Abstract:
A release agent application apparatus includes a liquid-permeable member, a first release agent metering member abutting the liquid-permeable member, and a pump operatively connected to the liquid-permeable member to pump the release agent therethrough.

Description:
TECHNICAL FIELD  
       [0001]     The presently disclosed embodiments relate to applying release agents to fusers to facilitate heat and pressure fixing of marking particles in imaging devices such as, for example, xerographic printing devices.  
       BACKGROUND  
       [0002]     The basic principles of electrostatographic printing with dry marking material (hereinafter generally referred to as “xerography,” “xerographic printing,” and/or the like) are well known: a light image of an original to be copied is typically recorded in the form of a latent electrostatic image upon a photosensitive member with subsequent rendering of the latent image visible by the application of electroscopic marking particles, commonly referred to as toner. The visual toner image can be either fixed directly upon the photosensitive member or transferred from the member to another support, such as a sheet of plain paper, with subsequent affixing of the image thereto in one of various ways, for example, as by heat and pressure. To affix or fuse electroscopic toner material onto a support member by heat and pressure, the temperature of the toner material is typically elevated to a point at which its constituents coalesce and become tacky while and pressure is simultaneously applied, thus causing the toner to flow to some extent into the fibers or pores of the support member or otherwise upon the surface thereof. Thereafter, as the toner material cools, solidification of the toner material occurs and the toner material becomes bonded firmly to the support member.  
         [0003]     One approach to heat and pressure fusing of electroscopic toner images onto a support has been to pass the support with the toner images thereon between a pair of opposed roller members, at least one of which is internally heated. During operation of a fusing system of this type, the support member to which the toner images are electrostatically adhered is moved through the nip formed between the rolls with the toner image contacting the fuser roll thereby heating the toner images within the nip. By controlling the heat transferred to the toner, virtually no transfer or “offsetting” of the toner particles from the copy sheet to the fuser roll is experienced under normal conditions. This is because the heat applied to the surface of the roller is insufficient to raise the temperature of the surface of the roller above the “hot offset” temperature of the toner whereat the toner particles in the image areas of the toner liquefy and cause a “splitting” action in the molten toner resulting in “hot offset.” Splitting occurs when the cohesive forces holding the viscous toner mass together become less than the adhesive forces tending to offset it to a contacting surface such as a fuser roll. Occasionally, however, toner particles may be offset to the fuser roll by an insufficient application of heat to the surface thereof (i.e. “cold” offsetting), by imperfections in the properties of the surface of the roll, or by the toner particles insufficiently adhering to the copy sheet by the electrostatic forces which normally hold them there. In such cases, toner particles may be transferred to the surface of the fuser roll with subsequent transfer to the backup roll during periods of time when no copy paper is in the nip. Moreover, toner particles can be picked up by the fuser and/or backup roll during fusing of duplex copies or simply from the surroundings of the reproducing apparatus.  
         [0004]     One arrangement for minimizing some of the problems associated with heat and pressure fusing, particularly offsetting, has been to provide the fuser roll with an outer surface or covering of polytetrafluoroethylene, widely distributed under the trademark TEFLON®, to which a release agent such as silicone oil is applied, the thickness of the TEFLON® material being on the order of several mils and the thickness of the oil being less than 1 micron. Alternatively, a layer of silicone rubber or Viton has been be used. The silicone rubber layer may provide conformability with the paper roughness resulting in more uniform fixing and image gloss. Silicone based (polydimethylsiloxane) oils possessing a relatively low surface energy have been found to be suitable for use in the heated fuser roll environment where TEFLON® material constitutes the outer surface of the fuser roll. In practice, a thin layer of silicone oil has been applied to the surface of the heated roll to form an interface between the roll surface and the toner images carried on the support material, thus presenting a low surface energy layer to the toner as it passes through the fuser nip and thereby preventing toner from offsetting to the fuser roll surface. A fuser roll construction of the type described above is fabricated by applying in any suitable manner a solid layer of adhesive material to a rigid core or substrate such as the solid TEFLON® outer surface or covering of the aforementioned arrangement.  
