Electric tool, particularly a handtool, with torque control

• US 4,487,270 A
• Filed: 11/23/1982
• Issued: 12/11/1984
• Est. Priority Date: 11/24/1981
• Status: Expired due to Term

• Current Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Original Assignee: Black & Decker Incorporated (Stanley Black & Decker, Inc.)
• Inventors: Huber, Siefried
• Primary Examiner(s): Yost, Frank T.
• Assistant Examiner(s): PHAN, HIEN HUY
• Application Number:
  US06/444,032
• Time in Patent Office: 749 Days
• Field of Search: 173/2, 173/11, 173/12, 173/15, 173/16, 310/47, 310/50, 310/68 B, 73/862.31, 73/862.29, 73/862.49, 318/488, 318/481, 318/357, 318/358, 318/349, 81/469, 338/99, 338/103, 338/110, 338/112, 338/114, 83/58, 83/62, 408/9, 408/11, 74/412 TA
• US Class Current: 173/176
• CPC Class Codes: B23B 45/02 driven by electric power
• CPC Class Codes: B25B 23/147 specially adapted for electrically operated wrenches or screwdrivers
• CPC Class Codes: G01L 5/12 for measuring axial thrust in a rotary shaft, e.g. of propulsion plants
• CPC Class Codes: H02K 11/24 Devices for sensing torque, or actuated thereby H02K11/27 takes precedence
• CPC Class Codes: H02K 11/33 Drive circuits, e.g. power electronics H02K11/38 takes precedence
• CPC Class Codes: H02K 23/66 Structural association with auxiliary electric devices influencing the characteristic of, or controlling, the machine, e.g. with impedances or switches
• CPC Class Codes: Y10T 408/165 to control Tool rotation
• CPC Class Codes: Y10T 74/19847 torque actuated safety devices

Abstract

A power tool has an electric motor with a motor shaft having a spiral gear through which the motor drives the tool. A pressure sensor is disposed so as to be subjected to the axial thrust of the motor shaft created by the spiral gear during operation of the tool. A torque control device is connected to the pressure sensor for influencing the motor in response to such axial thrust, for example to control or limit the torque of the motor. Preferably, the pressure sensor comprises a disk of electrically conductive plastic and is located between a thrust bearing of the motor shaft and an axial support therefor. Such disk is disposed between a pressure plate and an electrode plate having spaced apart electrodes.

Claims

1. A power tool, comprising:

an electric motor having a motor shaft;

said motor shaft having a spiral gear through which said motor drives the tool;

a pressure sensor disposed so as to be subjected to the axial thrust of said motor shaft created by said spiral gear during operation of the tool;

torque control means connected to said pressure sensor for influencing said motor in response to said axial thrust; and

said pressure sensor comprising electrically conductive plastic disposed between a pressure plate of electrically insulating material and an electrode plate having spaced apart electrodes, the electrical resistance of said conductive plastic changing as a function of the pressure exerted thereupon.

2. The power tool of claim 1, wherein said pressure sensor is located between said motor shaft and means for axially supporting the motor shaft in the power tool.

3. The power tool of claim 1, wherein said spiral gear is located at one end of the motor shaft, and the other end of the motor shaft is mounted in a bearing, said pressure sensor being located between said bearing and an axial support therefor.

4. A power tool, comprising:

an electric motor having a motor shaft;

said motor shaft having a spiral gear through which said motor drives the tool;

a pressure sensor disposed so as to be subjected to the axial thrust of said motor shaft created by said spiral gear during operation of the tool;

torque control means connected to said pressure sensor for influencing said motor in response to said axial thrust;

said spiral gear being located at one end of the motor shaft, and the other end of the motor shaft being mounted in a bearing, said pressure sensor being located between said bearing and an axial support therefor;

said pressure sensor comprising electrically conductive plastic the electrical resistance of which changes as a function of the pressure exerted thereupon; and

said conductive plastic being in the form of a disk disposed between a pressure plate and an electrode plate, said electrode plate having spaced apart electrodes.

5. The power tool of claim 4, wherein said disk, said pressure plate, and said electrode plate are annular and are juxtaposed said bearing.

6. The power tool of claim 5, wherein said electrode plate is a printed circuit board having an inner conductive ring with outwardly extending radial electrodes and an outer conductive ring with inwardly extending radial electrodes, the inwardly and outwardly extending electrodes being interleaved in spaced apart relationship.

7. The power tool of claim 5, wherein said bearing is mounted in a bore in a bearing support member, and said pressure sensor is located in said bore in contact with said bearing.

8. The power tool of claim 7, wherein said bearing is a ball bearing and is mounted in a resilient ring, said resilient ring being mounted in said bore.

9. A portable power tool, comprising:

a housing;

an electric motor having a motor shaft extending form opposite ends thereof, said motor being mounted in said housing;

said motor shaft having spiral gearing at one end and being mounted in a thrust bearing at the other end;

means, located in said housing, for supporting said bearing against axial thrust;

a pressure sensor comprising electrically conductive plastic the electrical resistance of which changes as a function of the pressure exerted thereon, said pressure sensor being disposed axially between said bearing and said supporting means;

torque control means for influencing said motor responsive to the axial thrust created by said spiral gearing and exerted by said bearing upon said pressure sensor; and

a rubber ring mounted in a bore in said supporting means and resiliently supporting said bearing therewithin, said ring having a radially inwardly projecting flange engaging said bearing on the opposite axial side thereof to said pressure sensor.

10. An electric hand tool, comprising:

a housing;

an electric motor having a motor shaft extending from opposite ends thereof and having a stator;

a spiral gear at one end of said motor shaft meshing with another spiral gear through which gearing said motor drives the tool;

a bearing in which the other end of said shaft is mounted;

a yoke mounted on said stator, said yoke having a bore therein in which is mounted said bearing;

a snap ring engaged in a groove in said bore for supporting said bearing against axial thrust imparted to said bearing through said motor shaft by said spiral gearing during operation of the tool;

a pressure sensor disposed in said bore between said bearing and said snap ring and being subjected to said axial thrust;

said pressure sensor comprising an annular pressure plate, an annular electrode plate, and a ring-shaped disk of electrically conductive plastic therebetween, the resistance of said conductive plastic changing as a function of the pressure exerted thereon;

said electrode plate having outer and inner conductive rings from which extend radially electrodes, the electrodes of the outer ring being interleaved between the electrodes of the inner ring;

means supporting said motor and said yoke in said housing; and

means for influencing the torque of said motor in response to the axial thrust exerted by said bearing upon said pressure sensor.