US2251315A - Switch - Google Patents

Description

Aug5 1941- P. s. BEAR 2,251,315

' SWITCH Filed March 2, 1938 3 Sheets-Sheet 1 Aug 5, 1941. p. SjBEAR# '2,251,315'

swIvTcH Filed March 2, 1958 5 Sheets-Sheet 2 if yfmfwww P. S. BEAR Aug 5, 1941.

5 sheets-smet s SWITCH Filed March 2, 1958 INVENTOR. P/V 6- BERE #22M/775.' MMM A TTORN E YS.

Patented Aug. 5, i941 SWITCH Paul S. Bear, Elkhart, Ind., assigner, by mesne assignments, to Bucklen-Bear Laboratories, Inc., Elkhart, Ind., a corporation of Indiana Application March Z, 1938, Serial No. 193,464

(Cl. 20G-152) l Claims.

This invention relates to switches, and more particularly is directed to a switch of the metallic envelope type using a liquid contactor formaking and breaking the circuit through the switch.

The present application is directed generally to switch structures of the type shown in my copending application, Serial No. 745,842, filed September 28, 1934, of which this application is a c-ontinuation in part, with certain modifications and improvements in the structure oi the switch and certain improvements in the manner of enclosing the switch for use in various situations.

It is one of the primary objects of my invention to provide a switch structure of the type having a metal envelope or shell closed at one end, and arranged at the opposite end to receive a ceramic insert which in turn supports an electrode within the open end of the envelope. The open end of the shell is spun over to secure the insert and electrode in xed position within the switch envelope and to provide an effective seal. Suitable gasket means are provided between the insert and the envelope and between the electrode and the insert for preventing any leakage therethrough. In the preferred embodiment of the present invention, such gasket means are of a type capable ci withstanding relatively high pressures and temperatures which may be employed in situations Where the switch envelope is subjected to high temperatures, or where relaf tively high internal pressures may develop.

Another feature of the present invention is the provision of a novel type of terminal lug construction for facilitating the connection of terminal conductors to the terminal points of the switch structure. This type of terminal construction is especially desirable when the switch envelope is to be enclosed within a case member such as a molded case or the like as described in detail in my copending application Serial No. 53,146, filed December 6, 1935, now Patent No. 2,132,921, issued October 11, i938.

Another feature of the present invention is the provision of a switch structure provided with suitable gaskets which means and have the characteristic of withstanding high temperatures caused by the coating of the switch with rubber or the like.

I have found that one of the restrictions against use of glass some of the earlier forms of the metal envelope switches, has been the inability to immerse the same in hot solutions, acids, alkalies, vapors or the like. With the construction disclosed herein, I `am able to provide a mercury switch which are effective as sealing type mercury switches, or

can be directly immersed in hot acid solutions, alkaline solutions, or any other deteriorating solutions, without in any way affecting the switch envelope, switch parts or operating. mechanisms. This is accomplished by coating the entire switch envelope and leads with a relatively heavy coating of material such as Neoprene or a similar chemical and temperature resisting material.

The switch if coated in this manner is entirely covered, together with its leads, by a coating of sufficient thickness to prevent any possible contact of the switch parts with the solution in which it may be immersed. However, in order to apply such a coating to the switch, relatively high temperatures are necessary for vulcanizing, and it is therefore essential that the gasket means in the switch be of a construction such that they will withstand these temperatures without any loss of sealing ability or resiliency.

For this reason I preferably employ a metallic asbestos gasket, or gaskets, comprising a copper, stainless steel, or aluminum sheet enclosing the asbestos, which are readily deformable under pressure into sealing engagement between Vthe respective parts, and are able to withstand relatively high temperatures 4and pressures without any loss of effectiveness as a sealing means.

