US2776351A - Mercury switches - Google Patents

Description

Jan. 1, 1957 L. MITCHELL 2,776,351

MERCURY SWITCHES Filed May 10, 1954 .v I 30 a I 2 .2! I "I I? V I I 34 -r z lllll J IIIIIHIIIIII iNSUL'LATION 1.. I I

9 7 I. I I g is GLASS i mvmc L.M|TCHELL' I. 2/ f BY W0! W ATTORNEY INVENTOR United States Patent MERCURY SWITCHES Irving L. Mitchell, Rockville Centre, N. Y. assignor to Ebert Electronics Corporation, Queens Village, N. Y., a corporation of New York Application May 10, 1954, Serial No. 428,535

Claims. (Cl. 200-112) The present invention relates generally to mercury switches, and more particularly to systems of multiple mercury displacement switches, having novel actuating coils.

It is known in the prior art to provide mercury displacement switches including a vitreous envelope, containing a pool of mercury permanently in contact with one lead of an electrical circuit, and a further lead which may be brought into and out of circuit with the first mentioned lead by varying the level of the mercury pool. The level of the mercury pool many be raised or lowered by means of an electro-magnetically actua'ble plunger, the latter being actuated from externally of the vitreous envelope in response to electrical energization of an actuating coil. Switches of the character described are commonly employed to make and break two phase or three phase lines, one switch being employed in each line, and a common actuating coil being employed for actuating the armatures of the several switches.

In designing actuating coils for multiple mercury switches, the general practice has been to provide coils of circular cross-section, a symmetrical shape being desirable in order that the several armatures be symmetrically disposable with respect to the coil, and thereby synchronously operable, and further for reasons of simplicity and economy of winding. It is found, however, that coils of circular cross-section have extremely high leakage with respect to the switch armatures, so that either a large coil current is required to secure high velocity of switch operation, or a large number of coil turns.

In accordance with the present invention the actuating coil for a multiple mercury switch is arranged to have a cross-section which minimizes leakage, maximizes actuating force on the switch armatures, assures symmetry of this force at the several armatures, reduces the total quantity of coil copper required, and yet which retains the simplicity and economy of fabrication inherent in coils of circular cross-section.

In the case of a double switch assembly I employ an actuating coil cross-section having rounded ends which snugly fit the contour of the switch containers, the rounded ends being joined by rectilinear elements. The total circumference of the coil cross-section is thereby minimized, and its coupling with the switch armatures maximized.

In the case of a triple switch, intended for use in a three phase circuit, a similar expedient is employed, leading to generally triangular coils, which are symmetrical in crosssection, employ a minimum of copper, and the coupling of which to the three switch armatures is maximized and symmetrical.

It is, accordingly, an object of the present invention to provide a novel multiple mercury switch assembly, having an actuating coil which is symmetrical with the several switches, the coupling of the coil with the switch armatures being maximized, and the quantity of copper in the coil minimized.

It is a more specific object of the invention to provide a three phase mercury switch assembly employ-ing three discrete mercury displacement switches, in which a common actuating coil for the switches is of generally triangular cross-section, the switches being located within the apices of the triangular cross-section.

It is a more general object of the present invention to provide an operating coil for a plurality of mercury displacement switches, in which the coil is in maximum proximity to the switch envelopes.

It is a further general object of the invention to provide a novel actuating coil for multiple mercury displacement switches in which the coil includes curvilinear portions, each partially embracing one of the switches, and joined by relatively rectilinear portions, whereby an economically fabricated coil, of simple configuration, provides maximum force at the armatures of the switches.

The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of a specific embodiment thereof, especially when taken in conjunction with the accompanying drawings, wherein:

Figure 1 is a view in elevation, partially in crosssection, of a switch assembly including two mercury displacement switches;

Figure 2 is a view in elevation of a switch assembly including three mercury displacement switches;

Figure 3 is a view in plan of the system of Figure 1;

Figure 4 is a view in plan of a three switch system, in accordance with Figure 2; and

Figure 5 is a view in plan of a modification of the system of Figure 4.

Referring now more particularly to Figures 1 and 3 of the accompanying drawings, the reference numeral 1 denotes a first mercury displacement switch and the reference numeral 2 a duplicate switch. The switches 1 and 2 are arranged with their longitudinal axes parallel, within an operating coil 3.

Describing the structure of the switch 1, as typical of the several switches employed in the practice of my invention, the switch 1 includes a vitreous envelope 5, having generally cylindrical longitudinal walls, an upper end wall 6, and a lower end wall 7. Extending through the lower end wall 7 is a vitreous column 8, through which extends a lead 9. The column 8 terminates at its upper end in a hollow vitreous cup 10, into which the lead 9 extends,

" and the lead 9 extends externally of the envelope 5 in the form of an insulated wire 11.

A second lead 12 extends internally of the lower end wall 7 into permanent contact with a body of mercury 13, and extends externally of the envelope 5 in the form of an insulated wire 14.

extending nubs 19, which ride on the interior surface of the vitreous envelope 5, and serve to guide the movement of the armature 16 parallel to its longitudinal axis. Coil springs 20 and 21 encompass the upper and lower end portions of the interior insulating sleeve 17, and extend beyond the limits of the latter. The springs 20 and 21 serve to take up shock due to violent translation of the armature 16 during energization of the armature 16.

