US2764132A - Piston-mounted end lock for hydraulic actuators - Google Patents

Description

wt. 25, 1956 E. H. BAKKE 2,764,132

PISTON-MOUNTED END LOCK FOR HYDRAULIC ACTUATORS Filed May 6, 1954 INVENTOR. 506,42 4. EAL/K5 BY I ATTORNEY-5 United States Patent G PISTON-MOUNTED END LOCK FOR HYDRAULIC ACTUATORS Edgar H. Bakke, Seattle, Wash., assignor to Boeing Airplane Company, Seattle, Wash., a corporation of Delaware Application May 6, 1954, Serial No. 428,063 Claims. (Cl. 121-40) Hydraulic jack means, or struts, are used, in aircraft construction particularly, as a means of effecting movement of a controlled part from one position to another. It is usually desirable to lock the strut in at least one position, and frequently in each limit position. As an example, hydraulic jack means are employed to move a landing unit from a retracted to a projected, or landing, position and vice versa, and it is essential that the landing unit be locked in each such limit position against the possibility of accidental movement therefrom. Such locking mechanism should be positive and mechanical, to guard against the possibility of failure or leakage in the hydraulic system. In addition, it is desirable that such locking mechanism be releasable in advance of, and often desirably by the same pressure fluid as is employed to effect, actuation of the jack means, or strut, from its locked position. v

Mechanisms to the general ends above are old and Well known. A highly desirable form of such mechanism is disclosed in the co-pending application of Richard A, Chace and George C. Newell, Ir, Serial No. 355,522, filled May 18, 1953. This particular mechanism is desirable in that it employs toggle link mechanism mounted upon one of the relatively movable members of the jack, in conjunction with looking dogs carried by the same member, and projectable and retractable with respect to that member, which locking dogs are beveled at their outer ends for interengagement with a similarly beveled shoulder on the other member of the jack or actuator, being the member which does not carry the toggle link mechanism and the locking dogs. In the Chace and Newell arrangement, the toggle link mechanism and the locking dogs, and pressure actuated means for initiating release of the lock, are all carried by the cylinder head, and the complemental beveled shoulder is carried by the piston. While two such mechanisms might be employed, one at each end of the cylinder, it is believed to be preferable, and more economical of space and weight, to mount two such locking mechanisms in the piston and to engage them alternatively with beveled shoulders provided in the cylinder Wall adjacent the respective ends of the cylinder. The present invention is concerned, therefore, with incorporation of the general principles disclosed in the Chace and Newell application, in a construction wherein the locking devices and the actuators therefor are all mounted in and movable axially with the piston, and the cylinder is provided simply with two com plemental beveled shoulders. The Chace and Newell application discloses specifically a form wherein the piston is skirted and the skirt thereof is formed internally with a beveled circumferential groove; the cooperating toggleactuated locking devices are supported from the cylinder head, in position to project axially within the pistons skirt when the piston reaches a limit position at an end of its travel. projectible r-adially outwardly into engagement withthe groove of the pistonsskirt. The specific disclosure of Thereupon the locking devices are 2 the Chace and Newell application is of a lock only of the pistons travel.

In distinction to the above, the specific disclosure of this application includes a lock at both ends of the pistons travel. The present disclosure accomplishes this by reversing the arrangement in the Chace and Newell disclosure, in that the toggle-actuated locking device-in the preferred arrangement, for convenience, two such locking devices, each with its toggle actuator-is mounted within the piston for bodily movement axially therewith, wherefore the complemental beveled groove is formed in the respective ends of the cylinder wherein the piston is axially movable.

This application is generic to the idea of effecting a lock by such a toggle-actuated locking device at each end of the travel of a piston or like guided element, Within the cylinder or corresponding guide for the same. Contrariwise, the Chace and Newell application is generic to the idea of the toggle-actuated locking device, including the beveled groove in one such relatively axially movable component and the complementally beveled locking dog means in the other such component, radially shiftable in the locking sense under the influence of the toggle links, and in the releasing sense under the influence of the axial force applied to the two axially movable components and communicated to the locking dog means through its beveled surface or the beveled surface of its engaged groove, whether that generic idea be incorporated in the double-ended form disclosed in this application, or in the single-ended form disclosed in the Chace and Newell application, or whether the same be incorporated in a cylindenmounted locking device as in this disclosure, or in connection with a locking device that is mounted in or supported from the cylinder head, as in the Chace and Newell disclosure.

