APPARATUS AND METHOD FOR APPLYING A LUBRICANT TO A XEROGRAPHIC IMAGE

Abstract: An apparatus for increasing the rubbing resistance of a fused substantially dry image formed by xerographic means on a substrate web (12), comprises a first guide roller (25) over which the web (12) passes, a movable lubricant application roller (102) and means (101) for urging the lubricant application roller (102) into rolling contact with the image on the web (12) as the web (12) passes over the first guide roller (25).

Description: APPARATUS AND METHOD FOR APPLYING A LUBRICANT TO A XEROGRAPHIC IMAGE Field of the invention This invention relates to an apparatus and a method for applying a lubricant on a xerographic image formed on a recording medium in order to render this image more scratch protective. This allows handling of these printed mediums for example by post sorters and the like without causing image defects. Background of the invention In a xerographic apparatus, a latent image is formed on an image-forming member by image-wise exposure. The image- forming member is usually an endless member such as a drum or a belt. Typical xerographic processes include amongst others magnetography, lonography and electrography, particularly electrophotography. In the latter process for instance, the latent image is formed on a charged photosensitive member by image-wise exposure to light. The latent image is subsequently made visible on the image- forming member at a development zone. After the development of the latent image, the developed image is transferred to a recording medium, directly or via one or more intermediate members, where it may be permanently fixed. When the developer used is a dry developer instead of a liquid one and substantially no release agent or lubricant is applied on the image carrying members or on the developed image itself during the xerographic process, a substantially dry image is formed on the recording medium. Particularly a substantially dry toner image may be fixed on a recording medium such as paper in web or sheet form as m United States patent US 5455668 (De Bock et al . / Xeikon NV) . Finishing means, as in United States patent US 5805969 (Elsermans et al. / Xeikon NV) , may be provided to alter the appearance of the image, for example to give the substantially dry image a glossy instead of a matte appearance. A clear advantage of such a substantially dry image is that it can be easily varnished. A possible disadvantage of such substantially dry images formed on a recording medium can be as follows. When such a recording medium is subjected to handling or sorting by a mail sorter or by other equipment exerting a rubbing force on said substantially dry image, toner can be rubbed off by this rubbing force leading to serious image distortions. OBJECTS OF THE INVENTION It is an object of the present invention to decrease the surface friction of a substantially dry image to thereby increase its resistance against rubbing. It is a further object of the present invention to provide a lubricant application and supply apparatus and a method enabling a predetermined amount of lubricant to be applied uniformly on a substantially dry image formed on a recording medium. A preferred object of the invention is that the lubricant application and supply apparatus can be detachably mounted on a xerographic tool such as a printer or copier, without the need to modify the controls thereof. SUMMARY OF THE INVENTION According to a first aspect of the invention, there is provided an apparatus for increasing the rubbing resistance of a fused substantially dry image formed by xerographic means on a recording medium, comprising a first guide roller over which a substrate web comprising the recording medium passes; a movable lubricant application roller; and means for urging the lubricant application roller into rolling contact with the image on the recording medium as the web passes over the first guide roller. The lubricant application roller is preferably carried on a pivoted arm, the means for urging the lubricant application roller into rolling contact with the image on the recording medium as the web passes over the first guide roller being constituted by means for pivoting the arm. In a first preferred embodiment of the invention, a movable second guide roller is also provided, over which the substrate web passes downstream of the first guide roller, the lubricant application roller and the second guide roller being coupled together such that tension m the substrate web as it passes over the second guide roller urges the lubricant application roller into rolling contact with the image on the recording medium as the web passes over the first guide roller. In a second embodiment of the invention, the means for pivoting the arm comprises an eccentric rod in contact with the arm and means for rotating the rod. The apparatus may be part of a xerographic tool, such as a printer or copier. The substrate web is partially entrained around a first guide roller and moves along a predetermined path to the second guide roller, and thence to downstream components of the tool, such as a drive and/or tensionmg device for the substrate web and optionally a web cutting and sheet stacking device. The substantially dry fused image is an image formed using a dry type developer instead of a liquid one and which has preferably not been exposed to a release agent during its formation and fusing process or has been exposed to a very limited amount of release agent, i.e. being an amount corresponding to 0.1 mg, or less, per