US2342354A - Metal-clad switch - Google Patents

Description

Feb. 22, 1944. R. P. MATTERN METAL CLAD SWITCH Filed Aug. 9, 1941 Patented Feb. 22, 1944 METAL-CLAD SWITCH `Raymond P. Mattern, Minneapolis, Minn., alsignor to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application August 9, 1941, Serial No. 406,130

- 14 claims. (ci. 20o- 152) The present invention is directed broadly to a switch of the type in which electrically conductive fluid, such as mercury, makes and breaks an electric circuit by bridging and unbridging a pair of electrodes. The invention is more particularly concerned with a metal clad switch; that is, a switch in which the envelope containing the mercury is made of metal.

In such switches the metal casing is made in two parts which are separated electrically by a partition of insulating material upon which the two parts of the casing are seated. The partition is provided with an opening so arranged that for certain positions of the switch the partition separates the mercury into two separate pools, at which time the circuit through the switch is broken, and for certain other postions of the switch the two pools of mercury are Joined through-the 'opening in the partition, at which time the circuit through the switch is made. 'Ihese switches may be divided into two general types, one the rotating or "button type, the other the tilting or tubular type. My invention is applicable to both types.

One oi' the principal problems in the design of a metal clad switch is in getting the proper seal between the two metal parts or cups which form the casing. 'Ihese switches are usually pumped and then filled with hydrogen in order tofsuppress arcing and reduce the heat generated in making and breaking the circuit through the switch. It is therefore very imporvent air from getting in and hydrogen from getting out. It has been found that glass is the best seal, mainly because it thoroughly wets the two metal cups when it is in its plastic form and therefore is in intimate contact with them when it hardens.4

Another problem encountered in the design of a metal clad switch is the choice of a proper composed roughly oi about 27% chromium and the rest iron. 'I'his metal has about the same ythermal expansion characteristics as the glass which seals the two cups together. It has been found however that the thermal expansion characteristics of the lava or molded ceramics which have all of the other desirable characteristics diiler somewhat from those of the metal and glass.

It is therefore a prime object of the present invention to design a metal clad switch in which the glass which seals the two metal cups together is spaced from the partition to allow for differences in thermal expansion characteristics.

A further object is to space the glass from the partition by means oi a resilient washer made of some suitable material such as asbestos. Asbestos is chosen because this washer must resist the heat of fusion of the glass.

It has been found that the mercury does not wet the metal cups very well and therefore the electrical resistance between the mercury and the'cups is fairly high. It is a further object of the invention to avoid this difliculty by welding some metal which is readily wet by mercury, to the cups to reduce the electrical resistance between the mercury and the cups. object to so locate these metals that they are submerged in the mercury before the two pools of mercury are connected through the opening in the partition. This tends to prevent the arc A tant that the switch be perfectly sealed to prematerial for the partition. This material must been found through experience and testing that a very high grade of lava makes an excellent partition as well as certain molded ceramics having substantially the same characteristics as lava.

The metal chosen for the two metal cups is from striking directly to the metal cups.

In certain instances it is desired that the rotating type switch be made so that it will break the circuit when it is rotated slightly in either direction from its circuit closed" position. With a single hole through the partition it requires considerable rotation in either direction to raise the hole out of the`mercury to break the circuit through the switch.

It is an object of the present invention to overcome the above diiliculty by staggering the opening through the partition so that one end of the hole can be raised out of the mercury by a slight rotation of the switch in one direction, and the other end of the hole can be raised out of the mercury by a. slight rotation of the switch in the opposite direction. It is a further object to make the partition in two parts which are rotatably adjustable with respect to each other so that the angle of rotation of the switch in each direction necessary to break the circuit may be predetermined.

These and other objects will readily become apparent as the following specification is read in It is also anl f the light oi the accompanying drawing, in which:

Figure i is an end view illustrating the rotary or button type switch, this view being a section taken along the line i--i of Figure 2;

Figure 2 is a center section oi the switch shown in Figure 1 and taken along the line 2-2 of Figure l;

Figure 3 is a view similar to that shown in Figure 2, being a center section of a slightly modia ned type of switch showing a two part partition;

Figures 4 and 5 are detailed views of the two parts of the partition shown in Figure 3, and

Figure 6 is a longitudinal section of a tilting or tubular type switch.

Referring now to Figure 2, the two metal cups forming the casing for the switch are indicated at Hand i2. .These two. cups cooperate with a partition i3 which is composed of a high grade of lava or molded ceramic having substantially the same characteristics as lava.. The partition i3 is provided with a circumferential ilange Il which forms a. pair of shoulders I5 and I8. A pair of notches l1 and i8 are cut in the partition i3 and are adapted to receive the projections 2li and 2| of the two cups Il and I2, said cups il and I2 seating respectively on the shoulders i5 and I6.

