EP0596595A1

EP0596595A1 - Improvements Relating to railway track switches

Info

Publication number: EP0596595A1
Application number: EP93306373A
Authority: EP
Inventors: Andrew Raymond Foan
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1992-08-13
Filing date: 1993-08-12
Publication date: 1994-05-11
Also published as: GB9217160D0

Abstract

A claw lock mechanism for a railway turnout comprises a pair of stock rail brackets (1), each of which is located on a stock rail (2) at a position in the region of the toe of an adjacent tongue rail, and each of which has an open-ended passage extending transversely beneath the stock rail (2), a drive bar (20) which extends through and beyond the passage of each bracket (1) for moving the tongue rails between each operating position, and a pair of claw arms (22) each of which extends through the passage of one of the brackets (1). One end of each arm (22) is pivotally fixed (at least indirectly) to one of the tongue rails and the other end thereof has a claw (23) which can engage a notch (34) in the drive bar (20) to allow both the drive bar and the claw arm to slide through the passage until the associated tongue rail contacts the stock rail (2). Further movement of the drive bar through the passage forces the claw (23) out of the notch (34) and locks the arm (22) in the passage thereby preventing inadvertent movement of the tongue rail away from the stock rail. According to the invention each stock rail bracket (1) is immovably secured to its associated stock rail and at least a major part of the peripheral surface of each transversely extending passage is defined by a carriage (24) that is located within the bracket (1) and can be moved at least to a limited extent in a direction lengthwise with respect to the stock rail (2) directly by the drive rod (20) or the claw arm (22) bearing on a surface of the carriage (24) defining the passage. This form of mechanism is relatively simple to manufacture and is reliable.

