CA1064995A - Electric switch with pivotally slidable contact - Google Patents

Abstract

TITLE ELECTPIC SWITCH WITH
PIVOTALLY SLIDABLE CONTACT

ABSTRACT OF THE DISCLOSURE

The present invention provides an electric switch having a mechanism comprising an actuator, a contact member capable of being moved along a path by the actuator and two spaced apart electric contacts arranged along said path;
wherein one of said contacts functions, in use, as a fulcrum and wherein said member is so shaped and the switch is con-structed and arranged such that said member is moveable, from a first position in which it is in contact with said contacts, slideably with respect to said contacts and in so doing initially rotates in one direction and thereafter pivots about the fulcrum in a rotation of opposite direction whereby to come out of contact with the other of said contacts;
The above can be applied to a host of switches including those with arcuately, linearly and rotary moveable actuators.

Description

1~ 95 This invention relates to elec~ric switches. It also relates to contact bridging members for electric switches.
SUMMARY OF THE INVENTION
The present invention provides an electric switch having a mechanism comprising an actuator, a contact bridging member capable of being moved along a path by the actuator, and two spaced apart electric contacts arranged along said path, wherein one of said contact functions, in use, as a fulcrum, the actuator being operable to apply force to said member at an area intermediate its ends and on one side thereof, said member having an opposite side which, in use, contacts said contacts, said opposite side being comprised of first and second surface portions which are at an angle to one another diverging from said path, said surface portions, in a first position of said member, contacting respective ones of said contacts and being inclined to a straight line joining suraces of said contacts which are contacted by said member when in said irst position, said area being located to the side of said fulcrum adjacent the other of said contacts whereby to closely nest part of said member with and between said contacts, said force being applied by said actuator in a direction urging said part into such nesting relation, said member being slidably movable by the actuator from said ~irst posit-ion with respect to said contacts with the trailin~ one of saicl surface portions moving with a component of motion in said direction of said force such that said member initially rotates in one directionl said nested part moving to become relatively less nested against said force tending to restore said part to the nested condition, said area approaching said fulcrum and, after said area has passed the fulcrum, p:ivoting about the fulcrum in a rotation of opposite direction whereby to come out of contact with the other of said contacts.

- 2 -. ' lo6~g9s . The switch can comprise a number of such mechanisms which are preferably located side by side ~although they could be located in line or one above the other) and which share a common operator adapted to operate the actuator of each indiv-idual mechanism. Such a switch is able to achieve a numberof relatively complex circuits ~ithout being unduly expensive.
In another aspect this invention provides an electric switch having a mechanism comprising a contact ~ridging member, two spaced apart contacts having surfaces adapted to be con-tacted by said member, said surfaces lying on a surface and.sàid contacts adjacent said surfaces lying on one sjde of said surface, wherein in one position of the mechanism said member extends between said contacts and contacts said surf-aces, wherein said member has portions which, in said one .~ 15 position, are inclined to said surface and away therefrom towards- the other side thereof and each of which portions contacts a respective one of said contacts and wherein an intermediate portion of said member, in said one position lies to said one side of said surface; means biasing said member, at said intermediate portion, to lie~on said one side of said surface, and an actuator adapted to slide said member relative . .to said contacts; and constructed and arranged such that said member is slideable with respect to said contacts by said actuator from said one position and in so sliding to move said intermediate portion towards said surface against said biasing means tending to resist such movement.
The above descrlbed a.rrangement and certain other ~ .
Banana ,, , :

