, effectively prevent spring back of print sheet caused by a damping member thereby, achieve further sound pacifying formation of impact sound of print sheet by a simple constitution, and further alleviate spring back of print sheet caused by impact and excellently align sheet. Embodiments may make a damping member further easy to escape in the direction of discharging print sheet (space portion side) and drop print sheet impacted to a damping member further in a constant direction along a surface of the damping member, dispose a damping member at a position capable of damping effectively impact of print sheet in correspondence with paper quality of the print sheet, and be capable of adjusting a position of the damping member such that the impact of the print sheet can effectively be damped in correspondence with paper quality of the print sheet. When the print sheet impacts the damping member the impact force is transmitted from the protection sheet to the sponge sheet and is damped by the sponge sheet. Further, impact sound is alleviated. The sponge sheet is protected by the protection sheet and, accordingly, durability against impact of the print sheet is promoted. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a view of an inner structure of a stencil printing machine to which a paper discharge base according to the present invention is applied; Fig. 2 is a perspective view of a paper discharge base according to the present invention; Fig. 3 is a front perspective view showing the paper discharge base not according to the first embodiment not useful in understanding the present invention; Fig. 4 is a sectional view of an impact wall taken along a line 5-5 of Fig. 3; Fig. 5 is a front perspective view showing a state in which a damping plate is positioned at an upper position in a paper discharge base not according to the present invention but useful in understanding the present invention; Fig. 6 is a sectional view of an impact wall taken along a line 5-5 of Fig. 5; Fig. 7 is a front perspective view showing a state in which a damping plate is positioned at an upper position in a modified example of the paper discharge base according to the the present invention; Fig. 8 is a sectional view of an impact wall taken along a line 5-5 of Fig. 7; Fig. 9 is a sectional view of an impact wall taken along the line 5-5 of Fig. 7 showing other modified example of the paper discharge base; Fig. 10 is a perspective view of the paper discharge base according to the present invention; Fig. 11 is a front perspective view showing a state in which the damping plate of the paper discharge base which is not according to the present invention is positioned at a lower position but useful in understanding the present invention; Fig. 12 is a sectional view of an impact wall taken along the line 5-5 of Fig. 5 in the paper discharge base which is not according to the present invention but useful in understanding the present invention; Fig. 13 is a view of integrating a position adjusting mechanism of the paper discharge base which is not according to the present invention; but useful in understanding the present invention; Fig. 14 is a rear perspective view of the paper discharge base according to the the present invention; Fig. 15 is a front perspective view showing a state in which a damping plate is positioned at a lower position in a modified example of the paper discharge base according to the present invention; Fig. 16 is a sectional view of an impact wall taken along the line 5-5 of Fig. 7 in the modified example of the paper discharge base according to the further embodiment; Fig. 17 is a view of integrating a position adjusting mechanism in the modified example of the paper discharge base according to the further embodiment; and Fig. 18 is a sectional view of an impact wall taken along the line 5-5 of Fig. 7 in other modified example of the paper discharge base according to the further embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Fig. 1 is a view of an inner structure of a stencil printing machine as an image forming apparatus having a paper discharge base 10 which is not according to the present invention but useful in understanding the present invention. At an inner portion of a main body 14 of the stencil printing machine 12, there is arranged a printing drum 16 constituted by a cylindrical shape rotatably around an axis line of its own. At an outer peripheral face of the printing drum 16, there is provided a clamp member 18 for clamping an end portion of a stencil sheet 48, mentioned later. The stencil sheet 48 pinched by the clamp member 18 is wound to set to the outer peripheral face of the printing drum 16 by rotating the printing drum 16 in the counterclockwise