WO2002049902A1

WO2002049902A1 - Actuator arrangements

Info

Publication number: WO2002049902A1
Application number: PCT/GB2001/005557
Authority: WO
Inventors: Anthony Roger Davies
Original assignee: General Signal Uk Limited
Priority date: 2000-12-19
Filing date: 2001-12-17
Publication date: 2002-06-27
Also published as: AU2002222231A1; DE60132813T2; DE60132813D1; PT1345803E; CN1487893A; ATE385936T1; DK1345803T3; ES2300306T3; CN1209262C; EP1345803B1; CY1107378T1; EP1345803A1

Abstract

An actuator arrangement for moving first and second members (3, 4), the two members (3, 4) being interconnected with one another by a linkage (5) extending between them. The arrangement comprises first and second actuator means (6, 7) arranged to bear against respective movable members (3, 4) such that actuation of the first actuator (6) causes both movable members (3, 4) to move in one direction and actuation of the other actuator (7) causes both movable members (3, 4) to move in the opposite direction. A locking mechanism (20, 21) is coupled with the first and second actuators (6, 7) and is so arranged as to allow free movement in opposite directions caused by actuation of the first and second actuator means respectively but to prevent movement in either direction when not caused by actuation of the respective actuator means.

Description

DESCRIPTION

"ACTUATOR ARRANGEMENTS"

This invention relates to actuator arrangements.

Various kinds of actuator arrangements are used to switch railway points or

switchgear. A main drive actuator bears against the switch rail close to its free end or toe

and acts to push this against the side of the fixed stock rail. Where the switch rail has a

long curved section it may be necessary to have one, two or up to three additional

actuators, or backdrive actuators, spaced along the switch rail to push it and hold it in

position relative to the stock rail. The main drive actuator usually includes some form

of clamp or latch that positively locks the switch rail against the stock rail. This ensures

that the switch rail is held in the correct position even if the force applied by the actuator

itself should fall. Because railway points may be held in a switched period for prolonged

periods, perhaps for several days, there is inevitably some relaxation in the actuator, such

as caused by leakage of hydraulic fluid and, therefore, a gradual loss of force. It is less

easy to lock the switch rails in the desired position at the location of the backdrive

actuators because the switch rails may be spaced from the stock rail. For this reason, the

usual practice is to monitor displacement of the switch rails from the desired position and

to correct for this as necessary by reapplying power from the backdrive actuator. Any

detected deviation of the switch rails from their desired position will cause a momentary

failure indication before repowering of the actuator has corrected for this. This can lead

to the generation of a danger signal on the railway line with consequent interruptions to rail traffic.

It is an object of the present invention to provide alternative actuator

arrangements.

According to one aspect of the present invention there is provided an actuator

arrangement for moving first and second members, the two members being

interconnected with one another by a linkage extending between them, the arrangement

including first and second actuator means arranged to bear against respective movable

members such that actuation of the first actuator causes both movable members to move

in one direction and actuation of the other actuator causes both movable members to

move in the opposite direction, and a locking mechanism coupled with the first and

second actuators, the locking mechanism being arranged to allow free movement in

opposite directions caused by actuation of the first and second actuator means

respectively but to prevent movement in either direction when not caused by actuation

of the respective actuator means.

The actuator arrangement is preferably a hydraulic actuator. The locking

mechanism preferably includes two rods movable along their lengths and having

respective sliders movable along a channel, the sliders being arranged to apply an

outward locking force on walls of the channel when one rod is pushed towards the other.

The sliders may have cooperating inclined faces. The first and second members are

preferably switch rails.

A railway point actuator arrangement according to the present invention will now

be described, by way of example, with reference to the accompanying drawings, in which:

Figure 1 is a plan view of the arrangement;

Figure 2 is a more detailed view of the locking mechanism; and

Figures 3 to 5 show alternative locking mechanisms.

With reference first to Figures 1 and 2, the actuator arrangement is located

between a pair of fixed stock rails 1 and 2 and a pair of movable members in the form of

switch rails 3 and 4 extending between the stock rails. The switch rails 3 and 4 are linked

together by a linkage or stretcher bar 5 extending laterally between the rails.

