US2887770A

US2887770A - Method of stabilizing and processing cushioning units

Info

Publication number: US2887770A
Application number: US513358A
Authority: US
Inventors: Spence Lorna Slater
Original assignee: National Malleable and Steel Castings Co
Current assignee: National Malleable and Steel Castings Co
Priority date: 1955-06-06
Filing date: 1955-06-06
Publication date: 1959-05-26
Anticipated expiration: 1976-05-26
Also published as: DE1036584B; GB797164A

Description

May 26, 1959 H. L. sPENcE METHOD OF'- STABILIZING AND PROCESSING CUSHION'ING UNITSl Filed June 6,' 1955 n @Wigs Kw Y United Seres Pafsf METHoD or STABILIZING AND'PROCESSINGk t cUsHroNlNG UNrrs Hubert L. Spence, deceased, lateof East Cleveland, Ohio,

, by Lorna Slater Spence, executrix, East Cleveland, Ohio,

assignor to National Malleable and Steel 'Castings Company, Cleveland, Ohio,` a corporation of hio Application .lune 6, 1955, Serial No. 513,358

9 Claims. (Cl. 29-407) will not substantially deviatel from that standard after a period of service operation;

In recent years, both natural and synthetic types of -rubber have been widely used as the resilient material in cushioning units for devices of the aforementioned character. Because of the restrictedy space available in the conventional railway car, the rubber is usually of' 'a "relatively high strength composition, of more than average hardness, to provide suilicient capacity at a given xed travel or compression of the cushioning mechanism andv to prevent damage to the rubber units under the high stresses to which railway cushioning Amechanisms are usually subjectedin service.

It has been found that high strength rubber `cushioning units, after an` initial period in service, generally show a decrease in free length and a corresponding decrease,V

in cushioning capacity for a given travelf of the mechanism. TheA reason for this is that the rubber takes a permanent set in the early, stages of its'use; which .results in an actual decrease inthe-thickness Vof the rubber.

In `many rubber cushioned draft fgears, the ymetal followers of the gear and thecushioning'units 'are so ar- 4 ranged that the units 1are under an initial compression i when the gear is in neutral position in the draft gear pocket of the car in order to eliminate all free slack between the gear, the pocket, and associated draft gearl yoke. Furthermore, in rubber cushioned draft gears that `have multiple cushioning units, one or more of the units are. sometimes assembled under greater or lesser initial compression than the other units'to provide what 1s` known as compensating action. This difference in initialicompression between the." units is usually rather critical insofar as obtaining theproper operating char- "vacteristics of the draft gear isconcerned.

Any decrease in the rubber thickness of the cushioni ing units of a draft gear in service due to the thinning out or setting of the rubber may cause slack to develop Aand mayjcompletely alter the gears operating characteristics.

In addition,` the As'sociationof American Railroads has .set up standard specifications fr'certain types of rubber cushioned draftA gears.

` `A.A.R. approvalof a particulardraft gear design, certainjminimum standards for capacity at a specified travel In` order to obtain conditional must be met during various tests which Iare performed on specimens of the gear. Subsequently, in order to obtain 'unconditional A.A.R. approval, a few of the gears `are :taken from service and tested. If the gears takenfrom service do not, within certain limits, `measure up to those nitiall" tested,` AA'.ARz."' Iapprovall Iriayfbe revoked.

n2,887,770 Patented May 26, 1959 ICC It will be understood therefore that it is highly `desirable to provide cushioning devices comprising cushioning units employing resilient material such as rubber which have been stabilized or set prior to their vbeing placed in service so .that the cushioning capacity of; the units will not change appreciably after a period` of serv.- ice operation.

Accordingly, the primary object of the invention is to provide a method of processing a resilient cushioning unit, such as a rubber cushioning unit, so that its cushioning capacity will not vary significantly from a predetermined value after being in service. f

Another object of the invention is to provide a method of the aforementioned character which includes a selective assembly 'and testing procedure -to ensure that the cushioning unit will conform to certain predetermined dimensional and operating standards.

A further object of the invention is to provide a method of the aforementioned character which includes an inspection procedure.

