Color sorter and rice milling plant

Abstract

The present invention provides a color sorter capable of performing highly accurate sorting in a short time, and a rice milling plant equipped with the color sorter. [Solution] The color sorter 1 comprises a feeder 4 that sends out rice grains to be sorted, a supply cylinder 3 that supplies rice grains 10 to the feeder 4, a chute 5 that allows the rice grains 10 sent out by the feeder 4 to flow down, a color sorting unit 2 that identifies and removes defective rice grains 10b that have a different color from good rice grains 10a discharged from the chute 5, and a defective product removal means 12 that removes the defective rice grains 10b sorted by the color sorting unit 2. Multiple flow grooves 51 are formed adjacent to each other in the chute 5, and the groove width X of the flow grooves 51 is set within the range of 1.05 to 1.5 times the average width W of the rice grains 10.

Description

Technical Field

[0001] The present invention relates to a color sorter for sorting rice grains into good and defective products, and a rice milling plant equipped with the color sorter.

Background Art

[0002] Conventionally, a color sorter (color sorting device, optical sorter, optical sorting device) laterally feeds a layer of raw rice grains falling from a storage tank while slightly vibrating a feeder to make the rice layer as thin as possible and feed (supply section) it to a chute that allows the grains to flow down at high speed like a slide. Due to the action of the acceleration during the fall, the rice grain group is dispersed back and forth more and more as it goes downward, and the rice grains discharged as single grains from the rice grain group are discriminated for quality (discrimination section) by arranging an illumination unit consisting of a light-emitting light and a light-receiving camera in front and behind in an opposing manner at the place where the chute exits. Then, abnormal grains are blown off and separated from normal grains (separation section) by an ejector that instantaneously jets high-pressure air (compressed air) according to the signal transmitted from it.

[0003] However, since the raw rice grain group is an extremely large group of rice grains, in order to distinguish and sort the abnormal grains mixed in it one by one, it has to flow down little by little, which takes an extremely long time and is not practical. Therefore, in the rice industry, this type of optical sorting device has not been incorporated into rice milling plants and was originally only used for special products with a small amount but specially without abnormal grains by a single machine.

[0004] As the times progress and consumers' demands for product quality improvement increase, there have been more claims regarding the presence of so-called abnormal grains such as damaged grains, dead rice, colored grains (so-called burned rice), insect-eaten rice, seeds other than rice grains, stone grains, and glass pieces mixed in rice products. For this reason, although an optical sorting device has become necessary during the process of a rice milling plant in a rice milling factory, as described above, it is not practical enough, so it could not be added to the process of the rice milling plant.

[0005] To solve the above problems, a sorting device for flowing materials equipped with a secondary sorting device, as shown in Patent Document 1, has been used. This sorting device has made it possible to incorporate optical sorting devices into rice milling plants. The reason for the complex configuration shown in Patent Document 1 is that, at the time, it was not possible to ensure that large quantities of rice grains flowed evenly in a single line without uneven distribution. Even with such a complex sorting device, it became possible to process large quantities of rice grains, and as a result of being incorporated into rice milling plants, the quality of rice products has dramatically improved, leading to increased consumer satisfaction.

[0006] However, after a while, complaints began to emerge from consumers and rice millers. Complaints from consumers, especially restaurants, included (1) the occasional presence of abnormal grains in the product. Other complaints from rice millers to the equipment manufacturer included (2) a decrease in product yield (and consequently, a reduction in profits) due to a large number of normal grains being mixed in with the group of rice grains discharged as abnormal.

[0007] The cause of (1) was thought to be that when the optical sorting device is used for a certain period of time, the highly viscous bran attached to the rice grains adheres to the feeder, and as this gradually grows into a snowball-like ball of bran, turbulence is created in the group of rice grains moving horizontally on the feeder, causing the group of rice grains to fall unevenly into the chute, and as the group of rice grains sliding down the chute becomes a large group of rice grains that are only partially illuminated by the light from the light source, some of which fall from the bottom of the chute, resulting in "missed grains".

