Ventilation and cooling device for a photocopier

Abstract: A ventilation device for a photocopier draws ozone mixed air (45) from a developing and image transfer unit (12, 24) and forwards it to ventilate a fusion unit (16, 18) where the subsequent heating of the air reduces the ozone content. The air flow evacuates the condensate water issued by the sheets of paper during the fixing.

Description: Field of the Invention The present invention refers to a ventilation and cooling device suitable for use in a photocopier. Background of the Invention Electrically powered photocopiers laser printers and the like contain operating units and/or elements which work at high temperatures, which causes them to heat the photocopier during operation. Such units/elements include the fusion unit, lighting bulbs, motors, transformers, etc., which generate a quantity of heat which needs to be evacuated. Moreover, the developing unit generally comprises at least two corona effect devices, one of which loads the photoconductor with electrostatic charges of appropriate polarity before the image is printed and the other of which unloads residual charges after cleaning of the photoconductor. The transfer of the developed image may also be performed by a corona device. During their operation, these corona devices generate a certain quantity of ozone, which must be evacuated and/or reduced both for ecological reasons and because it can damage the photoconductor. To accomplish this photocopiers employ air flows actuated by suitable ventilators situated in different parts of the photocopier to individually ventilate the various units and/or elements generating heat and ozone. Each of these air flows issues from the photocopier by its own separate route. In the case of, for example, EP-A-0 316 010, these separate routes are combined at a single air discharging device. This scattered configuration of ventilators and their relative air routes renders machines very bulky and costly. Summary of the Invention Preferred embodiments of the present invention is to provide a ventilation and cooling device for a photocopier which is simple in structure, and which operates to evacuate heat from the hot zones and to efficiently remove and reduce the ozone inside the machine. The invention is defined in the appended claims to which reference should now be made. Brief Description of the Drawings A preferred embodiment of the invention will now be described in detail, by way of example with reference to the accompanying drawings, in which: Figure 1 shows the interior of a photocopier using a ventilation and cooling device embodying the invention; Figure 2 is a simplified representation of the air flow configuration in an embodiment of the invention; Figure 3 is an enlarged schematic representation of a ventilated zone in Figure 1; Figure 4 shows a different form of embodiment of the zone in Figure 3. Referring now to Figure 1, a photocopier 1 essentially comprises a developing unit S, a paper conveyor system TC and a unit F for thermally fixing or fusing the developed image on a sheet of paper P. The developing unit S, which is of a conventional type, develops the latent image on the photoconducting coating of a drum 10. The said image is printed by an optical system O. The drum 10, rotating, for example, in clockwise direction, transports the thus developed image opposite a transfer device C which uses a loading element 12 operating with corona effect to transfer the image to the sheet of paper P. The sheet of paper P has been previously collected from a box 14 and forwarded to the develping unit by the conveyor system TC. The sheet of paper P bearing the developed image is forwarded by the conveyor system TC to unit F to fix the image indelibly to the sheet P. The fixing unit F comprises a pair of rollers 16 and 18. The top roller 16 is heated by a known means and pressed against the bottom roller 18. The sheet P passes between the two rollers 16 and 18, which fix the developed image by thermal effect and pressure. The sheet P is then discharged from the machine by rollers 20 via a slit 22. A second corona device 24 is provided against the drum 10. The said device 24 operates to remove the residual electrostatic charges from the said drum 10. A bulb L is provided adjacent the corona 24 for the same purpose. The device 24 is also used selectively to charge the photoconductor before the optical printing. As has been noted, the two loading devices 12 and 24 operating by corona effect generate a certain quantity of ozone. If the ozone is not quckly eliminated, it can chemically attack the photoconducting coating on drum 10, react with certain components of the toner powder used to develop the images, and also damage parts of the delicate components of the electronic circuits inside the photocopier. Ozone is a thermolabile gas which can be almost totally reduced at a temperature of around 200°C. In this embodiment of the present invention, a single ventilator 30 is used to draw the ozone-mixed air from the developing unit S) and the transfer device C) and convey it outside the machine. The other parts of the photocopier illustrated in Figure 1 are not described in detail as they have bearing on the present invention. We refer now to Figure 2, which shows a basic representation of a ventilation and cooling device embodying the invention. A single conduit 32 for conveying an air flow 34 is disposed between a ventilator 30 and an outlet window 36 from the machine. A deflector wall 38 is inserted in conduit 32 to divert a branch flow 39 from the main flow 34 via a primary aperture 40 to directly ventilate a photocopier zone 41 outside the conduit 32. Zone 41) represents, for example, the chamber containing the fusion unit, which will be described below. The branch flow 39) is conveyed through a second aperture 42) and fed back into the main flow 34) downstream from wall 38) through a gap in said wall 38) and by the diverging form of the end walls 43 of the conduit 32. Figure 3 shows a typical application of the invention process to the fusion unit of a photocopier. An air flow 45 from the developing unit not shown in Figure 3 is forced by a ventilator 30 and partially deflected through a primary aperture 47 in conduit 32 by means of a wall 48 protruding inside the said conduit. The flow 45 contains a certain guantity of ozone evacuated from the corona devices 12 and 24) Figure 1). The deflected part 50) of the flow encounters rollers 16) and 18) which are at high temperature. In particular, roller 16) is maintained at a temperature of between 190 and 200 C. The heat evacuated from the rollers 16 and 18 heats the ozone contained in the branch flow 50, which is released in the form of oxygen. The branch flow 50 is then drawn into conduit 32 through an aperture 49 situated downstream from wall 48 either by a gap formed in wall 48 or due to the divergent form of the wall 43 of conduit 32 downstream from wall 48. The corner 48' of wall 48 projects inside conduit 32 to restrict the section of conduit 32) by a value of between 20% and 50%, inclusive, of the said section. The reduction in pressure formed downstream from the corner 48' in air flow direction is of the order of a 10 - 50 mm water column in relation to the flow pressure 45 corresponding to the primary aperture 47. Moreover, the branch flow 50 evacuates the steam released by the paper, which would cause deposits of condensate water on the metal and/or plastic parts 52 on the paper route downstream from the fusion rollers 16 and 18, particularly at the start of the photocopier activity, when its internal structure has not yet attained operating temperature. Figure 4 illustrates the application of the ventilation and cooling device embodying the invention to a belt-driven fusion unit F1, for example, of the type described in Italian application No. T091A000832 of 5th November 1991 filed by the applicant. The branch flow 50 is subsequently subdivided into a primary flow 51 which is fed towards the fusion unit F1 by the wall curves 53 and 54 and a secondary flow 55 which, via an aperture 56) in wall 54), contacts the two rollers 57) and 58) which eject the sheets. After having cooled the fusion unit F1) and ventilated rollers 57), 58) and the paper guides 60), respectively, the two flows 51) and 55) are conveyed through an aperture 63) situated downstream from the deflector wall 38) and are ejected from the machine along with the remaining part of the main flow 45). It goes without saying that modifications, additions and replacements of parts may be made to the ventilation and cooling device for a photocopier without, however, affecting the scope of the present invention. For example, the outlet orifice 31 Figure 3 of ventilator 30 is provided with an array of vanes 33 tilted downwards to direct the air flow 45' prevalently towards aperture 47 and thus aid in tapping flow 50.

