GB2173641A

GB2173641A - Electrical switches

Info

Publication number: GB2173641A
Application number: GB08606798A
Authority: GB
Inventors: Peter Alec Alexander
Original assignee: ITW Ltd
Current assignee: ITW Ltd
Priority date: 1985-04-12
Filing date: 1986-03-19
Publication date: 1986-10-15
Also published as: IT8521024A0; GB8606798D0; DE3538667A1; FR2580425A1; GB8509372D0

Abstract

A switch e.g. for use with the shaft of a gas tap for igniting the gas includes a first housing part (12) having an opening (14) for receiving the shaft, an actuator (16) mounted for movement axially with respect to the opening (14), and second housing part (20) having an opening for receiving the actuator means (16). The first (12) and second (20) housing parts are secured together by ultrasonic welding around a substantial part of the peripheries of said openings to retain at least a part (22) of the actuator (16) between the housing parts. A movable contact (24), a part of which is also retained between the housing parts, is operable by axial movement of the actuator to make electrical contact with fixed contacts (26). In further embodiments: the actuator rotates with the shaft and the contacts are closed by means of an axial cam. <IMAGE>

Description

SPECIFICATION Electrical switches The present invention relates to electrical switches which are primarily, but not exclusively, suitable for use in association with a spindle or shaft of a gas tap assembly to ignite, or re-ignite, gas supplied by the gas tap assembly to a domestic appliance such as a cooker.

Examples of electrical switches known for this purpose are disclosed in our British Patents 1 469 931 and 1 490 995 to which the reader is instructed to refer for further background information.

An aim of the present invention has been to improve upon the above-noted examples of electrical switches by enabling them to be very much smaller in size and very much easier to assemble.

An electrical switch, according to the present invention, comprises first housing means having an opening extending axially therethrough for receiving a spindle or shaft, actuator means mounted for movement axially and/or rotationally with respect to the opening, second housing means having an opening extending axially therethrough for receiving the actuator means, the first and second housing means being secured together by ultrasonic welding around a substantial part of the peripheries of said openings to retain at least a part of the actuator means between the first and second housing means, and movable contact means having at least a part which is also retained between the first and second housing means, and is operable by said axial and/or rotary movement of the actuator means to make electrical contact with fixed contact means.

There is no need for the movable contact means to make contact with the fixed contact means by a snap action.

It will be appreciated that, by ultrasonically welding the first and second housing means together, it is possible to reduce the overall size, to avoid the use of screws, rivets and adhesive which had been awkward to handle, and to assemble by automatic machinery.

Preferably, the movable contact means is a stressed blade contact, which may include a pair of outer bridging contacts separated by a central flex ible part for abutment with the actuator means.

The arrangement may be such that, with operation of the actuator means, the outer contacts remain stationary while the central part is deflected by the actuator means until such time that the outer contacts and the central part all flex together, relatively to a fixed part of the stressed blade contact mounted between the first and second housing means. Preferably, the fixed contact means includes a pair of stationary terminals which lie in the paths of movement of the outer contacts of the stressed blade contact.

The advantage of the preferred features for the movable and fixed contact means is that unwanted bending of the outer contacts of the stressed blade contact may be avoided even if operation of the actuator means continues after said outer contacts have been brought into abutment with the stationary terminals.

In one arrangement, the actuator means is movable axially and has a projection, which extends through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with the central part of the stressed blade contact. In another arrangement, in which the actuator means is also movable axially, the central part of the stressed blade contact extends through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with the actuator means.In both of these arrangements, rather than relying solely on any resilience of the stressed blade contact for return of the actuator means to an initial non-operating position, mechanical return means may be provided and may take the form of a spring such as a helical compression spring.

It is also possible, as indicated hereinbefore, for the actuator means to be movable rotationally, in which case the central part of the stressed blade contact may extend through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with a cam presented by the actuator means.

Preferably, the first housing means is in the form of a base, to which both the movable and fixed contact means are attached, and the second housing means is in the form of a lid. There may be a slot in the movable contact means for sliding engagement with a T-shaped guide on the base. If the movable contact means is the above-noted stressed blade contact, the slot would be formed in the fixed part with respect to which the outer contacts and the central part are all capable of flexing.

There may initially be at least one energy director in the form of a rib on the base or the lid or both for assisting in the ultrasonic welding to the lid.

