GB2094553A - Operating lever assembly for electrical switch - Google Patents

Abstract

In an operating lever assembly for an electrical switch of the kind having a metallic operating lever 11 formed with a part spherical fulcrum portion 19 which is located in a recess 18 within a metallic housing 10 by a pair of spaced resilient 'O' rings 20, 21 a pair of generally parallel electrically conductive resilient strips or wires 30 engage opposite sides of the operating lever 11 or an electrically conductive extension thereof, so as to extend in a direction perpendicular to the pivotal axis of the operating lever 11 and are electrically connected to the metallic switch housing 10 whereby the switch housing 10 and the operating lever 11 can be earthed when the housing 10 is mounted on a metallic panel 16. <IMAGE>

Description

SPECIFICATION Operating lever assembly for electrical switch This invention relates to an operating lever assembly for an electrical switch which is especially (but not exclusively) intended for use in communications equipment, the assembly being of the kind which includes a metallic housing and a metallic operating lever. In one earlier known construction the operating lever was provided with a pair of opposed projecting spigots on which the lever pivoted and the spigots also acted to earth spurious radio signals (e.g. signals in the higher frequency ranges such as 400-500 Mhz) which may have been picked up by the operating lever which would then have acted (in the absence of an earth path) as a receiving or transmitting aerial, thus causing malfunctioning of the communications equipment in question.It is however also important to seal the assembly against the ingress of dirt and moisture and consequently in a later known assembly the operating lever was provided with an integral partspherical portion which forms a fulcrum for the lever, said portion being located in a recess in the housing by means of a pair of resilient spaced '0' rings or the like which then provide the desired seal. This latter construction does not however provide an earth connection for the operating lever. Furthermore it is difficult, with this kind of operating lever assembly, to make use of earthing straps for connecting the lever to the frame of the associated communications equipment.

Consequently, it is the object of the present invention to provide an improved operating lever assembly for an electrical switch in which the operating lever can be effectively earthed and in which at the same time the ,assembly is sealed against the ingress of dirt and moisture.

In accordance with the invention there is provided an operating lever assembly for an electrical switch of the kind having a metallic housing and a metallic operating lever which is formed with a part-spherical fulcrum portion located in a recess within the housing by a pair of spaced resilient '0' rings or the like, characterised in that there is provided a pair of generally parallel electrically conductive portions which each extend in a direction perpendicular to the pivotal axis of said operating lever and which engage opposite sides of said operating lever or an electrically conductive extension thereof, said electrically conductive portions being themselves electrically connected to said metallic switch housing, the arrangement being such that in use the latter can be mounted on a metallic panel whereby the switch housing and the switch operating lever can be earthed.

The aforementioned pair of electrically conductive portions may comprise a pair of separate resilient metallic strips or wires or alternatively they may comprise the legs of a resilient metallic strip or wire of generally hairpin configuration.

The invention will now be more particularly described with reference to the accompanying drawing wherein: Figure 1 its a sectional elevation of one example of an operating lever assembly for an electrical switch constructed in accordance with the present invention, the switch being shown mounted on a panel by means of a securing nut indicated by chain dotted lines, and Figure 2 is an end view, looking in the direction of arrow 'A', of the switch shown in Figure 1.

Referring to the drawings, the switch shown therein has a metallic housing 10 which is conveniently formed of aluminium or an aluminium alloy, together with a metallic operating lever 11 which may also be formed of aluminium or an aluminium alloy. The exterior of said housing 10 is formed with a screw thread 12 adapted to receive a securing nut shown in chain dotted lines and indicated by reference numeral 13.Furthermore, said housing 10 has a radially outwardly directed flange 14 formed with a groove which is adapted to receive a sealing ring 1 5, the arrangement being such that the switch can be mounted upon a metallic panel 1 6 by engaging said flange 1 4 with one face of said panel 1 6 whereafter said nut 1 3 can be tightened on the screw thread 12 to engage the opposite face of the panel 16 and thereby clamp the switch in position.The exterior of the housing 10 and the switch operating lever 11 may, if desired, be coated with paint or other insulating coating such as will be provided by anodising but in this case the edge which is indicated by reference numeral 1 7 of the flange 14 is left uncovered in order that a good electrical connection will be made between said flange 14 and the metallic panel 1 6 when the switch is in its mounted position.

The interior of said housing 10 is formed with a recess 1 8 which serves to receive an integral partspherical portion 1 9 of the switch operating lever 11 and said portion 1 9 provides a fulcrum on which the operating lever can be pivoted. As shown in Figure 1, said part-spherical portion 1 9 is located within said recess 1 8 by means of a pair of spaced resilient '0' rings 20 and 21 such as rubber '0' rings or the like.In addition, there is provided an adjusting ring 22 which is in screw threaded engagement with the interior of said housing 10 and which can be tightened to apply pressure to said resilient '0' rings 20 and 21 in order to provide a firm seating for said part-spherical portion 19 and also to provide a predetermined sealing pressure to prevent the ingress of dirt and moisture.

