Electronic balance

Abstract

To provide an electronic balance capable of accurate measurement while preventing adverse effects of air flow, regardless of the size of a sample. [Solution] The measuring device comprises a case 3 from which the weighing dish 2 is exposed on the top surface, a fixed windshield ring 32 which is provided integrally with a dustproof plate 31 provided on the top surface of the case 3 so as to surround the weighing dish 2 and has its upper edge positioned lower than the height position of the top surface of the weighing dish 2, and a detachable windshield ring 34 which is detachably disposed on the upper edge of the fixed windshield ring 32 and has its upper edge positioned higher than the height position of the top surface of the weighing dish 2 when disposed on the fixed windshield ring 32. If the sample to be measured is large and comes into contact with the detachable windshield ring 34, removing the detachable windshield ring 34 will make the upper edge of the fixed windshield ring 32 lower than the top surface of the weighing dish 2, so that the sample can be measured without coming into contact with the fixed windshield ring 32.

Description

[Technical field]

[0001] The present invention relates to an electronic balance that weighs a sample placed on a weighing pan. [Background technology]

[0002] In electronic balances, if the air flow 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 as wind pressure on the weighing pan, it will adversely affect the weighing. Conventionally, in order to prevent this adverse effect, a windshield is provided with a door that can be opened and closed to close the weighing space in which the weighing pan is provided. However, when the door is opened to place a sample to be weighed on the weighing pan and the windshield is in an open state, air flows into the windshield, and the air that has flowed in will adversely affect the weighing pan even after the door is closed. For this reason, a ring-shaped wall member called a windshield ring is provided inside the windshield so as to surround the weighing pan, to prevent the air that has flowed into the windshield from adversely affecting the weighing pan.

[0003] For example, there is known an electronic balance (Patent Document 1) in which a windshield is provided on the top of the balance body (a case having a weighing mechanism connected to a weighing pan), a dust plate is placed on a floor material fixed to the top of the balance body, and a windshield ring is placed on this dust plate so as to surround the weighing pan located within the windshield. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent No. 7008386 Summary of the Invention [Problem to be solved by the invention]

[0005] The wind ring in Patent Document 1 is set so that its upper edge is sufficiently higher than the upper surface of the weighing dish to prevent the air flow from acting as wind pressure on the weighing dish. Therefore, if the sample to be weighed is solid and larger than the weighing dish, the sample may come into contact with the wind ring, especially its upper edge, and in this case, the entire weight of the sample is not applied to the weighing dish, making it impossible to weigh accurately. In addition, the wind ring may become an obstacle to the task of placing the sample on the weighing dish, causing the sample to spill outside the weighing dish, preventing smooth and reliable placement.

[0006] The present invention has been made in consideration of these problems, and has as its object to provide an electronic balance that enables a sample to be securely placed on the weighing pan regardless of its size and enables accurate weighing while preventing the adverse effects of air flow. [Means for solving the problem]

[0007] In order to solve the above problem, the inventors focused on the positional relationship between the height of the wind ring and the top surface of the weighing pan, and as a result of repeated experiments, they found that the repeatability in a windy environment is good when the height position of the upper edge of the wind ring is higher than the top surface of the weighing pan, and is far better than when there is no wind ring even when the height position of the upper edge of the wind ring is lower than the top surface of the weighing pan. This result is shown in Figure 7, which is a graph showing the repeatability under different wind speeds using a 50g weight in the following cases: (1) when the wind ring has a height of the upper edge 7mm higher than the top surface of the weighing pan when in use, (2) when the wind ring has a height of the upper edge 3mm lower than the top surface of the weighing pan when in use, and (3) when there is no wind ring. Here, σ indicates the standard deviation, and d indicates the minimum display of the electronic balance used, which is 10μg.

