RAILWAY SWITCH ACTUATOR

Abstract: A railway line switch actuator which is selectively operated between two switching positions, and which is capable of being locked in either of its switching positions in order to maintain a railway switch or points system in any selected position. The switch actuator comprises an actuator element (19) connected to the moving part (12) of a railway switch or points system, a pivotable driving device (14), and a connecting element (21) provided on the driving device (14) and engaging with the actuator element (19) so as to apply linear movement to the actuator element (19) upon pivoting of the driving device (14). The actuator element (19) operates a conventional stretcher bar (12) or the like in order to displace moving rails in a railway switch or points system. A rack and pinion arrangement (15, 16) is provided for pivoting the driving device (14) so as to move the connecting element (21) through more than 180<o> about the pivot axis of the driving device (14) between the two switching positions, whereby the actuator element (19) is displaced linearly by the connecting element in order to carry out a switching operation. The connecting element (21) therefore has two "over-centre" positions, corresponding to the switching positions of the switch actuator, and abutment means (18) is provided to limit the pivotal movement of the driving device (14) from either one of its switching positions to the other of the switching positions, and thereby to lock the switch actuator in any switched position.

Description: Rail ay switch actuator This invention relates to a railway line switch actuator which is selectively operable between two switch- ing modes in order to effect actuation of a railway points . or switch system, the actuator being capable of being locked in either of said modes in order to maintain the system in any selected position. It is known to provide a railway line switch actuator which operates a stretcher bar of a points system via an hydraulically, electrically or pneumatically operat direct motion linkage, or a mechanical "lever-box" employing an "over-centre" spring-loaded crank. Alternat- ively, motion is transferred to the stretcher box by means of a series of rod and bell-crank levers in well known manner. It is also known to provide switch or so-called swing-nose crossing locks comprising separate or associated devices which, by a combination of moving blocks and slides, ensure that once a switch rail movement has been completed, it cannot move again without intentional operation of the sw τ itch actuator. The moving block arrangement is necessarily a relatively massive and robust arrangement so as to be able to lock any desired switch-rail position.-.. This is particularly important now with High Speed Trains which travel regularly at speeds in excess of 100 .p.h. Although the moving block arrangement operates reliably, .~>-*' ; i/ " sST -2- it is a relatively expensive item which has to be. engineered to high standards in all of its operating parts, and particularly the locking elements. Yi ' hile the arrangement will operate repeatedly in satisfactory manner 5 for all normal switch operation, it is vulnerable to improper travel of a rail vehicle through the points system- Inadvertent travel through the points system with the points set in the wrong direction will cause application of very high breakin loads to the locking parts of the 10 arrangement. In view of the robust nature of these parts to provide satisfactory locking for normal use, very considerable damage is done to the parts of the arrangement in the event of improper travel through the points system. This tends to make repair of the broken parts difficult, 15 or uneconomic, so that usually the entire unit has to be replaced. Accordingly, there exists a. need to provide a railway line switch actuator which can operate satisfactor- 20 ily during normal use, but which is simplified in construction and therefore cheaper to produce. Also, it would, be preferable to provide for simple replacement of any part of the actuator in the event of improper travel of a rail vehicle through a points system which 25 has been set in the wrong position. According to the invention there is provided a railway line switch actuator which is selectively operable between two switching modes and which is capable of being 30 locked in either of said switching modes in order to maintain a railway switch or points system in any selected position, the switch actuator being characterised by; an actuator element connectible to the moving part(s) of a railway switch or points system; 35 " pivotable driving device; a connecting element provided on the driving device and engaging with said actuator element so as to apply linear movement to the actuator element upon pivoting of the driving device; means for pivoting said driving device so as to move the connecting element through more