JPS59159023A - Roberval balance - Google Patents

Abstract

PURPOSE:To form a highly sensitive, durable roberval balance having a thin plate thickness, by providing supporting points, to which a force is applied in the direction toward a fixing part when a load is applied on a receiving pan, at points, which are deviated to the fixed point from the movable ends of links; and providing the supporting points of the fixed part for the links at the positions, which are deviated to the movable side from the fixing ends of the links. CONSTITUTION:When a load W is applied on a receiving pan 1, an arm 22 is subjected to bending moment M in the clockwise direction. The upper end of a movable post 21 receives an inward force F1. The lower end thereof receives an outward force F2. Therefore, elastic supporting points 13 and 14 on the movable side receive only a tensile force. Parallel links 4 and 5 also receive only the tensile force. Therefore, elastic supporting points 11 and 12 on the fixed side receive only the tensile force. When the load is applied to the receiving pan in a deviated manner, the magnitude of the bending moment is changed. Since the arm 22 is protruded by the length of radius of the pan, the direction of the arm is not changed. Therefore, only tensile stress is yielded at four elastic supporting points and the parallel links 4 and 5, and compression stress is not yielded. Therefore, the thin elastic supporting points having small spring constants can be used, and sensitivity can be increased without decreasing load resistance.

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 skeleton diagram of a precision balance used in a conventional electronic balance, and FIG. 2 shows only the parallel motion 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 has one end connected to a fixed part 3, thereby forming a parallel movement mechanism. 2
is connected to a lever 7 via a link 6, and this lever 7
An electromagnetic force generating mechanism 8 is provided at the tip of the upper plate 1, and a lever displacement detecting mechanism 9 is provided, and the lever displacement is balanced by generating an electromagnetic force that balances the load acting on the upper plate 1. There is.

In such a mechanism, both ends of two parallel links 4.5 are connected to elastic supports 11, 12, 13 . ], 4 to the fixed part 3 and the movable column 2, compressive force is applied to the elastic fulcrum and there is a risk of the elastic fulcrum buckling. It was not possible to obtain a sensitive balance mechanism.

(c) Purpose The purpose of the present invention is to solve the above-mentioned drawbacks, to provide a structure in which tensile force always acts on any elastic fulcrum, and there is no risk of buckling. Our goal is to provide dish balances.

(D) Structure In summary, the present invention is a plane on which parallel motion is performed by the parallel motion mechanism, and 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, and the fulcrum point on which the force acts in the direction toward the fixed part when a load is applied to the upper plate is the link. 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 I of the upper plate 1 is located at a position offset inward by the radius of the upper plate 1 with respect to the vertical line connecting the movable support points of the parallel links 4, 4.
An arm 22 is provided inwardly from the central part of the movable column 21 connected to the movable fulcrum of the parallel link and rigidly connected to the central axis IA, and the lower end 23 of this movable column 21 is parallel as before. The upper end 2 of this movable column 21 is located outside the movable end 5B of the link 5 and connected therebetween by an elastic fulcrum 14.
4 is positioned inside the movable end 4B of the parallel link 4 and connected therebetween by an elastic fulcrum 13. In addition, in the lower parallel link 5 in which the movable side fulcrums are connected in the conventional manner, the fulcrum 25 of the fixed part 3 is located outside the link fixed end 5A as in the conventional case for the fixed end, and the elastic fulcrum 12 is used to connect therebetween. . 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, 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. 4, and the upper end of the movable column 21 receives an inward force F1. The lower end receives an outward force F2. Therefore,
Both of the movable elastic fulcrums 13 and 14 receive only tensile force, and both parallel links 4 and 5 also receive only tensile force. Therefore, both the fixed side elastic fulcrums 11 and 12 are only subjected to tension. When a load is unevenly applied to the upper plate 1, the magnitude of the bending moment M changes, but since the arm 22 protrudes by the radius of the plate, its direction does not change, and the parallel links 4, 5, and 4
At each elastic fulcrum, only tensile stress is always generated, and no compressive stress is generated.

FIG. 5 shows another embodiment of the invention. This embodiment differs from the previous embodiment 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, the parallel links 4.5 and the four elastic supports 11
．． Only tensile stress always occurs at 12, 13, and 14.

(f) Effects According to the present invention, only tensile force 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 the drawing]

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 links 11.12, 13.14 - Elastic fulcrum 21 - Movable column 22 - Arm Patent applicant Shimadzu Corporation Representative Patent attorney Nishi 1) New

Claims (1)

[Claims] The above parallel movement is performed 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 a fulcrum of a fixed part and a fulcrum of a movable column, respectively, via an elastic fulcrum. The center axis of the upper plate is provided at a position on a plane where the upper plate 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. A link that is rigidly connected to the shaft and connects the end of the upper and lower ends of the movable column on the side where force is applied in the direction toward the fixed part when a load is applied to the upper plate. The movable end of the link and the end of the movable column are connected by an elastic fulcrum, and the fulcrum attachment part of the fixed part to be connected to the link is provided at a position biased toward the fixed part from the movable end of the link. By connecting the fixed end of the link and the fulcrum attachment part of the fixed part with an elastic fulcrum by providing it at a position biased toward the movable fulcrum side than the end, the parallel link and the elastic fulcrum are both configured to receive mainly tensile load. Precision balance.