[0008] The present invention has been made based on the above-mentioned findings, and one aspect of the electronic balance of 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, a dustproof plate provided on the top surface of the case, a fixed windshield ring provided integrally with the dustproof plate so as to surround the weighing pan and with the height position of its upper edge set lower than the height position of the top surface of the weighing pan, and a detachable windshield ring removably arranged on the fixed windshield ring and, when placed on the fixed windshield ring, the height position of its upper edge set higher than the height position of the top surface of the weighing pan. According to this embodiment, if the sample to be weighed is large and comes into contact with the detachable windshield ring, or if the windshield ring impedes the operation of placing the sample on the weighing dish, the detachable windshield ring can be removed so that the height position of the upper edge of the fixed windshield ring is lower than the top surface of the weighing dish, allowing the sample to be weighed without coming into contact with the fixed windshield ring, and also allowing the operation of placing the sample on the weighing dish to be carried out smoothly and reliably.

[0009] In another embodiment, the fixed windshield ring in the above-mentioned embodiment is provided with an engagement portion, for example an engagement step portion, at its upper edge with which the lower edge of the detachable windshield ring engages. According to this embodiment, the detachable windshield ring can be reliably placed on the fixed windshield ring.

[0010] In yet another aspect, in each of the above aspects, the fixed windshield ring is provided with a notch that extends from its upper edge to the dustproof plate. According to this aspect, dust and the like that has accumulated on the dustproof plate inside the fixed windshield ring can be swept out from the notch to the outside of the fixed windshield ring.

[0011] In still another aspect, in the above-mentioned further aspect, the detachable windshield ring is provided with an engagement piece that engages with the notch of the fixed windshield ring so as to close the notch. According to this aspect, when the detachable windshield ring is placed on the fixed windshield ring, it is possible to prevent air from entering through the notch. Effect of the Invention

[0012] According to the present invention, it is possible to prevent the adverse effects of air flow on the weighing dish, and the height of the wind 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 wind ring, allowing accurate weighing. Furthermore, since the wind ring does not interfere with the operation of placing the sample on the weighing dish, the operation can be carried out reliably. [Brief description of the drawings]

[0013] [Figure 1] FIG. 1 is a perspective view showing an electronic balance according to an embodiment. [Diagram 2] FIG. [Diagram 3] FIG. 11 is a cross-sectional view showing the height relationship between the weighing pan and the fixed windshield ring. [Figure 4] FIG. [Diagram 5] FIG. 11 is a cross-sectional view showing the height relationship between the weighing dish and a windshield ring that is made up of a fixed windshield ring and a detachable windshield ring. [Figure 6] FIG. 13 is a perspective view showing a detachable windshield ring according to another embodiment. [Figure 7] Graph showing the relationship between the height of the windshield ring and the effect of air flow on the weighing pan. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] A preferred embodiment of the present invention will now be described with reference to the accompanying drawings, FIGS. 1 to 3. As shown in Figures 1 and 2, an electronic balance 1 includes a case 3 that includes 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 provided with a control panel 4. The upper surface of the control panel 4 is provided with a display unit 4a that displays weighing results, a plurality of touch panel type switches 4b for various operations, and a level 4c that detects the inclination state of the case 3. A pair of height-adjustable feet 5, 5 are provided on the front underside of the case 3, and support legs (not shown) are provided on the rear underside, supporting the case 3 at three points so that the level can be adjusted.

[0015] As shown in Fig. 1, a bottomless box-shaped windshield 10 consisting of a front panel 7, a pair of left and right side doors (only the right side door 8 is shown), a back panel (not shown), and a top door 9 is provided on the top panel 6 of the case 3, and the rectangular parallelepiped internal space forms a measuring chamber. The front panel 7, the pair of left and right side doors 8, the back panel, and the top door 9 constituting the windshield 10 are made of transparent bodies, and the measuring chamber can be seen through, but for convenience, the measuring chamber is illustrated in an invisible state in Fig. 1. The windshield 10 closes the measuring chamber during measurement, and prevents air flows during measurement, such as wind from an air conditioner, a person's breath during measurement, and air flows generated when a person walks, from acting as wind pressure on the load-bearing portion centered on the measuring dish 2 and affecting the measurement.

[0016] Support boxes 11 and 12 are arranged at the left and right upper ends of the windshield 10, and the upper end of the right side door 8 is slidably suspended in the support box 11, and the upper end of the left side door (not shown) is slidably suspended in the support box 12. The lower ends of the right side door 8 and the left side door are positioned opposite the side surface of the top plate 6, and are restricted by restricting members 13 and 14 (see FIG. 2) so that the lower ends do not move away from the opposing positions of the side surface of the top plate 6 and do not rattle when sliding. The right side door 8 and the left side door can be opened and closed by sliding manually or automatically, and are provided with manual handles 15 and 16, respectively. The support boxes 11 and 12 also slidably support the left and right side ends of the top door 9. The top door 9 is manually slidable and is provided with a knob 17.