printed A4 side (21.0 x 29.7 cm) . This limited amount of release agent may have been applied externally during an image processing step or the release agent may be incorporated m the toner itself, or m the recording medium, or in another surface with which the image comes into contact during the printing process. In particular, a two-component developer comprising carrier particles and toner particles adhered thereto can be used to create a dry toner image. The lubricant application roller and the second guide roller are preferably pivotally coupled together. In an embodiment of the invention, the lubricant application roller and the second guide roller are carried on a common rigid member, which is pivotally mounted to act as a lever. The lubricant application roller and the second guide roller advantageously together comprise a detachable or removable assembly. The apparatus may further comprise means for mounting the assembly on the first guide roller. The lubricant application roller itself can advantageously be removable from the assembly. The construction according to the invention is such as to enable there to be no forced contact between the lubricant application roller and the substrate when the substrate is less tensioned. By this tensionmg, a force is exerted by the substrate on the second guide roller, which thereby initiates a pivot motion to cause the lubricant application roller to be pressed against the first guide roller while the substrate with the images thereon passes in-between. An advantage of this construction is that it is both space and cost effective as the number of parts required to implement this m a xerographic tool is limited amongst others because no extra means are required to press the lubricant application roller against the substrate. The substrate web can be the recording med±um m the form of a web, such as a paper web, to which the images have been fixed. Alternatively, the substrate web can also be a conveyor belt carrying the recording medium, such as paper, in sheet form. In the latter case the images are formed on the recording medium. By the rolling contact between the lubricant application roller and the recording medium with the images thereon, a predetermined amount of lubricant is applied to the recording medium to thereby increase the resistance against rubbing. A lubricant is preferably applied at a rate ranging from 0.3 mg per A4 side to 3 mg per A4 side. Preferably the lubricant is a silicone oil, with a viscosity m the range from 100 to 10,000 cStokes, more preferably from 2,000 cStokes to 6,000 cStokes. The lubricant can be applied to the lubricant application roller from a separate supply member, as for instance a lubricant reservoir. Preferably however, a given amount of lubricant is held in the lubricant application roller itself, and the whole lubricant application roller is exchanged when the lubricant held therein has been used up. To achieve this, the lubricant application roller may comprise a permeable (e.g. perforated) hollow core with a lubricant held therein. This hollow core is at start partially filled with lubricant. Typically, at start, up to about 70% of the reservoir is filled with lubricant. An intermediate layer impregnated with the lubricant is preferably positioned around the hollow core, for example by being wound around the core, the intermediate layer being provided with a covering layer, which will contact the recording medium. The intermediate layer may be formed of paper or felt and the covering layer may be formed of felt or a brush surface. More preferably, a rolling contact is established between the lubricant application roller, which contacts the recording medium, and a lubricant supply roller in order to improve the application uniformity to the recording medium. To establish this, preferably the outer layer of the lubricant application roller is a material with a low lubricant uptake ability. Examples of such materials are materials with a low swelling factor selected from the group including polyurethane elastomers, PTFE, polyorganosiloxanes, rubber, fluoroelastomers, fluorosilicones and PFA. In this embodiment of the invention, the lubricant application roller may further comprise a core and a spongy rubber intermediate said core and said outer layer to increase the conformability of the application roller. Where a lubricant application supply roller is used, it preferably comprises a permeable (e.g. perforated) hollow core with a lubricant held therein. This hollow core is at start partially filled with lubricant. An intermediate layer impregnated with the lubricant is preferably positioned around the hollow core, for example by being wound around the core, the intermediate layer being provided with a covering layer, which will contact the recording medium. The intermediate layer may be formed of paper or felt and the covering layer may be formed of felt or a brush surface. The lubricant supply and application rate is determined by the composition and thickness of the lubricant impregnated intermediate layer as well as the size and the distribution of the perforations in the core determine together with the temperature and the viscosity of the lubricant. The lubricant is typically applied at a temperature m the range from room temperature to 70°C. Cooling means may be provided for cooling the first guide roller to a temperature of 70°C or below. According to a second aspect of the invention, there is provided a method for increasing the rubbing resistance of a substantially dry image on a recording medium, comprising