US3756162A

US3756162A - Car body roll dampening spring bolster

Info

Publication number: US3756162A
Application number: US00121258A
Authority: US
Inventors: C Wulff
Original assignee: Holland Co
Current assignee: Holland Co
Priority date: 1971-03-05
Filing date: 1971-03-05
Publication date: 1973-09-04
Anticipated expiration: 1990-09-04

Abstract

An arrangement for controlling roll in high capacity railroad freight cars when loaded, while providing a soft car protecting ride when the car is empty, in which a dampening type volute spring is incorporated in the truck spring groups that support the respective truck bolsters, with the volute spring having a trap free height that is less than the height range that the bolster rids in when the car is empty, but is greater than the height range that the bolster rides in (including possible roll) when loaded. This permits the absorption potential of the roll controlling volute springs to be independent of the bolster empty riding height, which makes available for roll control purposes full utilization of the usable absorption potential that can be built into a volute spring of this type.

Description

United States Patent Wulfi Sept. 4, 1973 CAR BODY ROLL DAMPENING SPRING Primary ExaminerGerald M. Forlenza BOLSTER Assistant Examiner-Howard Beltran Inventor: Cal w. Elmhurst, In. Att0rney-Mann, Brown, Mcwllliams & Bradway [73] Assignee: Holland Company, Lombard, Ill. [22] Filed: Mar. 5, 1971 [57] ABSTRACT An arran ement for controllin roll in hi h ca acit 21 A 1.N.:121258 g g g p y 1 PP o railroad freight cars when loaded, while providing a soft car protecting ride when the car is empty, in which [52] U.S. Cl. 105/197 D, 267/4 a dampening type volute spring is incorporated in the B61f 1361f truck spring groups that support the respective truck [58] Field of Search 105/197 R, 197 D, bolsters, with the volute spring having a trap free height 105/197 DB, 197 DP; 188/33; 267/3, 4 that is less than the height range that the bolster rids in when the car is empty, but is greater than the height [56] References Cited range that the bolster rides in (including possible roll) U IT STATES PATENTS when loaded This permits the absorption potential of 930,630 M933 symington t 105,197 R X the roll controlling volute springs to be independent of 2,065,992 12/1936 Barrett 105 197 DP the bolster empty rldmg height, whlch makes avallable 2,105,651 1/1938 1161mm 267/4 for control P p full utilization of the usable 2,571,519 10/1951 Barber 105/197 DB absorption potential that can be built into a volute 2,587,315 2/1952 Haynes 105/197 DB spring of this type. 2,649,298 8/1953 Wulff et a1 267/62 5 Claims, 16 Drawing Figures U N ITS 0F ABSORPTION PATENIEDB 4 i973 3.755.162

MEI"! 0F 7 {F X Y SPRING GROUP HEIGHT IN INCHES W 1 INVENTOR CAL W WULFF ATT 'YS.

CAR BODY ROLL DAMPENING SPRING BOLSTER This invention relates to a method and apparatus for controlling body roll in high capacity railroad cars, and more particularly, to a method and apparatus for controlling roll in high capacity cars when loaded that provides for a soft ride for the car when empty.

Certain kinds of freight cars, as, for instance, hopper cars, gondola cars, tank cars and the like, usually run under either full load or empty load conditions. Single purpose trains are an outgrowth of this economic fact, and typical of such trains are coal, potash and ore trains as well as trains carrying bulk liquids or gases in tank cars.

There have been attempts over the years to increase the capacity of freight cars of this type so that today, 100 ton cars are commonplace. As such cars have gone up in capacity and carry larger loads, the center of gravity of the cars as loaded has moved upwardly, and, of course, the greater mass and higher center of gravity combine to accentuate the tendency of the car to rock or sway about its longitudinal axis as it moves along the track, when such factors as the truck and rail joint spacing, speed of movement, and basic spring rates of the truck spring groups are taken into consideration and with the end result being wheel lift and in many cases actual derailment.

Numerous ways have been devised for attempting to control the roll problem of these high capacity cars. For instance, hydraulic damping devices have been included in the spring groups interposed between the truck bolster and the truck frame, but this type of solution has fallen short of its mark. One successful way to control the roll problem that has come into wide use has been to substitute for one or more of the coil springs in the bolster spring group one or more volute springs of the type generally shown and described in Wulff et al. U.S. Pat. No. 2,649,298, granted Aug. 18, 1953. This volute spring is of the dampening type and has a special arrangement characterized by having a helix angle that increases upwardly from the outer active coil to the inner active coil, and has an as-coiled" pitch which increases from the outer active coil to the inner active coil (sometimes referred to as reverse pitch), with the result that as the spring is compressed, controlled friction forces are developed between the adjacent coils, whereby the spring serves as an energy absorber of the dissipative type.

In considering springs of this type there are several terms of art that need to be kept in mind, and these are as follows:

A critical dimension of a spring of this type is its socalled trap free height," which is the equilibrium position that the spring assumes on release, that is, the equilibrium between the spring design load or strength on release and friction resistance forces acting due to the radially compressed coils of the volute.