LO~gS, arrangements in accordance with this invention, stabilizes the location of said member.
It is preferred that the length of said member is at least twice that of the spacing of said contacts.
The above described arrangements have advantages other than in stabilizing said member and enables a whole host of special purpose switches to be made.
It is to be noted that said means biasing said member can be adapted to conduct current to or from said member.
Accordingly, in another aspect, this invention provides an electric switch having a mechanism comprising a contact bridging member, three contacts spaced along and defining a path to be traversed by said membe~; the intermed-iate contact comprising a fulcrum extending tran'sverse to said path and with the other two of said contacts defining the path to have two portions making an angle of 180 or less w;th one another; said contact member having a length greater than the spacing apart o~ said other two of said contacts and ~20 having end portions which are inclined away from said path and which can contact two adjacent said contacts, means b~asing said member towards the path at a point ~ntermediate said end port~ons, and an actuator adapted to move said member along sa~d path; and constructed and arranged such that said member is moveable along said path slideably with respect to two adjacent said contacts when in conkact therewith and said point is intermediate said any two adjacent said contacts, Banana - 4 10th November, 1975 6 ~9 9 5 ana constructed and arranged such that in so sliding the means biasing said member acts to cause the trailing end to approach said path and the leading end to move away from said path whereby to be out of contact with the other of said contacts and said member is pivotable about said-fulcrum when said point is intermediate said fulcrum and said other of said contacts whereby to come into con~act with said other of said contacts.
In the above arrangement it will be realized that ~10 said member can be likened to a boat lying in a trough between wave crests (adjacent contacts) rising up at its leading end and lowering at its trailing end in passing over the middle crest (the fulcrum~ and then sliding down into.the next trough (the space between the ~ulcrum and the other contact). This movement of the boat enables very positive making and breaking contact.
Further it is to be particularly noted that this arrangement can be applied to an indefinite number of contacts : which may define an arcuate or circular path with said member within the arc or circle.
A large number of other arrangements are possible when the contacts lie in a plane and instances include appl~cation in rocker switches, push-pull switches, sliding switches and rotary switches;
In a modification, .the leading end of said member, in moving away from the path, contacts a body which will exert a force on the leading end until such t.ime as said point passes the fulcrum. This may assist operation.

Banana 5 10th November, 1975 ' ~6~9g5 ;
- Said member may take various shapes but.it is preferred that it is arcuate or has a flat middle portion with upturned end porti ons.
In another aspect this invention provides and electric switch having a mechanism comprising a contact bridging member four contacts spaced along and defining a path to be traversed - by said member; two of said contacts each comprising a fulcrum extending transverse to said path and intermediate the other two of said contacts and the fulcrums and said other two of ~ 10 said contacts defining said path to have an intermediat'e : portion and two end portions each making an an~le o~ greater than 180 with said intermediate portion; means biasing ,said member towards the path at a point intermediate its,ends, and an actuator adapted to move said member along said path; and constructed and arranged such that said member is moveable along said path slideably with respect to any two adjacent said contacts when in, contact therewith and said, point is inter-mediate said any two adjacent said contacts, and said member is pivotable about a respective one of the fulcrums when in contact therewith and said point'-is intermediate said respective one of the fulcrums and another of said contacts ~adjacent thereto with respect to which said member is out of contact whereby to come into contact with said another of said contacts.
Sa~d member may be flat but it is preferred that said member is shaped to have portions which are inclined away from said path and which inclined portions contact,any Banana - 6 - 10th November, 1975 .

