Dampened Railway Car Truck

Abstract

A railway car truck which includes a bolster supported at each end on load springs which are in turn supported by the side frames of the truck. The load springs are of length which exceeds that of conventional load springs to attain softer, full-load cushioning. To avoid mispositioning of the car coupler at a greater height than allowed, the car truck includes cushioning devices between the bolster and the upper part of each side frame.

Description

DESCRIPTION

The railway companies are continually subject to damage claims arising out of lading damaged in transit. Much of this damage is due to vertical impacting of the lading because of the hard-riding characteristics of the freight cars. To date, efforts, in so far as springs are concerned, to improve the ride of freight cars have been directed primarily to using the longest travel springs possible that are consistent with a permissible coupler height above the rails, and then controlling bolster oscillation by some type of friction snubbing system. At the moment, the softest springs that can be used on standard trucks have about 3 11/16 inches total deflection and 2 7/16 inches deflection under full load because of the standard coupler height established by the Association of American Railroads (A.A.R.), i.e., the height of the coupler axis above the tops of the rails. This standard requires that the coupler height of a standing car may vary between 311/2 and 341/2 inches. This is an overriding consideration that the truck designer must respect when seeking any modification of present designs.

Thus, an essential problem in designing softer riding freight cars is to provide cushioning which achieves easy riding while keeping the coupler height within the required coupler height range at both empty and loaded conditions of the car. The designer must also work within a maximum vertical side frame dimension in providing a modified side frame structure.

There are prior art arrangements which disclose car trucks equipped with coil or leaf springs placed between the bolster and the underside of the overhanging compression member. The disclosures thereof indicate that such springs were used primarily to change the oscillation of the load springs and to snub upward oscillation of the bolster. Experience with these arrangements did not result in commercial success because such trucks simply functioned at a new spring frequency without satisfactory dampening or cushioning of bolster oscillation. In many instances, especially when the springs have low initial compression, such expedience merely adds to the rigidity of the trucks and substantially prevents any cushioning at empty load conditions. It was especially difficult to achieve satisfactory results with prior art arrangements because of incompatibility thereof with, or the impediments imposed by A.A.R. standard dimensions, such as the spacing of the side frame top surface, the side frame undersurface, the center plate, the coupler, etc., from the rail tops, and various lateral and longitudinal contour dimensions of the car truck.

Hence, the primary object of the present invention is to provide freight car trucks of improved riding characteristics without departing from A.A.R. standard specifications.

It is especially an object to improve the ride of loaded railway vehicles.

In achieving these and other objects, the emphasis of the present invention is on the use of load springs of maximum length in order to utilize springs having maximum softness in relation to load capacity, and reduced frequencies of oscillation.

According to this invention, a car truck is provided which comprises load springs of maximum length that can be inserted in a practical manner into a side frame bolster opening with the bolster positioned against means defining one extremity of the opening. Such springs have a deflection, while under compression at fully loaded condition of a vehicle in stationary condition, disposing the coupler of the vehicle within the lower portion of a predetermined standard range of height above rails supporting the vehicle. The car truck further comprises cushioning means, preferably a cushion of rubberlike material, disposed between the bolster and a member defining the upper extremity of the bolster opening, and constructed to a free height enabling it, under an initial condition of compression, to dispose the bolster at a height placing the coupler, at empty car condition, in the upper portion of its allowed height range.

In the drawing with respect to which the application is described:

FIG. 1 is a plan view of a car truck in accordance with the invention;

FIG. 1a is a fragmentary schematic side elevation of a railway car having a truck such as illustrated by FIGS. 1 and 2;

FIG. 2 is a side elevation of the car truck in FIG. 1;

FIG. 3 is a fragmentary section in elevation of the car truck in FIGS. 1 and 2 taken along line III-III of FIG. 2;

FIG. 4 is a fragmentary section in elevation taken along line IV-IV of FIG. 1;

FIG. 5 is a schematic plan view of the load springs as seated in the lower portion of a side frame; and

FIG. 6 is a fragmentary schematic view in transverse cross section of a bolster and side frame illustrating a stage of load spring installation.

The FIGS. of the drawing portray a car truck in accordance with the present invention which is typical as to overall dimensions of a standard 61/2.times.12 freight car truck, such as used on railways in the United States. FIG. 1a partially illustrates a freight car 1 equipped with a coupler 2 having a longitudinal axis A-A attached to the car body 3 in the conventional manner, and a truck 5 attached by king pin (not shown) to the car body 3 in the conventional manner. The reference herein made to coupler height above the rail is that distance, e.g., between the axis A-A and the top surface of the rail 4. As a major component, the car truck 5 comprises a pair of wheel and axle assemblies 6 and 7, a pair of side frames 8 and 9 supported by conventional bearing structure on journal sections of the axles of the axle-wheel assemblies, a bolster 10 having end sections received in bolster openings of the side frames of conventional arrangement, load springs 11 received within the bolster openings of the side frames to receive bolster end-sections thereon, and a cushioning unit 12 of rubber or rubberlike material disposed between an undersurface of the side frame compression member and the underlying bolster section. The truck herein disclosed embodies a bolster snubbing system such as described in U.S. Pat. No. 3,254,612. The term "standing-car" is used herein in connection with measurements conventionally made on a railway car with reference to a datum plane such as that defined by the tops of the rails on which a car is standing. The term denotes a motionless car standing at rest on a level track as, e.g., required by the A.A.R. in measuring coupler heights under various load conditions of the car.

