US2417763A - Mercury switch relay - Google Patents

Description

March 18, 1947. LARSON 2,417,763

MERCURY SWITCH RELAY Filed Nov. 24, 1941 2 Sheets-Sheet l INVENTOR.

C cZ/ZZ/ fllaneom BY ATTORNEYS March 18, 1947. c. H. LARSON MERCURY SWITCH RELAY Filed Nov. 24, 1941 2 Sheets-Sheet 2 IN VEN TOR. Paul fiflaflsorz ATTORNEYS.

Patented Mar. 18, 1947 IVIERCURY SWITCH RELAY Carl H. Larson, Elkhart, Ind, assignor to The Adlake Company, a corporation of Illinois Application November 24, 1941, Serial No. 42%,213

14 Claims. 1

This application is a continuation-in-part of application, Serial No. 335,659, now Patent No. 2,303,371, dated December 1, 1942, entitled Mercury switch relay.

At present mercury switches of the displacer type cannot generally be manufactured by the socalled mass production methods, as many of the essential parts of these switches are of glass which cannot be easily formed to exact dimensions. Because of this the various assembled units going to make up the switch cannot be prepared independently as sub-assemblies and later assembled, with any assurance that the operating characteristics of th finished switches will be within permissible tolerances. The use of glass as an em velope material has other limitations; for exam ple, a high pressure gas fill cannot be safely used, and there are several applications in which. switches having a glass envelope cannot be com ployed due to the possibility of breakage by excessive vibration or accidental blows.

An important object of my invention is, there fore, to provide a shock resistant displacer type mercury switch formed of materials which may be readily shaped within close dimensional tolerances.

Other objects are to provide a switch having high breakdown potential and low contact resistance capable of functioning either a front or back contact switch, according to its position; to provide a displacer switch with a non-magnetic metal envelope having external means of adusting an internal time delay; to provide a switch composed of sub-assemblies which are interchangeable with corresponding parts of similar switches of like design; to provide improved mercury displacing means for use in mercury switches having metallic envelopes; to provide a relay highly resistant to accidental damage and short circuiting; and to provide improved means of joining together these sub-assemblies.

Other objects and advantages will become apparent from the description and drawings, in

which Fig. 1 is a vertical sectional view of my improved mercury switch positioned to operate as a front contact switch;

Fig. 2 is a vertical sectional view of the same switch positioned to operate as a back contact switch;

Fig, 3 iilustrates a modified form of my switch, incorporating a time delay element;

Fig, 4 is a diagrammatic view of an apparatus suitable for use filling my switch with a Fig. 5 illustrates another form of my invention, incorporating a modified switch envelope;

Fig. 6 is a sectional view of a reversible time delay element in an upright position; and

Fig. '7 is a sectional view of the same time delay element in an inverted position.

Referring to Fig. l, th switch envelope H is tubular in form, and has a uniform external diameter. The interior is polished to decrease friction, and counterbored at each end, as shown at it, to form an internal shoulder i i. The en" velope consists of a non-magnetic metal which will not amalgamate or otherwise harmfully com bine with mercury, and which is capable of being machined or formed within reasonably close dimensional tolerances.

Becaus of their high strength, ready availability, and other desirable properties, I prefer to use ferrous alloys in forming my switch envelope, and I have found that steel properly alloyed with suflicient amounts of manganese or chromium and nickel, or combinations thereof, have suitable non-magnetic properties. The non-magnetic properties of these alloys is believed to be due to the action of the alloying ingredients, which act to hold the iron in the form of austenite during the cooling process-austenite being the non-magnetic form. of iron. An example of such an alloy is stainless steel having an approximate composition of 13 per cent chromium and 8 per cent nickel (generally termed 18-8 steel). I have found that this particular steel is well suited for use as an envelope material, particularly as it is both non-magnetic and resistant to wetting by mercury.

Another example is the steel known as Hatfield steel, one of the best known examples of which has about 12.5-13% manganese, 1.05-1.29?) carbon, and l8% silicon. Any other manganese steel having therein sufficient manganese (at least 9 or 10%) to maintain the steel in its austenitic form as it cools to the lower atmospheric temperatures can be used. However, no metal readily amalgamating with mercury should be used in sufiicient proportions in any steel that is in contact with mercury to amalgamate appreciably under the conditions of use unless alloyed in such form as to prevent substantial amalagamation. Except for cost, tungsten or molybdenum could be used for the switch envelope inasmuch s each is both non-magnetic and non amalgamating. Any other non-magnetic metal, such, for example, as brass, could be used, if plated on its inner side with chromium, or other metal which will not amalgamate under conditions encountered.

The non-amalgamating metal used in this plating may even be magnetic, as iron, provided the plating is of such thinness that the tubular en velope as a whole is substantially non-magnetic.

A specific steel of the general type known as 18-3 is Carpenter stainless steel No. 4, having a composition (beside iron) of chromium 18%, nickel 9%, and carbon .O8-.1%. For commercial reasons this is probably the most desirable at the present time. The following description will, therefore, be confined to the use of this material, although it is to be understood that other alloys having similar non-magnetic and non-amalgamating properties may be substituted if desired.

t is important that the metal chosen for the switch envelope be essentially non-magnetic. A magnetically responsive displacer 33 moves within the switch to change the mercury level, and if the envelope is of magnetic material the displacer may be held to the envelope by the magnetic force employed to actuate the switch or the residual magnetism resulting therefrom. As the functioning of the switch depends upon the movement of the displacer, it is apparent that any force preventing such movement will also prevent the functioning of the switch, and as substantially no air gap exists between the displacer and the envelope even a slight magnetic force in the envelope may have undesirable effects. Furthermore, the magnetic actuating force would be shunted away from the displacer by a magnetic envelope.

