JPH0228413Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a scale, and particularly to one that measures weight by converting it into an electrical signal.

Previously, the inventor of this invention proposed a force measuring device as shown in FIGS. 1 and 2. This is the first
As shown in the figure, it has a main elastic body 1 and a secondary elastic body 2, one end of these elastic bodies 1 and 2 is fixed on a fixed base 4 via a member 3, and a string 5 is inserted between the other ends. established,
A permanent magnet 6 is provided around the string 5, and an amplifier 7 is connected to the string 5 as shown in FIG.

In this force measuring device, when a downward load W is applied to the other end of the main elastic body 1, the main elastic body 1 undergoes a deflection △1 proportional to the load W, as shown in FIG.
occurs, pulling the lower end of string 5 downward. The tension P applied to the string 5 acts on the other end of the elastic body 2, causing the other end to bend downward by Δ2. Here, if the spring constant of the main elastic body 1 is K1, the spring constant of the secondary elastic body is K2, and the elongation of the string 5 is ignored, then P=△2・K2 holds, and △1=△2= Since △, W=△(K1+K2) P=W·K2/(K1+K2) The tension P is proportional to the load W, and the load W can be measured by measuring P.

Tension P is measured by string 5, permanent magnet 6 and amplifier 7. In other words, a magnetic field is applied to the string 5 by a permanent magnet 6 perpendicular to its length direction, and when the string 5 bends slightly in a direction that cuts the magnetic field due to the tension P, Fleming's right-hand rule applies. Accordingly, a current flows through the string 5, this current is supplied to the amplifier 7 via the capacitor 8 and amplified, and its amplified output is supplied to the string 5 via the resistor 9. This output flows in a direction that causes the string 5 to further bend in the same direction, and the string 5 further bends in a direction that cuts the magnetic field. The string 5 is bent to a position where the energy applied from the amplifier 7 and the bending reaction of the string 5 are balanced, and then returns in the opposite direction. As a result, a current flows in the opposite direction to the string 5, and the reverse current is supplied to the amplifier 7 via the capacitor 8 and amplified, and the amplified reverse current is supplied to the string 5. , bend string 5 in the opposite direction. After that, repeat this to make the frequency oscillate. This frequency is determined by =n/2√pg/r. However, n is the harmonic number of vibration,
is the effective length of the string 5, g is the gravitational acceleration, and r is the mass per unit length of the string 5. Therefore, by measuring the number of changes in the output of the amplifier 7, the frequency can be measured, thereby the tension P can be measured, and naturally the load W can be measured.

The object of this invention is to provide a scale that is configured so that only a vertical load can be applied to the string, thereby improving measurement accuracy.

Hereinafter, this invention will be explained in detail based on five embodiments shown in FIGS. 3 to 7. FIG. 3 shows a first embodiment. In the same figure, 10 is a Roberval type elastic body, and one vertical beam part 12 is a fixed base 4.
An upper plate 16 is attached to the other vertical beam part 14.

In the cavity 18 of the Roberval type elastic body 10, a support part 20 protrudes from the inner surface of the vertical wall part 12, and one end part of the sub elastic body 2 is attached to this support part 20 via a member 22. It is being This secondary elastic body 2 is a horizontal beam portion 2 of the Roberval type elastic body 10.
4 and 26, and the Roberval elastic body 10 and the auxiliary elastic body 2 are constructed separately, but are made of the same material or materials with the same temperature coefficient to form a flexible portion (strain-generating portion). ) 10a and 2a are formed so that the maximum bending stress generated is equal.

Further, a string attachment portion 28 projects from the inner surface of the vertical beam portion 14 into the cavity 18, and the string 5 is vertically attached between the string attachment portion 28 and the auxiliary elastic body 2.
The string 5 and the member 22 have the same coefficient of linear expansion,
The effective length of the string 5 is made equal to the length of the member 22. A permanent magnet 6 is attached to the inner surface of the vertical beam portion 14 so as to apply a magnetic field perpendicular to the length direction of the string 5. This string 5 is connected to an amplifier 7 in the same way as shown in FIG.

This scale measures the weight of the article placed on the upper plate 16 in the same way as the force measuring device shown in FIGS. only vertical load is applied to
Weighing accuracy can be improved. Moreover, since the secondary elastic body 2, the string 5, and the permanent magnet 6 are accommodated within the cavity 18 of the Roberval type elastic body 10, the cavity 1
By sealing 8, it is possible to prevent iron powder or the like from adhering to the permanent magnet 6 and affecting the measurement accuracy.

