US2143162A - Electric snap switch - Google Patents

Description

Jan. 10, 1939.:

G. J. MEUER 2,143,162

ELECTRIC SNAP SWITCH Filed Nov. 13, 1936 2 Sheets-Sheet l G. J. MEUER ELECTRIC SNAP SWITCH Jan. 10, 1939.

Filed No. 15, 1936 2 Sheets-Sheet 2 Patented Jan. 10, 1939 UNITED STATES PATENT OFFICE ELECTRIC SNAP SWITCH George J. Meuer,

poration of Delaware Milwaukee, Wis., a cor- Application November 13, 1936,, Serial No. 110,704

10 Claims.

This invention relates toimprovements in electric snap switches.

A primary object of the invention is to provide a novel form of snap switch including a novel 5, form of operating means therefor.

Another object is to provide a snap switch which is particularly adapted for use in conjunction with a known form of clockwork. timing mechanism.

Another object is to provide a device including a snap switch which is manually operable to closed circuit position and automatically operable to open: circuit position upon expiration of a predetermined variable period of time.

Another object is toprovide a snap switch hav ing stationary and movable contacts of novel form.

Another object is to provide novel mounting means for the stationary and movable parts of the snap switch.

Another object is to provide simple means for guiding the movements. of the switch contactors and for limiting the degree of movement thereof in one direction.

Another object is to provide a switch adapted for alternative use with binding screws or plug jacks for connection thereof in the controlled circult.

Another object is to provide a. snap switch affording at least six breaks in series in the controlled circuit.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate a pre- 15, ferred embodiment of my invention, and a slight modification of said preferred embodiment, which will now be describedit being understood that the illustrated embodiment is susceptible of change in respect of certain details of construction thereof without departing from the scope of the appended claims.

In the drawings, Figure 1 is a front elevation (actual size) of a preferred form of timing device in conjunction with which my improved snap .3 switch mechanism may be employed.

Fig. 2 is a bottom plan View of a device like that shown in Fig. l, the same illustrating the manner of attaching the various parts to the insulating base of the switch.

Fi 3 is an enlarged sectional view, on the line 3-3 of Fig. 1, illustrating the operative relationship between the clockwork timing mechanisrn and my improved snap switch.

Fig. 4 is a view of the inner surface of the insulating base shown in Fig. 2, illustrating the stationary contact and terminal members, other parts of the switch mechanism being omitted.

Fig. 5 is a fragmentary View similar to Fig.

4, but on an enlarged scale, illustrating the movable elements of the switch mechanism in the 5 circuit interrupting position thereof.

Fig. 6 is a further enlarged fragmentary sectional view, on the line 66' of Fig. 5, illustrating one pair of stationary contacts and the contactor adapted for movement into and out of 10 engagement therewith.

Fig. 7 is a fragmentary sectional View of the casing for the complete device, illustrating somewhat schematically the means enabling bodily movement of the timing mechanism along with the central shaft (see Fig. 3) whereby the switch mechanism is operated, and

Fig. 8 is a fragmentary view partly in elevation and partly in vertical section illustrating the manner of substituting plug jacks for the wiring terminal screws shown in Figs. 2 and 3.

Referring first to Figs. 1 to 7 of the drawings, the numeral [0 designates a substantially cylindrical molded hollow member composed of a suitable insulating material, such as that sold commercially under the trade name of Bakelite. Member Hi forms the main portion of the enclosing casing for a combined switch and clockwork timing mechanism, the character of which is best illustrated in Fig. 3. Member ID is adapted to fit within a substantially circular opening of corresponding size formed in a panel or the like (not shown) to which the same may be attached in any desired manner. Member i0 is provided at its forward end with a flange ll which overlies the aforementioned panel, and said member is provided with an integral lug or projection l2, which cooperates with the walls of a notch formed in the panel opening to restrain said member from rotary displacement.