Stated in other words, the trap free height of a volute spring made with reverse pitch, in accordance with the said Wulff et al. U.S. Pat. No. 2,649,298, is the point of equilibrium between the friction forces due to the radial compression of the coils and the stresses in the volute spring which are tending to extend the length of the spring. Any time that the spring is compressed, the radial friction forces between adjacent coils is increased, and upon release the spring will return to a given height, called trap free height, when equilibrium is established between the radial friction forces and the forces tending to extend the spring.

It is a phenomenon of a spring of this type that when such a spring is at its trap free height it can be extended in length by inflicting it with hammer blows, which have the effect of vibrating the coils and so disturbing the face-to-face frictional contact as to permit the spring to further extend. A spring that is properly designed, when given one or more hammer blows of unit force, will on each blow elongate to a new and longer dimension up to an asymptotic relation; this is called the rap-out length of the volute and the rapout length for production purposes may be different than it is for fatigue testing purposes. The unit. force for each hammer blow required to effect extension of the volute spring under rap-out conditions depends upon the inherent design of the particular volute, including the extent of the reverse pitch, distribution of metal within the coils, chemical composition, etc.

With certain volute springs of reverse pitch, made in accordance with Wulff et al. U.S. Pat. No. 2,649,298, the radial friction forces that are present may be such that, when the spring is given a sharp blow of larger unit force, it may extend beyond its rap-out height to what is called jump-out height, which merely means that the vibration on the spring due to the blow so releases the frictional forces as to cause the spring to extend suddenly to or perhaps even beyond (due to momentum established by sudden release) its design-free height or length.

The design-free height of a volute spring is the height that the spring would have if there were no friction between coils. The asymptote of the rap-out height for all practically purposes may be considered the design-free height, and even the jump-out height is approximately the same as the design-free height, except that with jump-out the momentum of the coil extension with the subsequent action of friction between coils may hold the coil in an extended position somewhat above design-free height.

My studies of the problem of how to minimize body roll or sway in high capacity cars have revealed that little, if any, attention has been paid to the fact that such cars ordinarily run either fully loaded or empty. In recent years the problems experienced with fully loaded high capacity cars have been such that efforts to control the roll problem have been concentrated on the action in transit of such cars under loaded conditions. As a result, too much attention has been given to full load condition and almost no attention to empty load conditions. Experience has shown that significant car damage has been occurring while the cars are traveling empty such as wear, metal fatigue and derailment due to excessive rocking. This has suggested to me that any suspension systemwhich might effectively deal with the car fully loaded may not be appropriate to the running of such car under empty load conditions.

It is therefore a principal object of this invention to provide a suspension system for railroad cars which protects the car for both fully loaded operation and empty load running conditions.

Another important object of the invention is to provide a spring group for supporting the truck bolster on the truck frame which is characterized by the fact that at the loaded car running height of the bolster, volute roll control absorbers operate to effectively control body roll, and at the bolster empty car running height,

only such snubbing effect as is required to control pure vertical movement is operative.

Heretofore, springs of the type disclosed in said Wulff et al. patent have been used in spring groups for roll control purposes in which the spring trap free height has been equal to or greater than the empty car bolster riding height. One of the difficulties which has been experienced in making this type of roll control device is that each heat of steel" (i.e., the particular batch of metal from which the volutes are made) has to be tested to be sure that such volutes will have a spe cific minimum energy absorption under specified fatigue testing conditions. It has been found that in practice a very fine balance has existed between such trap free height and absorption requirements, with the result that frequently numerous costly trials have had to be run, with variations being made in the spring specifications relative to coiling roll pressure, heat treatment, and the like, for a particular heat, before that particular heat can be approved for manufacturing purposes.

It is therefore another principal object of this invention to provide a roll control volute spring in which the absorption potential is freed from the empty car riding height limitation so that the volute spring can be arranged to achieve full utilization of the usable absorption potential of which its particular heat of steel is capable.

Other objects of the invention include: to provide in conjunction with a ride stablized bolster of a freight car, a spring group for supporting the bolster which is characterized by having a relatively low spring rate for providing a smooth ride when the car is running empty and with substantially no roll control needed or provided under those conditions, but when the car is running fully loaded, the spring group provides full control over body roll; to provide means for supporting one or more roll control volute springs in a group in such a manner that the volute spring or springs are inactive under empty car running conditions; to provide roll control volute springs arranged for full utilization of their usable energy absorption or dampening potential of which each heat of steel from which such springs are made is capable; and to provide aroll control arrangement that is economical of manufacture, that is readily installed, that permits marked savings in time and money in testing for heat approval purposes, and is readily applicable to standard truck designs, and is long lived in operation.

