JP2008072176A - Explosion-proof antenna - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an explosion-proof antenna which is compact/lightweight, inexpensive, and capable of transmitting and receiving radio waves over a long distance. <P>SOLUTION: The explosion-proof antenna comprises: an antenna unit 3 constituted by arranging a radiator element 12 and a parasitic element 13 on a ground plate in order in parallel and electrically connecting the ground plate 11 and parasitic element 13 to each other; a front panel 2 mounted on the ground plate 12 and covering the radiator element 12 and parasitic element 13 in a sealed state; a cable 5 penetrating the ground plate 11 to have a crimp type terminal 29 fixed to an exposed core wire in internal space formed by the front panel 2, the crimp type terminal 29 being fixed to the radiator element 12; and a connection box 4 fixed to the ground plate 11 and housing a lead-out portion of the cable 5 from the ground plate 11. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an explosion-proof antenna used in a factory plant or the like.

  2. Description of the Related Art In recent years, plants for handling hazardous materials such as petroleum refining and petrochemicals have increased the need to build a wireless local area network (LAN) network for safety monitoring.

  Conventionally, rod (rod-shaped) type antennas have already been put into practical use as explosion-proof antennas used in such wireless LAN networks in factories. However, rod-type antennas have a short reach and a small amount of data to be transmitted, and have insufficient performance for transmitting surveillance camera images and transmitting / receiving data between personal computers.

For this reason, the need for a planar antenna having a larger transmission distance and transmission capacity is increasing. As an explosion-proof antenna using such a planar antenna, for example, a housing in which a planar antenna and a radio base station apparatus are housed inside a housing is known (for example, see Patent Document 1). In this explosion-proof antenna, the surface facing the planar antenna in the housing is made of a non-metallic material, so that transmission / reception with the outside can be performed without projecting the antenna outside the housing. ing.
JP 2005-348542 A

  However, the conventional explosion-proof antenna has a configuration in which not only the antenna but also the radio base station apparatus is accommodated in the casing. For this reason, it becomes very large and expensive. Moreover, it is comprised so that the opposing surface with an antenna may be accommodated in the housing | casing comprised with the nonmetallic material. Actually, the casing is made of heat-resistant glass, and the range over which radio waves can reach is limited (about 100 m). For this reason, if it is a large place such as a plant, a large number is required, and it is not practical because it is large, heavy and expensive (for actual products, see http://www.miyaki-elec.co (See .jp / hp / catalog / boubaku / eap-50.pdf).

  In view of the above, an object of the present invention is to provide an explosion-proof antenna that is small, lightweight, inexpensive, and capable of transmitting and receiving radio waves over a long distance.

As a means for solving the above problems, the present invention provides:
Explosion-proof antenna
An antenna unit formed by sequentially arranging a radiator element and a parasitic element with respect to the ground plate, and electrically connecting the ground plate and the parasitic element to each other;
A front panel mounted on the ground plate and covering the radiator element and the parasitic element in a sealed state;
A cable that passes through the ground plate and is connected to a core wire exposed in an internal space formed by the front panel, and the crimp terminal is fixed to the radiator element;
A junction box that is fixed to the ground plate and accommodates a lead-out portion of the cable from the ground plate;
It is set as the structure provided with.

  With this configuration, the explosion-proof antenna can be formed by simply covering the antenna portion with the front panel and covering a part of the drawn cable with the connection box. The formed explosion-proof antenna can be manufactured at low cost because it is small and light and can be composed of only the above components. Moreover, a firm connection state can be obtained by using a crimp terminal to connect the core wire of the cable to the radiator element. For this reason, it is excellent in antenna performance and can be used in a good state for a long time.

  It is preferable that the ground plate includes a vent filter that allows ventilation and can discharge steam only from the internal space to the outside.

