JPH02124433A - Electronic balance - Google Patents

Abstract

PURPOSE:To increase weighing capacity and improve sensitivity by a method wherein a roberval mechanism, a plurality of levers and respective elastic supporting points are integrally formed while a portion supporting the elastic supporting point of at least one of the levers is coupled to a fixed rod portion by a separate member. CONSTITUTION:Load functioning to a pan 17 is transmitted to a lever 5 via elastic coupling portions 7a, 7b, and the lever 5 tilts with respect to an elastic supporting point 9 as the center with the coupling portion 7b as a point of force. Tilt of this lever 5 is transmitted to a lever 6 via elastic coupling portions 8a, 8b. The lever 6 tilts with respect to an elastic supporting point 10 as the center with the coupling portion 8b as the point of force, and this tilt is transmitted to a load sensor 21 by an arm 20. The supporting point 10 of the lever 6 is directly supported on a fixed rod portion 3, but the supporting point 9 of the lever 5 cannot be supported on the fixed rod portion 3 due to limitation of integrally formed constitution, but is supported by a portion for supporting the supporting point. However, by tightly coupling the supporting portion 11 on the fixed rod portion 3 with coupling members 12, 13 separate from a base metal, the supporting point 9 can be substantially supported by the fixed rod portion 3.

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to an electronic balance equipped with a Roberval mechanism.

<Prior art> In general, in electronic balances, in order to prevent the dish from tilting or falling over, the dish is supported by a roberval mechanism (also called a parallel guide) and the direction of displacement is restricted only up and down. will be held. The Roberval mechanism is a mechanism in which a fixed column and a movable column are disposed at both ends of two mutually parallel beams via flexible parts, and the dish is supported by the movable column. The load acting on the plate is transmitted to a load sensor such as a balanced electromagnetic force generator by a lever mechanism connected to a movable column of such a Roberval mechanism.

Here, the movable column of the Roberval mechanism only moves up and down, that is, it moves in parallel, and the lever needs to tilt around the fulcrum. Therefore, in order to prevent interference between the movements of these members, elastic members are commonly used at the connection between the movable column and the lever and at the above-mentioned fulcrum. On the other hand, for the movable palm bar, a rigid body is preferable to an elastic material in view of its function. Therefore, conventionally,
Materials that are different from the Roberval mechanism, levers, and connecting parts, etc.
For example, die-cast aluminum alloy and high elastic steel.

They were made of wood and assembled together by screwing, caulking, or gluing.

By the way, according to the electronic balance having such a structure, due to the difference in coefficient of thermal expansion between the connecting part including the above-mentioned fulcrum and the robo-hull mechanism and lever, the difference in the coefficient of thermal expansion due to the change in ambient temperature causes a change in relative dimensions. Drift and drift due to deformation (when two materials with different coefficients of expansion are put together, like a bimetal), bending occurs depending on the temperature, and especially when mounting an elastic fulcrum, the deformation of the part will affect the performance. There was a drawback that it occurred.

Furthermore, there is also the problem that the number of different parts increases, the number of assembly steps increases, and the cost increases.

Therefore, the present inventor has already developed an electronic balance that solves the above problems by integrally forming the Roberval mechanism, the lever, the elastic connecting part, and the elastic fulcrum by cutting through a single base material. 62-113133), and for a similar purpose, a plurality of thin plates were cut through and stacked on top of each other, and the roberval mechanism, lever, and even elastic connection parts were formed integrally with substantially the same material. We are proposing an electronic balance (Utility Application No. 62-98853).

<Problems to be solved by the invention> Based on the above proposal (electronic balances with an integrally formed mechanism are subject to limitations due to their integral structure. One of these is the lever ratio problem; One of these is the issue of sensitivity.

In other words, in order to increase the capacity of an electronic balance using a predetermined load sensor without making the electronic balance particularly large, it is necessary to increase the lever ratio. It is relatively easy to do this by adopting a three-dimensional configuration such as not arranging the part (force point) and the elastic fulcrum on the same straight line, but shifting one of them from the straight line, and dividing it into two places sandwiching the straight line. The lever ratio can be increased. On the other hand, with an integrally formed mechanism, it is impossible to adopt such a three-dimensional configuration in terms of manufacturing, and the lever ratio is restricted.

