JPH0329716Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a convection preventer for an electronic balance that prevents convection due to self-heating of a highly sensitive electronic balance.

<Prior art> Highly sensitive electronic balances with a reading limit of about 0.1 mg are sensitive to the movement of airflow that hits the weighing pan because of their high sensitivity. Therefore, all electronic balances in this class are equipped with a weighing chamber that is separated from the outside world by a windshield in order to prevent the wind from hitting the pan.
A weighing pan is placed in this weighing chamber. When loading and unloading a sample on this plate, open the door provided in the weighing chamber.

<Problem that the invention aims to solve> By the way, electronic balances use electronic circuit parts such as ICs and transistors, and as is well known, these parts generate heat, and various measures have been taken to release this heat to the outside as much as possible. However, a certain amount of heat flows into the capacity chamber. Due to this inflow of heat, the temperature of the air in the capacity chamber increases, albeit slightly, and the air density decreases. When the door is opened to load and unload the sample onto the plate, convection as shown by the solid line in Figure 9 occurs due to the density difference with the outside air. Air flows, which are dashed lines in the figure, remain and each influence the dish 3. As a result, as shown by the solid line in the graph in Figure 10, the balance's indication changes not only from code a to b when the door is opened, but also from code b to c after the door is closed, and the indicated value changes immediately. is not stable. The time it takes for the indicated value to stabilize and reach the true value after the door is closed depends on the size of the dish 3 and the weighing chamber 1.
Although it depends on the amount of temperature rise within the
It takes ~20 seconds. This time is a major factor in prolonging the measurement time.

For this reason, the conventional reading limit was 0.1 mg.
In the case of high-sensitivity electronic balances, the generation of heat and the addition of heat to the weighing chamber have been tried to be avoided as much as possible.

The purpose of this invention is to prevent the generation of convection due to the opening and closing of the door of the weighing room, and to prevent the generation of convection by opening and closing the door of the weighing room. The purpose of the present invention is to provide a convection preventer for an electronic balance that can shorten the time until the indicated value shows the true value after closing.

<Means for solving the problems> This will be explained using the embodiment drawings FIGS. 1 to 7. The convection preventer for electronic balances of the present invention has a weighing pan 3 in a weighing chamber 1 having a door 2 that can be opened and closed.
A convection preventer 10 for an electronic balance is disposed outside and below the door 2 of an electronic balance, the heat generating part 11 having a length substantially equal to the opening width w of the door 2 of the electronic balance. , it is characterized in that it has a mounting part 13 for the balance which is thermally isolated from the heat generating part 11 by a heat insulator 12 .

<Function> The convection preventer 10 is placed at the mounting position 4 near the outside of the door 2 shown in FIG. As a result, an upward airflow is generated outside the door 2 as shown by the solid line in FIG. When the door 2 is opened in this state, there is almost no density difference between the air inside the capacity chamber 1 and the outside air, and the convection preventer 10
Convection due to the inflow of outside air and outflow of indoor air as in the case of the electronic balance shown in Fig. 9, which is not equipped with a movement is small.
Furthermore, even if a downward airflow occurs in the weighing chamber 1 as shown by the broken line in FIG. 8 due to slight convection at the moment when the door 2 is closed, almost the same amount of
Door 2 is countered by a slight upward airflow from
After closing, rotational flow is difficult to occur in the capacity chamber 1, and a stationary state quickly appears.

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

Figures 1 to 6 show a convection preventer that is an embodiment of the present invention; Figure 1 is a perspective view thereof, Figure 2 is a plan view, Figure 3 is a sectional view, and Figure 4 is an enlarged view of the main parts. A sectional view, FIG. 5 is a plan view of the main part, and FIG. 6 is a front view of the main part.

The convection preventer 10 has a heat generating part 11 and a mounting part 13 provided to the heat generating part via a heat insulator 12.

The heating section 11 has the opening width w of the door 2 of the electronic balance.
(Refer to Figure 7) The shape is elongated and has a length approximately equal to
formed to a length of The configuration of the heat generating section 11 is such that the internal heat generating element 4 is covered with a cover 15. The heating element 14 can be constructed, for example, by winding a nichrome wire 14a around mica 14b, sandwiching it with mica 14c, and then wrapping it with a thin metal plate 14d. This heating element 14 is sandwiched between the heat insulator 12 and the cover 15, and the heat insulator 12
Attachment part 1 consisting of adhesive tape on the front side of the
3 is provided. 16 is a plug for connection.
In the figure, the nichrome wire 14a is normally wound, but it is desirable to wind it in a non-inductive manner so as not to generate external magnetism. In addition, the present invention is provided with a heat insulator 12, but if the heat from the heat generating part 11 is conducted to the balance base, the temperature rise in the weighing chamber will increase. This is to ensure that only the air in the area is heated.