~06~995 two adjacent said contacts when said member is loc^ated therebetween This arrangement results in a more stable location of said fulcrums, than if said member was flat.
In one aspect of this, said member is arcuate and in another aspect said member comprises a flat intermediate portion and flat ends which are inclined to said flat intermediate portion and in these aspects the stabil;ty of location will be dependent on the shape of the arc and in particular the radius thereof if the arc is an arc of a circle or on the angl~s that the flat ends make wtth said flat intermediate port;on.
As an alternative, or preferably addl~ional, means-of stabilizing the location of said member, particularly when in contact with both of sàid fulcrums, a cam and a cam Follower may be provided, one of which is carried by the actuator and the other of which is carried by a casing for the sw~tch. Thls use of a cam and cam follower is appl~cable in other aspects of this invention.
The above defined mechanism has three positions and is particularly useful in a switch intended to have a "centre-off" position.
A particular advantage achievable as a result of.th~s invention is that by chos~ng the shape of said member and the pos~tioning of the contacts which it contacts it will generally be found to be possible to comply with standards set by electric approval authorities concerning minimum spacings of electrical conductors. In this respect, it is well known that many prior art switches tend to arc immediately before , Banana - 7 - IOth November, 1975 mètal parts come into actual contact but with certa;n switches in accordance with this invention there is a component of motion of said member away from a contact at the same time that it is being brought to a position from which it can pivot from being relatively remote from that contact, and this not particularly prone to arcing, to actually contact that contact.
- In certain constructions it has been found possible to achieve a minimum of a 3mm. gap at all times except when said member is actually engaged in pivoting about the, or one of thea 10 ~ fulcrums~
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~ nother advantage, of course, lies in the indexing that said member can give.
Still other advantages result from the large variety of switches that can be made.
Further advantages arise from the fact that said member itself is quite inexpensive and other parts used in switches incorporatlng it are simple and also inexpensive~
Still further, assembly of switches in accordance with this invention has not, in general, be found to be d~ifficult.
Another advantage ;s that although a large variety .of switches can be made, many of them can be de~igned to use parts common to other switches and thus economies are achieved.
Still further, rigorous testing of switches dn accordance wiLh this invention has shown them to compare very favourably with prior art switches in respect to switch life.
and arcing problems.

Banana - 8 - lOth November, 1975 ~ . . . ~

6499~5 '- Various aspects of this invention will now be exemplified with the aid of the accompanying drawings.
BRIEF DESCRIPTION OF THE VIEWS OF THE DRAWINGS
Figure 1 is a schematic. elevational view of one switch mechanism which is useful in certain aspects of this invention, - Figures 2-4 are a schematic elevational view of another switch mechanism.which is useful in certain aspects of this invention .and show the mechanîsm in various stages of operation, Figure 5 is a perspective view of a conta t b~idging member.which is useful in certain aspects of this invention, : - Figure 6 is a sectional view on line 6-6 i~n Figure 5, Figure 7 is a perspective view of an electrical contact wh~ch i.s useful in cer.tain aspects of tKis invention, Figure 8 is a sectional view o~ another contact bridging member which is use~ul in certain aspects of this invention, Figure 9 is a schematic exploded perspective view of another switch mechanism in acco.rdance with this invent~on, : Figure 10 is;a cross-section o~ the mechan;sm shown in Figure 9, Figure 11 is a perspect~ve vlew o~ a specific switch in accordance wlth this invention which embodies the mechanism of F1gure 1.but which is modifiable, to have a mechanism inter alia as shown in Figures 2-4, Flgure 12 is a cross-section through the switch of . .
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: Banana - 9 - 10th November, 1975 ~ / . .
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; 1~6~995 Figure 11, Figure 13 is another cross-section through the switch of Figure 11, . Figure 14 is another cross-section through the switch of Figure 11 and is a view on line 14-14 in Figure 13, Figure 15 is a schematic drawing.exemplifying one manner of use of the switch shown in Figures 11-14, Figure 16.is a perspective view of another specific switch in accordance with this inven~ion which.embodies the mechanism of Figures 2-4, Figure 17 is a cross-sectional view on line 17-17 in Figure 16, Figure 18 is a cross-sectional view on line 18-18 in Figure 17, Figure 19 is a developed cross-sectional view oF
the switch of Figure 16, Figure 20 is a cross-sectional detail of the switch of Figure 16, and . Figure 21 is a-cross-section on line 21-21 in 20: Figure 17.
: . , . . DETAILED DESCRIPTION
The mechan~sm schematically shown in Figure 1 compr~ses ~our contacts (21~ 22, 23 and 24) and of them the upper ends of contacts 22 and 23 lie in a first plane below a second plane in which lie the upper ends of contacts 21 and 24, Banana -10- 10th November, 1975 ~06~995 A contact bridgi,ng member 30 is provided and is bi'assed downwardly in the direction of arrow 31 by means which is not shown and which acts on po;nt 32. Bridging member 30 can also be moved in the direction of arrow 33 (and in the reverse direction) by means which also is not shown. As shown in Figure 1, bridging member 30 bridges contacts 21 and 22.
It is also to be noted that bridging member 30 is curved and that the radius of curvature of the bridging member 30 is less than the radius of a circular arc (indicated by dotted line 36) which intersects the upper ends of contacts 21, 22, 23 and 24. , ,' When bridging member 30 is moved in the direction of arrow 33 it will slide on contacts 21 and 22.and,in so doing the right and left hand ends (in F;gure 1) will rotate res-pectively anti-clockwise and clockwise and respéctively rlse and fall so that although the right hand end is being moved towards contact 23 it also has a component of motion away from contact 23. This motion proceeds until point 32 passes contact 22 whereupon ~the bias in the direction of arrow 31 will cause the bridging member 30 to pivot about contact 22 with contra-rotation o~ the'ends of member 30 to those .rotations described above so that the right hand end comes into contact with contact 23 and the left hand end comes out of contact with contact 21 and so that contacts 22 amd 23 are bridged. Continued movement in the direction of arrow 33 will cause contacts 23 and 24 to be bridged and contact with contact 22 to be broken.

