Electronic balance

Abstract

To provide an electronic balance that enables accurate weighing regardless of sample size, while preventing adverse effects from airflow. [Solution] The weighing system includes a case 3 in which the weighing pan 2 is exposed from above, a fixed draft shield ring 32 integrally with a dustproof plate 31 provided on the top surface of the case 3 and surrounding the weighing pan 2, with the height of its upper edge set lower than the height of the top surface of the weighing pan 2, and a removable draft shield ring 34 that is detachably positioned on the upper edge of the fixed draft shield ring 32, with the height of its upper edge set higher than the height of the top surface of the weighing pan 2 when it is positioned on the fixed draft shield ring 32. If the sample to be weighed is large and would come into contact with the removable draft shield ring 34, removing the removable draft shield ring 34 will lower the height of the upper edge of the fixed draft shield ring 32 below the height of the top surface of the weighing pan 2, allowing the sample to be weighed without contact with the fixed draft shield ring 32.

Description

Technical Field

[0001] The present invention relates to an electronic balance for weighing a sample placed on a weighing pan.

Background Art

[0002] In an electronic balance, if the flow of air around the weighing pan, such as the wind from an air conditioner, the breath of a person during weighing, or the air flow generated when a person walks, acts on the weighing pan as wind pressure, it will have an adverse effect on weighing. Conventionally, in order to prevent this adverse effect, a wind guard is provided with a door that can open and close to block the weighing space provided with the weighing pan. However, when the door is opened to open the wind guard in order to place the sample to be weighed on the weighing pan, air flows into the wind guard, and the air that has flowed in will still have an adverse effect on the weighing pan even after the door is closed. For this reason, a ring-shaped wall member called a wind guard ring is provided inside the wind guard so as to surround the weighing pan, preventing the adverse effect on the weighing pan caused by the air flowing into the wind guard.

[0003] For example, a wind guard is provided on the upper surface of the balance body (a case having a weighing mechanism connected to the weighing pan), while a dust plate (dust-proof plate) is placed on a floor material fixed to the upper surface of the balance body, and a wind guard ring is placed on this dust plate so as to surround the periphery of the weighing pan located inside the wind guard (Patent Document 1).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The draft shield ring described in Patent Document 1 has its upper edge positioned significantly higher than the top surface of the weighing pan to prevent airflow from acting as wind pressure on the weighing pan. Therefore, if the sample to be weighed is solid and larger than the weighing pan, the sample may come into contact with the draft shield ring, particularly its upper edge. In this case, the entire weight of the sample is not applied to the weighing pan, making accurate weighing impossible. Furthermore, the draft shield ring can hinder the process of placing the sample on the weighing pan, potentially causing the sample to spill outside the pan and preventing smooth and reliable placement.

[0006] This invention has been made in view of these problems, and aims to provide an electronic balance that can reliably place a sample on the weighing pan regardless of its size and perform accurate weighing while preventing adverse effects from airflow. [Means for solving the problem]

[0007] To solve the above problem, the inventors focused on the positional relationship between the height of the windbreak ring and the upper surface of the weighing pan, and after repeated experiments, they found that the repeatability in a windy environment is good when the height of the upper edge of the windbreak ring is higher than the upper surface of the weighing pan, and even when the height of the upper edge of the windbreak ring is lower than the upper surface of the weighing pan, it is significantly better than when there is no windbreak ring. Figure 7 shows these results, and is a graph showing the repeatability under different wind speeds for each of the following cases using a 50g weight: (1) when the height of the windbreak ring's upper edge is 7mm higher than the upper surface of the weighing pan in use, (2) when the height of the windbreak ring's upper edge is 3mm lower than the upper surface of the weighing pan in use, and (3) when there is no windbreak ring. Here, σ represents the standard deviation, and d represents the minimum display of the electronic balance used, which is 10μg.

[0008] The present invention is based on the above-mentioned findings, and one embodiment of the electronic balance according to the present invention is an electronic balance for weighing a sample placed on a weighing pan, comprising: a case from which the weighing pan is exposed from the top surface; a fixed draft shield ring provided integrally with the dustproof plate on the top surface of the case, surrounding the weighing pan, with the height of its upper edge set lower than the height of the top surface of the weighing pan; and a removable draft shield ring detachably arranged on the fixed draft shield ring, with the height of its upper edge set higher than the height of the top surface of the weighing pan when arranged on the fixed draft shield ring. According to this embodiment, if the sample to be weighed is large and comes into contact with the detachable windbreak ring, or if the windbreak ring obstructs the process of placing the sample on the weighing pan, removing the detachable windbreak ring lowers the height of the upper edge of the fixed windbreak ring below the top surface of the weighing pan. This allows the sample to be weighed without contacting the fixed windbreak ring, and also enables the smooth and reliable process of placing the sample on the weighing pan.

