Automatic pressure relief and snubbing in hydraulic actuators

Claim 2

In combination with a hydraulic actuator including a housing defining a working chamber divided into subchambers on opposite sides of piston means relatively movable in said chamber; a. means providing a hydraulic pressure fluid source; b. a pressure line for conducting hydraulic pressure fluid from the source to one of said subchambers; c. an exhaust line leading from the other of said subchambers and having a pair of spaced restrictions therein; and d. means referenced to said one subchamber to operate in response to initial pressure build up in said one subchamber to relieve pressure in said exhaust line between said restrictions for accelerating running stroke of the piston.

Claim 3

In a combination according to claim 1, including a return line to said source, and said means for relieving pressure comprising a bypass from said exhaust line to said return line and a normally closed dump valve in said bypass referenced to and driven open by predetermined pressure in said one subchamber greater than normal running pressure.

Claim 4

In a combination according to claim 2, said return line having a restriction therein which is less than the restriction in said exhaust liNe located downstream from said bypass, whereby to maintain the return line in a filled hydraulic system and enabling bypass pressure relieving dumping from the exhaust line into the return line upon opening of said dump valve.

Claim 5

In a combination according to claim 1, means connected directly to said pressure line and referenced to said other subchamber for relieving pressure in the pressure line upon development of excessive pressure in said one chamber.

Claim 6

In a combination according to claim 4, said pressure line including spaced restrictions therein, and said pressure line pressure relief means communicating with said pressure line between said restrictions.

Claim 7

In a combination according to claim 5, a return line to said source, said pressure relief means for the pressure line being connected to said return line and including a dump valve normally closed but responsive to excessive pressure in said other chamber to open a passage from the pressure line to said return line.

Claim 8

In a combination according to claim 6, means providing an excess pressure crossover relief for each of said subchambers communicating with said return line, and anti-cavitation hydraulic fluid make-up means communicating with each of said subchambers and leading from said return line.

Claim 9

In combination with a hydraulic actuator including a housing defining a working chamber divided into subchambers on opposite sides of piston means relatively movable in said chamber; means providing a hydraulic pressure fluid source; a pressure line for conducting hydraulic pressure fluid from said source to one of said subchambers to drive said piston means; an exhaust line leading from the other of said chambers and communicating with a low pressure means; overload pressure relief means communicating directly with said pressure line upstream from said one subchamber and referenced for response to pressure buildup in said other subchamber to bypass pressure from the pressure line to said low pressure means; a return line to said low pressure means in addition to said pressure and exhaust lines, and said overload pressure relief means communicating with said return line; said overload pressure relief means comprising a duct leading from said pressure line to said return line and having a normally closed dump valve therein; a duct leading from said other subchamber and connected in referencing relation to said dump valve to effect opening of the dump valve in response to overload pressure from said other subchamber; and startup pressure relief means connected to said exhaust line and discharging into said return line and responsive to pressure in excess of running pressure developed in said one subchamber during startup; said startup pressure relief means comprising a dump valve in a bypass duct from said exhaust line to said return line and normally closed, with a referencing passage leading from said one subchamber to said startup pressure dump valve.

Claim 10

In combination with a hydraulic actuator including a housing defining a working chamber divided into subchambers on opposite sides of piston means relatively movable in said chamber; means providing a hydraulic pressure fluid source; a pressure line for conducting hydraulic pressure fluid from said source to one of said subchambers to drive said piston means; an exhaust line leading from the other of said chambers and communicating with a low pressure means; overload pressure relief means communicating directly with said pressure line upstream from said one subchamber and referenced for response to pressure buildup in said other subchamber to bypass pressure from the pressure line to said low pressure means; a return line to said low pressure means in addition to said pressure and exhaust lines, and said overload pressure relief means communicating with said return line; said overload pressure relief means comprising a duct leading from said pressure line to said return line and having a normally closed dump valve therein; a duct leading from said other subchamber and connected in referencing relation to said dump valve to effect opening of the dump valve in response to overload pressure from said other subchamber; and startup pressure relief means connected to said exhaust line and discharging into said return line and responsive to pressure in excess of running pressure developed in said one subchamber during startup; said startup pressure relief means comprising a dump valve in a bypass duct from said exhaust line to said return line and normally closed, with a referencing passage leading from said one subchamber to said startup pressure dump valve.

