JPH01302124A - Load cell - Google Patents

Abstract

PURPOSE:To easily adjust four corners in order to accurately measure load, by connecting the upper arm of a check link and a fixing part by a differential screw. CONSTITUTION:Two check links 19, 20 are integrated on the leading end sides thereof to form a movable piece 22 and have a wide fixing part 23 in common on the base end sides thereof. A beam body 21 is arranged between the links 19, 20 to be mounted to the fixing part 23, and the load transmitting part 24 provided to the movable piece 22 so as to protrude therefrom and the movable part 26 of the beam body 21 are connected by a shaft 28. Four strain gauges 17 are formed to the thin strain generating part 27 of the beam body 21 and the base ends 30, 38 of the upper arms 29, 37 of the links 19, 20 are connected to the fixing part 23 by differential screws 35, 39. A receiving tray not shown in a drawing is mounted to the movable piece 22 and a load cell 18 is used as a weighing balance. The differential screws 35, 39 are regulated so that a weighing result becomes equal even when eccentric load is generated with respect to the load applying point of the beam body 21.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a load cell using a check-linked donkey pal mechanism.

BACKGROUND OF THE INVENTION First, a conventional example of this type of load cell will be described with reference to FIGS. 5 and 6. This load cell 1 consists of a check link 2 and a beam body 3 protruding therein. First, in this check link 2, for example, two parallel flat arms 4 and 5 correspond to the upper and lower sides of a rectangle, and a prismatic movable piece 6 corresponds to the left side, and a prismatic part fixed to a base B. The fixing portion 7 is formed in a frame shape corresponding to the right side. Here, the arms 4 and 5 each have two thin cutouts 8 to 11 each having a circular groove cut out on the inner surface. On the other hand, the bead 71 body 3 is attached below the fixed part 7 in parallel with the arms 4 and 5, and similarly, a prismatic load transmitting part 12 is integrally formed above the movable piece 6. It is formed. Here, this beam body 3 is provided with an irregularly shaped hole 13, which communicates two circular holes adjacent to each other, approximately in the center of the beam body 3. In other words, this portion serves as a thin strain-generating portion 14 that operates as a donkey pal mechanism. Further, a stepped portion 15 is formed at the tip of the beam body 3, and a shaft 16 erected from the load transmitting portion 12 is attached thereto, thereby connecting the movable piece 6 to the beam body 3. There is. Here, two strain gauges 17 are attached to each of the upper and lower surfaces of the thin strain-generating portion 14 . These strain gauges 17 are connected to a detector (not shown), and constitute a Wheatstone bridge circuit (not shown) together with various compensation circuits (not shown) that correct bridge balance, temperature characteristics, etc. .

In such a configuration, for example, a saucer (not shown) is attached to the movable piece 6 and a load is applied thereto.

At this time, the movable piece 6 moves downward in parallel as the thin cutouts 8 to 11 bend extremely minutely.

At the same time, the load transmitting part 12 presses the step part 15 of the beam body 3 via the shaft 16, and the thin strain-generating part 14 of the beam body 3 is deformed. At this time, this thin strain-generating portion 14
The degree of deformation is proportional to the load applied to the movable piece 6. On the other hand, the strain gauge 17 attached to the thin-walled strain-generating portion 14 is an element whose electrical resistance varies in proportion to the amount of strain, and these are connected as a Wheatstone bridge circuit. It is possible to obtain an amount of electricity proportional to the degree of deformation. In other words, fl! The load will be measured visually.

When such a load cell 1 is used as a weighing scale, high accuracy is required. Therefore, various extremely strict adjustment operations are required at the time of product shipment, and one of these adjustment operations is four-corner adjustment. This means that the measurement results of unbalanced loads applied at positions equidistant in the longitudinal direction of the beam body 3 and at equal positions in the left-right direction from the load application point at the tip of the beam body 3 are consistent. It is something that makes you

Such four-corner adjustment is performed, for example, as shown in Figure 6.
This is done by cutting the right or left side of the thin cutout 9. In other words, measure the weighing error of load cell 1,
Depending on the result, use a file, router, etc. to cut the left and right sides or the entire surface of the predetermined thin-walled notches 8 to 11, and use the needle xk again.
Measure the error. In this way, by repeatedly performing cutting and measuring the weighing error, the adjustment of the four corners of the load cell 1 is completed.

