US3104300A

US3104300A - Two circuit door switch

Info

Publication number: US3104300A
Application number: US55053A
Authority: US
Inventors: Hutt Philip
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1960-09-09
Filing date: 1960-09-09
Publication date: 1963-09-17
Anticipated expiration: 1980-09-17
Also published as: DE1172757B; GB990171A; FR1299909A

Description

Sept. 17, 1963 -r 3,104,300

TWO CIRCUIT DOOR SWITCH Filed Sept. 9, 1960 7 A 71, /W/yb Mu 3'27,

w 6 by Maw Attorney United States Patent 3,104,300 TWO CIRCUIT DOGR SWITCH Philip Hntt, Milford, Conn., assignor to General Electric Company, a corporation of New York Filed Sept. 9, 1960, Ser. No. 55,053 6 Claims. (Cl. 200-?) This invention relates to an improved electric switch of the kind which is actuated by a pushbutton, and particularly to a pushbutton switch which is located near a door and is operated by movement of the door between open and closed positions.

Pushbutton door type switches have found widespread and various applications as appliance switches for refrigerators, ovens, dryers, and the like. For example, in refrigerators, ovens, and dryers, a normally closed pushbutton switch is often used to turn on one or more interior lights of the appliance when the door is opened. In many of these appliances, such as a dryer, it is often desirable that more than one circuit be controlled by movement of the door to an open or closed position. For example, in a dryer, a normally open switch has been used to control a circuit which stops the dryer motor, and a separate normally closed switch has often been used to control a circuit which turns on an interior light, with both of these switches being mechanically linked to the dryer door so as to stop the motor and turn on the light .when the dryer is opened. In view of the widespread use of such switches and the various applications which they have been designed to satisfy, it has been found desirable to provide an improved pushbutton switch which is extremely flexible and elficient and readily lends itself to numerous appliance switching requirements. It has also been found to be advantageous that such a switch be relatively small in size so that it occupies a minimum space in the appliance in which it is utilized. In addition, it has been found desirable that such a switch be simple in construction, sturdy, have a long life, and be relatively inexpensive in over-all cost.

Accordingly, it is a primary object of this invention to provide an improved pushbutton switch which is very flexible and is capable of controlling a plurality of circuits.

Another object of this invention is to provide an improved pushbutton switch which is efiicient in operation and simple in construction.

It is a further object of this invention to provide an improved pushbutton operated door switch that is relatively small in size, sturdily constructed, and which comprises a low cost means for controlling two circuits.

'In carrying out one aspect of my invention, in one form thereof, I provide a pushbutton operated switch for controlling two circuits by the reciprocating movement of an actuating plunger. To support and contain the ele ments of this switch, I have provided an insulating housing having a cavity therein. This cavity of the housing includes first and second pairs of angularly spaced channels which are formed in the interior walls thereof. These channels extend longitudinally within the housing, and a fixed contact is positioned in each of them to provide first and second pairs of associated fixed contacts for the switch. The plunger is extended through an aperture in one end of the housing into the cavity. First and second movable bridging contacts are arranged inwardly of the inner end of the plunger and a pair of contact sections of each of these contacts is guided for movement within one of the pairs of channels so as to cooperate with a pair of associated fixed contacts to control a circuit. The first bridging contact is normally closed into engagement with its mating fixed contacts to close a first circuit when the plunger is in its outermost position, and is opened upon depression of the plunger. The second bridging contact is normally open from its mating fixed contacts but is movable into closed position therewith upon the depression of the switch plunger. By guiding the movement of the two movable bridging contacts and also positioning the fixed contacts in the longitudinally extending channels of my switch, and operating these contacts in response to the reciprocating movement of the plunger, 1 have thus provided a simplified and flexible switch mechanism which is relatively small in size, efficient, and low in cost.

'By a further aspect of my invention 1, provide an improved arrangement for fastening the parts of the housing of a pushbutton switch together. This improved arrangement may, of course, be combined with the aforesaid structure to provide a particularly desirable pushbutton switch. In this arrangement, there is provided a U- shaped mounting spring for fastening the switch within an aperture of a supporting panel, and a hollow base and cover plate cooperate to form the switch housing. The spring has a pair of oppositely disposed resilient arms and an intermediate connecting section. A plurality of transversely extending projections are formed in each of the arms of the spring near the intermediate section. These projections engage surfaces of longitudinally extending channels which are formed in the external wall of the base to securely fasten the spring to the base with the connecting section of the spring extending across the outer surface of the cover plate to attach the cover plate to the hollow base and thus form the switch housing. The arms of the spring thus serve not only to fasten the switch to a panel aperture, but also to secure the parts of the housing together.

