JP3163554B2 - Pneumatic instrument - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pneumatic instrument such as a pneumatic indicating controller, an electropneumatic converter, a positioner, a pneumatic operator and the like.

[0002]

2. Description of the Related Art For example, in a pneumatic instrument such as a pneumatic indicating controller, an electropneumatic converter, a positioner, or a pneumatic calculator, a nozzle / flapper mechanism, a link mechanism for displacement transmission,
A display mechanism based on a pointer for displaying various instructions is incorporated in an appropriate place. The nozzle / flapper mechanism is a pneumatic element that converts a minute displacement into a large pressure change.
It is usually used as a first stage amplifying element, such as a pneumatically operated control instrument or converter. Its basic structure is composed of a nozzle and a flapper arranged in close proximity to each other and a fixed throttle, and has a constant pressure (for example, 1.2 to 1.4 kg / cm).
² ) While the supply air is supplied to the nozzle via the fixed throttle and the nozzle back chamber, when the flapper is displaced by an input signal, the gap between the nozzle and the flapper, that is, the nozzle gap changes, thereby increasing or decreasing the nozzle ejection resistance. For this reason, the nozzle back pressure changes, and this nozzle back pressure is taken out as an output signal.

For example, in a valve positioner, as is apparent from Japanese Utility Model Application No. 2-119365, the position of the drive shaft is always maintained accurately so that the relationship between the instrument signal and the position of the drive shaft can be accurately maintained against disturbance. A kind of servo mechanism that adjusts the output air pressure to the drive unit as a detection end. It converts a normal input signal (displacement signal) as a swing displacement of the flapper, and converts it into a pneumatic signal by the nozzle / flapper mechanism and amplifies it. After that, the pressure is supplied to the actuator of the valve as a driving pressure to drive and control the valve. Further, in this type of positioner, the actual operation amount of the valve is fed back to the flapper by a feedback mechanism so as to balance the force by the input signal.

Incidentally, in such a pneumatic instrument using the supplied air pressure, it is necessary to discharge the consumed air supplied from the air pressure supply source to the nozzle / flapper mechanism and jetted from the nozzle to the outside of the case. Therefore, FIG.
As shown in (a) to (c), the case 1 is provided with an exhaust hole 2 for communicating the inside and the outside. In such a case, in the case of a pneumatic instrument of the field type, rainwater hardly enters through the exhaust hole 2 because the internal pressure of the case 1 increases due to the exhaustion of the supply air, but when the operation is stopped, the instrument is transported, stored, and installed. When the air pressure is not supplied, such as during construction, the internal pressure of the case drops, so rainwater etc. enters and rusts the nozzle / flapper mechanism and other internal mechanisms / parts, etc. There was a problem of doing.

Therefore, conventionally, in order to solve such a problem, the position where the exhaust hole 2 is formed is set to the lower surface side of the case (a) A cover 3 is provided for the exhaust hole 2 formed on the side surface (b). The exhaust port 2 was closed by a seal member, and the seal member was removed during operation to prevent rainwater from entering. In the case where the mounting posture of the instrument is not determined at the design stage, the cover 5 having the notch 4 in a part of the outer circumference is screwed to the case 1 with the screw 6 or the like via the gasket 7 as shown in FIG. The notch 4 is positioned downward during installation to prevent intrusion of rainwater and the like.

[0006]

In the field type pneumatic instrument, the internal pressure of the case is high due to the exhaustion of the consumed air during operation as described above, and the intrusion of rainwater or the like can be prevented. However, when the supply of the supply air pressure is stopped due to the stoppage of the operation of the instrument or the like, the case internal pressure becomes the atmospheric pressure, so that there is a problem that intrusion of rainwater or the like cannot be completely prevented. Therefore, there is a demand for a structure capable of reliably preventing rainwater or the like from entering even when supply of supply air pressure is stopped.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems and demands, and has as its object to reduce the pneumatic pressure at the time of transportation, storage and installation of equipment and at the time of stoppage of instrument operation. When there is no supply, the vent hole is closed to prevent rainwater, etc.
It is an object of the present invention to provide a pneumatic instrument with improved reliability and the like.

[0008]

In order to achieve the above object, the invention according to claim 1 has an air consuming portion such as a nozzle / flapper mechanism inside a case, and has an exhaust hole communicating the inside and outside with the case. In the provided pneumatic instrument, a closing member for controlling the opening and closing of the exhaust hole, and when no air pressure is supplied to the air consuming unit, the closing member is always displaced to a position where the exhaust hole is closed, and to the air consuming unit. An exhaust hole opening / closing mechanism including an elastic member for displacing the closing member to a position where the exhaust hole is opened by using the air pressure whenever air pressure is supplied is provided.

