Pressure drop detector with testing means, centrifugal force compensating means, and temperature compensating means

Claim 2

In a pressure drop detector which is connectable to a sealed enclosure for detecting leakage from said enclosure and comprising a casing which forms a chamber, a flexible wall element disposed within said chamber and responsive to the pressure existing within said enclosure, and a switching unit controlled by said flexible wall element so as to carry out a reversal of state when the pressure within the enclosure falls as a result of leakage, wherein, in order to compensate for pressure variations arising from variation in the ambient temperature and in order to render the apparatus unresponsive to ambient pressure, said chamber is subdivided into two cavities separated from each other by said flexible wall element, one of said cavities which is utilized for a measurement of pressure being connectable to the enclosure to be monitored while the other cavity is filled with gas at a reference pressure which is substantially in the vicinity of the pressure which prevails within the enclosure to be monitored in order that the variations in ambient temperature should modify the pressure to be checked and the reference pressure in the same manner, the reference cavity having in addition a volume which reduces to a negligible value the variation in volume corresponding to the range of travel of the wall element which is necessary for the operation of the switching unit, and wherein, in order to compensate for pressure variations resulting from the movement of rotation of the enclosure about an axis, a movable portion of the flexible wall element has a mass which is such that centrifugal force applied to said mass is equal to the variation in the force exerted by the pressure on said portion of the flexible wall of the detector, and said movable flexible wall portion being additionally oriented so that centrifugal force is applied in the direction which compensates for the variation.

Claim 3

A pressure drop detector which is connectable to a sealed enclosure for detecting leakage from said enclosure and comprising a casing which forms a chamber, a flexible wall element disposed within said chamber and responsive to the pressure existing within said enclosure, and a switching unit controlled by said flexible wall element so as to carry out a reversal of state when the pressure within the enclosure falls as a result of leakage, wherein, in order to compensate for pressure variations arising from variation in the ambient temperature and in order to render the apparatus unresponsive to the ambient pressure, said chamber is subdivided into two cavities separated from each other by said flexible wall element, one of said cavities which is utilized for a meAsurement of pressure being connectable to the enclosure to be monitored while the other cavity is filled with gas at a reference pressure which is substantially in the vicinity of the pressure which prevails within the enclosure to be monitored in order that the variations in ambient temperature should modify the pressure to be checked and the reference pressure in the same manner, the reference cavity having in addition a volume which reduces to a negligible value the variation in volume corresponding to the range of travel of the wall element which is necessary for the operation of the switching unit, wherein, in order to control the operation and sensitivity thereof, said detector comprises a slide valve for the purpose of isolating the measuring cavity from the sealed enclosure to be monitored, a plunger which is integral with said slide valve for varying the volume of the measuring cavity which is isolated from said enclosure, a metallic bellows element which is connected to said casing and to said plunger for ensuring the imperviousness thereof with respect to the exterior, a control knob located outside said casing and rigidly fixed to said plunger, and a safety cap which is screwable on said casing over the aforesaid control knob in the normally depressed position thereof.

Claim 4

A pressure drop detector which is connectable to a sealed enclosure for detecting leakage from said enclosure and comprising a casing which forms a chamber, a flexible wall element disposed within said chamber and responsive to the pressure existing within said enclosure, and a switching unit controlled by said flexible wall element so as to carry out a reversal of state when the pressure within the enclosure falls as a result of leakage, wherein, in order to compensate for pressure variations arising from variation in the ambient temperature and in order to render the apparatus unresponsive to the ambient pressure, said chamber is subdivided into two cavities separated from each other by said flexible wall element, one of said cavities which is utilized for a meAsurement of pressure being connectable to the enclosure to be monitored while the other cavity is filled with gas at a reference pressure which is substantially in the vicinity of the pressure which prevails within the enclosure to be monitored in order that the variations in ambient temperature should modify the pressure to be checked and the reference pressure in the same manner, the reference cavity having in addition a volume which reduces to a negligible value the variation in volume corresponding to the range of travel of the wall element which is necessary for the operation of the switching unit, wherein, in order to control the operation and sensitivity thereof, said detector comprises a slide valve for the purpose of isolating the measuring cavity from the sealed enclosure to be monitored, a plunger which is integral with said slide valve for varying the volume of the measuring cavity which is isolated from said enclosure, a metallic bellows element which is connected to said casing and to said plunger for ensuring the imperviousness thereof with respect to the exterior, a control knob located outside said casing and rigidly fixed to said plunger, and a safety cap which is screwable on said casing over the aforesaid control knob in the normally depressed position thereof.

Claim 5

The pressure drop detector as defined in claim 2, wherein the switching unit is of the snap-action type and is unresponsive to accelerations and to vibrations while the casing comprises means for guiding the flexible wall element so that the detector should be unresponsive to accelerations which are directed transversely, and stationary abutment means for limiting the range of travel of said flexible wall element.