Member ID is provided adjacent to its forward end with an inwardly extending annular flange l'3 (Fig. 3) against which a circular metal plate I4 is adapted to seat; said plate l4 forming the forward end wall of the casing. Member I0 is provided with an integral inwardly extending lug or projection l5 and plate i4 is provided with a notch IE to accommodate said lug, whereby said plate is restrained from rotary displacement relatively to member ID. Flange l3 and plate I4 are offset inwardly from the forward end of member l0 whereby a cylindrical recess I7 is provided. Located within recess l1 and adapted to cover substantially the entire outer surface of plate 14 is a flange or plate I8 formed integrally with the main body portion IQ of a handle member of molded insulating material, a separately molded manually operable insulating knob portion being fitted against the outer end of por tion l9.

In practice I prefer to provide the body portion I B with a pair of diametrically opposed openings or through passages and 22 of circular cross section; and I provide the inner face of knob portion 28 with an integral pair of diametrically opposed projections 23 and 25 of circular cross section which are adapted to fit rather snugly within the outer ends of the respective openings 2i and 22, whereby said knob portion 25 is restrained against rotation with respect to portion l9. Body portion i9 is provided centrally thereof with a passage 25 of circular cross section; said passage having at the inner end thereof a portion 25 of greater diameter. A machined metal hub member is provided with portions 27 and 28 which are freely insertable into passage 25 and portion 25, respectively.

Rigidly and non-rotatably secured to the inner end of said hub member, in the manner indicated in Fig. 3, is a flat sheet metal plate 29, the opposite ends of which are reduced and bent upwardly at right angles to the main body thereof as indicated at 30 and. 3! for reception with a fairly close fit in the inner ends of the aforementioned passages 2! and 22. Said hub-member is provided at its upper end with a cylindrical recess 32 to freely accommodate the smooth cylindrical portion 33 of a 'machined fastening member the flat and slotted head portion 34 of which is adapted to seat within a recess 35 provided in the outer surface of knob 20.

The inner end portion of the hub member 2'! is provided with a central opening 36 of polygonal form (preferably square) in cross section to ac commodate the shaft portion 3'! of corresponding size and shape in cross section, whereby said hub member and the shaft are constrained to rotate with each other. Said shaft is provided adjacent to the portion 3'! with a reduced and threaded portion 38 which is adapted for cooperation with the threaded recess 39 in the portion 33 of the fastening member. In this manner the parts aforedescribed are interlocked with each other for rotation thereof in each direction with respect to plate i l and casing member It. A circular flexible insulating disk 49 (such' as Celluloid of the desired color) is inserted with a press fit into the recess 35 in a relation substantially flush with the outer surface of knob portion 25 to provide a more finished appearance of the latter. The periphery of knob 25 is preferably milled or grooved, as best illustrated at 4| in Fig. 1, to facilitate manipulation thereof.

The flange H is provided at one point thereof with a non-beveled edge portion '42, which is provided with a V-shaped or arrowhead legend 43 for cooperation with a similar legend 44 (Fig. 1) formed upon the outer surface of flange I8. Flange i8 is provided at legend Mi with a circular opening 45 (Fig. 3) to freely accommodate the cylindrical stud or projection 46 which is rigidly attached to plate l4 in the manner illustrated in Fig. 3; and when these parts are in the respective positions thereof illustrated in Figs. 1 and '3, the shaft comprising portions 3'! and 38 is permitted to move to its inner extreme position under the bias of a pair of. spring members, one of which is shown at 47 in Fig. 7. Flange I8 is provided in its under surface with an approximately annular groove 48 of channel-shape in cross section (see Fig. 3). As shown in dotted lines in Fig. 1, one end 49 of groove 58 leads to and ends with the aforementioned opening 45 in flange l8, whereas the other end 50 of said groove is spaced a short distance to the right of said opening 45.