In addition, in a so-called one-stage lever that transmits the load acting on the movable column part to the load sensor by one lever, a load approximately equal to the capacity load is applied to the elastic connection part (force point) and elastic fulcrum, respectively. Because of this, it must be strong enough to withstand that load.

In an integrally formed structure, an elastic connection part or an elastic fulcrum is formed by providing a constricted part in the base material, but in order to obtain the above-mentioned strength, it is necessary to make the constricted part too thin. This limits the ability to increase sensitivity.

In order to eliminate such restrictions, it is conceivable to adopt a so-called multi-stage lever mechanism that transmits the applied load to the load sensor via a plurality of levers. However, it is necessary to create a structure in which each lever is equipped with an elastic connection part (force point, point of action) and an elastic fulcrum, and each lever is tilted in a convenient direction by the load on the pan, and there is no measurement error. Therefore, it was extremely difficult to penetrate the base metal together with the Roberval mechanism, and only very limited structures could be realized.

The purpose of this invention is to eliminate various restrictions on integrally formed structures at once, to enable relatively flexible lever configurations even though the structure is essentially integrally formed, and to easily increase the capacity and increase sensitivity. The object of the present invention is to provide an integrally formed electronic balance that can achieve the

<Means for Solving the Problems> In order to achieve the above object, in the present invention, for example, as shown in FIGS. 1 and 2 corresponding to the embodiment, an elastic beam portion 1
, 2, a robo-hull mechanism R consisting of a fixed column part 3 and a movable column part 4, and a plurality of levers 5.6 for transmitting the load of the plate 17 supported by the movable column part 4 to the load sensor 21. ,
Each elastic connection for each lever 5, 6? a, 7b, 8
a, 8b and the elastic fulcrums 9, 10 are integrally formed separately through one base material, and a portion of each lever 5.6 that supports the elastic fulcrum 9 of at least one lever 5. (Fulcrum support part) 11 is rigidly connected to fixed column part 3 by a member (connection member) 12.13 different from the base material.

<Function> Basically, large capacity and high sensitivity can be achieved by using multiple levers. In other words, by providing multiple levers, the load on the plate is transmitted to the load sensor 21 based on the product of the lever ratios of the multiple levers, so even if there is a restriction on the lever ratio of each lever, It can be quantified to a large extent.

Furthermore, since a force smaller than the load on the plate is applied to the lever 6 at the final stage connected to the load sensor 21 by the lever ratio of the lever 5 at the previous stage, its elastic connection portion (point of force) 8b and make the elastic fulcrum 10 thinner (weaker).
In addition, the first lever 5 can be replaced with the conventional 1.
Similar to the step lever, an elastic connecting portion 7b and an elastic fulcrum 9 strong enough to withstand the weighing load are required, and although the displacement of the first step lever 5 in response to a certain minute load is minute, the displacement is as follows. Since it is magnified by the lever 6 of the stage and transmitted to the load sensor 21, the load sensor 21 is eventually exposed to the sensitive lever 6 due to the action of the minute load on the plate 17.
A large displacement is transmitted through the oscilloscope, and high sensitivity can be achieved.

The above-mentioned effects of having multiple levers are well known in electronic balances having a normal assembly type structure.

