JPH0756460B2 - High resolution weighing device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a weighing device having a weighing dish, and more particularly to an electronic device configured to prevent deterioration of weight measurement accuracy due to air flow inside the device. Regarding a weighing device.

[Conventional technology]

There is a weighing device called an electronic balance as an electromagnetic balance weighing device having high resolution. The basic structure of this device is that the weighing pan on which the weighing object is placed, the shaft that transmits the load applied to the weighing pan, the load that is transmitted through this shaft, and this load is converted into an electric quantity. And a display unit for displaying the load by a suitable display means such as a liquid crystal according to a signal output from the mechanism unit. Depending on the device, in addition to the structure in which the mechanical part is placed under the weighing pan and the load is directly transmitted to the mechanical part by the shaft, the load is indirectly applied to the mechanical part near the weighing pan via the beam. There is also a structure that transmits.

Although the electronic balance having the above-described structure has high accuracy, it is easily influenced by the outside, and the influence of the air flow is particularly great. That is, there is a problem that the weighing pan is agitated by the air flow, correct measurement becomes impossible, and it takes a long time until the weight display becomes stable. For this reason, in a device that requires particularly high precision, the weighing section centering on the weighing dish is housed in the case. That is, the weighing pan is housed in a case (usually a glass case having an openable / closable sliding door), and the mechanism section is housed in another room. With this configuration, it is possible to almost completely escape from the influence of the external air flow, and it is possible to prevent dust and the like from entering. However, the following problems have been pointed out in this configuration as well.

In the above configuration, the weighing chamber and the mechanism room having the mechanism section are partitioned by a floor, a wall surface, etc., so that the weighing chamber is not affected by the heat loss in the mechanism section. That is, although an air flow is generated inside the device due to heat loss, the weighing chamber and the mechanism chamber are separated in order to prevent the influence of this air flow. However, in order to transmit the load of the weighing object placed on the weighing dish to the mechanical section, this shaft must be inserted through the floor partitioning these rooms. The lower part of the weighing chamber is a mechanism room, and the temperature of the mechanism chamber becomes higher than that of the weighing chamber due to heat loss of electronic parts and electromagnetic parts.Therefore, the air in the mechanism chamber and the shaft body insertion hole formed in the floor Ascends into the weighing chamber through the gap between and. For this reason, the rising air flow hits the lower part of the weighing pan, and this weighs the weighing pan, which adversely affects the measurement.

[Problems to be solved by the invention]

For the above reasons, there have been proposed some types of configurations for preventing the adverse effect of the air flow rising from the mechanism room. As one of the configurations, there is Japanese Patent Laid-Open No. 57-153223. In this configuration, the lower plate (air flow protection plate) is fixedly installed under the weighing pan,
A sleeve is formed in the center of the lower plate, and the shaft for transmitting the load is inserted into the sleeve, and the outer diameter of the shaft is made to be close to the inner diameter of the sleeve. The air gap resistance of this gap is increased, the air gap resistance of this gap is increased, the gap between the sleeve and the floor surface opening formed around the sleeve is increased, and the air flow resistance of the floor surface opening is reduced. . As a result, most of the airflow from the mechanism chamber rises on the outer peripheral portion of the sleeve having a small airflow resistance, and the ascending airflow hits the lower tray fixed to the floor surface.
Therefore, the weighing pan itself is not hit by the upward flow, and high weighing accuracy is guaranteed.

However, in this configuration, it is necessary to make the gap between the sleeve and the shaft body as small as possible. Therefore, when the weighing object is placed away from the center of the weighing pan, even if the weighing plate is slightly tilted, And the inner wall surface of the sleeve come into contact with each other, and it may not be possible to accurately transmit the load to the mechanism portion. Even if the sleeve is eliminated and only the opening for inserting the shaft is formed in the lower plate arranged close to the weighing pan, it is necessary to minimize the gap between the opening and the shaft body. Therefore, if the weighing pan is tilted, the shaft body still comes into contact with the opening. In other words, since the center of swing of the shaft due to uneven distribution of the weighing object on the weighing pan is at the connecting part between the shaft and the mechanism part or the beam which is the lower end of the shaft, the lower plate is located close to the weighing pan. In the structure, a slight displacement of the shaft causes the upper part of the shaft, which has a large displacement, to come into contact with the opening. Further, in order to suppress the swing, a very strong shaft body must be used, and it becomes necessary to significantly strengthen the connection structure between the shaft body and the mechanism part or the beam.