It is also an object of the present invention to provide a double circuit switchcontrol mechani'sm, which embodies two metal envelope switches of the type employed herein, soldered, or otherwise secured in end to end relation so that tilting of the switch in either direction causes opening of one circuit and closing of a second circuit. With such a construction I have provided also a novel type of molded enclosing case which is formed to fit closely about the switch parts, and provides a full. protection for the switch against corrosive atmospheric conditions or the like, and also enhances, to an appreciable extent, the appearance of the switch itself. With such a construction, I preferably incorporate our novel terminal lug assembly to facilitate the connection and disconnection of conductors to the terminals of the switch.

Other objects and advantages of the present invention will appear more fully from the following detailed description, which taken in conjunction with the accompanying drawings, will disclose to those skilled in the art the particular construction and operation of a preferred form of the present invention.

In the drawings:

Figure 1 is an elevational view, partly in secy tion, of a switch envelope constructed in accordance with the present invention;

Figure 2 is an enlarged elevational view of one end of the completed switch;

Figure 3 is an end elevational View of the portion of the switch shown in Figure 2;

Figure 4 shows a modied manner of attaching 'a terminal co-nductor to a switch terminal;

Figure 5 shows the completed connection of Figure 4;

Figure 6 is an eleva'tional view of a switch covered with a protective coating, the switch per se being shown in dotted lines;

Figure 7 shows the switch of Figure 6 in plan;

Figure 8 is an enlarged view of one of the members used to form a molded casing for a double acting switch structure;

Figure 9 is an end elevational view of the member shown in Figure 8;

Figure 10 is an elevational View of a double acting switch structure;

Figure 1'1 is an elevational view of the switch structure shown in Figure 10 provided with the molded cover of Figures 8 and 9;

Figure 12 is `a sectional View thorugh a modified form of switch employing the gasket means of the switch shown in Figure 1;

VFigure 13 is a transverse sectional view through a switch operating in the 'manner of the switch shown in Figure 1'2;

Figure 14 is a sectional view through the switch shown in Figure 13; and

Figure 15 is a View showing the switch in Figure 13 in switch closed position.

VReferring now in detail to the drawings, I l

have shown in Figure 1 a metallic switch envelope 5 which is preferably a drawn metal shell having the closed end 6 and an enlarged cylindrical end 'I joined to the main body portion by the frusto-conical shoulder 8. the enlarged open end 'I of theswitch is a ceramic insert 9 having the tapered bore I0 opening toward the elongated body portion of the shell 5.

At its smaller end the bore IIJ terminates in a radially extending shoulder I2 which forms an acute angled cutting edge of the type described in detail in my lcopending application, Serial No. 53,146, filed December 6, 1935. .At the outer periphery of the shoulder I2 an axially extending cylindrical wall I3 is provided which terminates in a radially outwardly extending shoulder I4 separated from the external surface of the insert by the cylindrical flange I5.

Disposed between the external tapered surface of the insert 9 and the internal surface of the frusto-conical shoulder 8 I provide a gasket member I6 of frusto--conical form, this gasket member consisting of a metallic annulus I'I which encloses an asbestos annulus I8. Axial pressure on the insert 9 is adapted to compress *the metallic asbestos gasket I6 into sealing en gagement between the insert and the shoulder 8 to provide a seal for effectively preventing loss of pressure therebetween.

Seated in the annular opening defined by the sur-face I3 is an electrode 2U having a peripheral Vshoulder 22 seated against a similar metallic asbestos gasket 23 which bears against `the shoul- Axial pressure on the der I4 ofV the insert. Velectrode therefore results in compression of the gasket 23 to provide an effective seal between the interior of the insent 9 and the electrode 2li. The front or inner radial face of the electrode 20 forms with the shoulder I2 an annular groove Disposed within f which is adapted to retain a body of mercury 24 in stable position therein. This retention of the stable body of mercury is for the purpose of insuring positive repeat performance of the switch; that is to say, the switch will open and close the circuit at the same operating angles due to the retained body of mercury 24 being of such volume as to retain its stability and position regardless of the inclination of the switch within the operating range. A second body of mercury 25 is disposed within the body portion of the shell 5 and is adapted to move up and down the surface of the bore I8 into and out of contact with the stable body of mercury 24 to make and break the -circuit lthrough the switch.