Banana - 11 - 10th November, 1975 .

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- The effect of the blas on point 32 will -be discussed in respect of Figures 2-4.
The mechanis'm s~own in Figure 1 is particularly effective as a centn~off switch when contacts 22 and 23 are active and has a position on each side of centre in which current wil'l flow to contact 21 or 24.
- Other arrangements of the mechanism shown in Figure l that are particularly desirable are those where a number of such mechanisms are arranged side-by-side to be operated by a common operator. An example of this is that the circuit of Figure 18 (to be discussed in detail later) can be a~chieved.
' In the mechanism shown in Figures 2-4 like integers are represented by the same reference numerals as used in respect of Figure 1. It is to be noted that ,Figures 2-4 have been drawn to show s~ages in the operation of t~e mechanism;
the whole mechanism being schematically shown in Figure 4.
It is to be noted also that the upper ends of contacts 21, 22, 23 and 24 all lie in one and the same plane.
The manner,of operation of the mechanism shown 'n Figures 2-4 is similar to that of Figure l but is set out below. ! ~ ~
. From the position shown in Fig~re 2 with bridging member 30 evenly located between contacts 21 and 22 it is moveable to the right in the direction of arrow 33. In so moving, bridging member 30 slides on contacts 21 and 22, rotates as described with respect to Figure l and it is,to Banana -12- IOth November, 1975 ~L06499S
be noted that point 32 moves from initially below $he aforesaid plane and rises to the ~evel of the aforesaid plane against the bias which tends to act against such movement.
The bias also, while point 32 is between contacts 21 and 22, will cause end 35 of the bridging member 30 to approach the aforesaid plane and, in the sliding, end 34 is, as a consequence, caused to rise further above the aforesaid plane until the position shown in Figure 3 ~s reached when end 34 isabove but not in contact wi$h contact 23.
` This being above but not in contact with contact 23 is considered highly desirable as there is little prospect of arcing but switching can be rapidly effected.
Continued movement in the dirqction of arrow 33 will cause point 32 to pass contact 22 whereupon the bias wtll cause end 34 to fall (see Figure 4) to contact contact 23 and end 35 will rise to break contact with contact 21.
Thus, as shown in Figures 2-4, (the mechanism of Figure 1, as mentioned before, operates similarly), the bridging member 30 is akin to a boat rising up on crests and descending into troughs with its leading end rising to locate above each crest be~ore ~alling to contact that crest.
Although the contact bridglng member 30 ls shown curved, the ~mportant features of its shape and its operat~on are that the bias in the direct~on of arrow 31, ~s at an area intermediate the ends and on one side of the contact bridging member 30 . Further the opposite side of the contact bridging member 30 engages the contacts 21 and 22 and, when moved will 334F ~ - 13 -.~,i ' J~l r~

