US3143606A

US3143606A - Depressible trigger switch with manual adjustable contact means

Info

Publication number: US3143606A
Application number: US194811A
Authority: US
Inventors: Harry W Brown
Original assignee: Cutler Hammer Inc
Current assignee: Cutler Hammer Inc
Priority date: 1962-05-15
Filing date: 1962-05-15
Publication date: 1964-08-04
Anticipated expiration: 1981-08-04
Also published as: GB973549A

Description

Aug. 4', 1964 H w.

BROWN 3,143,606 DEPRESSIBLE TRIGGER SWITCH WITH MANUAL ADJUSTABLE CQNTACT MEANS Filed May 15, 1962 5 Sheets-Sheet 1 AM'NX wgdxm 89 m. z, m

4, 1964 H. w. BROW 3,143,606

DEPRESSIBLE TRIGGER S C ITH MANUAL ADJUSTABLE CON T MEANS Filed May 15, 1962 3 Sheets-Sheet 2 by; I

1 z, salsa 1 Aug. 4, 1964 J H. w. BROWN 3,143,606

DEPRESSI TRIGGE WITCH H MANUAL A STABLE TACT M s Filed May 15, 1962 s Sheets-Sheet :5

v v 5mm MAM/v 'w fixmmv Wmg United States Patent 3,143,606 1 DEPRESSIBLE TRIGGER SWITCH WITH MANUAL ADJUSTABLE CONTACT MEANS Harry W. Brown, Mukwonago, Wis., assignor to Cutler- Hammer, Inc., Milwaukee, Wis., a corporation of Delaware Filed May 15, 1962, Ser. No. 194,811 15 Claims. (Cl. 200-6) This invention relates to selector switches and more particularly to an electrical switch which is selectively adjustablefrom a first condition wherein it is operable to perform a first switching operation to a second condition wherein it is operable to perform a second or diiferent switching operation.

While not limited thereto, the invention is especially applicable to depressible trigger switches for selectively controlling reverse energizations of portable tool motors or the like.

An object of the invention is to provide an improved electrical switch.

Another object of the invention is to provide an improved reversible trigger switch for use on a portable tool handle.

A more specific object of the invention is to provide an improved electrical selector switch operating mechanism.

Another specific object of the invention is to provide a depressible switch operator with improved means for selecting different switch contacts for operation.

Another specific object of the invention is to provide a switch with two pairs of contacts adapted for connection to external circuits and depressible trigger operated means for bridging the contacts of the respective pairs thereof and selector means extending through such trigger for resetting said switch so that the contacts of one pair are connected to the respective contacts of the other pair when the trigger is depressed.

v A further specific object of the invention is to provide an improved depressible trigger switch operable to bridge forwardly motor operating contacts and being provided with readily adjustable selector means extending through the trigger and being rotatable to select reversely motor operating contacts for bridging when the trigger is depressed.

Other objects and advantages of the invention will hereinafter appear.

According to the invention there is provided a trigger switch of the preselector type which is adapted for mountingin the handle of a portable electric tool or the like. When so mounted, the body of the switch is within the handle and the trigger projects from the handle so that it may be pressed to close the switch. The switch is provided with selectable. contacts and a selector shaft extends through the trigger and has an external button which may be rotated ninety degrees to select pairs of contacts for bridging when the trigger is pressed. The switch is constructed so that the selector shaft cannot be rotated while the. trigger is depressed. The selection must first be made and then the trigger is pressed to close the selected contacts.

These and other objects and advantages of the invention and the manner of obtaining them will best be understood by reference to the following detailed description ice FIG. 4 is a cross-sectional view of the switch taken along line 44 of FIG. 2;

FIG. 5 is an isometric exploded view of the parts of the switch of FIG. 1;

FIG. 6 is a rear view of the selector shaft;

FIG. 7 is a front view of the base showing the interior thereof;

FIG. 8 is a cross-sectional view taken along line 8-8 of FIG. 7;

FIG. 9 is a front view of the switch of FIG. 1; and

FIGS. l0, ll, 12 and 13 are front views of the selector shaft, the movable bridging contacts and the stationary contacts showing the four positions thereof.

Referring to FIGS. 1 and 2, there is shown a trigger switch of the selector type comprising a supporting member or base 2, a switch frame 4, an insulator 6 between the base and the frame, a trigger 8 for actuating the switch and a selector shaft 10 for selecting different pairs of contacts for bridging when the trigger is pressed. The switch also comprises a pair of

helical compression springs

12 and 14 for restoring the trigger and opening the switch contacts when the trigger is released.

