US3699850A

US3699850A - Fluid actuator with lock and cushion

Info

Publication number: US3699850A
Application number: US193055A
Authority: US
Inventors: Douglas A Wagner
Original assignee: Motors Liquidation Co
Current assignee: Motors Liquidation Co
Priority date: 1971-10-27
Filing date: 1971-10-27
Publication date: 1972-10-24
Anticipated expiration: 1989-10-24

Abstract

A fluid actuator in the form of a differential fluid pressure operated piston rod in a cylinder has the piston rod retained in a retracted position by a spring biased pin and lock arrangement which in its normal biased position has the lock in locking engagement with the piston rod, the lock and pin being acted upon by the fluid pressure to effect its unlocking from the piston rod, a cushion cup being positioned behind the enclosed end of the piston rod to move axially upon movement of the piston rod into position to restrict movement of the lock into its normal locking position.

Description

United States Patent Wagner I [54] FLUID ACTUATOR WITH LOCK AND' CUSHION [72] Inventor: Douglas A. Wagner, Indianapolis,

Ind.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Oct. 27, 1971 211 App]. No.: 193,055

52 US. Cl ..92/24, 74/527 [51] Int. Cl ..F15b 15/26 [58] Field of Search ....92/l5, 24, 27, 28, 30', 188/67; 1 74/527; 251/94 [56] References Cited UNITED STATES PATENTS 2,130,618 9/1938 Gnavi ..92 27- 2,815,736 12/1957 Wright ..92/24 3,398,651

8/1968 Folmer ..92/27 Oct. 24, 1972 3,584,544 6/1971 Haberman ..92/24 FOREIGN PATENTS OR APPLICATIONS 943,791 3/1949 France ..74/527 Primary Examiner-Martin P. Schwadron Assistant Examiner-A. Hershkovitz Attorney-J. L. Carpenter et a1.

[57] ABSTRACT A fluid actuator .in the form of a differential fluid pres-- sure operatedpiston rod in a cylinder has the piston rod retained in a retracted position by a spring biased pin and lock arrangement which in its normal biased position has the lock in looking engagement with the piston rod, the lock and pin being acted upon by the fluid pressure to effect its unlocking from the "piston rod, a cushion cup being positioned behind the enclosed end of the piston rod to move axially upon movement of the piston rod into position to restrict movement of the lock into its normal locking position.

7 Claims, 2 Drawing Figures FLUID ACTUATOR WITH LOCK AND CUSHION This invention herein described was made in the course of work under a contract or subcontract thereunder with the Department of Defense.

This invention relates to a fluid actuator which is adapted to be operated and controlled by pneumatic or hydraulic fluid under pressure and, in particular, to a differential fluid pressure operated actuator having a locking mechanism and a cushion mechanism for the piston rod of the unit.

The device of this invention falls generally into a class of actuators which are described as linear actuators. By the word linear, it is meant that the actuating device operates in a straight line.

Linear actuators of the piston type are usually con trolled by hydraulic or pneumatic amplifiers such as, for example, a pneumatic or hydraulic servo valve.

Although the device of this invention may be utilized either as a pneumatic or hydraulic device, it is described herein as a hydraulic fluid actuator.

It is sometimes desirable to use hydraulic fluid actuators in systems wherein the actuator is operated upon by hydraulic fluid at relatively high pressure such that although a pressure differential normally exists onopposite sides of the piston of the actuator, the pressure on the low pressure side of the piston may still be in the range of up to 400 pounds per square inch pressure. Under these circumstances, if there is a malfunction in the unit, this relatively high pressure fluid on the low pressure side of the piston is still sufficient to actuate the piston if there is a sudden pressure drop opposing this fluid. Accordingly, it is desirable to provide a positive locking mechanism for the piston in such a fluid actuator. in addition, it is also desirable in many circumstances, due to the shortness of the stroke of the piston and the fluid pressures used in the unit, to provide a reasonable cushioning effect on the piston as it is moved on its return stroke.

lt is, therefore, a primary object of this invention to improve an actuator whereby a positive locking mechanism is provided to retain the piston rod of the actuator in its retarded position while still permitting unlocking of this locking mechanism when desired to effect linear movement of the piston rod.