Further aspects of my invention will become apparent hereinafter, and the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which I regard as my invention. This invention, however, as to organization and method of operation, together .with other objects and advantages thereof, may best be understood by reference to the following description when taken in conjunction with the accompanying drawings in which:

FIG. 1 is an elevational view of an improved pushbutton door switch ernbobodying my invention;

FIG. 2 is a fragmentary view of the switch of FIG. 1, showing part of the mounting spring and the manner in which it engages the housing;

FIG. 3 is an enlarged cross-sectional elevation view taken generally along the line 3-3 of FIG. 6 and showing the normally open bridging contact, and the fixed contacts with which it cooperates;

FIG. 4 is an exploded view of the switch of FIG. 1, showing in detail the individual parts which comprise the preferred embodiment of my invention;

FIG. 5 is an enlarged cross-sectional elevation view taken generally along the line 5-5 of (FIG. 6 and showing the normally closed bridging contact and the fixed contacts with which it cooperates; and

FIG. 6 is a bottom view of the switch of FIG. 1, with the cover plate and mounting spring removed from the base to show the interior structure of the switch.

Referring now to FIG. 1, there is shown a pushbutton operated switch 1 which embodies one form of my invention. This type of switch is relatively small in size and is often referred to as a door switch since it has seen widespread use in appliance applications where it is ac tuated by the movement of a door. The switch 1 includes an insulating base 3 which, for example, is formed of molded phenolic thermosetting plastic, and a flat generally round base plate 5 which is formed from a suitable insulating material and is securely mounted to base 3 by a means which, as will be described in detail hereinafiter, constitutes an important aspect of my invention.

Cover plate 5 and base 3 cooperate to provide a housing for switch 1 and also support the various parts thereof.

To efliciently guide, insulate, and contain the moving parts of switch 1 and furnish a complement for a flexible switch structure having a relatively diminutive over-all size, I have provided base 3. Base 3 comprises top wall 7 having an aperture9 formed in the center thereof, and an annular flange 16 formed on its outer periphery. (See FIG. 4.) From wall 7, body section 11 of the base extends perependicularly downwardly (as shown in FIG. 4) to form cavity or recess (FIG. 3). Body section 11 has a generally cylindrical outer configuration (FIG. 4) and an open bottom end 13 (FIG. 3). Cavity 15, which is formed by section 11, serves to contain and guide the movable contacts and actuating mechanism of (the switch. To enable base 3 to effectively Contain the various switch parts with an optimum space utilization, cavity 15 includes a diametrically opposed pair of longitudinally extending cylindrical surfaces 17 (as shown in FIG. 6) and two pairs of angularly spaced and diametrically opposed longitudinally'extending

channels

18 and 20.

Considering first the functions served by surfaces 17, it will be noted that to actuate the switch 1, as shown in FIG. 3, plunger 21 extends into cavity 15 through base aperture 9. Flange 1? is formed at the inner end of the plunger, and it has a diameter slightly less than the diameter of curvature of surfaces 17 so that these surfaces serve to guide the reciprocating movement of the plunger within the cavity. As shown in FIG. 3, the dimensional relationship between the upright cylindrical walls of the plunger and aperture 9 provides additional guidance for the reciprocating movement of the plunger between its positions. In addition to guiding the reciprocation of plunger 21, the surfaces 17 also serve to guide the lateral movement of coiled compression spring 23. (See FIG. 6.) Spring 23 is disposed with-in cavity 15, as shown in FIG. 3, and it serves to continuously bias the plunger toward its outermost position.

Turning now to channels 18 and 2d of base 3, as shown in FIG. 6, it will be noted that these channels are angularly spaced from each other and from the center of surfaces 17. These channels extend longitudinally between top wall 7 and open bottom end 13 of the base, being formed in the configuration of diametrically opposed

parallel pairs

18 and 20. In the preferred form of my invention, as illustrated in FIG. 6, each of the

channels

18 and 26 is angularly spaced from the center of its nearest cylindrical surface 17 by approximately 60. Adjacent channels 18 and are also angu'larly spaced by approximately 60. become apparent, an improved utilization of space is achieved in my switch, thus permittingthe manufacture of a switch embodying my invention which is relatively small in over-all size.