As shown in FIGS. 3, 7 and 8, base 2 is substantially cup-shaped having sides and a closed end and an open end as seen in FIG. 8. The open end has a generally square configuration as shown in FIG. 7 and the profile thereof is broken by four grooves 2a, one such groove adjacent each corner, for receiving securing straps of the switch frame which are bent around the edge of the base as hereinafter more fully described. Base 2 is provided with a projection 2b in its closed end which is illustrated as being round and which is provided within the base with a flat round recess 20 to provide room for the rear end of shaft 10 when the trigger is pressed all the way in.

Base 2 is provided with a pair of

grooves

2d and 22 on each corner thereof extending from the closed end to a point near the open end thereof. Groove 2d is deeper than and communicates with strap groove 2a to provide an overhanging edge 2 on each corner of the base most clearly shown in FIG. 8 to the rear side of which the end of each frame strap can be bent to secure the frame to the base. Groove 2e is on the other side of each corner of the base from groove 2d. Groove 2e is wider than and long as groove 2d to provide room for the contact terminals which extend through edge 2 as hereinafter more fully described.

Base 2 is provided with an inner cavity having a generally round and elongated or cylindrical configuration as most clearly shown in FIGS. 7 and 8 and extending all the way from recess 20 to the open end of the base. The inner walls of this cavity are provided with four grooves 2g spaced ninety degrees from each other and extending toward the middle of each side of the square-shaped base as shown in FIG. 7'. These grooves are provided to accommodate stationary contacts hereinafter described. Ad-' jacent' each such groove 2g and between such groove and the clockwise corner of the base in FIG. 7, a slot 2h extends all the way through overhanging edge 2 into communication with exterior groove 2e.

Between grooves 2g within the cavity of base 2, there are provided inwardly projecting ridges 2 as shown in FIG. 7 which prevent turning of shaft 10 when the trigger is in its depressed position. As shown in FIG. 8, ridges 2j extend from the closed end of the base about halfway toward the open end thereof and are each provided with a beveled end to prevent interference with movement of the bridging contacts whenthe trigger is pressed.

As most clearly shown in FIGS. 4 and 5, there are provided four like'stationary contact clips. or

springs

16, 18, 20 and 22. Each contact clip such as contact clip 16 in FIG. 5 is of generally U-shaped configuration. One leg 16a forms a stationary spring contact and is bent inwardly within the base cavity as shown in FIG. 3 to form a cam surface for cooperation with a movable contact bridge or contactor hereinafter described. The other leg 16b thereof extends through slot 2h to the exterior of the base and further extends partway along groove 2e to form an electrical terminal or connector member to which an electrical conductor maybe connected.

Trigger 8 is provided with ,a rearwardly curved front end 8a which is rounded for engagementby the finger of the operator. A hole 8b extendsthrough the trigger and the center portion of the curved front end thereof is provided with a recess 8c to accommodate the enlarged end a of shaft 10. As most clearly shown in FIGS. 2 and 9, the diameter of enlarged end 1011 of the shaft is greater than the lateral width of trigger 8. Recess 8c is open at its opposite sides and the opposite sides of enlarged end 10a of the shaft extend beyond the opposite sides of the trigger so that end 10a can be gripped by the fingers and rotated. Enlarged end 10a is provided with milled grooves or is suitably roughened on its rounded portion to facilitate turning thereof. The bottom of recess 80 is provided with four rounded grooves 8d spaced ninety degrees apart as shown in FIG. 5. The rear surface of en-- larged end 10a of shaft 10 is provided with a pair of oppositely disposed rounded ridges 10b shown in FIGS. 3 and 6 for complementary engagement in linearly arranged grooves Sd in the trigger to stop the shaft at ninety degree intervals when it is rotated.

The central portion of the trigger at the rear end thereof is provided with a substantially square projection 8e through which hole 8b extends. A pair of round recesses 8f are provided in the rear end oftrigger 8, one on each side of projection 8e for retaining compression springs 14. A hole 8g slightly larger in diameter than hole 8b extends part way into projection 8e from the rear end thereof to provide space for a helical compression. spring 24 which biases shaft 10 so that ridges 10b snap into one or the other pair of oppositely disposed grooves 8d when the shaft is rotated. Return springs 12 and 14 also assist in biasing the trigger against enlarged end 10a of selector shaft 10 to bias the ridges in the grooves for selector shaft indexing purposes.

