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Differential pressure sensing devices

  • US 4,173,149 A
  • Filed: 05/02/1978
  • Issued: 11/06/1979
  • Est. Priority Date: 05/02/1977
  • Status: Expired due to Term
First Claim
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1. A pressure sensing device wherein a first part of the device contains a first volume of liquid and has a side wall comprising a flexible separator diaphragm through which, in use, pressure is transmitted from a working fluid to said first volume of liquid, sensing means are provided for sensing pressure applied to said first volume of liquid or a difference between the pressure applied to said first volume of liquid and pressure of a fluid outside said first part of the device, a first overload diaphragm has opposed surface thereof subjected to the pressure of the first volume of liquid and the pressure of the outside fluid, respectively, said first overload diaphragm comprises a dished plate having an inner section which extends inwardly of said first part of the device relative to a peripheral section thereof, said first overload diaphragm is inflexible or substantially inflexible over a working range of differential pressures between said first volume of liquid and the outside fluid but becomes flexible and changes in shape when the pressure of the working fluid increases to a value such that the pressure applied to said first volume of liquid exceeds the pressure of the outside fluid by a predetermined amount, there then being a movement of said inner section relative to said peripheral section in a direction outwardly of said first part of the device sufficient to allow a movement of said separator diaphragm inwardly of said first part, and means are associated with said separator diaphragm which serve, when said separator diaphragm has moved inwardly by a predetermined amount, to cause a resistance to further inwards movement and to prevent any further increase in the pressure of the working fluid from being applied via said first volume of liquid to said sensing means, changes in said first volume of liquid, when the said associated means have operated, being accommodated by changes in shape of said first overload diaphragm.

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