[0009]

In the present invention, when the supply air pressure is being introduced while the pneumatic instrument is operating, the closing member is moved against the elastic member by the supply air pressure and opens the exhaust hole. On the other hand, when the supply air pressure is no longer supplied, the closing member is pressed and moved by the elastic member to close the exhaust hole.

[0010]

FIG. 1 is a sectional view of an essential part showing an embodiment in which a pneumatic instrument according to the present invention is applied to a valve positioner. In FIG. 1, a positioner indicated by reference numeral 10 includes a case 1 having an exhaust hole 2 and nozzles and nozzles inside and outside thereof.
A flapper mechanism 11, a feedback mechanism 12, a span adjustment mechanism 13, a zero point adjustment mechanism 14, a magnet unit 15 for converting an input signal I0 into displacement of a movable coil, a pilot relay 16, a terminal board 17, and the like. (Not shown).

The nozzle / flapper mechanism 11 includes a flapper 22 having an intermediate portion pivotally supported by a fulcrum 21.
And a nozzle 23 which is in close proximity to one end of the flapper 22
And one end of a zero-point adjusting spring 24 forming the zero-point adjusting mechanism 14 is connected to the opposite side of the nozzle. The other end of the flapper 22 is connected to the magnet unit 15.
Is connected via a strap 26 to the output stem 25. The nozzle 23 is connected to an air supply source (not shown) via a supply air pipe 27, and is fixed (normally 1.4).
Kgf / cm ² ) of supply air pressure Psup is supplied. In the middle of the supply air pipe 27, a pressure reducing valve 28, a supply air pressure gauge 29, the pilot relay 16, a throttle 30, and the like are provided.

The feedback mechanism 12 includes a valve 1
A feedback lever 32 having one end protruding outside the case 1 and connected to the valve shaft 31 for feeding back the actual operation amount of the valve shaft 31 to the flapper 22;
One end is rotatably supported by a rotating shaft 33 and is connected to the flapper 22 via a feedback spring 34 via a feedback spring 34; a span adjusting screw 37 attached thereto; and a rotating shaft of the feedback lever 32. A feedback plate 39 attached to 38;
It is constituted by a plate contact member 40 for span adjustment and the like, which is attached to the span adjustment screw 37 so as to be vertically movable and whose tip abuts on the feedback plate 39.

The magnet unit 15 includes a case 1
An explosion-proof case 42 is provided so as to penetrate the inside, and the inside is partitioned into two chambers by a partition wall 43,
On one side, the terminal board 17 is provided, and on the other side, an annular magnet 44, a movable coil 45 surrounding the outer periphery thereof, first and second yokes 46 for sandwiching the magnet 44,
47 and the like are stored. And the lead wire 48,
When an input signal I0 (4 mA to 20 mA) corresponding to the measured amount is input to the movable coil 45 via the terminal board 17, a predetermined displacement amount is applied to the output stem 25 in the axial direction based on the principle of electromagnetic induction. Provided by the flapper 22
Is swung about the fulcrum 21 as a fulcrum.

For example, if the output stem 25 is displaced to the left in the figure, this displacement is transmitted to the flapper 22 via the strap 26, so that the flapper 22 moves clockwise about the fulcrum 21 in the figure. Nozzle 2 with rotational displacement
Narrow the gap with 3. For this reason, the nozzle back pressure PN increases, and this nozzle back pressure PN is amplified by the pilot relay 16 and then guided to the actuator 50 as the output air pressure Pout through the output air pipe 49 to operate it. As a result, the valve shaft 31 moves upward to adjust the opening of the valve 18. In addition, the movement of the valve shaft 31 is transmitted to the flapper 22 via the feedback mechanism 12, and balances the clockwise turning force by the input signal I0 acting on the flapper 22, thereby stabilizing the movement of the flapper 22. When the output stem 25 is displaced rightward in the figure, the valve shaft 31 is moved downward, contrary to the above.

The pilot relay 16 has a housing internally partitioned into four chambers, namely, an air supply chamber 53, an output chamber 54, an air release chamber 55, and a nozzle back pressure chamber 56 by two diaphragms 51a and 51b and a partition wall 52. 57, a poppet valve 58, a piston 59, and the like. As is well known, the output air pressure Pout is obtained by amplifying the nozzle back pressure PN, but a detailed description thereof is omitted.
In the figure, reference numeral 60 denotes a pressure gauge for output air pressure.

