Suction Cutoff Unloader Valve For Compressor Capacity Control

Abstract

A reciprocating compressor includes a first cylinder and a second cylinder, first and second suction cutoff unloader valve assemblies, and a controller. The first and second suction cutoff unloader valve assemblies are integral to the compressor and are capable of a rapid cycling to interrupt flow of refrigerant to the first and second cylinders. The controller operates at least one of the first suction cutoff unloader valve assembly or second suction cut-off unloader valve assembly in the rapid cycling and monitor a number of rapid cycles. In another aspect, a multi-stage compressor comprises a lower pressure stage and a higher pressure stage, and at least one suction cutoff unloader valve assembly capable of a rapid cycling to interrupt flow of refrigerant to a lower stage cylinder.

1 . A reciprocating compressor, the compressor comprising:
 a first cylinder and a second cylinder;   a first suction cutoff unloader valve integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the first cylinder;   a second suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the second cylinder; and   a controller configured to operate at least one of the first suction cutoff unloader valve assembly or second suction cutoff unloader valve assembly in the rapid cycling and monitor a number of rapid cycles for at least one suction cutoff valve.   
     
     
         2 . The reciprocating compressor of  claim 1 , wherein the compressor includes three or more suction cutoff unloader assemblies and wherein at least one of the suction cutoff unloader assemblies operates in the rapid cycling while at least one of the suction cutoff unloader assemblies does not operate in the rapid cycling. 
     
     
         3 . The reciprocating compressor of  claim 1 , wherein the rapid cycling includes an alternating cycling mode that operates the first suction cutoff unloader valve assembly in the rapid cycling, while the second suction cutoff unloader valve assembly is not operated in the rapid cycling but is disposed either in a fully unloaded position blocking the flow of refrigerant to the second cylinder or a fully loaded position allowing for uninterrupted flow of refrigerant to the second cylinder. 
     
     
         4 . The compressor of  claim 3 , wherein the controller operates the first suction cutoff unloader valve assembly in the rapid cycling for a first time period and the controller does not operate the second suction cutoff unloader valve in the rapid cycling during the first time period and then the controller operates the second suction cutoff unloader valve assembly in the rapid cycling for a second time period and does not operate the first suction cutoff unloader valve assembly in the rapid cycling during the second time period. 
     
     
         5 . The reciprocating compressor of  claim 1 , wherein the controller counts the number of cycles for each valve and alternates the first and second suction cutoff unloader valve based on the count to assure that the first suction cutoff unloader valve does not rapid cycle a substantial number of times more than the second suction cutoff unloader valve. 
     
     
         6 . The compressor of  claim 1 , wherein the first and second suction cutoff unloader valve assemblies have a cycle period of between 0.3 seconds and 180 seconds, when operated in the rapid cycling. 
     
     
         7 . The compressor of  claim 1 , further comprising a third cylinder and wherein the first cylinder is a lower stage cylinder and the second cylinder is a lower stage cylinder and the reciprocating compressor is a multi-stage compressor. 
     
     
         8 . The compressor of  claim 7 , wherein both the first suction cutoff unloader valve assembly and the second suction cutoff unloader valve assembly operate simultaneously in the rapid cycling. 
     
     
         9 . The compressor of  claim 1 , wherein rapid cycling is achieved through pulse width modulation of the first and second suction cutoff unloader valve assembly. 
     
     
         10 . A reciprocating compressor, the compressor comprising:
 a first cylinder and a second cylinder;   a first suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the first cylinder;   a second suction cutoff unloader valve assembly integral to the compressor and capable of rapid cycling to interrupt flow of refrigerant to the second cylinder; and   a controller configured to operate the first suction cutoff unloader valve assembly or second suction cutoff unloader valve assembly in rapid cycling as an alternating cycling mode which operates the first suction cutoff unloader valve assembly in the rapid cycling while the second suction cutoff unloader valve assembly is not operated in the rapid cycling.   
     
     
         11 . The compressor of  claim 10 , wherein the controller operates the first suction cutoff unloader valve assembly in the rapid cycling for a first time period and the controller does not operate the second suction cutoff unloader valve in the rapid cycling during the first time period and then the controller operates the second suction cutoff unloader valve assembly in the rapid cycling for a second time period and does not operate the first suction cutoff unloader valve assembly in the rapid cycling during the second time period. 
     
     
         12 . The reciprocating compressor of  claim 10 , wherein the controller counts the number of cycles for each valve and alternates the first and second suction cutoff unloader valve based on the count to assure that the first suction cutoff unloader valve does not rapid cycle a substantial number of times more than the second suction cutoff unloader valve. 
     
     
         13 . The compressor of  claim 10 , wherein the first and second suction cutoff unloader valve assembly have a cycle period of between 0.3 seconds and 180 seconds, when operated in rapid cycling. 
     
     
         14 . The compressor of  claim 10 , further comprising a third higher stage cylinder and wherein the first cylinder is a lower stage cylinder and the second cylinder is a lower stage cylinder and the reciprocating compressor is a multi-stage compressor. 
     
     
         15 . The compressor of  claim 10 , wherein rapid cycling is achieved through pulse width modulation of the first and second suction cutoff unloader valve assembly. 
     
     
         16 . A multi-stage reciprocating compressor, the compressor comprising:
 a lower stage cylinder and a higher stage cylinder, the higher stage arranged to receive refrigerant compressed in the lower stage cylinder;   at least one suction cutoff unloader valve assembly integral with compressor and capable of rapid cycling to interrupt flow of refrigerant to the lower stage cylinder; and   a controller configured to operate the at least one suction cutoff unloader valve assembly in the rapid cycling.   
     
     
         17 . The compressor of  claim 15 , wherein the at least one suction cutoff unloader valve assembly has a cycle period of between 0.3 second and 180 seconds, when operated in rapid cycling. 
     
     
         18 . The compressor of  claim 15 , wherein rapid cycling is achieved through pulse width modulation of the first suction cutoff unloader valve assembly. 
     
     
         19 . The multi-stage compressor of  claim 15 , further comprising:
 a second lower stage cylinder; and   a second suction cutoff unloader valve assembly capable of rapid cycling to interrupt flow of refrigerant to the second lower stage cylinder.   
     
     
         20 . The multi-stage compressor of  claim 18 , wherein the controller operates both the first suction cutoff unloader valve assembly and the second suction cutoff unloader valve assembly simultaneously in rapid cycling.