US2752048A - Cushion underframes - Google Patents

Description

June 26, 1956 s. H. FILLION 2,752,048

CUSHION UNDERFRAMES Filed Feb. 12. 1954 5 Sheets-Sheet l FIG. lb

IN V EN TOR.

72m; amwwz ATTORNEYS June 26, 1956 s. H. FlLLlON CUSHION UNDERFRAMES I5 Sheets-Sheet 3 Filed Feb. 12, 1954 INVENTOR.

A TORNEYS United States Patent 6 CUSHION UNDERFRAMES Stanley H. Fillion, Scarsdale, N. Y., assiguor to Waugh E uipment Company, New York, N. Y., a corporation Maine Application February 12, 1954, Serial No. 409,973

14 Claims. (Cl. 213-8) This invention relates to cushion underframes for use on railway cars, which include a movable center sill or draft and butting column extending substantially the length of the car and attached at its end to the couplers, the column being moved endwise against the resistance of cushioning means when forces in buff and draft are applied to the couplers. More particularly, the invention is concerned with a cushion underframe of novel construction, which is superior to prior similar underframes in that it has greatly increased capacity with little increase in weight. In addition, much of the energy applied to the new underframe is absorbed and dissipated as heat, although a sufi'icient proportion of the energy is stored to effect restoration of the column to its original position upon complete release of the applied forces. As a further feature, the new underfi'ame includes main cushioning means, which are of novel construction and can be easly installed and removed.

Most of the cushion underframes now in use on railway cars in this country are of the Duryea type, one example of which is disclosed in Duryea Patent 1,693,194, issued November 27, 1928. In such underframes, coil springs near the opposite ends of the column are ordinarily used to resist the movements of the column and cushion blows applied to the couplers. A link extend through each spring and is connected at one end to a spring anchor on the center filler casting of the adjacent bolster, while at the other end, the link is connected to a follower. The construction is such that the springs are compressed when the column is moved endwise in either direction and part of the energy applied to the column through the couplers is stored in the springs, while the remainder is dissipated as heat resulting from the friction occurring as the column is moved on its supports. While underframes of the construction described have been satisfactory in service, the demand has arisen for a cushion underfrarne of greater capacity than those heretofore available commercially.

The present invention is directed to a novel cushion underframe, which has a much larger capacity than prior underframes but without a corresponding increase in weight. in addition, the main cushioning means of the new underframe can be assembled out of the underframe and installed as a unit, with the result that the labor cost for constructing the new underframe is substantially reduced.

For a better understanding of the invention, reference may be made to the accompanying drawings, in which:

Fig. 1a is a horizontal longitudinal section view of the right-hand end of the new cushion underframe with parts omitted and others shown in plan taken on line 1a1a of Fig. 3;

Fig. 1b is a view similar to Fig. 1:: showing the lefthand end of the underframe;

Fig. 2 is a vertical longitudinal sectional view of the right-hand end of the underframe with parts broken away;

Fig. 3 is a transverse sectional view on the line 33 of Fig. la;

Fig. 4 is a vertical longitudinal sectional view of part of an underframe of modified construction;

Fig. 5 is a partial sectional View on the line 5-5 of Fig. 4;

Fig. 6a is a horizontal longitudinal sectional view of the left-hand end of another modified form of the new underframe;

Fig. 6b is a view similar to Fig. 6a showing the portion of the underframe to the right of that shown in Fig. 6a; and

Fig. 7 is a sectional view on the line 77 of Fig. 6b.

In the drawings, the railway car underframe illustrated is of the type which includes the usual end and side sills, cross bearers, and bolsters. Each bolster is formed of a pair of sections 16a, 1012, the inner ends of which are spaced apart and connected at the top by a cover plate 11 and at the bottom by a center filler casting 12. The casting is provided at each side with extensions 13 and 14, the first of which lies against and is secured to the inner end of the adjacent section of the bolster, while extension 14 is secured to the undersurface of the bolster section. A torque arm 15 of Z-section may be secured to the inner end of each bolster section and, when such torque arms are used, each arm projects forwardly and rearwardly from its bolster section and is connected at its opposite ends to the adjacent end sill at one side of the bolster and the adjacent cross bearer at the other. The center casting has a central body portion 16, which extends upwardly into the space between the bolster sections and is formed at its top with a semi-cylindrical seat extending lengthwise of the car.

