Abstract:
With a fuser apparatus, for example having a pair of rollers in nip relation to transport a receiver member therebetween, to permanently fix a marking particle image to such receiver member, a skive mechanism for stripping a receiver member adhering to a fuser apparatus roller from the roller, and a mechanism for applying a release oil to the fuser rollers. The skive mechanism includes a plurality of skive fingers formed as elongated, thin, flexible members located so as to engage the fuser apparatus rollers in a manner so as to substantially prevent damage to such associated fuser apparatus rollers. Each of the skive fingers have capillary micro-grooves formed therein for the purpose of channeling release oil away from the respective skive finger tips, thereby substantially eliminating image degradation by build up of the release oil.

Description:
FIELD OF THE INVENTION 
     This invention relates in general to skive fingers for fuser apparatus of reproduction equipment, and more particularly to reproduction equipment fuser apparatus skives which have capillary micro-grooves to substantially prevent build up of image-degrading fluid on the fuser apparatus skive fingers. 
     BACKGROUND OF THE INVENTION 
     In typical commercial reproduction equipment (electrostatographic copier/duplicators, printers, or the like), a latent image charge pattern is formed on a uniformly charged dielectric member. Pigmented marking particles are attracted to the latent image charge pattern to develop such image on the dielectric member. A receiver member is then brought into contact with the dielectric member. An electric field, such as provided by a corona charger or an electrically biased roller, is applied to transfer the marking particle developed image to the receiver member from the dielectric member. After transfer, the receiver member bearing the transferred image is separated from the dielectric member and transported away from the dielectric member to a fuser apparatus at a downstream location. There the image is fixed to the receiver member by heat and/or pressure from the fuser apparatus to form a permanent reproduction on the receiver member. 
     One type of fuser apparatus, utilized in typical reproduction apparatus, includes at least one heated roller and at least one pressure roller in nip relation with the heated roller. The fuser apparatus rollers are rotated to transport a receiver member, bearing a marking particle image, through the nip between the rollers. The pigmented marking particles of the transferred image on the surface of the receiver member soften and become tacky in the heat applied in the roller nip. Under the pressure in the nip, the softened tacky marking particles attach to each other and are partially imbibed into the interstices of the fibers at the surface of the receiver member. Accordingly, upon cooling, the marking particle image is permanently fixed to the receiver member. 
     It sometimes happens that the marking particles stick to the peripheral surface of the heated roller and result in the receiver member adhering to such roller; or the marking particles may stick to the heated roller and subsequently transfer to the peripheral surface of the pressure roller resulting in a receiver member adhering to the pressure roller. It has therefore been a general practice to apply a release oil coating to elements of the fuser apparatus (e.g., the fuser roller and/or pressure roller). The release oil is selected to have properties, well known in the prior art, which will inhibit the sticking of marking particles to the fuser apparatus elements. However, the release oil is not completely effective in preventing receiver members from adhering to the fuser apparatus elements. 
     In view of the receiver member adherence problem, a skive mechanism, including mechanical skive fingers or separator pawls for example, has been employed to engage the respective peripheral surfaces of the fuser apparatus rollers to strip any adhering receiver member from the rollers in order to substantially prevent receiver member jams in the fuser apparatus. Typically a fuser apparatus skive mechanism includes a plurality of skive fingers. The skive fingers are generally formed as elongated members respectively having a relatively sharp leading edge urged into engagement with a fuser apparatus roller. For example, the skive fingers may be thin, relatively flexible, metal shim stock. The respective leading edge of each of the skive fingers is directed in the opposite direction to rotation of the fuser apparatus roller with which such skive finger is associated so as to act like a chisel to strip any receiver member adhering to such roller from the peripheral surface thereof. 
     Skive fingers, oriented as described, as currently found in exemplary fuser apparatus, have a tendency during operation of the reproduction equipment to become wetted with fuser release oil that accumulates on the fingers during the fusing process. The receiver members, bearing images to be reproduced, as they are released from the fuser, will come in contact with skive fingers as they are guided away from the fuser apparatus. The accumulated release oil then becomes wetted to the receiver members during such contact, and the oil is transported back through the elements of the reproduction equipment, particularly when the receiver member is recirculated for forming a duplex reproduction. Some of release oil is then transferred from the receiver members onto the reproduction equipment elements, and may then potentially cause undesirable image defects on subsequently reproduced images. 
     SUMMARY OF THE INVENTION 
     In view of the above, this invention is directed to a fuser apparatus, for example having a pair of rollers in nip relation to transport a receiver member therebetween to permanently fix a marking particle image to such receiver member, a skive mechanism for stripping a receiver member adhering to a fuser apparatus roller from the roller, and a mechanism for applying a release oil to the fuser rollers. The skive mechanism includes a plurality of skive fingers formed as elongated, thin, flexible members located so as to engage the fuser apparatus rollers in a manner so as to substantially prevent damage to such associated fuser apparatus rollers. Each of the skive fingers have capillary micro-grooves formed therein for the purpose of channeling release oil away from the respective skive finger tips, thereby substantially eliminating image degradation by build up of the release oil. 
