Transducer for torque and/or angular displacement measurement,

Abstract

A transducer arrangement for torque and/or angular displacement measurement, especially in power screwdrivers, operates in accordance with the eddy current principle. The transducer arrangement is constructed as a self-contained structural unit having its own transducer casing which is connected by appropriate coupling and connecting parts to the housing of the power screwdriver and to the driving and driven members of the screwdriver. A torsionally deformable member, especially shaft, is interposed between the driving and driven members, being connected thereto for joint rotation therewith. When torque is applied to the deformable member, its end portions are angularly displaced relative to one another. Two slotted members, especially sleeves, are respectively connected to the end portions of the deformable member for joint angular displacement therewith, and they influence the magnetic field in the vicinity of the deformable member in proportion to their relative angular displacement. The changes in the magnetic field are detected by an electric coil arrangement whose impedance changes accordingly, and the thus obtained signal is evaluated to obtain the magnitude of the applied torque. A cable connected to the coil arrangement and extending to the exterior of the casing through an opening provided in the latter is accommodated in a tube. The tube extends along a handgrip portion of the housing of the screwdriver to protect the hand of the user.