A movable center sill or draft and bufiing column 17 extends from end to end of the car through the spaces between the two sections of each bolster and through openings through the cross bearers. The column is made of a pair of Z-bars arranged with their top flanges 17a extending toward each other and welded together and their bottom flanges 17b extending outwardly. The lower flanges 17b of the bars of the column are supported on the center filler castings 12 and the bottom portions of the several cross bearers. The column extends from end to end of the car and, at each end, it is formed with aligned openings in its vertical webs and carries cheek plates 18, which surround and have portions extending into the openings. inward from the cheek plates, the column is provided at each end with a pair of rear draft lugs 19 secured to the inner faces of the vertical webs of the column, and each draft lug is formed with a stop 20 at its outer end. inwardly from each bolster, the column is provided with an abutment member 22, which is secured to the inner faces of the vertical webs of the column and extends across the interior of the column. The bottom flanges of the column are connected by a plate 23 adjacent the inner ends of the openings at each end of the column and the flanges are also connected by plates 24, 25, which lie on opposite sides of each bolster and may engage the center filler casting to limit endwise movement of the column.

A cushioning unit 26 is mounted within each end of the column and is supported on plate 23. Cushioning units of various kinds may be employed at the locations mentioned and that shown comprises a plurality of rubber springs with adjacent springs separated by flat divider plates and followers 27, 28 at opposite ends of the spring group. The inner follower 28 of the cushioning unit at each end of the column normally lies against the outer stops 24) on the plates 19 at that end of the column.

A self-contained cushioning device, generally designated 29, is mounted on each center filler casting to project beyond opposite ends thereof and the device and casting may be handled as a unit. The device may include cushioning means of difierent types and is preferably constructed for he y du y- The device. shown emp oy ring springs and comprises a tube 30, which is seated in the cylindrically curved seat at the top of the casting and is secured rigidly in place, .as by welding. The innerend of the tube is partially closed by a ring 31 inserted into the end of the tube and having a circumferential flange 31a overlying the end of the tube and secured thereto, as by Welding. At its other end, the tube is slightly enlarged and internally threaded and a ring 32 is screwed into the end of the tube. A plunger 33 having a circumferential flange at its inner end is mounted within the inner end of the tubeand projects'out through ring 31 and a similar plunger 34 is mounted in the outer end of the tube and projects out through ring 32. The plungers are held in tight contact with the rings by a ring spring unit, generally designated 35, and, made up of an inner series and an outer series of rings, which have contacting wedging Surfaces and are of conventional construction. in the operation of the device, the rings are guided and held in Place by tube as.

In order to maintain the tube 30 with its axis parallel to the united top flanges 17a of the column, the tube may be provided with guides 36 attached to the top of the tube and projecting upward to terminate close to the flanges. The guides are illustrated as U-shaped straps Welded to the outer surface of the column. Similar guides 37 may be attached to the bottom of the tube to lie above the plates 24, .25 connected to the lower flanges of the column; Instead of employing guides attached to the tube, the function of such guides may be performed by providing the column with diaphragms having openings through which the column extends. When the tube is provided with straps at top and bottom, or the diaphragms are employed, the torque arms may be dispensed with, if desired.

When the column is installed, the outer cushioning unit 26 at each end of the column is placed under desired precompression and the shank 38 of a coupler C is inserted into the end of the column and connected thereto with its inner end tightly engaging follower 27 by a key 39, which extends through openings through the cheek plates and the vertical Webs of the column, and through an opening through the coupler shank. When the compressing force is released, each unit 26 is held under precompression against the outer stops of the adjacent stop plates .19 and the inner end of the coupler shank 38 held in place bykey 39.

The ring spring unit within each cushioning device 29 is also installed under desired precompression, which, is

applied before the device is mounted within the column and is greater than the precornpression, under which the units 26 are installed. The tube 30 of the device is rigidly secured to its center filler casting and, with the casting detached from the bolster and the tube in place, the plunger 33 is inserted to extend through ring 31 and the group of rings is placed in position and the outer plunger 34 inserted in the end of the tube. Ring 32 is then slipped overthe end of plunger 34 and force is applied to the plungers to compress the ring spring unit to the desired extent. The ring 32 is then screwed into the end of the tube, so that, when the load is released, the spring unit will be under the desired precompression. To facilitate the turning of ring 32, the exposed portion of plunger 34 may have a polygonal shape and the ring 32 may have an internal opening of corresponding shape. A wrench can then be applied to turn the plunger and screw the ring in or out of the tube.