In the valve positioner 10 constructed as described above, an exhaust hole opening / closing mechanism 61 is further provided inside the case 1 so as to correspond to the exhaust hole 2. The exhaust hole opening / closing mechanism 61 normally opens the exhaust hole 2 when the valve positioner 10 is operated,
The exhaust hole 2 is closed at the time of transportation, storage, installation work, operation stop, or the like when the supply air pressure Psup is not supplied to prevent rainwater or the like from entering the case 1. 2 (a) and 2 (b) show the configuration of the exhaust hole opening / closing mechanism 61 and the like.
The exhaust hole opening / closing mechanism 61 includes a piston 63 serving as a closing member for controlling the opening and closing of the exhaust hole 2.
And a cylinder 64 which communicates with a supply air flow path 27a which forms a part of the air pipe 27 and movably accommodates the piston 63. The piston 63 is connected to the exhaust hole 2 when the supply air pressure Psup is supplied. And a compression coil spring 65 as an elastic member for moving the piston 63 to a position for closing the exhaust hole 2 when the supply air pressure Psup is not supplied, and a plurality of O-rings 66 (66a to 66a).
66c) and the like. The piston 63 is provided with two large-diameter portions 6 having the same diameter and spaced apart in the axial direction.
3A, 63B and three small diameter portions 63a, 63b, 63c provided between and on both sides of the large diameter portions 63A, 63B.
The outer diameters of the large diameter portions 63A and 63B are set slightly smaller than the inner diameter of the cylinder 64. A total of four communication holes 67a to 67d are formed on the peripheral surface of the cylinder 64, 67a communicates with the exhaust hole 2, 67b communicates with the supply air flow path 27a, and 67c and 67d communicate with the inside of the case 1. And the inside of the cylinder 64.
The communication holes 67b and 67c are formed near both ends of the cylinder 64, and the communication holes 67a and 67d are formed substantially at the center in the longitudinal direction of the cylinder 64 so as to be located on both sides of the O-ring 66b. The O-ring 66a has a communication hole 67
c and 67d, and the remaining O-ring 66c is located between the communication holes 67a and 67b. The O-rings 66a, 66b, 66c are connected to the cylinder 64
The O-rings 66a and 66c are fixedly fitted to the annular groove formed on the inner peripheral surface of the large diameter portion 6 with a part of the peripheral surface projecting therefrom.
3A and 63B are always in contact with the peripheral surfaces thereof, and the O-ring 6
6b is provided at a position where it contacts the large diameter portion 63A only when air pressure is not supplied. The compression coil spring 65 is fitted to the small-diameter portion 63b of the piston 63, is located at one end side inside the cylinder 64, and urges the large-diameter portion 63A downward in FIG.

The exhaust hole opening / closing mechanism 6 having the above-described structure.
2, (a) shows a state when the valve positioner 10 is operating, and (b) shows a state when the valve positioner 10 is stopped. In the operation state of the valve positioner, the exhaust hole 2
To release the air in the case 1 to the outside. For this reason, the piston 63 is moved by the air pressure Psup supplied from the communication hole 67b into the cylinder 64 as shown in FIG.
As shown in (a), the large-diameter portion 63A is moved above the O-ring 66b against the compression coil spring 65, so that the communication holes 67a and 67d communicate with each other. Accordingly, in this state, the air in the case 1 is exhausted from the exhaust hole 2 to the outside of the case 1 through the communication hole 67d-the space between the large-diameter portions 63A and 63B-the communication hole 67a inside the cylinder 64. You.

On the other hand, the supply air pressure Psup is not supplied during transportation, storage, installation work or operation shutdown,
The piston 63 is moved downward as shown in FIG. 2B by the spring force of the compression coil spring 65, and the small diameter portion 63c comes into contact with the inner wall surface of the cylinder 64 on the side opposite to the compression coil spring 65 side and stops. , A large-diameter portion 63A having two O-rings 6
6a and 66b. Therefore, the communication hole 6
7a and 67d do not communicate with each other.
To prevent rainwater or the like from penetrating into the case 1.

Thus, according to the valve positioner 10 having such a configuration, it is ensured that rainwater or the like enters the case 1 during transportation, storage, installation work, operation stop, or the like where the supply air pressure Psup is not supplied. This can prevent the nozzle / flapper mechanism 11, the feedback mechanism 12, the span adjustment mechanism 13, the zero point adjustment mechanism 14, the magnet unit 15, the pilot relay 16 and the like from being rusted or deteriorated in function. In addition, the reliability, durability and the like of the valve positioner 1 can be improved. Further, since the exhaust hole 2 is automatically closed when the operation is stopped, it is not necessary for the operator to open and close the exhaust hole 2 each time, and the handling is easy.

