JPH0416644B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an explosion-proof instrument that can withstand use in an explosive gas atmosphere.

[Conventional technology]

In general, instruments such as electro-pneumatic converters and electro-pneumatic positioners for control valves are sometimes used in explosive gas atmospheres, so they are required to have a structure with sufficient explosion-proof performance. For this reason, conventionally, a structure has been adopted in which the entire instrument is housed within an explosion-proof case cover.

[Problem that the invention seeks to solve]

However, with such conventional explosion-proof instruments, it is extremely troublesome and dangerous to remove the explosion-proof case cover and adjust the conversion mechanism or repair or replace parts in a dangerous location. In addition, since the case cover is explosion-proof, it requires a certain thickness, etc., which increases the size of the entire instrument and increases cost.

Therefore, Japanese Unexamined Patent Publication No. 148271/1989 proposes a structure in which the entire drive unit (torque motor) including the excitation coil and the core as its magnetic path is housed in an airtight container. Since an independent airtight container is still required, the overall size of the instrument cannot be avoided.

[Means for solving problems]

In order to solve these problems, in the present invention, the excitation coil is elastically supported by a spring member in a narrow magnetic path space formed by a permanent magnet and both bowl-shaped and columnar yokes that sandwich it. The opening of the shaped yoke and the opening of the explosion-proof case containing at least electrical external connection means are sealed and integrated with a connection structure that satisfies explosion-proof standards, and the opening passing through the central axis of both yokes is The output stem was installed to protrude, leaving an explosion-proof gap.

[Effect]

With this configuration, the opening of the yoke containing permanent magnets, excitation coils, etc. is closed by the terminal box serving as an explosion-proof case, and the output stem forms part of the explosion-proof container, leaving an explosion-proof gap. Since it protrudes from the yoke, the entire instrument has an explosion-proof structure.

〔Example〕

This embodiment shows an example in which the present invention is applied to an electro-pneumatic positioner. Fig. 1 is a longitudinal sectional view of a yoke and a terminal box of an electro-pneumatic positioner to which this is applied, and Fig. 2 is a plan view of a stem support spring. , FIG. 3 is a plan view taken from A in FIG. 1, and FIG. 4 is a schematic diagram of the entire electropneumatic positioner to which the present invention is applied. In the figure, reference numeral 1 denotes a first yoke formed in the shape of a bowl, and a second yoke 2 formed in the shape of a column is concentrically connected to the center of the bottom of the first yoke via a disk-shaped permanent magnet 3. The yoke 1, the permanent magnet 3, and the yoke 2 are fixed in place, and a stem hole 4 is bored through the center of the yoke 1, permanent magnet 3, and yoke 2. Further, a pair of leaf springs 5A, 5B formed in an S-shape, as shown in a plan view in FIG. A mounting plate 6, which is formed in an annular shape and is connected to the center part by a cross-shaped arm, is screwed to the tip of 5B. 7 is an annular excitation coil fixed to the mounting plate 6,
It is housed in a narrow annular space formed between the yoke 1, the permanent magnet 3, and the yoke 2, that is, a narrow magnetic path space formed by both the yokes 1 and 2.
It is elastically supported by a leaf spring 6. On the other hand, on the upper surface of the yoke 1, as shown in FIG. An output stem 10 whose lower end is fixed to the mounting plate 6 is inserted into the stem hole 4 and the end protruding from the yoke 1 is elastically supported by a leaf spring 8. Between the output stem 10 and the stem hole 4, an explosion-proof gap is formed, which is indicated by the symbol d in the figure. Reference numeral 11 denotes a terminal box serving as an explosion-proof case in which a terminal board 12 is housed, and the interior is separated into a terminal board housing portion and a space facing the opening of the yoke 1 by a partition plate 11a. and
The outer wall 11b of the space and the mounting seat 1a of the yoke 1 are fixed with a plurality of bolts 13 so as to have a connection structure that satisfies explosion-proof standards. Terminal box 1
Glass terminals 16A and 16B are embedded in the partition plate 11a of No. 1 to connect lead wires 14A and 14B connected to the excitation coil 7 and lead wires 15A and 15B connected to the terminal board 12. 17,
18 is an inlet for external wiring connected to the terminal board 12.

