US3350987A

US3350987A - Hydraulic cylinder

Info

Publication number: US3350987A
Application number: US520153A
Authority: US
Inventors: Dell A Johnson
Original assignee: Thiokol Corp
Current assignee: ATK Launch Systems LLC
Priority date: 1966-01-12
Filing date: 1966-01-12
Publication date: 1967-11-07
Anticipated expiration: 1984-11-07

Description

Nov. 7, 1967 D. A. JOHNSON HYDRAULIC CYLINDER 3 Sheets-Sheet 1 Filed Jan. 12, 1966 FIG.

INVENTOR. DELL A. JOHNSON BY EM D. QM:-

ATTORNEY Nov. 7, 1967 D. A. JOHNSON 3,350,987

HYDRAULIC CYLINDER Filed Jan. 12, 1966 3 Sheets-Sheet '2 FIG. 3

I NVENTOR. DELL A JOHNSON BY W ATTORNEY D. A. JOHNSON 3,350,987

HYDRAULIC CYLINDER Nov. 7, 1967 3 Sheets-Sheet 5 Filed Jan. 12, 1966 QM" Q 32 m FIG. 4

INVENTOR.

DELL A. JOHNSON FIG.5

BY Magma;-

ATTORNEY United States Patent C) 3,350,987 HYDRAULIC CYLINDER Dell A. Johnson, Nihley, Utah, assignor to Thiolrol Chemical Corporation, Bristol, Pa., a corporation of Delaware Filed Jan. 12, 1966, Ser. No. 520,153 2 Claims. (Cl. 92-24) This invention relates to a fluid pressure actuator and locking device, and more particularly to a hydraulic cylinder having an extensible shaft that can be locked in variable position relative to the casing of said hydraulic cylinder.

lthough hydraulic cylinders have been Widely used as the actuating mechanisms of various holding devices, their use in such apparatus has certain disadvantages For example, if the pressure applied against the piston of a conventional hydraulic cylinder used in a holding device is not maintained at a constant level, a workpiece or other article can be prematurely released from the holding device with disastrous consequences. The present invention provides a hydraulic cylinder having an internal locking mechanism that holds the piston of said cylinder in any desired position along its range of travel, leakage of hydraulic fluid past said piston or even complete loss of fluid pressure in said hydraulic cylinder having no effect on the locked condition of the piston after a shaft connected thereto has been moved against a workpiece or other body that is to be held in fixed position. As will be explained in detail hereinafter, this advantageous locking arrangement is achieved by means of a hydraulic cylinder comprising a shell slidably disposed within the casing therof, a piston slidably disposed within said shell and connected to a hollow shaft that extends through apertures in said shell and casing respectively, and one or more locking wedges carried by said shell and adapted to engage the wall of an opening in said piston and the surface of a projection that is connected to said casing and coaxially disposed therein. For reasons that will become manifest in the following specification of the invention, the aforementioned shell and piston each contain a vent passage in which is disposed a check valve permitting fluid flow in one direction therethrough.

It is accordingly an object of this invention to provide a fluid pressure actuator and locking device having an extensible shaft that can be locked in variable position relative to the casing of said device.

Another object of this invention is to provide a fluid pressure actuator and locking device having an extensible shaft that can be moved to a selected position relative to the casing of said device by means of fluid pressure introduced into one end of said casing automatically locked in said position, and subsequently unlocked by means of fluid pressure introduced into the other end of said casing.

Other objects and advantages of the present invention will become apparent in the following specification thereof, in which reference is made to the accompanying drawings, wherein:

FIGURE 1 is a pictorial view illustrating a preferred embodiment of the invention, portions of certain of the components of said embodiment being cut away for clarity;

FIGURES 2, 3 and 4 are longitudinal sectional views of the preferred embodiment of the invention, illustrating the relation of its components in different operational positions thereof; and

FIGURE 5 is a cross-sectional view of the preferred embodiment of the invention, taken along the plane represented by line 5-5 of FIGURE 4.

Throughout the specification and drawings like reference numbers refer to like parts.

