Method for cooling down a printer, printer and software product

Abstract

A method for shutting down a printer that includes an endless cleaning member and an endless image transfer member includes a step of cooling down the printer by allowing the cleaning member and the cleaning zone to cool down to a predetermined cooling temperature, the predetermined cooling temperature being a temperature lower than the elevated temperature; and during cooling down of the cleaning member and the transfer zone to the predetermined cooling temperature, continuing the surface of the cleaning member being in moving contact with the surface of the image transfer member in the cleaning zone.

Claims

1. A method for shutting down a printer, the printer comprising: an endless image transfer member for receiving consecutive images of toner on its surface, the image transfer member being urged, in printing state of the printer, into moving contact with a counter member to form a transfer zone therebetween for transferring the respective consecutive images to respective sheets of a recording medium fed consecutively through the transfer zone; an endless cleaning member having, in a printing state of the printer, a surface in moving contact with the surface of the image transfer member in a cleaning zone downstream of the transfer zone, the surface of the cleaning member carrying a layer of tacky substance; wherein in the printing state the endless cleaning member and the cleaning zone having an elevated temperature, the method for shutting down the printer comprising the steps of: cooling down the printer, by allowing the cleaning member and the cleaning zone to cool down to a predetermined cooling temperature in a shutting down procedure, the predetermined cooling temperature being a temperature lower than the elevated temperature; during cooling down of the cleaning member and the transfer zone to the predetermined cooling temperature, maintaining a continuous moving contact between the surface of the cleaning member and the surface of the image transfer member in the cleaning zone.

2. The method according to claim 1, wherein the cleaning member is a rotatable cleaning roller having a surface with a plurality of spaced-apart perforations therein.

3. The method according to claim 1, wherein the tacky substance comprises toner.

4. A printer comprising: an endless image transfer member for receiving consecutive images of a toner on its surface, the image transfer member being urged, in printing state of the printer, into moving contact with a counter member to form a transfer zone therebetween for transferring the respective consecutive images to respective sheets of a recording medium fed consecutively through the transfer zone; an endless cleaning member having, in a printing state of the printer, a surface in moving contact with the surface of the image transfer member in a cleaning zone downstream of the transfer zone, the surface of the cleaning member carrying a layer of tacky substance; a control unit configured to control the printer to perform a method according to claim 1.

5. A software product comprising program code on a non-transitory machine-readable medium, wherein the program code, when loaded into a controller of a printer with at least an endless image transfer member, and an endless cleaning member, causes the printer to perform a method according to claim 1.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

(2) FIG. 1 shows a schematic view of a printing system in which a method according to the invention may be used, and

(3) FIG. 2 shows a perspective view of a first example of a cleaning roller.

(4) In the drawing, same reference numerals refer to same elements.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

(5) The present invention will now be described with reference to the accompanying drawing, wherein the same reference numerals have been used to identify the same or similar elements throughout the several views.

(6) A printing system capable of printing on sheets of a recording medium is depicted in FIG. 1. The printing system comprises an image transfer member, which can be moved cyclically. The image transfer member is an endless member, such as e.g. a drum or a belt. In this case the image transfer member is a cylindrical drum (1), which can be moved in the direction of arrow (3). The image transfer member is constructed of a metal sleeve, e.g. aluminium, with an elastomeric covering (2). Optionally, the image transfer member may be provided with an outer layer of silicone rubber, e.g. by means of coating. One or more process colours are available on the printing system dependent whether it concerns a monochrome or a multi-colour printing system. For each process colour, an image forming unit (4)(5)(6) is disposed along the path of rotation of the intermediate transfer member. Each of these image forming units comprises a cylindrical image forming member (7) on which a colour separation image of the corresponding process is formed. In an operative state, the image forming members are all in pressure contact with the image transfer member, the force with which the image forming members are pressed against the image transfer member being at maximum 1000 N per linear meter, e.g. 250 N per linear meter.

(7) Each image forming member is formed of a metal drum with a photo-conductive outer layer thereon, the various image forming devices being positioned along the circumference of the image forming member. These image forming devices comprise a charging device (11), e.g. a corona device, an exposing device (12), e.g. a LED array, for image-wise exposure of the photo-conductive surface to thereby form a latent charge image thereon, a development device (13) for developing the latent image with toner, a cleaning device (14) for removing any residual toner present on the image forming member after transfer of the developed separation image to the image transfer member. The development device is in this case a magnetic brush development device which comprises a magnetic roller (17) consisting of a rotatable sleeve with a stationary magnet system therein. The magnetic roller is positioned along the circumference of the image forming member with its surface at short distance from the image forming member surface without contacting it. A reservoir (18) with electrically conductive magnetically attractable dry particulate toner is positioned near the surface of each of the magnetic rollers (17). Each reservoir contains toner in one of the process colours. A stripper (19) is provided at each reservoir to ensure that an even layer of particulate toner is applied to the sleeve of the magnetic roller.

