FI58765B - ELECTRONIC SAW CHARACTERISTICS - Google Patents

Description

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Patent- och raglstarstyralaan 'AnttUun utiigd och utUkrifttn pubiiund 31.12.80 (32) (33) (31) Requested «tuolkuui — Bujlrd priority (71) Elevator GmbH, Poststrasse 9» CH-6300 Zug, Switzerland-6chveiz (CH) (72) The present invention relates to an electronic safety strip for preventing the collision of a moving object which controls a control device such as a relay. The present invention relates to an electronic safety strip for preventing the collision of a moving object which controls a control device such as a relay. Pekka Torenius, Hyvinkää, Seppo Suur-Askola, Hyvinkää, Finland-Finland (FI) , and comprising at least one antenna forming a capacitor with a substrate in its vicinity, a voltage source such as a generator from which an AC voltage is applied to said antenna, an amplifier to which the control device and the antenna are connected so that a voltage change due to capacitive interference in the antenna is transmitted to the control device. the object includes, for example, automatic elevator doors, controllable mounting platforms or transport and transfer equipment.

For example, automatic devices are generally equipped with protective devices to prevent door users from getting caught between the doors, as well as the doors from colliding with people. Likewise, such protective devices can be constructed for other purposes, such as to prevent collisions between guided mounting platforms and transport and transfer devices with each other or against another obstacle. Such devices are mechanically operated sensor strips, photocells, ultrasonic devices and sensors based on capacitive measurement. Of the said devices, those operating on the capacitive principle are the most advantageous. An advantage is the architecturally suitable appearance, as all parts of the equipment 2,58765 can be placed invisible. Another advantage of capacitive sensors is good reliability, as the device is made to operate without mechanically moving and wearing parts.

Capacitive sensors of this kind are known e.g. the following publications: U.S. Patent 3,370,677, U.S. Patent 3,743,058, British Patent 1,108,884 and Finnish Publication No. 5329 4.

The weakness of the apparatus according to said U.S. Patent 3,370,677 is the difficulty caused by the change in the characteristics of the apparatus. This is manifested in the fact that, for example, the ground capacitances caused by the elevator's creators are different in different layers due to mechanical tolerances. In this case, the sensitivity of the equipment cannot be set very high because the wrong signal can be obtained to control the doors. Moisture and bumps from the antennas at the edges of the doors also change the capacitance conditions and limit the sensitivity. Another weakness of the equipment is the sensitivity to the capacitance between the shield plate and the sensor plate. This capacitance must be as small as possible compared to the ground capacitance to be measured in order for the signal to be measured to be sufficient. The requirement for low capacitance results in a mechanically expensive and thus disadvantageous antenna structure.

Another weakness of the capacitive sensor according to said U.S. Pat. No. 3,743,058 is the occurrence of excitation at the beginning of the door opening movement. In this case, the change in the capacitive conditions in the antennas located at the edge of the door after the start of the opening movement interferes with the operation of the control device and thus the door.

The sensor according to British Patent 1,108,884 has the same drawbacks mentioned above. Ts. the equipment is sensitive to disturbances caused by changes in the mechanical equipment itself and capacitance conditions. Still the weakness of the British device is the potential difference between the protective voltage and the measuring antenna. Although the protective voltage can prevent the effect of interfering ground capacitances, the capacitance of the protective voltage parts must not be large with respect to the measuring antennas, because this capacitance attenuates the obtained measuring signal. Therefore, the use of shielded coaxial lines 3,58765 in the transmission of the measurement signal from the antenna to the amplifier is limited. To increase the sensitivity, the amplifier has to be installed in a mechanically difficult place, such as in the immediate vicinity of the sensor strip, attached to a moving door. If two movable door halves are used, two separate amplifier devices are required.

In the device according to Finnish publication 53294, some of the above-mentioned drawbacks have been eliminated. In the device, the tuning unit is connected so that the set-hold circuit is tuned at the beginning of the door closing movement, so that only the voltage difference caused by a capacitive disturbance of varying magnitude during the closing movement reaches the control device through the set-hold circuit and the amplifier. In said device, the doors cannot be closed completely without a separate override field, with which the capacitance measurement is stopped. The weakness is precisely this. a switch that makes hardware more susceptible to failure and more expensive.

The object of the present invention is to eliminate the above-mentioned drawbacks and to provide a new type of simple and reliable safety strip.

The safety strip according to the invention is characterized in that the voltage from the amplifier is fed via a rectifier to an amplifier connected so that its DC voltage gain is +1, but which amplifies the voltage change at the incoming DC voltage by a multiple and further controls the control device via a comparator. The invention makes it possible to measure the change in capacitance continuously over a very wide range, in which case obstacles of very different sizes can affect the device when it enters the detection field at a speed exceeding a certain pre-set speed. When an obstacle enters the detection field of the device, the capacitance measured by the device increases and a voltage rise proportional to the increase in capacitance enters the control device through the amplifier.

