JPS62179615A - High resolution weighing apparatus - Google Patents

Abstract

PURPOSE:To achieve accurate weighing, by protecting a weighing plate from an updraft with a windshield on the side of a weighing chamber. CONSTITUTION:While a weighing apparatus is in operation, the temperature of a mechanism chamber 3 rises higher than a weighing chamber 2 with passage of time owing to a heat loss of a mechanism section. For that reason, air in the mechanism chamber 3 tends to rise, but because of a higher fluid resistance at a shaft body insert part of a windshield 11 at the mechanism section, the air mostly bypasses the windshield at the mechanism section and flows into the weighing chamber 2 via an opening from outside of a window shielding ring 13. In addition, the current flowing from an opening 12 hits the windshield 9 which protects a weighing plate 5 effectively from the updraft of the air. As the opening 7 of a floor board 1 is made much larger than the diameter of a shaft body 6, the shaft body is kept from contacting the inner wall of the opening regardless of swing, if any, thereof 6, thereby enabling accurate weighing.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a weighing device having a weighing pan, and particularly to an electronic weighing device configured to prevent the accuracy of weight measurement from decreasing due to the flow of air inside the device. Regarding a weighing device.

[Conventional technology]

There is a weighing device called an electronic balance as an electromagnetic balance type weighing device having high resolution. The basic structure of this device is a weighing pan on which the object to be weighed is placed, a shaft that transmits the load applied to the weighing pan, and a shaft that receives the load transmitted through the shaft and converts this load into an electrical quantity. A display section is connected to the mechanism section for displaying the load using a suitable display means such as a liquid crystal display based on a signal output from the mechanism section. Depending on the device, the mechanical part is placed below the weighing pan and the load is directly transmitted to the mechanical part by the shaft, or the load is transmitted indirectly to the mechanical part close to the weighing pan via a beam. There are also structures that transmit information.

Although the electronic balance having the above configuration has high accuracy, it is therefore susceptible to external influences, particularly air currents. That is, there are problems in that the weighing pan is agitated by the air flow, making it impossible to perform accurate measurements, or that it takes a long time for the weight display to become stable. For this reason, in devices that require particularly high precision, the weighing section, including the weighing pan, is housed in a case. That is, the weighing plate is housed in a case (usually a glass case with a sliding door that can be opened and closed), and the mechanism section is housed in a separate room. With this configuration, it is possible to almost completely escape from the influence of external airflow, and it is also possible to prevent the intrusion of dust and the like. 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 separated by a floor, wall surface, etc., so that the weighing chamber is not affected by heat loss in the mechanism section. That is, although an air flow is generated inside the apparatus due to heat loss, the weighing chamber and the mechanism chamber are separated from each other in order to prevent the influence of this air flow. However, in order to transmit the load of the weighed object placed on the weighing pan to the mechanism, this shaft must necessarily pass through the floor that partitions these rooms. The lower part of the weighing chamber is a mechanism room, and since the mechanism room becomes hotter than the weighing chamber due to heat loss from electronic components and electromagnetic parts, the air inside the mechanism room is pumped through the shaft body and the shaft body insertion hole formed in the floor. It rises into the weighing chamber through the gap between the

As a result, the rising airflow hits the lower part of the weighing pan, agitating the weighing pan and adversely affecting the measurement.

[Problem that the invention seeks to solve]

For the above reasons, several types of configurations have been proposed for training camps to prevent the adverse effects of airflow rising from the mechanism room. One example of this structure is Japanese Patent Application Laid-Open No. 57-153223. In this configuration, a lower plate (airflow protection plate) is fixed to the lower part of the weighing plate, a sleeve is formed in the center of the lower plate, and the shaft body that transmits the load is inserted and positioned within this sleeve.
By making the outer diameter of the shaft body close to the inner diameter of the sleeve, the gap between the sleeve and the shaft body is reduced, thereby increasing the ventilation resistance of this gap. The gap between the floor and the floor is made large, and the ventilation resistance of the floor opening is designed to be small. As a result, most of the airflow from the mechanism chamber rises along the outer circumference of the sleeve where ventilation resistance is low, and the rising airflow hits the lower plate fixed to the floor surface.

