TORQUE AND THRUST OVERLOAD DETECTION SYSTEM FOR A MACHINE TOOL

摘要

An overload detection system for a machine tool wherein a toolholder assembly (1) is divided into a drive toolholder (2) coupled to a drive spindle (17) for joint rotation therewith and a driven toolholder (21) having a collet chuck (23) for holding a cutting tool (13) such as a drill, the driven toolholder being coupled to the drive toolholder so as to be rotatable relative to the same through a preassigned angle about a toolholder axis, and wherein a coiled torsion spring (25) is provided between the drive and the driven toolholders for torque transmission from the former to the latter. For accurate overload detection, a set of drive teeth (34) are formed on the drive toolholder (2) at constant circumferential spacings about the toolholder axis whereas a set of driven teeth (31) are formed on the driven toolholder at constant circumferential spacings about the toolholder axis. The drive and the driven teeth are arranged interdigitatingly, with clearances (a, b or c) therebetween. A phase detector such as a proximity switch (45) is provided for detecting a relative phase displacement that will occur between the drive and the driven teeth in opposition to the force of the resilient means (25) upon development of abnormal torque load on the cutting tool (13).