Spring compensated differential pressure cell

Claim 2

A differential pressure system comprising a pair of diaphragms with different effective areas, a chamber between said diaphragms for containing essentially incompressible fill liquid, and connection means between said diaphragms within said chamber, said connection means at least in part comprising compressible-extensible means whereby the distance between said diaphragms is variable by movement of the one of said diaphragms having the larger effective area without significant movement of the other of said diaphragms, in response to fill pressure change in said chamber.

Claim 3

A differential pressure system according to claim 1 in which an output is taken externally from the diaphragm, having the smaller effective area, for use in a force balance system.

Claim 4

A differential pressure system according to claim 1 in which an output is taken internally from the diaphragm having the smaller effective area, for use in a motion balance system.

Claim 5

A differential pressure system according to claim 1 in which an output is taken from the diaphragm having the smaller effective area, in structure suitable for an application selected from a system of motion balance and a system of force balance.

Claim 6

A differential pressure system according to claim 1 in which an output is taken externally from the diaphragm having the smaller effective area, for use in a force balance system, wherein said output is electromagnetic, with a movable core therefore secured to said diaphragm having the smaller effective area.

Claim 7

A differential pressure system according to claim 4 as a temperature compensated system wherein said fill pressure change is in terms of temperature change applied to said liquid fill.

Claim 8

A two-diaphragm differential pressure cell with internal spring compensation for fill volume change due to temperature change, said cell comprising a support body, two unequal size diaphragms mounted on said support and forming a fill chamber between said diaphragms, and a connection between said diaphragms, centrally thereof and within said chamber, said connections comprising an elongate end-to-end assembly of a rigid rod connected to one of said diaphragms and spring connected between the free end of said rod and the other of said diaphragms, said spring being extendable by increased internal pressure in said chamber as applied to said other of said diaphragms, due to volume increase of fill in said chamber as a result of temperature change.

Claim 9

A two-diaphragm differential pressure cell with internal spring compensation for fill volume change due to temperature change, said cell comprising a support body, two unequal size diaphragms mounted on said support and forming a fill chamber between said diaphragms, and a connection between said diaphragms, centrally thereof and within said chamber, said connections comprising an elongate end-to-end assembly of a rigid rod connected to one of said diaphragms and spring connected between the free end of said rod and the other of said diaphragms, said spring being extendable by increased internal pressure in said chamber as applied to said other of said diaphragms, due to volume increase of fill in said chamber as a result of temperature change.

Claim 10

A pressure cell according to claim 7 wherein said rigid rod is connected to the smaller of said diaphragms and said spring is applied to the larger of said diaphragms, whereby volume change of said fill in said chamber results in movement of said larger of said diaphragms and said spring, without significant movement of said rigid rod and said smaller of said diaphragms.

Claim 11

A pressure cell according to claim 8 with means for taking off a differential pressure signal in response to movement of said rigid rod.

Claim 12

A pressure cell according to claim 9 including a support within said diaphragm chamber, and a range spring based between said support and the smaller of said diaphragms.

Claim 13

A pressure cell according to claim 9 wherein said signal takeoff means is electromagnetic, with part of said rigid rod as the movable core of said takeoff.

Claim 14

For use in industrial instrumentation in process and/or energy control, a temperature compensated differential pressure cell comprising a support body, two diaphragms of different size mounted in said body and forming a chamber between said diaphragms, a backing plate in said chamber, an opening through said backing plate centrally of said diaphragms, a shaft connected to the smaller of said diaphragms and extending into said backing plate opening, a spring mounted in said backing plate opening and between the larger of said diaphragms and the end of said shaft in said backing plate opening, electrical signal takeoff coils about said shaft, with a portion of said shaft as a moving core therefor, and a range spring mounted between an outwardly facing shoulder of said backing plate and an inwardly facing shoulder of said connection shaft, whereby, upon volume expansion of fill in said chamber due to temperature change, said connection spring will be extended, and the larger of said diaphragms moved outwardly, essentially without movement of the smaller of said diaphragms and consequently essentially without movement of said signal takeoff core.

Claim 15

For use in industrial instrumentation in process and/or energy control, a temperature compensated differential pressure cell comprising a support body, two diaphragms of different size mounted in said body and forming a chamber between said diaphragms, a backing plate in said chamber, an opening through said backing plate centrally of said diaphragms, a shaft connected to the smaller of said diaphragms and extending into said backing plate opening, a spring mounted in said backing plate opening and between the larger of said diaphragms and the end of said shaft in said backing plate opening, electrical signal takeoff coils about said shaft, with a portion of said shaft as a moving core therefor, and a range spring mounted between an outwardly facing shoulder of said backing plate and an inwardly facing shoulder of said connection shaft, whereby, upon volume expansion of fill in said chamber due to temperature change, said connection spring will be extended, and the larger of said diaphragms moved outwardly, essentially without movement of the smaller of said diaphragms and consequently essentially without movement of said signal takeoff core.

Claim 16

A differential pressure system according to claim 1, wherein said connection means includes a rigid member connected to said diaphragm having the smaller effective area, said compressible-extensible means joining said rigid member and said diaphragm having the larger effective area.

Claim 17

A differential pressure system according to claim 13, wherein said compressible-extensible means is a coil spring.