A further and subsidiary object of the invention is to incorporate one or more volute springs of reverse pitch type into a spring group of a car truck in such a manner that not only is the trap free height of the volute spring below the lower amplitude of bolster height for empty car operation, but also to operate the volute spring on that portion of its load deflection curve which has substantially constant spring rate characteristics. In the past, where the trap free height of the volute spring in the group has been at or above bolster empty load height, or static empty load condition, the volute spring, when operating under fully loaded car conditions, and when resisting roll, has under maximum roll conditions operated in part on that portion of its load deflection curve which has increasing rate, and has therefore had a tendency to transmit roll forces into the car truck rather than absorb them. This is not in itself a serious objection and may be employed in practicing the basic aspects of this invention, but there are circumstances in which it is more desirable to utilize the roll control volute spring only in the area of its load deflection curve where it exhibits constant rate.

In accordance with this invention, there is provided for supporting the truck bolster on its side frames a spring group arrangement that includes a plurality of the usual bolster helical springs, and with the vertical motion of the bolster being dampened in any suitable manner, as by employing one of the conventional socalled built in control arrangements, and at least one dampening type roll control volute spring having a trap free height that is below the bolster empty car riding height (including its amplitude of movement at that height), and that is above the bolster loaded car running height sufficiently to accommodate roll amplitudes. In other words, the roll control volute spring is normally not functional during any phase of light car operation, but always functional during loaded car operation. In this connection, the spring group helical springs, to the exclusion of the roll control volute springs, provide the softer ride that is desirable for the car when empty, while when the car is loaded, the roll control springs, in addition to supplementing the load supporting function of the helical springs of the group, insure roll control at critical speeds which produce roll. As the trap free height criteria of the roll control volute springs is not equated to empty car bolster height, the volute springs may be designed to better attain desired utilization of the usable absorption potential of which the particular heat of steel involved is capable for improved roll control.

Other objects, uses and advantages will be obvious or become apparent as the disclosure proceeds and the description is read in conjunction with the accompanying drawings, in which like reference numerals indicate like parts throughout the several views.

In the drawings:

FIG. 1 is a diagrammatic end view of a high capacity railroad car showing the body and major components of the truck in largely block diagram form, and illustrating the basic nature of the instant invention;

FIG. 2 is an end elevational view of a spring group arranged in accordance with this invention interposed between one end of a ride stabilized bolster and truck side frame of a standard make, with the bolster shown at its empty load height;

FIG. 3 is a diagrammatic plan view of the spring group of FIG. 2, illustrating the positioning arrangement of the elements making up this spring group;

FIG. 4 is a bottom plan view of a bolster for another standard make of truck which has been modified in accordance with this invention;

FIG. 5 is a sectional view through the bolster end shown in FIG. 4, taken substantially along line 55 of FIG. 4;

FIG. 6 is a view similar to that of FIG. 2 illustrating the bolster of FIGS. 4 and 5 applied to its truck side frame with the spring group of FIG. 3 interposed therebetween;

FIG. 7 is an enlargement of the volute spring and associated parts shown in FIG. 2;

FIG. 8 is a plan view of the volute spring, with its dead coils being indicated by distinctive crosshatching;

FIGS. 9, l0 and 11 are graphs illustrating the manner in which this invention acts in operation;

FIG. 12 is a curve illustrating the relation between roll control volute trap free height, design free height and rap-out height in devices of the type to which the invention relates;

FIG. 13 is a graph similar to that of FIG. 9, but for a modified form of the invention;

FIG. 14 is a graph illustrating the manner in which the modified form of the invention operates;

FIG. 15 is a fragmental view of the volute base of the embodiment of FIGS. 13 and 14; and

FIG. 16 is a graph similar to that of FIG. 11 but illustrating that absorptive action of the volute of FIGS. 13

GENERAL DESCRIPTION Reference numeral 10 of FIG. 1 generally indicates a railroad car equipped with this invention. Car 10 includes the usual body 12, including underframe l4 applied in the usual manner adjacent each end thereof to bolster 16 of the individual car trucks 18 (though only one truck is shown), which bolster 16 at its

ends

18 and 20 rests on

spring groups

22 and 24 that are in turn sup ported by the truck side frames 26 and 28 which are journaled in the usual manner on truck axles 30 riding on wheels 32 which engage the usual track rails 34.

The body 12 illustrated is largely in block diagram form and is intended to represent the various types of high capacity car bodies that are commonly employed today in 100 ton cars and the like.

The single truck 18 that is illustrated is only diagrammatically shown to bring out the principal novel features of same for illustrative purposes, it being understood that the truck 18 is intended to represent any commercial railroad car ride stabilized truck equipped with a bolster 16 or its equivalent for supporting car body 12, either at the center plate structure 36, or at the side bearings 38, or both.

As is well known in the art, the function of the

spring groupings

22 and 24 is to resiliently support the body 12 so that it has a smooth ride. I-Ieretofore, it has been the practice to form the

spring groupings

22 and 24 by inserting a number of helical springs such as

springs

40 and 42, or springs 40 alone, between

spring seats

44 and 46 defined by the bolster and side frames, respectively, with the number and size of springs employed depending on the load to be carried. In more recent years, this has been accompanied by snubber devices of various types to control the vertical movement of the bolster. The volute spring of the said Wulff et al. patent is an example of one type of ride stabilization device, it being arranged to take the place of one or more of the springs 40 in the spring group and be interposed between and directly bear against the bolster and side frame spring seats for ride stabilization purposes. Another familiar form of snubbing device involves friction shoes carried by the bolster that are spring biased against hardened friction surfaces applied to the side frame columns.

