US3494557A - Rail holddown units and assembly - Google Patents

Description

'Feb. 10,1970 "D; D. BRoW 3,494,557

RAIL HOLDDOWN UNITS AND ASSEMBLY Filed March 6, 1968' 320 mun- 24 I111"! INVENTOR. DELMONT D. BROWN wwmzw United States Patent 3,494,557 RAIL HOLDDOWN UNITS AND ASSEMBLY Delmont D. Brown, North Baltimore, Ohio, assignor to The D. S. Brown Company, North Baltimore, Ohio, a corporation of Ohio Filed Mar. 6, 1968, Ser. No. 711,038 Int. Cl. E01b 9/40, 9/62, 9/68 U.S. Cl. 238349 11 Claims ABSTRACT OF THE DISCLOSURE Rail holddown system embodying holddown assembly with pivoted holddown member (plate) having inner end portion pressed downwardly against upper face of rail flange and opposite outer end portion urged upwardly by a. compressively distorted, resilient bias member; resilient bias member preferably is compressed elastomer body positioned beneath said opposite, outer end of pivoted holddown member.

BACKGROUND OF THE INVENTION The present invention concerns holddown systems particularly adapted to securely position a railroad rail on a support member or underlying structure. The invention particularly concerns the holddown systems adapted for use with concrete ties, concrete beds, metal superstructures, and the like support structures. It further pertains to other uses wherein one member is to be held in position relative to another member and may be used in lieu of bolt connections, welded connections, etc.

Railroad rails traditionally have been mounted on wooden cross ties spaced at close intervals by the driving of railroad spikes into the ties with the head portion of the spike overlapping the base flange of the rail. This has been true of below ground and on ground rail systems and above ground, or elevated, rail systems. With the fairly recent advent of improvements in the structural strength of concrete, rail systems embodying concrete ties or concrete beds have awakened the interest of railroad designers. Concrete beds or ties require considerably less maintenance and have a longer useful life than do the traditional wooden ties.

The adaptation of rail systems to the use of concrete ties and concrete road beds, however, also require a departure from the traditional concept of holding the rail on the ties, i.e., by spikes being driven into the wooden ties. Holddown systems for rails on concrete ties and/ or concrete road beds or metal superstructures have been developed in recent years. Known holddown systems embody heavy metal structures. Some utilize metal components in torsion stress as the force-exerting members. A specific object of the present invention concerns improvements in rail holddown systems wherein the traditional, wooden ties concept is abandoned in favor of pre-stressed concrete ties, metal superstructures and/or concrete road beds in below ground, on ground or elevated rail systems.

BRIEF SUMMARY OF THE INVENTION Briefly, the invention concerns improvements in holding systems in general, i.e., systems for holding one member in fixed position on or relative to a second member by a holddown member, e.g., a plate, pivotally supported on or thrust against a member providing a pivot axis extending transversely across an intermediate portion of said holddown member. A portion of the holddown member on one side of the pivot axis is thrust against a mem ber to be held down or against an underlying support by a thrust provided by a compressively distorted resilient bias member thrusting against the portion of the pivot plate or member on the opposite side of the pivot axis in a direction opposite to the direction of thrust or force exerted by the first portion of the pivoted member against the member to be held down.

An exemplary use thereof comprises rail holddown systems wherein the railroad rails are secured by a series of holddown devices materially different from and considerably improved over the traditional railroad spike. A base member of such device may be fixedly secured relative to a concrete bed or tie or to other structural systems supporting the rail, such as metal superstructures in the case of elevated rail systems. This base member may be a base plate bolted or otherwise attached to the road bed, concrete tie or superstructure. The system further embodies a holddown member comprising a holdddown or pressure plate pressed downwardly against the upper face of the base flange. The pressure exerted thereby is of a relatively high magnitude, i.e., in the order of at least several hundred p.s.i. and a total force of at least two thousand pounds.

The pressure is provided by a resilient bias member, preferably a compressively distorted elastomer body or block, acting against a face of the holddown member near an end thereof to provide a first class lever action of the holddown member to press the opposite end thereof against the member to be held down, e.'g., against the upper face of the base flange of a rail. The elastomer body is distorted compressively from its normal, unstressed state whereby the elastic recovery thrust forces resulting from the compressive distortion exerts a pressure thrust force of relatively high magnitude, suflicient to secure'the rail tightly on ties or other rail support members.