In the normal condition of the column illustrated, the outer plunger 34 of each cushioning device 29 lies spaced a short distance, such as A", from the inner face of the inner follower 2 8 and the inner pluugerfifi of each device lies spaced a short distance from the adjacent .stop mcmber- 22. Thespacing between. the plungers and the follower 28 in one case and the stop member '22 in-the other maybe the same, but, preferably, the spacing-"between each inner plunger 33.,and the stop member 22 is slightly greater than the spacing between each outer plunger 34 and the follower 28.

The operation of the new cushion underframe is as follows. When a force in buff is applied, for example, to the coupler at the right-handcndof the column (Fig. la), the near cushioning unit 26, that is, the unit adjacent the point of application of the force, is immediately subjected. to compression between the shank of the coupler and the stops ZQ-on the column until the load overcomes the sill friction, whereupon the column beigns to move.

.When the column has travelled A, the inner follower 28 of the'near cushioning unit 26- engages the outer plunger 34 of the near'cushioning device 29 and, if the spacing between the stop members 22 and the inner plungers of the cushioning devices 29 is the same as the spacing between the outer plungers 34 and the inner followers 23 ofthe cushioning units 26, such movement of the column will cause the far 'stop member 22 to engage the inner plunger 33 of the farcushioniug device 29. Upon a further increase in the force applied to the coupler, the column continues to move and the near cushioning unit is further compressed until the load thereon is equal to the sum of the. precompression loads. upon the two ring spring devices 29, following which further movement of the column is resisted by the near cushioning unit 26 acting in series with thering spring devices 29 acting in parallel. After the column has been moved as far as is permitted by the stops 24, 25 engaging the center filler castings, further load applied to the coupler acts to compress the near cushioning unit 26. During the application of the force as described, about two-thirds of the'force applied to each ring springv unit 29 is converted into frictional heat by the action of the ring springs and such heat is dissipated, so that thelenergy is lost.

When the application of force to the coupler terminates, the energy stored in the ring spring units causes the column to move back to its initial position. if, in such movement, the column passes by its initial position, it will be returned thereto, because there is sufficient restoring force available for the purpose in the ring spring units by reason of thcirprecompression,

In the application of a force in pull to .a coupler, for example, the coupler at the right-hand end of the column ,(Fig. l ar), no :resistance other than staticfriction is ofliered to therinitial movement of they column and, when the force applied to the coupler exceeds the sill friction, the coupler and column start to move. When the column has moved M4", the abutment member 22 engages the inner plunger 33 of the near cushioning device 29 and the, outer plunger 34 of the far cushioning device 2.9 is engaged by thexfollower .23 atthe inner end of the, far cushioning unit '26. Since each cushioning unit 26 has a lower precompression than a cushioning device 29, further movement of the column is resisted by the near device 29 and, the far unit 26 only until the load on the unit 2 6. equals the, precompression of the far device 29. Thereafter, farther movement of the column is resisted by the far cushioning unit 26 and the far ring spring device 29acting in series with each other and by the near spring device-29 acting in parallel with the combination of the far unit and the far device. As the far unit and far deviceactingin series have a greater travel than the near device alone, the force required to move the column to the limit of its travelis less. in pull than in bulk, when, as, described, the near spring unit operates in series with both ring spring devices in parallel. Accordingly, the new cushion underframe has a softer action and less capacity in pull than in buff. g a

The modified-form of the new underframe shown in Figs. 6a and 6b is generally similar to that shown in Figs; 1a and lb and includes a cushioning unit 25' mounted'within each end of the movable draft and butting column 17' and engaged by the shank 38" of the coupler C. Inwardly from each cushioning unit 26". aself g Contained cushioning device 29' is mounted rigidly on the top of a center filler casting 12 at a bolster. Each device 29 is of the same construction as the devices 29 and includes an inner plunger 33 engageable with a stop 22' attached to the column and an outer plunger 34' engageable with the follower 28' at the inner end of the adjacent cushioning unit 26'.

