Alarm and alarm system

Abstract

To provide an alarm and an alarm system, which generate a sufficient sound volume even with minute power which does not generate sparks in a substantially safe explosion-proof structure without having pressure-resistant explosion-proof structure.SOLUTION: An alarm 1 includes: a non-closed type housing 2 having sound emission holes 3; and an alarm circuit device 4 disposed within the housing 2. The alarm circuit device 4 includes: a piezoelectric sound emitting component 6 mounted on a circuit board 5; and a resonance tube 7 disposed between the piezoelectric sound emitting component 6 and the sound emission holes 3. An alarm system includes: the alarm 1; and a substantially safe explosion-proof safety holder 15, which restricts a power value to a prescribed value or less and supplies it to the alarm 1.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to an alarm and an alarm system, and more particularly to an alarm and an alarm system used in an intrinsically safe explosion-proof structure.

Background Art

[0002] Conventionally, when installing an electronic device in a dangerous place where there is a risk of generating explosive gas, in order to prevent the explosion of the explosive gas caused by the sparks generated from the electronic device and to use the alarm installed in the dangerous place safely, a pressure-resistant explosion-proof structure and an intrinsically safe explosion-proof structure are known.

[0003] The pressure-resistant explosion-proof structure is a structure that obtains explosion-proof performance by enclosing the electronic device in a pressure-resistant housing. The intrinsically safe explosion-proof structure inserts an intrinsically safe explosion-proof safety barrier (for example, Patent Documents 1 to 3, etc.), called a barrier, into the power transmission line as a repeater in a safe place, limits the voltage and current to a safe value so as not to ignite the explosive gas, and supplies it to the electronic device. The intrinsically safe explosion-proof safety barrier has a conversion function of making the values of the maximum current and maximum voltage flowing from a non-dangerous place (also called a safe place) to a dangerous place into essentially safe values in the dangerous place.

[0004] When the electronic device is an alarm, if the alarm has a pressure-resistant explosion-proof structure or the voltage is limited using a barrier, the volume emitted is limited. Therefore, an explosion-proof buzzer that can obtain the required volume without using a barrier has been proposed by attaching a resonance housing to the housing of the pressure-resistant explosion-proof structure (Patent Document 4).

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, in order to exhibit explosion-proof performance, the above-mentioned conventional explosion-proof buzzer needs to be incorporated into a thick safety increased explosion-proof case or a pressure-resistant explosion-proof case for the housing body of the alarm, so that it becomes large-sized and heavy in mass.

[0007] Therefore, a main object of the present invention is to provide an alarm and an alarm system that can generate a sufficient volume even with a minute power that does not generate a spark in an intrinsically safe explosion-proof structure without using a pressure-resistant explosion-proof structure.

MEANS FOR SOLVING THE PROBLEMS

[0008] To achieve the above object, an alarm according to an aspect of the present invention includes an unsealed housing having a sound emitting hole, and an alarm circuit device disposed in the housing. The alarm circuit device includes a piezoelectric sound generating component mounted on a circuit board, and a resonance tube disposed between the piezoelectric sound generating component and the sound emitting hole.

[0009] In one embodiment, the piezoelectric sound generating component has a piezoelectric diaphragm accommodated in a casing. The casing has a cylindrical outer shape having a top surface and a bottom surface, and a sound emitting hole is provided at a central portion of the top surface. The resonance tube is externally inserted and attached to the casing.

[0010] The resonance tube can be a flexible tube that closely adheres to the outer peripheral surface of the casing.

[0011] The resonance tube can be made of soft vinyl chloride.

[0012] The alarm circuit device includes an oscillation unit, a sounder drive unit, a sounder unit, and a power supply unit. The oscillation unit includes a semiconductor element, and an operating voltage of the semiconductor element is supplied from the power supply unit, thereby outputting an AC signal with a predetermined frequency to the sounder drive unit. The sounder drive unit generates AC power for sounding the sounder unit from the AC signal input from the transmission unit and supplies the AC power to the sounder unit. The power supply unit supplies a predetermined voltage supplied from the outside as the operating voltage of the semiconductor element. The sounder unit can include the piezoelectric sound generating component.

