GB2037468A

GB2037468A - Drive for railway points

Info

Publication number: GB2037468A
Application number: GB7940485A
Authority: GB
Original assignee: FABEG GmbH
Current assignee: FABEG GmbH
Priority date: 1978-11-24
Filing date: 1979-11-22
Publication date: 1980-07-09
Also published as: SE438565B; BE880158A; SE7909656L; NL7908366A; IT7927535A0; DE2850855C3; DK495279A; DE2850855B2; CH643958A5; FR2442377A1; IT1125858B; DE2850855A1

Abstract

A push/pull rod (1) for driving points is arranged within an enclosing coupling sleeve (2) between two spaced bearing bushes (3 and 4). The coupling is by means of a ring of bearing balls (14) which are held in an annular groove (15) by the force of cup springs (6) and (7), biasing pressure discs (12) and (13) displaceable on the push/pull rod (1) and radially by a ball guide ring (16). The coupling permits setting of the points by movement of the sleeve 2 but can release to allow relative movement of rod and sleeve when a train moves over incorrectly set points. <IMAGE>

Description

SPECIFICATION A coupling The present invention relates to a coupling for use in inter alia drives of points or switches in for example railway systems.

Widely varying fieids of engineering require safety and slip couplings. For linear movement transmission, couplings have been disclosed which are based upon the fact that the forces acting between the coupling parts are transmitted by spring-loaded balls which are situated in grooves of a part disposed transversely to the direction of movement. At a predetermined force, the balls are pushed back and the parts can slide past each other.

In a known apparatus for sealings in a cable coupling, for example, a detent sleeve equipped with peripheral detent grooves is used, an associated detent rod of which possesses a transverse bore in which a ball spring detent consisting of two balls with an intermediate spring is situated (e.g. DE-OS 1755919 Fig. 2, components 47-51).

For high actuating forces to be transmitted, such as are required, for example, in drives for changing over railway points, such ball couplings cannot be used. Here, the holding force for the switch tongues must be above the maximum actuating force by a safety margin, which is effected by mechanical fixing and locking while nevertheless the running-on of the wheels of a train dnto an incorrectly positioned switch is guaranteed.

According to the present invention there is provided a coupling comprising a rod member provided with an annular recess and slidably mounted in a surrounding sleeve, at least one ball disposed between the rod member and the sleeve and locatable within the recess, pressure members each disposed at a respective opposite side of the or each ball, resilient biasing means to urge the pressure members axially of the rod member to bear against the or each ball when in the recess, and an element disposed to radially inwardly engage the or each ball, the or each ball being displaceable from the recess on application of a predetermined force to the sleeve or the rod axially thereof.

The pressure members may each comprise a disc member.

The rod member may be slidably journalled in spaced bushes.

Each pressure member may comprise a respective bushing provided with a flange, the biasing means comprising spring means each extending between a respective one of the spaced bushes and a respective one of the bushings.

The spaced bushes may be threadably displaceable towards and away from each other to vary the biasing effect of the spring means.

The recess may be provided with chamfered side walls to facilitate said displacement of the balls.

The sleeve may be provided internally with a recess which receives the element.

The element may be annular and comprise a portion which tapers radially inwardly thereof.

The sleeve may comprise two tubular members and the recess therein may comprise a respective recess portion in adjacent end portions at each tubular member.

The sleeve may be provided with abutments each disposed to engage a respective flange of each pressure member to limit the minimum spacing therebetween.

Each abutment may comprise a step in the internal wall of the sleeve.

The biasing means may comprise cup springs.

An embodiment of the present invention will now be more particularly described by way of example and with reference to the accompanying drawings in which: Figure 1 shows a coupling in a detent position and Figure 2 shows the coupling in a disengaged position.

In the drawings reference 1 denotes a push/pull rod which is slidably journalled in end bearing bushes 3 and 4 inside a coupling sleeve 2 assembled from two tube parts 2a and 2b. The bearing bushes are provided with threads 5 and can be screwed into the coupling sleeve 2. Flanged bushes 8 and 9 are pressed against abutments 10 and 11 in the internal wall of the coupling sleeve 2 by means of columns of cup springs 6 and 7 which thrust against the bearing bushes 3 and 4. The flanged bushes 8 and 9 firmly hold, via hardened pressure discs 1 2 and 13, a ring of bearing balls 1 4 in an annular groove 1 5 provided in the push/pull rod 1. For additional radial fixing of the bearing balls 14, a ball guide ring 1 6 is introduced between the two tube parts 2a and 2b.The push/pull rod is hardened in its central region.