One of the advantages inherent in this and in the Chace and Newell structure is that by the use of the beveled shoulders, and of rotatable toggle links which hold beveled locking dog means in secure engagement with such shoulders, it is possible by rotation of the toggle links from their locked, or aligned, positions with respect to the locking dog means, to effect sudden collapse of the lock after extremely slight relative movement be tween the interengaged beveled surfaces, and While there is still substantially full face engagement between such surfaces. As a result there is no gradually decreasing area of contact between locking dog means and the shoulders they engage, until ultimatelythe area of contact becomes zero, all the while a strong force is urging parts to movement in opposition to the look, It follows that the sudden collapse, possible by virtue of the principles disclosed in the Chace and Newell application, avoids the grinding away of metal, which is the inevitable result of such sliding movement to zero contact under heavy pressure, and eliminates the necessity for frequent replacement of parts,o1' alternatively, the danger of failure due to wear of the parts. The same advantages are capable of achievement by the present invention, in a constructional arrangement wherein the locking dog at one end means, the toggle links, and the plungers for effecting releasing movement of the same, are all mounted in the piston element of the actuator, and wherein preferably the cooperating beveled surfiaces are duplicated at the opposite ends of the piston, to elfec-t locking and releasing at the two limit positions.

Whereas the Chace and Newell specific disclosure is of a single end lock only, the disclosure herein is of a double-end lock. inasmuch as each such lock is releasable byapplication locking, effects reciprocative movement of the piston within the cylinder, it is oneof the objects of this invention to provide a construction including yield'able meof the same pressure which, upon un-' axially disposed bore of the piston.

'posite face of the piston.

chanical biasing means, operable in addition to hydraulic biasing means, and capable of retaining parts in either locked position, against accidental hydraulic release, even though there may be. a momentary surg of pressure in one side or the other of the cylinder.

In accordance with the specific disclosure of the present invention, and without limitation of its scope, otherwise than as is indicated in the claims, there is, according to the present invention, a cylinder and a piston which is slidably fitted therein for reciprocation between two limit positions, the cylinder having ports for admission of pressure fluid to each end thereof, and for discharge of such pressure fluid, and the two locking devices, both carried by the piston but one adjacent each end face thereof, each includes one or more locking dog means (as hereinafter defined more specifically), one element or more of which is guided in the piston for radially outward and inward movement, a toggle link rotatable to effect such movement of each locking dog means, and movable by such rotation into alignment with its locking dog means. Such movement of the toggle link is effected by a pressure-fluid-actuated plunger axially reciprocable in an Each such locking dog means, or the radially outermost element thereof, is beveled complementally to and for engagement with a beveled shoulder at the respective ends of the cylinder. Each such actuating plunger is received Within its bore in the piston, defining thus a pressure chamber behind the plunger which is ported for communication with the op- Thus, as pressure fluid is admitted into one end of the main cylinder and applied to one face of the piston to urg the latter towards the opposite end, the same pressure is applied to the outer end of the plunger that protrudes from the same face of the piston, to urge that plunger towards unlocked position. This plungers pressure chamber, communicating with the opposite face of the piston, is vented to low pressure, hence the plunger shifts inwardly, in opposition to spring means, and the lock is thereby suddenly released. Movement of the piston towards its opposite limit position ensues.

Since the other plungers pressure chamber, at the opposite (now lower pressure) face of the piston, is in communication with the now higher pressure face, this higher pressure tends to urge this second plunger outwardly in its bore, and so to move the locking dog means for the opposite end into locked position. This it can not do until it reaches the opposite limit position, for projection of the locking dog means is restrained by their engagement with the cylinder wall, but once the piston reaches that opposite limit position, the plunger is shifted in its bore by the still-applied pressure and the locking device at this end comes into locking engagement with the beveled shoulder at this end of the cylinder.