One embodiment is an automatic door of an elevator, in which the antennas placed on the edge of the opposite doors are at the same potential with each other. This allows the doors to be closed without a separate overconnection, because as the doors approach each other, the capacitance to be measured decreases, as the effect of the opposite door surface increases.

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Another embodiment is controllable mounting platforms, as well as transport and transfer devices in which an antenna is placed on the edge of the devices. As the device approaches the object, the antenna and the capacitance between the objects, whereby the control device reacts and the collision is prevented.

The invention will now be described in detail by way of example with reference to the accompanying drawings:

Figure 1 shows the overall arrangement of the safety strip connected to the automatic doors of the elevator,

Fig. 2 shows the electrical implementation of one function block of the safety list according to Fig. 1 by means of generally known components and

Figure 3 shows a cross-section of a safety strip according to the invention attached to the automatic doors of an elevator.

The operation of the safety list is based on the measurement of the capacitance between the antenna 1 placed on the end face of the car door and its surroundings 2. The measurement principle is shown in Figure 2. The capacitance to be measured is Co. When Co is connected by resistor R to the alternating voltage produced by generator 3, a voltage Uc is formed over Co, the value of which is proportional to the magnitude of Co. Due to the high impedance levels of R and Co, the voltage Uc to be measured must be connected to the measuring circuit by means of an amplifier 4. After amplifier 4, the voltage is rectified and filtered to point P.

Amplifier 5 measures the voltage at point P. If the voltage is constant (= Co constant), amplifier 5 acts as amplifier 4. Its output voltage is the same as the voltage at point P. In this case, the output voltage of the comparator 6 is positive and the relay 7 is released. As the edge of the door approaches a person or object, the value of Co increases, whereby the voltages Uc and P decrease. Amplifier 5 amplifies the voltage change at point P by a multiple. As the absolute value of the voltage P decreased, the output voltage of the amplifier 5 becomes more negative. The change to negative is greater the greater the voltage change at point P. If the output voltage of amplifier 5 falls below the operating threshold of comparator 6, the output voltage of comparator becomes negative. Transistor T1 receives the main current and relay 7 pulls.

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Since the amplifier 5 is connected as an AC amplifier, its output voltage starts to rise toward positive immediately after the Corn value no longer increases. When the output voltage of the amplifier 5 exceeds the operating threshold of the comparator 6, the relay 7 is released. That is, the relay 7 can only pull if the value of Co increases and remains energized only for a moment if the value of Co remains constant and returns. The operating sensitivity of the measuring circuit is adjusted by a trimmer 8, which determines the operating threshold of the comparator.

In practice, the end faces of the doors are covered with an electrically conductive material 9. In order to improve the measurement sensitivity, the end face of the door half is divided into two equal blocks. The capacitance Co of the second pole forms an electrically conductive surface 1 the second pole is ground 2. The capacitance of each block is measured by its own channel. The channels independently control the relay 7 by means of the comparator 6.

In the closing phase of the doors, the value of Co decreases sharply, as the area between the antenna 1 and the ground 2 decreases and the effect of the opposite door surface at the same potential increases. Since only an increase in the value of Co can cause the relay 7 to pull, the doors can close despite the approach of the opposite door leaf.

The sensitivity of the measurement is considerably improved when the antenna block 1 is constructed and connected as shown in Fig. 3. The antenna plate 1.9 is formed by two electrically conductive surfaces with an insulator 10 between them. When the output voltage of the amplifier 4 is connected to the electrically conductive surface 9, the capacitance caused by the door leaf does not switch along with Co, because the surface 9 is always at the same potential as surface 1. It follows that the value of Corn is small, and even a small disturbance (= change in capacitance) causes a large change in the rest value of Corn.

A diode 12 is connected to each channel separately between the amplifier 5 and the comparator 6 in order to enable the parallel operation of several antennas. For practical reasons, it is advantageous to connect several antennas in parallel, as this further improves the measurement sensitivity.

Claims (2)

6,58765 An electronic safety bar to prevent a collision of a moving object, which controls a control device such as a relay (7), comprising at least one antenna (1) which forms a capacitor with the surrounding base (2), a voltage source such as a generator (3) from which an alternating voltage is derived to said antenna, an amplifier (4) to which the control device and the antenna are connected so that a voltage change due to capacitive interference in the antenna is conducted to the control device (7), characterized in that the voltage from the amplifier (4) is passed to the amplifier (5) , which is connected so that its DC voltage gain is +1, but which amplifies the voltage change at the incoming DC voltage by a multiple and which further controls the control device (7) via the comparator (6). Electronic safety strip according to Claim 1, characterized in that a trimmer potentiometer (8) is connected to the comparator (6) for adjusting the operating sensitivity. Electronic safety strip according to Claim 1, characterized in that a diode (12) is connected between the amplifier (5) and the comparator (6).