Patent Grant
8469685
This application relates to commonly assigned, copending U.S. application Ser. No. 11/746,083, filed May 9, 2007, entitled: “IN-LINE METHOD TO REFURBISH FUSER MEMBERS”, U.S. application Ser. Nos. 11/472,771, 11/472,888, 11/472,918 each of which were filed on Jun. 22, 2006, and each entitled: FUSER MEMBER, U.S. application Ser. No. 11/472,919, filed Jun. 22, 2006, entitled: METHOD OF MAKING FUSER MEMBER, U.S. Ser. No. 11/746,089, filed May 9, 2007, entitled: ELECTROPHOTOGRAPHIC APPARATUS, U.S. application Ser. No. 12/277,392 filed Nov. 25, 2008, entitled: METHOD FOR REFURBISHING PRESSURE MEMBERS, and U.S. application Ser. No. 12/335,791 filed Dec. 16, 2008, entitled: METHOD FOR REFURBISHING CYLINDRICAL MEMBERS.
This invention generally relates to electrostatographic devices and methods for refurbishing cylindrical members such as fuser and pressure members, and is particularly concerned with the refurbishment of a pressure roller or member which is coated with an outermost layer of fluoropolymer resin.
The surface (or the topcoat) for both fuser and pressure members in oil-less fusing of toner material requires ultra low surface energy to release the substrate. An improved topcoat material for oil-less fusing is high-temperature tolerant thermoplastic, such as FEP, PFA, or PTFE described in US Published Applications 2007/0298252, 2007/0298251, 2007/0298217, and 2007/0296122 each of which were published on Dec. 27, 2007.
However, the applicants have observed during fuser printing performance tests that paper edges, particularly of thick paper, can occasionally leave wear marks on the topcoat of the fuser surface. These paper edge marks can show up on wider paper as gloss-variation artifacts when subsequent prints are made on a substrate covering the worn area. Moreover, for printing special images, particularly one with in-track stripes of area of no toners, foreign materials from paper are seen to periodically accumulate on the surface of the topcoat due to the absence of toners. Such foreign materials may be, for example, the fine particulate clay or calcium carbonate fillers often present on the surface of the paper being printed. The accumulation of such foreign particulate material on the surface of the topcoat can result in undesirable artifacts, such as a gloss variation band artifact occurring when printing different image content subsequently as a full page image.
In the past, to avoid such artifacts, the fuser members were simply replaced. To obviate the need and expense associated with completely replacing the fuser members, the applicants developed an in-line apparatus for refurbishing fuser members in-situ which is described and claimed in commonly assigned, copending U.S. application Ser. No. 11/746,083.
The applicants have subsequently observed that paper edges, particularly of thick paper, can also leave wear marks on the topcoat of the pressure member surface, and that foreign materials from paper can also periodically accumulate on the surface of the pressure member topcoat. Consequently, undesirable image artifacts may be caused by the pressure members as well as the fuser members in electrophotographic printers. The present invention is an apparatus for refurbishing cylindrical members within an electrophotographic printer that obviates the need and expense associated with completely replacing the members
The practice of the proposed refurbishing scheme and the accessory surface cleaning scheme depends on the severity of the artifact present on the member surface, which in turn is a function of the service history of the member.
The present invention provides an apparatus of resurfacing a cylindrical member having an outer surface formed from a high temperature, low surface energy, semicrystalline thermoplastic such as a fluorothermoplastic. When it is determined that the outer surface is in need of resurfacing, the cylindrical member is rotated at a speed of at least 1 rpm while engaging the outer surface of the fuser member with at least one heating roller at a pressure of at least 5 psi at a temperature of between 10° C. below the thermoplastic melting temperature and the melting temperature of the thermoplastic for a time sufficient to resurface of the outer surface of the cylindrical member.
