US3165598A - Arc-suppressing multiposition electric switch - Google Patents

Description

'Jan. 12,1965 J. L. MGCLURE 3,155,598

ARC-SUPPRESSING MULTIEOSITION ELECTRIC swncn Filed Aug. 14, 1961 2 Sheets-Sheet 1 f g': .L f 23 INVENTOR. JOHN L. MCCLURE Jan. 12, 1965 J. L. MCCLURE 3,165,593

ARC-'SUPPRESSING MULTIPOSITION ELECTRIC SWITCH 2 Sheets-Sheet 2 Filed Aug. 14, 1961 JOHN L. Mc CLURE.

BY W United States Patent 3,165,598 ARC-SUPPRESSHNG MULTKPGSETifiN ELECTREC SWlTCl-ll John L. McClure, Berwyn, IlL, assignor to General Electric Company, a corporation of New York Fiied Aug. 14, 1961, Ser. No. 131,393 4 (Ilaims. (Cl. ass-s This invention relates to electric switch devices, and in particular, to a multiple position switch for selecting any one of a plurality of different electric circuits. Although not in any sense restrictive thereto, a switch embodying the invention is particularly useful in connection with the energization of the heating elements of an electric range. The invention affords a switch which is of low cost, small size, and simple operation.

The conventional electric cooking range has a cooking surface on which are supported a plurality of electric resistance heating elements known in the art as surface cooking units; that is, the cooking units on which are performed cooking operations involving broiling, frying and the like. It is common practice to employ a S-heat switch and cooking units having a pair of resistance heating elements. When the power source comprises a threewire Edison 236-volt system, the cooking unit may be connected into the available power circuit in any one of five heat-output conditions, ranging from maximum heat output wherein the heating elements are in parallel across 236 volts, to a minimum wattage condition in which the two resistance elements are connected in series across 118 volts.

Contemporary ranges utilize either a push-button type switch as exemplified by Andrews US. Patent 2,431,904, granted December 2, 1947 or an adaptation of the rotary switch typified by Illian US. Patent 2,483,831, granted October 4, 1949. Each of these patents is assigned to my present assignee; and in each case huge quantities of switches embodying the respective inventions have been manufactured, sold, and very successfully used.

Broadly peaking, each of these switches utilizes camming devices which engage a movable contact and separate it from an associated fixed contact when it is desired to break the electrical circuit into which the contacts are connected. In some situations a movable contact is disengaged from one fixed contact and moved into engagement with another, as part of the same switching operation. The push-button mechanism is quite complex, requiring at least four apertured or notched plates of insulating material mechanically associated with several push buttons. The operation of the various buttons individually effects longitudinal movement of the plates relativeto each other to bring about the necessary co action of the movable and the fixed contact elements. The rotary switch is of simpler construction, although it requires a rotating cam and push-pins operated thereby to accomplish the necessary switching actions.

A disadvantage of some stature in each of these switch types is that an electric arc can generate as the contacts are separated. This can result in deterioration of the contact elements and a shortening of the effective life of the switch as a complete unit. I Also, the contact elements are not self-cleaning'and maytherefore accumulate dusty or greasy deposits which increase the electrical resistance across the contacts. e

It is an object of the present invention to provide a multi-position electric switch in which the switch actuat- I tion. The cam block is mounted upon a selection lever "ice ing mechanism protects against contact deterioration byutilizing a mechanism which, while eifectuating the contact separation, immediately interposes an insulating wall of tangible thickness between the fixed and the movable contact, thus reducing sparking to a minimum and providing a positive insulation barrier rather than a mere air gap between the separated contacts.

It is another object of the invent-ion to provide a switching mechanism having a single lever by means of which the contact devices may be established in any of several possible electrical circuit relationships.

It is yet another object of the invention to provide a switching mechanism having improved means for illuminating the designations or indices which identify each of the circuit conditions for which the switch is designed.

It is a further object of the invention to provide a switch contact actuating means which effects a mechanical cleaning action in its operation of contacts between open and closed circuit positions.

