US3128885A - Long travel hydraulic cushion device - Google Patents

Description

April 14, 1964 E. L. THOMPSON ETAL 3,128,885

LONG TRAVEL HYDRAULIC CUSHION DEVICE ON KN JNVENToRs. I= AR\. THOMPSON JAMES FORAND www S 2 SheebS-Sheei l @Y www April 14, 1964 E. THOMPSON ETAL 3,128,885

LONG TRAVEL HYDRAULIC CUSHION DEVICE 2 Sheets-Sheet 2 Filed OCt. 25, 1961 INVENTORS. EARL. L.THOMPSON JAMES L. FORAND WAM CSS Mx United States Patent Giifice 3,128,885 Patented Apr. 14, 1964 Filed ct. 23, 1961, Ser. No. 146,770 9 Claims. (Cl. 213-43) The present invention relates to hydraulic cushion devices and more particularly to an improved cushioning device of the type comprising basically two relatively telescoping components having arranged therebetween hydraulic fluid which is operative upon the application of a force on the components 4to dissipate the kinetic energy.

A cushioning device of the above type embodying the general principles is disclosed in US. patent application, Serial No. 856,963, filed December 3, 1959, now U.S. Patent No. 3,003,436, and U.S. patent application, Serial No. 782,786, filed December 24, 1958, now U.S. Patent No. 3,035,827, both assigned to the assignee of the present invention. These applications relate to a new and novel method and structure for providing a long travel cushioning arrangement achieving force-travel cushioning characteristics which are equivalent to -travels of the substantially constant Iforce type.

It is the primary object of the present invention to provide an improved cushioning device structure constructed and arranged in a manner to facilitate the ready assembly and disassembly of the interior cylinder head incorporated therein.

llt is still a further object to provide means fixing the interior cylinder head by way of a keying arrangement insertable from the exterior of the cylinder in which the cylinder head is mounted.

It is still another object to provide a keying arrangement .including a key movable by means located exterior of the cylinder from a keying position to hold the cylinder head fixed within the cylinder to a non-keying position whereby the cylinder head is axially movable within the cylinder.

Further objects and features will hereinafter appear.

FIG. l is a small scale longitudinal section of the cushioning device embodying the present invention and shown in full lines in its fully contracted position and by the phantom lines in its fully extended position.

FlG. 2 is an enlarged fragmentary section of the device in its 'fully contracted position as shown in FIG. 1 and showing one form of the present invention for keying the cylinder head to the cylinder.

FIG. 3 is a perspective view of lthe key employed in the keying arrangement of FIGS. l-2.

FIG. 4 is a cross-sectional view of the cushion device showing a further embodiment for keying the cylinder head within the cylinder.

FIG. 5 is a perspective View of one of the keying elements employed in the embodiment of FIG. 4 prior to being inserted.

Referring now to FIGS. l and 2, there is shown a cushioning device 1t? embodying the present invention including generally a cylinder 11 having a bore 12 charged with a suitable hydraulic fluid; a fluid displacement means 13 telescopingly arranged relative to the cylinder 11 between a fully extended position as shown by Ithe phantom lines of FIG. f1 -to a contracted position upon the application of a shock force applied to the device and being operative upon contraction to displace fluid within the bore 12 to dissipate le'netic energy in the form of heat; a metering pin 14 for controlling the rate of displacement of the fluid within the bore to provide substantially constant force-travel cushioning characteristics to the device; and a resilient means 15 dispose-d between the fluid displacement means and the cylinder for returning the members to their fully extended position upon dissipation of the shock.

The cylinder 11 includes a tubular shell formed preferably from a rigid metallic, preformed tube 16 capable of withstanding internal pressures without buckling, such as cold-drawn steel tubing of which the inner wall surface is sufficiently smooth to permit efficient operation of the fluid displacement means y13 disposed therein. it has been found that the smoothness ordinarily obtained by the conventional polished mandrel method of forming steel tubing is satisfactory. However, it is to be understood that a surface formed in any other manner having substantially the same smoothness characteristics may also be employed.

The tube or shell :16 is closed at one end by a cylinder head 17 having a groove 18 formed therein for receiving one end of the tube and the latter is xed therein as by Welding to form a leak-proof joint. The cylinder head 17 is of somewhat larger diameter than the diameter of the shell so as to provide a flange engaging one end ofdthe resilient spring-means .1S encompassing the cyl- 1n er.

Located between the cylinder head and the free end of the tube is a second cylinder head 19 preferably formed from steel tube or the like and includes an axial bore 2i), a hub 21, and a peripheral recess 22 for receiving an O-ring 23 and a circumferential groove 24 providing a keyway. If desi-red the cylinder head 19 may be formed from solid block material and fabricated to form the structure shown.