Description

This invention relates to railway tracks of the kind comprising two transversely spaced rails on which rolling stock travels and is retained by flanges on the wheels of the rolling stock bearing against inner side faces of upper parts of the rails, which upper parts are generally and hereinafter will be referred to as the rail heads.
In lay-outs of railway tracks, it is common practice to provide turn outs by means of which rolling stock can pass from one track to another or vice versa. A turn out comprises, in combination, a switch (or points) which diverts rolling stock travelling on a first track on to a second track or vice versa, and a crossing at which one rail of the second track effectively crosses one rail of the first track in such a way that passage of the flanges of wheels of rolling stock diverted from the first track to the second track can pass freely across said one rail of the first track and that passage of the flanges of wheels of rolling stock travelling from the second track to the first track can pass freely across said one rail of the first track.
In a switch (or points) of a turn out, one rail of the first track extends beyond the switch and continues to constitute one rail of said first track and the other rail of said first track extends beyond the switch and constitutes one rail of the second track (the part of each of which rails constituting a component part of the switch generally being referred to as a stock rail of the switch); each of the stock rails has associated with and on the inner side of the stock rail a tongue rail which, at one of its ends (generally referred to as the heel), is transversely spaced from the stock rail and is pivotally coupled to the tracks about an axis substantially normal to the tracks and which, at the other of its ends (generally referred to as the toe), is shaped to facilitate substantially smooth transfer of the flange of a wheel of rolling stock when said toe of the tongue rail is in interfacial contact with the inner side face of the head of the adjacent stock rail and the wheels of rolling stock are required to pass from the stock rail to the tongue rail or vice versa; a fixed length of rail extends from the heel of each tongue rail to the crossing of the turn out; and, at or near the toes of the tongue rails, means is provided for moving the toes of the tongue rails in a direction transverse to the stock rails between two operating positions, in the first of which operating positions the toe of one tongue rail is in interfacial contact with the inner side face of the head of the adjacent stock rail and the toe of the other tongue rail is transversely spaced inwardly from the adjacent stock rail and in the second of which operating positions the toe of said one tongue rail is transversely spaced inwardly of the adjacent stock rail and the toe of said other tongue rail is in interfacial contact with the inner side face of the head of the adjacent stock rail.
One drive means commonly used to move the toes of tongue rails of a switch transversely with respect to the adjacent stock rails is generally known as a claw lock mechanism.
In a claw lock mechanism a pair of stock rail brackets are located on the stock rails, one such bracket located on its associated stock rail in the region of the toe of the adjacent tongue rail, and each of which has an open ended passage extending transversely beneath the stock rail. A drive bar extends through and beyond the passage of each bracket for moving the tongue rails between each operating position, and a pair of claw arms is provided, each of which extends through the passage of one of the brackets, one end of each claw arm being pivotally fixed (at least indirectly) to one of the tongue rails and the other end thereof having a claw which can engage a notch in the drive bar to allow both the drive bar and arm to slide through the passage until its associated tongue rail contacts the stock rail. In this operating position the tongue rail and hence the arm cannot move further, so that further movement of the drive bar through the passage forces the claw out of the notch and locks the arm in the passage. This locking action prevents any inadvertent movement of the tongue rail away from the stock rail once it has reached its operating position. Means is provided for moving the drive bar transversely with respect to the stock and tongue rails in either direction from one of said operating positions to the other, in each of which operating positions the claw of the arm pivotally mounted on the bracket of the tongue rail whose toe is in interfacial contact with the inner side face of the head of the adjacent stock rail (the closed toe) protrudes outwardly beyond its associated passage through the bracket of said adjacent stock rail and is disposed inwardly of its associated notch in the drive bar and the claw of the arm pivotally mounted on the bracket of the tongue rail whose toe is transversely spaced inwardly from the adjacent stock rail (the open toe) is engaged in its associated notch and is disposed within its associated passage through the bracket of said adjacent stock rail. Each claw is so shaped with respect to the shape of its associated notch and of the boundary wall of the associated passage through the bracket of the adjacent stock rail that, as the bar is moved transversely with respect to the stock and tongue rails in either direction from one of said operating positions to the other, the notch associated with the claw of the "closed toe" will engage with the claw so that the moving drive bar will urge the toe towards the "open" state and the notch engaged by the claw of the "open toe" will emerge outwardly from the passage through the bracket of the adjacent stock rail, the claw will disengage from the notch and the toe will move towards the "closed" state.
When a switch incorporating a claw lock mechanism of the kind described is in use in an environment where the claw lock mechanism is likely to be subjected to a wide range of ambient temperatures, there is a risk that consequential longitudinal expansion or contraction of the stock rails and/or tongue rails relative to one another will cause the switch to jam or to operate in an otherwise unsatisfactory manner.
One form of claw lock mechanism that can accommodate relative movement between the stock rail and the tongue rail is described in DE-A-3115943. In this mechanism the stock rail bracket is slidable longitudinally with respect to the stock rail. In order to move the stock rail bracket along the stock rail a rigid carrier rod is provided below the drive bar by means of a tongue block and is accommodated in a recess of the stock rail bracket in order to transfer longitudinal thermal expansion forces. This is a relatively complex arrangement, which is caused by the fact that the stock rail bracket itself is required to move due to thermal expansion and contraction of the rails.
It is an object of the present invention to provide, for use in a switch incorporating a claw lock mechanism of the kind described, an improved bracket assembly for attachment to a stock rail of the switch, use of which bracket assembly which is relatively simple and which will eliminate or at least substantially reduce risk of malfunction of the switch due to longitudinal expansion or contraction of the stock rails and/or tongue rails relative to one another.
According to the invention each stock rail bracket is immovably secured to its associated stock rail, that is to say it is fixed to the stock rail in the longitudinal direction against movement caused by thermal expansion and contraction, and at least a major part of the peripheral surface of each transversely extending passage is defined by a carriage that is located within the bracket and can be moved at least to a limited extent in a direction lengthwise with respect to the stock rail by the drive bar or the claw arm bearing on a surface of the carriage defining the passage.
By virtue of the fact that the carriage, which defines the whole or a major part of the peripheral surface of said transversely extending passage, is constrained to move to a limited extent in a direction that will be lengthwise with respect to the stock rail, in the event that the stock rail or the adjacent tongue rail expands or contracts lengthwise to such an extent that the pivotal axis of the claw arm is caused to move lengthwise with respect to the main body, such lengthwise movement of the pivotal axis can be accommodated by automatic lengthwise movement of the carriage with respect to said other body.
Moreover, by virtue of the fact that the carriage can be relatively small compared with the stock rail bracket it is not necessary to provide a separate carrier rod for ensuring movement of the carriage, the movement being caused directly by the drive bar or arm, and so the mechanism can be relatively simple to manufacture. In addition, in contrast with the arrangement described in DE-A-31 15 943, the vertical distance between the point at which the carriage is supported and the point at which the longitudinal forces due to thermal expansion bear on it can be substantially reduced, thereby minimizing unwanted torque on the carriage about a horizontal axis transverse to the stock rail.
Preferably the stock rail bracket is formed from at least two separately formed parts adapted to be fixedly secured together in interfacial contact and to the outer side of the stock rail, one of the parts having a face of a shape complementary to that of the outer side face of the stock rail, so that, by means of differently shaped such parts, the bracket can be fixed to a range of stock rails of different shapes and sizes.
While, the stock rail preferably consists of two separately formed parts adapted to be fixedly secured together in interfacial contact and to the outer side face of a stock rail but, in some circumstances, one or more than one separately formed body part may be sandwiched between said two body parts of the main body to provide for lateral adjustment. The separately formed parts of the main body are adapted to be fixedly secured together in interfacial contact and to the outer side face of a stock rail preferably by at least two bolts mutually spaced lengthwise with respect to the stock rail.
The arrangement by means of which the carriage mounted within the bracket is constrained to move to a limited extent with respect to the bracket in a direction that will be lengthwise with respect to a stock rail may take any convenient form but, preferably, the carriage is constrained to slide in a track or a surface of the bracket, which track or surface extends in a direction which will be lengthwise with respect to the stock rail and which inhibits transverse movement of the carriage with respect to the bracket. Alternatively or in addition, the carriage may be configured so as to inhibit transverse movement thereof, for example by the provision of legs or flanges thereon. Preferably, one or each of the contiguous surfaces of the track or bracket and/or of the carriage is or are made of a material having a low coefficient of friction. In some circumstances, instead of sliding along the track, the carriage may move on appropriately disposed wheels or roller bearings.
The extent of movement of the carriage with respect to the bracket in a direction that will be lengthwise in respect to the stock rail preferably is limited by a stop at each end of the track, which stop may be constituted by a transversely extending wall constituting an integral part of the bracket.
The invention also includes a railway track switch incorporating a claw lock mechanism of the kind described, wherein each stock rail has fixedly secured to its outer side face an improved bracket assembly as hereinbefore described.
One mechanism according to the invention is further illustrated, by way of example, by the accompanying drawings in which:

Figure 1: is a partly cut-away exploded perspective view of a bracket assembly for use in the mechanism according to the invention; and
Figure 2: is a perspective view of the bracket assembly of figure 1 together with part of a stock rail, drive rod and claw arm.

Referring to the accompanying drawings, a claw lock mechanism for a railway turn-out comprises a pair of stock rail brackets 1 (only one of which is shown), each of which is intended to be secured to the outwardly disposed side surface of a stock rail 2 at a position adjacent to the toe of one of the tongue rails. The bracket 1 is secured to the stock rail 2 by means of nuts 4 and bolts 6 that extend through holes in the stock rail 2. A fish bar 8 having a surface profile corresponding to the side surface of the stock rail 2 is provided in order to enable the bracket 1 to be securely fixed to the stock rail, and a pair of shims 10 are also provided for lateral adjustment of the bracket 1.
The bracket 1 has a lower part 12 that extends below the base-plate 14 of the stock rail and which has an aperture (not shown) in the side wall 16 (obscured by one of the end walls 18 thereof) to allow a drive bar 20 to extend through the lower part of each stock rail bracket 1. The drive bar 20 is connected to an appropriate mechanical electrical or hydraulic drive mechanism (not shown). Each tongue rail is fixed to one end of a claw arm 22 via a bracket so that the claw arm can pivot about a vertical axis through at least a certain arc and the other, free, end of the claw arm ends in a claw 23 that is wider than the remaining parts of the claw arm.
A carriage 24 is located within the stock rail bracket 1 so that it is supported by a horizontal surface 26 that connects the two end walls 18 of the bracket, and a flat element 28 of relatively low surface friction material is sandwiched between the carriage 24 and the horizontal surface 26. The length of the carriage 24 is such that it can slide along the surface 26 for a limited distance, for example 1 to 2 cm, before it abuts the end wall 18 of the bracket. The carriage 24 has a pair of edge walls 30a and 30b which, together with base 32 of the carriage define a major part of a passage that extends transversely and through which the drive bar 20 and claw arm 22 extend. The carriage is prevented from transverse movement by means of legs 33 which hang over the sides of surface 26.
The drive bar 20 has a notch 34 of a shape that corresponds to the shape of the adjacent side of the claw 23, so that the claw 23 can be received by the notch 34. The edge walls 30a and 30b of the carriage 24 are separated by a distance that will accommodate the claw 23 and the drive bar in a sliding fit only when the claw 23 is received by the notch 24. When the claw 23 is not received in the notch 24 so that the claw arm 22 is separated from the drive rod by a distance corresponding generally to the depth of the notch 34, the separation of the edge walls 30a and 30b of the carriage can accommodate the drive rod 20 and central region of the claw arm, but not the claw 23.
In operation, when the turn out is at an operating position the toe of one tongue rail (the open toe) will be transversely spaced apart from its associated stock rail and the toe of the other tongue rail (the closed toe) will be in contact with its associated stock rail. The claw 23 of the claw arm 22 associated with the open toe will be received in the notch 34 of the drive bar 20 and the claw and drive bar will be located within the carriage 24 of the stock rail bracket 1. In order to set the turn out in the other operating position, the drive mechanism moves the drive rod 20 through the aperture in the stock rail bracket so that it slides in the carriage 24. Because the claw 23 is received in the notch 34 in the drive bar 20, the claw arm 22, and hence the tongue rail, are also caused to move along with the drive rod. The notch 34 emerges from the carriage just as the tongue rail comes into contact with the stock rail. The notch 34 and claw 23 each have a correspondingly sloped shoulder 36 and 38 which causes the claw to be released from the notch at this point since the claw arm 22 is prevented from moving further by the tongue rail. Further movement of the drive bar 20 results in the configuration shown in figure 2 in which the claw arm 22 is prevented from sliding in the carriage 24 and the tongue rail is thus locked in its closed position. The tongue rail can only be released from this position by movement of the drive bar 20 to such an extent that the claw 23 is again received by the notch 34.
The width of the aperture in the wall 16 of the stock rail bracket 1 is slightly greater than required to accommodate the drive bar 20 and claw arm 22 so that the passageway is defined by the separation of the edges 30a and 30b of the carriage. The carriage 24 is relatively small in comparison with the size of the stock rail bracket so that it is possible to accommodate relative longitudinal movement between the tongue rail and the stock rail due to thermal expansion and contraction by sliding of the carriage 24 on the bottom surface 26 of the bracket 1. This movement can be caused directly by the drive bar 20 or the claw arm 22 acting directly on the surface of the corresponding edge wall 30a or 30b of the carriage 24. Because the vertical distance between the edge wall 30a and b and the underside of the carriage is relatively small, little torque is generated about a horizontal transverse axis when the carriage is caused to move.

