GB2146175A - Push-push switches - Google Patents

Abstract

A switch of the push-on, push- off type which can activate sequentially car headlamps and sidelamps or car windscreen wipers and car windscreen washers comprises a pushbutton 14 which is slidable relative to a housing 12, both the housing and the pushbutton carrying electrical contact members 16, 18, 20, 110, 112; and a cam and a resiliently flexible cam follower 52 one mounted on the housing and the other mounted on the pushbutton. The cam and cam follower 52 may be so configured that the pushbutton 14 is movable from a first stable position in which contacts 20, 112 are closed to a second stable position in which contacts 16, 110 are closed from which it may be moved to a third unstable position in which contacts 16, 18, 110 are closed. The pushbutton may be moved between the two stable positions either directly or via the third unstable position. Alternatively, the switch may have three stable rest positions. <IMAGE>

Description

SPECIFICATION Push-push switch The present invention relates to switches of the "push-on, push-off" type, commonly known as "push-push" switches and particularly, but not exclusively, to switches of this type for use in road vehicles.

A known push-push switch which is used for activating car wiper blades comprises a housing mounted in the dashboard of a car and which is electrically connected to the car battery. The housing forms a sleeve around an actuator which is slidably mounted in the housing. The actuator carries a cam having two longer sides which converge to a point and a shorter side having a recess, known in the switch making art as a "heart-shape" cam. A resiliently flexible arm is attached to the housing and is positioned so that, when the actuator is pushed into the, housing, the arm is caused to move from a starting position and to ride up one side of the cam and to locate in the recess in the cam thereby holding the actuator in its depressed state relative to the housing.In this position, electrically conductive plates on the actuator are brought into contact with electrically conductive plates on the housing to close a circuit thereby activating a wiper mechanism.

When it is desired to switch off the wipers, the actuator is again pushed inwardly into the housing. This causes the flexible arm to be urged out of the recess and to ride down the other side of the cam back to the starting position thereby separating the electrical contacts and disconnecting the wiper circuit.

A barrier is positioned relative to the cam to compel the flexible arm to seat in the recess in the cam once it has ridden up the side of the cam thereby preventing the arm overshooting the cam and bypassing the "on" position.

The invention is based upon the idea that by a relatively inexpensive modification, a simple push-push switch can be used to operate more than one function.

According to the present invention we provide a push-push switch which is manipulable sequentially to activate at least two different circuits.

The term "different circuits" is to be understood to refer to individual circuits or portions of a complex circuit capable of separately controlling, for example, windscreen wipers and windscreen washers in a motor vehicle.

A push-push switch according to the present invention can be used to enable two related mechanisms in a motor vehicle to be controlled by a single actuator on the vehicle dashboard. This is more convenient for the driver and also simplies the dashboard arrangement thereby reducing manufacturing costs.

In a particular embodiment, one of the circuits is activated by intermittent manipulation. In this embodiment repeatedly pushing the switch can cause intermittent activation of the same circuit.

According to a particular embodiment of the present invention a push-push switch comprises a housing, an actuator which is slidable relative to the housing, wherein both the housing and the actuator carry electrical contact members; a cam and a movable cam follower one mounted on the housing and the other mounted on the actuator; wherein the cam is configured so that repeatedly pushing the actuator into the housing causes the cam follower to traverse the successive portions of the periphery of the cam thereby controlling sequential engagement or disengagement of at least two different sets of electrical contact members during each complete traversal of the cam periphery.

The term "cam" is not restricted to a single cam member which provides a continuous camming surface but is to be understood to include a plurality of cam members each providing a part of a continuous or discontinuous cam surface. In a particular embodiment, the cam is configured a switch as claimed in any of claims 3 to 7, wherein the cam comprises a plurality of cam members separated by one or more guide channels for the cam follower.

The term "set of contact members" refers to at least two contact members, one being carried by the housing and the other being carried by the actuator, which, when engaged, activate a circuit which controls a particular mechanism, for example, windscreen wipers in a motor vehicle. The reference to "different" sets of electrical contact members is not restricted to sets which are entirely separate but encompasses two sets in which a particular electrical contact member is common to both.

Preferably, the cam comprises two lips defining a recess and the recess comprises an elongate slideway enabling intermittent engagement and disengagement of a set of contacts. The slideway may terminate in a formation which provides a tangible increase in resistance to pushing. In this embodiment, the contact members may be arranged so that a first set are in contact once the follower is located in the reccss and a second set are brought into contact as the follower slides along the slideway.

In this arrangement, the first set of contact members can activate a first mechanism once the follower is located in the recess and a second mechanism can be activated as the cam follower is caused to slide along the slideway. Optionally, the electrical contact members Can be arranged so that the first mechanism continues to operate during the operation of the second mechanism. Means may be provided for preventing a predetermined one of the mechanisms from being activated as the switch moves towards an "off" position.

Optionally, the cam may be configured to permit selective activation of only one of the circuits in a complete switching cycle.