In any event, the function of such snubbing devices is to provide ride stabilization for the bolster in the sense that pure vertical movement, as distinguished from rocking or rolling motion, will be controlled.

In this connection, it is pointed out that, in practice, the

spring groups

22 and 24 are designed to support the bolster l6 and the load it carries at a predetermined elevation relative to the track rails 34, which may be spoken of in terms of positioning the spring seats 44 of the bolster a specified distance above the spring seats 46 of the side frames. For instance, considering the matter in these terms, the bolster 16 when car body 12 is riding empty will be riding at a riding height or level 48 (see FIG. 1), while when loaded to rated capacity, bolster 16 will be riding at a lower riding height or level 50 (it being assumed that

levels

48 and 50 are horizontally aligned with the bolster spring seats 44). The height involved in such terms as trap free height and design free height that have already been defined means a distance measured from the same point of reference as bolster riding height.

More recently, high capacity railroad cars have come into wide use which have, by virtue of the higher center of gravity and heavier loads involved, made critical the problem of body roll insofar as high capacity equipment is concerned.

Car body roll is caused by a number of factors, including location of center of gravity, weight being carried, truck and rail joint spacing, speed of movement and basic spring rates of the resilient supports for the car body. The problem is particularly acute in connection with 100 ton hopper cars when loaded, though experience has shown that any fully loaded car of 100 tons and up moving at speeds of 15 17 mph. that passes over three low rail joints in a row will develop a severe tendency to roll with significant likelihood of derailment.

Efforts to overcome the roll problem have been centered on controlling in some suitable manner the motion of the bolster under fully loaded conditions. One roll preventing arrangement that has been highly successful in providing full control over roll in high capacity cars when loaded has involved the replacement of one or more standard helical springs of each spring group with a corresponding number of volute springs of the type disclosed in said Wulff et al. patent that are specifically designed for roll control purposes in addition to providing resilient support for the load and have a trap free height that is intended to be at least equal to or greater than the bolster empty load riding height.

However, as stated heretofore, the emphasis has been on ride control for loaded condition, with little or no attention being paid to empty car ride.

In accordance with this invention, the

spring groups

22 and 24 are arranged to provide a sufficiently cushioned ride for the body 12 while empty, while yet provide adequate roll control for the body when loaded. More specifically, the

spring groups

22 and 24 are arranged so that when the truck bolster 16 is riding at the empty car level 48, the roll control devices that are included are inoperative and car body 12 is supported solely by the helical springs 40 and 42 (suitably snubbed for vertical movement control), which provide a comparatively soft ride for the car body when empty. However, when the car body 12 is loaded, the roll control devices are rendered fully operative to control body roll through its normal anticipated amplitude and also contribute to the resilient load support provide by the spring group.

In terms of specifics, reference may be had to FIG. 9, which is a graph illustrating the results of a specific application of the principal involved, and plots roll control volute spring assembly height in inches against load in thousand pound units for a volute roll absorbing spring of the type shown in said Wulff et al. patent that is designed for ton hopper car use, in which compression and release curves 60 and 62 show the action of a conventionally designed volute spring of this type on compression and release, while compression and release curves 64 and 66 show the corresponding curves for a volute spring made in accordance with this invention. Curve 65 is the dynamic curve showing the design characteristics of the volute springs when considered purely as load supporting springs, as distinguished from energy absorbers.

As indicated in FIG. 9, it is assumed for purposes of disclosure that the bolster empty car riding height will be about 9 isths inches with a bolster vertical movement amplitude ranging from about 9 to about 9 7/8 inches while the bolster loaded car riding height will be about 7 7/8ths inches with a maximum roll amplitude of about 2 inches, varying from about 7 to 9 inches in riding height (though it should be understood that these dimensions in practice will depend on a number of factors including type of car involved, spring rate character of the spring groups employed, etc).

Heretofore, damping type volute roll absorbers of the type shown in said Wulff patent have been designed with the intention that they maintain contact with the bolster throughout its entire range of movement (for convenience these roll absorbers are termed, for purposes of this disclosure, constant bolster contact absorbers or roll control devices); it will be observed from FIG. 9 that the release curve 62 for the conventional constant contact volute roll absorber indicates a trap free height that is substantially equal to the empty car riding height of the bolster. In accordance with the instant invention, the trap free height of the volute roll absorber is substantially less than the empty car riding height (including amplitude of movement X at empty load conditions), but exceeds the loaded car roll amplitude, as indicated at Y in FIG. 9, wherein the release curve 66 indicates that the volute roll absorber of the present invention will have a trap free height of about 9 /4 inches. The dynamic curve (which neglects energy absorption) for the improved roll absorber will follow curve 65.