Preferably, there are a plurality of said ribs of which one extends continuously around a substantial part of the periphery of said opening in the base.

The base may have mounting means for use in attachment of the base to a support. It may be more suitable, in any given application, for the mounting means to be in the form of a detachable member having at least a pair of prongs for use in resisting any undesired turning of the base with respect to the support. The detachable member may be an annular washer having a notch on its inner periphery for co-operation with a spline on the base, with the annular washer being sandwiched between the base and the support, and the prongs lying to either side of a bolt or other part of the support. Alternatively, the mounting means may be in the form of a member integral with the base and having at least a pair of scallops for use in resisting any undesired turning of the base with respect to the support. The scallops may receive a pair of the above-noted bolts or other parts of the support.If a plurality of pairs of the scallops are provided, it may be possible to adjust the orientation at which the base is mounted to the support.

The fixed contact means may be staked into position, but preferably the fixed contact means is of barb-like construction allowing press fitting thereof. Moreover, the fixed contact means may be of flat-blade construction extending centrally of a cavity for receiving an appropriate external conductor, but preferably the fixed contact means permits use with external conductors of the pokehome kind. To comply with British regulations, tool-operable means such as cam means may be provided in association with the preferred pokehome form of the fixed contact means.

Naturally, the support is preferably in the form of a gas tap assembly including a spindle or shaft which extends through the opening in the first housing means and is operatively secured to the actuator means. Operation of the actuator means brings the movable contact means into electrical contact with the fixed contact means to cause operation of a conventional ignition or re-ignition electrical circuit. It may be appropriate, depending on the details of the gas tap assembly, for the actuator means to be retained in its operating position for as long as any gas is being supplied in case re-ignition of that gas supply is required.

Several electrical switches, in accordance with the present invention, will now be described, by way of example only, with reference to the accompanying drawings, in which: Figure 1 is a plan view of a first of the electrical switches omitting the lid; Figure 2 is a section taken along the line ll-ll of Figure 1 including the lid; Figure 3 is a section taken along the line Ill-Ill of Figure 1 including the lid; Figures 4, 5 and 6 are, respectively, underneath, end and side views of the lid; Figure 7 is an end view of the base, taken in the direction of the arrow VII of Figure 2, and half-sec tioned on the line Ill-Ill of Figure 1 before being staked to a fixed contact; Figure 8 is an underneath view of the base, showing only the scalloped portion of the base;; Figure 9 is a view of the stressed blade contact from the left hand end of Figure 2; Figure 10 is a view of the stressed blade contact from the right hand end of Figure 2 omitting the outer contacts; Figures 11 and 12 are, respectively, plan and section views of a second of the electrical switches, corresponding to Figures 1 and 2; Figure 13 is a sectional view of the actuator means illustrating the cam; Figures 14 and 15 are, respectively, plan and section views of a third of the electrical switches, corresponding to Figures 1 and 2; Figures 76 and 17 are, respectively, underneath and end views of the detachable member; Figure 18 is a plan view of a variation applicable to any of the switches of Figures 1 to 17; Figures 19 and 20 are, respectively, side and plan views of the stationary contact of Figure 18;; Figures 21 and 22 are, respectively, fragmentary plan and sectional views, the latter view being taken on the broken line XXII-XXII of Figure 21, of a further variation applicable to any of the switches of Figures 1 to 17, or the variation thereof of Figures 18 to 20; and Figure 23 is a perspective view of the stationary contact of Figures 21 and 22.

A first electrical switch 10, in accordance with the present invention, is shown in the accompanying Figures 1 to 10. The switch 10 includes a first housing means in the form of a base 12, integrally moulded of plastics material to present an opening 14 extending axially therethrough for receiving a spindle or shaft (not shown) of a gas tap assembly.

Actuator means 16, also integrally moulded of plastics material, is mounted for movement axially with respect to the opening 14, and the actuator means 16 is received in an appropriate opening 18 extending axially through second housing means.

The second housing means is in the form of a lid 20, again integrally moulded of plastics material and secured to the base 12 by ultrasonic welding.

It is important, from the point of view of resisting ingress of iiquid by for example splashing, that the ultrasonic welding extends around a substantial part of the peripheries of said openings 14 and 18.

It will also be noted that the ultrasonic welding acts to retain at least a part 22 of the actuator means 16 between the base 12 and the lid 20.