direction of Fig. 1. At the inner portion of the printing drum 16, there are arranged a squeegee roller 20 in contact with an inner peripheral face thereof and a doctor roller 22 arranged to the squeegee roller 20 with a very small interval therebetween. Between the squeegee roller 20 and the doctor roller 22, ink supplied from an ink supply source, not illustrated, forms an ink store portion in a shape of a wedge. Ink at the ink store portion is supplied to the inner peripheral face of the printing drum 16 while being measured by passing through the very small interval by rotating the squeegee roller 20 in the counterclockwise direction of Fig. 1. Right under the printing drum 16, there is arranged a press roller 24. The press roller 24 is arranged at a position opposed to the squeegee roller 20. Further, the press roller 24 is provided liftably to be brought into contact with and separated from the outer peripheral face of the printing drum 16. At a left side face of the main body 14 in Fig. 1, there is provided a sheet supply base 26 loaded with print sheet P. On an upper side of the paper discharge base 26, there are provided a scraper roller 28 and a pickup roller 30. The scraper roller 28 and the pickup roller 30 feed the print sheet P stacked on the sheet supply base 26 sheet by sheet to between the printing drum 16 and the press roller 24. Further, a pair of upper and lower timing rollers 32 are provided contiguously to the pickup roller 30. The print sheet P fed by the scraper roller 28 and the pickup roller 30 is accurately fed by the timing rollers 32 at timings in cooperation with operation of the printing drum 16 and the press roller 24. Further, one-way clutches are built in the scraper roller 28 and the pickup roller 30. Further, when the print sheet P is transferred by the timing rollers 32, the scraper roller 28 and the pickup roller 30 are driven to follow by the print sheet P. On a right side of the printing drum 16 in Fig. 1, there are provided a sheet separator claw 34, a transfer belt 36 and a suction unit 37. After passing between the printing drum 16 and the press roller 32, the print sheet P is separated from the printing drum 16 by the sheet separator claw 34. The separated print sheet P is sucked to the transfer belt 36 by the suction unit 37. Thereafter, the print sheet P is discharged to the paper discharge base 10 by the transfer belt 36. At an upper portion of the main body 14, there is provided a lid 38. A line image sensor 40 is attached to a rear side of the lid 38. At an upper face of the main body 14 opposed to the line image sensor 40, there is arranged a draft handling roller 42. An upper portion of the draft handling roller 42 is partially projected from the main body 14. Further, a draft base 44 is mounted with draft before reading. The draft 46 mounted on the draft base 44 is supplied between the draft handling roller 42 and the line image sensor 40 from an outer side of the lid 38 and image data of the draft is read. At inside of the main body 14, there is contained a stencil sheet roll wound with the stencil sheet 48 in a rotatable state. The stencil sheet 48 drawn from the stencil sheet roll passes between a thermal head 60 and a platen roller 62 arranged to be opposed thereto. Further, there is carried out perforation in accordance with the image data. Successively, the stencil sheet 48 is cut in a single print amount by a cutter 54 and thereafter, transferred to the clamp member 18 of the printing drum 16. On a side of the printing drum 16 opposed to the cutter 54, there is provided a stencil separator claw 56. The stencil separator claw 56 separates a front end of the stencil sheet 48 which has been used by finishing printing operation and relieved of pinching of the clamp member 18, from the printing drum 16 in accordance with rotation of the printing drum 16. The stencil sheet 48 which has been separated from the printing drum 16 by the stencil separator claw 56, is contained in a stencil disposal box 58. The printing operation is started by starting the stencil printing machine 12. The print sheet P stacked on the paper supply base 26 is fed between the printing drum 16 and the press roller 24 sheet by sheet by the scraper roller 28 and the pickup roller 30. In accordance therewith, the printing drum 16 is rotated and the print sheet P is pressed between the printing drum 16 and the press roller 24 lifted at the predetermined timing. Thereby, ink oozed from the inner portion of the printing drum 16 by the stencil sheet 48 is transcribed onto the print sheet P and the printing operation is carried out. Further, the printed print sheet P is separated from the printing drum 16 by the sheet separator claw 34 and