[0013] The semiconductor element can be a TTL IC or a CMOS logic IC that functions as an inverter.

[0014] The oscillation unit includes a plurality of the semiconductor elements, a first resistor, a second resistor, and a capacitor. The plurality of the semiconductor elements include a first semiconductor element and a second semiconductor element. An input terminal of the first semiconductor element is connected to a first terminal of the first resistor. An output terminal of the first semiconductor element is connected to an input terminal of the second semiconductor element. A second terminal of the first resistor is connected to a first terminal of the second resistor. A second terminal of the second resistor is connected to the output terminal of the first semiconductor element. A first terminal of the capacitor is connected to the second terminal of the first resistor. A second terminal of the capacitor is connected to an output terminal of the second semiconductor element. The AC signal can be output from the output terminal of the second semiconductor element.

[0015] The semiconductor element can be a NAND element with its input terminals short-circuited.

[0016] An alarm system according to an aspect of the present invention includes the above-described alarm device according to the present invention and an intrinsically safe explosion-proof safety arrester that restricts a power value to a predetermined value or less and supplies the power value to the alarm device.

Effects of the Invention

[0017] According to the alarm device and alarm system of the present invention, without requiring a pressure-resistant explosion-proof structure, even a minute current that does not generate a spark in an intrinsically safe explosion-proof structure can generate a sufficient volume. Further, in the alarm system according to the present invention, although it is necessary to install an intrinsically safe explosion-proof safety arrester in a safe location, it is possible to reduce the size and weight of the alarm device installed in a dangerous location.

Brief Description of the Drawings

[0018]

Figure 1

Figure 2

Figure 3

Figure 4

Embodiments for Carrying Out the Invention

[0019] Embodiments of the alarm device and alarm system according to the present invention will be described below with reference to FIGS. 1 to 4.

[0020] The alarm device 1 includes, with reference to FIGS. 1 and 2, a housing 2 and an alarm circuit device 4 disposed within the housing 2. The housing 2 is an unsealed housing provided with a sound emission hole 3 for emitting sound on the upper surface. The housing 2 is a rectangular parallelepiped shape in the illustrated example, but may have other shapes.

[0021] The alarm circuit device 4 is a hybrid integrated circuit in which electronic components described later are mounted on a circuit board 5 made of a glass epoxy printed circuit board. The circuit board 5 may be a ceramic board printed with a circuit pattern.

[0022] A piezoelectric sound - producing component 6 of an electronic component is mounted on a circuit board 5. The piezoelectric sound - producing component 6 is an electronic component having a piezoelectric diaphragm 6b in a casing 6a. A piezoelectric sound - producing component 6, a piezoelectric buzzer is preferably used, but a piezoelectric buzzer can also be used. A piezoelectric sounder is a sound - producing component that does not incorporate an oscillation circuit and produces sound in response to an input signal. A piezoelectric buzzer is a sound - producing component that incorporates an oscillation circuit and produces a single tone. In this embodiment, a piezoelectric sounder is used as the piezoelectric sound - producing component 6. A surface - mount type or discrete - type piezoelectric sound - producing component 6 can be preferably used. Since the piezoelectric sound - producing component is driven by a voltage applied to piezoelectric ceramics, the current consumption is extremely small compared to an electromagnetic buzzer. Also, in the case of an electromagnetic buzzer, due to its structure, the temperature rises during sounding, so the continuous sounding time is only about 5 to 10 minutes, while the piezoelectric sound - producing component can perform continuous sounding for a longer time.

[0023] The casing 6a of the piezoelectric sound - producing component 6 is made of plastic and has a cylindrical outer shape with a top surface and a bottom surface, and a sounding hole 6c for emitting sound is formed at the center of the top plate of the top surface. The casing 6a also has the function of a resonator.

