JP7380255B2 - analytical balance - Google Patents

Description

The present invention relates to an analytical balance equipped with a windshield case.

For high-precision, high-resolution analytical balances, external airflow has a large effect on measurement accuracy, so a weighing chamber must be provided with a windshield case surrounding the weighing pan to prevent it from being affected by external airflow. is commonly practiced.

That is, the conventional analytical balance is constructed as shown in FIG. 4, and the windshield case 52 of the analytical balance 51 has a rectangular parallelepiped box shape with an open bottom, and is equipped with an electric circuit for measuring the weight of the sample and a display for displaying the weight value. A windshield case 52 is disposed on the upper surface of the main body case 54 that houses the parts 53 and the like, and the measuring pan 55 provided on the upper surface of the main body case 54 is surrounded by the windshield case 52 to prevent external airflow from flowing inside the windshield case 52. An unaffected weighing chamber 56 is formed. A top surface 57 and four side surfaces 58 of the windshield case 52 are made of, for example, transparent glass so that the weighing chamber 56 can be viewed from the outside (see, for example, Patent Document 1).

At this time, the top surface 57 and left and right side surfaces 58 of the windshield case 52 are formed to be openable and closable, and when taking out and taking out the weighed object, either the top surface 57 or the left and right side surfaces 58, whichever is easier to take in and out, is opened. A possible configuration will be adopted. An analytical balance equipped with such a windshield case is usually installed in a measurement environment such as a predetermined measurement room with stable external airflow and temperature.

JP2011-257305A (Paragraphs 0002-0003 and Figure 7)

Incidentally, the measurement environment in which the analytical balance 51 is installed is usually equipped with air conditioning equipment in order to maintain its temperature constant, but in the case of the conventional windshield case 52 as described in Patent Document 1, air conditioning equipment is installed in order to maintain the temperature constant. It was thought that it would not be affected. However, as a result of intensive research, the inventor of the present application discovered that even in an analytical balance equipped with a conventional windshield case 52 as described in Patent Document 1, convection occurs within the windshield case 52. The cause of this is that cold air or hot air hits the top surface 57 of the windshield case 52, causing a temperature change on the top surface 57 of the windshield case 52, and a temperature difference between the top surface 57 and the area around the weighing pan 55 below the weighing chamber 56. It was also determined that the temperature change caused convection within the windshield case 52.

In this way, for example, in an air-conditioned environment, when the temperature of the top surface 57 of the windshield case 52 drops, the temperature of the air in the upper part of the weighing chamber 56 becomes lower than that in the lower part. The upward movement of the air and the downward movement of the upper air are promoted, and air convection occurs within the weighing chamber 56, which may result in a decrease in the stability of measurement and a deterioration in reproducibility.

The present invention has been made in view of the above-mentioned problems, and it is possible to prevent the occurrence of air convection in the weighing chamber in the windshield case, thereby preventing a decrease in weighing stability and deterioration in reproducibility performance. The purpose is to

In order to achieve the above object, the analytical balance of the present invention is an analytical balance equipped with a windshield case, in which at least the top surface of the windshield case has a heat insulation structure that blocks the influence of external heat into the inside of the windshield case. It is characterized by having the following.

Further, the top surface may be formed by disposing at least two plates with a heat insulating layer interposed between them, and the heat insulation structure may be configured, and the top surface may be configured such that the top surface excludes the top surface. The heat shielding structure may be formed of a plate material having a lower thermal conductivity than other surfaces of the windshield case.

Moreover, in the analytical balance equipped with a windshield case, a heating means may be provided on the top surface of the windshield case to heat the top surface.

According to the present invention, even if the temperature of the top surface of the windshield case decreases due to air conditioning in the measurement environment of the analytical balance, it is possible to prevent the temperature inside the top surface of the windshield case from changing as in the past. An analytical balance with excellent weighing accuracy that can prevent air convection inside the windshield case caused by changes in internal temperature, preventing a decline in weighing stability and reproducibility. It becomes possible to provide

FIG. 1 is a perspective view of an analytical balance according to a first embodiment of the present invention. FIG. 2 is an exploded perspective view of the top surface of the windshield case in FIG. 1. FIG. FIG. 3 is a plan view of a portion of an analytical balance according to a second embodiment of the present invention. FIG. 1 is a perspective view of a conventional analytical balance.

<First embodiment>
A first embodiment of an analytical balance according to the present invention will be described with reference to FIGS. 1 and 2. Note that FIG. 1 is an overall perspective view, and FIG. 2 is an exploded perspective view of the top surface of the windshield case.

As shown in FIG. 1, an analytical balance 1 according to the present embodiment includes a main body case 2 that has a built-in electric circuit for measuring the weight of a sample, and a display section 3 that is disposed on the front upper surface of the main body case 2 and that displays weighed values. , a weighing pan 4 disposed on the top surface of the main body case 2, and a rectangular box-shaped windshield case 5 having an open bottom surface and covering the main body case 2 from the top side to surround the measuring pan 4. A weighing chamber 6 that is not affected by external airflow is formed inside the windshield case 5.

The windshield case 5 includes a top windshield 7 that constitutes the top, a left windshield 8a and a right windshield 8b that constitute the left and right sides, respectively, and a front windshield 8c that constitutes the front and rear sides, respectively. and a rear windshield 8d, and handles 9 are attached to the top windshield 7 and the left and right side windshields 8a, 8b, and the handles 9 are gripped to open these windshields 7, 8a, 8b. Each windshield glass 7, 8a, 8b is provided so that it can be opened and closed.