:~Ci 64995 engage other ones of the contacts 21 - 24. Further, said opposite side is comprised of first and second surface portions which are at an angle to one another diverging from a path along which the contact bridging member can be moved and which is approximately along the arc 36. Further, those first and second surface portions will, in a first position (such as shown in Fig. 2), engage respective ones of the contacts (21 and 22 in the case of Fig. 2) and be inclined to a straight line joining surfaces of the contacts which are engaged and said area is nested closely with and between the contacts. The arrangement is such that the contact bridging member is movables from said first position, slidably with respect to the contacts and in so doing the trailing one of said portions moves with a component of motion in the direction of arrow 31 so that the contact bridging member ~nitially rotates in one direction, said area becomes relatively less nested and does so against the bias acting in the direction of the arrow 31, said area approaches a fulcrum (such as the contact 22 such as is shown in Fig. 3) and thereafter, after said area has passed the fulcrum the member 30 pivots ~such as is generally shown in Fig. 4) about the fulcrum whereby it disengages one contact (21 in Fi9. 4) and engages another contact (23 in F19. 4).
As mentioned, Figures 1 and 2-4 are schematic and it will be realized that an enormous number of switches can be made which embody those mechanism and without wishing to be restricted applicant menticns rocker~ sliding and rotary switches all of which can come in various forms.
As further exemplification applicant mentions that ~' 1.. 1. ( ,y,~ ! 334F - 13a -, - ~06~995 ; ' , ' the mechanism of Figure 1 can be applied to simple rocker switches having three or more contacts or to rotary switches having a plurality of contacts (for instance 6, 12, 14, 18 or Z4) which extend radially, which deFine a circular path, and which have axially extending surfaces which are contacted by bridg;ng member 30.
: The mechanismof Figures 2-4 is considered by ~~-~
applicant to be particularly meritorious as sliding switches of any length can `be made and also rotary swi~ches can aiso . be made.
The contact bridging members shown in Figures 5 and 6, and Figure 8 are specific examples of contact briding members which can be used in the mechanism of Figures 1 and 2-4.
The contact briding member 40 shown in Figures S and 6 is curved along its length and has a dunk 37 in one side with a corresponding projection on the other side. Because of that projection the member 4U needs to be used with contacts having a slot 106 therein, such as is shown in Figure 7.
The c~ntact bridging member 50 shown in Figure 8 has 20 ~ a flat intermediate portion and two flat end portions which are upwardly inclined to the intermediate portion., The member 50 also has a dunk 37 but it is Formed in a bossed up portion so that there ~s no projection below the plane oF the lower sur~ace of the intermediate portion~
Another bridging member which is particularly useful for rotary switches is the member 70 which can be seen ~n plan in Figure 18 wherein it is seen to be curved, and in Banana - 14 - 1~th. Wouember, 1975.

~6~995 vertical cross-section in Figure 19, wherein it is` seen to also be arcuate in respect of that view. ..
An example'of a switch mechanism emb,odying the mechanism of Figure 3 is shown schematically in Figures 9 and 10 and once again,like reference numerals denote like integers excepting. tha,t it is to be noted that a further contact Z5 is providedtj bridging member 30 is dish shaped and has a dunk 37 in its centre which serves as a locant for means for'~bia,ss-' . ' r ' ~. ' ing it in the direction of arrow 31, and a linearly extending contact 26 is also provided.
- In the arrangement sh~wn in Figures 9 and 10 the bridging member 30 makes sliding contact at all times with contact 26 and engages contacts 21-25 in like' man'ner as described with respect to Figures 2-4.' Thus, at any one time, , 15 a circuit is established between contact.26 and any two adjac-ent ones of contacts 21-25.
A variant on the switch mechanism shown in Figures 9 and 10 has contacts equivalent to 21-25 which have concave .~ upper surfaces arranged at right angles to the concave surfaces shown in'Figure~9 so that, as well as ~orming circuits between contact 26 and any two adjacqnt ones of contacts 2}-25 in a ~similar manner as described wlth respect to Figures 9 and 10', , it ~s also possible to ~orm c~rcu~ts between contact 26 and any .~ one of contacts 21-25.
The arrangements shown in Figures 9 and 10 and the var~ant t'hereon are particularly suitable for use in rotary switches in that if contact 26 is made into an annulus and .

