APPARATUS FOR SEPARATING AGRICULTURAL PRODUCE FROM SPURIOUS MATTER

Abstract: Apparatus for separating a mixture of agricultural pro­ ducts and stones including an impact element (12) defining an impact surface, which element is operative to absorb ap­ preciable kinetic energy from stones but to absorb a signifi­ cantly lower amount of kinetic energy from agricultural pro­ ducts sought to be separated therefrom and apparatus for causing the mixture of agricultural products and stones to impinge on the impact surface.

Description: This invention relates to agricultural apparatus generally and more particularly to apparatus for separating agricultural produce from spurious matter such as clods and stones. Certain agricultural products, such as potatoes, which grow underground, may need to be separated from clods and stones before being marketed. There is described in Applicant/Assignee's published German Application P 33 06 769.4, apparatus for separation of a mixture of soil plods from potatoes by bouncing the mixture to be separated on a cylindrical drum. This apparatus operates on the basis of a difference of about 0.4 in the restitution coefficient of the potatoes and soil clods. The aforesaid apparatus has met with considerable commercial success. The separation of potatoes from stones is not achieved by the apparatus of the aforesaid German Patent Application, since the restitution coefficients of potatoes and stones against a rigid surface are nearly the same, and the restitution coefficient of the stones normally may even exceed that of the potatoes. British Patent No. 900,784 discloses crop-sorting apparatus wherein a mixture of crop and spurious matter is first fed to a series of resiliently loaded rods to effect a crude separation. The mixture is then dropped onto a rapidly rotating drum having a soft, springy and damp surface, serving to grip stones and to fling them away, while the crop merely falls off the drum. Thus, in accordance with the present invention, there is provided apparatus for separating a mixture of agricultural products and spurious matter, comprising a drum and a plurality of adjacent, resiliently mounted regions against which the mixture can be directed, characterised in that the adjacent regions are mounted concentrically about the surface of the drum and spaced from one another in the axial direction of the drum and so as to be independently operable of one another, the regions being harder than the appropriate agricultural product, the apparatus being arranged such that each region is normally impacted by only one item of produce or spurious matter at any given instant, and at least one collection means being arranged to collect produce bouncing from the regions and thereby separated by the apparatus from individual stones and other spurious matter. In accordance with a preferred embodiment of the present invention, the resilient regions comprise plate elements. The term "plate element" is used to denote a relatively thin element which is susceptible to bending. The plate element may comprise a slab of material for example, curved into a continuous ring defining a cylindrical surface. Although the phenomenon of energy absorption by the element is not fully understood by Applicants, it is understood that the primary mechanism for kinetic energy absorption by the plate element is through bending thereof and the propagation of vibrations therethrough. According to the present invention, whose effectiveness has been demonstrated empirically, stones, which are characterised by greater density and hardness than agricultural produce such as potatoes, lose relatively more energy to the impact element than do potatoes and the like, whose softer structure allows more compression and spreading out of the impact forces over a longer contact time, with the result that the potatoes bounce further from the impact surface than do stones and are separated thereby. Selection of an appropriate element and mounting for separation of a given agricultural product having given characteristics of density, elasticity, hardness and mass from stones and clods of known characteristics is achieved empirically, based on the herein described teachings of the present invention. Additionally, in accordance with the preferred embodiment of the invention, during the characteristic dwell time of stones in contact with the drum, significant energy absorption occurs, while during the longer dwell time of agricultural produce thereon, the net energy absorption is relatively insignificant, thereby causing the restitution coefficient of the agricultural produce to exceed that of the stones. The drum comprises a plurality of independently mounted sections, each of which is arranged to be impacted by a single stone or item of agricultural produce at any given instant. In accordance with a preferred embodiment of the invention, the above-described apparatus is also operative for separating agricultural products from clods at the same time as it separates the agricultural products from stones. As noted above, in separating stones from agricultural produce, the drum absorbs most of the kinetic energy of the stones, which are relatively hard, by displacement of the mass of the plate element due to the provision of the resilient material underlying the plate element, bending of the plate element and propagation of vibrations therethrough, or any combination of the above. In accordance with this preferred embodiment of the invention, the plate elements are stiff enough to be generally unaffected by the impact thereon of softer agricultural products, which rebound therefrom, as from a rigid surface. As for clods, if they are hard and not brittle, they behave as stones and are separated as hereinabove described. If the clod is soft or brittle, as is usually the case, impact of it on the plate element causes an irreversible deformation of the clod, such as breaking up or plastic deformation, thus absorbing most of its kinetic