Abstract:
A cleaning apparatus for a surface, particularly for a surface in the graphics industry and more particularly for the surface of a cylinder used in the graphics industry. A pressing element has a cleaning cloth thereover. The pressing element is movable toward and away from the surface. A pressurizable pressure chamber which when pressurized acts on the pressing element to move the cloth to the surface. A pneumatic circuit feeds compressed air to the pressure chamber and vents the pressure chamber. The circuit includes a compressed air storage chamber which can be alternatively connected to the pressure chamber to pressurize the pressure chamber or to a compressed air source to refill the chamber with compressed air. The volume of the storage chamber and the pressure therein are higher than that of the pressure needed in the pressure chamber for rapid refilling of the pressure chamber. A second air path communicates between the compressed air source and the pressure chamber and includes valving enabling venting of the pressure chamber to maintain a selected pressure level.

Description:
BACKGROUND OF THE INVENTION 
     The invention pertains to a cleaning apparatus for cleaning a running dirty surface in a machine in the graphics industry and particularly to a pneumatic pressure apparatus for moving a cleaning cloth to and away from the surface, e.g., of a cylinder. 
     A cleaning apparatus of this type is disclosed by U.S. Pat. No. 4,344,361 (DE 30 05 469 C2). On its path from a clean cloth roller to a pressing element in the form of an inflatable rubber lip, a cleaning cloth is moistened by a nozzle apparatus. After the rubber lip, the cloth is wound up onto a dirty cloth roller. The onward transport or advance of the cleaning cloth is carried out in each case only when the cleaning cloth is not pressed by the rubber lip against the surface to be cleaned, but is moved out of contact with that surface and, as a result, is at a short distance from it. 
     Further prior art concerning such apparatus includes DE 196 05 957 A1, DE 195 16 422 C2, DE 41 42 422 A1, DE 30 05 469 C2, U.S. Pat. Nos. 5,842,418, 5,699,738. 
     Dirty surfaces in machines in the graphics industry, in printing machines, include the various cylinders, such as the blanket cylinders, printing-plate cylinders and impression cylinders, and also paper webs and paper sheets to be printed. In paper cutting machines (slitters or sheet cutters) and in paper coating equipment, further dirty surfaces are the paper webs or paper sheets, and particularly also cylinders and rollers which are used to transport and to treat the paper webs and paper sheets. “Dirt” is, in particular, printing ink and paper dust, but includes any other contamination. 
     During a cleaning operation, the machine being cleaned continues to run, but without paper sheets or paper webs being able to be printed, if printing ink and other types of contamination are being removed from one of the cylinders, such as a printing-plate cylinder, blanket cylinder or impression cylinder. This means that paper broke (rejects) is produced by the paper running during the cleaning operation. During the cleaning operation, the cleaning cloth is pressed cyclically many times, either by the rubber lip or by another pressing element, against the surface to be cleaned and the cloth is then lifted off the surface again. The cleaning cloth is transported onward by a predetermined cloth section in each case when it is lifted off, in order that when the cloth is again placed against the surface to be cleaned, a fresh cloth section is available. 
     SUMMARY OF THE INVENTION 
     The invention is intended to achieve the object of shortening, in a straightforward way, the time required for a cleaning operation. 
     The invention concerns a cleaning apparatus for a surface and particularly for a surface in the graphics industry and more particularly for the surface of a cylinder in the graphics industry. A pressing element has a cleaning cloth thereover and the pressing element is movable toward and away from the surface. A pressurizable pressure chamber which when pressurized, acts on the pressing element to move the cloth to the surface. A pneumatic circuit feeds compressed air to the pressure chamber and vents the pressure chamber. The circuit includes a compressed air storage chamber which can be alternatively connected to the pressure chamber or the pressure element to pressurize the pressure chamber or connected to a compressed air source to refill the chamber with compressed air. The volume of the chamber and the pressure therein is higher than that of the pressure needed in the pressure chamber for rapid refilling of the pressure chamber. A second air path communicates between the compressed air source and the pressure chamber and includes valving enabling venting of the pressure chamber to maintain a selected pressure level. 
     The invention provides a cleaning apparatus for cleaning a running dirty surface, wherein the pneumatic circuit contains a compressed-air store with a compressed-air storage chamber, which can be connected alternatively to the pressure chamber of the pressing element, in order to press the pressing element into the in-contact position by means of stored compressed air, or to a compressed-air source, in order to fill that chamber with compressed air again. The volume of the compressed-air storage chamber is less than the volume of the pressure chamber, and the compressed air stored in the compressed-air storage chamber is at a significantly higher pressure than a predetermined desired pressure value to be produced in the pressure chamber in the in-contact position of the pressing element, for the cleaning operation. This causes a high flow velocity of the compressed air from the compressed-air storage chamber into the pressure chamber is achieved. 
