Point drive system with a plurality of drive units

Abstract

 A drive system for railway points, comprising a plurality of drive units (10) connected to respective cranks (32) for moving rails at respective locations along the points, each drive unit (10) comprising drive means (26) and a drive output for connection to a respective crank (32), characterised in that the outputs of the units (10) are connected, such that operation of any single drive unit (10) causes driving of all of the cranks (32).

Description

[0001] The present invention relates to the driving of railway points.

[0002] A supplementary drive system for operating long railway points in a coherent and synchronised manner which can be manually operated from one position and that locks the switch rail of a set of points to its adjacent running rail at all supplementary input positions, which is not dependent upon the movement of the switch blade to provide supplementary inputs, and which is tolerant to changes in temperature, rail creep and train run-through is the subject of EP-A-1512603.

[0003] In that drive system, shown in Figure 1, a drive unit 10 comprises a drive means, e.g. a motor, which drives a drive member 30 along a first axis, substantially parallel to the railway tracks 1-4. The drive member engages a crank 32 connected to a drive bar 11, such that movement of the drive member along the first axis is converted by the crank into movement of the drive bar along a second axis orthogonal to the first axis. The drive bar is connected to the movable rails 2, 3 of a point system, causing the state of the points to change by suitable operation of the drive means. An important feature of the system is that additional cranks 39, 40 may be connected in-line with the drive member so that the rails can be moved at various locations along their length.

[0004] A disadvantage of this system is that the drive unit has to be placed at the "toes" or ends of the movable rails. In congested areas such as those that exist in large railway station areas and their approaches, this may be problematic to arrange.

[0005] It is an object of the present invention to provide a supplementary drive system for operating long railway points in a coherent and synchronised manner in which the drive unit may be positioned at any location along the length of the points.

[0006] In accordance with a first aspect of the present invention, there is provided a drive system for railway points, comprising a plurality of drive units connected to respective cranks for moving rails at respective locations along the points, each drive unit comprising drive means and a drive output for connection to a respective crank, characterised in that the outputs of the units are connected, such that operation of any single drive unit causes driving of all of the cranks.

[0007] Preferably, operation of the or each drive unit may be effected manually.

[0008] In accordance with a second aspect of the invention there is provided a set of railway points comprising a pair of movable rails connected to the above drive system.

[0009] The or each drive unit may be located between the rails.

[0010] The invention will now be described by way of example with reference to the following figures, in which:-

Figure 1 shows a schematic plan of a points system not in accordance with the present invention,

Figure 2 shows a schematic plan of a drive unit suitable for use with the present invention,

Figures 3 and 4 show schematic plans of drive systems not in accordance with the present invention incorporating the drive unit of Fig 2, and

Figures 5 to 7 show schematic plans of multiple drive unit systems in accordance with the present invention, incorporating the drive unit of Fig. 2.

[0011] Referring now to Figure 2, an electro-mechanical point machine drive unit 10 comprises a prime mover 26, which in this case is a controllable electric motor. This drives, via reduction gear train 27, a linear ballscrew 28, thus converting the rotary motion of the motor to linear movement of ballnut 29 along an axis running from left to right as shown in the figure. The linear movement of the ballnut is transferred to drive member 30 at an intermediate point between its two ends. Drive member 30 is elongate in the direction of linear movement, so that both ends are capable of protruding beyond the drive unit for at least a portion of the range of travel of the drive member.

[0012] Roller 31 is attached to the drive member 30, and this engages with the profiled end of crank 32; the crank being free to rotate about fixed pivot 33. The other arm of the crank is connected to the output drive bar 11 via roller 34. The drive bar 11 is connected to the movable rails of a points system (not shown).

[0013] The point machine 10 thus generates two drive outputs which are positioned at right angles to each other. One drive 11 is transverse to the railway track whilst the other, drive member 30, is parallel to it. When the point machine is operating, the transverse drive output is intermittent, whilst the parallel drive is continuous. The phased sequence of drive outputs is achieved by use of the escapement crank 32.

[0014] Both ends of the drive member 30 incorporate means for connection to further drive means, which in turn may engage with further cranks.

[0015] Fig. 3 shows a drive system not in accordance with the present invention in which the drive unit 10 is located approximately halfway along the length of the points. In this case, both ends of the drive member 30 are connected to further drive means 43, 44 which engage with respective cranks 39, 40 via respective rollers 41, 42.

[0016] Fig. 4 meanwhile shows a further arrangement not in accordance with the present invention in which the drive unit 10 is located at the "heel" of the points. Here, only the end of the drive member which is nearest the toe of the points is connected to further drive means.

[0017] It is of course possible to have the drive unit at the toe end of the points, as shown in prior art Fig. 1. In this case, only the end of the drive member nearest the heel of the points is connected to further drive means.

[0018] Figs. 5 to 7 show arrangements in accordance with the present invention which include more than one drive unit 10 connected via their drive members. This is useful feature which incorporates a level of redundancy into the system, so that failure of a unit is not critical. At busy rail junctions failure of a point mechanism can cause costly delays and disruption to the operating timetable. It is therefore advantageous to have reliable point operating systems that provide the railway operator with immediate response and availability at all times. This may be achieved by introducing a level of redundancy into the system.