The preferred embodiment of this invention illustrated in FIGURE 1 comprises a cylindrical casing 10 having first and

second end closures

12, 14 respectively attached to opposite ends thereof. More specifically, as can be seen in FIGURE 2 end closure 14 is integrally joined to casing 10, whereas end closure 12 is threadedly engaged with said casing. End closure 12 has an aperture 16 formed therein, the central axis said aperture being coincident with the longitudinal axis of casing 10 and a circumferentially extending groove 18 being formed in the Wall of said aperture 16 to accommodate a seal ring 20. At each end of casing it there is a

fluid pressure port

22, 24. Disposed within casing 19 is a projection, generally designated by reference number 26, which has the form of a truncated pyramid that is square in cross-section. The longitudinal axis of projection 26 is coincident with the longitudinal axis of casing 10, and the large end of said projection is fixedly connected to end closure 14, as by means of being welded thereto. Thus each of the four planar surfaces 28- of projection 26 is convergent with respect to the longitudinal axis of casing lit in the direction of end closure 12.

A cylindrical shell 30 is slidably disposed within casing 10, said shell having first and

second end walls

32, 34 which are respectively attached to opposite ends thereof. More specifically, end wall 3 is integrally joined to shell 30, whereas end wall 32 is threadedly engaged with said shell. Each of the

end walls

32, 34 includes an

aperture

36, 38 through which projection 26 extends, the walls of said apertures being respectively spaced from surfaces 23 of said projection. End wall 32 also has a vent passage 4% formed therein. Shell 30 is provided with a circumferentially extending groove 42 in which is positioned a seal ring 4-4, and with a longitudinally extending groove 46 which faces the inner surface of casing 16. A pin 48 is fixedly mounted in a hole that extends through the wall of casing 19

intermediate end closures

12, 14, the inner end of this pin being slidably disposed in groove 46 and thus serving to prevent rotation of shell 30 relative to said casing.

A piston 50 is slidably disposed within shell 30, said piston having formed therein an opening 52 which is pyramidal in shape and through which projection 26 extends. More particularly, opening 52 has four planar Wall surfaces, is square in cross-section, and. its longitudinal axis is coincident with the longitudinal axis of casing 10. The large end of opening 52 faces end Wall 34, and each of its Wall surfaces is disposed opposite, and spaced from, a respective one of the surfaces 28 of projection 26. Thus the wall surfaces of opening 52 are also convergent with respect to the longitudinal axis of casing 10 in the direction of end closure 12, and more specifically, as can be seen in FIGURES 2, 3, and 4, said wall surfaces are inclined at a slightly greater angle with respect to the longitudinal axis of casing 10 than are surfaces 28 of projection 26. Piston 50 also has a vent passage 54 formed therein, the portion 56 of said vent passage that is adjacent end wall 32 having an increased diameter and the portion 58 of said vent passage that is adjacent end wall3 i being convergent in the direction of end wall 32. A seal ring 60 is positioned in a circumferentially extending groove 62 formed in the peripheral surface of piston 50.

Slidably disposed within aperture 36 in end wall 32 and aperture 16 in end closure 12 is a hollow cylindrical shaft 64. The outer end of shaft 36 is closed by a bulkhead 66, and the inner end of said shaft is fixedly connected to piston 50, as by means of being welded thereto. More specifically, the inner end of shaft 64 surrounds the opening 52 in piston 50, and thus the interior 68 of said shaft communicates with said opening.

Coaxially disposed Within shell 30 is a frustoconical guide member 70 the large end of which is integrally joined to end wall 34. Four rectangular slots 72 are formed in guide member 70 adjacent the free end thereof, these slots being evenly spaced circumferentially of said guide member and equidistant from end wall 34. Projection 26 extends through guide member 70 in spaced relation therewith, and four locking wedges, each of which is generally designated by reference number 74, are respectively slidably disposed in the slots 72 in said guide member and thus can be moved in a direction perpendicular to the longitudinal axis of casing 10. The inner surface 76 of each locking wedge 74 is planar and disposed adjacent a respective one of the surfaces 28 of projection 26, and the outer surface 78 of each locking wedge is also planar and disposed adjacent a respective one of the wall surfaces of the opening 52 in piston. Thus the outer surface 78 of each locking wedge 74 is also convergent with respect to the longitudinal axis of casing in the direction of end closure 12. As can be seen by inspection of FIGURES 2, 3 and 4, the lengths of casing 19, shell 30, projection 26, guide member 70 and locking wedges 74 are such that a portion of the wall of the opening 52 in piston 50 is disposed opposite locking wedges 74 in any position of piston 50 relative to casing 10 and shell 30. Therefore, movement of locking wedges 74 in a direction perpendicular to the longitudinal axis of casing 10 is limited, and said locking wedges are retained in the slots 72 in guide member 70 by the wall of opening 52 in piston 50. As can best be seen in FIGURE 3, when the inner surfaces 76 of locking wedges 74 are respectively in contact with surfaces 28 of projection 26 the outer surfaces 78 of said locking wedges are inclined at the same angle with respect to the longitudinal axis of casing 10 as the wall surfaces of opening 52 in piston 50.