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Banana - 15 - 10th. November, 1975.

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additional contacts like 2'1-25 are provided and arranged in a circle the switch ~s converted from being linear to rotary.
The..specific switch in accordance with this invention which is shown in Figures 11-14 uses the mechanism of F;gure 1.
As before, like re~erence numerals denote like integer~s.
The switch comprises a body 80 in which an operator ~ 81 is pivotally mounted by means of pivot pins 82. The body carries contacts 21-24 and it is to be noted that contacts 21 and 24 lie at a higher level than contacts 22 and 23. The body also has contacts 85, 86, 87 and 88.which lie behind, respectively, contacts 21, 22, 23 and 24 in Figure io and one of which, 85, is shown in Figure 14, Operator 81 is provided with a pin 89 whi.ch is ' slid.eably recei~ed in a bore 92 and is spring loaded by a - 15 's~pring'94. The pin 89 fo~ows~ a'càm s~rface 97 formed on an inte'rm`edia`te wall in the body 80 and co-op.eràtes with a .~ depression 99 in that. cam surface'to stabilizè the operatar '81 when l.t.-is.. in a centr~ai p'osit;on;` ~ '. . '. ' .hé;bridging membèr used in this instance for ~20 contacts 2'1-24 is the memp~er 40 shown in Figures 5 and 6 and it 'is to be not`ed ~hat it has'the dunk 37 in' ~ts contre.which cccommodates a pin 102 carried in a bore 103 ~in operator 81 and . whlch p1n 102 ~s spring loaded by a spr~ng'104. The bridging member for contacts 21-24 is o~ the same shape and is identi-fied by reference numeral 40a. It, too, has a dunk 37a equi-valent to 37 for a sim~lar reason.
To enable dunks 37 and 37a to pass, contacts 22, 23, ~,, .
Banana - 16 - 10th. November, 1975-'.

` 1~6499~ -6 and 87 are slotted at 106 as is best seen in Fig'ure 7.
The manner of operation of the switch.shown in Figures 11-14;is essentially the same as that.of the . . ' ,' , mechan.ism.shown i`n Figure.1 and lit will not be further~
~ . .. . . .
5,,-' e~plained; excepting, that i-t.is to be note`d~that p;n 102 exerts . the bias in the direction of arrow'32 me~tioned'in Claim 1 and , enables movement in ~he direction of arrow 33 and the opposite dire'ction.
' The.switch shown in Figures 11-14 can be`used in .
: 10 a progressive circuit which hitherto has only been achievable at great expense. Tha.t ci,rcuit is shown in Figure 15 where each of contacts 21-24 and 85-88 is represented by a cir,cle, A" means active or line supply and is connected t~o contacts 21, 24 and 87 and lines under "40" and "40a" indicate circuit con~
~ ditio,ns with an arrow indicating current passing and a dash line indicating no current pass~ng.
: ~ The switch of Figures 11-14 in the circuit shown in Figure 15 acts as a progresslve switch and in a first position ' (the;positio:n shown in'Figure 13) current flows between con~acts 21 to 22 but not between contacts 85 and 86.
In a second (centra,l) pos~tion, current qoes not 'flow between contacts 22 and 23 but does flow between contacts 86 a~nd 87. In a third position ~bridging members 40 and 40a ~n con~act with, respectively,'contacts 23 and 24, and 87 and 88) current flows between contacts 23 and 24, and 87 and 88.
The switch shown in Figures 11-14 can be modified to operate.as does the mechanism of Figures 2-4 if all .

Banana - 17 - 10th. November, 1975.