A cap, generally designated l5, consists of a metallic disk I5, adapted to be received in the counterbore l3 and to fit snugly against the internal shoulders l4. An opening is provided in the disk IE, to which is welded, or otherwise attached, a small metal tube H. The thickness of the disk l6 is somewhat less than the depth of the counterbore l3, so that when the disk I6 is inserted within the counterbore against the shoulders l4 portions |8 of the envelope will extend beyond the outer surface of the disk.

When it is desired to seal the cap l5 to the switch envelope H the cap is inserted, as described, against the internal shoulders I4, and the projecting portions |8 of the envelope are turned inwardly against the exterior portion of the disk l6, thereby pressing the disk firmly against the shoulders l4. The joint between the turned-down portion l8 of the envelope II and the outer surface of the disk It is subsequently sealed with hard solder, as indicated at l9, or by other suitable material, to form a strong gastight joint. The disk may also be welded in place, if desired, and it may be of any suitable metal not amalgamating with mercury, as stainless steel, ordinary iron, or a metal known in the trade as Kovar.

A base 2| consists of a disk of metal adapted to be received in the counterbore l3, in a manner similar to that described in connection with the cap |5, and is provided with an opening 22 in which an electrode 23 may be positioned. The disk 2| is formed of a metal having a coefiicient of thermal expansion substantially equal to that of hard glass and molybdenum. A metal having these characteristics is commercially available under the trade name of Kovar, and consists essentially of an alloy of iron, cobalt and nickel.

The electrode 23 is preferably of molybdenum, and is covered for a portion of its length by insulating sleeve 24 of hard glass, such as Cornin (3-705 AJ, which has a coefiicient of thermal expansion substantially equal to that of molybdenum and Kovar. The insulating sleeve 24 is preferably heat bonded to the electrode 23. The electrode 2.3 and. the insulating sleeve 24 are positioned within the opening 22 in the base 2| by forming bulges or shoulders 26 in the insulating sleeve, adjacent to both sides of the opening 22, and subsequently applying sufiicient heat to cause the glass to bond to the base 2|. This, forms a strong gas-tight seal, as the electrode, the glass and the base all have approximately the same coefiicient of thermal expansion.

The insulating sleeve 24 surrounding the electrode 23 extends into the switch envelope H for slightly less than half the distance between the base 2| and the cap l5, and serves to insulate the electrode from contact with the base 2| and the mercury fill, except for a portion 2? of the electrode which extends beyond the insulating sleeve. The upper end of the sleeve 24 has a shoulder 28 formed integrally therewith, and fused to this shoulder is a ceramic tube 29, formed of a ma terial, such as Alundum, which has substantially the same coefficient of thermal expansion as the glass. The shoulder 28 is gen rally circular in section, but is formed eccentrically with respect to the electrode 23, so that the exposed portion 21 of the electrode will be close to one side of the ceramic tube 29 after assembly. The upper end of the ceramic tube 29 is closed with a glass seal 3|, and an opening 32 is provided through the side wall of the tube 29 approximately midway between the top and bottom thereof, and at a point furthermost removed from the eccentrically positioned electrode 23. The exposed portion 21 of the electrode 23 extends into the tube 29, and terminates adjacent to the glass seal 3|.

I prefer to form the entire electrode structure separately from the balance of the switch, and to seal this sub-assembly into the switch envelope in a manner similar to that described in connection with the cap l5.

The displacer, generally designated 33, is telescoped over the electrode assembly, and may consist of a tube 34 of magnetic material, such as iron, telescoped over a sleeve 36 of insulating material, such as glass, the latter sleeve being somewhat longer than the tube 34. The ends of the iron tube 34 are reduced in external diameter, forming an external shoulder 31. Guide washers |2 are fitted over the insulating sleeve 36 and the reduced portion of the iron tube 34 against the external shoulders 31, and may be of the type described in my Patent No. 2,060,811. These washers serve to prevent any appreciable sideward movement of the displacer assembly 33 by contact with the inner walls of the switch envelope Coil springs 38 are fitted over the projecting ends of the interior insulating sleeve 36, and frictionally engage said sleeve to maintain the component parts or" the displacer assembly 33 in their proper relation. These springs are of non-magnetic material, and serve to prevent the sticking of the displacer to either the cap |5 or the base 2|, and are particularly necessary when the cap i5 is formed of a magnetic material, such as iron.

As the switch envelope serves as one of the electrodes of the switch, it is often desirable, but not essential, to provide means of insulating the envelope H from other adjacent external portions of the switch assembly, and from accidental contact or short circuiting. This may be conveniently accomplished by mounting the assembled switch mechanism within a rigid tube 39, having a length somewhat greater than that of the switch mechanism. The tube 39 may be suitably formed of an insulating material, such as Bakelite, and the switch assembly held within the tube by applying a suitable sealing material, such as sealing wax, to the ends of the tube after the switch mechanism is positioned therein, as indicated at at.

If the switch assemb y is to be mounted within an insulating tube, it necessary to provide means of forming a connection with the electrodes, viz. the switch envelope H and the cen trally positioned electrode 23. This may be accomplished by attaching a connecting wire 42 to the switch envelope at any desired point, the wire being of suiilcient length to extend beyond the tube 3%. Electrode 23 may also be joined with a connecting wire in a similar manner, or extended beyond the tube. Connecting wires of this nature may be attached to the switch when the tube 39 is not employed.