When the cylindrical member is in operation in an electrophotographic printer having a fuser member that is externally heated by a heater roller assembly, the apparatus may further carry out the steps of replacing the fuser member with another cylindrical member, rotating the cylindrical member at the aforementioned speed via the fuser member drive, and implementing the aforementioned temperature and pressure on the outer surface of the pressure member via the heater roller assembly of the printer. To expedite these steps both the fuser member and the pressure member may be mounted within the electrophotographic printer by a quick-release assembly that allows the operator to quickly and easily remove the fuser and pressure members from their normal, operational positions on the frame of the printer and to install the pressure member in the operational position of the fuser member.
a and 5b are side, cross-sectional schematic views of the electrophotographic printer of
For a better understanding of the present invention together with other advantages and capabilities thereof, reference is made to the following description and appended claims in connection with the preceding drawings.
The present invention can be applied to refurbishing cylindrical members such as pressure members with low surface energy, semicrystalline thermoplastic topcoat materials, such as FEP (polyfluorinated ethylene-propylene), PFA (perfluoroalkoxy-tetrafluoroethylene), or PTFE (polytetrafluoroethylene). Low surface energy refers to materials having a surface energy of less than 30 ergs/cm2, preferably less than 25 ergs/cm2, and more preferably less than 20 ergs/cm2, as determined from the contact angle with a nonpolar and a polar liquid such as distilled water and diiodomethane and using the Good-Girafalco approximation to approximate the interfacial energy. The instant invention is not dependent on how the pressure member is manufactured, i.e., not affected by whether the topcoat is sleeve molded, sintered with dispersion, sprayed or transfer-coated, etc. The present invention will increase the usable life of the pressure member owing to its ability to remove surface irregularities and restore a uniform gloss surface finish to the pressure member.
For the purpose of this disclosure, the term melt temperature or Tm refers to the temperature at which the onset of melting occurs. This can be determined via various means known in the literature such as observing the onset of a latent heat using differential scanning calorimetry (DSC) or similar devices.
In all embodiments, the pressure members are preferably cylindrically symmetrical, i.e., a cross-section of the roller taken at a right angle to the roller axis anywhere along the length of the member or roller has radial symmetry around the roller axis. The length of the roller thereof determines the range of the printing width of the substrate.
The fuser member 110 includes a plurality of annular layers 112, 113, and 114 that surround a generally concentric central core 116. Core 116 is usually formed from a metal, such as stainless steel, steel, aluminum, etc. The primary requisite for the material for core 116 is that it be sufficiently stiff to support the force placed upon it during a printing operation, and able to withstand a possibly higher temperature than the surface of the member 110 where there is an optional internal heating source, such as the quartz-halogen light 117 illustrated in cross-section at the center of rotation of the member 110. For externally heated fuser members, the internal heat source 117 can be optional, though in most practical cases, the internal heat supply is used in combination with the external heat provided by the heater roller assembly 135, also known as a refurbishing apparatus, to fuse the toners for print quality manipulation. The various annular layers that overlie the core 116 include a resilient layer, also termed a cushion layer 113, and tie layers, adhesion promotion layers, and primer layers 114 for bonding the cushion layer with the outmost layer 112. The outermost layer 112 in one embodiment is a toner release layer which includes a thermoplastic fluoropolymer such as PTFE, PFA, and FEP, etc., which are preferred embodiments of low surface energy, semicrystalline thermoplastics suitable for use in this invention, and blends thereof. The fuser member 110 is detachably mounted to a frame 170 in the printer 100 by way of a quick release mechanism 182 (indicated in phantom) The fuser member 100 can be either manually or automatically moved to an alternate position, as shown in
The pressure member 160 preferably has the same structure and diameter as the previously described fuser member 110, including a plurality of annular layers 162, 163, and 164 that surround a generally concentric central core 166 formed from a metal, such as stainless steel, steel, aluminum, etc. Like the fuser member 110, the pressure member 160 includes an internal heat source in the form of a quartz-halogen light 167 illustrated in cross-section at the center of rotation of the member 160. The various annular layers that overlie the core 166 include a resilient layer, also termed a cushion layer 163, and tie layers, adhesion promotion layers, and primer layers 164 for bonding the cushion layer 163 with the outmost layer 162. Like the fuser member 110, the outermost layer 162 of the pressure member 160 is a toner release layer which includes a thermoplastic fluoropolymer such as PTFE, PFA, and FEP, etc. and blends thereof. The pressure member 160 is likewise detachably mounted to a frame 170 in the printer 100 by way of a quick release mechanism 182 (indicated in phantom) and shown in
The heater rollers 140, 150 of the heater roller assembly 135 are made of rigid materials, such as chrome-plated steel.