thereafter, successively discharged to the paper discharge base 10 by the transfer belt 36. An explanation will be given of the paper discharge base 10 for mounting the printed print sheet P as follows. As shown by Fig. 2, the paper discharge base 10 is constituted by an impact wall 70, a paper mounting floor 72 and a pair of fences 74. The impact wall 70 is for blocking advance of the discharged print sheet P and is impacted by the print sheet P discharged from the main body 14 of the stencil printing machine 12. The paper mounting floor 72 is stacked with the discharged print sheet P. The pair of fences 74 regulate positions of two side edges of the print sheet P. As shown by Fig. 3 and Fig. 4, the impact wall 70 is constituted by an impact wall main body 76 and a damping plate (corresponding to damping member) 78. The impact wall main body 76 is formed substantially in a rectangular shape. At a lower edge portion of the impact wall main body 76, there is formed a fixing portion 82 to project therefrom to be erected from and fixed to the paper mounting floor 72. Further, in the impact wall main body 76, the damping plate 78 is attached to a substantially central portion of a face thereof for receiving the discharged print sheet P. The damping plate 78 is constituted by a sponge sheet 84 and a protection sheet 86 covering a surface of the sponge sheet 84. The sponge sheet 84 is formed in a rectangular shape by a sheet made of, for example, soft foamed polyurethane. The protection sheet 86 is pasted on the surface of the sponge sheet 84 (face on a side impacted by the print sheet P). The protection sheet 86 is with high strength and thinness and fabricated by a film (commercial name: miler) made of polyethylene terephthalate having a property that a surface thereof is smooth. Further, the material of the protection sheet 86 is not limited to polyethylene terephthalate but there may be used a film made of other plastic or a film made of rubber. As shown by Fig. 4, the damping plate 78 is held in a holding member 88a. A double face adhering tape 90 is pasted on a surface of the holding member 88a. A rear face of the sponge sheet 84 is pasted to the double face adhering tape. Upper and lower end edges of the holding member 88a are formed to project by an amount of thicknesses of the double face adhering tape 90, the sponge sheet 84 and the protection sheet 86 and support the damping plate 78. The holding member 88a is screwed to the impact wall main body 76 by screws 102. Further, as shown by Fig. 3, the impact wall main body 76 is provided with regulating portions 80. The regulating portions 80 are formed at lower portions of both sides of the impact wall main body 76, that is, downward from an impact position for impacting the print sheet P to the damping plate 78. The regulating portions 80 are formed to sandwich the damping plate 78. The regulating portions 80 are formed to project from the impact wall main body 76 to the side of the apparatus main body 14. The regulating face 80 as the regulating portion is a plane in parallel with the impact wall main body 76 and is a plane orthogonal to a direction of discharging the print sheet P which has been printed and flown. Further, as shown by Fig. 4, the regulating face 80 is projected slightly from the surface of the damping plate 78 to the side of the apparatus main body 14. Therefore, a surface 78B at a lower end portion of the damping plate 78 is formed to be substantially flush with the respective regulating faces 80. Therefore, the lower end portion surface 78B of the damping plate 78 and the regulating faces 80 are provided continuously smoothly. Next, an explanation will be given of operation of this apparatus. First, before starting the printing operation, the paper discharge base 10 is installed at a predetermined position (position in Fig. 2) of the stencil printing machine 12. Further, the interval between the fences 74 is adjusted to be aligned with the width of the print sheet P and a position of the impact wall 70 in the forward and rearward direction is adjusted to be aligned with the length of the print sheet P. The printed print sheet P is separated from the printing drum 16 by the sheet separator claw 34 and thereafter, successively discharged to the paper discharge base 10 by the transfer belt 36. The discharged print sheet P is flown and a front end edge portion thereof is impacted to the damping plate 78 of the impact wall 70. At this occasion, impact of the print sheet P is transmitted from the protection sheet 86 to the sponge sheet 84 and is damped by the sponge sheet 84. The sponge sheet 84 is protected by the protection sheet 86 and accordingly, the sponge sheet 84 is not destructed by the impact of