US2471281A - Switching device - Google Patents

Description

y 1949. L. E. 01.5%: ETAL 2,471,281

SWITCHING DEVICE Filed Aug. 27, 1947 INVENTORS RICHARD WERTZLER LEONARD E, OLSON ATTORNEYS Patented May 24, 1949 SWITCHING DEVICE Leonard Eugene Olson and Richard Wertzler, Chicago, Ill., assignors to Sinclair Refining Company, New York, N. Y., a corporation of Maine Application August 27, 1947, Serial No. 770,932

(Cl. ZOO-81.6)

2 Claims. 1

This invention relates to switches and like devices actuated by movement of a liquid in a U- tube and has for its object the provision of an improved device of this character. The invention is particularly concerned with devices having switch means including a conducting liquid such as mercury in the U-tube and an electrical circuit which is opened and closed by movement of the mercury, and provides means in combination with such devices for operating the switch means on failure of the flow of liquid which actuates the device.

Our invention provides a very simple and positive switch means for protecting apparatus and operations dependent upon a continuous flow of liquid, such as cooling water. In an advantageous embodiment, our device is in the form of a cut-off switch comprising a U-tube in which the mercury is held in one operating position by the pressure of the flowing liquid but is moved to another operating position by failure of the flow of liquid. The U-tube is so constructed that it is continuously supplied with the liquid which holds the mercury in operating position while the liquid is flowing, but is emptied of liquid by drainage when the liquid ceases to flow. We provide a low level outlet or bleeder for the tube which is always open and a high level outlet as an overflow for controlling the pressure imposed on the mercury and a vent to ensure positive drainage through the low outlet.

The accompanying drawings illustrate in side elevation a switch device of our invention in the form of a cut-ofi switch. It will be apparent that the electrical terminals and mercury can be arranged to switch on or ofi, close or open the circuit, on failure of the flow of liquid.

The device illustrated in the drawings comprises a U-tube l of, say, 12 mm. glass tubing with a short leg 2 in which is sealed the tungsten contact leads 3 and 4 of the electric circuit 5. The long leg 6 extends some 30 cm. above the short leg and has a lower drain extension 1, an upper drain extension 8, a vent 9, and an inlet connection Hi, all preferably an integral part of the tube. The body of mercury I2 is shown in its position of rest with only the small residue of water l3 in the bottom of the long leg 6. In this position the mercury is out of contact with contact 3 and the circuit is broken. The low outlet hole [4- of the extension I is quite small, say, 2 mm. in diameter, and serves essentially as a bleeder for the long leg. The hole I in the drain extension 8 is larger than hole l4 and serves as an overflow to regulate the pressure of liquid acting on the mercury. Hole 15 may be about 30 cm. above hole I l. The vent 9 is about 1 to 2 mm. in diameter and serves to insure positive drainage of leg 6 through hole [4. The inlet It! may be connected by a hose or the like to the conduit through which the liquid is flowing. This liquid may be for cooling condensers, chemical equipment, and the like, the interruption of which may cause serious damage. By means of a valve (not shown) the flow of liquid into the long leg is controlled so that there is a continuous overflow through hole 15. This insures suflicient pressure on the mercury to hold it in contact with contact 3. Drain extensions 1 and 8 may be connected by rubber tubing to a waste line.

When the liquid ceases to flow, the liquid in the line to be protected drains out of the long leg 5 through hole M, the vent 9 preventing waterlock and the retention of liquid in the leg.

If the power load is too heavy to be connected directly through the mercury in the tube, a suitable relay system may be inserted in the circuit and the leads of circuit 5 need only be connected in series with the circuit.

We claim:

1. A liquid-flow failure switch comprising a U- tube of electrically non-conducting material having a short leg and a long leg, a body of mercury in the tube, electric contact means in the tube actuated by the mercury, inlet means on the lon leg for receiving liquid flowing in a conduit, means for the continuous removal of liquid from the long leg whereby a constant pressure of liquid is maintained on the mercury, a vent in the upper part of the long leg to insure drainage of the long leg, and a drain means which is continuously open on the long leg for removing liquid on failure of the flow in the conduit to change the position of the mercury.

2. A liquid-flow failure switch comprising a U- tube of electrically non-conducting material having a short leg and a long leg, a body of mercury in the tube, electric contact means in the tube actuated by the mercury, inlet means on the long leg for receiving liquid flowing in a conduit, an extension of the long leg having an upwardly extending vent and a lower outlet for the continuous removal of liquid from the long leg whereby a constant pressure of liquid is maintained on the mercury, and a drain means having a continuously open hole near the lower part of the long leg for removing the liquid therefrom on failure of the flow of liquid to decrease the pressure on the mercury.

The following references are of record in the file of this patent:

UNITED STATES PATENTS Name Date Hickman Feb. 12, 1935 Number

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