[0009] In another embodiment, as described above, the fixed windshield ring is provided with an engaging portion, such as an engaging step, on its upper edge, which engages with the lower edge of the detachable windshield ring. According to this embodiment, the detachable windshield ring can be securely positioned on the fixed windshield ring.

[0010] In yet another embodiment, the fixed windscreen ring is provided with a notch that extends from its upper edge to the dustproof plate. In this embodiment, dust and debris accumulated on the dustproof plate inside the fixed windscreen ring can be swept out to the outside of the fixed windscreen ring through the notch.

[0011] In yet another embodiment, as described above, the detachable windshield ring is provided with an engaging piece that engages with the notch in the fixed windshield ring so as to close the notch. In this embodiment, when the detachable windshield ring is positioned on the fixed windshield ring, it is possible to prevent air from flowing in through the notch. [Effects of the Invention]

[0012] According to the present invention, it is possible to prevent adverse effects of airflow on the weighing pan, and the height of the draft shield ring can be selected according to the size of the sample to be weighed, so that the sample does not come into contact with the draft shield ring, thereby enabling accurate weighing. Furthermore, since the draft shield ring does not hinder the process of placing the sample on the weighing pan, reliable placement can be performed. [Brief explanation of the drawing]

[0013] [Figure 1] A perspective view showing an electronic balance according to one embodiment. [Figure 2] A perspective view showing the weighing pan and windshield ring. [Figure 3] This is a cross-sectional view showing the height relationship between the weighing pan and the fixed windshield ring. [Figure 4] A perspective view showing the dustproof plate and fixed windscreen ring. [Figure 5] This cross-sectional view also shows the height relationship between the weighing pan and the windshield ring, which consists of a fixed windshield ring and a detachable windshield ring. [Figure 6] A perspective view showing a detachable windscreen ring of another embodiment. [Figure 7] A graph showing the relationship between the height of the windshield ring and the effect of airflow on the weighing pan. [Modes for carrying out the invention]

[0014] A preferred embodiment of the present invention will be described below with reference to Figures 1 to 3 of the attached drawings. As shown in Figures 1 and 2, the electronic balance 1 comprises a case 3 that houses a weighing mechanism (not shown), including a mass sensor such as an electromagnetic balance type or load cell type connected to a weighing pan 2 (see Figure 2), and a control unit (not shown) that controls various operations of the electronic balance. The front side of the case 3 is equipped with a control panel 4. The top surface of the control panel 4 is equipped with a display unit 4a that displays weighing results, a plurality of touch panel type operation switches 4b, and a spirit level 4c that detects the tilt state of the case 3. The front lower surface of the case 3 is provided with a pair of height-adjustable feet 5, 5, and the rear lower surface is provided with support legs (not shown), thereby supporting the case 3 at three points so that it can be horizontally adjusted.

[0015] As shown in Figure 1, a bottomless box-shaped windbreak 10 is provided on the top plate 6 of case 3, consisting of a front panel 7, a pair of left and right side doors 8 (only the right side door 8 is shown), a back panel (not shown), and a top door 9, forming a rectangular parallelepiped internal space that creates a weighing chamber. The front panel 7, the pair of left and right side doors 8, the back panel, and the top door 9 that make up the windbreak 10 are made of transparent material, and the weighing chamber is visible through them, but for convenience, the weighing chamber is shown as invisible in Figure 1. The windbreak 10 closes the inside of the weighing chamber during weighing, preventing airflow during weighing, such as airflow from an air conditioner, a person's breath during weighing, or airflow generated when a person walks, from acting as wind pressure on the load-bearing area centered on the weighing pan 2 and affecting the weighing.

[0016] Support boxes 11 and 12 are arranged at the upper left and right ends of the wind guard 10. The upper end of the right side door 8 is slidably suspended within the support box 11, and the upper end of the left side door (not shown) is slidably suspended within the support box 12. The lower ends of the right side door 8 and the left side door face the side surface of the top plate 6. When sliding, the lower ends are restricted by restricting members 13 and 14 (see Fig. 2) so as not to separate from the facing position on the side surface of the top plate 6 and rattle. The right side door 8 and the left side door can be slid open and closed manually or automatically, and manual handles 15 and 16 are provided respectively. Further, the support boxes 11 and 12 slidably support the left and right side ends of the top door 9. The top door 9 slides manually and has a knob 17 provided thereon.

