JP3638402B2 - Glass breakage detector - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an apparatus for detecting that glass has been broken, and more particularly to an apparatus for detecting that glass has been broken using a glass cutter.
[0002]
[Prior art]
Conventionally, there has been proposed an apparatus for detecting glass breakage by detecting vibrations generated when the glass is broken. This apparatus attaches a vibration detection means to the glass surface, and outputs a glass breakage detection signal when a frequency component generated when the glass is broken, for example, when it is broken, for example, vibrations of 100 KHz to 1 MHz is detected. .
[0003]
Here, when the glass is broken by the glass cutter, the vibration of the frequency component when the glass is smashed is not detected, and the vibration of the frequency component of about 50 KHz is generated. Therefore, in order to detect that the glass has been broken by the glass cutter, a circuit for detecting 50 kHz vibration has been provided. This 50 KHz vibration occurs not only when a glass cutter is used but also when a stone or the like collides with the glass. In order to prevent this erroneous determination due to the stone collision, the circuit described above outputs a glass breakage detection signal when 50 kHz vibration is detected continuously for a predetermined time.
[0004]
[Problems to be solved by the invention]
However, if the predetermined time is set to be long (for example, several seconds), the breaker cannot be detected unless the breaker continuously applies the glass cutter to the glass surface for several seconds. For this reason, when a breaker used a glass cutter for a short time, there existed a problem that it was not detectable. On the other hand, if the predetermined time is set short (for example, 1 second or less), there is a problem that erroneous detection due to a collision with a stone or the like occurs.
[0005]
An object of the present invention is to provide a glass breakage detection device that can reliably detect that glass has been broken by a glass cutter and distinguish it from other breakage.
[0006]
[Means for Solving the Problems]
FIG. 1A shows vibration detected when glass is broken by a glass cutter. Examining this waveform, it can be seen that there are a plurality of blank times t _{2 to} t ₃ , t ₄ to t ₅ , and t ₆ to when the signal is not output continuously but for a predetermined period. . On the other hand, when stone or sand hits the glass, only one block of waveform as shown in A of FIG. 1A is generated.
[0007]
The present invention has been made based on the above principle. The glass breakage detection apparatus of the present invention includes a vibration detection unit that detects glass vibration and converts it into an electrical signal, an extraction unit that extracts a signal component of 50 KHz or less from the output signal of the vibration detection unit, When it is detected that a blank period of a predetermined signal appears in the pattern of the output signal, the pattern detecting means outputs a glass breakage detection signal.
[0008]
In the present invention, when a predetermined pattern in which a blank period of a signal peculiar to glass breakage caused by a glass cutter appears is detected from the output signal of the extraction means, the pattern detection means outputs a glass breakage detection signal. In this way, by detecting a specific pattern from the vibration waveform of the glass, it is possible to detect only the glass breakage caused by the glass cutter, and prevent erroneous detection due to the vibration at the time of glass breakage due to other causes. be able to. Moreover, since this pattern can be detected in a short time, it is possible to reliably detect glass breakage even when the glass cutter is used for a short time.
[0009]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 2 is a diagram showing a circuit configuration of the present invention.
In FIG. 2, reference numeral 1 denotes vibration detection means for detecting glass vibration and converting it into an electrical signal. Reference numeral 2 denotes extraction means for extracting a signal having a frequency component of 50 KHz or less from the output signal of the vibration detection means 1. Reference numeral 3 denotes pattern detection means for detecting a predetermined blank period from the output signal of the extraction means 2. When the pattern detection unit 3 detects that a blank period of a predetermined signal appears in the pattern of the output signal of the extraction unit 2, the pattern detection unit 3 outputs a glass breakage detection signal.
[0010]
The pattern detection unit 3 includes a detection unit 4, a timing unit 5, and a counter 6. When detecting the output signal from the extracting means 2, the detecting means 4 outputs a signal and holds the output, and when detecting that the output signal from the extracting means 2 has stopped for a first predetermined time, that is, a signal When a blank period that lasts for a first predetermined time is detected, the signal output is stopped. When the signal output of the detecting means 4 changes, that is, when it changes from presence to absence or from absence to presence, the time measuring means 5 starts time counting from the beginning and outputs a signal when the second predetermined time (T ₂ ) elapses. Output. In FIG. 1c, the timing means 5 starts when the output of the detecting means 4 changes from absent to present. Here, the second predetermined time (T ₂ ) is a time sufficient to determine that the glass cutter is breaking.
[0011]
The counter 6 counts the number of outputs when there is a change in the output of the detection means 4, that is, a change from the presence of output to the absence or change from absence to presence. When the count reaches a predetermined number, the glass breakage is detected. The signal is output, but when the signal is output from the time measuring means 5 before counting up, the count is cleared and the signal is not output.
The operation of the circuit of FIG. 2 will be described with reference to the waveform diagram of FIG.