Another object of the invention is to provide a method of processing arubber cushioning unit so that the length of the unit, in its free or uncompressed state, will not substantially lchange after being placed in service.

A further object of the invention is to provide a method of processing resilient cushioning units, such as rubber cushioning units, so that the performance. and operating characteristics of the shock-absorbing mechanisrn, into which the units are assembled, can be maintained at certain predetermined standards.

A more specific object of the invention is to provide t a-method of. subjecting resilient cushioning units comprising rubber cushions to a predetermined compression in order to stabilize or set therubber of the unit before `,placing the latter in service.

`ber cushioning unit for a railway shock absorbing device, `so as to reduce the pressure required to assemble the unit into the draft gear and into the draft gear pocket of the car.

Another specific object of the invention is to provide a method of combined stabilization, assembling and inspection of a resilient cushioning unit, such as a rubber cushioning unit for a railway cushioning device,=com

. prising the steps of subjecting the unit to a predeterrnined compressive force and then checking and adjusting the unit for conformity with predetermined dimensional and operating tolerances while at the same time inspectling the unit for manufacturing defects and abnormalities. The foregoing and other objects will become'apparent from the following description taken in conjunction with the accompanying drawings, wherein:

Fig. `1 is a cross-sectional view of a resilient cushioning n unit in the form as received from the manufacturer,

i compressive stabilizing load.

disposed between a pair of followers.

Fig. 2 shows the same cushioning unit subjected to a Fig. 3 shows the cushioning unit in the condition immediately following release of the stabilizing load applied to Fig. 2 and displaying partial recovery.

Fig. 4 shows the stabilized cushioning unit fully recovered to its level of permanent set.

Fig. 5 is a pictorial view of a method of checking the stabilized cushioning unit for conformityvto apredeteris received from the manufacturer.

the stabilizing process.

mined standard of load required to compress the unit to a predetermined height.

Fig. 6 is a top plan View of a typical assembly of a stabilized cushioning unit in a conventional type of draft gear.

Referring to the drawings, there is shown a well known type of cushioning unit 10, such as is presently used rubber cushioned draft gears, disposed between a pair of

followers

12 and 14. The unit comprises a series of individual compression type rubber pads 16 which, when in usual operating position in the unit, are in longitudinally aligned relation to each other. The pads 16are preferably of composite construction comprising a steel plate insert 18 and rubber cushions 20 bonded to opposite sides thereof. Each group of pads terminates in end pads 22 which have rubber bonded to one face only, thus avoiding any metal-to-rubber contact at the working faces of the end pads. The surface of each rubber cushion, in its free or unstressed condition, is, in the form chosen for illustration, of a corrugated or hill and valley configuration. The pads shown herein have been described and claimed in United States Patent No. 2,686,667 of Donald Willison and Hubert L. Spence, granted August 17, 1954. It will be understood that lwhile the cushioning unit is shown as comprising a particular type of rubber pad, the invention is equally applicable to other types of pads in which rubber is subjected to compressive loads.

As shown in Fig. l, unit is at its free or uncompressed height and illustrates the condition in which it The resilient pads of the unit have ybeen inspected for conformity with certain specified standards of thickness and rubber hardness following manufacture.

In accordance with the invention the cushioning funit 10 is .placed in the cavity provided by a pair of spaced

followers

12 and 14 as seen in Fig. l, and subjected to a compressive stabilizing force. It has been found that to `obtain 'best results, the number of pads in the unit being stabilized or set should preferably be the same .number that comprise the finished unit for the cushioning 'device It has also |been discovered that the pads should be out of the rubber curing molds at least 24 hours before -the stabilizing process is commenced.

The stabilizing force may be applied by any press or desired, the size of the pads, and the physical characteristics'of the resilient material of the unit undergoing A specic manner of determining the necessary force will Ibe hereinafter set forth.