     According to a preferred embodiment of the invention, the compressed-air store has a piston which can be actuated pneumatically to force the stored quantity of compressed air from the compressed-air storage chamber into the pressure chamber of the pressing element. 
     Furthermore, the invention provides a compressed-air feed line from the compressed-air source to the compressed-air storage chamber which is provided with a pressure regulator which sets the pressure in the compressed-air storage chamber to a value which is significantly higher than the pressure with which the pressing element is to be held in the in-contact position. The pressure value and the volume of the compressed-air storage chamber are selected such that the stored quantity of compressed air is at least as great as the quantity of compressed air which is needed in the pressure chamber to produce the pressure with which the pressing element is to be held in the in-contact position. 
     In a particularly preferred embodiment of the invention, the compressed-air storage chamber is arranged in a first compressed-air path, which leads from the compressed-air source to the pressure chamber of the pressing element. A second compressed-air path leads from the compressed-air source to the pressure chamber of the pressing element. The second compressed-air path is provided with a pressure regulator which is set to the pressure with which the pressing element is to be held in the in-contact position. 
     In a further preferred embodiment of the invention, at its downstream end, each of the two compressed-air paths can alternatively be connected to the pressure chamber of the pressing element or isolated from this pressure chamber by a valve arrangement. 
     The invention is suitable in particular for cleaning printing-machine cylinders and, in particular, also for cleaning impression cylinders in sheet-fed printing machines. 
     Other objects and features of the invention are described below with reference to the attached drawings and using a preferred embodiment as an example. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 schematically shows a cleaning apparatus according to the invention for cleaning a running dirty surface in a machine in the graphics industry, for example an impression cylinder in a sheet-fed printing machine, 
     FIG. 2 schematically shows a valve arrangement of FIG. 1 in a position for carrying out a forward stroke of a piston in a compressed-air store of FIG. 1, 
     FIG. 3 shows the valve arrangement of FIG. 2 in a different switching position for a return stroke of the piston, and 
     FIG. 4 shows a further valve arrangement of FIG. 1 in a different switching position than in FIG.  1 . 
    
    
     DESCRIPTION OF PREFERRED EMBODIMENTS 
     The cleaning apparatus illustrated in FIG. 1 contains a pressing element  2 , which can move a section  4  of a cleaning cloth  6 , which extends over this pressing element, alternately into and out of contact with a running surface  8  to be cleaned. 
     The cleaning cloth  6  is transported cyclically from a clean cloth roller  10  to a dirty cloth roller  12 . Onward transport of the cleaning cloth  6  is carried out in each case when, as shown in FIG. 1, it is in its position out of contact with the surface  8  to be cleaned. When the cloth is in the position in contact with the surface  8  to be cleaned, the cleaning cloth  6  is held at a standstill. 
     In order to bring the cloth section  4  extending over the pressing element  2  into contact with the surface  8  to be cleaned, the pressing element  2  is expanded toward the surface  8  to be cleaned by means of compressed air in a pressure chamber  14  bounded at least partly by the pressing element. In order to move the pressing element  2  and the cloth section  4  lying on it out of contact with and away from the surface  8  to be cleaned, the pressure chamber  14  is vented. 
     On its way from the clean cloth roller  10  to the pressing element  2 , the cleaning cloth  6  can be moistened with water or another liquid by a moistening device  16 . This provides the option of washing the surface  8  to be cleaned in a moist or wet condition and then of drying it with a dry section  4  of the cleaning cloth  6 . In a different embodiment, the cloth  6  can also be a pre-moistened cloth, which is already moist when it is on the clean cloth roller  10 . 
     The surface  8  to be cleaned, or the dirty surface, in the embodiment shown in FIG. 1 is the cylindrical peripheral surface of an impression cylinder for printing sheets, for example paper sheets. The leading edge of each sheet, in the direction of rotation  18  of the impression cylinder, is in each case held by grippers  20  on the peripheral surface. After the gripper  20  had been pivoted away, the sheet can be lifted off the circumferential surface by pins  21 , in order that the sheets can run onto a transfer device. 
     In the embodiment illustrated, the pressing element  2  has the form of a rubber lip, but according to different embodiments can also be an inflatable hose or another element, for example an element which can be actuated by one or more cylinders which bound the pressure chamber  14  and, as a result, can be actuated by its pressure. 
     In order to feed compressed air into the pressure chamber  14  for moving the pressing element  2  with the cloth section  4  into contact with the surface  8  to be cleaned, and subsequently to vent the pressure chamber  14  in order that the pressing element  2  moves back again from the surface  8  to be cleaned as a result of its material elasticity, a pneumatic circuit as shown in FIG. 1 is provided. 