Knob 25 is preferably provided with a curved arrow 5! (Fig. 1) or a similar legend to indicate the direction in which said knob is to be turned manually to set the clockwork mechanism; and said knob is also preferably provided with the legend Pull out and turn, as indicated at 52,

the arrangement being such that when knob 2G is pulled outwardly against the action of the springs (one of which is shown at i! in Fig. 7), the same may be turned manually in a clockwise direction, with the result that the outer end of pin it enters groove 58. The peripheral upper surface of flange i8 is preferably divided into sixty sections, representing sixty minutes, and each five sections are designated by the numerals or legends 5, 10, etc., representing time periods of five minutes, ten minutes, etc. As will be understood from the foregoing the clockwork mechanism is adapted when unrestrained to effect rotation of knob i8, 25 at a rate corresponding to one complete rotation thereof in sixty minutes;

The means for restraining movement of the clockwork mechanism includes the aforementioned pin 45 when engaged with the walls of opening iii in flange it. In addition, I prefer to provide a circular fiat metal member 53 which is provided centrally thereof with a rectangular opening 54 for slidable but non-rotatable engagement with the rectangular portion H of the shaft. A metal tube or ferrule 55 is interposed between the lower end of hub member 27 and member 53,whereby upon tightening of fastening member 34 the member 53 will be held at the lower extremity of shaft portion 31. Member 53 is provided with a peripheral notch 55 (Fig. 3) which is preferably in the radial plane of the opening 35 in flange l8. Rigidly attached to plate M and extending from the inner surface thereof in the radial plane of the aforementioned pin 45 is a punched sheet metal member having a lug portion 51 offset inwardly from the inner surface of plate id for positioning thereof between the opposed walls of notch 56 in member 53 when the shaft is in its normal or inner extreme position. In this manner rotation of knob 25 in a counterclockwise direction (Fig. 1) by the clockwork mechanism is positively prevented.

However, said metal member is provided between lug 5'! and plate 14 with a notch 58 which is adapted to provide rotatable clearance for member 53 (as shown in dotted lines in Fig. 3) when knob 29 is pulled to its outer extreme position. The clockwork mechanism which may be of a known form, is represented by the dotted line rectangle 59 in Fig. 3, and is adapted to move bodily with the shaft upon inward and outward movement of the latter. The clockwork mechanism as a whole is restrained against rotation with respect to the casing parts I5, 15, as by mounting the upper and lower end plates 55 and 5! thereof (Fig. 7) for sliding movement upon a pair of rods or studs, one of which is shown at 52 in said figure. As shown in Fig. 7, the reduced upper ends of said rods (as represented by (52) are adapted to penetrate openings provided in plate l4 and are upset over the outer face of the latter, as indicated at 63,each rod having a coiled compression spring 41 interposed between plate and the upper end plate El -to bias-said mechanism towardits'innerextreme position.

As shown in Fig. 3' the end 64 of the main spring 65 of the clockwork mechanism isrigidly attached to an intermediate portion 66 of the shaft, as by means of a pin or rivet 61. From the foregoing description it will be apparent that, with the parts in the positions thereof shown in Figs. 1 and 3', upon a predetermined degree of outward pull upon the knob 20, IB- said knob may be rotated in a clockwise direction (Fig. l) to preselect a desired time period of operation of the clockwork mechanism. If a ten minute period is selectedthe legend 10 upon the flange I8 willbe registered or alined with the arrowheador similar legend 43 formed upon the aforementionedflange II.

I utilize such extreme outward movement of the shaft to effect operation of a snap switch mechanism to closed'circuit position. Said switch mechanism as shown is of the push-pull type, and the same comprises essentially a double-cone cam member 68, preferably formed of metal, the annular high point of said cam being designated by the numeral 69' in Fig. 3. Cam 58 is secured to a reduced lower end portion ID of the shaft in a manner to permit rotation of the shaft with respect to the cam while restraining said parts against axial movement relatively to each other. The securing means for'said parts preferably comprises a washer II which overlies the lower end of member 68, said washer being secured against endwise displacement as by upsetting or riveting thereover the extreme lower end of the shaft, as indicated at I2.