A cable holder is disposed between the ground plate and the junction box,
The cable holder includes a flange through which the cable passes, presses against the ground plate and seals the periphery of the cable, and a tube that extends through the connection box and leads the cable to the inside of the connection box. And consists of
The connection box is preferably fixed by bolts and nuts that pass through the connection box, the cable holder, and the ground plate and sandwich these members.

  With this configuration, the cable drawn from the internal space covered by the front panel can be guided to the connection box in a sealed state by the cable holder. Moreover, the connection box can be fixed to the ground plate together with the cable holder.

  It is preferable that radio waves can be transmitted and received not only on the front panel side but also on the side opposite to the front panel by fixing the connection box to the ground plate as a part of the ground plate.

  With this configuration, radio waves can be propagated over a wide range, and a wireless LAN network can be constructed with a small number of explosion-proof antennas.

  According to the present invention, the antenna portion is covered with the front panel, and the cable lead-out portion is covered with the connection box fixed to the antenna portion. Therefore, the antenna portion is simple and small, and can be manufactured at low cost. Since the crimp terminal can be used to connect the core wire of the cable to the radiator element, the desired antenna performance can be maintained over a long period of time.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, the top, bottom, left, and right in FIG. 1 are used as terms indicating the direction (position) as they are.

  1 to 3 show an explosion-proof antenna 1 according to this embodiment. The explosion-proof antenna 1 has a configuration in which an antenna unit 3 is mounted on a front panel 2 and a cable 5 is pulled out via a connection box 4 (in this embodiment, the dimensions of the front panel 2 shown in FIG. , Length × width = about 10 cm × about 10 cm.

  As shown in FIG. 6, the front panel 2 is formed into a dome shape by molding AES resin (acrylonitrile / ethylene-propylene-diene / styrene plastic). Ribs 6 are formed on the inner surface of the front panel 2 to reinforce the bulging portion. Further, a substantially V-shaped groove 8 is formed on the inner side of the opening edge of the front panel 2 by providing guide portions 7 at predetermined intervals along the opening edge. A silicon packing 9 is disposed in the groove 8. Further, boss portions 10 to which the bolts B1 are screwed are formed at the inner four corners of the front panel 2.

  As shown in FIG. 4, the antenna unit 3 includes a ground plate 11, a radiator element 12, and a parasitic element 13.

  As shown in FIG. 7, the ground plate 11 is made of stainless steel and is made of a plate material having a rectangular shape in plan view. First mounting holes 14 are formed at positions corresponding to the boss portions 10 of the front panel 2 at the four corners of the ground plate 11. In addition, the ground plate 11 has an opening 15 in the middle portion between the two first mounting holes 14 formed on the upper side, and a vent filter 16 is attached to the opening 15 (this position is in consideration of antenna performance). It is selected as a position that has little influence). The vent filter 16 is made of a material that allows air to pass therethrough but allows steam to pass only in one direction, that is, only from the inside of the front panel 2 to the outside (for example, Gore-Tex (registered trademark) is used). Can be used.) Further, the ground plate 11 is formed with a cord insertion hole 17 on the side opposite to the opening 15, and a second attachment hole 18 is formed at four locations around the hole. Further, the ground plate 11 is formed with third mounting holes 19 on both sides of the center position, and a screw hole 20 is formed in the vicinity of one of the third mounting holes 19.

  As shown in FIG. 8, the radiator element 12 is a thin plate having a rectangular shape in plan view, and the surface thereof is plated with nickel. A notch 12a is formed in the center of both sides of the radiator element 12, and a through hole 12b is formed in the vicinity thereof. Further, on the lower edge side of the radiator element 12, a cable insertion hole 21 through which a cable 5 described later is inserted, and a bolt hole 22 for fixing the crimp terminal 5b fixed to the tip of the core wire 5a are formed. In addition, escape holes 12 c are formed at two locations in the vicinity of the cable insertion hole 21.

  As shown in FIG. 4, the parasitic element 13 is made of brass as a thin plate having a rectangular shape in plan view and the surface thereof being nickel-plated, like the radiator element 12. A notch 13 a is formed at the lower edge of the parasitic element 13. The parasitic element 13 is formed with two escape holes 13b and through holes (not shown) provided in the vicinity of each escape hole.