Another object of this invention is to improve a fluid actuator to provide it with a locking mechanism to engage and lock the piston rod in its retracted position when desired and to unlock this locking mechanism from the piston rod to permit a forward stroke, with a cushioning mechanism being provided to retain the locking mechanism in an unlocked position until return of the piston rod to its retracted position, the cushioning mechanism also effecting a controlled return of the piston to its retracted position.

These and other objects of the present invention are attained by means of a fluid actuator having a piston rod reciprocably mounted therein for movement from a retracted position to an extended position, a radially extending spring biased pin forcing a lock mechanism into locking engagement with the piston rod when in its retracted position, the lock carrying radially positioned detent balls engagable with the walls of a sleeve in which the lock mechanism is slidably positioned to hold the lock in its radiallyextended locking position until fluid pressure acts upon the pin to permit radially inward movement of the ball detents to effect release of the lock which is then actuated by fluid pressure out of locking engagement with the piston rod. A spring biased cushion cup positioned axially behind the piston rod is movable by the spring uponmovement of the piston rod into position in abutting relationship'against the lock to permit its engagement with the piston rod on the piston rod when returned to its retracted position.

For a better understanding of the invention, as well as other objects and further features thereof, reference is had to the following detailed description of the invention to be read in connection with the accompanying drawings, wherein:

FIG. 1 is a plan view in section of the fluid-actuator with lock and cushion of the invention, with the lock engaging the piston rod of the actuator; and,

FIG. 2 is a view similar to FIG. 1 but with the lock disengaged from the piston rod and contacting the cushion of this mechanism.

Referring now to the drawings, there is shown a fluid actuator mechanism including a plunger or piston rod 10 slidably positioned in an actuator housing 12, one end or free end 10a of the piston rod extending externally of the housing for connection to a suitable element, not shown, to be acted on by the actuator. In the embodiment disclosed, the actuator housing 12 consists of a cylinder 14 provided with reduced end portions 14a at opposite ends thereof received in the stepped bores 16 and 18, of front and

rear cylinder heads

20 and 22, respectively,'the latter being secured together by equally spaced bolts 24 extending through front head 20 and threaded into rear head 22 with the cylinder 14 securely sandwiched between these heads.

Piston rod 10 is provided at one end with spaced apart

rigid piston flanges

26 and 28 slidably received in the bore 30 of cylinder 14, a piston seal in the form of annular retainers 32 and packing ring seal 34 being positioned between these flanges. Adjacent to piston flange 26, the piston rod is formed with an annular groove provided by a reduced lock engaging portion 36 adjacent to the tapered spool end 38 of reduced diameter of the piston rod.

The bore 18 in rear head 22 is closed byv a rear cover 40 having an axial extending annular flange 42 extending into an enlarged portion of the bore 18, the flange 42 slidably carrying a cushion cup 44 having an axially aligned aperture 45 through its radial wall, for a purpose to be described. The cushion cup 44 is normally biased to the right, as seen in these figures, towards the piston rod 10 by means of a spring 46 which abuts at one end against the inner wall of cover 40 and, at its other end, abuts against the radial wall of cup 44, with movement of the cup in this direction being limited by a radial wall 48 of rear head 22. In this spring biased position of the cup 44, it will be adjacent the lock 60, to be described in detail hereinafter, to limit or inhibit its movement into the path of the piston rod 10.

Fluid ports

50 and 52 are positioned to introduce fluid into cylinder 14 on opposing sides of

piston flanges

26 and 28, the ends of the cylinder 14 being notched at 14b to permit fluid entry into the bore 30 of the cylinder.

Fluid ports

50 and 52 are in communication, for example, with a source of hydraulic fluid at different pressures through a servo valve, not shown, by means of upset headed tubes 51 and 53, respectively,

held in place on the front and rear cylinder heads and 22 by

plates

54 and 56, respectively.