[0017] Detachable members 18 and 19 are detachably connected to the handles 15 and 16 of the right side door 8 and the left side door respectively, and the detachable members 18 and 19 are connected by a connecting plate 20 arranged under the case 3. The connecting plate 20 is connected to an air cylinder (not shown) arranged within the case 3, and moves in the front-rear direction of the case 3 by the driving force of the air cylinder, moving the detachable members 18 and 19 in the same direction. Therefore, when the detachable members 18 and 19 are respectively connected to the corresponding handles 15 and 16, the right side door 8 and the left side door are also slid in the same direction. The connection between the detachable members 18 and 19 and the corresponding handles 15 and 16 is achieved by moving the knobs 21a and 22a of the connecting members 21 (only shown for the detachable member 18) provided movably up and down on the detachable members 18 and 19 to the uppermost position, and the detachment from the connected state is achieved by moving the knobs 21a and 22a of the connecting member 21 to the lowermost position. When the handles 15 and 16 and the detachable members 18 and 19 are in a non-connected state, the right side door 8 and the left side door can be slid separately manually.

[0018] As shown in FIG. 2, the weighing pan 2 is located above the dust-proof plate 31 fixed to the top plate 6 of the case 3 and is exposed from the dust-proof plate 31. The dust-proof plate 31 prevents powdery or liquid dust, which is a sample spilled in the weighing chamber, from falling on the top plate 6 of the case 3 or entering the case 3, and facilitates the cleaning of the dust. As shown in FIG. 3, the dust-proof plate 31 is formed and provided with a fixed wind shield ring 32 integrally with the dust-proof plate 31 so as to surround the weighing pan 2. The height position of the upper end edge of the fixed wind shield ring 32 is set lower than the height position of the upper surface of the weighing pan 2.

[0019] As shown in FIGS. 2 to 4, the fixed wind shield ring 32 is provided with two cutouts 32a and 32b reaching the dust-proof plate 31 from the upper end edge on the rising part 31a side provided at the opposite end of the front plate 7 of the dust-proof plate 31. Further, an engaging step portion 32c with a lower inner side as an engaging portion is provided on the entire circumference of the upper end edge of the fixed wind shield ring 32.

[0020] As can be clearly understood from FIG. 4, the dust-proof plate 31 corresponding to each of the cutouts 32a and 32b is provided with raised portions 31g and 31h having inclined surfaces that rise from the inside to the outside. Further, the dust-proof plate 31 is provided with four arc-shaped raised portions 31b, 31c, 31d, and 31e extending in the vicinity of the fixed wind shield ring 32 and a ring-shaped raised portion 31f located at the center. Each of the raised portions 31b, 31c, 31d, and 31e has an inclined surface that rises from the inside to the outside, similar to each of the raised portions 31g and 31h. Also, the weighing pan 2 is connected to a weighing mechanism (not shown) in the case 3 through the central hole of the raised portion 31f.

[0021] As shown in Figures 2 and 5, a removable windshield ring 34, which has a lower flange portion 34c extending around its entire circumference, is detachably mounted on the engaging step portion 32c of the upper edge of the fixed windshield ring 32 by the lower flange portion 34c engaging with the engaging step portion 32c. The removable windshield ring 34 is mounted on the upper edge of the fixed windshield ring 32 in a stable state because the contact area between them is increased when the lower flange portion 34c engages with the engaging step portion 32c. With the removable windshield ring 34 mounted on the fixed windshield ring 32, the height of the upper edge of the removable windshield ring 34 is set higher than the height of the upper surface of the weighing pan 2. In addition, a pair of engaging pieces 34a and 34b are integrally formed on the lower edge of the removable windshield ring 34, which engage to close the notches 32a and 32b of the fixed windshield ring 32. The fixed windshield ring 32 and the detachable windshield ring 34 constitute the windshield ring.

[0022] The windbreak ring, consisting of the fixed windbreak ring 32 and the detachable windbreak ring 34, has the effect of preventing wind from affecting the weighing pan 2. The effect of this windbreak ring is particularly effective when at least one of the right side door 8, the left side door, and the top door 9 is open, but it is also effective when the windbreak 10 is closed and convection inside the weighing chamber has not subsided. Furthermore, in this embodiment, the notches 32a and 32b of the fixed windbreak ring 32 are closed by the engaging pieces 34a and 34b of the detachable windbreak ring 34, so the effectiveness of the above effect is further enhanced.