In each of the channels 18, as illustrated in FIGS.

5 and 6, I have positioned a normally closed fixed con being parallel to section 27 and having a detent aperture 33 for engagement within an associated quick-connecting terminal. The other end of contact 26 is turned angularly away from the surface of central section 27 in the same general direction as step 31 to form normally closed fixed contact section 35. When the fixed contacts 26 are positioned in the channels 18, contact sections 35 extend toward aperture 9 (as shown in FIG. 5) and they are normally in engagement with a movable bridging contact 37. Contact shoulders 38 engage stepped side Walls (not shown) of the channels '18 to accurately position contacts 26 therein. T 0 enable contact 37 to reciprocate with plunger 21, it includes a main strip 39 which extends underneath annular flange 19 of the plunger (as shown in In this manner, as shall hereinafter FIG. 5) and loosely supports the plunger, together with;

a pair of inwardly angled movable contact arms 41 connected to strip 39. When plunger 21 is in its outermost position, spring 23 biases movable bridging contact 37 to its upper position (viewing FIG. 5), where arms 41 of contact 37 are each held in engagement with fixed contact sections 35 to close a circuit connected through ter-' minals 29. When plunger 21 is depressed from its outermost position, the biasing force of spring 23 is overcome and movable contact 37 rnoves downwardly to its dotted position 37a as shown in FIG. 5, to disengage itself from contact members 26. During its reciprocating movement with plunger 21, the sides of contact 37 ride within channels 1S, and are efiiciently guide thereby. (See FIG. 6.) Turning now to the channels 20, as will be seen irom viewing FIGS. 3 and 6, in each of these channels, I have positioned a normally open fixed contact member 43.-

Member 43 comprises a flat longitudinally extending contact section 45 which is tapered at 47 to gradually diminish the thickness of the metal stock, and squared at the upper end 48. contact 43 is stepped at 49 and shortened in width to form tab terminal section 51. Terminal section 51 also lectively cooperate with the normally open fixed contact members 43, and engage these members when the plunger is depressed, underneath the normally closed bridging contact 37, as shown in FIG. 3, I have positioned movable bridging contact 53. (See also FIG. 5.) Contact 53 is best shown in FIG. 4 and it includes central strip 55 with a plurality of upwardly extending positiorn ing bosses 57 formed in the surface thereof to properly position the plunger flange 19 with respect thereto (FIG, 3). Strip 55 extends transversely, and in a crisscross manner with respect to main strip 39 of contact 3-7, being also disposed underneath flange 19 of the plunger. From each end of central strip 55, an inverted generally J- shaped spring section 59 is formed by bending a metal strip upwardly, downwardly and away from, and then in general slightly back toward the center of the'contact 53. Spring section 59 thus includes an upright portion 61 and two oppositely disposed and outwardly extending V-shaped resilient contact portions 63.

With bridging contact 53 positioned under bridging contact 37 in a crisscross manner (as shown in FIG. 6),

the underside of strip 55 is engaged by the upper end 23a of coil spring 23- (as shown in FIG. 3), and the spring runs in compression between contact strip 55 and cover plate 5 to normally bias contact 53 to an open position when plunger 21 is in its outermost position. When plunger 21 is depressed, bridging contact 53 moves downwardly against the force of spring 23 and the resilient contact portions 63 smoothly engage tapers 47 of the normally open fixed contact members 43 and ride along these tapers, moving thereafter downwardly in continuous contact with the inner surfaces of the fiat contact sectio-ns 45 to close a circuit connected between tab terminals 51. During the reciprocating movement of contact member 53, it is guided by cooperation of spring sections '59 with channels 20. (See FIG. 6.)

It will thus be seen that by angularly spacing the diametrically

opposed channels

18 and 20 within switch base 3 and longitudinally extending these channels parallel to the axis of movement of plunger 21, I have thus provided in my switch 1, an improved and very efficient means for positioning two pairs of fixed contacts in a switch housing, and also atthe same time, guiding two movable bridging contacts which cooperate with these fixed contacts to control two circuits.