Claim 11

In a combination according to claim 8, a control valve operative to connect or disconnect the pressure and exhaust lines simultaneously relative to said source, crossover pressure relief means connecting said subchambers with said return line, and anti-cavitation means connecting said return line with said subchambers.

Claim 12

In combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively effecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return liNe communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines having spaced restrictions therein; and said respective pressure relief means connected to said pressure exhaust lines between said restrictions.

Claim 13

In combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively effecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return liNe communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines having spaced restrictions therein; and said respective pressure relief means connected to said pressure exhaust lines between said restrictions.

Claim 14

In a combination according to claim 10, said return line having a restriction therein downstream from said pressure relief means and providing for less restriction than the respective restrictions in said pressure/exhaust lines which are located nearest to said control valve means.

Claim 15

In a combination according to claim 11, said valve means being operative to disconnect said pressure/exhaust lines from said source, crossover pressure relief means connecting said subchambers with said return line, and anti-cavitation means leading from said return line to each of the respective subchambers.

Claim 16

In a combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return line communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith; snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said ports being in respective surface defining the respective subchamber, and said snubber valve means comprising a valve member slidably engaging the respective surface and having progressively restricting orifice means operative to progressively throttle and close the associated port in the movement of the piston means toward the port; and said throttle valve members being normally biased into snubbing relation to said respective surfaces and being movable away from said port in response to fluid pressure to enable reversal of the piston drive.

Claim 17

In a combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return line communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith; snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said ports being in respective surface defining the respective subchamber, and said snubber valve means comprising a valve member slidably engaging the respective surface and having progressively restricting orifice means operative to progressively throttle and close the associated port in the movement of the piston means toward the port; and said throttle valve members being normally biased into snubbing relation to said respective surfaces and being movable away from said port in response to fluid pressure to enable reversal of the piston drive.

Claim 18

In combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return line communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith; snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said actuator being of the rotary type wherein said piston means comprise a vane carried by an oscillating wing shaft with which an abutment in the working chamber cooperates as a barrier to divide the working chamber with said piston vane into said subchambers and said ports are located in an end closure of the housing providing such surfaces; said snubber valve means comprising respective elongated plate members mounted on and projecting in respectively opposite directions from said piston vane; means connecting said valve members operatively to the piston vane and enabling limited movement of the valve members toward and away from said closure surfaces; means normally biasing the valve members toward said surfaces; and each of said valve members having a face slidably engaging with said surfaces and provided with a respective orifice groove diminishing from a leading end to a trailing end for progressively throttling discharge through the associated port as the respective valve member is moved over the port by advance of the piston vane in a driving stroke.

