JPS6227627A - Electromagnetic scale - Google Patents

Abstract

PURPOSE:To cope with the stress in up and down and right and left directions with respect to a measuring part by a simple structure, by providing flexibility in an arm itself, which transmits the weight of a material to be measured, and imparting stress absorbing ability to the arm. CONSTITUTION:An arm 2 is attached to the floating frame of an electronic balance. The arm 2 is formed in an approximately rectangular shape as a whole by two sheets of facing side plates 2a and 2b, a supporting rod 3c on the side of the floating frame and a supporting plate 2d at a tip part. In the side plates 2a and 2b of the arm 2, thin parts (a), (b), (c) and (d) of the plate material constituting the side plates are formed so that the thin parts are thinner then the other part. Therefore, the arm 2 has flexibility with respect to the entire arm, and stress from the lateral direction can be absorbed. On the other hand, there occurs a tendency that vibration is hard to stop. For preventing the vibration, attenuating plates 4a and 4b are attached between the side plates 2a and 2b of the arm 2. When a material to be measured is mounted and the stress is applied from the lateral direction on the arm 2, the arm itself absorbs the stress, and the concentration of the large stress on the specific part can be prevented.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to the structure of an electromagnetic scale, and in particular improves the mechanical structure of the device to improve impact resistance and durability as well as resolution. Regarding electromagnetic scales.

<Conventional technology and its problems> Electromagnetic balance type balances (electronic balances) have high resolution, but because of this, they react quickly to disturbances such as vibrations, air flow, and electrical noise. do. Therefore, when producing a highly sensitive scale, how to eliminate the influence of these disturbances is an extremely important issue. For example, air flow (
In order to avoid the influence of wind (wind), there is a device in which the tray on which the weighed object is placed is covered with a glass case.

Figure 3 shows the structure of an electronic balance. 30 is the device body, 31
is a glass case that forms part of this main body. 24
is an arm, and one end thereof is attached via a member 21 to 0002 for placing a weighed object. On the other hand, a floating frame 1 is connected to the end opposite to the plate mounting section. The floating frame 1 is supported by leaf springs 33a, 33b, 33c, and 33d, forming a donkey pal mechanism. A beam 35 having a fulcrum 36 is connected to the floating frame 1 via a temporary spring 34, and transmits the zero weight of the weighed object applied to the dish 32 to the measuring section (electromagnetic section). The measurement part is magnet 37, pole piece 3
8, a yoke 39, a coil 40, etc., converts the load into an electrical quantity and issues a weight display signal, and displays the display panel 4.
1 displays its weight. In this configuration, the glass case 31 usually has a structure in which the left and right surfaces and the top surface of the case can be opened and closed. Therefore, the object to be weighed is placed on the tray 32 from the side or top of the case.

In this case, when loading and unloading the weighed object, a load is applied in the lateral direction of the pan, and there is a risk that the leaf spring of the balance body may be bent. Furthermore, when loading and unloading from the top, the leaf spring may be damaged by dropping the weighed object or by placing an overloaded weighing object on it. For this reason, various structures have been proposed in the past to cope with such stress, but each has advantages and disadvantages, and the reality is that no structure has yet been proposed that fully satisfies the demands.

4 and 5 show a conventional stress absorbing structure disclosed in Japanese Utility Model Application Publication No. 58-69238.

In this structure, the arm 24 having the member 21 and the floating frame 1 are attached to each other via a coil spring 25.
The structure is such that the coil spring 25 absorbs lateral loads and prevents stress from being applied to the leaf springs and the like. Further, the stress (load) from above was dealt with by attaching a leaf spring 26. This structure absorbs stress from the side relatively well and is also effective against stress from above, but the number of parts increases and it becomes complicated, and the weight of the arm 24 increases. There is a risk that the accuracy itself may decrease. Furthermore, the use of large-area temporary springs may cause air movement within the device during weighing, which may adversely affect measurements.

Furthermore, as in Japanese Patent Application Laid-Open No. 60-71918, a device has been proposed in which an L-shaped extending arm is configured to rotate around a horizontal support axis, but this also has the problem of complicating the device. There is.

<Objective of the present invention> The present invention was constructed in view of the above-mentioned problems, and it is an object of the present invention to provide a device that has a simple structure, can sufficiently cope with vertical and horizontal stresses on a weighing part, and can improve measurement performance. With the goal.

<Summary of the present invention> In short, the present invention provides flexibility to the body of the arm that transmits the weight of a weighed object to impart stress absorption ability, and also provides a damping plate to the arm so as to damp vibrations caused by this deflection. This is the attached weighing device.

<Examples> Examples of the present invention will be specifically described below with reference to the drawings.

