JPH0257850B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a parallel movement mechanism for precision balances, and is particularly applicable to electronic balances.

(b) Prior Art Fig. 1 shows a framework of a precision balance used in a conventional electronic balance, and Fig. 2 shows only the parallel movement mechanism shown in Fig. 1. A movable column 2 that supports the upper plate 1 vertically from directly below is connected and supported by the other ends of two parallel links 4 and 5, each of which is connected at one end to a fixed part 3, thereby forming a parallel movement mechanism. 2 is connected to a lever 7 via a link 6, and an electromagnetic force generating mechanism 8 is provided at the tip of this lever 7, and a lever displacement detecting mechanism 9 is also provided to balance the load acting on the upper plate 1. It is configured to balance lever displacement by generating electromagnetic force.
In such a mechanism, two parallel links 4,
5 to the fixed part 3 and the movable column 2 via the elastic fulcrums 11, 12, 13, and 14, there is a risk that compressive force will act on the elastic fulcrums and cause the elastic fulcrums to buckle. It was not possible to obtain a highly sensitive balance mechanism by reducing the thickness of the leaf spring.

(c) Purpose The purpose of the present invention is to solve the above-mentioned drawbacks, and to provide a structure in which a tensile force always acts on any elastic fulcrum and there is no risk of buckling, and therefore the plate thickness can be reduced to provide high sensitivity and robustness. Our goal is to provide precision balances.

(D) Configuration In summary, the present invention is directed to a plane on which parallel motion is performed by the parallel motion mechanism, and which is biased inward or outward by at least the radius of the upper plate with respect to the vertical line connecting the movable elastic fulcrum. The central axis of the upper plate is provided at the fixed position, and the central axis of the upper plate and the movable part are rigidly connected. By providing the link in a position that is biased towards the fixed part rather than the movable end, and by providing the fulcrum of the fixed part of the link in a position that is biased towards the movable side than the fixed end of the link, a tensile load is applied to both the upper and lower parallel links. It is characterized by being configured to do so.

(e) Examples FIG. 3 shows an embodiment of the present invention.

The central axis 1A of the upper plate 1 is provided at a position offset inward by the radius of the upper plate 1 with respect to the upper and lower lines connecting the movable side fulcrums of the parallel links 4, 4, and the movable axis 1A is connected to the movable side fulcrums of the parallel links. An arm 22 protrudes inward from the center of the column 21 and is rigidly connected to the central axis 1A, and the lower end 23 of this movable column 21 is positioned outside the movable end 5B of the parallel link 5 as before, and an elastic link is formed between them. The upper end 2 of this movable column 21 is connected at a fulcrum 14.
4 is positioned inside the movable end 4B of the parallel link 4 and connected therebetween by an elastic fulcrum 13. Also,
Lower parallel link 5 that connects the movable side fulcrum in the conventional manner
In this case, the fulcrum 25 of the fixed part 3 is located outside the link fixed end 5A, and the elastic fulcrum 12 connects the fixed end with the fulcrum 25 of the fixed end 5A. However, regarding the other link 4, the fulcrum 26 of the fixed part 3 is placed around the inside of the link fixed end 4A, and the elastic fulcrum 11 connects the link between them.
In addition, in the description of the embodiment, the inside and outside are used for the central portions of the links 4 and 5, and the directions are opposite at the fixed end and the movable end.

In such a configuration, when a load W acts on the upper plate 1, a clockwise bending moment M acts on the arm 22 as shown in FIG.
The upper end of 1 receives an inward force F ₁ and the lower end receives an outward force F ₂ . Therefore, the movable elastic fulcrum 13,
14 are both subjected to only tensile force, and parallel links 4 and 5
Both receive only tensile force. Therefore, the fixed side elastic fulcrums 11 and 12 are also only subjected to tension. Upper plate 1
When the load is biased upward, the bending moment M
Although the size of the arm 22 changes, since the arm 22 protrudes by the radius of the plate, its direction does not change, and only tensile stress and compressive stress are always generated in the parallel links 4, 5 and the four elastic supports. There is no.

FIG. 5 shows another embodiment of the invention. This embodiment differs from the previous one in that the arm 22 projects outwards, and accordingly the upper link 4 is connected conventionally, and the lower link 5 is connected as described for the upper link of the previous embodiment. , the lower end 14 of the movable column 21 is made to go around inside the link movable end, and the fulcrum of the fixed part 3 is made to go around inside the link fixed end 5A. With this configuration, only tensile stress is always generated in the parallel links 4, 5 and the four elastic supports 11, 12, 13, 14.

(f) Effects According to the present invention, only tensile force mainly acts on the elastic fulcrum and no compressive force acts on it, so it is possible to use an elastic fulcrum with a small thickness and a small spring constant without reducing the load capacity. Sensitivity can be increased. Furthermore, since the spring constant of the elastic fulcrum can be made small, the zero point drift of the balance caused by temperature coefficients can be kept small.

[Brief explanation of drawings]

FIG. 1 is a skeleton diagram showing a conventional example, and FIG. 2 is a front view showing only the parallel movement mechanism of FIG. 1. FIG. 3 is a plan view showing an embodiment of the present invention, FIG. 4 is a skeleton diagram illustrating the operation of FIG. 3, and FIG. 5 is a front view showing another embodiment of the present invention. 1... Upper plate, 3... Fixed part, 4, 5... Parallel link, 11, 12, 13, 14... Elastic fulcrum, 2
1...Movable pillar, 22...Arm.

Claims (1)

[Claims] 1. In a precision balance equipped with a parallel movement mechanism in which the fixed end and movable end of two upper and lower parallel links are connected to the fulcrum of a fixed part and the fulcrum of a movable column via elastic fulcrums, respectively, the above parallel movement is performed. The center axis of the upper plate is provided at a position on a plane where the movable column is deviated from the axis of the movable column by at least the radius of the upper plate, and an arm is made to protrude laterally from the movable column so that the center axis of the upper plate is deviated from the axis of the movable column by at least the radius of the upper plate. of the upper and lower ends of the movable column, and the end on the side where force acts in the direction toward the fixed part when a load is applied to the upper plate is connected to the link connected to that end. The movable end of the link and the end of the movable column are connected by an elastic fulcrum, which is provided at a position biased toward the fixed part than the movable end, and the fulcrum attachment part of the fixed part to be connected to the link is connected to the fixed end of the link. By connecting the fixed end of the link and the fulcrum mounting part of the fixed part with an elastic fulcrum by providing it in a position biased toward the movable fulcrum side, the parallel link and the elastic fulcrum are both configured to receive mainly tensile loads. Precision balance.