Disposed in vent passage in end wall 32 is a valve, generally designated by reference number 80, which comprises a first cylindrical portion 82, a second integral cylindrical portion 84 having an increased diameter, and an integral tapered head portion 86 adapted to seat against a beveled edge 88 of said vent passage. The di ameter of portion 84 of valve 80 is slightly smaller than the diameter of vent passage 40 so that when the head portion 86 of the valve is not seated against edge 88 (see FIGURE 2) hydraulic fluid or air that may become trapped between end wall 32 and piston can pass through said vent passage 40. A Washer 90 is seated against the shoulder formed on valve 84 at the junction of portions 82 and 84 thereof, said washer having a serrated inner edge which permits hydraulic fluid or air to flow through vent passage 40 as described immediately hereinbefore. Valve 80 is biased into the open position thereof illustrated in FIGURE 2 by means of a spring 92 one end of which is positioned within portion 56 of vent passage 54 in piston 50.

Disposed in portion 58 of vent passage 54 is a second valve in the form of a ball 94 having a diameter slightly larger than the diameter of the middle portion of said vent passage. As can best be seen in FIGURE 5, four retaining members 84 are mounted on surface 86 of piston 50 and extend over vent passage 54 so as to hold ball 34 therein.

One use of the described embodiment of the invention is illustrated in FIGURES 2, 3 and 4, wherein casing 10 is mounted on a rigid support (not shown) and spaced a predetermined distance from a worktable 96 against which a workpiece 98 is to be clamped. With piston 50 in the fully retracted position thereof illustrated in FIGURE 2 and port 22 opened to a hydraulic return line (not shown), port 24 is opened to a high pressure hydraulic line (not shown) to admit fluid pressure into shaft 64, shell 30 and the space between end wall 34 of said shell and end closure 14. This fluid pressure moves ball 94 toward end wall 32, closing vent passage 54 in piston 50, and also moves piston 50 toward end closure 12, bringing the outer face of bulkhead 66 of shaft 64 into engagement with workpiece 98 (see FIGURE 3). Because of the area differential between the faces of end wall 34, the fluid pressure also moves shell 30 toward end closure 12. After bulkhead 66 contacts workpiece 98 fluid pressure continues to drive shell 30 toward end closure 12 until the outer surfaces 78 of locking wedges 74 respectively engage the wall surfaces of opening 52 in piston 50 (see FIGURE 3). Since the space between piston 50 and end closure 12 is not pressurized, spring 92 holds the head portion 86 of valve away from edge 88 of vent passage 40, and consequently any hydraulic fluid or air trapped between piston 50 and end wall 32 can pass through said vent passage as the distance between said piston and said end Wall decreases. It will be seen by inspection of FIGURE 3 that after bulkhead 66 contacts workpiece 98 any force exerted against shaft 64 which tends to move it toward end closure 14 causes locking wedges 74 to bind more tightly against the surfaces 23 of projection 26 and the wall surfaces of opening 52 in piston 50, thus preventing movement of said piston and said shaft. Furthermore, piston 50 can be locked in any position along its range of travel within casing 10, and thereafter it is not necessary to maintain fluid pressure within casing 10 in order to hold said piston in said position.

To move bulkhead 66 away from workpiece 98, port 24 is opened to the hydraulic return line and port 22 is opened to the high pressure hydraulic line. Fluid pressure thereby admitted into casing 10 between end closure 12 and end wall 32 overcomes the force exerted against valve 8%) by spring 92 and moves the head portion 86 of said valve against edge 88 of vent passage 40 to thereby close the latter. The fluid pressure also moves shell 30 toward end closure 14, thus withdrawing locking wedges 74 from engagement with the wall surfaces of opening 52 in piston 50. As shell 30 continues to move toward end closure 14, end wall 32 contacts piston 50 and carries it and shaft 64 connected thereto to their retracted position (see FIGURE 4). Since the space between piston 50 and end closure 14 is not pressurized, any hydraulic fluid or air trapped between end wall 32 and piston 50 forces ball 94 toward retaining members 84 and said hydraulic fluid or air flows through vent pas sage 54 as said end wall moves toward said piston.

