Patent ID: 6640685
Filing Date: 2003-11-04
Classification: F15B,G05B

Abstract:
A hydraulic control system for controlling expansion and contraction of a cylinder wherein said cylinder comprises an extension chamber and a contraction chamber and said hydraulic control system comprises:a first three way servovalve comprising a first pressure supply port and a first pressure discharge port and adapted to selectively communicate said expansion chamber with said first pressure supply port and with said first pressure discharge port; a second three way servovalve comprising a second pressure supply port and a second pressure discharge port and adapted to selectively communicate said contraction chamber with said second pressure supply port and with said second pressure discharge port; a four way servovalve comprising a third pressure supply port, a third pressure discharge port, a fourth pressure supply port and a fourth pressure discharge port and said four way servovalve is adapted to selectively communicate said expansion chamber with said third pressure supply port and said third pressure discharge port and to selectively communicate said contraction chamber with said fourth pressure supply port and with said fourth pressure discharge port; a feedback device capable of measuring at least one property of said cylinder and providing a signal proportional to said property; a controller capable of receiving said signal and comparing said property to a desired property to determine a difference and activating at least one of said first servovalve, said second servovalve or said four way servovalve to decrease said difference.