GB2271027A

GB2271027A - Insulator assemblies for a conductor rail

Info

Publication number: GB2271027A
Application number: GB9220330A
Authority: GB
Inventors: David Julian Hartland
Original assignee: Brecknell Willis and Co Ltd
Current assignee: Brecknell Willis and Co Ltd
Priority date: 1992-09-25
Filing date: 1992-09-25
Publication date: 1994-03-30
Anticipated expiration: 2012-09-25
Also published as: GB2271027B; GB9220330D0

Abstract

An insulator assembly for use with a conductor rail 18 comprises a base plate 11, an insulator body 10, and a cap having locking formations (16, Figures 1 and 2) to grip the bottom of the rail. The plate has a spigot 14 of non-circular cross-section which is received in a socket in the body. When the body is raised on the spigot, it can be rotated to lock or unlock the formations (16) about the rail 18. Shims 22 may be used to adjust the height of the rail. The body may be of polyester, epoxy resin or porcelain. In one embodiment (Figures 3 and 4) the porcelain body (23) has an iron locking cap (25) and a nylon sheath (26) between the spigot and the socket. <IMAGE>

Description

INSULATOR ASSEMBLIES Field of the Invention This invention relates to insulator assemblies for use in supporting conductor rails such as are used in electric railway systems and in other transportation systems such as overhead conveyors.

Traditional conductor rails have been of steel and the insulator assemblies have comprised a porcelain insulator fixed to a base plate which is attached to a sleeper and with a Ushaped cradle member fixed on top of the porcelain insulator so that the arms of the U extend one on each side of the conductor rail. During passage of a vehicle, the sleeper can drop and the arrangement is thus such that, as the sleeper moves downwardly relative to the rail, the cradle member will move downwardly with the sleeper but the arms of the cradle member are of such length that they will continue to embrace the conductor rail to prevent lateral movement thereof.

Although the insulator assemblies described above are satisfactory for use with steel conductor rails, and have been in use for many years, they are not satisfactory for use in connection with much lighter conductor rails which comprise a main body of aluminium and a facing layer of stainless steel.

Such a conductor rail, and a method of making such a conductor rail, are described in Patent Specification No. 2 231 544 to which reference should be made.

It is accordingly an object of the present invention to provide an improved form of insulator assembly for use with a conductor rail. More specifically, it is an object of the present invention to provide an insulator assembly for use with a conductor rail which comprises a main body of aluminium and a steel facing layer.

Summary of the Invention According to the present invention there is provided an insulator assembly for use with a conductor rail, said insulator assembly comprising a base plate, a spigot of noncircular cross-section extending upwardly form the base plate, an insulator body located above the base plate, said insulator body including a socket of non-circular cross-section within which said spigot is received in such manner that relative vertical movement between the insulator body and the base plate is permitted between a normal "in-use" position in which relative rotation between the insulator body and the base plate is prevented and a fitment position in which the insulator body is raised relative to the base plate and rotation of the insulator body relative to the base plate is permitted, said insulator body carrying or including a cap which is provided with or carries engagement means for engagement with the rail such that, when so engaged with the rail and with the insulator body in its normal "in use" position, relative vertical, lateral and rotational movement between the cap and the rail are restrained.

As mentioned above, during traffic, the base plate will tend to move downwardly relative to the conductor rail. The height of the spigot will thus be such that, during downward movement of the base plate relative to the rail as a result of application of traffic loads to the sleeper, the spigot will remain engaged with the socket and rotational movement of the insulator body relative to the base plate will be prevented.

The engagement means will thus remain engaged with the rail and inadvertent movement of the rail will be prevented. It is to be appreciated that the rail may be subjected to substantial lateral forces as a result, for example, of track curvature or because of exceptional loads which may arise as a result of a mis-placed shoe on a train.

When, however, it is desired for any reason, to remove the insulator assembly, the conductor rail can be lifted relative to the base plate a distance sufficient that the socket in the insulator body is raised clear of the spigot. It will then be possible to rotate the insulator body about a substantially vertical axis to effect disengagement of the engagement means on the cap from the rail.