The elastomer pressure member is inserted in the holddown system on the construction site. As is well known, it is difficult to insert an elastomer member in a high compressed state. To facilitate such insertion, the elastomer member may be compressively distorted or flattened, whereafter its temperature is lowered sufficiently to immobilize or freeze the member in the compressed or flattened state when the compression force is removed. It is maintained at this temperature until it is inserted on the job in the holddown system. Upon thawing or warming, the elastomer body regains its elastic recovery property and recovers toward its normal shape, which is the shape of the elastomer member before compressive distortion and low temperature immobilization thereof. The holddown system is dimensioned so that the inserted elastomer member cannot recover fully its original or normal shape, whereby the elastomer member is in a partially compressed state when it exerts its thrust force against the holddovm member. Thereby, there exists in effect the elastomer member in a partially compressed state. Through the utilization of the elastic recovery force of said member in attempting to return it to its original or normal state, it functions as the pressure exerting body in the holddown system.

The elastomer body or block or other compressible, resilient bias member may be compressed by other means. For example, a compression plate may be placed on top of the elastomer body. This plate may be pressed downwardly by a hydraulic or mechanical tool or machine to cause the bias member to compress sufficiently to allow the holddown member (plate) to be inserted in the system with the underface of the holddown member resting against the compression plate. Alternatively, the resilient bias member, e.g., the elastomer body or block, may be dimensioned so that it can be inserted in the assembled unit in the uncompressed state, and one or more shims may be driven between the elastomer body and a thrustbearing face of the assembly to compress the bias member. In general, the rail holddown systems are herein designed so that the holddown units may be assembled on the rail without the resilient bias. member, which is inserted in the assembly thereafter.

The components of the holddown units herein comprise a holddown member, preferably a holddown plate, mounted in the system so that the holddown member functions as a first-class lever, i.e., a lever having a pivot-support axis extending transversely of the plate along a line intermediate its opposite ends. The pivot axis is preferably slightly above and closely approximate to the longitudinal edge of the rail flange. In the preferred forms thereof the pivot axis is provided by a bar or rod extending transversely across the upper surface of the holddown member and forming a thrust-bearing support against upward movement of the holddown member without permanent attachment therebetween.

The resilient bias member thrusts upwardly against the outer end portion of the holddown member and the opposite, inner end portion of the holddown member is pressed downwardly against the upper face of the rail flange. The pivot axis is located closer to the inner end portion which thrusts downwardly against the base flange than it is to the outer end portion against which the bias member thrusts (preferably a ratio of at least 1:2 arid more, preferably a ratio of 1:3) to gain the mechanical advantage inherent in a first-class lever system in terms of pressure or thrust force of the inner end portion against base flange.

In the preferred form of the invention the holddown assembly for a rail preferably comprises a base plate extending transversely beneath the rail and a pair of holddown units as aforedescribed mounted on said base plate contiguous to opposite longitudinal edges of the base flange of the rail.

DESCRIPTION OF THE DRAWINGS Several preferred forms of the invention are illustrated in the drawings wherein:

FIGURE 1 is an end elevation of an embodiment of a rail holddown system with the railroad rail shown in cross section and the underlying concrete tie shown in fragment;

FIGURE 2 is a top plan view thereof with the rail and tie shown in fragment;

FIGURE 3 is a side elevation thereof with the rail shown in fragment;

FIGURE 4 is an enlarged, fragmentary, detail in side elevation of the pivot support of the holddown member; elevation of the pivot support of the holdown member.

FIGURE 5 is a similar fragmentary view of an alternate embodiment of FIGURE 4;

FIGURE 6 is an enlarged fragmentary detail in side elevation of the assembly of the resilient bias member and outer end of the holddown member;

FIGURE 7 is a similar detail of an alternate embodiment of FIGURE 6; and

FIGURE 8 is an enlarged, fragmentary detail of the rail flange and holddown plate.