[0019] The application of more than one points drive machine to drive a set of railway points has been tried and indeed is still in use. However, in these known arrangements the machines act in mechanical isolation from each other and each machine can only operate on that portion of the switch blade to which it is connected. A major disadvantage of multiple powered inputs to the switch rails is that if one machine should fail for any reason, then that part of the switch rail to which it is connected will not move whilst the other portions will. Malfunctions of this nature can lead to the switch rails becoming distorted and permanently deformed and can also create a condition where derailment of a passing rail vehicle could occur.

[0020] Another problem associated with the use of known multiple point machines is that when the electrical supply has failed and it is required to move the points to their opposite position, it is then usual to revert to manual operation by use of an emergency hand-cranking mechanism incorporated within each machine. Failures of this nature are not a problem when only one point machine is used to drive a set of points, however when there is more than one, each machine has to be operated individually. In order to avoid the problems of switch rail distortion it is necessary to move all machines connected to the switch rails at the same time. To achieve this requires a person at each machine, working in unison to ensure coherency of rail movement.

[0021] However, by using a plurality of inventive drive units as shown in Fig. 2, redundancy may be achieved whilst ensuring coherency of rail movement under all conditions.

[0022] With the present apparatus, rotary motion imparted to ballscrew 28 via motor 26 and reduction gear train 27 is converted to linear movement of the ballnut 29. The linear movement of the ballnut is transferred to the drive member 30. One of the beneficial properties of the linear ballscrew is that of high mechanical efficiency and by suitable selection of thread pitch it is possible to reverse the action and convert linear motion into rotary. Thus, should a thrust of sufficient magnitude be applied to drive member 30, then this will in turn act upon the ballnut and cause the ballscrew shaft and, in turn, the gear train and motor to rotate. This mechanical feature of the drive unit 10 means that it is possible to use multiple units working in unison. Should one unit fail then it will be driven by the remaining unit or units to ensure that the switch rails are still moved in a coherent manner.

[0023] The units, and indeed of any supplementary drive elements, such as further drive means 35, 36 in Fig. 3, have their drive members 30, 43, 44 connected together via link arms 45. This enables cranks 32 and / or 40 to lock the moveable switch blades in position at each end of movement of drive. This locking action is shown typically in Fig. 5, where the system is shown in its quiescent state, with moveable switch blade 2 closed against fixed rail 1. Movement of switch rail 2 away from fixed rail 1 would require rotation of cranks 32 about their pivots 33, however this movement is prevented by rollers 31. Thus even when one of the units is not operating via its electric motor drive, it will still provide the switch blade locking function.

[0024] In the event of loss of electrical power to all of the units, the system can still be operated in a coherent manner by use of a single hand crank applied to any one of the units.

[0025] Fig. 5 shows an arrangement where the drive members 30 of three drive units 10 are connected together via links 45. The arrangement may be used for driving a long point layout such as would be used for high-speed rail vehicles.

[0026] Fig. 6 shows an alternative arrangement whereby two drive units 10 and one supplementary drive element 36 are used in combination. Of course, many different combinations of units 10 and elements 36 may be envisaged.

[0027] Fig. 7 shows two drive units operating in tandem and positioned between the rails 1, 2, 3, 4. This arrangement is particularly advantageous for underground railways where space is often restricted.

[0028] Although the invention has been described with reference to the embodiments above, there are many other modifications and alternatives possible within the scope of the claims. For example, although the lead crank 32 is shown as being housed inside the point machine 10, it is possible for the crank to be separate from it, in a similar manner to the other cranks 39 and 40 shown.

[0029] Engagement between the crank and the drive member does not have to be via a roller, and indeed any low-friction engagement means could be used.

[0030] Although the drive system of the present invention has been described with reference to a points mechanism substantially similar to that shown in Fig.1, the inventive drive system could equally be used with virtually any points mechanism requiring a linear output drive, and so the invention is not limited to the points mechanism shown.

[0031] Regarding the multiple drive unit systems, such as shown in Figs. 5 to 7, it should be noted that the left-most unit as shown only could be replaced with a known unit as shown in Fig. 1.

Claims

1. A drive system for railway points, comprising a plurality of drive units (10) connected to respective cranks (32) for moving rails at respective locations along the points, each drive unit (10) comprising drive means (26) and a drive output for connection to a respective crank (32), characterised in that the outputs of the units (10) are connected, such that operation of any single drive unit (10) causes driving of all of the cranks (32).

2. A drive system according to claim 1, wherein operation of the or each drive unit (10) may be effected manually.

3. A drive system according to either of claims 1 and 2, wherein the controllable motor comprises a controllable electric motor.

4. A set of railway points comprising a pair of movable rails connected to a drive system according to any preceding claim.

5. A set of railway points according to Claim 4, wherein the or each drive unit (10) is located between the rails.

Drawing