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Delivery mechanism, fixing device and image forming apparatusRelated Patent Categories: Sheet Feeding Or Delivering, Delivering, Rotary ConveyorDelivery mechanism, fixing device and image forming apparatus description/claimsThe Patent Description & Claims data below is from USPTO Patent Application 20060170151, Delivery mechanism, fixing device and image forming apparatus. Brief Patent Description - Full Patent Description - Patent Application Claims
BACKGROUND OF THE INVENTION [0001] 1. Field of the Invention [0002] This invention relates to a sheet delivery mechanism in an image forming apparatus such as a printer, copier or facsimile and a fixing device and the image forming apparatus having the sheet discharging mechanism. [0003] 2. Background Art [0004] In the image forming apparatus, it is known that when a sheet with an image formed by an image forming section is delivered or discharged into an output tray, a paper delivery roll pair consisting of a follower roll and pinch roll which sandwich a nip are used. [0005] Until now, a sheet delivery mechanism is known which is a sheet delivery roll serving as an inverting roll for both-side printing, provided with a slope on the side acting when the convex portion of the kicking shape of a pinch roll is inverted (JP-B-7-17295). Another paper delivery mechanism is known in which the rising angle of the convex of the kicking shape on the side acting in delivery is set at 45.degree. or less (JP-A-11-79514). Still another paper delivery has been disclosed in which an elastic blade-like convex is provided so that in sheet feeding the convex is deformed inward in a radial direction and in kicking-out, the convex is acted on the sheet (JP-A-08-246034). [0006] However, if the sheet is discharged with the rear end slanted downward in a certain degree according to the convex in the kicking shape, the sheet interferes with the convex on the downstream side in a rotating direction and floats. Thus, the rear end of the sheet cannot be pushed by the portion of the kicking shape. This led to a problem of poor accommodation due to the leaving the rear end of the sheet. [0007] Further, in order to prevent damage when a thick sheet passes through a nip and poor rotation, it is necessary to reduce the height of the convexes attached to the pinch roll. This requires the performance of kicking out the sheet rear end to be lowered. When the sheet climbs over the convex, this influences the roll nip to generate bending of the sheet. Further, in the case of the elastic blade-like convex, if a fixing roll is arranged in the vicinity of the delivery roll, time-passage deformation was inevitable which is attributable to degradation of the material due to heat or the like. SUMMARY OF THE INVENTION [0008] A first object of this invention is to provide a sheet delivery mechanism which when a sheet is kicked out by a convex attached to at least one of a first roll and second roll of a sheet delivery roll pair, can prevent poor accommodation due to leaving of a sheet rear end without being hindered by another convex located on the downstream side of the convex. [0009] A second object of this invention is to provide a sheet delivery mechanism which when can deliver a thick sheet without damaging it. [0010] In order to attain the above object, the first feature of this invention is to provide a sheet delivery mechanism characterized by including a sheet delivery roll pair consisting of a first roll and a second roll in contact with each other, wherein at least one of the first roll and the second roll is provided with a plurality of convexes formed circumferentially for pushing the rear end of a sheet to be delivered, and one of these plurality of convexes is arranged to be more inside radially than the tangential line drawn from the radial tip of another convex upstream adjacent in the rotating direction to the one convex to the outer periphery of the roll. In accordance with this configuration, even where the sheet rear end delivered may be left on the first roll or the second roll, when the sheet rear end is kicked out by the convex immediately passed a nip, it is not hindered by the convex located on the downstream side of the above convex. This prevents poor accommodation due to the leaving of the sheet rear end. [0011] This invention is preferably a sheet delivery mechanism wherein a portion more upstream than the radial tip of the one convex has a tapered shape with a gradient approximately equal to the tangential line drawn from the radial tip of another convex upstream adjacent in the rotating direction to the one convex to the outer periphery of the roll. In accordance with this configuration, as compared with the case where a portion more upstream than the radial tip of the convex does not have a tapered shape with a gradient approximately equal to the tangential line drawn from the radial tip of another convex upstream adjacent in the rotating direction to the one convex to the outer periphery of the roll, a larger number of convexes can be arranged on the circumference of the roll and the number of times of kicking out the sheet rear end can be increased. This prevents poor accommodation due to the leaving of the sheet rear end. [0012] This invention is preferably a sheet delivery mechanism wherein the distance from the root of the one convex to a rotation center is shorter than the outer diameter of the roll. [0013] In accordance with this