Patent ID: 6397590
Filing Date: 2002-06-04
Classification: B64C,F04B,F15B

Abstract:
A hydraulic warming system for low ambient temperature operation comprising:(a) a two-stage jet pipe flow control electro-hydraulic servo valve means for providing a flow of pressurized hydraulic fluid from a source thereof to a plurality of hydraulic load driving passageways, said servovalve including an inlet port coupled to said source for receiving pressurized hydraulic fluid from said source, a plurality of outlet ports coupled respectively to said plurality of hydraulic load driving passageways, a fluid flow restrictor and a return port for releasing internal hydraulic leakage fluid at low flow rate from said electro-hydraulic servovalve through a return passageway, said low flow rate internal hydraulic leakage fluid being warmed by flowing through said fluid flow restrictor; (b) means for controlling said flow of pressurized hydraulic fluid in said plurality of hydraulic load driving passageways, including a spool and sleeve bypass-shutoff valve having a pre-loaded return spring, a plurality of inlet ports coupled respectively to said plurality of hydraulic load driving passageways and to said return passageway and a plurality of outlet ports; (c) a hydraulic motor coupled between said flow controlling means and a hydraulic system return passageway and driven by said pressurized hydraulic fluid from said hydraulic servo valve means through said plurality of hydraulic load driving passageways, said hydraulic motor having internal rotating components; and (d) a solenoid valve coupled to said bypass-shutoff valve for driving said bypass-shutoff valve between a first position and a second position, said first position utilizing said warmed low flow rate hydraulic leakage fluid from said servovalve to provide continuous warming of said internal rotating components of said hydraulic motor when said hydraulic motor is not operational, said second position diverting said warmed low flow rate hydraulic leakage fluid from said servovalve directly to said hydraulic system return passageway bypassing said internal rotating components of said hydraulic motor when said hydraulic motor is operational, said servovalve being constantly pressurized through said inlet port from said source.