It is also an important feature of the invention that the roll control device employed be arranged to stay in place when the car is empty in a manner that will avoid having to make significant modifications in either the bolster or the side frame.

A specific application of the invention is shown in FIGS. 2, 3 and 7 wherein the spring group 70 is shown interposed between the spring seat 44A of bolster 16A and spring seat 46A of side frame 71 that is part of a Barber S-2-C stabilized truck 75 of well known design having a snubbed bolster 16A.

Spring group 70, as indicated in FIG. 3, is of the nine position type in which the outer left and inner right spring positions are occupied by volute roll absorber devices or units 72 arranged in accordance with the present invention, the other positions being occupied by the

respective springs

40 and 42, though it is to be understood that functionally, the devices 72 could be located at any position in the group (assuming the bolster and side frames permit this).

The volute roll absorber devices 72 each comprise a volute spring 73 of the type disclosed in said Wulff et al. patent, but having its trap free height such that when the bolster is riding at the empty load level, as shown in FIG. 2, the upper end 74 of the volute spring is spaced from the bolster spring seat 44A for all amplitude of movement of the bolster under empty load conditions. Retainer spring 77 applied between spring 73 and the bolster resiliently holds unit 72 from displacement without having to significantly modify the truck parts involved.

In the embodiment of FIGS. 4 6, the invention is shown applied to an ASP Ride Control Truck 76 in which the bolster 16B is an A-3 Ride Control bolster, both made and sold by American Steel Foundries.

In trucks of the type shown in FIGS. 4 6, the bolsters conventionally include spring retainer flanges. For purposes of this invention, the spring retainer flanges at the outer left and inner right group spring positions are removed from the bolster, and bosses 82 are applied on center in these positions, as indicated in FIG. 4, to receive the retainer spring 77. Spring retainer flanges are present to permit alternate use of a conventional spring group, using the same bolster and a conventional roll absorber of different make located at the outer right and inner left spring group positions. The bosses may be of either Y" design (FIG. 4) or of circular design (FIG. 6) in cross-section. In the case of bolster 16A (FIGS. 2 and 7), the existing boss 83 in the same position may be utilized and no flange deletion is necessary.

FIG. 1 is intended to diagrammatically illustrate both the specific embodiments of FIGS. 2 6 in showing volute spring unit 72 applied between the bolster l6 and side frames 26 and 28 in the

respective spring groups

22 and 24, with the bolster 16 being shown in the empty load car height bolster riding position (indicated by the line 48), and the loaded car bolster riding position height being indicated by the line 50. FIGS. 1 6 are intended to illustrate application of the invention to a 100 ton hopper car which will have 263,000 pounds maximum weight on rail when fully loaded. However, the invention is equally applicable to any railroad car requiring both roll control in the loaded condition and a soft ride in the empty condition. Furthermore, the roll control devices 72 may be at any desired position in the group that is suitably prepared, as in the manner indicated, to accommodate reception of the units 72 therein.

In the embodiments of FIGS. 1 11, the trap free height relation of this invention is achieved by building into the devices 72 higher radial pressures that thus bring into fuller utilization the absorption potential that can be built into the volute. The degree to which the absorption potential is to be utilized for any particular application is (in light of this invention) a matter of choice and design, but since the volute trap free height no longer must be equal to or greater than the empty load bolster riding height, the full absorption potential of the volute, insofar as it can be used for roll control purposes, is now available to the designer.

The graphs of FIGS. 13 16 illustrate a roll control device 72A (FIG. 15) in which the prior art constant contact absorber represented by curves 60 and 62 is shortened in length as required to have its trap free height at about 9 A: inches, rather than at the constant bolster engaging height of 9 56 inches that is shown in FIG. 9. This not only brings into play the empty load riding benefits of this invention, but also results in the volute operating along the straight line portions of its deflection curves in controlling loaded car roll, as indicated by the absorption envelope 85 of FIG. 14.

In FIG. 10, the dynamic action of a spring group arranged in accordance with the showing of FIGS. 1 l1 and embodying volute roll control devices 72 each having the improved characteristics indicated in FIG. 9 is plotted, assuming the spring group is applied to a 100 ton car having 263,000 pounds maximum weight on the rail, with each spring group 70 having a group spring rate of 26,000 pounds per inch with a solid capacity of 112,546 pounds under dynamic conditions. The result is curve 90, wherein it will be seen that the portion AB of the curve lies along the straight line 92 that represents the dynamic action of the seven coil springs 40 and 42 (suitably snubbed as by employing built in type snubbing devices for vertical movement control) alone from zero load to the point where devices 72 are engaged, whereupon there is a break in the curve and no bolster deflection until the load represented by point C is reached, whereupon the curve portion CD is attained for further increases in load up to near solid conditions.