To cooperate with base 3 of switch 1 and provide a (See FIG. 3.) The other end of each housing for the various switch parts, as shown in FIG. 3, the open bottom end 13 of base 3 is closed by means of the round insulating cover plate 5. Plate ,5 may best be seen in FIG. 4, and it includes a diametrically opposed pair of recesses 65 which have been formed in its outer periphery, and four suitably configured slots 67 which are formed in the surface of the plate and which are angularly spaced apart from each other and from recesses 65 to receive the tab terminals of the switch. The slots 67 are vertically aligned with

channels

18 and 20 when cover plate 5 is secured to the open bottom end 13 of base 3, and the undersides of the

steps

31 and 49 of the normally open and normally closed fixed contacts engage the inner surface 5a of plate 5 radially outwardly of and adjacent to slots 67 (as shown in FIGS. 3 and 5) so that the plate 5 provides a secure support for accurately positioning and maintaining the fixed contact members in their channels within the switch recess.

Turning now to a further aspect of my invention, which provides a new and improved means for fastening the various parts of my switch together within the switch housing, as shown in FIG. 1, it will be noted that switch 1 includes a U-shaped mounting spring 69. Spring 69 includes a pair of oppositely disposed resilient arms 71 having a supporting section 7 3, with an intermediate connecting portion 75 joining these arms together. (See FIG. 4.) The arms 71 of spring 65 extend generally upwardly, as shown in FIG. 1, or forwardly with respect to flange 10, along opposite outer longitudinal sides of body section 11 of base 3. To guide the resilient arms and to serve another important purpose which shall be described hereinafter, a diametrically opposed pair of external channels 76 are extended longitudinally in the outer walls of body section 11. Each of the arms 71 is identical, being twisted and angled so that it has a resilient free end with a rearwardly and outwardly inclined front edge 77 formed upon it. The edges 77 of the spring 69 are inclined diagonally toward the extreme end points 78 of the arms in divergent parallel directions and positioned with respect to body section 11 so that each arm point 78 is disposed inwardly toward the axis of the switch (FIG. 1). With this arm arrangement, the switch may be conveniently and removably positioned in a circular aperture of a suitable supporting panel (not shown). With switch 1 positioned in such a panel aperture, front edges 77 engage the edges of the aperture to resiliently clamp the switch securely in place. Upon rotation and pulling of the flange of base 3 from the mounting aperture, the switch 1 may then be conveniently removed from the panel. The particular construction of the rearwardly and outwardly inclined diagonal front edges of the U-shaped mounting spring 69 and the manner whereby they cooperate with a circular aperture of a supporting panel, comprises the invention of Leon Cutler, and this construction and arrangement are described and claimed in his copending application Serial No. 55,054, which is filed concurrently herewith and assigned to the same assignee as the present invention.

For efficiently attaching cover plate 5 to base 3, and thus thereby achieving a dual purpose for spring 69, on each supporting section 73, by means of one aspect of my invention, 1 have formed oppositely disposed sets of sharp projections or barbs 79. The barbs 79 extend generally parallel to the plane of connecting section 75 from the side edges of section 73. (See FIG. 2.) When the U-shaped mounting spring is positioned on the switch housing, connecting section 75 lies diametrically underneath cover plate 5 and the bottoms of supporting sections 73 extend through the peripheral recesses 65 of the plate into the oppositely disposed exterior channels 76. With the spring positioned in this manner, the barbs press themselves into intimate engagement with the side walls 81 of the channels, as illustrated in FIG. 2, to securely afiix cover plate 5 to base 3. By means of forming the barbs 79 on the supporting sections 73 of the U-shaped mounting spring 69, I have thus provided an efiective and simplified integral means for fastening the housing of switch 1 together.

In viewing FIG. 6, it will be noted that the center lines of exterior channels 76 are generally in radial alignment with the center lines of surfaces 17. This arrangement substantially enhances the space utilization of switch 1 and provides a very compact switch structure.

The simplicity of my improved switch permits the overall dimensions to be relatively small compared to prior art switches which control two circuits. In addition, it will now be apparent to those skilled in the art, that by eliminating the normally open or the normally closed fixed contacts and their associated bridging contacts from the switch 1, a switch providing efficient control of only one circuit by means of the actuation of a normally open or a normally closed bridging contact may be readily obtained. -It will thus be seen by those skilled in the art that by means of my invention, I have provided an efficient switch structure which includes a relatively small 1 number of parts, and is very flexible with regard to its capability of satisfying various circuit requirements.

While in accordance with the patent statutes, I have described what at present is considered to be the preferred embodiment of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and I, therefore, aim in the following claims to cover all such equivalent variations as fall within the true spirit and scope of the invention.