The locking dog means may take the simple form of the Chace and Newell arrangement, or on the other hand, it is preferred that it take the form of a substantially circular segmental ring, which is received and retracted within a groove of the piston during movement of the piston, but which can be expanded and moved out of that groove into engagement with a circumferential groove of the cylinder wall in the locking position of the parts. This specific form lessens the loading on any given area, distributing it instead over virtually the entire circle of the groove.

The drawings and this specification are to be under stood as illustrative rather than as restrictive, other than as is required by the language of the accompanying claims.

Figure l is a longitudinal axial sectional view through the actuator, showing parts locked in the limit position of closest approach between its end fittings.

Figure 2 is a transverse sectional view on the line 22 of Figure 1, and Figure 3 is a similar transverse 4 sectional view, but showing parts in the retracted, or unlocked, position.

The actuator comprises a main cylinder 1 closed at its ends, and the piston 2 slidably fitted therein for reciprocative movement from one end of the cylinder to the other, its two faces being sealed from one another by suitable sealing means indicated at 20. The piston rod 21 projects through one end of the cylinder, where it is formed with an attachment end fitting 22, and the opposite end of the cylinder is formed with an attachment end fitting 12. Provision is made for admitting pressure fluid to and relieving the same from each such end. The precise manner of doing this is immaterial, and there are shown ports 11 at one end and 13 at the opposite end. Such details of the actuator are common and, in themselves, are not part of this invention.

Adjacent one end of the cylinder, its interior wall is formed with a beveled shoulder, preferably in the form of a circumferential groove or shoulder, as indicated at 14, and a similar shoulder 15 is formed at its opposite end. These shoulders 14 and 15 may be taken as defining, in a sense, the opposite limits of movement of the piston.

The piston is somewhat elongated axially and is axially V bored from each face as indicated at 23 and 24. A plunger 3 fits and slides axially within each bore, being exposed at its outer face to the sam pressure as is applied to the corresponding face of the piston, and a smaller extension at its inner end fits slidably within a smaller interior chamber defined by the cylindrical wall 27 extending axially and upstanding from the bottom of each bore. Port 28 affords communication between the lefthand end of the piston and this small chamber behind the right-hand plunger 3, and in like fashion, port 29 affords communication between the right-hand end of the piston and the small interior chamber behind the lefthand plunger 3. The purpose of these ports will appear shortly. Spring means 31 urge the respective plungers 3 axially outwardly in their bores. Stop means to be described later limit such projective movement.

Radial guide apertures 25, of which there are preferably several, equiangularly spaced, intersect each bore 23 and 24. Preferably, also, the piston 2 is formed with a circumferential groove 26 (see Figure 2) into which the radially outer ends of the radial guide apertures 25 admit. Radially slidable elements 4 of locking dog means, to be described later, are guided for radial sliding movement in these apertures 25.

The plungers 3 are, in effect, independently operable actuators for the individual locking means, one at each end of the cylinder. The plungers 3 are movable under the influence of the compression spring means 31, or additionally, by pressure admitted behind the small inner end of the plunger 3 within the chamber wall 27 by way of the ports 28 or 29 from the opposite face of the piston. When the plungers 3 are moved inwardly of their bores under the influence of pressure applied to the outer face of the plunger and likewise to the corresponding end of the piston, the ports 28 and 29 constitut vent ports to relieve and vent the fluid behind the smaller inner ends of the respective plungers.

