GB2276498A

GB2276498A - Rail insulator support

Info

Publication number: GB2276498A
Application number: GB9306256A
Authority: GB
Inventors: Michael Brian Page; Frederick James Liptrot
Original assignee: Allied Insulators Ltd
Current assignee: Allied Insulators Ltd
Priority date: 1993-03-25
Filing date: 1993-03-25
Publication date: 1994-09-28
Anticipated expiration: 2013-03-25
Also published as: GB9306256D0; GB2276498B

Abstract

An insulator cap 3 has ears 3b which allow the rail 4 to move up and down but prevent the rail from tipping because the ears act on the rail at a relatively high location. The cylindrical member 2e is cemented into a flange 2d. <IMAGE>

Description

RAIL SUPPORT INSULATOR This invention relates to a rail support insulator, for a conductor or so called third rail, more particularly but not exclusively of a type used in railways where locomotives travel along running rails supported on spaced, transverse sleepers, and a sliding contact moves along the conductor rail.

Such rail support insulators have been used for very many years on railways, but, even so it is believed that design of such insulators and conductor rails may be improved. It is known to provide an insulator cap receiving a steel conductor rail with opposed sides of the base flange of the conductor rail being loosely located by opposed vertical limbs of said cap. In this way the conductor rail can be made substantially in place relative to the ground while the insulator itself can move up and down relative to the rail and ground with associated up and down movement of the sleeper as the locomotive travels along the running rails.Thus, the insulator cap and more particularly the opposed vertical limbs of said cap can move up and down with the sleeper relative to the conductor rail but in an extreme case it is possible for the conductor rail itself to become dislodged from the insulator cap.

Lightweight aluminium rails have been employed in vehicle transportation systems abroad and thought has been given to the use of an aluminium rail to replace the existing steel conductor rail or third rail utilised by some railway systems. The problems involved with existing foreign transport systems that employ aluminium rails are very different to those which would be involved in a United Kingdom surface or Underground railway system since, for example, the conductor rail is usually mounted on pillars or on a side wall in the foreign systems rather than being supported on the sleepers as in the British systems. This factor alone will affect the forces exerted on the conductor rail in a manner sufficient to dramatically change design considerations.The advantages of employing an aluminium conductor rail replacing the present steel conductor rails used in British systems are clear, for example, due to the lower electrical resistance of an aluminium rail the ohmic losses could be reduced in the order of 5g to 8%, representing a very significant decrease in electrical energy costs. Additionally, power losses, particularly when accelerating and braking should be considerably reduced. An aluminium rail should provide the facility of allowing faster acceleration and deceleration of the locomotive thereby increasing traffic density.

However, in order to provide an adequate crosssectional area of aluminium rail to yield a sufficiently high current carrying capacity (several hundred amps) without undue heat and to provide a configuration rigid enough to withstand deformity from the sliding contact, the design of aluminium conductor rail is subject to certain dimensional constraints. For example, it is believed that a practical aluminium rail will require a comparatively narrow base and be comparatively high relative to steel rails currently in use. Also, aluminium itself is comparatively soft and would abrade under the sliding contact so it has also been proposed to employ a stainless steel strip rolled onto the aluminium rail in order to better support the sliding contact.

There is a tendency for the running rails themselves to move under the weight of the locomotive depressing the sleepers as the locomotive travels along said running rails and, overall, it is believed that problems in conductor rail stability would be much more acute with an aluminium conductor rail than with a steel conductor rail.

Indeed it is believed that a design of insulator is required for aluminium conductor rails which would help to alleviate tipping forces that would necessarily accrue with a suitable design of aluminium rail if used with the current design of insulator.

An object of the present invention is to provide a rail support insulator which at least alleviates one or more of the aforementioned disadvantages or other disadvantages, associated with the stability of the conductor rail or associated with known rail support insulators.

According to the present invention there is provided a rail support insulator which, in use, is connected to a railway sleeper, said insulator having a cap for receiving a rail in such a manner that the rail is able to move up and down in the insulator cap, said insulator cap being provided with anti-tipping means to prevent tipping of the rail, said anti-tipping means being for example in the form of two opposed ears which act on a web of the rail.

Preferably, the insulator has a base comprising two opposed flanges securable directly to a railway sleeper.

The base may have an upwardly projecting central flange receiving a downwardly projecting cylindrical member of the insulator, said member having a curved shell connected to the insulator cap. Usually, the cylindrical member is fixed relative to the base by a cement mortar.