IFor the purpose of facilitating the assembly and, if necessary, the removal of the cylinder head 19 within the shell 16 in accordance with the present invention there is provided a novel keying arrangement which permits the xing of the cylinder head without having to work within the contines of the cylinder bore.

In `one form of the keying arrangement as shown in FIGS. 1-3 there is employed a split, expandable ring 26 which serfves as a key selectively positionable within a keyway 27 formed in the inner wall of the cylinder and the keyway 24 of the cylinder head 19. The expandable key 26 is preferably formed of a spring steel and is sized so that when contracted, the upper surface thereof lies iiush with the outer surface of the hub, i.e., the keyway 24 is of suilicient depth to accommodate the thickness of the key.

For selectively positioning the split or snap ring key into its keying position as shown -in the full lines or to its unkeyed position as shown in the phantom lines there is provided key seating or positioner means which in the embodiment illustrated includes a plurality of radially spaced screws 2S threadable into the tube 16 and in alignment with the 'keyway 24.

For fixing or keyinU the cylinder head 19 to the tube 16 the screws 28 are retracted out of the cylinder keyway 27. The key 26 is positioned in the cylinder head keyway Z4 and contracted so as to be slidable within bore 12. Thereafter, the cylinder head is moved within the cylinder until the key aligns with the cylinder keyway 27 whereupon the ring expands and seats in its keying position.

For positioning the key to release the cylinder head, the screws are threaded inwardly to bear on and contract the key 26 so that it lies wholly within the cylinder head key- Way. In this position of the key, the cylinder head may be axially moved and removed from the free end of the tube 16.

ln another form of the invention, as shown in FIGS. 4

and 5, the cylinder is formed with radially spaced slots 30 into each of which there is inserted a key 29 of the type shown in FIG. 5. Each of the keys 29 is dimensioned so as to be snugly received within the slots 30 and is formed with an upper surface 31 having a radius substantially the same as the radius of the outer diameter of the tube. The lower surface is formed with an intermediate surface 32 having a radius substantially the same as the radius of the bottom wall of the keyway 24 and at each end with a surface 33 of smaller radius defining a pair of ear-like projections 34 at either end of the key. Transverse slots 36 are provided to separate the ear-like projections 34 from the intermediate surface 32.

To assemble the cylinder head 19 in the tube 16 the keyway 24 is located in alignment with the key slots 30 and the keys 31 inserted therein. The keys 31 are then forced as by hammering or the like so that the ear-like projections spread outwardly from the slots and are wedged between the inner wall of the tube 16 and the bottom wall cylinder head keyway 24 so as to securely fix the cylinder head in position.

Disassembly of the cylinder head 19 and tube 16 is readily accomplished by merely splitting each of the keys 29 between its ends such as by a chisel. Thereafter the split halves of the key may be slipped out from their wedging position whereby the cylinder head is freely movable within the tube for removal therefrom.

The fluid displacement device includes a piston rod 37 to one end of which there is connected a piston head 38 which is reciprocable within the bore between the cylinder heads 17 and 19 and to the other end of which there is connected a closure plate 39.

The piston rod 37 includes a bore 41 and may be formed of a rigid metallic material, such as cold-drawn steel tubing, and is provided adjacent the piston head 38 with a plurality of radially spaced ports 42 for providing communication between the cylinder bore 12 and the piston rod bore 41.

To preclude metal-to-metal contact, the outer diameter of the piston rod 37 is substantially less than the diameter of the coaxial opening in the cylinder head 19 so as to provide an annular opening 43 between the outer wall of the rod 37 and the wall defining the opening 20 of the cylinder head. The annular opening is sized to permit substantially free flow of hydraulic uid between an invagiating tube or flexible resilient fluid receiving member 44.

The piston head 38 is preferably formed from a metal such as steel and comprises a disc-like body having a planar forward face 46 and a planar rearward face 47. The planar rearward face 47 merges into a conical feed surface 48, which terminates in a rim 49 and defines the perimeter of an orifice 51 formed coaxially in the piston head. The piston head 38 is formed on its forward face 46 with a recess 52 which receives the terminal end of the piston rod 37 and the latter is fixed to the piston head 38 by way of a. weld.

For guiding the surface fluid displacement means for relative telescoping movement within the cylinder 11 and for forming a uid seal between the inner wall of the cylinder 11 and the piston head 38, the piston head 38 is provide with an elevated guiding surface means 53. The bearing surface means is preferably formed from a material having a high compressive strength, good surface abrasive resistance characteristic and which does not have an affinity for the material from which the cylinder is formed so as to be capable of withstanding the high stresses caused in part by the high unit pressures and high temperatures associated with the operation of the device without encountering fatigue such as galling of the cylinder walls.

