GB2108184A

GB2108184A - Fish plate

Info

Publication number: GB2108184A
Application number: GB08230902A
Authority: GB
Inventors: Raymond Edwin Pedley; Victor Albers Saich
Original assignee: J Burns
Current assignee: J Burns
Priority date: 1981-10-27
Filing date: 1982-10-27
Publication date: 1983-05-11

Abstract

The invention provides a fish plate having a metal core formed with through holes with an overall covering 23 of an electrically insulating material. The covering is an epoxy resin. The invention provides a method of forming the fish plate by casting the resin round the metal core in a mould box assembly (Fig. 4). <IMAGE>

Description

SPECIFICATION Fish plate The present invention relates to a fish plate for use in joining adjacent railway lines.

Although continuous welded rail is now employed in railway tracks, it is necessary to have breaks in the lines and connect adjacent rail ends at a break with an electrically insulating connection, in order electrically to isolate different sections of track for signalling purposes.

It is known on this account to provide some form of electrically insulating material between a metal fish plate and the rail ends to be joined and the securing bolts; and it is also known to adhere fish plates to the rail ends with an insulating adhesive.

It is an object of the present invention to provide an improved insulated fish plate.

It is also an object of the present invention to provide a method of producing an insulated fish plate.

In one aspect, the invention provides a fish plate comprising a metal core formed with through holes to admit passage of the shanks of the securing bolts and with a covering of an electrically insulating material, being a hardened epoxy resin; the covering extending into the through holes to prevent contact of the shank of a bolt with the metal core.

Hereinafter for convenience, the fish plate thus formed may be referred to as an encapsulated fish plate.

The fish plate preferably has the surfaces thereof which are to abut against the side faces of the rail ends, of a complementary profile to those faces; and in this case, in use, the abutment surfaces are adhered to the rail ends with epoxy resin, preferably one in thixotropic form. It is also preferred that the metal core generally have the same cross-sectional shape as the fish plate. The covering may have a thickness of some 2 to 5 mm. A thickness of between 2 and 4 mm is preferred.

In use, the fish plates are employed together with a pair of washer plates respectively to bear the heads and nuts of the securing bolts; and in a preferred embodiment of the invention, a washer plate is adhered to a fish plate by the epoxy resin covering thereof, the plate being laid on the respective surface of the covering before it has hardened; or alternatively, it may be adhered to the fish plate after hardening of the covering.

The fish plate may be formed by casting the resin round the metal core; and a mould box assembly may be used to effect the moulding, the assembly comprising a base wall, side walls and removable end walls and a removable top wall, and pin and/or screw elements to centre the metal core therein; the base and top walls being formed with holes or at least recesses respectively to receive the ends of core plugs by which the through holes in the fish plate are maintained during moulding.

The top wall may also be formed with a recess to accept washer plates, which may be held in place by magnets secured to the top wall.

In carrying out the moulding, the end walls are fastened in place and the core plugs located in the recesses or holes in the base wall. In one embodiment the moulding is carried out at ambient temperature. An amount of resin and hardener mix is introduced into the mould and "larded" onto the end and side walls. The mould is then vibrated to remove air from the mix and the metal core entered and pressed down until it is in firm contact with pin elements provided on the base wall; the lateral walls having screw elements and the end walls pin and/or screw elements to ensure that the metal core is "centred" in the mould, that is, occupies a position such that a predetermined gap exists between the surfaces of the core and the internal surfaces of the mould.

The filling of the mould with the resin hardener mix is then completed with a small excess of resin being introduced, and the top wall is then pressed down onto the surface of the mix until in position. This may be done by a clamping arrangement. In this operation, the excess mix is exuded from the mould.

The resin is then allowed to harden following which the top wall, core plugs and end walls are removed and the screw elements retracted to allow removal of the encapsulated fish plate. This may conveniently be done with jacking screws. It has been found advantageous to provide vent holes in the top wall, for instance, across one end and/or along a lateral margin of the top wall to permit air to escape from the resin hardener mix. It is also advantageous to coat metal mould parts with PTFE or other release agent, except for the screw elements.

In another embodiment, the mould box is heated before the resin and hardener mix is introduced into the mould box. The metal core of the fish plate may also be preheated. It is preferred that the mould and/or core be heated to a temperature of not more than 40"C.