Upon application of the stabilizing load, the cushioning unit is compressed to the position shown in Fig. 2. Thereafter, when the stabilizing load is withdrawn, the cushioning unit 10 expands and recovers to the position shown in Fig. 3. If the unit is then set aside or allowed to rest for a period of time, it will further recover from what is known as a condition of temporaryset, as shown in Fig. 3, to a condition of permanent set, as shown in Fig. 4. The period of time necessary forvsubstantially total recovery of the type of unit shown, from the temporary set condition, has been found to be approximately forty-eight to seventytwo hours. Any recovery of the rubber, after the expiration of the rest period, appears -to be of minor significance. It Will be seen, therefore, that the temporary set of the unit is defined by the difference in height of the cushioning unit substantially immediately after the release of the stabilizing load, as shown in v Fig. 3, and the height of the unit after it has rested and arrived at a condition of equilibrium or permanent set.as shown in Fig. 4. This difference in height or temporary set is designated in the drawings by the letter H. It will be seen from Fig. 4 that the height .4 of the stabilized cushioning unit is substantially less than the height of the unit before undergoing the stabilizing process. A datum line X-X in Figs. l-4 illustrates the height of the unstabilized cushioning unit as compared with the height of the unit during the stabilizing process and after 'the unit has reached a condition of equilibrium. The difference in height between the stabilized cushioning unit, as shown in Fig. 4, and the unstabilized cushioning unit as shown in Fig. 1 is the amount of permanent set which the unit has taken during the stabilizing process. This difference in height or permanent set is designated by the letter L.

The stabilizing load, which compresses the cushioning unit to the position shown in Fig. 2, may be applied in various ways. The preferred procedure for stabilizing a unit is to apply several, preferably three to iive, successive loads in fairly rapid order. Each of these loads for the cushioning unit illustrated is preferably at least as great as one-half of the design load for the pads of the unit at the latters maximum rated travel. For instance, for the unit shown, which comprises pads designed to carry a 600,000-pound load at a specified travel, the preferred stabilizing load is approximately 325,000 to 375,000 pounds, or justa little over half of the design load. vThe iinal stabilizing load applied to the unit is held while the edges of the individual pads are inspected for bond breakage and other defects, after which the load is withdrawn. If any of the pads show signs of bond failure or other defects, they are removed from the unit and replaced by cushioning pads that have been previously stabilized as above described. It will be seen therefore that effective inspection of the unit is accomplished while the pads are under compression and thus most likely -to show any manufacturing defects.

The stabilized unit is then set aside and it will immediately recover to its height of temporary set, as shown in Fig. 3. After the expiration of the aforementioned rest period, the unit will recover to its condition of equilibrium or permanent set, as shown in Fig. 4.

Another method of stabilizing the cushioning unit is to `apply a single relatively high compressive load and then release ythe same. For the unit shown this single load is preferably about 85 percent of the design load for the pads of the unit at the latters maximum rated travel. For instance, for pads which are designed to carry a 600,000-pound load at a specified travel, the preferred stabilizing load is approximately 500,000 pounds. The inspection of the pads for bond breakage and other defects may be accomplished before release of the single stabilizing load.

The length of time that the cushioning unit is held under compression by the stabilizing load or loads will -vary according to the degree of stabilization desired, the

magnitude of the stabilizing load or loads, and the type of resilient material being stabilized. Generally it has been found that the longer the cushioning unit is subjected to the stabilizing force, the greater will be the permanent set of the unit. For the preferred method whereby three -to live successive loads are applied to the unit the total time to complete the stabilizing ycycle is approximately one minute. Where a single relatively high compressive load is employed to stabilize the unit, the time is approximately one-half minute. Regardless of `the methodchosen for stabilizing the cushioning unit, the purpose is to set or stabilize the resilient material of the unit so that it will not subsequently set any substantial .amount after the cushioning service, in which the unit is used, is placed in service. Individual pads, if desired, can also be stabilized separately in accordance with the above `described procedure. The stabilized pads can then be assembled into stacks or groups Y ,for further processing and testing.

preferred procedure is to compress the unit to a predetermined height. This step is pictorially illustrated in Fig. which shows a stabilized cushioning unit 10 for use in a draft gear compressed by suitable press means 24 to a predetermined standard length of height, gauged by measuring means 26. The load required is shown as being indicated by gauge member 28 and must fall within a specilied load range. This step in the procedure determines whether the unit, together-with the other draft gear parts when inserted in the draft gear pocket of the car, will be placed under the aforementioned desired initial compression. If the load required to compress the unit to the predetermined length does not fall within the specified range the unit undergoing test may be adjusted by removing one or more of the pads and substituting therefor one or more stabilized pads, previously classified as to thickness and rubber hardness, in order to bring the unit within the predetermined tolerance set for the test load.

