Sheet containing device

Abstract

In a sheet conveying device comprising at least one conveying arrangement with a porous conveyor belt that can be moved in a circulating manner, at least one vacuum source and at least one air line whose one end is connected to the vacuum source and whose other end abuts against the porous conveyor belt, a simple and automatic control of the suction pressure for different sheets is achieved by at least one constant pressure controller in the air line in order to essentially maintain constant a pressure differential between the interior space of the air line and its environment.

1 . Sheet conveying device comprising:
 at least one conveying arrangement with a porous conveyor belt that can be moved in a circulating manner;   at least one vacuum source;   at least one air line whose one end is connected with the vacuum source and whose other end abuts against the porous conveyor belt;   at least one constant pressure controller provided in the air line in order maintain a substantially constant pressure differential between the interior space of the air line and its environment, wherein the air line comprises a main line that is connected, at its one end, to the vacuum source and comprising a plurality of branch lines, each of the plurality of branch lines leading to the conveying arrangement.   
     
     
         2 . Sheet conveying device as in  claim 1 , with the conveyor belt being arranged so as to circulate around at least two rollers. 
     
     
         3 . Sheet conveying device as in  claim 1 , with the air line containing downstream of the constant pressure controller a main flap in order to partially or completely seal the air line with respect to the vacuum source. 
     
     
         4 . (canceled) 
     
     
         5 . (canceled) 
     
     
         6 . Sheet conveying device as in Claim  4 , with one constant pressure controller being arranged in the region of each branch line. 
     
     
         7 . Sheet conveying device as in  claim 4 , with the main flap being arranged so as to shut off the branch line with respect to the main line. 
     
     
         8 . Sheet conveying device as in  claim 7 , with the constant pressure controller being arranged between the main flap and the free end of the branch line. 
     
     
         9 . Sheet conveying device  claim 1 , with the constant pressure controller being in an open position when a pressure differential between the interior space of the air line and its environment is greater than a threshold value. 
     
     
         10 . Sheet conveying device  claim 1 , with the constant pressure controller comprising a valve element and a spring that holds the valve element in a closed position. 
     
     
         11 . Sheet conveying device as in  claim 10 , with the spring displaying a spring characteristic that is variable along the spring path. 
     
     
         12 . Sheet conveying device as in  claim 10 , with the spring bias being adjustable. 
     
     
         13 . Sheet conveying device as in  claim 1 , said device further comprising a pressure sensor. 
     
     
         14 . Sheet conveying device as in  claim 4 , said device comprising at least one pressure sensor that is arranged in a branch line, respectively. 
     
     
         15 . Sheet conveying device as in  claim 13 , said device further comprising a controllably driven pressure control valve and a control device that communicates with the pressure sensor and the pressure control valve in order to control the actuation of the pressure control valve. 
     
     
         16 . Sheet conveying device as in  claim 1 , with the constant pressure controller comprising a flap valve. 
     
     
         17 . Sheet conveying device as in  claim 1 , with the constant pressure controller comprising a sliding valve. 
     
     
         18 . Sheet conveying device as in  claim 15 , with the opening cross-section of the sliding valve not increasing proportionally along its opening path. 
     
     
         19 . Sheet conveying device as in  claim 1 , said device being arranged in a sheet separating device. 
     
     
         20 . Sheet conveying device as in  claim 1 , said device being arranged in a feeder of a printing machine. 
     
     
         21 . The sheet conveying device  claim 1  further comprising a sheet support for the accommodation of a stack of sheets, with at least one part of the sheet conveying device being movable toward the sheet support and away therefrom in order to be able to lift a sheet off the stack of sheets on the sheet support. 
     
     
         22 . Sheet conveying device as in  claim 21 , with the sheet support being height-adjustable. 
     
     
         23 . Sheet conveying device as in  claim 21 , with the part of the sheet conveying device being the at least one conveyor belt. 
     
     
         24 . Sheet conveving device as in  claim 23 , with the part of the sheet conveying device being at least one of the rollers. 
     
     
         25 . Sheet conveying device as in  claim 21 , with the part of the conveying arrangement being at least one suction finger connected to the vacuum source. 
     
     
         26 . Sheet conveying device as in  claim 25 , with the suction finger being preferably separated from the vacuum source when said suction finger is in a position away from the sheet support. 
     
     
         27 . Sheet conveying device as in  claim 26 , with the connection of the suction finger with the vacuum source being preferably open toward the environment when said suction finger is in its position away from the sheet support. 
     
     
         28 . Sheet conveying in device as in  claim 21 , with the sheet conveying device being movable, as a whole, toward the sheet support and away therefrom. 
     
     
         29 . Sheet conveying device as in  claim 21 , with the part of the conveying arrangement being moved in linear direction. 
     
     
         30 . Sheet conveying device as in  claim 21 , with the part of the conveying arrangement being pivotable. 
     
     
         31 . Method for separating sheets in a sheet conveying device, comprising the following steps:
 providing a stack of sheets below a sheet conveying device operating with a vacuum;   attracting the uppermost sheet of the stack of sheets by means of a vacuum; limiting the level of the vacuum with which the sheet is being attracted to a prespecified value following the attraction of the sheet, that is, via a constant pressure control valve inside the sheet separating device.   
     
     
         32 . Method as in  claim 31 , wherein at least one part of the sheet conveying device is moved into the vicinity of the uppermost sheet of the stack of sheets before attracting the uppermost sheet by vacuum, and moving the at least one part of the sheet conveying device away from the stack of sheets after attracting the uppermost sheet. 
     
     
         33 . Method as in  claim 32 , wherein the step of moving at least one part of the sheet conveying device comprises the step of moving at least one suction finger to which a vacuum is being applied. 
     
     
         34 . Method as in  claim 32 , wherein, following the step of moving the part of the sheet conveying device away from the stack of sheets, the vacuum on the suction finger is shut off. 
     
     
         35 . Method as in  claim 32 , wherein the step of moving at least one part of the sheet conveying device comprises the step of moving at least one porous conveyor belt. 
     
     
         36 . Method as in  claim 32 , wherein the step of moving at least one part of the sheet conveying device comprises the step of moving the entire sheet conveying device. 
     
     
         37 . Method as in  claim 32 , wherein the steps of moving the part of the sheet conveying device away from the stack of sheets and of transporting away the sheet occur at the same time. 
     
     
         38 . Method as in  claim 32 , wherein the step of moving at least one part of the sheet conveying device comprises a linear movement. 
     
     
         39 . Method as in  claim 32 , wherein the step of moving at least one part of the sheet conveying device comprises a pivoting movement.