US3787653A

US3787653A - Electrical switch assembly

Info

Publication number: US3787653A
Application number: US00201640A
Authority: US
Inventors: R Maher
Original assignee: MOSSMAN D Inc
Current assignee: MOSSMAN D Inc
Priority date: 1971-11-24
Filing date: 1971-11-24
Publication date: 1974-01-22
Anticipated expiration: 1991-01-22

Abstract

An electrical switch assembly having a non-conductive switch body and three spaced conductor strips mounted therein is provided with a rockable contact member positioned adjacent the conductor strips for selectively bridging contact zones thereon. The contact member has first and second contact elements at opposite ends thereof, with first and second conductor strips disposed in the body to be engaged with the first contact element in one position of the contact member and the first and third conductor strips disposed to be engaged with the second contact element in another position of the contact member. In one embodiment, manually operable means is provided for selectively rocking the contact member between its respective positions to selectively engage or disengage the contact elements with their associated conductor strips.

Description

[ 1 Jan. 22, 1974 O United StatesPatent Maher ELECTRICAL SWITCH ASSEMBLY [75] Inventor: .Robert L. Maher, Somers, NY.

[73] Assignee: Donald P. Mossman, Inc., Brewster, N.Y.

[22] Filed: Nov. 24, 1971 [21] Appl. No.: 201,640

[52] US. Cl. 200/153 K, 200/153 LA, 200/164 R, 200/166 81-1 [51] Int. Cl. H01h 115/24 [58] Field of Search200/l53 K, 159 A, 154, 153 LA, 200/67 G, 6 R, 16 D, 166 B11, 68, 166 C, 153 W, 164 R [56] References Cited UNITED STATES PATENTS 3,312,800 4/1967 Mascioli 200/164 R X 2,909,624 10/1959 Colautti I 200/153 K X 1,986,527 1/1935 Rach et al. 200/153 LA X 1,666,338 4/1928 Meuer 200/67 G 3,249,725 5/1966 Hutt et a1. 200/153 LA 2,870,273 1/1959 Merchant 200/153 LA X 3,541,280 11/1970 Farrell 200/67 G 3,113,196 12/1963 Spooner et a1 200/166 C 3,305,650 2/1967 Duffield et a1 200/67 G 3,222,473 12/1965 Delhase 200/153 W UX FOREIGN PATENTS OR APPLICATIONS 489,713 6/1954 ltaly 200/68 Primary ExaminerRobert K. Schaefer Assistant ExaminerRobert A. Vanderhye Attorney, Agent, or FirmCurtis, Morris & Safford [57] ABSTRACT An electrical switch assembly having a non-conductive switch body and three spaced conductor strips mounted therein is provided with a rockable contact member positioned adjacent the conductor strips for selectively bridging contact zones thereon. The contact member has first and second contact elements at opposite ends thereof, with first and second conductor strips disposed in the body to be engaged with the first contact element in one position of the contact member and the first and third conductor strips disposed to be engaged with the second contact element in another position of the contact member. 1n one embodiment, manually operable means is provided for selectively rocking the contact member between its respective positions to selectively engage or disengage the contact elements with their associated conductor strips.

7 Claims, 5 Drawing Figures PAIENIEUJANZZW I I 3. 787. 653

INVENTOR. Robzsk'f. MAhER.

ELECTRICAL SWITCH ASSEMBLY This invention relates to electrical switch assemblies and more particularly to miniature electrical switches adapted to electrically interconnect different leads within a switch body of a miniature size.

Electrical switches of the above type have been previously proposed in which a plurality of conductor strips are rigidly mounted in a switch body for cooperation with a set of spring finger contact elements that are slidable with respect to the fixed conductor strips so as to provide multi-circuit switching as the position of the slidable fingers is varied. For example, in US. Pat. No. 3,499,126, issued Mar. 3, 1970. While such switches have been found to be generally satisfactory in use, they do not have a particularly long or extended life span since serious problems are created by the sliding action of the spring finger contact elements with respect to the conductor strips. For example, as the spring finger contact elements slide from the conductor strips to a non-conductive area, forming a break between conductor strips, arcing results between the finger and the adjacent strip. Such arcing causes pitting of the conductor strip at the edge where the sliding finger contact element breaks the connection and also causes pitting in the finger contact itself. After an extended period of use, such pitting causes an earlier break in the circuit than is desirable; this is particularly detrimental in precision type instruments and circuitry where accurate timing of circuit breaks or contacts are required. Moreover, where precious metals are used to form contact zones on the conductor strips, the sliding action of the spring contact finger with respect to the conductor zone wears the precious metal away and deteriorates the conductive capacity of the switch.

