Shear type prestressed piezoelectric force transducer

• US 4,211,951 A
• Filed: 09/11/1978
• Issued: 07/08/1980
• Est. Priority Date: 03/29/1976
• Status: Expired due to Term

• Current Assignee: A/S Bruel & Kjaer
• Original Assignee: A/S Bruel & Kjaer
• Inventors: Jensen, Joergen
• Primary Examiner(s): Budd, Mark O.
• Application Number:
  US05/941,060
• Time in Patent Office: 666 Days
• Field of Search: 310/329, 310/333, 340/17 R, 73/517 R
• US Class Current: 310/329
• CPC Class Codes: G01P 15/0915 of the shear mode type
• CPC Class Codes: H10N 30/302 Sensors

Abstract

An accelerometer having a base unit carrying one or more transducers and encapsulated in a housing. The base includes a base piece and a prism-shaped stud with a rectangular cross-section having shear sensitive transducing elements, with associated seismic masses, fixed on the opposite, wide faces of the stud. The stud is shaped like an inverted T, so that the cross-section of the lower T-bar part has the same thickness but a greater lateral dimension than the T-leg part which carries the transducing elements. The stud is affixed perpendicular to the base piece with high precision using the lower T-bar part of the stud as a guide, and is easily fastened to the base piece without the use of screws or cement.

Claims

1. An electromechanical force transducer comprising:

a base including a base piece and a rectangular stud, having opposed flat faces, fixed in the base piece;

a plurality of shear sensitive transducing elements, with flat faces, and associated seismic masses, with flat faces, fixed to the opposing faces of the stud by means of a clamping force directed toward the axis of the stud, the flat faces of said measuring elements being disposed in planar abutment with associated said flat faces of said seismic masses and said stud, said measuring elements being subjected to shear by the forces to be measured, thereby displaying a change in electrical charge, voltage, current, or impedance;

said stud having a rectangular cross-section and press fit into a complementary recess in the base piece, the part of the stud fixed in the base piece being wider but of the same thickness as the part of the stud carrying the measuring elements;

all of the surfaces of said abutting flat faces of the stud, the elements and the seismic masses being precisely machined; and

clip means embracing and engaging the seismic masses and providing said clamping force and sandwiching and maintaining under even pressure each element in flat precisely machined surface contact with and between its associated mass and an associated face of the stud.

2. An electromechanical force transducer according to claim 1, wherein a housing encloses said stud, elements and seismic masses and is joined to the base piece by a press fit.

3. An electromechanical force transducer according to claim 1, in which the stud is an inverted T-shaped with the T-bar part being press fit into the recess in the base piece, said recess being a slot.

4. An electromechanical force transducer according to claim 3, wherein said base piece is a stepped cylindrical member having an upper section of less diameter than its lower section and the upper section is diametrically slotted to provide the recess for said stud;

said clip means is a circular spring clip disposed around the upstanding T-leg part of said stud and maintaining said seismic masses and elements in predetermined assembly orientation on each side face of the stud T-leg.