The electrode 20 has an outwardly extending shank portion 26 which serves as one terminal of the switch, and which is adapted to project through a ceramic spacing member 2'I preferably formed of a thermally refractive member, such as described in detail in the copending application of Herbert E. Bucklen and myself Serial No, 148,946, filed June 18, 1937. A compression washer 28 preferably of metal, engages about the shoulder formed on the spacing mem# ber 21, and in the assembly of the switch structure is suitably engaged by pressure head for moving the entire insert and electrode assembly axially into the envelope 5 to compress the gaskets I6 and 23, and to hold the same in positive sealed position while suitable spinning rolls engage 'the outer end of the enlarged portion 'I of the shell and spin the same over as indicated at 29 to thereby hold the assembly in sealed position. With such a construction, the assembly is :capable of withstanding internal pressures in excess of 4,000 pounds per square inch with no leakage or destruction of the parts.

.After the insert and electrode have been sealed in position in the enlarged end of the switch, the mercury is introduced through the tapped opening 32 in the small end of the switch, andl the internal volume of the switch is then evacuated thoroughly and the switch is sealed by means of the sealing plug 33. If desired, a liquid ll of the type disclosed in detail in my cepending appli-cation, Serial No. 745,842, filed September 28, 1934, may be introduced into the interior of the envelope for the purpose of increasing the meniscus height of the mercury and for increasing the heat dissipatng characteristics and stability of operation of the switch.

The switch is preferably enclosed within a molded Bakelite casing consisting of a body member 35 which has the frusto-conical portion 36 tting over the shoulder 8, and has the enlarged extending portion 3'! projecting beyond |the spun over end of the shell. A suitable cap member 38 has la rabbeted engagement in the end of the portion 31, and is suitably secured thereto by means of cement or the like asy disclosed in detail in said copending application, Serial No. 148,946, filed June 18, 1937.

In order to provide for connection of conductors to the terminals of the switch I preferably provide a terminal lug 4'D as shown in Figure 3 which lies upon and is soldered or otherwise mechanically and electrically connected to the spun over edge 29 of the shell. This lug has an outwardly extending portion 42 which is bent over to form 'a lip 43 suitably tapped to receive the screw 44, The portion 42 isof a length `such that the bent over portion 43 lies substantially adjacent the external surface of the case 3'I. The terminal conductors may be secured to the lug 4U by the threaded engagement of th-e screw 44 therein.

The terminal lug for the electrode 20 consists of a body member 45 which engages about the projecting end of the shank 26, and which is suitably soldered or otherwise secured thereto. This lug has a bent over end 46 suitably tapped to receive the screw 47 whereby a terminal conduotor may be secured thereto. Thus, a positive electrical connection is extended from both the shell 5 and the electrode 20 to the external surface of the switch, and the terminal conductors may be secured thereto in any suitable manner. This facilitates the shipping of the switches in small size cartons, and prevents possible damage to terminal conductors which might occur if they were fastened to the switch prior to shipping.

In place of the lugs shown in Figures 2 and 3, I may, if desired, provide radially projecting studs 50 and 52 as shown in Figure 4, which supplant the bent over lips 43 and 46. The terminal conductors may be secured to the studs in the manner indicated in Figure 4, conductor 53 being wound about the stud as indicated, and then suitably soldered or otherwise electrically connected thereto. Ordinarily, the end of the insulation 54 on the conductor 53 will be frayed, and to prevent further unraveling thereof and to protect the connection, I preferably provide a short length of tubing 55 which may consist of varnished cambric tubing or the like that ts over the insulation and encloses the connection of the conductor 53 with the stud 52 or 50.

