Differential pressure responsive apparatus

Claim 2

A transducer, comprising a meter body having cavities in spaced apart walls thereof, a pair of opposied diaphragms each connected to a different one of said spaced apart walls and extending in spaced apart relationship over the cavities contained therein to form a fluid tight cover for the spaced apart walls of the meter body, a first flexible member within a first one of said cavities, forming a first chamber, a second flexible member forming a second chamber within a second one of said cavities, said first and second chambers being adjacent to and spaced from a first one of said diaphragms, a sensing transducer positioned within said second chamber and connected by means of spring means to a movable portion of said second flexible member to convert changes in displacement of said second flexible member into a force that is applied to said sensing transducer, a first fluid under pressure within the space between said first one of said diaphragms and its associated meter wall to a first outer wall of said first flexible member, to the outer wall of said second flexible member and to an area surrounding said sensing transducer, a passageway in said meter body to apply a second fluid under pressure within the space between said second diaphragm and its associated meter wall to the inside wall of said flexible members, and an overload valve passing through a passageway containing said second fluid and connected for movement with said first flexible member and wherein said chamber formed by said second flexible member is operable to relieve the pressure of either one of said fluids acting on said first flexible member whenever the pressure of either of said fluids approaches an overload pressure condition.

Claim 3

The differential pressure responsive apparatus comprising a meter body, a semi-conductor wafer positioned within said meter body having a resistive sensing element thereon to convert changes occurring in a relatively high and low incompressible fluid pressure under measurement into an electric output signal of proprotional magnitude, an overload valve having a soft and hard seat and positIoned in a first chamber formed by a body portion of the meter, said overload valve being mounted for movement with a first flexible member forming a soft seat position to a hard seated sealed off position with the meter body to cut off low pressure fluid on a low pressure side of said meter from being applied to said first flexible member during a condition in which said high incompressible fluid pressure approaches an overload pressure level, a flexible compliance member mounted within an aperatured wall formed in another body portion of the meter, a spring means connecting the flexible compliance member to said wafer to convert changes in displacement of the compliance member resulting from a change in the differential pressure of the fluids under measurement acting thereon into a proportional force that is applied to said wafer, a second chamber formed by the internal wall of said compliance member, passageways in said body for simultaneously applying said low incompressible fluid pressure being applied to the internal wall of said first flexible member and to the internal wall of the second chamber to expand said flexible compliance member and thereby maintain the low pressure fluid at a level that will not impair the sensing and transmitting characteristics of the semi-conductor wafer and its associated resistive sensing element.

Claim 4

The differential pressure responsive apparatus comprising a meter body, a semi-conductor wafer positioned within said meter body having a resistive sensing element thereon to convert changes occurring in a relatively high and low incompressible fluid pressure under measurement into an electric output signal of proprotional magnitude, an overload valve having a soft and hard seat and positIoned in a first chamber formed by a body portion of the meter, said overload valve being mounted for movement with a first flexible member forming a soft seat position to a hard seated sealed off position with the meter body to cut off low pressure fluid on a low pressure side of said meter from being applied to said first flexible member during a condition in which said high incompressible fluid pressure approaches an overload pressure level, a flexible compliance member mounted within an aperatured wall formed in another body portion of the meter, a spring means connecting the flexible compliance member to said wafer to convert changes in displacement of the compliance member resulting from a change in the differential pressure of the fluids under measurement acting thereon into a proportional force that is applied to said wafer, a second chamber formed by the internal wall of said compliance member, passageways in said body for simultaneously applying said low incompressible fluid pressure being applied to the internal wall of said first flexible member and to the internal wall of the second chamber to expand said flexible compliance member and thereby maintain the low pressure fluid at a level that will not impair the sensing and transmitting characteristics of the semi-conductor wafer and its associated resistive sensing element.

Claim 5

The apparatus as defined in claim 1 wherein the said sensing transducer is a wafer formed of a single crystal silicon material and said compliance member has a stop means associated therewith to limit its displacement during said overload pressure condition and to thereby limit the magnitude of force that the spring means transmits to the wafer to a level that is below the rupture level of the wafer.