DESCRIPTION OF PREFERRED EMBODIMENTS The embodiment of FIGURES 13 constitutes a rail holddown assembly wherein the assembly is attached, e.g., by bolts, to a rail supporting structure, which may be a series of railroad ties, an elevated, ground or below ground level railroad bed, or a series of cross structures such as steel structural members of an elevated monorail or dual rail system. The ties on railroad 'bed may be of any suitable material, but generally will be concrete. The rail 10 has the usual base flange 11, the upper surface 12 of which generally slopes outwardly but may be at right angles to the vertical axis of the rail if desired. In the illustrated embodiment the rail holddown system is mounted on the upper face of a concrete tie 13.

Each concrete cross tie has secured to its upper face a rail holddown unit comprising base plate 15 extending transversely beneath the rail 10. The base plate 15 is secured to the upper face of the rail-supporting understructure, e.g., tie 16, by bolts 14 imbedded in and projecting upwardly from the tie 13. The base plate 15 is held tightly against the upper face of the tie 13 by bearing or washer bolts 16 pressed tightly against the plate 15 by nuts 17 threaded on the upper ends of bolts 14.

The aforesaid pivot support for the holddown member is provided by an inverted U-strap 20, the lower ends of the side legs 21 of which are fixedly attached, e.g., welded, to the base plate 15. The upper ends of the side legs are connected by a rigid cross leg 22. The inverted U-straps 20 are positioned in close proximity to the longitudinal edges of the base flange 11 with the lower face of the cross leg 22 slightly above the outer edge of upper faces 12, i.e., a distance suflicient so that holddown member 24 may be positioned in the assembly substantially as shown in FIGURE 1.

The holddown member 24 preferably comprises a substantially flat holddown plate which extends through the inverted U-straps 20. In the embodiment illustrated in FIGURES 14, the corner 23 of the cross leg 22 forms a relatively sharp pivot axis for the holddown member 24. In the alternate embodiment shown in FIGURE 5, the cross leg 22a may have a rounded underface 25 which forms a more blunt pivot axis for the holddown member 24. Preferably, the upper face of the holddown member or plate 24 has one or more embossments or studs or the like projecting upwardly therefrom contiguous to the rail-opposing edge of cross leg 22 or 22a for the purpose of retaining the holddown member against working outwardly and also for the purpose of serving as a guide in the assembly of the holddown unit in terms of proper positioning of the holddown member therein.

The outer end portion 29 of the holddown member 24 is thrust upwardly by the compressively distorted resilient bias member 30 thrusting against the under face thereof. Such thrust, together with the pivot mounting of the holddown member or plate 24 on the underside of cross leg 22 or 22a, causes the underface 32 of inner end portion 33 of the member 24 to thrust downwardly against the upper face 12 of base flange 11 and thereby provide the holddown pressure as aforedescribed to securely hold the rail in position. If desired, a cross bar 34 may be provided contiguous to the inner side of the bias member 30 to prevent the latter from working inwardly toward the rail. If desired, the rail may rest on an elastomer pad 35.

In the embodiments of FIGS. 1-3 and 6, the opposing, thrust-bearing faces comprising the underface of outer end portion 31 and the upper face of the base flange 15 lie in diverging planes whereby the thrust forces exerted by bias member 30 in directions normal to such planes are angularly disposed. In the alternate embodiment of FIG. 7, a wedgelike bar 36 is secured to the upper face of base plate 15 and extends transversely thereacross beneath the compressively distorted bias member 300. The upper face 37 of the wedgelike bar 36 is oriented so that its plane is substantially parallel to the underface 38 of outer end portion 31 of the holddown member 24. In this embodiment the aforesaid angular disposition of the aforesaid thrust forces is eliminated.

The preferred resilient bias members (pressure exerting members) each comprise a block or body of solid elastomer which is compressively distorted in the holddown unit assembly. They are preferably distorted by compression into a flattened form, with a height or thickness dimension slightly less than the spaces between an underface of holddown member 24 and the upper face of plate 15 or wedgelike bar 36 when the holddown member 24 is positioned as illustrated, and its outer end raised to a point where a bind occurs by contact of face 32 with face 12 and with the underside of cross leg 22 or 22w.

Alternatively, particularly where the aforesaid shims are employed, the height or thickness dimension of the uncompressed body is of like nature.