To releasably-lock the piston rod in its retracted position, there is provided the lock 60, in the form of a permit lock 60 to move into the bore 18 in the rear head 22 into and out of engagement with the annular groove in the piston rod adjacent its spool end. The sleeve 64 is held axially in position by means of 1 a flanged cup-shaped cover 66 secured to the rear head 22 with the closed bore 67 of this cover concentric with the stepped bore 65 through sleeve 64. As shown, lock 60 is provided with an enlarged portion 60a at one end and a reduced portion 60b at its opposite end terminating in a frusto-conical end portion 600, and a lock tip 60d. Passages 60s through the frusto-conical end portion 600 communicatewith the axial stepped bore 61 in the lock. In addition, a plurality of circular apertures 60f extend radially outward through the wall of the lock, four in the embodiment disclosed, approximately midway of the reduced portion 6017, these apertures 60f being of a diameter to slidably receive the detent balls The detent balls 70 are adapted to move radially outward with respect to the outer periphery of the lock 60 for engagement against the chamfered shoulder 64a of an annular detent receiving groove provided at one end of the sleeve 64, so that when the balls are thus positioned, as shown in FIG..1, the lock is prevented from moving axially to an unlocked position with respect to the piston rod 10, that is to say, the lock 60 is maintained in a locked position with respect to the piston rod as shown in this figure;

Radial movement of the balls 70, and therefore of the lock 60, is controlled by a release pin 72 slidably received within the bore 61 in the lock 60 with this pin being normally biased into engagement with the lock by means of a spring 74 partly housed within the cover 66 and encircling one end or lower end of the pin, as seen in the figures, with the spring abutting at one end against the closed end of cover 66 and at its other end against an annular flange 72a on the pin 72. At its opposite end, the pin 72 is provided with a reduced portion 72b with a tapered shoulder 72c extending between this reduced portion of the pin and the nominal diameter portion of the pin. The reduced portion 72b of the pin 72 is of such a diameter that when this portion of the pin is adjacent to the balls 70, there is provided an annular cavity between this portion of pin 72 and the inner wall of lock 60 so the balls can move radially inward to release the lock 60 with respect to the sleeve 64 so that the lock may be moved inward or downward as seen with respect to FIG. 1, out of locking engagement with the piston rod.

The spring 74 and the working diameter of the release pin 72 against which hydraulic pressure acts, since the release pin is in effect a secondary piston within the lock which is also a piston, are so selected that the lock 60 will be forced by the pin 72, the shoulder 72a of which engages one end of the lock, into actuator is below 400 pounds per square inch.

In operation of the actuator in the particular application referred to above, when the piston rod 10 is in its normal retracted position as shown in FIG. I, the

hydraulic fluid pressure in port 52 would be 400 pounds per square inch or less and, the cup 44 and the lock components, including lock 60, pin 72, balls 70, would be in the positions as shown in this figure. The lock 60 prevents movement of the piston rod 10 forward to its extended position, to the right as seen in these figures, by bearing against the locking surface 36 or against the tapered edge of the spool end 38 of the piston rod. Although one end of the spool end 38 of the piston rod is tapered, it cannot function as a detent release mechanism with respect to the lock 60 because the balls now extending radially outward of the peripheral surface of the lock prevent the lock 60 from moving axially inward, downward with respect to the view in FIG. 1, in the sleeve 64 out of engagement with the piston rod 10.

