US3391798A - Hydraulic cushioning device - Google Patents

Description

July 9, 1968 J SPENCE ET A.

HYDRAULIC CUSHIONING DEVICE 3 Sheets-Sheet 1 Filed June 27, 1966 IN VE N TORS JOHN H. SPENCE MERRIL L 6. MA RSHA LL July 9, 1968 SPENCE ET AL 3,391,798

HYDRAULIC CUSHIONING DEVICE Filed June 27. 1966 5 Sheets-Sheet 2 E: as l2 #1 g 5.. INVEN TORS JOHN H. SPEN CE MERRILL a. MARSHALL y 9, 1968 H. SPENCE ET AL 3,391,798

HYDRAULI C CUSHION I'NG DEVICE Filed June 27. 1966 5 Sheets-Sheet 3 IN VE N TO RS JOHN H SPENCE MERRILL G. MAIiSHALL BY %M A ATT'Y.

United States Patent 3,391,798 HYDRAULIC CUSHIONING DEVICE John H. Spence, Chicago Heights, and Merrill G.

Marshall, Homewood, IlL, assignors to Pullman Incorporated, Chicago, 111., a corporation of Delaware Filed June 27, 1966, Ser. No. 560,712 12 Claims. (Cl. 21343) ABSTRACT OF THE DISCLOSURE In a hydraulic cushion device having an open end cylinder with a stop head and movable piston therein, a piston mounted reservoir closing the cylinder open end, passage means between the closed end of the cylinder and the reservoir, and a return spring between the piston and the cylinder, the improvement comprising snubber stop means in the cylinder for cushioned engagement with the cylinder head comprising a reciprocably movable piston mounted snubber member engageable with said cylinder head upon outward piston movement, a fixedly piston mounted snubber member engageable with the movable member upon outward piston movement, and biasing means between the movable member and the piston urging said movable member away from the fixed member.

The present invention relates to hydraulic cushioning devices and more particularly to an improved hydraulic cushion device of the type which may be used in cushion underframe railway cars for providing car body and lading protection.

A hydraulic cushion of the type to which the present invention relates is disclosed in US. Patent 3,218,052. The hydraulic cushion unit comprise generally a hydraulic fluid filled cylinder in which there is reciprocally disposed a fluid displacement means which may be in the form of a piston head having fixed to one face thereof one end of a tubular piston rod. The tubular piston rod extends through an intermediate cylinder head fixed inwardly of an open end of the cylinder. Fixed to the outwardly extending end of the cylinder is a base plate against which there abuts one end of a return spring means. The other end of the return spring abuts against a second base plate which is fixed to and closes off the other end of the tubular piston.

The cylinder and fluid displacement means are movable between a neutral extended and contracted position. During the extension and contraction of the cushioning unit, hydraulic fluid flows between a high pressure chamber defined between the forward face of the piston head and the closed end of the cylinder, and a low pressure chamber defined between the rear face of the piston head and the intermediate cylinder head.

A flexible reservoir is attached between the intermediate cylinder head and the outwardly extending end of the piston rod. The reservoir communicates with the low pressure chamber via fluid passages through the cylinder head and serves to receive hydraulic fluid displaced by the piston rod during the contraction of the cushion unit.

The hydraulic cushion unit is preferably of the type having an approximately constant resisting force travel characteristic. To this end, the piston head is provided with an orifice which is aligned with the piston rod bore having ports providing fluid communication with the low pressure chamber. Extending through the orifice is a metering pin which is constructed so as to vary the fluid flow through the orifice in a manner achieving the approximate substantially constant resisting or cushioning force during each increment of the travel of the cushioning unit from the extended to contracted position. The metering 3,391,798 Patented July 9, 1968 "ice pin is fastened at one end to the base plate so as to form a fluid tight seal.

