A process and apparatus for sorting potatoes

Abstract: A process for sorting potatoes based on square size, in which the potatoes are passed through a V-shaped channel, and of each potato the distance between the point of the V-shape and the highest point of the potato is measured, and the square potato size belonging to the measured distance is determined.

Description: This invention relates to a process for sorting potatoes based on a size of the potato, by passing the potatoes through a V-shaped channel and measuring of each potato the distance between a point of the V-shaped channel and a point of the potato located in the channel. The invention also relates to an apparatus for sorting potatoes based on square size, comprising at least one V-shaped channel; feeding means for feeding potatoes to the V-shaped channel; at least one sensor for detecting a distance between a point of a potato located in the channel and a point of the V-shaped channel. Such a process is known from the French patent application 2,528,972. According to this method the smallest distance between a point of the potato and a point of the V-shaped channel is measured as being the desired distance to be known. In potato trade and potato processing industry potatoes are alternatively sorted into different size classes by applying the so-called square size principle. Potatoes are then sorted by means of reciprocating riddles having square openings. A drawback of this prior sorting method is that there is a relatively great risk of the potatoes being damaged by the shaking riddles. The square size of a potato can be defined as the length of the side of the smallest square opening the potato can pass through. In the international potato trade this square size is generally used as a standard. The potatoes are mostly sorted into a number of classes, e.g., a first class of potatoes having a square size below 35 mm, a next class of potatoes having a square size ranging from 35 to 45 mm, subsequent classes 45/55 mm, 55/65 mm and, e.g., a class of potatoes having a square size above 65 mm. When sorting a lot of potatoes according to such a large number of classes, the potatoes that remain longest in the sorting process must pass through a relatively large number of shaking riddles, which proportionally increases the risk of damage. This is very disadvantageous, e.g., in case of table and seed potatoes. There is therefore a need for a method of sorting potatoes or similar bulbous or tuberous fruits at a low risk of damage while maintaining the square size principle. The object of this invention is to meet the above need. For this purpose a process of the above type is characterized according to the invention by determining the distance between the angular point of the V-shape and the highest point of the potato located in the channel and determining the square potato size from the measured distance. The U.S. patent 4,462,496 describes a method and apparatus wherein particles are placed in the grooves of an inclined surface to roll downwardly thereon. Vacuum pick-up means are used to remove those particles which do not roll down because of their spherical irregularities. The apparatus is used for separating the spheres from the non-spheres in a large number of particles of lamp fill material. The U.S. patent 3,744,628 describes a method of classifying poultry wherein the height of the keel bone area is measured by deflecting a deflective member. Furthermore, a classifying chute is positioned to receive the poultry responsive to the sensed deflection. An apparatus for sorting potatoes based on square size is characterized according to the invention in that the sensor detects the distance between the angular point of the V-shape and the highest point of the potato located in the channel and which sensor applies a signal corresponding to the detected distance to a control device capable of controlling guide means for passing the potato in question to a collection of potatoes having a square size corresponding to the detected distance. The invention will be further described hereinbelow with reference to the accompanying drawings, in which Fig. 1 schematically shows an example of a prior potato sorting apparatus in vertical arrangement; Fig. 2 schematically shows an example of a prior potato sorting apparatus in horizontal arrangement; Fig. 3 schematically illustrates the square size principle; Figs. 4 through 6 schematically illustrate the principle of the invention; and Fig. 7 schematically shows an example of an apparatus according to the invention. Fig. 1 schematically shows a potato sorting apparatus 1 with three superjacent riddles 2, 3, 4 having square passages. The upper riddle 2 has the largest passages and the lower riddle 4 the smallest. During operation, the riddles carry out a reciprocating