GB2034788A

GB2034788A - Rail Fastening Members

Info

Publication number: GB2034788A
Application number: GB7916524A
Authority: GB
Original assignee: LONDON TRANSPORT EXECUTIVE
Current assignee: LONDON TRANSPORT EXECUTIVE
Priority date: 1978-09-05
Filing date: 1979-05-11
Publication date: 1980-06-11

Abstract

An 'S' shaped rail fastening clip is located within grooves (5a, 6a) in the parallel vertical faces (5, 6) of a respective anchorage block (1, 2) a first straight portion (12) of the clip is located within one groove (5a), a second straight portion (13) is located within the other groove (6a) and the third straight portion of the clip exerts a force on the base of the rail (3) or on rail-locating blocks (8, 9). <IMAGE>

Description

SPECIFICATION Improvements in and Relating to Rail Fastening Members This invention relates to rail fastening members and particularly to rail fastening members for use with rails having a flanged base.

Heretofore rail fastening clips have been associated with respective mounting blocks located one on each side of a rail adjacent the base flange of the rail and the clips have been shaped such as to exert a force on the base flange of the rail in a fixed position with respect to the mounting blocks.

An object of the present invention is to provide a mounting block arranged to lie adjacent a rail and to accommodate a rail clip, the block being so formed that when part of the clip is located within the block, the clip is deformed to exert a force between the block and the rail to retain the rail in fixed relation to the block.

Thus, according to the present invention there is provided a rail fastening device comprising at least one mounting block arranged to be fixed adjacent a flanged base of a rail, said at least one mounting block having opposed surfaces extending substantially normal to the base on which the rail is mounted, each surface having a groove extending substantially parallel to the base flange of the rail, and a clip including two substantially parallel portions, which are arranged to be located in the respective grooves in the block, and the grooves in the block being formed such that when the said two portions of the clip are located in the respective grooves in the block, a third portion of the clip exerts either directly or indirectly, a force on the base flange of the rail.

In one embodiment of the invention the clip is of 'S' shape formed of five distinct portions, a first straight portion being followed by a first curved portion linking the first straight portion with a second straight portion lying parallel to the first straight portion and followed by a second curved portion reversely bent with respect to the first curved portion and linking the second straight portion to a third straight portion lying parallel to the first and second straight portions of the clip. A mounting block is arranged to be fixed to the track base or to a sleeper which may be of concrete, and is located adjacent the flanged base of a rail.Two mounting blocks are provided, one on each side of the rail and each block has two opposed surfaces extending substantially normal to the track base, each surface being provided with a groove lying parallel to each other and to the rail but slightly offset from one another such that when the first and second straight portions of the clip are located in the respective grooves of a block, the third straight portion of the 'S' clip lying parallel to the first and second straight portions, is located in contact with the base flange of the rail or in contact with means associated therewith such as to exert a force between the fixed mounting block and the base flange of the rail to retain the rail in position on the base track and in fixed relation to the mounting block.

The invention will now be described by way of example only with particular reference to the accompanying drawings wherein: Figure 1 is a perspective view of the rail fastening device of the present invention with part of the rail broken away; Figure 2 is a plan view of a 'S' type clip and Figures 2a, 2b and 2c show the dimensional features of the clip; Figures 3a and 3b are side and end elevations respectively of a mounting block; Figures 4a and 4b are side and plan views of a S-clip lying in a single plane; Figures 5a, 5b, Sc and 5d are various views of non-planar S-type clips; Figures 6a and 6b show plan and side elevation views of various S-shaped clips; Figures 7a and 7b are plan and side elevational views of a modified rail clip;; Figures 7c and 7d are plan and side elevational views of the clip of Figures 7a and 7b located in the groove of a mounting block; Figures 8a and 8b are plan and side elevational views respectively of a further modification of Sclip and Figures 8c, 8d and 8e show various contours for the ends of the S-type clips.

Referring initially to Figure 1, the rail fastening device includes a pair of mounting blocks 1, 2, located one on each side of a flat bottom rail 3, having a flanged base 4. Each block 1, 2, is of rectangular section having opposed parallel faces 5, 6, each formed with a groove 5a, 6a, for a purpose hereinafter described, the two opposed faces 5, 6, of each block being substantially normal to the plane containing the base 7 of the rail.

The blocks 1, 2, may be mounted immediately adjacent the base 4 of the rail 3, or locate.d adjacent intermediate blocks, 8, 9, located adjacent the base 4 of the rail as shown in Figure 1. The blocks 1, 2, are fixed to the track base or sleeper by means of projecting feet 10 (Figures 3a, 3b) set into the concrete of the base or sleeper.

An 'S' shaped clip 11, such as shown in Figures 4a, 4b, in which all the limbs lie in the same plane is arranged to be located within the grooves 5a, 6a, formed in the mounting blocks 1, 2. Each 'S' clip comprises 3 parallel straight sections 12, 13, 14, linked by curved portions 15, 1 6. As shown in Figure 1, a first straight portion 12 is located within groove 5a, a second straight portion 13, is located within groove 6a and the third straight portion exerts a force on the intermediate member 8, 9 to retain the rail 3 in fixed relation to the mounting blocks 1, 2.

Where no intermediate blocks 8, 9, are provided, the straight limbs 14 of the 'S' shaped clip exert a force on the flanges 4 of the rail 3.

The two grooves 5a, 6a of each mounting block 1, 2, are positioned on the respective faces 5, 6, such that when the clip is in position with limb 12 in groove 5a and limb 13, in groove 6a, the latter limb 13 is displaced below the level of the remaining straight limbs 12, 14. This displacement of the intermediate straight limb 1 3, results in torsional, shear and bending deformation of various parts of the clip, to produce the clamping effect which is applied to the flanged base of the rail.