[0024] A resonance tube 7 is arranged between the piezoelectric sound - producing component 6 and the sound - emitting hole 3. The resonance tube 7 is attached so as to surround the casing 6a of the piezoelectric sound - producing component 6. In this embodiment, the resonance tube 7 is attached to the casing 6a by external insertion.

[0025] The resonance tube 7 is preferably formed of a flexible tube such as soft vinyl chloride. The resonance tube 7 composed of a flexible tube preferably has an inner diameter that is the same as or slightly smaller than the outer diameter of the casing 6a. If the resonance tube 7 is an elastic flexible tube such as soft vinyl chloride, by press - fittingly externally inserting it into the casing 6a, the inner peripheral surface of the flexible tube can be made to adhere closely to the outer peripheral surface of the casing 6a for assembly. Therefore, fixing means such as an adhesive is not required and the assembly is easy. The material of the resonance tube 7 is not limited to soft vinyl chloride, and a soft synthetic resin material such as a flexible hose of silicone rubber can be used.

[0026] By arranging the resonance tube 7 between the sound emitting hole 3 and the piezoelectric sound emitting component 6 in this way, the work of fixing the piezoelectric sound emitting component 6 to the inner surface of the housing 2 by adhesion, screwing, etc. becomes unnecessary, and the work of wiring and connecting the piezoelectric sound emitting component 6 to the circuit board 5 becomes unnecessary. That is, when the resonance tube 7 is not provided, it is necessary to fix the top surface of the casing 6a of the piezoelectric sound emitting component 6 to the inner surface of the housing 2 so that the sound emitting hole 6c on the top surface of the casing 6a of the piezoelectric sound emitting component 6 is positioned at the sound emitting hole 3 of the housing 2, so that the sound emitted from the sound emitting hole 6c of the piezoelectric sound emitting component 6 is emitted from the sound emitting hole 3, and this fixing work is time-consuming. Further, when the top surface of the casing 6a of the piezoelectric sound emitting component 6 is fixed to the inner surface of the housing 2 in this way, the piezoelectric sound emitting component 6 is separated from the circuit board 5, so that it is necessary to perform the work of wiring and connecting the piezoelectric sound emitting component and the circuit board 5, and this soldering work and connector connection work are time-consuming.

[0027] The resonance tube 7 utilizes the resonance principle of the air column to resonate the sound waves generated from the sound emitting hole 6c of the piezoelectric sound emitting component 6 and has the function of increasing the volume of the sound emitted from the sound emitting hole 3. Therefore, the transmission frequency of the piezoelectric sound emitting component 6 is set so that the resonance tube 7 resonates. The length of the resonance tube 7 may be adjusted so that the resonance tube 7 resonates at the transmission frequency of the piezoelectric sound emitting component 6. If the resonance tube 7 is made of a flexible synthetic resin material such as soft vinyl chloride, since cutting processing is easy, length adjustment is easy.

[0028] As will be described later, the piezoelectric sound emitting component 6 is operated with weak power (for example, 35 mW or less) so that an arc due to a short circuit or the like cannot occur. When housed in the housing 2, the volume becomes small and it may not be able to serve as an alarm placed in a dangerous location. However, by providing the resonance tube 7, it is possible to prevent the diffusion of sound in the housing 2 and increase the volume of the sound emitted from the piezoelectric sound emitting component 6. Thereby, even if the piezoelectric sound emitting component 6 is operated with a weak current, the volume of the sound emitted from the alarm 1 can be increased, and the function as an alarm placed in a dangerous location can be achieved.

[0029] In FIG. 1, reference numeral 8 denotes an illuminated push button switch, and reference numeral 9 denotes a connector, which are respectively mounted on the circuit board 5. As the illuminated push button switch 8, a known commercially available switch (for example, YB series manufactured by NKK Switches) can be used.