the steps of: fixing a substantially dry image on a recording medium by exposure to heat; feeding a substrate web comprising the recording medium along a predetermined path, the path extending to a first guide roller; establishing rolling contact at the first guide roller between the fixed substantially dry image on the recording medium and a movable lubricant application roller, thereby to supply a layer of lubricant to the recording medium. Preferably, the method further comprises guiding the substrate web over a movable second guide roller positioned downstream the first guide roller, the movable lubricant application roller being coupled to the second guide roller. In a further embodiment of the invention, the method according to the invention further comprises the step of establishing a rolling contact between the lubricant application roller and a lubricant supply roller. The lubricant supply roller is preferably movable towards and away from the lubricant supply roller, and can be separately removable for ease of replacement. In the fixing step, the substrate may already carry an unfused substantially dry image which has been transferred directly from an image-forming member or from an intermediate image-carrying member. Alternatively the substantially dry toner image may be simultaneously transferred directly from an image-forming member or from an intermediate image-carrying member and fixed to the substrate. Substantially no lubricant or other release agent is applied during the image formation, transfer and fixing process . In a further embodiment of the invention, a dry finishing step or a cooling step or any combination thereof may follow the fixing step. An embodiment of the present invention provides an apparatus for increasing the rubbing resistance of fused substantially dry images formed by xerographic means on opposite faces of a substrate web (i.e. a "duplex" configuration) . The apparatus comprises a first guide roller over which the substrate web passes, a movable first lubricant application roller and a movable second guide roller over which the substrate web passes downstream of the first guide roller. The first lubricant application roller and the second guide roller are coupled together such that tension in the substrate web as it passes over the second guide roller urges the first lubricant application roller into rolling contact with the image on one face of the substrate web as the web passes over the first guide roller. A second movable lubricant application roller is positioned downstream of the second guide roller for rolling contact with the image on the opposite face of the substrate web. The second lubricant application roller may also be coupled together with the second guide roller such that tension in the substrate web as it passes over the second guide roller urges the second lubricant application roller into rolling contact with the image the opposite face of the substrate web as the web passes over a third guide roller. This third guide roller may also be omitted. Alternatively the lubricant application system for lubricating the opposite side of the substrate comprises a second lubricant application roller coupled together with a third guide roller to thereby form an assembly by analogy with the first assembly formed by the first lubricant application roller and the second guide roller. The invention will now be further described, purely by way of example, with reference to the accompanying drawings, in which: Figure 1 shows a section of a printer according to an embodiment of the invention, capable of simultaneous duplex printing; Figure 2 shows in detail a cross-section of one of the print stations of the printer shown in Figure 1; Figure 3 shows an alternative embodiment of a finishing station according to the invention; Figure 4 shows a detachable lubricating assembly for use in an apparatus according to the present invention; Figure 5 shows an embodiment of a lubricant application roller for use in the apparatus illustrated m Figure 4; Figure 6 shows an alternative embodiment of a detachable lubricating assembly for use m an apparatus according to the present invention; Figure 7 shows an embodiment of a lubricant application roller and lubricant supply roller for use m the apparatus illustrated in Figure 6; and Figure 8 shows a further alternative embodiment of a detachable lubricating assembly for use m an apparatus according to the present invention. The printer 10 shown m the Figures has a supply station 13 in which a roller 14 of web material 12 is housed, m sufficient quantity to print, say, up to 5,000 images. The web 12 is conveyed into a tower-like printer housing 44 in which at least one support column is provided. The number of support columns required depends on the desired application. If the printer has to be capable of duplex printing, i.e. printing on both sides of the web, two support columns have to be provided, otherwise a single support column suffices, i.e. a so-called simplex configuration. The present invention is applicable to both configurations. Figure 1 shows a configuration capable of duplex printing. Two support columns 46 and 46' are provided, each housing five similar printing stations A to E and A' to E'. The image-producing stations A, B, C and D and likewise A', B', C and D' are arranged to print yellow, magenta, cyan and black images respectively. The stations E and E' are provided in order to optionally print an additional colour, for example a specially customised colour, for example white. Each sub-group of printing