As most clearly shown in FIGS. 3, 5 and 6, the rear end of shaft 10 is provided on opposite sides thereof with keyways or grooves 100 extending from the rear end thereof a sufficient distance to receive the key-like ridges of a contact carrier 26hereinafter described. The extreme rear end of shaft'10 is provided with an annular groove 10d therearound for receiving a split ring 28 to retain the contact carrier on the shaft against the force of spring 24.

Frame-4 comprises a sheet metal stamping the body' portion of which has a substantially square configuration having a square aperture 4a therein of a size freely to slide over projection 8e of the trigger. 'Frame 4 is provided with, a pair of ears 4b and 4c extending in opposite directions from opposite edges of the frame to overlie recesses 8 in the trigger. Ears 4b and 4c are each provided on the front surface with a rounded raised portion or bead 4d. These beads fit Within the ends of

springs

12 and 14 to retain the springs from slipping off the ears. Bar 40 has integrally formed therewith a portion extending along the adjacent side of the frame and having a projection 4e extending forwardly at ninety degrees from the frame.

Projection 4e is provided with a hole 4] for supporting a locking pin 30. Looking pin 30 is of a known type and is provided with a cage or bushing 30a having a short sleeve 30b of smaller diameter which extends through hole 4 and is riveted on the other surface of projection 4e. A helical compression spring 300 surrounds reduced portion 30d of pin 3%. Reduced portion 30d extends through bushing 30a and through sleeve 30b and the end thereof is spread so that reduced portion 30dwill slide in sleeve 36b when the pin is depressed against the force of spring 300 but the pin' cannot be withdrawn from the bushing. Frame 4 is further provided with four straps 4g extending rearwardly from adjacent the corners T thereof for securing the parts together as hereinafter described. g

Insulator 6 is a flat piece of insulating material having an external configuration substantially corresponding to the square body portion of frame 4. Insulator 6 is' provided with a square aperture 6a corresponding to aperture 4a. Aperture 6a has radically extending slots 6b at the corners thereof for receiving projections 2k extending forwardly from the corners of the open end of the base adjacent connector terminal slots 2h. As will be apparent, projections 2k fit into slots 6b to fix the base and 6111. Carrier 26 is provided with a bore 26b therethrough 1 length of the bore.

' grooves 26d snugly receive a pair of arcuate bridging conrespective recesses 81 in the trigger. in hole 8g in the trigger around the shaft, and frame 4 which is round except for a pair of opposed key-like ridges 26c extending toward one another from opposite sides of the bore 180 degrees apart and throughout the Bore 26 is of a diameter whereby the contact carrier slides onto the end of shaft 10 with ridges 260 in complementary interfitting engagement in grooves in the shaft. A pair of arcuate grooves 26d are provided adjacent the rear end of the contact carrier and extend partway around opposite sides thereof. These tacts or

contactors

32 and 34. Each movable or bridging contact such as 32 is provided witha narrow central portion as shown in FIG. 5 for fitting fully within its associated groove 26d and wider end portions 32a which eX- tend beyond the outer surface of carrier26 for engaging a pair of stationary spring contacts as shown in FIG. 4.

To assemble the switch, shaft 10 is slid into the hole in trigger 8 and springs 12 and 14 are inserted in their. Spring 24 is placed and insulator 6 are placed on projection 8e so that ears 4b and debear against springs 12, and14, respectively, and lock pin mount or projection 4e is on the right side of the trigger and on the same sideas reference mark or recessv 8h as shown in FIG. 9. Contact carrier 26 is then slid on shaft 10 so that springs 12 and 14 are slightly compressed and spring 24 is compressed a substantially g'reateramount and retaining ring 28 is snapped into. groove 10d to retain. these parts together in subassembly. Alternatively retaining ring 28rand itsf annular groove 10d, could be replaced by a tubular extreme end on shaft- 10 which is riveted over a washer placed against the rear end of the contact carrier.

Combined stationary contact springs and

connector terminals

16, 18, 20 and 22 are then inserted in the base. 2.