[0030] FIG. 3 is a circuit diagram of the alarm circuit device 4. Referring to FIG. 3, the alarm circuit device 4 includes an oscillation unit 10, a sounder drive unit 11, a sounder unit 12, and a power supply unit 13. The oscillation unit 10 includes NAND elements IC1 and IC2, resistors R1 and R2, and a capacitor C1. Each of the NAND elements IC1 and IC2 is a semiconductor element, and their input terminals are connected to each other and function as an inverter that inverts the level of an input signal and outputs it. Thus, when a predetermined voltage for operation is supplied to the NAND elements IC1 and IC2, the oscillation unit 10 oscillates at a frequency determined by the resistor R2 and the capacitor C1. Note that the resistance value of the resistor R2 and the capacitance of the capacitor C1 can be set so as to be the transmission frequency at which the resonance tube 7 resonates as described above. The NAND elements IC1 and IC2 are, for example, TTL (Transistor Transistor Logic) ICs or CMOS (Complementary Metal Oxide Semiconductor) logic ICs.

[0031] The sounder drive unit 11 includes a NAND element IC3 and a resistor R3. The NAND element IC3 is a semiconductor element similar to the NAND elements IC1 and IC2, and its input terminals are connected to each other and function as an inverter. The resistor R3 is for protecting the NAND element IC3 from overcurrent. The sounder drive unit 11 supplies a drive voltage for operating the sounder unit.

[0032] The sounder unit 12 includes a piezoelectric sounder BZ that constitutes the piezoelectric sound - emitting component 6, and Zener diodes ZD1 and ZD2. The piezoelectric sounder BZ in the illustrated example sounds when a drive voltage is applied from the sounder drive unit 11. The Zener diodes ZD1 and ZD2 are connected in series in opposite directions and are connected to both ends of the piezoelectric sounder BZ. Due to external factors (mechanical external forces) such as vibration and collision, a high voltage of about 100V can be generated instantaneously at both ends of the piezoelectric sounder BZ, for example. The Zener diodes ZD1 and ZD2 can suppress this high voltage. Optionally, a plurality of the same configuration as the Zener diodes ZD1 and ZD2 may be provided and connected in parallel to the Zener diodes ZD1 and ZD2.

[0033] The voltage required for the NAND element ICs 1 - 3 to operate is supplied from outside the alarm 1 (specifically, a barrier described later) via the power supply unit 13. The power supply unit 13 includes terminals T1 and T2, a light - emitting diode LED, and a switch SW. The light - emitting diode LED and the switch SW are built into the above - mentioned illuminated push - button switch 8 (Fig. 1). The terminals T1 and T2 are provided on the above - mentioned connector 9 of the alarm 1. A predetermined voltage is supplied from the outside between the terminals T1 and T2. The terminal T2 is connected to the ground, and for example, about +5V is supplied to the terminal T1. The terminal T2 is also connected to a wiring (for example, the ground line GND on the circuit board 5) for connecting the NAND element ICs 1 - 3 to the ground.

[0034] One end (anode) of the light-emitting diode LED is supplied with the voltage supplied to terminal T1. The other end (cathode) of the light-emitting diode LED is connected to contact CT1 of switch SW. Switch SW includes contacts CT1 and CT2, and contacts CT3 and CT4. Switch SW is, for example, a push button. In the initial state, contacts CT1 and CT2 are connected (hereinafter referred to as on), and contacts CT3 and CT4 are not connected (hereinafter referred to as off). Contact CT2 of switch SW is connected to a wiring (for example, the power supply line Vcc on circuit board 5) for supplying voltage to NAND elements IC1 to IC3. Therefore, the voltage supplied to terminal T1 is supplied to NAND elements IC1 to IC3, and NAND elements IC1 to IC3 become operable. At this time, due to the flowing current, the light-emitting diode LED emits light. When NAND elements IC1 to IC3 start operating, oscillation occurs by oscillation unit 10, a drive voltage is supplied from sounder drive unit 11 to piezoelectric sounder BZ, and piezoelectric sounder BZ sounds. Note that a cylindrical resonance tube 7 (not shown in FIG. 3) shown in FIG. 1 is arranged around piezoelectric sounder BZ to increase the volume of piezoelectric sounder BZ.

