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US 4,534,420 AGranted
Electric tool with torque monitor
AssigneeBlack & Decker Inc.
InventorRainer Goldelius
Life of this patent
Estimating the term…
Abstract
An electric tool, especially a hand tool, is provided with a torque monitor. For this purpose the support bearings taking up the reaction torque of the electric motor in the housing of the tool are equipped with pressure sensors in the form of conductive plastic material, the electric resistance of which changes as a function of the pressure exerted.
Claims9
An electric tool having an electric motor, said electric motor comprising:
- a housing:
- a stator mounted inside said housing;
- support means, inside said housing and extending between said housing and said stator, for supporting said stator in said housing and transmitting the reaction torque of said motor to said housing;
- a pressure sensor incorporated in said support means;
- said pressure sensor comprising a platelet of electrically conductive plastic material, the resistance of the latter changing as a function of the pressure exerted upon it, disposed between two electrodes;
- said pressure sensor being subjected to said reaction torque to change the resistance of said conductive plastic material, whereby said change in resistance of said conductive plastic material can be used in controlling said motor;
- two such pressure sensors between which a support element is disposed, one of said support element and said pressure sensors being fastened to said stator, and the other connected to by said housing, whereby one of said pressure sensors is subject to the reaction torque of the motor in one direction of drive of the latter and the other of said pressure sensors is subject to the reaction torque of the motor in the opposite direction of drive of the latter;
- and
- said two pressure sensors are contained in a common enclosure, and wherein said support element protrudes outwardly through an opening in said enclosure.
6 more elements
An electric hand tool having an electric motor, said motor comprising:
- a housing having an inside surface with, in cross section, two diametrically opposed flats;
- a stator supported inside said housing and having two diametrically opposed flats disposed opposite those of said housing;
- opposed cavities in the housing flats;
- a pressure sensor located in each said cavity, each sensing element comprising a platelet of conductive plastic material the resistance of which varies in relation to the pressure applied thereto, and two electrodes between which said platelet is disposed;
- the pressure sensors forming support bearings for supporting said stator in said housing and transmitting the reaction torque of said motor to said housing, said stator flats engaging said pressure sensors;
- and
- said pressure sensors being subjected to said reaction torque to change the resistance of said conductive plastic material, whereby the torque of said motor can be limited in dependence on resistance changes of said conductive plastic material.
4 more elements
An electric tool having an electric motor, said motor comprising:
- a housing;
- a stator mounted inside said housing;
- two oppositely disposed support bearings each connected to both said housing and said stator and extending therebetween inside said housing to support said stator in said housing and transmit reaction torque of said motor to said housing;
- each support bearing comprising a member having opposite ends, one end being engaged in one of said housing and said stator and the other end engaging in a cavity in the other of said housing and said stator, said other end being sandwiched between a pair of pressure sensors contained in a casing of insulating material and having an opening therein, said member extending through said opening;
- each pressure sensor comprising a pair of electrodes between which is disposed a platelet of conductive plastic material, the resistance of the latter changing as a function of the pressure exerted upon it;
- and
- said reaction torque being transmitted through said members, depending upon the direction of drive of said motor, to one pressure sensor of said pair of pressure sensors of each support bearing to change the resistance of the conductive plastic material thereof, whereby said motor can be controlled in dependence on this resistance change to limit the torque of said motor.
4 more elements
Dependencies are inferred from the claim text.