[0017] Engagement and disengagement members 18, 19 are releasably connected to the handles 15, 16 of the right side door 8 and the left side door, respectively, and the engagement and disengagement members 18, 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 inside the case 3, and moves in the front-rear direction of the case 3 by the driving force of the air cylinder, moving the engagement and disengagement members 18, 19 in the same direction. Therefore, when the engagement and disengagement members 18, 19 are connected to the corresponding handles 15, 16, the right side door 8 and the left side door are also slid in the same direction. The engagement and disengagement members 18, 19 and the corresponding handles 15, 16 are connected to each other by moving knobs 21a, 22a of connecting members 21 (only the engagement and disengagement member 18 is shown) which are provided on the engagement and disengagement members 18, 19 so as to be movable up and down, to their uppermost positions, and the connection is released by moving knobs 21a, 22a of the connecting members 21 to their lowermost positions. When the handles 15, 16 and the engagement and disengagement members 18, 19 are in a non-connected state, the right side door 8 and the left side door can be manually slid separately.

[0018] As shown in Fig. 2, the weighing dish 2 is located above a dustproof plate 31 fixed to a top plate 6 of a case 3, and is exposed from the dustproof plate 31. The dustproof plate 31 prevents powdery or liquid dust, which is a sample spilled into the weighing chamber, from getting on the top plate 6 of the case 3 or entering the case 3, and also makes it easy to clean the dust. As shown in Fig. 3, the dustproof plate 31 is molded to provide a fixed windshield ring 32 integrally with the dustproof plate 31 so as to surround the weighing dish 2. The height position of the upper edge of the fixed windshield ring 32 is set lower than the height position of the upper surface of the weighing dish 2.

[0019] 2 to 4, the fixed windshield ring 32 has two notches 32a, 32b that extend from the upper edge to the dustproof plate 31 on the side of a rising portion 31a provided on the end opposite the front plate 7 of the dustproof plate 31. In addition, the upper edge of the fixed windshield ring 32 is provided with an engagement step portion 32c that is lowered on the inside along the entire circumference.

[0020] As can be clearly seen in FIG. 4, the dustproof plate 31 corresponding to each of the notches 32a and 32b is provided with raised portions 31g and 31h having slopes inclined upward from the inside to the outside. Furthermore, the dustproof plate 31 is provided with four raised portions 31b, 31c, 31d and 31e extending in an arc shape located near the fixed windshield ring 32, and a ring-shaped raised portion 31f located in the center. Each of the raised portions 31b, 31c, 31d and 31e has a slope inclined upward from the inside to the outside, similar to each of the raised portions 31g and 31h. In addition, the weighing pan 2 is connected to a weighing mechanism (not shown) in the case 3 through a central hole of the raised portion 31f.

[0021] As shown in Fig. 2 and Fig. 5, a detachable windshield ring 34 having a lower end flange 34c over the entire circumference is detachably mounted on an engagement step 32c on the upper end edge of the fixed windshield ring 32 by engaging the lower end flange 34c at a position corresponding to the engagement step 32c. The detachable windshield ring 34 is stably mounted on the upper end edge of the fixed windshield ring 32 by engaging the lower end flange 34c with the engagement step 32c, increasing the contact area between the detachable windshield ring 34 and the fixed windshield ring 32. When the detachable windshield ring 34 is mounted on the fixed windshield ring 32, the height position of the upper end edge of the detachable windshield ring 34 is set higher than the height position of the upper surface of the weighing pan 2. A pair of engagement pieces 34a, 34b that engage with the notches 32a, 32b of the fixed windshield ring 32 so as to close them is integrally formed on the lower end edge of the detachable windshield ring 34. The fixed windshield ring 32 and the detachable windshield ring 34 constitute a windshield ring.

