GB2185532A - Locking fluid power operated devices - Google Patents

Abstract

A fluid power operated device, for example of the kind utilised in the clamping of a workpiece during a machinery operation thereof, comprises an actuator 18 movable by a fluid under pressure between inoperative and operative positions, and a locking member 32 which is normally urged by a spring 36 into a locking position in which it engages the actuator to prevent any retractive movement thereof. The locking member 32 is moved to a release position, permitting retractive movement of the actuator, by the application of fluid under pressure thereto simultaneously with the utilisation of the fluid under pressure to retract the actuator, thus preventing retractive movement of the actuator in the event of a fluid pressure failure. The actuator 18 and locking member 32 are provided with respective inclined engagement surfaces 38, 40. The locking member moves in a direction at right angles to the axis of movement of the actuator. <IMAGE>

Description

SPECIFICATION Fluid power operated devices This invention is concerned with fluid power oper ated devices, particularly but not exclusively ofthe kind comprising a cylinder, a piston mounted in the cylinder for movement under the action of the pressure offluid admitted to the cylinder, and an actuator member (typically in the form of a piston rod) extending from the piston.

Such fluid power operated devices fulfull a variety offunctionssuch as partsofmachinery, inwhich they are utilised to perform clamping or gripping functions to retain a workpiece in a fixed position whilst an operation is being carried out ontheworkpiece.

It is ofcourse desirablethat in such usage,the clamping or gripping function be performed in a failsafe manner, particularly to retain the clamping or gripping active in the event of failure of hydraulic fluid.

According to this invention there is provided a fluid power operated device comprising an actuator member movable between operative and inoperative positions by the selective application offluid under pressure to the device, the device comprising a locking member urged by a first means towards a locking position in which it prevents movement of the actuator member in at least one direction, and which may be moved to a release position by the application offluid under pressure thereto.

Thus, the possibly inadvertent movement of the actuator memberto its inoperative position may greatly be reduced.

Preferably when the locking memberisurgedtow- ards its locking position by the first means, it is active to prevent movement of actuator memberfrom its operative to its inoperative position but not from its inoperative position.

Thus, the location of the locking member in a position to restrain retractive movement of the actuator member may be ensured, irrespective ofthe position of the actuator member. Thus failure ofthe actuator memberat any point during its movement from its inoperative to its operative position may be ensured.

Advantageously fluid under pressure is applied to the locking member to move itto its release position in consequence ofthe application offluid under pressure to move the actuator memberfrom its operativeto its inoperative position.

Thus it is ensured that should there be a failure of fluid under pressure, undesired retractive movement oftheactuatormemberwill not occur.

Desirablyfluid under pressure isappliedto move the locking memberto its release position from a supply thereof from which fluid under pressure is applied to the actuator memberto cause movement ofthe actuator member from its operative to its inoperative position, advantageously said supply including a passage or chamber in a housing within which both the actuator member and the locking member are mounted.

In this manner it may be ensured that in the event of a rupture in an hydraulic hose or the like, uncon trilled retractive movement of the actuator member, permitted by the controlled release of the locking member, cannot occur.

Preferablythe actuator memberand the locking member are provided with interactive faces so constructed and arranged that movement ofthe actuator member from its inoperative towards its operative position permits movement of the locking member from its release position towards its locking position underthe action of the first means.

Preferably the locking member is elongate, and has a longitudinal axis which extends generally at right angles to the axis of movement ofthe actuator member.

Movement ofthe locking member between its locking and release positions may be rotary movement about said longitudinal axis, but is preferably axial linear movement.

Advantageously the actuator member and the locking member each comprise interactive wedge faces.

Said first means may be provided by a spring, air pressureorthe like.

According to this invention there is also provided a method of controlling a fluid power operated device of the type comprising an actuator member movable between operative and inoperative positions by the selective application offluid under pressure to the device, in which a locking member is utilised to prevent or restrain movement ofthe actuator member from its operative condition in the event of failure of the fluid under pressure.

This invention is particularly suitable for use in relation to a fluid power operated device operated by hydraulic fluid, and is particularly desirable where the actuator member performs a clamping or gripping function on a workpiece, such as when a machinery operation is carried out on the workpiece.

Therewill now be given a detailed description,to be read with reference to the accompanying drawings, of a fluid power operated device which is a preferred embodiment of this invention, and which has been selected of illustrating the invention by way of example.

In the accompanying drawings: Figure 1 is an exploded perspective view of the preferred embodiment; Figure2 is a sectional viewtaken on the line 2-2 of Figure 1; and Figure 3 is a sectional view taken on the line 3-3 of Figure 1.

The fluid power operated device which is the preferred embodiment ofthis invention is specifically part of a clam ping mechanism to clampaworkpiece in a desired fixed position whilst the workpiece is being subjected to a machining operation, and comprises a housing 6which may be in the form of a casting and which is provided with a cylinder 8from which a cylindrical bore 10 extends. Mounted within the cylinder 8 is a piston assembly 12. Fluid passages extend into the cylinderfrom ports 14and 16, into which connectors 18 are secured, allowing the piston assembly 12 to be moved within the cylinder 8 bythe selective admission of fluid to the housing.

Extending from the piston assembly 12 within the bore loins a generally cylindrical actuator member 18, which exits from the housing 6through a gland 20, and to a remote end portion of which clamping mechanism (not shown) maybe secured.

Extending through the housing 6 generally at right angles to the cylindrical bore 10 is a cylindrical crossbore 24. Mounted over the cross-bore at one end is a head 26 provided with a chamber 28, and screwed into the opposite end ofthe cross-bore 24 is a counterbored plug 30.