A coil 43, having an iron circuit id, is provided with an opening in which the switch assembly is positioned. Pole sleeves 43 may be provided fitting around the tube 39 and in contact with the iron circuit is to define an air gap ll. If the coil is to be energized by an alternating current, the pole sleeves dd, or the iron circuit M, or both, may be split to overcome the undesirable magnetic effects of such current, as high eddy current loss. This split need not extend completely across the iron circuit, but may be positioned on the portions lying above and below the coil 43, extending from one edge of the iron circuit 44 to the opening in which the switch envelope is positioned. The split in the pole sleeves should be axial, and suflicient in width to prevent contact of the edges of the sleeve when positioned around the switch. The magnetic portion M of the displacer (-33 may also be split in a similar manner.

The pole sleeves 46 are not essential, but are desirable, as they render the switch more sensitive to small exciting currents in the coil, and the action of the displacer 33 in response to the coil may be controlled within certain limits by adjusting the position of the air gap 41.

The switch may be conveniently maintained in position within the coil 43 by means of a rubber sleeve lid, frictionally engaging the insulating tube 39, or the switch envelope ii if the insulating tube is not employed. The sleeve 53 is cylindrical in form and has a central opening of a diameter slightly less than the external diameter of the tube 39 or the switch envelope I i. The upper portion of the sleeve 48 is reduced in diameter to receive a bracket 49, of rigid material, which is adjustably secured to the iron circuit 44 by means of a machine screw 5i. The external diameter of the lower portion of the rubber sleeve 48 is greater than the diameter of the opening in the coil so that the switch is prevented from moving downwardly by the frictional engagement of the sleeve id with the tube 3%. Upward movement of the switch assembly is pro vented by the bracket 49, which may also be used to deform the rubber sleeve to into firmer contact with the tube 39 or with the switch en veiope I I, as the case may be. Other types of switch mountings may be used, but I have found the type described advantageous because of the ease with which the position of the switch within the coil may be adjusted.

The switch envelope H contains a quantity of mercury 52, and is filled with an inert gas, or

mixture of such gases, belonging to the class comprising helium, hydrogen, nitrogen, argon, or helium hydride. The gas fill is admitted to the switch through the small tube i! sealed to the disk It, the opening of the tube ll communicating with the interior of the switch. When the desired amount of gas has been admitted to the switch envelope the tube H is closed in a suitable manner, as by pinching and welding, indicated at 53. The gas fill may be of any desired pressure, either above or below that of the atmosphere, but I prefer to use relatively high pressures, on the order of 106 pounds to the square inch, as I have found that inert gas, particularly hydrogen at these pressures, has the property of quickly quenching any are formed when the circuit through the electrodes is made or broken, and gives a higher break-down potential. In certain instances even higher pressures may be employed, as the efficiency of inert gas in quenching the are increases with its pressure.

The displacer (iii floats on mercury fill 52 when the coil is deenergized, the amount of mercury in the envelope ii being such that when the displacer 33 is in its deenergized position the level of the mercury will be approximately half way between the base 21 and the cap 55. This is below the level which may be called the contact level of the electrode 21; i. e., the level to which the mercury must rise to complete the cir nit. The opening 32 of the ceramic cup 29 determines the contact level in the illustrated form, and is above the low level of the mercury when the switch is upright, so that when the displacer 33 is in its deenergized position there is no electrical contact between the electrode 23 and the switch envelope l l. The ceramic sleeve 29 forms a cup around the exposed portion El of the electrode and, in operation will always retain a certain amount of mercury in constant contact with the exposed portion of the electrode.

The air gap ll is positioned somewhat below the displacer 33. displacer 33 is drawn downwardly, causing the mercury to rise within the envelope ii and contact the pool of mercury remainin within the sleeve 29 through the opening 32, thereby completing the circuit between the electrode and the switch envelope ii. When the coil 53 is deenergized the displacer will rise, due to its own buoyancy, causing the mercury level to fall within the envelope and break the contact between the electrode and the switch envelope.

The type of switch above described is generally known as a front contact switch, that is, a switch in which the circuit through the elecrodes is normally incomplete when the controlling coil is deenergized. This switch may be converted into a back contact switch, wherein the circuit through the electrodes is complete when the coil is deenergized, and broken when energized by simply inverting the entire switch assembly. When the switch is inverted the parts will arsume the positions shown in Fig. wherein the mercury level, with the displacer in its deenergized position, lies above the opening 32 in the ceramic sleeve 25, and the air gap 4? is positioned above the displacer When the switch is in this position and the coil '23 is energized, the displacer 33 will be drawn upwardly, causing the mercury level to fall and break the contact between the electrode 23 and the switch envelope 5 5 through the opening 32.

Whether the switch is upright or inverted, the making or breaking of the circuit is always be- )Vhen the coil is energized the l tween mercury and mercury, for in the inverted position the ceramic sleeve 29 and the glass seal 31 also form a cup which retains a certain amount of mercury in constant contact with the exposed portion 27 of the electrode 23, regardless of the position of the displacer. The material from which the sleeve 29 is formed is also sufficiently porous to prevent entrapment of gas.

I have described in detail the method of forming my switch to obtain a front contact in the upright position and a back contact in the inverted position. By adjusting the mercury level, the position of the air gap 41 and the size and/or position of t opening I provide a switch functioning as front contact in either the upright or inverted positions, or as a back contact in either position.

It should be noted that the height of the mercury with respect to the base 2| in Fig. i is not necessarily the same as the height of the mercury with respec" to the cap it: in Fig. 2, as the insulating electrode sleeve 2'4 and the electrode assembly displaces a certain amount of mercury. Therefore, unless correction is made, the normal height of the mercury within the switch envelope, when the switch is in its upright position, will be greater than when the switch is in its inverted position, as shown in Fig. 2. This level may be adjusted by providing means of artificial displacement adapted to be covered with mercury when the switch is in its inverted position, as shown in 2. This may be suitably accom plished by enlarging the volume of the glass seal 3! to provide a displacement equivalent to that produced by the electrode assembly and insulating sleeve it.

