Abstract:
The present invention relates to an apparatus for detecting any abnormality in a cage of an elevator, characterized by comprising a transmitter which continuously transmits an ultrasonic wave inwardly of the cage of the elevator, a receiver which receives an ultrasonic wave retrogressing in such a manner that the ultrasonic wave transmitted from said transmitter is reflected by an object within the cage, and a processing circuit which detects the rate of movement of the object within the cage on the basis of a magnitude difference between frequencies of the ultrasonic waves of said transmitter and said receiver and which decides that an abnormality has occurred in the cage when the difference frequency has become at least a preset value.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates to the detection of abnormal action by a man or an object in the cage of an elevator. 
     Since the cage of an elevator becomes a closed room, crimes in the cage occur frequently. In order to prevent these abnormal actions, the function of operating the elevator so as to stop the cage at each floor in response to a cage call is sometimes added in a specified time zone. This measure, however, is not satisfactory for the prevention of these actions. 
     Meanwhile, there has not been introduced any device which prevents a governor from being tripped due to vibrations attributed to jumping or violent behaviour by a man in the cage during the running therof, and the elevator has been quite defenseless as to abnormal actions of a man in the cage. 
     SUMMARY OF THE INVENTION 
     This invention has been made in order to eliminate the disadvantages of the prior art described above, and has for its object to provide an apparatus for detecting any abnormality in the cage of an elevator in which the movement of a man or an object within the cage is monitored by an ultrasonic wave so as to prevent a crime or the abnormal operation of the elevator from occuring. 
     In the apparatus according to this invention, an ultrasonic oscillator and a receiver are mounted inwardly of the cage of the elevator, and the movement of a man or object within the cage is detected on the basis of a difference between the frequencies of the transmitter and the receiver. Thus, any action or operation dangerous to the elevator can be detected beforehand, and the apparatus is very effective in the prevention of crimes. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIGS. 1 and 2 are a plan view and a block diagram showing an embodiment of this invention, respectively; 
     FIG. 3 is a perspective view showing another embodiment of this invention; 
     FIG. 4 is a side view showing a part A in FIG. 3; 
     FIG. 5 is a top view corresponding to FIG. 4; 
     FIG. 6 is a circuit diagram showing the internal arrangements of a difference frequency detector circuit and a comparator shown in FIG. 2; 
     FIGS. 7 and 8 show the output signals of various parts in the difference frequency detector circuit for the cases where a man comes close to a transmitter as well as a receiver and goes away therefrom, respectively; and 
     FIGS. 9, 10 and 11 show the output signals at several points of the comparator in the cases where the frequency of the output of the difference frequency detector circuit is high, is low and is still lower, respectively. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Now, one embodiment of this invention will be described with reference to FIGS. 1 and 2. 
     FIG. 1 is a view showing the state of a cage. Numeral 1 designates the cage, numeral 2 the door of the cage, numeral 3 a cage control panel, numeral 4 a transmitter which transmits an ultrasonic wave inwardly of the cage, and numeral 5 a receiver which receives the ultrasonic wave reflected by an object or a man within the cage. The transmitter 4 and the receiver 5 are mounted near the ceiling of the cage. 
     FIG. 2 is a diagram illustrative of the principle of this invention. Numeral 6 indicates an oscillator, numeral 7 a man who has gotten into the cage, numeral 8 an amplifier, numeral 9 a difference frequency detector circuit which detects the frequency of the difference between the outputs of both the oscillator 6 and the amplifier 8, and numeral 10 a comparator which generates an abnormality signal 11 when the output of the difference frequency detector circuit has become greater than or equal to a preset frequency. 
     In the apparatus thus constructed, when the ultrasonic wave is transmitted from the transmitter 4 on the basis of the output of the oscillator 6, it either impinges on the man 7 within the cage 1 or reflects of the wall of the cage. The ultrasonic wave reflected of the man 7 arrives partly at the receiver 5 directly or while being reflected by the wall of the cage 1 as described to the above. The output of the receiver 5 is amplified by the amplifier 8, and the frequency difference between the output of the oscillator 6 and that of the amplifier 8 is detected by the difference frequency detector circuit 9. When no one is present within the cage, or when the man 7 is present while not moving, the difference frequency becomes zero. In contrast, when the man 7 is moving within the cage, the frequency of the ultrasonic wave reaching the receiver 5 is changed due to the Doppler effect, and the difference in frequency at the output of the difference frequency detector circuit 9 is directly proportional to the rate at which the man 7 moves. The comparator 10 provides an abnormality signal 11 on the basis of the difference frequency when the movement of the man 7 within the cage has become at least a preset rate i.e., the present difference frequency. Here, an elevator control circuit, not shown, is enabled to sound a buzzer in the cage in response to the abnormality signal 11, thereby warning to the man 7 within the cage; to execute the operation of opening the door during the stoppage of the cage; or to stop the cage at the nearest floor and then execute the door opening operation during the running of the cage. 
