Sheet paper feed apparatus

Abstract: A sheet paper feed apparatus has a hollow centre shaft (63), rollers (61) which have peripheral holes (62) and rotate around the centre shaft (63), and a negative pressure source (65) communicating with the centre shaft (63). Rotation of the roller (61) causes the peripheral holes (62) to connect successively with an opening in the centre shaft to allow the suction action to aid feeding of the sheet paper. The rollers are so formed that at least one of the peripheral holes (62) is effectively opposing the opening in the shaft (66) at any given time and thus interruption in the suction, likely to cause paper misfeed, is avoided.

Description: The present invention relates to a feed apparatus, and more particularly, to a sheet paper feed apparatus suited to an image forming apparatus. FIG. 1 generally shows an image forming apparatus 10 as one example of an apparatus to which a sheet paper feed apparatus of general type has been attached. Around the periphery of a photosensitive drum 11, are disposed a cleaner 12, a pre-charger 13, an exposer 14, a developer 15, a transfer unit 16 and the like. The photosensitive drum 11 rotates in the direction indicated by the arrow A and first forms a latent image, and then a toner image. 17 represents a flash light fixing apparatus. 18 and 19 represent sheet paper feed apparatus. The sheet paper 20 is supplied from a paper supply portion (not indicated in the figure), is fed in the direction of the arrow B by the feed apparatus 19 and then is conveyed in the direction of the arrow C by the feed apparatus 18, and discharged to the stacker portion (not indicated in the figure). The transfer unit 16 transfers the toner image on the photosensitive drum 11 to the sheet paper 20 and the toner image on the sheet paper 20 is fixed to the sheet paper 20 by the flash light fixing apparatus 17. In recent years, the operation of the image forming apparatus 10 has been becoming faster and accompanying this has been an increase in the feed speed of sheet paper. When sheet paper is fed at high speed, it is that much easier for the status of the sheet paper that is being fed, to become unstable, and thus for paper misfeed to occur. Because of this, it is necessary to improve the feed apparatus 18, 19 so that they have a higher reliability. FIG. 2 shows conventional sheet feed apparatus 31, 32 and 33 corresponding to the sheet paper feed apparatus represented by the numeral 18 in FIG. 1. The sheet feed apparatus 31, 32 and 33 are lined up in direction C for feeding the sheet paper. Each of the sheet feed apparatus 31, 32 and 33 have a structure where the hollow fixed center shafts 31-1, 32-1 and 33-1 carry the rollers 31-2, 32-2 and 33-2 so that they are rotatable. Each of the rollers 31-2, 32-2 and 33-2 have formed along their entire periphery a plural number of holes 31-2a, 32-2a and 33-2a. In addition, each of the hollow fixed center shafts 31-1, 32-1 and 33-1 have respectively formed in them openings 31-1a, 32-1a and 33-1a. Each of the hollow fixed center shafts 31-1, 32-1 and 33-1 communicate with a negative pressure source 34. The rollers 31-2, 32-2 and 33-2 are rotated in the counterclockwise direction as indicated by the arrow D, and of the plural number of holes 31-2a, 32-2a and 33-2a, the holes that successively oppose openings 31-1a, 32-1a and 33-1a produce a suction action that causes the sheet paper to adhere them while the rotational force of the rollers 31-1 through 33-2 applies them a feed force in the direction of the arrow C. The sheet paper 20 is adhered by the portions of each of the feed roller assembly units 31, 32 and 33 and is thereby fed. Here, the openings 31-1a, 32-1a and 33-1a are formed at portions that are inclined by the angle α= 10°) in the direction opposite the sheet paper feed direction (clockwise, in FIG. 2) with respect to the surfaces 35, 36 and 37 that are vertical with respect to the sheet paper feed surface 22 which passes through the centers of the roller assembly units 31, 32 and 33. This structure is adopted so as to adhere, as soon as possible, the sheet paper that has been fed and arrived. As is shown in the enlarged view shown in FIG. 3, each of the holes of the plural number of 33-2a perform suction action while it moves from a position on the forward side with respect to the topmost point of the roller assembly unit 33 to the topmost portion. The sheet paper 1 is thereby applied a feed force F1, as indicated by the arrow, in a direction inclining upwards by the angle α with respect to the sheet feed surface 22. Because of this, as shown in