GB2068172A

GB2068172A - Snap-action switch

Info

Publication number: GB2068172A
Application number: GB8102153A
Authority: GB
Original assignee: SWF Spezialfabrik fuer Autozubehoer Gustav Rau GmbH
Current assignee: SWF Auto Electric GmbH
Priority date: 1980-01-24
Filing date: 1981-01-23
Publication date: 1981-08-05
Also published as: JPS5737205B2; FR2474751B3; DE3002479A1; GB2068172B; FR2474751A1; BR8100212A; JPS56109414A

Abstract

An electric snap-action switch includes a slider (43) which is movable by a switch actuator (28) and which is coupled by a spring (80) to a snap-action member (44). The latter is lockable in each of its rest positions by at least one of two locking elements (90, 91) each of which cooperates with a stepped locking surface (97, 98). Upon movement of the slider (43) by the actuator (28) the spring (80) is stressed until one of the locking elements (90, 91) (depending on the direction of movement of the slider (43)) is released by the slider (43) from its locking step whereupon the spring (80) moves the snap action member (44) to its next rest position and the locking elements (90, 91) move onto the adjacent locking steps. <IMAGE>

Description

SPECIFICATION Snap-action switch This invention relates to an electric snapaction switch particularly for use on automotive vehicles.

When the contacts of electric switches switching direct currents are closed and, even more so, when then are opened, arcs are likely to appear which, depending on the applied voltage, only break off with a certain contact gap. Such arcs damage the electric contacts and burn them down, so that eventually the switch can no longer be used. Moreover, such a heat can be developed that the plastic material surrounding the contacts melts. This also results in a failure of the switch.

It is essential to open the electric contacts as quickly as possible so that the time during which the arc appears is as short as possible and as little heat as possible is developed.

Therefore switches have been developed which have an energy store built in, to which energy is conducted from outside during the operation of the switch and which moves the electric contacts abruptly and thereby releases the stored energy in the shortest possible time.

Such a switch with a snap-action device is known from the German published Patent Specification DE-OS 24 27 31 5. This switch has a number of locking pins supported on the switch housing via a spring and being movable in their longitudinal direction. The locking pins serve as stops for a snap-action disk and can be pushed backwards when a control disk is turned. The snap-action disk and the control disk are spring-loaded towards each other by a ring-type spring. When the control disk is turned, the snap-action disk is at first held in its position by a locking pin.

The ring-type spring is tensioned. Finally the locking pin releases the snap-action disk, so that the ring-type spring can release its energy and thus abruptly change over the snap-action disk as well as the electric contacts connected with the latter.

Between two switching positions, the path length of the snap-action member of a switch built up as described is at least as great as the width of a locking pin plus the width of the portion of the snap-action member located between the locking pins. Thus the switching path can reach a considerable length, particularly when the locking pins and the snapaction member are formed of plastics material and the parts being loaded during a changeover process must have a certain thickness for reasons of stability. Moreover, the number of spring-loaded locking pins of said switch increases in a straight line relationship with the number of desired switching positions. Finally, it is difficult to design the switch in such a way that it exhibits a snap-action behaviour as well when it is turned in a clockwise direction as when it is turned in an anti-clockwise direction.

The two last mentioned disadvantages do not appear in a switch which is known from German published Patent Specification DE-PS 10 74 11 3. This switch has tvvo resilient detents acting in parallel to each other and on which the locking member of the switch is formed. Each of the detents co-operates with a locking cam fixed on the housing. This locking cam is formd by two rectangular locking recesses and two rectangular teeth separating the locking recesses. The switching path of the switch is at least as long as the width of one tooth plus the width of one detent.

Upon switching over, the detents hit the upper portions of the teeth with great velocity, so that the material of these portions and of the detents deforms gradually. This happens, above all, when the individual parts of the switch are made of plastic material. When the switching speed is high, it is also possible that the detents do not engage quickly enough into the locking recesses, so that one switching position is left out. This is especially a danger when the material of the teeth and of the detents has already been somewhat deformed.

It is an object of the present invention to develop an electric snap switch in such a way that the disadvantages of known snap switches do not appear any longer. Thus a deformation of material in the area of the locking cams and of the locking elements has to be avoided as far as this is possible. The switch is to be brought safely from one switching position into a neighbouring one without involving the danger that the neighbouring switching position is left out. Furthermore it is to be ensured that the switching paths are selected as independently as possible of the dimensions of the locking elements depending on design and stability. All this has to be effected with a simple design and as little technical skill as possible, for instance with as small a number of locking elements as possible.

According to the invention in its broadest aspect, there is provided an electric snapaction switch, especially for motor vehicles, comprising a handle through which the switch may be externally changed over between at least three switching positions, a control element movable by the handle, a snap-action element which in each of its rest positions is lockable by locking elements which each cooperate with one locking cam and may be released by the control-element, and spring elements which, upon release of the locking elements, move the snap-action element into the next rest position, characterised in that the locking cam is stepped, that at least two locking cams rise in opposite directions and that to each locking cam is assigned a locking element in such a way that in one extreme position of the snap-action element a locking element co-operating with a locking cam rising in one direction is positioned at the bottom step of the respective locking cam and a locking element co-operating with a locking cam rising in the other direction is positioned at the uppermost step of the respective locking cam.

In such a switch each one of the locking elements hits the entire front surface of a locking step. A deformation of material, above all at the edges of the locking elements and of the locking cams, is thereby avoided as far as possible. Furthermore it is ensured that none of the switching positions is left out, when it is changed over. The reason is that the locking elements remain at the level of the following locking step and have not to enter into a locking recess. The spacing of the locking steps in the direction of movement of the snap-action element can, in principle, be made as short as desired, so that the switching paths can be selected nearly independently. Finally any desired number of switching positions can be reached in a switch according to the invention with two locking elements at the most. Only the number of the steps of the locking cams changes.If several locking cam and locking elements are acting in parallel to each other, the number of locking elements has, of course, to be increased.

It is true that the locking cams themselves could be arranged in a way that they are exchangeable. Then a different number of switching positions could be reached by mounting a different locking cam without having to change anything on the locking elements or in the way of arranging them. In this case however a separate tool would be necessary for each locking cam. It is therefore more favourable, above all when there are several locking cams and recesses for the locking elements to be arranged in the switch, to form the locking cams integrally on the switch housing or on the snap-action element. Then a different number of switching positions can be reached by mounting identical locking elements differently.

Spring-loaded locking sliders are advantageously used as locking elements, because a spring can be selected which has a stable spring constant over a wide temperature range, whereas the spring constant changes very much for instance when resilient lugs of plastics material are used.

Embodiments of the invention will now be described by way of example with reference to the accompanying drawings, in which: Figure 1 shows a first embodment of a switch according to the invention with the locking elements being located on the snapaction member and the locking cams on the housing, Figure 2 shows the same switch as Fig. 1 sectioned in the transverse direction, Figure 3 shows a top view on the snapaction member, Figure 4 shows a view on the locking cams being located in a switch housing which is slightly changed in comparison to that of Fig.

1 and 2, Figure 5 shows a locking slider having modified stop faces in comparison to those of Fig. 1 and 2, Figure 6 shows a diagrammatic view on the locking mechanism of a switch according to the invention which has the locking elements on the housing and the locking cams on the snap-action member and the two locking cams have the bottom step in common, Figure 7 shows a diagrammatic view of a version similar to that of Fig. 6 in which the locking cams and the locking elements are arranged beside each other, Figure 8 shows a diagrammatic view of two locking cams with steps of different height as well as two different stop faces on a control element and Figure 9 shows a diagrammatic view of a further locking cam with steps having the same height and stop faces of differing steepness.

The switch shown in Figs. 1 and 2 has a switch housing 11 with lateral walls 1 2 and 1 3 respectively, is closed by a bottom plate 14 and has two openings 1 5 and 1 6 respectively on the top. Into one opening 1 6 is engaged a transparent plate 1 7 below which a lamp 1 8 is anchored in the bottom plate 1 4. When the light of the vehicle is switched on the lamp 1 8 is illuminated, so that the position of the switch can easily be recognised even when it is dark because of the light penetrating the plate 1 7 and catching the eye.

The opening 1 6 is limited on one side by a wall 12, on two other sides by the walls 1 3 and on the fourth side by a transverse web 1 9 which projects into the interior of the housing over a certain length. At the level of its lower end the transverse web 1 9 is surrounded by a flange 20 on whose vertically joining inner edges are provided shields 21 and 22 which frame the opening 1 5. One of the shields 22 has a recess 23 in its centre.

The handle of the switch is developed as an actuating rocker 28 which has the shape of a turned-over box buckled in its centre. It is formed by a base 29, twb narrow sides 30 and two longitudinal sides 31 on which in the centre two locking pins 32 are formed which engage into circular recesses in the walls 1 3 of the switch housing 11 and thus secure the actuating rocker rotatably. Thus the side walls 30 and 31 of the rocker 28 are located in the gap 34 formed by the shields 21 and 22, the flange 20 and the walls 13, one wall 1 2 and the transverse web 1 9. One narrow side 30 of the rocker 28 is provided with an opening 35 behind which ends a light guide 36 held by the rocker which conducts part of the light radiated by the lamp 1 8 to the opening 35.In dependence on the position of the rocker 28 this light is (a) seen, (b) partly seen, or (c) not seen, thus giving an indication of which switching position the switch is occupying at a given time.

By means of two pins 37, the light guide 36 is rotatably mounted in two ribs 38 which project from the surface 29 of the rocker 28 between the shields 21 through the opening 1 5 into the switch interior and there engage into the control element 43. Thus the switch may be switched over to its various switching positions through the rocker 28 with the help of the ribs 38.

The control element 43 and the snap-action member 44 are developed in such a way that they function as sliders. The snap-action member 44 has a bottom 45 which rests on lateral rims 46 of the bottom plate 14 and in the centre of each front side has a prolongation 47. Two supports 48 and 49 whose one outer surface 50 is flush with the matching lateral edge and whose front side is flush with the front edge of the prolongations 47 project from the bottom 45. The two walls 52 extend from the supports 48 to the supports 49 and are staggered towards the outside relative to the supports by an amount approximately corresponding to the thickness of these supports. These walls are lower than the support.

Their front sides are shown by broken lines in Fig. 3. Beginning from the front sides they are continued in thin strips 53 formed on the support, whereby the top side of the strips lies in the prolongation of the upper surface of the walls 52.

Recesses 57 and 58 for the locl < ing elements are arranged on the sections of the bottom 45 projecting over the walls 52. On the one side there is only one recess 57 and on the other side the two recesses 58 are arranged one behind the other in the direction of movement of the snap-action slider. The recesses are closed on the inner side by the walls 52 and laterally by the supports 59, whereas they are open towards the outside.

The supports consist of two portions 60 and 61 of different height and are both higher than the walls 52. The grooves 62 in the sections 61 of the support 60 serve to secure the locking elements and guide them more effectively.

Studs 63 which directly and via pressure springs 64 control the movable contacts of the switch are formed onto the underside of the bottom 45 of the snap-action slider 44.

The movable contacts 65 co-operate with the stationary contacts 66 which are seated on metal sheets conducted to the outside in the shape of flat plugs 67.

The control element 43 is located between the snap-action slider 44 and webs 72 formed onto the flange 20 of the housing 11. It has a plane plate 73 which with its underside rests upon the supports 48 and 49 and laterally rests against the sections 61 of the supports 59. The length of the plate 73 is equal to the length of the snap-action slider 44. On the underside of the plate the control element 43 has two longitudinally extending webs 74 whose outside prolongs the corresponding outside of the plate 73 in a downward direction. The webs 74 which are thus located above the walls 52 of the snap-action slider 44 contribute to the lateral and horizontal guide of the control slider 43.The webs 74 are discontinued at two opposite places and, beginning at the lateral edge, the plate 73 is recessed, so that two recesses 75 for the ends 76 of the ribs 38 of the actuating rocker 28 have been created. In Fig. 2 the web 74 is shown on one side of the control slider 43 and the recess 75 with the end 76 of a rib 38 is shown on its other side.

Besides the webs 74, two elongated pins 77 and 78 are provided on the underside of the plate 73. These pins extend towards each other from the front sides 79 of plate 73 and their height and length correspond to the height and length of the supports 48 and 49 and their width to the spacing of the supports 48 and 49 respectively.

The control slider 43 and the snap-action slider 44 are coupled with each other by a helical spring 80 which is located in the recess 81 of the snap-action slider 44. This recess is formed by the walls 52, the supports 48 and 49 and the bottom 45. If no forces from outside are applied, each end of the helical spring 80 rests on the two supports 48 and 49 respectively and on the pins 77 and 78 respectively projecting between the supports and holds the two sliders 43 and 44 in a stable position relative to each other On each longitudinal side, the top surface of the plate 73 of the control slider 43 is provided with two brackets 85. They extend over a certain length towards each other from the front sides 79. Like the surface of the plate 73, their underside is located at the level of the upper end of the portion 61 of the support.The edges 86 extend towards each other and their sections laterally projecting over the plate 73 are chamfered. They cooperate with the locking elements on the snap-action slider 44.

These locking elements are developed as locking sliders 90 and 91 which are displaceable in the recesses 58 of the snap-action slider 44. Thereby the locking sliders are moved in one direction by a respective pressure spring 92 which rests on the bottom of a bore 93 in the locking sliders and on the bottom 45 of the snap-action slider 44. The sliders 90 and 91 have two sections 94 and 95, the cross-section of which corresponds to the parts of the recesses 58 located between the sections 60 and 61 respectively. The upper surface of the section 94 is gableshaped. One side of the gable serves respectively as contact face 96 for the edge 86 of a bracket 85. Because of the symmetric gableshape of the contact face 96, the two locking sliders 90 and 91 can be identical with each other. The section 95 of each locking slider is longer than the section 94 and of cuboid form.

The sections 94 and 95 of the locking sliders rest against the two locking cams 97 and 98 which are arranged behind each other and are formed onto the underside of the one longitudinal side of the flange 20. This is especially clearly to be seen from Fig. 4 which shows a housing, which differs from the housing according to the Fig. 1 and 2 only by the longitudinal arrangement of the webs 72, and the piece parts of which therefore have the same reference numerals. The locking cams 97 and 98 have the shape of a stair, rising in opposite directions and have the uppermost step in common. The steps are narrower than the section 95 of the locking sliders 90 and 91.

Fig. 4 shows that the longitudinal side of the flange opposite to the locking cams 97 and 98 carries a further locking cam 100 which is substantially formed by the stop 101. This locking cam has no effect unless a locking slider is put into the recess 57 of the snap-action slider 44. On the other hand, the locking cams 97 and 98 are not effective, when the two locking sliders 90 and 91 are removed and a locking slider is put into the recess 57. Then the switch has two switching positions. For this purpose at least one locking slider is necessary. For three or more switching positions, two locking sliders are sufficient. Then the number of switching positions still depends on the shape of the locking cams.

The switch shown in Fig. 1 and 2 has three switching positions, of which the left-hand lateral position is shown. In this position the locking slider 90 is positioned on the uppermost step 99 of the locking cam 97 and the locking slider 91 on the bottom step of the locking cam 98. The position is stable because the movable parts of the switch are secured to the left because of the stop of the actuating rocker 28 on the flange 20 and the control and snap-action slider on the lamp holder and to the right by the stop of the locking slider 91 on the centre step of the locking cam 98. Now the actuating rocker according to Fig. 1 is swivelled in an anticlockwise direction, in order to switch over to the central position. Thereby the control slider is moved to the right via the ribs 38, so that the locking slider 91 is pushed back with the help of the contact surface 96 and the edge 86.The snap-action slider is blocked, so that the pin 77 on the control slider 43 presses the spring 80 against the supports 49 on the snap-action slider 44. Finally the locking slider 91 is moved backwards by an amount corresponding to the height of the middle step of the locking cam 98. Now the spring 80 can relax abruptly by following up the snapaction slider 44. Though the locking slider 91 is already released by the control slider 43 before the latter has reached the central switching position, the sliders 43 and 44 as well as the rocker 28 are thrown into the central switching position because of the kinetic energy of the snap-action slider The locking slider 90 is moved forwards onto the middle step of the locking cam 97 by its pressure spring 92. Now the movable parts of the switch are secured in both directions by the two locking sliders.

If now the switch is to be brought into the right-hand lateral position the actuating rocker 28 is tilted further in the anti-clockwise direction. The actuating rocker again takes along the control slider 43. Because, in comparison to the position shown in Fig. 1, the locking slider 91 is positioned further backwards the edge 86 hits the stop face 96 only aftersa certain travel. Now the locking slider 91 is pushed backwards by an amount corresponding to the height of the step 99 during the further movement. Finally the locking is released. The spring 80 can relax and the switch parts jump into the right-hand lateral position in which they are secured by resting against the housing and by the locking slider 90.

For changing over from the central position to a lateral position a bigger force is necessary than for changing over from a lateral position to the central position for two reasons. Firstly, because of the bigger displacement of the control element 43 the spring 80 has to be tensioned more intensively until the locking slider 91 is released. This is the main cause for the necessary higher amount of force.

Secondly the spring 92 of the locking slider 91 has a slight effect due to the fact that in order to tension this spring, which, in comparison to the central position, is elevated in the initial lateral left-hand position, a bigger force is necessary.

The locking slider 90 is released with each changing-over process to the left, independently of whether it is effected from the righthand lateral or from the central position. Apart from the direction, the movements are thereby effected analogously to the manner described.

In order to avoid faulty switching it is desirable, as described above, that the force for the changeover operations increase from the one extreme position to the other extreme position. If the various lengths to which the spring 80 is pressed do not result in the desired differing forces, the locking sliders can be developed according to the embodiment of Fig. 5. The two symmetrical stop faces 105 of the locking slider 104 consists of two sections 105 and 107 each, of which the section 107 is steeper than the .section 106. If, instead of the locking sliders 90 and 91, two locking sliders according to Fig. 5 are inserted into a switch according to Fig. 1 and 2 the edges 86 of the brackets 85 co-operate with the steeper sections 107 during a change-over operation from a central position to a lateral position.The bigger steepness of the portion 107 thereby causes the difference between the necessary outer forces to be still increased.

Fig. 6 to 9 show schematically various locking mechanisms of a switch according to the invention in which the locking sliders 110 are guided on the housing 11, the locking cams 111 and 11 2 are located on the snapaction member 11 3 and two stop faces 11 4 are developed on a control element. Thus the locking sliders 110 retain their position in direction to the movement of the snap-action member 11 3 and of the control element even during a changeover operation, whereas the locking cams 11 2 and the contact surfaces 114 are simultaneously moved. This arrangement makes it possible to have in a simple way a construction, in accordance with which the switching paths of the control element are the same until the corresponding locking slider 110 is released.This is true for all the embodiments according to Fig. 6 to 9.

The embodiment according to Fig. 6 has locking cams 11 2 whose steps have the same height and, with the exception of the bottom step, the same width. The contact surfaces 11 4 are formed by plane surfaces whose steepness results from the width and height of the locking steps. The two locking cams have the bottom locking step in common. The snap-action member and the control element can therefore only be locked in one of the two extreme positions by one of the two locking sliders 11 0. For this, the width of the bottom step must correspond approximately to the width of the locking sliders.

The example of Fig. 7 is similar to that of Fig. 6. All steps of the locking cams 111 and 11 2 have the same height and width, but the contact surfaces are plane. Unlike Fig. 6 the two locking cams 111 and 112, the two locking sliders 110 and the two contact surfaces 11 4 seen from the direction of movement of snap-action member and control element are arranged beside each other, on different sides of the snap-action element.

In the version according to Figs. 6 and 7, the switching forces during the various switching-over operations are the same, apart from the small effect of the pressure springs 92. In order to achieve different switching forces, the steps of the locking cams 111 and 11 2 can be of different height. The contact surface 11 4 which is shown beneath the locking cam 11 2 consists of several portiohs 11 5 which are of differing steepness, so that the switching forces are different. The rise of an individual portion 11 5 thereby equals the quotient of height and width of the locking step assigned to this portion.The difference in the switching forces can be additionally increased by using the locking surface 11 4 located below the locking cam 111.

The locking surface 11 4 consists of several horizontal sections 11 6 and of the same number of inclined sections 11 7. The rise of the inclined portions 11 7 is greater than the quotient of height and width of the corresponding locking step.

Fig. 9 shows that, by an appropriate development of the stop faces 114 of a locking cam 111 whose steps all have the same height, different switching forces can be reached. For this purpose, the horizontal sections 11 6 from step to step are longer, and the inclined sections 11 7 from step to step are steeper.

For simplicity's sake Fig. 8 shows two differently-developed stop faces. When the same switching behaviour is to be achieved for both swiching directions the two stop faces will, of course, be equally developed in a specific case. Finally it is to be mentioned that also in the embodiments according to Fig. 6.to 9 the length by which the control element is moved with regard to the snap-action member during a change-over operation can be changed from one operation to another by appropriately developed stop faces.

Claims

1. An electric snap-action switch, especially for motor vehicles, comprising a handle through which the switch may be externally changed over between at least three switching positions, a control element movable by the handle, a snap-action element which in each of its rest positions is lockable by locking elements which each co-operate with one locking cam and may be released by the control-element, and spring elements which, upon release of the locking elements, move the snap-action element into the next rest position, characterised in that the locking cam is stepped, that at least two locking cams rise in opposite directions and that to each locking cam is assigned a locking element in such a way that in one extreme position of the snapaction element a locking element co-operating with the locking cam rising in one direction is positioned at the bottom step of the respective locking cam and a locking element co-operating with a locking cam rising in the other direction is positioned at the uppermost step of the respective locking cam.

2. A switch according to claim 1, characterised in that the section of a locking element resting against the locking cam is broader than at least some of the locking steps of the locking cam.

3. A switch according to claim 1 or 2, characterised in that two locking cams rising in opposite directions as well as the locking elements assigned to the locking cams are at least approximately arranged beside each other as seen in the moving direction of the snap-action member.

4. A switch according to claim 1 or 2, characterised in that two locking cams rising in opposite directions as well as the locking elements assigned to the locking cams are arranged one behind the other as seen in the moving direction of the snap-action member.

5. A switch according to claim 4, charactensed in that the two locking cams have one step in common.

6. A switch according to claim 5, characterised in that the two locking cams have the bottom step in common and that this step is approximately as broad as the portion of the locking elements resting against the locking cams.

7. A switch according to claim 5, characterised in that the two locking cams have the uppermost step in common and that in the two extreme switching positions one portion each of a switch member moved during a change-over operation rests against a part fixed to the housing.

8. A switch according to any one of the preceding claims, characterised in that the locking elements are insertable into recesses and that these are provided at least one further locking cam and at least one empty recess, assigned to the further locking cam, for a locking element.

9. A switch according to claim 8, characterised in that the locking cams for the one number of switching positions are located on one side of the switch housing or of the snapaction member and the locking cams for the other number of switching positions on the other side of the switch housing or snapaction member.

10. A switch according to any one of the preceding claims, characterised in that the locking elements are sliders pressed against the locking cams by a spring.

11. A switch according to any one of the preceding claims, characterized in that the locking cams are located on the snap-action member and the locking elements are on a part fixed to the housing.

1 2 A switch according to any one of claims 1 to 1 0, characterised in that the locking cams are located on a part fixed to the housing and the locking elements are on the snap-action member.

1 3. A switch according to claim 11 or 12, charactensed in that the locking elements may be released by inclined portions.

14. A switch according to claim 13, characterised in that the inclined portions are located on the control element.

1 5. A switch according to claim 13, characterised in that the inclined portions are located on the locking elements.

16. A switch according to claim 15, characterised in that the locking sliders have two inclined portions descending to different sides and symmetrically arranged with respect to each other.

1 7. A switch according to any one of claims 1 3 to 16, characterised in that the inclined portions are composed of various sections with differing incline and of which each is assigned to a transition from one switching position into a neighbouring one.

18. A switch according to any one of claims 1 3 to 17, characterised in that the incline of at least one section of the inclined portions, which section is assigned to a transition between two particular switching positions, is bigger than the quotient of height and width of the locking cam step which is assigned to the same transition.

1 9. A switch according to any one of claims 1 3 to 18, characterised in that the locking cams are provided with steps of differing height.

20. A switch according to any one of claims 1 3 to 19, characterised in that the locking cams have steps of differing width.

21. A switch according to any one of claims 1 3 to 20, characterised in that the edges co-operating with the inclined portions are chamfered on the control element or on the locking elements.

22. A switch according to any one of the preceding claims, characterised in that the control element and the snap-action member are sliders guided in each other and that the spring means is formed by a helical spring which on both ends is acted upon by both sliders.

23. An electric snap-action switch substantially as described with reference to the accompanying drawings.