The switch operating lever 11 has one end 1 1 a which projects outwardly from one side of said portion 1 9 and which is used is adapted to be gripped or engaged by the switch operator.

Opposite to said portion 1 a is another portion 1 b which is formed with a recess adapted to receive and locate one end of an operating pin 23 which may or may not be formed of an insulating material and which in use will be arranged to engage the mechanism of the communications equipment switch which is required to be operated by the operating lever.

There is also provided a metallic retaining plate 24 which has four turned-down tongues 32 and also has a pair of projecting wings 25 and 26 located in correspondingly shaped recesses formed in the outer face of said flange 14. Said retaining plate 24 is also provided with a central aperture 27 into which said portion 1 1b of the operating lever extends, said aperture having a pair of opposite sides which are bent inwardly to form a pair of parallel tongues or lips 28 and 29 which serve respectively to support spring wires 30 and 31 if the latter are stressed in directions at right angles to the direction of movement of the operating lever 11.Said spring wires 30 and 31 engage opposite sides of said portion 1 ib of the lever and guide it in its intended direction of movement, there being normally a siight clearance between the wires 30 and 31 and the tongues 28 and 29. Said part 1 b is either, as shown, an integral part of the lever projecting from the partspherical portion 1 9 in a direction away from the portion 1 1 a or alternatively said portion 1 b may comprise a separately formed metallic part which is in electrical connection with the operating lever.

In either case however said resilient wires 30 and 31 will form an electrical connection between the operating lever 11 and the metallic housing 10, since the opposite ends of said wires 30 and 31 are urged into engagement with the turned-down tongues 32 on the retaining plate 24. The latter itself is retained in position by peening over adjacent parts of said housing 10 at convenient points around the periphery of said plate 24. As previously indicated, an electrical connection is also established between said housing 10 and the panel 1 6 by virtue of the contact between said panel and the surface 17 and thus a complete earth connection will be made from the operating lever 11 to the panel 16, thereby eliminating any undesirable interference that might otherwise be caused by signals received or transmitted by the operating lever.

In an alternative construction the separate spring wires 30 and 31 are replaced by a hairpinshaped spring, the two legs of the latter being arranged in a spaced parallel relationship and positioned similarly to the aforementioned wires 30 and 31, the two ends of the hairpin-shaped spring being situated between the turned-down tongues 32 and the plate 24 as before. Similarly, the portion 1 1 b of the operating lever will be engaged on its opposite sides by said legs of the hairpin-shaped spring and an earth connection will thus be established again between the operating lever 11 and the panel 1 6.

Furthermore, instead of providing a pair of parallel tongues or lips 28 and 29 as described above, the width of the central aperture 27 in the plate 24 adjacent to the wires 30 and 31 may be reduced in comparison with the construction shown in Figure 2 by arranging that the opposite edges of said aperture which extend generally parallel to the wires 30 and 31 respectively overlie the central parts of said wires so as to be spaced apart by a distance only slightly greater than the diameter of the portion 1 b, said opposite edges then extending, together with the adjacent portions of the plate 24, in one common plane.

Claims (7)

1. An operating lever assembly for an electrial switch of the kind having a metallic housing and a metallic operating lever which is formed with a part-sphericai fulcrum portion located in a recess within the housing by a pair of spaced resilient '0' rings or the like, characterised in that there is provided a pair of generally parallel electrically conductive portions which each extend in a direction perpendicular to the pivotal axis of said operating lever and which engage opposite sides of said operating lever or an electrically conductive extension thereof, said electrically conductive portions being themselves electrically connected to said metallic switch housing, the arrangement being such that in use the latter can be mounted on a metallic panel whereby the switch housing and the switch operating lever can be earthed.

2. An assembly as claimed in Claim 1 wherein said pair of electrically conductive portions comprise a pair of separate resilient metallic strips or wires.

3. An assembly as claimed in Claim 1 wherein said pair of electrically conductive portions comprise the legs of a resilient metallic strip or wire of generally hairpin configuration.

4. An assembly as claimed in any one of the preceding claims wherein said pair of electrically conductive portions are disposed between a metallic switch housing and a metallic retaining plate having an aperture into which one end of said operating lever or said electrically conductive extension thereof projects.

5. An assembly as.claimed in Claim 4 wherein there is formed in said retaining plate on each of two opposite sides of said aperture an integral tongue which serves to engage and support the central part of the adjacent electrically conductive portion if the latter is stressed outwardly away from the operating lever.

6. An assembly as claimed in Claim 4 wherein the opposite edges of said retaining plate aperture which extend generally parallel to said electrically conductive portions overlie the central parts thereof and extend, together with the adjacent portions of the retaining plate, in one common plane.

7. An operating lever assembly for an electrical switch of the kind having a metallic housing and a metallic operating lever which is formed with a part-spherical fulcrum portion located in a recess within the housing by a pair of spaced resilient '0' rings or the like, said assembly being substantially as hereinbefore described with reference to and as shown in the accompanying drawing.