JPH09159491A - Site-type measuring instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a site-type measuring instrument which can satisfy an explosionproof regulation by a method wherein a terminal base which is provided integrally with a meter housing part having an opening part in a tip face protruding to the front is fixed to a housing and a terminal to which a connecting cable to an external apparatus is attached is arranged on the front. SOLUTION: In a terminal base 5, a body 5A in which a plurality of terminals 6 are installed and a cylindrical meter housing part 5B which is installed so as to protrude at its front face are formed integrally of a synthetic resin, and the outer circumferential part of the body 5A is fixed to a terminal-base mounting part 30 on the inner circumferential face of a housing 20 by a plurality of screws 28. A meter 12 is installed at the cylindrical housing part 5B so as to cover an opening part 33 on the front, and its printed-circuit board 34 and a printed-circuit board 31 at the terminal base 5 are connected by a lead wire 35. Cables 7 are inserted into the housing 20 from two insertion and passage holes 11, and connecting terminals 8 at their end parts are connected to the terminals 6 by screws 9. By this structure, the meter 12 does not become an obstacle to the terminals 6, and a site-type measuring instrument can be used as a differential-pressure and pressure transmitter which satisfies an explosionproof regulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a differential pressure / pressure transmitter which is installed on site and detects pressures of various process fluids,
The present invention relates to a field instrument suitable for application to an electromagnetic flowmeter and the like.

[0002]

2. Description of the Related Art FIGS. 5 and 6 show a conventional example of a standard type differential pressure / pressure transmitter known as a kind of field type instrument.
This differential pressure / pressure transmitter 1 is a body body (instrument body)
2, an electric equipment case 3 provided integrally with the body body 2, and a meter case 4 provided integrally with one side of the electric equipment case 3. The body body 2 applies each process fluid pressure to the high-pressure side and low-pressure side barrier diaphragm chambers (not shown), and guides the pressure due to the internal sealing liquid in the body body 2 to the semiconductor pressure sensor provided so as to partition the enclosed circuit, It is constructed so that the distortion is converted into an electric signal and taken out (eg, Japanese Utility Model Publication No. 59-30444). A terminal block 5 is provided inside the electric device case 3, and a terminal 6 provided at the center of the front surface of the terminal block 5 is connected to one end of a cable 7 for signal transmission and power supply with an external device. The terminal 8 is fixed by a set screw 9. Further, the front side opening of the electric device case 3 forms a terminal connection opening for connecting the connection terminal 8 to the terminal 6, and the opening is hermetically closed by the lid 10. An insertion hole 11 through which the cable 7 is inserted is provided on the side surface opposite to the meter case 4. The meter case 4 is provided separately from the electric equipment case 3 in order to meet the explosion-proof standard, accommodates the meter 12 for displaying the differential pressure inside, and has a front opening hermetically closed by a cover 13. The cover 13 has a transparent glass 14 so that the display of the meter 12 can be visually recognized from the outside.

On the other hand, when it is not necessary to meet the explosion-proof standard, it is known that a terminal and a meter are incorporated in one housing in order to reduce the size and weight of the entire apparatus. This non-explosion-proof differential pressure / pressure transmitter has a meter integrally incorporated inside a cover that covers the front opening of the housing.

[0004]

In the differential pressure / pressure transmitter satisfying the above-mentioned explosion-proof standard, it is prohibited to put a shield in front of the terminals, so that the electric equipment case 3 and the meter case are as described above. Although it was necessary to provide 4 separately, there was a problem that such a structure could not be reduced in size and weight, the number of parts and the number of assembly steps were increased, and the manufacturing cost was increased.

On the other hand, in a non-explosion-proof type differential pressure / pressure transmitter in which a terminal and a meter are incorporated in one housing,
Since the meter is integrated into the cover, SFC
When performing the zero adjustment, span adjustment, etc. called (Smart Field Communicator), if you remove the cover, the meter will also come out with the cover, so you cannot check the displayed contents of the meter during the adjustment. For this reason, it is necessary to connect a digital voltmeter or the like and adjust the content while checking the displayed contents. Also,
Conventionally, the cable is connected to the terminal and the extra length is pushed into the housing, so the terminal is hidden by the extra length or the screw part cuts into the extra length when the cover is screwed into the housing. There is a problem that the extra length portion is sandwiched between the terminal and the meter, but conventionally, no countermeasure has been taken. Usually, when a user lays a cable, the above-mentioned problem occurs because the cable is cut and connected long.