Still another problem with such sliding switches exists because of the smearing action of the slidable contact elements on the conductor strips. This smearing action causes migration of the material forming the fixed conductor strip onto adjacent non-conductive portions of the switch which the sliding spring finger contact element must traverse in its path of travel. As a result, the conductor strip is effectively elongated, and thus the circuit between the spring finger and the fixed contact element will remain closed longer than desirable. This is also a detrimental characteristic of such switches particularly in precision instruments since the switch will remain closed for an undesirably long period of time and may thus be closed when the device in which it is used requires the switch to be opened before the closing of another circuit.

Accordingly, it is an object of the present invention to provide'a multi-circuit switching assembly in which the detrimental qualities of sliding type switches are avoided. I

It is another object of the present invention to provide positive contact between a spring contact element and a fixed conductor strip with an integral non-sliding spring conductor element.

Yet another object of the present invention is to provide an electrical switching assembly which is relatively simple and inexpensive in construction.

In accordance with an aspect of the present invention, a miniature electrical switch assembly is provided wherein three spaced conductor strips are securely mounted in a non-conductive switch body. A generally arcuate U-shaped spring contact member is rockably mounted in the switch body adjacent the conductor strips for rocking movement between first and second positions. The arcuate contact member has first and second contact elements at the free ends thereof which are adapted to be selectively engaged with the conductor strips. The first and second conductor strips, in the preferred embodiment of the invention, are disposed in the switch body to be engaged by the first contact element in the first position of the contact member. In addition, the first and third conductor strips are disposed to be engaged with the second contact element in the second position of the contact member. A fiat nonconductive plate is positioned between the free ends of the contact member and is slidably mounted in the body for movement between first and second positions corresponding to the first and second positions of the contact member. In the first position of the plate, one side thereof engages an associated arm of the contact member to rock the member about its base or apex thereby moving its second contact element away from the first and third conductor strips and moving the first contact element into engagement with the first and second strips. ln the second position of the plate, the opposed side edge thereof engages its associated arm to rock the contact member in an opposite direction about its base or apex, thereby moving the first contact member away from the first and second strips and moving the second contact element into engagement with the first and third conductor strips, thus changing the circuit path formed by the switch.

Other objects and attainments of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings in which there are shown and described an illustrative embodiment of the invention. It is to be understood, however, that these embodiments are not intended to be exhaustive or limiting of the invention but are given for purposes of illustration in order thatothers skilled in the art may fully understand the invention and the principles thereof and the manner of applying it in practical use so that they may modify it in various forms, each as may be best suited to the conditions of a particular use.

FIG. 1 is anexploded perspective view of a preferred embodiment of a miniature electrical switch assembly, constructed in accordance with the present invention, with the top removed, a portion of the assembly broken away, and parts thereof shown in dotted lines for clarity in understanding the invention;

FIGS. 2-4 are schematic illustrations of the assembly, showing the rocking movement of the contact member under the influence of the fiat actuating plate; and

FIG. 5 is a plan view of the upper portion of the switch body with the fixed conductor strips therein shown mounted in dotted lines.

Referring to the drawings in detail, and initially to FIG. 1 thereof, it will be seen that a miniature electrical switch assembly 10, embodying the present invention, as shown therein, has a generally rectangular body 12 formed of a non-conductive material. Body 12 includes a relatively small base portion 14 and a complementary upper portion 16 (FIGS. 2 and 5) in which three

strips

18, 20 and 22, formed of conductive material, are mounted. These strips are cut from a blank and placed in the top portion I6 of body 12 with the ends thereof connected by an integral bar 24. This bar provides for convenience in assembly and handling of the relatively small conductor strips utilized in the switch 10. After assembly, bar 24 is cut along dotted line 26 to expose the free ends of the conductor strips and permit them to be soldered or otherwise connected to the electrical wiring of the circuits in which the switch is to be used.