In Fig. 1 the ball coupling is shown in the engaged (locked) state. Up to a force predeterminable by the prestress of the cup springs 6, 7 the coupling is rigid. If this force is exceeded, for example by a tensile force (for example corresponding to arrow in Fig. 2) exerted on the push/pull rod 1, the righthand flanged bush 9 together with the pressure disc 1 3 is pressed out of the end position against the cup spring 7 (column) acting on it by the bearing balls 14 lying in the annular groove 15, sufficiently far for the bearing balls 14 guided by the ball guide ring 1 6 to displace into a sleeve chamber 1 7 around the push/pull rod 1. This is illustrated in Fig. 2.

The coupling is thereby disengaged. The position of the left-hand flanged bush 8 here remains unchanged, since as before it still bears with its flange against the abutment 10 of the coupling sleeve 2. As a consequence of the displacement of the bearing balls 1 4 into he sleeve chamber 17, the push/pull rod 1 can now be pulled out with very little force.

In order to restore the disengaged ball couplings, the push/pull rod 1 must be guided back or the coupling sleeve 2 must be displaced in the opposite direction. As a result of the ball guide ring 16, the bearing balls 1 4 again engage in the central position into the annular groove 1 5. In the drawing, there is shown in broken line an actuating cylinder 18, which by means of entraining devices 1 9 can move the push/pull rod 1 via the ball coupling in two directions. By means of the screwing bearing bushes 3 and 4 the prestress of the cup springs 6 and 7 and thus the actuating force of the ball coupling can be separately adjusted. This force can, if necessary, be given directionally-specific different values.If one or more cup springs in the column should rupture, this holding force alters only comparatively slightly. For example, if three cup springs in each column should fail simultaneously, there is only a reduction in the holding force of about 5%. The cup springs are, moreover, loaded only statically, which improves reliability.

The walls of the groove 1 5 may be chamfered to aid displacement of the balls from the groove. By varying the angle of the chamfer the ratio of the force required to displace the ball to the residual force can be varied.

The coupling described above by way of example is eminently suitable in conjunction with drives for railway switches. Here, for example, the indicated hydraulic cylinder 18, after an idling preliminary stroke of the order of 20 mm, entrains the ball coupling via the dog 1 9 and with it the push/pull rod 1, which is connected to the switch tongue. In a limiting position after approximately 220 mm the ball coupling is externally locked at the coupling sleeve. The holding force of the push/pull rod 1 may be about 7.5 + 0.5 kN.

If a train runs onto an incorrectly positioned switch, the holding force of the ball coupling is exceeded and the push/pull rod 1 can, in spite of being locked, easily slide through the ball coupling up to a maximum distance of for example 1 60 mm.

The ball coupling described above by way of example permits, in switch drives, a release of the holding force independently of the locking as a vehicle runs onto the points and, after a short release travel, causes the push/pull rod 1 to slide with extremely low frictional force through the coupling sleeve 2. It furthermore permits, for a given holding force, a higher change-over resistance to the tongues of the points.

Claims

1. A coupling comprising a rod member provided with an annular recess and slidably mounted in a surrounding sleeve, at least one ball disposed between the rod member and the sleeve and locatable within the recess, pressure members each disposed at a respective opposite side of the or each ball, resilient biasing means to urge the pressure members axially of the rod member to bear against the or each ball when in the recess, and an element disposed to radially inwardly engage the or each ball, the or each ball being displaceable from the recess on application of a predetermined force to the sleeve or the rod axially thereof.

2. A coupling as claimed in claim 1, wherein the pressure members each comprise a disc member.

3. A coupling as claimed in either claim 1 or claim 2, wherein the rod member is slidably journalled in spaced bushes.

4. A coupling as claimed in claim 3, wherein each pressure member comprises a respective bushing provided with a flange, the biasing means comprising spring means each extending between a respective one of the spaced bushes and a respective one of the bushings.

5. A coupling as claimed in claim 4, wherein the sleeve is provided with abutments each disposed to engage a respective flange of each pressure member to limit the minimum spacing therebetween.

6. A coupling as claimed in claim 5, wherein each abutment comprises a step in the internal wall of the sleeve.

7. A coupling as claimed in any one of claims 4 to 6, wherein the spaced bushes are threadably displaceable towards and away from each other to vary the biasing effect of the spring means.

8. A coupling as claimed in any one of the preceding claims, wherein the sleeve is provided internally with a recess which receives the element.

9. A coupling as claimed in claim 8, wherein the sleeve comprises two tubular members and the recess therein comprises a respective recess portion in adjacent end portions of each tubular member.

10. A coupling as claimed in any one of the preceding claims, wherein the recess is provided with chamfered side walls to facilitate said displacement of the balls.

11. A coupling as claimed in any one of the preceding claims, wherein the element is annular and comprises a portion which tapers radially inwardly thereof.

1 2. A coupling as claimed in any one of the preceding claims, wherein the biasing means comprises cup springs.

1 3. A coupling substantially as hereinbefore described with reference to the accompanying drawing.

14. A points drive for a railway track switch and comprising a coupling as claimed in any one of the preceding claims.