US3358927A

US3358927A - Rail tie down assembly

Info

Publication number: US3358927A
Application number: US547233A
Authority: US
Inventors: Richard D Hein; John A Welch
Original assignee: General Tire and Rubber Co
Current assignee: Aerojet Rocketdyne Holdings Inc
Priority date: 1966-05-03
Filing date: 1966-05-03
Publication date: 1967-12-19
Anticipated expiration: 1984-12-19

Description

'Dec. 19, 1967 R. D. HEIN ET AL 3,358,927 I RAIL TIE DOWN ASSEMBLY Filed May 5, 1966 IIIIIIII IIIIIIII ZIIIIIVI IN VENTORS ch John A. We! lZchar-d D. Hczin 7 ATTORNEYS United States Patent 3,358,927 RAIL TIE DOWN ASSEMBLY Richard D. Hein, Wabash, Ind., and John A. Welch,

Northampton Township, Summit County, Ohio, as-

signors to The General Tire & Rubber Company, a corporation of Ohio Filed May 3, 1966, Ser. No. 547,233 6 Claims. (Cl. 238-338) ABSTRACT OF THE DISCLOSURE A railroad track is secured to a cross tie by an assembly comprising a pair of rail clamps secured to a base plate which is, in turn, anchored to the cross tie. A layer of reinforced elastomeric material is compressed between the rail and the assembly and serves to provide sound and vibration attenuation as well as electrical isolation.

The invention finds particular use in applications wherein concrete is used to replace wooden cross ties and/or the conventional rock and gravel roadbed without any appreciable increase in the magnitude of these aforementioned disturbances. These objectives are accomplished by using an assembly comprising a tie plate, a pair of clamps, and an elastomeric pad compressibly held between and separating the rail from the tie plate and clamps.

In designing and constructing a rail tie down assembly, several factors must be considered. The first of these is that the assembly must securely hold the rail, yet be compliant so as to permit a limited amount of longitudinal, vertical, and lateral movement. A second factor is the isolation of noise and other vibrations which are caused by the wheels rolling over the rail. Electrical isolation is also important. In addition to the above factors, the assembly should be simple yet rugged and should be easy to install and replace.

One of the intended objects of the present invention is to provide a rail tie down assembly which accomplishes all of the aforementioned purposes.

Another object is a rail tie down device comprising a tie plate, an elastomeric isolator pad, and clamping means adapted to'be secured to said tie plate and to hold the elstomeric pad under a state of compression.

These and other objects are accomplished in the mannertobe described in the following discussion, with particular reference being given to the drawings in which:

FIGURE 1 is a perspective view, partially in cross section, of the novel tie down assembly with a rail securely clamped therein; 1

FIGURE 2 is a cross section taken along lines 22 of FIGURE 1; and

FIGURE 3 is an enlarged partial view of a portion of the assembly shown in FIGURE 2.

Referring now to the drawings in which the same number is used to refer to identical parts, there is shown a tie plate 2 resting-on a cross tie 9' (FIGURE 2) and secured thereto by suitable means such as bolts 6 threaded into suitable anchors 8 embedded in the cross tie. Lock washers 10 are used to prevent loosening of the bolts 6. Means such as a plurality of additional bolt holes 7 are provided to permit lateral positioning and adjustment of the plate.

The tie plate is substantially rectangular in shape with its longitudinal direction extending at right angles to the rail 36. The plate is essentially planar except for a pair of elevations '12 extending parallel to one another and to the rail. Each elevation is joined to the planar surface of the plate by a pair of generally vertical side walls, an inner side wall 16 facing'the rail, and an outer wall 18 remote from the rail. The elevation and side walls cooperate to form an inverted U-shaped channel 14 on the underside of the plate.

A pair of side clamps 20, of approximately the same width as the tie plate, are disposed on either side of rail 36, each clamp containing a downwardly-extending leg 22 and an upper portion 24 which follows the contour of the flange 32 and web 34 of rail 36. Each clamp is secured to one of the elevations of the tie plate by suitable means such as a hex head nut 40 and bolt 38. The sides of the channel 14 are preferably sufliciently close to one another so that the nut cannot rotate in the channel when assembling the clamp 20 to the tie plate, thus obviating the necessity of using a wrench or special tool to hold the nut.

A downwardly depending shear flange 42 extends across the clamp 20 in abutting contact with the inner side wall 16. The purpose of this flange is to absorb any shear stresses that would normally be transmitted to the bolt 38 by the lateral forces developed when the rail is secured in place, as well as those resulting from a train traversing the rail. The flange also assists in aligning the clamps in relation to the tie plate during assembly. The thickness and length of each flange and the dimensions of the inner side wall 16 are designed so as to be capable of absorbing these various lateral forces, and are dependent upon such factors as the type of materials being used, the processes of fabrication, and the nature of various heat treatments of these parts, etc.

