GB2106570A

GB2106570A - Electrical insulator pad

Info

Publication number: GB2106570A
Application number: GB08128239A
Authority: GB
Inventors: Owen Hanson; David Julian Allen
Original assignee: KARMIC Ltd
Current assignee: KARMIC Ltd
Priority date: 1981-09-18
Filing date: 1981-09-18
Publication date: 1983-04-13

Abstract

An electrical insulator pad 1 of channel section for location between the underside 2 of a base flange 3 of a railway rail 4 and an upper surface 8 of a supporting sleeper 9 is a planar, polyurethane moulding having two opposed, parallel edges 11, and an upwardly projecting wing 12 provided at or adjacent each parallel edge 11, mutually opposed faces 13 of the wings being adapted, in use, to engage abuttingly opposite longitudinal edges 7 of the base flange 3. In modifications, (a) the wings extend the full length of the pad and/or (b) the wing portions are of polyurethane having a hardness different from that of the base portion, the three portions being moulded together and having a common mesh reinforcement. <IMAGE>

Description

SPECIFICATION Electrical insulator pad This invention relates to an electrical insulator pad for sections of rail track.

Known pads are located between the underside of a base flange of a railway rail andan upper surface of a supporting sleeper the rails usually being urged into firm seating engagement with the sleeper, via the pad, by means of a spring clip, a commonly used type being of circular section spring steel. Known pads have proved technically satisfactory but could be improved with regard to features such as length of service life; electrical insulating properties; ability to remain in their desired location and hence avoid creeping from this location due to vibrations and other forces resulting from passing rail traffic; and fatigue -- some five million axle passages is usually the most a pad can ensure before replacement is necessary.

According to the present invention, there is provided an electrical insulator pad for location between the underside of the base flange of a railway rail and an upper surface of a rail supporting sleeper, the pad being a planar polyurethane moulding and having two opposed parallel edges, and an upwardly projecting wing provided at or adjacent each parallel edge, mutually opposed faces of the wings being adapted, in use, to engage abuttingly opposite longitudinal edges of the base flange.

Thus, the pad in accordance with the invention, due to its moulding in polyurethane provides substantially improved durability and hence service life, offering up to ten times the life of prior art pads, while its electrical insulating properties (necessary for track signalling systems) provide some five times that normally demanded, and resistance to creep is provided by the wings positively engaging the base flange. As far as endurance and resistance of fatigue is concerned, a pad in accordance with the invention showed no signs of deterioration in tests simulating 48 million axle passes. Furthermore, tests have also revealed a beneficial reduction in traffic noise level due to the cushioning effects of the pads.

Preferably, the polyurethane employed is Adiprene (Registered Trade Mark) a Du Pont product, or alternatively this may form the bulk of an admixture of different polyurethanes and/or other ingredients, to suit particular service conditions. Furthermore, the wings may be of different polyurethane to the remainder of the pad, e.g. to provide harder polyurethane wings on a relatively soft polyurethane pad.

The wings may extend the full length of the opposed edges or only part of the length of those edges. In the latter case, they may be located slightly inwardly with respect to their adjacent edges. Conveniently, the pad may be rectangular in plan and preferably generally square.

The invention will now be further described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of pad in accordance with the invention; Figure 2 is an end elevation of a second embodiment of pad in accordance with the present invention; and Figure 3 indicates a third embodiment.

In all embodiments, like components are accorded like reference numerals.

In the drawings, a moulded polyurethane pad 1 is shown located between an underside 2 of a base flange 3 of a railway rail 4 having a web 5 carrying a head 6, the base flange 3 having opposed, parellel, longitudinally extending edges 7; and an upper surface 8 of a concrete sleeper 9.

The pad 1 comprises a planar base 10 and is produced by pouring a suitable quantity of flowable polyurethane -- preferably Adiprene (R.T.M.) into a suitably shaped mould. The pad 1 is generally square and has a pair of opposed, parallel edges 11. Integrally moulded with the base 10 are a pair of wings 12, extending part of the length of their adjacent edges 11, projecting upwardly from the base 10, and having mutually opposed faces 13 which abut against the edges 7. In the embodiment of Figure 1, each wing 12 is slightly inwardly spaced from its adjacent edge 11 and furthermore extends only a portion of the length of each edge 11. In the embodiment of Figure 2, the wings 1 2A are located at the edges 11 and extend the full length thereof.

For certain service conditions, it may be desirable to use differing polyurethane compositions for the base 10 and the wings 12, 1 2A to achieve differing characteristics, and Figure 3 illustrates how this may be attained. The wings 12B e.g. of harder polyurethane are premoulded onto opposed ends of a wire mesh carrier 14, to obtain an insert 1 5 which is subsequently loaded into a mould and a polyurethane mix, suitable for the characteristics required of the base, is then poured into the mould and the mesh carrier 1 4 is embedded therein.

Claims

1. An electrical insulator pad for location between the underside of the base flange of a railway rail and an upper surface of a rail supporting sleeper, the pad being a planar, polyurethane moulding and having two opposed parallel edges, and an upwardly projecting wing provided at or adjacent each parallel edge, mutually opposed faces of the wings being adapted, in use, to engage abuttingly opposite longitudinal edges of the base flange.

2. A pad as claimed in Claim 1, wherein the polyurethane employed is Adiprene (Registered Trade Mark).

3. A pad as claimed in Claim 1, wherein the polyurethane employed is an admixture containing a major proportion of Adiprene (Registered Trade Mark) and a minor proportion of different polyurethanes and/or other ingredients, to suit particular service conditions.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **.