[0008] Therefore, with the configuration described in Patent Document 2, the feeder is cleaned when the optical sorting device is idle, such as during lot changes, thereby eliminating "missed grains" due to bran clumping. However, even so, complaints of "missed grains" occasionally arose, but our industry could not deal with this, and we were forced to run multiple optical sorting devices in series in rice milling plants. In order to overcome this, we further diligently researched the cause of "missed grains" and found that, in the method of Patent Document 1, including Patent Document 2, in order to sort by primary sorting and remove abnormal grains, and to re-sort the many normal grains contained among them and recover the normal grains, a primary sorting means (primary sorting device) and a secondary sorting means (re-sorting device) are provided, and the group of rice grains judged as abnormal grains (defective products) by the primary sorting means is re-sorted by the secondary sorting means, and the secondary sorting means By sending the group of rice grains judged as normal (good quality) back to the primary sorting method, the sorting rate of non-standard, abnormal grains in the sorted material is improved. However, in proportion to the lot size, the amount of intermediate defective products (defective products that could not be accurately identified or separated due to disturbances in the flow on the chute) that are postponed in determining whether they are good or bad increases, resulting in a higher rate of defective products being mixed into the sorted material passing through the sorting method. While the ejector is suitable for sorting and removing a small number of defective products mixed in with a large number of good products, when a large number of defective products are mixed in with good products, the frequency of high-pressure air spraying cannot keep up. As a result, the rate of defective products mixed in with the sorted material increases as described above, leading to "missed selections" (overlooked selections). Consequently, it was found that even burnt rice, which is among the abnormal grains, was being missed due to "overlooked" selections. Furthermore, a problem arose where the sorting process would never be completed due to a so-called "loop phenomenon," where non-standard, abnormal grains repeatedly moved back and forth between sorting devices with multiple processes. Because the sorted grains kept moving back and forth between the primary and secondary sorting devices indefinitely, it took an incredibly long time for them to be discharged naturally. As a result, at the end of each batch, the remaining rice, including good grains, had to be removed manually from the machine.

[0009] In an industry where there was no solution to (1), we were quick to recognize the cause and, in order to solve this problem, we adopted a so-called "returnless system" in which the sorted material, which is an abnormal grain that does not meet the standards, does not repeatedly move back and forth between sorting means with multiple processes as described in Patent Document 3, thereby eliminating the complaint in (1). Furthermore, the configuration in Patent Document 3 also solved the problem in (2) at the same time, as it eliminated the discarding of remaining rice, including good rice, as defective products. This is because the returnless system significantly improved the proportion of abnormal grains (also called the defective product purity rate, where it is desirable to have few good grains mixed in with the defective products and a high proportion of defective products) in the group of rice grains discharged as abnormal grains. In addition, the removal of remaining rice during lot changes and at the end of a lot was eliminated, and moreover, the loss time caused by the "loop phenomenon" was shortened compared to conventional methods. Moreover, it was possible to eliminate "missed selections" with just one machine, whereas in conventional situations multiple optical sorting machines had to be passed through in series.

[0010] However, a new problem arose in the industry: (3) the work efficiency of rice milling plants had significantly decreased. The reason for (3) was that, in order to prevent contamination, the next batch of rice could not be fed into the rice milling plant until all the rice grains in the process had been removed from the process. Generally, rice milling plants have many pieces of equipment installed in series on the line, and the "return" of the groups of rice grains coming out of each piece of equipment by the bucket elevators that transport them to the equipment in the next process caused lost time.

[0011] To solve the problem described in (3) above, the configuration of Patent Document 4 is known. However, in general, rice milling plants have many pieces of equipment with different purposes installed on the line, so it has been found that not only the bucket elevator that sends the rice to the equipment for the next process, but also conventional optical sorting devices, including the optical sorting device of Patent Document 3, were causing lost time.

[0012] As described above, with the recent strict quality control of polished rice, it is necessary to install an optical sorting device with the configuration described in Patent Document 3 on the line of the rice milling plant in the rice milling factory. This is especially true if multiple optical sorting devices are installed in the process as before. Furthermore, even if the sorting device described in Patent Document 4 is installed, the speed of the sorted material flowing down the groove in the chute is very fast, so not only defective products but also good products are blown away by the high-pressure air jet. Therefore, the optical sorting machine described in Patent Document 3 (primary sorting means) has sorting means in multiple processes. In cases involving three or more processes (excluding the first three steps) or when multiple conventional color sorters are installed, the time required to pass the rice through several stages of sorting equipment becomes a loss of time, and this also contributes to the loss of time during lot changeovers at the rice milling plant. Therefore, it is desirable to reduce this loss of time as much as possible and increase the effective operating rate of the rice milling plant. It is desirable to perform sorting with higher accuracy in a shorter time, thereby achieving a sorting rate ("defect sorting rate") which is the rate at which defective products are removed from among the good products, and a "defect purity rate" which is the proportion of defective products among the good products after sorting and removal ("defect purity rate"). [Prior art documents] [Patent Documents]

[0013] [Patent Document 1] Japanese Patent Application Publication No. 59-6973 [Patent Document 2] Japanese Patent Publication No. 2010-125382 [Patent Document 3] Patent No. 5920236 [Patent Document 4] Japanese Patent Publication No. 2022-45604 [Overview of the project] [Problems that the invention aims to solve]

[0014] The problem that the present invention aims to solve in view of the above circumstances is a color sorter that achieves highly accurate sorting by passing the rice through a primary sorting means (main sorting device) only once, which effectively suppresses the mixing of defective products among good products and effectively prevents good products from mixing among defective products after sorting and removal, and a rice milling plant having the color sorter that can minimize the downtime during lot changeover in a rice milling plant. [Means for solving the problem]

[0015] The following describes the means to solve the above problems.