The downwardly depending leg 22 of each side clamp 20 contacts the upper surface of the tie plate outside of the elevation to which the clamp is secured, and serves to reduce the magnitude of the tensile stresses imposed on bolt 38 by the various static clamping forces and the dynamic flexural forces created by the wheels of a train rolling over the rail. These forces produce a moment about the leg 22 which is resisted by a moment applied in the opposite direction and comprising the product of the tensile force on the nut and bolt and the distance between the bolt and the point of contact between the clamp leg and the tie plate. An increase in the length of the leg causes a corresponding decrease in the tensile force on the bolt thereby relieving the stress thereon.

The web and flange of the rail are completely separated and isolated from the two side clamps 20 and the tie plate 2 by an elastomeric pad 28 inter-posed therebetween. This pad, preferably molded in two pieces for simplicity of installation, has a uniform thickness which may range from approximately 4" to When assembled and clamped into place, the body of the elastomer is uniformly compressed approximately 10 percent. The weight of a train passing over the rail can cause localized pressures as great as 1000 to 1500 p.s.i. to be imposed on the portion of the elastomer immediately beneath the rail while concomitantly causing a reduction in the amount of the pressure imposed on other portions of the pad. However, the amount of initial precompression is preferably sufliciently great to insure that all portions of the elastomer, particularly between the clamp and the rail, remain compressed. Thus, the assembly continues to firmly grip the rail even while the latter is undergoing longitudinal and transverse movement.

To increase the resistance of the elastomer to compressive deformation, it is desirable to utilize an elastomeric pad having a high shape factor, commonly described as the ratio of the load area to the bulge area. This is generally accomplished by controlling the dimensions of the pad or by embedding suitable reinforcing means in the elastomer in a plane which is perpendicular to the direction of the intended forces. One or more spaced apart, thin metal plates can be used for this purpose, but owing to the irregular shape of the isolation pad 28, and the difliculty of forming metal to this shape, pieces of textile such as square woven nylon or rayon, or other flexible material such as sheets of woven or matted glass fibers, are preferred. This reinforcing material is typically embedded within the elastomer in the mold, whereby vulcanization bonds the elastomer permanently to the material.

Referring now to FIGURE 3, showing the upper portion of the right hand clamp of FIGURE 2, it is noted that the rubber-contacting edge of each of the side clamps 24 is provided with a small lip or flange 26, the purpose of this lip being to contain the body of the elastomer within the dimensional confines of the side clamp. This lip preferably extends along the top and both sides of the clamp, including the flange 42 thereof.

The elastomeric pad 28 is provided with a suitable stiffening means such as fabric 30 embedded therein, and is molded so as to have an overlapping lip 29. The entire pad provides electrical isolation between the rail and the tie down assembly, this being desirable in circumstances where the isolation or stray electrical currents is necessary or where the rail is used as a current-transporting means. The lip 29 provides further insulation at the edges of the clamps and the tie plate thereby preventing a spark from jumping between the rail and the metal components of the tie down assembly. The dimensions of this lip are dependent on, among other factors, the thickness of the compressed pad, the magnitude of any stray currents, and the electrical properties of the various components.

The isolation pad can be fabricated from any one of a number of suitable elastomers including, but not limited, to neoprene, ethylene propylene rubber, or its terpolymer, natural rubber, butyl, chlorobutyl, and polypropylene oxide. Neoprene is notably resistant to oil, a property that is desirable for this type of installation. Although not as good in this former respect, the other elastomers generally have higher values of electrical resistance than does neoprene. Other properties which should also be considered are compression set, tensile strength, and hot and cold flexibility as well as the processing characteristics of the elastomer. Because the elastomer is under compression, ozone attack does not present a serious problem. Therefore, elastomers which do not have exceptional ozone resistance, but are otherwise suitable for the intended purpose, can be used.

The isolation pad used with the present invention is preferably produced by molding. In a typical molding operation, a masterbatch, including the elastomeric compound :as well as various fillers, curatives, and processing aids, is prepared and is calendered into thin sheets. These sheets are then laid into the mold cavity with the reinforcing layers of fabric or the like interposed therebetween until the required thickness is obtained. The mold is then closed and the contents thereof heated under pressure to produce the shaped cured product.

As an alternative, where permitted by the cross-sectional design of the pad, the elastomer can be extruded in continuous lengths and thereafter cut to the required width. This is permissible when the design of the pad does not include a lip.