Locking dog means, which term is intended to cover generically various forms of the dog means, such as that shown in the Chace and Newell application, or the means specifically disclosed herein, are provided for locking engagement with the shoulders 14 and 15, respectively. Such locking dog means include the referred to radially movable elements guided in the apertures 25, designated herein by the numeral 4, and which will be termed herein expanders. It would be possible to form the radially outer ends of these expanders 4 for direct engagement with the beveled shoulders 14 and 15, after the mannot suggested by Chace and Newell, but preferably the actual locking dog devices are made in the form of a sub t ntially circular, but segmental ring, the segments whereof are indicated at 41. Two such circular segmental rings are received one within each of the circum ferential grooves 26 of the piston, and the outer circumference of which rings can be withdrawn within the outer periphery of the piston, or can be projected therefrom behind the locking shoulders 14 and 15. The peripheral edge of such a ring, composed of the segments 41, is beveled at 40 complementally to the bevel of the shoulders 14 and 15, as is best seen in Figure 1. border to effect expansion or permit contraction of the ring segments 41, their ends are beveled at the inner periphery, and the expanders 4 are similarly double-beveled, as seen best in Figures 2 and 3, and as indicated at 44, whereby outward movement of the expanders 4 will react through the double bevels 44 and the complemental bevels on the ring segments to expand the ring and urge its segments outwardly, and retractive or inward movement of the expanders 4 will permit the ring segments 41 to retract within their groove 26.

Outward movement of the expanders 4 is accomplished by toggle means, such as the links 5, rockably connected between the plunger 3 and the several individual expanders 4. In Figure 1, the right hand plunger 3 having been moved to the right with respect to the piston, its toggle links 5 have been moved into alignment with the direction of movement of the expanders 4, and the ring segments 41 at this end of the piston have been expanded and are in locked engagement with the shoulder 15. The toggle links are held in this locked position by engagement with stop shoulders 30 on the plunger, and similar shoulders on the expander. The stop shoulders also constitute stops limiting outward movement of the plunger 3 in its bore 23 or 24. At the left hand end of the piston, the plunger 3 is withdrawn into its pressure chamber, defined by the wall 27, which has permitted the toggle links 5 at this end to collapse, and the expanders 4 to move inwardly. This, in turn, permits inward or retractive movement of the ring composed of the segments 41, and parts at this end are in the unlocked position. However, spring means 31 have been compressed at this left end, and yieldingly bias the toggle links to their radially outward aligned position, and the locking dog means to the locking position. It is restrained, of course, from movement into such position by the fact that the outer edge of the ring segments 41 bear, without great force, on the wall of the cylinder. At the right hand end, the spring means 31 have been expanded, and have effected the movement of parts at this end into the locked position, aided (if the ports 28 and 29 are so located as not to be obstructed by the skirt of plungers 3) by fluid pressure from behind the advancing plunger 2.

In order to insure the movement of parts to the locked position, it will be observed that pressure from the left hand end or face of the piston is applied by way of the ports 28 to the interior of the pressure chamber defined at 27 at the right hand end of the piston. This pressure is applied when parts of the actuator are in the fully extended position, with the piston 2 at the left hand end of the cylinder 1. The first effect of the application of pressure through the ports 11 is to urge the piston 2 toward the right hand end of the cylinder, but since it is locked by the left hand set of locking dogs, movement can not begin until the locking dogs at this side of the piston are released. The pressure applies also to the exposed end of the plunger 3 at the left of the piston, and since its chamber within the bore 27 is vented by way of the ports 29 to the right hand face of the piston 2, the pressure actin on the left hand plunger 3 urges it to the right, with respect to the piston 2, and the look at this end collapses. The pressure continuing to act on the main piston 2, moves it to the right. When it reaches the right hand limit of its movement within the cylinder 1, pressure entering by way of the ports 28, which has in the meantime been acting on the inner end of the right hand plunger 3, now urges this plunger outwardly and expands the right hand ring segments 41 into engagement with the shoulder 15. The plunger 3 at the right moves under the influence of this pressure and also under the influence of its springs 31, until the toggle links 5 are stopped in their aligned, and locked, position. Parts are now locked in the right hand limit position of the main piston 2. When reverse movement of the piston 2 is required, pressure is admitted at 13, the right hand plunger 3 is pushed inwardly of its pressure chamber, and the lock at this end is unlocked, whereupon movement of the piston 21 to the left begins, and the lock is reaccomplished. at the opposite end in engagement with the shoulder 14, in the manner already described.