Truck 5 differs from the conventional truck primarily in the greater free-length of the springs 11, the presence of the cushioning unit 12, and lateral enlargements or ledges 14 and 15 necessary for providing seats for the pads 12.

Because of the necessity for working within A.A.R. standards, that part of the compression member over the bolster opening must not stand more than 31 inches above the rail tops in order to provide sufficient clearance between the top of the side frame and car body bolsters. The frame must stand approximately 51/8 inches above the rail tops. Such specifications leave approximately 25 7/8 inches for side frame construction along a vertical transverse center plane of the side frame. With a compression member of 3 inches thickness and a tension member of 31/2 inches in thickness, the height of the bolster opening is necessarily about 193/8 inches. Under present design conditions, the thickness of the bolster end section between the spring seat undersurface and its top surface is about 4 inches.

Experience of the railway industry with side frames indicates that the lower seat for the load springs should be surrounded with a spring retaining flange of approximately 23/4 inches in height (see side frame flanges 18 and 19 in FIG. 3), and the upper spring seat on the bolster should be substantially circumscribed by a flange 21 of 1 inch in height. Hence, when the bolster 10 is elevated against the undersurface 23 of the compression member 24 of side frames 8 and 10 in preparation for the placement of the load springs 11 between the lower spring seat 26 and the upper spring seat 27, an open space of 153/8 inches exists. However, because the load springs must be inserted into this space on a bias, and the outer diameter of the larger set of springs is approximately 51/2 inches, load springs having a length of 14 inches are about the maximum that can be inserted without resorting to expensive means of precompression. To provide sufficient room for the springs to be inserted, the height of the bolster opening should be as great as the sum of the height of the bolster portion disposed therein and the length of a diagonal through the longitudinal axis and end loops of the largest load spring. During placement of the springs, the spring may thus be inserted under the bolster while positioned subjacent the compression member 24 and moved from a biased alignment to an alignment perpendicular to the spring seat on the tension member.

FIG. 6 illustrates the manner in which such insertion of springs may be accomplished. This FIG. shows one spring 11 of free-length in tilted position with its diagonal (dot-dash line 31) in perpendicular relation to the spring seat 26, thereby illustrating that the diagonal 31 and the height of the bolster portion (dot-dash line 32) are approximately equal to the height of the bolster opening. Another spring of free-length is shown in seated position on the seat 26.

To obtain the spring capacities currently desired, it is necessary that the load springs be provided as a plurality of spring units wherein each unit comprises three concentric springs of approximately equal length arranged, for example, as shown in FIG. 5. The difficulties of positioning such spring units in anything but their free-length condition may well be imagined, as spring unit capacities in the order of 8 to 10,000 pounds are contemplated.

However, when a truck of an empty car is assembled with springs of 14 inches free-length without including the above bolster-cushioning unit 12 in place, as shown in the side frames, the body of an empty car assumes a position placing its coupler with its longitudinal axis at a height of 36 3/16 inches above the rail tops if the empty weight of a 70-ton car is assumed to be approximately 22 tons. Under this situation, there is a clearance of 2 3/16 inches between the compression member and the top of the bolster since the height of the load springs had been reduced to 13 3/16 inches. However, this condition places the coupler axis 36 3/16 inches above the rail tops and 1 11/16 inches greater than the permissible height. At 341/2 inches coupler height, the load springs at 14 inches free height must be deflected 21/2 inches to a height of 111/2 inches. If a spring group of eight triple coil units is assumed with a total capacity of approximately 76,000 pounds and a spring rate of approximately 13,200 pounds per inch, based on 53/4 inches deflection, the bolster and the load springs must be forced downward another 1 11/16 inches, equivalent to 22,000 pounds of force, for a total deflection of 21/2 inches, to position the coupler within the allowed coupler height range.

Hence, at the highest permissible level of the car coupler, a clearance of approximately 37/8 inches in height must exist between the top of the bolster and the underside of the compression member 24. To provide 22,000 pounds of downward thrust on the bolster needed at this condition, the cushioning unit 12 has an elastomeric pad 28 of rubber or rubberlike material so constructed and designed as to provide 22,000 pounds of thrust at a height or thickness of 37/8 inches. At empty car condition, the spring height is thus 112/3 inches as a result of 21/2 inches of deflection produced by the aforesaid 22,000 pounds of thrust by the cushion 12 and approximately 11,000 pounds of empty car weight exerted on a single side frame. On the basis of a fully loaded car of 110 tons gross weight (70-tons capacity) and springs of 13,200 per inch deflection rate within a single side frame, the deflection between that of an empty car and that of a loaded car is the difference between 4 1/16 inches and 21/2 inches, or 1 9/16 inches which is well within the standard 3-inch range of permitted coupler height variation.