In the showing of FIG. 11, application of the invention (in the form of FIGS. 1 11) is illustrated in terms of units of energy absorption plotted against spring group height in inches for a truck of the type shown in FIGS. 4 6 equipped with the invention, in which line 94 illustrates energy absorbed by the operation of built in snubbers controlling the pure vertical motion of the bolster, curve 96 illustrates the operation of volute roll absorber units of the prior art type (which are in constant contact with the bolster), and curve 98 represents the improvement provided by the instant invention (with the portions of curve 98 that are coincident with curve 94 being set off slightly to clearly distinguish all three curves). Experience has indicated that roll control in 100 ton cars and the like requires that the roll control units have a damping factor of at least three to four times that necessary for control of pure vertical bolster motion with minimum loss in resiliency, and in the application of the invention to a 100 ton car, the energy absorption on deflection of the bolster from its empty car riding elevation to engagement with the units 72 will follow line 94 from maximum empty car riding height to the trap free height of units 72, whereupon the curve 98 will break and jump immediately to well above the level of curve 96 for full load ride control and roll control. The increased absorption that is indicated by curve 98, for loaded car ride and roll control is achievable by reason of the increased utilization of the absorption potential of the volute (in this case by increased radial pressures being built into the volute coils) which would not be possible if the trap free height of the volute had to approximate the bolster empty load height.

In the showings of FIGS. 9 l4, and 16, the amplitude of movement of the bolster in the empty load conditions is indicated by dimension X while the amplitude of movement of the bolster under loaded conditions, including roll amplitude, is indicated by dimension Y.

In the showing of FIG. 13, curves 60A, 62A and 65A correspond to

curves

60, 62 and 65 of FIG. 9, except that the roll control unit involved is shortened (by about one-half inch) to provide the trap free height relation contemplated by this invention, which results in

curves

60A, 62A and 65A being shifted to the right of corresponding

curves

60, 62 and 65 of FIG. 9.

FIG. 14 shows the dynamic action of a spring group arranged in accordance with the showing of FIG. 3 and embodying roll control devices 72A each having the improved characteristics indicated in FIG. 13, assuming the same loaded car conditions as in the case of FIG. 10. The curve 90A illustrates the dynamic action of the group (ignoring energy absorption) of which the portion EF lies along straight line 92A that represents the dynamic action of the seven coil springs 40 and 42 (suitably snubbed, as previously indicated) alone from zero load to the point where devices 72A are engaged, whereupon there is a break in the curve and no bolster deflection until the load represented at G is reached, whereupon the curve portion OH is attained for further increases in load up to near solid conditions. The action of the units 72A in controlling roll is thus along the straight line portions of the volute calibration curves, as indicated by envelope 85.

The showing of FIG. 16 is of the same type as FIG. 1], curves 94 and 96 being the same as

curves

94 and 96 of FIG. 11, respectively and curve 98A corresponding to curve 98 of FIG. 11.

Units 72A thus have the advantage of operating for roll control purposes entirely along the straight line portions of their deflection curves and at reduced stress levels, in addition to insuring the desired soft ride for the car under empty load conditions. Device 72A thus provides an energy absorbing action comparable to hydraulic roll control devices.

In all embodiments of the invention, it is to be understood that the roll control devices of this invention are arranged so that their volutes reach, on release, the trap free height relationship that has been described and maintain approximately this trap free height while the car runs empty in spite of the normal vibrations and shocks that the volutes will be subjected to in service. In other words, the volute units of this invention are so constructed that they will not move to rap out height or length, much less design free height, under normal service vibrations and shocks; but even if an excessive blow were received, the first compression of the spring would restore the desired trap free height.

The practice of the instant invention provides a number of important benefits. For instance, for empty car operation, the spring groups provide a 25 to 30 percent lower spring rate, all helical spring support, for the bolster that is controlled by suitable snubbing devices of the type indicated for optimum vertical movement only. This insures maximum riding spring cushioning action for the bolster and load carried thereby, a minimum transferability of forces involved, a lower natural frequency for the spring system involved, and a somewhat lower center of gravity as the bolster riding height will be lower since the load support heretofore provided by the roll control devices will not be present under empty load conditions. Furthermore, tendencies to rock under empty load conditions, which could not be controlled due to the stiffness of conventional spring groups, are cushioned and dissipated by the helical springs of the groups 70 to the exclusion of

devices

72 or 72A.

For loaded car operation, roll control of the car body is assured without affecting the dynamic riding height of the spring group. Furthermore, since the trap free height of the volute springs no longer has to be an approximation of the empty car bolster riding height, the absorption potential of the volute roll absorbers can be enhanced, if desired, up to the full usable potential of which each heat of steel is capable, with the result that when the necessary relationships between car geometry, center of gravity and truck centers exist, a single volute device 72 may be employed where two prior art volute roll absorber devices have formerly been employed (note FIG. 11).

Moreover, since fatigue test production control specifications can be met without having to be concerned with the trap free height approximating the light car bolster riding height, approvals for each heat of steel can be expedited and simplified.