SPECIFICATION Electrical insulator pad This invention relates to an electrical insulator pad for sections of rail track.

Known pads are located between the underside of a base flange of a railway rail andan upper surface of a supporting sleeper the rails usually being urged into firm seating engagement with the sleeper, via the pad, by means of a spring clip, a commonly used type being of circular section spring steel. Known pads have proved technically satisfactory but could be improved with regard to features such as length of service life; electrical insulating properties; ability to remain in their desired location and hence avoid creeping from this location due to vibrations and other forces resulting from passing rail traffic; and fatigue -- some five million axle passages is usually the most a pad can ensure before replacement is necessary.

According to the present invention, there is provided an electrical insulator pad for location between the underside of the base flange of a railway rail and an upper surface of a rail supporting sleeper, the pad being a planar polyurethane moulding and having two opposed parallel edges, and an upwardly projecting wing provided at or adjacent each parallel edge, mutually opposed faces of the wings being adapted, in use, to engage abuttingly opposite longitudinal edges of the base flange.

Thus, the pad in accordance with the invention, due to its moulding in polyurethane provides substantially improved durability and hence service life, offering up to ten times the life of prior art pads, while its electrical insulating properties (necessary for track signalling systems) provide some five times that normally demanded, and resistance to creep is provided by the wings positively engaging the base flange. As far as endurance and resistance of fatigue is concerned, a pad in accordance with the invention showed no signs of deterioration in tests simulating 48 million axle passes. Furthermore, tests have also revealed a beneficial reduction in traffic noise level due to the cushioning effects of the pads.

Preferably, the polyurethane employed is Adiprene (Registered Trade Mark) a Du Pont product, or alternatively this may form the bulk of an admixture of different polyurethanes and/or other ingredients, to suit particular service conditions. Furthermore, the wings may be of different polyurethane to the remainder of the pad, e.g. to provide harder polyurethane wings on a relatively soft polyurethane pad.

The wings may extend the full length of the opposed edges or only part of the length of those edges. In the latter case, they may be located slightly inwardly with respect to their adjacent edges. Conveniently, the pad may be rectangular in plan and preferably generally square.

The invention will now be further described, by way of examples, with reference to the accompanying drawings, in which: Figure 1 is a perspective view of a first embodiment of pad in accordance with the invention; Figure 2 is an end elevation of a second embodiment of pad in accordance with the present invention; and Figure 3 indicates a third embodiment.

In all embodiments, like components are accorded like reference numerals.

In the drawings, a moulded polyurethane pad 1 is shown located between an underside 2 of a base flange 3 of a railway rail 4 having a web 5 carrying a head 6, the base flange 3 having opposed, parellel, longitudinally extending edges 7; and an upper surface 8 of a concrete sleeper 9.

The pad 1 comprises a planar base 10 and is produced by pouring a suitable quantity of flowable polyurethane -- preferably Adiprene (R.T.M.) into a suitably shaped mould. The pad 1 is generally square and has a pair of opposed, parallel edges 11. Integrally moulded with the base 10 are a pair of wings 12, extending part of the length of their adjacent edges 11, projecting upwardly from the base 10, and having mutually opposed faces 13 which abut against the edges 7. In the embodiment of Figure 1, each wing 12 is slightly inwardly spaced from its adjacent edge 11 and furthermore extends only a portion of the length of each edge 11. In the embodiment of Figure 2, the wings 1 2A are located at the edges

11 and extend the full length thereof.

For certain service conditions, it may be desirable to use differing polyurethane compositions for the base 10 and the wings 12,

1 2A to achieve differing characteristics, and Figure 3 illustrates how this may be attained. The wings 12B e.g. of harder polyurethane are premoulded onto opposed ends of a wire mesh carrier 14, to obtain an insert 1 5 which is subsequently loaded into a mould and a polyurethane mix, suitable for the characteristics required of the base, is then poured into the mould and the mesh carrier 1 4 is embedded therein.

Claims

1. An electrical insulator pad for location between the underside of the base flange of a railway rail and an upper surface of a rail supporting sleeper, the pad being a planar, polyurethane moulding and having two opposed parallel edges, and an upwardly projecting wing provided at or adjacent each parallel edge, mutually opposed faces of the wings being adapted, in use, to engage abuttingly opposite longitudinal edges of the base flange.

2. A pad as claimed in Claim 1, wherein the polyurethane employed is Adiprene (Registered Trade Mark).

3. A pad as claimed in Claim 1, wherein the polyurethane employed is an admixture containing a major proportion of Adiprene (Registered Trade Mark) and a minor proportion of different polyurethanes and/or other ingredients, to suit particular service conditions.

4. A pad as claimed in any preceding Claim, wherein the wings are of different polyurethane to the remainder of the pad.

5. A pad as claimed in Claim 4, wherein the wings are of harder polyurethane than the remainder of the pad.

6. A pad as claimed in any preceding Claim, wherein the wings extend the full length of the opposed edges.

7. A pad as claimed in any one of Claims 1 to 5, wherein the wings extend only part of the length of the opposed edges.

8. A pad as claimed in Claim 7, wherein the wings are located slightly inwardly with respect to their adjacent edges.

9. A pad as claimed in any preceding Claim, being rectangular in plan.

10. A pad as claimed in any preceding Claim, being square in plan.

11. An electrical insulator pad for location between the underside of the base flange of a railway rail and an upper surface of a rail supporting sleeper substantially as hereinbefore described with reference to the accompanying drawings.