[0035] When switch SW is pressed, contacts CT1 and CT2 turn from on to off, and contacts CT3 and CT4 turn from off to on. Therefore, the voltage supplied to terminal T1 is no longer supplied to NAND elements IC1 to IC3, and NAND elements IC1 to IC3 stop operating. As a result, the sounding by piezoelectric sounder BZ of sounder unit 12 stops.

[0036] On the other hand, even when switch SW is pressed, the lighting of the light-emitting diode LED is maintained. When contacts CT3 and CT4 of switch SW are switched to on, the cathode of the light-emitting diode LED is connected to the ground. Therefore, if a voltage is applied to terminal T1, that voltage is applied to the anode of the light-emitting diode LED, and a current flows through the light-emitting diode LED.

[0037] Referring to Fig. 4, the power supply to the alarm 1 is relayed from an external power source 14 through an intrinsically safe explosion-proof safety barrier 15. A barrier circuit incorporated in the intrinsically safe explosion-proof safety barrier 15 can adopt a conventionally known one. As the intrinsically safe explosion-proof safety barrier 15, for example, an insulated safety barrier (model DB1011, DB1012) manufactured by Daido Kogyosho Co., Ltd. can be used. For example, the insulated safety barrier DB1011 manufactured by Daido Kogyosho Co., Ltd. has a maximum current of 13 mA and a maximum voltage of 10.5 V, and can limit the power value that does not cause ignition. The insulated safety barriers DB1011 and DB1012 are originally barriers for detecting contact ON-OFF in a dangerous location, but when power is input to the barrier, by utilizing the function of energizing the intrinsically safe device side, the piezoelectric sounding component 6 can be made to sound and the light-emitting diode LED can be lit.

[0038] The alarm 1 is arranged in a dangerous location where an explosion may occur, such as a factory handling flammable substances, and the intrinsically safe explosion-proof safety barrier 15 is arranged in a safe location separated from the dangerous location. Terminals T3 and T4 of the intrinsically safe explosion-proof safety barrier 15 are connected to terminals T1 and T2 of the alarm 1 by electrical wiring. Ordinary electrical wiring can be used for the electrical wiring, and electrical wiring with an explosion-proof function does not have to be used.

[0039] The power source 14 connected to the intrinsically safe explosion-proof safety barrier 15 is a DC power source. When a voltage is applied between terminals T1 and T2 of the alarm 1 from the power source 14 through the intrinsically safe explosion-proof safety barrier 15, as described above, in the alarm 1, the light-emitting diode LED lights up, the NAND element ICs 1 to 3 operate, and the piezoelectric buzzer BZ sounds. Thereby, an alarm can be issued at the dangerous location where the alarm 1 is arranged.

[0040] As described above, each element constituting the alarm device shown in FIG. 3 can be mounted on a printed circuit board. As described above, by using semiconductor elements (TTL IC or CMOS logic IC) for the NAND element ICs 1 to 3, the power value required to function as the alarm device 1 can be made weak. The power value flowing through the alarm device 1 can be, for example, about 35 mW or less. Therefore, the alarm device shown in FIG. 3 can be housed in a normal steel plate (such as SPCC) housing 2 without being housed in an explosion-proof case or the like, and can be arranged in a hazardous location.

[0041] The NAND element ICs 1 to 3 shown in FIG. 3 can be constituted by, for example, one IC package (general-purpose logic IC package such as 74 series) in which a plurality of NAND gates are sealed. In that case, the power supply line Vcc and the ground line GND are respectively connected to the power supply pin and the ground pin of one IC package.