The actuator arrangement includes two conventional hydraulic actuator cylinders

6 and 7 fixed at their bases 8 and 9 to a sleeper 10, or other fixed structure, and extending

laterally outwardly in line with one another. The cylinders 6 and 7 are driven by hydraulic fluid from a conventional supply indicated generally by the numeral 11. The

pistons 12 and 13 of the cylinders 6 and 7 each support a respective bracket 14 and 1-5 the

outer face of which carries a respective insulating nylon brush 16 and 17. The bushes 16

and 17 bear against the inside faces 18 and 19 of respective switch rails 3 and 4 so that

the switch rails can be pushed outwardly by actuation of the appropriate actuator. The

actuators 6 and 7 only make an abutting contact with the switch rails 3 and 4, enabling

them to be pushed out, and are not attached with the switch rails. The brackets 14 and

15 also support opposite ends of two locking mechanisms 20 and 21 of identical

construction.

Each locking mechanism 20 and 21 includes a first laterally-extending rod 22

connected at one end with left-hand bracket 14 by a pair of nuts 23. The opposite end of the rod 22 extends about halfway across the gap between the two brackets 14 and 15 and

carries a slider or wedge 24 having an outer face 25 extending parallel with the rod 22

and an inner face 26 inclined to the axis at an angle of about 30°. The slider 24 may carry

a roller 27, as shown in Figure 2. The locking mechanisms 20 and 21 also include a

second laterally-extending rod 28 extending inwardly from the opposite bracket 15. This

rod 28 has its outer, right-hand end secured with the bracket 15 by a pair of nuts 29 and

its inner, left-hand end carries a second slider wedge 30 shaped to cooperate with the first

slider 24. The second slider 30 has an outer face 31 extending parallel with the rod 28

and an inner face 32 inclined parallel with the face 26 of the first slider 24. The two rods

22 and 28 extend in a fixed channel 34 in the sleeper 10 having facing sides 35 against

which slide the outer faces 25 and 31 of the two sliders 24 and 30.

When the left-hand switch rail 3 is to be moved over to its adjacent stock rail 1,

a pump 40 in the supply unit 11 is operated to that fluid is supplied to the left-hand

actuator 6, thereby causing its piston 12 to extend, pushing out its bracket 14 and hence

pushing the switch rail 3 against the side of the stock rail 1. As it does this, it also pulls

the rod 22 and its slider 24 in both locking mechanisms 20 and 21 to the left along the

channels 34, along which they are free to slide. The stretcher bar 5 pulls the right-hand

switch rail 4 to the left. The inside surface 19 of the right-hand switch rail 4 bears against

the bush 17 on the bracket 15 and pushes in the piston 13 so that fluid in the cylinder 7

flows back to the supply unit 11. The two switch rails 3 and 4, therefore, both move over

to the left as a pair. The pump 40 is then turned off and a pilot-operated check valve 41

locks the left-hand actuator 6 in this position by preventing flow of fluid out of the actuator until the valve is opened. The locking mechanisms 20 and 21 prevent any

movement of the switch rails 3 and 4 to the right as a result of leakage of fluid from the

actuator 6. Movement of the switch rail 3 to the right will move the rod 22 slightly

inwardly so that the inclined surface 26 of its slider 24 slides along the inclined surface

32 on the slider 30 of the other rod 28. This causes the two sliders 24 and 30 to exert an

outward locking force on the surfaces 35 of the channel 34, so that the two sliders wedge

or jam with one another. It should be noted that the right-hand rod 28 will not be

displaced as a result of movement of the right-hand switch rail 4 to the right because the

bracket 15 supporting the rod is not attached to the rail. Thus, the switch rails 3 and 4

will remain in the left-hand position until the supply unit 11 supplies fluid to move the

piston 13 of the right-hand actuator 7 to the right. This moves the rod 28 and its slider

30 out of jamming engagement with the other slider 24.

The roller 27 of the slider 24 reduces friction between the two inclined surfaces

26 and 32 so that these can slide freely over one another. Alternatively, the inclined

surfaces 26 and 32 could be provided with a low friction by other means, such as by a

suitable coating. The outer surfaces 25 and 31 of the sliders 24 and 30 are given a higher

coefficient of friction with the surfaces 35 of the channel 34, such as by roughening, so

that they do not slide along the channel when jammed locked.

