FRICTION PAD FIXTURE

Abstract: The present invention has adopted a fixture as its principle device means for urging a friction pad (12) with pressure against the outer circumferential surface of a paper feed roller (8) disposed in an image forming appara­ tus to prevent duplicated paper feed. The fixture (B) ac­ cording to the present invention comprises a first sup­ port member detachably mounted on the body of said im­ age forming apparatus characterized in that said first support member is provided with a second support member for movably carrying said friction pad (12) together with a resilient means for urging said second support member against said paper feed roller (8). The present invention has adopted a method as its principle operational means to replace said friction pad fixture (B) including the resilient means according to operated papers different in kind.

Description: 1. Field of the Invention This invention relates to a fixture for a friction pad and its operational method used for applying pressure on the circumferential surface of a paper feeding roller provided in image forming apparatus like copiers, printers, facsimile devices and the like to prevent copy papers from being fed in duplication. 2. Description of the Prior Art There has been conventionally known a fixture arrangement of this kind for a friction pad used for copiers as shown in Fig. 5. In the conventional fixture arrangement A shown in Fig. 5, a friction pad 12 is disposed at a location on a frame 7' which is located opposite to a paper feed roller 8 provided on a snatch frame 7 of a clam shell type. The friction pad 12 is secured to a pad holder 13 that is supported vertically movable in a mounting opening 11 in the surface of frame 7' and is always elastically urged against the paper feed roller 8 by a spring not shown. At an upper portion of frame 7' there is provided an advancing feed roller 30 whose outer circumferential surface comes into contact therewith. This advancing feed roller 30 is provided for feeding copying papers carried on a stack table 9 into a nipping area between said paper feed roller 8 and friction pad 12. Advancing feed roller 30 is actuated to rotate continuously until a copying process has been completed once the copy button is depressed regardless of the presence of copying papers on said stack table 9. The friction pad 12 is replaced when worn out excessively by the frictional encounter with copying papers to prevent faults such as paper feeding errors or abnormal noise. In the conventional fixture arrangement A thus constructed, however, to replace the friction pad 12 requires the removal of the paper feed roller 8 from the frame 7 and further, the disassembly of parts including the pad holder 13 and the spring not shown within the mounting opening 11 since they are assembled within said mounting opening 11 together with the friction pad 12. This structure necessitates a high skill to replace the friction pad 12, which replacement conventionally is performed by a service engineer dispatched from a manufacturer involved. The arrangement of the paper feed roller 8 and the friction pad 12 aims at sorting a plurality of copying papers inserted between them by the advancing feed roller 30 and advancing only one paper that is nearest the paper feed roller 8 (the uppermost one). The duplication-free handling of copying papers like this is performed in such a way that the difference in coefficient of friction among the paper feed roller 8, copying paper, and friction pad 12 is utilized to feed the uppermost paper by the paper feed roller 8 while braking is applied to the carry of copying papers by the friction pad 12. Because of this there occurs a duplication paper feed when different frictional forces among these three elements (according to the difference in coefficient of friction) mentioned above change. The difference in these frictional forces will slightly change according to the pressure applied to the paper feed roller 8 by the friction pad 12 (pad pressure), the material of the pad as well as the kind of copying papers used. However, since a highly skillful technique is required to replace the friction pad in the conventional fixture arrangement of Fig. 5, users cannot readily replace the friction pad with the one optimum for another kind of paper to be used or adjust the pad pressure, and a service engineer is required every time such an operation is to be performed. From DE-A-3 328 872 a friction pad fixture for urging a friction pad with pressure against the outer circumferential surface of a paper feed roller disposed in an image forming apparatus to prevent duplicated paper feed is known. This prior fixture comprises a first support member mounted in a mounting opening provided in a frame of the image forming apparatus, a second support member swingably mounted on the first support member for movably carrying said friction pad, and a resilient means provided on the first support member for urging said second support member and thus said friction pad toward, respectively against, said paper feed roller. The first support member apparently is fixedly connected