It will be understood, therefore, that this testing and selective assembly procedure will ensure that the stabilized unit will conform to predetermined standards for precompression, cushioning capacity and size when the unit is initially assembled with the other draft gear parts in neutral position in the railway car. In this connection it will be seen that while a cushioning unit may comprise one or more pads, having a thickness or rubber hardness diiferent from the specied tolerances of thickness and rubber hardness for a standard pad, these substandard pads in combination with the other pads of the unit average out to produce a standard cushioning unit. In this way individual pads that may not exactly meet the manufacturing specifications as to thickness and rubber hardness, may still be utilized to produce a standard unit.

In the form of unit shown in Figs. l-4 of the drawings, a testing length of height of S15/16 inches is preferably used, which requires a compressive load of between 10,500 to 12,500 pounds, in order to provide a unit having an acceptable initial compression and other characteristics when the draft gear is assembled in the railway car. It will be noted that the test load at the predetermined height is considerably less than the stabilizing load or loads.

An alternative method of load checking the stabilized unit is to apply a given load to the unit and measure the height of the unit to determine whether it falls within a predetermined range. With either method the physical uniformity of the units will be maintained within identical limits.

It will be understood that the load checking may be done immediately after the aforedescribed stabilizing procedure before the unit has recovered from its temporary se This, of course, would entail a different set of tolerances for height and load than those utilized when the unit is allowed iirst to recover to its level of permanent set. Thus the rest period can be eliminated and the load checking of the units performed immediately upon completion of the stabilizing compressions. This method might preferably be used in connection with a machine in which the stabilization and the load check cycle are automatically timed. This combined procedure will, of course, save storage space and handling time.

After stabilization and adjustment as aforedescribed, the unit is ready for storage or for utilization in a draft gear. Fig. 6 shows a typical asembly of a conventional or non-compensating type draft gear utilizing a stabilized cushioning unit. The gear, as shown, comprises a stabi-lized unit 30 disposed between a pair of followers 32 and 33. The gear is under an initial compression between the front and rear abutments of the draft gear yoke 34 and front and rear stop lugs 36 and 38 of the draft gear pocket 40 of a railway car. Such a gear, comprising as aforesaid a stabilized cushioning unit, after a period of service operation will exhibit no substantial.

change in its cushioning capacity, initial compression or operating characteristics. y

Since a cushioning unit which has been stabilized in accordance' with the invention has a shorter free length than a unit which has not been stabilized, because of the permanent set taken by resilient material of the unit during the stabilizing compressions, a stabilized unit will, of course, require less space, in a longitudinal direction, in a standard draft gear pocket than does an 4unstabilized unit. Accordingly, for a standard draft" gear pocket, the usual draft gear followers must be proportioned to compensate for the reduced length of the stabilized unit.

It will be understood, therefore, thatan unstabilize cushioning unit, because of its longer length, will not generally iit between or into followers designed for use with a stabilized cushioning unit. Moreover, even if the unstabilized unit could be compressed suiciently to t between or into the followers, the precompression of the unit, when in neutral position in the gear, would be greater than desired. V, v

Conversely, it will be apparent that a cushioning unit which has been stabilized or set as aforedescribed can be precompressed to the necessary dimensional requirements for insertion 'between or into draft gearfollowers designed for use with an unstabilized unit, with lesser force than that required to precompress an unstabilized unit. This feature is especially advantageous if theV draft gear is being repaired or replaced under conditions where proper facilities for compressing the gear and applying it to the pocket of the car are not readily available. Such a situation might be the Icase if the cushioning `unit or units of a draft gear are repaired or replaced along the railroad right-of-way, Idistant from a repair yard.

From the foregoing description and accompanying drawings it will be readily understood that the invention provides a novel method of stabilizing a rubber cushioning unit so that its cushioning capacity and operating characteristics will not substantially change'after a period of service operation. It will'also be understood that the invention provides an inspection, testing and selective assembly procedure in combination with the stabilizing process which ensures that the physical and mechanical characteristics of the stabilized unit will conform with predetermined standards piior to its being placed in service.

