Protective arrangement for machine

摘要

A protective arrangement for a longitudinally extendible machine component, such as the measuring arm 4 of a coordinate measuring apparatus, comprises a bellows 7 which at least partially surrounds the machine component and has a plurality of structural parts at least one of which is deflectable relative to the longitudinal axis of the machine component in response to a contact of the bellows with an object or person. Each of the structural parts has a cutout 19 formed therein and the parts are disposed in the bellows so as to cause the cutouts to be mutually aligned in the undeflected condition of the bellows 7. A light barrier directs a light beam through the cutouts which becomes at least partially shaded in response to a deflection of the one structural part. The light barrier generates a signal in response to the shading and this signal is supplied to a protective circuit in the control unit of the machine which can, for example, initiate an emergency stoppage of the machine component thereby preventing damage. ……