The cushion unit is generally interposed between a sliding sill and an underframe so as to cushion the forces imposed upon the car body and the lading carried thereon. In operation, the cushioning unit is disposed between a pair of stops which are fixed to the sliding sill and the car underframe so that upon the imposition of a force to the sliding sill the cushion unit is contracted from its extended position and during this time serves to absorb and dissipate a portion of the impact energy of the draft or buff force applied at the couplers. After the force of the impact has been dissipated the return spring is operative to return the cushion unit to its neutral or extended position. Under some conditions the sliding sill may stick within the support on the underframe after the force has been dissipated. Under these conditions, the return spring is completely compressed so that when an impact is again applied on the extended end of the sill, the full force of the impact and the extension force of the spring is imposed on the cushioning unit. Thus, when the cushioning unit returns to its neutral position, the forces of the impact and the spring force create considerable stresses on the cushioning components, particularly on the base plate fixed to the tubular piston rod so that the base plate may be separated from the piston rod.

It is a principal object of the present invention to provide an arrangement for reducing the possibility of failure of the cushion unit by separation of the base plate from the tubular piston rod.

To this end there is provided a snubber arrangement for applying a snubbing force which is effective to reduce the stresses on the cushion unit as the latter returns from its compressed to extended neutral position.

Further objects and features will hereinafter appear.

In the drawings:

FIG. 1 is a cross sectional view of a cushion unit in the extended neutral positional thereof and embodying the snubbing arrangement of the present inveintion;

FIG. 2 is similar to FIG. 1 but showing the hydraulic cushion unit in its contracted position;

FIG. 3 is a fragmentary sectional view of the cushion unit and showing in particular the position of the components of the snubbing arrangement as the cushion unit returns from the compressed to extended position;

FIG. 4 is a view similar to FIG. 3 but showing the position of the components of the snubbing arrangement in the fully extended position of the cushion unit;

FIG. 5 is a view similar to FIG. 4 but showing the components of the snubbing arrangement immediately prior to becoming operative to provide a snubbing force as the cushion unit approaches the extended position.

FIG. 6 is a fragmentary sectional view of hydraulic cushion unit having a modified fluid displacement means and showing a further modification of a snubbing structure with the components thereof shown in the position immediately prior to obtaining the snubbing action; and

FIG. 7 is a fragmentary sectional view similar to FIG. 6 but showing the components of the snubbing structure in the extended neutral position of the cushion unit.

Referring now to the drawings, there is shown a hydraulic cushion unit or device 10 embodying the snubber arrangement 2% of the present invention. The hydraulic cushion unit it comprises generally a hydraulic fluid filled cylinder 11, a fluid displacement means 12 reciprocal within the cylinder 11, a flexible reservoir in the form of a boot 13 which is suitably connected at one end to the cylinder 11 and at the other end to the fluid displacement means 12, a metering pin 14 for controlling the fluid flow from a high pressure chamber 15 to a low pressure chamber 16, and return spring means 17 disposed between the cylinder 11 and the fluid displacement means 12.

The cylinder 11 includes a cylindrical tube 18 formed of steel or the like to one end of which there is fixed as by welding 21 base plate 19 which is of larger diameter than the cylindrical tube 18 to provide a projecting ledge 21.

Disposed within the cylinder bore 22 and inwardly of the open end of the tube 18 is an intermediate cylinder head'24 having an axial opening 26. The intermediate cylinder head 24 may be suitably fixed within the bore 22 by means of snap rings 27 seated within grooves formed within the periphery of the bore 22.

The fluid displacement means 12 includes the piston head 28 which is reciprocal within the cylinder bore 22 and defines on the closure plate side thereof the high pressure chamber 15 and on the intermediate cylinder head side the low pressure chamber 16.

Seated within a groove formed in the periphery of the piston head 28 is a guide and sealing ring 29 which is preferably formed of a laminated phenolic resin. The guide and sealing ring 29 is constructed so that the outer guiding surface thereof extends beyond the outer periphery of the piston head 28 and thereby precludes metal to metal contact with the cylinder wall.

Fixed to the piston head 28 as by welding is one end of a tubular piston rod 31 which extends through the axial opening 26 and defines therewith an annular passage 32 through which the hydraulic fluid flows from the low pressure chamber 16 to the boot or reservoir 13 upon contraction and extension of the cushion unit 10.