~6~iL995 contacts lie in the same plane but this is not preferred as operator 81 causes pins 102 to move arcuately.
The switch shown in Figues 11-14 can also be modified by omitting contacts 22 and 23, and 86 and 87 and by inserting a contact in Qroove 100b (and a corresponding~
contact in a corresponding groove with respect to bridging member 4~a). When so modified the switch becomes a two - ~ position switch and ln this instance the pin 89 is best omitted. Grooves 100a and 100c can be used to receive other contacts to thus enable different switchjng operations.
- The switch shown in F-igures 16-21 is an application of the mechanism shown in Figures 2 4 and parts similar to those o~ Figures 2-4 and 11-14 bear like reference numerals.
The switch shown in Figures 16-21 has a body 80~
an operator 81 which comprises a knob 110 and a shaft which passes through a cover 113 and which carries a block 113. The block is also supported by a post arising within the body 80.
The cover 114 for the body 80 has a series of indent-ations 115 arranged in a circle on its inner surface. The block 113 has two bores 116 arranged diametrically opposite one another and the bores locate spriny loaded balls 117 wh~ch serve to locate block 113 in any one of twelve di~ferent angular orientat~ons.
The body 113 has tweive contacts therein which are similar in form to the contacts of the switch shown in F~gures 11-14 (see also F~gure 7) but which are arranged in a c~rcle w~th thelr upper ends 119 exte~ding radially and in a `~f ~anana - 18 - IOth. November, 1975.

~g~
plàne. Only two of those contacts (21 and 22) are specific-ally numbered.
As.a bridging member is used the member ? previously mentioned and a similar member id~ntified by 70a. It is to bè
noted that as we11 as being arcuate when seen in cross-section (see Figure 19) in a slmilar manner to contact 40, bridging members 70 and 70a are also arcuate when seen in plan (see Figure 18).
Block 113 carries pins 102 in holes 103 and the pins 102 are spring loaded by springs 104.
- It is not considered necessary to describe the operation of the switch shown in Figures 12 and 13; the manner of operation being similar to the mechanism shown in.
Figures 2-4 with the exception that br~dging members move in a circular rather than a linear path. However, it ~s also to be noted that ends 34 and 35 o~ bridging members 70 and 70a contact the underside of block 113 and that this is believed to aid the operation in that a strong downward bias is exerted as pins 102 pass each of the contacts.
The switch shown in Figures 12 and 13 is a double pole twelve positions switch. It operates in an excellent manner and is extremely cheap to manufacture.
In some constructions in accordance with Figures 16 21 it is des~rable that p~ns 102 are electr~cally conducting and that current is supplied thereto.
In a particular construction in accordance with F~gures 11-14 all contacts are 1mm. thick , contacts 21 and .
Banana - 19 - 10th.~J~ember, 1975.

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22 and 23 and 24 are s'paced about 6.5 or 5.5mm. apart and contacts 22 and 23 are spaced about 6.5,6.0 or S;5 mm. apart.
(Spaces between adjacent surfaces, not centres.). The upper .
surfaces of contacts 22 and 23 lie in a plane spaced 2.12mm.
from a plane including the upper surfaces of contacts ~21 and 24 and the dis~ance from pin 82 to the upper surface of contact 2Z is 41 mm. The radius of outside curvature of contact bridgin~ member 40 is 0.359 inch ~about 9mm.) and its chord length is about 15mm. and thus the arc subtended is about 80'and has a length of about 20mm.
In-general, for constructions such as is sbown in ' Figures 11-14, it is pre~erred that the radius of curvature o~ the brid~ing member is from 1/5th to 2/3rdsj preferably 1/4th to 1/3rd, radius of movement of the end of the operator.
For constructions in which the contacts iie ~n plane it is preferred that the rad~us of curvature of the bridging member is from equal to or greater than the spacing of the contacts and preferably is no more than 4 times the spacing.-In general, the curvature of the bridging member should be such as to give the indexing required, or if this isnot particularly required, must be at least such as will allow it to pass from contact to contact having regard to the particular disposition of the'contacts; thus for contacts with ends Iying on a c~rcle as in Figures 11-14 the ralius of curvature of the contact bridglng member need to be greater than when they lie all in one plane. Further, consideration should be had to electric approva1 authorities regulations j ' . . . - .
Banana - 20 - 10th. November, 1975.

