Sorting apparatus provided with a chute

Description

Field of the invention

[0001] The present invention relates to a sorting apparatus comprising a chute, said chute being provided with an inclined surface for guiding products, in particular granular products, towards a detecting and selecting system of the sorting apparatus while moving under influence of gravity.

State of the art

[0002] A sorting apparatus for in-line sorting of granular products is disclosed in European patent EP0952895. This sorting apparatus comprises a detection system, a removal system and a transport device having a sloped distribution surface, which is convex over at least a certain distance in the direction of travel of the granular products. This transport device guides the products towards the detection and removal system such that products are analysed and selected while moving in a vertical downward direction. The curvature of this convex distribution surface is equal to or slightly less than then curvature of the path the falling products would follow if this convex distribution surface would be absent. It is claimed that this particular shape of the distribution surface forces the falling products to follow substantially congruent parabolic paths such that the position and speed of each falling product is predetermined, thereby rendering the process of analysing and selecting the falling products more easy. Although this convex shape is present, there is still a large variation on the trajectories of the falling products such that the spacing between the removal system and the falling products cannot be minimised, thereby resulting in an unwanted removal of high-quality products. The variation on the trajectory, i.e. position and speed, of each individual product renders the synchronisation of the detection system and the removal system more difficult. Moreover due to the convex shape of the distribution surface it is difficult to stabilise the orientation of the falling products towards the detection system such that a maximal projected area of the product is offered for analysis. Certainly if hard products are being transported such products tend to bounce on the distribution surface thereby following a path that deviates from the desired congruent parabolic path. Products having a trajectory, which differs from the mean congruent path of the product stream, may be deposited upon the detection system and consequently the quality of the detection system can be impaired.

[0003] Another sorting apparatus is disclosed in German patent DE19708457. This sorting apparatus also comprises a detection system, a removal system and a chute having a curved surface in the shape of a ski jump having a monotonic increase of the curvature of this surface towards the detection system. This chute projects the products in an upward direction towards the detection and removal system such that the products are analysed and selected while moving in a horizontal forward direction. It is claimed that while gliding downwards along the curved surface of the chute the position of the products is stabilised due to the centrifugal forces acting thereupon. Although a more stabile product stream can be obtained, the projection of the products in an upward direction when leaving the chute introduces variation on the trajectory of projected products which makes the subsequent analysis and removal process more complex and less selective. Also here the position of the detection system makes it more prone to be dirtied by products having a trajectory, which differs from the mean path of the product stream, and consequently the quality of the detection system can be impaired.
[0003b] Canadian patent CA 1 158 748 discloses an apparatus and method for sorting particles of radioactive materials. The apparatus comprises a feeder for arranging the radioactive particles in a line and to discharge the thus arranged particles into a normal gravity-accelerated trajectory by having them slide over a low-friction convex fixed slide plate. The apparatus further comprises means for detecting speed and position of each individual particle when being arranged and means for detecting the radioactive properties of the particles when being discharged by the slide plate.
[0003c] US patent US 6640158B1 is related to an apparatus for packaging solid particulate material that includes a deflectable, curved weighing pan with a given radius of curvature to receive a continuous flow of material and discharge the material along a first or second discharge pathway, depending on a measurement of the pan deflection.

Aims of the invention

[0004] The present invention aims to provide a chute that overcomes the above problems of the prior art solutions. In another aspect the invention aims to provide a sorting apparatus equipped with such a chute.

Summary of the invention

[0005] The present invention is related to a sorting apparatus as disclosed in the appended claims. The apparatus of the invention comprises a chute adapted for guiding a stream of products, moving under influence of gravity, in an essentially vertical downward direction allowing the analysis and selection of the products while in free fall. As the products are stabilised while moving along the chute the selection process can be performed more accurately, thereby reducing unwanted removal of good products or bad products not being removed. The chute configuration also offers a better control over the trajectory of the falling products such that the spacing between the selecting system and the product stream can be minimised.

[0006] In a first embodiment of the invention a chute is disclosed comprising a first guiding element. This first guiding element has a downwardly-curved surface over its entire length towards the detection system, i.e. along the direction in which the products propagate. If this surface is expressed by a function F1, this means in particular, that for the second derivative of this function F1 it holds that

over the complete width of said first guiding element.

