GB2329922A

GB2329922A - Railway turnout

Info

Publication number: GB2329922A
Application number: GB9810647A
Authority: GB
Inventors: Andrew Raymond Foan
Original assignee: BICC PLC
Current assignee: Balfour Beatty PLC
Priority date: 1997-05-20
Filing date: 1998-05-19
Publication date: 1999-04-07
Also published as: GB9810647D0; GB9710409D0

Abstract

A swing nose crossing of a railway turnout comprises a substantially vee-shaped section (1) that is formed by a pair of legs (2, 4) that are joined together at one end to form a nose (6). The nose (6) is movable laterally within a pair of wing rails (14,16) between two positions in accordance with the setting of the turnout. The wing rails (14, 16) are formed as a one- piece construction, preferably a casting, in the region of the nose (6) of the vee-shaped section (1). In a preferred embodiment the nose (6) rotates in a sense opposite to the rotation of the vee-shaped section (1) as it moves between the two positions. This advantageously enables the length of the nose (6) of the vee-shaped section (1) to be reduced from conventional values, and also enables a corresponding reduction in the length of the one piece construction of the wing rails (14,16) in the region of the nose.

Description

RAILWAY TURNOUT This invention relates to railway track, and in particular to turnouts therein.

In every turnout there is a crossing where one of the rails of one track crosses over one of the rails of the other track. The crossing includes a substantially veeshaped section that joins a pair of fixed rails (one rail of each track) and ends in a relatively sharp apex or nose. A pair of short wing rails are usually located on either side of the nose of the vee-shaped section in order to limit any lateral shift of the wheels of the rolling stock as they pass over the crossing, the wing rails being spaced apart from the nose by a small distance to accommodate the width of the wheels.

These gaps mean that the sharp nose of the vee-shaped section is physically isolated from the remainder of the rails, which causes wear of the nose and wing rails and also causes noise in impact of the wheels on the nose and wing rails.

In order to overcome this problem, swing-nose crossings or moving point frogs have been proposed in which the vee-shaped section is movable between two positions in accordance with the setting of the switch, the nose of the vee-shaped section normally abutting one or the other of the wing rails depending on the switch stetting, so that the nose and abutting wing rail together form a length of rail with substantially no discontinuity, thereby reducing the noise and wear due to the wheels of the stock.

However, since the ends of the legs of the vee-shaped section remote from the nose are joined to rails securely fixed relative to the ground, the relative overall length of the legs must change as the nose moves laterally from one position to the other. GB-A2,275,708, the disclosure of which is incorporated herein by reference, discloses a crossing in which, in each of the two positions, one leg of the vee-shaped section is flexed into a shallow serpentine shape, the leg of the vee-shaped section that is flexed changing as the nose moves from one of its positions to the other in order to accommodate a change in the relative overall length of the legs. That form of crossing has the advantage that the entire vee-shaped section can be formed in one piece, thereby eliminating the problems caused by multi-part sections as employed in the prior art.

The present invention is characterised in that the pair of wing rails are formed as a one piece construction (a monobloc), and preferably in the form of a casting at least in the region of the nose of the vee-shaped section, and preferably only in the region of the nose of the vee-shaped section (on the same side of the constriction in the wing rails as the vee-shaped section).

One problem that exists in the manufacture of turnouts is that the nose of the vee-shaped section moves from one position to the other, the vee-shaped section as a whole in effect rotates by a small degree about a vertical axis, and so the orientation of the nose of the vee-shaped section (as measured along its vertical plane of symmetry) also rotates by substantially the same amount. This has the result that the angle between the legs of the vee-shaped section in the region of the nose must be smaller than the angle at which the tracks begin to separate at the turnout by substantially the same amount by which the vee-shaped section as a whole rotates as it moves between the two positions. Because the angle at which the tracks separate is, in any case, very small (for example about 1:50 (corresponding to about 1 )), the angle between the legs of the vee-shaped section is significantly smaller, with the result that the length of the nose of the vee-shaped section (i.e. the part thereof before the rails forming the legs separate) must be relatively long, for example 7.5 to 8 metres or even longer. If one employs a casting for the part of the wing rails in the region of the nose (so-called "cast cradle" arrangements) any casting that is employed will be at least as long as the nose of the vee-shaped section, with the result that its length causes it to become difficult and expensive to manufacture. The use of the vee-shaped section in accordance with GB-A-2,275,708, however, causes the orientation of the nose of the vee-shaped section to rotate by a smaller degree than the vee-shaped section as a whole. In accordance with the present invention, the vee-shaped section is preferably designed so that the nose thereof undergoes substantially no rotation as it moves between the two positions.

This arrangement has the advantage that the angle between the legs of the vee-shaped section will be substantially the same as that between the tracks at the turnout, with the result that the length of the nose of the vee-shaped section, and thus the length of the casting required for the cast cradle, can be significantly reduced. Indeed, it is possible for the vee-shaped section to be designed such that the nose thereof undergoes a rotation opposite to that of the vee-shaped section as a whole as it moves between the two positions. This enables the angle between the legs of the vee-shaped sections to be greater than that between the tracks, and the length of the nose to be reduced yet further. Clearly, the particular angle between the legs of the vee-shaped section will depend on its design, which will in turn depend on a number of factors including the intended speed at which the rolling stock will pass over the turnout, the faster the intended speed, the smaller the angles must be. For a typical turnout, if the angle of the tracks at the crossing is 1:60, the angle between the legs of the vee-shaped section must be about 1:80. However, according to the present invention, for such a turnout, the angle between the legs of the vee-shaped section could be increased to 1:30 to 1:50, corresponding to a reduction in the length of the nose 7.5 metres down to about 6 metres or below, even below 5.5 metres.