Particular embodiments of the present invention will now be described, by way of example, with reference to the accompanying drawings in which: Figure 1 is a front view showing the interior of a switch according to the present invention in a first position; Figure 2 is a perspective view from above of the housing of the switch shown in Figure 1; Figure 3 is a fragmentary perspective view of a part of the housing shown in Figure 2; Figure 4 is a perspective view of a part of the actuator of the switch shown in Figure 1; Figure 5 is a side view showing the interior of the switch and viewed along line A in Figure 1; Figures 6-8 are front views of the interior of the switch in three further positions; Figure 9 is an enlarged, schematic view of the cam with the cam follower in the four different positions;; Figure 10 is an enlarged, schematic view of a modified cam for use in a switch according to the present invention.

Figure 11 is an enlarged, schematic view of a second modified cam for use in a switch according to the present invention; Figure 1 2 and Figure 1 3 are enlarged fragmentary views from the side and the front respectively of a modified switch according to the present invention; Figure 14 is a fragmentary section taken along line B-B of Figure 12; Figure 1 5 and Figure 1 6 are enlarged fragmentary views corresponding to Figure 12 and Figure 1 3 with the actuator in a different position relative to the housing of the switch; Figure 1 7 is a fragmentary front view of switch modified in accordance with Figure 1 2 to Figure 16.

Referring to Figures 1-5 of the drawings, a push-push switch indicated generally at 10 comprises a hollow, square section plastics housing 12 which forms a sleeve around a plastics actuator 14. The actuator 14 is slidable relative to the housing 1 2 along an axis indicated by the arrows in Figure 1.

The housing 1 2 is provided with three aligned -pairs 16, 1 8 and 20 of electrical contact members. Each of the contact members has a cylindrical prong 22 projecting from the housing 1 2 and contiguous with a flat arm 24 terminating in a curved contact portion 26. The contact portions 26 in each pair of contact members face each other (see Figure 5). Intermediate the arm 24 and the prong 22 is a substantially square retaining portion 28 having lugs (not shown) which cooperate with recesses in the housing 1 2 to retain the contact members therein.

The housing 1 2 has four side walls 13, 15, 17 and 19 and an upper rim 21. The side walls 1 3 and 1 7 of the housing 1 2 each comprise, on their interior, a pair 30 of vertically oriented ribs defining a channel 32. The channels 32 terminate at their lower ends in circular section sockets 33 and 35. (see figure 1).

The walls 1 3 and 1 7 also comprise slots 34, 36 which are positioned between the ribs 30 and extend beyond the ribs towards the rim 21. Also provided on the walls 13 and 15 are cut-outs 38 and 40 each of which is attached only at a lower end 41 to the respective wall 1 3 or 1 7 and comprises inclined portions 42 and 44 which define a shoulder 46. The cut-outs 38 and 40 are resilently compressible towards the interior of the housing 1 2 and, in practice, co-operate with a recess in a dashboard to retain the switch 10 in the dashboard.

The housing 1 2 also has a base wall 23 which is apertured to allow the prongs 22 of the pairs 16, 1 8 and 20 of the electrical contact members to pass therethrough.

Referring to Figures 2 and 3, an internal wall 48 co-operates with the side wall 1 5 to define a cavity 50 in which a cam follower 52 is located.

The cam follower 52 is a bent wire having a coil 54 at its lower end contiguous with an L- shaped arm 56. The arm 56 has a horizontal follower member 58 which extends perpendicularly with respect to the side wall 1 5. The coil 54 is seated on a horizontal ledge 60 formed in the wall 48 and termintes in an angled foot '62 which abuts an opposed ledge 64 in the wall 48 firmly to retain the cam follower 52 in the recess 50. The coil 54 is thus held firmly in the recess 50 so that, when the arm is moved sideways to the left or the right of the vertical position shown in Figure 1-3, the coil 54 will exert a spring force urging the arm 56 back into the vertical position.

Referring to Figures 1, 2, 4 and 5, the actuator comprises two plastics components, namely, a knob 66 and a cam carrier 68. The knob 66 has a body 70 which is square in section and comprises four walls 67, 69, 71, 73 (walls 71 and 73 are not visible in the drawings) and a flat lid 72 providing a rim 74 on the knob 66. The side walls 67 and 71 each have a horizontal slot 75. The lid 72 has a circular aperture (not shown) to enable a suitable symbol connected with the function of the switch 10 to be displayed. A light bulb may be located in the switch 10 to illuminate the symbol when the switch is operational.

The knob 66 has two columns, of which a fragment of one column 76 can be seen in Figure 5, which are L-shaped in section.

These columns are disposed on each side of the cam follower 52 and help to guide the actuator 14 as it is being pushed into the housing 12.

The cam carrier 68 comprises a square section base 78 having four side walls 79, 80, 81 and 82 and is fitted in the knob 66.

The base 78 is retained in the knob 66 by means of a lug 84 on the exterior of each of the side walls 80 and 82 which snap-engage in the horizontal slot 75 in each of the opposed walls 67, 71 of the knob 66.

Attached to the base 78 of the cam carrier 68 is a plate 86 comprising a cam 88 and a barrier 90. The plate 86, the cam 88 and the barrier 90 is an integral plastics moulding.