To facilitate diving and to deform the intermediate limb 13 of the clip below the level of the remaining limbs 12, 14, a sloping entry is provided on the groove in the face 6 of the mounting block nearest to the rail 3.

Although the drawings illustrate S-clips of circular cross-section, the clips may be of any required cross-section and the limbs need not lie in the same plane. Non-planar clips are shown in Figures 5a to 5d and various clip shapes are shown in Figures 6a and'6b. A vibration resistant ball ended type S-clip is shown in Figures 7a to 7d and in Figures 8a, 8b and Figures 8c, 8d and 8e, various end counter load distributing features are shown for the S-clips.

The S-clip in its simplest form is not handed and it would be difficult to insert the clip incorrectly in the track.

Altering the displacement of the three straight portions of the clip changes the force exerted on the rail. Other factors affecting the magnitude of the holding force are the size of the metal from which the clip is made, the radius of the reverse bends between the straight portions and the nature of the material in which it is made.

A formula relating these variables in a way that gives a close degree of approximation for circular bar is:- 4r2.L+ 1 .5.r3.,r 7d.r3 Q=- + G.J 2.E.I where Q=deflection at point of contact for a unit clamping force r=radius (mean) of reverse bends.

L=length from nodal plane to junction of first reverse bend and second straight portion G=Modulus of rigidity for material J=Section modulus for torsion E=Young's modulus for material l=Section modulus for bending The ratio circumference/diameter for a circle (see Figures 2, 2a, 2b, 2c) Some form of insulating material may be placed between the clip and the rail and the mounting block and rail to isolate the rail for signalling or other purposes. Because most insulating materials would be damaged by the intense pressure under the contact point of the clip the clip may be formed with a broad bearing surface to distribute the load. (See Figure 8).

If limits are fixed on the minimum permitted deflection under load and the maximum permitted principal shear stress it is possible to determine a range of diameters for round bar which will satisfy the requirements for a given configuration. For a simple, plane version of the clip it can be shown that to a close degree of approximation

k > D > 3Cwh F 32(4.r.2L+ 1 .5.r3.7r) 32r3 Q'min E z Q' min To xG E Q'min=minimum deflection permitted per unit load D=diameter of bar (unknown) 32.r C= To max=maximum permitted principal shear stress per unit load By way of example for a material and configuration such that:: E=206 KN/mm2 G=75.5 KN/mm2 r=25 mm L=35 mm Qmin=3 mm Tó max=0.45 KN/mm2 Load 'P'=500 Kgf=4.9033 KN Q'min=0.61 18328 mm/KN To max=0.0917749 KN/mm2/KN By calculation K=24165.838 mm5/KN C=254.64812 mm Thus but therefore

14.09 mm > D314.05 mm Any diameter of wire between the limits 14.05 mm and 14.09 mm would meet the specified requirements. In practice these requirements would probably be met sufficiently closely by wire 14 mm dia or 9/16" (14.3).

It will be appreciated that the invention is susceptible to considerable modification and is not to be deemed limited to the particular features described by way of example only. For instance, although the track base may be of concrete and sleepers of concrete have been specifically referred to, the track base may be formed of any material and the projecting feet 10 shown in Figures 3a, 3b may be dispensed with and any means used to fix the blocks 1, 2, or to locate the blocks in the track base.

Claims

1. A rail fastening device comprising at least one block arranged to be fixed adjacent a flanged base of a rail, said at least one mounting block having opposed surfaces extending substantially normal to the base on which the rail is mounted, each surface having a groove extending substantially parallel to the base flange of the rail, and a clip including two substantially parallel portions, which are arranged to be located in the respective grooves in the block, and the grooves in the block being formed such that when the said two portions of the clip are located in the respective grooves in the block, a third portion of the clip exerts either directly or indirectly, a force on the base flange of the rail.

2. A rail fastening device as claimed in Claim 1 wherein the clip is of 'S' shape and includes a first straight portion followed by a first curved portion linking the first straight portion with a second straight portion lying parallel to the first straight portion and followed by a second curved portion reversely bent with respect to the first curved portion and linking the second straight portion to a third straight portion lying parallel to the first and second straight portions of the clip.

3. A rail fastening device as claimed in Claim 2 comprising a pair of mounting blocks arranged to be located one on each side of the rail, the grooves in the two opposed surfaces of each block being sufficiently offset from one another such that when the first and second straight portions of the clip are located in the respective grooves of the block, the third straight portion of the clip is located in contact with the respective base flange of the rail or in contact with means associated therewith such as to exert said force between the mounting block and the respective base flange of the rail.

4. A rail fastening device as claimed in Claim 1 wherein said at least one mounting block is arranged to be located adjacent a respective intermediate block located adjacent the base flange of the rail, the third portion of the clip being arranged to exert a force on the intermediate member to retain the rail in fixed relation to the said at least one mounting block.

5. A rail fastening device as claimed in any preceding claim wherein all the said portions of the clip lie in the same plane.

6. A rail fastening device as claimed in any one of claims 1 to 4 wherein the clip is of non-planar configuration.

7. A rail fastening device as claimed in Claim 1 wherein said two substantially parallel portions of the clip terminate in ball-shaped extremities arranged to be located in complementary shaped grooves in the block.

8. A rail fastening device substantially as hereinbefore described and as shown in Figures 1 to 4a and 4b of the accompanying drawings.

9. An S-shaped clip for a rail fastening device and substantially as hereinbefore described and as shown in Figures 5a to 5d, or Figures 6a and Sb, or Figures 7a to 7d or Figures 8a to 8e of the accompanying drawings.