Improvements in or relating to shielding arrangements for protecting exterior windows against dust and dirt

摘要

1,032,936. Cleaning by air streams. GENERAL ELECTRIC CO. Ltd. May 20, 1964 [June 24, 1963], No. 25040/63. Heading A4F. [Also in Division G1] A window 2 in a housing 1 of an electrooptical apparatus is protected against dust and dirt by a shield 3 mounted on the body 1 and having an opening 4 therein through which light can pass to the window 2, and super-atmospheric pressure may be produced in the space between the shield 3 and the housing 1 by feeding air thereto by a compressor 6, so that air flows outwardly through the opening 4 to oppose the entry of dust or dirt therethrough. The illustrated electro-optical apparatus forms part of railway waggon recording equipment and contains a projector for illuminating code plates on passing railway waggons, and one or more photo-electric devices for receiving light returned from the code plates through the window 2 and converting it into electrical impulses to be fed to a recording device. An alternative embodiment is described in which the opening 4 is provided with a shutter, which is opened electro-magnetically when the air compressor is energized by a device for detecting an approaching train.