In effectuating a desired A.A.R. standard for coupler height, it is clear from the foregoing text that the range for coupler height is always directly related by the car structure to the height of the bolster end section within its respective side frame bolster opening. As the drawing shows, the bolster end section has an approximately equal range of position, e.g., a range of 3 inches along an intermediate minor portion of the height of the bolster opening.

A full load deflection of 4 1/16 inches leaves approximately 1 11/16 inches further deflection available until the solid height of the springs is reached. This potential resiliency of the spring group is substantially greater than the difference of 1 4/16 inches between the "full-load" height and "solid" height of the conventional maximum height springs of 3 11/16 inches total deflection. Since the pad 28 of the resilient unit 12 is designed with a free height of approximately 61/2 inches, it functions under substantially loaded conditions of the car in a nearly fully expanded condition in which it exerts minor influence on the oscillation rate of the load springs. The unit 12 comprises upper and lower steel plates 29 and 31 of, e.g., one-fourth inch in thickness. By loading the bolster 10 to effect nearly full deflection of the springs up to 71/8 inches maximum space available between the bolster and the compression member 24, the cushioning unit 12 may be easily inserted into operative position between the bolster and the compression member. When the bolster is released from its fully deflected position, it then assumes a proper empty load position, disposing the coupler of the vehicle in the upper portion of the allowed coupler height range.

In the proportions shown, the outer diameter of the pad 28 is approximately 8 inches and the inner diameter is approximately 3 inches in the free height condition of the cushioning unit. The pad is designed in accordance with formulations well known to rubber compounders in order to achieve 22,000 pounds of compression resistance upon 21/2 inches reduction of the pad height from about 61/2 inches to 37/8 inches in the overall height of the cushioning unit. On account of the limited space available between the bolster and the compression member 24, coil springs, obviously, are not available that will provide the deflection and resistance to compression values realized by the pad 28.

In comparing the presently utilized load springs of 53/4 inches deflection with conventional load springs of 3 11/16 inches deflection, it should be noted that the deflection rates are, respectively, approximately 13,200 pounds per inch of deflection and 20,400 pounds per inch of deflection in each side frame. For example, when a vehicle incorporating the car truck of this invention passes over a track irregularity of one-half inch height the truck sustains a force-blow from underneath of approximately 6,600 pounds instead of a blow in excess of 10,000 pounds, as in the case of the conventional truck. Obviously, the jolt transmitted to the lading is much softer whether the car is nearly empty or fully loaded. In this situation the side frame is jerked upwardly while the cushioning unit is expanding on upward motion of the side frame as it passes over an irregularity and snubbing the downward return motion of the side frame as it settles back to its normal travelling plane. In each motion, the bolster disturbance and impact on the lading is minimized. A further advantage realized from the subject pad is the hysteresis of rubber and rubberlike materials. That is to say, upward movements of the bolster relative to the side frame result in some absorption or consumption of energy rather than the complete storing of energy as the pad 28 undergoes compressive strokes.

Another major benefit of the longer load springs herein disclosed is slower oscillation rate inherent in the longer springs and, hence, a reduced hammering action on the lading when load irregularities are such as to induce oscillatory bolster motions relative to the side frames.

While the invention has been herein described with respect to but one design of resilient cushioning unit between the bolster and the compression member of the side frame, it is realized that rubberlike compositions may be produced to varying compositions and durometer hardness, and that the shape and lateral dimensions of the pad or a plurality of pads used in the cushioning unit may be varied.

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 as fall within the scope of the claims.

Claims

I claim:

1. A railway car comprising a body and a truck thereunder in supporting relation therewith, said truck comprising:

two pairs of wheels, each pair joined by an axle;

a pair of substantially identical side frames extending from axle to axle in journal-bearing relation therewith, each side frame having a top member and a bottom member with a bolster opening therebetween;

a bolster having an end section received in each of said openings;

each bolster opening defining an operating range of displacement extending from an empty car position to a fully loaded car position for the end section disposed therein at standing-car conditions, said range being measured along a minor intermediate portion of the height of the opening;

a cushioning system for each side frame which supports respective bolster sections within said range at empty to full load, standing-car conditions;

said cushioning means comprising a group of coil springs of similar height, the height of the bolster opening at least equaling the sum of the height of the bolster portion in said opening and the length of a diagonal passing through the longitudinal axis and the end loops of one of said springs in free-length condition;

an elastomeric vertically compressible, laterally expandable cushion disposed in a state of initial partial lateral expansion and vertical compression between each top member and the underlying bolster section in equilibrium with said springs to dispose the bolster downwardly within said range at empty standing-car condition.

2. The railway car of claim 1 wherein:

said body has a coupler projecting outwardly from an end thereof which is disposed along a generally horizontal pulling axis located approximately at a midpoint in the height of its face and said coupler is movable vertically along with said bolster to dispose the pulling axis within a range of elevation between 311/2 inches and 341/2 inches above a plane of railtop engagement for said wheels.

3. The railway car of claim 1 wherein:

the height of the side frame between the underside of said bottom member to the topside of said top member is not greater than about 257/8 inches.