The plate 86 extends widthways beyond the periphery of the square base 78 of the cam carrier 68 to provide an abutment surface which limits the insertion of the cam carrier 68 into the knob 66.

The plate 86 has two areas 92 and 94 of reduced thickness. The area 92 is L-shaped and comprises a relatively thin wall 96 which has a chamfered edge 98. There are apertures 100 and 102 between end portions of the wall 96 and the main body of the plate 86.

The area 94 is rectangular and comprises a relatively thin wall 104 having a chamfered edge 106 adjacent an aperture 108.

The plate 86 is fitted with two copper electrical contact strips 110 and 11 2. The contact strip 110 is shaped to fit into the area 92 around the wall 96 and has an upper portion 11 7 and a lower portion 119. The contact strip 110 has lugs 11 3 and 114 which are bent around the edges of the apertures 100 and 102 to retain the contact strip 110 on the plate 86. The contact strip 112 is substantially rectangular and comprises a lug 11 5 at each end, the lugs 11 5 being bent around the edges of the aperture 108 to hold the contact strip 11 2 on the plate 86.

When the contact strips 110 and 11 2 are fastened in this way, they lie within the general contour of the plate 86.

The plate 86 is provided at its lower end with two generally cylindrical pins 11 6 and 11 8 and a triangular section member 1 20 which extends along approximately three quarters of the width of the plate 86. There are two side pips 11 2 and 1 24 at the top of the plate 86 which are configured to locate in the slots 34 and 36 in the side walls 13 and 1 7 respectively of the housing 1 2.

The knob 66 of the actuator 1 4 is a close sliding fit in the housing 1 2 and the two columns 76 help to guide the actuator 1 4 as it is being pushed into the housing 1 2. The cylindrical pins 11 6 and 11 8 on the plate 86 are each inserted in the end of a coiled spring 126, 128, which springs are located in the circular sockets 33 and 35 at the base of the channels 32 in the housing 1 2. The springs 126 and 1 28 bias the actuator 14 upwardly out of the housing 1 2 and the actuator 14 is prevented from leaving the housing 1 2 by the pips 1 22 and 1 24 on the plate 86 which abut the tops of the slots 34 and 36 in the side walls 1 3 and 1 7 of the housing 1 2. The extent to which the actuator 14 can be depressed into the housing 1 2 is limited by the abutment of the bottom of the walls 79 and 81 of the base 78 of the actuator 14 against the tops of the pairs 30 of the ribs on the interiors of the walls 1 3 and 1 7 of the housing 12.

In the rest position (as shown in figure 1), the pips 122, 124 on the sides of the plate 86 abut the top of the slots 34, 36 in the housing 1 2 thereby preventing the actuator 14 being withdrawn from the housing 1 2.

As the user pushes the actuator 14 into the housing 12, the sides of the plate 86 slide in the channels 32 defined by the pairs 30 of the ribs on the interiors of the side walls 1 3 and 1 7 of the housing 1 2 and the springs 1 26 and 1 28 are compressed in the sockets 33 and 35. The actuator 14 can be pushed into the housing 1 2 until, in an extreme position, the bottom of the square base 78 of the cam carrier 68 abuts the tops of the ribs 30 in the housing 1 2. However, the first push is stopped as soon as a click is heard as will be explained.

As the actuator 14 is depressed relative to the housing 12, the cam follower 52 is brought into engagement with the cam 88.

The shape of the cam 88 and the barrier 90 will now be more particularly described with reference to Figure 9. The cam 88 comprises two sloping sides 140 and 142 which converge to a point 143. The sides 140 and 142 are contiguous with two fingers 144 and 146 which define a recess 148. The recess 1 48 has a horizontal abutment surface 1 50 contiguous with a vertical slideway 1 52. The barrier 90 comprises a vertical wall 1 54 contiguous with an angled wall 1 56 which is bevelled at its end to form an edge 1 58. The cam follower 52 is shown schematically in Figure 9 in four different positions. In each position only the upper end of the arm 56 and the end of the follower member 58 adjacent the arm 56 is shown.

Referring to Figure 9, before the actuator 14 has been depressed, the cam follower 52 is in a first position A relative to the cam 88.

In position A, the follower member 58 lies slightly to the right of the point 143 on the cam periphery. As the actuator 14 is depressed relative to the housing 12, the follower member 58 is caused to ride up the side 140 of the cam 88. During this movement, the arm 56 is being pulled rightwardly out of the position A and there is therefore a spring force acting to the left in the diagram which urges the follower member 58 against the cam periphery and, if the actuator 14 is pushed far enough into the housing 12, the follower member 58 will snap around the finger 144 and locate on the horizontal abutment surface 150, that is, position B in the diagram. As the follower member 58 snaps around the finger 144, the user will hear a click (referred to previously) which is a signal that he may stop pushing the actuator 1 4.