In a presently preferred embodiment of the invention, a terminal board of insulating material supports two parallel rows of terminal members which project through the board. Certain of the terminal members have contact base portions which extend inwardly of the board parallel to the undersurface thereof; other of the terminal members have spring contact elements or fingers extending into overlapping relation with the contact bases. Some of said spring contact elements may be above, and others below, the adjacent contact bases. The elements are biased to engage with the contact bases. A cam block of insulating material is disposed between the terminal rows and is guided for slideable movement parallel thereto. Said block has a plurality of longitudinally extending wall means which may engage a spring contact finger to separate it from a contact base by interposing itself therebetween, or may release a previously separated contact finger for return to engagement with a contact base. The wall means are preferably of an inherently smooth material such as nylon, and exert a rubbing action on the contact elements, thereby cleaning them at each operahaving an actuating knob extending forwardly of an escutcheon plate provided with transparent markings indicating the several circuit conditions which the switch may establish; and behind the escutcheon plate there is provided a lamp socket extending upwardly from a base fixed to the selection lever. The lamp socket has a lightpassage aperture so arranged that as the lever traverses the plate from one to another of the markings, the marking immediately front of the lamp socket is illuminated wherea'sthe adjacent markings are not. A feature. of interest in the invention resides in the use of the lamp socket itself as a detent or indexing mechanism for control of the movement of the lever from one to another operating position.

Other features and advantages of the invention. will be understood from the following description of a presently preferred embodiment thereof,-read in connection with the accompanying drawings in which: I

FIG. 1 is a front elevational view of a switch embodying the invention;

PEG. 2-is a side elevational view,.enlarged, and insection on lines 2-2 of FIG. 3; v

FIG. 3 is a topplan viewof the assembled switch;

FIG. 4 is a top plan view of the frame and circuit selector lever assembly;

FIG; is a top plan view of the contact-actuating cam block;

FIG. 6 is a front elevational view of the cam block; FIG. 7 is a rear elevational View of the cam block;

FIG. 8 is aview of the cam block and terminal board assembly showing contact positions with the selector lever in off position;

FIG. 9 is a rear elevational view showing the cam block and terminal board with the selector lever in the oil position; and FIGS. 10 through 14 are schematic representations of the five circuit conditions obtainable with the switch in a three-wire Edison power source connected to a twoelement heating unit.

Referring to FIGS. 2 and 4, the five heat switchl constituting a presently preferred embodiment of the invention, comprises a main frame structure 2 providing a base plate 3 having laterally spaced upstanding rear wall portions 4 and 5 separated by a substantially triangular base portion 6. A slot 7 in said base portion 6 slideably accommodates a pin 8 extending therethrough from the rear of the circuit-selector lever 10. Base plate 3 is also provided with an arcuate guide slot 12 which slideably accommodates a pin 13 extending from the lever 10. Immediately in advance of the guide slot 12 an intermediate portion of the baseplate is formed into an up standing transverse wall 14 which is parallel to the walls 4 and 5; said selector lever extends through a slot (not shown) having a length. suflicient to accommodate the movement of the arm throughout the several operating positions of theswitch. The rear wall portions and the wall 14 are formed with the upwardly extending tabs, respectively 4.1, 5.1, 14.1 and 14.2, by means of which a terminal board and associated mechanism are fixed relative to the base plate. The front of the base plate has separately extending leg portions 15, 16 to which the front escutcheon plate 18 (FIG. 1) is fixed by any.

suitable means such as the integral studs .19 and fasteners 20. Plate 18 is fitted with a transparent window 21 having on its rear an opaque screen arranged to provide, in transparent letters, the indicia Hi, 2, 3, Lo

and Wm to designate the five heats possible when the 7 switch is connected across a conventionalv three-wire 236-volt A.-C. Edison power source and supplying power to a two-unit resistance heater common in the surface cooking units of electric cooking ranges. The escutcheon plate itself is provided with the oil marking indicating complete disconnection of thepower leads from the conductors serving the heating elements. The selector lever 10 projects through an elongated slot 18.1 in the plate 18 and terminates in a knob 22. Said knob is advantageously shaped to provide a relatively sharp upper edge 23' which references against the several indicia as the handle traverses the escutcheon plate. In order more clearly to designate the position of the knob, the selector arm is provided with a light source positioned immediately behind the window.