energy and causing the clod to rebound much less than the agricultural products. Further in accordance with a preferred embodiment of the present invention, there is provided first collection means disposed in a first region with respect to the drum for receiving clods and stones bounced from the drum within a first range of distances, and second collection apparatus disposed in a second region with respect to the drum, , and separated from the first region, for receiving agricultural produce bounced from the drum within a second range of distances. Additionally, in accordance with a preferred embodiment of the invention, the apparatus for separating also comprises third collection apparatus, which may be disposed intermediate the first and second regions but need not be so disposed, for receiving a mixture of unseparated agricultural produce, clods and stones bounced from the drum, and apparatus for re-supplying the mixture of unseparated agricultural produce from the third collection apparatus back to the drum for repeated separation. Additionally, in accordance with an embodiment of the present invention, the above-described apparatus for separating stones and clods from agricultural produce includes apparatus for limiting the re-supply from the third collection apparatus to one re-supply cycle. The present invention should be more fully understood and appreciated from the following detailed description, in conjunction with the accompanying drawings in which: Figs. 1A and 1B are respective plan and side views of a drum comprising resiliently-mounted cylindrical plate elements constructed and operative in accordance with an embodiment of the present invention; Fig. 2 is a pictorial schematic illustration of apparatus for separating agricultural produce from clods and stones in accordance with one embodiment of the invention; Figs. 3A and 3B are respective plan and side views of apparatus for separating agricultural produce from clods and stones constructed and operative in accordance with an embodiment of the present invention; and Figs. 4A, 4B and 4C are respective plan, end and top views of apparatus for separating agricultural produce from clods and stones constructed and operative in accordance with an embodiment of the present invention. Whilst the present invention will be described in the context of a preferred embodiment relating to apparatus for the separation of agricultural products, such as potatoes, from clods and stones, it is to be appreciated that the present invention has application in various other contexts and is not limited to the context hereinafter described. Figs. 1A and 1B illustrate an embodiment of the present invention wherein the drum comprises a plurality of cylindrical rings 30 which are supported on a cylindrical layer of foam rubber 32, which in turn is supported on a cylinder 34, typically formed of steel. According to a preferred embodiment of the present invention, the specifications of the drum shown in Figs. 1A and 1B are as follows: Each ring 30 is made of steel 8 mm thick, 50 mm wide and having an outer diameter of 320 mm. The foam rubber layer 32 is 16 mm thick and of 35 shore (ASTM RE 43). This embodiment has provided efficient separation of potatoes and stones having the following characteristics (given approximately): Stone Density : 2.5 - 3.0 gr/cm³ Stone Weight : 120 - 470 gr Potato Density : 0.9 gr/cm³ Potato Weight : 40 - 300 gr Reference is now made to Fig. 2, which shows in a schematic pictorial illustration, apparatus for separating clods and stones from agricultural produce such as potatoes constructed and operative in accordance with a preferred embodiment of the present invention. The apparatus comprises a conveyor 60 which supplies a mixture of potatoes, clods and stones (and possibly other materials as well), so as to impinge on the drum 62. Preferably the height from which the mixture is dropped onto the drum 62 is limited to about 250 mm, so as to limit damage to the agricultural produce. The drum 62 is typically of the type described above in relation to Figs. 1A and 1B and is arranged to be impinged at a surface thereof which is inclined between the horizontal and the vertical, typically having a tangent of 45° with respect to the vertical. Preferably, the drum 62 is rotated about its cylindrical axis 64, such that the location on the surface on which the mixture impacts has a horizontal component of motion, in a direction opposite to the horizontal component of motion of the mixture as it falls, which component of motion is imparted thereto by the horizontal component of motion of conveyor 60. Alternatively the horizontal components of motion of the mixture and of the impact surface may be in the same direction. First and second collection zones are defined by first and second collection conveyors 66 and 68. The collection conveyor 66 nearer the drum receives the stones and clods, and the collection conveyor 68, further from the drum receives the potatoes. A divider element 70 separates the adjacent zones and ensures that material bounced from the drum reaches one of the two conveyors depending on its precise position. Reference is now made to Figs. 3A and 3B, which illustrate a multiple stage separation device according to the present invention. Here it is seen that a conveyor 100 supplies a mixture 102 of potatoes, stones and clods to a drum 104, which may be similar to the drum 62 illustrated in Fig. 2. The mixture impinges on the drum 104 at an impact surface location 106 having a tangent approximately 45° from the vertical and having a horizontal component of motion opposite to that of the mixture and a downward vertical component of motion. The potatoes, which bounce relatively far from the impact surface location, impinge on a slide 108 and are directed into a collection bin 110. The stones and clods, which bounce to a region relatively near the impact surface location impinge on a slide 112 and are directed into a collection bin 114. In