than 180 about the pivot axis of the driving device between two switching positions corresponding to said switching modes, whereby the actuator element is displaced linearly by the connecti element in order to carry out a switching operation via the moving part of a railway switch or points system to which it is connected in use; and abutment means arranged to limit the pivotal movementof the driving device from either one of its switching positions to the other of the switching positions and thereby to lock the switch acxuator in either of its switching modes. When the switch actuator according to the invention is used with a split switch, the actuator element may comprise a bracket which is secured to a conventional "stretcher bar" of a railway sw τ itch which is secured at each end to the free ends of (moveable) switch rails. The switching positions of the connecting element will be selected to correspond with the switched positions of the sw τ itch rails. Upon pivoting of the connecting element from one switching position to the other, the switch rails will be displaced from one switched position to the other, and will be locked in the new switched position by virtue of the cooperation between the connectin element and the abutment means. As indicated above, the connecting element pivots through more than 180° Cabout its pivot axis) between its R A SU_G . = i YE SHΞΞT ~W1I J -3a- two switching positions, and this gives rise to an "over- centre" arrangement whereby any tendency for a switch rail to move from a particular switched position is strongly resisted ' - via the stretcher bar, actuator element (bracket), connecting, element and the abutment means. Conveniently, ... -4- the connecting element pivots through approximately 190 , thereby giving 5° over-centre positioning for each position. Preferably, the means for pivoting the driving 'device ' effects reversible pivoting motion to the driving device, though it should be appreciated that the arrangement may be modified so that the driving, device car out intermittent uni-directional rotation between its switching positions. The driving device may comprise a cam-base having an off-centre pinion drive which is driven by any convenient means e.g. a piston-cylinder arrangement such as a double- acting hydraulic cylinder or two oppositely acting piston and cylinder arrangement s. or simple -mechanical lever However, any other .suit able means may be adopted, including proprietary rotary valve actuators. The drive to the pinion may be by means of a reciprocating rack, preferably a linearly moveable rectilinear rack, and the abutment means may comprise stops arranged to determine end limits for the reciprocatio of the rack. To enable fine adjustment of the switching position -of the cam base, the connecting element may be adjustably mounted thereon. Thus, the connecting element , which preferably takes the form of a rotatable cam block, may be adjustable along a diameter of the cam base so as to vary the "throw" of the cam block i.e. the extent , in degrees, of over-centre movement. Following fine adjustment to take into account track geometry, rail wear, inaccuracies in construction, and variation in the gauge of stock rails, the cam block may be fixed permanently in position relative to the cam base. Conveniently, proximity switches may be provided at the limit stops so as to generaxe signals e.g. to a ■ ' *=" :-r -5- signal box, regarding the status of the railway switch. To avoid severe damage to the switch actuator, in the event of forced opening of the switch by travel through the switch by a rail vehicle when the switch is set to the wrong setting, a frangible connection may be incorporated in the drive connection between the moving rails and the cam base. Conveniently, the connecting element may include a shear bolt e.g. a bolt having a deliberate design weakness, so that the bolt will shear before any further damage is done to the remaining parts of the switch actuator. In the event of such a failure of the switch actuator, it would be a simple, and cheap matter to replace the broken bolt. This will be a significant advantage over the known moving block arrangements, since repair can be carried out quickly, and also cheaply. Alternatively, a resiliently yieldable linkage may be provided to yield from a datum position when a predetermined minimum load is exceeded by the forced opening of the points system. The predetermined load will be -selected to have a lower value than the strength of the weakest link in the actuator. -The arrangement of the linkage is such that it is able to return to the datum position after the excessive load has been removed. While the switch actuator according to the invention has been described above in relation to use with a split switch, it should be understood that the switch actuator may readily be employed, with or without appropriate modification in manner readily apparent