The mounting for the light forms a part of an indexing or detent system which accurately positions the selector lever 10 at various circuit. establishing stations. As best shown in FIGS. 2 and 3, the lever 10 mounts immediately in front of the wall 1 4, an insulated upright cylinder 24 of insulation material having a slot 25 immediately facing the window. grees on each side of the longitudinal axis of the arm 10, whereby the narrow beam oflight permitted by the slot is suflicient to illuminate the index immediately in front of it but not to illuminate the indices onieach side of it.

' The open-topped cylinder zd'accommodates a neon bulb 26; such as a General Electric Company type NESl in end to the respective margins of the wall 14, as clearly appearsin FIG. 3.

The particular relationship of the lever ill to the slots '7 and 12 provide for a rectilinear rather than an arcuate movement of the knob 22, so that said knob is always immediately in front of the escutcheon plate regardless of the swinging movement of the arm ll). Thus, in any adjusted position of the knob, the sharp upper edge 23 thereof is directly in front of the particular window index.

The several electrical circuits which may be established by the switch mechanism result from the transverse shifting of a cam block having insulating camming surfaces and walls which establish the various movable contact elements or fingers in engagement with, or in insulated relationship with, the various fixed contact bases.

The cam block is in operative engagement with the selector lever it and is guided for rectilinear movement parallel to the wall 14, as presently explained. I

FIG. 3 shows the top plan view of a relatively heavy rectangular terminal board 30 which is supported on p the board are, from left to right, 34, 35, 36 and 37. As

is apparent, the respective groups of terminals are an ranged in parallel rows which are in turn parallel to the front wall i l of the'housing. The individual terminals extend through the terminal board and are appropiately staked thereto to prevent vertical or laterial displacement therein.

These contact base portions comprise the fixed contacts of the switch mechanism. For example, terminal 32 has a base portion 32.1 which extends rearwardly in ahorizontal plane; the terminal may be of brass with a silver or other good conducting metal inlay (not shown) which. extends through the contact base. The contact base portions of other of the terminals, presently identified, would e of similar construction. Terminal 33 is of brass, and just below the terminal board 3% it has a laterally extending flexible contact finger 33.1 of switch spring stock, mounting at its free end a contact button which extends toward the insert of the terminal contact base 32.1. Terminal 31 has near its bottom a laterally extending flexible contact finger 31.1 of switch spring stock. At its free end it has a contact button which extends toward the conducting metal insert of the terminal base 32.1. As presently explained, means are provided whereby either 7 or both, or neither, of the button contacts of the contact Said slot may comprehend about 3% de-' fingers may engage with the contact base 32.1.

Of the terminals in the rear row, terminal 36 is similar to terminal 32 in that it has a horizontal contact base 36.1 extending inwardly of the terminal board in parallel relationship to the undersurface thereof. Terminal 35 has a similar inwardly turned base 35.11 (FIG. 9) and it also has a laterally extending contact finger 35.2 provided with a contact button which extends toward the conduct-. ing metal inlay of the terminal base 36.1. The respec-.

tive bases 32.1, 35.1 and 36.1 occupy a common horizontal plane. extending contact finger 34.1 of switchspring stock having a contact button extending toward the conducting metal inlay of terminal base 35.1. Terminal 3'? hasnear its base a laterally extending contact finger 37.1 having. a contact button extending toward the conductingmetal inlay of the terminalbase 36.1; The inherent spring bias of the several contact fingers is such'that unless restrained the contact buttons of'fin'gers 31.1 and 33.1 will respec- I tively engage with the lower and the'upper surfaces of the conducting metal inlay of terminal base 3 2.1; the con tact buttons of fingers 37.1 and 35.2,will respectively en- Certain of the terminals have contact base portions which extend inwardly of the terminal board in parallel relationship to the undersurface thereof.

