Elevator – industrial lift truck – or stationary lift for vehicle – With barrier for regulating access to load support – Includes motor or motor driven linkage for shifting barrier
Reexamination Certificate
1999-10-12
2001-06-19
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
With barrier for regulating access to load support
Includes motor or motor driven linkage for shifting barrier
C049S025000
Reexamination Certificate
active
06247558
ABSTRACT:
FIELD OF INVENTION
This invention relates to apparatus for reducing power consumption in a elevator door protection system. The invention is applicable to systems which have an “infrared curtain”, for example, where infrared beam transmitters and receivers simulate a grid of infrared beams across a elevator door opening and where door control circuitry responds to the receiver output, when the beams are intercepted by an object in the elevator door opening, to produce a drive signal to operate elevator door control circuitry for opening the door or doors. The invention enables the power consumption of infrared devices used in such systems to be reduced, when they are not needed to detect an object, thereby providing an improvement in lifetime and reliability.
BACKGROUND TO INVENTION
A typical infrared beam curtain comprises a plurality of infrared emitting and receiving diode pairs, which are vertically spaced apart to simulate a grid-like barrier of infrared beams either between a single door and a slampost, or between centre-closing doors of a elevator car. However, the infrared emitting diodes consume a significant amount of electrical power when operating continuously and this reduces their lifetime.
OBJECTS OF INVENTION
An object of the present invention is increase the lifetime of such infrared emitting diodes in a cost effective and efficient manner.
PRIOR ART
WO-8402413 discloses a system which employs an infrared curtain and in which optical communication takes place, across the door gap, between transmitters and receivers attached to respective doors. However, this reference is primarily concerned with such “wireless” optical communication, whereby control information can be transferred that causes different transmitter/receiver pairs to cooperate to create different infrared beam “patterns” across the door opening. The reference does not teach any technique for reducing the power consumed by infrared emitting diodes (which are subject to continuous scanning under normal operation), in order to extend their lifetime.
Japanese Patent Publication 9315740 (Otis) discloses a system for reducing power supplied to pulsed light emitting diodes, when elevator doors are closed, by adjusting the pulse repetition rate. However, the diodes are provided with fixed width pulses which form a continuous train of pulses. On the other hand, in the present invention, when the doors close, a dead space is introduced or widened between the trains of pulses in each scan in order to conserve power. Otis does not employ such a “dead space” in a “standby mode”. Moreover, when the invention is in the “standby mode”, one scan can be given periodically in order to check the status of the elevator car.
Other less relevant cited art includes GB 2254916A (Trett); WO 96/08734 (Thomson); U.S. Pat. No. 5493812 (Teich); and JP 090303042 (Tsuuden KK).
SUMMARY OF INVENTION
The present invention is useful in reducing power consumption in a elevator door protection system of the kind having an infrared curtain. Such a system utilises infrared beam transmitters and receivers to provide a beam or beams across a elevator door opening and circuitry responsive to an output of the receivers (when the beam or beams are intercepted by an object in the elevator door opening) to produce a drive signal which causes elevator door control circuitry to open the door or doors in the event of beam interception. The detection circuitry responds when (a) the elevator door or doors are substantially closed, so that the usual power supplied to the transmitters can be reduced; and (b) the elevator door or doors are open or opening, so that the usual power supplied to the transmitter means can then be restored. The transmitters and receivers are normally scanned at a rate of N per second and power is reduced by interposing a predetermined standby interval between each scanning interval (i.e. between the trains of pulses).
Whilst the detection circuitry normally responds when the elevator door or doors are fully closed, it would also work when there is a small gap (e.g. in which there is little or no danger of any object being trapped), between a single door and a slampost, or between centre closing doors. In any event, the power dissipation would not normally be reduced whilst there is any risk of an object intercepting the beam or beams, in the elevator door opening, so as to ensure that the doors will be opened in the event of beam interception.
Preferably, the detection circuitry responds to the output of the infrared receivers to cause the reduction or the restoration of power. For example, the output of the infrared receivers can be used as a means of determining the distance between transmitters and receivers (when beam interception is ignored). Alternatively, or in addition, the output of the infrared receivers will cease changing, due to lack of door motion, when the doors are closed. In a preferred embodiment of the invention, the average receiver output is monitored and when this has been steady for a predetermined period, power reduction can be initiated. The strength of the signal from the infrared receivers is thereby usable to determine that the door or doors are substantially closed, assuming that there is no beam interception due to an object.
In order to take account of a slight possibility that an obstruction, having small dimensions, such as a dog lead or a child rein, might be trapped between the doors before intercepting a beam (to cause the doors to open), the detection circuitry preferably incorporates a time delay which is set so that the power dissipation is reduced only after a predetermined delay following door closure. For example, a delay of 10 seconds from the “door closed” signal would suffice to avoid the aforementioned risk.
Preferably, circuitry is included for maintaining the door or doors closed when the elevator is not in use. This enables power consumption to be reduced during quiet spells and overnight, when the elevator is essentially not in use.
In a typical installation which employs infrared emitter diodes as transmitters and receivers, each set of corresponding transmitter/receiver pairs of diodes are “scanned” at a rate of about 800 diodes per second. For example, if there are 40 IR transmitter diodes (and hence 40 IR receiver diodes in the transmitter/receiver pairs), there are 20 scans/sec of the 40 pairs of diodes. This is equivalent to scanning 800 transmitter diodes each second whereby each transmitter diode receives power for a short period ({fraction (1/800)} second) every {fraction (1/20)} second. During the period within which the transmitter diode of a diode pair is supplied with power, the transmitter emits an IR beam for the same period during which the receiver output is sampled to determine if there has been any beam interception. This is repeated for the next diode pair. The cycle is continuous from the first pair to the last pair, so that individual transmitter/receiver pairs receive power intermittently at a first cyclic rate.
In accordance with a preferred embodiment of the invention, when the doors are closed (preferably for a predetermined interval), the scanning rate of the set of diode pairs remains the same, but a dead space or standby period is introduced between the scans so as to conserve power, particularly the power supplied to the transmitters. This dead space or standby period which can be, for example, about 2 seconds, enables scanning to be maintained but at a much lower rate. As the individual transmitters (and receivers) receive power at a second cyclic rate lower than the first, the normally high power dissipation of the transmitter diodes can be drastically reduced. Surprisingly, this can reduce the power dissipation in the infrared diode emitters by a factor of about 40 times. As the diode emitters are subjected to more electrical stress than most other components in an infrared curtain and they consume about 50% of the power, a useful improvement in reliability and a reduction in wasted power is achieved.
Recovery from the reduced power dissipa
Bailey Peter Leslie
Gaskin David Charles
Cowan Liebowitz & Latman
Gable R. Lewis
Memco Limited
Salata Jonathan
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