         [0005]     Donor roll release agent management (“RAM”) systems have been used as parts of roll fuser apparatuses for some time. Such a RAM system is disclosed in U.S. Pat. No. 4,214,549 to Moser, issued Jul. 29, 1980 (“Moser”). Moser illustrates a heat and pressure roll fusing apparatus for fixing toner images to copy substrates, the toner comprising a thermoplastic resin. The apparatus includes an internally heated, fuser roll cooperating with a backup or pressure roll to form a nip through which the copy substrates pass with the images contacting the heated roll. The heated fuser roll is characterized by an outer layer or surface that, by way of example, is fabricated from a silicon rubber or Viton material to which a low viscosity polymeric release fluid is applied. Release fluid is contained in a sump from which it is dispensed by means of a metering roll and a donor roll, the former of which contacts the release fluid in the sump and the latter of which contacts the surface of the heated fuser roll. The release fluid oil is picked up onto the metering roll as it is rotated through the release fluid oil, which is then metered to a very thin film on the metering roll by a metering blade. In many similar apparatuses, oil is pumped into a trough or collected in a sump wherein it saturates and covers a swiper wick. The metering roll is then loaded to interfere with the swiper wick. Among other things, the wick prevents air entrapment between the moving metering roll and the stationary oil.  
         [0006]     Ensuring consistent applications of clean oil to metering rolls via capillary draws through swiper wicks has been challenging.  
       SUMMARY  
       [0007]     According to aspects illustrated herein, there is provided a release agent application apparatus including a liquid-permeable member, a first release agent metering member abutting the liquid-permeable member, and a pump operatively connected to the liquid-permeable member to pump the release agent therethrough. The apparatus could be used in a number of devices such as, for example, a xerographic printing device.  
         [0008]     According to aspects illustrated herein, there is provided a release agent application apparatus including a means for metering the release agent, a liquid-permeable means, abutting the metering means, for swiping the release agent onto the metering means, and a means, operatively connected to the swiping means, for pumping the release agent through the swiping means. The apparatus could be used in a number of devices such as, for example, a xerographic printing device.  
         [0009]     According to aspects illustrated herein, there is provided a release agent application method including pumping the release agent to a metering roll and metering the release agent on the metering roll.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  shows a simplified cross-sectional schematic view of an exemplary toner image heat and pressure fusing system;  
         [0011]      FIG. 2  shows an isolated perspective view of the exemplary receptacle of the exemplary toner image heat and pressure fusing system of  FIG. 1 ; and  
         [0012]      FIG. 3  is an enlarged fragmentary view of ends of the exemplary applicator, the exemplary metering roll, the exemplary metering blade, and the exemplary cleaning blade of the exemplary toner image heat and pressure fusing system of  FIG. 1 .  
     
    
     DETAILED DESCRIPTION  
       [0013]      FIG. 1  shows a simplified cross-sectional schematic view of an exemplary toner image heat and pressure fusing system  6 . System  6  includes a fuser roll subsystem  10 . Subsystem  10  includes a heated roll structure  12  and a non-heated backup roll structure  14 . Roll structure  12  cooperates with backup roll structure  14  to form a nip  16  through which a copy substrate  18  passes with toner images  20  formed thereon in a known manner. Toner images  20  contact roll structure  12  while a force is applied between roll structure  12  and backup roll structure  14  in a known manner to create pressure therebetween, resulting in deformation of backup roll structure  14  by roll structure  12  to thereby form nip  16 . As substrate  18  passes out of nip  16 , it is stripped from roll structure  12  by a plurality (only one shown) of stripping devices  22 , after which it is free to move along a predetermined path toward an exit of the machine (not shown) in which system  6  is installed. Meanwhile, subsystem  10  also includes a contact temperature sensor  24  that senses the surface temperature of roll structure  12  and, in conjunction with conventional circuitry (not shown), maintains the surface temperature to a predetermined value, for example, on the order of 375-400 degrees Fahrenheit.  
