APPARATUS FOR INDICATING THE RATE OF FLUID FLOW

• US 3,797,480 A
• Filed: 05/28/1971
• Issued: 03/19/1974
• Est. Priority Date: 05/29/1970
• Status: Expired due to Term

• Current Assignee: Garnet Montague Eveleigh Williams
• Original Assignee: Garnet Montague Eveleigh Williams
• Inventors: Williams, Garnet Montague Eveleigh
• Primary Examiner(s): Howell, Kyle L.
• Application Number:
  US05/148,077
• Time in Patent Office: 1,026 Days
• Field of Search: 128/2.08,2.07 272/57R 73/194E,204,228
• US Class Current: 600/537
• CPC Class Codes: A61B 5/0871 Peak expiratory flowmeters
• CPC Class Codes: A61B 5/0878 using temperature sensing means
• CPC Class Codes: G01F 1/6842 with means for influencing the fluid flow

Abstract

Apparatus for indicating fluid flow rate which includes a thermistor carried by a mesh and arranged for connection in an electrical circuit including an indicating instrument, the time dependent pattern of variations in the rate of flow of fluid through the mesh being indicated by the indicating instrument because the resistance of the thermistor varies with the fluid flow rate. The thermistor can be calibrated by a comparison of its output signals with the pressure differential across the mesh for one fluid flow rate. The element may be connected into the electrical circuit by leads having the properties of a hot wire anemometer element, the leads being disposed on opposite sides of the mesh and arranged to indicate the direction of fluid flow through the mesh. A peak flow meter having mechanical means for measuring the peak rate of flow of air blown by a human subject, has a thermistor carried by its gauze mesh filter and arranged to give an indication of the time dependent pattern of variations in the rate of flow of air blown by the subject.

Claims

1. Apparatus for indicating the rate of flow of fluid through a duct, comprising in combination:

a duct;

a mesh member mounted within the duct so as to define a plurality of flow restricting orifices;

a heat sensitive electrical resistance element being carried by said mesh member;

an indicating element;

a voltage source; and

means connecting said electrical resistance element, said indicating element and said voltage source together to form an electrical circuit in which an indicating signal is to be generated, the apparatus being arranged so that, during use, the flow of fluid to be indicated flows past said electrical resistance element and through the orifices of said mesh member, the electrical resistance of said element being dependent upon the rate of flow of fluid through the orifice of said mesh member.

2. Apparatus for indicating the rate of flow of a fluid through a duct as claimed in claim 1, wherein said heat sensitive electrical resistance element is a thermistor.

3. Apparatus for indicating the rate of flow of a fluid through a duct as claimed in claim 2, wherein said thermistor is positioned within one of the orifices of said mesh member.

4. Apparatus for indicating the rate of flow of a fluid through a duct as claimed in claim 3, wherein said mesh member has a central orifice, and wherein said thermistor is positioned within the central orifice of said mesh member.

5. Apparatus for indicating the rate of flow of fluid as claimed in claim 2, wherein said connecting means includes electrical terminals to which said indicating element and said voltage source are connected, and electrical conducting leads extending from said thermistor, said electrical conducting means connecting said thermistor to said terminals, said electrical conducting leads being threaded through said mesh member.

6. A peak flow meter comprising in combination:

a casing defining a chamber and having scale markings thereon;

a movable member mounted to said casing and serving as an indicator movable relative to said scale markings;

a mouthpiece mounted to said casing through which a human subject blows air into said chamber;

a gauze mesh filter mounted within said mouthpiece to prevent mucus being blown into said casing by a human subject;

means acting on said movable member to oppose movement thereof away from said mouthpiece;

said casing having a slot extending therethrough and into said chamber through which air passes out of said chamber;

the rate of flow of air blown into said mouthpiece being indicated by the position of said movable member relative to said scale; and

sensing means responsive to the rate of flow of air blown into said mouthpiece and arranged to produce a signal which varies with changes in the rate of flow of air blown into said mouthpiece, said sensing means comprising;

a heat sensitive electrical resistance element carried by said gauze mesh filter;

an indicating element;

a voltage source; and

means connecting said electrical resistance element, said indicating element and said voltage source together into an electrical circuit in which an indicating signal is to be generated, the arrangement being such that air blown into said mouthpiece by a human subject slows past said element, the electrical resistance of said element being dependent upon the rate of air blown into said mouthpiece.

7. A peak flow meter as claimed in claim 6, wherein said mouthpiece is separable from that part of the casing which defines said chamber.

8. In a peak flow meter as claimed in claim 6, wherein said electrical resistance element comprises a thermistor.