(8) Also disposed along the path of rotation of the image transfer member (1) is a rotatable counter roller (23) which is selectively movable towards and away from the image transfer member surface with controlled pressure. Means (not shown) are provided to drive this counter member. When pressing the counter member against the image transfer member surface a transfer zone is defined through which in operation sheets of recording medium are passed using feed means and sheet discharging means. This feed means consists of co-operating conveyor rollers (21) and a guide plate (22). The sheet discharging means includes co-operating conveyor belts (24) (25).

(9) Further disposed along the path of rotation of the image transfer member (1) downstream of the transfer zone is a rotatable cleaning roller having a tacky surface.

(10) The cleaning roller (30) may be driven by drive means (not shown) and is selectively movable into and out-of an operative position in which the cleaning member surface is in contact with the image transfer member surface. A helical perforation is formed in the cleaning roller surface and extends to a cavity within the roller for discharging any contaminants and/or excess cleaning substance assembled on the roller surface therein. This helical perforation defines in the axial direction an alternating pattern of grooves and non-perforated areas, referred to as dams. Although these parameters are not that critical, the width and pitch of the perforation is of importance as they determine the ratio between the cleaning area and the non-cleaning area of the roller. As cleaning is only performed in the dam area and not in the grooves, proper consideration should be given when determining these parameters. A large cleaning area is desirable but account should be taken of the fact that the contaminants and/or excess cleaning substance assembled on the cleaning roller surface dams must be able to reach the grooves. Hence, for instance the viscosity of the cleaning substance should be involved in this consideration. A position sensor (not shown) is provided to detect the axial position and optionally also the radial position of the cleaning roller as well as control means (also not shown) for controlling the position of the cleaning roller responsive to the detected position.

(11) The tackiness of the surface layer of the cleaning roller may be improved and the viscosity of the layer may be adjusted by heating the surface layer upstream of the cleaning zone. To enable this, a heating device may be provided for heating the cleaning substance on the cleaning roller surface to render the surface tacky prior to contact thereof with the transfer member surface. The heating device may be in the form of a lamp located in the inner core of the roller. Alternatively, especially when the cleaning roller has a conformable surface, external heating is preferred, for example by use of an external radiant heat source. Ideally, means are provided for controlling the heating of the toner particles, for example by the use of a heat sensor to sense the temperature of the cleaning member surface, this sensor being coupled to a control device for the heating device. Heating the toner particles on the cleaning roller surface has several benefits. The heating device can be energized selectively to control the temperature and tackiness of the cleaning roller surface. This is especially beneficial at start up where, in the absence of such a heating device, it would take a significant amount of time (and possibly wastage of receiving material) before the temperature equilibria would be reached.

(12) FIG. 2 shows a perspective view of a first example of a cleaning roller. The cleaning roller is a rotatable cleaning roller. The rotatable cleaning roller has a surface 41 with a plurality of spaced-apart perforations 40 therein.

(13) In operation, in order to reproduce an image a sequence of printing signals is generated. Responsive to this sequence of printing signals the printing system sequentially forms the respective separation images of toner of the corresponding process colour on the respective image forming members (7). In the respective pressure contact zones, the respective separation images are sequentially transferred in register to the image transfer member to thereby form a registered multi-colour image thereon. The toner substance is toner in dry particulate form. The registered multi-colour toner image on the image transfer member is heated by means known per se so that the toner softens and is rendered tacky. The printing system is such that the respective separation images of toner particles are formed complementary. This means that toner particles of a process colour are accumulated on the free surface of the image-carrying member and substantially not on coloured toner particles already accumulated on the image-carrying member. Substantially not means that any superimposed toner particles of different process colours may not lead to visual deficiencies, i.e. visual with the naked human eye, in the finally printed image.

(14) The printing system subsequently transfers the registered multi-colour toner image to a sheet of a recording medium which is controllably fed at the appropriate time by the conveyor rollers (21) through the transfer zone defined by establishing pressure contact between the rotating image transfer member and the rotating counter member. The sheet carrying the printed image is subsequently discharged by the co-operating conveyor belts (24) and (25). The image transfer member is further advanced towards the cleaning zone where any contaminants present on its surface may be removed by transferring them to the tacky surface of the rotating cleaning roller (30). When printing consecutive images, e.g. a document of several pages and/or plural copies of a single image or document, the printing job is defined such that the consecutive images are printed each on separate sheets fed in consecution through the transfer zone. Hence, for consecutive images both an inter-image area, being the area between consecutive images carried on the image transfer member, can be defined as well as an inter-sheet area, being the distance between the associated consecutive sheets. The part of the inter-image area coinciding with the inter-sheet area is referred to as the non-image area.

(15) During cooling down of the machine, the cleaning roller (30) may be kept in the operative position in which cleaning roller (30) surface is in contact with the image transfer member surface. The cleaning roller (30) may rotate and the image transfer member (1) may rotate as well. The rotation may continue until a cooling temperature has reached. A temperature sensor (not shown) may be provided to measure the temperature.