     FIGS. 3 to 5 show another embodiment of this invention, in which the same symbols as in FIGS. 1 and 2 indicate identical or corresponding portions. FIG. 3 is a view showing the state of the upper part of the doorway of the cage 1 of the elevator. Numeral 12 indicates a rail for the cage door, numeral 13 a guide rail which is disposed in the upper part of the cage door 2, and numeral 14 a roller which moves along the guide rail 13. FIG. 4 is a view showing the details of a part A in FIG. 3. It is a sectional view seen in the direction of the opening and closing of the door of the cage, and illustrates the state in which the cage door is midway of the opening or closure thereof. Numeral 15 designates a hanger which suspends the door 2, numeral 16 a changer roller which is mounted on the hanger 15 by a pivot not shown and which rolls on the rail 12, numeral 17 an arm which moves in interlocking relationship with the rollers 14, numeral 18 a guide for the arm 17, and numeral 19 a transmission and reception unit in which the transmitter 4 and the receiver 5 are assembled. Symbol 19a denotes the state of the transmission and reception unit under the fully open condition of the cage door 2, and symbol 19b the state of the transmission and reception unit under the fully closed condition of the cage door. Numeral 20 represents an anchor plate for the transmission and reception unit, and numerals 21 and 22 represent shafts respectively, which are constructed so as to permit the transmission and reception unit 19 to rotate relative to the transmission and reception unit anchor plate 20 and to permit the transmission and reception unit 19 and the arm 17 to rotate. Here, when the door 2 of the cage has shifted into the fully closed condition, the rollers 14 operate relative to the guide rail 13 in the upper part of the cage door 2, and the arm 17 moves in the lengthwise direction thereof. Owing to the linkage constructed of the shafts 21 and 22, the transmission and reception unit 19 is brought into the state 19b and is directed inwardly of the cage room, so that any abnormality in the cage can be detected in accordance with this invention. Conversely, when the cage door has shifted into the fully open condition, the rollers 14 operate relative to the guide rail 13 in the upper part of the cage door 2, and the arm 17 moves to bring the transmission and reception unit 19 into the state 19a. Then, the transmission and reception unit 19 is directed towards the hall of the elevator, and the apparatus is applicable to the detection of a man who comes close to the cage from the hall or is present in the hall, owing to a circuit arrangement similar to the foregoing one. 
     Next, the details of the difference frequency detector circuit 9 and the comparator 10 shown in FIG. 2 will be described with reference to FIGS. 6 to 8. 
     In FIG. 6, symbols 9a and 9b denote shaping circuits, which shape the outputs of the oscillator 6 and the amplifier 8 into rectangular waves a and b. An AND gate 9c takes the logical product between the outputs of the shaping circuits 9a and 9b. A low-pass filter (LPF) 9d deletes only a low frequency component in the output signal c of the AND gate 9c. A shaping circuit 9e shapes the output signal d of the LPF 9d into a rectangular wave. A monostable multivibrator 10a is activated by the output e of the difference frequency detector circuit 9. A low-pass filter (LPF) 10b deletes a low frequency component in the output signal f of the monostable multivibrator 10a. Shown at symbol 10c is a reference voltage with which a comparator 10d compares the output g of the LPF 10b. FIG. 7 is a diagram showing the voltage waveforms at various stages in the case where the frequency of the amplifier 8 is higher than that of the oscillator 6, for example, the case where the man 7 comes closer to the transmitter 4 as well as the receiver 5. a to e in the figure correspond to the respective output signals mentioned above. Similarly, FIG. 8 shows the signals appearing at various points in the case where the frequency of the amplifier 8 is lower than that of the oscillator 6, for example, the case where the man 7 comes away from the transmitter 4 as well as the receiver 5. 
     The operation of the comparator 10 in FIG. 6 will now be described with reference to FIGS. 9 to 11. Each time the output e of the difference frequency detector circuit 9 rises, the monostable multivibrator 10a operates to generate a pulse having a time width Tw. When the output signal f of the monostable multivibrator 10a has only the low frequency component deleted therefrom by the LPF 10b, a D.C. output is obtained as the output signal g thereof. FIG. 9 illustrates a case where the frequency of the output e of the difference frequency detector circuit 9 is high, FIG. 10 a case where the difference frequency is 1/2 of that in FIG. 9, and FIG. 11 a case where the difference frequency is 1/4 of that in FIG. 9. Owing to the combination of the monostable multivibrator 10a and the LPF 10b, the frequency can be readily converted into a D-C voltage. The comparator 10d compares the output g of the LPF 10b with the reference voltage 10c, and provides an output h when the difference frequency has become at least a frequency previously determined by the reference voltage 10c.