Various other forms of locking mechanism are possible that allow free movement

when pulled back but lock when pushed. For example, as shown in Figure 3, the rods 50

and 51 support a respective slider in the form of a clutch plate 52 and 53 with facing

surfaces 54 and 55 having profiled recesses 56 and 57 engaging an eccentric cam 58. The cam 58 is rotatable about an axis transverse to the rods 50 and 51 and is shaped such that

a pushing movement of one rod towards the other causes rotation of the cam in a sense

tending to force the two clutch plates 52 and 53 outwardly against the walls 59 of the

channel 60 in which they slide.

Figure 4 shows a locking mechanism having two rods 70 and 71 displaced

laterally with respect to one another and having their ends interconnected by a pivoted

linkage 72 extending at an angle to the rods. The rods 70 and 71 each have a high

friction bearing surface 73 on their outer faces so that movement of the rods

longitudinally towards one another causes them to be pushed laterally apart into locking

contact with the walls 74 of the channel 75 in which they slide.

Figure 5 shows a locking mechanism similar to that of Figures 1 and 2 except that

the sliders 124 and 130 have been modified each to have a hook portion 224 and 230

respectively at their ends, directed inwardly of the channel 134 towards one another. A

roller 127 is located between opposed faces 126 and 132 of the sliders 124 and 130. It

can be seen that, when either rod 122 or 128 is moved axially towards the other it will

cause the roller 127 to roll along the surfaces 126 and 132 on the sliders 124 and 130,

thereby applying a lateral force pushing them outwardly of the channel 134 and locking

the rods in position. If, however, either rod 122 or 128 is moved away from the other,

it will cause the roller 127 to locate between the two hook portions 224 and 230 so that

the slider on the moved rod will act to pull the other slider, and hence its rod along the

channel 134. This arrangement has the advantage that it will function without the need

for a stretcher bar. It will be appreciated that the invention is not confined to railway points systems

but could be used in other applications where it is necessary to lock two members against movement. The actuator need not be hydraulic but could, for example, be electromechanical or pneumatic.

Claims

1. An actuator arrangement for moving first and second members (3 ,4), the

two members (3,4) being interconnected with one another by a linkage (5) extending

between them, the arrangement including first and second actuator means (6,7) arranged

to bear against respective movable members (3,4) such that actuation of the first actuator

(6) causes both movable members (3,4) to move in one direction and actuation of the

other actuator (7) causes both movable members (3,4) to move in the opposite direction,

and a locking mechanism (20,21) coupled with the first and second actuators (6,7), the

locking mechanism (20,21 ) being arranged to allow free movement in opposite directions

caused by actuation of the first and second actuator means (6,7) respectively but to

prevent movement in either direction when not caused by actuation of the respective

actuator means (6,7).

2. An actuator arrangement according to claim 1, wherein the locking

mechanism (20,21) includes two rods (22,28) movable along their lengths and having

respective sliders (24,30) movable along a channel (34), the sliders (24,30) being

arranged to apply an outward locking force on walls of the channel (34) when one rod

(24,30) is pushed towards the other.

3. An actuator arrangement according to claim 2, wherein the sliders (24,30)

have cooperating inclined faces (26,32).

4. An actuator arrangement according to claim 2, wherein the sliders (24,30)

define opposing inclined surfaces (26,32) and a roller (27) is provided between the inclined faces of the sliders.

5. An actuator arrangement according to claim 4, wherein a hook portion

(224,230) is provided at the remote end of each slider (124,130), the hooks being

arranged to engage with the roller (127) when either rod (122,128) is moved away from

the other.

6. An actuator arrangement according to claim 3, wherein a low friction

coating is provided over each of the cooperating inclined faces of the sliders.

7. An actuator arrangement according to claim 2, wherein the sliders have

facing surfaces (54,55), each defining a profiled recess (56,57) and an eccentric cam (58)

is located between the facing surfaces of the sliders, with each end thereof in engagement

with a respective one of the said profiled recesses (56,57), the eccentric cam (58) being rotatable about an axis extending transversely to the rods.

8. An actuator arrangement according to claim 1, wherein the locking

mechanism includes two rods (70,71) movable along their lengths in a channel (75), the

ends of the rods (70,71) being interconnected by a pivoted linkage (72), the rods and

linkage being arranged to apply an outward locking force on walls of the channel (75)

when one rod is pushed towards the other.