stations A to E and A' to E' are mounted in a substantially vertical configuration resulting in a reduced footprint. The columns 46 and 46' may be mounted against vibrations by means of a platform 48 resting on springs 50, 51. The columns 46 and 46' may be mounted on rails enabling their relative movement. In this way the columns may be moved away from each other for servicing purposes. The web of paper 12 unwound from a supply roller 14 is conveyed in an upwards direction past the printing stations m turn. A brake 11 acts against the roller 14. After passing the last printing station E', the web of paper 12 passes over a reversing roller 150 and then downwards through an image-fusing station 16, and a cooling and finishing station. The web 12 then passes over a guide roller 25 and thence to a cutting station 20 to cut the web 12 into sheets and to a cut sheet stack 52. The web 12 is conveyed through the printer by two drive rollers 22a, 22b one positioned between the supply station 13 and the first image-producing station A and the second positioned between the cooling and finishing unit 17 and the cutting station 20. The drive rollers 22a, 22b are driven by controllable motors, 23a, 23b. One of the motors 23a, 23b is speed controlled at such a rotational speed as to convey the web through the printer at the required speed, which may for example be about 125 mm/sec. The other motor is torque controlled m such a way as to generate a web tension of, for example, about 1 N/cm web width. As shown in Figure 2, each image-producing station (for example printing station B) comprises a cylindrical drum 24 having a photoconductive outer surface 26. Circumferentially arranged around the drum 24 there is a mam corotron or scorotron charging device 28 capable of uniformly charging the drum surface 26, for example to a potential of about -600 V, an exposure station 30 which may, for example, be in the form of a scanning laser beam or an LED array, which will image-wise and line-wise expose the photoconductive drum surface 26 causing the charge on the latter to be selectively dissipated, for example to a potential of about -250 V, leaving an image-wise distribution of electric charge to remain on the drum surface 26. This so-called "latent image" is rendered visible by a developing station 32 which by means known m the art will bring a developer in contact with the drum surface 26. The developing station 32 includes a developer drum 33 which is adjustably mounted, enabling it to be moved radially towards or away from the drum 24 for reasons as will be explained further below. In a typical construction of a developer station, the developer drum 33 contains magnets carried within a rotating sleeve causing the mixture of toner and magnetizable carrier particles to rotate therewith, to contact the surface 26 of the drum 24 in a brush-like manner. Negatively charged toner particles, triboelectπcally charged to a level of, for example 9 μC/g, are attracted to the photo-exposed areas on the drum surface 26 by the electric field between these areas and the negatively electrically biased developer so that the latent image becomes visible. After development, the toner image adhering to the drum surface 26 is transferred to the surface 15 of the moving web 12 by a transfer corona device 34. The moving web 12 is in face-to-face contact with the drum surface 26 over a wrapping angle ω of about 15° determined by the position of the drums 24' and 24'' of the immediately adjacent opposed printing stations (for example printing stations A' and B'). As will be seen from Figure 1, the columns 46 and 46' are mounted closely together so that the web 12 travels in a generally vertical path defined by the facing surfaces of the imaging station drums 24, 24'. This arrangement is such that each imaging station drum acts as the guide roller for each adjacent drum by defining the wrapping angle. The transfer corona device, being on the opposite side of the web to the drum, and having a high potential opposite in sign to that of the charge on the toner particles, attracts the toner particles away from the drum surface 26 and onto the surface of the web 12. The transfer corona device typically has its corona wire positioned about mm from the housing which surrounds it and mm from the paper web. A typical transfer corona current is about 3 A/cm web width. The transfer corona device 34 also serves to generate a strong adherent force between the web 12 and the drum surface 26, causing the latter to be rotated in synchronism with the movement of the web 12 and urging the toner particles into firm contact with the surface 15 of the web 12. The web, however, should not wrap around the drum beyond the point dictated by the positioning of the drum of the next adjacent printing station and there is therefore provided circumferentially beyond the transfer corona device 34 a web discharge corona device 38 driven by alternating current and serving to discharge the surface 15 of the web 12 and thereby allow the web to become released from the drum surface 26. The web discharge corona device 38 also serves to eliminate sparking as the web leaves the surface 26 of the drum. Thereafter, the drum surface 26 is pre-charged to a level of, for example -580 V, by a pre-charging corotron or scorotron device 40. The pre-charging makes the final charging by the corona 28 easier. Any residual toner which might still cling to the drum surface may be more easily removed by a cleaning unit 42 known in the art. Final traces of the preceding electrostatic image are