GB2291538A

GB2291538A - Interlocks for electrical switches

Info

Publication number: GB2291538A
Application number: GB9414351A
Authority: GB
Inventors: Stephen William Barry
Original assignee: Delta Schoeller Ltd
Current assignee: Stoneridge Pollack Ltd
Priority date: 1994-07-15
Filing date: 1994-07-15
Publication date: 1996-01-24
Also published as: GB9414351D0; DE19525083A1

Abstract

An electrical switch has an operating member 3 movable in a first direction to operate the switch. A first stop member 10 is mounted fixedly for movement with the operating member 8 and extends generally transverse to the first direction. A second stop member 14 is mounted for movement from a first position, in which it is clear of the first stop member, to a second position in which it prevents movement of the first stop member. A cam member 20 provides a cam surface engaging a follower surface of the second stop member 14 and movable in a second direction generally transverse to the direction of movement of the second stop member, to move the second stop member from its first position to its second position. The cam member 20 is movable by a solenoid 32 having an armature 34 movable longitudinally in two spaced coils 42, 44 between two ferromagnetic end stops (68, Fig. 4). A permanent magnet (82, 84) enables the armature to be latched on one or other of the end stops when no power is applied to either coil. The interlock arrangement can be used to prevent a key from being removed from a vehicle ignition switch until an automatic transmission has been set to park. <IMAGE>

Description

.i -I- ELECTRICAL INTERLOCKS 2291538 This invention relates to electrical

interlocks. In one aspect the invention relates to electrical switches. In another aspect the invention relates to electrical solenoids.

Both aspects of the invention will be described with reference to a particular problem. The invention is not limited in its application, however, and other applications may occur readily to the reader.

It is important to prevent the engine of a motor vehicle which has an automatic transmission, from being started when the transmission is in drive. Starting the engine when the transmission is in drive can result in the vehicle careering off out of proper control. It is desired, therefore, to prevent the key from being removed from a vehicle's ignition switch until the transmission has be set to park. It is proposed to operate the interlock by means of a solenoid. However, the forces which can be produced by a solenoid are limited. The structure of the interlock would preferably be such that premature operation of the ignition key cannot overcome the limited force available from the solenoid.

Against this background, in accordance with one aspect of the invention, there is provided an electrical switch having an operating member movable in a first direction to operate the switch; afirst stop member mounted fixedly for movement i.i.4ith the operating member and extending generally transverse to the first direction; a second stop member mounted for movement generally transverse to the first direction from a first position, in which the second stop member is clear of the first stop member, to a second position in which the second stop member is in the path of the first stop member so preventing movement of the first stop member past the second stop member; and a cam member providing a cam surface engaging a follower surface of the second stop member and movable in a second direction generally transverse to the direction of movement of the second stop member, to move the second stop member from its first position to its second position.

It is well understood by those skilled in the art, how to design a cam and cam follower so that forces on the cam follower produce insignificant forces resolved in the direction of movement of the cam. The can member can thus conveniently be operated by a solenoid without great danger that premature operation of the switch operating member, e.g. by an ignition key, will overcome the force available from the solenoid.

It would not be desirable that premature operation of the switch member, e.g. by an ignition key, produced side loads on the cam member and/ or on a solenoid for operating it, which jammed the mechanism so that the limited force available from a solenoid was too small to operate it.

To alleviate such a potential problem one or both of the cam surface and the follower surface preferably includes a roller..1 Support means is preferably mounted opposite the second stop member to support the cam member against loads applied by the second stop member in a direction from its second position to its first position.

In order to further reduce friction in such an arrangement, one or both of the support means and the second stop member preferably includes a roller to engage the other.

So as to reduce the possibility that friction between the first and second stop members, produced by premature operation of the switch operating member, might jam the mechanism, the first stop member preferably comprises a step in a surface movable with the operating member, and the second stop member preferably includes a roller to engage the surface and too small to roll over the step.

For operation, say by a key, the operating member is preferably movable, as said, by rotation.

Conventional solenoids require current to be supplied continuously in order to generate a force. That is not desirable in the exemplary application. An arrangement would be preferred in which respective current pulses would reliably latch the interlock when the gear selector is moved out of the park position and release the interlock when the gear selector is returned to the park position.

Against this background, a second aspect of the invention provides a solenoid comprising: an armature movable longitudinally in two longitudinally spaced coils and between two ferronagnetic end stops each associated with a respective one of the coils; ferro magnetic yolk means providing ferro magnetic paths from a position proximate the armature and between the coils, to each of the two end stops, so providing two magnetic circuits each including part of the armature, part of the yoke means and a respective end stop, and including magnetising means separate from the said coils for magnetising the magnetic circuits, so that the armature latches on one or other of the end stops when no power is applied to either coil.