Next, in addition to the above-mentioned configuration, there is Jitsukai Sho 59-21735.

This structure is intended to simplify the means for preventing the effect of rising airflow. In other words, while the above-mentioned configuration uses the lower tray to protect the weighing dish from upward airflow, this configuration is covered by the weighing dish on the surface (floor surface) separating the weighing chamber and the mechanism chamber. By forming a plurality of openings in a portion other than the region where the rising air flows, it is possible to prevent the ascending air current from directly hitting the weighing pan. This structure is very simple and can suppress an increase in manufacturing cost, but has the following problems. In other words, because of its structure, the opening must be formed in a region other than the area covered by the weighing pan, so if this opening is formed on the floor surface, the weighing object that falls outside the weighing pan will open this opening. After that, it easily falls into the lower mechanism room. That is, the opening for the rising air flow is preferably formed in the lower part of the weighing pan, without considering the influence of the air flow on the weighing pan and only considering the fall of the weighing object into the mechanism chamber. By the way, if the opening is formed at this position, the weighing dish itself functions as a cover for preventing the falling of the weighing object.

[Means for solving problems]

The present invention is configured in view of the above problems,
A windshield is fixedly installed on the side of the weighing chamber to protect the weighing dish from the upward flow of air, and an opening for inserting a shaft body having a sufficiently large inner diameter with respect to the outer diameter of the shaft body is formed on the floor. Another windshield is placed in the lower mechanism room, the shaft insertion hole of the windshield in this mechanism room is made slightly larger than the shaft outer diameter, and the windshield of the floor plate in the weighing pan or the weighing chamber side is installed. This is a weighing device configured so that an opening for airflow passage is formed on the floor surface located at the lower part, and thereby an ascending airflow from the mechanism chamber is guided to the windshield lower surface side on the weighing chamber side.

[Action]

As described above, the present invention protects the weighing dish from the ascending air current by the windshield on the side of the weighing chamber for accurate weighing, and the opening for inserting the shaft body of the floor plate is sufficiently large with respect to the outer diameter of the shaft body. Therefore, the accuracy does not decrease even if the shaft swings,
Further, since all the air flow passage openings formed on the floor plate are located on the lower surface side of the weighing chamber windshield, the weighing object does not fall directly into the mechanism section.

〔Example〕

Embodiments of the present invention will be specifically described below with reference to the drawings.

In FIG. 1, reference numeral 1 denotes a floor plate which is a partition plate. The floor plate 1 defines a weighing chamber 2 in the upper part and a mechanism chamber 3 in the lower part. Of these, the weighing chamber 2 is hermetically sealed by a case made of a material such as glass so that the weighing chamber 2 is not affected by the outside during weighing. Reference numeral 4 shows a part of this case. Reference numeral 5 is a weighing dish located in the weighing chamber 2, and a shaft body 6 is connected to the center of the lower surface thereof. This shaft 6 is the floor plate 1
It is connected to an arm 8 located in the mechanism chamber 3 through the opening 7 formed in the above, and the arm 8 is further connected to a load measuring unit (not shown) to load the load of the weighing object placed on the weighing pan. It is configured to be transmitted to the load measuring unit via the shaft body 6 and the arm 8. Of these, the inner diameter of the opening 7 is formed sufficiently larger than the outer diameter of the shaft body 6 as described later, and even if the shaft body 6 swings, the shaft body may contact the inner wall of the opening portion. I try not to.