The cup Il is provided with an open end 23 which is of greater diameter than the cup i2 and which extends over the ilange Il of the par tition i3 and also telescopes over the open end of the cup i2. An asbestos washer 25 is placed against the shoulder I6 and the openrend of thev cup i 2 seats against this washer. In order to seal the interior of the switch from the external atmosphere a. ring oi' glass indicated at 2S is fused and it wets the two metal cups and seals the annular space between the two cups. The glass is also sealed to the asbestos washer 25.

lt will be obvious that the asbestos washer will be capable of absorbing any dierential expension which may occur between the partition iii on the one hand, and the glass and metal cups on the other, due to variations in temperature.

The metal cup i2 is provided with an opening @il through which the switch may be partially illled with some suitable electrically conducting duid indicated at 28. For the purposes of this description this iiuid will be referred to as niercury although any other suitable type oi electrically conductingv fluid may be used il desired.

The air within the interior or the switch is also removed through the opening 2l and the space is lled with hydrogen gas after which a. metal ball is inserted in the opening 2l and welded therein as indicated at llt.

The partition it is provided with an opening indicated at 3i by means of which the two pools ci mercury Si. and @il may be connected when the opening iii is in the position shown in Figure 2. switch is mounted for rotation by means ci resilient washer type blades 8d which may also act as electrical conductors for connecting the switch in an electrical circuit. These blades estacas time the partition will dividethe mercury into two separate pools and therefore break the circuit through the switch. The switch is indicated in Figure l with the operating handle in mid position. In order Yto move the switch to its o& position and break the circuit, the handle is lowered approximately 10 below the horizontal, which action raises the opening 3l above the level of the mercury. In order to move the switch to its on position and close the circuit, the handle is raised to a position about 10 above the horizontal, at which time at least a portion of the opening 3i is below vthe level of mercury.

It has len found that the mercury does not wet the metal cups Il and i 2 satisfactorily and therefore the electrical resistance between the mercury and the cups is-comparatively high, thus increasing the heat generated within the switch when the current is flowing therethrough. In

order to eliminate this difculty, a pair of contact elements indicated at 31 and 38 are welded to the metal cups. These contacts are composed of material which is readily wet by the mercury, preferably nickel, and therefore the resistance between the mercury and these contacts is relatively low. inasmuch as the contacts are welded to the metal cups, the resistance between them is also low and therefore the overall resistance of the switch is reduced by this expedient. It has been found that the shape and position of these contacts as shown in the drawing give the most satisfactory results. lt will be noted that a portion of these contacts are opposite the opening il and thatthey are so positioned that a. portion of them Vis immersed in the mercury 'before the opening Si is lowered suciently to permit the mercury to ilow therethrough and close the circuit through the switch. This assures a good contact between each pool of mercury and its associated metal cup before the circuit is closed through the opening 3i, this action tending to prevent the striking of an arc directly to one of the metal cups.

When the cups il and l2 are formed and the contacts 3l and 3e welded thereto the depressions 2@ and 2i will have a predetermined relaftionship with respect to the contacts 3l and @t so that when the switch is assembled and the depressions are located in the grooves il and it, the contacts 31 and 38 will be positioned properly with. respect to the opening Si. Also when the handle Si@ is located on the switch adjacent.

the depression 2t the switch will be in the proper position to control the circuit when the handle projects through the usual wall plate.

The switch just described is used when it is desired to mount the switch in such a manner that itis always rotated in one direction to break the circuit and in the opposite direction to make the circuit. in some instances, it may be desired to have a switch which in one position makes the circuit but which will break the circuit when rotated a slight amount in either direction from its made position. Ii' the switch shown in Figures il and 2 were to be used for this purpose, the opening .ill would be located in its lowerrnost position iior the made position of the switch. it can readily be seen that a considerable rotation would be necessary in either direction in order to break the circuit through the switch. The switch shown in Figures 3, d and 5 has been cles-igned with a staggered opening through the partition so that a slight rotation of the switch in either direction will cause one or the other of the two ends of the opening to be raised above the tion 66. at which time the circuit through the level of the mercury and therefore break the circuit.