The insulator body may be formed of a refractory material, for example porcelain, such as has been used in the traditional insulator assemblies mentioned above. Alternatively and, in some cases, preferably, the insulator body may be formed as a plastic moulding from a "dough moulding compound" in the form of a glass-reinforced polyester or epoxy resin. If the insulator body is formed of a "dough moulding compound", the outer surface thereof is preferably of stepped configuration to increase the resistance to electrical tracking. Insulator bodies formed of a "dough moulding compound" are more resistant to brittle fracture than porcelain insulator bodies and should accordingly be used in circumstances where, either because of impact from track debris, vandalism or any other reasons, the insulator bodies are liable to be subjected to fracture.

A friction pad is preferably interposed between the lower surface of the conductor rail and the upwardly presented surface of the cap on which the rail would otherwise rest, the friction pad being formed of a material which has a low coefficient of sliding friction with aluminium so that, as the conductor rail moves short distances longitudinally relative to the insulator body as a result of expansion and contraction of the rail, the forces transmitted to the insulator body will be minimised. The preferred material for the friction pad is nylon. The upwardly presented surface of the cap is preferably formed with a well within which the friction pad is received, the friction pad being a relatively close fit in said well.

The line of action of any forces arising as a result of longitudinal movement of the rail relative to the insulator body will be substantially horizontal and will be spaced only a relatively short distance above the top of the spigot. The extent to which any such longitudinal forces tend to cause tipping of the insulator body relative to the base plate will thus be minimised.

The socket within which the spigot is received may be constituted by a metal insert which, if the insulator body is of porcelain, will be cemented in position within a cylindrical aperture within the porcelain insulator body. If the insulator body is formed of a "dough moulding compound", the metal insert will be placed within the mould whereby it becomes keyed to the insulator body during the moulding process.

The socket within the spigot may alternatively be afforded by the material from which the insulator body is formed, whether of porcelain or of a "dough moulding compound".

If the insulator body is of porcelain, the aperture from which the socket is produced is preferably in the form of a cylindrical opening the wall of which is machined, prior to glazing of the porcelain, so that the opening becomes of generally square cross-section but with radiused corners.

Although square cross-section spigots and sockets are preferred, other non-circular cross-sectional configurations are possible, for example, elliptical cross-sections.

If the socket is of square cross-section, the square cross-section opening may be so positioned that, when the insulator assembly is assembled with the conductor rail, the sides of the square extend at 450 to the longitudinal axis of the rail. The sides of the square may, however, alternatively extend at right angles to and parallel to the longitudinal axis of the rail. The particular orientation of the socket is not important. What is important is that it should be consistent so that any one insulator body can be engaged with any base plate.

A resiliently deformable sheath formed of a material having a low coefficient of sliding friction with cast iron (this being the preferred material for manufacture of the base plate) is preferably interposed between the spigot and the socket. The preferred material for said sheath is nylon.

The spigot extending upwardly from the base plate is preferably formed with a slight taper to facilitate removal of the base plate from its mould. The nylon sheath will accordingly be formed with an inner surface having a corresponding taper.

The nylon sheath is preferably of generally top hat configuration having a rim which is interposed between the lower surface of the insulator body and the corresponding upwardly presented surface of the base plate.

In order to allow for height adjustment, provision may be made for the insertion of one or more spacers between the rim of the nylon sheath and the lower surface of the insulator body.

If the insulator body is of porcelain, the cap may be of cast iron comprising a generally flat plate having a downwardly depending skirt which fits over the upper portion of the insulator body and a pair of ears which constitute the engagement means and which are so shaped that they will fit over and retain the lower part of the rail. The action on installation of the insulator assembly is thus in the nature of a twist-lock operation in that, after the base plate has been fixed to the track, the rail is lifted up to provide clearance for insertion of the insulator body and cap which, when placed beneath the rail, will be twisted to move the ears over the lower part of the rail. The insulator body will then be so oriented that its socket is aligned with the spigot extending upwardly from the base plate.The insulator body, cap and rail will then be lowered to cause the spigot to enter the socket and effectively secure the rail in position.

The upper portion of the porcelain insulator body is preferably of generally cylindrical form and the outer surface thereof is preferably knurled, sanded or otherwise roughened to improve bonding of the cap to the porcelain by a cement or like bonding agent.