[0016] The color sorter according to the present invention comprises a feeder for sending out rice grains to be sorted, a supply cylinder for supplying the rice grains to the feeder, a chute for allowing the rice grains sent out by the feeder to flow down, and a color sorting unit for identifying and removing defective rice grains that have a different color from good rice grains discharged from the chute. The chute has a plurality of adjacent flow grooves through which the rice grains flow down, and the groove width of the flow grooves is set within a range of 1.05 to 1.5 times the average width of the rice grains.

[0017] With this configuration, the color sorter can accurately and timely remove defective products by ensuring that the rice grains are aligned, flow at a constant speed, and pass through the color sorting section. This prevents problems that can occur in conventional systems, such as the rice grains being pressed against the walls (sides) of the flow channel, slowing down the flow speed, or conversely, the rice grains turning sideways, tilting significantly, rotating, or otherwise losing their orientation, which can hinder the quality judgment and removal of defective products in the color sorting section. Furthermore, in the color sorting section, almost the entire surface of the rice grain can be seen, ensuring that defective products are not overlooked and are separated. In order to keep the trajectory of the defective rice grains being blown away by the ejector's steam constant (a constant trajectory reduces the chance of good products being discharged together with defective products due to the blown-away defective products coming into contact with surrounding good products), the rice grains flow with their bases and heads facing up and down in the direction of the chute flow, and their sides (between the belly and back) facing the chute groove (correct posture). This prevents problems that can occur in the color sorting section, such as when rice grains flow along the flow groove sideways or at a great incline, or when rice grains rotate within the flow groove, which can hinder quality judgment and the removal of defective products. Therefore, without repeatedly determining the quality of rice grains, such as with sorting methods that require multiple stages in a rice milling plant, it is possible to perform highly accurate sorting in a short time, effectively suppressing the mixing of defective products with good products, and effectively preventing good products from mixing with defective products. Furthermore, by significantly shortening the time that rice grains pass through the color sorter, downtime is reduced, and downtime during lot changeovers in the rice milling plant is reduced. It is also possible to prevent deterioration of rice grains due to repeated sorting of quality, and contamination of equipment by dust, etc., and the inside and outside of the equipment can be kept clean. As a result, there are advantages such as reducing the time-consuming and lengthy cleaning work performed by operators in a food factory such as a rice milling plant, and the downtime of operating time associated with cleaning work.

[0018] In addition, when a higher defective product sorting rate and a higher defective product purity rate are required than usual, the configuration of the present invention is installed in the same device in one or two additional rows and conveyed by the in-machine conveying means, and the sorting operation including the main sorting is performed two or three times, or a plurality of color sorters having the configuration of the present invention are passed through in series. However, in any case, since only a very small number of good products are mixed in the defective products separated by the first primary sorting means (main sorting device), compared with the case where a plurality of color sorters of Patent Document 3 or conventional color sorters that require four or more steps are installed, the loss time required for passing through the conventional re-sorting means is reduced, and the loss time at the time of lot change in the rice milling plant can be reduced.

[0019] Further, in the color sorter according to the present invention, it is preferable that the groove width of the flow-down groove is set within a range of 1.2 times to 1.4 times the average width of the rice grains.

[0020] According to this configuration, while maintaining the proper posture of the rice grains, by smoothly flowing the rice grains along the flow-down groove of the chute, the sorting operation of the rice grains in the color sorting unit can be executed more appropriately.

[0021] Further, in the color sorter according to the present invention, it is preferable that the groove depth of the flow-down groove is set within a range of 0.4 times to 1.0 times the average thickness of the rice grains.

[0022] According to this configuration, it is possible to prevent the rice grains from jumping out of the flow-down groove, directly lead the rice grains toward the color sorting unit, and prevent a plurality of rice grains from flowing along the flow-down groove in a state of overlapping vertically, and by leading them one by one toward the color sorting unit, the sorting operation of the rice grains in the color sorting unit can be executed more appropriately.

[0023] Further, in the color sorter according to the present invention, it is preferable that at least the cross-sectional shape of the bottom surface portion of the flow-down groove is formed in an arc shape or an elliptical arc shape.

[0024] According to this configuration, it is possible to further prevent the rice grains from colliding with the side surface of the groove and the flow velocity from becoming unstable, and to smoothly flow the side surface (between the belly and the back) of the rice grains having an elliptical cross-sectional shape along the bottom surface of the flow groove. At the same time, the center part of the rice grains can be moved along the center line of the flow groove using the bottom surface of the flow groove as a guiding surface, thereby effectively improving the sorting efficiency (improvement of sorting rate, improvement of defective product purity rate) by the color sorting unit.

[0025] In addition, the rice milling plant according to the present invention includes a brown rice supply unit that supplies brown rice, a rice milling unit that removes the bran of the brown rice by a rice milling machine to produce white rice, and a sorting unit that has the color sorter according to any one of claims 1 to 5.

