JPH07117462B2 - Beam-type load cell flameproof structure - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a pressure-resistant explosion-proof structure of a beam-type load cell in which a pressure-sensitive explosion-proof structure is formed by directly sealing a sensitive portion to which a strain gauge is attached.

[Conventional technology]

Generally, for load cells used in locations where explosive gas is handled, due to safety reasons, factors such as overheating of strain gauges and short-circuit accidents act as ignition sources, causing explosive gas explosions. The explosion-proof structure is obligatory so that the explosive force is contained in the load cell, a flame is generated outside the load cell, and the explosive gas outside does not catch fire.

And conventionally, as such a pressure-proof explosion-proof structure,
No. 5 with a gap allowed by the Industrial Safety Research Institute technical guidelines
The one shown in the figure is known.

That is, in FIG. 5, reference numeral 1 is a load cell main body, the right fixing portion 1a is fixed to the fixing base 3 with bolts 2, and the central beam portion 1b is formed with a skewer dumpling-shaped through hole 1b1 in the front-rear direction. And a plurality of strain gauges 4 are attached to the upper and lower surfaces,
The whole is covered with a thin metal bellows 5 in order to prevent intrusion of moisture, dust, etc., and the left load-bearing portion 1c is fixed to the left end with a facing member 8 described later with a screw 7a, and further facing. A load receiver 9 is fixed to the member 8 with a screw 7b.

Regarding the explosion-proof structure, a sturdy cylindrical cover 6 is fixed to the fixing portion 1a of the load cell main body 1 with screws 7c in order to withstand the explosive force, and the facing member 8 holds a gap t in the opening left end face 6a thereof. It is fixed to the load applying section 1c in a face-to-face state.

In the above configuration, when the load P is applied to the load receiver 9 during the measurement of the load, the beam portion 1b is slightly bent downward, and the facing member 8 is also rotated slightly to the left. Since t is provided, the operation is performed without hindrance (no hindrance to the measurement), the amount of bending is detected by the strain gauge 4, and the load value is displayed by a known electric circuit.

On the other hand, with regard to the pressure-proof explosion-proof means, if an explosive gas explodes due to ignition due to an accident such as heat generation of the strain gauge 4,
First, the weak bellows 5 is instantly broken, and at the same time, the explosive gas filling the space A in the tubular cover 6 is also ignited and explodes. 8 and the flame is provided with a clearance t and a clearance depth (corresponding to the wall thickness of the cylindrical cover 6 in FIG. 5) permitted by the technical guidelines of the Industrial Safety Research Institute. It is designed to prevent flame escape.

[Problems to be Solved by the Invention]

However, in the conventional explosion-proof structure shown in FIG. 5,
Since the entire structure of the beam portion (1b) including the bellows 5 where the strain gauge 4 is sealed must be covered, the structure of the cylindrical cover 6 is inevitably large, and the internal volume (A) is large accordingly. Then, since the explosive gas contained therein has a large explosive force, in order to withstand the explosive force, not only the thickness of the tubular cover 6 is necessarily increased, but also a guideline is provided so that flame escape does not occur. Since it is necessary to provide a depth of the gap defined by the numerical value, the thickness of the tubular cover 6 becomes large, the entire structure including the tubular cover 6 and the facing member 8 becomes large, and the load cell is not used. In addition to the restrictions, a bellows 5 sealed with a cylindrical cover 6
Since it was covered with, there was a problem that it became complicated in terms of manufacturing.

[Means for Solving the Problems]

Therefore, the present invention is directed to the beam unit 12 of the beam type load cell 10.
As a structure in which holes 12c are formed at right angles to the surfaces 12a and 12b of the flat strain element, a strain gauge 20 is attached to the inner peripheral surface 12d of the hole 12c, and the surface 12a has substantially the same inner diameter as the hole 12c. , A pair of circular members 14 and 15 respectively extending outward from 12b are provided in series, and the bases thereof are made relatively thin, and both ends of the circular members 14 and 15 are formed as thick structures suitable for welding. Part sealed (4
0, 41) to obtain a closed container for explosion-proof.

[Action]

Even if there is an explosion of explosive gas due to heat generation of the strain gauge 20, the strain gauge 20 attached to the beam section 12 is a pressure-proof explosion-proof sealed container (12, 14, 15, 40, 41). Since it is sealed, it not only withstands the explosive force, but also the flame generated there does not go out.

In addition, since the base of the cylindrical member 14 is thin, it does not adversely affect the straining action of the beam portion 12, and conversely, since both ends are thick, welding work is easy to perform.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. In the figure, reference numeral 10 denotes a beam type load cell body, which includes a fixing portion 11, a beam portion 12, a load applying portion 13, and a pair of cylindrical members 14 and 15, which are integrally configured.

Then, the fixed portion 11 has the cut surfaces 11a and 11b vertically except for both ends.
Are formed, and a plurality of attachment holes 11c for fixing are provided on the surface, and are fixed to a fixing base (not shown) with bolts.