Therefore, the weighing pan itself is not hit by the rising flow, ensuring high weighing accuracy.

However, in this configuration, it is necessary to make the gap between the sleeve and the shaft as small as possible, and for this reason, if the object to be weighed is placed away from the center of the weighing pan, even if the weighing pan is slightly tilted, There is a risk that the shaft body and the inner wall surface of the sleeve may come into contact with each other, making it impossible to accurately transmit the load to the mechanism section. Furthermore, even if the sleeve is eliminated and only an opening for shaft insertion is formed in the lower plate placed close to the weighing pan, the gap between this opening and the shaft must be minimized. Therefore, if the weighing pan is tilted, the shaft will come into contact with the opening. In other words, the center of the swing of the shaft due to uneven distribution of the weighed object on the weighing pan is at the lower end of the shaft, which is the connection between the shaft and the mechanism or beam. In this structure, even a slight swing of the shaft causes the upper part of the shaft, which has a large displacement, to come into contact with the opening. In addition, in order to suppress the swinging, a very strong shaft must be used, and the connection structure between the shaft and the mechanical section or beam must be significantly strengthened.

Next, apart from the above-mentioned structure, there is a Japanese Utility Model Application No. 59-21735.

This configuration is intended to simplify the means for preventing the influence of rising air currents. In other words, while the above configuration uses a lower pan to protect the weighing pan from rising air currents, this configuration uses a lower pan to protect the weighing pan from rising air currents, whereas this configuration uses a lower pan to protect the weighing pan from rising air currents, whereas this configuration uses a lower pan to protect the weighing pan from rising air currents. By forming a plurality of openings in areas other than the area where the weighing plate is weighed, the rising air η is prevented from directly hitting the weighing pan. Although this configuration is very simple and can suppress increases in manufacturing costs, it does have the problem of cost. In other words, due to its structure, the opening must be formed in an area other than the area covered by the weighing pan, so if this opening is formed on the floor, objects to be weighed that fall outside of the weighing pan will fall into this opening. In other words, if we only consider preventing the weighed object from falling into the mechanism chamber without considering the influence of the airflow on the weighing pan, the opening for the upward air flow should be It is preferable to form the opening at the bottom, because if the opening is formed at this position, the weighing pan itself will function as a cover to prevent the weighing object from falling and entering.

[Means for solving problems]

The present invention has been constructed in view of the above-mentioned problems.
A windshield is fixed on the weighing chamber side to protect the weighing pan from the upward flow of air, and an opening is formed in the floor to allow the shaft to pass through, with an inner diameter sufficiently larger than the outside diameter of the shaft. Another windshield is arranged in the lower mechanism room, and the shaft insertion hole of the windshield in this mechanism room is configured to be slightly larger than the outer diameter of the shaft, and the windshield in the weighing pan or weighing chamber side of the floor plate is This weighing device is configured such that an opening for airflow passage is formed in the floor surface located at the bottom, thereby guiding the rising airflow from the mechanism chamber to the lower surface of the windshield on the weighing chamber side.

[Effect]

As described above, the present invention protects the weighing pan from rising air currents by the windshield on the weighing chamber side to perform accurate weighing, and the opening for shaft insertion in the floor plate is configured to be sufficiently large relative to the outer diameter of the shaft. Therefore, accuracy will not decrease even if the shaft body swings (,
Furthermore, since all of the airflow passage openings formed in the floor plate are located on the lower surface side of the weighing chamber windshield, there is no possibility that objects to be weighed will 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 serving as a partition plate, and this floor plate 1 defines a weighing chamber 2 in its upper part and a mechanism chamber 3 in its lower part. Of these, the weighing chamber 2 is sealed with a case made of a material such as glass, and is configured so as not to be influenced by the outside during weighing.

Reference numeral 4 designates a part of this case, and 5 is a weighing pan located within the weighing chamber 2, with a shaft 6 connected to the center of its lower surface. This shaft body 6 is inserted through an opening 7 formed in the floor plate 1 and connected to an arm 8 located in the mechanism room 3, and the arm 8 is further connected to a load measuring section (not shown), and a weighing plate is placed on it. The load of the weighed object is transmitted to the load measuring section via the shaft 6 and the arm 8. The inner diameter of the opening 7 is made sufficiently larger than the outer diameter of the shaft 6, as will be described later, so that even if the shaft 6 swings, the shaft does not come into contact with the inner wall of the opening. I try not to. .

