Electricity: circuit makers and breakers – Fluid pressure – Diaphragm
Patent
1975-11-24
1977-12-13
Tolin, Gerald P.
Electricity: circuit makers and breakers
Fluid pressure
Diaphragm
200 83S, 200 83C, 340242, H01H 3534
Patent
active
040630579
ABSTRACT:
A pressure differential sensing device comprises a sealed housing having mounted therein a gas-filled flexible capsule and a switch operated by expansion of the capsule. The pressure differential sensing device is mounted to a pressurized chamber with the pressure of the chamber communicating with the interior of the housing and surrounding the capsule and monitors the chamber for gas leaks. The gas in the pressurized chamber and in the capsule both respond to variations in temperature in a like manner, and a relatively constant pressure differential is thereby maintained between the interior pressure of the capsule and the pressure of the housing. If gas leaks from the pressurized chamber, the pressure of the chamber decreases relative to the interior pressure of the capsule, and the capsule expands to operate the switch. Thus, the device is temperature compensated.
The pressure differential sensing device is calibrated by adjusting the position of the switch relative to the capsule. In one embodiment, the switch is mounted on a threaded collar positioned above the capsule, and the device is calibrated by adjusting the position of the switch. In another embodiment, the capsule is mounted on a first externally threaded collar which is fixed against rotation, and the first collar is mounted to a second interiorly threaded collar which is free for rotation and fixed against axial movement. Rotation of the second collar thereby adjusts the position of the capsule relative to the switch, and such adjustment may be made from outside the housing by providing an access to the second collar through a port in the housing.
In yet another embodiment, the switch is mounted by soldering its metal terminals to eyelets hermetically sealed in a glass header which includes a peripheral metal ring also hermetically sealed thereto. The metal ring is soldered to a cap which defines a substantial portion of the housing of the device, the cap is threadably mounted on the remainder of the housing, whereby the position of the switch relative to the capsule may be adjusted by turning the cap.
The pressure differential sensing device also includes means for testing its operability, and said means comprises a manually operable plunger carrying a plurality of O-seals. The plunger is mounted in an opening intersecting the passage from the pressurized chamber to the interior of the housing. The plunger normally permits communication between the pressurized chamber and the interior of the housing, but upon being manually depressed, operates to seal off the chamber and open the interior of the housing to the atmosphere, or other reference pressure lower than the pressure of the chamber, whereby the capsule expands to operate the switch provided the capsule has maintained its integrity and the device is in good working order. During testing, the O-seals are relieved by being positioned adjacent beveled grooves, and these grooves permit a short stroke of the plunger to the test position and prevent abrasion or excessive wear of the O-seals.
REFERENCES:
patent: 3046369 (1962-07-01), Hicks
patent: 3119910 (1964-01-01), Meisenheimer, Jr.
patent: 3200215 (1965-08-01), Good
patent: 3335241 (1967-08-01), Weber
patent: 3742165 (1973-06-01), Hellman
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