JPS58120140A - Composite load cell - Google Patents

Abstract

PURPOSE:To expand the range of measurement by a constitution wherein a plurality of load cells having different range of measurement are formed concentricaly with a gap space between them. CONSTITUTION:A load X is applied from above to a cylindrical first load cell 1. The middle part of the cell 1 is formed to be slender and is made to function as a strain generating element 2, while a strain gage 3 is stuck on the peripheral surface thereof. The base of the cell 1 is joined to a second load cell 8, and a strain generating element 8' is formed in the middle part of the cell 8. The upper part of the cell 8 is joined to a third load cell 10, and a strain generating element 10' is formed in the middle part of the cell 10, while a strain gage 3' is stuck on the side surface thereof. While the load X is small, it acts on the cell 10 as a compressing force through the intermediary of the cells 1 and 8. When the load X becomes large, the base of the cell 8 touches a bottom board 12. Thereby a gap (d) turns to be zero, and thus the load X is detected by the cell 1.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a composite load cell that can accurately measure forces applied from small loads to large loads.

Conventional load measuring instruments have a predetermined load rating, and if an overload exceeding the rated load is applied, it will not only be impossible to measure, but also cause the device to be destroyed. use is mandatory. However, depending on the equipment used, an extremely wide load measurement range may be required, for example from 0 tons to 50 tons.
When measuring a load up to □, if a large load cell with a ton rating is used as the object to be measured, the resolution becomes rough when measuring a relatively small load, making accurate load measurement impossible. Therefore, it is conceivable to prepare multiple load cells with different ratings in advance and install them in parallel in the device, but it is necessary to provide a stopper mechanism to prevent the load cells from breaking when a large load is applied. However, the size of the load cell body is also very large.

The present invention provides a novel load cell that was conceived in view of the above, and aims to realize a device that has the ability to cover a wide measurement range from extremely large loads to zero loads. That is. Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a longitudinal cross-sectional view of a composite load cell according to the present invention;
9. In the figure, 1 indicates a substantially cylindrical first load cell, to which a load indicated by X is applied from above.The middle part of the first load cell is formed to be slightly thinner, and functions as a strain-generating part 2. , and a strain gauge 3 shown in FIG. 2 is pasted on its circumferential surface. As is well known, the strain gauge 3 has a metal resistance material 5 formed in a predetermined pattern on an insulating substrate 4 such as a plastic sheet as a strain sensitive part, and has a lead wire 6.6 led out from the end of the pattern. The main component is a cover coat made of insulating material that covers the top.
It is equipped with an external lead wire 7.7 for measurement, and transmits strain such as expansion and contraction of the load cell to the metal resistance material 5, senses the change in resistance value, amplifies it, and detects it as a change in electrical signal. .

The first load cell 1 is connected and fixed to the second load cell 8 using bolts 9 at its bottom. The second load cell 8 extends upward in a cylindrical shape, and forms a strain-generating portion g in the middle. Second load cell 8
The upper part of is the third load cell lO and Holt 11.11
The third load cell 10 extends downward in a cylindrical shape and forms a strain-generating section in the middle, and the lower part 10# is connected to the bottom plate 12 and bolts 13.
It is connected and fixed by 13. A strain gauge 3' similar to that described above is attached to the strain generating part 10'.14
is a cover, and the diaphragm 15 can be covered from the top surface. An O-ring 16.16 is interposed between the cover 14 and each load cell 8.10.

The cover is fixed with set screws 17.

On the other hand, a gap d is set between the lower end of the second load cell 8 and the bottom plate 12.

The gap functions as a stopper when an overload is applied, as will be described later.

With the above configuration, the first load cell 1 has a large rated load, and the third load cell 10 has a small rated load. Assuming that the rating of the first load cell 1 is (capital) tons and the rating of the third load cell 1 is (tons), if the load X applied from above is between θ and 20 tons, the load will be applied to the first load cell. The force is transmitted to the second load cell 8 as a compressive force, converted to a tensile force to the second load cell 8, and finally transmitted to the third load cell 10 as a compressive force. Therefore, the strain-generating portion 10' of the third load cell IO is deformed to cause a change in the electrical resistance of the strain gauge to measure the load.