When hydraulic fluid at a pressure above 400 pounds per square inch is supplied to port 52, it will effect release of the lock 60 in the following manner. The spring 74 holds the release pin 72 in the position shown in-FlG. 1 until the pressure of hydraulic fluid entering through the passages 60e in the lock exceeds 400 pounds per square inch. Hydraulic fluid pressure over 400 pounds per square inch forces the release pin 72 to move inward against the biasing action of spring 74. Movement inward of the release pin 72 brings its reduced end portion 72b to a position adjacent to the apertures 60f in the lock 60 to provide an annular chamber between this reduced portion 7 2b and the interior of the lock 60 so that the balls 70 can move radially inward out of engagement with the chamfered shoulder 64a of the sleeve 64. This movement of the balls 70 is forced because the balls are seated on the chamfered shoulder surface 64a of the sleeve 64 and the hydraulic fluid pressure entering port 52 acting on the exposed-end portion of the lock 60 is forcing the lock inward in the direction the release pin 72 has just moved.

When the balls 70 have moved into the space created by movement of the release pin 72 as just described, the lock 60, pin 72 and balls 70 can move inward, down as seen in FIG. 1, against the biasing action of spring 74. As the lock 60 is moved inward to release the piston rod, the latter is free to move as a result of hydraulic fluid pressure entering through port 52 acting against the piston flange 26 of the piston rod to move it to its extended position, to the right as seen in the figures. It is, of course, realized that as high pressure fluid is permitted to flow to port 52, port 50 is vented to the low pressure side of the hydraulic system.

As the piston rod moves to the extended position, the cup 44 is biased in the same direction under theinfluence of spring 46 until its axial movement is stopped by the shoulder 48 in the bore 18 of the rear head 22. With the cup 44 in this position, as shown in FIG. 2, the lock 60, which has previously been'moved inward in the manner just described, is now prevented from returning to its original position, should the hydraulic pressure at port 52 drop below 400 pounds per square inch. When it is desired to retract the piston rod 10, pressure is released at port 52 and applied through port 50 to act onthe piston flange 28 of the piston rod tomove it towards the retracted position, to the left from its position as seen in FIG. 2. As the piston rod retracts, the spool end 38 of the piston rod engages the cup 44 closing the aperture 45 therein so that further retraction of the piston rod forces oil to flow out from the back of the cup between the cup 44 and the annular flange 42 of the cover 40. This flow of hydraulic fluid is restricted because of the close fit between the peripheral wall of the cup 44 and the annular interior wall of the flange 42, thus providing a hydraulic cushion at the end of the retracted stroke of the piston rod.

When the cup 44 is moved axially, to the left from the position shown in FIG. 2, it will uncover the lock 60 to permit the latter to move outward from the position shown in FIG. 2 to that shown in FIG. 1 to lock the piston rod in the retracted position until the hydraulic pressure at port 52 is again raised above 400 pounds per square inch.

Thus, as the hydraulic pressure at port 52 is reduced to 400 pounds per square inch or less, the spring 74 will be able to force release pin 72 outward, upward in terms of the figures, but its movement and that of lock 60 is at first prevented by engagement of the lock 60 against cup 44. However, as cup 44 is moved out of the way by return movement of the piston rod toward its retracted position, the release pin 72 by the biasing action of spring 74 moves outward so that its tapered portion 72c engages the balls 70, held in axial position with respect to the lock in the apertures 60f, to move them and the lock 60 axially upward with respect to the sleeve 64 until such time as the apertures 60f in the lock are opposite the annular groove and the shoulder 64a of the sleeve at which time the balls 70 are cammed radially outward by the inclined surface of the tapered portion 72c of the pin 72. The release pin then moves upward relative to the lock until its nominal diameter portion is adjacent to the balls to prevent their return movement radially inward. As this occurs, the pin 72, having moved relative to the lock 60, now has its flange 7 2a abutting against the bottom of the lock so that the spring 74 now biases the lock and pin to the lock position relative to the piston rod as seen in FIG. 1.

What is claimed is:

1. A linear actuator comprising, in combination, an actuator housing including piston cylinder means closed at one end, piston means positioned to move in said piston cylinder means between a retracted position and an extended position with one end of said piston means extending externally of said actuator housing, a lock groove in said piston means at its other end, said actuator housing including means for applying fluid pressure to said piston means to selectively move said piston means between said retracted position and said extended position, a lock receiving bore in said housing in communication with said piston cylinder means, a lock piston means p sitioned to move in said lock receiving bore from a first position engaging said groove to a second position out of engagement therewith, spring means positioned to normally bias said lock piston means to said first position, said lock piston means including releasable detent means operable to releasably retain said lock piston means in said first position and pressure actuated means operable to release said detent means.