SPECIFIC DESCRIPTION The specific nature of the truck bolsters and side frames indicated in FIGS. 2, 4, and 6 are well known to the art, the Barber stabilized truck being shown at page 797 of the 21st Edition of Car Builders Cyclopedia, and the Amsted ride control truck being shown at page 785 of the same publication. In the arrangement of FIG. 2, the columns 100 and 102 are provided with hardened friction surfaces 104 and 106 against which the respective friction shoes 108 and 110 (carried by the bolster 16A) are spring biased for snubbing purposes. The bolster 16B and side frames 79 of the embodiment of FIG. 6 (only one side frame is shown) are similarly equipped as indicated by corresponding reference numerals employing the suffix A.

The volute spring units 72 (see FIGS. 7 and 8) each comprise a volute spring 73 made in accordance with the said Wulff et al. patent and having a trap free height in accordance with the standards that have been here indicated, such that when the bolster is riding at its empty car height, the upper end 74 will have the spacing below the bolster spring seat that as indicated in FIG. 7. Spring 73 is wound to provide a reverse pitch, negative helix in the as coiled condition; in other words, spring 73 has a negative helix angle and an increasing axial pitch, as defined by said Wulff et al. patent. In FIG. 8, the outer dead coil is indicated at 122, the inner dead coil at 124, the outer active coil at 126, the middle active coils at 128 and 130, and the inner active coil at 132.

As previously indicated, the combination of steel chemistry, material distribution from coil to coil, and coiling roll pressure are the prime factors controlling absorption potential of the volute spring. For 100 ton car applications, it is preferred that the spring 73 be fabricated to provide minimum absorption (difference between compression and release loads) of 4,500 pounds at 6 l5/16ths volute height after 50,000 cycles of compression and release for each of two trial snubbers for each heat of steel, with 100,000 cycles minimum to spring failure.

The inner inactive coil 124 has received within same retainer cylinder 134 through which extends stem 136 of bolt 138 having a head 140 which is seated in recess 142 of the base disc 144 of the unit (see FIG. 7). The base disc 144 includes a hub portion 146 through which bolt 138 extends, and on which rests the retainer 134.

Retainer 134 is secured in place by suitable nut 148 applied against lock washer 150 seated against washer 153, which in turn is seated against retainer cylinder 134.

As indicated in FIG. 7, the base disc 144 of the unit 72 rests against the spring seat area 46 of the side frame, and has its spring seat engaging surface 151 excised thereabout as at 152 to allow for lateral and roll motions of the bolsters.

The retainer spring 77 has one of its ends 154 received about the bolster

boss

82 or 83 and the other of its ends 156 received about the nut 148 and against the washer which thus serves as a spring seat for the spring end 156. Spring 77 is a comparatively light compression type spring of sufficient strength to hold unit 72 in place when spring 73 is separated from the bolster.

The retention in place of spring 73 by spring 77 provides a simple but expedient way to satisfy the need to insure that unit 72 is retained in its operating position when the car is running empty so that it does not require special attention each time the car is loaded. Moreover, this is achieved without requiring significant structural changes to the bolster or side frame (a very critical factor in the railroad field).

With reference to the embodiment of FIGS. 13 16, roll control device 72A is essentially the same as device 72 except for the characteristics of its volute spring 73A that have been mentioned, which are achieved in the form illustrated by employing a base disc 144A that is of reduced thickness as compared to the corresponding base disc 144 of device 72. As indicated in FIG. 15, base disc under surface 151A in the fonn shown is flat in nature for flush engagement with spring seat area 46 of the side frame but flattness is not required. The remaining parts of device 72A are the same as device 72.

FIG. 12 is a graph illustrating the relation of volute spring trap free height, design free height and rap out height in devices arranged in accordance with the invention. FIG. 12 plots rap out providing blows against spring group height in inches. In a standard manufacturing procedure that is employed to make volutes 73 and 73A, these volutes are subjected to a series of ten hammer blows with a hammer suitable for this purpose (such as a two pound machine hammer), and the rap out achieved for each blow, on the average, tends to follow the curve 160, which tends to go asymptotic at the volute design free height. IF the volute is struck with a heavier blow, it may jump out in one jump to design free height or perhaps somewhat more.

In accordance with this invention, the volute units are characterized by maintaining their trap free height when the car is running empty against the action of what vibrations and impacts they will be subjected to under normal operating conditions for the car. Such vibrations and impacts will thus apply less force to the volute units than the unit forces needed to achieve rap out or jump out in the sense indicated by FIG. 12.

It will therefore be seen that this invention provides a method and apparatus for controlling roll of high capacity freight cars wherein the car when empty has the soft resilient ride best suited to protect the car structure when in route, considering the differences in center of gravity and weight as compared to the fully loaded condition, whereas the car when fully loaded is provided with full body roll control. Moreover, since the absorption potential of the roll control devices 72 can be increased as desired up to approaching theoretical limits, due to the freeing of the trap free height criteria from the empty car bolster riding height level, the control provided by each volute unit 72 may be significantly improved.

The invention is fully applicable to existing and new equipment and can be readily applied to existing spring groups.

While it is intended that under normal conditions the roll absorbers of this invention will not be operating when the car is runr i'ng empty, it is contemplated that under some extremfi'condition the bolster when the car is running empty may contact the roll absorber.