Surrounding cam member 68 is a coiled tension or garter spring 13 which automatically moves with a snap action to one side or the other of the high point 69 of the cam, according to the direction of movement of the latter. Spring 13 is held captive between the upper surface of a substantially circular punched insulating plate I and the lower surface of a sheet metal plate 15 which has arms 16, TI and 'IBbent downwardly at substantially right angles to the plane thereof, said arms having reduced lower ends which penetrate suitable openings provided in plate '34 and are bent inwardly over the lower surface of the latter, as shown at 19.

Plates I I and I5 are respectively provided with centrally located circular openings 83 and 81 to provide clearance for cam member 58. As shown in Figs. 3 and 5 the degree of upward movement of plate I4 is limited by engagement of the upper surface thereof with the flat lower surfaces of the heads of three posts 22, 83 and 84, the lower ends of which are upset over the lower of the insulating switch base 85 in the manner indicated at 86 (post 82). Plate 14 is provided in its periphery with segmental notches as shown in dotted lines at 87, 88 and 89 in Fig. 5 to accommodate the intermediate cylindrical portions of posts 82, 83 and 84, whereby said plate 14 is restrained against rotary movement and tilting thereof to a substantial degree is prevented.

Positioned below the surface of insulating plate M are three substantially circular bridging con tactors 90, 9| and 92, the same being equidistantly spaced from the respective posts 82, 83 and 84. Said bridging contactors are preferably punched from a sheet of composite metal and stamped to the form thereof best illustrated at 90 in Fig. 6. Said composite metal is preferably approximately one-fiftieth of an inch thick, the upper half SI! of said thickness preferably consisting of hard copper and the lower half 90* thereof preferably consisting of fine silver. Each contactor is provided with a central opening 99 to freely accommodate the intermediate portion 93 of a pin or rivet the head 94 of which is received within an upward depression formed in said contactor.

The reduced upper end 95 of each pin is adapted to penetrate an opening provided in plate T4 and is upset over the upper surface-of the latter, as indicated at 96 in Figs. 3 and 6, a metal washer 9'! being preferably interposed between and clamped by the plate 14 and the shoulder formed by the portion 93 of the pin. By this arrangement each contactor (such as 95) is free to move upwardly and downwardly to a limited extent upon the portion 93 of the pin and to tilt with respect thereto, to provide for a substantial degree of self-adjustment of the contactors with respect to the stationary contacts of the switch.

The stationary contacts of the switch preferably consist of the flat heads of rivets formed of fine silver and arranged in pairs, as best illustrated at 98, 39; led, IBI; and I02, I03 in Fig. i, for cooperation with the respective contactcrs 90, 9| and 92 (see dotted line illustration in Fig. 5). Contact 93 is rigidly attached to a terminal plate I04 of the form illustrated in Fig. 4, the manner of attaching said contact being shown at 98 in Fig. 6. Terminal plate I94 is preferably of a binding screw I88, which extends upwardly through a clearance opening provided therefor in base 85.

Contacts 99 and Idil are attached to a terminal plate I09, and the latter is attached to base 85 as by means of rivet I ID, the binding screw I I I when threaded into the opening I I2 assisting in preventing displacement of plate IE9 with respect to base 85. Contacts IGI and 102 are attached to opposite ends. of a plate II-3, which is secured to base 85 by a rivet II I, a pair of studs H5, H5 being formed on base 85 to restrain plate Iii; against rotary displacement. Contact m3 is attached to one end of a terminal plate I H, which is secured to base 85 by rivets H8 and H5, said terminal plate having a tapped opening I2Il to receive the threaded shank of binding screw I2I.

The complete device herein described is par ticularly applicable to control of the duration of the time for supplying electrical heat in so-oalled permanent waving devices used by hairdressers.

Assuming connection of two circuit wires to the respective binding screws I08 and IN, it will be apparent that upon snap operation of the switch to circuit interrupting position the contractors 90, 9| and 92 will be raised simultaneously to provide six breaks in series between the binding screws I98 and I2I. Binding screw IiI provides for connection of one terminal of a voltmeter with respect to the controlled circuit. The form, composition and arrangement of the stationary contacts are such as to provide a relatively high current carrying and controlling capacity of switch as a whole, while insuring a relatively long life for the switch parts.