FIG. 2, the sheet paper 20 rises up from the sheet feed surface 22 and the distal end of the sheet paper 20 catches on the step portion 24 of the lower surface of the flash light fixing apparatus 17 and causes paper misfeed. FIG. 4 shows a conventional sheet paper feed apparatus 41, corresponding to the sheet paper feed apparatus represented by the number 19 in FIG. 1. The sheet paper feed apparatus 41 is provided with a negative pressure source 44 passing through a hollow member 42 which is provided with a rotatable roller 43, and is disposed so as to be opposite and in the vicinity of the photosensitive drum 11. Along the entire periphery of the roller 43 are formed a plural number of holes 46. The hollow member 42 is formed with a single opening 47 that opposes the sheet paper peeling position 48 on the peripheral surface of the photosensitive drum 11. The roller 43 rotates in the direction indicated by the arrow D, and the holes 46 come to successively oppose the opening 47 so that the hole 46 opposing the opening 47 produce a suction action. Accordingly, the sheet paper 20 is adhered to the roller 43 and is peeled from the photosensitive drum 11, at the same time as it is being conveyed in the direction of the arrow B by the rotation of the roller 43. The holes 46 and the openings 47 have their relationship determined by the length a of the wall portion 50 between adjacent holes 46 and by the diameter b of the opening 47, where a > b. Because of this, between the time when one of the holes 46 has passed the portion of the opening 47, and the next hole 46 is about to oppose the opening 47, there is the status the wall portion 50 completely covers the opening 47. At times such as this, the apparatus 41 does not generate a suction peeling force and so there is therefore no feed force. For example, when the portion of the holes 46-1 through 46-3 rotates over the position of the opening 47, the holes 46-1 through 46-3 apply a suction force as indicated by the lines 51, 52 and 53 in FIG. 5 (A) through (C), and the suction force is intermittently applied in the sectional portion as indicated by the line 54 in FIG. 5 (D). In addition, each of the holes 46-1 through 46-3 apply a feed force as shown by the lines 55, 56 and 57 in FIG. 6 (A) through (C), and the application of the feed force is intermittently in phase as shown by line 58 in FIG. 6 (D). Because of this, when the photosensitive drum 11 in particular, is rotating at high speed and feeding the sheet paper 20 at high speed, there is the likelihood that the feeding of the sheet paper 20 will become unstable. An example of the conventional sheet feeding apparatus is to be found in DE 1011438 which discloses a roller, for feeding paper, having a plurality of holes in the surface thereof and an opening in a fixed hollow central shaft of the roller connected to a vacuum source and which opening allows a vacuum to be applied to a sheet being fed through one of the holes in the roller surface as it aligns itself with the opening. Such a sheet feeding apparatus contains no provision for allowing stable feeding of the paper at high speed. A further example of a conventional sheet feeding apparatus is given in EP 0 313 088 in which a suction roller is used to draw sheets off an image-sensitive drum onto a conveyor belt. The roller comprises an inner fixed hollow shaft connected to a suction generator and having an opening. An outer rotatable part of the roller has further openings which transmit suction to the paper as they align themselves with the inner opening. Further rollers of the same construction are provided to feed the sheet past the flash light fixing unit 107. In the above example the weakness of the prior art discussed before is present, namely that the feed force is intermittent. This is exactly the situation as shown in Fig. 5 herein. The discontinuity of the force leads to frequent misfeeding of the paper if any attempt is made to increase the feed speed of the paper. DE 2 433 545 discloses a sheet coating apparatus that uses suction rollers to feed the sheets. FR 912,812 relates to a feed arrangement for a printing apparatus. Here a suction roller is used that has its outer peripheral holes are arranged sufficiently close together to give continuous suction. DE 2 760 141 discloses a means for peeling paper from an image carrier in the form of a master sheet adhered to a drum. The means is a bump on the drum and a suction roller is placed beyond the bump to carry the paper forward. Accordingly, it is a general object of the present invention to provide a novel and useful sheet paper feed apparatus in which the problem described above has been eliminated A further object of the present invention is to provide a sheet paper feed apparatus comprised so that at least one of the plural number of holes in the roller always opposes an opening of a hollow fixed centre shaft while a roller is rotating. In accordance with the present invention there is hence provided an image forming apparatus comprising means for separating a sheet of paper from a toner image carrier and feeding said sheet of paper, to which a toner image formed on said toner image carrier has been transferred wherein the said means has a plurality of rollers that rotate in the direction of sheet paper feed and which have a hollow fixed centre shaft that has an opening on a side of the surface of sheet paper that is fed, a plurality of holes around their periphery in contact with the shaft and a negative pressure source communicating with said hollow fixed centre shaft, rotation of said roller causing said peripheral holes to successively communicate with said opening, thus creating a suction action to adhere and feed said sheet of paper, wherein said hollow fixed center shaft is disposed so as to confront said toner image carrier at a position where said paper is to be separated from said toner image carrier characterised in that said rollers are formed so that at least one of said plurality of holes is always effectively opposing said opening of said hollow fixed centre shaft while said roller is rotating, thus creating a suction action to adhere and feed said sheet of paper continuously and without interuption. For a better understanding of the invention, and to show how the same may be carried into effect, reference will now be made, purely by way of example, to the accompanying drawings, in which:- Fig.1 is a view of an image forming apparatus which is one example of an apparatus to which a general sheet paper feed apparatus has been incorporated; Fig.2 is a view showing one example of a conventional sheet paper feed apparatus; Fig.3 is a view for describing the sheet paper feed by the apparatus in FIG. 2; FIG. 4 is a view describing another example of a conventional sheet paper feed apparatus; FIG. 5 is a view for describing the operation for the action of the sheet paper suction force by the apparatus of FIG. 4; FIG. 6 is a view for describing the operation for the action of the sheet paper feed force by the apparatus of FIG. 4; FIG. 7 is a view of one configuration describing a development of the sheet paper feed apparatus of the present invention; FIG. 8 is a view of one example of curled sheet paper; FIG. 9 is a sectional view taken along the section lines IX-IX of FIG. 10, describing the sheet paper feed apparatus of one embodiment according to the present invention on the basis of the principle described in FIG. 7; FIG. 10 is a plan view of the sheet paper feed apparatus of FIG. 9 in a state where a part thereof being cut away; FIG. 11 is a view showing another embodiment of a sheet paper feed apparatus according to the present invention on the basis of the principle described in FIG. 7; FIG. 12 is a view of a configuration describing the general principle of a sheet paper feed apparatus of a primary embodiment of the present invention; FIG. 13 is a view describing the sheet paper suction action of the apparatus of FIG. 12; FIG. 14 is a view describing the sheet paper feed action of the apparatus of FIG. 12; FIG. 15 is an elevational view showing a first embodiment of the present invention on the basis of the principle of FIG. 12; FIG. 16 is a plan view of the apparatus of FIG. 15; FIG. 17 is an enlarged view of the roller, hollow member and sleeve in FIG. 15; FIG. 18 is a view showing the relationship between the sleeve and the hole in the periphery of the roller in FIG. 16; and FIG. 19 is an enlarged sectional view taken along the section lines XIX-XIX of FIG. 16. The description will commence with a description of one schematic configuration and the action of a sheet paper feed apparatus of the present invention. FIG. 7 shows a schematic configuration of a sheet paper feed apparatus 60 according to an embodiment of the present invention. A roller 61 has a plural number of holes 62 around its entire periphery, and is provided so as to be rotatable around a hollow fixed center shaft 63, and rotates in the direction shown by the arrow D so that a portion 64 in contact with a sheet 20 moves in the direction of sheet paper feed as shown by the arrow C. A negative pressure source 65 is provided so as to communicate with the hollow fixed center shaft 63. An opening 66 is formed so as to make a predetermined angle b in the direction of sheet paper feed C (the direction D of rotation of the roller 61), with respect to the surface 68 which is perpendicular to sheet paper feed surface 22 and extends through the center of the hollow fixed center shaft 63. Each of the holes 62 adheres the sheet paper 20 via the opening 66 and the hollow fixed center shaft 63 due to the negative pressure source 65, inside the region that rotates with respect to the opening 66, and simultaneously, the rotation of the roller 61 applies a feed force shown by the arrow F2. Here, the opening 66 forms an angle in the direction of sheet paper feed, with respect to the surface 68 and so the feed force to the sheet paper 20 is applied in a direction that is inclined at the angle β in the direction inclining downwards with respect to the sheet feed surface 22. Because of this, even in the case where the distal end 20a in the direction of feed of the sheet paper 20 is curled in the upwards direction as shown by the numeral 29 in FIG. 8, when the sheet paper 20 is fed by the roller 61, the height on the side of the distal end 20a is held in the downwards direction from the sheet paper feed surface 22 so that it does not rise upwards from the sheet paper feed surface 22. Accordingly, the distal end 20a of the sheet paper 20 does not catch on the step portion 24 of the lower surface of the flush light fixing apparatus 17, and no paper jams occur. The following is a description of a sheet paper feed apparatus 80 of one embodiment according to the present invention on the basis of the principle shown in FIG. 7. The description is made with reference to FIG. 9 and FIG. 10. In FIG. 9 and FIG. 10, a first sheet paper feed apparatus 81, a second sheet paper feed apparatus 82, and a third sheet paper feed apparatus 83 are provided in line in the direction of sheet paper feed. Each of the sheet paper feed apparatus 81, 82 and 83 have a structure so that rollers 81-2, 82-2 and 83-2 are rotatably engaged with hollow fixed center shafts 81-1, 82-1 and 83-1, and each of the rollers 81-2, 82-2 and 83-2 are belt driven to rotate in the counterclockwise direction indicated by the arrow D. Each of the rollers 81-2, 82-2 and 83-2 have formed around their entire peripheries a plural number of holes 81-2a, 82-2a and 83-2a. In each of the hollow fixed center shafts 81-1, 82-1 and 83-1 are formed openings 81-1a, 82-1a and 83-1a. Opening 81-1a is formed so as to make a predetermined angle  (of 10°) in the clockwise direction, with respect to the surface 84 which is perpendicular to sheet paper feed surface 22 and extends through the center 81-1b of the hollow fixed center shaft 81-1. Openings 82-1a and 83-1a are formed so as to make predetermined angle  (of 10°) in the clockwise direction, with respect to surfaces 85 and 86 which are perpendicular to sheet paper feed surface 22 and extend through the centers 82-1b and 83-1b of the hollow fixed center shafts 82-1 and 83-1. Each of the hollow fixed center shafts 81-1, 82-1 and 83-1 communicate with a negative pressure source (blower) 87. The sheet paper 20 is successively adhered by each of the sheet paper feed apparatus 81, 82 and 83, and is supported and guided by the guide 88 and fed in the direction shown by the arrow C. The upper surface of the guide 88 serves as the sheet paper feed surface 22 already described. The feed force applied to the sheet paper 20 by each of the sheet paper feed roller assembly units 81, 82 and 83 is as shown by the arrows F3, F4 and F5. More specifically, the feed force F3 applied by the first sheet paper feed apparatus 81 which is at the entrance portion to the sheet paper feed apparatus 80 is in a direction which is inclined by the angle  in the upwards direction with respect to the sheet feed surface 22. The feed forces F4 and F5 which are applied by the second and third sheet paper feed roller assemblies 82 and 83 which are in the middle and exit portions of the sheet paper feed apparatus 80 and in which paper misfeeds of the sheet paper 20 are most likely to occur are in the direction which is inclined by the angle  in the downwards direction with respect to the sheet feed surface 22. Because of this, the sheet paper 20 is fed without rising from the sheet feed surface 22, and even in cases where the distal end of the sheet paper 20 is curled in the upwards direction, it can still be fed without catching on the step portion 24 of the downwards surface of the fixing unit 17. The following is a description of the sheet paper feed apparatus 90 of another embodiment according to the present invention, based on the principle shown in FIG. 7. The description is made with reference to FIG. 11. In FIG. 11, portions corresponding to similar portions in FIG. 9 are indicated with the same numerals. The first, second and third sheet paper feed apparatus 81A, 82A and 83A are configured so that hollow fixed center shafts 81A-1, 82A-1, 83A-1 are provided with two openings 81A-10 and 81A-11, 82A-10 and 82A-11, and 83A-10 and 83A-11 respectively, at positions that are at the angle γ in both the clockwise direction and the counterclockwise direction with respect to the surfaces 84, 85 and 86. Each of the sheet paper feed apparatus 81A, 82A and 83A firstly adhere the sheet paper, due to the openings 81A-11, 82A-11, and 83A-11 that are shifted in the clockwise direction, and apply a feed force in the direction inclined downwards with respect to the sheet feed surface 22, due to the openings 81A-10, 82A-10 and 83A-10 that are shifted in the counterclockwise direction. In the present embodiment as well, the sheet paper is fed without rising from the sheet feed surface 22 and is fed without the likelihood of paper misfeed occurring. The following is a description of a primary embodiment of the sheet paper feed apparatus of the present invention, and the action thereof. FIG. 12 is a view of such an embodiment. A roller 102 is provided on a hollow member 101 so as to be rotatable. A negative pressure source 103 is provided so as to communicate with the hollow member 101. The roller 102 is formed with many holes 104 around its entire periphery. The hollow member 101 is formed with a single opening 107 that opposes the paper peeling portion 48 on the peripheral surfaces of the photosensitive drum 11. The holes 104 have their pitch and size determined along with the size of the opening 107 so that the opening 107 is always opposing two or three of the holes 104. The photosensitive drum 11 rotates in the direction shown by the arrow A, and the roller 102 rotates in the direction shown by the arrow D. When the roller 102 rotates, each of the holes 104 opposing the opening 107 produce a suction action and the sheet paper 20 is adhered to the peripheral surface of the roller 102 and is peeled from the photosensitive drum 11 and fed in the direction of the arrow B by the rotation of the roller 102. The following is a description of the action of the holes 104-1 through 104-4 that are lined in the direction opposite to the direction of rotation of the roller 102. The holes 104-1 through 104-4 perform a suction action as shown by lines 110 through 113 in FIG. 13 (A) through (D). In addition, the holes 104-1 through 104-4 perform feed action as shown by the lines 114 through 117 in FIG. 14 (A) through (D). The time that suction action being performed by adjacent holes of the holes 104-1 through 104-4 partially overlaps. In FIGS. 13 and 14, the time t indicates the time that suction action are overlapped. Because of this, the suction force due to the holes 104-1 through 104-4 is continuously applied without interruption, as shown by the lines 118 of FIG. 13 (E). Also, the feed force due to the holes 104-1 through 104-4 is continuously applied without interruption, as shown by the lines 119 in FIG. 14 (E). Accordingly, the apparatus 100 applies a peeling force and a feed force to the paper peeling portion 48. As a result, the peeling of the sheet paper 20 from the photosensitive drum 11 is performed much more definitely than in the case of a conventional embodiment, and the sheet paper 20 is fed in the direction of the arrow B more stably than conventionally. The following is a description of a sheet paper feed apparatus 120 of one embodiment according to the present invention based on the principle described above, with reference to FIG. 15 through FIG. 19. As shown in FIG. 16, the sheet paper feed apparatus 120 are provided at intervals in the direction of the shaft of the photosensitive drum 11, that is, in the direction shown by the arrow G perpendicularly intersecting with respect to the direction of feed B of the sheet paper. Sheet paper feed apparatus 121 of belt type are provided between adjacent sheet paper feed apparatus 120. FIG. 17 through FIG. 19 are enlarged views of one portion of each of the sheet paper feed apparatus 120. As shown in FIG. 19, a roller 122 is supported on a hollow member 123 by a bearing 124 so as to be rotatable. The roller 122 has two rows of a plural number of holes in zigzag shape. A first row hole group 125-1 comprises holes 125-1-1 through 125-1-N. A second row hole group 125-2 comprises holes 125-2-1 through 