configuration, even where the degree of the convex from the outer periphery of the roll body is relatively small, the sheet rear end can be effectively pushed out. This obviates damages on the image on the sheet which is attributable to the convexes. [0014] The second feature of this invention is to provide a sheet delivery mechanism characterized by including a a sheet delivery roll pair consisting of a first roll and a second roll in contact with each other, wherein at least one of the first roll and the second roll is provided, on its roll body, with a plurality of convexes formed circumferentially for pushing the rear end of a sheet to be delivered to shift inwardly in the radial direction through their elastic deformation; and where a sheet, which receives pressure not lower than a predetermined pressure when it passes a nip, passes the nip, the convex passing the same position as the nip in the rotating direction shifts inwardly in the radial direction, and where the sheet, which receives the pressure lower than the predetermined pressure when it passes the nip, passes the nip, the convex keeps its normal convex shape. In accordance with this configuration, when the thick sheet which receives the pressure not lower than the predetermined pressure passes the nip, the thick sheet can be prevented from being damaged owing to the convex shape. Conventionally, if the degree of the convex from the. outer periphery of the roll is increased, the convex must have a lower height permitting the sheet to climb over the convex so that the performance of the convex of kicking out the sheet rear end was limited. But in the above configuration, the degree of the convex can be increased, the performance of kicking out the sheet rear end can be improved. [0015] This invention is preferably is a sheet delivery mechanism wherein the roll body and the convexes are integrally formed of resin, and the convexes are formed in a lightening shape or a shape with recesses on both ends in the axial direction. In accordance with this configuration, as compared with the conventional roll shape, without increasing the production cost and with no time-passage deterioration such as abrasion or settling of the convex, the performance of kicking-out the sheet rear end can be maintained and the image quality can be improved. [0016] This invention is preferably a sheet delivery mechanism wherein the roll body and the convexes are formed separately from each other and made of different materials from each other. In accordance with this configuration, even where the sheet passing distance from the fixing device to the delivery roll pair is so short that the delivery roll is required to have the releasiablity, the image quality and performance of kicking out the sheet rear end can be improved. [0017] This invention is preferably a sheet delivery mechanism wherein the roll body is made of the material selected from the group consisting of tetrafluoroethylene-perfluoroalkylvinylether copolymer (PFA), polytetrafluoroethylene (PTFE) and tetrafluoroethylene-ethylene copolymer (ETFE). For this reason, the roll made of the above material can be given improved slidability and toner releasiablity. [0018] This invention is preferably a sheet delivery mechanism wherein the convexes are made of the material selected from the group consisting of polyacetal (POM), polypropylene (PP) and polycarbonate (PC). For this reason, the convexes can be given improved elastic force and abrasion resistance. [0019] This invention is preferably a sheet delivery mechanism wherein the sheet delivery roll pair serves as an inverting roll for duplex printing. In accordance with this configuration, in the case of duplex printing, in the sheet delivery mechanism, the sheet can be fed out to the inverting path. [0020] This invention is preferably the fixing device wherein the sheet delivery mechanism is internally arranged. In accordance with this configuration, where the sheet delivery mechanism has broken down, the fixing device can be taken out from the image forming apparatus for its replacement or repair. For this reason, as compared with the repair or replacement of the image forming apparatus itself, the cost for repair or replacement can be reduced. [0021] This invention includes an image forming apparatus provided with the sheet delivery mechanism. BRIEF DESCRIPTION OF THE DRAWINGS Continue reading about Delivery mechanism, fixing device and image forming apparatus... Full patent description for Delivery mechanism, fixing device and image forming apparatus Brief Patent Description - Full Patent Description - Patent Application Claims Click on the above for other options relating to this Delivery mechanism, fixing device and image forming apparatus patent application. ###  How KEYWORD MONITOR works... a FREE service from FreshPatents1. Sign up (takes 30 seconds). 2. Fill in the keywords to be monitored. 3. Each week you receive an email with patent applications related to your keywords. Start now! - Receive info on patent apps like Delivery mechanism, fixing device and image forming apparatus or other areas of interest. ### Previous Patent Application: Device for cycling blast or suction air in a sheet processing machine Next Patent Application: Football playing table Industry Class: Sheet feeding or delivering ### FreshPatents.com Support Thank you for viewing the Delivery mechanism, fixing device and image forming apparatus patent info. 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