If the insulator body is formed of a "dough moulding compound", the cap may be either an integral part of the moulding or a separate fabrication attached to the moulding. In either case, the cap will include ears which are shaped, as to described above, to provide a twist-lock action on fitment of the insulator assembly to the rail.

Insulator assemblies having the various features described above are illustrated in the accompanying drawings in which:- Figure 1 is a plan view of a first form of insulator assembly, Figure 2 is a side view of the insulator assembly of Figure 1 in use, Figure 3 is a plan view of a second form of insulator assembly, and Figure 4 is a part-sectional side view of the insulator assembly of Figure 3 in use.

Description of the Preferred Embodiments The insulator assembly shown in Figures 1 and 2 comprises a main body 10 formed as a plastic moulding from DMC, i.e.

dough moulding compound, which is a glass-fibre-reinforced polyester or epoxy resin. The main body 10 is supported on a cast iron base plate 11 which is bolted to a transom 12 by bolts 13. The cast iron base plate 11 includes an upstanding spigot 14 of non-circular cross-section which fits within a socket 15 of complementary cross-section within the main body 10. The exterior of the main body 10 is stepped as shown to increase the resistance to tracking.

The upper portion of the main body 10 includes a pair of upwardly projecting locking formations 16 which are so shaped that they can fit over and retain the lower part 17 of the conductor rail 18 which runs alongside and parallel to the running rail 19. The two locking formations 16 extend upwardly from a flat face 20 which is rebated as shown to provide a well within which a nylon friction pad 21 is fitted. The conductor rail 18 rests on the nylon pad 21 to minimise the frictional restraint against longitudinal movement of the rail relative to the main body 10.

A series of nylon shims 22 are fitted over the spigot 14 to ensure that the flat face 20 is at the required height for supporting the conductor rail 18.

The main body 10 can be lifted relative to the base plate 11 to disengage the spigot 14 from the socket 15. The main body 10 can then be turned about a vertical axis to disengage the locking formations 16 from the lower part 17 of the rail 18 and the main body 10 can then be removed.

To assemble the insulator assembly, the base plate 11 is fixed in position, The height at which the conductor rail 18 is to be supported is assessed and the appropriate number of shims 22 are then placed in position. The conductor rail 18 is then raised relative to its normal position and the main body 10 is moved into a position in which the locking formations 16 are engaged with the lower part 17 of the conductor rail 18. The conductor rail 18 and main body 10 are then lowered so that the spigot 14 is caused to enter the socket 15 and the main body 10 thereby held against rotation relative to the base plate 11.

The conductor rail 18 is then held against inadvertent movement, as described above.

In the embodiment shown in Figures 3 and 4, the same reference numerals are used to indicate the parts which correspond to the like parts of Figures 1 and 2. In this case, however, the main body 23 is of porcelain and the locking formations 24 are afforded by parts of a separate cast iron locking cap 25 attached to the porcelain body 23. A nylon cap or sheath 26 of somewhat top-hat configuration is interposed between the spigot 14 and the wall of the socket 15 formed in the porcelain main body 23.

The method of assembling and disassembling the assembly of Figures 3 and 4 is as described above in relation to the assembly of Figures 1 and 2.

Claims

Claims:

1. An insulator assembly for use with a conductor rail, said insulator assembly comprising a base plate, a spigot of non-circular cross-section extending upwardly form the base plate, an insulator body located above the base plate, said insulator body including a socket of non-circular cross-section within which said spigot is received in such manner that relative vertical movement between the insulator body and the base plate is permitted between a normal "in-use" position in which relative rotation between the insulator body and the base plate is prevented and a fitment position in which the insulator body is raised relative to the base plate and rotation of the insulator body relative to the base plate is permitted, said insulator body carrying or including a cap which is provided with or carries engagement means for engagement with the rail such that, when so engaged with the rail and with the insulator body in its normal "in use" position, relative vertical, lateral and rotational movement between the cap and the rail are restrained.

2. An insulator assembly as claimed in Claim 1, in which the insulator body is formed of a refractory material, for example porcelain.

3. An insulator assembly as claimed in Claim 1, in which the insulator body is formed as a plastic moulding from a "dough moulding compound" in the form of a glass-reinforced polyester or epoxy resin.

4. An insulator assembly as claimed in Claim 3, in which the outer surface of the insulator body is of stepped configuration to increase the resistance to electrical tracking.