A windshield 9 is arranged below the weighing dish 5, and has a diameter larger than that of the weighing dish 6 so as to cover the lower surface of the weighing dish 5. An opening having an inner diameter substantially equal to that of the opening 7 formed in the floor plate 1 is formed in the center thereof. The windshield 9 thus formed is arranged on the floorboard 1 so that its opening matches the opening 7 of the floorboard. In this state, the windshield 9 and the inner peripheral edge of the opening of the floorboard 1 are sandwiched by the ring-shaped connecting member 10 made of a flexible material such as rubber, whereby the windshield 9 is fixed to the floorboard 1. In this case, if the wall thickness of the connecting member 10 is made sufficiently thick, the connecting member end edge portion 10a on the side of the windshield 9 serves as a weir, and liquid or the like can be prevented from flowing into the mechanism chamber. However, the attachment means of the windshield 9 is not limited to the above method, and may be directly fixed to the floor plate 1 with a screw, for example. 12 is this floor board 1
One or a plurality of openings for air passage are formed in the area where the floor plate occupies within the area occupied by the weighing pan 5 or at least the windshield 9, that is, at least the lower portion of the windshield 9. And

Next, reference numeral 11 is a windshield (hereinafter referred to as "mechanical portion windshield") arranged in the mechanism chamber 3. An opening 11a for inserting a shaft is formed at the center of the mechanism windshield 11, and the inner diameter of this opening is set to a value close to the outer diameter of the shaft 6 as long as there is no risk of the shaft 6 contacting. The gap between the shaft body 6 and the opening 11a is reduced to increase the air flow resistance. Reference numeral 13 is a wind shield ring interposed between the lower surface of the floor plate 1 and the upper surface of the mechanism windshield 11. The wind shield ring 13 may be made of metal, but if it is made of a flexible material such as rubber or sponge, it is easier to make close contact with the floor plate 1 and the mechanism windshield 11,
Airtightness can be improved. Although not shown, the mechanism windshield can be configured by using a pressing plate that supports the calibration weight. Further, reference numeral 14 is a dust protector arranged on the floor of the weighing chamber.

In the above configuration, when the weighing device is operated, the temperature of the mechanism chamber 3 becomes higher than that of the weighing chamber 2 over time due to heat loss of the mechanism portion. For this reason, the air in the mechanism chamber 3 tries to rise, but most of the air is inserted into the mechanism windshield 11 because the shaft insertion portion of the mechanism windshield 11 has high flow resistance as described above.
And flows into the weighing chamber 2 through the opening 12 from the outside of the wind shield ring 13. Further, the air flow flowing in through the opening 12 hits the windshield 9, but since the windshield is fixed, it is not agitated, and the windshield 9 effectively protects the weighing pan 5 from this upward flow of air. Further, since the opening 7 of the floor plate 1 is formed to be sufficiently larger than the diameter of the shaft body 6, even if the shaft body 6 swings, the shaft body does not come into contact with the inner wall of the opening portion, so that it is accurate. Can weigh. Further, since the mechanism windshield 11 is close to the connecting portion of the arm 8 which is the swing center of the shaft, the displacement amount is small, and the thickness of the mechanism windshield 11 is about 1 mm, so there is no problem.

FIG. 2 shows a second embodiment.

In this embodiment, a glass plate is arranged above the floor plate 1, and the glass plate is used as a virtual floor plate. Some of the weighing objects are corrosive, and if the flooring board is made of metal, plastic, etc., the weighing board spilled from the weighing dish may cause the flooring board to corrode or discolor. Therefore, a glass plate material having a high corrosion resistance is arranged on the floor plate 1.