What I claim as new and desire to secure by Letters Patent of the Uni-ted States is:

1. A switch comprising a generally cylindrical insulating housing with a cavity therein, said cavity including first and second pairs of angularly spaced and diametrically oposed longitudinally extending internal channels formed in the inner walls of said cavity, a fixed contact positioned in each of said channels thereby to provide first and second pairs of diametrically opposed fixed contacts, a diametrically opposed pair of external channels extending longitudinally in the outer walls of said housing, said external channels being angularly spaced from said internal channels, said internal and external channels being :generally parallel to the axis of said housin a plunger extending axially through a wall of said housing into said cavity and guided for movement by said cavity, a first movable bridging contact actuated by said plunger and guided rfor movement within the first pair of internal channels to cooperate with the first pair of fixed contacts thereby to control a first circuit, a second movable bridging contact actuated by said plunger and guided for movement within the second pair of internal channels to cooperate with the second pair Olf fixed contacts thereby to control a second circuit, and a U-shaped mounting spring for fastening said switch within an aperture of a supporting panel, said spring having a pair of resilient arms positioned in said external channels and engaged with the panel aperture thereby to fasten the switch to the panel, said arms including a means for holding said arms within said external channels.

2. A switch comprising a hollow insulating base having an open bottom end, fixed and movable contact means disposed within said base, a switch actuator extending into said base for selectively operating said contact means, a cover plate engaging the bottom end of said base thereby to :form a housing tor said switch, and a U-shaped mounting spring for fastening said switch within an aperture of a supporting panel and attaching said plate to said base, said spring having a pair of oppositely disposed resilient arms and an intermediate connecting section, a plurality of transversely extending projections formed in said arms adjacent the intermediate section, recessed means formed in the external side walls of said base for receiving said projections, said projections engaging the recessed means thereby to securely fasten said spring to said base with the connecting section extending across the outer surface of said cover plate, whereby said U-shaped mounting spring securely attaches said plate to said base to (form the switch housing.

3. A switch comprising a hollow cylindrical insulating base having an open bottom end, fixed and movable contact means disposed within said base, a switch actuator extending into said base for selectively operating said contact means, a cover plate engaging the bottom end of said base thereby to form a housing for said switch, and a U-shaped mounting spring for fastening said switch within an aperture of a supporting panel and attaching said plate to said base, said spring having a pair of oppositely disposed resilient arms and an intermediate connecting section, a pair of oppositely disposed longitudinally extending channels formed in the external walls of said cylindrical base for receiving the arms of said spring, a plurality of transversely extending barbs formed in said arms adjacent the intermeidate section of said spring, said barbs engaging surfaces of said channels thereby to securely fasten said spring to said base with the connecting section extending across the outer surface of the cover plate, whereby the U-shaped mounting spring securely attaches the plate to the base to [form the switch housing.

4. A switch comprising a hollow cylindrical insulating base having an open bottom end and a top end with an aperture therein, at least one pair of fixed contacts disposed w ithin said base, a plunger extending into said base through said aperture, at least one movable bridging contact disposed in said base and cooperating with said fixed contacts to form a circuit controlling contact means,

said plunger arranged in said base to selectively engage said movable contact to open and close said contact means, a circular cover plate engaging the bottom end of said base thereby to iorm a housing for said switch,

and a U -shaped mounting spring for fastening said switch within an aperture of a supporting panel and attaching said plate to said base, said spring having a pair of oppositely disposed resilient arms and an intermediate connecting section, a pair of oppositely disposed longitudinally extending channels formed in the external walls of said cylindrical base for receiving the arms of said spring, a plurality of transversely extending barbs formed in the sides of each of said arms adjacent the intermediate section of said spring, said barbs engaging side surfaces of said channels thereby to securely fasten said spring to said base with the connecting section extending diametrically across the outer our-face of the cover plate,

whereby the U-shaped mounting spring securely attaches the plate to the base to form the switch housing.

