Abstract:
An upper skive plate and a method for quickly installing and removing the skive plate in the fuser section of an electrophotographic apparatus without damaging the roller therein. The skive plate carries a plurality of skives which strip a sheet of paper from the roller during operation of the apparatus. To install the skive plate, guide openings in the plate are positioned on locator pins which are affixed to the load arms which, in turn, support the roller. The plate is moved forward on the pins and is releasably latched in position by a pair of rotatable pawls on the plate which cooperate with clamping surfaces on the load arms. To remove the skive plate, this procedure is reversed.

Description:
FIELD OF THE INVENTION 
     The present invention relates to the installation of the upper skive plate in the fuser section of a electrophotographic copier/printer apparatus and in one of its aspects relates to an upper skive plate and to an assembly for removing and replacing the upper skive plate in the fuser section of an electrophotographic machine wherein the assembly prevents the blades on the skive plate from cutting or digging into the pressure roller of the fuser section while the upper skive plate is being installed and/or removed. 
     BACKGROUND OF THE INVENTION 
     In a typical electrophotographic machine (e.g. copier, duplicators, printers, etc.), a continuous loop of photoconductor film is commonly used to transfer an image from an input section onto a receiving medium (e.g. a sheet of paper). The film is initially charged and then passes through an input section where an image (i.e. analog or digital) is projected onto the charged film. The film then moves through a developing section where a toner is applied to the charged image, and on through an image transfer section where the image is transferred to the sheet of paper or other medium. The paper is subsequently passed through a fuser section where the toner forming the image is fixed to the paper by elevated temperature and pressure. This is typically accomplished by passing the paper between two, opposed rollers in the fuser section, i.e. a pressure roller and a fuser roller, one of which is heated. 
     In fuser sections such as described above, the nip between the pressure and fuser rollers is extremely tight. To ensure that the paper will continue on through this nip and not stick to one or the other of the rollers, “skive plates” (i.e. upper and lower skive plates) are normally provided to strip the paper off the rollers (i.e. fuser and pressure rollers, respectively) after the toner is fused onto the paper. Each plate carries a plurality of thin, extremely sharp “skives” (i.e. blades) (e.g. 0.004 inches thick) which effectively ride on its respective roller. These plates are rigidly mounted near the rollers at a precise location and angle to provide the proper stripping force without digging or gouging into the roller. As will be appreciated in this art, during assembly and service of the electrophotographic machine, the skive plates are frequently removed and then reinstalled. During this operation, the skive plates must be carefully handled so that the sharp skives do not gouge the respective rollers. 
     In known, prior art machines of this type, the installation of these skive plates presents a number of problems for a service technician, since there is usually nothing in the fuser section which prevents the skives from touching and possibly damaging the rollers if a technician mishandles the skive plate during a service operation. For example, in prior art fuser sections, the upper skive plate, to which the present invention is directed, must be carefully manipulated and then held in the proper position by a single service technician until he can secure the upper plate with screws or the like. While a competent technician can be trained to carry out the required, precise procedures, they still require the use of special tools and more importantly, involve the risk of human error which can lead to severe damage to the pressure roller. 
     Accordingly, those skilled in this art will recognize the need of simplifying the installation of the upper skive plate in the fuser section of an electrophotographic machine and making such installation effectively “fool-proof” to prevent the accidental gouging of the pressure and fuser rollers during the installation. Further, it is highly beneficial if the servicing of the upper skive plate can be carried out by a single technician without the need of special tools. 
     SUMMARY OF THE INVENTION 
     The present invention provides a fuser section for an electrophotographic apparatus which includes an upper skive plate which, in turn, can be easily and quickly installed in and removed from within the fuser section without the risk of accidentally damaging the pressure roller and the method for installing the skive plate in the fuser section. The upper skive plate carries a plurality of skives (i.e. sharp blade-like elements) thereon which are designed to ride on the pressure roller which, in turn, is rotatably mounted between two pivoted, load arms in the fuser section and strip sheets of paper off the pressure roller as the paper passes thereover. 
     Basically, the upper skive plate of the present invention is comprised of a plate having a front, rear, top, bottom, and two ends. A plurality of skives (i.e. sharp blade-like members) are mounted on and spaced across said bottom of said base plate so that the skives will ride on said pressure roller when said upper skive plate is in its operable position within the load arms of the fuser section. The skive plate has guide openings which cooperate with locator pins on the load arms to guide the plate to its operable position. The plate has at least one releasable latch thereon which releasably latches the plate in place once the plate has been properly positioned. 