2. A linear actuator according to claim 1 wherein said lock receiving bore includes an enlarged bore portion adapted to receive said detent means and wherein said lock piston means includes a lock in the form of a piston partly open at one end and open at its other end with radial apertures through the side walls thereof, said detent means including detent balls slidably received in said apertures, a release pin slidably received in said lock to control the radial position of said detent balls in said apertures, and spring means adapted to bias said release pin in a direction to force said detent balls into locking engagement with said enlarged bore portion and to normally bias said lock to said first position.

3. A linear actuator according to claim 1, further including an apertured cushion cup slidably positioned in the closed end of said piston cylinder means and second spring means positioned to normally bias said cushion cup to a position adjacent said lock receiving bore when said piston means is moved toward said extended position to releasably block movement of said lock piston means as it moves from said second position toward said first position, said cushion cup being movable against said second spring means by said piston means upon movement of said piston means to said retracted position.

4. A linear actuator including an actuator housing having an axial bore therein closed at one end and including a bored piston cylinder, a piston means positionedto move in said actuator housing and in said piston cylinder from a retracted position to an extended position with one end of said piston means extending externally from said actuator housing, said piston means having an annular groove at its opposite end, bore means in said actuator housing normal to said axial bore and positioned in alignment with said groove of said piston means when said piston means is in said retracted position, a lock, in the form of a hollow piston with a groove engaging portion at one end, slidably positioned in said bore means for movement from a first position in which said lock engages in said annular groove of said piston means to a second position in which said lock is out of engagement with said piston means, said bore means including an annular ball receiving detent means, said lock having apertures through the walls thereof, detent balls slidably received in the apertures in said lock for movement radially outward into said ball receiving detent means to lock said lock in said first position, said detent balls being also movable radially inward to release said lock for axial movement in said bore means to said second position, and a spring biased release pin slidably received in the open end of said lock, said release pin having a cam portion thereon to effect radial outward movement of said detent balls and a reduced diameter portion to pro vide a cavity between said reduced portion and the interior of said lock to permit radial inward movement of said detent balls, and means for applying fluid pressure to said piston means and to said lock and release pin.

5. A linear actuator according to claim 4 further including an apertured cushion cup slidably positioned in the closed end of said axial bore and spring means in said axial bore to normally bias said cushion cup to a position in said axial bore to partly cover said bore means when said piston means is moved toward said extended position and said lock is moved to said second position and movable to uncover saidv bore means upon movement of said piston means to said retracted position.

6. A linear'actuator comprising an actuator housing means, a first'bore in said housing closed at one end, and a second bore in said housing at right angles to said first bore and in communication at one end therewith, a

first piston means positioned to slide in said first bore,

means in said actuator housing means for introducing fluid pressure to opposing sides of said first piston means to effect selected movement of said first piston means from a retracted position to an extended position, an annular groove in said first piston means axially positioned thereon to be adjacent said second bore when said first piston means is in said retracted posiion, a second piston means slidably positioned in said second bore to move into and out of engagement with said annular groove of said first piston means, said second piston means including an outer piston lock means with radially movable detentmeans thereon engagable in said second bore when said outer piston lock is in engagement with said annular groove, an inner piston release pin positioned to slide in said second bore and in said outer piston lock to controlmovement of said detent means and, spring means adapted to bias said piston release pin into said outer piston lock and to bias said outer piston lock into engagement with said annular groove, said detent means being positionable to lock said outer piston lock into engagement with said annular groove.