to those skilled in the art, to actuate other railway switches or points, including turnouts and double turnouts, crossing switches and movable "swing-nose" crossings. -6- One embodiment of railway line switch actuator according to the invention will now be described in detail by way of example only, with reference to the accompanying drawings in which:- Figure 1 is a schematic illustration of the switch actuator mounted in position to operate switch rails of a split switch; Figure 2 is a sectional view illustrating, in more detail, part of the switch actuator shown in Figure 1; Figure 3 is a further sectional view of the part of the switch -actuator shown in Figure 2; Figure 4 is a schematic illustration of a resiliently yieldable linkage for use with the switch actuator; Figure 5 is a schematic illustration of further arrangements for locking moving switch rails in either of two switching positions; Figure 6 is a detailed view of a driving connection for operating a locking beam shown in Figure 5; Figure 7 is a schematic illustration of a drive connection from the switch actuator of Figures 1 to 3 for providing additional driving of long (high speed) switches; Figure 8 is a detailed illustration of a locking shoe shown schematically in Figure 5; and Figures 9a and 9b illustrate two alternative means for driving the locking shoe shown in Figure 8, Referring now to the drawings, there will be described in detail the parts of a railway line switch actuator which is selectively operable between two switching modes and which is capable of being locked in either of the switching modes in order to maintain a railway switch or points system in, any selected position. The switch actuator comprises an actuator element connectible to the moving partCs) of a railway switch ^ " -7- or points system, a pivotable driving device, and a connecting element provided on the driving device and engaging with the actuator element so as to apply linear movement thereto. Means is provided for pivoting the driving device so as to move the connecting element through more than 180 about the pivot axis of the driving device between two switching positions corresponding to the switching modes, whereby the actuator element is displaced linearly by the connecting element in order to carry out a switching operation via the moving part(s) of a railway switch or points system to which it is connected in use. Abutment means is arranged to limit the pivotal movement of the driving device from either one of its switching positions to the other of the switching positions and thereby to lock the switch actuator and to resist any tendency for the connecting element to move unintentionally from either of the switching positions. Referring now to Figure 1 of the drawings, Figure . ' La is a plan view of a railway line switch actuator 1O arranged to operate a pair of switch rails 11 of a split switch via a conventional stretcher bar 12. The switch is shown in Figure la in a straight- through switching mode, " ' ' : -8" in which a rail vehicle will continue to travel along stock rails 13 after passage through the railway switch. In Figure lb, the switch actuator 10, and the switch rails 11, are shown occupying an alternative switching mode, in which a rail vehicle travelling along stock rails 13 will be diverted to the right. Figure lc is an end view of the actuator 10. As shown in Figures la to lc, the switch actuator 10 comprises a driving device in the form of a cam base 14 which has a .pinion drive 15 engaged by a rectilinea ϊy movable rack 16. The rack 16 is reciprocated between end limits by means of a double piston and cylinder arrangement 17, and rack stops 18 serve to define limits to the movement of the rack 16. The particular means adopted to pivot the cam base 14 is not critical, and any convenient means may be provided in order to pivot the cam base 14 through approximately 190 between its two switching positions. An actuator element in the form of a bracket 19 is provided , which serves to transmit linear motion to the stretcher bar 12 from the actuator 10. The bracket. 19 is secured to the stretcher bar 12, and has an elongate cam follower slot 20 in which is slidable a connecting element provided on the cam base 14. The connecting element comprises a cam block which is shown in more detail in Figures 2 and 3. When the cam base 14 is pivoted to -either of its switching positions, as shown in Figures la and lb, the apparatus is set-up in such a way that the rack 16 will be in firm engagement with a respective one of JTΪ *T ~ -9- the stops 18 , and the swit ch rai ls 11 will be pressed firmly into the selected swit ching positions . Any tendency for the swit ch rails to move away from the switched positions will be resisted strongly via the stret cher bar 12 , bracket 19 , the cam block , the cam base 14 , the rack 16 and the respective stop 18. This arises , by virtue of the over-centre