Fluid pressure actuated switch with prestressed diaphragm

Claim 2

A fluid pressure responsive switch comprising a housing, a fluid inlet in said housing, first and second diaphragms in said housing to define a first chamber therebetween, fluid in said first chamber, a second chamber in communication with said fluid inlet, said second chamber being located on the opposite side of said first disphragm from said first chamber, switch means on said housing actuatable by said second diaphragm after the sensing of a predetermined pressure in said second chamber by said first diaphragm, and means for presetting the sensitivity of said switch wherein said means comprises said first diaphragm being prestressed beyond the amount it would be stressed by the ambient pressure of fluid in said first chamber, whereby a force is exerted by said first diaphragm which acts in conjunction with the force of fluid in said second chamber, and the sensitivity of said switch being dependent on the amount said first diaphragm is prestressed.

Claim 3

A fluid pressure responsive switch as set forth in claim 1 including pressure sensing tube means for providing a column of gas, said pressure sensing tube means having first and second ends with said first end being in communication with said second chamber, and exposure means on said second end of said pressure sensing tube for exposure to a force creating a compressive force on said gas in said pressure sensing tube means to thereby cause said force to be sensed in said second chamber.

Claim 4

A fluid pressure responsive switch as set forth in claim 2 wherein said exposure means comprises inverted cup means for permitting liquid to rise therein.

Claim 5

A fluid pressure responsive switch as set forth in claim 1 including a partition member located between said first and second diaphragms so as to divide said first chamber into third and fourth chambers, aperture means in said partition member, valve means associated with said aperture means to permit flow of fluid from said third chamber to said fourth chamber upon the sensing of fluid pressure in said second chamber while preventing reverse flow from said fourth chamber to said third chamber, and bleed aperture means in said partition member for permitting flow of fluid from said fourth chamber to said thirD chamber at a controlled rate upon the relieving of said sensed fluid pressure in said second chamber.

Claim 6

A fluid pressure responsive switch as set forth in claim 4 wherein said housing comprises first and second halves having first and second rims, respectively, and wherein said fluid inlet is in said first half of said housing, and wherein said partition member is relatively thin and has an outer edge portion located between said first and second rims, a first outer edge on said first diaphragm located between said outer edge portion and said first rim, a second outer edge on said second diaphragm located between said outer edge portion and said second rim, a plurality of fastener means extending through said first and second rims and said outer edge portion for holding said first and second halves of said housing and said partition member and said first and second diaphragms in assembled relationship, and wherein said aperture means comprise a plurality of apertures in said partition member, and wherein said valve means comprise a flapper valve having a first portion attached to said partition member and a second portion overlying said plurality of apertures, said second portion being circular and substantially planar and lying substantially parallel to said partition member in said fourth chamber, said first portion being centrally attached to said second portion, said first portion including first and second spaced enlarged portions with a reduced portion therebetween, a flapper valve holding aperture in said partition member, said reduced diameter portion fitting in said flapper valve holding aperture, said first enlarged portion being remote from said second portion of said flapper valve means and being located in said third chamber, said second enlarged portion being in contiguous relationship to said second portion and being located in said fourth chamber to space said second portion from said partition member, said first enlarged portion being resilient for squeezing through said flapper valve holding aperture, and said second portion including an annular lip on its outer periphery for engaging said partition member to effect a sealing relationship relative to said plurality of apertures.

Claim 7

A fluid pressure responsive switch as set forth in claim 5 including a fifth chamber in said housing for receiving said switch means, a cover plate on said housing for permitting selective access to said switch means, said housing including portions for locating said switch means therein including a second partition member for supporting said switch means, a third aperture in said second partition means, and a switch element on said switch means extending through said third aperture for engagement by said plate.

Claim 8

A fluid pressure responsive switch as set forth in claim 6 wherein said second partition member includes wall means thereon for positively positioning said switch means in a predetermined location in said fifth chamber.

Claim 9

A fluid pressure responsive switch as set forth in claim 7 including a first series of lugs formed integrally with said partition member and extending into said third chamber, a second series of lugs formed integrally with said partition member and extending into said fourth chamber, said first and second series of lugs being positioned in the form of first and second circles, respectively, for selective direct engagement by said first and second diaphragms, respectively, for preventing said first and second diaphragms from contacting the remaining portions of said partition member.