Flow measuring device

Claim 1

A device for measuring differential fluid pressure comprising: a closed hollow conduit, a first pressure port and a second pressure port wherein said first pressure port and said second pressure port are spaced apart on said conduit and wherein said first pressure port is in fluid communication with a first source of pressure by a first Pitot tube and said second pressure port is in fluid communication with a second source of pressure by a second pitot tube, the pressure of said first source being greater than the pressure at said second source; a freely movable piston loosely fitted within the conduit between the pressure ports such that fluid is permitted to flow from said first pressure source past the loosely fitted piston and back to said second pressure source; a spring member interposed between said one end of said conduit and one side of said piston for urging said piston towards said first pressure port; and means for indicating the position of said piston.

Claim 2

A device for measuring differential fluid pressure comprising: a closed hollow conduit, a first pressure port and a second pressure port wherein said first pressure port and said second pressure port are spaced apart on said conduit and wherein said first pressure port is in fluid communication with a first source of pressure by a first Pitot tube and said second pressure port is in fluid communication with a second source of pressure by a second pitot tube, the pressure of said first source being greater than the pressure at said second source; a freely movable piston loosely fitted within the conduit between the pressure ports such that fluid is permitted to flow from said first pressure source past the loosely fitted piston and back to said second pressure source; a spring member interposed between said one end of said conduit and one side of said piston for urging said piston towards said first pressure port; and means for indicating the position of said piston.

Claim 4

A device for measuring a fluid flow parameter in a fluid flowing in a pipe, said pipe having an opening in the exterior thereof to receive said device comprising a closed hollow conduit, a pressure port at each end of said conduit and a piston loosely fitted in said conduit between said pressure ports, a spring member interposed between said piston and one end of said conduit to control movement of said piston, a pair of Pitot tubes for establishing a pressure differential across the piston, each tube being connected to a different pressure port, each said Pitot tube having a pressure opening, one of said pressure openings adapted to face upstream of said flowing fluid and the other downstream of said flowing fluid to create and measure a pressure differential in said flowing fluid, said flowing fluid flowing into one pressure port and into said conduit under the influence of said pressure differential, only a small amount of said fluid being permitted to flow past said loosely fitting piston sufficient to lubricate the said piston and minimize friction errors.

Claim 5

A device for measuring a fluid flow parameter in a fluid flowing in a pipe, said pipe having an opening in the exterior thereof to receive said device comprising a closed hollow conduit, a pressure port at each end of said conduit and a piston loosely fitted in said conduit between said pressure ports, a spring member interposed between said piston and one end of said conduit to control movement of said piston, a pair of Pitot tubes for establishing a pressure differential across the piston, each tube being connected to a different pressure port, each said Pitot tube having a pressure opening, one of said pressure openings adapted to face upstream of said flowing fluid and the other downstream of said flowing fluid to create and measure a pressure differential in said flowing fluid, said flowing fluid flowing into one pressure port and into said conduit under the influence of said pressure differential, only a small amount of said fluid being permitted to flow past said loosely fitting piston sufficient to lubricate the said piston and minimize friction errors.

Claim 7

A device for measuring differential fluid pressure in a flowing fluid and its line pressure comprising a hollow closed conduit having at least two pressure ports therein, a freely movable piston loosely fitted within said conduit between said two pressure ports, first and second spring members interposed between an end of the said conduit and the said piston, said first spring member being mounted on said piston, a double Pitot tube comprising two concentric tubes each having one end in said flowing fluid, one of said tubes having an opening facing upstream of said fluid flow and the other having an opening facing downstream of said fluid flow, each of said tubes being connected to a different one of said pressure ports, and a valve between one of said openings and the corresponding one of said pressure ports and having a solid valve face, a first valve port and an interconnected second valve port, said valve being adjustable between a first position on which one of said openings communicates with said first valve port and said second valve port communicates with one of said pressure ports, and a second position for measuring line pressure in which said one of said openings is sealed by the valve face and in which said first valVe port communicates with said one pressure port and said second valve port communicates with the atmosphere.

Claim 8

A device for measuring differential fluid pressure in a flowing fluid and its line pressure comprising a hollow closed conduit having at least two pressure ports therein, a freely movable piston loosely fitted within said conduit between said two pressure ports, first and second spring members interposed between an end of the said conduit and the said piston, said first spring member being mounted on said piston, a double Pitot tube comprising two concentric tubes each having one end in said flowing fluid, one of said tubes having an opening facing upstream of said fluid flow and the other having an opening facing downstream of said fluid flow, each of said tubes being connected to a different one of said pressure ports, and a valve between one of said openings and the corresponding one of said pressure ports and having a solid valve face, a first valve port and an interconnected second valve port, said valve being adjustable between a first position on which one of said openings communicates with said first valve port and said second valve port communicates with one of said pressure ports, and a second position for measuring line pressure in which said one of said openings is sealed by the valve face and in which said first valVe port communicates with said one pressure port and said second valve port communicates with the atmosphere.

Claim 10

A device for measuring a fluid flow parameter in a fluid flowing in a pipe comprising a closed hollow conduit, a pressure port at each end of said conduit and a piston loosely fitted in said conduit between said pressure ports, a spring member interposed between said piston and one end of said conduit to control movement of said piston in response to an applied pressure differential across said piston, means in said flowing fluid for creating a pressure differential therein, said means being connected to said pressure ports for establishing the said pressure differential across said piston, said means permitting some fluid from said pipe to flow into one of said pressure ports, past the loosely fitted piston and back into the pipe in response to the applied pressure differential, said piston being small enough to permit only enough fluid to flow past said piston as is necessary to lubricate the said piston to minimize friction errors, whereby movement of said piston is effected substantially by the established pressure differential.

Claim 11

A device for measuring a fluid flow parameter in a fluid flowing in a pipe comprising a closed hollow conduit, a pressure port at each end of said conduit and a piston loosely fitted in said conduit between said pressure ports, a spring member interposed between said piston and one end of said conduit to control movement of said piston in response to an applied pressure differential across said piston, means in said flowing fluid for creating a pressure differential therein, said means being connected to said pressure ports for establishing the said pressure differential across said piston, said means permitting some fluid from said pipe to flow into one of said pressure ports, past the loosely fitted piston and back into the pipe in response to the applied pressure differential, said piston being small enough to permit only enough fluid to flow past said piston as is necessary to lubricate the said piston to minimize friction errors, whereby movement of said piston is effected substantially by the established pressure differential.