Claim 19

In combination with a hydraulic actuator comprising a housing having a working chamber therein divided into subchambers by piston means movable in respectively opposite directions in response to pressure differential in the respective subchambers, and a symmetrical hydraulic control system for the actuator; including means providing a hydraulic pressure fluid source; low pressure means; respective pressure/exhaust lines communicating with said subchambers; multi-position control valve means operative for selectively and alternatively affecting pressure or exhaust relation between said lines and said source and said low pressure means; a separate return line communicating with said low pressure means; respective pressure relief means communicating said return line with said pressure/exhaust lines upstream from the subchambers and respectively referenced to be operative in response to overload pressure sensed in the other of the subchambers in each instance; each of said pressure/exhaust lines communicating with its respective subchamber through a port by which pressure fluid is delivered to either respective subchamber to move the piston means into the other of the subchambers from which hydraulic fluid is discharged through the port communicating therewith; snubber valve means carried by the piston means operative to terminate driving stroke of the piston means by closing the discharge port whereby overload pressure in the associated subchamber referenced to the overload relief means of the pressure fluid delivering line bypasses the pressure therefrom to the return line; said actuator being of the rotary type wherein said piston means comprise a vane carried by an oscillating wing shaft with which an abutment in the working chamber cooperates as a barrier to divide the working chamber with said piston vane into said subchambers and said ports are located in an end closure of the housing providing such surfaces; said snubber valve means comprising respective elongated plate members mounted on and projecting in respectively opposite directions from said piston vane; means connecting said valve members operatively to the piston vane and enabling limited movement of the valve members toward and away from said closure surfaces; means normally biasing the valve members toward said surfaces; and each of said valve members having a face slidably engaging with said surfaces and provided with a respective orifice groove diminishing from a leading end to a trailing end for progressively throttling discharge through the associated port as the respective valve member is moved over the port by advance of the piston vane in a driving stroke.

Claim 22

In combination with a hydraulic actuator including a housing providing a working chamber, piston means movably operative in said chamber in response to hydraulic pressure fluid differential, means for delivering hydraulic pressure fluid to one side of said piston, and means for exhausting hydraulic fluid from the opposite side of said piston including a surface having an exhaust port therein, the improvement comprising: a snubber valve member carried by the piston means and comprising an elongated plate movable therewith on said surface toward said port and having a face slidably engaging said surface; said valve member having progressive throttling orifice means comprising a groove in said face of substantially the same width throughout its length and diminishing in depth from a leading end to a trailing end operative as the valve member moves over the port and the groove advances from said leading end in alignment with the port to effect progressive throttling of exhaust flow through the port; said groove having a first portion diminishing in deptH from said leading end at a greater angle than a second portion of the groove which diminishes at a shallower angle to said trailing end, for smooth progressive throttling effect in the advance of the groove over the port.

Claim 23

In combination with a hydraulic actuator including a housing providing a working chamber, piston means movably operative in said chamber in response to hydraulic pressure fluid differential, means for delivering hydraulic pressure fluid to one side of said piston, and means for exhausting hydraulic fluid from the opposite side of said piston including a surface having an exhaust port therein, the improvement comprising: a snubber valve member carried by the piston means and comprising an elongated plate movable therewith on said surface toward said port and having a face slidably engaging said surface; said valve member having progressive throttling orifice means comprising a groove in said face of substantially the same width throughout its length and diminishing in depth from a leading end to a trailing end operative as the valve member moves over the port and the groove advances from said leading end in alignment with the port to effect progressive throttling of exhaust flow through the port; said groove having a first portion diminishing in deptH from said leading end at a greater angle than a second portion of the groove which diminishes at a shallower angle to said trailing end, for smooth progressive throttling effect in the advance of the groove over the port.

Claim 24

A combination according to claim 16, wherein said piston includes a wing shaft having a radial vane rotatably movably operative in said chamber relative to an abutment in said chamber, said means for delivering hydraulic pressure fluid delivering the pressure fluid into the chamber between said abutment and one side of said vane and said exhaust port being located between the opposite side of said vane and said abutment, said vane having a mounting recess therein at the side of the vane which faces toward said port, said valve member comprising an elongated plate having lug mounting structure at one end received in said recess and with the remainder of the valve plate projecting from the vane toward said port, and means connecting said mounting lug to said vane within said recess enabling limited relative movement of the valve plate toward and away from said surface but retaining the valve plate against transfers relative movement.

Claim 25

A combination according to claim 17, said connecting means comprising a pin mounted in said vane across said recess, said mounting lug having a clearance hole therein elongated in the direction of permissible movement of the valve plate toward and away from said surface, said mounting lug having a slot therein across which the pin extends, and a torsion biasing spring engaged about the pin in said slot and having one end thrusting against the valve plate and an opposite end thrusting against the vane in said recess.