the print sheet P. The impacted print sheet P drops by its own weight. At this occasion, the print sheet P rubbingly drops in a state in which the front end edge portion is being brought into contact with the surface of the protection sheet 16. Further, when the print sheet P rubbingly drops to the position of the lower end portion 78B of the damping plate 78, the both sides of the front end edge portion of the print sheet P are brought into sliding contact with the regulating faces 80. Further, the print sheet P is successively stacked on the paper mounting floor 72 in a state in which the front end edge portion is aligned and is contained. Further, as the protection sheet 86 of the damping plate 78, a film made of polyethylene terephthalate may be applicable. The film made of polyethylene terephthalate is provided with high strength. Therefore, even when the protection sheet 86 is thinned to promote damping operation of the sponge sheet 84, the sponge sheet 84 can sufficiently be protected against impact force of the print sheet P. Further, the film made of polyethylene terephthalate is provided with a property that a surface thereof is smooth. Therefore, the print sheet P impacted to the protection sheet 86 is made to drop smoothly along the surface of the protection sheet 86. Next, an explanation will be given of an embodiment of the present invention. Portions the same as those in the first apparatus are attached with the same notations and an explanation thereof will be omitted. As shown by Fig. 5 and Fig. 6, this example is an example in which a space portion 92 is formed on a rear face side of the damping plate 78 in the apparatus shown by Fig. 3 and Fig. 4. In this case, when the print sheet P is impacted to the damping plate 78, by the impact force, as shown by two-dotted chain lines in Fig. 6, the damping plate 78 is elastically deformed to escape in a direction of discharging the print sheet P constituting the side of the space portion 92. Thereby, both of impact sound of the print sheet P and spring back of the print sheet P caused by impact are alleviated. Therefore, not only sound pacifying formation is achieved but also excellent sheet alignment can be carried out. Further, as shown by Fig. 7 and Fig. 8, the lower end portion 78B of the damping plate 78 may be provided in the direction of discharging the print sheet P from an upper end portion 78A of the damping plate 78. In this case, as shown by Fig. 7 and Fig. 8, the surface of the damping plate 78 is formed in a shape of a gradual curved face slightly inclined in the direction of discharging the print sheet P gradually from the upper end portion 78A toward the lower end portion 78B. When the surface of the damping plate 78 is formed in the shape of the curved face in this way, the print sheet P impacted to the surface of the damping plate 78 is directed to the discharge direction along the curved surface of the damping plate 78. Thereby, the kinetic energy of the print sheet P is gradually reduced. Further, the print sheet P drops along the curved face of the damping plate 78 and is led to the restricting faces 80. Thereby, the print sheet P is smoothly stacked on the paper mounting floor 72 while preventing spring back by the damping plate 78. Further, as shown by Fig. 7 and Fig. 8, there may be constructed a constitution in which in the example of Fig. 3 and Fig. 4, the lower end portion 78B of the damping plate 78 is inserted slidably in the up and down direction to a receive portion (corresponding to holding portion) 88B having a section substantially in a shape of a channel directed upwardly formed at a lower portion of a support member 88a. In this case, when the print sheet P is impacted to the damping plate 78, the damping plate 78 is elastically deformed in the discharge direction and the lower end portion 78B is lifted. Thereby, the damping plate 78 becomes easy to escape in the direction of discharging the print sheet P on the side of the space portion 92. Further, since the position of the lower end portion 78B of the damping plate 78 is held by the receive portion 88B, the print sheet P impacted to the damping plate 78 drops in a constant direction along the surface of the damping plate 78. Successively, the print sheet P drops while the front end portion is being aligned along the restricting faces 80 and is stacked onto the paper mounting floor 72. Further, as shown by Fig. 9, there may be constructed a constitution in which in the example of Fig. 3 and Fig. 4, the upper end portion 78a of the damping plate 78 may be inserted slidably in the up and down direction to a receive portion (corresponding to holding portion) 88C having a section substantially in a shape of a channel directed