As seen in FIG. 5, which illustrates the inner surface 28 of top 16,

strips

18,20, and 22 each have a different configuration, with the strips 18 and having electri-- cal contact zones 30 located adjacent each other and with

strips

18 and 22 having electrical contact zones 32 located adjacent each other.

By the switching assembly 10 of the present invention, the

contact zones

30 and 32 are selectively bridged, i.e'., electrically interconnected, by a contact member 34, formed of a resilient conductive material, in order to selectively connect either

strip

20 or 22 to strip 18, in accordance with the circuit requirements of the device in which the switch is utilized. The

strips

18, 20, and 22 are maintained in a fixed spaced relation within top portion 16 by a plurality of bosses or

spacers

35, 36 and 37 formed on the inner surface 28 of top portion 16, in a predetermined configuration correspondingto that of the strips. Contact member 34 is a generally U-shaped or arcuate member (the terms U- shaped and arcuate are used herein interchangeably in describing the configuration of member 34) and has a rounded or arcuate support portion 38 seated on the base 40 of body 12. The configuration of member 34 is illustrated in FIGS. 1-4 and it is noted that in FIG. 1 top 16 has been removed to facilite illustration of the invention.

Extending outwardly and upwardly from support portion 38 are a pair of

resilient arms

42, 44 having reversely curved

arcuate contact surfaces

46 and 48 respectively formed at the free ends thereof. These contact surfaces are positioned to be selectively engaged with the

contact zones

32 and 30 respectively, so

as to selectively bridge the space between the zones and provide an electrical connection therebetween.

Support portion 38 is located at the base or apex of member 34 and is generally elongated in a direction transverse to the

arms

42, 44. The lower surface of support 38 provides the bearing surface upon which rocking motion of the contact member 34 takes place. A plurality of blocks 50 engage the side edges of sup port portion 38 to prevent the support from sliding 1ongitudinally in switch body 12 during rocking movement of member 34. Similarly, side wall 52 and the intermediate wall 54 of body 12 prevent movement of the contact member 34 in a transverse direction.

Rocking motion of contact member 34 is accomplished by means of a flat plate 56, a portion of which is shown in dotted lines in FIG. 1 for clarity, which plate is positioned between

arms

42, 44 in the manner illustrated in FIG. 2. Plate 56 is mounted for sliding movement in body 12, as indicated by the arrows A in FIG. I and has opposed edges 62 and 64 respectively positioned

adjacent arms

42, 44. The plate may. be manually operated as by a push button 58 connected to the plate by shaft 60, or alternatively, it may be provided with a contact actuator button or the like for use in automatic equipment. It is noted that plate 56 has cut-out portions 66 formed therein to accommodate the edges of the wall 54 through which it extends.

In the illustrative embodiment, plate 56 is slidably movable between two positions, the extremes of which a i are illustrated in FIGS. 3 and 4, by means of manual push button 58, with stem 60 extending through one of the walls in housing 12. In one position thereof, illustrated in FIG. 3, the edge 64 is engaged with arm 44 of contact member 34 and causes the contact member to rock upon base 38 so that its contact element 48 is moved away from the contact zones 32 of

strips

18 and 22, while its contact element 46 is moved in a clockwise direction upwardly into engagement with contact zones 30 of

strips

18 and 20. In the other position of the plate 56 (FIG. 4), its edge 62 is engaged with the arm 42 of contact member 34 so that the contact member is rotated in a counterclockwise direction to move its contact element 46 away from contact zones 30 and raise the contact element 48 upwardly into engagement with the contact zones 32 formed on

strips

18 and 22.