One material found to be particularly suitable for use as a guiding surface with the long travel cushioning device constructed in accordance with the present invention is a laminated phenolic resin, as for example having an 4 NEMA (National Electrical Manufacturers Association) designation of 9 Coarse, Grade C.

The raised guiding surface means 53 formed of laminated phenolic resin is constructed as a split expandable ring which is seated within a groove 54 formed on the periphery of the piston head 38. The guiding ring 54 is constructed so that it is snugly received within the groove 54 and expands and contacts the inner wall surface of the cylinder, thereby to form an efficient seal while at the same time providing a guiding surface which distributes the bearing stresses associated with the reciprocable movement of the piston head 38 within the bore 12 without resulting in a rupturing of the inner wall surface. It is to be particularly observed that the piston head is formed of reduced diameter and that the edges are formed with a distinct radius so as to substantially preclude metal-tornetal contact between the piston head 38 and the tube 16.

The closure plate 39 is preferably formed from a mild steel and includes a hub 56 and a flange 56a against which an end of the resilient return spring means abuts. The hub is of substantially the same diameter as the tube 16 and as shown in FIG. 2, the end of the latter abuts the hub 56 in the fully contracted position. The closure plate 39 is fastened to the piston rod 37 by way of a bolt threaded into a plug which is secured as by welding into the bore adjacent the closure end thereof.

For metering the rate of flow from a high-pressure chamber 57 on one side of the piston 38 and through the orice 51 of the piston head 3S the piston bore 41 and the ports 42 of the tubular piston rod to a low-pressure chamber 58 on the opposite side of the piston, there is provided the metering pin. The metering pin 14, as shown, comprises essentially a rod of constant circular crosssectional area along its length and which is provided with a plurality of flutes 60, of which only one is shown, gradually tapering toward the rearward end thereof. The pin 14 is fixed at its head 59 as by threading into the cylinder head 17 of the cylinder 11. Upon relative movement between the cylinder 11 and the fluid displacement means 13 during the application of a shock to the unit, the piston head 38 is positioned relative to the metering pin 14 so that the iiow through the orifice 51 and the flutes 60 at any given distance of travel imparts a constant-force travel characteristic to the cushioning device. To this end, the flutes 60 are designed to conform substantially with the relationship ber 3,003,436, issued October 10, 1961.

Fixed on and located forwardly of the ports 42 of the `piston rod 37 is a stop ring 61 which, as shown in the phantom line position of FIG. 1, engages the cylinder head 19 so as to limit the travel of the fluid displacement means 13 `to its fully extended position. This provides a minimum load pressure volume in the chamber 58 for receiving the fluid from the chamber 57 via the orifice 51 and bore 41 of the piston rod 37.

For further extending the low pressure volume, there is provided the invaginating tube 44 which, as above described, has one end thereof xed to the hub 21 of the cylinder head 19 as by hose clamps and the infolded end fixed to the piston rod 37 for movement therewith also by a hose clamp. The invaginating tube 44 is formed of a fluid impervious flexible material which is capable of resisting corrosive effects of the hydraulic liquid employed in the unit and advantageously may be a neoprenebuna type of rubber having special additives for low temperature iiexibility.

As shown, the resilient means 15 includes three helical compression springs 15a, 15b and 15C arranged in tandem and are employed for the purpose of extending the device to its fully extended position. The compression springs may be formed of a heat treated spring steel. If desired, the resilient spring means 15 may be in the form of either single or dual springs.

Located in the head 59 of the metering pin 14 is a charging check valve device 62 for charging hydraulic fluid into the unit. The head 59 is formed with an inner axial recess 63 which communicates with an enlarged recess 64 provided adjacent the terminal end thereof. Threadably secured with the inner recess is a plug 65 provided with an open-ended bore 66 which communicates at one end with an axial passage 67 and at its other end with the outer recess 64. The passage 67 is in constant communication with a diametrical passageway 68 formed in the body portion of the metering pin and located so as to communicate with the bore 12 of the cylinder when the metering pin 14 is assembled in the cylinder head 17.

Disposed within the recess is the check valve device 62 including a ball 71 biased by way of a compression spring 72 into seating engagement over the plug bore 66. For precluding leakage through the check valve structure, the enlarged recessed end of the metering pin head has screwthreaded therein a sealing plug 73 which is preferably in the form of an Allen-type pipe plug.