In position B, the cam follower 52 holds the actuator 14 relative to the housing 1 2 by virtue of its engagement in the recess 148 of the cam 88. It will be noted that, in position B, the arm 56 of the cam follower 52 is to the right of position A and there is therefore a sideways force acting to urge the follower member 58 against the vertical slideway 1 52 in the recess 148.

As the actuator 14 is further pushed into the housing 12, the follower member 58 is caused to slide along the slideway 1 52. If the user stops pressing the actuator 14 at any point during the sliding movement of the follower member 58 along the slideway 152, then the springs 1 26 and 1 28 will urge the actuator 14 out of the housing 1 2 until the follower member 58 again rests on the horizontal abutment surface 1 50. The follower member 58 can therefore be slid repeatedly along the slideway 1 52. When the follower member 58 reaches the finger 146, the user will sense a resistance to the sliding movement of the actuator 14 and by continued pushing can cause the follower member 58 to ride up the inside slope 147 of the finger 146.In so doing, an increased sideways force is generated in the coil 54 urging the arm 56 to the left so that the follower member 58 will snap around the top of the finger 146 into position D.

In position D, the follower member 58 is not retained on the cam periphery and the actuator 14 will be urged out of the housing by the springs 126 and 1 28. As the actuator 14 slides out of the housing 12, the follower member 58 slides down the side 142 of the cam 88. Due to the inclination of the side 142, during this movement the arm 56 is pulled further to the left of position A so that when the follower member 58 reaches the point 143 on the cam 88, the arm 56 will spring rightwardly to resume position A.

The barrier 90 prevents the cam follower 52 "over shooting" the recess 148. If the user pushes the actuator 14 from the rest position forcibly into the housing 12, then the follower member 58 will ride up the side 140 of the cam 88 and will snap around the finger 144 and may be forced upwardly. against the wall 1 56 of the barrier 90 or even up as far as the wall 1 54. The follower member 58 cannot reach the uppermast end of the wall 1 54 because, before that stageXis reached, the base member 78 of the cam carrier 68 abuts the tops of the ribs 30 on the sides 1 3 and 1 7 of the housing 1 2 to prevent.any further depression of the actuator 14 into the housing 12.

When the user releases the actuator 14, this allows the follower member 58 to slide down the walls 1 54 and 1 56 of the barrier 90 and into the recess 148 of the cam 88. By virtue of the sideways force then urging the follower member 58 against the slideway 152, further pushing the actuator 14 will cause the follower member 58 to travel along the slideway 1 52. The barrier 90 acts therefore to ensure that the follower member 58 follows the entire contour of the cam 88 once the actuator 14 has initially been pushed into the housing 1 2 so that the follower member 58 passes the finger 144.

As the cam follower 52 moves relative to the cam 88 so do the pairs 16,18,20 of the electrical contact members move relative to the electrical contact strips 110 and 11 2. The curved contact portions 26 on each of the contact members slideably abuts the faces of the plate 86 as the actuator 14 is pushed into the housing 12.

The relative positions of the pairs 16,18,20 of the electrical contact members with respect to the electrical contact strips 110 and 11 2 will be described with reference to Figures 1-8. The component parts in Figures 6--8 are identical to those in Figures 1-5 and have not been re-labelled.

When the cam follower 52 is in position A, (see Figure 1) the pair 20 of the electrical contact members make electrical contact with the contact strip 11 2. In practice, this engagement short circuits the motor which drives the windscreen wipers so that, as soon as the switch 10 is pressed to turn off the wipers and the wipers have returned to a rest position in which they do not obstruct the windscreen; no further movement of the wipers will occur. In this "off" position, neither of the pairs 16 and 18 of the electrical contact members are in contact with the contact strip 11 0.

When the cam follower 52 is in position B relative to the cam 88 (Figure 6), then the pair 1 6 of the electrical contact members are in contact with the lower portion 11 9 of the contact strip 110 thereby activating a first circuit which controls a first mechanism, for example, windscreen wipers. In position B, the pair 18 of the electrical contact members do not contact the strip 110. Also, the curved contact portions 26 of the pair 20 of the electrical contact members no longer abut the contact strip 112.

On causing the follower member 58 of the cam follower 52 to travel along the slideway 1 52 of the cam 88, i,e. position C in Figure 9, the pair 18 of the electrical contact members are brought into contact with the upper portion 11 7 of the contact member strip 110 thereby activatihg a sec'ond circuit which con-.

trols a second mechanism, for example, wind screen washers. As previously described, the follower member 58 can be repeatedly slid up and down the slideway 1 52 successively to activate and deactivate the second mechanism. It should be noted that, at whatever position the follower member 58 is at on the slideway 152, the first mechanism is still operative because the pair 1 6 of the electrical contact members contacts the strip 110 in both positions B and C of the follower member 58.

When the follower member 58 is in position D relative to the cam 88, (Figure 8) both the pairs 1 6 and 1 8 of the electrical contact members are still in contact with the upper portion 11 7 of the contact strip 110 so that both the first and second mechanisms are operational. As the follower member 58 slides down the side 142 of the cam 88, the pair 18 of the electrical contact members will move out of contact with the upper portion 11 7 of the contact strip 110 thereby deactivating the second mechanism. As the follower member 58 moves towards position A, then the pair 16 of the electrical contact members will move out of contact with the lower portion 11 9 of the contact strip 110 thereby de-activating the first mechanism.The time lapse between the de-activation of the first and second mechanisms in practice will be so small as to be unnoticeable.

