JP2024038658A - load cell - Google Patents

Abstract

An object of the present invention is to provide a small, sealed load cell for detecting tensile and compressive loads that eliminates the influence of screws in a load acting part. [Solution] A load cell 1 in which a connecting part 2g and a strain generating part 2f are arranged in series in the axial direction, and a load in the axial direction AX is detected by a strain sensitive resistor 4 attached to the strain generating part 2f, A threaded insert 5 is embedded in at least one end of the portion 2g in the axial direction AX, and a pilot hole for tapping the threaded insert 5 is provided in the connecting portion 2g and the strain-generating portion 2f in the axial direction AX. . [Selection diagram] Figure 2

Description

The present invention relates to a load cell that measures compressive and tensile loads.

Load cells that detect tensile and compressive loads are known.

Japanese Patent Application Publication No. 2006-184153

In order to detect a tensile load in addition to a compressive load, the load cell described in Patent Document 1 has a female thread cut in the load acting section on which the load acts, and a male threaded member of the object to be measured is inserted into this female thread. used. In contrast to such load cells, there is a demand for a small, closed-type load cell with a small size. There is a problem that a bolt or the like of the object to be measured may be inserted up to the incompletely threaded portion of the female thread, and strain is generated in the incompletely threaded portion, which affects the strain-generating portion.

In view of these problems, an object of the present invention is to provide a small, hermetically sealed load cell that eliminates the influence of screws in the load application section.

In order to achieve the above object, the load cell of the present invention has the following features:
A load cell in which a connecting part and a strain-generating part are arranged in series in the axial direction, and a load in the axial direction is detected by a strain-sensitive resistor attached to the strain-generating part,
At least one end of the connection has a threaded insert embedded in the axial direction;
A prepared hole for tapping a screw insert is provided in the connecting portion and the strain-generating portion in the axial direction.

In order to achieve the above object, the load cell of the present invention has the following features:
A load cell in which a connecting part and a strain-generating part are arranged in series in the axial direction, and a load in the axial direction is detected by a strain-sensitive resistor attached to the strain-generating part,
At least one end of the connection has an internal thread arranged in the axial direction;
A hole larger than the diameter of the valley of the female thread is provided in the extending portion extending from the female thread of the connection portion to the straining portion and in the straining portion in the axial direction.

Further, it has a hollow cylindrical cover that covers at least the strain-generating portion and includes a protrusion that protrudes inward in the radial direction,
The connecting portion has a flange portion that sandwiches the strain-generating portion in the axial direction,
The flange has a circumferential groove and a recess on the outer circumferential surface, and a sealing member is fitted into the circumferential groove,
The connecting portion and the cover are configured such that the cover is inserted into the connecting portion in the axial direction and is brought into close contact with the connecting portion via the sealing member, and the protrusion of the cover is engaged with the recess to be positioned and fixed.

According to the load cell of the present invention, it is possible to provide a sealed compact load cell that eliminates the influence of screws in the load acting portion.

FIG. 1 is an external perspective view of a load cell according to a first embodiment of the present invention. FIG. 1 is an exploded perspective view of a load cell according to a first embodiment of the present invention. FIG. 1 is a sectional view of a load cell according to a first embodiment of the present invention. FIG. 3 is a sectional view of a load cell according to a second embodiment of the present invention.

Hereinafter, load cells according to each embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is a perspective configuration diagram of a load cell 1 according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view of the load cell according to the first embodiment of the present invention. The load cell 1 detects a tensile load and a compressive load applied in the axial direction AX. The load cell 1 includes a main body 2, a strain-sensitive resistor 4, a screw insert 5, a cover 30, and a seal member 32 (FIG. 2).

The main body 2 has a hexagonal portion 2a, a collar portion 2b, and a strain-generating portion 2f. The main body 2 is made by cutting a metal material such as stainless steel. The hexagonal parts 2a are parts for fixing the load cell 1 with a tool such as a spanner, and are provided on both sides of the main body 2. Two collar portions 2b are provided inside the two hexagonal portions 2a along the axial direction AX. A circumferential groove 2c is provided on the outer peripheral surface of the collar portion 2b. Further, a recessed portion 2d is provided on the outer periphery of one of the collar portions 2b. A strain-generating portion 2f having a rectangular cross section is provided so as to be sandwiched between the two collar portions 2b along the axial direction AX. The strain-generating portion 2f is hollow and thin. A strain-sensitive resistor 4 is attached to the outer surface of the strain-generating portion 2f. The strain-sensitive resistor 4 is, for example, a strain gauge in which resistor filaments in a folded pattern are laminated on a polyimide base.

Threaded inserts 5 are inserted into the ends of the two hexagonal parts 2a in the axial direction AX. The threaded insert 5 is a hollow cylindrical metal member made of stainless steel or the like, and has a male thread on its outer circumferential surface and a female thread on its inner circumferential surface. The threaded insert 5 may be formed by a coil or by cutting.

Further, a sealing member 32 is fitted into the circumferential groove 2c. The seal member 32 is, for example, a rubber O-ring.

The cover 30 has a hollow cylindrical shape, and the diameter of the inner peripheral surface is such that it can be inserted into the flange 2b along the axial direction AX with a small gap from the outer periphery of the flange 2b.

With the above configuration, the tensile load and compressive load in the axial direction AX can be measured by inserting the member to be measured into the threaded insert 5 provided in the connecting portion 2g.