In the integrally formed structure, the elastic fulcrum 9 of each lever 5, 6
．． 10 to the fixed column 3 due to structural constraints, for example, as shown in FIG. 6 (al.
limited to those shown in

That is, in this example, a lever L1 is elastically connected to the movable column M of the Roberval mechanism, and a lever is elastically connected to the lever L and connected to the load sensor S via the arm A. L2 constitutes a two-stage lever, but in order to connect the elastic fulcrums r and 2 of each lever Ll and Lz to the fixed column F, the shape of the fixed column F can be moved as shown in the figure. In order to protrude greatly toward the column M side and to support the load sensor S on the fixed column F, it is necessary to secure the holding member B by sandwiching the fixed column F as shown in Fig. 6 (bl). In addition, in this example, it is not possible to create a structure with a built-in calibration weight that is lighter than the lever compared to the weighing load, as in the mechanism shown in Fig. 5, which will be described later.
In addition to the mechanism in this example, there were no other particularly effective mechanisms in mind, and the degree of freedom in design was extremely narrow. Here, the part supporting the elastic fulcrum 9 or 10,
For example, the fulcrum support part 11 is connected to a fixed column part 3 of a balance case, etc.
If it is fixed to a fixed part other than the above, a relative displacement will occur between the fulcrum 9 and the roberval mechanism when an eccentric load is applied or an external force is applied to the balance case, resulting in a measurement error. This fulcrum support part 11 is connected to a connecting member 12 separate from the motherboard.
．． 13 to rigidly connect to the fixed column part 3, structural constraints are removed and the intended purpose can be achieved.

<Embodiment> FIG. 1 is a front view showing an embodiment of the present invention with the connecting member 12 on the near side removed, and FIG. 2 is a partially exploded perspective view thereof.

Roberval mechanism R, two levers 5.6, and an elastic connecting portion 7a that interconnects these parts.

7b, 8a, 8b, and the elastic fulcrum 9 of each lever 5, 6.
10 and a fulcrum support part 11 that supports one elastic fulcrum 9 are integrally formed by piercing a flat base material such as an aluminum alloy.

The Roberval mechanism R has flexible portions 1a and lb at both ends, respectively.
This is a mechanism in which a fixed column part 3 and a movable column part 4 are connected by two mutually parallel elastic beam parts 1 and 2 in which 2a and 2b are formed.

The Roberval mechanism R is fixed to the balance base 22 at its fixed column 3, and the plate 17 is fixed to the movable column 4 with a screw 18 via a spacer 19.

The movable column part 4 is connected to a lever 5 by elastic connecting parts 7a and 7b, and this lever 5 is supported by a fulcrum support part 11 via an elastic fulcrum 9, and is supported by an elastic connecting part 8.
It is connected to the lever 6 by a and 8. Lever 6
is supported by the fixed column part 3 via an elastic fulcrum 10, and this lever 6 has a hole 1c bored in the elastic beam part 1;
The arm 2o disposed above the Roberval mechanism R is connected to the screw 2a through the spacers 6a and 6b passing through the fd.
It is fixed with 2Qb. And this arm 20
The tip thereof is connected to the load sensor 21 by a screw 21a. Note that the arm 20 is provided with a hole 2Qc through which a spacer 19 is passed in order to fix the plate 17 to the movable column portion 4.

Each of the above-mentioned flexible parts 1a, lb, 2a, 2b, each elastic connection part 7a, 7b, 8a, 8b, and each elastic fulcrum 9.
10 are obtained by forming a narrowed portion in the base material.

Plate-shaped connecting members 12 and 13 having a predetermined thickness are arranged on both sides of the integrally formed mechanism body as described above, and are connected by screws 3a, 3b, 11a, l1b, etc., respectively. It is fixed to the fixed column part 3 and the fulcrum support part 11. That is, the fulcrum support part 11 is rigidly connected to the fixed column part 3 by the connecting members 12 and 13. The connecting members 12 and 13 are made of the same material as the body forming mechanism;
Alternatively, it is desirable to use a material with an equivalent coefficient of thermal expansion. As shown in a partial plan view in FIG. 3, the connecting members 12 and 13 are provided with an inner side at the fastening portion to the fixed column portion 3 and the fulcrum support portion 11 so as not to contact other parts of the integrally formed mechanism. Projections t2a and 12b are provided. Further, the load sensor 21 is fixed on a sensor stand 23 which is sandwiched and fixed between the connecting members 1213.