The modified underframe construction of Figs. 6a and 6b also includes a self-contained cushioning device 2912 between the devices 29 mounted on the center filler casting 12. The device 29a is supported on one or more filler elements 49 secured to fixed longitudinal sills 41 of channel form, which extend between the car bolsters. If the device 29a is supported on a single filler element 40, the element will be placed midway between the ends of the device, but, if a plurality of filler elements are employed, they will be distributed along the device 29a. The cross-bearers of the car are attached to the fixed sills 41 and each cross-bearer includes a pair of flanged plates 42 extending from the fixed sills to side sills 43 and connected by a cover plate 44 lying above the column 17. The plates 42 of each cross-bearer are also connected at the bottom by an angle iron 45 and the tops of the plates 42 of the cross-bearers have longitudinal Z-bars 46 attached thereto.

The central cushioning device 29a illustrated is of the ring spring type and, in the construction shown, its tube 390 is mounted on a central body portion 40a of the filler element 40, which projects upwardly into the column 17. The device includes plungers 33a projecting out of the tube 39a and the column is provided with stops 47, 48 in position to engage respective plungers as the column is moved endwise. The stops are of U-form and include plates secured to the inner faces of the vertical webs of the column and cross-pieces strengthened by stiffening ribs. The central cushioning device 29a may be provided, if desired, with guides 36a similar to guides 36.

The cushioning devices, which include ring springs and are typified by the devices 29, may be replaced, if desired, by cushioning units, in which the cushioning elements are rubber. Such a device for replacing the cushioning device 29a is illustrated in Figs. 4 and as mounted on a filler element 49, which is connected to the fixed longitudinal sills 41' of the car structure and extends up into the movable column 17 pieces 50 stiifened by ribs 51 and connected by a top bar 52 to enclose a space, within which the cushioning device indicated at 53 is enclosed. The device is made up of a group of rubber springs separated by divider plates and a follower 54 is interposed between each end of the group and each end piece 50 of the filler element. The end pieces are narrower than the space between the vertical webs of the movable column and the rubber springs and followers project laterally beyond the end pieces. Pairs of stop plates 55, which are similar to stop plates 19, are mounted on the inner faces of the vertical webs of column 17' in contact with the outer faces of followers 54.

When mounted in place within the filler element 49, the rubber springs, divider plates, and followers make up a self-contained cushioning device 53, which can be handled with the filler element as a unit. Preferably, the group of rubber springs, etc., is installed under desired precompression. When the bufiing column is moved endwise in either direction, one pair of stop plates on the column engages the adjacent follower 54 and compresses the spring group against the remote end piece on the filler element. When the direction of movement of the column is then reversed, the spring group centrally expands and the follower is restored to its original position. Continued movement of the movable column in the reverse direction acts to cause compression of the spring group against the other end piece of the filler element.

While the modified form of cushioning device including rubber springs has been illustrated as replacing .the cen- The filler element has vertical end tral cushioning device in an underframe construction, in which three such devices are employed, it is to be understood that the rubber spring device may be used at the ends of the movable column, if desired Also, the cushioning devices employed to resist the movement of the column may include other forms of cushioning elements, such as coil springs, etc., if desired. Devices of the ring spring type exemplified by devices 29 are preferred, because of their great capacity.

I claim:

1. In a railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underframe, of a movable draft and bufling column extending lengthwise of the car and having at least one longitudinallyextending opening in its bottom, filler means attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device rigid throughout its length against transverse movement and mounted rigidly on and supported by the filler means within the column, a stop on the column inward from the cushioning device and acting on the device to compress it on outward movement of the column, and means on the column outward from the cushioning device and acting on the device to compress it upon inward movement of the column.

2. In a railway car, the combination with an underfrarne including transverse structural members in pairs, with one pair being near each end of the underframe, of a movable draft and buffing column extending lengthwise of the car and having at least one longitudinallyextending opening in its bottom, a filler element attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device mounted rigidly on and supported by the filler element within the column, a stop on the column inward from the cushioning device and acting on the device to compress it on outward movement of the column, a cushioning unit engageable with the outer end of the cushioning device, and means connected to the column outwardly from the unit and moving the unit against the outer end of the cushioning device to compress the unit and the device, when the column is moved inwardly.

