Abstract:
A device for controlling blast and/or suction air in a sheet processing machine, especially a printing press, includes a rotary valve for making ready different positive and negative pressure levels during a work cycle. The rotary valve is connected as a bypass parallel to a supply line between a consumer or load and a positive and negative pressure source. The rotary valve is connected at an input side thereof with the ambient air.

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The invention relates to a device for cycling blast or suction air in a sheet processing machine, especially a printing press. 
     It is known, for example, from German Published, Non-Prosecuted Patent Application 100 10 057 A1, corresponding to U.S. Pat. No. 6,364,311, to employ a lateral pulling device for a cycled control of negative pressure, in which the lateral pulling device is connected between a suction source and a load or consumer. In that regard, a problem arises in that the rotary or rotational valve employed in machines for processing paper sheets can be easily fouled or soiled by accumulating paper dust and can be cleaned again only at considerable cost. 
     SUMMARY OF THE INVENTION 
     It is accordingly an object of the invention to provide a device for cycling blast or suction air in a sheet processing machine, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which is constructed so as not to be susceptible to soiling. 
     With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for controlling blast and/or suction air in a sheet processing machine, especially a printing press. The device comprises a rotary valve for making ready different respective positive and negative pressure levels during a work cycle. The rotary valve is connected as a bypass parallel to a supply route between a consumer or load and a respective positive and negative pressure source. The rotary valve is connected at an input side thereof with surrounding air. 
     In accordance with another feature of the invention, the rotary valve and the positive and negative pressure source respectively have a common mixing chamber. 
     In accordance with a further feature of the invention, the mixing chamber is disposed in the housing of the rotary valve. 
     In accordance with an added feature of the invention, the mixing chamber is provided with an exchangeable filter element. 
     In accordance with an additional feature of the invention, the filter element is disposed so as to be accessible through a cover in the housing. 
     In accordance with yet another feature of the invention, the device further includes a filter leading to the surrounding air. The filter is connected upstream of the rotary valve. 
     In accordance with yet a further feature of the invention, the rotary valve has a rotor formed with a control slot, which has an axial and a radial connection. 
     In accordance with a concomitant feature of the invention, the rotary valve is associated with a suction region of a feed table in a feeder of the printing press. 
     An advantage of the invention lies especially in that greater maintenance intervals as well as longer service lives of the rotary valves is afforded, because the main air flow is guided past the rotary valve to the consumer or load. An especially simple accessibility through a removable cover to the interior of the rotary valve housing permits simple cleansing as well as easy replacement of a cylindrical sieve. An additionally provided filter reduces the intrusion of dirt particles from the surrounding air. 
     In an especially effective application, the rotary valve at a feed table is subjected to suction air. The feed table is in a feeder of a sheet processing machine. The latter is formed, for example, of three suction chambers disposed one after the other which, respectively, have a suction source. The suction air of the suction chamber facing towards the printing press has a suction chamber capable of delivering the suction air in a working or operating cycle of the machine with a varying pressure level. The device according to the invention exhibits this in an advantageous development. 
     Other features which are considered as characteristic for the invention are set forth in the appended claims. 
     Although the invention is illustrated and described herein as embodied in a device for cycling blast or suction air in a sheet processing machine, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. 
     The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic, longitudinal-sectional view of a rotary printing press; 
         FIG. 2  is a fragmentary, longitudinal-sectional view of the printing press of  FIG. 1 , showing a feed table thereof with the device for cycling blast or suction air according to the invention; and 
         FIG. 3  is a more-detailed, sectional view of the blast or suction-air cycling device according to the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Referring now to the figures of the drawings in detail and first, particularly, to  FIG. 1  thereof, there is seen a processing machine for sheets, for example a printing press  1  having a feeder  2 , at least one respective printing unit  3  and  4  and a delivery  6 . Sheets  7  are removed from a sheet pile  8  and fed singly or in a shingle-shaped manner over a feed table  9  to the printing units  3  and  4 . The printing units  3  and  4  each include a respective plate cylinder  11 ,  12  in a conventional manner. The plate cylinders  11  and  12  each have a respective device  13 ,  14  for securing flexible printing plates thereon. Furthermore, a device  16 ,  17  is assigned to each plate cylinder  11 ,  12  for semi-automatic or fully automatic printing plate exchange. 