Claims: A ventilation and cooling device for a photocopier in which primary operating units (16, 18) generate heat and secondary operating units (12, 24) generate thermolabile gases, comprising means (30) for ventilating the units by generating an air flow (45) along a conduit (32) disposed between the units and a window (36) to the outside of the photocopier, characterised in that the conduit comprises a primary and a secondary aperture (47, 49) and deflector means (48) disposed between the apertures to divert one part (50) of the flow containing the gases through the primary aperture (47) to contact the primary units and then convey the flow part through the second aperture (49) into the conduit (32), by which means traces of humidity are evacuated and the thermolabile gases are transformed by heat evacuated from the primary units. A device according to claim 1, characterised in that the deflecting means comprise a wall (48) projecting inside said conduit to intercept said part of flow and to create a depression in relation to said second aperture. A device according to claim 2, characterised in that the wall (48) restricts the cross-section of said conduit by 20% to 500%. A device according to any preceding claim, characterised in that the ventilation means comprise a ventilator (30) disposed between the gas generating secondary units (12, 24) and the conduit (32) and the ventilation mean comprises means (33) for directing air flow towards the primary aperture. A device according to claim 4, characterised in that the directing means comprise an array of vanes (33) tilted towards the primary aperture, whereby said ventilator generates an increased flow towards the primary aperture. A device according to any preceding claim, characterised in that conduit (32) comprises walls (43) diverging in the direction of the window (36), to generate a depression in relation to the second aperture. A device according to claim 6, characterised in that the depression differs by 10 -20 mm of water column from the pressure existing in relation to the primary aperture. A method for ventilating and cooling a photocopier characterised by comprising the steps of directing a flow of air firstly past thermolabile gas generating units in the photocopier and then past heat generating units in the photocopier.

Inventors: BORTOLIN RENATO, GUELFO ROBERTO, BORTOLIN, RENATO, GUELFO, ROBERTO
Applicants: OLIVETTI CANON IND SPA, OLIVETTI-CANON INDUSTRIALE S.P.A.
Application year: 1993
Main classification: G03G21
IPC codes: G03G21, G12B15, B41J29, G03G15