Movable contact means 24 is also retained between the base 12 and the lid 20 and is operable by said axial movement of the part 22 of the actuator means 16 to make electrical contact with fixed contact means 26.

With particular reference to Figures 2, 7 and 8, the base 12 is shown provided on its underneath with integral mounting means formed as a member 28 having eight scallops 30. When the base 12 is mounted on the gas tap assembly, two upstanding bolts of the gas tap assembly may be received by an opposed pair of the scallops 30. An internal cylindrical wall 32 on the base 12 not only defines the opening 14 but also locates a helical compression spring 34 which urges the actuator means 16 towards its non-operating position as illustrated. A pair of studs 36 on the base 12 may be used to stake into position, in conventional manner, a pair of apertured brass stationary contacts 38 forming the fixed contact means 26. A T-shaped guide 40 on the base 12 may be slidingly engaged by the movable contact means 24 in the manner to be discussed below. A total of four ribs 42, each hav ing a pointed apex to permit use as an energy di rector during the ultrasonic welding, are formed on outer walls 44 of the base 12. These include a short end wall 44 by the T-shaped guide 40, two side walls 44 running parallel to the fixed contacts 38 and a curved end wall 44, which is integral with the two side walls 44, has portions extending transversely of the base 12 towards the part 22 of the actuator means 16 and is concentric with the cylindrical wall 32. The ribs 42 are fused during as sembly with the lid 20. A pair of locating holes 46 receives a complementary pair of studs 46' on the lid 20.

With particular reference to Figures 4, 5 and 6, it will be seen that, in addition to the studs 46', the lid 20 is provided with a pair of L-shaped walls 48.

Transversely-extending parts of the walls 48 are located, in assembly, opposite a similar pair of transversely-extending walls 48' on the base 12 to provide slits therebetween. The brass contacts 38 extend through the slits into the middle of respective generally rectangular cavities, each being defined between a bottom wall 50 of the base 12, the lid 20, one of the side walls 44 of the base 12 and an adjacent longitudinally-extending inner wall 52 of the base 12. A locating stud 54 on the lid 20 further helps to retain the movable contact means 24 in engagement with the T-shaped guide 40 on the base 12. A somewhat longer stud 56 on the lid 20 helps to maintain the movable contact means 24 in a prestressed condition in which there is a known gap between the movable contact means 24 and the adjacent brass contacts 38.

With particular reference to Figures 1, 2, 9 and 10, the movable contact means 24 is shown as an integrally formed, metallic, stressed blade contact 58 including a pair of outer bridging contacts 60 separated by a central flexible part 62. The outer contacts 60 and the central part 62 are formed at the free end of limb 64 which extends to an angle to another limb 66 forming a fixed mounting part of the stressed blade contact 58. A slot 68 in the limb 66 allows the stressed blade contact 58 to be slid into engagement with the T-shaped groove 40 on the base 12. The free ends of the outer contacts 60 may be shaped to have a curved appearance.

The central part 62 of the stressed blade contact 58 extends out of the plane of the outer contacts 60 and towards the part 22 of the actuator means 16.

The part 22 of the actuator means 16 projects through a gap in the ultrasonic welding around a substantial part of the peripheries of the openings 14 and 18 in the base 12 and the lid 20. A spindle or shaft (not shown) may be operatively secured to an aperture 70 in the actuator means 16.

In operation, as the actuator means is moved axially downwardly, as shown in Figure 2, the part 22 presses against the central part 62 of the stressed blade contact 58 and causes said central part 62 to deflect while the outer contacts 60 remain stationary. Eventually the limb 64 including the outer contacts 60 and the central part 62 is caused to flex relatively to the limb 66 which remains fixed to the base 12. The outer contacts 60 are thus brought into contact with the adjacent brass contacts 38 constituting the fixed contact means 26. When the actuator means 16 is released, the helical compression spring 34 returns the actuator means 16 to its initial non-operating position.

A second electrical switch 10a is shown in Figures 11 to 13. The components of the second switch which correspond to components of the first switch will be given the same reference numerals with the addition of the suffix "a". It is therefore merely necessary to say that the actuator means 16a is movable rotationally relatively to the opening 14a in the base 12a. The central part 62a of the stressed blade contact 58a extends through the above-noted gap in the ultrasonic welding around a substantial part of the opening 14a. This permits the free end of the central part 62a to lie beneath a cam 72 formed on the bottom face, as shown in Figure 12, of the part 22a sandwiched between the base 12a and the lid 20a.