Reference numeral 15 is a glass plate arranged on the upper part of the floor plate 1 and functions as a virtual floor plate. Reference numeral 16 is an opening for passing an air flow formed in the glass plate 15, and is formed so as to be located under the windshield 9 on the weighing chamber side for the reason described in the first embodiment. In the configuration shown, this opening 16 is an opening formed in the floorboard 1.
Although it is formed at a position corresponding to 12, the openings 12 and 16
It is also possible to shift the formation position of the above to complicate the flow path of the ascending airflow to reduce the flow velocity of the airflow entering the weighing chamber. The opening 19 for inserting the shaft body 6 formed in the glass plate 15 is provided.
Again, for the reason shown in the first embodiment, the shaft body 6 is formed to have an inner diameter sufficiently larger than the outer diameter. Reference numerals 17 and 18 are wind-shielding rings arranged concentrically, and are interposed between the floor plate 1 and the glass plate 15. Similar to the ring 13 described above, these rings can be formed with a material having flexibility to obtain high adhesion.

In this structure, the air in the mechanism chamber 3 first passes through the opening 12 of the floor plate 1, and then enters the weighing chamber 2 through the opening 16 of the glass plate 15. Furthermore, this air flow hits the windshield 9 and bypasses it.

In this embodiment, since the glass plate 15 is placed on the floor plate 1, the glass plate can be easily removed, and the dirt attached to the glass plate can be easily removed.

〔effect〕

According to the present invention, as described above, the windshield on the side of the weighing chamber can protect the weighing dish from the ascending air current, and the weighing can be performed accurately.

Further, since the shaft body insertion opening of the floor plate (glass plate) is configured to be sufficiently larger than the shaft body outer diameter, the shaft body does not contact the inner wall of the opening even if the shaft body swings. It can be kept high all the time.

Further, all the air flow passage openings formed on the floor plate are located on the lower surface side of the weighing pan or the draft shield of the weighing chamber, and these weighing pans and the like function as a cover, so that the weighing object does not fall directly into the mechanism section. .

[Brief description of drawings]

FIG. 1 is a partial sectional view of an electronic balance showing a first embodiment of the present invention, and FIG. 2 is a partial sectional view of an electronic balance showing a second embodiment. 1 ... Floor board, 2 ... Weighing chamber, 3 ... Mechanism chamber, 5 ... Weighing dish, 6 ... Shaft, 7 ... Shaft insertion opening, 8 ... Arm, 9 ... Weighing chamber side windshield , 10 ...... Connection member, 10a ...... Edge part of the connection member on the windshield side, 11 ...... Mechanical part windshield, 11a ...... Shaft insertion hole, 12, 16 ...... Airflow passage hole, 13, 17, 18 ...... Windshield ring, 15 …… Glass plate

Claims (1)

[Claims] 1. A floor plate defines a weighing chamber and a mechanism chamber below the floor, and a shaft inserted through the floor plate directly or indirectly connects a weighing dish arranged in the weighing chamber to a load receiving portion in the mechanism chamber. In the weighing device configured as described above, the inner diameter of the shaft body insertion opening 7 of the floor plate 1 is formed sufficiently larger than the outer diameter of the shaft body 6, and the windshield 9 is provided below the weighing dish 5 on the weighing chamber 2 side. The windshield 9 is located at the center and has an opening having the same diameter as the opening 7 at the center of the paragraph, and the opening at the center of the paragraph and the opening 7 are substantially aligned with each other. The windshield 9 is fixed to the floorboard 1, and an opening 12 for airflow is formed in the floorboard 1 so as to be located in the lower portion of the windshield 9, and a mechanism chamber 3 located in the lower portion of the floorboard 1 is formed.
The mechanism windshield 11 is disposed inside, and the windshield ring 13 is interposed between the mechanism windshield 11 and the floor plate 1, so that the mechanism windshield 11 is located on the load receiving side of the shaft body 6. It is located close to the connecting portion, and further, the gap between the shaft body insertion hole 11a of the mechanism windshield 11 and the shaft body 6 is made small, and the opening 12 of the floor plate 1 is located at the outer peripheral portion of the wind shield ring 13. A high-resolution weighing apparatus characterized in that the influence of the air flow on the weighing dish is reduced by the above configuration.