The switch base 85 (Figs. 3 and 4;) is provided with an upstanding annular flange I22 of a size to fit within the lower end of casing member It, said base having integral upstanding lugs I23 and I24 which are drilled and tapped, as indicated at I25 and I26, in alinement with radial openings I27 and I28 provided in member IE to receive the shanks of screws H9 and I31! whereby said parts are secured to each other. Base 85 is preferably further provided with tapped recesses l3! and E32 for the reception of screws or bolts (not shown) whereby the unit as a whole may be retained in position with respect to the aforementioned panel or similar support.

As shown in Fig. '7 the pair of bolts (one of which is shown at 62) are provided at their lower ends with reduced and threaded ends i33 and ltd (Fig. 2) which penetrate corresponding openings in base 85 and are secured to the latter by nuts 435 and I36 rotatably received in recesses in the lower surface of said base.

In Fig. 8 I have shown a slight modification wherein a plug jack member l3? is substituted for each of the binding screws I98, ill and i2! aforementioned. Each plug jack is provided with a threaded shank I38 for cooperation with the tapped openings provided in the respective terminal members, such as sea; and as indicated at 39 the inner ends of the threaded shanks are upset over the respective terminal members to rigidly and permanently connect the same. With the device modified in the manner illustrated in Fig. 8 any one of a number of heating devices may be plugged onto the timing device herein described, by merely providing the several heating devlces with female plug connectors for cooperation with the set of plug jacks, such as I31.

As shown in Fig. 3, base 85 is provided centrally thereof with a circular recess M to accommodate one end of cam member 68 and to limit the degree of inward movement of the latter. An opening l ll which communicates with recess Mil is adapted to afford clearance for washer H and the upset end 12 of the shaft. If desired, of course, a sub-recess corresponding in diameter with opening l4! might be provided, a diaphragm integral with base 85 being provided at the rear face of the latter, to render the complete casing substantially dust-tight.

While I have shown the switch parts as arranged to provide six breaks in series in the circuit to be controlled thereby, it is to be understood that various other arrangements of switch parts may be provided. For instance, by providing terminal members individual to therrespective stationary contacts of each set, a switch adapted to control three separate circuits may be produced.

Various other modifications will at once suggest Letters Patent is:

1. In a device of the character described, in combination, a casing, a clock-spring operated timing mechanism carried by said casing, a reciprocable and rotatable shaft engaged with said mechanism for rotation by the latter in one direction, a knob rigidly attached to said shaft at one end of the latter, said knob and said casing having cooperating legends formed thereon to indicate the relative rotary positions thereof, spring means for biasing said knob and said shaft inwardly with respect to said casing, cooperating means on the upper surface of said casing and on said knob to provide for extreme inward movement of the latter in only one rotary position thereof, said knob providing for outward movement of the same and of said shaft against the bias of said spring means whereby said knob and said shaft may be set at will in a given rotary position with respect to said casing, a push-pull switch mechanism associated with said shaft and having a plurality of bridging contactors resiliently biased jointly to one extreme position thereof or the other, and means for effecting snap operation of said bridging contactors jointly to closed circuit and open circuit positions thereof upon outward and inward movements respectively of said shaft. I

2. In a device of the character described, in

combination, a casing, a clock-spring operated timing mechanism carried by said casing, a reciprocable and rotatable shaft engaged with said mechanism for rotation by the latter in one direction, a knob rigidly attached to said shaft at one end of the latter, said knob and said casing having cooperating legends formed thereon to indicate the relative rotary positions thereof, spring means for biasing said knob and said shaft inwardly with respect to said casing, cooperating means on the outer surface of said casing and said knob to provide for extreme inward movement of the latter in only one rotary position thereof, said knob providing for outward movement of the same and of said shaft against the bias of said spring means whereby said knob and said shaft may be set at will in any desired rotary position with respect to said casing, a push-pull switch mechanism associated with said shaft, means for effecting snap operation of said switch mechanism to closed circuit and open circuit positions thereof upon outward and inward movements respectively of said shaft, said last mentioned means comprising a double-cone cam attached to said shaft at the inner end thereof, a garter spring encircling said cam, a cage for said spring, a relatively thin, flat insulating plate attached to said cage, a plurality of bridging contactors carried by said insulating plate, and a plurality of pairs of stationary contacts into and out of engagement with which said contactors are adapted to move.

