Tool measurement apparatus for a machine tool

Abstract

A tool measurement apparatus for a machine tool includes a transmitter portion including a light source for generating a light beam and a receiver portion including a detector for detecting the light beam, the light beam being passed from the light source to the detector along an optical path. At least one of the receiver portion and the transmitter portion includes a protection device including a gas expulsion aperture configured to expel a bleed gas supplied from an external gas source. The optical path also passes through the gas expulsion aperture. The protection device further includes a check valve located in the optical path. The bleed gas is supplied to the gas expulsion aperture through the check valve and the flow of the bleed gas through the check valve causes the check valve to adopt an open configuration defining a passageway through which the light beam can pass.

Dependencies are inferred from the claim text.