Problems to be Solved by the Invention The load cell 1 as described above is effective in being able to measure even minute loads. However, the above-mentioned four-corner adjustment requires repeated extremely delicate cutting and strict error measurement, which is difficult and time-consuming, and is dependent on the intuition of the operator.

Furthermore, it is impossible to restore the part that has been shaved off by -degree, and therefore, if cutting is repeated during rA adjustment, the strength of the check link 2 may decrease and the durability of the load cell 1 may become insufficient.

Means for Solving the Problems A check link formed in a parallelogram shape by a movable piece, at least two parallel arms, and a fixed part located at the base end of these arms is provided, and has a strain-generating part. The movable part of the check link is connected to the movable piece of the beam body with one end fixed, and a flexible part is formed between the base end of the arm located at the top of the check link and the fixed part, and the base of the arm facing each other is connected to the movable part of the check link. The end and the fixed part were connected with a differential screw.

A flexible part is formed between the base end of the arm located at the top of the action check link and the fixed part, and the base ends of the arms facing each other and the fixed part are connected with a differential screw, so that the arm and the fixed part You can subtly and freely change the distance between
The four corners rAm of the load cell can be performed without cutting the thin notch.

Embodiment An embodiment of the present invention will be explained based on FIGS. 1 and 4. Note that the same parts as in the prior art example described above are given the same names and symbols, and explanations thereof will be omitted. First, the load cell 18 of this embodiment consists of two check links 19 and 20 and a prismatic beam body 21 provided at the center thereof. Here, these two check links 19 and 20 are integrated at their distal ends to form a movable piece 22, and their proximal ends share a wide fixed portion 23 and are formed, for example, in the shape of a triangular prism. . On the other hand, the beam body 21 is disposed at the center of the check link 19, 20 and is mounted on the fixed part 23, facing the load transmitting part 24 protruding below the movable piece 22. There is. Here, this beam body 21
An L-shaped irregularly shaped groove 25 is cut out from the base end to approximately the middle end.

In other words, the movable portion 2 extends from the distal end toward the proximal end.
Further, the top of the irregularly shaped groove 25 becomes a thin strain generating part 27, and four strain gauges 17 are formed by thin film technology or the like. Moreover, the movable part 26
is connected to the movable piece 22 via the load transmitting portion 24 and a shaft 28 erected thereon. Further, between the base end 30 of the arm 29 corresponding to the upper side of the check link 19 and the fixed part 23, a circular groove 31 is dug in the horizontal direction to form a thin flexible part 32.

Here, the base end 30 and the fixed part 23, which face each other with the thin flexible part 32 interposed therebetween, each have screw holes 33.3 with a pitch of 0.75 m++ and 0.70 nwm, respectively.
4 is formed. Then, a differential screw 35 of the same pitch is screwed in here, and the base end 3o of the arm 29 and the fixing portion 23 are coupled. In addition, this differential screw 3
Two flexible portions 36 are formed near the center of 5. These flexible portions 36 bend in the width direction, but have high strength in the length direction, and their lengths do not change due to, for example, loads during weighing, stress due to various adjustments, etc. That is, by rotating the differential screw 35 once, the interval between the thin flexible portions 32 changes by 0.05 m. Incidentally, such screwing of the differential screw 35 is performed while the base end 30 is pressed toward the fixed portion 23 and the thin flexible portion 32 is deformed. This is done to compensate for the gap between the thin flexible portions 32 being expanded when the differential screw 35 is screwed in. By being screwed in, it returns to its normal value.

Further, the base end 38 of the right arm 37 has a similar structure, and is connected to the fixed portion 23 by a differential screw 39.