7. A linear actuator according to claim 6 further .including an apertured cushion cup slidably positioned in said first bore between the closed end thereof and said first piston means, and second spring means in said first bore adapted to bias said apertured cushion cup to a position to partly cover said second bore to restrict movement of said-outer piston lock against the biasing action of said spring means when said first piston means is moving to and from said extended position, said apertured cushion cup being moved against the biasing action of said second spring means by said first piston means as it is moved from said extended position to said retracted position.

Claims

1. A linear actuator comprising, in combination, an actuator housing including piston cylinder means closed at one end, piston means positioned to move in said piston cylinder means between a retracted position and an extended position with one end of said piston means extending externally of said actuator housing, a lock groove in said piston means at its other end, said actuator housing including means for applying fluid pressure to said piston means to selectively move said piston means between said retracted position and said extended position, a lock receiving bore in said housing in communication with said piston cylinder means, a lock piston means positioned to move in said lock receiving bore from a first position engaging said groove to a second position out of engagement therewith, spring means positioned to normally bias said lock piston means to said first position, said lock piston means including releasable detent means operable to releasably retain said lock piston means in said first position and pressure actuated means operable to release said detent means.

4. A linear actuator including an actuator housing having an axial bore therein closed at one end and including a bored piston cylinder, a piston means positioned to move in said actuator housing and in said piston cylinder from a retracted position to an extended position with one end of said piston means extending externally from said actuator housing, said piston means having an annular groove at its opposite end, bore means in said actuator housing normal to said axial bore and positioned in alignment with said groove of said piston means when said piston means is in said retracted position, a lock, in the form of a hollow piston with a groove engaging portion at one end, slidably positioned in said bore means for movement from a first position in which said lock engages in said annular groove of said piston means to a second position in which said lock is out of engagement with said piston means, said bore means including an annular ball receiving detent means, said lock having apertures through the walls thereof, detent balls slidably received in the apertures in said lock for movement radially outward into said ball receiving detent means to lock said lock in said first position, said detent balls being also movable radially inward to release said lock for axial movement in said bore means to said second position, and a spring biased release pin slidably received in the open end of said lock, said release pin having a cam portion thereon to effect radial outward movement of said detent balls and a reduced diameter portion to provide a cavity between said reduced portion and the interior of said lock to permit radial inward movement of said detent balls, and means for applying fluid pressure to said piston means and to said lock and release pin.

5. A linear actuator according to claim 4 further including an apertured cushion cup slidably positioned in the closed end of said axial bore and spring means in said axial bore to normally bias said cushion cup to a position in said axial bore to partly cover said bore means when said piston means is moved toward said extended position and said lock is moved to said second position and movable to uncover said bore means upon movement of said piston means to said retracted position.

6. A linear actuator comprising an actuator housing means, a first bore in said housing closed at one end, and a second bore in said housing at right angles to said first bore and in communication at one end therewith, a first piston means positioned to slide in said first bore, means in said actuator housing means for introducing fluid pressure to opposing sides of said first piston means to effect selected movement of said first piston means from a retracted position to an extended position, an annular groove in said first piston means axially positioned thereon to be adjacent said second bore when said first piston means is in said retracted position, a second piston means slidably positioned in said second bore to move into and out of engagement with said annular groove of said first piston means, said second piston means including an outer piston lock means with radially movable detent means thereon engagable in said second bore when said outer piston lock is in engagement with said annular groove, an inner piston release pin positioned to slide in said second bore and in said outer piston lock to control movement of said detent means and, spring means adapted to bias said piston release pin into said outer piston lock and to bias said outer piston lock into engagement with said annular groove, said detent means being positionable to lock said outer piston lock into engagement with said annular groove.

7. A linear actuator according to claim 6 further including an apertured cushion cup slidably positioned in said first bore between the closed end thereof and said first piston means, and second spring means in said first bore adapted to bias said apertured cushion cup to a position to partly cover said second bore to restrict movement of said outer piston lock against the biasing action of said spring means when said first piston means is moving to and from said extended position, said apertured cushion cup being moved against the biasing action of said second spring means by said first piston means as it is moved from said extended position to said retracted position.