To provide a switch functioning as a back contact switch in either position, I may, for example, enlarge the diameter of the opening 32 in the sleeve 28, so that in its upright position the level of the mercury will be above the lower margin of this opening. If necessary, I also increase the volume or" the glass seal 3i, so that in its inverted position the level of the mercury will also be above the opening 32. The position of the displacer with respect to the air gap 47 is then altered by moving th switch envelope within the coil to a point where the air gap lies above the nolmal position of the displacer, so that when the coil 43 is energized the displacer 33 will be drawn upwardly, causing the level of the mercury to fall and break the normally existing electrical contact between the electrode 23 and the mercury fill The switch will function in the same inanne' in the inverted position, the position or" the switch within the coil being altered, however, in each case, so that the air gap ll will be above the displacer.

My switch be made to function as a front contact switch in either position by forming the opening 32 in the sleeve 29 at a point substantially half way between the cap l5 and the base 2i, and adjusting the mercury level to a point normally below this opening in either position. In this modification, the air gap must be posi tinned below the normal level of the displacer, so that movement of the displacer in response to the coil 43 will be downwardly, causing the level of the mercury to rise and complete the contact between the mercury fill 52 and the electrode 23.

It may be seen, therefore, that by very minor adjustments I may obtain extreme flexibility in operation, and may provide a, switch operating as a front contact when in one position and as a back contact when inverted, or as a front contact in either position, or as a back contact in either position. There are, of course, methods other than that described of controlling the operating characteristics, as the function of the switch depends upon the disposition of the opening 32 with respect to the mercury level. Broadly, if the Switch is to function in the same manner, whether upright or inverted, the opening 32 should be substantially midway between the cap and the base, and the height of the morcury above the base in an upright position, substantially equal to the height of the mercury above the cap in an inverted position.

If, on the other hand, the switch is to function as a front contact switch in one position and as a back contact switch when inverted, the opening 32 will be positioned above the normal mercury level with the switch in one position, and below the normal level when inverted. In each case, it is understood that the direction and extent of movement of the displacer is such as to cause movement of the mercury fill to change the condition of the circuit between the mercury and the elec rode 23, and that the direction and extent of this movement may be controlled by changing the position of the switch envelope, and hence the displacer, with respect to the air gap 4'! in the iron circuit 44.

Due to the large area of the foot electrode or switch envelope ll, the contact resistance of my switch is extremely low, thereby making it efficient to operate. The switch is also highly resistant to damage by accidental blows, and may therefore be used under circumstances which would prohibit the use of a switch having a glass envelope.

Fig. 3 illustrates a modified form of my invention incorporating a time delay element, generally designated 54. The envelope II is the same as that described in connection with Fig. l, as is the base 21 and the lower portion of the electrode assembly. The cap, generally designated 56, is cylindrical in form, and is provided with an outwardly extending end flange 51, which is proportioned to be received in the counterbore I3 in the end of the envelope II. The thickness of the flange 57 is somewhat less than the depth of the counterbore l3, so that when the cap 56 is inserted in the end of the envelope it will fit tightly against the shoulder l4, and may be attached to the envelope in a manner similar to that described in connection with Fig. l. The cap 55 is provided with an axial opening 58, communicating with the interior of the switch envelope. A lateral opening 49 is also provided intercepting the axial opening 58, and proportioned to receive atapered plug or stop cock 6 I containing a transverse opening 62, adapted to register, when in one position, with the opening 58, and when turned ninety (96) degrees therefrom to close said opening. The upper portion of the cap is somewhat reduced in external diameter and is provided with external threads, as indicated at 63.

In this modification the insulating electrode sleeve 24 is formed with a larger external diameter, and extends upwardly to a point somewhat below the low mercury level, where the diameter of the insulating sleeve 24 is enlarged to form a shoulder 64, to which is fused a gas impervious thimble 5B of a material such as glass. The electrode 23 extends upwar .ly beyond the shoulder 64 within the thimble 66, and is insulated for a portion of its length by an extension 61 of the insulating sleeve 24. This extension 67 also has a shoulder 68 formed upon its upper portion, to which a small ceramic sleeve 69 of Alundum, or other suitable ceramic material having a coeiiicient of thermal expansion substantially equal to that of the glass, is fused. This sleeve it fits around the exposed portion 2'! of the electrode 23, forming a cup in which a small pool of meronly is retained. If desired, the sides of this sleeve t9 may be truncated.

An opening H i provided in the side of the thimble 65, the diameter and position of the opening being such that the upper portion thereof is below the lip of the small ceramic cup 69. Another opening i2 is provided in the upper portion of the thimble 95, adapted to receive a plug E3 of porous material, through which gas may pass.

The displacer, in this instance, comprises a tube i l of magnetic material, such as iron, having its external diameter reduced at each end to form an external shoulder "it. Guide washers l2 are fitted over the ends of the displacer and against the external shoulder l6. Portions of the tube i4 extend beyond the shoulder 76 and the guide washers it, which maybe bent sharply outwardly, after the guide washers have been placed in position, to hold the washers in place, and then bent inwardly at an angle, forming legs ll, substantially as shown. These legs 11 serve to prevent any sticking cf the displacer to the cap 5% or the base 2 l.