The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention of excluding such equivalents of the invention described or of the portions thereof as fall within the purview of the claims.

What is claimed is:

l. In a method of making a cushioning unit for a railway-'car cushioning mechanism from a group of resilient pads of rubber or rubber-like material, said mechanism having means providing a cavity of predetermined length for receiving the unit, the steps of subjecting said pads to a predetermined compressive force in the approximate range of from 50 to 85 percent of the designed compressive capacity of the pads whereby the thickness of the resilient material is reduced by a permanent set induced therein, releasing said force, assembling a group of the penrnanently set pads into a unit having length greater than said cavity, applying a compressive loading substantially less than said force to the unit to reduce its length to less than that of said cavity, and conforming said loading and said reduced length of the unit to standard values lying within predetermined tolerance ranges by substitution of pads of the unit from pads of said group varying in hardness and thickness.

2. The method of claim l in which said force is applied to the pads in one to five successive loadings, each loading within said named range.

3. The method of claim 1 wherein said pads are designed for operative loads of approximately 600,000 pounds' and said step off permanently setting the pads comprises three to ve successive applications of force of approximately 325,000- to 375,000 pounds.

4.` The method of, claimI 1I wherein the step of setting the pads comprises a single application of force of approximately 85 percent' of said design load 5f. The method of claim l wherein the design load of the pads; is. approximately 600,000 pounds and said padsettin'g step. comprises loading: said pads to approximately 500;000 pounds.

6. In a-method of makinga cushioning unit for a railway-car cushioning: mechanismy from a Igroup of resilient pads of rubber or rubber-like material, said mechanism having meansvproviding` a cavity of predetermined length for receiving. the unit the steps of subjecting said pads to a' predeterminedy compressive force in the approxi- `materange of. from 50'tor85 percent of the designed compressive capacity of the pads whereby the thickness of the resilient material is reduced by :a permanent set inducedY therein, releasing said force, assembling a group of the permanently-set pads into a unit having a length greater than that of said cavity, applying a compressive loading substantially less than said force to said unit to reduce the length thereof `to a predetermined shorter length adapting the unitl to enter said cavity, measuring said loading and in the event that said loading is above or below a -desired tolerance range, selecting pads from said permanently set group varying in hardness or thickness and substituting them in said unit to obtain a loading value within said tolerance range providing said shorter length.

7. In a method of processing a cushioning unit for a railway-car cushioning device; the unit comprising a series of resilient pads of rubber or rubber-like material of approximately the same hardness and thickness, the steps of subjecting the unit to a predetermined compressive force in the approximate range of from 50 to 85 percent of' the des'mned operative compressive strength of the unit to produce a permanent set in said material which reduces the free length of the unit, releasing said force andl thereafter applyingl a predetermined loading substantially4 less than said force to the unit to compress it, measuring the length of the-unit for conformity a standardl lengthfor said unit, and in the event the unit length isabove or below al desired tolerance range including said standardV length, adjusting the length of the unit subjected to saidy loading by substituting one or more permanently set pads of different hardness or thickness for pads of the unit to bring itsy length within said tolerance range.

8. In a method of making a cushioning unit for a railway-car cushioning mechanism from a group of resilient pads comprising a rubber or rubber-like material which may include pads varying slightly in thickness and hardness, the steps of grouping a stack of a standard number of said pads into a unit, subjecting the stack to a compressive force in the approximate range of from to 85 percent of the design strength of the unit in compression to induce in the unit a permanent set and a temporary set which reduces the length of unit, releasing the force and allowing the unit to recover from its temporary set, applying a compressive loading substantially less than said force to the unit to reduce its length, and conforming said loading andthe length of unit tol standardV values lying within predetermined tolerance ranges by pads within the unit from said group having different capacities for compression.

9. The method of claim 8 wherein the unit is set aside after said releasing step and prior to said loading step for a period of at least 48 hours to recover from its condition of temporary set` References Cited in the le of this patent UNITED STATES PATENTS