Proximity detector

Movable or removable closures – Radiant energy control

Patent

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Details

49 27, E05F 1520

Patent

active

048949523

DESCRIPTION:

BRIEF SUMMARY
BACKGROUND OF THE INVENTION

1. Field of the Invention
The invention relates to a proximity detector for the detection of the presence and position of objects and people or parts thereof in the path of moving mechanical devices, such as automatic sliding doors, automatic swing doors or moving vehicles of robots, to, for example, enable corrective safety action to be taken.


THE PRIOR ART

It is common practice in the construction of automatic doorways to include means of ensuring that the doors cannot close on a person causing discomfort or injury. A number of contactless systems are known for detecting the presence of a person in a doorway, particularly the presence of a person in the space which the door is approaching. British patent specification Nos. 711515, 856985, 1108884, PCT/GB82/00022 and European Pat. No. 0097139 are but a few which describe systems of this nature.
All of them involve positioning a proximity detector on the door establishing conditions whereby a person can be identified in the space or volume which the door is approaching but being able to ignore walls and other fixed objects by balance bridge techniques or by reducing the sensitivity when the door is close to the fixed object.
While this approach works satisfactorily in many instances, it is not always reliable in practice and tends to be prone to false firing under changing site conditions. For example, when very close to fixed objects the slightest variation in door position may cause a balance bridge circuit to give a false detection. If the sensitivity is reduced under these conditions, then `nulls` often occur where detection is not possible.
This invention provides a means of increasing the sensitivity and range of detection and maintaining and often increasing the sensitivity when the sensor is very close to objects not to be detected, without false firing.
It is preferable with sliding or swing doors to provide types of protection as follows:
(1) For a person very close to the leading edge or side of a closing door detection is necessary over the full length of the leading edge or side of the door, this detection range must be adequate to prevent a person (hand, foot, etc.) being touched by the door, i.e. to be greater than the stopping distance of the door.
(2) For a person approaching a door, detection is necessary to establish the presence of the person to delay the door closure.
(3) With building sliding doors it is necessary to establish detection of a person approaching a door to open the door.
(4) With a swing door it is necessary to establish separate detection of persons approaching a door from either side to operate a stop circuit to prevent the door from hitting one of the persons.
(5) With a swing door it is necessary to establish detection also outside the path of the door opening to allow timely response.
The invention uses as its basis a method of, and apparatus for, controlling the range and angular vision of a detection unit which is mounted on or near a moving object (e.g. door) for the purpose of providing information as to the position of other objects, stationary or movable, within a specified space or volume. Two types of detection units are discussed, namely reflective acoustic (e.g. sonic or ultrasonic) and electromagnetic.


SUMMARY OF THE INVENTION

According to the present invention there is provided a movable door incorporating a proximity detection system for sensing obstructions in the path of the door, the system comprising a transmitter mounted adjacent a surface of the door to transmit an energy in directions inclined to the direction in which the said door surface is movable, a receiver mounted to receive the energy transmitted from the transmitter when reflected by obstructions in the path of the door, and a barrier mounted between the transmitter and the receiver to prevent energy transmitted by the transmitter from being directly received by the receiver.


BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example, with reference to the accompanying d

REFERENCES:
patent: 4029176 (1977-06-01), Mills
patent: 4565029 (1986-01-01), Kornbrekke et al.
patent: 4581526 (1986-04-01), Brattgard

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