[0007] In a preferred embodiment the dimensions of the first guiding element are selected from the following ranges:

• the height of the first guiding element measured between point (I) and point (E), is selected from the range 0.3m to 0.8m, and is preferably at about 0.5m and
• the width of the first guiding element, i.e. the horizontal distance between point (I) and point (E), is selected from the range 0.05m to 0.4m, preferably selected from the range 0.05m to 0.2m, and is preferably about 0.15m,and
• the angle α is selected from the range 70 to 90 degrees, preferably selected from the range 80 to 90 degrees, more preferably this angle is about 90 degrees, and
• the angle β is selected from the range 20 to 85 degrees, preferably selected from the range 40 to 85 degrees and is preferably about 80 degrees.

[0008] In another embodiment the curvature of this first guiding element can be described by a B-spline function F1 having a knot sequence given by K₁ =[0 0 0 0 κ l l l], where 0 is the origin, κ is a sliding knot controlling the curvature and l is the horizontal dimension of the first guiding element, further specified by the following constraints: F1(0)=0, F1(1)=h, F1 (κ)= κ_y, DF1 (1)=tanα , DF1 (0)=tanβ. DF1 hereby denotes the first derivative.

[0009] In an advantageous embodiment the chute comprises, in addition to the first guiding element, a second guiding element. This second guiding element has a surface which is adapted for redirecting products which are propelled by the first guiding element towards the second guiding element and received by the second guiding element in an essentially vertical downward direction.

[0010] The surface of the second guiding element is upwardly-curved over at least a certain section along the movement of the product stream such that products propelled towards this upwardly-curved section are redirected by this upwardly-curved section in an essentially vertical downward direction. As the stream of products when being propelled towards this upwardly-curved section is characterised by a mean velocity vector, the surface of the second guiding element is preferably shaped to be initially tangential to this mean velocity vector.

[0011] In a specific embodiment the second guiding element is convexly curved in the downward direction over its entire length.

[0012] In another embodiment the second guiding element has downstream an upwardly-curved section parallel with the product stream and upstream a downwardly-curved section.

[0013] In a preferred embodiment a chute provided with a first and a second guiding element has dimensions selected from the following ranges :

• the height of the chute , i.e. the vertical distance between point (I) and point (m), is selected from the range 0.1m to 1.2m, whereby
  the height of the first guiding element, measured between point (I) and point (E), is selected from the range 0.3m to 0.8m, and
  the height of the second guiding element, measured between point (n) and point (m), is selected from the range 0.05m to 0.4m,
• the width of the chute, i.e. the horizontal distance between point (I) and point (m), is selected from the range 0.15m to 0.7m., whereby
  the width of the first guiding element, measured between point (I) and point (E), is selected from the range 0.05m to 0.4m, and the width of the second guiding element, measured between point (n) and point (m), is selected from the range 0.02m and 0.3m.,
• the angle α is selected from the range 70 to 90 degrees and is preferably about 80 degrees, and
• the angle β is selected from the range 20 to 80 degrees and is preferably about 50 degrees.

[0014] In another embodiment the curvature of the second guiding element can be described by a spline function characterised by the following control points :

[0015] The invention is thus related to an apparatus for sorting products, in particular granular products such as raisins, blueberries but also pellets e.g. plastic pellets. The sorting apparatus comprises a supply system for providing products in a continuous stream to a chute as previously described. This chute guides the supplied products, while moving under gravity, towards a detection system and a removal system, the chute comprising a first guiding element having a downwardly-curved surface and, optionally, a second guiding element as in the above-mentioned embodiments of the invention. The detection system is positioned to analyse the products when moving in a substantially vertical direction. Preferably the configuration of the sorting apparatus is such that the first guiding element is positioned on one side of the product stream and the removal system and, if present, the second guiding element is positioned at the opposite side of the product stream.

Short description of the drawings

[0016] For the purpose of teaching the invention schematic viewings and cross-sections of a sorting apparatus or chute according to various embodiments of the invention are given. These drawings are not to scale. Like numerals are given to like elements in each drawing.

[0017] Fig. 1 represents a schematic view of a sorting apparatus according to an embodiment of the invention.

[0018] Fig. 2 represents a schematic view of the chute illustrating the parameters determining the shape and relative position of the first guiding element of the chute.

[0019] Fig. 3 represents a schematic view of a sorting apparatus provided with a first and a second guiding element according to an embodiment of the invention.

