Vacuum tables

Abstract

There is disclosed a vacuum table 400 comprising a vacuum plate 402 separating a first vacuum chamber 406 from a substrate zone 60 for receiving a substrate 50. The vacuum plate has a plurality of suction holes 404 for conveying a gas flow from the substrate zone 60 to the first vacuum chamber 406. There is an evacuation port 422 in communication with a second vacuum chamber 420 to evacuate gas from the substrate zone 60 when a substrate 50 is received over the suction holes 404 of the vacuum plate 402, and a vacuum port 424 for discharging gas received in the second vacuum chamber 420 to a vacuum source 423. The first vacuum chamber 406 and the second vacuum chamber 420 are in fluid communication via a valve 430 so that gas flows from the first vacuum chamber 406 to the vacuum port 424 via the second vacuum chamber 420. The valve 430 is controllable to vary a gas flow rate through the vacuum plate 402 and thereby vary a retaining force on a substrate 50 received thereon.

1 . A vacuum table comprising;
 a vacuum plate separating a first vacuum chamber from a substrate zone for receiving a substrate, the vacuum plate having a plurality of suction holes for conveying a gas flow from the substrate zone to the first vacuum chamber;   an evacuation port located at a side of the substrate zone to evacuate gas from above the vacuum plate into a second vacuum chamber;   a vacuum source connected to evacuate both the first and second vacuum chambers;   a valve between the first vacuum chamber and the vacuum source to vary a first gas flow rate from the first vacuum chamber from a second gas flow rate from the second vacuum chamber.   
     
     
         2 . The vacuum table of  claim 1 , further comprising a controller to operate the valve to selectively vary the first gas flow rate from the first vacuum chamber. 
     
     
         3 . The vacuum table of  claim 2 , wherein the controller is to vary the first gas flow rate from the first vacuum chamber based on a type of substrate to be received in the substrate zone. 
     
     
         4 . The vacuum table of  claim 3 , wherein the controller is to determine a substrate type of the substrate to be received in the substrate zone, and to control the valve to vary the gas flow rate through the vacuum plate based on the substrate type. 
     
     
         5 . The vacuum table of  claim 1 , wherein the valve fluidly connects the first vacuum chamber with the second vacuum chamber. 
     
     
         6 . The vacuum table of  claim 1 , wherein the first gas flow rate is less than the second gas flow rate through the evacuation port. 
     
     
         7 . The vacuum table of  claim 1 , wherein valve is controllable to vary gas flow from the first vacuum chamber from between 0% and 1% of a total flow through the evacuation port. 
     
     
         8 . The vacuum table of  claim 1 , wherein the second vacuum chamber surrounds the first vacuum chamber. 
     
     
         9 . The vacuum table of  claim 1 , wherein the first vacuum chamber is disposed within the second vacuum chamber in a nested arrangement. 
     
     
         10 . The vacuum table of  claim 1 , wherein the evacuation port is located at a side of, and above, the vacuum plate. 
     
     
         11 . The vacuum table of  claim 1 , wherein the evacuation port is located in a same plane as the vacuum plate. 
     
     
         12 . A partition for retrofitting a vacuum table having a vacuum plate above a single compound vacuum chamber, the partition to separate the single compound vacuum chamber into a first vacuum chamber and a second vacuum chamber, the partition comprising;
 a partition wall to separate the single compound vacuum chamber into the first vacuum chamber within the partition wall and the second vacuum chamber outside of the partition wall; and   a valve communicating through the partition wall so that the first vacuum chamber is fluidly connected through the valve with the second vacuum chamber.   
     
     
         13 . The partition of  claim 12 , further comprising a controller to operate the valve to selectively vary a first gas flow rate from the first vacuum chamber. 
     
     
         14 . The partition of  claim 13 , wherein the controller is to vary the first gas flow rate from the first vacuum chamber based on a type of substrate to be received in a substrate zone atop the vacuum plate. 
     
     
         15 . The partition of  claim 14 , wherein the controller is to determine a substrate type of the substrate to be received in the substrate zone, and to control the valve to vary the gas flow rate through the vacuum plate into the first vacuum chamber based on the substrate type. 
     
     
         16 . A method of operating a vacuum table, the vacuum table comprising a single vacuum source for evacuating a first vacuum chamber and a second vacuum chamber, the vacuum table further comprising a vacuum plate with a plurality of suction holes for separating the first vacuum chamber from a substrate zone for receiving a substrate, the second vacuum chamber fluidly connected to the substrate zone through a separate evacuation port, the method comprising:
 operating a valve of the first vacuum chamber to regulate a gas flow out of the first vacuum chamber separately from a gas flow out of the second vacuum chamber.   
     
     
         17 . The method of  claim 16 , further comprising programming a controller to operate the valve to selectively vary the gas flow from the first vacuum chamber. 
     
     
         18 . The method of  claim 16 , further comprising varying the gas flow from the first vacuum chamber based on a type of substrate to be received in the substrate zone. 
     
     
         19 . The method of  claim 18 , further comprising:
 programming a controller to operate the valve to selectively vary the gas flow from the first vacuum chamber; and,   with the controller, determining a substrate type of the substrate to be received in the substrate zone, and controlling the valve to vary the gas flow based on the determined substrate type.   
     
     
         20 . The method of  claim 16 , further comprising maintaining the gas flow from the first vacuum chamber to be less than a second gas flow from the second vacuum chamber.