FIG. 3 is a sectional view of the load cell 1 according to the first embodiment of the present invention. Along the axial direction AX, the range between the hexagonal portion 2a and the flange portion 2b is the connecting portion 2g, and the portion sandwiched between the connecting portions 2g is the strain-generating portion 2f. The connecting portion 2g is thick and has high rigidity, and is not deformed by tensile and compressive loads applied in the axial direction AX. On the other hand, the strain-generating portion 2f is thin and elastically deforms under tensile and compressive loads, and as a result, the load can be detected by the strain-sensitive resistor 4 attached to the strain-generating portion 2f.

In order to insert the screw insert 5 into the hexagonal portion 2a, first, a pilot hole 6 for a tap with a diameter D1 is formed throughout the entire axial direction AX. Next, a threaded insert female thread 2e corresponding to the external diameter of the external thread of the threaded insert 5 is formed in the tapped hole 6 by approximately the length of the threaded insert 5 using a thread cutting tool. Then, the screw insert 5 is inserted using a special tool or the like.

As a result, the bolt of the part to be measured can be inserted into the threaded insert 5 of the connecting part 2g. The bolt of the part to be measured has an outer diameter of a male thread of D2. The diameter D1 of the tapped hole 6 is larger than the bolt outer diameter D2. Therefore, even if the bolt of the part to be measured is inserted deeply beyond the range of the threaded insert 5, the bolt will not interfere with the pilot hole 6 for tapping, and the strain-generating part 2f can be prevented from being affected.

On the other hand, the hollow cylindrical cover 30 is inserted into the flange 2b along the axial direction AX with a slight gap between the outer peripheral surface of the flange 2b and the outer peripheral surface of the flange 2b. At this time, the sealing member 32 is deformed, and the cover 30 and the main body 2 can maintain airtightness of the strain-generating portion 2f sandwiched between the flange portion 2b. A strain-sensitive resistor 4 is attached to the strain-generating portion 2f, and the strain-sensitive resistor 4 is protected from the influence of external humidity. Furthermore, the protrusion 31 provided to protrude inward in the radial direction of the cover 30 engages with the recess 2d of the collar 2b, so that the cover 30 and the main body 2 are positioned in the circumferential direction and the axial direction AX. . The protrusion 31 may be provided on the cover 30 in advance, or may be formed using a press tool or the like after the cover 30 is inserted into the collar portion 2b.

FIG. 4 is a sectional view of a load cell according to a second embodiment of the invention. In the second embodiment, the threaded insert 5 is replaced with a female thread 20. That is, a female thread 20 is provided in the hexagonal portion 2a of the connecting portion 2g. In order to form this female thread 20, a tapped hole of the female thread 20 is machined to have a diameter D3. Then, based on this, a female thread 20 having a diameter D5 is tapped. Further, the extended portion 21 and the strain-generating portion 2f, including the incompletely threaded portion of the female thread 20, are enlarged to a diameter D4 by boring. Note that the diameter D4 is larger than the diameter D5. Therefore, even if the bolt of the part to be measured is inserted beyond the range of the female thread 20, the bolt will not interfere with the counterbore having the diameter D4, and the strain-generating part 2f can be prevented from being affected.

Since the load cell 1 of the first embodiment of the present invention uses the threaded insert 5, it can be applied to a load cell that is compatible with objects to be measured that have bolts of relatively small dimensions. On the other hand, since the load cell according to the second embodiment of the present invention performs boring, it is applied to a load cell having a relatively large internal thread 20.

In the described embodiment, the wiring cable pulled out from the strain-sensitive resistor 4 and the cover 30 that fixes the wiring cable are not shown, but the method of fixing the cable gland to the cover 30 and the cover 30 are not illustrated. Wiring is done by known methods, such as by making holes and passing wiring cables through them and securing them with adhesive.

Although the present invention has been described above based on the preferred embodiments, the present invention is not limited to the above-described embodiments, and various changes can be made without departing from the gist thereof.

As an example of the use of the present invention, it is possible to apply it to a load measuring device, a load sensor, etc.

1 : Load cell 2 : Main body 2a : Hexagonal part 2b : Flange part 2c : Circumferential groove 2d : Recessed part 2e : Female thread for screw insert 2f : Strain-generating part 2g : Connection part 4 : Strain-sensitive resistor 5 : Thread insert 6 : Tap Prepared hole 20 : Female thread 21 : Extension part 30 : Cover 31 : Protrusion 32 : Seal member

Claims (3)

A load cell in which a connecting portion and a strain-generating portion are arranged in series in the axial direction, and a load in the axial direction is detected by a strain-sensitive resistor attached to the strain-generating portion,
A threaded insert is embedded in at least one end of the connection portion in the axial direction,
A load cell, wherein the connecting portion and the strain-generating portion are provided with prepared holes for tapping of the screw insert in the axial direction. A load cell in which a connecting portion and a strain-generating portion are arranged in series in the axial direction, and a load in the axial direction is detected by a strain-sensitive resistor attached to the strain-generating portion,
A female thread is arranged in the axial direction at at least one end of the connection part,
A load cell, wherein an extending portion extending from the female thread of the connection portion to the strain-generating portion, and a hole larger than a diameter of a valley of the female screw are provided in the axial direction in the strain-generating portion. a hollow cylindrical cover that covers at least the strain-generating portion and includes a protrusion that protrudes inward in the radial direction;
The connecting portion has a flange portion that sandwiches the strain-generating portion in the axial direction,
The flange portion has a circumferential groove and a recess on an outer circumferential surface, and a sealing member is fitted into the circumferential groove,
The connecting portion and the cover are positioned and fixed by the cover being inserted into the connecting portion in the axial direction and brought into close contact via the sealing member, and the protrusion of the cover engaging with the recess. The load cell according to item 1 or 2.

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