[0020] Fig. 4 represents a schematic view of the chute illustrating the parameters determining the shape and relative position of the first and second guiding element of the chute.

[0021] Fig. 5 represents a detailed schematic view of the chute illustrating a particular shape and relative position of the first and second guiding element of the chute according to the present invention.

Detailed description of the invention

[0022] The present invention discloses an apparatus for sorting products, in particular granular products such as raisins, blueberries but also pellets e.g. plastic pellets, which are supplied in a continuous stream. In particular the present invention discloses a chute for guiding the stream of products when moving in a vertical downward direction due to gravity, which can be used in such sorting apparatus.

[0023] Figure 1 illustrates a sorting apparatus (10) according to a first embodiment of the present invention. This apparatus for sorting products (1) comprises a supply system (3), at least one detection system (6,6'), a removal system (8) and a chute (P) which guides the stream of products, supplied by the supply system (3), towards the detection system (6, 6') and the removal system (8) while moving under influence of gravity. This supply system (3) can be a conveyor belt, a shaker, a vibrating table or any transporting means known in the art. After leaving the chute (P) the product granules are individually scanned by a detection system (6, 6'), preferably both from a front (6) and a rear position (6'). The detection system (6, 6') can comprise at least one light source directing a concentrated light beam (7, 7'), such as a laser beam, for scanning the products (1') and at a least one detector, such as a photo multiplier tube, but likewise a CCD camera is suitable as well, for receiving light reflected from the products (1'). In any case the sensed signal will be analysed and lesser quality products or foreign bodies will be detected. When the decision is taken to remove certain products from the product flow, a signal is given to the removal system (8). Typically this removal system (8) is a manifold of air pressure valves which can be opened on command. This allows the rejected element (1") to be blown out of the product stream as soon as it enters the cone of high pressured air produced by such a valve, while the accepted elements (1"') continue their movement. The present invention is however not limited to an air pressure based removal system. Optionally an element (2) can be mounted above the supply system (3) at the point where the products (1) are transferred from the supply system (3) to the chute (P). The products (1) when going from the supply system (3) to the chute (P) will be pushed again this element (2) such that products are more uniformly distributed over the product stream and a thinner product stream towards the chute (P) is obtained. This element (2) can be a flexible flap mounted on a horizontal axis and which is made of rubber, plastic, leather or any kind of flexible material known in the art. This axis is located at the end of the supply system (3) adjacent the chute (P) and is perpendicular to the direction (9) in which the products (1) are being propagated.

[0024] The first guiding element (P₁) of the chute (P) has a downwardly-curved surface, i.e. the curvature of this surface is concave in the gravitational direction. The first guiding element (P₁) has a surface which is downwardly-curved over its entire length towards the detection system (6, 6'), i.e. along the direction (9) in which the products (1') propagate. The products will fall from the supply system (3) on the chute (P) and glide downwards to the detection system (6, 6'), the position of the products being stabilised due to the centrifugal forces acting thereupon. When leaving the chute (P) at its bottom point, the stream of products will have a substantially uniform thickness, with a small thickness distribution in a direction perpendicular to the chute (P). Typically the thickness of the product stream is substantially equal to the thickness of a single product (1). The first guiding element (P₁) of the chute (P) illustrated in Fig. 1 thus has a downward parabolic surface such that the chute is downwardly sloped over its entire length along the propagation direction (9) of the products (1'). As can been seen in Fig.1 first guiding element (P₁) of the chute (P) is shaped such that when the falling products (1') leave the chute (P), they are propelled downward towards the detection system (6, 6'). At the bottom end (E) of the first guiding element (P₁) of the chute (P), each granule normally has a nominal speed of approximately

At that point E the product goes into free-fall thereby describing a parabolic curve. Following this parabolic path the products (1') will finally propagate in an essentially vertical downward direction. From this point onwards products (1') will be analysed by the detection system (6, 6'). As shown in Fig.1, the concentrated light beam (7, 7') of the detection system (6, 6') is directed to the product stream where propagating in an essentially vertical direction.