movement so that potatoes successively come to lie on the riddle in different positions and a potato that does not fall through the riddle openings is conveyed to a discharge end of the riddle. The potatoes are passed from a chute 5 to the upper riddle. The potato schematically shown at 6 is so large that it cannot even pass through the openings of the upper riddle 2 and this potato eventually falls from the riddle, as indicated at 7. The potato indicated at 8 can pass through the openings of the upper riddle but not through the openings of the second riddle 3 and falls from the second riddle at 9. Similarly, the potato shown at 10 falls through the upper riddle 2 and the second riddle 3 and leaves the third riddle at 11. The smallest potato shown at 12 falls through the openings of all the riddles, as indicated at 13. In such an apparatus, therefore, the smallest potatoes must pass all the shaking riddles so that they run a substantial risk of being damaged, such as, e.g., blueing. The apparatus 15 shown in Fig. 2 has, in a horizontal arrangement, successive riddles 16 through 18 with riddle openings ever increasing from the chute 19. In such an apparatus the largest potatoes 20 must pass through all the riddles 20 before leaving the apparatus. In this case, too, there is a substantial risk of damage. Moreover, in both arrangements it applies that more riddles are required as the sorting is to be carried out more accurately. This, however, also increases the risk of damage. Fig. 3 illustrates the square size principle. The square size M is given by the length of the side of a square opening 12 through which a potato 23 can just pass. Fig. 4 schematically illustrates the fundamental idea underlying the invention. Fig. 4 shows, in cross section, a V-shaped channel 30 containing a purely spherical potato 31. In Fig. 4 the square size is indicated by v. The height h of the highest point of the purely spherical potato located in the channel is also indicated. For this channel height it applies in the case of a channel with an opening angle, i.e. the angle between the two channel walls, that α = 45° : h = r + r √2 . It further applies that v = 2r , so there is a fixed relation between the channel height h and the square size. Consequently, once the channel height has been measured, the square size is also known. The problem, however, is that potatoes are not purely spherical in practice, but rather approach the shape of an ellipsoid. When a potato is not purely spherical, the channel height strongly depends on the position of the potato at the moment of measuring the channel height. This is illustrated by Fig. 5, in which the channel 30 is shown again. A potato 32 having a substantially ellipsoid shape is located in the channel 30. The channel height of the potato in horizontal position, drawn in full lines, is h1. The same potato in "vertical" position is indicated in broken lines. Now the pertinent channel height is h2. The channel heights h1 and h2 are different, so that the square size can be determined from a measured channel height only if the position of the potato is also considered. During further experiments, which the Agrotechnical and -physical Department of the Agricultural University of Wageningen conducted at the request of and in cooperation with applicants, it was found, however, that the measured channel height of normal potatoes is positively a measure of the square size if there is used a channel having an adapted opening angle α. It was found that good results are obtained if the opening angle of the channel ranges from ± 60° to ± 65°. Preferably, the opening angle α = 62.5°. Fig. 6 automatically shows a channel having an opening angle α = 62.5° in which one and the same substantially ellipsoidal potato is drawn in "vertical" and in "horizontal" position. It can be seen that in these positions the channel heights h1 and h2 are equal, so that now a measured channel height is a measure of the square size. An apparatus for determining the channel height and thereby the square size may consist of, e.g., a plurality of juxtaposed channels having an opening angle of 62.5°. For each channel there must be at least one sensor which detects the channel height and then generates a signal to open a flap arranged in the bottom or side wall of the channel, which flap allows the measured potato to pass to a receptacle in which potatoes having a square size which is within a predetermined range and corresponds to the measured channel height are collected. When a potato has a channel height belonging to another range of square sizes, a corresponding other flap is opened. It is also possible to dispose at the end of each channel a rotatable discharge channel or pipe, which, in response to the signal generated by the sensor or sensors, passes the potatoes to a receptacle