The switch of Figure 3 is provided with a pair of metal cups generally similar to those shown in Figure 2. Ihey are indicated at 40 and 4|. 'I'he partition in this instance is composed of two separate members 42 and 43, each having a cutaway` portion forming an intermediate chamber 44. The member 42 is -provided with an opening 46 and the member 4l is provided with an opening 46, these two openings being offset with re` spect to each other. 'Ihe two parts of the partition are provided with interfitting shoulders indicated at 41 and in assembling the switch the two pieces 42 and 43 are rotated with respect to each other until the two openings 46 and I6 have the correct angular relationship with respect to each other, at which time the two pieces 42 and 43 are connected together by means of a high temperature cement located at 46. The switch is then assembled in the same manner as described in connection with the modification shown in Figures l and 2, being sealed by means of an annular fused glass member 46 which seats against an asbestos washer 66.

Figure 4 illustrates the member 42 and shows the position of the opening 45 withrespect to the vertical. Figure shows themember 46 and indicates the position of its opening 46 with respect to the vertical. Looking at these figures, -it will be seen that a slight rotation of the switch in a counterclockwise direction will cause the opening 46 to be raised above the level of the mercury and break the circuit through the switch and also a slight clockwise rotation of the switch from the position indicated in Figures 4 and 5 will cause the opening 46 to be raised above the level oi the mercury and break the circuit through the switch. This switch is therefore much more sensitive to rotation fin either direction than would be the switch of Figures 1 and 2. Moreover, the two members 42 and 43 may be adjusted rotatably with respect to each other before the switch is assembled in order to predetermine )the angular rotation of the switch in each direction necessary to break the circuit.

It will be understood that this switch maybe filled with mercury and hydrogen through the opening 6| in the same manner as the switch shown in Figure 2. The opening 6| is 'then sealed by means of a metal ball, not shown, which is welded in the opening 6i.

The switch shown in Figure 6 is of the tubular type as distinguished from the button type shown in the first five figures. This switch ris provided with a partition 60 having a rather large center ,opening The partition 66 is provided with a circumferential flange 6I which forms a shoulder 62. A relatively long tube 63 has an enlarged open end 64 forming a shoulder which seats against the shoulder 62 of the partition 60. A smaller metal cup 65 has an open end which telescopes within the open end 64 or tube 66 and seats against an asbestos washer 66, which in turn seats against the opposite side of the flange 6|. Thespace between the open end 64 of the tube 63 and the cup 65 is sealed by means of fused glass, indicated at 61, which is also sealed to the asbestos washer 66 which absorbs any differential of expansion between the partition 66 on the one hand and the glass and metal members on the other.

This switch is adapted to contain a quantity of mercury which in one position of the switch will be divided into two separate pools by the partiswitch will be broken. Tilting .the switch in a counter-clockwise direction, as seen in Figure 6,

' will cause the mercury to flow towards the lefthand end of the switch and close the circuit between the mercury and the metal members, a pair of rings 66 and 66 are welded to the metal members 66 and 66, respectively. These rings are formed of a metal which is readily wet by the mercury, as in the modification shown in Figures 1 and 2. and therefore forms .a good electrical contact therewith. These rings are so positioned that they will be contacted by the mercury at the time the two pools of mercury are joined through the partition 60.

The metal cup 66 is provided with a tubular member 10 through which the switch may be filled with mercury and hydrogen. The tubular member 10 is then sealed off and may be used as one terminal of the switch.

'I'he partition is out away as shown at 1i so that it will retain a larger quantity of mercury when the switch is tilted in a clockwise direction to break the circuit.

It will therefore be seen that I have designed a metal clad switch which may bel efficiently sealed by means of fused glass and which may utilize a partition of any desired material without regard to the thermal expansion characteristics with respect to the glass or the metal portion of the switch. It will further be seen that I have designed a switch which is very sensitive to rotation in either direction from a made position and in which the sensitivity to rotation may be predetermined at the time the switch is assembled. Various changes and modiiloations of the switches disclosed may occur to those who are skilled in the art, and I therefore wish it to be understood that the specific embodiments disclosed are for the purpose of illustrating my invention and that I intend to be limited only by the scope of the appended claims.

I claim as my invention:

1. A switch comprising in combination, a pair of oppositely disposed dished metal cups, a partition of insulating material interposed between said cups separating them electrically, a quantity of lelectrically conductive fluid partially lling said cups, said uid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, an annular member of glass located between said cups andsealed thereto for sealing the interior of said cups from the atmosphere, and a compressible member located between said partition and glass member to prevent said glass member from wetting said partltion, whereby said partition and glass members may expand relatively to each other upon changes in temperature.

