Fluid pressure apparatus

• US 3,882,723 A
• Filed: 10/08/1971
• Issued: 05/13/1975
• Est. Priority Date: 10/26/1970
• Status: Expired due to Term

• Current Assignee: Westcode, Inc.
• Original Assignee: David John Wickham
• Inventors: Wickham, David John
• Primary Examiner(s): Gill, James J.
• Application Number:
  US05/187,614
• Time in Patent Office: 1,313 Days
• Field of Search: 73/203,25R,39,199 116/55 137/501,503
• US Class Current: 73/199
• CPC Class Codes: B60T 13/26 Compressed-air systems
• CPC Class Codes: B60T 17/228 for railway vehicles
• CPC Class Codes: G01F 1/34 by measuring pressure or differential pressure
• CPC Class Codes: Y10T 137/7788 Pressures across fixed choke

Abstract

A fluid pressure comparison apparatus including a pressure responsive member displaceable by the difference between two pressure sources being compared to vent fluid from one of the sources, when its pressure is greater than the other, through a port whose aperture is varied by the displacement of the pressure responsive member. The flow of vented fluid is measured in one of many possible ways to determine the excess pressure. The measurement may be displayed on an indicator or applied to control associated equipment. Various arrangements embodying the apparatus may be used for flow indication, flow control, leakage detection and indication and as warning or control equipment. The pressure responsive member is shown as a nylon reinforced rubber diaphragm but the nature of the member will depend on the absolute as well as the relative values of the pressures compared.

Claims

1. Fluid pressure responsive apparatus for sensing measuring and controlling fluid flow in a conduit, comprising a fluid tight vessel internally divided into a first and a second chamber by a pressure responsive member, said first chamber having a first port for a first fluid pressure signal, said second chamber having a second port for a second fluid pressure signal, and said second chamber having a third port, said pressure responsive member comprising a flexible fluid-tight membrane with a surface portion deformable to itself close said third port when the force exerted on said pressure responsive member, including the pressure in the first chamber, exceeds the opposing force exerted on said member, including the pressure in the second chamber, the third port being vented through a restricted passage to atmosphere, the fluid pressure in said passage from said second chamber depending on the degree of closure of the third port by the deformation of the member in response to said excess force, the flow in said passage giving rise to a third fluid pressure signal indicative of the difference between the first and second pressures, a fluid pressure signal utilization arrangement responsive to said third signal, said first port being connected to a first point on said fluid pressure conduit and said second port being connected to a second point on said fluid pressure conduit upstream from a first flow restrictor, which is itself upstream from said first poiNt, through a second flow restrictor of similar flow characteristics to said first flow restrictor such that the flow through one simulates the flow through the other under the same conditions, the fluid pressure utilization arrangement being responsive to the magnitude of said third signal to indicate the flow in said fluid pressure conduit, said fluid pressure conduit having a full-bore by-passing the first restrictor and including a valve for said by-pass controlled by a closure element operable in response to the pressure difference across the first restrictor produced by fluid flow through the restrictor to the downstream part of the conduit.

2. Apparatus as claimed in claim 1 in which the closure element is operated by a further pressure responsive member, to one side of which said further member is applied the fluid pressure in the first chamber, to part of the other side of which is applied the pressure in the fluid pressure conduit downstream from the first restrictor, and to part of the other side of which is applied the pressure in said by-pass upstream of said by-pass valve.

3. Apparatus as claimed in claim 1 in which said fluid pressure conduit is a railway.

4. Apparatus as claimed in claim 2 in which the further pressure responsive member is a further diaphragm.

5. Apparatus as claimed in claim 4 and including a resilient bias means for said further diaphragm.

6. Apparatus as claimed in claim 5 and including a follower through which the thrust of the resilient bias means is applied to the further diaphragm.

7. Apparatus as claimed in claim 6 in which the closure element incorporates a further follower which transmits to the further diaphragm the fluid pressure in said by-pass fluid path upstream of the valve over the full-bore of said path.

8. Apparatus as claimed in claim 5 in which resilient bias means is sized so as to apply to said further diaphragm a differential loading to close the closure element until the pressure in said by-pass upstream of said valve exceeds that downstream of the valve by a predetermined amount.

9. apparatus as claimed in claim 8 in which said predetermined amount is selected to be greater than that pressure drop across the restrictor created by the fluid flow through said restrictor necessary to maintain a fluid pressure system connected downstream of said first point in a charged, quiescent condition.

10. Fluid flow indicator apparatus for sensing and indicating fluid flow in a conduit in a railway vehicle brake system by comparing first and second fluid pressures, comprising a fluid-tight vessel internally divided into a first and second chamber by a pressure responsive member, said first chamber having a first port connected to a first point on said fluid pressure conduit for receiving a first fluid pressure signal, said second chamber having a second port connected to a second point on said fluid pressure conduit for receiving a second fluid pressure signal, said second point on said fluid pressure conduit being upstream from a first flow restrictor, which is itself upstream from said first point, said second port being connected to said second point through a second flow restrictor of similar flow characteristics to said first flow restrictor, said second chamber having a third port, said pressure responsive member having a fluid-tight membrane with a surface portion deformable to itself close said third port when the force exerted on said pressure responsive member by the pressure in the first chamber exceeds the force exerted on said member by the pressure in the second chamber by a predetermined amount, the third port being vented through a restricted passage to atmosphere, the fluid flow in said passage from said second chamber depending on the degree of closure of the third port by the deformation of the diaphragm in response to said excess force, the flow in said passage giving rise to a third fluid pressure signal, and means responsive to the magnitude of said third signal to indicate the flow iN said fluid pressure conduit, said conduit having a valve-controlled bypass around said first restrictor.

11. Apparatus as claimed in claim 10 in which the bypass in the fluid pressure conduit is a full-bore by-passing the first restrictor and the valve for said by-pass is controlled by a closure element operable in response to the pressure difference across the first restrictor produced by fluid flow through the restrictor to the downstream part of the conduit.