Patent ID: 6547042
Filing Date: 2003-04-15
Classification: E05F,G01V

Abstract:
A method of gap scanning wherein a first working member (such as a door) in conjunction with a second working member (such as another door, a door frame or a fixed surface) serves to define or include the gap to be scanned; the method comprising the steps of: locating on one side of the gap an array of emitters of electromagnetic radiation; location on the other side of the gap to the one side an array of receivers of the electromagnetic radiation; each emitter in the array thereof being adapted to provide for the emission of a beam of radiation along an axis of transmission from the emitter across the gap to one or more of the receivers in the array thereof; each receiver in the array thereof being adapted to detect a beam of radiation from one or more of emitters in the array thereof along an axis of reception to the receiver across the gap from the emitters; providing an output channel for each receiver in the array thereof by way of which in the event the receiver detects a beam of radiation as aforesaid the receiver emits an output signal; characterized by the steps of:1. linking a group of at least two receivers by way of their output channels by way of a common line to a switch such that on the switch receiving an output signal along the common line from the group it is unable on the basis of that output signal alone to discriminate as to which of the receiver or receivers in the group generated or contributed to the output signal; 2. causing the switch on receiving an output signal as aforesaid to transmit to a processor a second signal; 3. enabling the processor to identify the member or members of the group causing the generation of the second signal by virtue of the time of arrival of the second signal relative to some time datum and/or to the location of the group relative to some geometric datum; and 4. comparing the second signal or a function thereof with a predetermined value in order to establish whether the second signal represents: a first state of the gap such as could arise from an obstruction resulting in radiation emitted from one or more emitter being prevented by the obstruction from falling on one or more members of the group; or a second state such as could arise from an anomalous condition, and 5. in the event the second signal represents the first state then initiating a control change to occur to cause, in the case of a variable size gap, a change in the spatial relationship between the first and the second working members from that existing prior to the comparing step (such as by causing the gap to stop changing or to cause it to increase) or, in the case of a fixed size gap, modifying some pre-existing control condition dependent on whether or not the first state exists.