US2303161A

US2303161A - Time delay switch

Info

Publication number: US2303161A
Application number: US423412A
Authority: US
Inventors: Walter H Gerisch
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1941-12-18
Filing date: 1941-12-18
Publication date: 1942-11-24
Anticipated expiration: 1959-11-24

Description

Nqv. 24,1942.

'w. H. samscu TIME DELAY SWITCH Filed m. 18, '1941 lhvehbof: Walter H. Gerisch tor-neg;

ENS 1X) Patented Nov. 24, 1942.

UNITED STATES PATENT OFFICE mlfxglsl I Walter H. Gerisch, North Bergen, N. 1., assignor New York pany, a co poration of Application December 10,1941, SerlalNoJtSAll '6 Claims. (Oi. zoo-s3) vlde an improved liquid contact switch having a v time delay characteristic.

Certain mercury switches are now available in which the switch enclosure is constituted of cooperating metal parts'separated by an apertured diaphragm having therfunction of interrupting the mercury circuit through the switch when the switch is moved to its openpositiona In. order to 1 import a time delay characteristic to switchesof this kind, it has been proposed to employ. a baiile having a restricted oriilce for the purpose of controlling the rate of flow of the mercury as the ing is constituted of a pair of cup-shaped metal members I, I, consisting of iron or chrome-iron alloy. .These are separated by means of a ceramic barrier I and are hermetically sealed by a ring ofglass 8 fused to the parts-l, I at their adjoining edges. The switchis preferably filled with a gas, such as hydrogen, or with a mixture of hydrogen and air and contains a quantity of mercuryindicated at 4. An aperture I provided in th barrier 2 atan appropriateslocation enables the mercury to form a continuous conductive path between the parts I, I when the switch is in the position illustrated in Fig. 1, However.

- when the. switch is tilted, for example to the switch is moved from one position to another.

However, due to the limited amount of mercury which is employed in switches of the type under consideration, and to the resultant smallness of the flow-producing "head which exists when the switch is actuated, difliculty is experienced in getting the mercuryv to flow in" a dependable fashion through an orifice of suiiicient smallness to'give any'appreciable time delay effect. The presentinvention is primarily concerned with the provision of means for effectively overcoming this dimculty.

In this connection, I havefound that the ability of mercury to pass through a restricted orifice is enhanced'by so arranging matters that'at least some of the surfaces of the orifice are constituted of a non-oxidizable metal which is readily wet by mercury. In a preferredcase, the metal employed for this purpose is platinum.

The features of the invention which I desire to protect herein are pointed out with particularity in the appended claims. The invention itself. to-

gether with furtherobjects and advantages thereof, may best be understood by reference to the following description taken in connection with the drawing, in which Fig. 1 is a sectional view of. a mercury switchsuitably embodying the illvention; Fig. 2 shows the switch of Fig. 1 in its open circuit position; Fig. 3'isan enlarged fragmentary view of a portion of the structure of Fig. i;- Fig. 4 is a top-view of the elements shown in Fig. 2; Fig.5 represents an alternative embodiment of theinvention; Figs. B and 7 are different sectional views illustrating another mode f application of the invention; and Figs. 8 and 9 i lusposition illustrated in Fig. 2, the circuit through the switch is interrupted by the action of the barrier in dividing the mercury into two pools as illustrated.

For some uses of a switch of the character described, it is desirable that an appreciable time shall intervene between the action of'an operator I in tilting the switch fromclosedt o open position trate the'intemal conditions of the switch of Fig.

a liquid contact switch inwhich the switch hous- 5 and the actual interruptionof the switch circuit. For this purpose the switch of Fig. i is provided with a flow-impeding baifle I i e. g. of steel or other ferrous metal) which extends between one surface of the apertured barrier I and the opposing cup-shaped part I. In order that the bailie I may not entirely prevent motion of the .mercury when the switch is tilted to the left, the heme is provided at its left hand edge with a small orifice (see l ig;v 3), this orifice being of such size as to permit the mercury to flow through it at a rate calculated to give a desired time delay effect.

As has been previously stated herein, difiiculty is experienced ingetting mercury to flow smoothly through a small orifice. Thisis especially the case if the orifice exists in a body which is not consistently wet by mercury, this being true, for example, when the part in question is constituted of ferrousmetalsuch as steel. In accordance with the-present invention, this dimcultyis overcome by assuring that at leasta portion of the bounding surface of the orifice desired to be utilizedconsists superficially of a non-oxidizable metal which is readily wet by mercury. This result can be effected in one way by providing on the inner wall surface of the cup-shaped metal part i a small rectangular tab 8 which either consists of platinum or of ironwhich has been plated with"platinum, the tab being so located that it coincides with the outer extremity of the notch I. The tab 8 is suitably of the character described in Walker Patent 2,101,115, granted December (I, 1937, and if of such character, serves the further function of providing wetting and a low resistance contact between the mercury and the inner surface of the cup-shaped part i, Wetting of the platinum surface by the mercury may be improved by heating the switch enclosure to a temperature of several hundred degrees centigrade after the switch is fabricated.