The present invention has been made in order to solve the above-mentioned problems of the prior art. The object of the present invention is to make it possible to reduce the size and weight while satisfying the explosion-proof requirement, and to store the cable well. The present invention provides a field instrument that enables adjustment work while observing the display contents of the meter when performing adjustment work such as zero adjustment and span adjustment.

[0007]

In order to achieve the above object, the present invention provides a housing integrally provided in the instrument main body having a terminal connection opening portion on the front surface, and a front end projecting forward in the center of the front surface. A terminal block integrally having a cylindrical meter accommodating portion with an opening provided on the surface and fixed in the housing, and a terminal provided on the front surface of the terminal block to which a cable for connecting to an external device is attached And a meter incorporated in the meter accommodating portion of the terminal block, and a cover for closing the terminal connection opening of the housing, the meter having a window whose display is visible from the outside. Characterize. Further, the present invention is characterized in that at least a part of the periphery of the meter storage portion is used as a cable storage space.

According to the present invention, since the meter is arranged in the meter accommodating portion of the terminal block and the terminals are arranged around the terminal block, the meter does not serve as a shield against the terminals and satisfies the explosion proof standard. However, the meter and the terminal can be housed in one housing. The space between the meter housing portion and the inner peripheral surface of the housing forms a cable housing space.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in detail based on an embodiment shown in the drawings. 1 is a partially cutaway side view showing an embodiment in which the present invention is applied to a differential pressure / pressure transmitter, FIG. 2 is a front view of a housing, and FIG. 3 is a cross-section of the housing showing the inside with a cover removed. It is a figure. In addition, the same components as those described in the section of the prior art are denoted by the same reference numerals, and the description thereof will be appropriately omitted. In these figures, the differential pressure / pressure transmitter 1 includes a body 2 and a housing 20 integrally provided on a neck 2a of the body 2.

The housing 20 is formed into a cylindrical body whose front and rear surfaces are open, and its front end side opening portion forms a terminal connection opening portion 22 for connecting the cable 7 to the terminal 6. The terminal connection opening 22 is airtightly closed by the cover 23 being screwed through the O-ring 24. The cover 23 has an opening 23a that is hermetically covered with the transparent glass 14.
The window is formed to allow the user to see. On the other hand, the rear end side opening 25 of the housing 20 has an O
It is screwed through a ring 26 and fixed by a plurality of bolts 27. The housing 20
On the side surface of the housing 20, two insertion holes 11 into which the cable 7 for signal transmission and power supply with an external device is inserted are arranged vertically and point-symmetrically with respect to the center of the housing 20. Is formed in. The terminal block 5 is fixed inside the housing 20 by a plurality of setscrews 28. The terminal block 5 is integrally formed of an insulating material such as synthetic resin, and a main body 5A having a plurality of terminals 6 is provided,
The main body 5A comprises a cylindrical meter accommodating portion 5B which is integrally provided so as to project toward the front at the center of the front surface. It is fixed to the part 30. The terminals 6 are located so as to be located above and below the meter storage portion 5B.
Two of them are provided in the upper and lower parts of A, and their rear ends extend to the rear of the terminal block 5 and are connected to the electric circuit of the printed circuit board 31. The printed circuit board 31 is fixed to the rear opening of the terminal block 5. The meter storage portion 5B is formed in a horizontally long cylindrical body, and has an opening 33 on the front surface thereof.
A meter 12 is arranged in the meter housing portion 5B so as to cover 3. The printed circuit board 34 of the meter 12 and the printed circuit board 31 are electrically connected by a lead wire 35. The two insertion holes 11 are formed so that their axes are substantially parallel to the longitudinal direction of the meter storage portion 5B.

The cable 7 is inserted into the housing 20 through each of the insertion holes 11, and the connection terminal 8 fixed to the insertion end is connected to each of the terminals 6 by a set screw 9. On the front side of the terminal block 5, the meter storage section 5B
An appropriate space is formed between the inner peripheral surface of the housing 20 and the inner peripheral surface of the housing 20, and this space forms a storage space 40 for storing the extra length portion 7A of the cable 7.

In the differential pressure / pressure transmitter 1 having such a structure, the meter 12 is arranged in the center of the inside of the housing 20, and the terminals 6 are arranged behind the meter 12 and above and below it. Therefore, the meter 12 does not become an obstacle to the terminal 6 and can be used as a differential pressure / pressure transmitter that satisfies the explosion-proof regulations. Further, since the meter 12 is arranged in the housing 20, connection of the cable 7,
Even if the cover 23 is removed during adjustment work such as zero adjustment and span adjustment, the meter 12 does not come out together with the cover 23, and the adjustment work can be performed while observing the display contents of the meter 12.