Operation Assuming the device is assembled and devoid of hydraulic uid and in its fully extended position, as shown by the phantom lines of FIG. 1 and the plug 73 is removed from the metering pin head 59, a hydraulic fluid, such as a noncorrosive, high-viscosity oil which retains its viscosity over a relatively wide range of temperatures, is introduced in the bore 66 of the plug 65 whereupon the flow of hydraulic liuid unseats the ball 71 to supply hydraulic iiuid into the high-pressure chamber 57 via the recess 63, passage 67, and diametrical passageway 68 of the bore 12. At the same time, hydraulic liuid flows through the orifice 51 in the piston head 3S, the iiutes 6i) of the metering pin 14, the piston bore d1 and ports 42 to the low-pressure chamber 58 and via the annular passageway 43 into the invaginating tube 4d. The device is charged so that the pressure exerted by the uid is maintained at a minimum, for example, about 2 p.s.i.

Assuming further that the cushioning device is employed in a railway car having a superstructure mounted for movement relative to the underframe wherein the device 1@ is mounted in a pocket-like structure arranged to isolate shock imparted to the underframe from the superstructure, during normal transit and in the `absence of bu or draft forces, the cushioning device is in the fully extended position shown in FIG. 1 with the stop-ring 61 contacting the cylinder head 19. Upon the application of a shock in either buff or draft to the cushioned underframe, the tubular cylinder and the piston 26 and cylinder start movement toward each other. As the cushioning device contracts under the force being cushioned, the metering pin 1d displaces hydraulic fluid contained within the bore 41 of the piston rod 37 and the high-pressure chamber 57 on one side of the piston head 38 causing a hydraulic uid iiow through the orifice 51 into which the metering pin 14 extends. The metering pin as heretofore described is formed with the flutes 60 which are designed to provide a constant force-travel characteristic as the hydraulic cushion contracts under the shock force imposed upon the latter, i. e., the flutes 60 of the metering pin 14 are cooperative with the orifice 51 in the piston head 3S so that the ow of hydraulic uid therethrough for every unit of travel of the piston head 3S relative to the cylinder 11 imparts a substantially constant cushioning effect to the cushioning device.

The hydraulic flow initiated byv the relative movement of the piston head 38 and the cylinder 11 ows from the high-pressure chamber 58 through the oriice 51 and into the bore 41 of the piston rod 37 and thence radially outward through the ports 42 into the low-pressure chamber 53 of the bore 12. The hydraulic fluid flow through the ports 42 occurs at a relatively high velocity so that a turbulence is created as the displaced fluid enters the lowpressure chamber 58. This turbulence is caused at least in part by the radially directed liow of hydraulic fluid impinging directly against the inner wall of the tube so that a major portion of the kinetic energy of the hydraulic iiuid is dissipated in the form of heat. In this connection, it is to be noted that the stop-ring 61 contacting the cylinder head is effective to limit the volume of the low-pressure chamber 5S and in this manner provides a chamber into which the hydraulic fluid displaced by the piston may freely enter as described above and thereby dissipate the kinetic energy in the form of heat under minimum shock conditions.

Upon further contraction of the cushioning device, the high-pressure chamber 57 continues to reduce in volume because of the advancement of the piston head 38 toward the cylinder head 17. The hydraulic fluid passing through the oriiice 51 iills the low-pressure chamber 5S, While at the same time a volume of hydraulic liquid equivalent to that displaced by the total entry into the uid chamber of the piston rod passes through the annular opening 43 of the cylinder head and into the pocket deiined by the invaginating boot 44, which iniiates or expands and assumes substantially the position shown in the full line position of FIG. 1. The relationship of the diameter of the piston rod 37 and the opening 20 in the cylinder head 19 is such as to provide a relatively large volume annular opening resulting in a low-pressure hydraulic liquid flow from the low-pressure chamber into the invaginating boot.

Aititer the shock has been fully dissipated, the compression springs 15a, 15b and 15C acting in tandem are operative to return the hydraulic cushion components to the initial extended position. During this movement, under -the action of the compression spring-s, the oil ovv previously `described is reversed and the invaginating tubular member deiiates and returns tothe position shown. thereby insuring that the hydraulic liquid displaced by the piston is restored toits normal operative position.

What is claimed is:

1. A hydraulic cushioning device comprising a hyidraulic fluid containing cylinder including an open-ended tube, a first cylinder head closing one end of said tube, a second cylinder head located between the open and closed ends of `said tube and including a peripheral keyway, a plurality of peripherally spaced openings extending through the ywall of said tube, key means disposed in said keyway and accessible through said openings for positioning lsaid key means to iix said second cylinder head against axial movement Within said tube, fluid displacement means movable through said second cylinder head and including a piston head located between said cylinder heads and defining a high-pressure chamber adjacent said irst cylinder head `and a low-pressure chamber adjacent said second cylinder head, a liexible iiuid receptacle connected to said uid displacement means and said second cylinder head adjacent the open end of said tube and in constant communication with said low-pressure chamber, and oriiice means providing communication between said high and low-pressure chambers.