upwardly formed at an upper portion of the support member 88a. In this case, when the print sheet P is impacted to the damping plate 78, the damping plate 78 is elastically deformed in the discharge direction and the upper end portion 78A is lowered. Thereby, the damping plate 78 becomes easy to escape in the direction of discharging the print sheet P constituting the side of the space portion 92. Further, since the position of the upper end portion 78A of the damping plate 78 is held by the receive portion 88C, the print sheet P impacted to the damping plate 78 drops in the constant direction along the surface of the damping plate 78. Successively, the print sheet P drops while the front end edge portion is being aligned along the regulating faces 80 and is stacked onto the paper mounting floor 72. Next, an explanation will be given of embodiments of the present invention. Portions the same as those in the first and the second apparatus are attached with the same notations and an explanation thereof will be omitted. As shown by Fig. 10 through Fig. 14, this example is an example in which in the impact wall shown by Fig. 5 and Fig. 6, there is provided position adjusting means for freely adjusting the position of the damping plate 78 in the up and down direction. As shown by Fig. 10 through Fig. 14, the damping plate 78 is supported by the impact wall main body 76 by being attached to a slider 88b. According to the damping plate 78, the upper end portion 78A is adhered to a support portion 88A formed to project to an upper portion of the slider 88b by the double face adhering tape 90. The slider 88b is arranged slidably in the up and down direction along a slit 77 shown in Fig. 11 formed at the impact wall main body 76. Further, a height position of the slider 88b is adjusted by a position adjusting mechanism 94 (refer to Fig. 10, Fig. 12, Fig. 14) provided on the rear face side of the impact wall main body 76. That is, by the position adjusting mechanism 94, the damping plate 78 can be moved to a position for effectively damping impact of the print sheet P. As shown by Fig. 12 and Fig. 13, the position adjusting mechanism 94 is constituted by a claw plate 96, a leaf spring 98 and an operation knob 100. A pair of bosses 89 is formed at a rear face 88D of the slider 88b. The claw plate 96 and the leaf spring 98 are formed with holes 97 (holes of leaf spring 98 are not illustrated) for inserting the pair of bosses 89. The bosses 89 are perforated with screw holes 89A. The screw holes 89A are screwed with the setscrews 102 from an outer side of the operation knob 100. Thereby, the slider 88 and the operation knob 100 are connected to sandwich the impact wall main body 76 via the claw plate 96 and the leaf spring 98. Further, the leaf spring 98 is elastically deformed by being sandwiched between the claw plate 96 per se and the operation knob 100. The claw plate 96 is urged to the rear face side of the impact wall main body 76 by urge force of the elastically deformed leaf spring 98. On the rear face side of the impact wall main body 76, there are formed a pair of projected streak portions 104 along both sides of the slit 77. At upper portions of the projected streak portions 104, there are formed recess portions 104A to be engaged with upper claws 96A of the claw plate 96. Further, at lower portions of the projected streak portions 104, there are formed recess portions 104B to be engaged with lower claws 96B of the claw plate 96. Further, recess portions 104C are formed also at centers of the projected streak portions 104. When the upper claws 96A are engaged with the recess portions 104A, the recess portions 104C are engaged with the lower claws 96B. Further, the recess portions 104C are engaged with the upper claws 96A when the lower claws 96B are engaged with the recess portions 104B. According to the position adjusting mechanism 94 constituted in this way, a click mechanism is constituted by the claws 96A and 96B and the recess portions 104A, 104B and 104C. By the click mechanism, the damping plate 78 is positioned at an upper position shown by Fig. 5 or a lower position shown by Fig. 11. Further, the slider 88b is pressed to the surface 76A of the impact wall main body 76 by the urge force of the leaf spring 98 to thereby provide pertinent friction. Therefore, the damping plate 78 can be positioned not only at the upper position shown by Fig. 5 or the lower position shown by Fig. 11 but also at an arbitrary position. Further, as shown by Fig. 10 and Fig. 14, on both side faces of the operation knob 100, there are formed projected portions 101 for pinching the operation knob 100 by the thumb and the forefinger. An explanation will be given of operation of this example