In order to move the armature from one stop to the other, sufficient current is supplied to the coil associated with the other end stop to attract the armature to that end stop. Once the armature has moved into contact with the other end stop the magnetising means is sufficient to retain the armature there, although with less force than would be available by use of the coils. Especially in the exemplary application, the magnetising means is preferably a permanent magnet.

In order to transmit the notion of the armature a non magnetic shaft connected to the armature preferably projects through an aperture in one or both of the end stops.

In a preferred arrangement, the ferro magnetic yolk means includes a Ushaped frame and a member closing the arms of the U.

In that arrangement, one stop member is preferably mounted in the base of the U and the other is nounted on the member closing the arm of the U. c An embodiment of both aspects of the invention, -1 given by way of example only, will now be described with reference to the accompanying drawings, in which:

Figure 1 is a pictorial view, partly broken away to show the interior, of an interlock of an ignition switch embodying the invention; Figure 2 is a pictorial view of the interlock, without its casing, seen from the left hand side of Figure 1; Figure 3 is an elevation of parts of the interlock seen from the right hand side of Figure 1; Figure 4 is a pictorial view of the solenoid of the interlock of Figure 1, showing the armature in one position; and Figure 5 shows the armature in another position.

Referring to the drawings, a casing 2 contains at its right hand end a barrel lock (not shown), at its left hand end an ignition switch mechanism (not shown) which is operated by rotation of the barrel lock, and between the two a first stop member 10 which is fixedly rotatable with the lock and the switch by means of a tongue which projects from the lock through an aperture 3.

The first stop member 10 has the general form of a disc which as a step 12 in its periphery. A second stop member 14 has the form of an arm which is pivotally mounted at 16 for movement of its end 18 into and away from the path of the step 12. When in the path of the step 12 the stop member 14 prevents the barrel lock from rotating to a position where the key can be withdtawn.

The position of the end 18 is determined by a cam member 20 which is in the form of a bell crank pivotally mounted at 22. The can member has a stepped cam surface 24 (see Figure 3) for engagement with a cam follower of the stop member 14, which follower is in the form of a roller 26. As will be appreciated, pivotal movement of the cam member in an clockwise direction urges the end 18 of the stop member into the path of the step 12. Movement of the cam member 20 in an anti- clockwise direction. allows the stop member 16 to retract from the path of the step 12 under the bias provided by a spring (not shown).

In order to support the end 18 of the arm 14 against any thrust radial to the disc, which might be transmitted from the step 12 on a premature attempt to positinn the barrel lock to withdraw the key, a support is provided in the form of a roller 28. The roller 28 is positioned on the opposite the roller 26 on the other side of the cam member 20. Even if a premature attempt to operate the barrel-lock does result in thrust being applied through the stop member and the cam member to the roller 28, the rollers provide such low friction, that only a low force is required when the gear selector (not shown) is correctly positioned in park, to reposition the cam member so that the stop member retracts. The cam member will thus retract reliably even if the operator prematurely tries to retract the key from the lock and then moves the gear selector to the park position.

In order to prevent friction from jamming the stop member 14 against the step 12 if the operator attempts to rotate the barrel lock prematurely, the end 18 of the arm 1 carries a roller 30 which engages the step 12. The roller 30 is too small to roll over the step 12 when the arm is fully extended by the cam surface 24.

Forces radial to the disc 10, which may be transmitted from the step 12 to the stop member 14 result in only a comparatively small force tending to pivot the cam member 20 anti-clockwise, dependent on the slope of the cam surface 24 as is well understood. If at the position where the stop member 14 is fully extended the slope of the cam surface is zero, there is theoretically no force transmitted from the stop member 14 tending to pivot the cam member 20 anti-clockwise. The interlock mechanism is thus particularly suited to operation by a solenoid from which only limited force can be obtained. Indeed, the mechanism can be operated by a self latching solenoid in which current is not maintained once the position of its armature has been toggled.