If the user ignores the click heard as the follower member 58 snaps around the finger 144 on the cam 88 and continues pushing the actuator 14, then the follower member 58 is caused to ride up the walls 1 56 and 1 54 of the barrier 90. While the actuator is held depressed with the follower member 58 in this position, the pairs 1 6 and 1 8 of the electrical contact members are held in contact with the upper portion 11 7 of the contact strip 110 thereby activating the first and second circuits so that both the first and second mechanism are functioning.On releasing the actuator 14, the follower member 58 slides down the walls 1 54 and 1 56 of the barrier 90 and into the recess 148, that is, position B in Figure 6. As explained above, in position B only the first circuit is activated so that only the first mechanism is functioning.

Further pushing causes the cam follower 58 to slide along the slideway 1 52 in the manner described above.

In practice, the switch 10 may be mounted in the dashboard of a car with the front lid 72 of the actuator 14 flush with the contour of the dashboard. A symbol representing the dual function of a switch, in this case the washer and wiper functions can be displayed in the lid 72 of the switch 10.

When the user wishes to operate the washers or wipers, he presses the actuator 1 4 until it clicks into position B at which point the wipers are activated The user can then operate the windscreen washers by repeatedly pushing the actuator 14 to generate squirts of water, that is, causing the follower member 58 to move between positions B and C on the cam 88. During this time the windscreen wipers are still operating. To turn off the wipers, the user needs to firmly push the actuator 14 to cause the follower member 58 to assume position D and then to return to position A.

In the described embodiment the bias of the spring arm 56 of the cam follower 52 is such as to urge the follower member 58 to contact the cam periphery throughout a switching cycle. Alternatively, the cam follower may be non-resilient and may be caused to follow the cam periphery by other means such as a roller bearing or simply by virtue of the shape of the cam in relation to the position of the cam follower.

It will be understood that a dual purpose switch of the type herein described can be used in a car to operate any selected pair of functions, for example headlamps and sidelamps and the actuator can be shaped so that the first and second functions do not overlap but operate separately.

A switch according to the present invention may have a cam shaped so that more than two functions can be controlled by the switch, for example, by providing at least two recesses in the cam 88 in the described embodiment. Referring to Figure 10, a modified cam 1 60 for use in a switch according to the present invention comprises two recesses 1 62 and 164. There is a barrier, 1 66 and 168, associated with the recesses 1 62 and 1 64 respectively.

The cam 1 60 comprises two sloping sides 1 70 and 1 72 which converge to a point 1 74.

The cam 160 has three fingers 176, 1 78 and 180, pairs of which define the recesses 1 62 and 1 64 respectively.

The recess 1 62 has a horizontal abutment surface 1 82 contiguous with a vertical slideway 1 84. The recess 1 64 comprises a horizontal abutment surface 186 adjacent the finger 1 80.

The cam follower 1 88 is identical to the cam follower 52 described in connection with the first embodiment and has a follower member 1 90. Similarly, to the first embodiment described, the cam follower 1 88 is attached to the housing of a switch according to the present invention and the cam 1 60 and barriers 1 66 and 1 68 are attached to the actuator of the switch so that as the actuator is pushed into the housing the cam follower 188 is caused to engage the periphery of the cam 160.

The follower member 1 90 traverses the right hand portion of the periphery of the cam 1 60 in a similar manner to that described in connection with Figure 9. The barrier 166 acts to prevent the follower member 1 90 "overshooting" the recess 1 62.

When the follower member 1 90 is at the top of the vertical slideway 1 84 and is caused to ride up the finger 178, it will spring leftwardly onto the horizontal abutment surface 1 86 of the recess 1 64 due to the spring bias of the cam follower 1 88 tending to pull the cam follower 1 88 into alignment with the rest position shown in Figure 10.In this position, the cam follower 1 90 holds the actuator relatively further depressed into the housing of the switch than when the cam follower 1 90 is resting on the horizontal abutment surface 1 82 of the recess 1 62. The barrier 1 68 acts to prevent the cam follower overshooting the recess 1 64.

On again pushing the activator into the housing of the switch, the cam follower 1 90 snaps around the finger 1 80 and, when the presssure on the actuator is released, slides down the side 1 72 of the cam 1 60 and springs back into the rest position shown in Figure 10. The actuator and housing of the switch incorporating the cam 1 60 have not been illustrated but these may be similar to the housing 1 2 and the actuator 14 of the switch 10 described above apart from the arrangement of the electrical contact members.

If a switch incorporating the cam 1 60 is a dual function switch, then the contact members may be arranged as described in respect of the switch 10 and the engagement of the cam follower 1 90 in the recess 1 64 may simply hold both sets of contacts in engagement so that both the first and second mechanims are operational.