Considering now in detail the modication of the invention shown in Figures 6 and 7, it will be noted that I provide the standard metallic envelope type of switch case, such as indicated at 5, and which may comprise the switch shown in Figure l. Corresponding reference numerals are applied to the switch itself for the purpose of identification. The envelope 5 with the conductors Bil and 62 connected respectively to the shell 5 and the electrode shank 26 is placed within a suitable mold cavity, and the coating is flowed therearound and vulcanized thereto in such manner as to provide a complete covering for the envelope 5 and the sealed end thereof, which coating or covering 65 has the extension 65 forming a reinforcing boss through which the conductors 60 and 62 are led out and the rubber coating is carried and continued along the conductors as indicated at B'l and 68. This, in effect, provides a totally vulcanized covering over the entire switch and the conductor which seals the switch itself, and also provides a protective coating over the conductors so that the switch and portions of the conductors may be subjected to corrosive atmospheres, acid or alkali solutions, hot oils and the like without any detrimental action.

I prefer to use a rubber of the Neoprene type impervious to the action of acidic or basic solutions, and oils of the type used for transformers or for bearing lubrication and the like. This rubber coating may be applied to the switch case by flowing the same about the switch case within a molded cavity and then heating the same under pressure to vulcanize it securely about the case and conductor leads.

In the form of the invention shown in Figures 8 to 11 I rst provide a double ended switch structure of the type shown in Figure 10 in which two switch cases 'lll and 'l2 are soldered or otherwise mechanically secured together, and electrically bonded at their small ends as indicated 3 at 73. The conductor 'I4 forms a terminal lead to the switch case 15, and consequently through the connection 13 to the switch case 12.

The shank 15 of the electrode carried within the ceramic spacer le of the switch 10 has a suitable conductor 'Il connected thereto whereby one circuit is controlled by the mercury making and breaking contact within the switch case 10 and closing the circuit between the conductors 14 and TI.

The shank 'I3 of the electrode carried by the switch case 'I2 has a conductor 'i9 connected thereto. The movement of the mercury in the switch case 'l2 controls the circuit between the conductors 14 and 19.

It will be apparent that when the unit asa whole is rotated or tilted in a clockwise direction, the circuit in switch case 'Ill will be opened and the circuit in switch case 'I2 will be closed, thereby closing the circuit between the conductors 14 and l. When rotated in the opposite direction, this circuit is opened and the circuit between the conductors 'lil and il is closed within the switch case "i0, Therefore, the unit is capable of making and breaking two independent circuits upon alternate operations.

In order to protect the structure shown in Figure 10 I preferably provide a molded case formed of insulating material such as a phenol condensation product, which is formed in two halves, one of the sections being shown in Figure 8 and indicated generally by the numeral Sil. This section is generally semi-cylindrical in form with enlarged end portions 82 and $3 which respectively engage over the enlarged ends of the switch cases l'il and T2. The one defining lateral edge of the member 8i! is provided with a tongue formation such as indicated at 84 in Figure 9, while the opposite lateral edge is provided with the groove indicated at 85. Two such members formed in the same manner are tted together over the construction shown in Figure 10, and are suitably sealed together along the tongue and groove engaging edges indicated by the line 86 in Figure 11. End cap members 88 and 8d are provided for closing the ends of the switch cases 'lil and 12, and may have rabbeted engagement in the ends 82 and 83 of the members 8b. Preferably, suitable notches 90 are formed in the switch caps for leading out the two conductors Tl and I9. One of the members 8i! may also be provided with a notch as indicated at 92, whereby the conductors M may be passed through the case Bil and connected to the shell of one of the switch cases 1i) and l2. In order to secure the cap members 88 and 89 positively in position, suitable sealing compound of the type described in detail in said copending application, Serial No. 148,946, filed June 18, 1937, is provided, which positively secures the cap members to the ceramic spacer 16 and over the electrode connections.

Referring now in more detail to the structure shown in Figure 12, the switch herein disclosed is of the type operated by rotation of the switch about its longitudinal axis.

In the preferred form of the structure I provide a base lili? having the two supporting stands |62 and |03 which, at their upper ends. provide journals for mounting th-e switch case m4 for rotation. The switch idd is provided with the body portion forming one chamber i215, and with an enlarged end portion lilii joined thereto by the frusto-conical section lill. The member 664 is preferably of drawn metal and provides a cupshaped shell which farms one electrode for the switch.