Claim 6

The apparatus as defined in claim 2 wherein the resistive sensor is comprised of a fully active wheatstone bridge pattern and an adjustable stop means is mounted on said meter body to adjust the amount of movement that said flexible compliance member can be expanded or compressed by said high and low incompressible fluid pressures.

Claim 7

The apparatus as defined in claim 2 wherein a substantially motionless electrical connection extends between the resistive sensing element, through an electrical feed through member in the wall of the meter and through an electrical power transmitting circuit positioned outside the meter and wherein said compliance member has a stop means associated therewith to limit its displacement during said overload pressure condition and thereby limit the magnitude of force that the spring means transmits to the wafer to a level that is below the rupture level of the wafer.

Claim 8

The apparatus as defined in claim 2 wherein the overload valve has a second soft and hard seat for engagement with a portion of said meter body in a manner similar to but in a direction opposite to that in which said soft and hard seat of said overload valve is closed when the magnitude of the low pressure fluid being applied to the inner wall of said first flexible member exceeds an overload pressure condition and causes said first flexible member to expand, the expansion of said first flexible member being accompanied by a corresponding compression of said flexible compliance member as said low over load incompressible fluid pressure is applied thereto and an adjustable stop associated with a stationary base wall of said flexible compliance member is employed to limit the displacement of the flexible compliance member during the time when either one of said overload fluid pressure conditions are present.

Claim 9

The apparatus as defined in claim 2 wherein a portion of the wafer and its associated diffused resistive sensing element is supported by one end of a hollow block, a wall forming one of said cavities in said body surrounds and is in spaced apart relation with said block, a seal is mounted in an outer wall of the block and extends outwardly into contact with the wall forming said last mentioned cavity in the body, the open end of said fLexible compliance member being supported by a wall portion that forms an aperature in the other end of the hollow block and said seal forming a fluid tight joint for separating said high incompressible fluid pressure acting on the sensor and the external surface of the compliance member from the low incompressible fluid pressure acting on the internal wall of the said compliance member.

Claim 10

The apparatus as defined in claim 1 wherein the said sensing transducer is a wafer formed of a single crystal silicon material and said second flexible member has a stop means associated therewith to limit its displacement during said overload pressure condition and to thereby limit the magnitude of force that the spring means transmits to the wafer to a level that is below the rupture level of the wafer, said second flexible member is a bellows, the spring means is of a coiled spring configuration having a first end fixedly connected to said wafer and its other end fixedly connected to a plate member forming a closed end of said second flexible bellows, a first stop member is connected for movement with said plate member, a second stop member is adjustably mounted in a fixed position on a plate on which the open end of said second flexible bellows is fixedly mounted, and said first stop member being operably positioned for movement toward and into non-movable engagement with said second stop member when the second flexible member is moved in one direction and said plate member forming the closed end of the bellows being operably positioned for movement toward and into non-movable engagement with said second stop member when the second flexible member is moved in an opposite direction.

Claim 11

The apparatus as defined in claim 2 wherein the wafer is of a single crystal silicon material in which said resistive sensing element is a doped piezoresistive pattern and said compliance member has a stop means associated therewith to limit its displacement during said overload pressure condition and thereby limit the magnitude of force that the biasing means transmits to the wafer to a level that is below the rupture level of the wafer, and an insulated supporting means to support said compliance bellows, spring means and sensing element in electrically isolated contact with said meter body to thereby prevent leakage current passing from said wafer through said meter body to ground.

Claim 12

The apparatus as defined in claim 2 wherein the wafer is of a single crystal silicon material in which said resistive sensing element is a doped piezoresistive pattern and said compliance member has a stop means associated therewith to limit its displacement during said overload pressure condition and thereby limit the magnitude of force that the spring means transmits to the wafer to a level that is below the rupture level of the wafer, an insulated supporting means to support said compliance bellows, spring means and sensing element in electrically isolated contact with said meter body to thereby prevent leakage current passing from said wafer through said meter body to ground, and wherein the biasing means is of a U-shaped configuration.