It will be observed that the larger area of the bores 23 and 24 are vented so that the pressure acts on the respective plungers 3 only to the extent of the area entered and slidably fitted within the smaller pressure chambers 27. Were it not so, the pressure over the entire area of the plunger would be rather appreciable, and during sliding of the piston might cause scoring of the cylinder wall by reason of the force applied to the outwardly urged ring segments 41.

It will be observed that the packing seal at 20 is not required to pass over any lines of junction or past the respective locking shoulders 14 and 15. This is true be cause the locking means are at the respective ends of the piston, outwardly beyond the seal at 20.

When parts are in the locked position, springs 31 tend to hold the one plunger 3 projected from its bore, and parts at the one end in locked position. Were entire dependence to be placed on hydraulic pressure to keep parts in locked position, it is possible that a sudden relief of pressure, or a surge of pressure, in the hydraulic lines to the actuator, such as might occur by relief of pressure in or application of pressure to some other device served by the same hydraulic system, would cause a release of the lock. The springs 31 are strong enough to retain parts in locked position, under such circumstances, and until application of full pressure to effect unlocking and movement of the piston.

I claim as my invention:

1. In combination with a cylinder, a piston slidably fitted therein for reciprocation between two limit positions, and means to admit fluid under pressure to and to discharge such fluid from the respective ends of the cylinder, to effect reciprocative movement of the piston by application of pressure forces to its respective faces, two locking devices, one adjacent each face of the piston, and each including a locking dog means guided in the piston for radially outward movement into locking position and inward movement into retracted, unlocked position, a toggle link rockably engaged by one end with the locking dog means, and a fulcrum member mounted in the piston and shiftable axially relative to the piston, whereon the other end of the toggle link is fulcrumed, yieldable means reacting between the piston and the fulcrum member of each locking device, biasing the fulcrum member towards a position wherein the toggle link is aligned with its dog means and the dog means is projected and retained in its projected position, the outer tip of each dog means being beveled, and the cylinder wall being correspondingly beveled in position to be engaged by the bevel of a corresponding dog means, when the piston reaches one limit position and the dog means is projected, and to be retained in such locked position so long as the projected dog means and the toggle link remain aligned, and a pressure-actuated member operatively connected to said fulcrum member, and located to be subject to and moved by a pressure force acting upon a given face of the piston to move the piston towards the opposite limit position, thereby to move the fulcrum member in the axial sense to shift the toggle link from alignment with the dog means, and so to enable retraction of the dog means under the influence of the same pressure force tending to move the piston, acting through the dog means beveled tip.

2. The combination of claim 1, wherein the piston is recessed axially at each pressure face to define a lock cylinder, and the fulcrum member is slidably fitted as a plunger into said lock cylinder, and exposed to main cylinder pressure exteriorly of the lock cylinder, to constitute also the pressure-actuated member, the interior of each lock cylinder being vented to the opposite face of the piston.

3. The combination of claim 1, wherein the dog means comprises a circular segmental ring, the piston being circumferentially grooved for axial projection and retraction of said rings segments, the outer circumferential edge of the ring being beveled, and the cylinder wall being correspondingly circumferentially beveled for locking engagement with the ring, when projected, and the dog means further including a plurality of expander elements distributed angularly about the pistons axis and guided in the piston for radially outward and inward movement, into and from alignment with corresponding toggle links, said expander elements being operatively engaged with the rings segments to project or to enable retraction of the latter.

4. The combination of claim 3, wherein the adjoining ends of the ring segments are oppositely beveled, and the expander elements are complementally double-beveled, to urge apart and outwardly the ring segments upon radial outward movement of the expander elements.