to the machine frame of the image forming apparatus. The latter likewise applies to a further known friction pad fixture (IBM Technical Disclosure Bulletin, Vol. 19, No. 6, November 1976, pages 1976-1977) in which, to permit periodic replacement of the friction pad, a first support member is provided on which a second support member, having fixed thereto the friction pad, is pivotally and detachably mounted by a pair of tabs engaging pins carried by the first support member. These tabs are provided with open slots thereby facilitating rapid replacement of the second support member together with the friction pad. The present invention is aiming at eliminating the above mentioned problems and providing an improved fixture for a friction pad and its operational method in which the replacement of the friction pad or adjustment of the pad pressure is readily performed by an operator without the help of a service engineer. SUMMARY OF THE INVENTION The present invention, in conformity with one aspect thereof, provides for a friction pad fixture for urging a friction pad with pressure against the outer circumferential surface of a paper feed roller disposed in an image forming apparatus to prevent duplicated paper feed, said fixture comprising: a first support member mounted in a mounting opening provided in a frame of the image forming apparatus, a second support member swingably mounted on the first support member for movably carrying said friction pad, and a resilient means provided on the first support member for urging said second support member and thus said friction pad toward, respectively against, said paper feed roller, which fixture is characterized in that said first support member has engaging hooks to engage with the frame for detachably holding the fixture on said frame when it is mounted within the mounting opening, and that said second support member, said friction pad, said resilient means and said first support member are detachable integrally from said frame. The subject invention, according to a further aspect thereof, provides for a method of using a friction pad fixture for urging a friction pad with pressure against the outer circumferential surface of a paper feed roller disposed in an image forming apparatus to prevent duplicated paper feed, said fixture comprising: a first support member mounted in a mounting opening provided in a frame of the image forming apparatus, a second support member swingably mounted on the first support member for movably carrying said frictionpad, and a resilient means provided on the first support member for urging said second support member and thus said friction pad toward, respectively against, said paper feed roller, which method is characterized in that the first support member is provided with engaging hooks to engage with the frame for detachably holding the fixture on said frame when it is mounted within the mounting opening, and that said friction pad fixture or said resilient means is replaced according to the kind of paper to be fed. The friction pad fixture of the subject invention permits easy replacement of the friction pad by removing the first support member, which is detachably mounted on the body of the image forming apparatus,, together with the second support member, the friction pad and the resilient means. Such a replacement method will prevent fault including paper feed failure caused by the abrasion of the friction pad or the first support member and abnormal noise. Further, when the fixture or the resilient member is made to be replaced according to various operated papers different in kind, an optimum duplicated-feed preventive function may be realized. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of a copying machine comprising a friction pad fixture according to one embodiment of the present invention; Fig. 2(a) is a perspective view of the friction pad fixture of Fig. 1; Fig. 2(b) is a sectional view along the line C-C' of Fig. 2(a); Fig. 3 is an exploded perspective view of the friction pad fixture of Fig. 1; Fig. 4 is a schematic side sectional elevation of the copying machine shown in Fig. 1; and Fig. 5 is a perspective view of a copying machine comprising a conventional friction pad fixture. DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Referring now to the accompanying drawings one embodiment of the present invention will be described for better understanding of the invention. In the following description, the elements of the embodiment similar to those of the conventional friction pad fixture arrangement A shown in Fig. 5 are given the same reference numerals. Reference now is made to Fig. 4 showing a copying machine 3 to which the present invention may be applied. The copying machine 3 is of a simple type which utilizes paper feed by way of a cassette a and a stack table 9 and discharge by a paper discharge tray b which receives copied papers. The original carried on a moving table c is impinged with a light beam from a light source d, and the light reflected on the surface of the original is focused on the surface of a photosensitive drum f through a lens array to form an