In FIGS. 1 and 2, reference numeral 1 indicates a floating frame of an electronic balance, and 2 indicates an arm attached to this floating frame. Arm 2 is
The two opposing side plates 2a and 2b, the support rod 2c on the floating frame 1 side, and the support plates 2d and 2d' at the tip end form a substantially rectangular shape as a whole. Reference numeral 5 designates a support plate for placing a calibration weight attached to arm 2, and reference numeral 7 designates a mounting member for connecting a plate for placing a weighed object (see FIG. 3). Of the arm 2 with this configuration, the side plates 2a and 2b are marked with
As shown in Figures 1 and 2, the thickness of the plate material constituting the side plate is thinner than other parts.
See B)]. Next, reference numeral 8 is a stopper that is installed with a slight gap in between so that the member 7 can be inserted into the position, but as will be described later, since the double arm body is flexible, the formation of the gap is difficult. The problem like the prior art shown in FIG. 3 does not occur. Further, reference numeral 9 denotes a coil spring, which is attached through a plate to absorb excessive stress when it is applied to the member 7 side.

Reference numerals 4a and 4b indicate damping plates extending between the side plates 2a and 2b of the arm 2. Since the arm 2 has thin parts A, C, C, and II on its side plates 2a and 2b, the entire arm has flexibility (spring properties), so when stress is applied to the arm from the side, Although it can absorb stress, it tends to make it difficult to stop vibration.

For this reason, a damping plate is installed as a necessity to prevent vibration.

Next, the principle of operation of the damping plates 4a and 4b will be specifically explained. The basic function of the damping plate is to damp the vibration of the arm using frictional force. Here, the frictional force F can be expressed as F=μN (μ is the friction coefficient and N is the normal pressure). If the materials forming the arms are the same, this μ is the same, so by changing the normal pressure N, the frictional force F changes. Since the load of the object to be weighed is applied to the member 7 when it is attached, the vertical pressure in the arm 2 changes in the length direction of the side plate. Therefore, if two damping plates are arranged in the length direction of the side plate, vibrations with different amplitudes can be damped. In the case shown, two damping plates 4a and 4b are arranged, so that vibrations Two types of damping effects can be obtained. The vertical pressure N is large in the area where the damping plate 4a is arranged, and therefore the frictional force F is also large, mainly damping vibrations with large amplitudes, and is small in the area where the damping plate 4b is arranged, so the frictional force F is small. This mainly damps amplitude vibrations.

Here, if the frictional force at the location of the damping plate 4a is Fa, then as the amplitude gradually decreases, the following equation finally holds true.

Here, δ is the amount of movement, b is the plate width, h is the plate thickness, E is Young's modulus, and 1 is the plate length. In other words, when the above equation is satisfied, the damping plate 4a moves (vibrates) together with the arm 2,
Thereafter, amplitudes smaller than this will be attenuated by the damping plate 4b, and the vibrations of the arm will be effectively damped by both of them. It is possible to install three or more damping plates, but this would cause problems such as the weight of the arm becoming excessive and the measurement accuracy decreasing, so as in this example, it is effective to use two or more damping plates. It is true.

In the above configuration, if stress is applied to the arm from the lateral direction when placing an object to be weighed, the body of the arm absorbs this stress due to its flexibility, and Prevent large stress from concentrating on one part.

Note that at this time, the vibration of the arm is well damped by the damping plate. Further, excessive stress from above is absorbed by a stress absorber (shock absorber) such as a coil spring.

Effects> Since the present invention is configured as described above, it can sufficiently cope with stress from various directions, does not cause problems such as damage to parts, and has a simple device configuration and achieves high resolution. can do.

[Brief explanation of the drawing]

1(A) is a plan view of an arm of an electromagnetic frame showing an embodiment of the present invention, FIG. 1(B) is a partially enlarged view of FIG. 1(A), and FIG. 2 is a plan view of an arm of an electromagnetic frame showing an embodiment of the present invention. 3 is a side view of the device showing the overall structure of the electronic balance, FIG. 4 is a plan view of the arm of another conventional device, and FIG. 5 is a plan view of FIG. 4. 1...Floating frame 2...Arms 2a, 2b--Side plates 4a, 4b--Attenuation'ui
7...Plate connection member 9...Coil spring A, mouth, C, 2...Thin wall part

Claims (4)

[Claims] (1) In a device that transmits the load of a weighed object placed on a weighing object mounting surface such as a plate connected to an arm to the measurement unit via the arm, the two side plates that make up this arm By forming at least one thin-walled portion in each of the two side plates, flexibility is imparted to the entire arm, thereby absorbing the stress applied to the arm, and at least one thin-walled portion is formed on the two side plates. An electromagnetic scale characterized in that two damping plates are arranged across each other to damp vibrations of the arm. (2) For the member that connects the weighed object placement surface to the arm,
An electromagnetic scale according to claim 1, characterized in that a shock absorber such as a coil spring is arranged to cope with an excessive load from a vertical direction. (3) The electromagnetic scale according to claim (1) or (2), wherein the thin wall portion is formed at two locations on each of the two side plates. (4) Two damping plates are arranged across the two side plates at different positions so that one damping plate damps vibrations with large amplitude and the other damping plate damps vibrations with small amplitude. An electromagnetic scale according to any one of claims (1) to (3).