belonging to the measured size, optionally through further channels or other transport means. Fig. 7 schematically shows in side elevation view an apparatus for sorting potatoes based on square size by measurement of the channel height. The apparatus comprises a plurality of channels which are slightly inclined downwardly, and one of which, indicated by 40, is visible. The channel 40 is supported by a frame 41 and is provided with a chute 42 for feeding in potatoes to be sorted. Disposed above the channel is a schematically shown sensor 43 capable of detecting the channel height of a passing potato 44. The sensor may be, e.g., a spring-suspended sensor 45, as shown, but the sensor may also be a plurality of light barriers arranged in the channel at different heights, each of which comprising a light source and a photosensitive cell disposed opposite the light source. The sensor 43 generates a signal, preferably electric, corresponding to the measured channel height, which signal is applied to a control device 46 capable of controlling a plurality of flaps 47, 48, 49, which are arranged further down the channel, as indicated by a broken line 59. The control device 46 selectively opens one of the flaps or no flap at all, so that the potato just measured falls at one of the receptacles or compartments 51 through 54. It is to be noted that after the foregoing different variants are obvious to a skilled worker. Thus, e.g., the channel may be provided with transport means to promote the movement of the potatoes through the channel. As shown in Fig. 7, this is achieved by an endless rope, band or belt 55 extending in the longitudinal direction of the channel wall. It is also possible to compose both channel walls essentially of suitably supported conveyor belts or to use a vibratory channel. Furthermore, a plurality of sensors may be used. A sensor may further comprise a roll or an endless tape as a sensor element to minimize the risk of damage to a potato. Also, a channel may be set in a reciprocating movement transverse to its longitudinal direction under a sensor. These and similar modifications are deemed to fall within the scope of the invention.

Claims: A process for sorting potatoes (31,32,44) based on a size of the potato, by passing the potatoes (31,32,44) through a V-shaped channel (30,40) and measuring of each potato the distance between a point of the V-shaped channel (30,40) and a point of the potato located in the channel, characterized by determining the distance between the angular point of the V-shape and the highest point of the potato (31,32,44) located in the channel (30,40) and determining the square potato size from the measured distance. A process as claimed in claim 1, characterized in that the opening angle (α) of the V-shaped channel (30,40) ranges from ± 60° to ± 65°. A process as claimed in claim 2, characterized in that the opening angle (α) of the V-shaped channel (30,40) is substantially 62.5°. An apparatus (1) for sorting potatoes (31,32,44) based on square size, comprising at least one V-shaped channel (30,40); feeding means (42) for feeding potatoes to the V-shaped channel (30,40); at least one sensor (43,45) for detecting a distance between a point of a potato (31,32,44) located in the channel and a point of the V-shaped channel, characterized in that the sensor detects the distance between the angular point of the V-shape and the highest point of the potato (31,32,44) located in the channel (30,40) and which sensor applies a signal corresponding to the detected distance to a control device (46) capable of controlling guide means (47,48,49) for passing the potato (31,32) in question to a collection (51-54) of potatoes having a square size corresponding to the detected distance. An apparatus as claimed in claim 4, characterized in that the V-shaped channel (30,40) has an opening angle (α) ranging from ± 60° to ± 65°. An apparatus as claimed in claim 5, characterized in that the opening angle (α) is substantially 62.5°. An apparatus as claimed in any of claims 4 through 6, characterized in that at least one of the channel walls is provided with an endless transport means (55). An apparatus as claimed in any of claims 4 through 6, characterized in that the at least one V-shaped channel is provided beyond the at least one sensor with a plurality of controllable flaps (47,48,49) through which a potato (44) can be passed to a desired collection (51-54) of potatoes already sorted. An apparatus as claimed in any of claims 4 through 6, characterized in that means are provided for vibrating the at least one channel.

Inventors: DE VRIES HENDRIK CORNELIS PIET, MIDDEL JAN, DE VRIES, HENDRIK CORNELIS PIETER, MIDDEL, JAN
Applicants: ZIJLSTRA & BOLHUIS BV, ZIJLSTRA & BOLHUIS B.V.
Application year: 1991
Main classification: B07C5
IPC codes: B07C5