  The radiator element 12 and the parasitic element 13 are fixed to the ground plate 11 via a spacer 23. At this time, the fixed position of the parasitic element 13 with respect to the radiator element 12 is a position slightly shifted upward (here, about several mm) as shown in FIG. As a result, the desired antenna performance is maintained even when the crimp terminal 29 is connected to the core wire 5a of the cable 5 and the crimp terminal 29 is fixed to the radiator element 12 with the bolts B2 and nuts N2, as will be described later. Meanwhile, an insulation distance from the head of the bolt B2 (or the nut N2) can be secured.

  As shown in FIG. 4B, the spacer 23 is formed by forming a first support portion 24 and a second support portion 25 having different heights by molding polyoxymethylene. A through hole 24 a is formed in the first support portion 24, and a female screw portion 25 a is formed in the second support portion 25. Further, a relief recess 23a is formed between the first support portion 24 and the second support portion 25 on the surface opposite to the female screw portion 25a. The first support portion 24 is located between the ground plate 11 and the parasitic element 13. Both the members 11 and 13 are inserted through the bolt B3 from the third mounting hole 19 of the ground plate 11, and are passed through the through hole 24a of the spacer 23 and further through the through hole 13c of the parasitic element 13 and screwed into the nut N3. To be integrated. As a result, the ground plate 11 and the parasitic element 13 are at the same potential and are grounded. The second support portion 25 is located between the ground plate 11 and the radiator element 12, and the radiator element 12 is integrated with the spacer 23 by screwing the bolt B4 into the female screw portion 25a.

  As shown in FIGS. 2 and 3, the connection box 4 includes a box body 26, a lid body 27, and a cable gland 28 connected to the box body 26.

  The box body 26 and the lid body 27 are made of aluminum die-casting, and a communication hole 26a is formed on the bottom surface of the box body 26, and mounting holes 26b are formed at four locations around the communication hole 26a. The cable gland 28 ensures a sealed state at a portion where the cable 5 is pulled out from the box body 26.

  As shown in FIG. 5, the cable 5 has a crimp terminal 29 connected to a core wire 5 a exposed at one end. The crimp terminal 29 is fixed to the bolt hole 22 formed in the radiator element 12 by a donut-shaped connecting portion 29a at the tip by a bolt B2 and a nut N2. A cable holder 30 is provided on one end side of the cable 5. On the other hand, a retracting device 31 is provided on the other end side of the cable 5, and a plug 32 is connected to the other end portion.

  As shown in FIG. 9, the cable holder 30 includes a cylindrical portion 33 whose outer peripheral surface is knurled and a flange portion 34 on one end side thereof. An annular groove 30b is formed around the center hole 30a on the end face of the flange portion 34, and an O-ring 35 is disposed there. In addition, through holes 34 a corresponding to the communication holes 26 a of the box body 26 are formed in the four corners of the flange portion 34. The cable holder 30 is disposed between the ground plate 11 and the box body 26. Then, by inserting the bolt B3 through the communication hole 26a of the box body 26 and passing through the second mounting hole 18 of the ground plate 11 from the center hole 30a of the cable holder 30, these are screwed together. Integrated. The tubular portion 33 is covered with a polyolefin heat shrinkable tube 36 with the cable 5 inserted therethrough. Further, a waterproof packing 37 and a packing presser plate 38 are interposed between the nut N5 and the box body 26, so that the waterproof property in the communication hole 26a of the box body 26 is secured. Moreover, the waterproofness of the 2nd attachment hole 18 is maintained by providing the packing which is not shown in figure between the head of volt | bolt B5, and the earth board 11. FIG.

  The explosion-proof antenna 1 having the above-described configuration is assembled as follows.