as follows. First, before starting printing operation, the paper discharge base 10 is installed at a predetermined position (position of Fig. 10) of the stencil printing machine 12. Further, the interval of the fences 74 is adjusted to align to the width of the print sheet P and a position of the impact wall 70 in the forward and rearward direction is adjusted to align to the length of the print sheet P. Next, the height of the damping plate 87 of the impact wall 70 is adjusted by the position adjusting mechanism 94 and the damping plate 78 is positioned to a position of effectively damping impact of the print sheet P. For example, in the case of the light print sheet P, the damping plate 78 is positioned to the upper position shown by Fig. 5. Conversely, in the case of the heavy print sheet P, the damping plate 78 is positioned to the lower position shown by Fig. 11. Further, as shown by Fig. 12, depending on the weight of the print sheet P, the upper claw 96A is positioned between the recess portions 104A and the recess portions 104C and the lower claw 96B is disposed between the recess portions 104C and the recess portions 104B. Thereby, the damping plate 78 can be positioned to a predetermined position. Further, after the printed print sheet P is separated from the printing drum 16 by the sheet separator claw 34, the print sheet P is successively discharged to the paper discharge base 10 by the transfer belt 36. As shown by the first embodiment, the discharged print sheet P is stacked on the paper mounting floor 72 in the state in which the front end edge portion is aligned and contained. Further, this example is applicable als to the example shown in the impact wall of Fig. 7 and Fig. 8 in which as shown by Fig. 15 through Fig. 17, the lower end portion 78B of the damping plate 78 is provided in the direction of discharging the print sheet P relative to the upper end portion 78A of the damping plate 78. Further, as shown by Fig. 15 through Fig. 17, the example is applicable also to the example shown in the impact wall of Fig. 7 and Fig. 8 in which the lower end portion 78B of the damping plate 78 is inserted slidably in the up and down direction to the receive portion (corresponding to holding portion) 88B having the section substantially in the shape of a channel directed upwardly formed at the lower portion of the support member 88a. Further, as shown by Fig. 18, the example is applicable also to the example shown in the impact wall of Fig. 7 and Fig. 8, in which the upper end portion 78A of the damping plate 78 is inserted slidably in the up and down direction to the receive portion (corresponding to holding portion) 88B having the section substantially in the shape of a channel directed downwardly formed at the upper portion of the support member 88a. In this way, according to the present invention, by the position adjusting mechanism 94, in correspondence with the paper quality of the print sheet P, the damping plate 78 is previously disposed at the position of effectively damping impact of the print sheet P. Therefore, impact sound when the print sheet P is impacted to the damping plate 78 can significantly be alleviated. Further, the position adjusting mechanism 94 is provided with the click mechanism for positioning the upper and lower positions of the damping member 78 to predetermined positions. Therefore, the position of the damping member 78 can be made to easily correspond to the height of impact of the print sheet having predetermined paper quality. Further, although according to the embodiment, a description has been given of an example in which the paper discharge base 10 is applied to the stencil printing machine 12 constituting the printing apparatus, the paper discharge base 10 of the present invention is not limited to the printing apparatus but is applicable to a copying apparatus, also, for example. As has been explained above, the impact force of print sheet is transmitted from the protection sheet to the sponge sheet and can be damped by the sponge sheet. Further, the sponge sheet is protected by the protection sheet and accordingly, durability against impact of the print sheet can be promoted. The strength of the protection sheet may be promoted and, thereby, the damping operation of the sponge sheet can be promoted by thinning the protection sheet while the sponge sheet is still sufficiently be protected against impact force of print sheet. By providing a smooth surface, print sheet impacted to the protection sheet can be made to drop smoothly along the surface of the protection sheet. Further, the dropping print sheet may successively be stacked on the paper mounting floor is a state in which the front end edge portion of printsheet