3. In railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underfrarne, of a movable draft and bufiing column extending lengthwise of the car and having at least one longitudinally-extending opening in its bottom, a filler element attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device mounted rigidly on and supported by the filler element within the column, a stop on the column inward from the cushioning device and acting on the inner end of the device to compress the device on outward movement of the column, a cushioning unit having its inner end opposed to the outer end of the cushioning device, a coupler having its shank engaging the outer end of the cushioning unit, and means connecting the coupler shank to the column for movement inwardly therewith, the coupler in its inward movement acting to compress the unit and the device.

4. In a railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underframe, of a movable draft and butting column extending lengthwise of the car and having at least one longitudinallyextending opening in its bottom, a filler element attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device mounted rigidly on and supported by the filler element within the column,

a stop on the column inward from the cushioning device and acting on the inner end oi the device to compress the device on outward movement of the column, a cushioning unit having its inner end opposed to the outer end of the cushioning device, a coupler having its shank engaging the outer end of the cushioning unit, a key connecting the coupler shank to the column for movement inwardly therewith, the coupler in its inward movement acting to compress the unit and the device, and stops on the column engaging the inner end of the cushioning unit.

5. In a railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underframe,

of a movable draft and butting column extending lengththe bottom opening, a cushioning device rigid throughout its length against transverse movement and mounted rigidly on and supported by the filler means within the column and extending lengthwise of the column beyond the ends of the element, a stop on the column spaced inward from the inner end of the cushioning device and acting on outward movement of the column to compress the device, and means movable with the column and operable after a short travel inwardly with the column to engage the outer end of the cushioning device and compress the device.

6. In a railway car, the combination with an underframe including a pair of bolster sections adjacent each end of the underframe, each pair of bolster sections having a center filler element, of a movable draft and bufiing column extending lengthwise of the car and having at least one longitudinally-extending opening in its bottom, the tiller elements extending into the column through the bottom opening, a cushioning device rigid throughout its length against transverse movement and mounted rigidly on and supported by each filler element within the column, a stop on the column inward from each cushioning device, each acting independently on the inner end of the adjacent cushioning device to compress that device on outward movement of the column relative to the device, and means on the column outward from each cushioning device and acting on the outer end of the device to compress the device upon inward movement of the column relative to that device.

7. In a railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underframc, of a movable draft and buifing column extending length.- wise of the car and having at least one longitudinallyextending opening in its bottom, a filler element attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device mounted rigidly on the filler element within the column, means mounted on the column and operable after a short travel of the column inwardly to engage the outer end of the cushioning device and compress the device, and a stop on the column spaced from the inner end of the cushioning device a distance greater than said travel and acting on said end of the device on outward movement of the column to compress the device.

8. In a railway car, the combination with an underframe including transverse structural members in pairs, with one pair being near each end of the underframe, of a movable draft and btlffing column extending lengthwise of the car and having at least one longitudinallyextending opening in its bottom, a filler element attached to the structural members of each pair on opposite sides of the column and projecting into the column through the bottom opening, a cushioning device mounted rigidly on the element and including a tubular casing attached to the element, a plunger mounted movably in each of the opposite ends of the casing and projecting out of the casing, and a ring spring group within the casing urging the plungers apart, a stop on the column inward from the cushioning device and acting on the inner plunger to compress the device on outward movement of the column, and means on the column outward from the cushioning device and acting on the outer plunger to compress the device upon inward movements of the column.

9. In a railway car, the combination with an underframe including bolsters and fixed longitudinal sills connecting the bolsters, of a movable draft and bufiing column extending lengthwise of the car between the fixed sills and having at least one longitudinally-extending opening in the bottom, a filler element attached to each bolster and lying beneath the column, the element projecting into the column through the opening, a central filler clement attached to the fixed sills between the bolsters and extending beneath the column, said filler element projecting into the column through the opening, a cushioning device mounted rigidly on each filler element within the column, a stop on the column inward from each cushioning device at a bolster and acting on the device to compress it on outward movement of the column, means on the column outward from each cushioning device at a bolster and acting on the device to compress it upon inward movement of the column, and stops on the column at opposite ends of the central device alternately operable to compress the device upon movements of the column in opposite directions.