The coil 53 and the iron circuit 44 are similar to those described in connection with Fig. 1, but in place of the rigid tube 39 sleeves 18, of insulating material, may be interposed between the pole pieces 56 and the switch envelope II, to insulate the iron circuit as. The switch may be supported in the same manner as that previously described, with the rubber sleeve 68 in direct contact with the switch envelope I i Mercury is added to the envelope H and the assembled switch connected with any suitable filling apparatus. In fillin these switches with gas, particularly those incorporating a time delay element, I prefer to use an apparatus similar to that described in my Patent No. 1,967,949, illustrated diagrammatically in Fig. l. This apparatus may consist of a pipe line it, having a pressure gauge it a high frequency discharge device 8| connected to the pipe line through a valve 35, a three-way stop cock 82, a vacuum pump 33, and a source as of inert gas having a control valve 86. The gas supply 3% and the vacuum pump 88 are connected with the pipe line 19 through the stop cock All parts of the system are preferably of metal with the exception of the extension 81, containing the electrode of the high frequency discharge device ti, which is of glass.

pies or other suitable connecting means, provided on the pipe line if-l, by means of oh the switches may be attached and are, in this case, threaded to cooperate with the threaded portio E3 of the cap at. When the switches have been bed to the pipe line '59, substantially the cock iii in the cap 56 is turned no open position, in which the transverse ening risters with the axial opening '53,

of the switch envelope. The stop cook 82 is ned to a position cutting oil the gas supply and connecting the pipe line itwith the vacuum pump Air is exhausted from the interior of the switch envelope, the degree of vacuum being eby alicwing communication with the integauged by the appearance of the high frequency discharge, or, if desired, by means of a suitable gauge, not shown. During this process the valve 85 is open, allowing communication between the 5 extension hi and the pipe line 19. When the desired degree of vacuum has been obtained, valve is closed and the position of the stop cock 82 changed to disconnect the vacuum pump from the pipe line is and to connect the gas supply The valve 85 is opened and gas is allowed to fill the switches.

' operation is repeated several times to incomplete removal of all air, and in the operation is admitted to the desired the stop cock 82 turned to a position both the pump 83 and the gas supfrom the pipe line 19. The stop cock 6| in the valve cap 55 is turned to the oil position, thereby effectively sealing the switch envelope I I. If de red, switches may now be connected to a suitable testing circuit and their operating characteristics determined without removal from the filling apparatus.

It is, of course, obvious that the action of the time delay element will be governed largely by the density of the gas within the envelope H, and time delay characteristics, may, therefore, be conveniently varied by adjusting the gas pressure either while the switch envelope is connected to the filling apparatus or after it has been removed. When the desired characteristics have been obtained, the switch is removed from the apparatus and the cap t6 dipped in hard solder, indicated at $53, completely covering the exposed portion of the cap 5%.

The time delay element 5:3 is simply illustrative of one of the many types which may be incorporated my invention, and operates in the following manner: When the coil 43, surrounding the switch, is energized the displacer 74 is drawn downwardly into the mercury, causing the meron y within the envelope ii to rise rapidly until it reaches the upper limit of the opening H The "cury outside of the thimble 56 will continue to ise rapidly, but as a certain amount of gas is trapped by the mercury within the thimble the se of the mercury therein is delayed until a sulfiit amount of the entrapped gas has escaped the porus plug l3, allowing the mercury in the thimble to rise to the lip of the interior ceramic cup 59 and complete the circuit between the switch envelope H and the electrode 2 When the coil as is deenergized the displacer will rise rapidly, due to its own buoyancy, causing the mercury outside of the thimble 56 to fall. Tl. mercury remaining within the thimble, however, does not fall rapidly until the le l of the mercur outside of the thimble has fallen belor the upper portion of the opening H, which t me the mercury column remaining within the thimble undermined and the circuit abruptly broken. This type of time delay element provides a delayed make, but it is obvious that by modifying th construction other types of time delay action may be secured.

The type of envelope shown in Fig. 3 is interchangeable with the type illustrated in Figs. 1 and 2; that is, its capacity internal and external diameter and counterbore are equal. The cap l5, illustrated in Fig. l, and the displacer 33 are also terchangeable with the cap 56 and the displacer described in connection with Fig. 3. The elecbase 25 is also standardized to receive any several possible types of electrode assems, including those having various time delay functions, and to fit any or the various forms of switch envelopes. In my switch it is practical to provide for the interchangeability of parts as described, because the portions of the switch having critical dimensions are of metal which may be readily formed within close dimensional tolerances.

The advantages accruing from this type of construction are obvious. For example, I may form several sub-assembli s, consisting of the base, electrode structure and time delay element, each having different predetermined operating characteristics. When a switch having certain characteristics is required the sub-assembly having these characteristics is chosen and simply attached to the standardized envelope, together with the other necessary parts. The assembled switch will have the desired characteristics, all portions of the switch affecting its operating characteristics may be accurately controlled, and testing may be eliminated except for occasional check tests. It would be impractical, from a manufacturing viewpoint, to form interchangeable sub-assemblies from glass, as the parts could not be economically formed within suiiiciently close dimensional tolerances.

As previously mentioned it is possible, within certain limits, to control the action of the time delay element 54 by the pressure of inert gas within the envelope ii. If it is necessary to alter the characteristics of the switch after assembly the stop cock 6! may be carefully turned toward the open position, allowing a small quantity of the gas within the envelope to escape, until the desired operating characteristics have been obtained.

Fig. illustrates particularly a modified form of switch envelope H, in which the envelope is formed in the shape of an elongated cup. The counterbore II! at the open end of this envelope, as well as the internal and external diameters and the capacity, are the same as those previously described. An opening 9! is provided in the closed end of the envelope, to which the small tube H, similar to that described in Fig. 1, may

be attached by welding or otherwise. This tube may also be sealed in a similar manner. The remaining parts of the switch are similar to those described in Fig. 3, with the exception of the electrode structure, which is shown in its simplest form, comprising the insulating sleeve 24 having a shoulder 68 upon its upper end, to which is attached the small ceramic cup 59 surrounding the bared end of the electrode 23. The switch operates in a manner similar to that previously described.

