Rail fastening device

Abstract

A rail fastening device comprises a clip (10) having a base (11) and a nose (12) for engaging a rail flange (F). The base (11) comprises circular aperture (14) in which a circular cam (13) is rotatably mounted, the cam (13) being provided with an eccentric aperture (24) for receiving a ground anchor (25), the cam aperture (24) being radially offset from the rotational centre of the cam (13) to define a cam lobe (15). The cam (13) may comprise a ramped circumferential shoulder (18) to engage a complementary shoulder (21) inside the base aperture (14) such that any rotation of the cam (13) under the applied load of the rail causes the cam (13) to move axially of the base aperture (14) thereby tightening the engagement of the anchor (25) on the cam (13) and preventing movement of the clip (10). The degree of rotation of the cam (13) may be limited so that it can only turn in the tightening direction under load.

Claims

1. A rail fastening device comprising a clip having a base and a nose for engaging a rail, the base comprising a circular aperture in which a circular cam is rotatably mounted, the cam being provided with an eccentric aperture for receiving a ground anchor, the cam aperture being radially offset from the rotational centre of the cam to define a cam lobe, wherein the cam is seated in the base aperture, in such a way that the cam cooperates with the base aperture to cause the cam to move axially of the base aperture as the cam is rotated.

2. A rail fastening device as claimed in claim 1, in which the degree of rotation of the cam is constrained.

3. A rail fastening device as claimed in claim 2, in which the degree of rotation of the cam is constrained to 180° or less.

4. A rail fastening device as claimed in claim 2, in which the degree of rotation of the cam is constrained to a point where the lobe of the cam is directed substantially towards the head.

5. A rail fastening device as claimed in claim 1, in which, in use, the cam only rotates in a direction which moves it axially towards a head or bolt of the ground anchor when the nose of the clip is displaced towards the ground anchor.

6. A rail fastening device as claimed in claim 5, in which the direction is a clockwise direction.

Description

(1) An embodiment of the present invention will now be described by way of an example only and with reference to the accompanying drawings, in which:

(2) FIG. 1 is an isometric view of a rail fastening device in accordance with the present invention, when in a retracted position;

(3) FIG. 2 is an isometric view of the rail fastening device of FIG. 1, when in an extended position;

(4) FIG. 3 is an exploded isometric view of the rail fastening device of FIG. 1;

(5) FIG. 4 is a side view of a cam of the rail fastening device of FIG. 1; and

(6) FIG. 5 is a side view of the rail fastening device of FIG. 1, when in use.

(7) Referring to the drawings, there is shown a rail fastening device comprising a metal clip 10 having a base 11 and a raised nose 12 provided with an elastomeric member 112 on its underside which engages the flange F of a rail. The rail fastening device further comprises a circular metal cam 13 that is rotatably mounted in a circular aperture 14 formed in the centre of the base 11.

(8) The cam comprises upper and lower end surfaces 15, 16 which face in opposite axial directions and a circumferential side surface 17 which faces radially outwardly. The side surface 17 comprises a radially-extending shoulder 18 at its upper end around the periphery thereof. The underside of the shoulder 18 defines a helically-extending surface 19 which extends axially of the cam 13 from a position P1 to a position P2 which are circumferentially separated by approximately 350°.

(9) The aperture 14 in the base 11 comprises a circumferential side surface which faces radially inwardly and is provides with a radially-extending shoulder 20 at its lower end around the periphery thereof. The upper side of the shoulder 20 defines a complementary helically-extending surface 21 which extends axially and circumferentially of the aperture 14.

(10) The shoulder 18 of the cam comprises a pair of radially extending stop surfaces 22A, 22B which are circumferentially offset from each other by approximately 180° and which face each other around the circumference of the cam 13. The aperture 14 in the base 11 comprises a stop 23 which extends radially inwardly and which is arranged to abut the stop surfaces 22A, 22B in respective rotational positions of the cam 13.

(11) The cam 13 comprises an axially extending eccentric aperture 24 for receiving a ground anchor bolt 25. The cam aperture 24 is radially offset from the rotational centre of the cam to define a cam lobe 26. A hexagonal formation 27 extends around the cam aperture 24 on the upper surface 15 of the cam 13.

(12) In use, the ground anchor 25 is set in the ground or other support surface and the rail fastening device of the present invention is fitted onto the upstanding ground anchor 25 such that it extends through the cam aperture 24. Initially, the rotational position of the cam 13 is such that the lobe 26 thereof is directed away from the nose 12 of the clip 10, as shown in FIG. 1. In this position, the nose 12 is at its furthest distance from the flange F of the rail and hence the clip 10 is relatively loose. A nut 28 and washer are then loosely fitted to the upper end of the upstanding ground anchor 25. At this point the cam 13 is at its most axially raised position. A wrench or spanner is then engaged with hexagonal formation 27 and used to turn the cam 13 in the clockwise direction (when the cam 13 is viewed from above) from the position shown in FIG. 1 towards the position shown in FIG. 2. The cam 13 is displaced axially towards the ground as it is turned by virtue of the complementary helical engagement surfaces 19, 21 on the cam 13 and base 11. The rotational movement of the cam 13 causes the clip 10 to slide towards the rail flange F by virtue of the eccentric cam aperture 24. A very high locking force of the clip 10 against the rail flange F can be achieved even by applying a relatively modest turning force to the cam 13.

(13) Once the clip 10 is in the desired position against the rail flange F, the nut 28 of the ground anchor bolt can be tightened against the upper surface 15 of the cam 13 to rotationally lock the cam 13 in position and to hold the clip 10 in-situ against the rail flange F.

(14) The degree of rotation of the cam 13 is constrained, by the interaction of the stop surfaces 22A, 22B with the stop 23, to substantially 180° between the position of FIG. 1 (where the lobe 26 of the cam 13 is directed directly away from the nose 12) and the position of FIG. 2 (where the lobe 26 of the cam 13 is directed directly towards the nose 12). In this manner, any force applied to the clip 10 by movement of the rail can only cause the cam 13 to rotate in the counter clockwise direction and hence axially upwardly against the nut 28 of the ground anchor 25. This tightens the engagement of the nut 28 on the cam 13 and prevents movement of the clip 10.

(15) A rail fastening device in accordance with the present invention is simple in construction yet is able to resist very substantial forces that might be applied by the rail.