A third electrical switch 10b is shown in Figures 14 to 17. The components of the third switch which corresponds to components of the first switch will be given the same reference numerals with the addition of the suffix "b". It is therefore merely necessary to say that, apart from some dimensional differences, the main difference from the switch is that the third switch has different mounting means.

In particular, instead of an integral member 28 with scallops 30, there is a detachable member 74 including a pair of prongs 76 which lie to either side of an upstanding bolt on the gas tap assembly.

The prongs 76 thus resist undesired turning of the base 12b with respect to the gas tap assembly. The detachable member 74 may take the form of an annular washer whose inner periphery has a notch 78 for co-operation with a spline 80 on the base 12b.

A variation which is applicable to any of the above-described switches is shown in Figures 18 to 20. The variation is concerned with the manner in which the stationary contacts are to be secured to the base. A disadvantage of staking the stationary contacts into position, by spreading or upsetting the free ends of a pair of studs formed on the base and passed through complementary apertures in the stationary contacts, is that it reduces the areas of the stationary contacts available for electrical contact with the free ends of the outer contacts on the movable stressed blade contact. The variation overcomes this disadvantage by omitting the studs on the base and the complementary apertures in the stationary contacts, and instead provides barbs on the stationary contacts for engagement in complementary grooves in the base.

Components of this variation which correspond to components of the first switch will be given the same reference numerals with the addition of the suffix "c".

Each of two brass stationary contacts 82 includes, as in the above-described switches, an elongate flat blade 84 extending substantially perpendicularly to an upstanding flange 86, which itself extends substantially perpendicularly to a flat contact area 88. In this variation, however, there is no hole in the flat contact area 88, and an inclined barb 90 is provided opposite the upstanding flange 86. The transversely-extending portions of the curved end wall 44c of the base 1 2c are formed with a respective pair of grooves 92 into which the barbs 90 are to be pressed. When the upstanding flange 86 of the stationary contact 82 abuts the transversely-extending wall 48'c of the base 12c, and the flat contact area 88 of the stationary contact 82 abuts the bottom wall 50c of the base 12c, the barb 90 is resiliently deflected within the groove 92 into a more upright attitude and thus acts to resist disengagement of the stationary contact 82 from the base 12c.

A further variation which is applicable to any of the above-described switches is shown in Figures 21 to 23. The further variation is concerned with the manner in which the stationary contacts are to be secured to the external conductors. In some countries it is permissible for the external conductors to be of the so-called poke-home kind, where a bared end of a solid or stranded wire conductor is merely pushed past a resiliently deflectable barbed contact to make an acceptabie electrical connection, but in Britain it is necessary to use a tool for positively fixing and releasing the electrical connection. The aim of the further variation is to provide stationary contacts for use with external conductors of the poke-home kind, with the optional capability of those stationary contacts being tool-operable.

Components of this further variation which correspond to components of the first switch, and the above-noted variation thereof, will be given the same reference numerals with the addition of the suffix "d".

A brass stationary contact 94, for use with one or two external conductors 96 having bared ends 98, inciudes a flat contact area 88d provided with an inclined barb 90d for resiliently deflected engagement within a complementary groove 92d formed in the transversely-extending portion of the curved end wall 44d of the base 12d. That edge of the flat contact area 88d running alongside a side wall 44d of the base 12d is provided with an upstanding flange 100 extending substantially perpendicuiarly to the flat contact area 88d. A notch 102 is formed in the flange 100 to aliow location over the adjacent transversely-extending wall 48'd, which may itself be formed with a notch 102' for receiving the flange 100 and thereby assisting in accurate location of the stationary contact 94 with respect to the base 12d.Two resiliently deflectable barbs 104 extend from the flange 100 and initially occupy the free position shown in dashed line in Figure 21. In that position, the bared end or ends 98 of the or two of the conductors 96 can be freely pushed into the switch through complementary holes formed in the side wall 44d. Indented end surfaces 106 of the barbs 104 are movable into electrical connection with the bared end or ends 98, namely the locked position shown in full line in Figure 21, by turning an eccentric cam 108 formed between a pair of cylindrical end studs 110. The end studs 110 are freely rotatably received in complementary holes formed in the base 12d and the lid (not shown). At least one of the end studs 110 is formed with a groove 112 into which a conventionally bladed screwdriver can be inserted to effect the turning of the cam 108.