Terminal 34 has near its base a laterally gage with the upper and lower surfaces of the metal inlay of the terminal base 36.1; and the contact button of contact finger 34.1 will engage with the inlay of terminal base 35.1.

The actuation of the respective contact fingers is controlled by the positioning of various insulating wall members extending from the longitudinal sides of the cam block 40, shown best in FIGS. 5, 6 and 7. Said cam block may be formed of superimposed pieces secured together by rivets or the like, or may be an integral body molded or otherwise devised, from an insulating material such as nylon, which has an inherently smooth or lubricous surface. A stud 41 symmetrically arranged relative to the overall base dimensions of the block 40 is arranged :to ride slideably within a slot 42 in the selector lever 10, whereby there is no conflict between rectilinear movement of the block Miami the swinging movement of the lever. The upper wall portions 43, 44 (FIG. 5) engage with guides such as the studs 45, 46 (FIG. 2) whereby the cam block is accurately guided for rectilinear movement parallel to wall 14 as the selector lever traverses the slot 18.1. Advantageously, there are four such studs appropriately arranged for maximum guidance. In FIG. 6, which pictures the cam face looking toward the wall 14, there are illustrated five horizontally projecting wall portions arranged in upper and lower groups to define therewith a horizontal slot or guideway 48 within which will ride the base portion 32.1 of terminal 32. The

upper group of said walls comprises an elongated wall 50 having a downwardly sloping cam surface 51; a short wall 52 having the upwardly sloping cam portion 53 and the downwardly sloping portion 54; and a short end wall 55 having the upwardly sloping camming wall 56. The three walls are separated by the two openings 57 and 58 through which the contact portion'of contact finger 33.1 will pass to engage the contact base 32.1 of terminal 32 under conditions of operation later described. The lower wall 60 has an upwardly sloping cam face 61; the lower wall 62 has a downwardly sloping cam face 63 and an upwardly sloping face 64. The elongated space 65 accommodates movement of the contact fingers under various circuit selection conditions. The reverse of the cam block 41) (FIG. 7) similarly has groups of upper and lower walls, separated by a longitudinal slot 67 within which ride the contact bases 35.1 and 36.1. For example, a relatively short upper wall-68 has the sloping face 70; a gap 71 separates wall 68 from the longer wall 72 having the cam face 73. The lower wall group comprises-the elongated wall 74 with its'illustrated sloping end faces and a short wall 75 with appropriately sloping ends. The gap 76 between the walls 74 and 75 and the opening 77 to the left of wall 74 accommodate contact finger movement. It will be understood, of course, that the variously identified cam faces or sloping walls are for the purpose of insuring a quick but not abrupt separation of the several contact finger contact buttons and to quickly interpose an insulating wall between the spaced contacts to prevent any possibility of destructive arcing. Quite importantly, the movement of the various wall members along the faces of the contact buttons, and in some degree, at least, along the operating faces of the contact base portions, serves to wipe these contact elements clean of any dust or grease accumulations.

FIGS. 8 and 9 represent the contact relationships when the selector lever 16 has moved block 40 to its off position. In FIG. 8 it is noted that the contact fingers 33.1 and 31.1 areisolated from the contact base 32.1 by the insulating walls 50 and 60 respectively; and according to FIG. 9 the contact base 35.1 is insulated from contact fingers 34.1 and 35.2 by the respectivewalls 74 and 72,

and contact base 36.1 is insulated from the contact fingers 35.2 and'37.1 by the interposedwalls 72 and 75.

