| 摘要 |
1,236,830. Photo-electric monitoring. ELECTRO DYNAMICS & TELECOM Ltd. Oct.2, 1968 [April 8, 1968], No.46651/68. Heading G1A. [Also in Divisions F2 and G2] A zone monitoring arrangement comprises an elongated light source the light from which tranverses the zone, an elongated lens assembly having a plurality of juxtapositioned lenses each of which is positioned in staggered relationship to at least one adjacent lens so that the assembly forms, in a predetermined region a number of staggered, spaced apart shadows when an object is present in the zone and a plurality of spaced apart photodetectors located in the region so that a number of shadows fall on at least one of them irrespective of the position of the object in the zone. In a machine guard arrangement which may cut off the power to the machine in the presence of an object a fluorescent tube provides the illumination and multiple shadows produced by lenses 19 Fig.2a are detected by cells 18. The lenses are cylindrical in shape, may have their curved surfaces towards or away from the photo-cells, may be cemented together or may be formed as a unit. The detector circuit which may include an integrator includes a transient suppressing circuit around the relay to enhance response and a by-pass circuit whereby the arrangement may be rendered ineffective during setting up. Feedback to the amplifier is provided. The arrangement may use photo-diodes, photo-transistors, photo-emissive cells, photo-voltaic cells, photo-conductive cells or photo-multipliers and may be applied to burglar alarms, automatic doors, process control, and fire and smoke detection. Dimensions are exemplified in the case of machine tools. |