         [0014]     Roll structure  12  includes a hollow cylinder  26  having a radiant quartz heater  28  disposed in the hollow thereof. When suitably energized via the aforementioned circuitry, the heating element radiates heat that is conducted to the outer surface of an outer layer  30  of roll structure  12 , which is made from Viton. Alternatively, outer layer  30  may be made from silicone rubber, TEFLON®, or any other suitable material.  
         [0015]     Backup roll structure  14  includes a solid metal core  32  to which is adhered a relatively thick layer  34  of deformable material such as, for example, an elastomer known as ethylene-propylene terpolymer, which is based on stereospecific linear terpolymers of ethylene, propylene and small amounts of non-conjugated diene which is commonly referred to as EPDM and carries a thin overcoat of PFA or a thick layer of silicone rubber. Due to the construction of backup roll structure  14  it is deformed by the harder roll structure  12  when the required pressure is applied therebetween, the pressure being a function of the desired deformation which corresponds to the desired length of nip  16  as known.  
         [0016]     As discussed further below, outer layer  30  is coated with a liquid release agent  36  that circulates through, among other things, a trough-like receptacle  38 . Release agent  36  may be made from a polymeric release agent having functional groups such as carboxy, hydroxy, epoxy, ammo, isogenate, thioether or mercepto groups. In the case of a TEFLON® or silicone rubber outer layer  30  the functional group may be omitted. The oil viscosity of release agent  36  is in the order of 100-250 cs.  
         [0017]     For coating outer layer  30  of roll structure  12 , system  6  includes a release agent management (“RAM”) subsystem  40 . RAM subsystem  40  includes receptacle  38 , a donor roll  42 , a metering roll  44 , a metering blade or “doctor blade”  46 , a cleaning blade  48 , and a liquid-permeable release agent applicator  50 .  
         [0018]     Applicator  50  is configured to, among other things, apply amounts of release agent  36  to metering roll  44  and is fabricated from medium density, non-woven (non-weaved) “Nomex” fibers typical of Nomex fibers conventionally used in heat and pressure fusers for wicking oil to the fuser rolls or, alternatively, applicator  50  may be made from any other suitably material. Applicator  50  includes a generally rectilinear, generally plank-shaped head portion  52  that caps receptacle  38  further includes and a generally rectilinear sidewall  54  extending generally perpendicularly from head portion  52  into deeper immersion in release agent  36 . As discussed further below, sidewall  54  facilitates backup wicking, among other things. It is noted that sidewall  54  may be omitted when backup wicking is not desired.  
         [0019]     Receptacle  38  is positioned in a sump  68 . Receptacle  38  is configured to, among other things, retain applicator  50 , receive a volume of release agent  36 , transfer amounts of release agent  36  to applicator  50 , and direct residual amounts of release agent  36  into sump  68 . Receptacle  38  includes an end-wall  56  and a relatively shorter opposing end-wall  58 . As discussed further below, end-wall  58  may alternatively be the same height as end-wall  56 .  
         [0020]      FIG. 2  shows an isolated perspective view of receptacle  38 . End-wall  56  and end-wall  58  are also discernable in  FIG. 2 .  
         [0021]     Returning to  FIG. 1 , metering roll  44  is rotatably supported in contact with an exterior surface of head portion  52  of applicator  50 . Metering roll  44  is supported for rotation, such rotation being derived by means of the positively driven roll structure  12  via rotatably supported donor roll  42 . Through head portion  52 , applicator  50  applies release agent  36  to metering roll  44  as discussed further below.  
         [0022]     Donor roll  42  includes a deformable base layer  60  and an outer layer  62  which form a first nip  64  between metering roll  44  and donor roll  42  and a second nip  66  between donor roll  42  and roll structure  12 . Nip  64  and nip  66  also permit satisfactory transfer of release agent  36  between metering roll  44  and donor roll  42 , and in turn between donor roll  42  and roll structure  12 , respectively.  
         [0023]     Metering blade  46  is configured as known to squeegee or otherwise remove undesired amounts of release agent  36  from metering roll  44  and thus meter the amount of release agent  36  transferred to donor roll  42 . Metering blade  46  is positioned such that the amounts of release agent  36  that are metered off metering roll  44  fall into receptacle  38  proximal to end-wall  58 .  