According to the embodiment of the present invention described above, the load acting on the plate 17 is transmitted to the lever 5 via the elastic coupling parts 7a and 7b. The lever 5 tilts around the elastic fulcrum 9 with the elastic connecting portion 7b as the point of effort. This inclination of the lever 5 is transmitted to the lever 6 via the elastic coupling parts 8a, 8b. Lever 6
is tilted about the elastic fulcrum 10 with the elastic connecting portion 8b as the point of effort, and this inclination is transmitted to the load sensor 21 by the arm 20.

Here, the elastic fulcrum 10 of the lever 6 is directly connected to the fixed column 3.
However, the elastic fulcrum 9 of the lever 5 is directly fixed to the fixed column 3 due to restrictions due to the integral structure.
Therefore, it cannot be supported by the fulcrum support part 11. However, by rigidly connecting this fulcrum support portion 11 to the fixed column portion 3 using a connecting member 12.13 separate from the base material, the elastic fulcrum 9 is substantially supported by the fixed column portion 3. .

The present invention can employ not only the two-stage lever mechanism as described above but also a three-stage, four-stage, etc. lever mechanism.

FIG. 4 is a diagram showing the configuration of another embodiment of the present invention, and is a front view shown with the connecting member 12 on the near side removed, similar to FIG. 1. In this figure, members equivalent to those in FIG. 1 are given the same reference numerals, and their explanations will be omitted.

In this example, the load on the plate 17 acting on the movable column part 4 is
It is configured to transmit to the load sensor 21 via three levers 30, 31 and 32.

That is, the movable column part 4 is an elastic connection part 35a.

35b to the lever 30;
is supported by the fulcrum support part 11 at the elastic fulcrum 33, and
It is connected to the lever 31 by elastic connections 36a, 36b.

The lever 31 is supported on the fixed column part 3 at an elastic fulcrum 37, and is connected to the lever 32 by elastic coupling parts 38a and 38b. Further, the lever 32 is supported by the fulcrum support part 11 at an elastic fulcrum 34, and the arm 20 connected to the load sensor 21 is fixed thereto.

A fulcrum support portion that commonly supports the elastic fulcrums 33 and 34 of the levers 30 and 32 is connected to the fixed column portion 3 by a connecting member 12.13 that sandwiches this integrally formed mechanism.

Further, according to the present invention, the degree of freedom in designing the lever mechanism is increased even when the lever mechanism is integrally formed, so that there are the following advantages even when a calibration weight is built in.

FIG. 5 is an explanatory diagram of a preferred embodiment in which a calibration weight W is built in, and similar to FIGS. 1 and 4, the connecting member 1 on the front side
2 is a front view shown with parts 2 removed.

In this example, a configuration is adopted in which the load on the pan is transmitted to the load sensor 21 by two levers 40 and 41, and a calibration weight W can be added to or removed from the point of action of the second lever 41.

The movable column portion 4 is connected to a lever 40 by elastic connecting portions 44a and 44b, and the lever 40 is supported by the fulcrum support portion 11 at an elastic fulcrum 42. And this lever 40
is connected to the lever 41 via the elastic connecting parts 45a and 45, and the lever 41 is connected to the fulcrum support part 11' at the elastic fulcrum 43.
The lever 41 is supported by a load sensor 21.
An arm 20 connected to is fixed.

The fulcrum supports 11 and 11' of the elastic fulcrums 42 and 43 of the levers 40 and 41 are similarly connected to the screws lla, llb, l by means of the connecting members 12 and 13 on both sides, respectively.
It is rigidly connected to the fixed column part 3 by la', llb', 3a and 3b.

Further, pin-shaped weight hooks 50 for loading a calibration weight W are installed on both sides of the connecting portion between the elastic connecting portions 45a and 45b.
It protrudes outside the mechanism body through a through hole drilled in 2.13. Calibration weights W of equal mass can be loaded or unloaded from both sides of the weight hook 50 by a known weight addition/removal mechanism (not shown).

With such a configuration, it is possible to load the calibration weight W onto the force point of the second stage lever 41 and tilt this lever 41 in the same direction as when the load is applied onto the pan 17. This makes it possible to carry out calibration with a built-in weight that is as light as the first lever 40 for the weighing load, which is advantageous in terms of space.