3. A time controlled switching device, comprising a casing, a clock mechanism carried by said casing, said casing having indicating means formed thereon at the front face thereof, said casing having portions of said front face located in different planes, a shaft member extending inwardly through said front face of the casing, sprin means engaged with said shaft to bias the same to its inner extreme position, a knob attached to the outer end of said shaft, said knob having indicating means formed thereon for cooperation with the, indicating means aforementioned, a projection at the front face of said casing and a cooperating recess in said knob to provide for extreme inward movement of said shaft K under said bias in only one rotary position of said knob, said projection and said knob cooperating in other rotary positions of the latter to prevent inward movement of said shaft under said bias, and a push-pull snap switch mechanism operable by said shaft to make and break circuit with a snap action upon outward and inward movements respectively of the latter.

l. In an electric snap switch, in combination, an insulating base having a substantially central recess formed therein, a plurality of pairs of stationary contacts located upon one face of said base and secured thereto in symmetrical relationship to said recess, a plurality of terminal members, said terminal members being electrically and mechanically connected with certain of said contacts, certain contacts of the several pairs being electrically and mechanically connected with each other, a flat plate of insulating material overlying said pairs of staionary contacts, a num- 7.

ber of bridging contactors interposed between the respective pairs of contacts and said plate and supported by the latter with a predetermined degree of lostmotion, said plate having a plurality of notches formed in the periphery thereof, a corresponding number of studs secured to said base and cooperating with thewalls of said notches to assist in guiding said plate and to restrain the latter against rotation relatively to said base, said studs having heads formed thereon to limit the degree of movement ofsaid plate away from said base, a frame member secured to said plate, said plate and said frame member having openings formed thereinin alinement with said base recess, a garter-spring positioned betweensaid plate and said frame member, a double-cone cam member having the portion of greatest diameter at a point intermediate the length thereof, said cam member being adapted upon movement thereof to each extreme position to effect movement of said plate in the opposite direction with a snap action through the medium of said spring, and means comprising a rod rigidly attached to said cam member to provide for movement of said parts in the manner aforedescribed.

5. In an electric snap switch of the push-pull type, in combination, an insulating base, a plurality of sets of stationary contacts secured to one surface of said base, a flat plate of insulating material positioned above said sets of contacts, a plurality of flat substantially circular contactors supported by said plate in a manner to provide for rotation and a predetermined degree of tilting movement of the former with respect to the latter, said contactors being movable joint- 1y by said plate into and out of engagement with the respective sets of contacts, said plate and said base having cooperating means to restrain the former against rotation with respect to the latter and to limit the degree of movement of said plate away from said base, a metal frame member positioned upon and secured to the surface of said plate remote from the contacts, said plate and said frame member having alined openings formed therein, a double-cone cam member movable through said openings, a garter spring surrounding said cam member and positioned between said plate and said frame, said spring cooperating with said plate and said frame member to effect snap movements of said plate to opposite extreme positions thereof upon reciprocating movement of said cam member in reverse directions respectively, means including a member attached to said cam member for effecting reciprocating movements of the latter in reverse directions respectively, and associated means for limiting the degree of reciprocating movement of said cam member in each direction.