Movable bridging contacts

32 and 34 are inserted in grooves 26d in the contact carrier. The contact carrier portion of such subassembly is then inserted inside the base so that projections 2kv enter slots 6b in the-insulator;

This insertion causes straps 4g of the frame to slide along grooves 2a in the base whereafter the ends of the straps are bent inwardly and forwardly to rigidly secure the switch subassembly to the base. To prevent the bentover ends of the straps from slipping oifthe overhanging edge of the base, the rear surface of the overhanging edge at the end of each groove 2d is undercut at an angle of substantially thirty degrees. As a result, the ends of the frame securing straps can be bent about '120 degrees securely to grip and retain the base attached to the frame.

FIG. shows a first position of selector shaft 10. In this position, depression of the trigger causes movable contact 32 to bridge

contacts

16 and 18 and causes movable contact 34 to bridge

stationary contacts

20 and 22. FIG. 10 also shows a circuit diagram illustrating an exemplary use of the switch. In FIG. 10, alternating current may be connected to lines L1 and L2. Line L1 is connected through winding W1 of a two-winding alternating current motor to contact 16. Line L2 is connected to contact 20. Contact 18 is connected through winding W2 of the motor to contact 22.

When the selector shaft is in the position shown in FIG. 10 and the trigger is depressed, the motor will be energized for rotation in one direction. When the selector shaft is rotated ninety degrees to the position shown in FIG. 11 and the trigger is depressed, the phase of winding W2 will be reversed to cause the motor to be energized for rotation in the opposite or reverse direction. When the selector shaft is rotated another ninety degrees to the position shown in FIG. 12', the switch will be in the same condition as in FIG. 10. A further ninety degrees rotation of the shaft to the position shown in FIG. 13 will restore the condition shown in FIG. 11. As will be apparent, each ninety degree rotation of the selector shaft will set the switch for reversing the motor from its immediately preceding direction of rotation. Also, ninety degree forward and ninety degree reverse rotation of the selector shaft will do the same thing. It will, therefore, be apparent that the invention provides a double-pole double throw switch which can be preset for either its first or second throw by turning the selector shaft ninety degrees. 7

When the selector shaft is turned, ridges 10b on the enlarged end of the shaft are forced out of alined grooves 8b in the trigger recess 8c against the force of spring 24. Spring 24 is compressed between contact carrier 26 and the trigger. As the contact carrier is held rigidly to shaft 10 by split ring 28, spring 24 biases the trigger against the rear surface of enlarged end 10a of the shaft. Consequently, when the shaft is turned ninety degrees, this bias causes ridges 10b to snap into the other pair of alined grooves 8b. Alternatively, spring 24 could be omitted and hole 812 left unenlarged at 8g and springs 12 and 14 would then be relied upon to bias ridges 1012 into grooves 8d for indexing purposes.

The switch is constructed so that the selector shaft can be turned only when the trigger is undepressed to prevent damaging the contacts. As shown in FIG. 3,

movable contacts

32 and 34 are disengaged from

stationary contacts

16 and 20 when the trigger is restored so that the shaft can be turned. Also, the movable contacts are clear of ridges 2j shown in FIGS. 7 and 8 to permit the contact carrier and the movable contacts to be rotated with the shaft.

When the trigger is depressed, return springs 12 and 14 are compressed. The trigger carries spring 24, selector shaft 10, contact carrier 26 and

contacts

32 and 34 with it;

Movable contacts

32 and 34 engage the offset portions at the ends of the stationary contact springs and slide therealong almost to the ends thereof. The bias of the stationary contact springs maintains good electrical connection between the stationary and movable bridging contacts. Release of the trigger causes

springs

12 and 14 to restore the switch to the position shown in FIG. 3 with the contacts open.

It will be apparent that the selector shaft cannot be turned when the trigger is depressed. When the trigger is depressed, the wider end portions 32a of contact 32 enter on opposite sides of the corresponding ridge 2 as shown in FIG. 4 thereby to prevent rotary movement of contact 32. Since the movable contacts are confined in grooves 26d in the contact carrier and the contact carrier is keyed to the shaft, ridges 2 also prevent rotation of the shaft while the trigger is in its depressed position. Restoration of the trigger causes

contacts

32 and 34 to clear ridges 2 as shown in FIG. 3 so that the shaft can be rotated.

While the device hereinbefore described is effectively adapted to fulfill the objects stated, it is to be understood that I do not intend to confine my invention to the particular preferred embodiment of selector switch disclosed, inasmuch as it is susceptible of various modifications without departing from the scope of the appended claims.

