Apparatus for release of thin coated sheets from a roller coating machine

Abstract

The present invention obviates the use of a vacuum while providing reliable release of thin coated sheets from roller coating machines. Reliable release of a coated sheet is achieved by using dual sets of air nozzles, one set producing a constant flow of a sheet of air and the other producing a short pulse of a sheet of air at an appropriate time in the travel of the front edge of the sheet through the rollers. An optical sensor is employed to provide the properly timed signal to initiate the pulsed air blast. The respective sets of nozzles are configured to position the nozzles in two rows, one above the other, with offset or alternating horizontal positioning so that nozzles of one set do not interfere with nozzles of the other set. Each set of nozzles is connected to a common plenum or air bar extending in parallel relation to the rollers. Each such plenum or air bar is connected to an air pressure source by suitable regulators, filters, solenoids, valves, hoses and connectors.

1 . In a roller coating machine having a plurality of rollers for coating thin sheets of material and a conveyor belt for transporting the sheets as they exit the rollers, an apparatus for promoting release of the sheets from the rollers for transfer onto the conveyor belt; the apparatus comprising: 
 a first plurality of air nozzles positioned adjacent said rollers where each said coated sheet exits said rollers, said first plurality of air nozzles creating a layer of constant air flow towards each said sheet; and    a second plurality of air nozzles positioned adjacent said rollers where each said coated sheet exits said rollers, said second plurality of air nozzles creating a layer of pulsed air flow towards a front edge of each said sheet.    
   
   
       2 . The apparatus recited in  claim 1  wherein said first and second pluralities of nozzles are positioned adjacent one another.  
   
   
       3 . The apparatus recited in  claim 1  wherein said first and second pluralities of nozzles are positioned one above the other relative to each said coated sheet.  
   
   
       4 . The apparatus recited in  claim 1  wherein said first and second pluralities of nozzles are positioned in an alternating configuration so that air layers of the respective pluralities of nozzles do not substantially affect each other.  
   
   
       5 . The apparatus recited in  claim 1  wherein each of said pluralities of nozzles is connected to a respective air plenum for delivering pressurized air to said nozzles.  
   
   
       6 . The apparatus recited in  claim 5  wherein each said air plenum is positioned in parallel to the axes of said rollers.  
   
   
       7 . The apparatus recited in  claim 5  wherein each said air plenum is connected at its respective ends to a source of pressurized air.  
   
   
       8 . The apparatus recited in  claim 5  wherein each said air plenum is connected to a source of pressurized air through a solenoid valve for selectively switching air flow to said plenum on and off.  
   
   
       9 . The apparatus recited in  claim 1  further comprising a sensor for generating a signal in response to passage of each said sheet through said rollers and means for receiving said signal to initiate said pulsed air flow of said second plurality of air nozzles.  
   
   
       10 . A method for releasing thin coated sheets from the rollers of a roller coating machine, the method comprising the following steps: 
 directing a layer of constant air flow toward each said coated sheet as the sheet exits the rollers; and    directing a layer of pulsed air flow toward a front edge of each said coated sheet as the sheet exits the rollers.    
   
   
       11 . The method recited in  claim 10  wherein each of said directing steps is carried out simultaneously during said pulsed air flow.  
   
   
       12 . The method recited in  claim 10  further comprising the step of sensing the passage of each said sheet through said rollers for initiating said pulsed air flow.