     The sheet pile  8  lies on a controlled liftable pile or stack plate  10 . The removal of the sheets  7  takes place from the upper side of the sheet pile  8  by a so-called suction head  18  which, among others, has a number of lifting and pull suckers  19 ,  21  for the singling or separation of the sheets  7 . Moreover, blowing or blast devices  22  are provided for aerating or loosening up the upper sheet installation, and test elements  23  for pile or stack resetting. A number of lateral and rear stops  24  are provided for adjusting or aligning the sheet pile  8 , especially the upper sheet  7  of the sheet pile  8 . 
     The feed table  9  is formed as a so-called suction-belt table having first, second and third suction chamber regions or consumers or loads  27 ,  28 ,  29  disposed behind one another, as is shown more particularly in  FIG. 2 . The first suction chamber region  27  is disposed downstream of the sheet pile  8  as seen in the sheet transport direction. A first suction source  31  acts upon the first suction chamber region  27  through a supply line  32 . As is further shown in  FIG. 3 , the supply line  32  is provided with a controllable by-pass flap  33  for surrounding or ambient air. 
     A second suction source  34  acts upon the second suction chamber region  28  through a supply line  36 . The supply line  36  has an adjustable throttle flap  37  for controlling throughput quantities of the suction air, and a switchable bypass flap  38  for surrounding air. The second suction chamber region  28  is longer in the sheet transport direction than the respective first and third suction chamber regions  27  and  29 . The second suction chamber region  28  is therefore further subdivided into several smaller suction chambers for reducing leakage losses, all of which can be acted upon in common by the second suction source  34 . 
     A third suction air source  39  acts upon the third suction chamber region  29  with suction air through a supply line  41 . The supply line  41  has a switchable bypass flap  42  to the surrounding air and a rotary valve  43  for making ready pressure levels of varying height within a work cycle of the sheet processing machine  1 . The three suction sources  31 ,  34  and  39  may also be replaced by a single suction source having an output of corresponding size. 
     The rotary valve  43  has a housing  44 , which accommodates therein a rotatably mounted rotor  46  driven in the work cycle of the printing press  1 . Moreover, a mixing chamber  47  is provided, which is connected through an axial passage  48  with a control slot or groove  52  of the rotor  46 , through a connector  49  to the supply line  41  and through a passage opening  51  to the third suction chamber region  29 . 
     The control slot  52  of the rotor  46  of the rotary valve  43  connects the axial passage  48  with a radial inlet  53  to the surrounding air. The radial inlet  53  is provided with an exchangeable filter  54  for cleaning the intake air from the surroundings. A removable cover  56  closes an opening at an end side of the housing  44 . Access to the mixing chamber  47  is made available by removing the cover  56 . Due to this feature, a cylindrical filter tube or filter element  57  may be removed from the mixing chamber  47  and cleaned or exchanged. The filter tube  57  is formed with at least one first opening  58 , which faces towards the passage opening  51 , and at least one second opening  59 , which faces towards the connection  49 . 
     Control of the suction air and the negative pressure level in the suction regions  27 ,  28  is respectively effected by the suction sources  31 ,  34 , preferably through the bypass flaps  33 ,  38  respectively assigned to the suction regions  27 ,  28 . 
     The negative pressure supply in the suction region  29  is controlled by the suction source  39  with which, additionally, the assigned bypass flap  42  may be employed. Air from the surroundings is added through the control groove  52  of the rotor  46  of the rotary valve  43  to the mixing chamber  47  for cycling the negative pressure level in the suction region  29 . Since the main suction flow at the rotor  46  of the rotary valve  43  is conducted past, or in parallel over, the mixing chamber  47 , the rotary valve  43  remains substantially free of fouling or dirtying such as by dust or powder. 
     This application claims the priority, under 35 U.S.C. §119, of German Patent Application 10 2005 004 562.6, filed Feb. 1, 2005; the entire disclosure of the prior application is herewith incorporated by reference.