Strain gauge transducer assembly

• US 4,553,124 A
• Filed: 05/10/1985
• Issued: 11/12/1985
• Est. Priority Date: 09/16/1983
• Status: Expired due to Term

• Current Assignee: Delphi Technologies, Inc. (BorgWarner Incorporated)
• Original Assignee: Carron & Company
• Inventors: Malicki, Raymond W.
• Primary Examiner(s): Albritton, C. L.
• Assistant Examiner(s): LATEEF, MARVIN M
• Application Number:
  US06/733,396
• Time in Patent Office: 186 Days
• Field of Search: 338/2, 338/5, 338/6, 73/761, 73/768, 73/862.62, 73/862.64, 73/862.65, 73/862.66
• US Class Current: 338/5
• CPC Class Codes: F16B 31/025 with a gauge pin in a longitudinal bore in the body of the bolt
• CPC Class Codes: G01L 5/0004 Force transducers adapted for mounting in a bore of the force receiving structure G01L5/0009 takes precedence
• CPC Class Codes: G01L 5/24 for determining value of torque or twisting moment for tightening a nut or other member which is similarly stressed

Abstract

A strain gauge transducer (10) disclosed has particular utility when utilized with a bolt (12) to sense loading and has a construction which permits accurate axial alignment, testing before installation, removal for inspection and any necessary repair, and accurate readings that are not substantially affected by bending loading. The transducer (10) includes a body (30) having a web (40) extending between a threaded inner end (32) and an enlarged outer head (34). An annular seat (36) on the head (34) engages a bolt hole surface as the threaded inner end (32) is received by a threaded portion of the bolt hole. At least two strain gauges (46) are utilized with each mounted on one of the parallel web surfaces (42), and wires (50) connected to the strain gauges extend through a wire passage (48) in the enlarged head to permit a signal to be sensed by the strain gauges and fed to suitable instrumentation. In the preferred construction, the web (40) has a thickness in the range of about 0.020 to 0.060 of an inch and most preferably, about 0.040 of an inch in order to minimize twisting of the web upon installation while still providing accurate readings that are not substantially affected by bending loading. Round inner and outer portions (52,54) provide uniform loading of the web (4) without any stress concentrations.

Claims

1. A strain gauge transducer assembly comprising:

a bolt having a central axis and including a head having a counterbored hole extending therethrough along the central axis of the bolt;

said counterbored hole including a threaded inner portion, an intermediate portion extending outwardly from the threaded inner portion, an outer portion of a larger size than the intermediate portion, and an outwardly facing surface that extends between the intermediate and outer portions in a perpendicular relationship to the central axis;

a transducer received within the counterbored hole of the bolt;

said transducer including a body having a central axis coaxial with the central axis of the bolt and including a threaded inner end threaded into the inner portion of the counterbored hole;

said transducer body also including an outer end having an enlarged head;

said enlarged head having an annular seat that faces toward the inner end thereof extending perpendicular to the central axis thereof in engagement with the outwardly facing surface of the counterbored hole in the bolt;

the transducer body also including an intermediate portion having a web that connects the inner and outer ends thereof and has oppositely facing parallel surfaces;

said web having a thickness in the range of about 0.020 to 0.060 of an inch and also having a width that is a plurality of times the thickness thereof and less than the diameter of the threaded inner end;

at least two strain gauges each of which is mounted on one of the surfaces of the web to sense deformation of the web;

a wire passage through one end of the transducer body; and

wires connected to the strain gauges and extending through the wire passage to permit sensing of the web deformation and stress of the bolt.

2. A transducer assembly as in claim 1 wherein the web of the intermediate portion has a thickness of about 0.040 of an inch.

3. A transducer assembly as in claim 1 or 2 wherein the intermediate portion of the transducer body includes inner and outer portions of a larger size than the web and respectively located adjacent the inner and outer ends of the body with the web therebetween.

4. A transducer assembly as in claim 3 wherein the inner and outer portions of the intermediate portion of the transducer body are round.

5. A transducer assembly as in claim 1 or 2 wherein the wire passage comprises a groove in the head of the outer end of the transducer body.

6. A transducer assembly as in claim 1 or 2 wherein the head of the outer end includes a wrench socket opening.

7. A transducer assembly as in claim 1 or 2 wherein the annular seat on the head of the transducer body has a surface finish of about 25 RMS.

