Gas flow detector

Details Gas flow detector Gas flow detector

1998-03-10

2000-09-19

Hofsass, Jeffery A.

Communications: electrical

Condition responsive indicating system

Specific condition

340606, 340610, 340611, 7386154, G08B 2100

Patent

active

061218847

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

This invention relates to a gas flow detector.
Inflammable gases such as liquid petroleum gas (LPG) are used for purposes such as cooking, refrigeration, and water heating in boats and in recreational vehicles of many types such as caravans and campers. Inflammable gases are also used in industry as well as holiday homes and cottages which are not supplied with electricity.
Such gases are heavier than air and if there is a leak the gases accumulate in the bottom of the boat, at the caravan floor, in a basement, etc. depending on where the gas supply is located. Even a minute leak can result, over a period of time, in gas collecting in sufficient volume to give rise to a potentially explosive mixture.
Conventionally there is a shut-off valve and regulator at the gas bottle but, once the bottle is in use, this valve is generally left open. It is thus of no value in preventing escape of gas through an open but unlit burner, through a pilot light that is out, or through a leak in a pipe or a pipe fitting.
The present invention seeks to provide a detector which is sensitive to very low rates of gas flow and thus reacts should there be a slow leak from the gas system.


BRIEF SUMMARY OF THE INVENTION

According to the present invention there is provided a gas flow detector comprising a casing having a gas inlet and a gas outlet, a cylinder within said casing, a piston in said cylinder, a flow path from said inlet to a space below said piston, a flow path from a space above said piston to said outlet, lifting of said piston from a lower position it occupies when there are equal gas pressures at said inlet and outlet to an upper position it occupies when the pressure at said outlet is lower than the pressure at said inlet placing said spaces in communication with one another, a magnet carried by said piston at the lower end thereof, and a magnetically operated switch below said piston and which is subjected to the field of said magnet when said piston is in said lower position.
Said cylinder is preferably arranged with its axis vertical so that the piston moves vertically but it can be at an angle of up to, say, 45 degrees with respect to vertical.
In the preferred form, the piston is hollow and comprises a base wall and a cylindrical side wall, said magnet being carried by said base wall. In this form there is preferably a recess in the underface of said base wall and said magnet is in said recess.
To minimise shocks when the piston lifts, there can be a resilient shock absorbing buffer carried by said piston at the upper end thereof.
In the preferred form, said cylinder is constituted by the bore of an open ended sleeve located in a chamber of said casing. In this form, the sleeve can be stepped externally to provide an upper part of larger external diameter and a lower part of smaller external diameter, there being an external sealing surface between said parts of the sleeve and a sealing ring carried by said casing, said sealing ring encircling said sleeve, and said surface bearing on the sealing ring to prevent gas leaking from said inlet to said outlet between the sleeve and said casing. It is also possible for the sleeve to be stepped internally so as to provide an upper part of larger internal diameter and a lower part of smaller internal diameter, the upper part having an array of internal, axially extending ribs, the effective internal diameter of said upper part, measured diametrically across said ribs, being the same as the internal diameter of said lower part.
To enable the device to cope with the flow rates needed for cooking and water heating one or more holes can be provided in said upper part which holes place the interior of the sleeve in communication with said outlet.
The chamber can be stepped at its upper end so as to provide an annular surface, the upper end of the sleeve being in contact with said annular surface and there being notches in said upper end to permit gas flow between said sleeve and said annular surface. In this form, the detector can include a rec

REFERENCES:
patent: 3070232 (1962-12-01), Casaleggi
patent: 3446986 (1969-05-01), Cox
patent: 3805611 (1974-04-01), Hedland
patent: 4181835 (1980-01-01), Stadler et al.
patent: 4315436 (1982-02-01), Mc Cabe
patent: 4738395 (1988-04-01), Chilton et al.
patent: 4763114 (1988-08-01), Eidsmore
patent: 5304757 (1994-04-01), Hansel
Abstract of Japanese JP 01-224670 Dated Sep. 1989.

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