US3494558A

US3494558A - Rail holddown assembly

Info

Publication number: US3494558A
Application number: US707500A
Authority: US
Inventors: Delmont D Brown
Original assignee: Brown DS Co
Current assignee: Brown DS Co; DS Brown Co
Priority date: 1968-02-23
Filing date: 1968-02-23
Publication date: 1970-02-10
Anticipated expiration: 1987-02-10

Description

Feb. 10, 1970 D. D. BROWN 3, 9

RAIL HOLDDOWN ASSEMBLY Filed Feb.-25. 1968 I I I gjmmk 3 27 MI 25 27 2a mva/vroe.

aauawr 0. BROWN 9W, QLLIM ifiziriig Lga United States Patent O 3,494,558 RAIL HOLDDOWN ASSEMBLY Delmont D. Brown, North Baltimore, Ohio, assignor to The D. S. Brown Company, North Baltimore, Ohio, a corporation of Ohio Filed Feb. 23, 1968, Ser. No. 707,500 Int. Cl. E01b 9/44 U.S. Cl. 238-349 6 Claims ABSTRACT OF THE DISCLOSURE Rail holddown system embodying holddown assembly with resiliently biased holddown members pressing against upper face of base flange of railroad rail; resilient bias preferably is compressed elastomer body positioned between holddown member and upper leg of loop strap fitted around base plate and seated in groove therein.

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 like rail 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 tie concept is abandoned in favor of prestressed 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 holding systems in general, i.e., systems for holding one member relative to another comprising a first member, a second member contiguous thereto to be held in fixed position relative to said first member, and means for transmitting thrust between said members including a compressively deformed bias member, preferably a solid elastomer body having opposite substantially parallel faces exerting an outward elastic recovery thrust against substantially parallel faces with lines of thrust forces in said compressively deformed members being essentially at right angles to said faces. 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 holddown 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. This pressure is provided by a resilient bias member, preferably elastomer pressure body, positioned between a fixed inverted U- member and the holddown member. 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, sufficient 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 highly 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 holddown 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 th pressure exertin body in the holddown system.

The elastomer member may also be compressed between opposing, preferably substantially parallel faces of a holddown system or the like by other means. For example, the elastomer member may be inserted in an uncompressed state, and one or more shims may be driven between the body and the contiguous face of the holddown member to compress the elastomer member. Alternatively, the holddown device may be made in separate parts and assembled on the job site in a manner whereby the elastomer member is compressed upon assembly. In rail holddown systems, the holddown units may be mounted on the rail without the elastomer member, which is inserted later.

RELATED APPLICATIONS This invention concerns improvements in holddown systems of the type disclosed in the pending application of Frank Kenneth Hall, filed of about even date herewith. The improvements in said Hall application reside in holddown structures embodying a base plate, preferably extending transversely beneath the railroad rail. The base plate has provided thereon a holddown unit comprising an inverted U-member having a substantially flat cross leg extending transversely across and above the base (substantially parallel with the rail). The inverted U- member is adjacent the base flange of the railroad rail and there are preferably two, opposed, holddown units on each base plate on opposite sides at the base flange. The holddown member has an inner portion resting against the upper face of the base flange of the rail and extends from said base flange outwardly through the inverted U-member. A resilient bias member, preferably a solid elastomer body, under compressive distortion, is provided between the aforesaid cross leg and the holddown member. The elastic recovery of the resilient bias member presses the flange-contacting portion of the holddown member downwardly against the upper face of the base flange to give a secure mounting of the railroad rail on the aforesaid base plate, which is in turn securely mounted by bolts or the like on concrete railroad ties, concrete rail beds, metal superstructures, or the like.

IMPROVEMENTS HEREIN My improvements in the aforesaid Hall holddown systems reside primarily in the utilization of a loop strap, preferably of substantially rectangular configuration, as a member for mounting the compressively distorted, resilient bias member in the rail holddown unit. The loop strap is dimensioned to slip over the end of the base plate, and the lower cross leg thereof is seated in a transverse groove in the undersurface of the base plate. The upper leg preferably has a substantially flat, lower face opposing the upper face of the rail holddown member, e.g., a substantially flat plate. The compressively distorted, resilient bias member exerts its resilient (elastic) recovery thrust between the preferably substantially flat lower face of the upper cross leg of the loop strap and the preferably substantially parallel upper face of the holddown member and thereby press the latter downwardly against the upper face of the rail base flange.

DESCRIPTION OF THE DRAWINGS A preferred form of the invention is illustrated in the drawing wherein:

FIGURE 1 is an end elevation of an embodiment of a I 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; and

FIGURE 3 is a side elevation thereof with the rail and tie shown in fragment.

