JPH0221733B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a load cell mainly used in a scale, and is intended to improve the durability of the load cell without reducing its accuracy.

This type of load cell is configured to electrically detect the amount of strain in a strain-generating body corresponding to an applied load using a strain gauge attached to the strain-generating body. In the case of load cells for weighing scales, which are often used in humid environments, it is necessary to protect the strain gauges from water and humidity in order to obtain the required durability.
Therefore, in the past, moisture-proofing treatments such as coating strain gauges with silicone rubber or the like or sealing them with metal foil have been performed.

However, with these moisture-proof treatments, the covering material such as silicone rubber or metal foil is directly adhered to the strain gauge, so the expansion and contraction of the strain gauge due to the deformation of the strain body is restricted by the covering material. This causes a problem in that the linearity of the load-electrical output characteristics of the load cell is impaired.

The present invention addresses the above-mentioned problems in a load cell in which a strain gauge is attached to a flexure element, and the strain gauge is subjected to moisture-proof treatment so as not to impede the function of the strain gauge.
It is an object of the present invention to improve the durability of a load cell without reducing its accuracy.

That is, in the load cell according to the present invention, a Teflon sheet that is chemically resistant to scratching is non-adhesively covered over a strain gauge attached to a strain-generating body, and an appropriate covering material is coated on top of the Teflon sheet. It is characterized by having a configuration in which: According to such a configuration, the expansion and contraction of the soot rain gauge is not hindered by the covering material, and the covering material protects the strain gauge from water and humidity, thereby achieving the above object.

Hereinafter, the present invention will be explained based on embodiments shown in the drawings.

In Fig. 1, reference numeral 1 denotes a load cell installed via brackets C and D between a scale body A and a weighing pan B provided on its upper part. The strain body 2 has a fixed rigid body part 3 at one end fixed to the scale body A via the bracket C, and a movable rigid body part 4 at the other end to which the weighing pan B is fixed via the bracket D. An upper beam section 5 and a lower beam section 6 provided between the upper and lower ends of both rigid body sections 3 and 4 form a hollow quadrilateral shape. Then, the upper beam part 5
And the lower beam part 6 has semicircular notches 5a,
Flexible parts 5b, 6b whose wall thickness is reduced by 6a
are formed at two locations each, and strain gauges 7 . . . 7 are respectively attached to the surface of each flexible portion.

As shown in FIGS. 3 and 4, each strain gauge 7 is covered with a Teflon sheet 8, and a coating of silicone rubber, butyl rubber, polyurethane, etc. is placed over the Teflon sheet to completely cover the Teflon sheet. The material 9 is coated by coating or dipping. Here, the Teflon sheet 8 is simply placed on each strain gauge 7 in a non-adhesive manner, that is, it is simply placed on the strain gauge without using an adhesive or the like.
It is fixed to the surface of the strain-generating body 2 by a coating material 9 coated thereon.

According to the above configuration, each flexible portion 5 of the strain body 2
Strain gauge 7 affixed to the surface of b, 6b
... 7 are protected from water and humidity by the covering material 9. In this case, a Teflon sheet 8 is provided between each strain gauge 7 and the covering material 9.
are interposed non-adhesively to the strain gauges, so that each strain gauge 7 is joined only to the strain body 2.

Therefore, when an object to be weighed is placed on the weighing pan B shown in FIG. When the surface of each flexible portion 5b, 6b is expanded or contracted, each of the strain gauges 7...7 attached to the surface of the flexible portion is not constrained by the covering material 9, and the surface of the flexible portion is It will expand and contract faithfully following the expansion and contraction of . This results in
The amount of strain in the strain body 2, ie, the weight of the object to be measured, is detected with high precision as an electrical output from the strain gauge.

Next, other embodiments of the present invention shown in FIGS. 5 to 7 will be described. In addition, in the following examples,
"Aluminium-deposited tape" refers to a material in which an aluminum-deposited film is provided on one side of a base material, and an adhesive is further coated on the other side or on the aluminum-deposited film in advance; "aluminum-deposited film" refers to Refers to one with an aluminum vapor-deposited film on one side.

The embodiment shown in FIG. 5 uses an aluminum vapor-deposited tape 9' as a covering material instead of the silicone rubber coating in the above embodiment.
This aluminum vapor-deposited tape 9' is made by providing an aluminum vapor-deposited film 9b' on one surface of a base material 9a' made of polyester or the like, and further coated with an acrylic adhesive 9c' in advance. In this embodiment, a Teflon sheet 8 is non-adhesively placed on each strain gauge 7 attached to the surface of the flexible part of the strain body 2, and then the aluminum vapor-deposited tape 9' is applied from above. It is pasted. Incidentally, instead of the aluminum vapor-deposited tape 9', an aluminum vapor-deposited film 9 is provided on one surface of the base material 9a'.
b′, and then adhesive 9 on top of this aluminum vapor-deposited film.
An aluminum vapor-deposited tape coated with c' in advance may also be used.

Further, the embodiment shown in FIG. 6 uses an aluminum vapor-deposited film 9'' as a covering material. This aluminum vapor-deposited film 9'' has an aluminum vapor-deposited film 9b'' provided on one surface of a base material 9a''. Then, after applying the adhesive 10 to the upper surface and the surrounding area of the Teflon sheet 8 that was non-adhesively placed on the strain gauge 7,
The aluminum vapor-deposited film 9'' is attached.

Furthermore, in the embodiment shown in FIG. 7, aluminum foil 9 is used as the covering material, and the aluminum foil 9
is attached to cover the Teflon sheet 8 placed over the strain gauge 7 using an adhesive 10 as in the embodiment shown in FIG.

In each of the embodiments shown in FIGS. 5 to 7, the aluminum vapor deposited films 9b', 9b'' or the aluminum foil 9 protect the strain gauge 7 from water and moisture.
In these embodiments as well, the strain gauge 7 and the covering material 9',
Since the Teflon sheet 8 is interposed between the strain gauges 9'' and 9, the strain gauge can accurately follow the deformation of the strain body.

As described above, the present invention provides a load cell in which a strain gauge is attached to a flexible portion provided on a strain-generating body. Since the strain gauge is coated with a coating material, the strain gauge is protected from water and moisture without being restricted by the coating material from expanding and contracting due to deformation of the strain-generating body. As a result, a load cell with excellent durability and high weighing accuracy can be realized as a load cell for a scale that is often used in an environment with a lot of moisture or humidity.

[Brief explanation of drawings]

Fig. 1 is a front view showing the load cell of the present invention in use, Fig. 2 is a front view showing the first embodiment of the load cell of the present invention, and Figs. 3 and 4 are a perspective view and an enlarged view of the main parts of the embodiment. The sectional view and FIGS. 5, 6, and 7 are perspective views of essential parts showing second, third, and fourth embodiments of the present invention, respectively. 1... Load cell, 2... Strain body, 5b, 6b
... Flexible part, 7 ... Strain gauge, 8 ... Teflon sheet, 9, 9', 9'', 9 ... Covering material.

Claims (1)

[Claims] 1 A load cell in which a strain gauge is attached to a flexible part provided on a strain-generating body, and the strain gauge is appropriately attached to a covering material through a Teflon sheet that is non-adhesively placed thereon. A load cell characterized by being covered with a twist.