     The invention, and its objects and advantages, will become more apparent in the detailed description of the preferred embodiment presented below. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     In the detailed description of the preferred embodiments of the invention presented below, reference is made to the accompanying drawings, in which: 
     FIG. 1 is a side elevational view of a reproduction fuser apparatus having a receiver member skive assembly, according to this invention, with portions removed or broken away to facilitate viewing; 
     FIG. 2 is a view, in perspective, of the receiver member skive assembly of FIG. 1, with portions removed or broken away to facilitate viewing; and 
     FIGS. 3-10 are respective top plan views, on an enlarged scale, of different embodiments of a receiver member skive finger, from the skive assembly as shown in FIG. 1, including capillary micro-grooves, according to this invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to the accompanying drawings, FIG. 1 shows a typical fuser apparatus, designated generally by the numeral  10 , for a common commercial electrographic reproduction apparatus. The fuser apparatus  10  includes a fuser roller  12  in nip relation with a pressure roller  14 . Rotation of the rollers by any suitable drive mechanism (not shown) will serve to transport a receiver member (designated for example by the letter R in FIG.  1 ), bearing a marking particle image I, through the nip under the application of heat and pressure. The receiver member may be, for example, a sheet of plain bond paper, or transparency material. The heat will soften the marking particles and the pressure will force the particles into intimate contact with each other and with the surface of the receiver material, such that the particles are at least partially imbibed into the receiver material fibers. Thus, when the marking particles cool, they are permanently fixed to the receiver member in an image-wise fashion. 
     The fuser roller  12  includes a core  16  with a cylindrical fusing blanket  18  supported on the core. The blanket  18  is typically made of a rubber material particularly formulated to be heat conductive or heat insulative depending upon whether the fuser heat source is located within the core  16  or in juxtaposition with the periphery of the blanket. In the illustrated preferred embodiment as shown in FIG. 1, the heat source is an internal heater lamp designated by the numeral  20 . A well known suitable surface coating (not shown) may be applied to the blanket  18  to substantially prevent offsetting of the marking particle image to the fuser roller  12 . Additionally, a suitable applicator device, designated generally by the numeral  50 , is provided to coat the surface of the fusing blanket  18  with release oil. The release oil serves to further prevent the offsetting of marking particles to the fuser roller  12 . 
     The pressure roller  14  has a hard outer shell  22 . Typically, the shell  22  is made of metal, such as aluminum or steel for example. The shell  22  may also have a well known suitable surface coating (not shown) applied thereto to substantially prevent offsetting of the marking particle image to the pressure roller  14 . Further, a cleaning assembly (not shown) may be provided to remove residual marking particle, paper fibers, and dust from the fuser apparatus rollers. 
     As noted above, under certain circumstances, such as when fusing heavy marking particle images, the receiver member may adhere to one or the other of the fuser apparatus rollers (i.e., fuser roller  12  or pressure roller  14 ). Therefore, a skive mechanism, designated generally by the numeral  30 , is provided. The skive mechanism  30 , shown in FIG. 1 in operative relation with the fuser roller  12 , includes a frame  32 , having a curved end  32   a,  mounted on a pivot rod  34 . The pivot rod  34  has its longitudinal axis parallel to the longitudinal axis of the fuser roller  12 , and extends for a length substantially equal to the length of the fuser roller. The frame  32  defines a plurality of openings  36  for a plurality of skive finger assemblies  38  respectively (see FIG.  2 ). A resilient member  43  (see FIG.  1 ), such as a coil spring, urges the frame  32  in a direction about the pivot rod  34  to maintain the skive assemblies of the skive mechanism in operative engagement with the fuser roller. 
     Each skive finger assembly  38  includes a skive finger  40  and a skive finger support  42 . The skive finger  40  is formed as an elongated, substantially planar, relatively flexible element having a sharp chisel-like leading edge (for example, formed from a thin metal sheet). The skive finger support  42  is formed as a main body having features for capturing and supporting a skive finger. The body of the skive finger support  42  includes a slot  42   a  and a lead edge  42   b.  The slot  42   a  is adapted to be received on the pivot rod  34  to locate each skive finger support  42  adjacent to a respective opening  36  such that the skive fingers  40  extend through the openings toward the fuser roller  12 . When the skive finger support  42  is mounted on the pivot rod  34 , the action of the resilient member  43  causes the lead edge of the skive finger  40  to contact the fuser roller, and the lead edge  42   b  to be normally spaced from the fuser roller  12 . However, during certain jam conditions as discussed, the skive finger support  42  will pivot about the rod  34  until the lead edge  42   a  of the support engages the fuser roller  12 . By so limiting the action of the skive fingers  40 , damage to the fuser roller  12 , or the skive fingers themselves, is substantially prevented. 