10. An assembly for use in a railway car having an underfrarne with bolsters, which comprises a center filier element forming part of a bolster, and a cushioning device mounted on the element and including a tubular casing attached to the element, plungers mounted movably in opposite ends of the casing and projecting out of the casing, and spring'means within the casing urging the plungers apart, said center filler element having extensions at opposite sides of the axis of the tubular casing for securing it to a car bolster.

ll. In a railway car, the combination with an underfrarne including spaced fixed longitudinal members, of a movable draft and bufling column extending lengthwise of the car between the members and having at least one longitudinally-extending opening in the bottom, a filler element attached to said fixed members and projecting into the column through the opening, a cushioning device rigid throughout its length against transverse movement and mounted rigidly on the filler element within the column, and means on the column at opposite ends of the device operating to compress the device upon movement of the column in either direction.

12. In a railway car, the combination with an undeu frame including structural members, of a movable draft and bufiing column extending lengthwise of the car and having at least one longitudinally-extending opening in the bottom, a filler element attached to structural members on opposite sides of the column and extending beneath the column, the element projecting into the column through the opening and having spaced end members, a cushioning device mounted on the element between the end members and including a group of rubber springs and followers at opposite ends of the group in contact with the end members, and stops on the column engageable with the followers and operable through the followers alternately to compress the rubber springs upon movements. of the column in opposite directions.

13. In a railway car, the combination of a movable draft and bufling column extending lengthwise of the car and having at least one longitudinally-extending opening in the bottom, a pair of cushioning devices mounted within the column and spaced longitudinally thereof at opposite sides of the transverse center of the car, a stop on the column inwardly from and adjacent each cushioning device, each stop being located at a position to engage and to compress its adjacent cushioning device on outward movement of the adjacent end of the column, a cushioning unit within the column between each cushioning device and the adjacent end of the column, each cushioning unit being engageable with the adjacent cushioning device on inward movement of the adjacent end of the column, and means connected to the column outwardly from each cushioning unit for moving the adjacent unit against the outer end of the adjacent cushioning device to compress said adjacent device when the adjacent end of the column is moved inwardly, the construction and arrangement of the cushioning devices and cushioning units being such that when either end of the column is subjected to a force in bufi the cushioning unit adjacent that end acts in series with the combination of the two cushioning devices and the two cushioning devices act in parallel; and when either end of the column is subjected to a force in pull, the cushioning device adjacent that end acts in parallel with the combination of the cushioning device and the cushioning unit adjacent the opposite end and the cushioning device and cushioning unit at the opposite end act in series.

14. In a railway car, the combination with an underframe including a bolster located adjacent each end of the car, each having a center filler element, of a movable draft and bufling column extending lengthwise of the car and having at least one longitudinally-extending opening in the bottom, the filler elements extending into the column through the opening, a cushioning device mounted on each filler element within the column, a stop on the column inwardly from and adjacent each cushioning device, each stop being located at a position to engage and to compress its adjacent cushioning device on outward movement of the adjacent end of the column, a cushioning unit within the column between each cushioning device and the adjacent end of the column, each cushioning unit being engageable with the adjacent cushioning device on inward movement of the adjacent end of the column, and means connected to the column outwardly from each cushioning unit for moving the adjacent unit against the outer end of the adjacent cushioning device to compress said adjacent device when the adjacent end of the column is moved inwardly, the cushioning device and the cushioning unit at each end being spaced to provide a clearance, the construction and arrangement of the cushioning devices and cushioning units being such that when either end of the column is subjected to a force in buff the cushioning unit adjacent that end acts in series with the combination of the two cushioning devices and the two cushioning devices act in parallel; and when either end of the column is subjected to a force in pull, the cushioning device adjacent that end acts in parallel with the combination of the cushioning device and the cushioning unit adjacent the opposite end and the cushioning device and cushioning unit at the opposite end act in series.

References Cited in the file of this patent UNITED STATES PATENTS 1,858,730 Duryea May 17, 1932 1,979,359 Wikander Nov. 6, 1934 2,010,391 Duryea Aug. 6, 1935 2,022,253 Nortz Nov. 26, 1935 2,271,608 Simonson Feb. 3, 1942 2,345,652 Bierman et al. Apr. 4, 1944 2,652,158 Simonson Sept. 15, 19 53

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