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1. US4355565 - Fluid circuit with zero leak load check and by-pass valve

Office
United States of America
Application Number 06206192
Application Date 24.03.1980
Publication Number 4355565
Publication Date 26.10.1982
Grant Number 4355565
Grant Date 26.10.1982
Publication Kind A
IPC
F15B 11/00
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
11Servomotor systems without provision for follow-up action
CPC
F15B 11/003
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
11Servomotor systems without provision for follow-up action; ; Circuits therefor
003Systems with load-holding valves
F15B 2211/20523
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
2211Circuits for servomotor systems
20Fluid pressure source, e.g. accumulator or variable axial piston pump
205Systems with pumps
20507Type of prime mover
20523Internal combustion engine
F15B 2211/20592
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
2211Circuits for servomotor systems
20Fluid pressure source, e.g. accumulator or variable axial piston pump
205Systems with pumps
20576with multiple pumps
20592Combinations of pumps for supplying high and low pressure
F15B 2211/30505
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
2211Circuits for servomotor systems
30Directional control
305characterised by the type of valves
30505Non-return valves, i.e. check valves
F15B 2211/30515
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
2211Circuits for servomotor systems
30Directional control
305characterised by the type of valves
30505Non-return valves, i.e. check valves
30515Load holding valves
F15B 2211/30525
FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
15FLUID-PRESSURE ACTUATORS; HYDRAULICS OR PNEUMATICS IN GENERAL
BSYSTEMS ACTING BY MEANS OF FLUIDS IN GENERAL; FLUID-PRESSURE ACTUATORS, e.g. SERVOMOTORS; DETAILS OF FLUID-PRESSURE SYSTEMS, NOT OTHERWISE PROVIDED FOR
2211Circuits for servomotor systems
30Directional control
305characterised by the type of valves
30525Directional control valves, e.g. 4/3-directional control valve
Applicants Caterpillar Tractor Co.
Inventors Bianchetta Donald L.
Agents Grant John W.
Title
(EN) Fluid circuit with zero leak load check and by-pass valve
Abstract
(EN)

A load check valve is normally employed in association with a double-acting hydraulic cylinder, such as the type used to raise and lower the boom of a construction vehicle. Conventional check valves of the poppet type are difficult to modulate whereas check valves of the spool type generally do not insure leakage control at an acceptable rate during normal operation. The spool-type load check valve (20) of this invention, used in conjunction with additional check valves (60,61), overcomes the latter problem by providing a series of interconnecting passages and chambers (36) for communicating equalized fluid pressure from a cylinder (11) to either end of the spool (27) thereof to provide for minimal leakage. When a pair of such cylinders (11,12) are utilized, the load check valves (20,20') associated therewith are interconnected by a balance line (50) and resolver valves (47') to insure equalization of fluid pressure in the cylinders upon actuation thereof and to further insure a gradual descent of a load carried by the cylinders upon loss of fluid pressure between the check valves.