Variable orifice gas flow sensing head

• US 4,083,245 A
• Filed: 03/21/1977
• Issued: 04/11/1978
• Est. Priority Date: 03/21/1977
• Status: Expired due to Term

• Current Assignee: Critikon, Inc. (Johnson & Johnson)
• Original Assignee: UAB Research Foundation (University of Alabama System)
• Inventors: Osborn, John J.
• Primary Examiner(s): Goldstein, Herbert
• Application Number:
  US05/779,557
• Time in Patent Office: 386 Days
• Field of Search: 73/207, 73/210, 73/211, 128/2.08
• US Class Current: 73/861.53
• CPC Class Codes: A61B 5/08 Detecting, measuring or recording devices for evaluating the respiratory organs A61B5/0205 takes precedence
• CPC Class Codes: G01F 1/42 Orifices or nozzles

Abstract

A gas flow meter employing means for obtaining a differential pressure across a resistance orifice in a line of gas flow. Although flow through the orifice may be turbulent thus making the differential pressure non linear with respect to the amount of flow, the effect of that turbulence is offset by the provision of a hinged flap within the orifice which opens upon increase in gas flow thereby lowering the orifice'"'"'s resistance to that flow. Because of the variable resistance orifice the resultant pressure differential is linear with respect to the amount of flow. The differential pressure is sensed by pressure tubes disposed on opposite sides of the orifice and the hinged flap is arranged to flex over the downstream pressure tube so as to protect it from eddy currents. Moreover, the flap is hinged at the top and opens from the bottom whereby free liquid may pass through the orifice without any significant change in calibration.

Claims

1. A gas flow sensing head comprising a housing having gas inlet and gas outlet ports, an orifice membrane disposed across the interior of said housing between said inlet and outlet ports, said orifice membrane being formed of an elastic material, said orifice membrane including a partially cutout portion defining an orifice and a flap integral with and hingably connected to the membrane and substantially coextensive with the orifice, said flap including sides which converge to form the narrowest portion of the flap at that portion thereof most remote from the hinged connection to the orifice membrane whereby the flow of gas through said housing varies the size of said orifice, said hinged connection being narrower than the widest portion of said flap and means disposed on each side of said orifice membrane for sensing the pressure thereat.

2. A gas flow sensing head as defined in claim 1 wherein said orifice membrane includes top and bottom sides, said hinged connection being at the top of said orifice membrane and said narrowest portion of the flap being at the bottom whereby liquid may pass through said orifice without interference with said hinge.

3. A gas flow sensing head as defined in claim 2 wherein said orifice membrane defines but a single flap.

4. A gas flow sensing head as defined in claim 1 wherein said flap being wide at its base and narrow at its apex, the elasticity of the hinge and the annular shape of the flap being so matched that the resistance across the orifice is constant over a wide range of flow.

5. A gas flow sensing head comprising a housing having gas inlet and gas outlet ports, an orifice membrane disposed across the interior of said housing between said inlet and outlet ports, said orifice membrane being formed of an elastic material, said orifice membrane having top and bottom sides and including a partially cut-out portion defining an orifice and a flap integral with and hingably connected to the membrane and substantially coextensive with the orifice, said hinge connection being at the top of said orifice membrane, said flap including sides which converge to form the narrowest portion of the flap at the bottom thereof whereby the flow of gas through said housing varies the size of said orifice and liquid may pass through said orifice without interference with the hinge, and means disposed on each side of said orifice membrane for sensing pressure thereat, said means for sensing pressure including a tube disposed on each side of the membrane, the tube on the outflow side of said membrane being disposed adjacent the top of said membrane whereby said flap may extend under the tube to protect it from eddies when the gas flow rate is high.