In one embodiment of the present invention (FIGS. I and 3), a compression spring 70 may be placed between the wall 72 of housing 12 and the end 74 of plate 56, so as to bias the plate into the position illustrated in FIG. 3. Thus, this switch will maintain the circuit between contact zone 30 closed in the switchs normal operating configuration and the circuit would onlybe opened by depressing the push button 58 to engage edge 62 of the plate against arm 42 of contact member 34.

In the illustrative embodiment of the invention plate 56 is supported for sliding movement between its respective surfaces by the blocks 50 in base 14. The lower surface of plate 56 rests on the upper surfaces 82 of the blocks and both plate 56 and blocks 50 are formed of a plastic material having natural lubricity so that substantially friction free sliding can take place therebetween. The upper surface 84 of plate 56 is provided with a raised runner portion 86 which slides on the flat portion 88 of top portion 16 during operation of the switch. Member 86 spaces surface 84 from

spring fingers

18, 20 and 22 so that metal to plastic contact is avoided. In addition, boss 36 includes a raised portion 90 i.e., a runner, in the form of a thin strip of plastic, to assist in spacing plate 56 from the contact strips (See FIG. 2) and to provide a minimum sized bearing surface for guiding the plate during sliding movement thereof.

As shown in FIG. 2, the contact element 34, in the illustrative embodiment, is dimensioned such that at the intermediate position of plate 56, that is when the plate is centered between the

arms

42, 44,

contact elements

46 and 48 are out of engagement with the arms. If plate 56 were not present, the

contact elements

46 and 48 would simultaneously engage the

zones

30 and 32. Thus, the plate 56 is dimensioned to contact both legs at this intermediate position to hold them out of contact with the contact zones and therefore the contact elements will be separately engaged with the contact zones only upon rocking movement of the contact member 36. As a result, one contact is broken before the next can be made.

Alternatively, plate 56 may be formed of smaller dimensions such that in its intermediate position the contact elements will simultaneously engage the

contact zones

30 and 32. Thus, for example, the engagement of contact 46 with zones 30 will not be broken until the edge 62 of plate 56 is moved into engagement with arm 42 (as in FIG. 4) to positively rock member 34. As a result, the desired contact is made before the former is broken, with plate 56 merely acting to hold unwanted contact open. This arrangement is utilized in circuits where a make in the circuit is desired before a break.

It is noted that the

contact zones

30 and 32 may be inlaid or plated with precious metals so as to improve the contact between

contact elements

46 and 48 and the contact zones. Moreover, because the contact member 34 is formed of a resilient spring metal material, the

contact elements

46, 48 will slide slightly on the contact zones when engaged therewith in order to wipe the contact zones and thereby provide and insure a good electrical contact therebetween. By the construction of the invention it is seen that this wiping action occurs without the undesirable sliding movement of previously proposed switch assemblies.

Accordingly, it is seen that a relatively simple and inexpensively constructed electrical switch assembly is provided for selectively interconnecting different leads in an electrical circuit. The rocking motion of the contact element 36 avoids the problems inherent in conventional slide type electrical switches.

What is claimed is: 1

1. An electrical switch assembly comprising a nonconductive switch body; first, second, and third spaced conductor strips mounted in said body; a contact member rockably mounted in said body adjacent said conductor strips for movement between first and second positions therein; said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first and second conductor strips being disposed in said body to be engaged with said first contact element in the first position of said contact member and disengaged in the second position and said first and third conductor strips being disposed in said body to be engaged with said second contact element in the second position of said contact member and disengaged in the first position; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said rocking means comprising a generally flat non-conductive plate positioned between the arms of said U-shaped contact member and having first and second opposed side edges each of which is located adjacent a respective one of said contact elements, said plate being slidably mounted in said body for sliding movement between first and second positions corresponding to the first and second positions of said contact member whereby in the first position of said plate, said first side edge engages its associated arm to rock said U-shaped contact member about its apex thereby moving said second contact element away from said first and third strips and moving said first contact element into engagement with said first'and second strips, and in the second position of said plate said second side edge engaging its associated arm to rock said U-shaped contact member in an opposite direction thereby moving said first contact member away from said first and second strips and moving said second contact element into engagement with said first and third strips; spring means biasing said flat plate into one of its first and second positions; said arms of said U-shaped conductor member being slightly concave and said edges of said plate being shaped to be generally complementary thereto, and the contact elements being slightly convex.

