Patent ID: 6050172
Filing Date: 2000-04-18
Classification: C03B,F15B,Y02P,Y10S

Abstract:
A system for displacing a piston between opposite ends of a cylinder comprisinga first conduit communicating with one end of the cylinder and a second conduit communicating with the other end of the cylinder,a first pressure valve settable either at a first position connecting the first conduit to a source of pressure or to a second position connecting the first conduit a highly restrictive exhaust,a second pressure valve settable either at a first position connecting the second conduit to a highly restrictive exhaust or a second position connecting the second conduit to a source of pressure,a first speed control valve settable at a first position where no flow occurs or at a second position connecting the first conduit to a slightly restrictive exhaust,a second speed control valve settable at a first position connecting the second conduit to a slightly restrictive exhaust or to a second position where no flow occurs, anda controlfor operating in a first mode for a selected period of time prior to the beginning of displacement of the piston from the other end of the cylinder to the one end including means for setting said first pressure valve to said second position, said second pressure valve to said first position, said first speed control valve to said second position and said second speed control valves to the first position,for operating in a second mode for a predetermined period of time following the passage of said selected period of time including means for changing the setting of said second pressure valve and said second speed control valve to the second position at the beginning of the predetermined period of time, andfor operating for a set period of time, following said predetermined period of time, in a third mode including means for changing the setting of said first speed control valve to the first position at the beginning of the set period of time.