Electronic capacity control valve for portable screw compressor

Abstract

A spiral valve and a screw compressor having a compressor housing and the spiral valve are provided. The spiral valve includes an actuator module disposed adjacent an exterior of the compressor housing, the actuator module includes an electric motor, a gearbox mechanically coupled to the electric motor to transmit torque from the electric motor, a shutter coupled to the gearbox to rotate in response to a transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on the rotational position of the shutter, wherein the compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports.

What is claimed: 
     
         1 . A spiral valve for a screw compressor having a compressor housing, the spiral valve comprising:
 an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising:
 an electric motor; 
 a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor; 
   a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of a plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter,   wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports.   
     
     
         2 . The spiral valve of  claim 1 , wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port;
 within a distance between the first bypass port and the second bypass port is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.   
     
     
         3 . The spiral valve of  claim 1 , wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing;
 wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.   
     
     
         4 . The spiral valve of  claim 1 , wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing;
 wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.   
     
     
         5 . A screw compressor comprising:
 a compressor housing defining a compression chamber;   a female compression screw disposed within the compression chamber;   a male compression screw disposed within the compression chamber and interfacing with the female compression screw;   a plurality of bypass ports formed in the compressor housing and providing fluid communication through the compressor housing;   a spiral valve comprising:
 an actuator module disposed adjacent an exterior of the compressor housing, the actuator module comprising:
 an electric motor;
 a gearbox mechanically coupled to the electric motor to transmit a torque from the electric motor; 
 
 
   a shutter coupled to the gearbox to rotate in response to the transmitted torque from the electric motor, wherein the shutter is positioned to open and close one or more of the plurality of bypass ports formed in the compressor housing based on a rotational position of the shutter,   wherein a compression length of the screw compressor may be controlled by controlling the opening and closing of the one or more bypass ports of the plurality of bypass ports.   
     
     
         6 . The screw compressor of  claim 5 , wherein the plurality of bypass ports includes a first bypass port and a second bypass port adjacent to the first bypass port;
 within a distance between the first bypass port and the second bypass port, is less than 120% of a manufacturing tolerance of the compressor housing, and greater than or equal to 100% of the manufacturing tolerance of the compressor housing.   
     
     
         7 . The screw compressor of  claim 5 , wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing;
 wherein the shutter is positioned and shaped to open and close the pair of bypass ports simultaneously.   
     
     
         8 . The screw compressor of  claim 5 , wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along the a length of the compressor housing;
 wherein the shutter is positioned and shaped to open one bypass port of the pair of bypass ports in sequence with an other bypass port of the pair of bypass ports.   
     
     
         9 . The screw compressor of  claim 5 , wherein the plurality of bypass ports include at least one pair of bypass ports, each bypass port of the pair of bypass ports being positioned at a same position along a length of the compressor housing;
 wherein one bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the female compression screw;   wherein another bypass port of the pair of bypass ports is aligned with a largest diameter region of a lobe of the male compression screw; and   wherein the lobe of the female compression screw and the lobe of the male compression screw are located at regions of equal pressure within the compression chamber.   
     
     
         10 . The screw compressor of  claim 5 , wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and
 wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the female compression screw closest to the compression chamber inlet.   
     
     
         11 . The screw compressor of  claim 5 , wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and
 wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber inlet is aligned with a largest diameter region of a lobe of the male compression screw closest to the compression chamber inlet.   
     
     
         12 . The screw compressor of  claim 5 , wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet;
 wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the female compression screw; and   wherein compression chamber volume between the lobe of the female compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.   
     
     
         13 . The screw compressor of  claim 5 , wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet;
 wherein a bypass port of the plurality of bypass ports that is positioned closest to the compression chamber outlet is aligned with a largest diameter region of a lobe of the male compression screw; and   wherein compression chamber volume between the lobe of the male compression screw and the compression chamber outlet corresponds to minimum compression volume of the screw compressor.   
     
     
         14 . The screw compressor of  claim 5 , wherein the plurality of bypass ports define a bypass window along an area of the compressor housing between compression chamber inlet and a compression chamber outlet; and
 wherein an area, A w , of the bypass window is defined by the equation:
     A   w =10%±5%* D   RB   /N   L  
 
   wherein D RB  equals the diameter of the rotor bore of each bore of the compressor housing surrounding each of the male and female compression screws, and N L  equals the number of lobes of the male and female compression screw associated with each bore.