Pressure-resistant explosion-proof container having a slit waveguide

Abstract

To provide a pressure-resistant explosion-proof container in which a wireless circuit housed inside the pressure-resistant explosion-proof container can transmit and receive a high frequency signal, without installing an antenna outside. A pressure-resistant explosion-proof container includes a container made of metal, a slit functioning as an explosion-proof clearance that is formed by penetrating a wall surface of the container, and a cavity resonator that is provided in the container and in which an antenna is built that transmits and receives a high frequency signal by using the slit as a waveguide.

Claims

1. A pressure-resistant explosion-proof container comprising: a container made of metal; a slit opening connecting an interior of the container and an outside of the container, functioning as an explosion-proof clearance; and a cavity resonator that is provided in the container and in which an antenna is configured to wirelessly transmit and receive a high frequency signal by using the slit opening as an open ended waveguide, the high frequency signal being transmitted to or received from the outside of the container, wherein when the cavity resonator that is built in the container is set as a first cavity resonator, and an antenna that is built in the first cavity resonator is set as a first antenna, a second cavity resonator in which a second antenna is built is provided on an outer wall surface of the container to be opposed to the first cavity resonator, and a third antenna is provided in an outer space of the second cavity resonator, and the second antenna and the third antenna are connected by a high frequency cable.

2. The pressure-resistant explosion-proof container according claim 1, wherein the container has a rectangular parallelepiped or cubic shape, and the slit opening is formed horizontally, vertically, or in a cross shape on at least one surface of the container.

3. The pressure-resistant explosion-proof container according to claim 2, wherein when the cavity resonator that is built in the container is set as a first cavity resonator, and an antenna that is built in the first cavity resonator is set as a first antenna, a second cavity resonator in which a second antenna is built is provided on an outer wall surface of the container to be opposed to the first cavity resonator, and a third antenna is provided in an outer space of the second cavity resonator, and the second antenna and the third antenna are connected by a high frequency cable.

4. The pressure-resistant explosion-proof container according claim 1, wherein the slit opening has a width of 0.15 mm and a length of 60 mm.

5. The pressure-resistant explosion-proof container according claim 1, wherein the cavity resonator comprises a material that reflects the high frequency signal.

6. The pressure-resistant explosion-proof container according claim 1, wherein the cavity resonator comprises a material of at least one of Fe, Cu, and Al.

7. The pressure-resistant explosion-proof container according claim 1, wherein the cavity resonator is configured to resonate the high frequency signal.

8. The pressure-resistant explosion-proof container according claim 1, wherein the open ended waveguide is configured to directly couple the high frequency signal to free space.

9. The pressure-resistant explosion-proof container according claim 1, wherein the cavity resonator is an enclosure formed by welding or adhesion to an inner surface of the container having the slit opening.

Description

BRIEF DESCRIPTION OF DRAWINGS

(1) FIG. 1A is a cross-sectional view of a pressure-resistant explosion-proof container of the present invention.

(2) FIG. 1B is a view of FIG. 1A as seen from a Z direction.

(3) FIG. 1C is a plan view of FIG. 1A.

(4) FIG. 2A is a cross-sectional view showing another embodiment of the present invention.

(5) FIG. 2B is a view of FIG. 2A as seen from a Z direction.

(6) FIG. 2C is a plan view showing a transmission and reception state of a high frequency signal when a slit is provided on respective opposed surfaces of wall surfaces of the pressure-resistant explosion-proof container in FIG. 2A.

(7) FIG. 2D is a view showing a state in which a part of the pressure-resistant explosion-proof container in FIG. 2A is a cavity.

(8) FIG. 2E is a view showing a state in which a part of the pressure-resistant explosion-proof container in FIG. 2A is a cavity.

(9) FIG. 2F is a view showing a state in which a part of the pressure-resistant explosion-proof container in FIG. 2A is a cavity.

(10) FIG. 3 is a cross-sectional view showing another embodiment of the present invention.

(11) FIG. 4 is a view showing a flow of electromagnetic energy when the embodiment in FIG. 3 is struck by lightning.