FIGS. through 14 illustrate schematically the relationship of the several contact fingers and terminal contact base portions to produce the several circuit conditions within the scope of the illustrated switch embodiment. It will be noted that for simplicity of illustration the contact elements and the several insulating wall members do not occupy precisely the same relationship in the schematic figures as in the illustration of the cam block. Terminal 32 is arranged for connection to line conductor L1; terminal 37 is connected to line conductor L2 and terminal 35 is connected to neutral conductor N. The load is illustrated as comprising resistance elements R1, R2 of a surface heating unit of electric range or the like. In the circuit diagrams, resistance elements energized across 236 volts are shown in heavy line; when across 118 volts are shown in light line; and when deenergized are shown in dotted line. The 118-volt connection to the pilot light 26 has been detailed only in FIG. 10.

FIG. 10 shows the elements R1 and R2 at Hi heat; that is, each is energized in a parallel circuit across L1 and L2. The circuit can be traced from L1 to contact base 32.1 and then by way of the respective contact fingers 31.1 and 33.1, which jointly make contact with contact 32.1, to terminal 33 connected to an end terminal of R 1 and to terminal 31 connected to an end terminal of R2. L2 is connected to terminal 37, whereupon by way of its contact finger 37.1 and contact base 36.1 of terminal 36 to the juncture of R1 and R2. As shown by the broken line, terminal 34 is open relative to R2 by way of the interposition of the insulating wall 74 between the contact of finger 34.1 and the contact base 35.1 of terminal 35. Similarly, the neutral terminal contact finger 35.2 is isolated from contact base 36.1 by interposition of insulating wall 68. The pilot light is energized between the neutral line and terminal 33 by the obvious circuit.

For second heat, represented by FIG. 11, load element R1 is energized across 236 volts whereas element R2 is deenergized. Contact finger 33.1 is insulated from line terminal contact base 32.1 by way of the insulating Wall 52 therebetween. Thus, the right-hand terminal of R2 is disconnected from power. The lefit-hand terminal of R1 is connected to L1 by way of the contact finger 31.1 and the contact base 32.1 of line terminal 32. The junction terminal of R1 and R2 is connected to L2 by way of contact 36.1 and finger 37.1 of line terminal 37. Finger 34.1 of terminal 34 is insulated from the neutral contact base 35.1 by way of the insulating wall 74 and the neutral terminal contact finger 35.2 is insulated from contact 36.1 by the interposition of insulating wall 68.

For third heat represented by FIG. 12 the respective load elements R1 and R2 are in parallel across 118 volts. The respective end terminals of the resistance elements are each connected to line L1 by way of the contact fingers 31.1 and 33.1 which jointly engage the line terminal contact base 32.1. The junction terminal of said resistances is connected to the neutral line by way of the engagement of the neutral terminal contact finger 35.2 and the load terminal contact element 36.1. As is illustrated, the insulating wall 74 isolates the load terminal 34 and its contact finger 34.1 from the neutral terminal contact base 35.1 and isolates the line terminal L2 from the load contact element 36.1.

FIG. 13 illustrates the L0 circuit arrangement whereby the single resistance element R1 is connected across 118 volts. The switching arrangement differs from that of the FIG. 12 only in the sense that insulating wall 50 has been interposed between the contact finger 33.1 and the load terminal contact finger 32.1.

FIG. 14 illustrates the warm circuit arrangement tral terminal contact finger 35.2 from the load terminal contact element 36.11., and the upper insulating wall 72 has interposed itself between the load terminal contact 326.1 and the line terminal contact finger 37.1.

It will thus be apparent from the foregoing description that the illustrated switch embodiment provides for selection among a plurality of possible electric circuits by a simple arm mechanism having a relatively short travel between its maximum heat and its off positions. The compactness of the switch will be understood when it is considered that F168. 1, 3 and 4 are full size represent-ations of an actual range surface unit control switch constructed according to the present invention, and that FIGS. 5, 6 and 7 are full scale drawings of the cam block as.

While there has been described what is at present thought to be a preferred embodiment of the invention,

' it will be understood that it is intended to cover in the appended claims all modifications which fall within the true spirit and scope of the invention.