6. In a device of the character described, in combination, a contactor carrier for electric snap switches of the push-pull type, said carrier comprising a substantially circular fiat punched plate of insulating material, a metal frame member positioned upon the upper surface of said plate, said plate and said frame member having alined openings formed therein to provide clearance for a cam member of the double-cone type, a garter spring held captive between said plate and said frame member and adapted to surround said cam member in all positions of the latter, said base having guiding means associated therewith and said plate being formed at the periphery thereof for cooperation with said guiding means, and a plurality of bridging contactors carried by said plate at the lower surface thereof and tiltable with respect thereto, said contactors being adapted for cooperationwith sets of contacts of suitableform.

7. In a device of the character described, in combination, a contactor carrier for electric snap switches of the push-pull type, said carrier comprising a substantially circular fiat punched plate of insulating material, a metal frame member positionedupon the upper surface of said plate, said plate and said frame member having alined openings formed therein to provide clearance for a cam member of the double-cone type, a garter spring held captive between said plate and said frame member and adapted to surround said cam memberin all positions of the latter, said base having vertical" guiding means associated therewith and said plate having a plurality of notches formed in the periphery thereof for cooperation with said guiding means, said plate having a plurality of symmetrically arranged studs rigidly attached thereto at points spaced inwardly from the periphery thereof, each stud having a head portion projecting downwardly from the lower surface of said plate, and a corresponding number of bridging contactors rotatably and tiltably supported by said head portions for cooperation with sets of stationary contacts of suitable form.

8. In a device of the character described, in combination, a contactor carrier for electric snap switches of the push-pull type, said carrier comprising a substantially circular flat punched plate of insulating material, a, metal frame member positioned upon the upper surface of said plate, said plate and said frame member having alined openings formed therein to provide clearance for a cam member of the double-cone type, a garter spring held captive between said plate and said frame member and adapted to surround said cam member in all positions of the latter, said plate having a plurality of notches formed in the periphery thereof for cooperation with guiding means of suitable form, said plate having a plurality of symmetrically arranged studs rigidly attached thereto at points spaced inwardly from the periphery thereof, each stud having a head portion projecting downwardly from the lower surface of said plate, a corresponding number of bridging contactors rotatably and tiltably supported by said head portions for cooperation with sets of stationary contacts of suitable form, each of said contactors comprising a punched and stamped disk of composite sheet metal, the lower surface of each disk consisting of a layer of silver and the upper surface of each disk consisting of a layer of copper.

9. As an article of manufacture, a bridging contactor for electric snap switches of the pushpull type, said contactor consisting of a punched and stamped composite metal member of substantially circular contour, said member having a centrally located circular depression formed therein and opening to the lower surface thereof, said member having a central opening of circular contour within the area of said depression, said depression and said opening being respectively adapted to accommodate the head and shank of a supporting member of suitable form, the lower portion of the thickness of said metal member consisting of silver, and the upper portion of such thickness consisting of copper.

10. In a device of the character described, in combination, a clockwork timing mechanism, a casing enclosing the same, a shaft located within said casing and having a portion projecting from the forward face of the latter, said shaft being 7 rotatable and reciprocable with respect to said casing, a manually operable knob rigidly attached to the projecting portion of said shaft, spring means normally biasing said shaft toward its inner extreme position, cooperating means on said knob and said casing at the outer surface of the latter to restrain said shaft against inward movement under said bias except in one rotary position thereof, a spring associated with said clockwork mechanism and said shaft to be tensioned by the latter upon rotation thereof in one direction, associated means including the aforementioned restraining means for restraining said shaft against rotation pending movement thereof to its outer extreme position against said bias, said spring acting to return said shaft to said one rotary position thereof within a predeter'-- mined period of time depending upon the degree of manual rotation of said knob, said shaft when so returned being movable by said spring means to its inner extreme position, means associated with said casing and said knob to indicate the time period selected by adjustment of the latter, an electric snap switch of the push-pull type associated with said shaft at the inner end of the latter, said switch being operable by said shaft to closed circuit position upon movement of the latter to its outer extreme position, and said switch being operable by said shaft to open circuit position upon movement of the latter to its inner extreme position.

GEORGE J. MEUER.

Images