I claim:

1. An electric switch comprising:

an insulating base having a cavity therein;

a plurality of stationary contacts supported by said base within said cavity;

a movable contact carrier confined within said cavity and having at least one contact mounted thereon;

a trigger member externally of said base;

a contact selector member havinga portion extending into said cavity to which said contact carrier is coupled and having an external portion;

means coupling the external portion of said selector member to said trigger member including a portion of said selector member externally of said trigger member to afford movement of said contact carrier by said selector member relative to said trigger member and said base thereby to preselect one or another of said stationary contacts for engagement by said movable contact;

spring means between said trigger member and said base biasing said trigger member a limited extent in a direction away from said base to maintain said movable contact separated from the selected stationary contact;

and said trigger member being movable against the force of said spring means to afford movement of said selector member and said contact carrier therewith to close the selected contacts.

2. The invention defined in claim 1, wherein said trigger member comprises a guiding portion at the side thereof adjacent said base;

and means confining said guiding portion to afford non-rotatable linear movement of said trigger member against the force of said spring means.

3. The invention defined in claim 1, wherein said selector member and coupling means comprises:

a rotatable shaft extending through a hole in said trigger member into said cavity and having an enlarged head portion bearing against said trigger member and by which said shaft may be turned to rotate said contact carrier into different selective positions.

4. The invention defined in claim 3, together with:

indexing means between relatively rotatable portions of said switch comprising interfitting projections and notches for maintaining said rotatable shaft in each selected angular position under the force of said spring means.

5. The invention defined in claim 1, wherein each said stationary contact comprises:

a U-shaped member having one leg for engagement by the movable contact and another leg for connection to an external circuit.

6. An electrical switch comprising:

an insulating base;

a plurality of stationary contacts in said base;

a contact carrier having at least one movable contact 'mounted thereon;

a contact selector member connected to said contact carrier and being operable to preset said movable contact and thereby to preselect any one of said stationary contacts for engagement by said movable contact; and a spring biased'actuator for'moving said selector f member and saidcontact carrier so that said movable contact engages the selected stationary contact; and said insulating base comprising: a cup-shaped molded housing having closed side Walls and bottom and an open end;

' means closing said open end and having an aperture a plurality of stationary contacts in said base;

a contact carrier having arcuate movable contacts mounted thereon for bridging pairs of said stationary contacts;

a contact selector member connected to said contact w carrier and being operable to preset said movable contacts and thereby to preselect one or another pair of stationary contacts for engagement by a movable contact; e e

and a spring biased actuator for moving said selector memberand said contact carrier so that said movable contact engages the selected-stationarycontacts;

and saidinsulating base comprising: t

a cup-shaped molded housing having closed side walls and bottom and an open end;

means closing said openend and having an aperture through which said selector member extends into saidhousing, said-contact.carrier being secured to said selector member within said housing;

' and means molded on the-inner walls of said housing for retaining said stationary contacts in angularly spaced relation.

I 8. The invention defined inclaim 7; wherein said closing means comprises:

- to secure said frame to said housing;

and. an insulator between said frame and housing for insulating the stationary contacts within said housing from said frame. 1 1 a 9. An electrical switch comprising: 7 an insulating base; a plurality of stationarycontacts in said base; a contact carrier having at least one movable'contact mounted thereon; V is a contact selector member connected to said contact carrier and being operable to preset said movable contact and thereby to preselect any one of said stationary contacts for engagement by said movable contact; i a spring biased actuator for moving said selector mem ber'and said contact carrier'so that said movable contact engages the selected stationary contact; said actuator comprising a trigger which is depressible to close the switch contacts; V 7 said selector member comprising a rotary shaft extending through said trigger into said base;

a frame secured to said trigger and shaft by said contact carrier; 7

spring means biasing said trigger away from said frame;

and means on said frame for rigidly securing the same to said base.

10. The invention defined in claim 9, wherein said contact carrier comprises:

a cylindrical member keyed to the end of said selector shaft within said base;

and arcuate grooves on said cylindrical member for accommodating movable contacts which are retained in said grooves by the inner walls of said base.

11. An electrical switch comprising:

an insulating base;

a plurality of stationary contacts in said base;

a contact carrier having movable contacts mounted thereon;

a contact selector member connected to said contact carrier and being operable to preset said movable contacts and thereby to preselect one or another of said stationary contacts for engagement by respective movable contacts; 7

a spring-biased actuator for moving said selector memher and said contact carrier so that said movable contacts engage the selected stationary contacts;

and cooperating means on the inner walls of said base and on said movable contacts for preventing actuation of said selector member when the contacts are closed.