A double acting solenoid is shown at 32 without its yoke. The armature 34 is linked by a non-ferrous shaft 36 to an end 38 of the other arm 40 of the bell crank so as to control the position of the can surface. Energisation of a coil 42 positions the armature 43 to the left as seen in Figure 1 so as to pivot the cam member 20 to extend the stop member 14 into the path of the step 12. Conversely energisation of a coil 44 position the armature to retract the stop member 14 from the path of the step 12. Current pulses are supplied selectively to the coils via electrical contacts 46, 48 and 50. -c The solenoid is shown in more detail in Figures 4 1 and 5. The two coils 42 and 44 (not shown in Figures 4 and 5) are wound on respective bobbins 52 and 54. These are supported on a brass tube 56. The armature 34 is slidable in the tube 56. A soft iron yoke comprises a U-shaped portion and a plate 62 which closes the arms of the U-shape. The base 64 of the U and the plate 62 both contain central apertures 66 (only that in the plate 62 is shown in the drawing). A generally cylindrical end stop 68 is mounted in each aperture 66. A shoulder 70 locates on the inside of the plate 62 or base 64, to prevent the end stop from being pushed through the aperture. Each end stop has a bore which is partly cylindrical and partly tapered. The tapered portion 72 of the bore faces inwardly in both cases. The ends 74 of the armature are each formed with a shoulder 76, to engage an end 78 of the end stop 68 and a tapered section 80 to engage the tapered portion 72 of the bore.

Permanent magnets 82 and 84 create magnetic circuits from between the coils via the yoke to both end stops and via the armature 34 and an air gap 86 to the magnets. When one end of the armature is engaged with its end stop, it will require some force to overcome the combination of magnetic attraction between the armature and the end stop, and the friction between the taper 80 and the tapered bore 72, in order to move the armature. The armature thus remains stably latched in one position without the application of current to either of its coils and can reliably resist any force which may be transmitted via the cam member due to premature operation of the barrel lock.

In order to move the armature and thus reposition 11 1 -g- the cam member 20, a current pulse is applied to the appropriate coil. Thus to move the armature from the position in Figure 4 to that shown in Figure 5, a pulse is applied to the coil wound on bobbin 52 so as to create a large attraction between the armature and the end stop 72. The armature latches in its new position. Similarly, to move the armature from the position shown in Figure 5 to that shown in Figure 4, a pulse is applied to the coil wound on the bobbin 54.

In an alternative arrangement, the coil adjacent the end stop engaged by the armature is energised in a sense to de-magnetise that circuit thus freeing armature to move under the attraction of the other end stop.

c

Claims

1. An electrical switch having an operating member movable in a first direction to operate the switch; a first stop member mounted fixedly for movement with the operating member and extending generally transverse to the first direction; a second stop member mounted for movement generally transverse to the first direction from a first position, in which the first stop member is clear of the second stop member, to a second position in which the second stop member is in the path of the first stop member so preventing movement of the first stop member past the second stop member; and a cam member providing a cam surface engaging a follower surface of the second stop member and movable in a second direction generally transverse to the direction of movement of the second stop member, to move the second stop member-from its first position to its second position.

2. A switch as claimed in claim 1, wherein one or both of the can surface and the follower surface includes a roller.

3. A switch as claimed in claim 1 or 2, including support means mounted opposite the second stop member to support the cam member against loads applied by the second stop member in a direction reverse to said first direction.

4. A switch as claiffied in claim 3, wherein one or both of the support means and the second stop member i' t includes a roller to engage the other.

A switch as claimed in any preceding claim, wherein the first stop member comprises a step in a surface movable with the operating member, the second stop member including a roller to engage the surface and too small to roll over the step.

6. A switch as claimed in any preceding claim. wherein the operating member is movable, as said, by rotation.

7. A switch as claimed in any preceding claim, including a solenoid to move the cam member.

8. A solenoid comprising: an armature movable longitudinally in two longitudinally spaced coils and between two ferromagnetic end stops; ferro magnetic yolk means providing ferro magnetic paths from a position proximate the armature and between the coils, to each of the two end stops, so providing two magnetic circuits each including part of the armature, part of the yoke means and a respective end stop, and including magnetising means separate from the said coils for magnetising the magnetic circuits, so that the armature latches on one or other of the end stops when no power is applied to either coil.

9. A solenoid as claimed in claim 8, wherein the magnetising means comprises a permanent magnet.

10. A solenoid as claimed in claim 8 or 9, wherein a non magnetic shaft connected to the armature projects through an aperture in one or both of the end stops.

1 A solenoid as claimed in any of claims 8 1 to 10, wherein the ferro magnetic yolk means includes a Ushaped frame and a member closing the arms of the U.

12. A solenoid as claimed in claim 11, wherein one stop member is mounted in the base of the U and the other is mounted on the member closing the arm of-the U 41