As shown in particular in FIG. 1, a second follower or base plate 33 is connected to the outer end of the tubular piston rod 31. In order to fixedly secure the base plate 33 to the tubular piston rod, a fastening plug 34 is inserted into the end of the piston rod bore 35 and fixed therein as by welding. The end of the piston rod bore 35 may be slightly enlarged so that fastening plug 34 seats against a shoulder 36. At the terminal end the fastening plug 34 is fixed within the bore as by welding.

' The base plate 33 is formed on its inner face with a recess 37 which snugly receives the terminal end of the piston rod 31. On its outer face the base plate 33 is formed with a circular recess 38 which accommodates the head 39 of the bolt 41.

The piston head 28 is reciprocal within the cylinder bore 22 and includes an axial orifice 44 through which the hydraulic fluid flows between the high pressure chamber 15 and the low pressure 16 via the piston rod bore 35 and an array of ports 46 formed in the piston rod adjacent the piston head 28.

As shown in particular in FIGS. 3-5, the forward or high pressure face of the piston head 28 is formed with a circular recess 51 in which there is disposed a flap valve ;52. The flap valve 52 is movable from a position overlying a plurality of angularly spaced openings 53 formed in the piston head 28 to a position spaced therefrom against the snap ring 54. The flap valve 52 serves as a means for providing fluid communication between the low pressure chamber 16 and the high pressure chamber 15 during the return stroke of the cushion device from the contracted position shown in FIG. 2 to the extended position shown in FIG. 1.

Extending through the axial orifice is the metering pin 14 which is fixed at one end to the base plate 19. The metering pin is formed with flutes 57 which serve to Vary the volume or flow of liquid through the orifice 44 in a manner imparting a substantially constant force travel characteristic as the cushion unit moves from its extended to the contracted position upon the imposition of an impact to the base plates 33 or 19. For a more complete description of the construction of the metering pin, reference is made to Peterson patent U.S. Patent 3,218,052.

Limiting the movement of the cushion device 10 to its extended position is the snubber arrangement 20 which serves as a stop to prevent a further extension of the cylinder 11 and fluid displacement means 12 against the force of the return spring 17 which is disposed between the base plates 33 and 19. The return spring 17 may be a single spring or a plurality of springs arranged in tandem as shown.

The snubber arrangement 20 includes a snubber cylinder 61 having an open end 62 and a closed end 63 formed with an opening 64 through which there slidably extends the piston rod 31. In the neutral extended position, as shown in FIGS. 1 and 4, the snubber cylinder 61 engages the inboard face of the intermediate cylinder 24 and compresses a compression spring 65 disposed between the end walls 66 of the cylinder 61 and the first stop ring 67 fixed to the piston rod 31. Fixed to the piston rod 31 is a piston ring stop 68 which in the extended position of the cushion unit, as shown, seats within the bore 69 of the snubber cylinder 61 with the outboard face abutting against the inner end wall 71 of the cylinder bore 69. In this manner the piston ring stop serves as a stop to limit the lengthwise movement of the cylinder 11 and fluid displacement means 12.

When the cushion unit moves from its extended to contracted position the biasing spring 65 of the snubber arrangement 20 is operative to slide the snubbing cylinder 61 lengthwise of the rod into abutting engagement with a second stop ring 70 fixed to the piston rod 31 and spaced lengthwise of the first stop 67. However, when the piston rod 31 and cylinder 11 return toward the extended position under the force exerted by the return spring 17, upon contact of the intermediate cylinder head 24 with the snubber cylinder 61, the latter is moved away from the stop 70 against the force of the snubber spring and is slid lengthwise of the piston rod 31 toward the stop 67 as shown in FIG. 4. During this movement of the snubber cylinder 61, the piston stop ring 68 enters the cylinder bore 69. Thus, pressure force of the hydraulic fluid within the bore 69 is increased and thereby creates a resisting force which forms in the nature of a snubbing action which absorbs a portion of the energy and reduces the stresses imposed on the bolt 42, fixing the base plate 32 to the piston rod 31. When the piston stop 68 strikes the inner wall or shoulder 71 of the bore 69, the unit is held in its neutral extended position by way of the force of the return spring 17 acting between the base plates 19 and 33.