The tie plate and side clamps can be produced by any of the conventional metal forming techniques such as casting or the like. However, because of their simplicity of design, these components readily lend themselves to shaping by cold or hot rolling.

The track tie down assembly of the present invention can be used with present road beds of rock, and gravel and utilizing wooden timbers as cross ties, or alternatively can be used with the more advanced concepts of railroad construction involving the use of modern structural materials such as concrete for the road bed and/or the cross ties. Furthermore, the tie plate can be secured to the cross tie by means other than those described, and can be provided with a variety of means for adjusting and centering the tie plate in respect to the rail. Moreover, it is contemplated that a thin layer of elastomer or a film of polymeric material such as polyethylene can be interposed between the tie plate and the cross tie.

There are several design factors of this novel device which appear to contribute to the dampening of vibration. One is the use of a layer of elastomer to completely separate the rail from the tie assembly. The stiffening layer of fabric embedded in the rubber is also felt to be a contributing factor. Securely gripping the web as well as the flange of the rail is also felt to contribute to the diminution of the noise level.

Through the use of a shear flange and a tension-absorbing leg, the side clamp is designed to not only grip the rail and compressibly hold the rubber, but also to alleviate the stress on the bolt which secures the clamp to the tie plate thereby minimizing the likelihood of this bolt becoming sheared or otherwise broken. Instead, any forces which are great enough to cause any damage are likely to shear or snap one of the bolts holding the tie plate to the substructure, i.e., the cross tie. Thus, even though the rail becomes detached from the cross tie, it will still be clamped securely by the .tie down assembly which would continue to at least partially attenuate noise and vibration.

The optimum distance between adjacent tie down assemblies along the length of a rail is determined by a number of factors including the length and other dimensions of the rail section and the size of each assembly. A typical spacing between tie down assemblies that are about 6" wide is 30" to 36".

In the past, spaces were provided between adjacent rails to allow for thermal expansion and contraction of each rail. More recently, however, it has been found that by securely gripping the rail this normal longitudinal movement can be limited and converted into internal stresses within the rail, thus making it possible to weld the sections together into long continuous expanses of track. Using the tie down assemblies of the present invention, the rail can be tightly held so as to effectively prevent slipping between the rail and the elastomer and to resist these thermal forces which are on the order of 2000 to 3000 pounds. These forces cause the elastomer to deflect a slight amount in the longitudinal direction. For example, when a 6-inch wide 60 durometer neoprene isolation pad having an initial thickness of about 0.40" and reinforced with a single layer of square woven fabric is subjected to about 10 percent compression during assembly, this longitudinal deflection amounts to less than A3" in either direction. It should be noted that the deflection rate can be easily adjusted by changing one or more of the variables such as thickness, hardness, or width of the isolation pad.

It should be noted that dimensional variations can be made in the tie down assembly without adversely affecting the operation of the assembly and Without departing from the scope of the invention. For example, the width and length of the tie plate, as well as the width of the side clamps, can be varied within certain limits. If desired, the assembly can be used at the junction of two rails to hold the ends of the rails together. For this use, however, the width of the assembly is preferably considerably greater than that of a similar unit used on the rail intermediate its ends.

Instead of being provided with one tension-relieving leg in continuous contact with the tie plate, the side clamp can be provided with two or more spaced-apart legs straddling the plate tie down bolt. Although the upp Portion of the side clamp is shown extending up slightly more than one half of the distance between the flange of the rail and the top of the nail, this variable can be changed within limits. For example, the side plate can extend by nearly the entire height of the web, or it can be made considerably shorter than shown to provide greater or lesser Sound attenuation, If necessary, reinforcing gussets or other means can be used to strengthen this part of the side clamp in contact with the web of the rail.

Although the thickness of the compressed portion of the rubber, as shown in FIGURE 2, is uniform, it is understood that the portion of the pad underneath the rail can be made thicker or thinner than the portion between the rail and the side clamps. Furthermore, the shape factor of the rubber in these two locations can differ from one another.

The underside of the tie plate elevation is channelshaped for convenience in bolting the side clamps to the tie plate. However, this portion of the plate can be made solid and then tapped to receive the clamp hold-down bolt thereby eliminating the need for a channel and hex head nut.