By the way, as shown in FIG. 2, the top windshield 7 is formed of so-called double glass, and the peripheries of the two rectangular glass plates 7a, 7b are rectangular having approximately the same outer dimensions as these glass plates 7a, 7b. It is formed by being bonded to the top and bottom of a frame-shaped spacer 7c. Here, a heat insulating layer is formed between the two glass plates 7a and 7b, and by adopting a heat shielding structure using double glass, the influence of external heat on the weighing chamber 6 inside the windshield case 5 is blocked. .

The heat insulating layer between the two glass plates 7a and 7b may be formed by filling a gas with a lower thermal conductivity than glass, such as nitrogen gas or argon gas, in addition to dry air, or a layer with a thermal conductivity of glass. It may also be formed by filling a transparent resin with a lower temperature than 100 ml or by inserting a transparent resin plate. Here, as the transparent resin, for example, acrylic resin, polycarbonate resin, polyvinyl chloride resin, polyethylene terephthalate resin, etc. may be used.

By adopting a heat-insulating structure with double glass on the top surface of the windshield case 5, even if the top windshield glass 7 of the windshield case 5 is hit by air conditioning wind in the measurement environment, the air in the upper part of the weighing chamber 6 Since the temperature difference between the air in the upper part of the weighing chamber 6 and the air in the lower part of the weighing chamber 6 can be prevented from changing, the generation of air convection in the weighing chamber 6 can be suppressed.

Therefore, with conventional analytical balances equipped with a windshield case, convection could only be suppressed outside the windshield case, but according to the above-described embodiment, the cooling air of the air conditioner in the measurement environment It is possible to prevent the temperature of the upper part of the weighing chamber 6 from lowering than the lower part due to the temperature of the front windshield glass 7 decreasing, and it is possible to prevent the temperature of the upper part of the weighing chamber 6 from becoming lower than that of the lower part. It is possible to prevent the occurrence of air convection within the case, thereby preventing deterioration in weighing stability and reproducibility, and providing an analytical balance with excellent weighing accuracy.

At this time, by forming the top windshield glass 7 of the windshield case 5 with double glass, the transparency of the top surface of the windshield case 5 can be maintained and the weighing chamber 6 can be visually recognized from the outside. Measurement work can be carried out while checking the situation in step 6.

<Second embodiment>
A second embodiment of the analytical balance according to the present invention will be described with reference to FIG.

This embodiment is different from the above-described first embodiment in that, as shown in FIG. A hot wire resistor 11 is pasted on the surface of the top windshield 7 using ITO (Indium Tin Oxide) film formation technology, and the top windshield 7 is heated by energizing the hot wire resistor 11 with a power supply not shown. This is what we did. At this time, in order to prevent air convection from occurring in the weighing chamber 6, the heat generation amount of the hot wire resistor 11 is set so that the air above the weighing chamber 6 can be heated to an extent that does not interfere with measurement. It is preferable to leave it there.

By constantly energizing the hot wire resistor 11, which is the heating means, from a power supply device (not shown), even if the cooling air from the air conditioner in the measurement environment of the analytical balance 1 hits the top windshield 7 of the windshield case 5, the Since the surface windshield 7 is heated, the temperature of the air in the upper part of the weighing chamber 6 is prevented from becoming lower than that in the lower part.

Therefore, according to the second embodiment, similar to the first embodiment described above, the convection of air in the weighing chamber 6 due to a decrease in the temperature of the top windshield glass 7 of the windshield case 5 as in the conventional case. It is possible to provide an analytical balance that can prevent such occurrence and has excellent weighing accuracy without deteriorating weighing stability or reproducibility.

Note that the present invention is not limited to the embodiments described above, and various changes other than those described above can be made without departing from the spirit thereof. For example, in the first embodiment described above, an example has been described in which the top surface of the windshield case 5 is made of the top windshield glass 7 made of double glass. The top surface may be made of a transparent resin plate material with a low resistance.

In addition, in the first embodiment described above, an example was explained in which the heat isolation structure using double glass was adopted only on the top surface of the windshield case 5, but all sides of the windshield case 5 on the front, back, left and right also have a heat isolation structure using double glass. may be adopted.

Further, in the second embodiment described above, a case has been described in which the hot wire resistor 11 serving as a heating means is arranged at the peripheral edge of the surface of the top windshield 7, but the hot wire resistor 11 is limited to the case where it is arranged at the peripheral edge. The heating means is not limited to the hot wire resistor 11 either.

Further, in the second embodiment described above, the top surface of the windshield case 5 is constantly heated by the hot wire resistance 11, but the temperature of the air in the upper and lower parts of the weighing chamber 6 is detected by the sensor, and the temperature of the air in the upper and lower parts of the weighing chamber 6 is detected. When the temperature of the upper part is lower than that of the lower part and air convection is likely to occur in the weighing chamber 6, the heating means may be energized to heat the top surface.

Further, in the second embodiment described above, the power supply device may use a solar cell that generates power using the light of an indoor light in the measurement environment, and further stores the electric energy generated by the solar cell in a power storage area to supply power to the heating means. You can do it like this.

Further, the present invention can be applied to an analytical balance equipped with a windshield case.

1...Analytical balance 5...Windshield case 7...Top windshield glass (top)
11...Hot wire resistance (heating means)

Claims (2)

For analytical balances equipped with a windshield case,
At least a top surface of the windshield case has a heat isolation structure that suppresses convection within the windshield case by blocking the influence of heat outside the windshield case on the inside of the windshield case;
An analytical balance characterized in that the top surface is formed of a plate made of a material having a lower thermal conductivity than other surfaces of the windshield case other than the top surface, and the heat isolation structure is configured. 2. The analytical balance according to claim 1, wherein the top surface is formed by disposing at least two plates with a heat insulating layer interposed therebetween, and the heat shielding structure is configured.

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