2. The electrical switch assembly as defined in claim 1 including means providing lateral support for said support portion to prevent sliding movement thereof on said base.

3. The electrical switch assembly as defined in claim 9 including a plurality of spacer members in said body for maintaining said conductor strips substantially in a given plane and in predetermined spaced locations.

4. The electrical switch assembly as defined in claim 7 wherein said means for selectively rocking said contact member includes a an externally engagable stem secured to said plate extending beyond said body.

5. An electrical switch assembly comprising a nonconductive switch body; first, second, and third spaced conductor strips mounted in said body; a contact member rockably mounted in said body adjacent said conductor strip for movement between first and second positions therein; said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first and second conductor strips being disposed in said body to be engaged with said first contact element in the first position of said contact member and disengaged in the second position and said first and third conductor strips being disposed in said body to be engaged with said second contact element in the second position of said contact member and disengaged in the first position; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said rocking means comprising a generally flat non-conductive plate positioned between the arms of said U-shaped contact member and having first and second opposed side edges each of which is located adjacent a respective one of said contact elements, said plate being slidably mounted in said body for sliding movement between first and second positions corresponding to the first and second positions of said contact member whereby in the first position of said plate, said first side edge engages its associated arm to rock said U-shaped contact member about its apex thereby moving said second contact element away from said first and third strips and moving said first contact element into engagement with said first and second strips, and in the second positions of said plate said second side edge engaging its associated arm to rock said U-shaped contact member in an opposite direction thereby moving said first contact member away from said first and second strips and moving said second contact element into engagement with said first and third strips; and said contact member being made of resilient conductor material and dimensioned such that said contact elements engage their associated conductor strips when said plate is at a position between its first and second positions whereby each of said contact elements engages its associated conductor strips before the other of the elements is member mounted in said body adjacent said conductors for movement between first and second positions therein, said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first group of spaced contact zones being positioned for engagement only by said first contact element in the first position of said contact member and said second group of spaced contact zones being positioned for engagement only by said second contact element in the second position of said contact member; said contact elements being dimensioned to bridge the spaces between the contact zones of a given group; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said contact elements of said contact member being each respectively formed at the free end of each spring arm; said contact member being formed from a thin sheet of conductive spring metal; said rocking means comprising a non-conductive spacer positioned between the arms of said contact member and slidably mounted in said body for movement between first and second positions corresponding to the first and second positions of said contact member to engage the arms of said contact member adjacent their free ends, thereby rocking said contact member between its first and second positions; said containing means comprising a portion of said body engaging the support portion of said contact member so as to permit rocking of said support portion on said body while preventing displacement therealong; said rocking means further comprising a carrier slidably mounted beside said contact member, said spacer being a flat plate mounted on the side of said carrier, a biasing means for positioning said plate between its two operative positions, and an externally actuator shaft; said spacer contacting only said arms; and said carrier sliding on thin runners; and said conductors being stamped from flat conductive metal positioned within said body substantially in a single plane above said contact member and its rocking means.

7. The electrical switch assembly as defined in claim 18 wherein said conductors comprise spaced strips of metallic material having precious metal inlays defining said contact zones.

Patent 3,787,653 Dated January 22, 1974 Robert L. Maher Inventor(s) It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Claim 4, line 13 cancel "a";

Claim 3, line 8, "'9" should be -'-2-;

Claim 4, line 12, "7" should be --3--;

Signed and sealed this 17th day of September 1974.