This particular type of switch envelope possesses certain advantages, particularly in respect to the strength of the envelope, as it may be seen that one of the seals, viz: that formed between the cap and the envelope, is eliminated by this type of envelope. This feature is impor tant in my switch, for, as previously mentioned, I prefer to use high gas pressures, and the envelope must, therefore, be sufficiently strong to safely retain the gas, and the omission of one seal avoids that source of possible defect in the seal.

The resistance to wetting, by mercury, of the metals referred to for envelope H and the disks l5 and .H seems to be advantageous in connection with the seals. With such metals the mercury is unable to penetrate between the envelope H and the disk 2! to reach the solder is with which it might amalgamate. At present, nonamalgamating metals are also non-wetting. Of course, if a non-amalgamating metal, which is wet by mercury under the conditions encounter-ed, were found, and the illustrated seal were found unsafe, a different seal could be used. However, at present th non -wetting characteristic, as well as the non-amaigamating, desired for best operation of the switch.

For the utmost dependability in the seal the junction between 2.! and envelope H should be exposed the gas fill before this junction is subjected to contact with the mercury at high pressure. If there are any small cleanances, the non-wetting characteristics of the metal will have the mercury out of the clearances at low i essure, and the entrapment of the gas will copendably keep the mercury away from the so der on the outside of the seal, even at high pressure. As a matter of fact, there will rarely be any ,1 recs, especially if the projecting portion of the envelope l l is upset and pressed against the disk 2! with considerable pressure, as in a press.

The time delay device 54, described in connecr tion with Fig. 3, is, of course, adapted to operate only in an upright position. Figs. 6 and '7 illustrate a time delay element operable in either an upright or inverted position, and adapted for use in any one of the various modifications of my invention hereinbefore described.

ig. 6 illustrates my reversible time delay element in its upright position. The element comprises a sleeve I92 of insulating material, such as glass or ceramic, attached to a shoulder i8! formed integrally with the insulating sleeve 2-5, and is closed at the top by a glass seal N13. The electrode 23 is positioned eccentrically with respect to the sleeve I92 and extends into said sleeve, terminating adjacent to the glass seal M33. The lower portion oi the electrode within the sleeve m?! is insulated by an extension I04 of the insulating sleeve 24, the end portion of the electrode also being insulated by a cup I38 telescoped over the end of the electrode an: heat bonded thereto, leaving exposed a centrally located contact Hi1.

Substantially identical mercury metering orifices I08 and IE9 are provided the wall of the sleeve Hi2, and are positioned above and below the level of the contact I01, the orifice 558 being adjacent to the shoulder lS-i, and the orifice if!!! being adjacent to the glass seal I03. A r latively large opening HI is also provided in the wall of the sleeve at approximately the level of the contact I07, all three of the above-mentioned openings being in the portion of the tube furthermost removed from Lie eccentrically positioned electrode 23.

When properly positioned within the switch the level of the mercury, with the displacer in its deenergized position, will be approximately at the level indicated by the line A, below the level of the contact 501, and preferably above the mercury metering orifice Hi8. In this position there is, of course, no electrical connection between the mercury and the electrode 23. When the coil is energized the displacer is drawn downwardly, causing the level of the mercury outside of the sleeve I02 to rise rapidly. The rise or the mercury within the sleeve however, gov-- erned in this case by the size of the mercury metering orifice I08, and will therefore rise more slowly, eventually reaching th level of the mercury outside of the sleeve, indicated by the line B, in which position the mercury is in electrical connection with the contact llll. When the coil is cleenergized the displacer rises, causing the mercury outside of the tube M2 to fall. This does not, however, break the contact between the electrode 23 and the mercury immediately, as the fall of the mercury within the sleeve m2 is delayed by the mercury metering orifice it, through which the mercury slowly escapes.

Under the above described conditions it may 3e seen this time delay element provides a delayed make and a delayed break, provided the high mercury level 13 is above the level of the contact ill! and below the lower margin of the relatively large opening iii. If desired, however, the switch may be adjusted to provide a quick mat: with a delayed breal: by causing the mercury to rise to the level by the line C, in which the mercury will immediately fill the sleeve ii -2 through the opening ill when the displacer is energized, completing the circuit between. the contact It! and the mercury. In this instance, when the displacer is deenerglzed, the mercury metering orifice we delays the fall of mercury within the sleeve H32 in a manner similar to that previously described.

The amount of mercury displaced by move ments of the displacer depends, of course, upon the depth to which the displacer is drawn, and the high level of the mercury may, therefore, be adjusted by varying the position of the air gap between the pole sleeves with respect to the displacer. The mercury therefore, be made to rise to either the level indicated by the line B, or that indicated by the line C, by adjusting the position of the switch within the coil; or, if desired, the high level of the mercury may be controlled by varying the amount of mercury added to the envelope.

Fig. 7 illustrates the time delay element shown in Fig. 6, in an inverted position. In this position there is normally electrical contact between the electrode 23 and the mercury when the displacer is in its deenergized position, the level of the mercury being normally at either the level indicated by the line D c. that indicated by the line F. When the coil is energized the displacer is drawn upwardly, causing the mercury level outside of the sleeve to fall rapidly. This action does not immediately break the electrical connection between the mercury and the contact lil'l, due to the action of the mercury metering orifice lilt which delays the passage of mercury out of the sleeve Hi2, thereby providing a delayed break. When the coil deenergized the displacer falls to its normal position, the mercury level outside of the sleeve to rise either to the level indicated by he line D or the level indicated by the line In the former case the mercury will immediately fill the sleeve 62 through the openin ill, provid .g' a quick make. only to the level indicated by the line F, the element will provide a delayed make, as the mercury will rise slowly within the sleeve m2, due to the action of the mercury metering orifice IE9.