     The pneumatic circuit contains a compressed-air source  22  with a compressed-air regulator  24  and two parallel compressed-air paths, via which the outlet of the pressure regulator  24  of the compressed-air source  22  can be provided with a flow connection to the pressure chamber  14  of the pressing element  2 . One compressed-air path, starting from the outlet of the pressure regulator  24  of the compressed-air source  22 , contains, in sequence, a feed line  28  to a compressed-air storage chamber  30  and an outgoing line  34  from the compressed-air storage chamber  30  to the pressure chamber  14  of the pressing element  2 . The feed line  28  contains a pressure regulator  36 , which sets the pressure in the compressed-air storage chamber  30  to a value which is significantly higher than the pressure with which the pressing element  2  is to be held in the in-contact position. In the feed line  28 , between the pressure regulator  36  and the compressed-air storage chamber  30 , there is a first on/off valve  40 . There is a second on/off valve  42  in the outgoing line  34 . 
     The desired pressure value set on the pressure regulator  36  of the feed line  28  and the volume of the compressed-air storage chamber  30  are chosen such that the quantity of compressed air which can be stored in the compressed-air storage chamber  30  is at least as great as or greater than the quantity of compressed air which is needed in the pressure chamber  14  to produce sufficient pressure to hold the pressing element  2  in the in-contact position. 
     FIG. 1 shows the unpressurized state of the compressed-air storage chamber  30  and of the pressure chamber  14 . To fill the compressed-air storage chamber  30  with compressed air, the second valve  42  is closed and the first valve  40  is opened. 
     The compressed-air store  32  contains a piston  44  which can be pneumatically actuated to force the stored quantity of compressed air from the compressed-air storage chamber  30  into the pressure chamber  14  of the pressing element  2 . 
     In the embodiment of FIG. 1, the piston  44  is mechanically connected for axial motion to a control piston  46 . The control piston  46  has a forward stroke pressure side  48  and a return stroke pressure side  50 . Both sides  48  and  50  are vented via a valve arrangement  52 . 
     FIG. 2 shows a switching position of the valve arrangement  52 . The forward stroke pressure side  48  is connected to the outlet of the pressure regulator  24  of the compressed-air source  22 , so that a quantity of compressed air stored in the compressed-air storage chamber  30  is forced into the pressure chamber  14  if the first on/off valve  40  is closed and the second on/off valve  42  is open. 
     In order to return the piston  44  from the forward stroke position into the return stroke position shown in FIG. 1, the valve arrangement  52  is changed into the switching position shown in FIG.  3 . In this switching position, the forward stroke pressure side  48  is vented and the return stroke pressure side  50  is connected to the outlet of the pressure regulator  24  of the compressed-air source  22 . Depending on the desired type of method, during this return stroke of the piston  44 , one or other of the two valves  40  and  42  can be open or closed. 
     To refill the compressed-air storage chamber  30  with the quantity of compressed air needed to actuate the pressing element  2 , the second valve  42  of the outgoing line  34  is closed and the first valve  40  of the feed line  28  is opened. 
     According to a modified embodiment (not shown) the piston  44  can be moved back into the return stroke position shown in FIG. 1 as a result of the filling of the compressed-air storage chamber  30  with compressed air. In this case, the return stroke side  50  of the control piston  46  need not be able to be connected to the compressed-air source  22 . 
     A second compressed-air path leads from the outlet of the pressure regulator  24  of the compressed-air source  22 , along a path parallel to the first compressed-air path, into the pressure chamber  14  of the pressing element  2 . The second compressed-air path contains a further compressed-air regulator  56  in a feed line  58 . In addition, this second pressure line path between the further pressure regulator  56  and the pressure chamber  14  of the pressing element  2  contains a further valve arrangement  62 , with which the further pressure regulator  52  can alternatively be connected to the pressure chamber  14  or isolated from it. In the switching position shown in FIG. 1 of the further valve arrangement  62 , the further pressure regulator  56  is isolated from the pressure chamber  14 , and the pressure chamber  14  is vented into the atmosphere. 
     The further pressure regulator  56  is set to a desired pressure value which is approximately as high as the pressure with which the pressing element  2  is to be held in the in-contact position, that is in the position in which the pressing element  2  presses the cleaning cloth section  4  onto the surface  8  to be cleaned. 
     The further pressure regulator  56  sets the pressure on its outlet side to this pressure value, both in the event of upward pressure fluctuations and in the event of downward pressure fluctuations. This means that the further pressure regulator  56  vents the pressure chamber  14  when the pressure in the chamber  14  rises above the desired value. On the other hand, the pressure regulator  56  opens in order to feed further compressed air from the compressed-air source  52  when the pressure in the pressure chamber  14  falls below the desired value. 