The mercury pool 13 extends, in the open position of the switch, to a level below the cups 10, and the armature 16 may be in its upper position, all as illustrated in Figure 1 of the accompanying drawings. The armature 16 may be caused to move to a lower position, in response to current flow in the coil 3, and in so moving displaces mercury, causing the level of the mercury to rise sufficiently to overflow the cup 10, thereby completing a circuit between lead 9 and lead 12, through the mercury.

When the coil 3 is de-energized the armature 16 ascends, and the circuit is broken.

It will be clear that the armature 16 may be sufiiciently weighted that its normal position will serve to close the circuit, in which case the coil 3 may be so located as to cause the armature 16 to rise, when energized, and thus to break the circuit.

The switches 1 and 2 fit snugly each within a cell of a cellular insulating form 22, having the shape of a figure eight, and which serves as a coil form during the winding of the coil 3. The form and shape of the latter represents a primary point of novelty in the present invention. The coil 3 includes two rounded substantially semi-circular portions 24 and 25, when viewed in plan, joined by rectilinear portions 26 and 27. Use of the specially shaped core results in closer coupling between the coil 3 and the armatures of the switches 1 and 2, and further in the reduction of the total copper employed in the core. The latter result flows from the shape of the coil, which inherently contains less copper than would a circular coil, but also from the fact that closer coupling with the armatures is accomplished, which enables use of a coil of fewer turns, if desired.

In the system of Figures 3, 4 and 5, the novel concept of the system of Figures 1 and 2 is carried forward to a a. triple switch, suitable for use in three-phase circuits. Three switches 30, 31, 32 are employed, which are similar in structure to the switch 1, and which are arranged with longitudinal axes parallel, and occupying the apices of an equilateral triangle. This configuration results in maximum compactness.

The switches 30, 31, 32 are surrounded by a common actuating coil 34, which includes three arcuate sections 35, 36, 37, each following roughly the arc of a circle, and established roughly at the apices of an equilateral triangle. The arcuate sections 35, 36, 37 conform closely in curvature to the shape of the envelopes of switches 30, 31, 32. Adjacent arcuate section pairs of the coil 34 are joined by rectilinear sections 38, 39, 40, to form a generally triangular coil.

The virtue of the generally triangular coil above described resides in the fact that closer coupling is attainable with the armatures of switches 30, 31, 32, than is possible when utilizing the conventional circular coil. The triangular coil is not more difiicult to wind than is a circular coil, and contains less copper for a corresponding number of turns, and is therefore not only more advantageous operationally, but is also more economical of fabrication.

In the system of Figure 4 the coil form 41, in which the coil 39 is wound, is fabricated of insulating material, and includes three parallel thin-walled tubes or cells 42, 43, 44, each adapted to fit snugly about one of the switches 30, 31, 32. The tubes42, 43, 44 are joined at their lines of contact and in the adjacent areas 45, and serve to locate accurately the switches 30, 31, 32, within the coil 34.

In the embodiment of my invention illustrated in Figure 5 of the accompanying drawings, a coil form 46 is employed which hugs the inner wall of the coil 34, along its entire surface, and thereby serves only to space the switches 30, 31, 32 from the inner wall of coil 34. In this embodiment the envelopes of the switches 39, 31, 32 are in direct contact along three lines, and the coil form 46 is designed to provide a snug fit of the switches therewithin.

While I have described and illustrated specific forms of the invention it will be clear that variations thereof may be resorted to without departing from the true scope of the invention as defined in the appended claims.

What I claim and desire to secure by Letters Patent of the United States is:

1. A circuit maker and breaker system including a plurality of separate switch elements, each of said switch elements including a circular cylindrical vitreous envelope, a pair of separated contacts, a pool of mercury, one of said contacts permanently within said pool of mercury, the other of said contacts located at a predetermined level with respect to the surface of said pool of mercury, means for varying the level of said pool of mercury to a position above and below said other of said contacts, said means for varying including an armature located within said vitreous envelope and submersible in said pool of mercury, and a common actuating coil for all the armatures of said plurality of separate switch elements, said common actuating coil including arcuate portions having inner Walls conforming in radius substantially with the outer walls of each of said vitreous envelope, and having portions tangential to and joining said arcuate portions.

2. The combination in accordance with claim 1 wherein said coil is approximately of triangular shape, having arcuate apices, said vitreous envelopes located at said apices.

3. The combination in accordance with claim 1 wherein said coil includes only two substantially parallel substantially rectilinear portions.

4. The combination in accordance with claim 1 wherein said coil includes three substantially rectilinear portions, making an angle of substantially 60 one with the other.

5. The combination in accordance with claim 1 wherein is provided a cellular coil form for said coil, said cellular coil form providing a plurality of circular cylindrical cells, each of said cells arranged snugly to accept one of said vitreous envelopes.

References Cited in the file of this patent UNITED STATES PATENTS 2,095,604 Larson Oct. 12, 1937 2,113,595 Larson et al Apr. 12, 1938 2,166,163 Larson July 18, 1939 2,213,100 Cianchi Aug. 27, 1940 2,289,830 Ellwood July 14, 1942 2,318,405 Leveridge May 4, 1943 2,397,123 Brown Mar. 26, 1946 FOREIGN PATENTS 485,824 Great Britain May 25, 1938

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