After its insertion in the holddown unit, the elastomer block or body 30 or 30a is allowed to recover via its inherent elastic forces toward its normal state, i.e., the shape it would assume without any compressive forces exerted thereon. In this elastic recovery, the elastomer bodies 30 and/or 30a press outwardly and upwardly against the underface of the outer end portion 31 of holddown member 24, resulting in a downward thrust of the lower face 32 of inner portion 33 against the upper face 12 of the base flange 11.

The elastomer bodies or blocks 30 or 30a preferably have opposing, planar, thrust-exerting faces in the relaxed (undistorted) state. These faces may have a divergence corresponding to the divergence of the underface of holddown member 24 and upper face of base plate 15 for the embodiment illustrated in FIGURE 6. For any of the embodiments, they may be generally rectangular parallelepipeds in said relaxed state, generally with a height or thickness considerably greater than the distance between opposing thrust-receiving faces when the bodies are in the relaxed or undisturbed state.

As aforesaid, it normally would be difiicult to insert the compressively distorted, elastomer bodies between said faces. To facilitate such insertion, it is-preferred that the elastomer bodies be compressively distorted in a flattened shape and frozen or immobilized in this state. They are held at the freezing or low temperature immobilization until inserted. As the elastomer bodies warm their resilient properties are restored and they seek to resume their shape prior to compressive distortion and freezing. In so doing, they become wedged between said faces and thus exert a downward thrust on the holddown members.

The terms freezing and thawing above, are nontechnical descriptions. In practice, the elastomer bodies are formulated so that the elastomer composition will rigidify, through loss of elastic properties, at relatively low temperatures, i.e., in the order of 40 F. and below. The elastomers also should have good resistance to atmospheric deterioration in the presence of sunlight, atmospheric oxygen, and ozone, and should retain their elastic properties also at relatively high temperatures on the order of 100 to 120 F. The elastomer compositions useful for this purpose may be formulated from elastomers which crystallize at relatively low temperatures with the loss of elastic properties upon crystallization. Exemplary thereof are low crystallization neoprene elastomers. However, elastomers which are usually considered to be noncrystalline elastomers, e.g., natural rubber and most synthetic rubbers, can be immobilized or rigidified in the compressively distorted state at low temperatures in the order of F. to l00 F. or even lower. The invention herein contemplates use of any natural or synthetic rubber composition wherein such low temperature immobilization can be attained. The selection of a particular elastomer composition will depend in part on the climate of the locale where the installation is made. In northern parts of the temperate zone, a low temperature immobilizafion of -30 F. or below is recommended. In the arctic zone, a low temperature immobilization of -60 F. or below is recommended, whereas in southern parts of the temperate zone and in the tropical zone 0 F. or below would be suitable. In each instance, the low temperature immobilization is selected so that it will not be reached and preferably not even closely approached under the coldest climate conditions of the particular locale.

Thus, in its broader concepts the invention herein provides a system for holding one member relative to another by a compressively distorted, resilient bias member, preferably a solid elastomer body or block. The system embodies a first member and a second member to be held in fixed position relative to the first member. In a form such as illustrated in FIGURE 7, the system embodies substantially parallel, opposed faces against which the compressively distorted elastomer body is positioned with its opposite faces pressing against said opposed faces to give an elastic recovery thrust force urging said faces apart along lines of thrust force at right angles to said faces.

The holddown systems herein utilize the elastic recovery forces in the compressed elastomer body more effectively than would be the case if the elastomer body were subject to twisting. In the latter case, the torque elastic recovery forces in the twisted elastomer adopt a sine curve-like configuration. Such recovery forces are considerably less effective in terms of amount of elastic recovery thrust forces per unit of distortion or deformation of the elastomer body as compared against the thrust force orientation achieved by this invention.

In lieu of a base plate 15 with inverted U-straps 20 fixedly secured thereto, the invention also embraces a holddown system wherein bars or rods, made into inverted U-yokes corresponding in orientation and function to U- straps 20, have their lower ends fixedly secured to other components mounted on the rail-underlying structure or fixedly imbedded in the concrete tie or other concrete railroad bed structures. In the latter case, each pair of rods or bars form the equivalents of opposing pairs of the illustrated inverted U-straps 20. These pairs may be tied together in a unitary structure which in turn may be a separate or integral part of the reinforcing metal work of a reinforced concrete tie or roadbed.