FIG. 3 is a sectional view of a main part showing another embodiment of the present invention. In this embodiment, a flapper 71 is used as a closing member, a bellows 72 is used as a pressure responsive member, and the flapper 71 is connected to an inner opening end surface of the exhaust hole 2 via an O-ring 66 by a spring force of a compression coil spring 65 when the operation is stopped or the like. The exhaust port opening / closing mechanism 61 is configured by being closely contacted. In the state shown in the figure, since the exhaust hole 2 is closed by the flapper 71, rainwater or the like does not enter the case 1 through the exhaust hole 2. During operation, the bellows 72 is expanded by the air pressure Psup supplied from the supply air flow path 27a, thereby displacing the flapper 71 upward in FIG. 3 against the compression coil spring 65 and separating it from the O-ring 66. Therefore, the exhaust hole 2 is opened, and the air in the case 1 is exhausted to the outside through the exhaust hole 2.

Even in such a configuration, the exhaust port 2 can be automatically closed at the time of transportation, storage, installation work, operation stop, or the like where the supply air pressure Psup is not supplied, as in the above embodiment. Intrusion of rainwater or the like can be reliably prevented, and the nozzle / flapper mechanism 11, the feedback mechanism 12, the span adjustment mechanism 13, the zero point adjustment mechanism 14, the magnet unit 15, the pilot relay 16
Can be prevented from being rusted and the functions from being deteriorated. Therefore, reliability, durability and the like of the valve positioner 1 can be improved.

It should be noted that the present invention is not limited to the structure of the embodiment described above, and it is needless to say that various modifications and changes are possible. For example, the small diameter portions 63b and 63c of the piston 63 are not always necessary. In addition, a diaphragm, a capsule air cylinder, or the like can be used as the pressure responsive member.

[0023]

As described above, according to the pneumatic instrument of the present invention, the closing member for controlling the opening and closing of the exhaust hole and the closing member in the position where the exhaust hole closes when the air pressure is not supplied. Displacement, an exhaust hole opening and closing mechanism provided with an elastic member that displaces the closing member to a position where the exhaust hole is opened at the time of supplying air pressure, when the device is operating,
Open the exhaust port, transport, storage,
At the time of installation work, operation stop, etc., the exhaust hole is closed, so despite its simple structure,
It is possible to reliably prevent rainwater or the like from entering the case when the operation is stopped. Therefore, the mechanism and components inside the case are not rusted or the functions are not deteriorated, and the reliability and durability of the meter can be improved. Further, since the exhaust hole can be automatically opened and closed by the supply air pressure and the elastic member, it is not necessary for the operator to open and close each time, and the handling is simple.

[Brief description of the drawings]

FIG. 1 is a schematic sectional view of a main part showing an embodiment in which a pneumatic instrument according to the present invention is applied to a valve positioner.

FIGS. 2A and 2B are diagrams for explaining the operation of the exhaust hole opening / closing mechanism and the like, wherein FIG. 2A is a diagram showing a state when the valve positioner is operating, and FIG. It is.

FIG. 3 is a sectional view of a main part showing another embodiment of the present invention.

FIGS. 4A, 4B, and 4C are cross-sectional views each showing a conventional example of a case used for a pneumatic instrument.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Case, 2 ... Exhaust hole, 10 ... Valve positioner (pneumatic instrument), 11 ... Nozzle / flapper mechanism, 12 ... Feedback mechanism, 15 ... Magnet unit, 16 ... Pilot relay, 18 ... Valve, 22 ... Flapper, 23
... Nozzle, 27 ... Supply air piping, 61 ... Exhaust hole opening / closing mechanism, 63 ... Piston, 64 ... Cylinder, 65 ... Compression coil spring, 71 ... Flapper, 72 ... Bellows, Psup ... Supply air pressure, Pout ... Output pressure.

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) F15B 5/00 G01D 5/42

Claims (1)

(57) [Claims] 1. A case in which a nozzle / flapper mechanism or the like is provided inside the case .
A pneumatic instrument having an air consuming portion and having an exhaust hole communicating the inside and outside of the case, wherein a closing member that controls opening and closing of the exhaust hole; and the air consuming portion.
When no air pressure is supplied to the air consuming section, the closing member is always displaced to the position where the exhaust hole is closed.
A pneumatic instrument comprising an exhaust hole opening / closing mechanism including an elastic member for displacing the closing member to a position where the exhaust hole is opened by using the air pressure whenever air pressure is supplied .