The present invention will now be described with reference to the accompanying drawings, in which: Figure 1 is an end elevation of a fish plate according to the present invention; Figure 2 is a plan view thereof; Figure 3 is a vertical longitudinal section through the fish plate of Fig. 1; Figure 4 is an exploded view of a mould box assembly for use in carrying out the method of the invention, and Figure 5 shows a top wall of the assembly in vertical longitudinal section.

Referring to Figs. 1 to 3 of the drawings, the fish plate provides a top surface 1 a part of which 1A together with a rear lateral surface 3 and a bottom surface 5 forms a complementary shape to the profile of a side face of a rail, these surfaces abutting against the rail side face in use of the fish plate. The remaining portion 1 B of the top surface is in the form of a groove or recess passing along the entire length of the fish plate to avoid obstructing the flange of a locomotive or carriage wheel. On the opposite, front, lateral surface 9 spaced apart washer plates 11, 1 3 are secured by means which will be made evident below.The body of the fish plate provides four through holes 1 5 to permit passage of the shanks of securing bolts (not shown) and each washer plate provides two through holes 1 7 and is positioned to align the holes thereof with respective ones of the holes 1 5. Two kinds of washer plate are employed, one being a flat plate as shown in the drawings to bear the nuts of the securing bolts and the other having diametrically opposed tongues pressed out from the plate to bear the heads of the securing bolts. Thus, any one fish plate will use one or the other kind of washer plate.

The fish plate comprises a steel core 21 covered on all its surfaces including those defining the through holes 1 5 with a layer 23 of hardened epoxy resin. Thus, the crosssectional shapes of the fish plate body and of the metal core are substantially the same. The thickness of the hardened resin layer is preferably 3mm, but may be between 2 and 5 mm.

Along the surface 1 B the thickness of resin is somewhat thinner and may, in theory, be absent altogether. In practice, a resin coating is always present. The hardened resin is an electrical insulator and insulates the metal core from the rail ends and from the securing bolts, and thereby insulates the rail ends from one another.

The fish plate in use is secured to the rail ends not merely by the securing bolts, but also by adhesion with an epoxy resin adhesive, i.e. the surfaces 1A, 3 and 5 of the fish plate being adhered to the respective portions of the respective side face of the rail ends; the adhesive preferably being one in thixotropic form. The epoxy resin is preferably a filled epoxy resin.

A fish plate as above described may be formed in the moulding box assembly illustrated in Figs. 4 and 5.

The assembly comprises a base wall 31 and integral therewith lateral walls 33, 35, those three walls forming a trough-like structure of a general "U" shape in cross-section. The trough is closed at each end by end walls in the form of detachable plates 37, 39; the plates being fastened in place by cap screws 41 passing through bores in the plates and received in blind bores in the lateral walls 33, 35 of the mould.

The base wall 31 has four through bores 4-1 formed therein to seat respective core members 43; each core member being formed at the respective end with a spigot or stub 45 to fit into the respective bore firmly to hold the core member upright.

Each of the lateral walls 33, 35 adjacent each end thereof is also bored to receive therethrough the shank of dome-ended screw 51 used for positioning the metal core of a fish plate in the mould. A similar screw may be provided also in one or both of the end walls although in this instance each end wall is shown provided with a dome-headed spacer or stand-off pin 53; and similar pins 55 are mounted in the base wall. These pins determine the space to be left between the end walls and the base wall from the respective surfaces of the metal core and thereby determine the thickness of the resin covering on those surfaces.

The mould box is closed by a top wall which may be regarded as being formed of two parts, namely, a flat plate 61 and a filler block 63; the purpose of the latter being to conform the internal cross-sectional shape of the mould box to produce the surface 1 B of the fish plate.

The top plate 61 comprises four through bores 71 therein in which are received the upper ends of the respective core members; and the plate is also recessed as at 73 on its underside to accept therein a washer plate such as washer plate 11 or 13; the washer plate being held in place by magnets 75 secured in recesses formed in the top plate.

The top plate is also formed with a series of small bores 81 for venting air from the mould therethrough, and further bores 83 to receive jacking screws (not shown) by which the plate is lifted after a moulding operation.

In forming a fish plate, the precedure described above is followed, the space or standoff pins providing the requisite spacing of the metal core from the respective surfaces of the mould and the stand-off screws being adjusted correctly to position the metal core with respect to the lateral walls of the mould. The filler block is positioned in the mould prior to introduction of the second lot of resin/hardener mix and it is sufficient for it merely to be pressed into position although it could be held in position by suitable supports. After opening of the mould following completion of the moulding operation, the core members may be knocked out from the bores in the base wall.