[0042] In the oscillation unit shown in FIG. 3, the NAND element ICs 1 to 3 are shown, but it is not limited thereto. Each element may be a semiconductor element that functions as an inverter. Further, as the oscillation unit 10, a low-power arithmetic element (such as an MCU (Micro Controller Unit) and a CPU (Central Processing Unit)) may be used. By using such an arithmetic element, the piezoelectric buzzer BZ can be intermittently sounded, and the frequency at which the piezoelectric buzzer BZ is sounded can be made variable.

[0043] The present invention is not limited to the above-described embodiment, and various modifications are possible without departing from the spirit of the present invention. For example, in the above-described embodiment, an illuminated push-button switch including a light-emitting diode is exemplified, but a switch not including a light-emitting diode may also be used.

Explanation of Reference Numerals

[0044] 1 Alarm device 2 Housing 3 Sound emission hole 4 Alarm circuit device 5 Circuit board 6 Piezoelectric sound component 7 Resonance tube 10 Oscillator section 11 Sounder drive section 12 Sounder section 15 Intrinsically safe explosion-proof safety arrester BZ Piezoelectric sounder C1 Capacitor CT1, CT2, CT3, CT4 Contacts IC1, IC2, IC3 NAND elements LED Light-emitting diode R1, R2, R3, R4 Resistors SW Switch T1, T2, T3, T4 Terminals ZD1, ZD2 Zener diodes

Claims

1. An unenclosed housing having a sound emission hole, and an alarm circuit device disposed within the housing, wherein the alarm circuit device includes a piezoelectric sound - generating component mounted on a circuit board and a resonance pipe disposed between the piezoelectric sound - generating component and the sound emission hole.

2. In the piezoelectric sound - generating component, a piezoelectric diaphragm is accommodated within a casing, the casing has a cylindrical outer shape having a top surface and a bottom surface, and a sound emission hole is provided at the central portion of the top surface, and the resonance pipe is externally inserted and attached to the casing. The alarm device according to Claim 1.

3. The alarm device according to Claim 1, wherein the resonance pipe is a flexible pipe that adheres to the outer peripheral surface of the casing.

4. The alarm device according to Claim 3, wherein the flexible pipe is made of soft vinyl chloride.

5. The alarm circuit device includes an oscillation unit, a sounder drive unit, a sounder unit, and a power supply unit, the oscillation unit includes a semiconductor element, and when an operating voltage of the semiconductor element is supplied from the power supply unit, an alternating current signal of a predetermined frequency is output to the sounder drive unit, the sounder drive unit generates alternating current power for sounding the sounder unit from the alternating current signal input from the transmitting unit and supplies it to the sounder unit, the power supply unit supplies a predetermined voltage supplied from the outside as the operating voltage of the semiconductor element, and the sounder unit includes the piezoelectric sound - generating component. The alarm device according to Claim 1.

6. The alarm device according to Claim 5, wherein the semiconductor element is a TTL IC or a CMOS logic IC that functions as an inverter.

7. The oscillation unit includes a plurality of the semiconductor elements, a first resistor, a second resistor, and a capacitor, the plurality of the semiconductor elements include a first semiconductor element and a second semiconductor element, an input terminal of the first semiconductor element is connected to a first terminal of the first resistor, an output terminal of the first semiconductor element is connected to an input terminal of the second semiconductor element, a second terminal of the first resistor is connected to a first terminal of the second resistor, a second terminal of the second resistor is connected to the output terminal of the first semiconductor element, a first terminal of the capacitor is connected to the second terminal of the first resistor, a second terminal of the capacitor is connected to an output terminal of the second semiconductor element, and the alternating current signal is output from the output terminal of the second semiconductor element.

8. The alarm device according to claim 5, wherein the semiconductor element is a NAND element with its input terminals short-circuited. **Claim 9** An alarm system comprising: the alarm device according to any one of claims 1 to 8; and an intrinsically safe explosion-proof safety arrester that restricts a power value to a predetermined value or less and supplies the power value to the alarm device.

Images