With regard to FIGS. 9 and 13, it is pointed out that the curves there illustrated are theoretical for design purposes and do not show actual operational curves.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

I claim:

1. In a railroad car truck for high capacity railroad cars with the truck including a bolster supported from the truck side frames at either end of the bolster by a spring group interposed between the spring seats of the respective bolster ends and the side frames supporting same, whereby said bolster has normal empty and loaded car riding heights relative to the respective side frames, the improvement wherein said groups each comprise:

a plurality of coil springs and at least one damping type roll control volute spring unit interposed between the bolster and side frames supporting same,

said coil springs engaging the spring seats of the bolster and side frames, respectively, and being of sufficient strength to support the bolster at its empty car normal riding height whereby the bolster operates in an empty car riding height amplitude when the car moves over the rails of track,

means exclusive of said volute units acting between the respective bolster ends and the side frames supporting same for damping said coil springs to con trol vertical movement of said bolster when operating in said empty car normal ridingheight amplitude,

said coil springs having their strength limited such that when the car rides loaded, the bolster loaded car normal riding height amplitude is below and spaced vertically from the bolster empty car riding amplitude,

said units each comprising a roll control volute spring supported by the side frame beneath it and having a trap free height that is below the bolster empty car normal riding height amplitude and that is above the bolster loaded car normal riding height amplitude,

said volute springs when operative for roll control purposes providing said groups with a damping factor that is at least in the range of from about three to about four times the damping factor of said damping means,

said volute springs each having an absorption potential that is independent of the empty car riding height,

and including means for holding said volute springs seated within the respective groups when the bolster operates at a car riding height above said trap free height,

whereby said coil springs providle ride characteristics for the car, to the exclusion of said volute springs, that give spring cushioning action suitable for the car when the car rides empty, but said volute springs provide full damping roll control when the car rides loaded.

2. The improvement set forth in claim 1 wherein:

said volute springs each have a negative helix angle and a reverse axial pitch.

3. The improvement set forth in claim 1 wherein:

said volute springs are each oriented to dispose outer coils of same at the upper end thereof and the inner coils of same at the lower end thereof,

said volute springs each including coil spring means interposed between said inner coils thereof and the bolster resilient maintaining the respective volute springs seated within the respective groups when the car is empty, and comprising said holding means.

4. The improvement set forth in claim 1 wherein:

said volute springs have a load deflection relation such that part of the compression and release curves thereof are of the upwardly curving type.

5. The improvement set forth in claim 1 wherein:

said volute springs have a load deflection relation such that in providing said damping roll control, said volute spring operate on a substantially straight line load deflection basis.

* l i t

Claims

1. In a railroad car truck for high capacity railroad cars with the truck including a bolster supported from the truck side frames at either end of the bolster by a spring group interposed between the spring seats of the respective bolster ends and the side frames supporting same, whereby said bolster has normal empty and loaded car riding heights relative to the respective side frames, the improvement wherein said groups each comprise: a plurality of coil springs and at least one damping type roll control volute spring unit interposed between the bolster and side frames supporting same, said coil springs engaging the spring seats of the bolster and side frames, respectively, and being of sufficient strength to support the bolster at its empty car normal riding height whereby the bolster operates in an empty car riding height amplitude when the car moves over the rails of track, means exclusive of said volute units acting between the respective bolster ends and the side frames supporting same for damping said coil springs to control vertical movement of said bolster when operating in said empty car normal ridingheight amplitude, said coil springs having their strength limited such that when the car rides loaded, the bolster loaded car normal riding height amplitude is below and spaced vertically from the bolster empty car riding amplitude, said units each comprising a roll control volute spring supported by the side frame beneath it and having a trap free height that is below the bolster empty car normal riding height amplitude and that is above the bolster loaded car normal riding height amplitude, said volute springs when operative for roll control purposes providing said groups with a damping factor that is at least in the range of from about three to about four times the damping factor of said damping means, said volute springs each having an absorption potential that is independent of the empty car riding height, and including means for holding said volute springs seated within the respective groups when the bolster operates at a car riding height above said trap free height, whereby said coil springs provide ride characteristics for the car, to the exclusion of said volute springs, that give spring cushioning action suitable for the car when the car rides empty, but said volute springs provide full damping roll control when the car rides loaded.

2. The improvement set forth in claim 1 wherein: said volute springs each have a negative helix angle and a reverse axial pitch.

3. The improvement set forth in claim 1 wherein: said volute springs are each oriented to dispose outer coils of same at the upper end thereof and the inner coils of same at the lower end thereof, said volute springs each including coil spring means interposed between said inner coils thereof and the bolster resilient maintaining the respective volute springs seated within the respective groups when the car is empty, and comprising said holding means.

4. The improvement set forth in claim 1 wherein: said volute springs have a load deflection relation such that part of the compression and release curves thereof are of the upwardly curving type.

5. The improvement set forth in claim 1 wherein: said volute springs have a load deflection relation such that in providing said damping roll control, said volute spring operate on a substantially straight line load deflection basis.