[0023] In normal weighing, the detachable windbreak ring 34 is placed on the fixed windbreak ring 32, as shown in Figures 2 and 5. If the sample to be weighed is large and a part of it comes into contact with the detachable windbreak ring 34, preventing accurate weighing by the weighing pan 2, the detachable windbreak ring 34 is removed from the fixed windbreak ring 32, and the weighing is performed with only the fixed windbreak ring 32, as shown in Figure 3. As shown in Figure 3, the upper end height of the fixed windbreak ring 32 is lower than the height of the upper surface of the weighing pan 2. Therefore, even if the sample is larger than the weighing pan 2 and lies at the upper edge of the fixed windbreak ring 32, the sample will not come into contact with the fixed windbreak ring 32, and the sample can be placed on the weighing pan 2 in a normal state for accurate weighing.

[0024] Furthermore, if dust accumulates on the dustproof plate 31 inside the windbreak ring, for example, due to spillage of the sample from the weighing pan 2, the detachable windbreak ring 34 can be removed from the fixed windbreak ring 32, and the dust can be swept out to the outside of the fixed windbreak ring 32 through the notches 32a and 32b of the fixed windbreak ring 32. In this case, the raised portions 31g and 31h corresponding to the notches 32a and 32b are provided with slopes that rise from the inside to the outside, so that the sweeping operation can be performed easily and reliably. The raised portions 31g and 31h prevent dust from entering the fixed windbreak ring 32, and the raised portions 31b, 31c, 31d, and 31e prevent dust from entering in the direction of the raised portion 31f. The spacing between each of the aforementioned raised sections 31b, 31c, 31d, and 31e is set so that the outer side is narrower than the inner side, making it difficult for debris to enter the inside, while the presence of a slope that rises from the inside to the outside makes it easy to sweep the debris outwards.

[0025] It should be noted that the present invention is not limited to the embodiments described above. For example, the detachable windbreak ring 34 may not have engaging pieces 34a and 34b, as shown in Figure 6. In this case, since the notches 32a and 32b cannot be closed when the detachable windbreak ring 34 is placed on the fixed windbreak ring 32, the effect of preventing wind from affecting the weighing pan 2 will be inferior to that of the embodiments described above. However, this effect is still sufficiently better than when the detachable windbreak ring 34 is not present. Furthermore, a configuration without notches 32a and 32b on the fixed windbreak ring 32 can also be adopted. In this case, cleaning work will be inconvenient when dust accumulates on the dustproof plate 31 inside the windbreak ring, but the effect of preventing wind from affecting the weighing pan 2 will be improved. Moreover, the engaging portion provided on the upper edge of the fixed windbreak ring 32 is not limited to the engaging step portion 32c. Furthermore, the raised portions 31b, 31c, 31d, 31e, 31f, 31g, and 31h of the dustproof plate 31 are not necessarily required. Moreover, the configuration in which the fixed windshield ring 32 is integrally provided with the dustproof plate 31 is not limited to molding. [Explanation of Symbols]

[0026] 1. Electronic balance 2 Weighing pan 3 cases 4. Control Panel 5-legged piece 6. Top plate 7 Front view 8 Right side door 9 Top door 10. Windshield 31 Dustproof plate 31b~31h Raised part 32 Fixed Windscreen Ring 32a, 32b Notches 32c Engagement stepped part 34 Detachable Windshield Ring 34a,34b Engagement piece 34c Lower end flange

Claims

1. In an electronic balance used to weigh a sample placed on a weighing pan, In the case where the measuring pan is exposed from the top surface, A fixed windbreak ring is provided on the dustproof plate on the top surface of the case, integrally with the dustproof plate, so as to surround the weighing pan, and the height of its upper edge is set lower than the height of the top surface of the weighing pan. A removable windshield ring is detachably positioned on the upper edge of the fixed windshield ring, and when positioned on the fixed windshield ring, the height of the upper edge is set higher than the height of the upper surface of the weighing pan. An electronic balance characterized by having the following features.

2. The fixed windshield ring is provided with an engagement portion at its upper edge, which engages with the lower edge of the detachable windshield ring. The electronic balance according to feature 1.

3. The fixed windshield ring is provided with a notch that extends from its upper edge to the dustproof plate. The electronic balance according to claim 1 or 2.

4. The detachable windshield ring is provided with an engaging piece that engages with the notch in the fixed windshield ring, so as to close the notch. The electronic balance according to feature 3.

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