Differential pressure transducer

• US 4,306,460 A
• Filed: 12/13/1979
• Issued: 12/22/1981
• Est. Priority Date: 12/22/1978
• Status: Expired due to Term

• Current Assignee: Hitachi, Ltd.
• Original Assignee: Hitachi, Ltd.
• Inventors: Nagata, Takeo, Matsuoka, Yoshitaka, Shimada, Satoshi, Sakurai, Yutaka, Ai, Mitsuo
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US06/103,407
• Time in Patent Office: 740 Days
• Field of Search: 73/721, 73/720, 73/726, 73/727
• US Class Current: 73/721
• CPC Class Codes: G01L 13/025 using diaphragms
• CPC Class Codes: G01L 9/0052 of piezoresistive elements circuits therefor G01L9/06

Abstract

A differential pressure transducer having a cantilever and a semiconductor strain gauge attached to each side of the cantilever at an intermediate portion of the latter. The cantilever has one end fixed by electron beam welding to a fixing member and the other end left for free displacement in response to a differential pressure. The displacement of the other end of the cantilever is detected as changes in the electric resistances of the semiconductor strain gauges.

Claims

1. A differential pressure transducer having a cantilever fixing member with a bore therethrough, a cantilever, said cantilever being an elongated rod-like member having first and second ends, and at least one strain gauge attached to a surface of said cantilever at an intermediate portion of the latter, said cantilever having its first end received in the bore of said cantilever fixing member and fixed thereat while the second end is left for free displacement such that said displacement is detected as a change in the electric resistance in said strain gauge, characterized in that said cantilever is fixed at said first end by means of welding to said cantilever fixing memberd at the upper periphery of said first end.

2. A differential pressure transducer as claimed in claim 1, wherein the welding between said cantilever and said cantilever fixing member is made substantially symmetrically with respect to the axis of said cantilever.

3. A differential pressure transducer as claimed in claim 1 or 2, wherein each of said cantilever and said cantilever fixing member is provided with a projection, the projections being contacted and welded to each other thereby to fix said cantilever to said cantilever fixing member.

4. A differential pressure transducer as claimed in claim 3, wherein said first end of said cantilever has a cylindrical fixing portion adapted to be received by said bore in said cantilever fixing member, the end surfaces of said cylindrical fixing portion being welded at the upper periphery thereof to said cantilever fixing member thereby to fix said cantilever to said cantilever fixing member.

5. A differential pressure transducer having a main body member connected between a high-pressure flange and a low-pressure flange each of which having a pressure inlet port, a high-pressure diaphragm and a low-pressure diaphragm attached to said high-pressure flange and said low-pressure flange, respectively, center means connected to said high-pressure and low-pressure diaphragms, a connecting shaft through which said center members are connected to each other, a spring associated with said connecting shaft, a cantilever in the form of an elongated rod-like member with first and second ends, at least one semiconductor strain gauge adhered to at least one surface of said cantilever at an intermediate portion of said cantilever, a cantilever fixing member to which said first end of said cantilever is fixed, and a hermetic member through which said cantilever fixing member is fixed to said main body member, said cantilever being connected at said second end to said spring, the space defined by said main body member, said high-pressure and low-pressure diaphragms, said center members, said connecting shaft, said cantilever, said fixing memer and said hermetic member being filled with a fluid, said high-pressure diaphragm and said low-pressure diaphragm being adapted to receive a high fluid pressure and a low fluid pressure introduced through said high and low pressure inlet ports such that said second end of said cantilever is displaced by the differential pressure, the displacement being detected as a change in the electric resistance of said strain gauge.

characterized in that the fixing of said first end of said cantilever to said cantilever fixing member is made by welding, said welding being made substantially in symmetry with respect to the axis of said cantilever and that said hermetic member has an annular projection and is fixed at said annular projection by welding to said main body member.

6. A differential pressure transducer having a cantilever in the form of an elongated rod-like member with first and second ends, at least one semiconductor strain gauge adhered to at least one surface of said cantilever at an intermediate portion of said cantilever, a fixing member to which said cantilever is fixed at said first end, and a hermetic member through which said fixing member is fixed to a main body member of said transducer, said second end of said cantilever being left for free displacement in response to a differential pressure, said displacement being detected as a change in electric resistance said strain gauge, characterized in that said cantilever is fixed at said first end thereof to said fixing member by welding, and that said hermetic member has an annular projection and is fixed at said annular projection to said main body member by welding.

7. A differential pressure transducer comprising:

a main body member having a high-pressure and a low-pressure introduced thereto in opposition;

diaphragms disposed in said main body member and arranged to come into contact with the high-pressure and low-pressure;

connecting means connected to both of said diaphragms so that both of said diaphragms move together;

a fixing member connected to said main body member, said fixing member having a through bore therein;

a cantilever in the form of an elongated rod-like member having first and second ends, said first end being received in the bore of said fixing member and being fixedly joined thereto by a welded connection at the periphery of the end surface thereof, and said second end being disposed between said diaphragms and connected to said connecting means for being displaced by movement of said diaphragms; and

at least one strain gauge adhered to a side surface of said cantilever for providing an output in accordance with the displacement of said cantilever.

8. A differential pressure transducer according to claim 7, wherein an end edge of said first end of said cantilever received in the bore of said fixing member and an end edge of the bore of said fixing member are provided with a projection extending in the axial direction of the cantilever, respectively, said cantilever and said fixing member being fixedly joined together by welding at each said projection.

9. A differential pressure transducer according to claim 7 or claim 8, wherein said cantilever and said fixing member are fixedly joined by welding which is symmetric with respect to an axis of said cantilever.

10. A differential pressure transducer according to claim 9, wherein said projections are annular projections and said cantilever and said fixing member are fixedly joined by an annular welding at said projections.

11. A differential pressure transducer according to claim 9 wherein said welding is an electronic beam.

12. A differential pressure transducer according to claim 7, wherein said strain gauge is a semiconductor strain gauge.