Disposed within fractory insuiator |98,

the switch is a ceramic or rewhich has a tapered portion spaced from the tapered portion itil of the shell by a metallic asbestos gasket its correspending to the gasket IS of Figure i. The meri ber |63 is provided with an axially directed recess l'l which is shouldered as indicated at i i to provide a seat for the electrode H2, which electrode has the iiange portion il spaced from the shoulder |i| by means of a inetailic asbestos gasket H4 of a type similar to that shown at iii in Figure 1.

In order to provide for increased surface contact between the body of mercury ifi-5 and the electrode H2, I preferably recess the inner` face of the electrode, as indicated at iii, to thereby provide an increased area of surface with which the mercury is in contact.

The electrode H2 is held in position by a refractory compression lil which prefern ably is formed of a material having relativeiy good heat conductivity. The compression meinber is held in position by a compression ring I I8 which is forced inwardly against the shoulder on the compression member to force the electrode H2 and the ceramic Hi8 axially inwardly of the shell by beading or spinning over the edge i iii of the shell |06. This locks the parts in fixed position and provides for compression of the gaskets |09 and ||3 so as to prevent leakage 0i pressure therepast toward the open end of the shell. A suitable insulating member i125 is disposed about the shank |22 of the electrode lill to space the shell from the standard i, and to thereby insulate the shell therefrom and from the shank |22.

The shank |22 is journalled in 'the standard |03 and has electrical Contact therewith. At its outer end it is preferably provided with an arm |24 having a pin |125 projecting therefrom which is adapted to be engaged by any suitable actuating mechanism or by a thermally responsive member if the switch is employed with temperature controlling mechanism. Rotation of the arm iii results in rotation of the switch It@ in the journals it?, and i3?, the switch being evacuated through the end li oi' the shell, which is closed by a threaded plug forms the journal for the switch envelope in the standard |32.

The inner end of the ceramic is provided with a septum |28 which is provided with a relatively small opening |2i of a size the meniscus height oi a body of mercury. Through this opening the bodies of mercury |35) and H5 have contacting engagement when the switch is rotated to a position such that the opening |29 is below the level oi mercury in the chamber |05 and in the chamber i IEB. Rotation of the switch in such manner as to bring the opening |29 above this level will csult in breaking of contact between the shell itil and electrode |52, the parting of the mercury bodies over the edge of the opening |29 effecting this breaking o contact. It will be noted that the defining edges of the opening i253 are of a shape such that the making and breaking of contact will occur at substantially the mid-plane of the opening, and will produce a relatively sharp action whereby the surface tension of the mercury will eifect a snap action opening and closing of the circuit and thus reduce the tendency to arcing in the switch.

I may employ a partial li uid ll over the merin connection :ci that alsa f slightly larger than f cury in a switch of this type, such as described in detail in my copending application, Serial No. 745,842, iiled September 28, 1984, in the nature of an ethanolamine, such as triethanolamine. With such a liquid the rate of movement in opening and closing the circuit will not have any serious tendency to produce excessive arcing in the switch, even when the switch is rotated very slowly under the influence of a thermally sensitive or 'humidity sensitive member.

In the embodiment of the invention shown in Figures 13 to 15, inclusive, I have disclosed a switch comprising a refractory separating member, indicated at |35, which is provided with a central portion of reduced diameter, having the web |35 partially closing the same and forming the passageway |31 between opposite ends of the member |55. Preferably, the web |36 is provided with a defining edge of spade-like section as indicated at |33 providing a sharp point over which the two bodies of mercury |46 and H52 contact and part in closing and opening of the switch.