Referring now to FIGS. 6 and 7, there is shown a snubber arrangement incorporated in a cushion unit 101 having a modified fluid displacement means 102. In all other respects the structure of the cushion unit 101 is identical to that described in connection with FIGS. 1-5 and, accordingly, like parts are designated the same.

The fluid displacement differs essentially in that the piston head assembly 103 is formed as a casting including a head 104, from which there extends a hollow shank 106 having a bore 107. Fixed to the end of the shank 106 within a recessed .groove is one end of the tubular piston rod 31 with the bore 35 axially aligned with the shank bore 107. The shank 106 is formed at its outer end with an enlarged rim 108 which is spaced from the piston head 104. The rim 108 serves as a stop and snubber piston ring as more fully to be explained hereafter.

The piston head 104, similar to the piston head 28 of the embodiment shown in FIGS. 1-5, may be formed with an axial orifice 109 through which there extends the metering pin 14. Formed on the forward or high pressure face is a circular recess 111 in which there is located a flap valve which is movable from a position overlying a plurality of angularly spaced openings 113 to a position spaced therefrom against a snap ring 116. The flap valve 112 serves to permit fluid communication between the low pressure chamber and the high pressure chamber 15 during the return of the cushion unit from the contracted to extended position.

Providing fluid communication between the piston rod bore 35 and the low pressure chamber 16 are ports 117 formed in the shank 106. Thus, upon contraction of the cushion unit 10 from the extended neutral position upon impact at either of the base plates 19 or 33, the hydraulic fluid within the high pressure chamber 15 via the orifice 109, shank bore 107 and ports 117 flows into the low pressure chamber 16. The flow through the orifice 119 is controlled by the flutes 57 in the metering pin 14 to impart a substantially constant force travel characteristic to the cushion unit 101.

Upon dissipation of the impact energy, the return spring 17 is operative to return the fiuid displacement means 109 and the cylinder to the neutral position. As the unit 191 approaches the neutral position, the snubber arrangement 120 is operative to reduce the impact of the stop rim 108 when the latter reaches its limit position against the intermediate cylinder head 24.

The snubber arrangement 120 includes a snubber cylinder 121 having a closed end 122 formed with an opening 123 through which the piston rod 31 slidably extends. The other end of the snubber cylinder is open and abutting against a rim 124 is one end of a spring 126 of which the other end abuts against a stop ring 127 fixed to radially spaced ribs 128 on the piston head casting. The spring 126 serves to normally bias the snubber cylinder 121 against a stop ring 129.

As the cushion unit 181 approaches the neutral position the outboard face of the snubber cylinder 122 strikes the intermediate cylinder head 24 whereupon the snubber cylinder 121 slides along the piston rod against the force of the biasing spring 126. Of course, during this move ment of the snubber cylinder 121, the piston rod continues to move in the direction of the arrow as shown in FIG. 6 so that the stop rim 108 enters the snubber cylinder bore 131 causing an increase in pressure forces therein which resist the movement of the piston rod 31. In this manner the relative acceleration forces of the piston rod 31 and cylinder 18 are reduced so that when the stop rim 108 strikes the inner wall 132 of the snubber cylinder bore 131, the stresses imparted through the length of the piston rod 31 to the base plate fastening bolt 39 are materially reduced.

What is claimed is:

1. In a hydraulic cushion device comprising a hydraulic fluid filled cylinder, a first base plate fixed to one end of said cylinder, an intermediate cylinder head fixed within the bore of said cylinder inwardly of the open end thereof, first fluid displacement means including a piston head reciprocable within said cylinder bore for movement between said base plate and said intermediate cylinder head to and from an extended position and a contracted position and a tubular piston rod fixed at one end to said piston head and extending through said intermediate cylinder head outwardly of said open end of said cylinder, a flexible boot fixed between said intermediate cylinder head and said outwardly extending end of said tubular piston rod, hydraulic fluid passage means through said intermediate cylinder head providing hydraulic fluid communication between said cylinder bore and said flexible boot, a second base plate fixed to said outwardly extending end of said tubular piston rod, return spring means interposed between said first and second base plates, an axial orifice through said piston head providing hydraulic fluid communication with said bore, port means in said fluid displacement means providing hydraulic fluid communication between the piston rod bore and said cylinder bore, a metering pin fixed to said second base plate for metering the flow of the hydraulic fluid through said orifice, the improvement comprising stop means for limiting the extended length of said cylinder and second fluid displacement means including a snubbing cylinder means slidably mouted on said piston rod and positioned between said piston head and said intermediate cylinder head, said cylinder means having a closed end and an open end, a piston ring stop means fixed to said first fluid displacement meaus for entry into said cylinder means, and biasing means yieldably holding the open end of said cylinder means displaced outwardly of the piston ring stop means, said snubbing cylinder means being located on said piston rod so as to be displaced over said piston ring stop means when said first fluid displacement means and said cylinder reach said extended position from said contracted position thereby to provide a hydraulic snubbing force.

