JPS6150419B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an excitation device that is connected to a gas pipe through which combustible gas such as city gas flows and excites (feeds) high-frequency power (high-frequency signal) into the pipe. This is related to the safety barrier constructed.

Generally, when high-frequency signals such as VHF band or UHF band signals are transmitted within the pipe through a gas pipe through which city gas or the like flows, excessive electrical energy flows into the excitation part or contact between the excitation probe and the gas pipe wall occurs. It is necessary to take explosion-proof measures to prevent the generation of sparks caused by gas explosions and to prevent accidents such as gas explosions.

For this reason, conventional devices of this kind include a resistance barrier, which inserts a resistor in series in the transmission path of the high-frequency signal sent out from the transmitter, and a zener, which absorbs the voltage applied to the transmission path when it exceeds a predetermined value. Diode barriers, or barriers constructed using relays, transformers, photocouplers, etc., are known. However, this type of barrier has a large transmission loss of high-frequency signals, and since its input and output are not directly cut off, the following problems have arisen. In other words, in order to prevent corrosion of gas pipes buried underground, a negative DC voltage is applied to the pipe body relative to the ground potential, and the excitation probe inserted into the gas pipe or its transmission line is grounded. If the probe were to reach a potential, a direct current potential difference would occur between the excitation probe and the gas pipe, and there was a risk that sparks would occur if the two came into contact due to some kind of impact.

This invention was made in view of these points, and it is possible to transmit high-frequency signals with low loss, and furthermore, it prevents the inflow of excessive energy, and also cuts off the input and output with direct current, thereby transmitting gas. The purpose is to provide a safety holder that prevents explosion accidents, etc.

An embodiment of the present invention shown in FIGS. 1 and 2 will be described below. In FIGS. 1 and 2, 1 is a gold-layer case having a flange-shaped case electrode 1a protruding from the center of the inner wall in the high-frequency signal transmission direction, 2 and 3 are made of conductive members, and the case electrode 1a is A first and a second conduit are arranged and supported in the case 1 through insulating members 4 and 5, respectively, so as to face each other and to be separated from each other in the direction of the axis of the tube (that is, in the direction of high-frequency signal transmission). Annular pipe electrodes 2a, 3a are formed at the pipe ports on the side where the channels 2, 3 are separated from each other, and connector portions 2b, 3b for connecting the transmission line are formed at the pipe ports on the other end side, respectively. 6 and 7 are provided in the first and second conduits 2, 3, respectively, and the respective conduits 2, 3
together with the first and second coaxial lines l ₁ , l ₂ forming
The connector part 2b of each conduit 2, 3 is the center conductor of
Connector center conductors 6a and 7 are provided on the 3b side, respectively.
a is formed. 8 and 9 are first and second insulating members that support each center conductor 6, 7 at the center of the tube axis of each conduit 2, 3 and hermetically seal a part of each conduit 2, 3; 10 and 11 are connected to the insulating members 8 and 9 between the inner walls of the pipes on the opposite sides of the pipes 2 and 3 and their center conductors, respectively, and absorb electrical energy other than required high-frequency signals ( or reflective) first and second
Each of the absorption circuits 10 and 11 includes a coil L and a diode connected in antiparallel.
It is composed of D ₁ and D ₂ . 12 and 13
are provided between the case electrode 1a and the conduit electrodes 2a and 3a, respectively, and form capacitors C ₁ and C ₂ of a predetermined capacity between the respective electrodes. A dielectric member for connecting the center conductors, in which the center conductors 6 and 7 are provided between opposing conductor ends, and capacitors C ₃ and C ₄ of a predetermined capacity are formed in series between the ends, and the outer periphery is surrounded by a cylindrical conductor 15.
covered by.

Note that the connector portion 2b of the first conduit 2 and its connector center conductor 6a are connected to a high-frequency power supply source, for example, a transmitter (not shown), and the second
The connector portion 3b of the pipeline 8 and its connector center conductor 7a connect to the gas pipe 1 buried underground via the transmission pipeline 16 and its center conductor 17, respectively.
8 and an excitation probe 19 inserted into the tube.
are connected to each. Further, in order to protect the gas pipe 18 buried underground, a negative voltage of about -2V with respect to the ground voltage is applied to the pipe body from the DC power supply 20.

In such a configuration, a high frequency signal sent out from a transmitter etc. is transmitted through the first coaxial line l ₁ formed by the first conduit 2 and its center conductor 6, and the dielectric members 12 and 13 for conduit connection. The formed capacitor C ₁ ,
C ₂ , capacitors C ₃ and C ₄ formed by the dielectric part 14 for connecting the center conductor and its outer conductor 15, a second coaxial line l ₂ formed by the second conduit 3 and its center conductor 7, and transmission It is transmitted to the gas pipe 18 with low loss through the coaxial line _l3 formed by the pipe line 18 and its center conductor 17, and is transmitted to the gas pipe 18 by the excitation probe 19.
excited within.