(SEAL) Attest:

MCCOY M. GIBSON JR. C. MARSHALL DANN Attesting Officer Commissioner of Patents FORM (10459) uscoMM-Dc scam-P69 Q U.$, GQVEBNHENT PRINTING OFFICE! 969 0"66'3,

Claims

1. An electrical switch assembly comprising a non-conductive switch body; first, second, and third spaced conductor strips mounted in said body; a contact member rockably mounted in said body adjacent said conductor strips for movement between first and second positions therein; said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first and second conductor strips being disposed in said body to be engaged with said first contact element in the first position of said contact member and disengaged in the second position and said first and third conductor strips being disposed in said body to be engaged with said second contact element in the second position of said contact member and disengaged in the first position; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said rocking means comprising a generally flat non-conductive plate positioned between the arms of said U-shaped contact member and having first and second opposed side edges each of which is located adjacent a respective one of said contact elements, said plate being slidably mounted in said body for sliding movement between first and second positions corresponding to the first and second positions of said contact member whereby in the first position of said plate, said first side edge engages its associated arm to rock said U-shaped contact member about its apex thereby moving said second contact element away from said first and third strips and moving said first contact element into engagement with said first and second strips, and in the second position of said plate said second side edge engaging its associated arm to rock said Ushaped contact member in an opposite direction thereby moving said first contact member away from said first and second strips and moving said second contact element into engagement with said first and third strips; spring means biasing said flat plate into one of its first and second positions; said arms of said U-shaped conductor member being slightly concave and said edges of said plate being shaped to be generally complementary thereto, and the contact elements being slightly convex.

5. An electrical switch assembly comprising a non-conductive switch body; first, second, and third spaced conductor strips mounTed in said body; a contact member rockably mounted in said body adjacent said conductor strip for movement between first and second positions therein; said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first and second conductor strips being disposed in said body to be engaged with said first contact element in the first position of said contact member and disengaged in the second position and said first and third conductor strips being disposed in said body to be engaged with said second contact element in the second position of said contact member and disengaged in the first position; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said rocking means comprising a generally flat non-conductive plate positioned between the arms of said U-shaped contact member and having first and second opposed side edges each of which is located adjacent a respective one of said contact elements, said plate being slidably mounted in said body for sliding movement between first and second positions corresponding to the first and second positions of said contact member whereby in the first position of said plate, said first side edge engages its associated arm to rock said U-shaped contact member about its apex thereby moving said second contact element away from said first and third strips and moving said first contact element into engagement with said first and second strips, and in the second positions of said plate said second side edge engaging its associated arm to rock said U-shaped contact member in an opposite direction thereby moving said first contact member away from said first and second strips and moving said second contact element into engagement with said first and third strips; and said contact member being made of resilient conductor material and dimensioned such that said contact elements engage their associated conductor strips when said plate is at a position between its first and second positions whereby each of said contact elements engages its associated conductor strips before the other of the elements is moved away from its associated strips by the rocking of said contact member by said plate.

6. An electrical switch assembly comprising a non-conductive switch body; a plurality of spaced conductors mounted in said body defining two groups of at least two dielectrically spaced contact zones; a contact member mounted in said body adjacent said conductors for movement between first and second positions therein, said contact member being of a generally open U-shape with the apex thereof forming a support portion upon which said member rocks and having two spring arms extending up from either side of said apex with each arm forming the respective first and second contact elements; said first group of spaced contact zones being positioned for engagement only by said first contact element in the first position of said contact member and said second group of spaced contact zones being positioned for engagement only by said second contact element in the second position of said contact member; said contact elements being dimensioned to bridge the spaces between the contact zones of a given group; means for containing said contact member in its operative positions; and means for rocking said contact member between said first and second positions; said contact elements of said contact member being each respectively formed at the free end of each spring arm; said contact member being formed from a thin sheet of conductive spring metal; said rocking means comprising a non-conductive spacer positioned between the arms of said contact member and slidably mounted in said body for movement between first and second positions corresponding to the first anD second positions of said contact member to engage the arms of said contact member adjacent their free ends, thereby rocking said contact member between its first and second positions; said containing means comprising a portion of said body engaging the support portion of said contact member so as to permit rocking of said support portion on said body while preventing displacement there-along; said rocking means further comprising a carrier slidably mounted beside said contact member, said spacer being a flat plate mounted on the side of said carrier, a biasing means for positioning said plate between its two operative positions, and an externally actuator shaft; said spacer contacting only said arms; and said carrier sliding on thin runners; and said conductors being stamped from flat conductive metal positioned within said body substantially in a single plane above said contact member and its rocking means.