2. A switch comprising in combination, a pair of oppositely disposed dished metal cups. a partition of insulating material interposed between said cups separating them electrically, a quantity of electrically conductive fluid partially flllnected through said opening for certain positions of said switch, an annular member of glass located between said cups and sealed thereto for sealing the interior of said cups from the atmosphere, and an asbestos member located between said partition and glass member to prevent said glass member from wetting said partition, whereby said partition and glass members may expand relatively to each other upon changes in temperature.

3. A switch comprising in combination, a pair of oppositely disposed dished metal cups, a partition of insulating material interposed between said cups separating them electrically, a quantity of electrically' conductive fluid partially filling said cups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions I 'of said switch, said cups having relatively telescoping portions, and an annular member of glass located between the telescoping portions of said cups and sealed thereto for sealing the interior of said cups from the atmosphere, said glass member being spaced from said partition to prevent the glass member from wetting said partition, whereby said cups and partition may expand relatively to each other upon changes in temperature.

4. A switch comprising in combination, a pair of oppositely disposed dished metal cups, a partition of insulating material interposedbetween i said cups separating them electrically, a quantity of electrically conductive fluid partially lling said cups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, said cups having relatively telescoping portions, an annular member of glass located between the telescoping portions of said cups and sealed thereto for sealing the interior of said cups from the atmosphere, and a compressible member separating said partition and glass members to prevent the glass member from wetting said partition, whereby said compressible member will absorb any differential expansion between said partition and glass member upon changes in temperature.

5. A switch comprising in combination, iirst and second metal cups, said rst cup having a first portion of substantially the same diameter as said second cup and an open end portion of larger diameter, a cylindrical insulating partition having reduced portions forming opposed shoulders, said second cup fitting over one reduced portion, the rst portion of said iirst cup fitting over said other reduced portion, said larger open end portion of said second cup extending over said 'partition and telescoping with respect to the open end of said second cup, a quantity of electrically conductive iiuid partially iilling said cups, said iiuid being separated into two pools by said partition, an opening in said partition whereby said two pools of fiuid are connected through said opening for certain positions of said switch, and sealing means between the open end portions of said cups for sealing the interior of said cups from the external atmosphere.

6. A switch comprising in combination, first and second metal cups, said first cup having a iirst portion of substantially the same diameter as said secondv cup and an open end portion of larger diameter, a cylindrical insulating partition having reduced portions forming opposed shoulders, said second cup fitting over one reduced portion, the first portion of said first cup fitting over said other reduced portion, said larger open end portion of said second cup extending over said partition and telescoping with respect to the open end of said second cup, a quantity of electrically conductive duid partially lling said cups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, and a glass member sealed between the open end portions of said cups for sealing the interior of said cups from the external air, said glass being spaced from said partition.

7. A switch comprising in combination, first and second metal cups, said first cup having a iirst portion of substantially the same diameter as said second cup and an open end portion of larger diameter, a cylindrical insulating partition having reduced portions forming opposed shoulders, said second cup tting over one reduced portion, the first portion of said iirst cup fitting over said other reduced portion, said larger open end portion of said second cup extending over said partition and telescoping with respect to the open end of said second cup, a quantity of electrically conductive fluid partially filling said cups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, a glass member sealed between the open end portions of said cups for sealing the interior of said cups from the external air, and a compressible washer between said glass member and said partition for absorbing any differential expansion between said glass and partition upon changes in temperature.

8. A switch comprising` in combination, first and second metal cups, said first cup having a rst portion of substantially the. same diameter as said second cup and an open end portion of larger diameter, a cylindrical insulating partition having reduced portions forming opposed shoulders, said second cup fitting over one reduced portion, the rst portion of said first cup tting over said other reduced portion, said larger open end portion of said second cup extending over said partition and telescoping with respect to the open end of said second cup, a quantity of electrically conductive fluid partially filling said cups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, sealing meansbetween the open end portions of said cups for sealing the interior oi said cups from the external atmosphere, and a compressible washer between one of said cups and the adjacent shoulder on said partition to absorb any diferential expansion between said cups and said partition on changes in temperature.