[0022] The windshield ring consisting of the fixed windshield ring 32 and the detachable windshield ring 34 has the function of preventing the influence of wind on the weighing pan 2. This function of the windshield 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 convection in the weighing chamber does not subside even when the windshield 10 is in the closed state. In this embodiment, the engagement pieces 34a, 34b of the detachable windshield ring 34 close the notches 32a, 32b of the fixed windshield ring 32, so that the effectiveness of the function is further increased.

[0023] In normal weighing, the detachable windshield ring 34 is placed on the fixed windshield ring 32 as shown in Fig. 2 and Fig. 5. If the sample to be weighed is large and part of it comes into contact with the detachable windshield ring 34, making it impossible to accurately weigh using the weighing dish 2, the detachable windshield ring 34 is removed from the fixed windshield ring 32 and weighing is performed using only the fixed windshield ring 32 as shown in Fig. 3. As shown in Fig. 3, the height position of the upper end of the fixed windshield ring 32 is lower than the height position of the upper surface of the weighing dish 2. Therefore, even if the sample is larger than the weighing dish 2 and is located corresponding to the upper edge of the fixed windshield ring 32, the sample will not come into contact with the fixed windshield ring 32 and can be placed on the weighing dish 2 in the normal state and accurately weighed.

[0024] In addition, if dust accumulates on the dustproof plate 31 inside the windshield ring due to, for example, the sample spilling out of the weighing dish 2, the removable windshield ring 34 can be removed from the fixed windshield ring 32, and the dust can be swept out of the fixed windshield ring 32 through the notches 32a and 32b. At this time, the raised portions 31g and 31h corresponding to the notches 32a and 32b have 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 windshield 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 the raised portions 31b, 31c, 31d, and 31e is set narrower on the outside than on the inside, making it difficult for dirt to get inside, while a slope rising from the inside to the outside is provided, making it easy to sweep dirt out to the outside.

[0025] The present invention is not limited to the above-mentioned embodiment. For example, the detachable windshield ring 34 may not have the engagement pieces 34a, 34b as shown in FIG. 6. In this case, the notches 32a, 32b cannot be closed when the detachable windshield ring 34 is placed on the fixed windshield ring 32, so the effect of preventing the influence of wind on the weighing pan 2 is inferior to that of the above-mentioned embodiment, but the effect is sufficiently better than that in the case where the detachable windshield ring 34 is not present. Also, a configuration in which the notches 32a, 32b of the fixed windshield ring 32 are not provided may be adopted. In this case, it is inconvenient to clean the dustproof plate 31 inside the windshield ring when dust accumulates, but the effect of preventing the influence of wind on the weighing pan 2 is improved. Furthermore, the engagement portion provided on the upper edge of the fixed windshield ring 32 is not limited to the engagement step portion 32c. Furthermore, it is not essential to provide the respective raised portions 31b, 31c, 31d, 31e, 31f, 31g, and 31h of the dustproof plate 31. Furthermore, 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 Foot 6. Tabletop 7 Front version 8 Right side door 9 Top door 10 Windshield 31 Dustproof plate 31b~31h Raised part 32 Fixed windshield ring 32a, 32b Notch 32c Engagement stepped part 34 Removable windshield ring 34a,34b Engagement piece 34c Lower end flange

Claims

1. In an electronic balance that weighs a sample placed on a weighing pan, a case from which the weighing dish is exposed; a fixed windshield ring that is integral with the dustproof plate provided on the top surface of the case and surrounds the weighing dish, the height position of the upper edge of the fixed windshield ring being set lower than the height position of the top surface of the weighing dish; a removable windshield ring that is detachably disposed on an upper edge of the fixed windshield ring, and that has an upper edge that is set higher than an upper surface of the weighing pan when the removable windshield ring is disposed on the fixed windshield ring; An electronic balance comprising:

2. The fixed windshield ring is provided at its upper edge with an engagement portion with which the lower edge of the detachable windshield ring is engaged.

2. The electronic balance according to claim 1 .

3. The fixed windshield ring is provided with a notch extending from its upper edge to the dustproof plate.

3. The electronic balance according to claim 1 or 2.

4. The detachable windshield ring is provided with an engagement piece that engages with the notch of the fixed windshield ring so as to close the notch.

4. The electronic balance according to claim 3.

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