positions of the cam base and cam block . Referring now to Figures 2 and 3 , the arrangement of the cam block on the cam base 14 is shown in more detail . The cam block is designated generally by reference numeral 21 and comprises an outer stepped sleeve 22 of cast iron , an inner bronze bush 23 , - and an Allen bolt 24 whi ch mounts the cam block on cam base 14. The cam block 21 is slidably moveable along the cam follower s lot 20 in bracket 19 , as shown in Figure 1. The arrangement of the cam base 14 and the cam block 21 , in relation to drive pinion 15 , is such that the cam block 21 will occupy over-centre positions i . e . pivot through more than 180° , when the rack 16 moves between the stops 18. To provide fine adjustment (see arrows XY) of the "throw" of the cam block , the latter is adjustable along a diameter of the cam base 14 . To this end, the -Allen bolt 24 extends through the cam b ase 14 into t apped slug 25 which is received in a radial bore 26 formed in the cam base 14. Radial adjustment of the tapped slug 25 will effect minor variation in the degree of over- centre movement of the cam block 21 for its switching positions . Once the fine adjustment has been completed, to take into account track geometry, rail wear , other inaccuracies and the variation in the gauge of the stock rails . the cam block can be permanently secured in • position .- This may be " achieved by firm clamping of the » ■ -10- Allen bolt 24, and then additionally, if desired, by tack-welding the slug 25 to the cam base 14. To avoid severe damage to the switch actuator in the event of forced opening of the switch by illegal traffic, the clamp bolt 24 may be provided with a shear plane e.g. by grooving, so that any unusual force will result in the cam block 21 shearing-off, rather than damage being caused to the remaining parts of the switch actuator. If desired, proximity switches may be arranged to cooperate- ith the stops 18 , so as to generate appropriate signals to indicate the status of the switch. Accordingly, as has been disclosed in detail abov with reference to the drawings, the present invention provides a simple design of switch actuator which combines switch movement and switch locking in one self-contained unit. In the preferred embodiment, a simple rack and pinion is employed to rotate a cam base through 190 . This rotating motion is converted to linear movement by a sliding block cam. At each extreme of the rack movement, a positive mechanical stop is employed. These positions relate to the open and closed switch positions. Once the intended position is achieved, any opening thrust on th switch rail is resisted by the 5° "over-centre" position of the cam block, which transmits the thrust directly to the rack stops, thereby locking the switch in position. Operation of the rack in the opposite direction immediately releases the cam , which is free to rotate through 190°, enabling the switch to take up its alterr position, in which it is again in a locked state. -11- Referring now to Figure 4 of the drawings, there is shown a modified construction for the connection between the actuator and the stretcher bar of the points system. In particular, the bracket 19 is modified to comprise a slotted plate 27 having a slot 28 in which the connecting element of the actuator is received, in similar manner to that described above for the bracket 19.. A spring housing 29 is mounted on the plate 27, and a stretcher bar 30 is taken through the spring housing 29. The stretcher bar 30 is of round cross- ' section, as currently in use in most up-to-date designs of British railways switches. A disc 31 is welded to the stretcher bar 30, and the disc 31 tends to be maintained in a datum position, as shown, -by means of a pair of heavy duty coll springs 32 which are arranged on the stretcher bar 30, one on either side of the disc 31. The springs 32 are compression springs which maintain a rigid connection between slotted plate 27 and stretcher bar 30, up to a minimum predetermined load. This will enable the actuator to displace the switch rails whenever it is actuated. Accordingly, thusfar, the arrangement shown in Figure 4 can operate in similar manner to that described above with reference to Figures 1 to 3. However, in the event of forced opening of the railway switch by incorrect travel of a rail vehicle through the switch, when the latter has been set in the wrong direction, the resiliently yieldable linkage illustrated in Figure 4 operates so as to yield, rather than cause any damage to the operating parts of the actuator. The design parameters are set up such that there will be a minimum predetermined load to cause the linkage to yield, this minimum load having a lower -12- value than the strength of the weakest element in the actuator. When the railway switch is forced open , . a respective one of the springs 32 will undergo compressi but when the excessive load has been removed, the