What is claimed is:

1. A switching device for selecting an electric circuit from among a plurality of possible circuits, comprising. in combination, a terminal board; a plurality of electric terminals spaced about said terminal board and extend- I ing therethrough, certain of said terminals having end portions constituting fixed contact elements occupying a common plane, other of said terminals having means providing spring contacts overlying certain of said fixed contact elements and still others having means providing spring contacts extending beneath certain of said fixed contacts, all of said spring contacts being biased to assome a normally closed circuit relationship with the associated fixed contact elements; a cam block; means for mounting said cam block for longitudinal sliding movement in a plane parallel to said fixed contact elements; Said cam block including a body section and upper and lower insulating wall members extending laterally from said body section and collectively providing a groove into which said fixed contact elements extend, said Wall members being positioned and formed to intrude between said fixed cont-act elements and spring contacts to separatethe same, said wall members, further, being provided at selected locations along their length with apertures through which spring contacts can reach the associated fixe'd contact elements, whereby according to the lateral displacement of said cam block relative to said fixed contact elements various electric circuit conditions may be established; and means for effecting said cam block movement.

2. A switching device for selecting an electric circuit from among a plurality of possible circuits, comprising, in combination, a terminal board; an index plate extending vertically therefrom and having at spaced intervals therealong indicia for identifying the respective circuits; a plurality of electric terminals spaced about said terminal board and extending therethrough, certain of said terminals having'end portions constituting fixed contact elements occupying a common plane, other of said terminals having means providing spring contacts overlying certain of said fixed contact elements, said spring contacts being biased to assume a normally closed circuit relationship' with the associated fixed contact elements; a cam block; means for mounting said cam block for longitudinal sliding movement in a plane parallel to said fixed contact elements; said cam block including a body section and an insulating wall member extending laterally from c said body section to intrude between said fixed contact 7 elements and said spring contacts, said wall member beg ing with said cam block for effecting said lateral displace-- ment, said lever having an indexing element for registr-a tion with the respective indicia on said indexing plate and having a manually operable end portion projecting in front of said plate; and lever mounting means providing for substantially rectilinear movement of said'indexing element in parallel relation to said index plate during arcuate movement of said lever comprising a base plate having a straight slot formed therein perpendicularly to said index plate and a curved slot formed therein between said straight slot and said index plate, said lever having pins extending into said slots so as to be guided thereby, said curved slot being formed so that substantially a constant length of lever end portion projects in front of said,

plate in all positions of said lever.

3. An electrical switching device comprising, in combination, structure providing a base plate, a selector lever pivotally mounted on said base plate for movement in the plane thereof, an insulating terminal board fixed to said structure in spaced parallel relation to the plane of operation of said selector lever, at least one row of electrical terminals mounted on said board in a straight row, 1

each of said terminals being spaced from the other, at least one of said terminals having a portion projecting inwardly of said terminal board in parallel spaced relation thereto, to provde a fixed switch contact and other terminals having flexible contact fingers disposed in overlapping relation to said fixed switch contact on opposite sides thereof, an actuating block of insulating material, said block including a body section and having a plurality of insulating walls projecting laterally from said body section and arranged in upper and lower rows in a plane parallel to said terminal board, said fixed switch contact being disposed between said upper and lower rows and certain of said plurality of walls in each of said upper and lower rows being spaced one from the other a sutlic-ient distance to permit said spring contact fingers to engage with said fixed switch contact, means for mounting said actuating block for movement relative to said line of terminals for selective interposition of said actuating block walls between said contact finger-s and said fixed switch I contact, and means connecting said lever and said actuating block for movement of said block by said lever.