Reference numeral 9 denotes a windshield disposed below the weighing pan 5, which is formed to have a larger diameter than the weighing pan 6 and covers the lower surface of the weighing pan 5. An opening having an inner diameter approximately equal to the opening 7 formed in the floor plate 1 is formed in the center thereof.
A windshield 9 formed in the above is placed on the floorboard 1 so that its opening coincides with 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 held between the ring-shaped connecting member 1o made of a flexible material such as rubber, thereby fixing the windshield 9 to the floorboard 1. In this case, if the wall thickness of the connecting member 10 is made sufficiently thick, the end edge 1 of the connecting member on the windshield 9 side
0a serves as a weir and can prevent liquid etc. from flowing into the mechanism chamber. However, the means for attaching the windshield 9 is not limited to the above method, and may be directly fixed to the floorboard 1 using screws, for example. Reference numeral 12 designates one or more air passage openings formed in the floorboard 1, and the openings are formed in the area occupied by the weighing pan 5 or at least the windshield 9 out of the area occupied by the floorboard, that is, at least in the area occupied by the windshield 9. The range corresponds to the bottom.

Next, reference numeral 11 is a windshield placed in the mechanism room 3 (hereinafter referred to as "mechanism windshield").The mechanism windshield 11 has an opening 11a formed in the center for passing the shaft. The inner diameter of the opening should be the same as the shaft 6 as long as there is no risk of it coming into contact with the shaft 6.
The gap between the shaft body 6 and the opening 11a is set to a value close to the outer diameter of the opening 11a, thereby increasing air flow resistance. 13 is a ring interposed between the lower surface of the floor plate 1 and the upper surface of the mechanism windshield 11. This windbreak is ring 1
3 may be formed from metal, but it is better to form it from a flexible material such as rubber or sponge so that the floor plate 1 and mechanism windshield 1
1, and can improve airtightness. Although not shown in the figure, the mechanism windshield has a retainer that supports the calibration weight,
It is also possible to construct it by using a plate. Further, reference numeral 14 is a dust protector placed on the floor surface on the side 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 in the mechanism section. Therefore, the air in the mechanism chamber 3 tries to rise, but since the shaft insertion part of the mechanism windshield 11 has high flow resistance as described above, most of the air bypasses the mechanism windshield 11 and the windshield is ring-shaped. It flows from the outside of 13 into the weighing chamber 2 through the opening 12. Further, the airflow flowing in from the opening 12 hits the windshield 9, but since this windshield is fixed, it is not fanned, and the windshield 9 effectively protects the weighing pan 5 from the upward flow of this air. In addition, since the opening lower of the floor vi1 is formed sufficiently large compared to the diameter of the shaft body 6, even if the shaft body 6 swings, this shaft body will not come into contact with the inner wall of the opening, and accurate Able to weigh. In addition, since the mechanism windshield 11 is close to the connection part of the arm 8, which is the center of swing of the shaft, the amount of displacement is small, and the thickness of the mechanism windshield 11 is about 1 inch, so there is no problem.

FIG. 2 shows a second embodiment.

In this embodiment, a glass plate is placed above the floor plate 1, and this glass plate serves as a de facto floor plate. Some types of weighing objects are corrosive, and if the floorboard is made of metal, plastic, etc., the floorboard may be corroded or discolored by the weighing object spilled from the weighing pan.

For this reason, a plate material of glass, which is a material with high corrosion resistance, is placed on the floor plate 1.