5. In combination with a guide element and a cooperating element guided therein for reciprocative movement between two limit positions, the guide element having two surfaces, one at each limit position, each of which is beveled with relation to the direction of reciprocation,

means to lock the two cooperating elements in each such limit position, comprising axially spaced locking dog means each carried and guided by the guided element for movement transversely of the direction of reciprocation between a projected locking position and a retracted unlocked position, each dog means having a beveled tip surface complemental to the beveled surface at the corresponding end of the guide element, and being positioned for locking interengagement of the corresponding beveled surfaces when parts are in the respective limit positions, two toggle devices carried by the guided element and operatively engaged each with its corresponding dog means to move the latter into projected position as the toggle device rotates into alignment with the direction of movement of its dog means, stop means to retain the toggle devices in such aligned position, means to rotate each toggle device, independently of the other, from such aligned position, and means operable simultaneously with application of such rotative force to a given toggle device, to apply a force to the guided element in the sense tending, through the interengaged beveled surfaces, to effect retraction of the projected dog means to its unlocked position, and consequent rotation of the toggle device from its aligned position, and finally to effect movement of the guided element towards the opposite limit position.

6. The combination of claim 5, wherein the guide element and the guided element constitute a pressure fluid actuator, and fluid pressure means are arranged to apply force to the guided element and to the respective toggle means, to rotate that one into aligned position which will engage at the limit position towards which the guided element is caused to advance by such application of force.

'7. In combination with a closed cylinder formed for admission of pressure fluid to, and discharge of such fluid from, its two ends, and formed also with a circumferentially directed beveled groove adjacent each end, a piston fitted within said cylinder for reciprocative movement, said piston having two non-communicating axial bores opening to its respective faces, and a plurality of radial guide apertures intersecting each bore near the exterior end thereof, and said piston being also formed with two circumferential grooves, one adjacent each end, into which its radial guide apertures open, a plunger fitted into each axial bore for axial sliding movement, to seal off a pres-. sure chamber at the bottom of the respective bores, expander elements received and radially slidable in the respective radial guide apertures, toggle links operatively inter-connecting each plunger and the expander elements at the corresponding ends of the piston, each toggle link being rotatively connected with each of its expander element and its plunger for rotation into and from alignment with said expander element by reciprocation of the plunger in the axial direction, and a segmental, substantially circular locking ring, beveled complementally to the cylinders corresponding circumferential groove, received in each of the pistons circumferential grooves, for projection from the pistons groove into engagement with the cylinders groove, and for retraction within the pistons groove, the expander elements and the corresponding locking ring segments being operatively interengaged for projection of the ring upon outward movement of the expander elements as their toggle links come into alignment with the latter, and ports communicating between each pressure chamber and the opposite face of the piston, for biasing of the toggle links and their associated parts at one face of the piston towards locked position during movement of the piston under the influence of fluid pressure applied to its other face, and for venting each pressure chamber behind its plunger, upon application of pressure to the opposite face of such plunger.

8. The combination of claim 7, wherein each expander element is double-beveled, and is located radially inwardly of the adjoining ends of two ring segments, such ring segment ends being beveled complementally to the bevels of the expander element, to constitute the operative interengagement for projection of the ring.

9. The combination of claim 7, including compression springs reacting between the piston and each plunger, biasing each such plunger yieldingly in the sense to urge the toggle links and their associated part-s towards locked position.

10. 'In combination with a closed cylinder formed for admission of pressure fluid to, and discharge of fluid from, its respective ends, and formed also with a beveled shoulder adjacent each end, a piston fitted within said cylinder for reciprocative movement under the influence of fluid pressure applied to its respective faces, said piston having two non-communicating axial bores opening to its respective faces, and a plurality of radial guide apertures intersecting each bore near the exterior end thereof, a plunger fitted into each axial bore for axial sliding movement relative to the piston, to seal off a pressure chamber at the interior end of the respective bores, projectible and retractable means at each end of the piston, including elements radially movable in the guide apertures, to interengage with the cylinders beveled shoulder at the corresponding end, and complement-ally beveled toggle links interconnecting the plunger at each end and the corresponding radially movable elements, to urge the latter outwardly as such toggle links are urged toward alignment with the radially movable elements, and fluid ports connecting each pressure chamber in the piston with the pistons opposite face.

References Cited in the file of this patent UNITED STATES PATENTS 1,842,776 "Bogslowsky Jan. 26, 1932

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