" - 1C164~95 some of which require a minimum 3mm. gap under certain circumstances; and it is mentioned in this respect that the r- location of end 34 above but not in contact with contact 23 mentioned in respect of Figures 2-4 is easily achievable to the extent of a 3mm. spacin~.
In modifications of the constructions above described the contacts may have enlarged contact surfaces, such as by bending them, to pxovide greater areas for contact.
In the specific constructions described above all of the contact bridging members have the dunk 37 and corresponding projection on the other side of the contact bridging members and use contacts with slots 106 as shown in Figure 7. While effective for many purposes, these slotted contacts do not have the current load carrying capacity of plain ended contacts, tend to promote arcing and seem to re-sult in decreased switch life. If desired, alternatives such as the contact bridging members and terminals shown in co-pending Canadian Patent Application Nos. 240,328 and 240,331 filed on the same date as this application by the same applicant may be used.
Modifications and adaptions may be made to the constructions disclosed herein without departing from the spirit and.scope of this invention which includes every novel feature and combination o~ ~eatures di~closed he.rein.
25The claims form part of the disclosure o~ this specification.

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Claims (13)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. An electric switch having a mechanism comprising an actuator, a contact bridging member capable of being moved along a path by the actuator, and two spaced apart electric contacts arranged along said path, wherein one of said contacts functions, in use, as a fulcrum, the actuator being operable to apply force to said member at an area intermediate its ends and on one side thereof, said member having an opposite side which, in use, contacts said contacts, said opposite side being comprised of first and second surface portions which are at an angle to one another diverging from said path, said surface portions, in a first position of said member, contacting respective ones of said contacts and being inclined to a straight line joining surfaces of said contacts which are contacted by said member when in said first position, said area being located to the side of said fulcrum adjacent the other of said contacts whereby to closely nest part of said member with and between said contacts, said force being applied by said actuator in a direction urging said part into such nesting relation, said member being slidably movable by the actuator from said first position with respect to said contacts with the trailing one of said surface portions moving with a component of motion in said direction of said force such that said member initially rotates in one direction, - 22a -said nested part moving to become relatively less nested against said force tending to restore said part to the nested condition, said area approaching said fulcrum and, after said area has passed the fulcrum, pivoting about the fulcrum in a rotation of opposite direction whereby to come out of contact with the other of said contacts.

2. An electric switch as claimed in claim 1, wherein said opposite side has an arcuate shape.

3. An electric switch as claimed in claim 1, wherein said opposite side has two end portions and a portion intermediate the two end portions and wherein the end portions are inclined to the intermediate portion.

4. An electric switch as claimed in claim 1, wherein said fulcrum is defined by an edge of a strip of metal.

5. An electric switch as claimed in claim 1, wherein the actuator is linearly reciprocable.

6. An electric switch as claimed in claim 1, and including a third electric contact to the side of the fulcrum opposite to the second electric contact and with which third electric contact the leading end of the contact bridging member is brought into contact in consequence of the aforesaid pivoting.

7. An electric switch as claimed in claim 1, wherein the length of said contact bridging member is at least twice that of the spacing of adjacent ones of said contacts.

8. An electric switch as claimed in claim 1, wherein in moving along said path, the leading end of said contact bridging member contacts a body adapted to exert a force thereon until the member pivots about the fulcrum.

9. An electric switch as claimed in claim 1, wherein the surfaces of said contacts which are contacted by said member lie in a plane.

10. An electric switch as claimed in claim 1, wherein said contacts lie on an imaginary convexedly curved surface and said contact bridging member has a curvature greater than that of said surface.

11. An electric switch as claimed in claim 1 wherein the switch is a rotary switch.

12. An electric switch as claimed in claim 1, further including a second mechanism having a second contact bridging member and two second spaced apart electric contacts duplicating the contact bridging member and two spaced apart contacts of the first-mentioned mechanism, said second contact bridging member being actuated by the actuator of the first mechanism.

13. An electric switch as claimed in claim 1 and including a cam and a cam follower, one of which is carried by the actuator and the other of which is carried by a casing of the switch, the cam and cam follower co-operating to stabilise the contact bridging member in a pre-determined position.