Method and apparatus for detecting position of an elevator door

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

Utility Patent

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C187S393000, C049S025000

Utility Patent

active

06167991

ABSTRACT:

TECHNICAL FIELD
The present invention relates to elevators and, more particularly, to a method and apparatus for detecting distance between emitters and receivers mounted on opposing sides of an elevator door system.
BACKGROUND OF THE INVENTION
In elevator installations, many elevator door systems are equipped with safety systems designed to detect potential interference with the closing operation of the doors of the elevator cab, i.e., the elevator doors. Such safety systems typically include a plurality of signal emitter sources disposed on one elevator door, and a plurality of signal receiver sources disposed on the other elevator door. The signal emitters emit a curtain of signals across the threshold of the elevator door which are received by the signal receivers. When the curtain of signals is interrupted, the safety system communicates with a door controller in order to either stop the door closing operation and open the doors, or to maintain the doors in an opened position, depending on the current door position.
Several prior art doorway safety systems create a zone of detection which extends into the entryway. One such doorway safety system is described in U.S. Pat. No. 4,029,176 (Mills) that utilizes acoustic wave emitters and receivers to detect objects or persons within an area near the elevator doors, i.e., within a zone of detection. The emitters send out a signal at an angle into the entryway. When an obstruction enters the detection zone, the signal reflects from the obstruction and is detected by the receivers.
Another alternative doorway safety system described in U.S. Pat. No. 5,886,307 (Full, et al.) also discloses a three-dimensional system for detecting objects across the threshold and in the entryway. This system projects a curtain of light beams across the threshold and illuminates the area directly in front of the entryway with three-dimensional detection beams. The system detects obstructions between the elevator doors and across the threshold if an obstruction breaks one or more of the beams. In addition, if energy from the three-dimensional beams reflects off of an object in the entryway into the three-dimensional receivers, the obstruction is also detected.
One shortcoming of the existing prior art safety systems is detection of objects after the elevator doors have been partially closed. As the elevator doors are closing, the detection zone is also moving and structural obstructions, such as walls supporting the doors or an outside set of hallway doors, fall within the detection zone. By way of example, a center opening elevator door system typically comprises a set of hallway doors and a set of elevator cab doors with the emitters and receivers mounted on the elevator doors. Both sets of doors slide open and close together across a threshold with the hallway doors closing and opening slightly ahead and behind, respectively. However, as the hallway doors slide ahead of the elevator doors, they often extend into the changing zone of detection. Once the signal from an emitter is intercepted by a hallway door, it is reflected to the opposing hallway door, and is subsequently reflected again to be detected by the receivers.
As the elevator doors are closing and the distance between the emitters and receivers becomes progressively smaller, the signal that is reflected from the hallway doors and other architectural obstructions travels shorter distances and still remains strong when received by the receivers. The existing safety systems are not able to discriminate between the signal that is reflected from false targets (such as hallway doors) at relatively short distances between the elevator doors and a signal reflected from a true obstruction.
European Patent Application No. EP 0699619A2 (Memco Limited) describes a three dimensional system for detecting objects or persons in the entryway. Memco Limited attempts to solve the above-described problem with false targets by progressively reducing the gain of the receivers, as the elevator doors are closing. The doorway safety system described above in Full, et al. attempts to solve the problem by progressively reducing the amount and intensity of the transmitted signal as the doors are closing. A doorway safety system described in a patent U.S. patent application Ser. No. 08/1876,127, filed on Jun. 23, 1997 which is now U.S. Pat. No. 5,925,868 issued on Jul. 20, 1999 to Gary G. Full, et. al., of Otis Elevator Co. and entitled “A Safety System for Detecting Small Objects Approaching Closing Doors” attempts to solve the problem by significantly modifying the way that the emitters are driven, as well as by modifying the way that the system interprets the received signals.
Each of these methods of solving the problem are dependent upon the ability to determine actual elevator door position. Most existing safety detection systems, of the kind described above, are stand-alone systems, meaning they do not obtain elevator door position information from the door operator. These systems must determine elevator door position information independently. Since the “curtain” of signals being transmitted directly across the elevator door opening increases in intensity as the doors close, that relative intensity is used to represent elevator door position.
However, a major drawback to using curtain beam intensity to determine elevator door position is that it is extremely difficult to obtain consistent curtain intensity values, as they relate to actual door positions, from manufactured system to system, and from installation to installation. There are several factors involved which can affect curtain beam intensities, e.g., variation in optical components, individual curtain beam alignments, emitter and/or receiver unit alignments, aging of optical components (emitters, receivers, lens materials), the accumulation of dust on the lenses, and the presence of smoke or condensation.
One prior art solution to the problem of curtain beam intensity variation involves compensating for potential intensity variation by designing in a very loose tolerance requirement for door position values. Problematically, the overall effect is to significantly compromise system performance.
Another prior art solution is to calibrate each system to its particular installation by providing a manual calibration procedure whereby door positions can be directly associated with actual curtain beam intensities for the particular system in its particular installation. A limitation for this method is that the system cannot automatically compensate for component aging, dust accumulation or smoke/moisture in the environment.
A doorway safety system described in a pending patent Japanese Patent Application Serial No. 9-237578, filed on Sep. 3, 1997 to Masanori Nakamori, et. al., of Nippon Otis Elevator Co., entitled “Elevator Passenger Detection Device” attempts to solve the problem by utilizing a binary method of distance measurement. This method depends upon the simple detection of curtain beams by curtain receivers which are off axis to the curtain beam emitters. This is a simple, binary, connect-no-connect method, where, the further off center the curtain beams are detectable, the further open the doors are considered to be. However, this method lacks sufficient resolution. This is because curtain beams typically are not binary entities. Rather, the beam intensity peaks at the center of the emission pattern and gradually diminishes in strength as angles increase from center, yielding no definitive and repetitive point in such an emission pattern to use for distance measurement.
There is a need, therefore, for an improved method of detecting the position of elevator doors to enhance the ability of elevator door safety systems to discriminate between false targets and true obstructions.
SUMMARY OF THE INVENTION
This invention offers advantages and alternatives over the prior art by providing a method and apparatus for detecting the distance between opposing sides of an elevator door system. The invention enhances the ability of an elevator door safety s

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