It is desirable that all cases the mercury metering orifices m8 and Hill l normally below the low mercury level, to in this position the surface tension effect of the mercury does not affect the flow through the orifice. If desir d, the insulating members iii-i and 566, lying withn the sleeve i252, may be formed in the shape of cups to provide a mercury to mercury contact.

By incorporating rny reversible time delay ele- If, on the other hand, the mercury v ment any one switch may be made to function in an upright position as a front contact switch having either a delayed make and a delayed break, or a quick make and a delayed break. The same switch, in an inverted position, will also function as a back contact switch having a delayed. make and a delayed break, or, if the normal mercury level be properly adjusted in the manufacturing process, will provide a quick maize and a delayed break. Any one switch in corporating the above described time delay element will, therefore, provide any three of four distinct types of action without alteration of any of the component parts of the assembled switch.

It will be noted that the construction of the reversible time delay element illustrated in Figs.

"l is. in many respects, similar to the electrode cap described in connection with Figs. 1 and It is therefore possible, by adjusting the diameter and position of the relatively large opening l the position of the air gap 4'5, and/or the height of the mercury fill, to provide a switch having the time delay functions hereinbefore described operating as a front contact switch in either position, or as a back contact switch in either position, the adjustments being similar to those described in connection with Fig. l.

Specifically, if it is desired to provide a switch incorporating a time delay function, and operating as a front contact switch in either position, the opening 5 l i, corresponding to the opening 32 in Fig. l, is positioned approximately midway within the switch envelope H, and the level of the mercury adjusted to normally lie below the level of the contact lii'l, as for example. the line designated A in Fig. 6, or at the level designated by the line in Fig. 7. The switch envelope 5 l is positioned with respect to the air gap i? to draw the displacer downwardly into the mercury, causing the level of the mercury to rise to the level indicated by the line B the line C in Fig. 6, or to the level indicated by the lines D or F in Fig. '7.

The same switch may be made to function as a back contact switch in either position by locating the opening H l approximately midway within the envelope, and providing a normal mercury level at approximately the levels indicated by the lines C or D in Fig. 6, or the lines D or F in. Fig. '7. If the switch is to function as a back contact switch, the position of the air gap must always be above the displacer, so that energization of the coil 25 will cause the displacer to rise out of the mercury, thereby lowering the mercury to a level such as that indicated by the line A in Fig. 6 or the line E in Fig. 7, these levels both instances being below the level of the contact Elli. In either case, the displacement of the electrode assembly and insulating sleeve 2:!- may be compensated by increasing the volume of the glass MB, or by other suitable means.

If, as previously described, the switch to opcrate as a front contact switch in one position, and a back contact when inverted, the opening ll 1 is positioned to lie above the normal mercury level in one position, and below the mercury level when inverted.

Due to its simple and efiicient construction, my switch is capable of operating on extremely low exciting currents, and as it has very low contact resistance it is efficient in operation. The materials from which the switch is manufactured are not subject to break-down under excessive loads, and are strong and durable, thereby increasing both the safety and durability of the switch. The preferred metals for envelope H have an electrical resistance about forty times that of copper, and there is no danger that, with an alternating exciting curr eddy currents will set up in the envelope of sufficivt value to require an 0bjecticnably higher ex current. Likewise, when direct current used there will be no objectionable lag in the er ization upon open ing the energizing cicint. impervious nature of permits the advantageous use of a high pressure gas fill which cannm, of cours be safely U conjunction with the conventional type switch envelop One reason for the prefer-e for the 1S8 type steels is that the walls, "2;- I polished, may be relatively thin and still be i pervious. The h. strength and permeability of the metal ts the advantageous use of a hi pressure gas fill which cannot, of course, be sa used in conjunction with the conventional t5, of glass switch envelope, and by use of the type oi cap described in connection with Fig. 3 the operating characteristics of the switch be adjusted after assembly without to the switch envelope.

The joint ford ed between the switch envelope and the cap or base '11 retain the high gas pres sures within th swit indefinitely, and is particularly e llS respect when compared to similar joints in other types of switches employing rubber or other organic materials as a sealing medium.

Th foregoing description has been by way of illustration only, and it is to be understood that the specif c embodiments herein described are merely examples of the many ways in which my invention may be embodied within the scope of the appended claims. The claims, therefore, are to be construed as broadly as the prior art will permit.

I claim as my invention:

1. A mercury switch assembly ncluding an envelope, a quantity of mercury within the envelope, an electrode at mes completing a circuit t ough the mercury, a" d magn ically responsive means within the adapted to be actuated by 12 ans externa the l of the envelope for ch CilidltlO'l'l of the electrical circuit 1, mercury, characteriz "y the formation 0 envelope of at least the metal s bstantially in contact with one another along a oi" junc- Y M 1g Dy Lil-e2."

culy wl'i par of j notion is prevented.

2. A mei ury switch assembly including an envelope, a quantity of mercury within the envelope, an electrode at times completing a circuit through the mercury, magnetically responsive means withi the envelope adapted to be actuated by means external of the envelope for changing the condition of the electrical circuit through the mercury, characterized by the formation of the envelope of at least two metal parts substantially in contact with one another along a line of junction, both of said parts resisting wetting by mercury whereby the flow or" the mercury between the parts at the line of junction is prevented, and a seal along the line of junction comprising a metal, which will amalgamate with mercury, fused to the parts along the line of junction but externally thereof in a position in which the mercury cannot penetrate.