(12) FIG. 5 is a block diagram showing an example of a high frequency wireless communication system to which the present invention is applied.

(13) FIG. 6 is a cross-sectional view showing an example of a pressure-resistant explosion-proof container in the related art.

(14) FIG. 7A is a view showing another embodiment of the pressure-resistant explosion-proof container in the related art.

(15) FIG. 7B is a view showing another embodiment of the pressure-resistant explosion-proof container in the related art.

DESCRIPTION OF EMBODIMENTS

(16) FIG. 1A is a cross-sectional view of a pressure-resistant explosion-proof container of the present invention. FIG. 1B is a view of FIG. 1A as seen from a Z direction. FIG. 1C is a plan view of FIG. 1A.

(17) In these drawings, a pressure-resistant explosion-proof container 40 is a container made of a metal having a rectangular parallelepiped or cubic shape and a slit 44 penetrating the inner surface of the container is formed in one surface of side surfaces. As shown in FIG. 1B, for example, the silt is made to have a width of 0.15 mm and a length of 60 mm when a high frequency signal k to be transmitted and received is 2.4 GHz. In addition, the thickness of the pressure-resistant explosion-proof container 40 is approximately 12.5 mm, which is sufficient for a pressure-resistant explosion-proof container. The thickness is designed to function as a pressure-resistant explosion-proof container depending on the size of the container.

(18) Moreover, the slit 44 functions as an explosion-proof clearance and a waveguide. An outer wall side of the slit functions as a slot antenna 44a as shown in FIG. 1C.

(19) Furthermore, a cavity 43 functions as a cavity resonator so as to resonate the high frequency signal k which is transmitted and received. As shown in FIG. 1A, the cavity 43 is fixed by welding and adhesion on one surface of the inner walls of the pressure-resistant explosion-proof container 40 so as to cover the slit 44. The cavity 43 has a rectangular parallelepiped shape in which one surface on the side of the slit 44 is opened at least to receive the high frequency signal from the slit 44. The size of the cavity 43 is determined by the resonance magnitude of the high frequency signal which is transmitted and received. As for materials, for example, the cavity 43 is made of metals such as Fe, Cu and Al, and any material which reflects the high frequency signal may be used even when the material is not metal.

(20) The reference number 41 shown in FIG. 1A is an antenna disposed in the cavity 43, and the antenna transmits and receives the high frequency signal k which is resonated in the cavity 43 to and from a wireless transmitting and receiving circuit (not shown) disposed in the pressure-resistant explosion-proof container 40, for example, through a coaxial cable (high frequency cable) (not shown).

(21) In the above-described configuration, during the transmitting operation, the transmitting circuit generates a high frequency signal. The generated high frequency signal is emitted to the inside of the cavity 43 through the antenna 41. The high frequency signal k which is resonated in the cavity is guided to the slot antenna 44a through the slit functioning as a waveguide and an explosion-proof clearance, and the high frequency signal is emitted to an outer space from the slot antenna 44a as a high frequency signal k.

(22) Furthermore, during the receiving operation, the high frequency signal k arrived from the outside is received by the slot antenna 44a, and guided to the inside of the cavity 43 through the waveguide formed with the slit to be emitted in the cavity 43. The high frequency signal k which is resonated in the cavity is received by the receiving circuit (not shown) through the antenna 41. In addition, since the pressure-resistant explosion-proof container 40 in FIGS. 1A to 1C is horizontally fixed and the slit is formed in a horizontal direction, a horizontal polarization high frequency signal can be transmitted and received.

(23) According to the above-described configuration, since the pressure-resistant explosion-proof container is made of metal, and the wireless circuit housed in the container can transmit and receive the high frequency signal, without installing the antenna outside, a risk of breakage can be decreased. Moreover, deterioration in the material of the container by environmental conditions in the field can be avoided. Furthermore, since the container can be formed to have a simple structure, costs can be reduced.