         [0024]     Cleaning blade  48  is configured as known to scrape or otherwise remove stray toner particles and/or other debris from metering roll  44  and thus clean metering roll  44 . Cleaning blade  48  is positioned such that the debris that is cleaned off metering roll  44  substantially falls into sump  68  rather than into receptacle  38 .  
         [0025]      FIG. 3  is an enlarged fragmentary view of ends of applicator  50 , metering roll  44 , metering blade  46 , and cleaning blade  48 . As at least partially discernable in  FIG. 3 , metering blade  46  is as long as or longer than metering roll  44  and applicator  50 . Metering roll  44  is also longer than donor roll  42 . Further, metering roll  44  is rotatably supported by bearings  72  (only one shown) which, in turn, are supported by a fixed shaft  74 . Metering roll  44  is also rounded at its ends as indicated by reference character  76 , thus providing smooth areas of contact between the conformable metering blade  46  and metering roll  44  and between the conformable cleaning blade  48  and metering roll  44 , respectively, so as to hinder degradation of metering blade  46  and cleaning blade  48  by metering roll  44 .  
         [0026]     Returning to  FIG. 1 , subsystem  40  also includes sump  68 , a drain bottle  88 , and a feed pump  92 . A drain  96  of sump  68  is hydraulically coupled to an inlet  116  of drain bottle  88 . An outlet  120  of drain bottle  88  is hydraulically coupled to an inlet  124  of feed pump  92 . An outlet  128  of feed pump  92  is hydraulically coupled to an inlet  132  of receptacle  38 .  
         [0027]     In operation, metering roll  44  rotates as indicated by directional arrow  140 . Further, donor roll  42  rotates as indicated by directional arrow  144 . Also, roll structure  12  rotates as indicated by directional arrow  148 , and backup roll  14  rotates as indicated by directional arrow  152 .  
         [0028]     Feed pump  92  fills receptacle  38  with release agent  36  and pumps suitable amounts of release agent  36  through head portion  52  of applicator  50  (which filters suitable amounts of any debris from release agent  36 ) to metering roll  44 . As metering roll  44  rotates, head portion  52  of applicator  50  swipes suitable amounts of release agent  36  onto metering roll  44 .  
         [0029]     Metering blade  46  removes undesired amounts of release agent  36  from metering roll  44 . The amounts of release agent  36  that metering blade  46  meters off metering roll  44  fall into receptacle  38  proximal to end-wall  58 . These metered off amounts of release agent  36  (along with the bulk of any excess release agent  36  that passes through applicator  50  but is not effectively transferred to metering roll  44 ) fall over end-wall  58  into sump  68  as indicated generally by directional arrow  160 . While the relatively shorter height of end-wall  58  as compared to end-wall  56  facilitates the flow of release agent  36  over end-wall  58 , it is noted that the rotation of metering roll  44  encourages the flow over end-wall  58  as well and, thus, end-wall  58  may alternatively be the same height as end-wall  56 .  
         [0030]     Metering roll  44  transfers suitable amounts of release agent  36  to donor roll  42  at nip  64 .  
         [0031]     Cleaning blade  48  removes suitable amounts of any debris from metering roll  44 . This removed debris substantially bypasses receptacle  38  and substantially falls into sump  68 , where it mixes with the amounts of release agent  36  that have fallen over end-wall  58 .  
         [0032]     Gravity delivers suitable amounts of release agent  36  from sump  68  to drain bottle  88 .  
         [0033]     Usually, feed pump  92  draws release agent  36  from drain bottle  88 , and feed pump  92  pumps release agent  36  as discussed above. However, in the event that feed pump  92  fails, applicator  50  provides “backup wicking” of release agent  36  by wicking amounts of release agent  36  from receptacle  38  (via sidewall  54 ) to head portion  52 , where these amounts of release agent  36  are in turn presented to metering roll  44 .  
         [0034]     It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations, or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims. The words “printer,” “printing device,” and the like as used herein encompass any apparatus, such as a digital copier, bookmaking machine, facsimile machine, multi-function machine, etc. which forms a print outputting function for any purpose.