125-2-N. Holes 125-1-1 through 125-1-N and holes 125-2-1 through 125-2-N are arranged in zigzag shape. When a predetermined holes is not to be specified, these holes are indicated by the number 125. The hollow member 123 is in fixed engagement with a sleeve 126. A single opening 127 is formed in the hollow member 123 and sleeve 126 so as to oppose the paper peeling portion 48 on the peripheral surface of the photosensitive drum 11 (refer to FIG. 15). The opening 127 has a size that spans the first row and the second row of holes described above. The size of the opening 127 and the pitch of the holes 125 are determined so that the opening 127 always opposes three or four of the holes 125. In FIG. 18, the holes 125-1-2, 125-1-3 and 125-2-2 and 125-2-3 oppose the opening 127. The terminal side of the hollow member 123 communicates with the negative pressure source 129. The roller 122 forms a unit with a pulley portion 122a around which a belt 131 is wound. In FIG. 15, the photosensitive drum 11 is rotated in the direction indicated by the arrow A, and the roller 122 rotates by way of the belt 131 at the same speed as the photosensitive drum 11 and in the direction indicated by the arrow D. In addition, the negative pressure source 129 also operates. While the roller 122 is rotating, three or four of the holes 125 are always opposing the opening 127. Because of this, the negative pressure source 129 always has a continuous suction force operating with respect to the sheet paper 20 and the rotation of the rollers 122 act to continuously feed the sheet paper 20. Accordingly, even though the feed speed of the sheet paper 20 is relatively higher when compared to the conventional apparatus, the sheet paper 20 is definitely peeled and conveyed by the photosensitive drum 11. In addition, the holes 125 are in two rows in a zigzag shape and so when compared to the case where there is only one row of holes, it is sufficient to have a small opening opposing the three holes. Because of this, this portion of the suction force acts concentratedly to the paper peeling position 48 and the sheet paper 20 is definitely peeled from the drum 11. The apparatus 120 having the configuration described above is provided in plural at equidistant intervals in the direction of the shaft of the photosensitive drum 11 and the sheet paper 20 is sucked at these plural number of places across the width thereof and is peeled from the photosensitive drum 11 and fed definitely across its entire width. As shown in FIG. 15 and FIG. 16, the sheet paper feed apparatus 121 has a structure where a belt 131 having many holes is fitted around the pulley portion 122a and the rollers 132 and 133 (as shown by the double-dotted line in FIG. 16). An arc-shaped block 136 is provided, which is convex in the upwards direction and has a ventilation groove 134 on the upper surface thereof. Along the block 136, there is provided with a plural number of guide rollers 135 to guide the belt 131. Furthermore, the ventilation groove 134 described above communicates with the negative pressure source 129. The belt 131 runs in the direction of the arrow I at the same speed as the peripheral speed of the roller 122 and a suction force acts in the region running on the block 134. Accordingly, the sheet 20 that has been peeled and conveyed by the apparatus 120 is quickly adhered to the belt 131 and is fed in the direction of the arrow I. The suction force due to the negative pressure source 129 also acts on the belt 131. Even if the belt 131 is pressed, the belt 131 is actually guided by the guide roller 135 and runs with a comparatively light load. As shown in FIG. 16, this sheet paper feed apparatus 121 is provided in a plural number, between adjacent apparatus 120, in the direction of the shaft of the photosensitive drum 11 and performs the smooth an definite feed of the sheet paper 20 after it has been peeled from the photosensitive drum 11. Further, the present invention is not limited to these embodiments, but various variations and modifications may be made without departing from the scope of the present invention. It will be clear to the skilled man that a hybrid of the two embodiments may be constructed and this can be done in two ways. The first is to construct a sheet feed apparatus wherein separate ones of the plurality of rollers are made according to different embodiments. The second is to build a single roller in which the opening from the fixed hollow shaft is tilted in the direction of paper feed and in which at least one hole of the plurality of holes of the roller is always opposing the opening.