A glass plate 15 is placed above the floor plate 1 and functions as a de facto floor plate. Reference numeral 16 denotes an opening for airflow passage formed in this glass plate 15, and is formed so as to be located at the lower part of the windshield 9 on the weighing chamber side for the reason shown in the first embodiment. In the illustrated configuration, the opening 16 is formed at a position corresponding to the opening 12 formed in the floor plate 1, but by shifting the formation positions of the openings 12 and 16, the flow path of the rising airflow is complicated, and the opening 16 is formed in the weighing chamber. It may be configured to reduce the flow rate of the incoming airflow. The opening 19 formed in the glass plate 15 through which the shaft 6 is inserted is also formed to have an inner diameter sufficiently larger than the outer diameter of the shaft 6 for the same reason as described in the first embodiment. Windbreaks 17 and 18 are rings arranged concentrically, and are interposed between the floor plate 1 and the glass plate 15. If these rings are made of a flexible material like the ring 13 described above, high adhesion can be obtained.

In this configuration, the air in the mechanism room 3 is first introduced into the opening 12 of the floor plate 1.
and then enters the weighing chamber 2 through the opening 16 of the glass plate 15. Further, this airflow hits the windshield 9 and bypasses it.

In addition, in this embodiment, since the glass plate 15 is placed on the floor plate 1, it is easy to remove the glass plate.
Any dirt that may have adhered to the glass can be easily removed.

〔effect〕

As described above, the present invention allows the weighing pan to be protected from rising air currents by the windshield on the weighing chamber side, thereby making it possible to perform accurate weighing.

In addition, the opening for inserting the shaft in the floor plate (glass plate) is sufficiently thick compared to the outside diameter of the shaft, so even if the shaft swings, the shaft will not come into contact with the inner wall of the opening. It is possible to maintain high weighing accuracy at all times.

Furthermore, all of the airflow passage openings formed in the floorboard are located on the underside of the weighing pan or weighing chamber windshield, and since these weighing pans function as a cover, objects to be weighed do not fall directly into the mechanism. .

[Brief explanation 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 plate 2... Weighing chamber 3... Mechanism room 5... Weighing pan 6... Shaft 7... Shaft insertion opening 8... Arm 9... Weighing chamber side Windshield 10... Connection member 1
0a...Windshield side edge of the connection member 11...Mechanism part windshield 11a...Shaft body insertion hole 12.16...Air flow passage hole 13.17.18...Windshield ring 15... glass plate

Claims (5)

[Claims] (1) A weighing chamber and a mechanism chamber are defined by a floor plate, and a shaft passing through the floor plate connects directly or indirectly the weighing pan placed in the weighing chamber and the load receiving part in the mechanism chamber. In the configured weighing device, the inner diameter of the shaft insertion opening in the floor plate is formed sufficiently larger than the outer diameter of the shaft, and a windshield is fixedly installed on the weighing chamber side so as to be located at the bottom of the weighing pan. In contrast, an opening for airflow passage is formed at the bottom of this windshield, a mechanism windshield is placed in the mechanism room, and the gap between the shaft body insertion hole of this mechanism windshield and the shaft body is reduced. A high-resolution weighing device further comprising: a windshield ring interposed between the floor plate and the mechanism windshield; and an opening in the floor plate positioned at the outer periphery of the windshield ring. (2) A plate made of highly corrosion-resistant material such as glass is placed on top of the floor plate to form the actual floor plate, and an air flow passage opening is formed in this corrosion-resistant plate to be located at the bottom of the windshield on the weighing chamber side. The present invention is characterized in that two windshield rings are arranged concentrically between the corrosion-resistant board and the floorboard, and the airflow passage opening formed in the corrosion-resistant board and the floorboard is located between the two windshield rings. A high-resolution weighing device according to claim (1). (3) Claim (2) characterized in that the airflow passage opening formed in the corrosion-resistant plate material and the airflow passage opening formed in the floorboard are displaced to complicate the airflow passage. High-resolution weighing device as described. (4) Structure in which the weighing chamber side windshield is fixed to the floor plate or corrosion-resistant plate material by sandwiching the inner peripheral edge of the shaft insertion opening formed in the floor plate or corrosion-resistant plate material with a flexible ring-shaped connecting member. A high-resolution weighing device according to claim (2) or (3), characterized in that: (5) Claim (4) characterized in that by increasing the wall thickness of the ring-shaped connecting member, the windshield side end edge of the connecting member functions as a weir for preventing liquid inflow. High-resolution weighing device as described in section.