Preferably, the ears of the cap are tapered in a direction towards the web both vertically and horizontally. The ears are, preferably, provided with opposed, parallel inclined surfaces, preferably angled at 45" to the rail axis. Preferably, upper surfaces of the ears taper upwardly and inwardly.

Other advantages of the present invention will be apparent from the following description and drawings.

An embodiment of a rail support insulator in accordance with the present invention will now be described by way of example only with reference to the accompanying drawings in which: FIGURE 1 shows a front view of the insulator, and FIGURE 2 shows a plan view of the insulator.

Referring to the drawings, FIGURE 1 shows an insulator 1 having a lower portion 2 generally of a known type and an upper insulator cap 3 of novel construction.

The lower portion 2 of the rail support insulator 1 has a base 2a consisting of two opposed flanges 2b which are secured directly to a railway sleeper (not shown) via fixing holes 2c (see FIGURE 2) in a known manner. Base 2a has an upwardly projecting central circular flange 2d which receives the downwardly projecting cylindrical member 2e of the porcelain insulator 2f having a curved insulator shell 2g which is in turn connected to the insulator cap 3. Cylindrical portion 2e is secured in the upwardly projecting base flange 2d by a cement mortar to form a rigid construction in known manner. Thus, there is no relative movement between the base 2a and the insulator shell 2f.

The insulator cap 3 has a generally circular base 3a provided with two opposed generally vertical limbs L terminating in two opposed generally horizontally ears 3b which extend inwardly of the rail 4 (shown schematically by dash lines in FIGURE 1) to act on central vertical web 4a at spaced locations from one another on opposed sides of the web. Advantageously, the ears are tapered in a direction towards the web both vertically and horizontally and are provided with opposed inclined surfaces 3c (parallel to one another and arranged at 45" to the axis of the rail) which surfaces are spaced apart by a distance D. Distance D is just wide enough to allow introduction of the base 4b into the cap 3. Once the base 4b is below the level of the ears 3b the insulator can be rotated relative to the rail 4 to the position as shown in FIGURE 1 in a manner which should be easily understood.

Since the ears 3b act on the central web, at a relatively high location, it should be evident from the FIGURE that the rail 4 itself can move vertically upwards and downwards within the confines of the cap in between the base 3a of the cap and the ears 3b. Thus the rail itself is unable to spring out of the insulator cap.

The distance E shown in FIGURE 1 (i.e. the distance that the rail 4 can move up and down relative to the cap 3) is governed by the maximum distance by which the associated sleeper may be moved by a locomotive travelling on the running rails resting on the sleeper. Thus, the distance may be 28 mm. It is conceivable from a different system, where vertical movement of the sleeper is located to 2 mm, that distance is also as little as 2 mm.

Advantageously, the upper surface 3'b of the ears taper upwardly inwardly of the rail in order to maintain sufficient clearance from the sliding contact (not shown) that moves along the upper portion of rail 4, even in the cases of a substantial amount of wear.

It is to be understood that the scope of the present invention is not to be unduly limited by the particular choice of terminology and that a specific term may be replaced by any equivalent or generic term. Further it is to be understood that individual features, method or functions related to the insulator or parts thereof (in particular the cap) might be individually patentably inventive. The singular may include the plural and vice versa.

Claims

1. A rail support insulator which, in use, is connected to a railway sleeper, said insulator having a cap for receiving a rail in such a manner that the rail is able to move up and down in the insulator cap, said insulator cap being provided with anti-tipping means to prevent tipping of the rail.

2. An insulator as claimed in Claim 1 in which said anti-tipping means is in the form of two opposed ears which act on a web of the rail.

3. An insulator as claimed in Claim 2 having a base comprising two opposed flanges securable directly to a railway sleeper.

4. An insulator as claimed in Claim 3 in which the base has an upwardly projecting central flange receiving a downwardly projecting cylindrical member of the insulator, said member having a curved shell connected to the insulator cap.

5. An insulator as claimed in Claim 4 in which the cylindrical member is fixed relative to the base by a cement mortar.

6. An insulator as claimed in Claim 2 or any claim dependent therefrom in which the ears of the cap are tapered in a direction towards the web both vertically and horizontally.

7. An insulator as claimed in Claim 6 in which the ears are provided with opposed, parallel inclined surfaces.

8. An insulator as claimed in Claim 7 in which the ears are angled at 450 to the rail axis.

9. An insulator as claimed in Claim 2 or any claim dependent therefrom in which upper surfaces of the ears taper upwardly and inwardly.

10. A rail support insulator substantially as herein described with reference to the FIGURES of the accompanying drawings.