Claims: An image forming apparatus comprising means for separating a sheet of paper from a toner image carrier and feeding said sheet of paper, to which a toner image formed on said toner image carrier has been transferred wherein the said means has a plurality of rollers (102) that rotate in the direction of sheet paper feed and which have a hollow fixed centre shaft (101) that has an opening (107) on a side of the surface of sheet paper that is fed, a plurality of holes (104) around their periphery in contact with the shaft (101) and a negative pressure source (103) communicating with said hollow fixed centre shaft, rotation of said roller causing said peripheral holes to successively communicate with said opening, thus creating a suction action to adhere and feed said sheet of paper, wherein said hollow fixed center shaft is disposed so as to confront said toner image carrier at a position where said paper is to be separated from said toner image carrier characterised in that said rollers are formed so that at least one of said plurality of holes is always effectively opposing said opening (107) of said hollow fixed centre shaft while said roller is rotating, thus creating a suction action to adhere and feed said sheet of paper continuously and without interuption. An image forming apparatus as claimed in claim 1, wherein a plurality of holes of said roller are formed in two zigzag-shaped rows (125-1, 125-2) on a peripheral surface of said roller such that, relative to a longitudinal axis of the roller, a hole in one row is not aligned with any adjacent hole in the other row and, said opening (127) of said hollow fixed centre shaft is of a size to span both rows (125-1, 125-2) of said holes such that said two zigzag-shaped rows and said opening are arranged so that holes of both of the zigzag-shaped rows always communicate with said opening of said hollow fixed shaft. An image forming apparatus according to claim 1 or claim 2 wherein additionally said hollow fixed centre shaft (63,101) of at least a first of the said plurality of rollers has said first opening (66,107) at a position shifted by a predetermined angle (β) in the direction of sheet feed (C) with respect to a line (68) that is vertical with respect to said sheet paper feed surface as it comes into contact with the roller (22,102) and passes through the centre (67) of said hollow fixed centre shaft (63,101). An image forming apparatus as claimed in claim 3 wherein the predetermined angle (β) is substantially 10 degrees. An image forming apparatus having rollers (81-2, 82-2, 83-2) as claimed in claim 3 or 4, the hollow fixed centre shaft of any one of the said plurality of rollers having a second opening at another position shifted at a second predetermined angle (γ) opposite the direction of sheet paper feed with respect to said vertical surface (86). An image forming apparatus as claimed in claim 4 wherein said second predetermined angle (γ) is substantially 10 degrees. An image forming apparatus as claimed in any preceding claim, further comprising guides (88) extending along said sheet paper feed surface and supporting and guiding sheets of paper that are fed. An image forming apparatus as claimed in any one of the preceding claims, wherein a plurality of sheet paper feed apparatus (82,83) are provided in the direction of feed (C) of the sheet paper. An image forming apparatus as claimed in any one of the preceding claims wherein at least a second of said rollers is so formed that at least one hole of said plurality of holes around the periphery is always effectively opposed to said first opening in said hollow fixed centre shaft whilst said roller is rotated. An image forming apparatus as claimed in claim 1 wherein said hollow fixed centre shaft is positioned so that said opening (107) opposes a photosensitive drum at a paper peeling portion thereof, thus creating a continuous suction action to adhere to the rotating photosensitive drum, and feed, a portion of said sheet paper approaching the paper peeling portion of the drum.

Inventors: HIRAO NAOTO, HIRAO, NAOTO
Applicants: FUJITSU LTD, FUJITSU LIMITED
Application year: 1991
Main classification: B65H5
IPC codes: B65H5