The presence of the platinum-surfaced part I makes it possible for the mercury .to fiow smoothly through the notch 8, even though the notch may be of very small dimensions (e. g. 100 mils or less). Consequently, by the use of this combination the switch can be given when opening the circuit an appreciable time delay characteristic. by the time required for a sufficient amount of mercury to run through the notch l to cause the mercury to be separated over the right hand edge of the barrier in the aperture 5, as shown in Fig. 2. When the switch is tilted back to the vertical position, contact is reestablished without time delay. As appears in Fig. 2, sufficient mercury remains in the main switch chamber below the apertured baifle I to immediately complete the circuit.

Substantially the same effect as that related above can be obtained in another way by plating the surfaces an orifice provided in a flowimpeding baiile at some other location than the edge of the baffle. This construction is illustrated in the fragmentary view of Fig. wherein a restricted orifice is indicated at ll in connection with a battle I which may be constituted of steel and which corresponds in nature and function to the baille I of Fig. 1.

In this case a platinum coating ll (shown with exaggerated thickness) serves to facilitate flow of mercury through the orifice l0. Because of the difficulties of depositing platinum within the confines of a small opening, this construction is in some respects less desirable than that of Fig, 3.

In the arrangement described in Fig. lit is assumed that the intended mode of use of the switch is such as to cause it to be tilted to the left when the switch circuit is to be opened. A time delay switch intended for a different mode of rotation is illustrated in Fig. 6 wherein it is assumed that the pictured switch is intended to be rotated about a horizontal axis parallel to the surface of the paper (e. g. by incorporation in a switch holder of the general character described in R. F. Sambleson Patent No. 2,142,153 granted January 3, 1939). In this construction the switch includes two cup-shaped metal parts i2, i2 separated by a barrier l1 and rier includes an aperture II which is below the surface of a body of mercury II when the switch is in closed circuit position (see Fig. 8).

On both sides cf the barrier I! there are provided similar bailles. I1, I! which extend from the barrier to the inner surface of the parts l2, l2 approximately at the surface of the mercury [6.

As appears most clearly in Fig. 7, each of the baffies i1 is provided near its outer edge and at a point relatively removed from the barrier aperture I5 with a small notch through which mercury may flow when the switch ,is rotated, for example to the position shown in Fig. 9. Each of the notches is contiguous with-a platlnized strip which serves to facilitate the flow The actualdeiay realized is determined the principles described above. With this arrangement it will be understood that as the switch is rotated from the position which it occupies in Fig. 8 to the position of Fig. 9, the

mercury flows at a restricted rate through the orifices, .only one of which is shown at It. The switch circuit is broken over the edge of the barrier aperture elapsed to cause the level of the mercury as shown in Fig. 9, to fall below the aperture ll.

While the invention has been described by reference to particular embodiments thereof, it will be understood that numerous modifications may be made by those skilled in the art, and I therefore aim in the appended claims to cover allsuch equivalent variations as come within the true spirit and scope of the foregoing disclosure What I claim as new and desire to secure by letters Patent of the United States is:

1. An electric switch including a body of mercury which is adapted by'its flow to control the transition of the switch from open to closed circuit condition and vice versa, and means procury flows in restricted fashion to produce a time delay effect, at least certain of the bounding surfaces of the said opening consisting of platinum.

3. An electric switch including a body of mercury which is adapted by its flow to control the transition of the switch from open to closed circuit position and vice versa, means defining a small opening through which the mercury flows in restricted fashion to produce a time delay effect, said means being constituted principally of a material which is not consistently wet by mercury, and a quantity of non-oxidizable metal which is readily wet by mercury covering at least certain of the bounding surfaces of the said hermetically joined by a glass ring H. The barof mercury through the notch in accordance with an aperture through which the mercury ijiows as, the switch is moved from one position to another,

and means for limiting the rate at which the mercury may flow through the'said aperture so as to produce a time delay effect, said means providing a restricted opening arranged in the path of flow of the mercury and having at least certain of its bounding surfaces constituted of platinum, whereby easy passage of mercury through the opening is assured.

5. An enclosed electric switch formed of a pair of cup-shaped ferrous metal parts, a quantity of mercury providing a conductive circuit between the said parts when the switch is in closed position,at least one of said parts having a platinumsurfaced area forassuring wetting by the mercury, a ceramic barrier insulatingly separating the said parts and effective to interrupt the circuit-through the mercury when the switch is in open position, said barrier having an aperture after a sumcient time has through which the mercury flows as the switch is moved from one position to another, and means for impeding the flow of mercury to provide a time delay effect, said means comprising a baiile which extends between said barrier and said one of the cup-shaped parts and which has its edge portion notched at a point contiguous with said platinum-surfaced area so as to provide a small aperture through which mercury may pass freely but at a restricted rate.

6. An electric switch comprising a pair of metal parts sealed together to form a hollow enclosure,

said members being insulated from one another,'

mercury in said enclosure for providing a conductive circuit between the parts in the closed position of the switch, at least one or said parts having a platinum-surfaced element attached to its interior to facilitate wetting by the mercury, a circuit-interrupting barrier dividing the switch enclosure into two compartments and having an aperture from which the mercury flows as the switch is moved from one position to another, and means for impeding the flow of mercury to provide a time delay eflfect, said means comprising a baiile which extends between the barrier and the said one 01 said 'wall parts and which has its edge portion notched at a point contiguous with said platinum-surfaced element, whereby the resulting aperture transmits mercury freely but at a WALTER H. GERISCH.

restricted rate.