Both the fuser member 110 and pressure member 160 can be a fuser or pressure plate, fuser or pressure roller, fuser or pressure belt or any other member on which a release coating is desirable. The support for the fuser or pressure member can be a metal element with or without additional layers adhered to the metal element. The metal element can take the shape of a cylindrical core, plate or belt. The metal element can be made of, for example, aluminum, stainless steel or nickel. The surface of the metal element can be rough, but it is not necessary for the surface of the metal element to be rough to achieve good adhesion between the metal element and the layer attached to the metal element. The additional support layers adhered to the metal element consist of layers of materials useful for fuser and pressure members, such as silicone rubbers, and an adhesion promoter layer to the metal element.
The fluoropolymer resin outer layer in one embodiment includes a fluoropolymer material, such as a semicrystalline fluoropolymer or a semicrystalline fluoropolymer composite. Such materials include polytetrafluoroethylene (PTFE), polyperfluoroalkoxy-tetrafluoroethylene (PFA), polyfluorinated ethylene-propylene (FEP), poly(ethylenetetrafluoroethylene), polyvinylfluoride, polyvinylidene fluoride (PVFE), poly(ethylene-chloro-trifluoroethylene) (PCTFE), polychlorotrifluoroethylene and mixtures of fluoropolymer resins. Some of these fluoropolymer resins are commercially available from DuPont as Teflon™ or Silverstone™ materials.
With reference now to
The fuser mounting frame 170 includes a pair of opposing side plates 172 (of which only one is shown) connected together by horizontal support members 174a, b, and c. The pressure roller 160 has a pair of opposing, disc-shaped side plates 178, each of which includes a stub shaft or gudgeon 180 extending from its center. The gudgeons 180 on either side of the pressure member 160 are rotatably mounted in the quick-release assemblies 182. As will be explained in more detail hereinafter, the quick-release assemblies 182 may be slid into and secured within a square shaped recess 209 present in each of the side plates 172 of the mounting frame 170.
Each quick-release assembly 182 includes a support frame 183 having plate-like inner and outer portions 184a, 184b which are spaced apart to define slots 185a, 185b on either side of the support frame 183. These slots 185a, 185b are dimensioned to slidably receive the side edges of the square shaped recess 209 of the fuser mounting frame 170. The support frame 183 also carries a roller bearing 186 into which the gudgeon 180 is journalled, and a drive gear 187 that is non-rotatably coupled to the gudgeon by a keyway formed by the engagement of a flat side 188 of the gudgeon against a flat side 189 in the central opening of the drive gear 187. A locking plate 190 slides into an annular groove at the distal end of the gudgeon 180 to secure the quick-release assembly 182 to the gudgeon 180 in much the same fashion that a common cotter pin functions. A set screw 194 secures the locking plate 190 in place. The stem 196 of the quartz-halogen light extends from the distal end of the gudgeon 180 as shown, and is mounted on a support flange 197.
With specific reference to
a shows the pressure member load arm assembly 220 including a load arm 200. There could be one or more load arm assemblies 220. Each load assembly 220 includes a pivot point 210 and a support 230 such that the support arm 200 can rotatably move the pressure member 160 from the first position to the second position discussed above. The support frame 230 also can include a roller bearing or other similar mechanism 240 to allow the arm to rotate and optionally a drive gear 250 coupled to move the load arm 200. The load arm 200 and the drive can be coupled to a controller to automate the refurbishing process.