     More specifically, the upper skive plate has a pair of releasable latches, one on each end of the plate. Each of these latches has a locking pawl which is affixed to one end of a shaft which, in turn, extends through the plate. A handle is fixed on the other end of the shaft and can move longitudinally with respect to the shaft but can not rotate with respect thereto. A spring, e.g. Belleville washer, is positioned between the handle and the shaft, the compression of which provides the clamping force necessary to latch the plate in place. 
     A guide assembly is affixed to each of the load arms and is comprised of a vertical guide element and a lateral guide element, the latter having a back surface thereon. A tapered, locator pin extends from the front of the back surface and is adapted to cooperate with guide openings in the upper skive plate to guide the plate to its operable position between the load arms. Once the plate is moved along the locator pins and against the front of the back surface, the latches are rotated to move the locking pawls in behind a respective clamping surface which, in turn, is on the rear of the back surface. As the pawls are moved onto the clamping surfaces, they will compress their respective springs thereby providing the force necessary to securely latch the upper skive plate in its operable position. To remove the upper skive plate, the procedure is merely reversed. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The actual construction operation, and apparent advantages of the present invention will be better understood by referring to the drawings, not necessarily to scale, in which like numerals identify like parts and in which: 
     FIG.  1 . is a schematic view of an electrophotographic apparatus (e.g. copier/printer machine) in which the present invention can be incorporated; 
     FIG. 2 is a simplified, partial sectional view of the fuser section lying within line  2 — 2  of FIG. 1 showing the upper skive plate of the present invention in its operable position therein; 
     FIG. 3 is a perspective, rear view of the upper skive plate of the present invention; 
     FIG. 4 is a perspective view of a portion of one of the pivoted arms on which one end of the pressure roller (removed) is carried and on which one of the locating pins for the upper skive plate is affixed; 
     FIG. 5 is a top view of one of the latch members on the upper skive plate of FIG.  3 : 
     FIG. 6 is a cross-sectional view taken along line  6 — 6  of FIG. 5; 
     FIG. 7 is an enlarged, front perspective view, partly broken away, of one end of the upper skive plate of FIG. 3 in a latched, operable position within the fuser section; and 
     FIG. 8 is an enlarged, rear perspective view, partly broken away, of the upper skive plate of FIG. 3 in a latched, operable position within the fuser section. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring briefly to FIG. 1, a typical electrophotographic apparatus or machine  10  (e.g. copier, duplicator, printer) of the kind that has an endless photoconductor member  11  (e.g. photographic film) which moves through a closed loop past a charging station  12 , a an expose or input station  13 , a developing station  14 , a transfer station  15 , and an erase/clean section  16 . A copy medium (e.g. a sheet S of paper) is fed from a supply (not shown) through transfer station  15  where the toner image on the film  11  is transferred to the paper S. The paper S is then fed between a fusing roller  21  and a pressure roller  22  in fuser section  20  to fix the toner image on the paper S before the paper exits the machine. 
     FIG. 2 is a simplified, sectional view of a portion of the fuser section  20  of FIG. 1 to which the present invention is directed. As illustrated, fuser section  20  is comprised of a frame or housing  25  in which pressure roller  21  and fuser roller  22  are rotatably mounted. Pressure roller  21  is rotatably mounted between two load arms  23  (only one shown) which, in turn, are pivoted in housing  25  about pivot  24  and each is biased towards the fuser roller  22  to thereby maintain contact between the pressure and fuser rollers during operation of the fuser section. 
     An upper skive plate  26  and a lower skive plate (removed and not shown in FIG. 2) carry a plurality of skives which in turn, are positioned to effectively ride on pressure roller  21  and fuser roller  22 , respectively. These skives are thin blades (e.g. 0.004 inch thick) and are extremely sharp and are designed to strip the paper S from the respective rollers as the paper passes therethrough. Front and rear latches  28 ,  29  are used to releasably latch the lower skive plate in its operable position within housing  25 . For a complete description of the lower skive plate and its positioning and latching mechanism  27 , see U.S. Pat. No. 6,295,436 issued Sep. 25, 2001. 
     Upper skive plate  26  is positioned and secured in housing  25  as shown in FIG.  4 . As best seen in FIG. 3, upper skive plate  26  is comprised of a substantially, rectangular plate  30  having an upturned portion  31  at either end thereof. Plate  30  also has an elongated, perpendicularly-extending base element  32  which is secured to the bottom of plate  30  and which extends substantially across the width thereof. Base element  32  has a plurality of spaced openings  34  therein (seven shown), each of which is adapted to receive a skive plate  33 . Skives  33  (two shown in dotted lines in FIG. 3) are thin (e.g. 0.004 inches) blade-like members which are very sharp and which, when in an operable position, are adapted to strip a sheet of paper off pressure roller  21  and thereby keep it from sticking thereto. 