9. A, switch comprising in combination, first and second metal cups, said first cup having a first portion of substantially the same diameter as said second cup and an open end portion of larger diameter, a cylindrical insulating partition having reduced portions forming opposed shoulders, said second cup tting over one reduced portion, the rst portion of said rst cup tting over said other reduced portion, said larger open end portion of said first cup extending over said partition and telescopng with respect to the open end of said second cup, a quantity of electrically conductive fluid partially filling saidcups, said fluid being separated into two pools by said partition, an opening in said partition whereby said two pools of fluid are connected through said opening for certain positions of said switch, a glass member sealed between the open end portions of said cups for sealing the interior of said cups from the external air, and a compressible washer between said glass and said partition and between the open end of said second cup and the adjacent shoulder of said partition for absorbing any diil'erential expansion between said glass and cups on the one hand and partition on the other.

l0. A rotary electric switch comprising in combination, a pair of opposed metal cups, a partition in the form of a disc, said cups being seated on opposite Vsides of said partition and being electrically separated thereby, a quantity of electrically conductive iluid partially filling said cupsl and separated into two pools by said partition, means supporting said switch for rotation about the axis of said cups, an opening through said partition, said opening being alternately raised and lowered into and out of said fluid for alternately connecting and separating said two pools as said switch is rotated back and forth, means between said cups for sealing their interior from the exterior atmosphere, and a metal readily wet by said fluid in intimate electrical contact with at least one of said metal cups, one portion of said metal being opposite said opening through said partition and another portion extending toward said fluid whereby said metal is always in contact with said fluid before said opening is lowered to permit connection of said two pools of fluid.

11. A switch of the tilting type comprising in combination, a pair of opposed metal cups, a partition in the form of a disc. said oups being seated on opposite sides of said partition and being electrically separated thereby, a quantity of electrically conductive fluid partially filling said cups and separated' into two pools by said partition, an axial opening through said partition, said switch being adapted to be tilted back and forth for alternately separating and connecting said pools of fluid through said opening, rings of metal of the iron group in intimate electrical contact with each cup, said rings being so located as to be immersed in said fluid before the two pools are connected through the opening in said partition and having a portion opposite said opening, and means between the cups for sealing their interior from the external atmosphere.

l2. A rotary electric switch comprising in combination, a pair of oppositeiy disposed metal cups, a partition of insulating material between said cups separating them electrically,` and a quantity of electrically conductive fluid partially filling said cups, said fluid being separated into two pools by said partition, said cups being provided with means for mounting said switch for rotation about the axis of said cups, said partition being formed by two generally similar disks which are mounted in annular engagement with each other, each disk being provided with an opening therethrough, one of said disks having a chamber formed therein for connecting said openings for closing the circuit through said switch when both of said openings are below the surface of said liquid, said chamber being of such configuration that when both of said openings in the disks are below the level of the electrically conductive fluid a portion of said chamber extends above the level of the electrically conductive fluid, said disks being capable of assuming various different rotative positions with respect to each other for varying the angle through which the switch must be rotated in each direction in order to raise the corresponding opening out of the liquid and hence break the electrical circuit through said switch. 1

13. A rotary electric switch comprising in com bination. a pair of oppositely disposed metal cups, a partition of insulating material between said cups separating them electrically, and a quantity of electrically conductive fluid partially fillving said cups, said iluid being separated into two pools by said partition, said cups being provided with means for mounting said switch for rotation about the axis of said cups, said partition being formed by two generally similar disks which are mounted in annular engagement with each other, each disk being provided with an opening therethrough, each of said disks having an opposed recess thereby forming a chamber for connecting said openings for closing the circuit through said switch when both of said openings are below the surface of said liquid, said chamber being of such configuration that when both of said openings in the disks are below the level oi' theelectrically conductive fluid a portion of said chamber extends above the level of the electrically conductive fluid, said disks being capable of assuming various different rotative positions with respect to each other for varying the angle through which-the switch must be rotated in each direction in order to raise the corresponding opening out of the liquid and hence break the electrical circuit through said switch.

14. A rotary electric switch comprising in combination, a pair of oppositely disposed metal cups, a partition of insulating material between said cups separating theml electrically, and a quantity of electrically conductive fluid partially filling said cups, said fluid being separated into two pools by said partition, said cups being provided with means for mounting said switch for rotation about the axis of said cups, said parti*- tion being formed by two generally similar disks which are provided with annular interfltting portions for properly positioning said disks, one of said cups housing said two disks each disk being provided with an opening, said two disks to gether forming an enlarged chamber for connecting said openings for closing the circuit through said switch when both of said openings are below the surface of said liquid, said chamber being of such configuration that when both of said openings in the disks are below the level of the electrically conductive fluid a portion of said chamber extends above the level of the electrically conductive iluid, said disks being capable of assuming various different rotative positions with respect to each other for varying the angle through which the switch must be rotated in each direction in order to raise the 'corresponding opening out of the liquid and hence break the electrical circuit through said switch, an annular member of glass located between said cups and sealed thereto for sealing the interior of said cups from the atmosphere, and a resilient washer between said glass member and said partition for absorbing any differential expansion between said glass and partition upon changes in tem- Derature.

RAYMCND P. MATTERN.

Images