     Thus, only the pressure of the pressure regulator  36  in the first compressed-air path is set to be significantly higher than the desired value which is needed in the pressure chamber  14  in order to press the cleaning cloth onto the surface  8  to be cleaned, while the pressure regulator  56  in the second compressed-air path is set to a desired value which is essentially as high as the pressure value needed in the pressure chamber  14  to bring the pressing element  2  into contact with the surface  8  to be cleaned. 
     The foregoing apparatus achieves the following: 
     The pressure chamber  14  is quickly filled by the over pressured compressed air from the compressed-air storage chamber  30 . This moves the pressing element  2  forward quickly from the out-of-contact position shown in FIG. 1 into the position in contact with the surface  8  to be cleaned. Any excess pressure which develops in the pressure chamber  14  is corrected via the pressure regulator  56  in the second pressure line path. According to another embodiment, this correction could also be made by an additional overpressure valve. However, the further pressure regulator  56  in the second pressure line path has the effect that if the pressure in the pressure chamber  14  falls below the desired value, the desired value is immediately established again. This is advantageous in the case of an impression cylinder for sheet-fed printing machines, since increased pressure in the pressure chamber  14  is produced briefly by the grippers  20  pressing against the pressing element  2 , and, as a result, the pressure chamber  14  is vented by the further pressure regulator  56  (or by an overpressure valve). After the grippers  20  have passed the pressing element  2 , there is a slight lack of pressure in the pressure chamber  14 . This lack of pressure is detected by the further pressure regulator  56  and balanced out immediately. 
     An electronic and/or program-controlled control device  63  is provided in order to control the valves  40  and  42  and the valve arrangements  52  and  62 . 
     The second compressed-air path contains an on/off valve  64  between the valve arrangement  62  and the pressure chamber  14  of the pressing element  2 . This valve is closed when the compressed air under high pressure is delivered from the compressed-air storage chamber  30  into the pressure chamber  14  to prevent the compressed air escaping via the valve arrangement  62  and/or via the pressure regulator  56  of the second compressed-air path. The on/off valve  64  is opened, for example only fractions of a second later, after the pressure in the compressed-air storage chamber  30  has been relieved into the pressure chamber  14 , to a pressure value which essentially corresponds to the compressed-air value set on the pressure regulator  56  of the second compressed-air path. In a modified embodiment, the on/off valve  64  can be replaced with a different valve arrangement  62  which fulfills the same function, for example, a valve arrangement identical to the valve arrangement  52  for controlling the control piston  46 . 
     If the pressure regulator  36  in the first compressed-air path is not a permanently set pressure regulator but one which can be set variably, then the complete pneumatic circuit can be used for pressure chambers  14  of different sizes, for example for pressure chambers  14  of different lengths along a cylinder, corresponding to cylinders of different lengths having a surface  8  to be cleaned. 
     Instead of the valve arrangement  52  for controlling the control piston  46 , a different valve arrangement can also be used, for example a so-called 5/2-way valve, which has 5 line connections and two different valve positions. 
     A preferred operating method of the invention is described. 
     1. In the starting situation, the valve  42  is closed and the pressure chamber  14  is vented into the external atmosphere via the opened valve  64  and the valve arrangement  62 . The compressed-air storage chamber  30  is filled via the opened valve  40 , for example with a pressure of 5 bar, set on the pressure regulator  36 , and a volume of the compressed-air storage chamber  30  of one liter. 
     2. Close the valves  64  and  40 . 
     3. Open the valve  42  and, as a result, relieve the pressure of the compressed-air storage chamber  30  into the pressure chamber  14 , which is significantly larger than the compressed-air storage chamber  30 . This produces the contact pressure to be produced in the pressure chamber in order to move the pressing element  2  into contact with the surface  8  to be cleaned, and the contact pressure to be produced during the cleaning, which may be 0.4 bar, for example. 
     4. Close the valve  42  and, at the same time or later after a delay, close the valve  64 , switch the valve arrangement  62  to straight through and switch the valve  40  to straight through. Now the pressure in the pressure chamber  14  is regulated by the pressure regulator  56 , and the compressed-air storage chamber  30  is filled again to 5 bar with compressed air via the pressure regulator  36  and the opened valve  40 . 
     5. Vent the pressure chamber  14  via the opened valve  64  and the valve arrangement  62 , which for this purpose is changed over from the straight-through position into the venting position shown in FIG.  1 . This lifts the pressing element  2  off the surface to be cleaned. Then advance the cleaning cloth  6  by one cloth section  4 . 
     6. Perform a predetermined number of repetitions of the above steps  2  to  5 . 
     Although the present invention has been described in relation to a particular embodiment thereof, many other variations and modifications and other uses will become apparent to those skilled in the art. It is preferred, therefore, that the present invention be limited not by the specific disclosure herein, but only by the appended claims.