Although there is a possibility of forming the walls of the mould of plastics material, it is presently preferred to form them of metal with the base, side and end walls being of steel or cast iron and the top plate of aluminium. The filler block and the core members may be formed of polyethylene or any other plastics material that will give an easy release from the hardened epoxy resin. For this purpose, all the metal parts of the mould, other than the stand-off and jacking screws, may be coated with PTFE. Further to assist release from the mould, jacking screws may also be provided in the base wall and the recesses 73 may be formed with a slight draught.

In positioning the top plate in a moulding operation, the underside of the washer plate is laid on the resin/hardener mix although it is not impressed therein to any appreciable extent, i.e., it lies substatially on the surface of the mix. Once the mix hardens, this is sufficient to provide a firm bond between the washer plate and the layer of hardened resin.

The moulding operation may be effected by injection of the resin/hardener mix into the closed mould box viz by injecting the mix under pressure through a suitable port or ports formed in the mould box.

Claims

1. A fish plate comprising a metal core formed with through holes to admit passage of the shanks of the securing bolts and with a covering of an electrically insulating material, being a hardened epoxy resin; the covering extending into the through holes to prevent contact of the shank of a bolt with the metal core.

2. A fish plate as claimed in claim 1, in which the surfaces thereof which are to abut against the side faces of the rail ends, have a complementary profile to those faces; and in use, the abutment surfaces are adhered to the rail ends with epoxy resin.

3. A fish plate as claimed in claim 2, in which the epoxy resin is in the thixotropic form.

4. A fish plate as claimed in claim 1, 2 or 3, in which the epoxy resin is a filled epoxy resin.

5. A fish plate as claimed in any preceding claim, in which the metal core has generally the same cross-sectional shape as the fish plate and that the covering has a thickness of 2 to 5 mm.

6. A fish plate as claimed in any preceding claim, further comprising a pair of washer plates which are adhered to the fish plate by the epoxy resin covering thereof.

7. A fish plate constructed and arranged substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

8. A method of forming a fish plate having a metal core with an overall electrically insulating covering of epoxy resin comprising casting therein round the metal core.

9. A method as claimed in claim 8, in which a mould box assembly is used to effect the moulding.

10. A method as claimed in claim 9, in which the mould box assembly comprises a base wall, side walls and removable end walls and a removable top wall, and pin and/or screw elements to centre the metal core therein; the base and top walls being formed with holes or at least recesses respectively to receive the ends of core plugs by which the through holes in the fish plate are maintained during moulding.

11. A method of forming a fish plate having a metal core with an overall electrically insulating covering of epoxy resin comprising positoning the metal core in a mould so that it contacts pin elements provided on a base wall of the mould, centering the core in the mould by means of pins or screws mounted in the lateral walls and end walls, said pins or screws determining the thickness of the epoxy resin coating to be applied, positioning a top wall on the mould and introducing resin and hardener mix into the mould.

1 2. A method as claimed in claim 11, in which the resin and hardener mix is introduced in two stages; the first prior to insertion of the core into the mould, and the second prior to positioning the top wall on the mould.

1 3. A method as claimed in claim 11, in which the resin and hardener mix is injected under pressure into the closed mould through a suitable port or ports in the mould box.

14. A method as claimed in claims 11, 1 2 or 13, in which the mould box is preheated.

1 5. A method as claimed in any of claims 11 to 14, in which the core is pre-heated.

16. A method as claimed in claim 14, in which the mould is preheated to a temperature of not more than 40"C.

1 7. A method as claimed in claim 11 or 12, in which placing the top wall in position causes excess mix to be exuded from the mould.

1 8. A method as claimed in any of claims 10 to 17, in which vent holes are provided in the top wall of the mould.

1 9. A method as claimed in any of claims 10 to 18, in which the mould parts with the exception of the screw elements are coated with a release agent.

20. A method as claimed in claim 19, in which the release agent is P.T.F.E.

21. A method as claimed in any of claims 10 to 20, in which the top wall is formed with a recess to accept washer plates, which may be held in place by magnets secured to the top wall.

22. A method of forming a fish plate having an overall electrically insulating covering substantially as hereinbefore described with reference to the accompanying drawings.