Here, the second load cell 8 has a function of converting the load applied to the first load cell 1 into tensile strain and transmitting it as compressive strain to the third load cell IO, and sets a gap d as described later. It functions as a load cell for Natsui 1 expansion.

Next, when the load X applied from above exceeds the load, the bottom of the second load cell 8 comes into contact with the bottom plate 12, and the gap d between them becomes zero, so to speak. 5- The bottom plate 12 acts as a stopper for the load X, No further load is transmitted to the third load cell 10. Therefore, a load X of 9 to (capital) tons is detected by the strain generating section 2 of the first load cell 1, and a measurement signal is taken out.

FIG. 3 shows a graph of the relationship between the outputs (mv/v) of the first load cell 1 and the third load cell 10 with respect to the load X (ton). As shown in the figure, the load X is θ~20
When the load exceeds a ton, a large output is generated in the third load cell 10, and when the load exceeds a ton, it becomes saturated. On the other hand, the first load cell 1 shows a linear output over the entire load X of θ to 50 tons.

Regarding the composite load cell of the present invention, the operational aspects will be further detailed below.

(1) When the load When strain occurs, the θ strain-generating portion 10' generates compressive strain. At this time, the gap d is adjusted so that the sum of the deflection of the strain-generating portion g and the deflection δ4 of the strain-generating portion 10' approximates 9.

(3) When a load of more than ton is applied, the above rf,+pile≧d, the gap d becomes zero, the stopper works, and the load X is transmitted to the bottom plate 12.

(4) When the load fluctuates up and down by tons, the above operation becomes reversible and the output of the load cell can be obtained from 1 or 10.

The structure and operation mode of the composite load cell according to the present invention have been described in detail above, but when implementing the present invention, the dimensions of the strain-generating portions of the load cells 1 and 10, that is, the plate thickness and height, should be appropriately selected. It is necessary to set the gap d in advance so that it becomes zero when the rated load is applied to the load cell 10 side. At this time, since the second load cell 8 transmits the load X as a tensile force, it has the effect of increasing the total deflection on the load cell 10 side at the rated load, and the adjustment of the gap d, that is, the operating point of the stopper, is effective. becomes easier.

Furthermore, in the case of the present invention, when the load X is within a small range, the third load cell 10 with a small rating can perform measurements with high resolution, and when the load X becomes large, the first load cell can continuously perform measurements. , it has the advantage of being able to prevent destruction of the third load cell, and by combining the cylindrical load cell with the first load cell, the entire structure is made more compact, and the size of the main body can be reduced even under a large load X. This has the effect of being able to be configured without increasing the size.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of a composite load cell showing an embodiment of the present invention, FIG. 2 is a plan view showing an example of a strain gauge, and FIG. 3 is a graph showing the relationship between load and load cell output. 1... First load cell 2... Strain generating part 3.3...
・Strain gauge 8...Second load cell 9.
13... Bolt 10... Third load cell 12.
...Bottom plate 14...Cover 15...Diaphragm 1
6...0 ring 17...Cover set screw Patent applicant Showa side type Co., Ltd. 9 -

Claims (2)

[Claims] (1) A cylindrical load cell 1 is arranged at the center position, and a cylindrical load cell 8 and a cylindrical load cell 10, which are arranged outside the load cell and receive tensile strain due to loads applied from the top and bottom directions, and a cylindrical load cell 10 which receives compressive strain, are arranged at the center. A composite load cell characterized in that a gap d of a predetermined length is provided between the cylindrical load cell 1 and the bottom plate 12, which are connected to each other. (2) The cylindrical load cell 1 provided at the center constitutes a strain-generating part for large loads, and the cylindrical load cell 1
The composite load cell according to claim 1, wherein 0 constitutes a strain-generating portion for small loads.