However the arrangement may be such that, when the cam follower 1 90 is located in the recess 1 64 of the cam 1 60 the actuator of the switch is held depressed relative to the housing so that a third set of contact members are bought into engagement thereby activating a third mechanism. Alternatively, the engagement of third set of contact may modify the operation of the first or second mechanism, for example, by speeding up the windscreen wipers.

It will be understood that the shape of the cam can be modified as desired to permit the intermittent or continuous control of as many different mechanisms as is practically feasible.

Referring to Figure 11, a modified cam, indicated generally at 200, comprising three cam members 202, 204 and 206. The cam 200 can be used in accordance with the switch 10 as previously described and is positioned adjacent a barrier 208 on the actuator 14 of the switch 10. A cam follower 210 is identical to the cam follower 52 described in connection with the first embodiment and has a follower member 212.

The cam member 202 is generally heartshaped and comprises two sloping sides 214 and 216 which converge to a point 218. The cam member 202 has two fingers 220 and 222 defining a recess 224 therebetween. The recess 224 comprises a horizontal abutment surface 226 and a vertical slideway 228.

The cam member 204 has four side walls 230, 232, 234 and 236. The side 234 extends parallel to the side 216 of the cam member 202 with a channel 238 therebetween.

The third cam member 206 is of relatively narrow width and comprises two portions 240 and 242 angled alightly relative to one another. The portion 242 terminates in a Vshaped lip 244. The portion 240 extends parallel to the side 236 of the cam member 204 with a channel 246 therebetween. The portion 242 of the cam member 206 overlies the mouth of the channel 238.

The barrier 208 is in the fo'rm of a finger having two sides 247 and 248. The side 247 extends parallel to one side of the V-shaped lip 244 on the cam member 206 and is continuous with an angled wall 250 which extends parallel to the portion 242 of the cam member 206 providing a channel 252 therebetween. The side 248 of the barrier 208 extends parallel to the finger 220 of the cam member 202 providing a channel 254 therebetween. The side 248 of the barrier 208 is contiguous with a vertical wall 256.

In Figure 11, four positions WXYZ of the cam follower 210 are shown. As the actuator 14 is depressed relative to the housing 1 2 of the switch 10, the cam follower 210 can traverse the peripheries of the cam members 202, 204 and 206 in two possible ways which will be described as follows.

Starting at position W, as the actuator 1 4 is depressed into the housing 1 2 of the switch 10, the cam follower 21 2 is caused to ride up the side 214 of the cam member 202 so that it is moved "ightwardly of its central position thereby creating a spring force acting to the left urging the follower member 212 against the side 214 of the cam member 202. As the follower member 212 reaches the finger 220 of the cam member 202, it will spring leftwardly due to the spring force into the channel 254 and onto the horizontal abutment surface 226.If the actuator 14 is pushed forcefully so as to cause the follower member 212 to ride up onto the wall 248 of the barrier 208, when the actuator is released the leftward spring bias will cause the follower member 212 to slide along the side 248 of the barrier 208 into the channel 254 and onto the horizontal abutment surface 226.

The presence of the barrier 208 thus ensures that from the starting position W the cam follower 210 next assumes position X in the diagram. 8 In position X, there is a spring force acting leftwardly urging the follower member 212 against the vertical sideways28 on the cam member 202. On further depressing the actuator 14, the follower member 21 2 slides along the slideway 228. If the actuator 14 is pushed gently, the user will feel a click as the follower member 21 2 reaches the top of the finger 222 of the cam member 202 and springs leftwardly to abut the side 234 of the cam member 204-position Y.If the actuator 14 is then released, the cam follower 212 will ride down the channel 238 along the side 216 of the cam member 202 and, when it reaches the point 21 8 of the cam member 202, will then be to the left of its unstressed position W so that it will spring rightwardly back to the starting position W.

As the cam follower 212 moves relative to the cam members 202, 204 and 206, so do the pairs 16, 18, 20, of the electrical contact members move relative to the electrical contact strips 110 and 112 of the switch 10.

Referring to the path WXYW traversed by the cam follower 210 as just described, as the cam follower 210 moves from position W to position X, this causes the pair. 1 6 of the electrical contact members to contact the lower portion 11 9 of the contact strip 110 thereby adtivating a first circuit which controls a first mechanism, for example, windscreen wipers. In position X, the pair 1 8 of the electrical contract members do not contact the strip 110.

The role of the contact strip 11 2 and-the pair of contact members 20 is the same as previously described with regard to Figures 1 to 9.

As the cam follower 210 moves from positon X to position Y along the slideway 228, the contact members 1 6 slide over the lower portion 11 9 of the contract strip 110 but, at position Y, the pair 1 8 of the electrical contact members are still not in contact with the strip 110 so that only the first mechanism is operating As the cam follower 210 moves from position Y to position W, the pair 1 6 of the electrical contact members slide downwardly relative to the lower portion 11 9 of the contact strip 110 and out of contact with the.

contact strip 110 so that, at position W, neither of the first or second mechanisms are operating. Thus, as the cam follower follows the path WXYW only the first mechanism is activated.