It will be recognized that various modifications can be made in the disclosed fluid pressure actuator and locking device without departing from the principles of the invention, the scope of which is limited only by the terms of the appended claims. For example, locking wedges 74 could be connected to end wall 34 of shell 30 by means of links adapted to maintain said locking wedges in the proper position relative to surfaces 28 of projection 26 and at a predetermined distance from said end wall 34, and also adapted to permit said locking wedges to move in a direction perpendicular to the longitudinal axis of casing 10. Obviously the construction and arrangement of the disclosed embodiment of the invention can also be modified to include more, or fewer, than four locking wedges 74. Other changes of similar nature will be readily apparent to those skilled in the art to which the invention pertains.

What is claimed is:

1. A fluid pressure actuator and locking device comprising:

a tubular casing having first and second end closures respectively attached to opposite ends thereof, said first end closure having an aperture formed therein, said casing having a fluid pressure port at each end thereof;

a projection disposed within said casing and connected at one end to said second end closure, at least one surface of said projection being convergent with respect to the longitudinal axis of said casing in the direction of said first end closure;

a tubular shell slidably disposed within said casing, said shell having first and second end walls which are respectively attached to opposite ends thereof and each of which is provided with an aperture through which said projection extends, said first end wall facing said first end closure and having a vent passage formed therein;

a piston slidably disposed Within said shell, said piston having an opening formed therein which is substantially coaxial with said casing and through which said projection extends, the portion of the wall of said opening that faces said convergent surface of said projection also being convergent with respect to the longitudinal axis of said casing in the direction of said first end closure, said piston having a vent passage formed therein;

a tubular shaft slidably disposed in said apertures in said first end wall and said first end closure respectively, said shaft being closed at one end and connected at the other end to said piston so that the interior thereof communicates with said opening in said piston;

at least one locking Wedge disposed within said shell, said locking wedge having an inner surface which is disposed adjacent said convergent surface of said projection and an outer surface which is convergent with respect to the longitudinal axis of said casing in the direction of said first end closure;

means connected to said shell and adapted to maintain said locking wedge a predetermined distance from said second end wall while permitting it to move in a direction substantially perpendicular to the longitudinal axis of said casing;

first valve means mounted on said first end wall and adapted to close said vent passage therein when fluid pressure is admitted into said casing between said first end wall and said first end closure; and

second valve means mounted on said piston and adapted to close said vent passage therein when fluid pressure is admitted into said casing between said piston and said second end closure.

2. A fluid pressure actuator and locking device comprising:

a cylindrical casing having first and second end closures respectively attached to opposite ends thereof, said first end closure having an aperture formed therein, said casing having a fluid pressure port at each end thereof;

a projection centrally disposed within said casing and connected at one end to said second end closure, said projection having a plurality of planar surfaces each of which is convergent with respect to the longitudinal axis of said casing in the direction of said first end closure;

a cylindrical shell slidably disposed within said casing, said shell having first and second end Walls which are respectively attached to opposite ends thereof and each of which is provided with an aperture through which said projection extends, said first end walls facing said first end closure and having a vent passage formed therein;

a piston slidably disposed within said shell, said piston having an opening formed therein which is substantially coaxial with said casing and through which said projection extends, the wall of said opening including a plurality of planar surfaces each of which is convergent with respect to the longitudinal axis of said casing in the direction of said first end closure, said piston having a vent passage formed therein;

a cylindrical shaft slidably disposed in said apertures in said first end wall and said first end closure respectively, said shaft being closed at one end and connected at the other end to said piston so that the interior thereof communicates with said opening in said piston;

a frustoconical guide member coaxially disposed within said shell and connected at its large end to said second end wall, said guide member having a plurality of slots formed therein which are spaced apart circumferentially thereof, said slots being adjacent the free end of said guide member and equidistant from said second end wall, said projection extending through said guide member in spaced relation therewith;

a plurality of locking wedges respectively slidably disposed in said slots so as to be movable in a direction perpendicular to the longitudinal axis of said casing, each of said locking wedges having an inner surface Which is disposed adjacent a respective one of said convergent planar surfaces of said projection and an outer surface which is convergent with respect to the longitudinal axis of said casing in the direction of said first end closure;

References Cited UNITED STATES PATENTS 1,631,369 6/1927 Gartin 92-15 X 2,259,815 10/1941 Greve 92-28 X 2,811,951 11/1957 Bodem et a1. 9214 2,876,746 3/1959 Storrs 92-28 3,050,943 8/1962 Thorel et a1. 92-23 3,135,171 6/1964 Michalak 92-29 X 3,272,087 9/1966 Culver 9224 MARTIN P. SCHWADRON, Primary Examiner. I. C. COHEN, Assistant Examiner.

