Torque wrench

• US 4,257,263 A
• Filed: 06/18/1979
• Issued: 03/24/1981
• Est. Priority Date: 07/01/1978
• Status: Expired due to Term

• Current Assignee: Werkzeug-Union GmbH-Dwu
• Original Assignee: Werkzeug-Union GmbH-Dwu
• Inventors: Herrgen, Rudolf
• Primary Examiner(s): WOODIEL, DONALD
• Application Number:
  US06/049,495
• Time in Patent Office: 645 Days
• Field of Search: 73/139, 73/DIG. 4
• US Class Current: 73/862.23
• CPC Class Codes: B25B 23/1425 by electrical means
• CPC Class Codes: G01L 1/16 using properties of piezoelectric devices
• CPC Class Codes: Y10S 73/04 Piezoelectric

Abstract

The present invention is directed to a torque wrench wherein a head comprises an engaging member capable of being coupled, antirotationally, with a screw or the like. A handle lever is movable within limits relative to the engaging member and a load sensor is provided between the engaging member and the handle lever and controls an indicating means. The load sensor according to the present invention is a piezoelectric member fitted with electrodes connected with the input of an electric amplifier which is fed by a battery housed in the handle lever. The electric amplifier controls an electronic indicator which indicates the torque applied to a screw or the like.

Claims

1. A torque wrench having a head comprising:

an engaging member capable of being coupled antirotationally with a member to be tightened;

a handle lever movable within limits relatively to the engaging member;

a load sensor provided between the engaging member and the handle lever and controlling an indicating means;

wherein the load sensor is a piezoelectric body (21) fitted with electrodes connected with the input of an electric amplifier (24) which is fed by a battery (18) housed in the handle lever (10) and which controls an electronic indicator (16) and wherein the indicator (16) is inserted before a peak value memory (25) for retaining the maximum value of the measured torque.

2. A torque wrench according to claim 1, wherein the contents of the peak value memory (25) is erasable by an erasing switch (26).

3. A torque wrench according to claim 1 or 2, wherein the engaging member (12) has a lever arm (20) pointing approximately towards the handle lever (10) and forming a first clamping element for the piezoelectric body (21), while the other clamping element is connected to the handle lever (10) which is hinged at the engaging member (12).

4. A torque wrench for indicating the tightening torque applied to a member to be tightened comprising:

a head including engaging means for antirotationally being coupled to a member to be tightened;

a handle lever being movable to a limited degree relative to said engaging means;

a load sensor being operatively positioned between said engaging means and said handle lever, said load sensor being a piezoelectric cell including electrodes;

an indicating means being operatively connected to said load sensor;

an electric amplifier being operatively connected to said electrodes of said piezoelectric cell and to a battery;

said electric amplifier being operatively connected to said indicating means to actuate said indicating means to indicate the torque sensed by said load sensor; and

a peak value memory for retaining the maximum value of the torque sensed by said load sensor.

5. A torque wrench according to claim 4, wherein said indicating means is a digital read out display.

6. A torque wrench according to claim 4, and further including an erasing switch for erasing the contents of said peak value memory.

7. A torque wrench according to claim 4, wherein said engaging means includes a lever arm extending along said handle lever, said lever arm forming a first clamping element connected to said piezoelectric cell, a second arm being hinged to said engaging means and connected to the handle lever forming a second clamping element connected to said piezoelectric cell.