JPS62167415A - Electronic scale - Google Patents

Abstract

PURPOSE:To always enable stable and accurate measurement to be conducted by providing a pressure regulating mechanism for maintaining the pressure in a casing constant without communication between the inside and outside of the casing. CONSTITUTION:In a condition that a pan receiving post 4 freely displaces with a prescribed gap between the through-hole 1a of a casing 1 and a load on a weighing pan 3 can be transmitted to a load detector 2, the space in the casing 1 and the space under a collar 5 including the through-hole 1a are sealed from outside by the collar 5 and an oil in a circumferential groove 6a. Although the displacement of the collar 5 due to that of the pan receiving post 4 changes the volume of the sealed space, the pressure in the sealed space is maintained at a constant value like the outside air pressure due to the deformation of a membrane member 8. Further, even when the air in the casing 1 expands on heating of the load detector 2, the pressure in the sealed space is kept constant by the deformation of the membrane member 8. Furthermore, since a pressure regulating mechanism 7 does not allow a communication between the inside and outside of the casing 1, a stable and accurate measured value can always be obtained under a constant pressure.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to electronic scales, and in addition to so-called electronic scales that use a load cell or the like as a load detection section, the present invention also applies to so-called electronic balances of electromagnetic force balance type. It includes the following:
In this specification, the electronic scale includes the above-mentioned electronic balance.

<Prior art> In general, an electronic scale has a load detection unit housed in a case, and a weighing pan for placing a sample to be measured is removed from the load detection unit in the case through a through hole drilled in the case. It is supported by a plate supporting post that protrudes in the opposite direction.

The gap between the support column and the through-hole of the case provides a path for particles, corrosive gases, chemicals, mists, etc. to enter the case from the outside world, so this gap is usually blocked by various mechanisms. It is kept small.

<Problems to be Solved by the Invention> In order to completely prevent dust and the like from entering the case, it is sufficient to provide a mechanism that makes the inside of the case substantially airtight from the outside world. However, in this case, a problem arises in that the pressure inside the case fluctuates due to the following reasons, which affects the measured values of weight and mass.

One is that when a load is placed on the weighing pan, the weighing pan and the pan supporting support are displaced. This amount of displacement is relatively large for devices that use a load cell as the load detection unit, and is extremely small for electronic balances with electromagnetic force balance, but in any case, this displacement changes the volume inside the airtight case. hand,
This is because the internal pressure fluctuates.

Another reason is that electrical elements such as a load detection section inside the case generate heat, and this heat expands the gas inside the airtight case, changing the internal pressure.

The purpose of the present invention is to prevent the intrusion of dust and other substances from the outside world by substantially sealing the inside of the case from the outside world, or even if the inside of the case is brought into a nearly sealed state, without causing a change in the pressure inside the case. The objective is to provide an electronic scale that can always perform stable and accurate measurements.

<Means for Solving the Problems> The configuration for achieving the above object will be described with reference to FIG. 1, which is an embodiment drawing. In a scale in which a weighing pan 3 located outside a case 1 and used to place a sample to be measured is connected by a pan support post 4 passing through the case 1, the case 1 is connected to the inside of the case 1 and the outside world. It is characterized by the provision of a pressure regulating mechanism 7 for maintaining the pressure within the case 1 constant without communication.

For example, as shown in FIG. 1, the outer circumferential portion of the collar 5 provided on the pan support post 4 is provided with a through hole 1 for passing the pan support post 4 through.
When configured to substantially seal the space inside the case 1 from the outside world and prevent dust etc. from entering from the outside world by immersing it in the liquid in the circumferential groove 6a surrounding the pan support post 4 Pressure fluctuations in the sealed space inside the case 1 due to displacement of the sensor or heat generated by the load detection section 20 are canceled by the pressure regulating mechanism 7, so that measurement can always be performed under a constant pressure.

Moreover, since this pressure regulating mechanism 7 does not have a gap that communicates the inside of the case I with the outside world, there is no intrusion of dust or the like from this part.

<Example> Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a longitudinal sectional view of an embodiment of the present invention.

Inside the case 1, a load detection section 2 constituted by a load cell, an electromagnetic force balancing mechanism, or the like is housed. A weighing pan 3 for placing a sample to be measured is arranged above the outside of the case 1, and this weighing pan 3 is attached to the case 1.
It is connected to the load detection part 2 by a plate support post 4 that passes through a through hole 1a bored in the upper part of the body with a predetermined gap therebetween.

At a predetermined portion of the tray support post 4 that protrudes from the through hole 1a to the outside, a neck portion 5 is provided that is in close contact with the entire outer circumferential surface of the support post 4.
A disk-shaped collar 5 with a is fixed thereto. The entire circumference of the outer end of the collar 5 is bent downward to form a cylindrical hanging portion 5b.