8. A strain gauge transducer assembly comprising:

a bolt having a central axis and including a head having a counterbored hole extending therethrough along the central axis of the bolt;

said counterbored hole including a threaded inner portion, an intermediate portion extending outwardly from the threaded inner portion, an outer portion of a larger size than the intermediate portion, and an outwardly facing surface that extends between the intermediate and outer portions in a perpendicular relationship to the central axis;

a transducer received within the counterbored hole of the bolt;

said transducer including a body having a central axis coaxial with the central axis of the bolt and including a threaded inner end threaded into the inner portion of the counterbored hole;

said transducer body also including an outer end having an enlarged head;

an annular seat on the head facing axially toward the inner end extending in a perpendicular relationship to the central axis thereof in engagement with the outwardly facing surface of the counterbored hole in the bolt;

a wire passage extending axially through the head;

the transducer body also including an intermediate portion having a web that connects the inner and outer ends thereof and has oppositely facing parallel surfaces;

said web having a thickness in the range of about 0.020 to 0.060 of an inch and also having a width that is a plurality of times the thickness thereof and less than the diameter of the threaded inner end;

at least two strain gauges each of which is mounted on one of the web surfaces to sense deformation of the web; and

wires connected to the strain gauges and extending through the wire passage of the head to permit sensing of the web deformation and stress of the bolt.

9. A strain gauge transducer assembly comprising:

a bolt having a central axis and including a head having a counterbored hole extending therethrough along the central axis of the bolt;

said counterbored hole including a threaded inner portion, an intermediate portion extending outwardly from the threaded inner portion, an outer portion of a larger size than the intermediate portion, and an outwardly facing surface that extends between the intermediate and outer portions in a perpendicular relationship to the central axis;

a transducer received within the counterbored hole of the bolt;

said transducer including a body having a central axis coaxial with the central axis of the bolt and including a threaded inner end threaded into the inner portion of the counterbored hole;

said transducer body also including an outer end having an enlarged head;

said enlarged head having an annular seat that faces toward the inner end thereof extending perpendicular to the central axis thereof in engagement with the outwardly facing surface of the counterbored hole in the bolt;

the transducer body also including an intermediate portion having a web that connects the inner and outer ends thereof and has oppositely facing parallel surfaces;

said web having a width less than the diameter of the threaded inner end and a thickness in the range of about 0.020 to 0.060 of an inch;

at least two strain gauges each of which is mounted on one of the web surfaces to sense deformation of the web;

a wire passage through one end of the transducer body; and

wires connected to the strain gauges and extending through the wire passage to permit sensing of the web deformation and stress of the bolt.

10. A strain gauge transducer assembly comprising:

a bolt having a central axis and including a head having a counterbored hole extending therethrough along the central axis of the bolt;

said counterbored hole including a threaded inner portion, an intermediate portion extending outwardly from the threaded inner portion, an outer portion of a larger size than the intermediate portion, and an outwardly facing surface that extends between the intermediate and outer portions in a perpendicular relationship to the central axis;

a transducer received within the counterbored hole of the bolt;

said transducer including a body having a central axis coaxial with the central axis of the bolt and including a threaded inner end threaded into the inner portion of the counterbored hole;

said transducer body also including an outer end having an enlarged head;

said enlarged head having an annular seat of a flat shape facing axially toward the inner end and extending in a perpendicular relationship to the central axis thereof in engagement with the outwardly facing surface of the counterbored hole in the bolt;

a wire passage extending axially through the head of the transducer body;

the transducer body also including an intermediate portion having a web that connects the inner and outer ends thereof and has oppositely facing parallel surfaces;

said web having a width less than the diameter of the threaded inner end and a thickness in the range of about 0.020 to 0.060 of an inch;

at least two strain gauges each of which is mounted on one of the web surfaces to sense deformation of the web and stress of the bolt; and

wires connected to the strain gauges and extending through the wire passage to permit sensing of the deformation.

11. A strain gauge transducer assembly comprising:

a bolt having a central axis and including a head having a counterbored hole extending therethrough along the central axis of the bolt;

said counterbored hole including a threaded inner portion, an intermediate portion extending outwardly from the threaded inner portion, an outer portion of a larger size than the intermediate portion, and an outwardly facing surface that extends between the intermediate and outer portions in a perpendicular relationship to the central axis;

a transducer received within the counterbored hole of the bolt;

said transducer including a body having a central axis coaxial with the central axis of the bolt and including a threaded inner end threaded into the inner portion of the counterbored hole;

said transducer body also including an outer end having an enlarged head;

said enlarged head having a wrench socket opening and also having an annular seat that faces toward the inner end thereof extending perpendicular to the central axis thereof in engagement with the outwardly facing surface of the counterbored hole in the bolt;

an axial groove defining a wire passage through the head of the transducer body;

the transducer body including an intermediate portion having inner and outer round portions respectively connected to the inner and outer ends and also having a web that extends between the inner and outer round portions and has oppositely facing parallel surfaces;

said web having a width less than the diameter of the threaded inner end and a thickness in the range of about 0.020 to 0.060 of an inch;

at least two strain gauges each of which is mountd on one of the web surfaces to sense deformation of the web; and

wires connected to the strain gauges and extending through the wire passage to permit sensing of the web deformation and stress of the bolt.