3. A mercury switch assembly including an envelope, a quantity of mercury within the envelope, an electrode at times completing a circuit through the mercury and magnetically responsive means 16 within the envelope adapted to be actuated by means external of the envelope for changing the condition of the electrical circuit through the mercury characterized by the formation of the envelope of at least two metal parts substantially in contact with one another along a line of junction, and the provision of a hermetic seal along said line on the outside of the envelope formed of a material which is deleteriously affected by mercury, one of said metal parts being resistant to wetting by mercury whereby the flow of mercury between the parts the line of junction is prevented.

4. A mercury switch assembly including a metal switch envelope having an integrally formed seat at one end, a mercury fill, a metal plate having aperture and an electrode assembly including an electrode and an insulating sleeve sealed through the aperture, the metal plate having a thickness less than the depth of the seat and adapted to be received by the seat whereby the metal plate may be sealed to the envelope by turning the extending ends of the envelope inwardly against the external surface of the metal plate.

5. In a mercury witch relay, a coil, a nonmagnetic metal switch envelope associated with said coil and closed at one end by an electrode assembly comprising a plate of magnetic material through which an electrode is hermetically sealed, contact means and a mercury fill within the envclope, a magnetically responsive displacer for shifting the level of the mercury fill, and spacing means within the envelope for preventing magnetic adherence of the displacer to the magnetic metal plate.

6. For use in a mercury switch, a metal switch envelope having an open end, said open end having an internal shoulder, a metal cap adapted to rest upon said internal shoulder, and means for sealing said metal cap to the envelope, said mean including metal all along the seam therebetween in the intimate contact resulting from its application as a molten metal.

7. A mercury switch of the displacer type having predeterminable operating characteristics formed by joining prefabricated subunits, said sub-units comprising a non-magnetic metal switch envelope, and an electrode assembly comprising a metal base, an electrode and an insulating sleeve sealed to said base and electrode.

8. A mercury switch of the displacer type having predeterminable operating characteristics formed by joining together prefabricated subunits, said prefab 'icated sub-units comprising a non-magnetic metal switch envelope and an electrode assembly comprising a metal base having an opening, an electrode, and an insulating sleeve heat bonded to said electrode, said insulating sleeve being positioned within said opening and sealed to said metal plate.

9. A mercury switch of i racer type havprecletermirable operating characteristics together prefabricated subit fusion, mprising envelope, a o velope exertit sure substantially in exess of atmos eric iressure, l

positioned within said open- 17 ins and said insulating sleeve being sealed to said metal plate.

10. A mercury switch assembly including a metal switch envelope having an internal annular seat formed at one end, a mercury fill, a metal closure cap having an aperture therethrough, an electrode hermetically sealed through the aperture and insulated therefrom, the outer margin of the metal cap having a thickness less than the depth of the seat and adapted to be received by the seat whereby the metal cap may be sealed to the envelope by causing the extending ends or the envelope to overlay the adjacent external surface of the cap.

11. In a mercury switch relay, a coil, a nonmagnetic metal switch envelope associated with said coil and closed at one end by an electrode assembly comprising a plate of magnetic material through which an electrode is hermetically sealed, contact means, and a, mercury fill within the envelope, a magnetically responsive displacer for shifting the level of the mercury fill, and spacing means Within the envelope for preventing magnetic adherence of the displacer to the magnetic metal plate, said spacing means comprising a stop of non-magnetic material projecting beyond the end of the displacer and establishing a minimum air gap between the magnetic displacer and the magnetic plate.

12. In a mercury switch, the combination of a metal switch envelope formed of non-magnetic tubing, an electrode assembly adapted to close one end of the envelope and comprising a cap having an electrode extending therethrough and hermetically sealed to the cap, a mercury fill, a magnetically responsive displacer for shifting the mercury fill to actuate the switch, and a cap closing the other end of the envelope, and means for hermetically sealing the junction between the envelope and the top and bottom caps.

13. The method of fabricating a metal envelope mercury switch comprising taking a metal envelope having an opening at one end thereof, closing said opening with a metal cap fitted into the opening and having its side Wall in close proximity to the adjacent wall of the envelope but leaving an infinitesimal annular space therebetween, at least one of the metal parts being resistant to wetting by mercury, exteriorly sealing the mating walls of the envelope and cap With a substance that amalgamates with mercury, and then introducing a mercury fill and high pressure gas fill into the envelope, but subjecting at least a portion of the annular space to he high pressure gas fill before permitting it to be covered by mercury at said high pressure whereby a high pressure gas pocket is formed in the annular space which together with the nonwetting characteristic of said one metal part effectively prevents mercury from permeating the annular space to reach the sealing substance.

14. The method of fabricating a metal envelope mercury switch which comprises taking a metal envelope open at both ends, closing one end of the envelope with a metal cap and sealing the annular space between the envelope and the cap with a material that amalgamates with mercury, and then introducing a mercury fill and high pressure gas fill into the envelope but subjecting at least a portion of the annular space to the high pressure gas fill before permitting it to be covered by mercury at said high pressure, whereby a high pressure gas pocket is formed in the annular space which effectively prevents mercury from permeating the annular space to reach the sealing material.

CARL I-I. LARSON.

REFERENCES CITED The following references are of recordin the file of this patent:

UNITED STATES PATENTS Number Name Date 2,209,984 Larson a- Aug. 6, 194-0 2,232,879 Larson Feb. 25, 1941 1,384,478 Hatay Dec. 18, 1934 2,158,010 Marr May 9, 1939 2,266,469 Larson Dec. 16, 1941

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