On the upper surface of the case l, there is an annular circumference a6 surrounding the through hole 1a.
A circumferential groove forming member 6 that forms a circumferential groove 6a is disposed, and this circumferential groove 6a is filled with oil. The entire circumference of the hanging portion 5b of the collar 5 is immersed in the oil in the circumferential groove 6a without contacting the circumferential groove forming member 6.

An opening 1b is formed at a predetermined location on the side wall of the case 1, and the opening 1b is formed by a membrane 8 formed of rubber or synthetic resin material and loosely fixed to the wall of the case 1. Its entire circumference is covered. This membrane body 8
is bent freely according to the pressure inside the case 1, and the pressure inside the case 1 is always maintained at the same level as the outside air pressure.The pressure regulating mechanism inside the case 1 is 7.

According to the above-described embodiment of the present invention, the pan supporting column 4 can be freely displaced with a predetermined gap between the through hole 1a of the case l and transmit the load on the weighing pan 3 to the load detection section 2. In this state, the space inside the case 1 and the space below the collar 5 including the through hole 1a are substantially sealed from the outside world by the collar 5 and the oil in the circumferential groove 6a.

Here, the displacement of the collar 5 due to the displacement of the dish support post 4 changes the volume of the sealed space, but at this time, due to the deformation of the membrane body 8 based on Pascal's principle, the sealed space is actually The volume of the sealed space does not change, and the pressure inside the sealed space is maintained at a constant pressure similar to the outside pressure. In addition, the load detection section 2
Even if the air inside the case 1 expands due to heat generation, the membrane body 8
Due to this deformation, the pressure in the sealed space is kept constant.

Furthermore, since the pressure regulating mechanism 7 constituted by the opening 1b and the membrane body 8 does not communicate the inside of the case 1 with the outside world, there is no risk of dust or the like entering from this part.

Note that the membrane body 8 may also be bellow-shaped.

In the above embodiment, the case where the present invention is applied to an upper pan type electronic scale has been explained, but as shown in FIG. The present invention can also be applied to this invention. In FIG. 2, the same components as in FIG. 1 are given the same numbers and their explanations are omitted. In this case, the space surrounded by the case 1, the collar 5, and the oil is sealed from the outside world, and the pressure within the space is kept constant by the pressure regulating mechanism 7.

In addition to the above-mentioned mechanisms, there are other pressure regulating mechanisms.
A mechanism whose principal part is shown in cross-section in FIG. 3 can be adopted. This pressure regulating mechanism 7' stores a liquid such as oil in a U-shaped tube 9 whose both ends communicate with the space inside the case 1 and the external space in order to maintain airtightness between these spaces. It has become.

Similarly to the pressure regulating mechanism 7 described above, this pressure regulating mechanism 7' also allows the case 1 to be kept airtight between the inside of the case 1 and the outside world.
The airtight space inside can always be maintained at the same pressure as the outside pressure.

Furthermore, in addition to the electronic scale having a sealing structure using oil in the collar 5 and the circumferential groove 6a as shown in FIGS. Of course, it can also be applied to electronic scales that are in a similar state.

<Effects of the Invention> As explained above, according to the present invention, the case housing the load detection section is provided with a pressure regulating mechanism that maintains the pressure inside the case constant without connecting the inside of the case to the outside world. Therefore, even if the inside of the case is substantially sealed or almost sealed from the outside world to prevent dust from entering from the outside world, the displacement of the tray support support and the inside of the case can be prevented. There is no change in the pressure inside the case due to heat generation in the heavy detection section, and stable and accurate measurement values can always be obtained under a constant pressure, improving the reproducibility of measurements. In addition, since this pressure regulating mechanism does not communicate the inside of the case with the outside world, there is no intrusion of dust etc. from this part, and by using it in conjunction with the sealing structure of the penetrating part of the plate supporting column, it can be used under any environment. It also prevents the intrusion of dust, etc., and allows accurate measurement values to be obtained.Furthermore, the mechanism is simple, does not require any special adjustment, and can be manufactured at low cost.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view of an embodiment of the invention, FIG. 2 is a longitudinal sectional view of another embodiment of the invention, and FIG. 3 is a sectional view of a main part of still another embodiment of the invention.

Claims (3)

[Claims] (1) In a scale in which a weighing pan outside the case for placing a sample to be measured is connected to a load detecting section housed in the case by a pan supporting post penetrating the case, An electronic scale, characterized in that it is provided with a pressure regulating mechanism for maintaining the pressure inside the case constant without communicating the inside of the case with the outside world. (2) The electronic device according to claim 1, wherein the pressure regulating mechanism is a mechanism in which an opening is provided in the wall of the case and the opening is covered with a flexible membrane. Scales. (3) The pressure regulating mechanism is a mechanism in which a liquid is housed in a U-shaped tube whose both ends communicate with the inner space of the case and the outer space, and which is used to shut off both spaces. An electronic scale according to claim 1.