[0026] According to this configuration, it is possible to perform highly accurate sorting in a short time with a simple configuration without repeating the color sorting operation of the rice grains supplied from the brown rice supply unit through the rice milling unit to the color sorter, effectively suppressing the mixing of defective products into good products, effectively preventing the mixing of good products into the sorted and removed defective products, and above all, improving the actual operation rate of the rice milling factory, reducing the installation space of the rice milling plant as much as possible, and having advantages such as effectively simplifying the configuration.

Effect of the Invention

[0027] As described above, according to the color sorter and the rice milling plant equipped with the color sorter according to the present invention, it is possible to perform highly accurate sorting in a single sorting step without repeating the sorting operation of the rice grains, obtain excellent sorting results in a short time, and have advantages such as effectively simplifying the structure of the rice milling plant.

Brief Description of the Drawings

[0028] [Figure 1] Side view showing an embodiment of the color sorter according to the present invention. [Figure 2] Side view showing the configuration of the chute. [Figure 3] Cross-sectional view taken along line III-III of FIG. 2. [Figure 4] A cross-sectional view showing the specific configuration of the drainage channel. [Figure 5] A front view showing the specific configuration of the color sorting unit. [Figure 6] (a) is a graph showing the relationship between groove width and defective product sorting rate, and (b) is a graph showing the relationship between groove width and defective product purity rate. [Figure 7] A diagram showing the flow pattern of rice grains. [Figure 8] A block diagram showing an embodiment of a rice milling plant according to the present invention. [Modes for carrying out the invention]

[0029] First, a color sorter 1 according to the first embodiment of the present invention will be described with reference to Figures 1 to 5. The color sorter 1 according to this embodiment includes a feeder 4 that sends out rice grains 10 to be sorted, a supply cylinder 3 that supplies rice grains 10 to the feeder 4, a chute 5 having multiple rows of flow grooves for the rice grains 10 sent out by the feeder 4 to flow down, and a color sorting unit 2 that identifies and removes defective rice grains 10b that have a different color from good rice grains 10 discharged from the chute 5.

[0030] The supply cylinder 3 supplies rice grains 10, which have been sent out from the rice milling unit 30 (described later), onto the feeder 4 from its lower end. The lower end of the supply cylinder 3 is provided with a shutter (not shown) for adjusting the amount of rice grains 10 supplied onto the feeder 4.

[0031] The feeder 4 has a slightly downward-sloping guide passage 41 that guides the rice grains 10 supplied from the supply cylinder 3 toward the chute 5, and a vibrator 42 provided below the guide passage 41. By vibrating the guide passage 41 with the vibrator 42 and supplying the rice grains 10 onto the guide passage 41 from the supply cylinder 3, the feeder 4 is configured to sequentially send the rice grains 10 toward the chute 5 from the tip of the guide passage 41.

[0032] As shown in Figures 2 to 4, the chute 5 has a bottom plate 52 with multiple flow grooves 51 formed adjacent to each other on its surface through which the rice grains 10 flow down, and a pair of left and right side plates 53, and is attached to the body of the color sorter 1 at a certain angle of inclination (see Figure 1). As shown in Figure 4, each flow groove 51 of the chute 5 has at least its bottom surface formed in a circular arc shape in cross-section. Furthermore, the flow grooves 51 are set to a range of 1.05 to 1.5 times the average width W of the rice grains 10, so that the rice grains 10 can be guided out in a posture and at intervals that allow for proper sorting in the color sorter 2.

[0033] For example, if the rice grains 10 to be sorted are Koshihikari rice with an average width W of 3.0 mm, an average thickness H of 2.0 mm, and an average length L of 5.0 mm, then if the groove width X of the flow channel 51 is less than 3.15 mm, the smooth flow of the rice grains 10 may be hindered, such as the rice grains 10 being pressed against the wall of the flow channel 51 or falling outside the chute 5 without settling into the groove. On the other hand, if the groove width X of the flow channel 51 is wider than 4.5 mm, the sorting operation in the color sorting unit 2 may not be performed properly, as rice grains 10 smaller than the average length L (5.0 mm) of Koshihikari rice may flow along the flow channel 51 sideways or at a great incline, or the rice grains 10 may rotate within the flow channel 51.

[0034] Therefore, in the present invention, as described above, the groove width X of the flow groove 51 is set within a range from 1.05 times the average width W of the rice grains 10 (3.15 mm in the case of Koshihikari) to 1.5 times the average width W of the rice grains 10 (4.5 mm in the case of Koshihikari), thereby maintaining the rice grains 10 in a vertical position suitable for sorting, while allowing the rice grains 10 to flow smoothly along the flow groove 51. Furthermore, in order to enable more appropriate sorting in the color sorting unit 2, it is preferable to set the groove width X of the flow groove 51 within a range of 1.2 times the average width W of the rice grains 10 (3.6 mm in the case of Koshihikari) or more, and 1.4 times the average width W of the rice grains 10 (4.2 mm in the case of Koshihikari) or less.