is aligned and the sheet can be aligned excellently. Thereby, there is eliminated time and labor of aligning print sheet after taking out print sheet from the paper discharge base. Further, the damping member may be elastically deformed and escaped in the direction of discharging print sheet constituting the side of the space portion. Thereby, impact sound of print sheet and spring back of print sheet caused by impact can be alleviated. Further, the surface of the damping member may be formed in a shape of a gradually curved face inclined in the direction of discharging print sheet gradually from an upper end portion to a lower end portion thereof. Kinetic energy of print sheet can be reduced gradually by directing print sheet impacted to the surface of the damping member in the discharge direction along the curved surface of the damping member. Thereby, spring back of print sheet caused by the damping member can be prevented further effectively. Further, the damping member may be impacted with print sheet which is elastically deformed and escaped to the side of the space portion with the upper end (lower end) as a fulcrum and accordingly, by a simple constitution, sound pacifying formation of impact sound of print sheet can be achieved. Thereby, sheet can be aligned excellently by alleviating spring back of print sheet caused by impact. Further, the lower end portion (upper end portion) of the damping member may be held at a holding portion on the side of the impact wall slidably in the up and down direction and accordingly, the damping member becomes easy to escape in the direction of discharging print sheet (side of space portion). Thereby, print sheet impacted to the damping member can be dropped in a constant direction along the surface of the damping member. Further, the damping member may be disposed at a position capable of damping effectively impact of print sheet. Further, a click mechanism may be provided, the position of the damping member can be made to correspond easily to impact height of print sheet having predetermined paper quality.

Claims: A paper discharge base of an image forming apparatus comprising: an impact wall (70) impacted by print sheet discharged from a printing section; a damping member (78) provided on a surface of the impact wall (70) for damping impact caused by impacting the print sheet; a paper mounting floor (72) loaded with the print sheet which is impacted to the damping member (78) and drops; wherein the damping member (78) comprises a sponge sheet (84) and a protection sheet (86) covering a surface of the sponge sheet (84) so as to be impacted by the print sheet; wherein the damping member (78) includes a space portion on a rear face side of the impact position, and wherein a lower end portion of the damping member (78) is provided further in a direction of discharging the print sheet relative to an upper end portion of the damping member (78) the apparatus being characterized in that : the protection sheet (86) is attached to the surface of the sponge sheet (84); and wherein either one of the upper end portion and the lower end portion of the damping member (78) is fixed to a side of the impact wall (70) and other thereof is held slidably in an up and down direction relative to the side of the impact wall (70). The paper discharge base of an image forming apparatus according to claim 1, further comprising: position adjusting means (94) provided at the impact wall (70) and capable of adjusting a position of the damping member (78) in the up and down direction. The paper discharge base of an image forming apparatus according to claim 2, wherein the position adjusting means (94) comprises a click mechanism for positioning a position in the up and down direction of the damping member (78) to a predetermined position. The paper discharge base of an image forming apparatus according to claim 1: wherein the protection sheet (86) of the damping member (78) is made of polyethylene terephthalate. The paper discharge base of an image forming apparatus according to claim 1, further comprising: regulating portions (80) projected from a portion of the damping member (78) on a lower side of an impact position to a side of an apparatus main body on both sides of the impact wall (70) formed on the lower side of the impact position at which the print sheet is impacted to the damping member (78) for leading a front end edge portion of the dropping print sheet to the lower side while being brought into sliding contact therewith.

Inventors: TSURUMAKI TAKESHI, TSURUMAKI, TAKESHI, Tsurumaki, Takeshi, c/o Riso Kagaku Corporation
Applicants: RISO KAGAKU CORP, RISO KAGAKU CORPORATION
Application year: 2001
Main classification: B65H31
IPC codes: B65H31