Output stem 1 of the drive unit configured as above
0 is inserted into a case 19 shown by chain lines in FIG. 4, and within this case 19, a nozzle flapper mechanism and a feedback mechanism are organically arranged. Of these, the nozzle flapper mechanism is equipped with a balance beam 21 whose one end is rotatably supported by a fulcrum 20, and the free end of this balance beam 21 is connected to the insertion end of the output stem 10 as a connecting means. They are connected by a cross spring 22, and a nozzle 23 faces the middle part of the balance beam 21. On the other hand, the feedback mechanism is for feeding back the movement of the actuator 24 to the balance beam 21, and includes a feedback lever 26 whose intermediate portion is rotatably supported by a fulcrum 25. The back lever 26 has one end connected to the balance beam 21 by a feedback spring 27, and a long hole 28 formed at the end protruding from the case 19 has a pin 2 on the actuator 24 side.
9 is involved. And actuator 2
4 and the nozzle 23 are connected by a pipe 31 with a pressure amplifier 30 receiving pressure supplement P _sup from an air source.

In the electro-pneumatic positioner configured as described above, when a current signal corresponding to the measured amount is applied to the excitation coil 7 via the lead wires 15A and 15B, the output stem 10 receives a predetermined signal based on the principle of electromagnetic induction. The amount of displacement is given. For example, output stem 10
If an upward displacement occurs, the balance beam 21 rotates clockwise about the fulcrum 20 to open the nozzle 23, so that the back pressure on the nozzle 23 decreases. This nozzle back pressure is
0 is amplified and guided to the actuator 24, which is actuated to operate the valve in the opening direction, and is transmitted as a force that rotationally displaces the feedback lever 26 in the counterclockwise direction about the fulcrum 25. This force is then balanced by the clockwise rotational force acting on the balance beam 21 by the output stem 10, thereby stabilizing the movement of the balance beam 21.

FIG. 5 is an overall schematic configuration diagram showing an example in which the explosion-proof instrument according to the present invention is applied to an electro-pneumatic converter,
Components with the same reference numerals as those in FIG. 4 have the same configurations, so a description thereof will be omitted. In this electro-pneumatic converter, a feedback force acts on the balance beam 21 by the bellows 32, and
Due to this feedback force, the balance beam 2
The fact that 1 is stable is the same as in the case of the electropneumatic positioner shown in FIG. With this configuration, an air output P _OOT corresponding to the amount of displacement of the output stem 10 can be obtained.

In each of the above embodiments, the present invention has been applied to an electro-pneumatic positioner and an electro-pneumatic converter, but it goes without saying that it can be similarly applied to other instruments. Further, in each of the above embodiments, an example was shown in which the external signal was directly connected to the excitation coil 7, but various elements and functional units such as arithmetic and amplification units may be interposed in the middle.

〔Effect of the invention〕

As is clear from the above description, in an explosion-proof instrument according to the present invention, an excitation coil spring member is used to create an elastic force within a narrow magnetic path space formed by a permanent magnet and both bowl-shaped and column-shaped yokes that sandwich it. The opening of the bowl-shaped yoke and the opening of the explosion-proof case containing at least the electrical external connection means are sealed and integrated with a connection structure that satisfies explosion-proof standards, and forms part of the explosion-proof case. By protruding the output stem from the opening that passes through the central axis of the yoke, leaving an explosion-proof gap, the structure of the explosion-proof container itself is simplified and a special explosion-proof sealed container is not required, making the entire instrument compact. This makes manufacturing easier and reduces costs. In addition, since the volume of the internal cavity formed by the bowl-shaped yoke and the explosion-proof case can be minimized, it is easy to comply with explosion-proof standards, which generally require stricter measures as the internal volume of the device increases. It has the effect of being able to deal with.

[Brief explanation of drawings]

1 to 5 show an embodiment of an explosion-proof instrument according to the present invention, FIG. 1 is a vertical cross-sectional view of a yoke and a terminal box of an electropneumatic positioner to which this is applied, and FIG. 2 is a vertical cross-sectional view of a terminal box for supporting a stem. A plan view of the spring, FIG. 3 is a plan view from A in FIG. 1, FIG. 4 is a schematic configuration diagram of the entire electropneumatic positioner to which the present invention is applied, and FIG. FIG. 2 is a schematic configuration diagram of an applied electro-pneumatic converter. 1...Yoke, 1a...Mounting seat, 2...Permanent magnet, 3...Yoke, 4...Stem hole, 5A, 5B
... Leaf spring, 7 ... Excitation coil, 10 ... Output stem, 11 ... Terminal box, 11b ... Outer wall.

Claims (1)

[Claims] 1. An excitation coil elastically supported by a spring member is disposed in a narrow magnetic path space formed between a bowl-shaped yoke and a columnar yoke disposed at the center of its bottom via a permanent magnet, and the excitation coil is elastically supported by a spring member. The opening of the shaped yoke and the opening of the explosion-proof case containing at least the electrical external connection means are sealed and integrated with a connection structure that satisfies explosion-proof standards, and the central axes of the bowl-shaped yoke and the columnar yoke are An explosion-proof instrument, characterized in that an output stem that is displaced by excitation of the excitation coil is protruded from an opening through which an explosion-proof gap is left.