US2747176A

US2747176A - Automatic gas alarm

Info

Publication number: US2747176A
Authority: US
Inventors: Cox Ernest
Original assignee: Individual
Current assignee: Individual
Priority date: 1954-03-12
Filing date: 1954-03-12
Publication date: 1956-05-22
Anticipated expiration: 1973-05-22

Description

May 22, 19% X 234mm AUTOMATIC GAS ALARM Filed March 12, 1954 INVENTOR ERNEST cox gal 3 AUTQMATEC GAS ALARM Ernest Cox, Hempstead, N. Y.

Application March 12, 1954, Serial No. 415,788

1 Claim. (Cl. 340-237) The invention is a device intended for installation in dwellings and other buildings where natural gas, manufactured gas or both (hereinafter called gas) are used as fuel. Its function is to sound an alarm and shut oil? the flow of gas at its source in the building in the event of an undetected leak. Its purpose is to minimize the loss of life by asphyxiation and violent explosion which is incidental to the use of the gas as fuel.

The invention employs the difference in weights of equal volumes of gas and air which, using one cubic foot of each, would amount to .70 ounce approximately at sea level. Any sealed volume balanced in atmosphere against an equal weight of less volume is partially supported by buoyant force equal to the weight of air it displaces. It will descend if surrounded by a gas mixture of less weight and ascend when surrounded by a heavier mixture. To obtain a reaction to a comparatively harmless gas mixture, the invention must be of delicate construction, the moving parts must have a minimum of weight and friction and the electric contacts must be sealed against possible ignition of gas.

One form of the invention is illustrated in the accompanying drawing in which Figure 1 is the entire assembly and wiring in perspective. The device is placed above the window line of the building and convenient to the gas outlet. An electric Wire lead 1 connects to terminal screw 22 (see Figure 2) from source of current. Wire lead 2 connects from metal bushing 19 (see Figure 2) to solenoid shutoff 3 which is placed in gas line at source in building. Wire lead 4 connects from solenoid shutofi" 3 to source of current. Wire lead 5 connects from lead 2. to alarm bell 6 which is placed preferably on outside of building. Wire lead 7 connects from alarm bell 6 to wire lead 4. It is the function of the device to bridge Wire leads 1 and 2 thus closing an electric circuit which will then actuate the solenoid shutoflf 3 thereby shutting off the flow of gas, and the alarm bell 6 which will indicate trouble. I am aware that the method of signal and shutoff set forth here is only one of several possible arrangements, and since the wiring of this device is not the essence of the invention, I submit this one for its clarity.

Figure 2, a vertical section through the assembly shows a sealed hollow float 8 through which is fixed vertically a rigid stem 9 hooked at the upper end and suspended from lever 10 which is hooked at the outer end and attached at the inner end to the outer coil of a flat spiral spring 11.

Figure 3 is a right hand projection showing fiat spiral spring 11 attached on the inside coil to a slot in adjustable shaft 12 which is threaded through upright 13 and lock nut 14. It will be seen here that by turn- 2,747,176 Patented May 22, 1956 ing shaft 12 so as to tighten spiral spring 11, the stem 9 and float 8 will rise and remain freely suspended above the lower mechanism, and can be locked in any required position.

in Figure 2 the base 15 constitutes a sealed switch box made of non-conducting material and with a deep bore in the center. A diaphragm 16 suitably thin and fiexible, is sealed by gaskets 1717 on top and bottom and pressed between base 15 and cap 18 which has a hole through center to freely accommodate bottom end of stem 9.

Through the center of base 15 is fixed a metal bushing 19 and attached to this is electric wire lead 2. Through the center of bushing 19 is threaded an adjustable contact screw 20. From a point directly above contact screw 20 and touching diaphragm 16 a thin brass contact spring 21 slopes downward to base 15 and fastened by a terminal screw 22. To this is fastened electric wire lead 1. Four legs 23 are attached to base 15.

In operation, float 8 and stem 9 are suspended by adjustment of spring 11 so that bottom end of stem is within a very short striking distance of diaphragm 16. In this position the float 8 is balanced in atmosphere partially by tension on spring 11 and partially by the buoyant force of air equalling approximately the weight of air displaced by float 8. Adjustable contact screw 20 is adjusted to within a few thousandths of an inch from the contact spring 21. (Since it is enclosed, this micro adjustment is made by using a test light attached to terminal screw 22 and bushing 19.)

When float 8 is surrounded by a gas mixture of lighter weight than air, the atmospheric buoyant force, which partially supports it, will have been reduced by the difference in weight of the original volume of air and the same volume of gas mixture and it will descend carrying the stem 9 to strike diaphragm 16 and causing contact spring 21 to touch contact screw 20. This contact bridges electric leads 1 and 2 and closes a circuit which actuates solenoid shutoff valve 3 and rings alarm bell 6.

I am aware of existing patents covering devices which employ a float suspended from a beam and balanced by a counterweight. My invention differs in the method of suspension, which, as has been shown, is a lever with a spring as the fulcrum. This eliminates most of the loss of efficiency due to friction and reduces the cost of manufacture. My invention differs also in that it was designed to detect only gases lighter than air.

I claim:

A device for signalling the presence of gas, and in particular, manufactured or natural gas, such as is used for fuel, comprising a sealed hollow float and stem held in delicate suspension vertically in atmosphere by a lever and the tension on an adjustable flate spiral spring in such manner that when the float is surrounded by a gas or mixture of less weight than air, it will descend and strike the diaphragm of a sealed electric switch thus sounding an alarm and shutting the gas off at its source.

References Cited in the file of this patent UNITED STATES PATENTS 826,659 Hanger July 24, 1906 943,015 Groesbeck Dec. 14, 1909 1,995,870 Stone Mar. 26, 1935 2,675,816 Giannete Apr. 20, 1954