FIG. 7 is a perspective view showing a typical example of a high-sensitivity electronic balance, in which a weighing chamber 1 is formed within a door 2, and a weighing pan 3 is provided in the weighing chamber 1. Then, the balance base 5, which is located below and outside the door 2,
A mounting position 4 for the convection preventer 10 is provided on the side wall of the housing. When the convection preventer 10 is attached to this attachment position 4 and the heat generating portion 11 is heated, an upward airflow along the door 2 is generated as shown in FIG. The degree of heating of the heat generating portion 11 is determined in advance so that the air temperature within the airflow at this time is approximately equal to the air temperature within the capacity chamber 1. This eliminates the density difference between the inside and outside air, and even if the door 2 is opened, there is almost no air going in and out between the capacity chamber 1 and the outside. Therefore, when the door 2 is closed, rotational flow as shown by the broken line in FIG. 9 is unlikely to occur inside the weighing chamber 1 as in the conventional case, and even if some air enters and exits, the flow as shown by the broken line in FIG. Even if a downward airflow occurs along the inner edge of the door 2, it is canceled by an upward airflow caused by heating of the heat generating part 11 that enters the capacity chamber 1 just before the door 2 is closed. As a result, as shown in Figure 10, the true value stabilizes after the door 2 is closed, as shown in the graph of the time change of the balance reading due to the opening and closing of the door 2, in comparison with the case where the convection preventer 10 is not installed. The time it takes to reach point c' shown in Figure 1 is 1/2 to 1/3 of the conventional time.

Although the heating element 14 of the convection preventer 10 described above uses the nichrome wire 14a, the heating element 14 is not limited to this, and a sheathed heater, a ceramic heater, or a semiconductor heater can be used. Further, the cross-sectional shape of the heat generating portion 11 can be round, various polygonal shapes, or film-shaped. FIG. 11 is a perspective view showing an example of a convection preventer 10 showing such another embodiment, which has a heat generating part 11 having a round cross section and uses a sheathed heater as the heat generating element. Also, the mounting part 13
is composed of suction cups that also serve as insulation. Further, FIG. 12 shows a convection preventer 10 showing still another embodiment.
In this perspective view, the heating element 14 constituting the heating part 11 is made of a film-like heater, and the mounting part 13 made of adhesive tape is inserted through the heat insulating material 12 arranged in a plate-like layer.
is provided.

The surface temperature of the heat generating part 11 of the convection preventer 10 explained above will vary depending on the temperature rise in the capacity chamber 1 of the balance used, but the surface temperature should be 0.5°C to 20°C higher than room temperature. It is better to do so.
Therefore, the amount of heat generated by the heating element 14 of the heat generating section 11 can be set in a range of, for example, 0.1 W to 20 W, and the amount of heat generated can be variably adjusted.

The convection preventer 10 of the present invention may not be attached to the balance itself, but may be placed on the upper surface of the balance stand 6 outside the door 2 and below it, as shown in FIG. Further, it goes without saying that the convection preventer 10 may be installed only on the door side that is normally used, or may be installed on both door sides.

<Effects> The present invention has the above-mentioned configuration, and is used as a convection preventer for electronic balances, including a heat generating part with a length approximately equal to the opening width of the balance door, and a balance thermally isolated from the heat generating part by a heat insulating material. By placing this convection preventer outside and below the door of the electronic balance, air can be prevented from entering and exiting the weighing chamber when the door is opened. Furthermore, by suppressing the generation of air flow in the weighing chamber when the door is closed, it is possible to significantly shorten the time from when the door is closed until the measured value becomes stable and shows the true value. Therefore, the efficiency of weighing work can be improved. In addition, since less air enters and exits the weighing chamber when the door is opened, the indicated value will not deviate significantly from the true value when the door is open, making it effective even when weighing a certain amount, for example. It can be done.

[Brief explanation of drawings]

Figures 1 to 6 show a convection preventer that is an embodiment of the present invention; Figure 1 is a perspective view thereof, Figure 2 is a plan view, Figure 3 is a sectional view, and Figure 4 is an enlarged view of the main parts. A sectional view, FIG. 5 is a plan view of the main part, and FIG. 6 is a front view of the main part. Figure 7 is a perspective view showing a typical example of an electronic balance to which the convection preventer of the present invention is applied, Figure 8 is an explanatory diagram of air flow in an electronic balance equipped with the convection preventer of the present invention, and Figure 9 is Illustration of air flow in an electronic balance without a convection preventer installed, No. 10
The figure is a graph showing the change in indicated value over time as the door of the electronic balance is opened and closed with and without the convection preventer of the present invention installed, and Figures 11 and 12 respectively show other implementations of the present invention. FIG. 13 is a perspective view of an exemplary convection preventer, and FIG. 13 is a front view showing an example of the arrangement of the convection preventer. 1...Weighing room, 2...Door, 3...Dish, 4...
...Mounting position, 5...Balance base, 10...Convection preventer, 11...Heating part, 12...Insulator, 13
... Mounting part, 14 ... Heating element.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) A convection preventer for an electronic balance that is located outside and below the door of an electronic balance in which a weighing pan is disposed in a weighing chamber that has a door that can be opened and closed. An electronic balance, characterized in that it has a heat generating part with a length substantially equal to the opening width of the door of the electronic balance, and an attachment part to the balance that is thermally isolated from the heat generating part by a heat insulator. Convection preventer. (2) The convection preventer for an electronic balance according to claim 1, wherein the heating element constituting the heating section is a sheathed heater. (3) The convection preventer for an electronic balance according to claim 1, wherein the heating element constituting the heating section is a film heater. (4) The convection preventer for an electronic balance according to claim 1, wherein the heating element constituting the heating section is a ceramic heater. (5) The convection preventer for an electronic balance according to claim 1, wherein the heating element constituting the heating section is a semiconductor heater. (6) The convection preventer for an electronic balance according to any one of claims 1 to 5 of the utility model registration claim, in which the amount of heat generated from the heat generating part is variable. (7) The length of the heating part is 5 to 30cm, and the amount of heat generated is 0.1W.
20W. A convection preventer for an electronic balance according to any one of claims 1 to 6 of the utility model registration claims.