     The skive fingers  40 , as best shown in FIGS. 1 and 2, are of a particular preferred configuration best suited for engaging the roller of the fuser apparatus  10  which is relatively softer than the other nip-forming roller such that the nip shape is curved around the harder roller. Therefore, the receiver member on the exit from the nip is forced away from the skive finger-bearing softer roller. The thin flexible fingers could be placed very close to the nip (preferably 2 to 5 millimeters) under very low tip load (2 to 10 grams). The preferred skive fingers are long (free span 25 to 40 mms) and thin (0.1 to 0.13 mms). Because the skive fingers  40  are very thin, therefore, it is possible to place them very close to the fuser roller nip, and further when combined with the softer skive finger-bearing roller enables the skive fingers to work as guides rather than strippers for the receiver. Furthermore, when the skive fingers  40  are used as receiver member guides, a high tip force is not needed and thus roller surface damage is avoided. 
     As noted above, the skive fingers as currently found in exemplary fuser apparatus have a tendency during operation of the reproduction device to become wetted with fuser release oil that accumulates on the fingers during the fusing process. The receiver members, bearing images to be reproduced, as they are released from the fuser rollers, will come in contact with skive fingers as they are guided away from the fuser apparatus. The release oil then becomes wetted to the receiver members during such contact, and the oil is transported back through the elements of the reproduction device, particularly when the receiver member is recirculated for forming a duplex reproduction. Some of the release oil is then transferred off the receiver members onto the reproduction device elements, which may potentially cause undesirable image defects on subsequently reproduced images. 
     According to this invention, in order to reduce or eliminate the affect of release oil wetting of the receiver members, the probability that the oil will contact the receiver members is substantially reduced. This is accomplished by creating micro-groove channels  44  (see FIGS. 3-10) in the skive fingers  40  (some or all of the skive fingers in a skive mechanism  38 ) to allow oil that beads up and collects at the tips  40   a  of the skive fingers to be received in these channels and drain away. The skive fingers  40  are located so as to slope, by several degrees, from the fuser roller  12  (see FIG.  1 ). As such, gravity will be effective for moving the release oil liquid away from the skive finger/fuser roller interface. Additionally, the width of the micro-groove channels is selected to help cope with the oil variations that are encountered due to noises in the fusing process. 
     Another effect of the provision of the micro-groove channels  44  is that the channels create capillary action in the release oil which serves to aid in moving the release oil away from the skive finger tips. The micro-groove channels  44 , formed by etching for example, may have a cross-sectional configuration of a rectangular, semi-circular, or V shape. Of course, the channels may alternatively be integrally formed with injection molded skive fingers. When the release oil in a channel exhibits a positive-pressure meniscus (i.e., a concave liquid/vapor interface), the result is an unstable liquid configuration. Accordingly the positive-pressure will urge the release oil down the channel away from the skive finger/fuser roller interface. This can occur in the corners of the micro-grooves, if the grooves are not completely filled with fluid, or over the cross-section of the entire groove. The micro-groove channels may also be tapered along their length, becoming narrower away from the skive finger tip as shown in the drawings, so that capillary action can occur, and such variable width serves to pull the release oil to the back of the skive finger for drainage. 
     FIG. 3 shows an enlarged view of a single one of the skive finger assemblies  38  of the skive mechanism  30 , with a skive finger  40  mounted on a support  42 . Such assembly  38  may be located at any one, or more, of the assembly positions (shown in FIG.  2 ). According to a preferred embodiment of this invention, the plurality of micro-groove channels  44  of the skive finger  40  extend away from the lead edge tip  40   a  of the skive finger toward the end  40   b . The channels  44  are approximately 1.4 mms wide by approximately 43 mms long. The depth of the etched channels  44  is approximately 40 ums, which is about half the thickness of the skive finger. Etching of the channels to a much deeper level is not recommended in that it can cause etching through the skive finger. Of course the particular described dimensions of the channels  44  are only exemplary and depend upon the specific geometry of the associated skive finger. An opening  46  is provided in the skive finger  40  adjacent to the end  40   b  of the skive finger, in juxtaposition with the terminus of the channels  44 . The purpose of the opening  46  is to enable the skive finger to be secured on the support  42 , such as for example by a post extending from the support. 
     The micro-groove channels  44  have a geometry, which is selected to best match the flow characteristics (including viscosity) of the particular release oil being used in the specific fuser apparatus  10 . This will serve to facilitate feed of release oil away from the tip  40   a  of the skive finger toward the end  40   b  depending upon the physical arrangement and characteristics of the fuser apparatus  10  and the release oil. FIGS. 4-10 show different embodiments of the micro-groove channels formed in the skive fingers  40 . As can be seen, there may be a wide variety of number, width (degree of taper of the channels), and orientation (angle relative to the longitudinal center-line of the skive finger) of the channels. Further the channels  44  may have transversely formed, interconnecting passages  48   a  (see FIG.  7 ), or holes  48   b  (see FIGS.  8 - 10 ). The particular configuration of the interconnecting passages  48   a  is to aid flow in the channels, while the openings  48   b  enable release oil received from the channels  44  to drip into, and be collected by, the frame  32  of the skive mechanism  30 . Therefore the release oil will be collected remote from the transport path of the receiver members (R) and substantially prevented from contaminating other elements of the reproduction equipment. A wicking material, such as felt or Nomex, (for example, see element  47  in FIG.  3 ), may be urged into the opening  46  to enhancing wicking of the release oil away from the tip  40   a  of skive finger  40  via the channels  44 . 
     The invention has been described in detail with particular reference to certain preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention.