GB2046999A

GB2046999A - Electric switches

Info

Publication number: GB2046999A
Application number: GB8008253A
Authority: GB
Original assignee: SWF Spezialfabrik fuer Autozubehoer Gustav Rau GmbH
Current assignee: SWF Auto Electric GmbH
Priority date: 1979-03-29
Filing date: 1980-03-11
Publication date: 1980-11-19
Also published as: ES249704Y; DE2912363A1; ES249704U; BR8001880A

Abstract

An electric switch having a switch lever (11) carrying at its lower end a spring loaded locking ball or pin (13) having a hemispherical end which engages with a locking contour (30) which in order to reduce wear has a cross- section which is shaped to conform to the shape of the ball or pin (13). Thus the forces exerted by the spring (14) in a bore of the lever (11) are spread across the contour (30) instead of being confined to the centre line of the contour where the ball or pin (13) would make a point contact if the contour was not so shaped. The contour may be formed in the upper part of a switching rocker (20) the underside of which is adapted to carry one or more spring loaded bridging contacts (21) which co-operate with sets of stationary contacts (35) located in the switch housing. <IMAGE>

Description

SPECIFICATION Electric switches The invention refers to electric switches, particularly rocker switches.

Very often electric switches are designed so that a spring-loaded locking element moves along on a locking contour when the switch is changed over from one switching position to the other. Thereby stable switching positions can be achieved simply by the special design of the locking contour or by co-operation of the locking contour with stops fixed to the housing. It is also possible to design the locking contour in such a way that from particular switching positions the switch automatically moves into another switching position.

Several locking elements are known from a series of printed prior publications. So for instance German patent application 26 18605 shows a locking system having a spring-loaded bolt on whose end, which is adjacent to the locking contour, a roller is mounted.

This roller and the locking cam are resting on each other in a straight line, so that the surface pressure and thus the abrasion at the locking contour are relatively small.

Such a design with cylinder or roller is however very complicated and thus expensive. The roller may cant, so that the switching properties may change.

Moreover, in the support a receiver with rectangular cross-section has to be created for it, which above all is more difficult and expensive to produce than a bore, when the support is not injection-moulded.

It is cheaper, when a spring-loaded bolt acts directly upon the locking contour like in a locking system shown by the German petty patent 7 522 692.

Thereby the bolt can be wedge-shaped in its area adjacent to the locking contour, so that it rests against the lockingcontour in a straight line like a roller. If such a bolt has a rectangular cross-section with respect to the receiver in the support it is subject to the same difficulties as the roller or cylinder. However a round bolt may cant, when its straight contact line is uneven.

In other known switches one therefore uses locking elements having a semicircular surface in its portion adjacent the locking contour. Such a locking element is for instance disclosed in German published patent application 2 504 457, in which the locking contour is acted upon by a spring-loaded locking bolt which is guided in a switching stud of the actuating rocker of the switch shown in the drawing. This locking bolt can no longer cant when the cross-section of the locking bolt is round.

This is also no longer possible if the locking element is a ball as it is shown by the German patent application 2 600 368. The ball as well as the round locking bolt can easily be made with a smooth surface from steel. This is desired when exactly defined switching forces are needed, which are to be determined only by the shape of the locking contour and the force of the spring supporting the locking element are are not to be affected by friction forces which cannot be controlled exactly.

However the known locking systems with ball and circuiar bolt entail the disadvantage that the locking elements are only resting on the locking contour with point contact, as can especially clearly be seen from the German patent application 2 600 368.

Therefore the locking elements damage the locking contour very quickly. Above all the locking summits are rapidly worn, so that the switching forces are changed and loose their characteristic behaviour curve during a changeover process. The individual switching positions can hardly be recognised any longer, so that the switch soon becomes unserviceable.

According to the present invention there is provided an electric switch comprising a handle, a switching element which is movable by actuating the handle, and a locking system, wherein said switching element can be held by the locking system in at least one stable position, the locking system having a locking contour and a spring-loaded locking element which at a section transverse to the direction of its movement relative to the locking contour has a curved boundary line contacting the locking contour, the locking contour at least on a part of its length transverse the direction of the relative movement between itself and the locking element being shaped at least approximately to the boundary line of the locking element.

If the locking contour transversally to the movement of the locking element is adapted to the curved boundary line of said locking element which is adjacent to the locking contour, the locking contour and the locking element are resting on each other over a longer section similarly as in the case of rollers or locking bolts which are wedge-shaped in their end area. Thus the surface pressure is similarly small too, so that the wear between locking contour and locking element becomes considerably reduced.

In comparison to known systems with curved locking elements the wear is also diminished in that now, when the contact point between locking contour and locking element becomes a contact line, the spring acting upon the locking element can be weaker and achieve the same switching forces as the contact point support known until now. Thus the design of the locking contour has a double effect on the life of an electric switch.

It is not necessary that locking contour and locking element have completely exact complementary cross-sections from the beginning. This is not possible simply because of the tolerances appearing in production. For the capacity of resistance to wear it is sufficient, if for instance when a ball is used as a locking element, the radius of the locking cam is somewhat bigger. In this case a point support is provided at first, which however, with the slightest lateral wear extends to two further undamaged locking points, so that very quickly a line support comes into being. If the radius is somewhat smaller at first two outside points provide support which vary towards the centre with the slightest wear. In both cases an exact locking is achieved without disadvantageous wear.

The life of a switch can essentially be prolonged in that the areas of the locking contour which are especially endangered by abrasion are adapted to the curved boundary line of the locking element.

Above all these are areas in which the spring loading the locking element is tensioned most and therefore the surface pressure tod is biggest. Thus it is sufficient when the adaptation is effected round the locking summits of the locking contour, as far as locking summits are available. The best solution is, however, if the locking contour on its entire length is adapted to the boundary line of the locking element.

In principle the boundary line of the locking element can have any curved shape. However simpler and less expensive production locking elements are preferred which have a uniformly curved, semicircular boundary line, i.e. circular bolts and balls. Because the force component of the spring force, which is vertically acting on the higher lateral area of the locking contour is only small these areas alone can be shaped without shortening the life of the switch compared to the complete adaptation to an extent which is worth mentioning.

The design of the locking contour according to the invention can especially advantageously be used in a toggle switch which is provided for the use of several bridging contacts. Known switches of this type involve the disadvantage that if only one bridging contact is used the rocker is only loaded on one side and thus the life of the switch is shortened.

When two bridging contacts are used two locking bolts and pressure springs and, depending on the type of switch, two actuating rockers each are necessary. In addition to the increased number of parts needed this has the consequence that with the same pressure springs the switching forces are doubled, while with different pressure springs and use of one or more pressure springs there is the danger of mixing up the parts during the assembly and the dead centre area will enlarge.

These disadvantageous effects are avoided by a toggle switch having a single rocker adapted to receive one or more bridging contacts. The switching rocker again carries a locking contour which is adapted to the locking element. By adapting the locking contour to the shape of the locking element the switching forces remain the same for a great number of switching operations, also when a broad switching rocker with a relatively big mass is used.

If an odd number of bridging contacts is used, i.e.

especially one bridging contact, the design of the switching rocker is such that uneven loading of the bearings of the actuating and of the switching rocker are avoided, because in any case the bridging contacts are suspended symmetrically to the centre of the switching rocker. Thereby the life of the switch is not insignificantly prolonged.

In one embodiment the bridging contacts are resiliently supported on the switching rocker. This ensures that the contact making between bridging contacts and stationary contacts is reliable too, if the stationary contacts are not exactly located in one plane. At the same time the electric switching behaviour, especially the contact bouncing behaviour, is improved by the resilient support of the bridging contacts, because the springs are acting as damping elements. Thus the resilient support of the bridging contact entails already big advantages, so that this measure can in the same way be applied independently of the other measures and with a single bridging contact as well.

In a further development of a switch with resilient bridging contacts the angle formed bythe underside of the switching rocker is smaller than the angle at the inside of the bridge. Thereby contact bounce is already damped when the contact is made. Thereby the path of spring-action is limited. The shorter contact bouncing times also contibute to prolong the life of the switch.

The invention is described in detail in several embodiments and by means of the examples of the accompanying drawings in which: Figure 1 is the locking system of an electric switch according to the invention, Figure 2 is a top view on the locking contour of Figure 1, Figure 3 is a section taken on the line Ill-Ill of Figure 1, Figure 4 is a section through an electric switch comprising a switching rocker, Figure 5 is a top view on the contact panel of the switch, Figure 6 is a longitudinal section through a somewhat differently designed switching rocker, Figure 7 is a section taken on the line VII-VII of Figure 8 and Figure 8 is a view of the switching rocker of Figure 6 and 7 from below.

The locking system of Figure 1 to 3 has a ball 1 as a locking element which is guided in a bore 2 of the switch lever 3. A pressure spring 4 supports on the bottom 5 of the bore 2 and on the ball 1 and attempts to push the ball out of the guide ofthe switch lever 3.

The ball 1 co-operates with a locking contour 6 which is formed on a part 7 of the switch relative to which the switch lever 3 is swivelled with a changeover operation. As can clearly be seen from Figure 3 the locking contour 6 is adapted transverse the direction of movement of the switching lever 3 and thereby of the ball 1 to the boundary line 9 located nearest to it and transverse the direction of movement. The adaptation thereby only reaches as far as to the angle a, because firstly the switch lever 3 has to be moved beyond the locking contour 6 and secondly above the angle a the component of the spring force F vertical on the locking contour 6 becomes rapidly smaller, so that so far the contribution for diminishing the surface pressure would only be small.

In the embodiment shown the lever 3 has two possible stable switching positions which are located to the right and to the left of the locking summit 8. On changing over from one position to the other the ball 1 has at first to be pressed backward into the bore 2 against the force of the spring 4 by being moved to the locking summit 8. As soon as the locking summit is passed, the switching lever, because of the spring 4 which can thereby relax, moves by itself into the second switching position.

Thus the two switching positions can clearly be differentiated in the changing-over operation. In contrast, in known locking systems there was the dangerthatthe locking summits were gradually worn, so that in transition between the two switch ing positions the spring has to be compressed less and less. Finally the characteristic behaviour curve of the force during the switching movement vanishes completely.

The switch of Figure 4 is designed as a toggle switch. For this purpose an actuating rocker 11 is tiltably mounted in the housing 10. The actuating rocker 11 projects into the housing 10 with a switching stud 12 which in its interior guides a locking bolt 13. A pressure spring 14 which attempts to push the locking bolt 13 out of the guide 15 supports on a rib 16 of the switching stud 12 and on a rib 17 in the bore 18 of the locking bolt 13.

In addition to the actuating rocker 11 a switching rocker 20, which can receive several bridging contacts 21, is tiltably mounted in the switch housing 10.

For this purpose a resilient lug 22 is formed on each front side of the switching rocker 20, whereby said lug in accordance with the number of possibilities for suspension of the bridging contacts is provided with a particular number of detents 23 engaging with the locking apertures 24 of the bridging contacts 21.

The bridging contacts 21 are shaped like a yoke with two lateral shanks 25, into which locking apertures are made, and a web 26 which forms an angle transversally to the longitudinal direction.

Each bridging contact 21 is supported against the switching rocker 20 via helical springs 27, which are guided in hollow-cylindrically shaped studs 28 on the underside of the switching rocker 20. These spring elements 27 act as dampting elements against contact bouncing and ensure a reliable multipoint support with two and more bridging contacts available. The underside of the switching rocker 20 formed by the rims 29 of the hollow cylinders 28 forms an angle, however this angle is smaller than that of the yoke 26, so that the bouncing is already damped, when the contact is made.

On the upper side the switching rocker 20 is provided with a locking contour 30 with which the locking bolt 13 co-operates which in its lower area is semi-circular. As in the example of Figure 1 to 3 the locking contour is again adapted to the shape of the locking bolt 13. In longitudinal direction it is designed in such a way that the actuating rocker and the switching rocker have three stable switching positions, in which two each of a total of four stationary contacts 35 are interconnected in an electrically conductive manner via a bridge contact 21. In the embodiment shown the switching rocker serves for receiving either one or two bridging contacts 21. Therefore a total of 3 receivers are provided on the switching rocker, so that, when only one contact rocker 21 is necessary it can be suspended into the central receiver. Thus a one-sided load on the bearing spot is avoided.

How the stationary contacts are positioned, when only one bridging contact is used, is clearly shown by Figure 5. In the contact panel 36 two lines of four slots 37 and 38 each are arranged, through which the lugs 39 with the stationary contact 35 are conducted.

The lugs 39 (Figure 4) pointing outwards through the slots 38 are within the housing 10 bent with a right angle to a plate 40 which is elongated to the centre of the contact panel 36 and is there provided with the stationary contacts 34 which thus are exactly located below the single bridging contact 21. If there are two bridging contacts it is not necessary to elongate the plate 40. The stationary contacts 35 can rather be directly fixed on the bent part.

Figures 6 to 8 only show a slightly modified switching rocker 20, so that from these figures also the shape of the switching rocker of Figure 4 becomes clearer. In the longitudinal section according to Figure 6 one again recognises the locking contour 30, the somewhat modified lugs 22 with the detents 23 and the recesses 28 for the pressure springs, which as well are slightly modified in order to simplify the injection-moulding die, so that it is possible to remove both recesses 28 from the mould in the same direction.

In the middle of each of the longitudinal sides the switching rocker is provided with one bearing stud 45 with an oblong slot 46 open towards the bottom.

This design makes possible the different switching positions in a simple manner. As one can realise by means of Figure 4 with the given contact arrangement the centre part of the switching rocker on which the bearing studs 45 are formed in transition between the central and one lateral switching position must move upwards and downwards. This is ensured by the oblong hole 46.

Whereas the locking contour 30 can especially clearly be seen from Figure 7, Figure 8 shows clearly how the individual receivers for the bridging cqntacts are arranged on the switching rocker. The detents 23 are arranged on the resilient lugs 22 at equal intervals. In line with corresponding detents two receivers 28 for each of the spring elements are located. They are formed spaced apart on the switching rocker, so that the bridging contacts have two supporting points on the switching rocker which are located far away from each other.

If only two bridging contacts are necessary these are suspended into the two outer recesses. Thereby a symmetry with respect to the central plane in longitudinal direction of the switching rocker is achieved, so that all bearings are equally loaded. In contrast thereto a single bridging contact is inserted into the central receiver. This too results in a symmetric constellation and a uniform load on all bearings. In this embodiment the use of three bridging contacts at the same time is not possible because the distance between the individual receivers is too small. The contact panel 36 of Figure 5 is not provided with three lines of stationary contacts either. However one can also easily design a switch according to the invention with a maximum number of insertable bridging contacts which is bigger than two. With an odd maximum number the number of receivers can be equal to this maximum number, because then a symmetric construction is possible in any case.

Claims

1. An electric switch comprising a handle, a switching element which is movable by actuating the handle, and a locking system, wherein said switching element can be held by the locking system in at least one stable position, the locking system having a locking contour and a spring-loaded locking element which at a section transverse to the direction of its movement relative to the locking contour has a curved boundary line contacting the locking contour, the locking contour at least on a part of its length transverse the direction of the relative movement between itself and the locking element being shaped at least approximately to the boundary line of the locking element.

2. An electric switch according to claim 1, characterised in that around the points to which the spring loading the locking element exerts the biggestforce in a changing-over operation, the crosssection of the locking contour is adapted substantially to the boundary line of the locking element.

3. An electric switch according to claim 1 or 2, characterised in that around locking summits the locking contour is adapted substantially to the boundary line of the locking element.

4. An electric switch according to claim 1, 2 or 3, characterised in that in cross-section the locking contour is over its entire length adapted substantialliy to the boundary line of the locking element.

5. An electric switch according to any one of claims 1 to 4, in which the locking element has a uniformly curved semicircular boundary line.

6. A switch according to any one of claims 1 to 5 characterised in that the locking element is a locking pin.

7. A switch according to claim 5, characterised in that the locking element is a locking ball.

8. A switch according to any one of claims 5 to 7, characterised in that the locking contour is shaped to the curved low boundary line only in one area in which the angle which is normal on a point of the locking contour encloses with the direction of the spring force does not exceed a given value.

9. A switch according to any one of the preceding claims including a rocker adapted to receive one or more neighbouring bridging contacts selectively and provided with a locking contour co-operating with a spring loaded locking element, said locking contour being centrally located on the rocker.

10. A switch according to claim 9 having means for accommodating two groups of stationary contacts parallel to the direction of movement of the rocker and symmetrically placed with respect to the rocker axis, the rocker having three means for accommodating bridge contacts disposed parallel to the direction of movement and symmetrically about the centre of the rocker whereby when only one group of stationary contacts is inserted they are elongated towards the centre of the switch to be co-operative with a single central bridging contact on the rocker and when two groups of stationary contacts are inserted they are not so elongated and are co-operative with two bridging contacts positioned in the two outermost accommodating means of the rocker.

10. Aswitch according to claim 9 having means for accommodating two groups of stationary contacts parallel to the direction of movement of the rocker and symmetrically placed with respect to the rocker axis, the rocker having means for accommodating up to three bridging contacts disposed parallel to the direction of movement and symmetrically about the centre of the rocker whereby when only one group of stationary contacts is inserted they are elongated towards the centre of the switch to be co-operative with a central bridging contact on the rocker and where two groups of stationary contacts are inserted they are not so elongated and are co-operative with two bridging contacts positioned in the two outermost accommodating means of the rocker.

11. A switch according to claim 1, having yokeshaped bridging contacts provided with web formed like an inverted shallow pitched roof and two lateral shanks each having one opening into which the switching rocker engages with a locking stud.

12. A switch according to any one of the claims 9 to 11, in which the switching rocker is movable upwards and downwards in its bearing on the housing.

13. A switch according to any one of the claims 9 to 12 in which the bridging contacts are resiliently supported on the switching rocker.

14. A switch according to claim 13, characterised in that at two spots symmetrically located to their centre the bridging contacts are acted upon by springs.

15. A switch according to claim 13 or 14, characterised in that the springs are guided in receivers of the switching rocker.

16. A switch according to any one of the claims 13 to 15, characrerised in that the springs are helical springs which are located in cup-like receivers.

17. A switch according to any one of the claims 13 to 16, characterised in that an angle formed by the underside of the switching rocker is smaller than the angle which the inner side of the web of the bridging contact has.

18. An electric switch substantially as described with respect to the accompanying drawings.

New claims or amendments to claims filed on Date of Issue of Search Report Superseded claims 8 and 10 New or amended claims:

8. A switch according to any one of claims 5 to 7, characterised in that the locking contour is shaped to the curved low boundary line only in one area in which the angle between a normal on a point of the locking contour encloses and the direction of the spring force does not exceed a given value.