Elevator – industrial lift truck – or stationary lift for vehicle – Stationary lift for roadway vehicle or required component... – Having specific drive means for support
Patent
1982-09-16
1985-03-26
Truhe, J. V.
Elevator, industrial lift truck, or stationary lift for vehicle
Stationary lift for roadway vehicle or required component...
Having specific drive means for support
187 48, 340 19R, 318467, B66B 1326
Patent
active
045067651
DESCRIPTION:
BRIEF SUMMARY
This invention relates to proximity detector circuitry particularly though not exclusively for use in connection with lift or elevator closure doors.
It is common practice in the construction of elevator installations to include means for 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. 711,515, 856,085 and 1,108,884 describe systems of this nature. Specification 1,108,884 describes and claims a proximity detector circuit for elevator doors in which the circuit is responsive the variation in the capacitance to ground of antennae which are mounted at the edge of the closing door. The change in capacitance is determined using bridge circuits and appropriate voltage supply and amplifying means and suitable circuitry is provided to ensure that if the closing door detects the presence of a person or other object in the way, then the door is stopped or retracted and of course the elevator car prevented from moving until the door has closed properly.
As described in Specification No. 1,108,884, and particularly as shown in the left-hand side of the drawing, antennae are positioned in pairs along the leading vertical edge of the elevator car door. Each pair of antennae are used in a bridge type circuit with imbalances being detected rather than a mere change in capacity. This prevents false detections arising because of a change in the capacity between antennae to ground as the door itself moves. Thus, fixed items parallel to the detector such as the slam post against which the door eventually lodges or the metal work of the lift car door return adjacent the door edge when the door is fully open, do not affect the balance of the bridge circuit and are accordingly not detected as, would for example, people or other objects in the doorway which are not parallel to the door.
While this approach works satisfactorily in many instances, it is not always reliable in practice and it tends to be somewhat oversensitive. For example, if the slam post against which the door leading edge comes to lodge is not parallel to that leading edge as it approaches it, an imbalance may occur tripping the door retraction circuitry. A similar problem may arise with other parts of the car if they are not parallel to the door edge. Similarly, problems may arise with structural steel work such as landing doors adjacent to which the lift car may be brought to rest at an appropriate floor, and misalignments may vary from floor to floor. In the case of lift systems where the lift car and landings are each provided with sliding doors each running in tracks mounted in the car body and on the structure of the building respectively, if those tracks are not parallel, imbalance may arise. Other causes of imbalance can occur during use because of roller or guide wear on the door, particularly if it is sufficient to wobble the door as it is being moved. Even changes in temperature and humidity or moisture or dirt coming on to the lift components can cause the circuitry to go out of balance and generate or aggravate false detection problems.
According to a first feature of the present invention there is provided proximity detector circuitry for use in connection with a door closure or analogous apparatus which comprises three sensors located at spaced intervals along the edge of the door, the outputs of the three sensors being fed to two differential amplifiers each of which compares the outputs of two of the sensors, each producing an error signal if there is a difference in output from the two sensors connected thereto, and means for generating appropriate door control signals on the detection of an error signal.
By using three sensors connected to two differential amplifiers, problems associated with balanced bridge type systems and particularly with eliminating a null are provided.
According to a second feature o
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Payne Reginald K.
Trett John
Ip Paul Shik Luen
Truhe J. V.
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