JPH032943Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to an explosion-proof display device, which can be used as a means of transmitting and displaying information in a dangerous atmosphere such as oil or flammable gas.

[Prior Art] As a display device used in a dangerous atmosphere such as oil or flammable gas, the entire device has a pressure-resistant and explosion-proof structure so that there is no danger of igniting surrounding flammable materials. FIG. 2 is a diagram showing the relationship between the inductance used in the danger zone and the minimum ignition current applied thereto. In this way, inductances, coils, and the like have restrictions on the amount of current, so circuits, display means, and the like that utilize them must have a pressure-resistant and explosion-proof structure.

Electrical equipment should be installed in locations where there is no risk of explosion as much as possible, but if it is unavoidable to install it in a hazardous location, keep it to the minimum necessary and install electrical equipment with appropriate explosion-proof construction depending on the location and type of explosive gas. It is necessary to select. The standard that stipulates this explosion-proof structure is the ``Electrical Machinery and Appliance Explosion-proof Structure Standard'' (Notification of the Ministry of Labor).
Explosion-proof structures such as pressure-resistant explosion-proof structure, internal pressure explosion-proof structure, oil-filled explosion-proof structure, and intrinsically safe explosion-proof structure are defined.

Among these, a flameproof explosion-proof structure is a completely enclosed structure, meaning that if gas or steam enters the inside of the container and causes an explosion, the container will withstand the explosion pressure and the fire caused by the explosion will be transmitted to the outside of the container. A substance that prevents gas or steam from igniting. Therefore, a strong box is required. On the other hand, an intrinsically safe explosion-proof structure refers to a structure in which it has been confirmed through ignition tests that there is no risk of sparks, arcs, or heat generated by the parts that make up electrical machinery and equipment igniting gas or steam. Doesn't require structure.

FIG. 3 shows a conventional display device with a flameproof and explosion-proof structure, which consists of a control section 11 and a power supply section 12, and is housed in a strong box. The box is provided with display windows 13 and 14 for displaying a voltmeter, an ammeter, and the like.

[Problems to be Solved by the Invention] The conventional explosion-proof structure described above has the first drawback that the display section of the instrument is very small and difficult to see. This is due to the constraint that the area of the window must be reduced in order to obtain strength in order to satisfy safety standards as described above. Second
However, there is a problem in that the box needed to cover the entire device is very expensive. This is because if you run a long lead wire around a dangerous area, the inductance will become a problem and it will be dangerous, as explained earlier.
This is because the solution is to accommodate them in one box.

[Means for Solving the Problems and Their Effects] As shown in FIG. 1, this invention separates the control section 21 and the power supply section 24 so that at least the control section 21 can be placed in a safe area. The signal of this control unit 21 is transmitted through the optical communication cable 2.
A liquid crystal display device 23 with a wide display area that can be driven at low voltage is provided in the dangerous zone to display the signal from the optical communication cable. This allows the control unit 21 to be placed as far away from the danger zone as desired.

On the other hand, the power supply section 24 cannot be disposed far from the display section due to the relationship between the line inductance of the power supply section and the drive current, so it is made separate from the control section 21.

In this way, the area of the display section can be expanded,
In addition, the cost of explosion-proof boxes is also reduced. Furthermore, if the display section is located relatively close to a safe area, the explosion-proof box for the power supply section can be omitted.

[Embodiment] An embodiment of this invention will be described below with reference to the drawings.

In FIG. 1, it is assumed that area A is a safe area and area B is a dangerous area. A control section 21 is provided in the safe zone A, and its output signal is introduced into the dangerous zone B via an optical communication cable 22 and input to a display device 23 . The display device 23 includes a photoelectric converter 231, a drive circuit 232, and a liquid crystal display 233.
It is driven by the output of the power supply section 24. The photoelectric converter 231 converts the optical information from the optical communication cable 22 into a digital electrical signal, and the drive circuit drives the liquid crystal display 233 according to the content. In this case, since the power supply section 24 is located in the danger zone B, the barrier 242 for controlling the energy to non-explosive energy is installed in the box 24, which has a flameproof and explosion-proof structure.
It is housed in 1.

[Effects of the Invention] According to the display device of the invention described above, by separating the control unit 21 and the power supply unit 24, the control unit 21 can be disposed in a safe area. Since the display section is a liquid crystal display driven by a low voltage, the display area can be increased and the display can be made easier to understand. As a result, it is possible to contribute to improving safety in dangerous areas, and to reduce the cost of explosion-proof boxes.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing an embodiment of this invention, FIG. 2 is an explanatory diagram showing the relationship between inductance and minimum ignition current, and FIG. 3 is an explanatory diagram showing a conventional explosion-proof system. 21...control unit, 22...optical communication cable,
23...display device, 24...power supply unit.

Claims (1)

[Scope of utility model registration request] A control section disposed in a safe zone, an optical communication cable for introducing an output signal of this control section into a dangerous zone, and a photoelectric converter disposed in the dangerous zone to transmit the output from the optical communication cable. a display device that displays a liquid crystal display using a photoelectric conversion drive circuit;
The photoelectric converter is separated from the control unit;
An explosion-proof display device comprising a drive circuit and a power supply unit that supplies power to a liquid crystal display.