One form of turnout in accordance with the present invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 is a schematic top plan view of part of a crossing of a turnout in which the angles between the rails have been exaggerated for the sake of clarity; Figure 2 is a section along the line I-I of figure 1; Figure 3 is a section along the line II-II of figure 1.

Referring to the accompanying drawings, the crossing of a turnout according to the invention includes a vee-shaped section 1 that has a pair of legs 2 and 4 that come together at one end thereof and are welded together to form the nose 6 of the section, and which are joined at their other end to fixed rails 8 and 10. The distance between the end of the nose 6 and the point 12 at which the legs are joined to the fixed rails (the heal of the vee-shaped section) is in the region of about 12 metres.

A pair of wing rails 14 and 16 are arranged so that their separation decreases until a constriction 18 is reached, whereupon their separation increases. The nose 6 of the vee-shaped section is located between the pair of wing rails 14 and 16 to one side of the constriction 18, and can be moved, in accordance with the setting of the turnout so that the nose 6 abuts one or the other of the wing rails. As the wheels of the rolling stock passes over the crossing, for example from left to right as viewed from figure 1, the wheels are first supported by the wing rail 14 until it passes over the constriction 18, whereupon it is supported by the nose 6 of the vee-shaped section and thence by leg 2 thereof until it is supported by rail 10. If the turnout were set in its other position so that the nose 6 of the vee-shaped section abutted wing rail 16, the rolling stock wheels would pass from wing rail 16 via nose 6 to leg 4 and rail 8.

The part of the wing rails around the constriction 18 are formed as a monobloc or one-piece construction, for example formed by casting (a cast cradle) from manganese steel as shown in cross-section in figure 2, and which extends for some small distance along the wing rails on the opposite side to that which encloses nose of the vee-shaped section, and, on the same side as the vee-shaped section the casting extends substantially the same distance as the length of the nose, that is to say, from the constriction 10 (where the nose ends) to the point 22 where the legs forming the vee-shaped section begin to separate. At positions beyond the end of the casting, the wing rails 14 and 16 are fabricated separately and are separately fixed to the sleepers 24 for example by means of buttress brackets 26 bolted to the wing rails through the vertical web thereof.

The two wing rails subtend an angle a to one another, typically corresponding to a divergence thereof of about 1 in 50, while the legs of the vee-shaped section subtend an angle ss. In conventional turnouts, angle ss needs to be smaller than angle a in order to accommodate the rotation of the vee-shaped section as a whole as it moves between the wing rails. In the arrangement, the ends of both legs 2 and 4 of the veeshaped section are joined to the fixed rails 8 and 10 at the heal, with the result that the relative lengths of the legs must change as the vee-shaped section moves from one position to the other. This is achieved by allowing one of the legs to bend into a very slightly serpentine configuration. As shown in figure 1, leg 2 is straight while leg 4 is bent into a serpentine configuration to take up the excess length (this is too shallow a degree of bending to be seen in the drawing), while as the nose of the vee-shaped section moves toward wing rail 16 i.e. in an anti-clockwise direction as viewed in the drawing, leg 4 becomes straight while leg 2 becomes bent. This change of bending causes the nose of the vee-shaped section to rotate with respect to the vee-shaped section as a whole in the opposite direction. In the invention, the rotation of the nose with respect to the vee-shaped section as a whole is preferably substantially the same as the rotation of the vee-shaped section, with the result that the two rotations cancel one another out, and the nose thus moves laterally between the wing rails with no rotation. This enables the angle t3 to be increased so that it is the same as angle a. It is even possible for the nose to rotate with respect to the vee-shaped section by a greater degree than the angle through which the vee-shaped section rotates, with the result that the angle 13 could be larger than angle a. This enables the length of the nose of the vee-shaped section to be reduced from a conventional value of about 7.5 metres to a value of about 5 metres. This reduction of length of 2.5 metres in the length of the nose 6 enables a corresponding reduction of 2.5 metres in the length of the casting 20.

Claims

Claims: 1. A swing-nose crossing of a railway turnout, which comprises a substantially vee-shaped section that is formed by a pair of legs that are joined together at one end thereof to form a nose, each of which legs is joined to one of a pair of fixed rails at the other end thereof, the nose being movable laterally within a pair of wing rails between two positions in accordance with the setting of the turnout so that, in each of the two positions, one side of the nose contacts one or the other of the pair of wing rails, wherein, in each of the two positions, one leg of the vee-shaped section is flexed into a shallow serpentine shape, the leg of the vee-shaped section that is flexed changing as the nose moves from one of its positions to the other in order to accommodate a change in the relative overall length of the legs, characterised In that the pair of wing rails are formed as a one piece construction at least in the region of the nose of the vee-shaped section.
2. A crossing as claimed in claim 1, wherein the pair of wing rails are formed as a casting in the region of the nose of the vee-shaped section.
3. A crossing as claimed in claim 1 or claim 2, wherein the pair of wing rails are formed as a one piece construction only in the region of the nose of the vee-shaped section.
4. A crossing as claimed in any one of claims I to 3, wherein the nose of the veeshaped section extends for a length of not more than 6 metres.
5. A crossing as claimed in claim 4, wherein the nose of the vee-shaped section extends for a length of not more than 5.5 metres.
6. A crossing as claimed in any one of claims 1 to 5, wherein the nose undergoes substantially no rotation as it moves between the two positions.
7. A crossing as claimed in any one of claims 1 to 5, wherein the nose rotates in a sense opposite to the rotation of the vee-shaped section as it moves between the two positions.