The second embodiment is the same as the first embodiment except that the secondary elastic body 2, permanent magnet 6, and string 5 are installed in the cavity 18 in the opposite way to the first embodiment, as shown in FIG. It is configured similarly to the example. This example also applies to the first
The same effect as in the embodiment is achieved.

In the third embodiment, as shown in FIG.
By attaching it via a member 22a to a support base 20a provided on the outer surface of the body, the string attachment portion 28a is provided above the Roberval elastic body 10, and the string attachment portion 28a is provided on the outer surface of the vertical beam portion 14 of the Roberval elastic body 10. This embodiment differs from the first embodiment in this respect.

In the first embodiment, the secondary elastic body 2, the string 5, and the permanent magnet 6 are provided in the cavity 18, so the height of the Roberval type elastic body 10 must be increased to some extent. If the secondary elastic body 2 is provided above the Roberval type elastic body 10 as in the example, the height dimension of the Roberval type elastic body 10 can be reduced, and the size can be reduced.

FIG. 6 shows a fourth embodiment, which has the same structure as the third embodiment except that the sub elastic body 2 is provided below the Roberval type elastic body 10, and has the same effect as the third embodiment. demonstrate.

FIG. 7 shows a fifth embodiment, which is constructed in the same manner as the fourth embodiment, except that a compressive force is applied to the string 5 after the object to be weighed is placed on the tray 16. There is. In this embodiment, if a tension corresponding to a load larger than the maximum load is applied to the string 5 by the auxiliary elastic body 2, a signal inversely proportional to the change in load can be extracted.

As described above, since the scale according to this invention uses the Roberval type elastic body 10, only a vertical load is applied to the string 5, and there is no deflection at both ends of the string 5, which improves measurement accuracy. can. Moreover, the Roberval type elastic body 10 and the secondary elastic body 2 are
Since they are each configured separately, they have the following advantages: That is, as described above, the tension or compression force P applied to the force detector 5 is expressed as: P=W·K2/(K1+K2). From this equation, it can be seen that even if W is changed, P can be made the same by changing K1 without changing K2. Therefore, according to this invention, as long as multiple types of Roberval type elastic bodies with different K1 are manufactured, scales with different weights (maximum measurable weights) can be used as Roberval type without changing the secondary elastic body 2. It can be easily manufactured by changing only the elastic body. In the first and second embodiments, since the auxiliary elastic body 2, the string 5, and the permanent magnet 6 are provided in the cavity 18, it is possible to prevent iron powder etc. from adhering to the permanent magnet 6. In the fourth embodiment, since the sub elastic body 2 is disposed above or below the Roberval type elastic body 10, the height dimension of the Roberval type elastic body 10 can be reduced, and the size can be reduced. Furthermore, in the fifth embodiment, by measuring the compressive force, a signal that is inversely proportional to the load change can be obtained.

In each of the above embodiments, the tension or compression force was measured using the string 5 and the permanent magnet 6, but a crystal force detector, a tuning fork force detector, or the like may be used in place of these. Moreover, an electromagnet can also be used in place of the permanent magnet 6. Furthermore, although tension was measured in the first to fourth embodiments, it is also possible to detect compressive force as in the fifth embodiment. Further, although the upper plate 16 is used, a hanging type plate may also be used.

[Brief explanation of the drawing]

Fig. 1 is a side view of a conventional force measuring device, Fig. 2 is a circuit diagram of the device, Fig. 3 is a side view of a first embodiment of the scale according to this invention, and Fig. 4 is a second embodiment. 5 is a side view of the third embodiment, FIG. 6 is a side view of the fourth embodiment, and FIG. 7 is a side view of the fifth embodiment. 2... Sub-elastic body, 4... Fixed table, 5, 6... Force detector, 10... Roberval type elastic body, 12, 1
4... Vertical beam portion, 16... Upper plate (plating plate), 18...
...Cavity, 24, 26...Horizontal beam part.

Claims (1)

[Claims for Utility Model Registration] First and second vertical beams arranged parallel to each other at intervals, and parallel to each other at intervals so as to connect the first and second vertical beams. a Roberval type elastic body having two horizontal beams arranged, the first vertical beam part being fixed to a fixed base, and the second vertical beam part provided with a load receiving means; The device is arranged inside, above, or below the body, parallel to and spaced apart from the horizontal beam, and has its base end fixed to one of the first and second vertical beams, and the Roberval type A scale comprising: a secondary elastic body configured separately from the elastic body; and force detection means provided between the other of the first and second vertical beams and the tip side of the secondary elastic body. .