12. The invention defined in claim 11, wherein said cooperating means comprises:

slots on the movable contacts;

and molded ridges extending partway along the inner walls of the base, said slots riding onto said ridges when said actuator is depressed to prevent rotation of said selector member and being clear of said ridges when said actuator is underpressed to permit rotation of said selector member.

13. A trigger actuated selector switch comprising:

an insulating base having a cavity therein;

stationary contacts mounted in said cavity;

a trigger member externally of said base;

' means secured to said base for restricting said trigger member for linear movement toward said base and preventing rotation thereof;

a selector member extending through a hole in said trigger member into, said cavity and being confined to rotary movement relative to said trigger member;

spring means between said trigger member and said base biasing said trigger member away from said base and against a portion of said selector member;

a contact carrier secured to said selector member within said cavity including means coupling said selector member to said trigger member for linear movement .together and abutting said restricting means under the force of said spring means;

and at least one contact on said contact carrier for connecting a pair of stationary contacts when said trigger member is depressed and for connecting a dilferent pair of stationary contacts when said selector member is rotated before said trigger member is depressed.

14. The invention defined in claim 13, wherein said selector member comprises:

an enlarged head on the external end thereof against which said trigger member bears under the force of I said spring means;

and a recess in said trigger member accommodating a portion of said enlarged head leaving other portions of the latter accessible for tuning said selector member.

15. An electric switch of the self-enclosed trigger actuated type adapted for mounting in a housing so that; the self-enclosed switch is within the housing and the actuator extends through an aperture for manual depression comprising:

an insulating base;

a plurality of stationary contacts mounted within said base;

a movable contact carrier within said base having at least one contact mounted thereon;

a contact selector extending into said base to support said contact carrier and being operable to rotate said contact carrier thereby to preselect another stationary contact for engagement by said movable contact;

and a spring biased member through which said contact selector rotatably extends and being axially movable with said contact selector after said preselection has been made to close the selected contacts, said member having a narrow elongated cross-sectional shape and slidable in the aperture in the housing; and said contact selector having an enlarged head portion to facilitate rotation thereof in its undepressed position.

References Cited in the file of this patent UNITED STATES PATENTS Bluemle et a1 Sept. 9, 1941 Beveridge May 20, 1947 Brooks Oct. 21, 1958 Gerrie Oct. 10, 1961 FOREIGN PATENTS France Jan. 6, 1953 Germany Mar. 2, 1961

Claims

1. AN ELECTRIC SWITCH COMPRISING: AN INSULATING BASE HAVING A CAVITY THEREIN; A PLURALITY OF STATIONARY CONTACTS SUPPORTED BY SAID BASE WITHIN SAID CAVITY; A MOVABLE CONTACT CARRIER CONFINED WITHIN SAID CAVITY AND HAVING AT LEAST ONE CONTACT MOUNTED THEREON; A TRIGGER MEMBER EXTERNALLY OF SAID BASE; A CONTACT SELECTOR MEMBER HAVING A PORTION EXTENDING INTO SAID CAVITY TO WHICH SAID CONTACT CARRIER IS COUPLED AND HAVING AN EXTERNAL PORTION; MEANS COUPLING THE EXTERNAL PORTION OF SAID SELECTOR MEMBERS TO SAID TRIGGER MEMBER INCLUDING A PORTION OF SAID SELECTOR MEMBER EXTERNALLY OF SAID TRIGGER MEMBER TO AFFORD MOVEMENT OF SAID CONTACT CARRIER BY SAID SELECTOR MEMBER RELATIVE TO SAID TRIGGER MEMBER AND SAID BASE THEREBY TO PRESELECT ONE OR ANOTHER OF SAID STATIONARY CONTACTS FOR ENGAGEMENT BY SAID MOVABLE CONTACT; SPRING MEANS BETWEEN SAID TRIGGER MEMBER AND SAID BASE BIASING SAID TRIGGER MEMBER A LIMITED EXTENT IN A DIRECTION AWAY FROM SAID BASE TO MAINTAIN SAID MOVABLE CONTACT SEPARATED FROM THE SELECTED STATIONARY CONTACT; AND SAID TRIGGER MEMBER BEING MOVABLE AGAINST THE FORCE OF SAID SPRING MEANS TO AFFORD MOVEMENT OF SAID SELECTOR MEMBER AND SAID CONTACT CARRIER THEREWITH TO CLOSE THE SELECTED CONTACTS.