In such a configuration, the measurement results at positions equidistant in the longitudinal direction of the beam body 21 and equal in the left-right direction are made to coincide with each other, centering on the load application point of the beam body 21,
Four corners: A alignment is performed. Here, this load cell 18
Since it is composed of two integrated check links 19 and 20, when a load is applied to the movable piece 22, it is necessary that the left and right check links 19 and 20 deform equally. However, due to non-uniformity of the material.

If the amount of deformation of the parallelograms of the left and right check links 19.20 is different, the heights of the left and right base ends 30.38 can be adjusted separately by changing the screwing amount of the differential screws 35, 39 on the left and right sides. Displace it to. As a result, the left and right arms 29.
Tensions of different magnitudes are applied to 36, and adjustments are made so that the left and right check links 19, 20 deform equally in response to the load. Furthermore, the longitudinal adjustment of the beam body 21 can be performed using the left and right differential screws 35 in substantially the same way as the left and right adjustments.
．． 39 by the same amount in the same direction. In this manner, the four-corner adjustment is easily completed by performing the front, rear, left, and right adjustments. Further, as shown in FIG. 3, for example, when the differential screw 35 is tightened, the axes of the screw hole 33 of the base end 30 and the screw hole 34 of the fixing part 23 may be misaligned. This generates torsional stress in the check links 19, 20, etc., making measurement by the load cell 18 inaccurate. However, since the flexible portion 36 is formed on the differential screw 35, the deviation is absorbed by the flexible portion 36, and the performance of the load cell 18 is stabilized without adversely affecting the check links 19, 20, etc. . In addition, when an unbalanced load shifted to the left or right is applied to the movable piece 22, the arm 29.37 etc. can be biased in the horizontal direction by tightening the differential screw 35.39, so the check link 19 It can prevent twisting that tends to occur with .20. Furthermore, at these times, the differential screw 35 can be rotated smoothly. It goes without saying that the other differential screw 39 also performs a similar operation.

As mentioned above, this load cell 18 uses differential screws 35 and 39 having flexible portions 36 at two locations; however, the present invention is not limited to this; for example, as shown in FIG. This does not preclude the use of a general differential screw 40 such as this.

Further, although this load cell 18 is constructed from two check links 19 and 20 integrated in a 7-shape, the present invention is not limited to this. For example,
In a load cell (not shown) consisting of - check links, such as the conventional example shown in Fig. 5, a flexible part is provided at the base end of the upper arm, and two differential screws are screwed into it. It is also possible to think of things that have happened.

Effects of the Invention In the present invention, a flexible part is formed between the base end of the arm located at the upper part of the check link and the fixed part, and the base ends of the arms facing each other and the fixed part are connected with a differential screw. This allows the distance between the arm and the fixed part to be subtly and freely changed, making it easy to adjust the four corners, and this adjustment does not require cutting the fillet notch. Since the strength of the check link does not decrease, it is possible to obtain a load cell with excellent durability, and the four-corner adjustment work is simple and does not require the operator's intuition, so the adjustment work can be completed with high precision in a short time. It has the effect that it can be done.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2 is a perspective view of a differential screw, Fig. 3 is a longitudinal side view, Fig. 4 is a perspective view of another differential screw, and Fig. 5. 6 is a perspective view of a conventional example, and FIG. 6 is an explanatory diagram of adjustment work. 18...Load cell, 19.20...Check link, 21...Beam body, 22...Movable piece, 23...
・Fixed part, 26... Movable part, 27... Strain part, 29
···arm. 30... Base end, 32... Flexible part, 35... Differential screw, 36... Flexible part, 37... Arm, 38...
Base end, 39°40...Differential screw 3"

Claims (1)

[Claims] 1. A check link formed in a parallelogram shape by a movable piece, at least two parallel arms, and a fixed part located at the base end of these arms is provided, and has a strain-generating part. A movable piece of the check link is connected to a movable part of a beam body with one end fixed, and a flexible part is formed between the base end of the arm located at the upper part of the check link and the fixed part,
A load cell characterized in that the mutually opposing base ends of the arms and the fixing part are coupled with a differential screw. 2. The load cell according to claim 1, wherein the differential screw is formed with a flexible portion having high strength in the longitudinal direction.