[0035] Furthermore, in order to properly sort the rice grains in the color sorting unit 2, it is preferable to set the groove depth Y of the flow groove 51 within the range of 0.4 to 1.0 times the average thickness H of the rice grains 10. That is, if the groove depth Y of the flow groove 51 is less than 0.4 times the average thickness H of the rice grains 10, the rice grains 10 may fly out of the flow groove 51, making it difficult to guide them straight towards the color sorting unit 2. On the other hand, if the groove depth Y of the flow groove 51 is greater than 1.0 times the average thickness H of the rice grains 10, multiple rice grains 10 may flow along the flow groove 51 stacked on top of each other, which may hinder the sorting of the rice grains 10 in the color sorting unit 2. Therefore, in order to ensure proper sorting in the color sorting section 2, it is preferable to set the groove depth Y of the flow groove 51 to a range of 0.4 times the average thickness H of the rice grains 10 (0.8 mm in the case of Koshihikari) or more, and 1.0 times the average thickness H of the rice grains 10 (2.0 mm in the case of Koshihikari) or less.

[0036] In the above embodiment, specific values ​​for the groove width X and groove depth Y of the flow groove 51 were set with rice grains 10 made of Koshihikari rice as the sorting target. However, it is desirable to set the specific values ​​for the groove width X and groove depth Y of the flow groove 51 within an appropriate range depending on the type of rice grain 10. For example, if the maximum width dimension of large grain rice is said to be 3.6 mm and the thickness dimension is 2.7 mm, the specific value for the groove width X of the flow groove 51 will be in the range of 3.78 mm to 5.4 mm, and the preferred range for the groove width X of the flow groove 51 is 4.32 mm to 5.04 mm. The preferred range for the groove depth Y is 1.08 mm to 2.7 mm. Therefore, the specific value for the groove width X of the flow groove 51 of the chute 5 that can handle any variety is 3.8 mm to 4.5 mm, more preferably 3.8 mm to 4.2 mm, and the preferred range for the groove depth Y is 1.1 mm to 2.0 mm.

[0037] In the above embodiment, as shown in Figure 4, the groove width X of the flow channel 51 is defined using the apex of the partition wall provided on the side of the flow channel 51 as the starting point. However, if the width dimension of the partition wall is large, it is desirable to define the groove width X of the flow channel 51 excluding the width dimension of the partition wall. That is, the rice grains 10 to be sorted flow down the flow channel 51 along the inner circumferential surface, and the partition wall does not have a guiding function for the rice grains 10. Therefore, if the groove width X of the flow channel 51 is defined including the partition wall, it may not be possible to flow the rice grains 10 in the correct orientation. In such cases, it is desirable to define the groove width X of the flow channel 51 according to the distance between the sides of the flow channel 51, excluding the width dimension of the partition wall.

[0038] The color sorting unit 2 includes a front-side color discrimination sensor 6a, a back-side color discrimination sensor 6b, a front-side illumination unit 7, a back-side illumination unit 8, a defective product removal means 12, a separation hopper 13, a good product discharge unit 14, and a defective product discharge unit 15. As shown in Figure 5, the defective product removal means 12 includes an air nozzle 17 with multiple air injection ports 16 formed at regular intervals on the upper front side, a solenoid valve 18 (see Figure 1) positioned on the back side of the air nozzle 17, and an air supply pipe 19 that supplies compressed air to the solenoid valve 18.

[0039] Then, after the rice grains 10 flow along the multiple flow grooves 51 of the chute 5 while accelerating, light is shone on the rice grains 10 that have been led to the installation section of the color sorting unit 2 from the surface-side lighting unit 7 and the rear-side lighting unit 8, and the light that passes through or is reflected from the rice grains 10 is read by the surface-side color discrimination sensor 6a and the rear-side color discrimination sensor 6b. Here, the surface-side color discrimination sensor 6a and the rear-side color discrimination sensor 6b determine whether the transmittance, reflectance, light intensity, etc. of the light are within a predetermined threshold, based on the transmittance, reflectance, light intensity, etc. of the light that has been pre-shown toward the background provided in the surface-side lighting unit 7 and the rear-side lighting unit 8. If this determination confirms that the light transmittance, reflectance, light intensity, etc., are within predetermined thresholds, the rice grains 10 are identified as good quality 10a, and without activating the defective product removal means 12, they are led out of the color sorter 1 via the good product discharge section 14 provided in the separation hopper 13 and stored in a good product storage tank or rice bag, etc. (not shown).