[0012]
When a glass cutter is used, the glass generates a specific vibration having a frequency component of 50 KHz or less. The vibration detecting means 1 converts the vibration into an electric signal. The extraction unit 2 extracts a signal having a frequency component of 50 KHz or less from the output signal of the vibration detection unit 1. FIG. 1A shows an output waveform of the extraction means 2. When the glass cutter is used, the vibration signal has a frequency component of 50 KHz or less, and blank periods t _{2 to} t ₃ , t ₄ to t ₅ , and t ₆ to occur where the signal is interrupted. As described above, even when the stone hits the glass, vibration of 50 KHz or less is detected. In this case, only a single signal block indicated by A in the figure is detected.
[0013]
FIG. 1B shows the output signal waveform of the detection means 4. When the detection means 4 detects the output signal from the extraction means 2 (t ₁ , t ₃ , t ₅ ), the detection means 4 outputs a signal and holds the signal output. When the output of the extraction means 3 stops (t ₂ , t ₄ , t ₆ ) and the blank period continues for the first predetermined time (T ₁ ), the detection means 4 stops the output signal (t ₂₁ , t t _41, t _61).
[0014]
FIG. 1C shows the operating state of the time measuring means 5. When the detecting means 4 outputs a signal, the time measuring means 5 starts measuring the second predetermined time (T ₂ ) (t ₁ ). The detection means 4 stops outputting (t ₄₁ , t ₆₁ ) after the time measurement is started and before the time measurement is completed. When the detection means 4 outputs again, the time measurement is cleared and the time measurement is started again (t ₃ , t t _5). In the illustrated example, the state in which the time measuring means 5 has completed the time measurement, that is, the second predetermined time (T ₂ ) has not been shown. Also, the timing for starting the timing can be set when the detection means 4 stops the output (t ₂₁ , t ₄₁ , t ₆₁ ). Furthermore, the timing for starting the timing may be both the start and stop of the output of the detection means 4.
[0015]
FIG. 1D shows an output signal of the counter 6. The counter 6 increments the count value by 1 when the signal output of the detecting means 4 changes from non-existing to present (t ₁ , t ₃ , t ₅ ). When this count value reaches a predetermined value (3 in this example), a glass breakage detection signal, that is, an alarm signal is output. The count of the counter 6 may be counted when the signal output of the detection means 4 changes from presence to absence (t ₂₁ , t ₄₁ , t ₆₁ ).
[0016]
The operation of the circuit described above will be described over time using the flowchart of FIG.
The pattern detection means 3 waits for a 50 kHz signal output from the extraction means 2 in step S1. When the 50 kHz signal is extracted from the extracting means 2, the process proceeds from step S1 to step S2, and the time measuring means 5 starts measuring the second predetermined time (T ₂ ). In step S3, it is determined whether or not the timing has been completed. Until the timing is completed, it is determined in step S4 whether or not there is a signal blank period that lasts for the _first predetermined time (T ₁ ). If this blank period is not detected, step S3 and step S4 are repeated.
[0017]
When a blank period of the signal that continues for the first predetermined time (T ₁ ) is detected in step S4, the counter 6 increments the count value by 1 in step S5, and the time count of the time measuring means 5 is cleared in step S6. In step S7, it is determined whether or not the count value of the counter 6 has reached a predetermined value of 3. Until the count value becomes 3, the operations in steps S2 to S7 are repeated. When the count value becomes 3, the process proceeds to step S8, the counter 6 is cleared, and a glass breakage detection signal, that is, an alarm signal is output in step S9.
[0018]
Further, when a 50 kHz signal is output from the extraction means 2 even though the glass is not broken by the glass cutter, the signal is output only as a single block, as indicated by A in FIG. After the blank period (t _{21 to} t ₃ ), the 50 kHz signal is not detected again. Therefore, in this case, the time measurement of the second predetermined time (T ₂ ) is completed before the second blank period (t _{41 to} t ₅ ) is detected in step S4, and the process proceeds to step S10. 6 is cleared and the process returns to step S1 without outputting an alarm signal.
[0019]
In the example described above, when two blank periods are detected, it is determined that the glass has been broken by the glass cutter. In this example, the glass breakage by the glass cutter can be detected in the shortest time. However, even when a stone or the like only hits the glass, there is a possibility that a vibration signal of 50 KHz or less including two or more blank periods is detected by chance and a glass breakage detection signal is output. In order to prevent this, the count value set in the counter 6 may be increased to an appropriate value. In the apparatus of the present invention, even if this count value is increased, the time until glass breakage detection can be made extremely short.
[0020]
FIG. 4 shows a second circuit example of the present invention. In addition to the circuit for detecting that the glass has been broken by the glass cutter, the circuit in FIG. 4 also shows a circuit for detecting that the glass has been broken by other methods.