Other variations can be made without constituting a substantial departure from the essence of the present invention, which is defined by the following claims, in which are claimed:

1. An assembly for supporting and securing a rail on and to a substructure such as a cross tie and including (a) a substantially rectangular tie plate secured to said substructure underneath and transverse to said rail, said tie plate including a pair of inverted U-shaped channels extending in the direction of the rail and spaced laterally therefrom, each of said channels including a pair of sides, an inner side facing the rail and an outer side remote from said rail,

(b) a pair of rigid nail clamps and associated threaded means to secure the same to said channels, each clamp conforming to the contour of the flange and web of the rail and extending up a substantial disstance toward the upper part of said rail, provided with a downwardly extending flange adapted to engage the inner side of said channel to absorb transversely directed forces imposed on said assembly, and downwardly curving means in contact with the tie plate outside of said channel to relieve the tensile stress on the threaded securing means, and

(c) elastomeric means completely separating the rail from the tie plate and the clamps and providing electrical insulation therefrom, the portion of said elastomeric means interposed between the rail and said plate and clamps having a uniform thickness and being uniformly compressed, the improvement comprising flexible reinforcing means embedded within said elastomer, approximately midway between the two surfaces thereof in the portion under compression between the rail and the clamps and tie plate.

2. The assembly of claim 1 with said reinforcing means comprising a fabric.

3. The assembly according to claim 2 wherein said fabric is selected from the group consisting of square woven nylon fabric, square woven rayon fabric, and a mat of glass fibers.

4 The assembly according to claim 1 wherein the portion of the elastomeric means separating the rail and various parts of the assembly is compressed between approximately 5 and 15 percent.

5. The assembly according to claim 4 wherein the edge portion of the face of each clamp in oontact with the elastomeric isolator is provided with an elastomer restraining flange.

6. The assembly according to claim 5 wherein the elastomer is provided with a lip which overlays the elastomer restraining flange and at least partially covers the exposed edges of the clamps and the tie plate in proximity of said rail.

References Cited UNITED STATES PATENTS 1,858,868 5/1932 Welton 238304 2,670,136 2/1954 Moses 238283 3,189,279 6/1965 Horniblow et a1 '238-283 3,223,328 12/1965 Moses et a1. 238-249 FOREIGN PATENTS 1,178,883 1/1964 Germany.

ARTHUR L. LA POINT, Primary Examiner.

R. A. BERTSCH, Assistant Examiner.

Claims

1. AN ASSEMBLY FOR SUPPORTING AND SECURING A RAIL ON AND TO A SUBSTRUCTURE SUCH AS A CROSS TIE AND INCLUDING (A) A SUBSTANTIALLY RECTANGULAR TIE PLATE SECURED TO SAID SUBSTRUCTURE UNDERNEATH AND TRANSVERSE TO SAID RAIL, SAID TIE PLATE INCLUDING A PAIR OF INVERTED U-SHAPED CHANNELS EXTENDING IN THE DIRECTION OF THE RAIL AND SPACED LATEALLY THEREFROM, EACH OF SAID CHANNELS INCLUDING A PAIR OF SIDES, AN INNER SIDE FACING THE RAIL AND AN OUTER SIDE REMOTE FROM SAID RAIL, (B) A PAIR OF RIGID RAIL CLAMPS AND ASSOCIATED THREADED MEANS TO SECURE THE SAME TO SAID CHANNELS EACH CLAMP CONFORMING TO BE CONTOUR OF THE FLANGE AND WEB OF THE RAIL AND EXTENDING UP A SUBSTANTIAL DISSTANCE TOWARD THE UPPER PART OF SAID RAIL, PROVIDED WITH A DOWNWARDLY EXTENDING FLANGE ADAPTED TO ENGAGE THE INNER SIDE OF SAID CHANNEL TO ABSORB TRANSVERSELY DIRECTED FORCES IMPOSE ON SAID ASSEMBLY AND DOWNWARDLY CURVING MEANS IN CONTACT WITH THE TIE PLATE OUTSIDE OF SAID CHANNEL TO RELIEVE THE TENSILE STRESS ON THE THREADED SECURING MEANS, AND (C) ELASTOMERIC MEANS COMPLETELY SEPARATING THE RAIL FROM THE TIE PLATE AND THE CLAMPS AND PROVIDING ELECTRICAL INSULATION THEREFROM, BETWEEN THE RAIL AND ELASTOMERIC MEANS INTERPOSED BETWEEN THE RAIL AND SAID PLATE AND CLAMPS HAVING A UNIFORM THICKNESS AND BEING UNIFORMLY COMPRESSED, THE IMPROVEMENT COMPRISING FLEXIBLE REINFORCING MEANS EMBEDDED WITHIN SAID ELASTOMER, APPROXIMATELY MIDWAY BETWEEN THE TWO SUFACES THEREOF IN THE PORTION UNDER COMPRESSION BETWEEN THE RAIL AND THE CLAMPS AND TIE PLATE.