JPH0122889B2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to weighing devices.

Part 1 about an example of a scale using a load cell
This will be explained based on the diagram. Reference numeral 1 denotes an outer case of the scale main body, 2 a column erected on the bottom plate of the outer case 1, 3 a load cell, and vertical parts 3a, 3b and horizontal parts 3c, which are formed by hollowing out a metal block. 3d, and strain gauges (5a to 5d) affixed to each of the thin parts 4 formed near the ends of the horizontal parts 3c and 3d, while the vertical part 3a is connected to the support column. 2 is fixed with 6 bolts. Reference numeral 7 denotes an L-shaped rod fixed with bolts 8 to the other vertical portion 3b, and 9 is a weighing tray whose lower cylindrical portion fits into a pin 10 erected on the horizontal portion of the L-shaped rod 7.

In this configuration, when weighing, first perform zero adjustment and then adjust each strain gauge 5.
When the output values of a to 5d are set to zero and the weight to be weighed is then placed on the tray 9, a tensile force is applied to the strain gauges 5a and 5d, a compressive force is applied to the strain gauges 5b and 5c, and each Strain gauge 5a-5
The output voltage from d is A/D converted and the weight value is displayed digitally.

However, with this conventional configuration, if a relatively heavy weight to be weighed is placed on the tray 9 intentionally or by mistake, the following problem will occur. That is, taking the area near the strain gauge 5b of the cell body as an example, as shown in FIG. 6A,
Strong compressive force and tensile force are applied alternately, such as first being compressed by the initial impact force, then being pulled, and then being compressed. Then, when the compressive force and the tensile force have attenuated after a certain period of time, the weighed value is read, and when the heavy object to be weighed is unloaded from the tray 9, the weighed value may not become zero. In other words, due to the strong compressive force and tensile force,
This is due to so-called zero point drift, which causes weighing errors.

Therefore, the present invention provides a weighing device that prevents the zero point from drifting.

A first embodiment of the present invention will be described below with reference to FIGS. 2 and 3. Reference numeral 15 denotes a fixed block having a U-shaped planar shape fixed to the bottom plate of the outer case of the scale, and reference numeral 16 has both ends inserted into holes formed at both ends of the block 15, and is supported by this block 15. The horizontal axis 17 is a load cell, which has a pair of vertical parts 18a, 18b and a horizontal part 18.
It has a cell body 18 consisting of a cell body 18 consisting of a cell body 18 consisting of a cell body 18 and a strain gauge 5a to 5b affixed to a thin wall portion 19 formed at both ends of each of the horizontal portions 18c and 18d. is formed in a through hole 20 along the horizontal direction, and by fitting the through hole 20 into the horizontal shaft 16, the load cell 17 is configured to be able to move up and down about the horizontal shaft 16. 21 is a pair of screw holes formed near the lower part of the center portion of the block 15; 22 is screwed into each of the screw holes 21, and the tip thereof is in contact with the lower side of the base end side of the load cell 17; This is a stopper bolt that holds this load cell 17 in a horizontal state. Therefore, the load cell 17 cannot rotate downward from the horizontal state, but can freely rotate upward. 23 is a lock nut screwed onto the stopper bolt 22. 18e is a support part 18f located outside the other vertical part 18b at an appropriate distance from this vertical part 18b.
is the central portion of the support portion 18e and the vertical portion 18b.
It is a connecting part that integrally connects the central part of the . As shown in FIG. 1, the support portion 18
An L-shaped rod 7 is fixed to e with a bolt 8.
In this case, even if the support part 18e is distorted due to uneven tightening force of the bolt 8, this support part 1
8e and the vertical part 18b are only partially connected by the connecting part 18f.
8b is not distorted and the parallelogram of the cell body 18 is not distorted. Therefore, the bolt 8
It is possible to eliminate variations in the voltages output from each of the strain gauges 5a to 5d without requiring the skill of tightening the strain gauges, and when adjusting the four corners by placing a specified weight on the weighing tray 9, or It is possible to provide a highly accurate load cell 17 that can be held small.