If thought necessary, a stop indicated at 114 may be provided on the base 12d to sandwich the barbs 104 between the cam 108 and the stop 114, and thereby reduce any undesirable flexing of the barbs 104 when in their locked position. One or more stops, such as blisters or other small protuberances, may be formed on the cam 108 to limit rotary movement of the cam 108 with respect to the base 12d. There is no need for two barbs 104 if only a single poke-home conductor 96 is required.

If the cam 108 is turned back to its initial position to release the external conductor or conductors 96, the barbs 104 resiliently return to their initial free position shown in dashed line in Figure 21. It will be appreciated that the stationary contact 94 for use by the other side wall 44d of the switch will be a mirror image of that illustrated.

In some countries, it may be possible to omit the eccentric cam 108 in which case the barbs 104 would be designed to extend initially in the position shown in dot-and-dash line in Figure 21, whereby insertion of a bared end 98 of an external conductor 96 pushes the associated barb 104 into the above-noted locked position shown in full line in Figure 21.

Claims

1. An electrical switch comprising first housing means having an opening extending axially therethrough for receiving a spindle or shaft, actuator means mounted for movement axially and/or rotationally with respect to the opening, second housing means having an opening extending axially therethrough for receiving the actuator means, the first and second housing means being secured together by ultrasonic welding around a substantial part of the peripheries of said openings to retain at least a part of the actuator means between the first and second housing means, and movable contact means having at least a part which is also retained between the first and second housing means, and is operable by said axial and/or rotary movement of the actuator means to make electrical contact with fixed contact means.

2. An electrical switch according to claim 1, in which the movable contact means is a stressed blade contact including a pair of outer bridging contacts separated by a central flexible part for abutment with the actuator means.

3. An electrical switch according to claim 2, in which the actuator means is movable axially and has a projection, which extends through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with the central part of the stressed blade contact.

4. An electrical switch according to claim 2, in which the actuator means is movable axially, and the central part of the stressed blade contact extends through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with the actuator means.

5. An electrical switch according to claim 3 or claim 4, in which mechanical return means is provided for the actuator means in the form of a helical compression spring.

6. An electrical switch according to claim 2, in which the actuator means is movable rotationally, and the central part of the stressed blade contact extends through a gap in said ultrasonic welding around a substantial part of the peripheries of said openings in the first and second housing means, for abutment with a cam presented by the actuator means.

7. An electrical switch according to any preceding claim, in which the first housing means is in the form of a base, to which both the movable and fixed contact means are attached, and the second housing means is in the form of a lid.

8. An electrical switch according to claim 7, in which there is a slot in the movable contact means for sliding engagement with a T-shaped guide on the base.

9. An electrical switch according to claim 7 or claim 8, in which initially there is at least one energy director in the form of a rib on the base or the lid or both for assisting in the ultrasonic welding.

10. An electrical switch according to any one of claims 7 to 9, in which the base has mounting means for use in attachment of the base to a support.

11. An electrical switch according to claim 10, in which the mounting means is in the form of a detachable member having at least a pair of prongs for use in resisting any undesired turning of the base with respect to the support.

12. An electrical switch according to claim 10, in which the mounting means is in the form of a member integral with the base and having at least a pair of scallops for use in resisting any undesired turning of the base with respect to the support.

13. An electrical switch according to any preceding claim, in which the fixed contact means is of barb-like construction allowing press fitting thereof.

14. An electrical switch according to any one of claims 1 to 13, in which the fixed contact means is of flat-blade construction extending centrally of a a cavity for receiving an appropriate external conductor.

15. An electrical switch according to any one of claims -l to 13, in which the fixed contact means permits use with external conductors of the pokehome kind.

16. An electrical switch according to claim 15, in which tool-operable means are provided in association with the fixed contact means for positively fixing and releasing the poke-home electrical connection.

17. An electrical switch substantially as hereinbefore described with reference to Figures 1 to 10, Figures 11 to 13 or Figures 14 to 17, of the accompanying drawings.

18. An electrical switch according to any preceding claim in combination with a support in the form of a gas tap assembly including a spindle or shaft which extends through the opening in the first housing means and is operatively secured to the actuator means.