  First, the radiator element 12 is fixed to the spacer 23, and the parasitic element 13 is fixed to the ground plate 11 via the spacer 23. At this time, a shortest distance (insulation distance) of 3 mm or more is secured between the ground plate 11, the radiator element 12, and the parasitic element 13. Further, when the parasitic element 13 is fixed to the ground plate 11, the notch 13 a is formed on both sides of the parasitic element 13, so that an insulation distance of 3 mm or more is also provided between the nut N <b> 3 and the parasitic element 13. Can be secured. Furthermore, the head of the bolt B4 used for fixing the radiator element 12 to the spacer 23 protrudes from the upper surface of the radiator element 12, but the parasitic element 13 thereabove has a relief hole 13b. Therefore, an insulation distance of 3 mm or more can be secured also between the bolt B4 and the parasitic element 13.

  Next, the connection box 4 is fixed to the antenna unit 3, specifically, the ground plate 11. In fixing the connection box 4, first, the cable gland 28 is fixed to the lower end surface of the box body 26, and the cable 5 is inserted. The ground plate 11 and the box body 26 are fixed and integrated with bolts B5 and nuts N5 with the cable holder 30 interposed therebetween. Then, the lid 27 is put on the box body 26, and the connection box 4 is completed with the special bolt B6 (which cannot be opened by a general screwdriver). The connection box 4 fixed in this way occupies only the central portion of the lower half of the antenna unit 3. Therefore, radio waves transmitted and received by the radiator element 12 are propagated not only on the front side where the front panel 2 is provided, but also on the rear side where the connection box 4 is fixed (specifically, mainly the upper half without the connection box 4). It becomes possible.

  Further, the cable 5 is connected to the radiator element 12. When connecting the cable 5, the cable 5 is inserted into the cable insertion hole 21 of the radiator element 12, the crimp terminal 29 is crimped to the core wire 5 a, and the connection portion of the crimp terminal 29 is fixed to the bolt hole 22 with the bolt B 2 and the nut N 2. . Since a method of fixing the core wire to the radiator element 12 by using the crimp terminal 29 with the bolt B2 and the nut N2 is adopted, the connection state can be made strong. Further, as described above, the notch 13a formed at the edge of the parasitic element 13 is provided between the fixed part (more precisely, the nut N2) of the crimp terminal 29 and the parasitic element 13 facing this part. Thus, a sufficient insulation distance (3 mm or more) can be secured.

  Thereafter, the front panel 2 is attached to the ground plate 11. In mounting the front panel 2, the bolt B <b> 1 is screwed into the boss portion 10 from the first mounting hole 14 of the ground plate 11 with the packing 9 interposed in the groove portion 8 formed inside the front panel 2. As a result, the internal space is sealed. However, as described above, the vent plate 16 is attached to the ground plate 11 in advance. Therefore, the steam generated inside can be discharged to the outside through the vent filter 16.

  Of the bolts used for fixing each member, those that are exposed to the outside cannot be opened with a commercially available screwdriver using special bolts. Further, it is preferable to completely cover the bolt portion with an epoxy resin or the like according to the place of use. This makes it possible to more reliably prevent water and the like from entering the internal space of the explosion-proof antenna 1.

  The explosion-proof antenna 1 thus completed has a small and simple structure in which the antenna unit 3 is covered with the front panel 2 and the connection box 4 is fixed, and can be manufactured at low cost. Further, for example, a U-shaped belt (not shown) is attached to the connection box 4 and the belt is wound around an iron pole or the like, so that the explosion-proof antenna 1 is installed at an appropriate place in the factory and built in the factory. It can be used for signal transmission / reception in a wireless LAN. According to the explosion-proof antenna 1 having the above-described configuration, it can be used in two types of hazardous locations according to the factory electrical equipment explosion-proof guidelines.