Claims

A claw lock mechanism for a railway turnout, which comprises a pair of stock rail brackets (1), each of which is located on a stock rail (2) at a position in the region of the toe of an adjacent tongue rail, and each of which has an open-ended passage extending transversely beneath the stock rail (2), a drive bar (20) which extends through and beyond the passage of each bracket (1) for moving the tongue rails between each operating position, and a pair of claw arms (22) each of which extends through the passage of one of the brackets (1), one end of each arm (22) being pivotally fixed (at least indirectly) to one of the tongue rails and the other end thereof having a claw (23) which can engage a notch (34) in the drive bar (20) to allow both the drive bar and the claw arm to slide through the passage until the associated tongue rail contacts the stock rail (2), further movement of the drive bar through the passage forcing the claw (23) out of the notch (34) and locking the arm (22) in the passage thereby preventing inadvertent movement of the tongue rail away from the stock rail, characterised in that each stock rail bracket (1) is immovably secured to its associated stock rail and that at least a major part of the peripheral surface of each transversely extending passage is defined by a carriage (24) that is located within the bracket (1) and can be moved at least to a limited extent in a direction lengthwise with respect to the stock rail (2) by the drive rod (20) or the claw arm (22) bearing on a surface of the carriage (24) defining the passage.
A mechanism as claimed in claim 1, wherein the carriage (24) is constrained to slide to a limited extent within the bracket (1) on a track or a surface (26) of the bracket.
A mechanism as claimed in claim 2, wherein the carriage (24) slides on a surface of a material having a low coefficient of friction.
A mechanism as claimed in any one of claims 1 to 3, wherein the carriage (24) is provided with legs (33) which inhibit transverse movement thereof.
A mechanism as claimed in any one of claims 1 to 4, wherein movement of the carriage (24) in a direction lengthwise with respect to the stock rail (2) is limited by a transversely extending wall of the bracket (1).
A mechanism as claimed in any one of claims 1 to 5, wherein the stock rail bracket is formed from at least two separately formed parts adapted to be fixedly secured together in interfacial contact and to the outer side of the stock rail, one of the parts (8) having a face of shape complementary to that of the outer side of the stock rail.
A railway turnout that includes a claw lock mechanism as claimed in any one of claims 1 to 6.