Here, in order to give the lever 41 the above-mentioned inclination when the calibration weight W is loaded on the weight hanger 50, it is necessary to ) and the point of force (elastic connection portion 45b) of the second stage lever 41 must be displaced downward, and this displacement also causes the point of action (arm 20) of the second stage lever 41 to be displaced downward.
It is necessary to adopt a lever configuration in which the force is displaced upward and transmitted to the load sensor 22. In other words, the force point 44b of the first lever 40 can be provided closer to the point of action 45a than the fulcrum 42, and the fulcrum 43 of the second lever 41 can be provided closer to the point of action (arm 20) than the point of force 45b. Although it is necessary,
By rigidly connecting the supporting part of the elastic fulcrum of each lever to the fixed column part with a connecting member separate from the base material as in the present invention, such a free lever configuration can be achieved even in an integral structure. Therefore, it is possible to adopt

Note that the connecting member is not necessarily as in each of the above embodiments.
It is not necessary to provide it on both sides of the integrally formed mechanism, and it goes without saying that it is possible to fasten it to the fixing column etc. by caulking with a pin or the like in addition to screwing.

<Effects of the Invention> As explained above, according to the present invention, the donkey-hull mechanism, the plurality of levers, the elastic connection portions that interconnect them, and the elastic fulcrum of each lever are separated from the base material. At least one of the elastic fulcrums of each lever is integrally formed, and the supporting portion of at least one of the elastic fulcrums of each lever is configured to be rigidly connected to the fixed column portion of the Roberval mechanism by a connecting member separate from the base material. Therefore, the number of parts can be significantly reduced compared to balances with a normal assembly type structure, reducing manufacturing costs, and the amount of expansion and contraction due to temperature of each part is uniform, reducing distortion etc. Temperature drift is reduced without the occurrence of temperature drift. At the same time, regardless of the arrangement position of each lever or the position of the elastic fulcrum on the lever, all the elastic fulcrums are connected directly or via a connecting member to the fixed column of the roba-hull mechanism, so that eccentric The constraints on the structure of the multi-stage lever mechanism, which can result in errors caused by errors or errors caused by the action of external forces on the balance case, have been significantly eased, allowing for larger weighing capacity and higher sensitivity while maintaining high accuracy. can be easily achieved.

[Brief explanation of the drawing]

Fig. 1 is a structural explanatory diagram of an embodiment of the present invention, in which a front view is shown with the connecting member 12 on the near side removed, Fig. 2 is a partially exploded perspective view thereof, and Fig. 3 is the connecting member 12 and mechanism. FIGS. 4 and 5 are front views of other embodiments of the present invention with the connecting member 12 on the front side removed, and FIG. It is a front view showing a reference example in which a two-stage lever mechanism is configured with an integrally formed structure of only one piece of material. 1.2... Elastic beam part 3... Fixed column part 4... Movable column part 5.6, 30, 3 1゜32.40.41...Lever?a, 7b, 8a, 8b, 35a, 35b, 36a36
b, 38a, 38b, 44a, 44b. 45a, 45b... Elastic connection part 9.10.33, 34°37.42.43... 41.11'... 12.13... 17... - Elastic fulcrum, fulcrum support part, connection member・Dish 20 ・・Arm・Load sensor 22 ・・Base

Claims (1)

[Claims] The load acting on the plate supported by the movable column of a Roberval mechanism in which a fixed column and a movable column are arranged at both ends of two mutually parallel elastic beams is applied to the movable column. The load is transmitted to the load sensor by a plurality of levers, each of which includes a lever connected by an elastic connection part, and which is connected to each other through the elastic connection part and each supported via an elastic fulcrum. In the balance, the Roberval mechanism, the plurality of levers, the elastic connecting portions, and the elastic fulcrums are integrally formed by hollowing out one base material, and at least one of the levers is An electronic balance, characterized in that a portion supporting the elastic fulcrum of the lever is rigidly connected to the fixed column portion by a member different from the base material.