If, when the follower member is in position X, the actuator 1 4 is depressed firmly relative to the housing 12, this will cause the cam follower 210 to slide up the slideway 228 and to abut the portion 242 of the cam member 206 and to slide into the channel 246 between the cam members 204 and 206 so that the cam follower 210 is pulled leftwardly relative to position W. When the cam follower 210 reaches the end of the portion 240 of the cam member 206 it will spring rightwardly into position Z due to the spring bias and as the actuator 1 4 is released, it will slide downwardly into the channel 252 between the portion 242 of the cam member 206 and the angled wall 250 and further downwardly between the lip 244 and the barrier 208 and back to position X on the horizontal abutment surface 226.The cam follower 210 can thus also follow the path WXZX.

As the cam follower 210 moves from position X to position Z and passes position Y, this causes the pair 1 8 of the electrical contact members to contact the upper portion 11 7 of the contract strip 110 thereby activating a second circuit which controls a second mechanism, for example, windscreen washers. As the cam follower 210 slides downwardly from position Z towards position X, this causes the pair 1 8 of the electrical contact members to move out of contact with the strip 110 so that at position X only the first mechanism is operational. In this way, the second mechanism can be repeatedly operated in addition to the first mechanism by causing the cam follower 210 to move between positions X and Z.When it is desired to switch off the first mechanism, the actuator needs to be depressed more slowly so that the cam follower 210 will assume position Y and return to position W, the "off" position.

The arrangement described above enables the user to choose whether to operate only the first mechanism or seguentially to operate both the first and second mechanisms. This arrangement also ensuresthat the last function to operate is the first mechanism.

In the case where the first mechanism operates windscreen wipers and the second mechanism operates windscreen washers, the arrangement shown in Figure 11, has the advantage that the user can select to operate the windscreen wipers only and does not activate the windscreen washers when returning to the "off" position as was the case with the arrangement shown in Figure 9. Furthermore, when the windscreen washers are activated, the modified cam 200 ensures that the last function to operate will be the windscreen wipers so that no water is left on the windscreen.

Another way of ensuring that the first mechanism is the last to operate in a switching cycle is to modify the contact members of the switch as follows.

Referring to Figures 12-17, the centre pair 1 8 of the electrical contact members has been replaced by a modified contact arrangement 300 and a contact strip 302 on the actuator is of slightly different shape to the contact strip 110 as previously described with respect to the switch 10. Otherwise, the components are the same as in the switch 10 previously described and the previously used reference numerals will be retained.

Referring to Figures 1 2 and 13, the contact arrangement 300 comprises a single contact arm 304. The contact arm 304 has a lower portion 306 of the same width as the arms of the pairs of electrical contact members 1 6 and 20 and is bent to provide a bridge 308.

Extending upwardly from the lower portion 306 is a relatively thin contact finger 310 comprising a curved contact portion 312. The uppermost edges 314 and 31 6 of the lower portion 306 of the contact arm 304 are slightly out-turned. The contact finger 310 is joined to the lower portion 306 below the uppermost edges 314 and 31 6 so that the contact finger 310 can flex relative to the lower portion 306 of the contact arm 304.

The plate 86 of the cam carrier 68 comprises a rectangular recess 31 8 with a central aperture 320. A slider 322 is slidably located in the recess 318. The slider 322 comprises a U-shaped portion 324 (see Figure 14) contiguous with a flange 326. The U-shaped portion 324 extends substantially across the width of the recess 318. The flange 326 is located through the aperture 320 and has a head 328 which is a push fit through the aperture 320 to retain the slider 322 in the aperture 320 so that it can slide vertically but is retained against horizontal movement in the recess 31 8. The U-shaped portion 324 has side arms 330 and 332 which are B-shaped in side view (see Figure 12) defining a dip 333 across the front face of the slider 322.

The plate 86 is indented above the aperture 320 to form a trianglar lead-in 334 which is of slightly greater width than the aperture 320.

Figure 1 7 shows the reverse side of the plate 86 to that shown in Figures 1 3 and 1 6.

A contact plate 302 is fastened around the edge of the plate 86 and comprises a substantially square contact portion 336 and a relatively thin contact strip 338 extending laterally therefrom.

The operation of a switch with the modified contact arrangement 300 will be described using the positions A-D referred to in connection with Figure 9. When the cam follower 52 is in position A (Figure 17) neither the pair 16 of electrical contact members nor the contact arm 304 are in contact with the contact plate 302. The pair 20 of electrical contact members are in contact with the contact strip 11 2 for the purpose previously described. The slider 322 lies at the base of the recess 318.

On depressing the actuator 14 relative to the housing 12, the follower member 58 of the cam follower 52 is caused to assume position B which brings the pair 1 6 of electrical contact members into contact with the square portion 336 of the contact plate 302 thereby activating the first function, for example, windscreen wipers.

As the cam follower moves from position A to position B, the contact finger 310 of the contact arm 304 moves upwardly between the B-shaped portions 330 and 332 of the slider 322 and over the lead-in 334 in the plate 86. When the cam follower 52 has reached position B, the contact finger 310 has not yet reached the contact strip 338 of the contact plate 302 so that only the first mechanism is functioning.

