Oil-free air compressor system with inlet throttle

Abstract

The present air compressor system includes at least one piston stage connected to the air inlet of the compressor by an inlet valve and connected to the compressed air outlet of the compressor by an outlet valve; a motor driving the piston stage; and an adjustable throttle connected between the air inlet and the inlet valve. A controller controls the motor and the throttle to substantially close the throttle to unload the piston stage when necessary.

1 . An oil-free air compressor comprising:
 an air inlet and a compressed air outlet;   at least one piston stage connected to the air inlet by an inlet valve and the compressed air outlet by an outlet valve;   a motor driving the piston stage;   an adjustable throttle connected between the air inlet and the inlet valve; and   a controller controlling the motor and the throttle; the controller substantially closing the throttle to unload the piston stage.   
   
   
       2 . The compressor according to  claim 1 , wherein the throttle is a butterfly valve. 
   
   
       3 . The compressor according to  claim 1 , wherein the compressor has two piston stages; and the throttle is between the air inlet and the inlet valve of the first piston stage. 
   
   
       4 . The compressor according to  claim 1 , wherein the controller substantially closes the throttle to unload the piston stage for a pre-selected state of the compressor. 
   
   
       5 . The compressor according to  claim 4 , wherein the pre-selected state is the restart of the motor after a brief delay. 
   
   
       6 . The compressor according to  claim 1 , wherein the compressor includes a crankcase to which piston stage and the air inlet are mounted; and the throttle is mounted in a conduit connecting the crankcase to inlet valve. 
   
   
       7 . The compressor according to  claim 1 , wherein the piston stage includes two parallel connected pistons and each piston has an adjustable throttle connected to the inlet valve. 
   
   
       8 . An oil-free air compressor comprising:
 an air inlet connected to a crankcase and a compressed air outlet;   at least one piston stage mounted to on the crankcase, having an inlet valve connected to the crankshaft by conduit and having an outlet valve connected to the compressed air outlet; and   an adjustable throttle in the conduit between the crankcase and the inlet valve.   
   
   
       9 . The compressor according to  claim 8 , wherein the piston stage includes two parallel connected pistons, and each piston has an adjustable throttle mounted in the conduit connecting the inlet valve and the crankcase. 
   
   
       10 . A method of operating an oil-free air compressor which includes an adjustable throttle between an air inlet of the compressor and the inlet of a piston stage driven by a motor, the method comprising:
 determining the state of the compressor; and   substantially closing the throttle to unload the piston stage for a pre-selected state of the compressor.   
   
   
       11 . The compressor according to  claim 10 , wherein the pre-selected state is the restart of the motor after a brief delay.