In this form of switch, the member |35 is adapted to receive electrodes in the form of cup members |63 and idd at opposite ends thereof which are suitably secured to the member |35 and preferably are sealed with respect thereto by the gaskets |i5 and |555. Suitable electrical conductors Uil and Hi8 are connected to the respective electrodes and from the terminals of the switch. The entire switch is preferably coated with a cellulose acetate coating, indicated at |42, which entirely seals the switch and provides a protective coating thereover which may be colored in any desired manner for distinctive appearance.

In the operation of a switch of the type shown in Figures 13y to 15, rotation of the switch about its longitudinal axis produces closing of the switch by moving the web |36 from the position shown in Figure 13 to the position shown in Figure 15, in which it has been rotated out of position between the two bodies of mercury lli and H12, and the two bodies of mercury have consequently run together over the sharp edged peak of the defining edge Hi8 of the web. Similarly, when the switch is rotated from the position shown in Figure i5 to that shown in Figure 13, the web ISS forces its way through the body of mercury and parts the same over the dening edge |33 into the separate bodies |45 and |42, each of which is in contact with the respective electrodes M3 and Mii. The sharp edge on the web |35 insures a sharp breaking and making of Contact, and results in a snap action eiiect which prevents excessive arcing within the switch chamber. Preferably, the switch chamber is evacuated vthrough one of the electrodes, and the opening is then securely sealed by means of the plug |50.

The switch may be rotated in any suitable manner, such as by a plunger, having rocking engagement with the switch or by means of a rack meshing with a serrated surface |49 of the switch, or in any other suitable manner. In practice, the switch is never completely rotated, but oscillates between the position shown in Figure 13 and in Figure 15.

It is therefore believed that I have provided a switch structure which may be suitably sealed to withstand the high temperature required in vulcanizing a rubber covering thereover. Also this construction is capable of use to provide a double ended switch which may be enclosed within a suitable molded case for protection against atmosphere, or might be enclosed in a rubber covered case for protection against chemical solutions or hot oils in which the switch might be immersed.

While I am aware that many changes in details of construction might be made in the illustrated embodiments of the invention, I do not intend to be limited, except as defined by the scope and spirit of the appended claims.

I claim:

1. Gasket means for use in a mercury switch structure of the type having a cup-shaped rnetallic shell with a frusto-conical shoulder separating portions of different diameters, a ceramic insert in the enlarged portion of the shell having an external frusto-conical shoulder, an axial bore in the insert having a cylindrical shouldered recess at the outer end thereof, rand an electrode of disc shape seated in the shouldered recess, comprising metal enclosed asbestos gasket rings between the electrode and the shoulder on the recess and between the shell shoulder and said frusto-conical insert shoulder.

2. In a mercury switch, a cup-shaped metallic envelope, a ceramic insert sealed in the open end of said envelope, an electrode centered in said insert and having a projecting shank, said envelope having an arcuate lug member secured radially to the end thereof and having an extending end` directed axially of the envelope and radially spaced therefrom, a second lug secured to said shank and having a corresponding directed end, and an enclosing molded case for said switch having notches therein in which said lug ends are disposed.

3. In a metal envelope type mercury switch, said envelope having a radially inwardly directed end flange, a terminal lug comprising a planar curved body portion engaging said flange and having a radially outwardly directed end terminating in a normally extending apertured lip, and a molded insulating case covering said envelope and having an opening in which said lip is adapted to be located.

4. A switch structure comprising two metallic cup shaped shells disposed in axial alinement with their closed ends joined together, a ceramic insert sealed in the open end of each shell and centering an electrode therein, bodies of mercury movable in said shells and additional bodies of mercury retained by said inserts in contact with said electrodes whereby tilting of said switch results in closing the circuit in one switch and simultaneously opening the circuit in the other switch, and an insulating case including two similar semi-cylindrical members enclosing the annular surface of said structure and end cap pieces secured to the adjacent ends of said members, each of said end cap pieces having notches for leading out conductors, one end of one of said semi-cylindrical members also having a correspending notch.