Next, harmful electrical energy other than high-frequency signals sent from a transmitter etc. to the coaxial line ₁ , such as DC signals, low-frequency signals such as commercial frequencies, high-frequency signals exceeding a specified value, and excessive high-frequency signals such as surge voltage. The case where energy is applied will be described.

The first conduit 2 and its center conductor 6 forming this coaxial line l ₁ are held at the same potential in DC terms by the coil L of the first absorption circuit 10, that is, they are short-circuited, and both coaxial lines l ₁ , l ₂ has a capacitor C ₁ ,
Since C ₂ , C ₃ , and C ₄ are formed, DC signals and low frequency signals are absorbed in the coil L, that is, heat is consumed, and the high impedance of the capacitors C ₁ , C ₂ , C ₃ , and C ₄ causes their loss. Passage is blocked;
It is not transmitted to the coaxial line _L2 side. Furthermore, when excessive high-frequency energy is applied, either the diode D ₁ or D ₂ of the first absorption circuit 10 becomes conductive depending on the polarity, and the excessive energy is consumed as heat. Figure 3 shows the diode characteristics of these diodes D ₁ and D ₂ .
When a forward voltage of 0.6V or higher (excessive high-frequency energy in this case) is applied, it becomes conductive, and the line-to-line voltage of coaxial line _l1 is maintained within ±0.6V.

Similarly, the potential difference that occurs between the gas pipe 18 and the excitation probe 19 due to the soil in which the gas pipe 18 is buried, or the escape current from the gas pipe 18, is absorbed by the second absorption line provided in the coaxial line _l2. Since it is absorbed by the circuit 11, it will not be reversely transmitted to the coaxial line _l1 side, and will not have an adverse effect on the transmitter etc. connected thereto. In this case, even if the excitation probe 19 contacts the gas pipe 18, they are held at the same DC potential by the coil L in the coaxial line _l2 , and the coaxial line _l1 side is connected to the capacitor.
Since the direct current is cut off by C ₁ , _{C 2} and C 1 , C ₂ and C ₃ , C ₄ , there is no risk of electrical sparks occurring, and therefore, there is no risk of gas explosion or the like. FIG. 4 shows the configuration of FIGS. 1 and 2 as an electrical equivalent circuit, in which a high-frequency fuse 21 is connected in series to the connector center conductor 6a on the input side, and a diode D ₁ , This prevents D ₂ from burning out or excessive energy passing through due to an open failure in diodes D ₁ and D ₂ .
In the above embodiment, the case electrode 1a and the cylindrical conductor 15 are provided to connect the first and second conduits 2,
Two capacitors C ₁ , C ₂ and C ₃ , C ₄ were formed between C 3 and their center conductors 6 and 7, respectively.
It is also possible to form several capacitors. Further, in the above embodiment, the present invention is applied to excitation in the gas pipe 18, but it is also applicable to excitation of high frequency power in other combustible gases or atmospheres where combustible gas may exist. has the same effect.

As described above, according to the present invention, a dielectric member is interposed between the outer conductors of the first and second coaxial lines and between their center conductors to form a capacitor, and an absorption circuit is provided in each of the coaxial lines. Because of the provision of a This has the effect of suppressing the occurrence of gas explosions and preventing gas explosion accidents.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view showing an embodiment of the present invention;
2 is a cross-sectional view taken along the cutting line--line in FIG. 1, FIG. 3 is a diode characteristic diagram, and FIG. 4 is an electrical equivalent circuit diagram of FIG. 1. In the figure, 2 and 3 are the first and second pipes, 6
and 7 are first and second center conductors, 8 and 9 are first and second insulating members, 10 and 11
12 and 13 are the first and second absorption circuits, 12 and 13 are dielectric members for conduit connection, 14 are dielectric members for connecting the center conductor, 18 are glass tubes, 19 are excitation probes, 2
1 is a high frequency fuse. In each figure, the same or corresponding parts are designated by the same reference numerals.

Claims (1)

[Claims] 1. In a device that excites high-frequency power to equipment placed in a flammable gas atmosphere or an atmosphere where flammable gas may exist, first and second coaxial lines formed of a center conductor and an outer conductor; a dielectric member for connecting the center conductors provided between the center conductors of both coaxial lines and forming a capacitor therebetween; A dielectric member for connecting the external conductors is provided between the external conductors and forms a capacitor therebetween, and a dielectric member is provided for each of the coaxial lines to absorb (or reflect) the high frequency power above a predetermined value and electrical energy other than the high frequency power. ), the first coaxial line is used as the power source of the high frequency power, and the second coaxial line is used as the source of the high frequency power, and the second coaxial line is used as the source of the high frequency power, and the second coaxial line is used as the source of the high frequency power, and the second coaxial line is used as the power source of the high frequency power, and A safety barrier that is connected to equipment placed in a certain atmosphere. 2 The first and second
2. The safety retainer according to claim 1, wherein each of the absorption circuits is configured as follows.