The lower face 32 of hold down plate 24 preferably is not parallel to upper face 12 of base flange 11, but rather is oriented whereby its lower, inner edge 32a bites on upper face 12. An exaggerated illustration of the nonparallel orientation is shown in FIGURE 8.

In summary, the improvements herein comprise holddown systems characterized by a rail holddown unit embodying fulcrum means forming a pivot axis substantially parallel with said rail adjacent to a longitudinal edge of said base flange, a hold down member pivotally supported intermediate the ends thereof on said fulcrum means, the inner end of said holddown member bearing against the upper face of said base flange, and a resilient bias member under compressive distortion beneath the outer end portion of said holddown member and pressing said inner portion tightly against said base flange.

It is thought that the invention and its numerous attendant advantages will be fully understood from the foregoing description, and it is obvious that numerous changes may be made in the form, construction and arrangement of the several parts without departing from the spirit or scope of the invention, or sacrificing any of its attendant advantages, the forms herein disclosed being preferred embodiments for the purpose of illustrating the invention.

The invention is hereby claimed as follows:

1. In a rail holddown system embodying a railroad rail having a base flange extending along the base thereof and supported on an underlying structure, the improvement comprising a rail holddown unit embodying fulcrum means forming a pivot axis substantially parallel with said rail adjacent to a longitudinal edge of said base flange, a holddown member pivotally supported intermediate the ends thereof on said fulcrum means, the inner end of said holddown member bearing against the upper face of said base flange, and a body of solid elastomer under compressive distortion beneath the outer end portion of said holddown member and pressing said inner portion tightly against said base flange.

2. The improvement wherein the rail holddown system comprises two, opposing holddown units as claimed in claim 1, said units being disposed at opposite sides of said base flange, and said compressively distorted bodies of solid elastomer respectively acting against opposing, diverging faces.

3. The improvement wherein the rail holddown system comprises two opposing holddown units as claimed in claim 1, said units being disposed at opposite sides of said base flange.

4. The improvement as claimed in claim 1 wherein said pivot means comprises the cross leg of a fixed, inverted U-shaped member through which the holddown member extends.

5. The improvement wherein the rail holddown system comprises two opposing holddown units as claimed in claim 4, said units being disposed at opposite sides of said base flange.

6. The improvement as claimed in claim 4 wherein said holddown membercomprises a substantially flat plate pressed upwardly against the underside of said cross leg.

7. The improvement wherein the rail holddown system comprises two opposing holddown units as claimed in claim 6, said units being disposed at opposite sides of said base flange.

8. The improvement wherein the rail holddown system comprises two opposing holddown units as claimed in claim 6, said units being disposed at opposite sides of said base flange, and the lower, inner edges of said fiat plates biting into said upper face.

9. In a rail holddown system embodying a railroad rail having a base flange extending along the base thereof and supported on an underlying structure, the improvement comprising a rail holddown unit embodying an inverted U-shaped member with a horizontal cross leg substantially parallel with said rail and adjacent to a longitudinal edge of said base flange, a substantially fiat plate pressed upwardly against the underside of said cross leg and pivotally supported intermediate the ends thereof on said cross leg, the inner end of said flat plate bearing against the upper face of said base flange, and a body of solid elastomer under compressive distortion beneath the outer end portion of said fiat plate and pressing upwardly against the underside of said outer end portion to press said inner portion tightly against said base flange.

10. The improvement as claimed in claim 9, and retaining means projecting upwardly from said flat plate contiguous to the rail-opposing face of said cross leg to retain said flat plate against working outwardly and also serving as a guide in the assembly of said holddown unit in holding engagement with said base flange.

11. The improvement as claimed in claim 9 wherein said flat plate is in a plane angularly disposed to the plane of the upper face of said base flange with the inner edge of said flat plate biting into said upper face of said base flange.

References Cited UNITED STATES PATENTS 2,502,281 3/1950 Sann 238-349 3,338,520 8/1967 Dinger 238349 FOREIGN PATENTS 1,305,987 9/1962 France.

DRAYTON E. HOFFMAN, Primary Examiner R. A. BERTSCH, Assistant Examiner US. Cl. X.R.

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