5. A switch comprising a hollow cylindrical insulating base having an open bottom end and a top end with an aperture therein, first and second pairs of fixed contacts disposed within said base, a plunger extending into said base through said aperture, first and second movable bridging contacts disposed in crisscross fashion within said base and cooperating with said first and second pairs of fixed contacts respectively to form two groups of circuit controlling contacts, said plunger arranged in said base to selectively engage said movable contacts to open and close said contact groups, a circular cover plate engaging the bottom end of said base thereby to form a housing for said switch, and a U-shaped mounting spring for fastening said switch within an apenture of a supporting panel and attaching said plate to said base, said spring having a pair of oppositely disposed resilient arms and an intermediate connecting section, a pair of oppositely disposed longitudinally extending channels formed in the external walls of said cylindrical base for receiving the arms of said spring, a plurality of transversely extending barbs tfiormed in the sides of each of said arms adjacent,

the intermediate section of said spring, said barbs engaging side surfaces of said channels thereby to securely fasten said spring to said base with the connecting section extending diametrically across the outer surface of the cover plate, whereby the U-shaped mounting spring securely attaches the plate to the base to form the switch housing.

6. A switch comprising an insulating base with a cavity therein, said cavity including first and second pairs of angular-1y spaced and oppositely disposed longitudinally extending channels, a fixed contact positioned in each of said channels thereby to provide first and second pairs of oppositely disposed fixed contacts, a plunger extending through an outer wall of said housing into said cavity, a

first movable bridging contact actuated by said plunger and guided for movement within the first pair of channels to cooperate with the first pair of fixed contacts thereby to control a first circuit, a second movable bridging contact actuated by said plunger and guided for movement within the second pair oi channels to cooperate with the second pair of fixed contacts thereby to control a second circuit, a cover plate engaging the bottom end of said base thereby to form a housing for said switch,

and a U-shaped mounting spring for fastening said switch plate, whereby said U-shaped mounting spring securely attaches said plate to said base to form the switch housmg.

References Cited in the file of this patent UNITED STATES PATENTS 1,398,373 Graesser et al. Nov. 29, 1921 1,662,422 Hodges Mar, 13, 1928 2,712,047

Herterick June 28, 1955

Claims

1. A SWITCH COMPRISING A GENERALLY CYLINDRICAL INSULATING HOUSING WITH A CAVITY THEREIN, SAID CAVITY INCLUDING FIRST AND SECOND PAIRS OF ANGULARLY SPACED AND DIAMETRICALLY OPOSED LONGITUDINALLY EXTENDING INTERNAL CHANNELS FORMED IN THE INNER WALLS OF SAID CAVITY, A FIXED CONTACT POSITIONED IN EACH OF SAID CHANNELS THEREBY TO PROVIDE FIRST AND SECOND PAIRS OF DIAMETRICALLY OPPOSED FIXED CONTACTS, A DIAMETRICALLY OPPOSED PAIR OF EXTERNAL CHANNELS EXTENDING LONGITUDINALLY IN THE OUTER WALLS OF SAID HOUSING, SAID EXTERNAL CHANNELS BEING ANGULARLY SPACED FROM SAID INTERNAL CHANNELS, SAID INTERNAL AND EXTERNAL CHANNELS BEING GENERALLY PARALLEL TO THE AXIS OF SAID HOUSING, A PLUNGER EXTENDING AXIALLY THROUGH A WALL OF SAID HOUSING INTO SAID CAVITY AND GUIDED FOR MOVEMENT BY SAID CAVITY, A FIRST MOVABLE BRIDGING CONTACT ACTUATED BY SAID PLUNGER AND GUIDED FOR MOVEMENT WITHIN THE FIRST PAIR OF INTERNAL CHANNELS TO COOPERATE WITH THE FIRST PAIR OF FIXED CONTACTS THEREBY TO CONTROL A FIRST CIRCUIT, A SECOND MOVABLE BRIDGING CONTACT ACTUATED BY SAID PLUNGER AND GUIDED FOR MOVEMENT WITHIN THE SECOND PAIR OF INTERNAL CHANNELS TO COOPERATE WITH THE SECOND PAIR OF FIXED CONTACTS THEREBY TO CONTROL A SECOND CIRCUIT, AND A U-SHAPED MOUNTING SPRING FOR FASTENING SAID SWITCH WITHIN AN APERTURE OF A SUPPORTING PANEL, SAID SPRING HAVING A PAIR OF RESILIENT ARMS POSITIONED IN SAID EXTERNAL CHANNELS AND ENGAGED WITH THE PANEL APERTURE THEREBY TO FASTEN THE SWITCH TO THE PANEL, SAID ARMS INCLUDING A MEANS FOR HOLDING SAID ARMS WITHIN SAID EXTERNAL CHANNELS.