erased by the corona 28. The cleaning unit 42 includes an adjustably mounted cleaning brush 43, the position of which can be adjusted towards or away from the drum surface 26 to ensure optimum cleaning. The cleaning brush is earthed or subject to such a potential with respect to the drum as to attract the residual toner particles away from the drum surface. After cleaning, the drum surface is ready for another recording cycle. Referring to both Figures 1 and 2, after passing the first printing station A (of a printer 10 - see Figure 1), the web passes successively to image-producing stations B, C and D, where images in other colours are transferred to the web. It is critical that the images produced m successive stations be m register with each other. In order to achieve this, the start of the imaging process at each station has to be critically timed. However, accurate registering of the images is possible only if there is no slip between the web 12 and the drum surface 26. The electrostatic adherent force between the web and the drum generated by the transfer corona device 34, the wrapping angle determined by the relative position of the drum 24 and the drums 24' and 24' ', and the tension in the web generated by the drive roller 22 and the braking effect of the brake 11 are such as to ensure that the rotational speed of the drum 24 is determined substantially only by the movement of the web 12, thereby ensuring that the drum surface moves synchronously with the web. The cleaning unit 42 includes a rotatable cleaning brush 43 which is driven to rotate in a sense the same as that of the drum 24 and at a peripheral speed of, for example twice the peripheral speed of the drum surface. The developing unit 32 includes a brush-like developer drum 33 which rotates in the opposite sense to that of the drum 24. The resultant torque applied to the drum 24 by the rotating developing brush 33 and the counter-rotating cleaning brush 43 is adjusted to be close to zero, thereby ensuring that the only torque applied to the drum is derived from the adherent force between the drum 24 and the surface 15 of the web 12. Adjustment of this resultant force is possible by virtue of the adjustable mounting of the cleaning brush 43 and/or the developing brush 33 and the brush characteristics. The developing means comprises a developer which contains toner particles containing a mixture of a resin, a dye or pigment of the appropriate colour and normally a charge- controlling compound giving tπboelectric charge to the toner. In dual-component developers which are normally used, carrier particles are also present for charging the toner particles by frictional contact therewith. The carrier particles may be made of a magnetizable material, such as iron or iron oxide. In mono-component developers, the carrier particles are not present, the toner particles themselves containing a magnetisable material, or else a developing technology other than magnetic brush development is used. Although any cooling and finishing unit 17 may be provided downstream the fixing unit 16, preferably a configuration as shown in Figures 3 and 4 is used. The detachable apparatus of the present invention is mounted on guide roller 25 to enable the application of silicone oil on an image carrying surface of the web to thereby increase the resistance of said images against rubbing. Referring to Figure 3, the web 12 leaving the fixing station 16, at a temperature of, for example 110 to 150°C, passes over a pair of cooling rollers 201, 202, whereby each face of the web is cooled sufficiently to prevent hot offset, for example so as to bring the temperature of the toner image thereon below the glass transition temperature of the toner, for example below 65°C. These cooling rollers are hollow earthed aluminium rollers carrying a conductive elastomeric coating of PFA, fans 203, 204 being provided to blow cola air through the interiors thereof. The web 12 now enters a finishing station 217. The finishing station 217 comprises two housing parts 218, 219. A first pair of finishing rollers 220, 221 are provided at the entry of the finishing station and a second pair of finishing rollers 222, 223 are provided at the exit of the finishing station. The finishing rollers 220, 222 are carried in one housing part 218, while the finishing rollers 221, 223 are carried in the other housing part 219. The housing parts 218, 219 are biased towards each other by springs 224, 225, thereby biasing the finishing rollers of each pair into contact with each other to form a nip through which the web 12 extends. Each finishing roller 220, 221, 222 and 223 is provided respectively with a radiant heater 230, 231, 232, 233 to which electrical power is controllably supplied by means not shown, the radiant heaters each having a heat output under steady state conditions of from 50 to 200 watts. Temperature sensors 234, 235 are provided to measure the temperature of the surface of at least one finishing roller of each pair. These temperature sensors are coupled to the controllable power supply means for the radiant heaters 230, 231, 232, 233. The temperature of the surface of the finishing rollers 220, 221, 222 and 223 is so controlled as to contact the surface 15 of the web 12 at a temperature above the glass transition temperature T g of the toner to modify the finish of the toner image. For example, the temperature of the first pair of finishing rollers 220, 221 is from 80 to 110°C, while the temperature of the second pair of finishing rollers 222, 223 is from 90 to 120°C. In order to prevent