2. The invention as dened in claim l in which said tube is also provided with a keyway, said key means comprising a snap ring seatable -in a contracted position wholly ywithin the confines of said peripheral cylinder head keyway and seatable in an expanded position within both o-f said keyways to key said second cylinder head to said tube, and means in said openings for selectively expanding and contracting said ring.

3. The invention as delined in claim l in which said key means comprises a plurality of key members of which each is receivable 4Within a respective one of said openings and xedly positionable within said peripheral cylinder head keyway.

4. The invention as defined in claim 3 in which each of said openings is in the form of a rectangular slot, and each of said key members is Lformed yto be snugly received therein and includes a pair of spaced ear-like projections receivable Within said peripheral key way and wedgeable between the inner Wall of said tube and the bottom wall of said keyway.

5. In a hydraulic cushioning device including a tube having a first cylinder head fixed to one end and a `second cylinder head between the ends of said tube and a uid displacement means telescopingly arranged relative to said cylinder and operative to displace iiuid within said tube to dissipate kinetic energy of a :force applied to said device in the orm of heat, the improvement comprising a peripheral keyway formed in said second cylinder head,

keyway means in said tube having openings through the wall alignable with said keyway, and key means seated in said peripheral keyway and accessible through said openings to position said key means in a keying position.

6. The invention as defined in claim 5 in which said key means comprises a snap ring seatable in a contracted position wholly within the confines of said peripheral key- =way and seatable in an expanded position within both said peripheral keyway and keyway means to key said second cylinder head to said tube, and means in said openings for selectively expanding and contracting said ring.

7. The invention as defined in claim 5 in which said key means comprises a plurality of key members of which each is receivable within a respective one of said openings and iixedly positionable within said peripheral keyway.

8. The invention as defined in claim 7 in which each of said openings is in the form of a rectangular slot and each of said key members is formed to be snugly received therein and includes a pair of spaced ear-like projections receivable within said peripheral keyway vand wedgeable between the inner wall of said tube and the bottom wall of said keyway.

9. In a hydraulic cushioning device wherein a cylinder is provided with an intermediate cylinder head internally thereof through which piston means is rcciprocable within said cylinder, the provision of intermediate cylinder head keying means for cylinder head position fixing, said keying means comprising outer peripheral keyway means forming la part of said cylinder head, key means in said cylinder and projecting into said keyway means to position said cylinder head, and seating means for said key means carried by said cylinder and accessible externally thereof for controlled positioning of said key means relative to said cylinder head.

References Cited in the file of this patent UNITED STATES PATENTS

Claims (1)

1. A HYDRAULIC CUSHIONING DEVICE COMPRISING A HYDRAULIC FLUID CONTAINING CYLINDER INCLUDING AN OPEN-ENDED TUBE, A FIRST CYLINDER HEAD CLOSING ONE END OF SAID TUBE, A SECOND CYLINDER HEAD LOCATED BETWEEN THE OPEN AND CLOSED ENDS OF SAID TUBE AND INCLUDING A PERIPHERAL KEYWAY, A PLURALITY OF PERIPHERALLY SPACED OPENINGS EXTENDING THROUGH THE WALL OF SAID TUBE, KEY MEANS DISPOSED IN SAID KEYWAY AND ACCESSIBLE THROUGH SAID OPENINGS FOR POSITIONING SAID KEY MEANS TO FIX SAID SECOND CYLINDER HEAD AGAINST AXIAL MOVEMENT WITHIN SAID TUBE, FLUID DISPLACEMENT MEANS MOVABLE THROUGH SAID SECOND CYLINDER HEAD AND INCLUDING A PISTON HEAD LOCATED BETWEEN SAID CYLINDER HEADS AND DEFINING A HIGH-PRESSURE CHAMBER ADJACENT SAID SAID SECOND CYLINDER HEAD, A FLEXIBLE FLUID RECEPTACLE CONNECTED TO SAID FLUID DISPLACEMENT MEANS AND SAID SECOND CYLINDER HEAD ADJACENT THE OPEN END OF SAID TUBE AND IN CONSTANT COMMUNICATION WITH SAID LOW-PRESSURE CHAMBER, AND ORIFICE MEANS PROVIDING COMMUNICATION BETWEEN SAID HIGH AND LOW-PRESSURE CHAMBERS.

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