Power wrench with a torque sensing unit

Abstract

A power wrench with a torque sensing unit (20), comprising: a housing (10, 22), a motor, an output shaft (13), and a planetary reduction gear (14), the planetary reduction gear (14) connecting the motor Connected to an output shaft (13) and comprising a static ring gear (19) supported within a housing (10, 22), wherein the torque sensing unit (20) comprises a torque transmitting element (23) ) has a single radially extending reaction arm (25) arranged to transmit reaction torque from the ring gear (19) to the housing (10, 22) and carries a strain measuring sensor (36) for generating a signal corresponding to the transmitted reaction torque , 37). The torque transmission element (23) comprises an annular body (24) with two weakened parts (34, 35), which deforms elastically during torque transmission and has a Plane (32, 33).

Description

technical field [0001] The invention relates to a power wrench with a torque sensing unit for generating an electrical signal corresponding to the actual delivered output torque. [0002] In particular, the invention relates to a power tool comprising a housing, an electric motor, an output shaft, and a planetary reduction gear connecting the electric motor to the output shaft and including a static ring gear supported within the housing. The ring gear is arranged to transmit reaction torque from the gear to the housing, wherein the reaction torque within the ring gear corresponds to the output torque transmitted through the output shaft. Background technique [0003] Previously, a power wrench of this type was described in US 4,404,799, wherein the ring gear is secured to the wrench housing by a weakened neck portion provided with strain gauges. During torque transmission through the gear, the weakened portion elastically generates a reaction torque, and the transmitted ou...

AI Technical Summary

Problems solved by technology

[0006] The two prior art torque sensing arrangements described above have the very serious disadvantage that the torque sensing arrangement is connected to the ring gear and the housing at four points, which means that there is a significant delay in the manufacture of the power wrench components as well as in the sensor element itself. Spread over tolerances inevitably creates differences in load levels on individual arms

Thus, due to the measurement on the reaction torque transmitted between the ring gear and the housing, and the measurement on the transmitted output torque from the power wrench, this leads to a related change of poor tolerance and the signal generated by the strain gauge uncertainty

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