The beam 12 is formed by forming a hole 12c at a right angle with respect to the surfaces 12a and 12b of the flexure element having a substantially flat plate shape (see FIG. 3).
A plurality of strain gauges 20 are provided on the inner peripheral surface 12d surrounded by the dotted line of the hole 12c.
(See FIGS. 1 and 4) is attached in place, and the lead wire (not shown) of the strain gauge 20 is attached to the insertion pin 30 at the right end (see FIGS. 2 and 3) from the insertion hole (not shown). It is supposed to be connected.

The load applying section 13 is provided with a hole 13a for connecting a load, and the load application point coincides with the center of the hole 13a.

As can be seen from FIGS. 1 and 4, the cylindrical members 14 and 15 have the same inner diameter as the hole 12c formed in the beam portion 12 except for a part, and are formed by continuous cylinders. Ten
It is manufactured together with the beam part 12 by cutting the annular grooves 16 and 17 by machining, but within the range that does not adversely affect the measurement operation (distortion operation) of the beam part 12 and also withstands explosion-proof. The thickness of the base is as thin as possible, and both ends are thickened to facilitate welding. Here, the convex base portion that extends inward from the fixed portion 11 and the load applying portion 13
11d and 13b are formed when the annular grooves 16 and 17 are cut, and are used to attach a protective cover (not shown) that protects a sealed container portion described later.

Both ends of the cylindrical members 14 and 15 are provided with lids for sealing the end faces.
40 and 41 are fitted to each other, and convex ring-shaped frames 14a and 40a (third part)
(See the figure), and 15a and 41a are welded in close contact to form a closed container for explosion-proof. Here, the annular step portions 14b and 15b (see FIG. 4) are for determining the fitting position of the lids 40 and 41. In addition, at the time of sealing, an inert gas is filled in for the purpose of protecting the strain gauge 20 if necessary.

In such a configuration, when the load P is applied at the time of measurement, the beam portion 12 bends, and the amount of the deflection is detected by the plurality of strain gauges 20 attached to the inner peripheral surface 12d and measured by a known method. Although the value is displayed, since the bases of the cylindrical members 14 and 15 are thin, the output characteristics are not adversely affected.

Regarding the pressure-proof explosion-proof, when an explosive gas explodes due to the heat generation of the strain gauge 20, etc., the pair of cylindrical members 14 and 15 around the beam portion 12 and the thick end portions thereof are welded. The explosion-proof closed container composed of the end face sealing lids 40 and 41 that seals the strain gauge 20 suppresses the explosive force inside the container and also the flame generated inside. There is no need to worry about leaking outside.

In the above example, the cylindrical members 14 and 15 which are integrally formed with the load cell main body 10 are respectively covered with the lid 4 for end face sealing.
Although the structure of sealing with 0, 41 has been described, the cylindrical members 14, 1
It is also possible to prefabricate a cup-shaped bottomed cylinder with the respective lids 40 and 41 corresponding to 5 and to weld it to the beam 12 later. Furthermore, the axial lengths of the cylindrical members 14 and 15 do not necessarily have to be the same.

〔The invention's effect〕

The present invention uses a cylindrical member extending from the beam portion of the strain gauge attached to the beam portion of the beam type load cell, and at a position distant from the strain gauge, it has a thick wall not directly related to the beam portion. Since sealing welding can be performed at both ends, it has an explosion-proof structure and does not adversely affect output characteristics.
Further, the closed container can be made compact, and the overall structure becomes relatively small, so that not only the number of places where the beam type load cell is used increases but also the flame does not leak to the outside because of the closed container.

[Brief description of drawings]

FIG. 1 is a partially developed perspective view showing an embodiment of a beam type load cell according to the present invention, FIG. 2 is a front view of the same embodiment, and FIG.
The figure is also a plan view, FIG. 4 is a partially enlarged perspective view seen from the line BB, and FIG. 5 is a schematic explanatory view showing a conventional example. 1 ... Load cell body, 4 ... Strain gauge, 5 ... Bellows, 6 ... Cylindrical cover, 8 ... Opposing member, 9 ... Load receiving, 10 ... Beam type load cell body, 11 ... Fixed part, 12
...... Beam part, 12a, 12b ...... Surface, 12c ...... Hole, 12d ...... Inner peripheral surface, 13 ...... Load part, 14, 15 ...... Cylindrical member, 16, 17
…… Annular groove, 20 …… Strain gauge, 30 …… Insert pin, 40, 41
...... End sealing lid, A ... space, P ... load.

Claims (1)

[Claims] 1. A beam portion 12 of a beam type load cell 10 is formed by forming a circular hole (12c) at right angles to surfaces 12a and 12b of a substantially flat plate-shaped strain generating body, and the hole (12c) is formed. 12c) inner surface 12
A strain gauge 20 is attached at a proper position of d, and a pair of cylindrical members 14 and 15 which have substantially the same inner diameter as the hole (12c) and extend outward from the surfaces 12a and 12b centering on the hole (12c), respectively. Beams characterized in that the bases of the cylindrical members 14 and 15 are thin, the outer ends of each are thick, and the outer ends are sealed (40, 41). Explosion-proof structure of type load cell.