[0040] On the other hand, if the light transmittance, reflectance, light intensity, etc., of the rice grains 10 to be sorted are outside a predetermined threshold, the sorted items are identified as defective products 10b, and the solenoid valve 18 is activated so that compressed air is sprayed from the air nozzle 16 of the air nozzle 17 toward the center of the side of the defective product 10b, thereby blowing away the defective product 10b and discharging it toward the defective product discharge section 15 provided in the separation hopper 13. For example, if damaged grains, dead grains, discolored grains, or foreign matter such as seeds other than rice grains, stones, and glass fragments are mixed in with the rice grains 10, these damaged grains, dead grains, discolored grains, and foreign matter are identified as defective products 10b and removed.

[0041] In the above-described embodiment, items within the threshold are identified as good products 10a, and items outside the threshold are identified as defective products 10b. However, the invention is not limited to this, and items within the threshold may be identified as defective products 10b, and items outside the threshold may be identified as good products 10a. Furthermore, while it is preferable to use one type of threshold in the color sorting unit 2 used in the present invention, the invention is not limited to this, and two or more thresholds may be used as needed to sort items into two types: those within the threshold and those outside the threshold.

[0042] As described above, the color sorter 1 according to the present invention comprises a feeder 4 that sends out rice grains 10 to be sorted, a supply cylinder 3 that supplies rice grains 10 to the feeder 4, a chute 5 that allows the rice grains 10 sent out by the feeder 4 to flow down, and a color sorting unit 2 that identifies and removes defective rice grains 10b that have a different color from good rice grains 10 discharged from the chute 5. The chute 5 has a plurality of adjacent flow grooves 51 through which the rice grains 10 flow, and the groove width X of the flow grooves 51 is set within the range of 1.05 to 1.5 times the average width W of the rice grains 10. This has the advantage that it can perform highly accurate sorting in a short time and effectively suppress the mixing of defective rice grains 10b with good rice grains 10a, and can also effectively reduce the probability of good rice grains 10a being misidentified as defective rice grains 10b.

[0043] In other words, the sorted material consisting of rice grains 10 supplied from the supply cylinder 3 to the feeder 4 is sent to the top of the chute 5 in an orderly manner while the flow rate is adjusted by the feeder 4, and flows along the flow groove 51 of the chute. At this time, if the groove width X of the flow groove 51 is too narrow, the smooth flow of the rice grains 10 is hindered by the rice grains 10 being pressed against the wall surface of the flow groove 51, causing the flow speed to become unstable, which may hinder the quality judgment of the color sorter 2 and the removal of defective products 10b. Conversely, if the groove width X of the flow groove 51 is too wide, the rice grains 10 may flow along the flow groove 51 sideways or at a great incline, or rotate within the flow groove 51, making quality judgment of the color sorter 2 difficult. Furthermore, in this invention, when sorting with air, the rice grains 10 are in an elongated position as shown in Figures 7(a) and (b), so the air is more likely to hit the flat side surface of the rice grain 10 and fly straight, without involving the rice grains in front of or behind it. In contrast, in the conventional method, as shown in Figures 7(c) and (d), when the rice grains 10 are in an elongated position, the flat side surface of the rice grain 10 is narrow, making it difficult to capture a single grain with the air. Also, when the air hits the curved part of the rice grain, it does not fly straight but flies in various directions, and in any case, it involves the rice grains 10 in front of or behind it, which hinders the removal of defective products 10b.

[0044] Therefore, in this invention, by setting the groove width X of the flow groove 51 within the above range, the rice grains 10 to be sorted are guided to the color sorting unit 2 one by one in a vertical position at a constant distance from each other, and the light from the front-side lighting unit 7 and the back-side lighting unit 8 is properly irradiated to the middle part of both the front and back sides of the rice grains 10 to be inspected, thereby enabling accurate color sorting. If the sorting target is determined to be a defective product 10b, compressed air sprayed from the air nozzle 17 is blown toward the middle part of the side of the defective product 10b, thereby ensuring that the defective product 10b is reliably removed. Therefore, by performing quality sorting of the rice grains 10 only once, without repeating the sorting process, the proportion of defective grains 10b mixed in with good grains 10a can be reduced as much as possible, and the probability of good grains 10a being mistakenly identified as defective grains 10b can be effectively reduced. Furthermore, this method has the advantage of preventing deterioration of the rice grains 10 and contamination of the equipment that can occur due to repeated sorting of the rice grains 10.

[0045] For example, a sample consisting of 1980g of Koshihikari rice grains (good quality) mixed with 20g of black rice (defective quality), which is entirely colored deep purple due to the presence of deep purple anthocyanins in the pericarp. The sample was then subjected to a test to investigate the defect sorting rate and defect purity rate by varying the flow rate per channel (per flow channel) within the range of 3.7mm to 5.0mm at the rated flow rate (35kg / ch / h in this example) and the groove width X of the flow channel 51. The results were as shown in Figures 5(a) and (b). From this test data, it was confirmed that when the groove width X of the flow channel 51 was set to 4.5mm (1.5 times the average width W of Koshihikari), the defect sorting rate was 98.5% or higher, and the defect purity rate was 80% or higher, demonstrating that excellent defect sorting rates and defect purity rates can be obtained with just one sorting operation. Furthermore, when the groove width X of the drainage groove 51 was set to 4.2 mm (1.4 times the average width W of Koshihikari rice), the defective product sorting rate was approximately 99.0%, and the defective product purity rate was approximately 85%. This confirmed that the preferred range for the groove width X of the drainage groove 51 is 1.4 times or less the average width W of the rice grains 10.