Claims

1. A FLUID PRESSURE ACTUATOR AND LOCKING DEVICE COMPRISING: A TUBULAR CASING HAVING FIRST AND SECOND END CLOSURES RESPECTIVELY ATTACHED TO OPPOSITE ENDS THEREOF, SAID FIRST END CLOSURE HAVING AN APERTURE FORMED THEREIN, SAID CASING HAVING A FLUID PRESSURE PORT AT EACH END THEREOF; A PROJECTION DISPOSED WITHIN SAID CASING AND CONNECTED AT ONE END TO SAID SECOND END CLOSURE, AT LEAST ONE SURFACE OF SAID PROJECTION BEING CONVERGENT WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID CASING IN THE DIRECTION OF SAID FIRST END CLOSURE; A TUBULAR SHELL SLIDABLY DISPOSED WITHIN SAID CASING, SAID SHELL HAVING FIRST AND SECOND END WALLS WHICH ARE RESPECTIVELY ATTACHED TO OPPOSITE ENDS THEREOF AND EACH OF WHICH IS PROVIDED WITH AN APERTURE THROUGH WHICH SAID PROJECTION EXTENDS, SAID FIRST END WALL FACING SAID FIRST END CLOSURE AND HAVING A VENT PASSAGE FORMED THEREIN; A PISTON SLIDABLY DISPOSED WITHIN SAID SHELL, SAID PISTON HAVING AN OPENING FORMED THEREIN WHICH IS SUBSTANTIALLY COAXIAL WITH SAID CASING AND THROUGH WHICH SAID PROJECTION EXTENDS, THE PORTION OF THE WALL OF SAID OPENING THAT FACES SAID CONVERGENT SURFACE OF SAID PROJECTION ALSO BEING CONVERGENT WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID CASING IN THE DIRECTION OF SAID FIRST END CLOSURE, SAID PISTON HAVING A VENT PASSAGE FORMED THEREIN; A TUBULAR SHAFT SLIDABLY DISPOSED IN SAID APERTURES IN SAID FIRST END WALL AND SAID FIRST END CLOSURE RESPECTIVELY, SAID SHAFT BEING CLOSED AT ONE END AND CONNECTED AT THE OTHER END TO SAID PISTON SO THAT THE INTERIOR THEREOF COMMUNICATES WITH SAID OPENING IN SAID PISTON; AT LEAST ONE LOCKING WEDGE DISPOSED WITHIN SAID SHELL, SAID LOCKING WEDGE HAVIG AN INNER SURFACE WHICH IS DISPOSED ADJACENT SAID CONVERGENT SURFACE OF SAID PROJECTION AND AN OUTER SURFACE WHICH IS CONVERGENT WITH RESPECT TO THE LONGITUDINAL AXIS OF SAID CASING IN THE DIRECTION OF SAID FIRST END CLOSURE; MEANS CONNECTED TO SAID SHELL AND ADAPTED TO MAINTAIN SAID LOCKING WEDGE A PREDETERMINED DISTANCE FROM SAID SECOND END WALL WHILE PERMITTING IT TO MOVE IN A DIRECTION SUBSTANTIALLY PERPENDICULAR TO THE LONGITUDINAL AXIS OF SAID CASING; FIRST VALVE MEANS MOUNTED ON SAID FIRST END WALL AND ADAPTED TO CLOSE SAID VENT PASSAGE THEREIN WHEN FLUID PRESSURE IS ADMITTED INTO SAID CASING BETWEEN SAID FIRST END WALL AND SAID FIRST END CLOSURE; AND SECOND VALVE MEANS MOUNTED ON SAID PISTON AND ADAPTED TO CLOSE SAID VENT PASSAGE THEREIN WHEN FLUID PRESSURE IS ADMITTED INTO SAID CASING BETWEEN SAID PISTON AND SAID SECOND END CLOSURE.