hot offset at the second pair of finishing rollers, 222, 223, it is important that the temperature of the surface of these finishing rollers is above that of the - top surface of the toner image. Although some cooling of the toner image can be expected between the first and second pairs of finishing rollers, we prefer to ensure that hot offset is prevented by setting the temperature of the second pair of finishing rollers slightly above that of the first After leaving the finishing station 217, the web 12 passes over the guide roller 25, which is also m the form of a hollow cooling roller, to cool the toner image to, for example, below 65°C, the roller 25 being provided with a to blow cold air through the interior thereof. The printer 10 is provided with an apparatus for increasing the rubbing resistance of the fused substantially dry image formed on the surface 15 of the web 12. The apparatus includes the first guide roller 25 over which a substrate web 12 passes, exposing the image on the surface 15 thereof. A lubricant application roller 102 and a further guide roller 101 are carried on a support arm 103, pivoted by a pivot rod 104 to the frame of the printer. The substrate web 12 passes over the guide roller 101 downstream of the first guide roller 25. As a result of the lubricant application roller 102 and the guide roller 101 being coupled together, tension in the substrate web 12 as it passes over the second guide roller 101 urges the lubricant application roller 102 into rolling contact with the exposed image on the web 12 as the web 12 passes over the first guide roller 25. As shown m Figure 4, the lubricant application roller 102 and the second guide roller 101 together comprise a removable assembly 100. The assembly 100 comprises a pair of interface plates 105 which are shaped to fit on at each end of the first guide roller 25 for mounting the assembly 100 on the first guide roller 25. Each interface plate 105 carries a support arm 103, which is pivoted to the interface plates by a common pivot rod 104. The second guide roller 101 and the lubricant application roller 102 are carried in flanged oearmgs 111 at opposite ends of each support arm 103. The free ends of the pivot rod 104 pass through apertures m fixing plates 106 which are removably secured to the interface plates 105 by retention of detents 109 forming part of the fixing plates 106 in spring-loaded clips 108 carried by the interface plates 105. Referring to Figure 5, the lubricant application roller 102 comprises a permeable hollow core 60 with oil 61 held therein. An intermediate layer 62 formed of paper and impregnated with the oil is wound around the hollow core 60, the intermediate layer 62 being provided with a felt covering layer 64. As shown in Figure 6, the lubricant application roller 302, the lubricant supply roller 310 and the second guide roller 301 together comprise a removable assembly 300. The assembly 300 comprises a pair of interface plates 305 which are shaped to fit on at each end of the first guide roller 25 for mounting the assembly 300 on the first guide roller 25. Each interface plate 305 carries a support arm 303, which is pivoted to the interface plates by a common pivot rod 304. The second guide roller 301, the lubricant application roller 302 and the lubricant supply roller 310 are carried in flanged bearings 311 at opposite ends of each support arm 303. The free ends of the pivot rod 304 pass through apertures in fixing plates 306 which are removably secured to the interface plates 305 by retention of detents 309 forming part of the fixing plates 306 in spring-loaded clips 308 carried by the interface plates 305. Referring to Figure 7, the lubricant supply roller 310 comprises a permeable hollow core 360 with oil 361 held therein. An intermediate layer 362 formed of paper and impregnated with the oil is wound around the hollow core 360, the intermediate layer 362 being provided with a felt covering layer 364. In this embodiment, the lubricant application roller 302 comprises a core 368 and a spongy rubber layer 366 positioned intermediate the core and an outer layer 370 formed, for example, of PTFE. As shown m Figure 8, the lubricant application roller 402, the lubricant supply roller 401 together comprise a removable assembly 400. The assembly 400 comprises a pair of mounting plates 405 which are shaped to fit on at each end of the first guide roller 25 for mounting the assembly 400 on the first guide roller 25. Each interface plate 405 carries a support arm 406, which is pivoted to the interface plates at a pivot point 403. The support arms rest against a common eccentric rod 404, which carries a handle 407 at one end, whereby rotation of the eccentric rod 404 by the handle 407 pivots the support arms 406 to bring the lubricant application roller 402 into rolling contact with the image on the recording medium as the web 12 passes over the first guide roller 25. EXAMPLE In an example, a lubricant application roller used was a felt covered lubricant application roller with a perforated hollow core as described above. Initially the total amount of silicone oil held within this hollow core is 60 mg . The viscosity of the silicone oil used in this test was 7,500 cStokes. The oiling rate was 1 mg per A4 sheet, which means that the lubricant application roller is to be replaced at a rate equivalent with 60,000 A4 sheets. As the lubricant application roller is easily detachable, detection whether or not replacement is imminent can be performed by weighing the roller or by performing a simple rubbing test.