DESCRIPTION OF THE PREFERRED EMBODIMENT The illustrated embodiment 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 cross ties, an elevated, ground level or below ground railroad bed, or steel structural members of an elevated monorail or dual rail system. The ties or railroad bed may be of any suitable material, but generally will be concrete. The rail 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 15. The unit 15 comprises a base plate 16 mounted on the tie by bolts 17 and nuts 18 tightened against bearing or washer plates 19 having a stepped lower segment 20 seated in the rectangular apertures 14 in the outer portions of the base plate 16. The bolts 17 are fixedly embedded in the tie 13.

The base plate 16 has on opposite sides of rail 10 two

transverse deformations

21 and 22, which form respectively transverse, shallow grooves 23 and 24 in the underside of base plate 16. These grooves receive the lower, cross-legs 25 of rectangular loop straps 26, which are dimensioned to slip over the ends of base plate 16 prior to bolting of the latter to the tie 13.

The loop straps 26 comprise the lower, cross leg 25, side legs 27, and transversely sloped top cross leg 28. The loop straps 26 are seated in grooves 23 and 24 in an orientation whereby the lower faces of top cross legs 28 are substantially parallel to opposing, upper faces of holddown members 29.

A rail holddown member 29, e.g., a substantially flat plate, extends at an angular slope corresponding substantially to the respective slopes of upper surfaces 12 of base flange 11 through each loop strap. The under face 30 of plates 29 thereby substantially flatly rests on respective upper surfaces 12. The under face 30 is pressed tightly against the upper surface 12 by a compressively distorted, resilient bias member 31, which comprises in the illustrated embodiment a compressively distorted, solid elastomer body or block. There is a cross bar 32 extending transversely of the base plate 16 contiguous to the outer edges of each holddown member 29. The function of the cross bars 32 is to provide a seat or retainer against which the outer edge 33 of the substantially flat pressure plate 29 rests for proper positioning thereof, and also to prevent the latter from working outwardly. If desired, an elastomer pad 34 may be provided beneath the base flange 11 and underlying center portion of base plate 16.

The preferred pressure exerting members comprise an elastomer block or body which is compressively distorted in the assembly of the rail with the holddown devices. Prior to inserting them, these blocks or bodies are distorted by compression into a flattened form, with a dimension slightlydess than the spaces between cross legs 28 and holddown members 29. They are inserted in the distorted or compressed shape and thereafter allowed to recover via the elastic forces of the elastomer block or body toward its normal state, i.e., the shape it would assume without any compressive forces exerted thereon. In this elastic recovery, the elastomer bodies press against these holddown members and thus exert a downward thrust thereon. This force is in turn transmitted against the upper face 12 of the base flange 11 to hold the rail securely in position.

The opposing faces of the cross legs 28 and respective holddown members 29 are preferably substantially parallel, planar faces for achieving maximum effect of the thrust forces of the resilient bias members 3 1. The latter, in turn, are generally rectangular parallelepipeds in the relaxed (undistorted) state having a height or thickness considerably greater than the distance between said opposing faces.

As aforesaid, it normally would be diflicult 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 to 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 100 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 immobilization 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.

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. This combination utilizes 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.

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 illustraling 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 supported on members of a rail bed, the improvement comprising a rail holddown unit embodying a base plate, a loop-strap around said base plate adjacent said flange, said loop-strap having an upper cross leg extending transversely across and above said base plate, and a lower cross leg beneath said plate, a holddown member extending through said loop-strap with an inner portion thereof resting against the upper face of said flange, and a resilient bias member under compressive distortion between said upper cross leg and said holddown member and pressing said inner portion against said upper face.

2. The improvement as claimed in claim 1 wherein said bias member is a body of solid elastomer.

3. The improvement as claimed in claim 1 wherein said loop-strap is a substantially rectangular loop dimensioned to slip over an end of said base plate.

4. The improvement as claimed in claim 3 wherein said base plate has a transverse groove in the under face thereof, and the lower cross leg of said loop strap is seated in said groove.

5. The improvement as claimed in claim 4 wherein said holddown member comprises a substantially flat, cross plate extending through loop-strap, said bias member being compressively distorted between said upper cross leg and cross plate and pressing said cross plate downwardly, and the inner portion of the underface of said cross plate lying substantially flatly against said flange.

6. The improvement as claimed in claim 5 wherein said bias member is a body of solid elastomer.

References Cited UNITED STATES PATENTS 2,008,940 7/1935 Armstrong 238-304 2,215,104 9/1940 Kimmel 23 8-304 2,724,558 11/1955 Jones 23 8-349 ARTHUR L. LA POINT, Primary Examiner R. A. BERTSCH, Assistant Examiner US. Cl. X.R. 238283, 304, 310