4-. A switching device for selecting an electric, circuit from among a plurality of possible circuits, comprising, incombination, structure providing a base plate, an indcx plate mounted thereon, said index plate having along its length a successioniof light-permeabale indic-ia individually identifying the several possible circuits, a terminal board of insulation material, means for mounting said terminal board in spaced relation to said base plate, terminal members carried by said terminal board and providing fixed contact elements, terminal members carried by said terminal board andproviding movable contact elements for cooperation with said fixed contact elements in establishing any of the plurality of possible circuits, an actuating member movable relative to said fixed and movable contacts to operate said movable contacts into a desired relationship to said fixed contacts, a lever pivotally mounted on said base plateand arranged to traverse said index plate when pivoted, means engaging said actuating member with said lever to effect movement of said member, detent means fixed relative to said index plate, said detent means comprising a spring strip extending longitudinally behind said index plate and having a series of undulations, each one of which represents a position of said actuating member establishing a particular electric circuit condition, means on said lever cooperating with said detent means to lyieldably position said lever in registry with any of said circuit-identifying means comprising lamp means mounted on said lever for movement therewith, said lamp means includingfa cylindrical lamp housing disposed rearwardly of said index plate, said housing having a relatively narrow light passage whereby to illuminate only the circuit-identifying 9 10 indioia with which the lever comes into registry, said lamp 2,672,531 3/54 Stevenson 200-4 housing releasably engaging Within an undul at-ion for the 2,786,103 5/57 Bevins 200-151 X positioning of said lever relative to the circui r-identifying 2,868,930 1/ 59 Pistey 200-153 indieia. 3,117,207 1/64 Baldasare 200-167 FOREIGN PATENTS References Cited by the Examiner 327 933 7 /3 5 Italy UNITED STATES PATENTS 1,964,449 6/34 Carlson 200*167 BERNARD A. GILHEANY, Primary Examiner. 2,081,827 5/37 Lohe 200167 10

Claims (1)

1. A SWITCHING DEVICE FOR SELECTING AN ELECTRIC CIRCUIT FROM AMONG A PLURALITY OF POSSIBLE CIRCUITS, COMPRISING, IN COMBINATION, A TERMINAL BOARD; A PLURALITY OF ELECTRIC TERMINALS SPACED ABOUT SAID TERMINAL BOARD AND EXTENDING THERETHROUGH, CERTAIN OF SAID TERMINAL HAVING END PORTIONS CONSTITUTING FIXED CONTACT ELEMENTS OCCUPYING A COMMON PLANE, OTHER OF SAID TERMINALS HAVING MEANS PROVIDING SPRING CONTACTS OVERLYING CERTAIN OF SAID FIXED CONTACT ELEMENTS AND STILL OTHERS HAVING MEANS PROVIDING SPRING CONTACTS EXTENDING BENEATH CERTAIN OF SAID FIXED CONTACTS, ALL OF SAID SPRING CONTACTS BEING BIASED TO ASSUME A NORMALLY CLOSED CIRCUIT RELATIONSHIP WITH THE ASSOCIATED FIXED CONTACT ELEMENTS; A CAM BLOCK; MEANS FOR MOUNTING SAID CAM BLOCK FOR LONGITUDINAL SLIDING MOVEMENT IN A PLANE PARALLEL TO SAID FIXED CONTACT ELEMENTS; SAID CAM BLOCK INCLUDING A BODY SECTION AND UPPER AND LOWER INSULATING WALL MEMBERS EXTENDING LATERALLY FROM SAID BODY SECTION AND COLLECTIVELY PROVIDING A GROOVE INTO WHICH SAID FIXED CONTACT ELEMENTS EXTEND, SAID WALL MEMBERS BEING POSITIONED AND FORMED TO INTRUDE BETWEEN SAID FIXED CONTACT ELEMENTS AND SPRING CONTACTS TO SEPARATE THE SAME, SAID WALL MEMBERS, FURTHER, BEING PROVIDED AT SELECTED LOCATIONS ALONG THEIR LENGTH WITH APERTURES THROUGH WHICH SPRING CONTACTS CAN REACH THE ASSOCIATED FIXED CONTACT ELEMENTS, WHEREBY ACCORDING TO THE LATERAL DISPLACEMENT OF SAID CAM BLOCK RELATIVE TO SAID FIXED CONTACT ELEMENTS VARIOUS ELECTRIC CIRCUIT CONDITIONS MAY BE ESTABLISHED; AND MEANS FOR EFFECTING SAID CAM BLOCK MOVEMENT.

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