     Base plate  30  has a releasable latch  35  at each end therein near the top thereof. As best seen in FIG. 5, latch  35  is comprised of a locking pawl  36  having a shaft  37  extending therefrom. Shaft  37  has a reduced and “D-shaped” portion  37   a  (FIG. 6) which, in turn, extends through a matching Dshaped opening  39  in handle  40 . It can be seen that while shaft  37   a  is free to move longitudinally or axially within opening  39 , it can not rotate therein. While a D-shaped connection between shaft portion  37  and handle  40  has been shown, it should be recognized that other shaped connections (e.g. square, triangular, etc.) could be used so long as the shaft will not rotate with respect to handle  40  but will still allow longitudinal movement therebetween. Since the area within housing  25  in which the upper skive plate is located may be extremely hot, at least the knob on handle  40  is preferably molded from a heat-resistive material (e.g. plastic) to alleviate the possibility of a technician burning himself during servicing of the skive plate. 
     Pawl  36  is positioned from the rear through an opening in plate  30  and the opening  39  in handle  40  is positioned over portion  37   a  of shaft  37  on the front side of plate  30 . A compression spring, e.g. Belleville washer  41 , is positioned around shaft  37   a  and on top of handle  40  and is secured in that position by screw  42  which, in turn, forms an extension of shaft  37   a.  Washer  41  will normally bias shaft  37  away from handle  40  (i.e. biases locking pawl  36  towards the rear of plate  30 , for a purpose discussed below. Plate  30  has a handle or grip  43  centrally mounted thereon which is used by a technical in handling the upper skive plate  26 . Also, a guide opening  44  is provided through plate  30  at one end and a guide slot  45  is provided at the other end for purposes described below. Plate  30  has two tabs  46  thereon for limiting the rotation of handle  40  between a fully latched position and a fully released position. 
     Affixed to each load arm  23  is a guide and locator assembly  50  (FIG.  4 ). It is important to mount assemblies  50  on the pivoted load arms  23  since the exact position of the pressure roller  21  and the fuser roller  22  may vary subtly whereon the axes of the two rollers may not always be exactly parallel to each other. When this occurs, the upper skive plate  26  must, nevertheless, remain exactly parallel to axis of the pressure roller  21  and not dig into and constrain movement of the pressure roller. Since each end of the pressure roller  21  is mounted by means of bearings on the end of each respective load arm  23  and since the skive plate is carried by these same load arms, a constant relationship between the upper skive plate and the pressure roller will be maintained even when the axes of the roller are not parallel. 
     Since each assembly  50  is a mirror-image of the other, only one will be described in detail. Each assembly  50  is comprised of a lateral guide element  51 , affixed to the inside of respective load arm  23 , and having a back surface  52  thereon and a vertical guide element  53  affixed to the top of arm  23 . Back surface  52  has a tapered, locator pin  55  extending from the front thereof and has a clamping surface (i.e. button  56 ) on the rear thereof. 
     In installing upper skive plate  26 , it is extremely important that the plate not be inadvertently tipped towards the pressure roller  21  and thereby risk that the sharp skives  33  come into contact with the roller. With the present invention, this is not likely to ever happen. To install upper skive plate  26  into housing  25 , the technician holds plate  26  by grip  43  and positions it against lateral guides  51  and vertical guides  53  on respective load arms  23 . As upper plate  26  is moved forward, lateral guides  51  will keep the plate effectively centered while vertical guides  53  will direct opening  44  and slot  45  onto their respective locator pins  55 . Opening  44  is substantially the same diameter as that of pin  55  while slot  45  allows some tolerance in lining up the plate between load arms  23 . 
     Once upper plate  26  is pushed all the way onto pins  55  and is flush against back surface  52  of assembly  50 , the handles of latches  35  are rotated downward to rotate locking pawls  36  in behind respective clamping surfaces  56 , thereby releasably latching upper skive plate  26  in an operable position within fuser section  20 . Belleville washer  41  is compressed as handle  40  is rotated and pawl  36  is moved behind surface  56 . The compression of washer  41  provides the high clamping force which is necessary to tightly hold plate  26  in place during operation. Further, by locating the upper skive plate on the locator pins  55  and clamping directly behind the pins, the upper skive plate  26  will rotate on a respective pin when either side of the pressure roller  21  moves up or down relative to the fuser roller  22 . This ensures that the skive plate will remain parallel to the axis of the pressure roller during operation. 
     To remove upper skive plate  26 , the above procedure is reversed. The grip  43  is held by the technician and both latches  35  are rotated to release the skive plate from the assembly  50 . The plate can then be moved back off locator pins  55  and out of housing  25  to complete the removal operation.