2. The invention as defined in claim 1 wherein a first stop ring and a second stop ring are fixed to said second fluid displacement means for movement therewith in lengthwise spaced relationship, said closed end of the snubbing cylinder means being eugageable with said first stop ring, and said spring biasing means extending between said second stop ring and said snubbing cylinder means to yieldably retain the latter in engagement with said first stop ring.

3. The invention as defined in claim 1 wherein said piston ring stop means is located on said fluid displacement means between said intermediate cylinder head and said piston head so that upon engagement of said snubbing cylinder means with said intermediate cylinder head said snubbing cylinder means moves lengthwise of said piston rod against the force of said biasing spring and said piston ring stop means enters said snubbing cylinder means.

4. The invention as defined in claim 1 wherein said ports in said fluid displacement means are formed in said piston rod, and said stop means is disposed on said piston rod in proximity of said ports.

5. The invention as defined in claim 2 wherein said piston head is formed as a casting including a hollow shank having said ports formed therein, said first stop ring being fixed to said piston rod and said second stop ring to said piston head shank, and wherein said piston ring stop means is formed on said shank.

6. In a cushion device having a cylinder with an intermediate piston stop cylinder head and a closed end, fluid displacement means including a reciprocable piston rod havig a piston head movable between the cylinder head and the closed end and being extendable out of the cylinder, at rservoir coupling with the cylinder head and the portion of the piston rod extendable out of the cylinder, means including passage means inthe piston head and piston rod and cylinder head to provide communication on either side of the piston head and between the piston rod and the reservoir during expansion and contraction of the device, and resilient means being disposed between the fluid displacement means and the cylinder for expanding the device to an extended position subsequent to compression of the device to the contracted position, the improvement comprising a snubber stop arrangement adapted for engagement with the cylinder head and comprising a movable snubber member reciprocably mounted on the piston rod between the piston head and the cylinder head and adjacent the cylinder head, said movable snubber member having one side adapted for engagement with said cylinder head upon outward extension of the piston rod with respect to the cylinder, a fixed snubber member mounted on the piston rod on the other side of the movable snubber member and adatped for engagement with the movable snubber member upon relative movement of the piston rod outwardly of the cylinder attendant to compressing any fluid between the movable and fixed members to retard movement of the fixed member toward the movable member for snubbing the impact of the stop arrangement on the cylinder head, and biasing means fixed bei tween the movable member and the piston head and urging said movable snubber member away from the fixed snubber member toward said cylinder head and urging said piston rod toward the closed end of said cylinder.

7. The invention according to claim 6, and sad movable snubber member having a recessed portion to receive said fixed member upon moving of the movable 7 member to the fixed member to compress any fluid between the members.

8. The invention according to claim 7, and said movable member being an annular member having an annular recess about the piston member and said fixed member being a ring receivable in said movable member attendant to compressing any fluid between the members.

9. The invention according to claim 8, and a stop on the one side of the movable member limiting movement of the movable member toward the cylinder head and a fixed retainer mounted on the piston member on the other side of the movable member, said biasing means engaging said retainer and said movable member in mg ing the latter to the stop.

10. The invention according to claim 6, and said biasing means including a spring means urging the movable member away from the fixed member.

UNITED STATES PATENTS 3,028,019 4/1962 Settles et a1. 2138 3,218,052 11/1965 Peterson 267.-1

DRAYTON E. HOFFMAN, Primary Examiner.

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