Once the pressure member 160 is mounted in the position indicated in
(1) Raise the temperature of the heater roller higher than that for normal printing operation such that the pressure roller surface temperature is brought to a temperature of between 10° C. below the melt temperature and the melt temperature of the topcoat materials;
(2) Set the fuser roller and the heating roller over-temperature sensors to a pre-determined distance suitable for refurbishing temperature range, other than the normal printing mode set-points;
(3) Rotate the fuser member at a rotational speed at least 1 rpm, engage the heater roller with a contact pressure of at least 5 psi, in this embodiment measured as an average pressure transversely across the nip, and up to a needed level a temperature of between 10° C. below the melt temperature (Tm) and the melt temperature of the topcoat materials but the temperature could also be the pressure measured at least at one point on the roller, the average circumstantially or a minimum at one or more points so that the required temperature is reached at the portions necessary to effect the change required;
(4) Turn on the cooling air via air jets 155, 156 to cool the pressure member at a position away from the nip of the heater rollers 140, 150 to prevent overheating of the sublayers 163, 164 and to have fast recovery to the normal printing mode set-points;
(5) Engage the beater rollers 140, 150 on the pressure member surface with program-controlled functions of pressure and temperature for a period of time sufficient to refurbish the pressure member and at least one rotation, typically a range of 1 to 3 minutes in this embodiment. Note that this is the time necessary for a rotational speed of 1 rpm and normally the speed could be higher, especially during operation embodiments and then the time to achieve the changes are significantly less as is calculable based on the 1 rpm number and the diameter of the roller. The time been measured at 5 seconds in some circumstances.
(6) While rotating the cylindrical member engaged with the at least one heating member, various processing adjustment parameters are accessed and one or more of the pressure, time, or temperature are adjusted to compensate for these parameters and controlling the engaging and rotating steps accordingly for a time sufficient to resurface of the outer surface of the cylindrical member as is appropriate for the situation. Note that these processing parameters can be stored in a table, calculated or transmitted from another source.
The processing adjustment parameters could include one or more of a cylindrical material, diameter, shape and profile where the material includes material properties such as yield strength, melting temperature etc.
The present invention preferably is initiated after the pressure member has serviced a same print job for a period of time such that artifact may show up in a subsequent different print job, depending on the printing service requirement. Artifacts that require pressure member refurbishing include paper edge wear marks, foreign materials or paper dust from paper in the area of no toner stripes and/or scratch lines due to the fabric cleaning pad applied directly to the pressure roller surface or any other mishap. The initiation of the pressure member refurbishing program can also be a part of the scheduled maintenance. Alternately other members such as rollers, could also be refurbished in a similar manner.
Before activating the above refurbishing scheme, it is necessary to assure clean surfaces of the pressure member 160 and heater rollers 140, 150, i.e. the pressure member surface 162 should be free of contamination, such as, residual toner or deposit of foreign materials, such as from paper. The surfaces of the pressure member 160 as well as the heater rollers 140, 150 are first cleaned by non-invasive methods such as by applying soft rags with solvents.
An example is given on a pressure member made of 25-micron-thick PFA (of a melting temperature 305° C.) topcoat, under which is 35-micron-thick Viton, under which is 200-mil-thick silicone rubber. The pressure member serviced for 50,000 A4-equivalent prints of Tabloid sized paper of 300-micron thick on a Nexpress 2100 printing press with external heated fuser assembly and showed de-glossing along the in-track paper edge on the topcoat. The subsequent print on a wider coated paper showed a gloss drop in G60 value by 20 points along the de-glossed edge of the pressure member. The pressure member refurbishing program was activated. After exchanging positions with the fuser member, the pressure member was refurbished at temperature around 300 to 305° C. of the external heater rollers with a programmed pressure that started from 5 psi and increased to 30 psi for about 2 minutes in line to the extent that the paper edge de-glossing was not visible on the pressure member and the subsequent print on a wider coated paper showed non-measurable difference in G60 value on the print that contacted the Tabloid-sized paper edge area of the pressure member.
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.
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| 20100151068 A1 | Jun 2010 | US |