electrostatic latent image on the photosensitive surface thereof. The photosensitive drum f rotates clockwise as shown by the arrow in Fig. 4 and the electrostatic latent image is developed into a toner image at a developing portion g, and further carried to a transferring portion h. Meanwhile, a copying paper fed from the cassette a by a paper feed roller i is turned in its travelling direction by approximalety 180 degrees at a feed roller j,and its leading edge is inserted into the gap between resist rollers k. Copying paper fed from the stack table 9 is carried toward a paper feed roller 8 by an advancing feed roller 30 as previously described. The copying paper fed by the paper feed roller 8 is then supplied to the resist rollers k. Upon leaving the resist rollers k, the paper passes the transferring portion h where the toner image on the surface of the photosensitive drum f is transferred onto the paper. The paper with the toner image is further carried to fixing rollers m through a conveyer belt ℓ where the toner image is fixed on the paper. The paper is then finally discharged to the paper discharge tray b. The friction pad fixture B according to this embodiment (hereinafter referred to as "fixture B") is, as shown in Fig. 1, Fig. 2(a), Fig. 2(b) and Fig. 4, composed of a stack holder (first support member) 15 which is detacheably mounted in a mounting opening 16 notched in a frame 7' at a place opposite to the paper feed roller 8 provided in a frame 7, a pad holder 13 (second support member) for movably supporting a friction pad 12 on the stack holder 15, and a spring 14 (resilient means) for urging the pad holder 13 toward paper feed roller 8 with respect to stack holder 15. The stack holder 15 is provided with a housing 18 to hold the friction pad 12, pad holder 13 and spring 14, with both sides of housing 18 being provided with mounting holes 19 for receiving a shaft 13a of the pad holder 13 later described, and engaging holes 20 for receiving pawls 13b (see Fig. 3). A guide portion 22, which is provided on the upstream side in the paper feed direction, to form the bottom surface of housing 18 is made slanted for ease of removal of housing 18 from mounting opening 16, and an upstream end 25 has a tapered surface for preventing the leading edge of the copying paper fed in the direction shown by the arrow 4 from being caught by the end 25. The housing 18 has at its upper central portion a slot 21 for receiving a switch 27 (see Fig. 1) to detect the presence of the copying paper thereon when the housing 18 is mounted in the mounting opening 16 (see Fig. 1). A supporting portion 26 provided at an upstream location extended from the housing 18 in the paper feed direction has engaging hooks 24 to engage with an end of a body 3a for holding the housing 18 on body 3a when the housing 18 is mounted within the mounting opening 16. The supporting portion 26 also has at its extreme end a handle 23. The advancing feed roller 30 continuously rotates during a copying operation with it being in contact with the upper surface of a neck portion 15a of the support member 26 of stack holder 15. The pad holder 13 has, as shown in Fig. 2(a), Fig. 2(b) and Fig. 3, at its upper surface the friction pad 12 secured thereto. At both sides of pad holder 13 the pawls 13b are formed to engage with the engaging holes 20 of housing 18 for retaining the pad holder 13 within the housing 18 when it is held therein. In addition, the pad holder 13 has at its upstream sides the shaft portions 13a to be fit into the mounting holes 19 of housing 18 for swingingly supporting the pad holder 13. The fixture B is assembled in such a way that the pad holder 13 is mounted on the top end of the spring 14 which is engaged with a protrusion 17 within the housing 18 by fitting the shaft portions 13a into the mounting holes 19 of the housing 18 with these portions being flexed in the directions shown by the arrows 28, and further by fitting the pawls 13b into the engaging holes 20. The fixture B thus assembled can be installed in the copying machine 3 by inserting it in the direction shown by the arrow 4 from the upstream side in the paper feed direction, into a gap formed between the paper feed roller 8 and the body 3a when the stack table 9, that is detachably installed to the body 3a in the direction shown by the arrow 10, is removed to open the frame 7. The stack table 9 is then replaced to the body 3a with the handle 23 of stack holder 15 located below the stack table 9. In the fixture arrangement thus constructed, when the friction pad 12 is required to be replaced due to its excessive abrasion exceeding the specified amount, or to be replaced with one having a different coefficient of friction for changing the kind of paper to be used, an operator will follow the steps indicated below: First of all, the operator removes the stack table 9 from the body 3a of the copying machine 3 and makes a gap between friction pad 12 and paper feed roller 8 by opening the frame 7 as shown in Fig. 1. The operator then gets hold of the handle 23 of the stack holder 15 and pulls it in the direction shown by the arrow 5 to easily remove