[0046] Furthermore, in the above experiment, where all other conditions were the same except that the groove width X of the flow channel 51 was set to less than 3.7 mm, when the groove width X of the flow channel 51 was set to less than 1.05 times the average width W of the rice grains 10 (less than 3.15 mm in the case of Koshihikari), the phenomenon of the smooth flow of the rice grains 10 being sorted being hindered occurred frequently. Therefore, it was confirmed that the groove width X of the flow channel 51 needs to be set to 1.05 times or more the average width W of the rice grains 10. Also, when the groove width X of the flow channel 51 was set to 1.2 times or more the average width W of the rice grains 10 (3.6 mm or more in the case of Koshihikari), the phenomenon of the smooth flow of the sorted rice grains being hindered hardly occurred. Thus, it was confirmed that the preferred range for the groove width X of the flow channel 51 is 1.2 times or more the average width W of the rice grains 10.

[0047] Furthermore, as shown in the embodiment described above, when the groove depth Y of the flow groove 51 is set within the range of 0.4 to 1.0 times the average thickness H of the rice grains 10, it is possible to prevent the rice grains 10 from flying out of the flow groove 51 and to guide the rice grains 10 straight toward the color sorting unit 2. At the same time, it is possible to prevent multiple rice grains 10 from flowing along the flow groove 51 while overlapping each other, and to guide each grain toward the color sorting unit 2 one by one, thereby enabling more appropriate sorting of the rice grains 10 in the color sorting unit 2.

[0048] In the above-described embodiment, an example was given in which the cross-sectional shape of at least the bottom surface of the flow channel 51 is formed in an arc shape. However, instead of this configuration, it is also possible to provide a flow channel 51 in the chute 5 with a concave or V-shaped cross-section, where the bottom surface is formed as a flat surface. However, as shown in Figure 4, when the cross-sectional shape of at least the bottom surface of the flow channel 51 is formed in an arc shape, the lower surface of the rice grain 10, which has an elliptical cross-sectional shape, can be smoothly flowed along the bottom surface of the flow channel 51. Furthermore, the bottom surface of the flow channel 51 can be used as a guide surface to move the center of the rice grain 10 along the center line A of the flow channel 51, thereby effectively improving the sorting efficiency of the color sorting unit 2.

[0049] Figure 8 shows an example of a rice milling plant line according to the present invention, but the configuration is not limited to this line. Figure 8 shows a schematic configuration of a rice milling plant 50 according to the present invention, which comprises a brown rice supply unit 20 for supplying brown rice, a rice milling unit 30 for removing the bran from the brown rice supplied from the brown rice supply unit 20 using a rice milling machine to produce white rice, and a sorting unit 40 having a color sorter 1 for sorting the rice grains 10 sent out from the rice milling unit 30 into good and defective products.

[0050] Furthermore, the brown rice supply unit 20 may be equipped with a rice hulling machine for removing the husks to produce brown rice, a coarse sorting machine for sorting and removing coarse debris, the rice milling unit 30 may be equipped with a pre-washed rice processing machine, the sorting unit 40 may be equipped with a stone remover, and a packaging unit for filling and packaging the white rice may be provided after the brown rice supply unit 20, the rice milling unit 30, and the sorting unit 40. Moreover, in order to sort out dead grains and green dead grains from the brown rice grains, the sorting unit 40 having a color sorter 1 may be placed not only after the rice milling unit 30, but also between the brown rice supply unit 20 and the rice milling unit 30.

[0051] According to the rice milling plant 50, the sorting of rice grains 10 supplied from the brown rice supply unit 20 through the rice milling unit 30 to the color sorter 1 can be performed properly in a short time without repeating the sorting process, effectively reducing the amount of defective grains 10b mixed in with good grains 10a, and effectively reducing the amount of good grains 10a mixed in with defective grains 10b. Therefore, compared to conventional technology with a re-sorting mechanism, the time lost for sorting in the re-sorting mechanism is reduced, the configuration of the rice milling plant 50 can be simplified, there are fewer places to clean and fewer breakdowns, thus reducing maintenance costs, and there are also advantages such as fewer times the rice milling plant 50 is stopped due to cleaning or breakdowns, and shorter downtime, thus reducing lost time.