5. A closure for a double switch structure of the type comprising two individually complete metal envelope mercury switches having enlarged end portions and cylindrical closed body portions, means securing said body portions together with the end portions extending in opposite directions, comprise a multiple piece insulating case formed of two semi-cylindrical body members and two end cap members entirely closing the lateral and end surfaces of said structure, said semi-cylindrical body members having enlarged end portions corresponding to the enlarged 7 end portions of said switches.

- ating with the envelope 6. The combination, with a double switch structure comprising two individually complete metal envelope mercury switches having enlarged end portions and cylindrical closed body portions, and means securing said body portions together with the end portions extending in opposite directions, of an insulating case entirely closing the lateral and end surfaces of said structure, said casing comprising two body members having semi-cylindrical central portions with enlarged arcuate ends for enclosing the lateral surface of the structure, and two disc-like cap members secured in cylinders defined by the enlarged ends of said members for completing the enclosure.

7. In a metal envelope type mercury switch having an electrode therein radially insulated from the envelope and provided with an axially projecting shank, a terminal lug having an apertured end fitting over said shank and projecting radially therefrom in axially spaced relation to said envelope, the opposite end of said lug terminating in a normally extending apertured lip, and a molded case enclosing said envelope and shank and having an opening registering with said lip.

8. A mercury switch comprising a cup-shaped metal shell having an enlarged open end, a ceramic insert in said end having a cylindrical recess, a radial flange on said insert extending across the inner end of said recess and having an olf-center opening therein, an electrode centered in and closing the outer end of said recess and radially insulated from said shell by said insert, said electrode being disposed entirely within the outer end of said insert and having a projecting shank, an insulating member laterally enclosing said shank and telescoping into the outer end of said insert, and mercury bodies in contact with said shell and with said electrode and adapted to contact through said opening upon predetermined rotation of said switch.

9. A mercury switch comprising a cup-shaped metallic envelope having an enlarged open end, an insulating insert having a shoulder cooperment of said insert into said envelope, a soft metallic enclosed asbestos gasket means between said shoulder and envelope, said insert having an axial bore terminating at its outer end in a radially extending recessed shoulder, an electrode having a disc portion closing said bore and a radial flange, corresponding gasket means between said bore shoulder and said flange, an insulating rigid compression member engaging the outer face of said electrode, and means at the open end of said envelope for axially compressing said flange and insert against said gasket means.

10. The switch of claim 9 further characterized in that said compression member telescopes partially into the shouldered portion of the bore to enclose the disc and flange portions in the insert.

11. In a mercury switch comprising a metallic cup-shaped envelope having an intermediate shoulder and an enlarged open end, an insulating insert in said end and seated against said shoulder, said insert having an axial bore terminating at the outer end in a radial wall and an enlarged end bore portion, an electrode having a contact portion seated in said bore and having a radial ange seated in said end bore portion and of less axial extent, and an insulating compression member partially telescoping into said end bore portion against the radial outer face of said flange.

12. The combination of claim 11 further char- 6 acterized in that said compression member has a reduced cylindrical portion extending axially beyond the open `end of said envelope, and means engaging between the shoulder on said compression member and the spun-over envelope end for holding said assembled parts under pressure.

13. The combination of claim 11 further characterized in that the inner end of said bore is terminated by `an integral radial flange having an oil-center aperture therein providing cornmunication between said bore and the interior of said envelope.

14. In combination, a mercury switch comprising a cup-shaped metal envelope having an enlarged open end, a ceramic insert in said end having a cylindrical chamber therein dened at the outer end by a radial shoulder and an annular axially extending flange, a metal electrode disc closing said end of said chamber and centered Within said ange, gasket means between said shoulder and said disc, insulating compression means centered in said flange against the outer face of said electrode. said insert having a radial ange extending across the opposite end of said chamber and provided with an off-center aperture, and bodies of mercury in said envelope and chamber adapted to make and break contact through said aperture upon rotation of said switch.

15. The combination of claim 14 wherein said disc has an axially recessed extension telescoping into said chamber and contacted in all rotated positions of said switch by the mercury in said chamber.

' PAUL S. BEAR.

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