the fixture B from the body 3a. A new fixture B is then installed to the body 3a by reversing the above mentioned procedures for the removal, that is, by inserting it into the body 3a in the direction shown by the arrow 4, mounting the housing 18 of the stack holder 15 in the mounting opening 16, and engaging the hooks 24 with the end of the body 3a. Thus the friction pad 12 is replaced by way of changing the fixture B. This makes it possible to take appropriate corrective actions for those faults including an abrasion in the friction pad 12, an abnormally noisy operation due to the worn neck portion 15a of the stack holder 15 caused by its frequent contact with the advancing feed roller 30, and a lowered paper feed ability. The pad holder 13 can, of course, individually be replaced. The fixture B according to the present invention thus constructed may be replaced at the same time when an integrated unit comprising a developing device, cleaning device and the like in the copying machine, is replaced. For selecting a fixture B various in coefficient of friction and pad pressure dependent on the kind of paper used, it is also feasible to prepare a plurality of sets of fixture B which are composed of various combinations of friction pads with different coefficients of friction and springs with different compression pressures so that the optimum one of the fixtures B can be selected and replaced according to the kind of copying paper to be used. When only the pad pressure is required to be changed, the spring 14 may solely be replaced by removing the fixture B. It should be understood that the loading and unloading direction of the fixture B for replacement of the friction pad 12 will not be limited to the direction shown in the description of the above embodiment, that is, parallel to the paper feed direction. Since the feed roller 8 is mounted on the frame 7 of the copying machine 3 shown in the above described embodiment, there is formed a gap between the feed roller 8 and the friction pad 12 when the frame 7 is opened to make it easy to replace the friction pad 12. However, in the case of a copying machine of the kind in which there is formed no gap between these elements, a guide rail which slidably supports the fixture B may be provided for ease of its replacement.

Claims: A friction pad fixture (D) for urging a friction pad (12) with pressure against the outer circumferential surface of a paper feed roller (8) disposed in an image forming apparatus (3) to prevent duplicated paper feed, said fixture (D) comprising: a first support member (15) mounted in a mounting opening (16) provided in a frame (7') of the image forming apparatus (3), a second support member (13) swingably mounted on the first support member for movably carrying said friction pad (12), and a resilient means (14) provided on the first support member (15) for urging said second support member (13) and thus said friction pad (12) toward, respectively against, said paper feed roller (8), characterized in that said first support member (15) has engaging hooks (24) to engage with the frame (7') for detachably holding the fixture (D) on said frame (7') when it is mounted within the mounting opening (16), and that said second support member (13), said friction pad (12), said resilient means (14) and said first support member (15) are detachable integrally from said frame (7'). A friction pad fixture (D) as set forth in claim 1, wherein a portion (15a) of said first support member (15) located upstream of the mounting portion of said second support member (13) in the paper feed direction is made to keep in contact with an advancing feed roller (30). A method of using a friction pad fixture (D) for urging a friction pad (12) with pressure against the outer circumferential surface of a paper feed roller (8) disposed in an image forming apparatus (3) to prevent duplicated paper feed, said fixture (D) comprising: a first support member (15) mounted in a mounting opening (16) provided in a frame (7') of the image forming apparatus (3), a second support member (13) swingably mounted on the first support member for movably carrying said friction pad (12), and a resilient means (14) provided on the first support member (15) for urging said second support member (13) and thus said friction pad (12) toward, respectively against, said paper feed roller (8), characterized in that the first support member (15) is provided with engaging hooks (24) to engage with the frame (7') for detachably holding the fixture (D) on said frame (7') when it is mounted within the mounting opening (16) and that said friction pad fixture (D) or said resilient means (14) is replaced according to the kind of paper to be fed. A method of using a friction pad fixture (D) set forth in claim 3, wherein a portion (15a) of said first support member (15) located upstream the mounting portion of said second support member (13) in the paper feed direction (4) is made to keep in contact with an advancing feed roller (30).

Inventors: HIMEGI, TOORU
Applicants: MITA INDUSTRIAL CO. LTD.
Application year: 1988
Main classification: B65H3
IPC codes: B65H3, G03G15