| 摘要 |
The device for perforating a moving sheet for a strip of casing material for rod-shaped articles in the tobacco processing industry has a radiation head with an optical system for focussing coherent radiation on the part of the sheet of material to be perforated. The radiation head (41) is designed as a closed housing (42) with a beam-entry window (43) of an optical system, a beam-emission opening (44) designed to permit the discharge of a gas flow, and a gas-inlet opening (52). At a distance in front of the beam-emission opening (44), a cover plate (48) provided with a bore (49) is arranged at a point lying in the beam path (69) of the radiation emerging from the radiation head. The cover plate (48) forms a closed space (56) with the housing (42) or a supporting body (38) surrounding the housing. The closed space (56) has a gas-discharge opening. A gas flow is produced between the gas-inlet opening and the gas-discharge opening by a pressure gradient. <IMAGE>
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