(24) In addition, since the material which has deteriorated high frequency properties is not used for the path of the high frequency signal, deterioration in circuit performance can be prevented. Furthermore, since the antenna is not exposed to the outside of the container, the electromagnetic energy by lightning can be prevented from reaching the circuit.

(25) FIG. 2A is a cross-sectional view showing another embodiment of the present invention. FIG. 2B is a view of FIG. 2A as seen from a Z direction. FIG. 2C is a plan view showing a transmission and reception state of a high frequency signal when a slit is provided on respective opposed surface of wall surfaces of the pressure-resistant explosion-proof container in FIG. 2A. FIGS. 2D, 2E and 2F are views showing a state in which a part of the pressure-resistant explosion-proof container is a cavity. In addition, the same reference numerals are used for the same components as in FIGS. 1A to 1C.

(26) According to the embodiment in FIGS. 2A and 2B, since the slit is formed in a vertical direction in comparison with the embodiment in FIGS. 1A to 1C, a vertical polarization high frequency signal can be received. Moreover, as shown in FIG. 2C, when the slit is formed at 4 places of the respective opposed wall surfaces, the directivity of the high frequency signal can be improved. In this case, as shown in FIGS. 2D and 2E, a partition plate 46 may be provided to partition the inside of the pressure-resistant explosion-proof container 40 and form the cavity 43, and the slit may be formed on at least one wall surface of the cavity 43. In FIG. 2F, the slit is formed in a cross shape and can respond to the horizontal and vertical polarized high frequency signals.

(27) However, in this case, since the high frequency signal is resonated, there is limitation to the size and the shape of the pressure-resistant explosion-proof container. As describe above, the high frequency signal which is resonated in the cavity is received by the receiving circuit (not shown) though the antenna.

(28) FIG. 3 is a view showing still another embodiment. In the embodiment in FIG. 3, a second cavity 43b in which a second antenna 41b is built is provided to be opposed to a first cavity 43a in the pressure-resistant explosion-proof container 40. The second cavity 43b is an equivalent cavity to the first cavity and attached to the outer wall surface of the pressure-resistant explosion-proof container 40 with the slit 44 interposed therebetween. Furthermore, a third antenna 41c is provided in the outer space of the second cavity 43b. Then, the second antenna 41b and the third antenna 41c are connected by the coaxial cable (high frequency cable) 45.

(29) According to the embodiment in FIG. 3, since a transmission and reception source of the high frequency signal is the third antenna 41c provided at a tip end of the coaxial cable 45, there is no limitation to the installation place of the container.

(30) FIG. 4 is a view showing a path of the electromagnetic energy (R) when the third antenna 41c shown in FIG. 3 is struck by lightning (T), and a conductor to connect the receiving circuit (not shown) disposed in the container with the third antenna 41c installed in the space is not present. Accordingly, even when the electromagnetic energy by the lightning (T) reaches the antenna, a probability that the energy reaches the circuit inside the container is very low.

(31) In addition, in the above description, the specific and preferred embodiments are merely shown for the purpose of description and illustration of the present invention. Therefore, the present invention is not limited to the above-described embodiments and includes various changes and modifications without departing the scope of the invention.

(32) The present application is based on Japanese Patent Application (Japanese Patent Application No. 2010-279098), filed Dec. 15, 2010, the content of which is incorporated herein by reference.

REFERENCE SIGNS LIST

(33) 1 PRIVATE BRANCH EXCHANGE

(34) 2 COMMUNICATION LINE

(35) 3 FIXED WIRELESS DEVICE

(36) 4, 25, 41 ANTENNA

(37) 5 MOBILE TERMINAL

(38) 21 ANTENNA ATTACHMENT HOLE

(39) 22 EXPLOSION-PROOF DEVICE MAIN BODY

(40) 23 ELBOW-TYPE JOINT

(41) 24 ANTENNA COVER

(42) 40 PRESSURE-RESISTANT EXPLOSION-PROOF CONTAINER

(43) 42 GLASS WINDOW

(44) 43 CAVITY (CAVITY RESONATOR)

(45) 44 SLIT

(46) 45 COAXIAL CABLE (HIGH FREQUENCY CABLE)