JPH0230743Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Field of Application) The present invention relates to a load cell, and more particularly, to improvements in the moisture-proof and waterproof structure of the load cell.

(Prior Art and its Problems) Generally, a load cell has a structure in which a thin wall portion is formed on a horizontal beam spaced apart above and below a square-shaped strain-generating body, and a strain gauge is arranged in the thin wall portion.

A conventional waterproof structure for such load cells has been to surround the entire load cell with a frame, but this has a complicated structure and is difficult to assemble, making it difficult to assemble, and since the load cell is sealed, the load cell characteristics change due to changes in atmospheric pressure. I had a problem. In addition, as a waterproof structure that partially covers the load cell, as described in Japanese Utility Model Application Publication No. 57-201909, a narrow fence-like part made of a gum-like substance surrounds a strain gauge placed on a strain-generating body. However, a structure in which the hedge-like part and the inside are covered with a protective layer is known. However, the above conventional structure has the following problems.

The lead wires of the strain gauge must be drawn out from the wall, and gaps and pinholes are likely to form at the interface between the lead wires and the wall, easily allowing moisture and water to enter.

Once moisture or moisture has entered, it is difficult to escape due to the structure, which can lead to insulation failure of the strain gauge or deterioration of the strain gauge.

Further, the work of bringing the interface between the lead wire and the fence into close contact with each other without any gaps is difficult, and the workability is poor, and even then, as mentioned above, the yield rate is low.

Although only a moisture-proof and waterproof structure for only the strain gauge portion is disclosed, if the structure does not include wiring portions, terminal portions, etc., poor insulation will occur at these portions, and this is not necessarily sufficient.

Most of the load cells currently in use use a strain element made of duralumin, but duralumin is susceptible to corrosion, and even if only the strain gauge part could be made completely moisture-proof and waterproof, the rubber of the hedge-like part As the outer strain gauge bonding surface surrounded by the material corrodes, the corrosion penetrates into the strain body gauge bonding surface that is in close contact with the hedge, and easily passes through the narrow lower part of the hedge. There is a risk that moisture and moisture may enter from the corroded areas.

The present invention was devised in view of these conventional problems, and its purpose is to provide a load cell that is highly moisture-proof and waterproof, has excellent manufacturability, and is inexpensive.

(Means for Solving the Problems) The load cell of the present invention has a through hole formed in the connecting portion or the thick portion of the flexure element, one end of which extends to the strain gauge installation surface, An input/output wire with a waterproof jacket is inserted into the through hole through the mounting port of the through hole, and its tip is wired to each strain gauge, so that the gap between the mounting port and the input/output wire is airtight. It is characterized in that it is sealed with a joint, and the surface on which the strain gauge is arranged, including the strain gauge, wiring section, and through hole, is covered with putty coated with a waterproof sheet.

(Function) According to the present invention, since an airtight joint is provided at the installation opening of the through hole through which the input/output wire is inserted, the installation opening is sealed and the moisture-proof and waterproof effects of the through hole can be ensured, and the strain gauge can be Since the surface where the strain gauge is installed, including the strain gauge, wiring section, and through hole, is covered with putty, the lead wire of the strain gauge does not have to be pulled out of the putty and routed as in conventional structures, and the strain gauge can be routed through the mounting opening. It can seal the entire area up to the gauge, increasing its moisture-proofing and waterproofing effects.

In addition, since the adhesive area between the strain gauge placement surface and the putty increases and the putty is coated with a waterproof sheet, it is difficult for moisture to pass through the putty, and the exposed portion of the strain gauge surface where the strain gauge is placed increases. As a result, corrosion on the strain-generating body surface becomes difficult to reach the strain gauge, and the adverse effects of corrosion of the strain-generating body can be eliminated.

(Embodiment) The first embodiment of the present invention will be described with reference to FIGS. 1 and 2. In the figure, 1 has horizontal beams spaced apart vertically, and a connecting portion connecting both ends of the horizontal beam. It is a rectangle-shaped strain-generating body, with thin-walled parts formed on both the upper and lower horizontal beams, and strain gauges 3 affixed to the upper and lower surfaces 2 of each thin-walled part, respectively.

A through hole 4 passing vertically is formed in one side connecting portion of the strain body 1, and a cord passage 6 is formed by opening an attachment port 5 on the side surface of the connecting portion toward the through hole 4. A waterproof cord 10, which is an input/output wire, is connected to the attachment port 5 via an airtight joint 7.

Airtight joint 7 connects mounting port 5 and waterproof cord 10
This is to seal the gap between the

Conductive wires are routed from the waterproof cord 10 through the cord passage 6 and wired to each strain gauge 3.