[0052] Furthermore, since no residual recycled rice is generated by re-sorting, contamination by mixing rice from one processing lot with rice from the next processing lot is prevented, reducing downtime during lot changes. In addition, the phenomenon of the surface of the rice grains being worn down (damaged) by repeatedly circulating the milled rice grains 10 is suppressed, resulting in the advantage of very little deterioration in the quality of the rice grains 10.

[0053] As described above, with the color sorter 1 according to the present invention, even with the same flow rate as before, it was possible to achieve a defect sorting rate and defect purity rate equal to or better than that of conventional sorting devices that perform re-sorting, with only one sorting pass. In other words, even with only one sorting pass and the same flow rate as before, the rice grains could be slid into the chute 5 without uneven dropping, and each rice grain could pass through the lower end of the chute 5 in a single column.

[0054] Specifically, as shown in Figure 3, many grooves are formed parallel to each other in the chute 5. Therefore, even when a large quantity of rice grains flows from the feeder 4, as the rice grains flow down the chute 5 along each groove, the elongated, rugby ball-shaped rice grains can slide while fitting evenly into each groove. In this way, each rice grain naturally slides in a single file with a vertical orientation, so when it passes through the lighting unit installed near the bottom of the chute 5, abnormal grains that are different from normal grains can be accurately detected and ejected instantaneously from the ejector. In other words, the color sorter 1 can accurately detect and separate abnormal grains, so it can sort with a high defect sorting rate and defect purity rate in just one sorting pass.

[0055] The shape of chute 5 is such that the spacing between the numerous parallel chute grooves is approximately 3.8 millimeters. That is, the rice grains are elongated like a rugby ball, with approximate dimensions of 5 millimeters in length, 2 millimeters in thickness, and 3 millimeters in width. The applicant conducted experiments by changing the spacing between the grooves of chute 5 and found that setting it to approximately 3.8 millimeters resulted in all the rice grains being arranged in a consistent pattern.

[0056] Therefore, in the present invention, by devising the spacing between the grooves of the chute 5 as described above, the rice grains only need to be passed through the chute 5 once. As a result, there is no need for a conveyor that transfers the rice grains from one chute 5 to another chute 5 multiple times, as was done with conventional re-sorting devices. This eliminates the need for such a device, resulting in an extremely simple design that avoids unnecessary installation space and costs. In this way, the present invention achieves single-grain sorting at high flow rates, which was not possible with conventional optical sorting devices.

[0057] Furthermore, by repurposing it as an optical sorting device in the process of the rice milling plant 50, it is possible to prevent a deterioration in work efficiency at the rice milling plant. In other words, simply replacing the conventional optical sorting device with the present invention will give it the same value as a state-of-the-art rice milling plant that has been newly constructed at great expense and utilizes the latest technology. That is, by replacing the optical sorting device installed in conventional rice milling plants with the color sorter 1 of the present invention, it is possible to reduce costs.

[0058] Although embodiments of the present invention have been described, the present invention is not limited in any way to the embodiments described above. The feeder 4 may be a conveyor that moves rice grains horizontally, and the shape of the flow groove of the chute 5 may be a concave groove or a V-groove. Of course, the configuration can be changed without departing from the spirit of the present invention. [Explanation of Symbols]

[0059] 1. Color sorter 2. Color sorting section 3 supply cylinder 4 feeder 5. Shoot 6a. Surface-side color discrimination sensor 6b Rear side color discrimination sensor 7 Front side illumination unit 8 Rear lighting unit 10 Rice grains 10a Good product 10b Defective product 12 Defective product removal method 13 Separation hopper 14 Good product extraction section 15 Defective product discharge section 16 Air outlet 17 Air nozzle 18 Solenoid valve 19 Air supply pipe 20 Brown rice supply department 30 Rice milling department 40 Sorting section 41 Guide corridor 42 Vibrator 50 Rice milling plant 51 Flow groove 52 Bottom plate 53 Side panel

Claims

1. A feeder that sends out the rice grains to be sorted, A supply cylinder for supplying the rice grains to the feeder, A chute for flowing down the rice grains sent out by the feeder, The system includes a color sorting unit that identifies and removes defective rice grains having a different color from good rice grains discharged from the chute, Multiple flow grooves for the rice grains to flow down are formed adjacent to each other in the aforementioned chute. A color sorter in which the groove width of the flow groove is set within a range of 1.05 to 1.5 times the average width of the rice grains.

2. The color sorter according to claim 1, wherein the groove width of the flow groove is set within a range of 1.2 to 1.4 times the average width of the rice grains.

3. The color sorter according to claim 2, wherein the groove depth of the flow groove is set within a range of 0.4 to 1.0 times the average thickness of the rice grains.

4. The color sorter according to claim 3, wherein the cross-sectional shape of at least the bottom surface of the flow groove is formed in an arc shape.

5. A rice milling plant comprising: a brown rice supply unit that supplies brown rice; a rice milling unit that removes the bran from the brown rice using a rice milling machine to produce white rice; and a sorting unit having a color sorter as described in any one of claims 1 to 4.

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