Elevator – industrial lift truck – or stationary lift for vehicle – With monitoring – signalling – and indicating means – Monitors operational parameter
Reexamination Certificate
2000-01-24
2001-11-06
Salata, Jonathan (Department: 2837)
Elevator, industrial lift truck, or stationary lift for vehicle
With monitoring, signalling, and indicating means
Monitors operational parameter
C367S127000
Reexamination Certificate
active
06311803
ABSTRACT:
FIELD OF THE INVENTION
The invention relates to an apparatus for detecting the position of an object which can move along a predefined path. Such apparatus may be used for controlling the position of a lift cage or the like and thus ensuring its positioning at predetermined stops according to floor levels.
BACKGROUND OF THE INVENTION
European Patent 0 694 792 discloses an apparatus for detecting the position of a movable object, which has a sound signal conductor extending along a travel path and having a predetermined, uniform speed of sound propagation, as well as a signal injector, which is connected to a signal generator and is located on the movable object, for injecting a sound signal into the sound signal conductor. Arranged in this case at both ends of the sound signal conductor are signal extractors which are respectively connected to a counter, the two counters being clocked via a clock generator and connected to a subtractor for the output signals of the two counters. The output signal of the subtractor can be processed by an evaluation unit, as a measure of the delay time difference of the injected sound signal from the injecting point to the signal extractors, to form a signal which is representative of the instantaneous position of the movable object on the travel path, the signal injector operating with a signal spacing time which is greater than the sound delay time from one end of the travel path to the other.
The measured delay times from the sound injector to the signal extractors are assigned a positional value by means of the evaluation unit and a computational algorithm implemented in it. Specifically in the design of lifts, the evaluation unit is calibrated by assigning the flush point of each floor the result of the computational algorithm at this point and associating the lift position with this numerical value. Because of temperature-induced changes in buildings and/or changes in the length of the sound signal conductor, or owing to a change in the speed of sound in the sound signal conductor as a result of effects of temperature and diffusion, however, there is a shift in the assignment between the flush point and the numerical value assigned by the calibration.
SUMMARY OF THE INVENTION
It an the object of the invention to provide an apparatus for detecting the position of an object moveable along a prescribed distance, by a means of which it is possible to approach simply and accurately predetermined positions of the movable object on a travel path of great length.
An apparatus for detecting the position of an object moveable along a predetermined travel path according to the invention comprises
an acoustic signal conductor extending along the travel path and having a predetermined, uniform speed of propagation of sound;
a signal input coupler located on the moveable object, to couple a clocked acoustic signal into the acoustic signal waveguide,
a signal extractor being arranged at one end of the acoustic signal waveguide and being connected to an evaluation unit for determining the propagation-time of the sound signal from a position at which it is coupled in to signal extractor and for generating a signal representative of the instantaneous position of the moveable object on the travel path,
wherein at least one sensor actuatable by being passed over by the movable object is arranged at a predetermined distance from the middle of the sound signal conductor and is coupled to the evaluation unit, which in accordance with an error polynomial whose coefficients are derived from errors, compensates errors of calibration points along the travel path, the respective error assigned to a specific distance of the travel path being yielded by evaluating the pulse emitted by the sensor assigned to the distance upon being passed over by the movable object.
Further objects, embodiments and advantages of the invention will become apparent from the following description and the claims.
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K.A. Schmersal GmbH & Co.
Patterson Thuente Skaar & Christensen P.A.
Salata Jonathan
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