Patent ID: 8171831

Claim:
A working machine for manually fed workpieces, comprising: a working tool, a feeding area in front of the tool, within which a person's hand is present when feeding workpieces to be worked on to the tool, a detector covering at least a section of the feeding area for a contactless detection of human skin, the detector comprising at least one radiation unit and at least one receiver unit, the at least one radiation unit ( 32 , 34 ) emitting radiation towards said section of the feeding area, said radiation being emitted with at least two different wavelengths in the wavelength range between 900 nm and 1500 nm, whereas the at least one receiver unit receives the radiation reflected from the section of the feeding area, and a signal evaluation unit connected with the detector for calculating the quotients or differences of the intensities of the reflected radiations received by the receiver unit and the at least two different wavelengths emitted from the radiation unit, wherein based on the calculating, the signal evaluation unit determines whether the detector detects human skin, and wherein upon the detection of human skin, a protective means is configured to be activated for protection against potential injuries caused by the tool, or the signal evaluation unit determines whether the detector detects workpieces to be worked on, wherein the tool can be activated only if the detector detects workpieces to be worked on.