order to enhance the accuracy of separation, an intermediate region 116 is defined between the regions covered by respective slides 108 and 112. Into this region a mixture of stones, clods and potatoes fall into a rotary conveyor 118 which rotates about an axis 120 and conveys the mixture onto a slide 122 which returns it to conveyor 100 for re-supply to the drum 104. Figs. 4A - 4C illustrate an alternative embodiment of separation apparatus which is designed to eliminate overload of the system by repeated recycling of unsorted mixtures of potatoes, clods and stones. Here a principal conveyor 130 supplies an unsorted mixture of clods and stones to a drum 132. This drum 132 is typically an impact element of the type described hereinabove for separating stones from agricultural products, such as that shown in Figs. 1A and 1B. A divider 134 is associated with the conveyor 130 for defining a main area 136 thereof which carries a newly received mixture of clods, stones and potatoes and a side area 138 which carries a recycled mixture which was not previously separated. The mixture impinges on the drum 132 at an impact surface location 140 typically having a tangent approximately 45° from the vertical and having a horizontal component of motion opposite to that of the mixture and a downward vertical component of motion. The portion of the mixture impinging on the drum 132 from the side area of the conveyor impinges on a gapless slide assembly 142. The potatoes, which bounce relatively far from the impact surface location, impinge on a slide portion 144 and are directed into a collection bin 146. The stones and clods, which bounce to a region relatively near to the impact surface location impinge on a slide portion 147 and are directed into a collection bin 148. The mixture which impinges on the drum 132 from the main area 136 of the conveyor is supplied to a slide assembly 150, defining a first slide portion 152 which receives the potatoes and directs them to bin 146, a second slide portion 154, spaced from slide portion 152, which receives the stones and clods and directs them to bin 148 and an intermediate gap 156 which permits the unseparated mixture of stones, clods and potatoes bounced thereto to fall on a conveyor 158, which carries them to a raising conveyor 160, which supplies that mixture, via a slide 162 to side conveyor area 138 for a single recycle through the separation apparatus. According to an alternative embodiment of the invention the intermediate gap 156 may be eliminated and the stones and clods from the slide portion 154, which may contain unsorted agricultural produce, are supplied to conveyor 158 for recirculation. It will be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove. Rather the scope of the present invention is defined only by the appended claims.

Claims: Apparatus for separating a mixture of agricultural products and spurious matter, comprising a drum and a plurality of adjacent, resiliently mounted regions against which the mixture can be directed, characterised in that the adjacent regions are mounted concentrically about the surface of the drum and spaced from one another in the axial direction of the drum and so as to be independently operable of one another, the regions being harder than the appropriate agricultural product, the apparatus being arranged such that each region is normally impacted by only one item of produce or spurious matter at any given instant, and at least one collection means being arranged to collect produce bouncing from the regions and thereby separated by the apparatus from individual stones and other spurious matter. Apparatus according to claim 1 wherein said drum is rotatable. Apparatus according to claim 2 wherein said drum is adapted to be rotated in use. Apparatus according to any preceding claim wherein said resiliently mounted regions comprise plate elements. Apparatus according to claim 4 comprising a plurality of said plate elements in the form of rings. Apparatus according to any preceding claim 1 wherein said resiliently mounted regions are operative to absorb kinetic energy from items impacting thereon through bending and the propagation of vibrations therethrough. Apparatus according to any preceding claim wherein said resiliently mounted regions are operative to absorb kinetic energy from items impacting thereon as a positive function of the density, mass and hardness of such items. Apparatus according to any preceding claim wherein said resiliently mounted regions comprise plate elements mounted such that, during the characteristic dwell time of stones in contact with the impact surface, significant energy absorption occurs, while during the longer dwell time of agricultural produce thereon, the net energy absorption is relatively insignificant, thereby causing the restitution coefficient of the agricultural produce to exceed that of the stones. Apparatus according to any preceding claim further comprising: first collection means disposed in a first region with respect to the drum for receiving clods and stones bounced from the drum within a first range of distances; and second collection means disposed in a second region with respect to the drum, and separated from the first region, for receiving agricultural produce bounced from the drum within a second range of distances. Apparatus according to claim 9 and also comprising: third collection means for receiving a mixture of unseparated agricultural produce, clods and stones bounced from the drum; and means for re-supplying the mixture of unseparated agricultural produce from the third collection means back to the drum for repeated separation. Apparatus according to claim 10 and also comprising means for limiting the re-supply from the third collection means to one re-supply cycle.

Inventors: FELLER, RON, GAN-MOR, SHMUEL, MARGOLIN, EHUD, ZACHARIN, AVI
Applicants: STATE OF ISRAEL-MINISTRY OF AGRICULTURE
Application year: 1986
Main classification: B07B13
IPC codes: A01D33, B07B13