In the above configuration, when a relatively heavy weight to be weighed is placed on the weighing tray 9 with an impact, an impact force in the direction of arrow A is applied to the load cell 17 via the L-shaped rod 7. Taking the area near the strain gauge 5a of the cell body 18 as an example, since the load cell 17 does not rotate downward, a compressive force is first applied, but then a tensile force is applied as the load cell 17 freely rotates upward. It does not participate because it moves. Therefore, a compressive force as shown in FIG. 6B is applied, almost no tensile force is applied, and the impact force is halved. Therefore, when a heavy object to be weighed is lowered from the weighing tray 9, the weighed value becomes zero, and so-called zero point drift does not occur.

A second embodiment of the present invention will be described based on FIG. In this embodiment, a through hole 25 is formed in the main body of the block 15, and a bolt 26 is inserted into the through hole 25. The large-diameter head 27 attached to the tip of the bolt 26 contacts the lower side of the base end side of the load cell 17, and a spring 28 is disposed between the large-diameter head 27 and the block 15. be. 29 is a nut that is screwed onto the bolt 26, and by pressing this nut 29 against the block 15,
The spring 28 is compressed and preloaded to prevent the spring 28 from being overwhelmed by the weight of the heavy object to be weighed and the horizontal load cell 17 from rotating downward during normal weighing.

In the above configuration, as in the case of the first embodiment, when an impact force in the direction of arrow A is applied, the biasing force of the spring 28 is defeated by the impact force, and the compressive force is reduced. Therefore, in this embodiment, not only is no tensile force applied, but the compressive force is also significantly smaller than in the first embodiment, and so-called zero drift does not occur.

A third embodiment of the present invention will be described based on FIG. The cell main body 40 of this embodiment has three through holes 41 each consisting of three continuous round holes formed in the upper and lower parts of the cell main body 40, so that the cell main body 40 has a so-called "Japanese character" shape, and furthermore, both of the above-mentioned through holes 41
Both sides of the beam portion 42 formed by the above are cut, and strain gauges 43 that receive shearing force are attached to both sides of the cut beam portion 42.

The weighing device of the third embodiment has substantially the same structure as the weighing device of the first embodiment except for the above-mentioned points. Also, the weighing device of this third embodiment is used as a second weighing device.
It goes without saying that the structure may be similar to that of the embodiment.

As described above, according to the weighing device of the present invention,
The load cell is configured to be able to move up and down around the horizontal axis, and is provided with a holding means that holds the load cell in a horizontal state and allows the load cell to freely rotate upwards. Even if a heavy object to be weighed is placed on the weighing pan with an impact, the impact force will be halved by the free rotation of the load cell upwards, resulting in the so-called zero point drift of the weighed value. There isn't.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view showing a conventional example, FIGS. 2 and 3 show a first embodiment of the present invention, FIG. 2 is a partially cutaway front view, and FIG. 3 is a plan view. . Fourth
The figure is a partially cutaway front view showing a second embodiment of the present invention. FIG. 5 is a partially cutaway front view showing a third embodiment of the present invention. FIG. 6 is a graph showing the relationship between compressive force and tensile force applied to the cell body and time. 5a-5d, 43...Strain gauge, 15...
...Block, 16...Horizontal axis, 17...Load cell, 18, 40...Cell body, 18a, 18b...
...Vertical part, 18c, 18d...Horizontal part, 20...
Through hole, 22... stopper bolt (holding means),
26... Bolt, 28... Spring (holding means), 2
9...Natsuto.

Claims (1)

[Claims] 1. The load cell is configured to be movable up and down about a horizontal axis, and is provided with a holding means that holds the load cell in a horizontal state and allows the load cell to freely rotate upward. weighing device.