Slidably mounted in the cross-bore 24 is a locking member32 in theform of a piston rod,which is connected to a piston head 34 located within the chamber 28. The locking member 32 is urged into an operative position (leftwards, as viewed in Figure3) by a spring 36 located within the counterbore ofthe plug 30.

The cross-bore 24 intersects the cylindrical bore 10, and both the actuator member 18 and the locking member 32 are provided with respective inclined en gagementsurfaces38,40 respectively, so arranged thatthe partofthe actuator member 18which pro- jects into the cylindrical outline ofthe cross-bore 24, and the partofthe locking member32which projects intothe cylindrical outline ofthe cylindrical bore 10, are at the positions oven which said inclined engage mentsurfaces 38 and 40 are provided.

In the use of the fluid power operated device in the performance of a clamping function, fluid under pressure is admitted to the outlet port 16, to move the piston assembly 12 upwardly to cause the actua tormember 18to move from an inoperative position towards an operative position, in which it protrudes from the housing 6. Such movement effectively withdraws the inclined engagementsurface 38 of the actuator member from the locking member, permitting the locking member to move from a release position (shown in Figure 3) towards a locking position (i.e.

leftwards as seen in Figure 3) by the spring 36, maintaining the surfaces 38 and 40 in contact. If desired, the actuator member and the locking member may at this stage be free to rotate, to assist in maintaining good face-to-face contact between the inclined surfaces. Should at any stage fluid under pressure cease to be applied to the cylinder8 (such as by a rupture in an hydraulic hose), the spring-urged engagement of the locking member with the actuator memberwill prevent retractive movement of the actuator member.

However by the arrangement of the hydraulic passages within the device, on the application offluid under pressure to the port 14 to withdraw the actua tor member, fluid under pressure is simultaneously applied to the chamber 28, to urge the locking member 32 againstthe action of the spring 36 towards its release position, withdrawing the surface 40 from the actuator member and permitting retractive movementofthe actuator member.

Thus as will be observed, retractive movement of the actuator member from its operative position, such as in a release ofthe clamping function performed thereby, is only permitted in consequence of the application offluid under pressure to retract the locking member, and thus in the event offailure of fluid under pressure to the device, it is ensured that the actuator member is retained in its operative position.

Whereas the invention has been described above in its use as part of a workpiece clamping mech anism, it wi 11 be appreciated that the invention has numerous other uses, such as jacking systems, hydraulic support devices (such as are used in mining machinery) and the like.

The features disclosed in the foregoing description, orthefollowing claims, orthe accompanying drawings, expressed in their specific forms or in terms of a meansfor performing the disclosed function, or a method or process for attaining the disclosed result, our a class or group of substances or compositions, as appropriate, may, separately or in any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims (16)

1. Afluid power operated device comprising an actuator member movable between operative and inoperative positions by the selective application of fluid under pressure to the device, the device comprising a locking member urged by a first meanstowards a locking position in which it prevents movement ofthe actuator member in at least one direction, and which may be moved to a release pos tion bythe application offluid under pressure thereto.

2. A device according to Claim 1 wherein when the locking member is urged towards its locking position by the first means it is active to prevent movement of the actuator memberfrom its operative to its inoperative position but not from its inoperative position to its operative position.

3. A device according to one of Claims 1 and 2 wherein fluid under pressure is applied to the locking member to move itto its release position in consequence ofthe application offluid under pressure to move the actuator member from its operative to its inoperative position.

4. A device according to any one ofthe preceding claims wherein the fluid under pressure is applied to move the locking member to its release position from a supply thereof from which fluid under pressure is applied to the actuator member to cause movement of the actuator memberfrom its operat iveto its inoperative position.

5. A device according to Claim 4 wherein said supply includes a passage or chamber in a housing within which both the actuator member and the locking member are mounted.

6. A device according to any one ofthe preceding claims when the actuator member and the locking member are provided with interactive faces so constructed and arranged that movement of the actuator memberfrom its inoperative towards its operative position permits movements of the locking member from its release position towards its locking position underthe action of said first means.

7. A device according to any one of the preceding claimswhereinthelocking memberiselongate,and has a longitudinal axis which extends generally at right angles two the axis of movement of the actuator member.

8. A device according to Clai m 7 wherei n move mentofthe locking member between its locking and release position involves rotary movement about said longitudinal axis.

9. A device according to one of Claims 7 and 8 wherein movement of the locking member between its locking and release positions is linear axial movement.

10. A device according to Claim 9whereintheac- tuatormemberandthelocking membereachcom- prise interactive wedge faces.

11. Adevice according to anyone ofthe preceding claimswherein said first means is provided bya spring.

12. A method ofcontrolling afluid poweroperated device of the type comprising an actuator member movable between operative and inoperative positions by the selective application offluid under pressure to the device, in which a locking member is utilised to prevent or restrain movement ofthe actuator memberfrom its operative condition in the event of failure offluid under pressure.

13. The invention according to any one ofthe preceding claims wherein the actuator member forms parts of, or is connected to, a clamping mechanism adapted to hold aworkpiece in a desired position.

14. Afluid power operated device constructed and arranged substantially as hereinbefore described and shown in the accompanying drawings.

15. A method of controlling a fluid poweroperated device and carried out substantially as hereinbefore described with reference to the accompanying drawings.

16. Any novel feature or novel combination of feature as herein before described and/or shown in the accompanying drawings.