Electricity: magnetically operated switches – magnets – and electr – Permanent magnet-actuated switches
Reexamination Certificate
2000-01-27
2001-05-22
Barrera, Ramon M. (Department: 2832)
Electricity: magnetically operated switches, magnets, and electr
Permanent magnet-actuated switches
C200S0830SA
Reexamination Certificate
active
06236295
ABSTRACT:
BACKGROUND OF THE INVENTION
Pressure-sensing switches typically have a pressure-sensing region and an electrical region, with pressure information from the pressure region being communicated to the electrical region. When a pressure-sensing switch is designed for use in a hazardous environment, e.g. for monitoring gasoline vapor vacuum pressure or detecting pressure differential in a gasoline vapor flow, it is critical that the electrical region of the switch be sealed against penetration of explosive gasoline vapor from the pressure region. Typically, the necessary sealing may be provided by diaphragm displacement indication through mechanical means, with static or dynamic seals or flexible membrane devices.
SUMMARY OF THE INVENTION
According to one aspect of the invention, An explosion-proof, pressure responsive shut-off switch comprises a body defining a first, gasoline vapor system pressure region and a second, electrical region, and a vapor and liquid impermeable wall therebetween. A magnet is mounted in the first, gasoline vapor system pressure region for movement, in response to vapor pressure, between a first position spaced from the vapor and liquid impermeable wall and a second position relatively more closely adjacent the vapor and liquid impermeable wall. A reed switch is mounted in the second, electrical region in proximity to the vapor and liquid impermeable wall, and adapted to open and close a vacuum pump switch in response to movement of the magnet in between the first position and the second position.
Preferred embodiments of the invention may include one or more of the following additional features. The magnet is mounted on a pivot arm. The pivot arm has an adjustable pivot for adjusting a ratio of magnet movement relative to a given vapor pressure. The explosion proof, pressure responsive shut-off switch further comprises a spring to urge the magnet away from the vapor and liquid impermeable wall. The explosion-proof, pressure responsive shut-off switch further comprises a flexible diaphragm separating the gasoline vapor system pressure region from an atmospheric pressure region, the flexible diaphragm movable in response to a pressure ratio defined by a pressure differential between the atmospheric pressure region and the gasoline vapor system pressure region. The magnet moves in response to a movement of the diaphragm. The explosion-proof, pressure responsive shut-off switch further comprises an adjustment element for adjusting a threshold pressure ratio at which the magnet moves from the first position to the second position. The explosion-proof, pressure responsive shut-off switch further comprises an adjustable shaft mounted to the diaphragm. The reed switch is mounted on a flexure arm. The explosion-proof, pressure responsive shut-off switch further comprises a spring to urge the flexure arm away from the vapor and liquid impermeable wall. The explosion-proof, pressure responsive shut-off switch further comprises an adjustment element to adjust a position of the flexure arm relative to the vapor and liquid impermeable wall, against the spring. The explosion-proof, pressure responsive shut-off switch has unitary electrical components replaceable without removing the body from an attached vapor line. The vapor and liquid impermeable wall is a non-magnetic material, e.g., aluminum. The explosion-proof, pressure responsive shut-off switch is mounted with the diaphragm oriented vertically, to reduce gravity effects. The explosion-proof, pressure responsive shut-off switch has vapor connections in a lower portion of the gasoline vapor system pressure region to promote drainage of liquid from the region. The liquid in the gasoline vapor system pressure region is a result of condensation or overfill of an attached tank. The vacuum pump switch activates a central vane pump in a fuel dispenser. The explosion-proof, pressure responsive shut-off switch is adjusted to maintain vapor pressure in the gasoline vapor system pressure region A at −65 inch WC. The explosion-proof, pressure responsive shut-off switch is arranged to activate the vacuum pump switch in response to a pressure differential between the gasoline vapor system pressure region and a region exterior to the gasoline vapor system pressure region, e.g., an atmospheric pressure region. The explosion-proof, pressure responsive shut-off switch is adjusted to activate the vacuum pump switch when said pressure differential is ½-inch WC.
The pressure-sensing switch assembly of the invention provides substantial improvement over commercially available switches for gasoline vapor vacuum or pressure differential applications. In particular, the invention provides a pressure-sensing switch assembly in which the gasoline vapor system pressure region of the assembly is separated from the electrical region by a solid metal wall. There are no static or dynamic seals or flexible membrane devices required to separate the two regions, as necessary when providing diaphragm displacement indication through mechanical means. The separation wall is non-magnetic metal, preferably aluminum.
Other features and advantages of the invention will be apparent from the following description of a presently preferred embodiment, and from the claims.
REFERENCES:
patent: 3629532 (1971-12-01), Pisors
patent: 4132237 (1979-01-01), Kennedy et al.
patent: 4600034 (1986-07-01), Ko
patent: 5091612 (1992-02-01), Van Fossen
International Search Report, dated Apr. 6, 2000, for International Appl. No. PCT/US00/02197.
Barrera Ramon M.
Fish & Richardson P.C.
Healy Systems, Inc.
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