Since the space around the meter storage portion 5B is used as the storage space 40 for the cable 7, the housing 20
The inside of the cable can be effectively used, and particularly when the extra length portion 7A is too long, the cable 7 can be stored by winding it around the meter storage portion 5B. Further, as shown in FIG. 3, two insertion holes 11 are formed vertically and in point symmetry with the center of the housing 20 in between, and the upper insertion hole 1 is formed.
The cable 7 inserted from 1 is curved clockwise along the inner peripheral surface of the housing 20 and connected to the lower terminal 6,
When the cable 7 inserted from the lower insertion hole 11 is also curved clockwise along the inner peripheral surface of the housing 20 and connected to the upper terminal 6, an external force in the axial direction is applied to the cable 7. However, since it is caught on the corner of the meter storage portion 5B, a large stress is not applied to the terminal connection portion, and the disconnection of the cable 7 at the connection portion can be prevented.

FIG. 4 is a partially cutaway front view showing a housing according to another embodiment of the present invention. In this embodiment, the left and right insertion holes 11 are formed at symmetrical positions on both sides of the housing 20, and their axes are aligned with each other so as to pass through the center of the housing 20. Among them, the convex portions 45 are respectively provided at the two corner portions located on one of the diagonals so as to have a substantially rhombic shape in a front view. Other configurations are the same as those of the above-described embodiment.

In such a structure, the gap between the convex portion 45 of the meter housing portion 5B and the inner peripheral surface of the housing 20 is smaller than the gap between the corner portion where the convex portion is not formed and the housing. Since it is difficult to route the cable 7, erroneous connection to the terminal of the cable 7 can be reliably prevented.

Although the present invention has been described with reference to an example of a differential pressure / pressure transmitter as a field type instrument, the present invention is not limited to this and can be applied to an electromagnetic flow meter or the like.

[0017]

As described above, the field instrument according to the present invention has a housing integrally provided on the instrument main body with an opening for terminal connection on the front surface, and a front end projecting in the center of the front surface. A terminal block fixed in the housing, which integrally has a cylindrical meter accommodating portion provided with an opening in the surface,
It has a terminal provided on the front surface of this terminal block to which a cable for connecting to an external device is attached, a meter incorporated in the meter housing part of the terminal block, and a window part on which the display of this meter can be visually recognized from the outside. Since it is configured with a cover that closes the terminal connection opening of the housing, the meter does not become an obstacle to the terminal, and it is possible to achieve size reduction, weight reduction, and cost reduction while satisfying explosion-proof requirements.
Further, even if the cover is removed, the meter does not go out together with the cover, so that the adjustment work can be performed while observing the display contents of the meter during the adjustment work such as zero adjustment and span adjustment. Furthermore, since at least a part of the periphery of the meter storage portion is used as a cable storage space, the cable can be stored easily.

[Brief description of the drawings]

FIG. 1 is a partially cutaway side view showing an embodiment in which the present invention is applied to a differential pressure / pressure transmitter.

FIG. 2 is a cross-sectional view with a cover of a housing removed.

FIG. 3 is a front view of the housing with a cover removed.

FIG. 4 is a partially cutaway front view showing a housing according to another embodiment of the present invention.

FIG. 5 is a partially cutaway plan view showing a conventional example of a differential pressure / pressure transmitter.

FIG. 6 is a front view with the lid of the transmitter removed.

[Explanation of symbols]

1 ... Differential pressure / pressure transmitter, 2 ... Body body (instrument body),
3 ... Electrical equipment case, 4 ... Meter case, 5 ... Terminal block,
5A ... Main body, 5B ... Meter housing, 6 ... Terminal, 7 ... Cable, 8 ... Connection terminal, 11 ... Insertion hole, 12 ... Meter, 1
4 ... Transparent glass, 20 ... Housing, 22 ... Terminal connection opening, 23 ... Cover, 33 ... Opening, 40 ... Storage space.

Claims (2)

[Claims] 1. A housing having an opening for connecting terminals on the front surface and integrally provided in the instrument main body, and a cylindrical meter accommodating portion having a front end projecting forward and having an opening at the front end surface thereof. A terminal block that is integrally fixed in the housing, a terminal that is provided on the front surface of the terminal block and to which a cable for connecting to an external device is attached, and a meter incorporated in the meter storage portion of the terminal block. And a cover for closing the terminal connection opening of the housing, which has a window through which the display of the meter is visible from the outside. 2. The on-site instrument according to claim 1, wherein at least a part of the periphery of the meter accommodating portion is a cable accommodating space.