  In this case, as shown in FIG. 10, a control device (wireless LAN box) 37 is connected to the cable 5 extending from the explosion-proof antenna 1. Further, an explosion-proof camera 38 (for example, refer to Japanese Patent No. 3526814) is connected to the control device 37 via the cable 5. A personal computer 39 can be connected to the control device 37 as necessary. Further, the explosion-proof antenna 1 is provided inside or outside the factory, and the server 40 is connected to the cable via the hub 41. Here, the explosion-proof antenna 1 is used in the 2.4 GHz band, but may be used in other bands such as the 2.5 GHz band. For example, when video data captured by the explosion-proof camera 38 is transmitted to the server 40, the communication distance can be about 1200 m. If two explosion-proof cameras 38 are connected, the amount of data is doubled, so the communication distance is 600 m. Furthermore, if it is the data communication of the personal computer 39, transmission of about 2000 m is possible.

It is a front view of the explosion-proof antenna which concerns on this embodiment. It is a rear view of FIG. It is a side view of FIG. (A) is the front view of an antenna part, (b) is the top view. (A) is the enlarged view of the attachment part of the crimp terminal shown in FIG. 4, (b) is the top view. (A) is the rear view of a front panel, (b) is the sectional drawing. It is a front view of a ground plate. It is a front view of a radiator element. (A) is a front view of a cable holder, (b) is the sectional drawing. It is a schematic block diagram which shows the use condition of the explosion-proof antenna which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Explosion-proof antenna 2 ... Front panel 3 ... Antenna part 4 ... Connection box 5 ... Cable 5a ... Core wire 6 ... Rib 7 ... Guide part 8 ... Groove part 9 ... Packing 10 ... Boss part 11 ... Ground plate 12 ... Radiator element 12a ... Notch 12b ... Through-hole 12c ... Escape hole 13 ... Parasitic element 13a ... Notch 13b ... Escape hole 13c ... Through-hole 14 ... First attachment hole 15 ... Opening part 16 ... Vent filter 17 ... Cord insertion hole 18 ... Second attachment hole DESCRIPTION OF SYMBOLS 19 ... 3rd attachment hole 20 ... Screw hole 21 ... Cable insertion hole 22 ... Bolt hole 23 ... Spacer 23a ... Escape recessed part 24 ... 1st support part 24a ... Through-hole 25 ... 2nd support part 25a ... Female screw part 26 ... Box Main body 26a ... Communication hole 26b ... Mounting hole 27 ... Lid 28 ... Cable gland 29 ... Crimp terminal 29a ... Connection part 30 ... Cable holder 30a ... Center Hole 30b ... Annular groove 31 ... Retracting tool 32 ... Plug 33 ... Cylindrical part 34 ... Girder part 34a ... Through hole 35 ... O-ring 36 ... Heat-shrinkable tube 37 ... Waterproof packing 38 ... Packing presser plate

Claims (4)

An antenna unit formed by sequentially arranging a radiator element and a parasitic element with respect to the ground plate, and electrically connecting the ground plate and the parasitic element to each other;
A front panel mounted on the ground plate and covering the radiator element and the parasitic element in a sealed state;
A cable that passes through the ground plate and is connected to a core wire exposed in an internal space formed by the front panel, and the crimp terminal is fixed to the radiator element;
A junction box that is fixed to the ground plate and accommodates a lead-out portion of the cable from the ground plate;
An explosion-proof antenna characterized by comprising:   2. The explosion-proof antenna according to claim 1, wherein the ground plate includes a vent filter that allows ventilation and can discharge steam only from the internal space to the outside. A cable holder is disposed between the ground plate and the junction box,
The cable holder includes a flange through which the cable penetrates, presses against the ground plate and seals the periphery of the cable, and a tube that penetrates the connection box and extends to the inside, and guides the cable into the connection box And consists of
The explosion-proof antenna according to claim 1 or 2, wherein the connection box is fixed by a bolt and a nut that pass through the connection box, the cable holder, and the ground plate and sandwich these members.   By fixing the connection box to the ground plate as a part of the ground plate, radio waves can be transmitted and received not only on the front panel side but also on the opposite side of the front panel. The explosion-proof antenna according to any one of claims 1 to 3.

Images