As the follower member 58 is caused to slide along the slideway 1 52 of the cam 88, the curved contact portion 312 of the contact arm 304 makes contact with the contact strip 338 of the contact plate 302 to activate the second mechanism, for example, windscreen washers. The contact arm 304 is not part of a pair and the electrical circuit for activating the second mechanism is completed via one of the pair 1 6 of electrical contact members. As the follower member 58 moves from position B to position C, the bridge 308 on the lower portion 306 of the arm 304 abuts the bottom of the slider 322 and causes the slider 322 to slide upwardly in the recess 31 8 until the top of the slider 322 abuts the top of the recess 318. This position corresponds to position C relative to the cam 88 as shown in Figure 9.

On further depressing the actuator 14 into the housing 12, the user will sense a resistance to pushing both because of the abutment of the cam follower 58 against the slope 147 of the finger 146 of the cam 88 and also due to the fact that the slider 322 has reached the top of the aperture 31 8 and cannot be pushed further upwardly by the bridge portion 308. If the user pushes the actuator 14 to overcome this resistance, the bridge portion 308 rides over the lower halves of the B-shaped portions 330 and 332 of the slider 322 and nests in the dip 333 in the slider 322 (see Figure 1 5 and 1 6). The contact portion 31 2 of the arm 304 is thus deflected away from the plate 86 out of contact with the contact plate 302 so that the second function is no longer operating.

As the actuator 14 is then released, the contact member 304 slides downwardly relative to the plate 86 and the bridge portion 308 causes the slider 322 to slide downwardly in the recess 31 8 thereby holding the contact portion 31 2 of the arm 304 away from the contact plate 302 so that the second mechanism is not re-activated as the cam follower 58 moves from position D towards position A. When the slider 322 reaches the bottom of the recess 318, the bridge portion 308 then continues to slide downwardly and is freed from the dip 333 whereupon the contact portion 312 can again contact the plate 86. However, the contact portion 312 is then lower than the contact strip 338 of the contact plate 302 so that the second mechanism is not re-activated. As the cam follower 58 approaches position A, the pair 1 6 of the electrical contact elements slide downwardly out of contact with the plate 302 and the first mechanism is de-activated.

This arrangement ensures that the first mechanism is the last mechanism to operate before the switch is turned off so that, in the case of windscreen wipers and windscreen washers, no water from the windscreen washers is left unwiped on the windscreen.

The present invention is not limited to applications in motor vehicles but can be used wherever a multiple function switch is required, for example, in other types of vehicle or in control systems generally.

Claims (15)

1. A push-pushswitch which is manipulable sequentially to activate at least two different circuits.

2. A switch as claimed in claim 1 in which one of the circuits is activated by intermittent manipulation.

3. A switch as claimed in claim 1 or claim 2 comprising a housing, an actuator which is slidable relative to the housing, wherein both the housing and the actuator carry electrical contact members; a cam and a movable cam follower one mounted on the housing and the other mounted on the actuator; wherein the cam is configured so that repeatedly pushing the actuator into the housing causes the cam follower to traverse successive portions of the periphery of the cam thereby controlling sequential engagement or disengagement of at least two different sets of electrical contact members during each complete traversal of the cam periphery.

4. A switch as claimed in claim 3, wherein the cam comprises two lips defining a recess and wherein the recess comprises an elongate slideway enabling intermittent engagement and disengagement of a set of contacts.

5. A switch as claimed in claim 4 wherein the slideway terminates in a formation which provides a tangible increase in resistance to pushing.

6. A switch as claimed in claim 4 or claim 5, wherein the contact members are arranged so that a first set are in contact once the follower is located in the recess and a second set are brought into contact as the follower slides along the slideway.

7. A switch as claimed in any of claims 3 to 6, wherein the cam comprises at least two recesses.

8. A switch as claimed in any of claims 3 to 7, wherein the cam comprises a plurality of cam members separated by one or more guide channels for the cam follower.

9. A switch as claimed in any of claims 3 to 8, wherein the cam is configured to permit selective activation of only one of the circuits in a complete switching cycle.

10. A switch as claimed in any of claims 3 to 9, wherein the cam is mounted in the actuator and the cam follower is mounted on the housing.

11. A switch as claimed in any of claims 3 to 10, wherein the cam follower is a resiliently flexible arm.

1 2. A switch as claimed in any of claims 3 to 11, comprising a barrier which is fixed relative to the cam and disposed to ensure that, during operation, the cam follower follows the contour of the cam.

1 3. A switch as claimed in any preceding claim comprising means for preventing a predetermined one of the circuits from being activated as the switch moves towards an "off" position.

14. A switch as claimed in any preceding claim when fitted in a motor vehicle, wherein the said different circuits control windscreen wipers and windscreen washers.

1 5. A switch substantially as herein described with reference to Figures 1-9, Figure 10, Figure 11 or Figures 12-16 of the accompanying drawings.