spring will return the stretcher bar 30 and disc 31 to the datum position. A proximity switch 33 is arranged to cooperate with the disc 31, so as to give a warning signal when the points switch has been forced open. The proximity switch may also be arranged to provide a further signal when the situation has returned to normal. While the preferred embodiment of switch actuator has been described in relation to the operation of a split switch, it should be understood that the switc actuator is applicable , to actuate many other types of railway switches or points, with or without appropriate modification, and including particularly swing-nose crossings. . The switch actuator shown in Figures 1 to ' 4 may also be used to-operate additional devices which " control the locking of moving rails in different switching positions. . These additional devices may be provided for the purpose of further locking of the " moving rails, which is additional to that provided by the abutment stops 18 operating in conjunction with the movement of the connecting element 21 to its "over-centre"-, positions. One additional locking device is shown in Figures 5a to 5c, which comprises an arrangement of locking beams 34 which " are longitudinally moveable in order to lock the ends of switch rails 35 in a straight -13- ahead switching position relative to straight stock rails 36, as shown in Figure 5a, or in a switched position running into curved stock rails 37 as shown in Figure 5c. The moving switch rails 35 are shown in an intermediate position in Figure 5b. The movement of the switch rails 35 is carried out by means of the switch actuator device shown in Figures 1 to 3, or 4, which applies linear motion to a stretcher bar or the " like (.12) via cam base 14, connecting element 21 and actuator (19) '(this is not shown in Figures 5a to 5c). In order to ove the locking beams 34 longitudinall at the appropriate times, a drive connection is taken from cam base 14 which serves to move the beams 34 and release the switch rails 35 from one of the pair of stock rails Csay stock rails 36), so that the switch rails can be moved by the switch actuator to the other switching position (1B. line with curved stock rails 37), and then to move the beams to lock the switch rails ' in the new position. This longitudinal movement of the " beams 34 can * be seen from Figures 5a to 5c. The drive connection is shown only schematically in Figures 5a to 5c, comprising cams 38 (which are driven by a master " cam corresponding to cam base 14 of Figures 1 to 3) which naye a toothed drive connection with the beams 34, as shown in more " detail in Figure 6, Via teeth 39 on each cam 38 which mesh with rack teeth 40 on beam 34, Referring now to Figure 7, there is shown a linkage mechanism for use on long Chigh speed) switches, which provides additional pairs of« cams to drive the longer switch rails, positioned away from the toe towards the heel. These cams may be driven b the -"T " ~ -14- master cam, via the addition drive shown in Figure 7. There is shown a master (driver) cam 41 which drives a slave cam 42 via a drive chain 43, an adjustable connection rod 44, and an adjuster rod ' 45 having opposite male threads at each end, " and lock nuts 46. Thus, the switch actuator of Figures 1 to 3 may operate the switch rails at the toe end of the switch, whereas the arrangement shown in Figure 7 may be driven by the switch actuator so as to move the switch rails (on a long high speed switch) at a position away from the toe towards the heel. Referring again to Figures 5a to 5c, further (or alternative) locking of the switched positions may be obtained by means of a locking shoe arrangement composed of slidable locking shoes shown schematically as 47 in Figures 5a to 5c, The construction of the locking shoe 47 is shown in more detail in Figure 8, for co-operation with a typical stock rail 48. The locking shoes 47 also serve to lock together the adjacent ends of the switch rail 35 and stock rails 36 or 37, depending upon the switch position adopted. Each locking shoe is also displaced, in synchronism with the switch actuator of Figures 1 to 3, so as to release a pair of rail ends when a switching operation takes place, and then is moved back to lock together a pair of rail ends when the. new switched position is reached. This movement of the locking shoes will be apparent from Figures 5a to 5c. Referring now to Figures 9a and 9b, ' there are shown schematically drive connections to operate locking shoe 47. As shown in Figure 9a, a cam 49 is provided, which " may be driven as an idler can from a main driver cam, or mounted on the other end of a cam shaft, and which applies linear reciprocating movement to loj2te ~ r -15- shoe 47. Thus, rotating cam 49 can withdraw shoe 47 from a stock rail, follows the movement of the switch rail (35), and then moves the shoe 47 into locking engagement with a stock rail in the new switched