5. An insulator assembly as claimed in Claim 1, in which a friction pad is interposed between the lower surface of the conductor rail and the upwardly presented surface of the cap on which the rail would otherwise rest, the friction pad being formed of a material which has a low coefficient of sliding friction with aluminium so that, as the conductor rail moves short distances longitudinally relative to the insulator body as a result of expansion and contraction of the rail, the forces transmitted to the insulator body will be minimised.

6. An insulator assembly as claimed in Claim 5, in which the friction pad is of nylon.

7. An insulator assembly as claimed in Claim 5, in which the upwardly presented surface of the cap is formed with a well within which the friction pad is received, the friction pad being a relatively close fit in said well.

8. An insulator assembly as claimed in Claim 1, in which the socket within which the spigot is received is constituted by a metal insert, the insulator body is of porcelain, and the metal insert is cemented in position within a cylindrical aperture within the porcelain insulator body.

9. An insulator assembly as claimed in Claim 1, in which the insulator body is formed of a "dough moulding compound" and in which the socket within which the spigot is received is constituted by a metal insert, the method of production of the insulator body being such that the metal insert is placed within the mould whereby it becomes keyed to the insulator body during the moulding process.

10. An insulator assembly as claimed in Claim 1, in which the socket within the spigot is afforded by the material from which the insulator body is formed, said material being either porcelain or a "dough moulding compound".

11. An insulator assembly as claimed in Claim 10, in which the insulator body is of porcelain, and in which the aperture from which the socket is produced is in the form of a cylindrical opening the wall of which is machined, prior to glazing of the porcelain, so that the opening becomes of generally square cross-section but with radiused corners.

12. An insulator assembly as claimed in Claim 1, in which the socket is of square cross-section, the square cross-section opening being so positioned that, when the insulator assembly is assembled with the conductor rail, the sides of the square extend at 450 to the longitudinal axis of the rail.

13. An insulator assembly as claimed in Claim 1, in which the socket is of square cross-section and the sides of the square extend at right angles to and parallel to the longitudinal axis of the rail when the insulator assembly is assembled with the conductor rail.

14. An insulator assembly as claimed in Claim 1, in which a resiliently deformable sheath formed of a material having a low coefficient of sliding friction with cast iron is interposed between the spigot and the socket.

15. An insulator assembly as claimed in Claim 14 in which the sheath is of nylon.

16. An insulator assembly as claimed in Claim 14, in which the spigot extending upwardly from the base plate is formed with a slight taper to facilitate removal of the base plate from its mould and the resilient sheath is formed with an inner surface having a corresponding taper.

17. An insulator assembly as claimed in Claim 14, in which the resilient sheath is of generally top hat configuration having a rim which is interposed between the lower surface of the insulator body and the corresponding upwardly presented surface of the base plate.

18. An insulator assembly as claimed in Claim 17, in which, in order to allow for height adjustment, provision is made for the insertion of one or more spacers between the rim of the resilient sheath and the lower surface of the insulator body.

19. An insulator assembly as claimed in Claim 1, in which the insulator body is of porcelain and the cap comprises a generally flat metal plate having a downwardly depending skirt which fits over the upper portion of the insulator body and a pair of ears which constitute the engagement means, the ears being so shaped that they will fit over and retain the lower part of the rail.

20. An insulator assembly as claimed in Claim 19, in which the upper portion of the porcelain insulator body is of generally cylindrical form and the outer surface thereof is knurled, sanded or otherwise roughened to improve bonding of the cap to the porcelain by a cement or like bonding agent.

21. An insulator assembly as claimed in Claim 1, in which the insulator body is formed of a "dough moulding compound", and the cap is either an integral part of the moulding or a separate fabrication attached to the moulding.

22. An insulator assembly as claimed in Claim 21, in which the cap includes ears which are shaped to provide a twist-lock action on fitment of the insulator assembly to the rail.

23. The combination of a conductor rail and a plurality of insulator assemblies each as claimed in any one of the preceding claims.

24. The combination of Claim 23, in which the conductor rail is as claimed in Claim 1 of Patent No. 2 231 544 as granted.

25. An insulator assembly for use with a conductor rail substantially as shown in the accompanying drawings.