Next, the surface 2 to which the strain gauge 3 is attached is covered with a waterproof and moisture-proof adhesive putty 8 covered with a waterproof sheet 9. The putty is, for example, a natural rubber-based, synthetic rubber-based, or silicone-based viscoelastic body. The waterproof sheet may be ceramic coated with a metal foil coating that is impermeable to water vapor, or a rubber sheet or resin sheet that is less permeable, and is easier to work with than silicone coatings. At the same time, since it is pressed from above the waterproof sheet 9, there is almost no gap between the putty 8 and the surface 2, and even if a gap occurs, it will not break midway and will not reach the strain gauge 3 portion.

In the load cell of the above embodiment, the surface of the putty 8 is covered with a waterproof sheet 9, so that the penetration of moisture into the putty 8 is minimized, and a sufficient contact distance from the strain gauge 3 to the exposed part of the putty 8 is maintained. Because of this, moisture will not reach strain gauge 3. Furthermore, the upper and lower openings of the cord passage 6 are completely sealed with putty 8, and the lateral openings are completely sealed with an airtight joint 7, resulting in a completely waterproof and moisture-proof load cell.

In the embodiments described below, those having the same structure as those in the first embodiment are designated by the same reference numerals and the explanation thereof will be omitted.

The load cell of the second embodiment will be explained with reference to FIG. 3. The load cell of this embodiment is almost the same as the load cell of the first embodiment, but the peripheries of the putty 8' and the waterproof sheet 9' are enlarged and folded. It is more waterproof.

The load cell of the third embodiment will be explained with reference to FIG.
If the area is extremely wide, it is more economical to use the putty 8'' and the waterproof sheet 9'' to cover the strain gauge 3 and the through hole 4 with the minimum area necessary for waterproofing.

The fourth embodiment will be explained with reference to FIG. 5. The strain-generating body 1 of this embodiment has a strain gauge attachment surface 2 formed on the inner surface, and a strain gauge (not shown) is attached to the surface 2. A putty 8 and a waterproof sheet 9 are provided. The through holes 4 of this embodiment are each opened in a thick part formed between two thin parts of the upper and lower horizontal beams, and a waterproof cord 10 is connected to the outer surface of the through hole 4 through an airtight joint 7. They are provided at the top and bottom respectively.

In any of the load cells of the above embodiments, if putty is applied and then silicone coated, the space between the putty and the flexure element can be completely covered, and water penetration can be completely eliminated. Alternatively, silicon coating may be applied in advance and putty may be applied using the load cell in the above embodiment.

Silicon coatings are prone to pinholes, so if a multilayer coating is applied, it is rare for the pinhole positions in each layer to match, so airtightness can be improved. Moreover, such a silicon coating can also serve as a rust preventive treatment for the strain body.

(Effects) According to the present invention, the upper and lower opening ends of the through hole are sealed with putty, and the installation opening of the through hole is sealed with an airtight joint, so that the insertion passage for the input/output wire is completely sealed and the strain-generating body is sealed. The strain gauge installation surface, including the strain gauge and the wiring section connected thereto, is covered with putty, thereby increasing the moisture-proofing and waterproofing properties of the strain gauge and the surface of the strain-generating body in the vicinity thereof.

Since the putty is coated with a waterproof sheet, the moisture-proofing and waterproofing effects are even more complete.

Further, since the exposed portion of the surface of the strain body on which the strain gauge is arranged is reduced, even if corrosion occurs in the exposed portion of the strain body, it is difficult to reach the strain gauge, and the strain gauge can be protected.

[Brief explanation of the drawing]

FIG. 1 is a front view of the load cell of the first embodiment, FIG. 2 is a three-dimensional view of the same, FIG. 3 is a three-dimensional view of the load cell of the second embodiment, and FIG. 4 is a three-dimensional view of the load cell of the third embodiment. FIG. 5 is a three-dimensional view of the load cell of the fourth embodiment. In the figure, 1, 1'', 1... strain element, 2, 2'', 2
...Strain gauge attachment surface, 3...Strain gauge, 8,
8', 8'', 8... putty, 9, 9', 9'', 9...
... Tarpaulin.

Claims (1)

[Scope of utility model registration request] A rectangle-shaped structure in which a thin wall portion is formed near both ends of a horizontal beam spaced apart vertically, a strain gauge is arranged on a strain gauge installation surface provided in the thin wall portion, and a connecting portion is provided to connect both ends of the horizontal beam. In the strain body load cell, a through hole is bored in the connecting portion of the load cell or the thick wall portion formed between the thin wall portions of the horizontal beams, and one end of the hole extends to the strain gauge installation surface. An input/output wire having an outer sheath is inserted into the through hole through the connecting portion of the through hole or a mounting port in the thick wall portion, and its tip is wired to each strain gauge, and the input/output wire is connected to the mounting port and the input/output wire. The gap between the lines is sealed with an airtight joint, and the strain gauge, wiring section,
A load cell whose holes are covered with putty covered with a waterproof sheet.