In FIG. 4, reference numeral 11 denotes a piezoelectric element attached to the glass surface with an adhesive, and constitutes the vibration detecting means 1. The piezoelectric element 11 outputs an electrical signal corresponding to mechanical vibration. The filter comprising the reactor L ₁ and the capacitor C ₁ constitutes the extracting means 2. The filters L ₁ and C ₁ extract and output a frequency component of 50 KHz or less from the signal output from the piezoelectric element 11.
[0021]
The output of the piezoelectric element 11 is also output to the filter 12 composed of L ₂ and C ₂ . This filter 12 extracts a frequency component of 100 KHz to 1 MHz. When the glass is smashed, the glass vibrates at a frequency of 100 KHz to 1 MHz, so the filter 12 extracts a signal having this frequency component.
Q ₁ and Q ₂ are transistors which are turned on when a signal is output from the extraction means 2. Since the signal from the extracting means 2 vibrates at a frequency of 50 KHz, there is a moment when the signal becomes 0, but the state of the signal 0 is the first due to the time constant circuit composed of the resistors R ₁ and R ₂ and the capacitor C ₃ . If it does not continue for a predetermined time (T ₁ ), the output is held. If the signal blank period continues for the first predetermined time after being turned on, the output is stopped. That is, these circuits Q ₁ , Q ₂ , R ₁ , R ₂ , C ₃ constitute the detection means 4.
[0022]
6 is a counter, the signal of the collector potential of the transistor Q ₂ is input to the terminal 1, when changes to there from the signal without, to 1 increases the count value. When the count value reaches a predetermined value, a signal is output from the terminal 7.
The transistor Q ₃ is turned off when the detecting means 4 detects a blank period that continues for the first predetermined time (T ₁ ) and stops outputting (the transistor Q ₂ is turned off). When the transistor Q ₃ is turned off, the capacitor C ₅ is charged through the resistor R _5, the voltage of the capacitor C ₅ is input to the terminal 2 of the counter 6. When the second predetermined time (T ₂ ) determined by the time constants of C ₅ and R ₅ elapses and the voltage of the capacitor C ₅ exceeds the threshold value, the counter 6 is reset. The transistor Q ₃ is turned on when the detection means 4 outputs a signal, and discharges the capacitor C ₅ . These circuits constitute time counting means 5 that starts counting every time the detection means 4 stops outputting. If a signal is output from the detection means 4 before the second predetermined time (T ₂ ) elapses, the time counting means 5 is cleared and the counter 6 is not reset.
[0023]
The counter 6 outputs a signal to the transistor Q ₄ when the count value reaches a predetermined value, for example, 3. Further, signals from the filters L ₂ and C ₂ are input to the transistor Q ₄ . Therefore, the transistor Q ₄ is turned on by a signal from the counter 6 when the glass is broken by the glass cutter, and turned on by outputs from the filters L ₂ and C ₂ when the glass is smashed. the Q ₆ to turn on. When the transistor Q ₆ is turned on, an alarm signal is output from the output terminal 3.
[0024]
4 is different from the circuit of FIG. 2 in that the timing means 5 starts timing when the signal output of the detection means 4 stops. As described above, the timing of timing by the timing unit 5 can be set to any change from the absence to the presence or the presence or absence of the output from the detection unit 4. Similarly, the count timing of the counter 6 can also be the time when the signal output of the detection means 4 changes from presence to absence.
[Brief description of the drawings]
FIG. 1 is a diagram showing an output waveform of extraction means in the present invention.
FIG. 2 is a circuit diagram showing a first configuration example of the present invention.
FIG. 3 is a flowchart showing the operation of the circuit of FIG. 2;
FIG. 4 is a circuit diagram showing a first configuration example of the present invention.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Vibration detection means 2 ... Extraction means 3 ... Pattern detection means 4 ... Detection means 5 ... Timing means 6 ... Counter 11 ... Piezoelectric element Q ... Transistor C ... Capacitor L ... Reactor R ... Resistance T ... Terminal

Claims (2)

Vibration detection means for detecting glass vibrations and converting them into electrical signals;
Extraction means for extracting a signal component of 50 KHz or less from the output signal of the vibration detection means;
When detecting a predetermined pattern in which a blank period of the signal appears from the output signal of this extraction means, it comprises a pattern detection means for outputting a glass breakage detection signal ,
A glass breakage detection apparatus characterized by detecting breakage of glass using a glass cutter . The pattern detecting means includes
When an output signal from the extraction means is detected, a signal is output and held, and when the blank period of the signal lasting for a first predetermined time is detected from the output signal from the extraction means, the signal output is stopped Detecting means for
Time measurement means for starting or resuming timing when the signal output of the detection means changes to a predetermined value, and outputting a signal when a second predetermined time elapses;
A counter that counts the number of output changes of the detection means, outputs a glass breakage detection signal when the count value reaches a predetermined number, and clears the count value when a signal is output from the timing means; A glass breakage detection device for detecting breakage of glass using the glass cutter according to claim 1.

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