Claims: CLAIMS 1. An apparatus for increasing the rubbing resistance of a fused substantially dry image formed by xerographic means on a recording medium (15), comprising a first guide roller (25) over which a substrate web (12) comprising said recording medium (15) passes, a movable lubricant application roller (102, 302, 402), and means for urging said lubricant application roller (102, 302, 402) into rolling contact with said image on said recording medium (15) as said web (12) passes over said first guide roller (25) . 2. An apparatus according to claim 1, further comprising a movable second guide roller (101, 301) over which said substrate web (12) passes downstream of said first guide roller (25), wherein said lubricant application roller (102, 302) and said second guide roller (101, 301) are coupled together such that tension in said substrate web (12) as it passes over said second guide roller (101, 301) urges said lubricant application roller (102, 302) into rolling contact with said image on said recording medium (15) as said web (12) passes over said first guide roller (25) . 3. An apparatus according to claim 2, wherein said lubricant application roller (102, 302) and said second guide roller (101, 301) are pivotally coupled together. 4. An apparatus according to claim 1, wherein said lubricant application roller is carried on a pivoted arm (103, 303, 406), said means for urging said lubricant application roller (102, 302, 402) into rolling contact with said image on said recording medium (15) as said web (12) passes over said first guide roller (25) being constituted by means (101, 301, 404) for pivoting said arm (103, 303, 406) . 5. An apparatus according to claim 4, wherein said means for pivoting said arm comprises an eccentric rod (404) in contact with said arm (406) and means (407) for rotating 6. An apparatus according to any preceding claim, further comprising a lubricant supply roller (310, 401) in contact with said lubricant application roller (302, 402). 7. An apparatus according to claim 1, wherein said lubricant application roller (102) comprises a permeable hollow core (60) with a lubricant held therein. 8. An apparatus according to claim 7, wherein an intermediate layer (62) impregnated with said lubricant is positioned around said hollow core (60), said intermediate layer (62) being provided with a covering layer (64) . 9. An apparatus according to claim 7 or 8, wherein said lubricant is a silicone oil with a viscosity in the range from 100 to 10,000 cStokes. 10. An apparatus according to claim 6, wherein said lubricant supply roller (310) comprises a permeable hollow core (360) with a lubricant held therein and an intermediate layer (362) impregnated with said lubricant is positioned around said hollow core (360), said intermediate layer (362) being provided with a covering layer (364) . 11. An apparatus according to claim 6, wherein said lubricant application roller (310) comprises a outer layer (370) of a material selected from the group of polyurethane elastomers, PTFE, polyorganosiloxanes, rubber, fluorosilicones and PFA. 12. An apparatus according to claim 11, wherein said lubricant application roller (302) further comprises a core (368) and a spongy rubber layer (366) being positioned intermediate said core and said outer layer. 13. An apparatus according to claim 2, wherein said lubricant application roller (102, 302) and said second guide roller (101, 301) together comprise a removable assembly (100, 300) . 14. An apparatus according to claim 1, further comprising cooling means (251) for cooling said first guide roller (25) to a temperature of 70°C or below. 15. An apparatus according to claim 1, wherein said recording medium (15) is constituted by said substrate web (12) . 16. A method for increasing the rubbing resistance of an substantially dry image on a recording medium (15), comprising the steps of: fixing a substantially dry image on a recording medium (15) by exposure to heat; feeding a substrate web (12) comprising said recording medium (15) along a predetermined path, said path extending to a first guide roller (25) ; establishing rolling contact at said first guide roller (25) between said fixed substantially dry image on said recording medium (15) and a movable lubricant application roller (102, 302, 402), thereby to supply a layer of oil to said recording medium (15) . 17. A method according to claim 16, further comprising guiding said substrate web (12) over a movable second guide roller (101, 301) positioned downstream said first guide roller (25), said movable lubricant application roller (102, 302) being coupled to said second guide roller (101, 301) . 18. A method according to claim 16, wherein a lubricant is applied at a rate ranging from 0.3 mg per A4 side to 3 mg per A4 side. 19. A method according to claim 16, wherein said first guide roller (25) is cooled to a temperature of 70°C or below . 20. A method according to claim 16, further comprising the step of contacting said lubricant application roller with a lubricant supply roller (110) .

Inventors: ELSERMANS JOHAN DENISE GUSTAVE, ELSERMANS, JOHAN, DENISE, GUSTAVE
Applicants: ELSERMANS JOHAN DENISE GUSTAVE, XEIKON NV, ELSERMANS, JOHAN, DENISE, GUSTAVE
Application year: 2001
Main classification: G03G8
IPC codes: G03G8, G03G15