position. As shown in Figure 9b, a toothed cam 50 is provided which engages in a double sided " rack 51 mounted in a yoke 52. The locking shoe 47 sits in a slideway 53 cut in the yoke 52. As the cam 50 rotates, it causes the locking shoe 47 to be withdrawn (which is free to move in the slideway as the switch rail 35 moves) . The toothed section 54 of cam 50 then disengages from one side of double rack 51, and further rotation of the cam 50 brings the toothed section 54 into engagement with the other side of double rack 51, thereby to displace the locking shoe 47 again in the opposite direction so as to lock—over the stock rail in the new switched position. . As an alternative to the construction shown in Figure 9b, the toothed section 54 of the cam 50 may be replaced by a solid "dog" of the same shape, and the double rack 51 replaced by solid bars, with the shape shown dotted (on rack 51a of double rack 51) cut into them. 0 W:

Claims: -16- CLAIMS: 1. A railway line switch actuator which is selectively operable between two switching modes and which is capable of being locked in either of said switching modes in order to maintain a railway switch or points system in any selected position, the switch actutator being characterised by: an actuator element (19) connectible to the moving part (12) of a railway switch or points system; a pivotable driving device (14); a connecting element (21) provided on the driving device (14) and engaging with said actuator element (19) so as to apply linear movement to the actuator element (19) upon pivoting of the driving device (14); means (15, 16) for pivoting said driving device (14) so as to oye the connecting element (21) through more than .180 about the pivot axis of the driving device (14) between two switching positions corresponding to said switching modes, whereby the actuator element (19) is displaced linearly by the connecting element (21) in order to carry out a switching operation via the moving part 12) of a railway switch or points system to which it is connected in use; and abutment means C18) arranged to limit thepivotal movement of the driving device (14) from either one of its switching positions to the other of the switching positions, thereby to lock the switch actuator in either of its switching modes * 2. A switch actuator according to claim 1, characterised in that the means for pivoting the driving device " (14) comprises a rack and pinion arrangement (15, 16). 3, A, switch actuator according to claim 2, „_- -17- characterised in that the pinion (15) is secured to the driving device (14). 4. A switch actuator according to claim 3, characterised in that the rack (16) is a linearly moveable rack. 5. A switch actuator according to claim 4, characterised in that the abutment means (18) comprises a pair of stops arranged to define end positions for the linear movement of the rack (16). 6. A switch actuator according to claim 4 or 5, characterised in that a piston-cylinder arrangement (17) is provided to reciprocate the rack (16), 7. A switch actuator according to any one of thepreceding claims, characterised in that the connecting element (21) is adjustably mounted on the driving device (14). 8. A switch actuator according to claim 5, characterised by proximity switches arranged at the limit stops (18) to generate signals indicative of the status of the switch actuator. 9. A switch actuator according to any one of the preceding claims and including a rail— oving element (12) connected to the actuator element (19), characterised in that a frangible connection is provided in the connection between the " rail-moving element (12) and the actuator element (19) . 10. A switch actuator according to any one of, claims 1 to 8, characterised in that a res ' iliently yi.eldable linkage (29, 32) is provided in the connection between the actuator (27) and" a stretcher bar (30) which operates a railway switch. -18- 11. A switch actuator according to any one of the preceding claims, characterised by a locking beam arrangement (34) arranged to be driven in synchronism with the pivoting of the driving device (14) so as to reciprocate longitudinally between locking and unlocking positions relative to two adjacent rail ends. 12. A switch actuator according to any one of the preceding claims, characterised by a locking shoe " (47) arranged to be driven in synchronism with the pivoting • of the driving device (14) so as to move between locking and unlocking positions relative to two adjacent rail ends. 13. A switch actuator according to any one of the preceding claims, characterised by an additional driving arrangement (41 to 46) for displacing switch rails in a long switch, said additional drive arrangement being driven in synchronism with the pivoting of the driving device (14).

Inventors: HANCOCK JAMES JUSTINIAN
Applicants: HANCOCK JAMES JUSTINIAN, THOS WARD W LTD
Application year: 1982
Main classification: B61L5
IPC codes: B61L5