[0025] As can be seen in Fig.1 the chute (P) is positioned below the product stream to carry the product stream. Due to this configuration one can position the removal system (8) downstream the product stream and opposite the side where the chute (P) is placed. The removal system (8) can even be positioned such that the distance between the removal system (8) and the product stream is minimised. Given the fact that the product stream is more confined, the average distance between the removal system (8) and the free-falling products can be greatly reduced. Thus if the removal system (8) comprises a manifold of air-pressure valves, which often is the case, the effective removal area of one such valve at this short distance from the falling product is, contrary to prior art sorting apparatus, no more much larger than the size of a typical granule such as a raisin or a peanut. As a result the false reject, i.e. the amount of good product which has been removed, is considerably reduced.

[0026] To further illustrate the invention, a detailed description is given below to determine the configuration of the first guiding element (P₁) of a chute (P) according to a first embodiment of the invention, the shape of which can be selected according to the description given below. Fig.2 illustrates the mathematical modelling of this first guiding element (P₁).

[0027] The curvature of this first element (P₁) is fully described by a B-spline F1. By convention the origin of this B-spline function is placed on the outgoing point of the first guiding element (P₁), i.e. at is lowest point E. The knot sequence describing P₁ is given by


where 0 is the origin, κ is a sliding knot with which we can control the curvature and l is the width of the first element (P₁), i.e. its horizontal dimension. The following constraints are further specified: F1(0)=0, F1(1)=h, F1 (κ)= κ_y, DF1 (1) =tanα, DF1 (0) =tanβ. The first derivative dF1/dx is hereby denoted DF1.

[0028] In this set-up it is clear that P₁ describes a cubic spline, i.e. the number of knots minus the number of constraints is four. The current invention is however not limited to this particular mathematical formulation, as long as the first guiding element (P₁) is downwardly sloped over its entire length along the propagation direction (9) such that the products (1') are leaving the first guiding element (P₁) in a direction which is equal or less than the horizontal direction X as shown in Fig.1.

[0029] The gravitational force F, as a function of x, acting on a granule which glides along a surface described by F₁ is given by


where g is the acceleration due to gravitation. Because one is only interested in the speed of a granule at the point where it leaves the first guiding element (P₁), M can be assumed to be one, i.e. the speed is independent of mass.

[0030] The work done by a granule following the path F1 can be expressed as


where s denotes the parameter space in which F1 and F are described. In a Cartesian system with x- and y-axes this becomes


Finally one can calculate the speed at any position on the surface described by F1 as

[0031] In particular applications where products are sticky or have a tendency to deposit dirt at least on the first guiding element (P₁), it can be taken into account that not all work is converted into kinetic energy. The speed of such a product is then given by


where λ_p is product specific and indicates the tendency of that product to stick or deposit dirt and hence to increase the friction along the first guiding element (P₁).

[0032] If the product enters the first guiding element (P₁) of the chute (P) having a given speed v₀, the resulting speed is calculated as


Once the product leaves the first guiding element (P₁), it enters a free-fall curve described by


where ν(E) denotes the speed of a granule when it leaves the first guiding element (P₁).
The tangent line at a certain point X is then given by

[0033] Preferably the dimensions of the first guiding element are selected from the following ranges :

• the height of the first guiding element (P₁) measured between point (I) and point (E), is selected from the range 0.3m to 0.8m, and is preferably at about 0.5m and
• the width of the first guiding element (P₁), i.e. the horizontal distance between point (I) and point (E), is selected from the range 0.05m to 0.4m, preferably selected from the range 0.05m to 0.2m, and is preferably about 0.15m, and
• the angle α, indicative for the slope of the first guiding element (P₁) near the supply system (3) and measured counter clockwise relative to the horizontal axis, is selected from the range 70 to 90 degrees, preferably selected from the range 80 to 90 degrees, more preferably this angle is about 90 degrees, and
• the angle β, indicative for the slope of the first guiding element (P₁) at the end remote from the supply system (3) and measured clockwise relative to the horizontal axis, is selected from the range 20 to 85 degrees, preferably selected from the range 40 to 85 degrees and is preferably about 80 degrees.

[0034] In a preferred embodiment of the first aspect to the invention, the speed of a product at point (E) is

The angle α should preferably be between 70 and 90 degrees, preferably selected from the range 80 to 90 degrees, more preferably this angle is about 90 degrees. The angle β is selected from the range 20 to 85 degrees, preferably selected from the range of 40 to 85 degrees and is preferably about 80 degrees.

[0035] The knot (κ,κ_y) is varied to such an extent that the first guiding element (P₁) of the chute (P) is concave in the downward direction. This means in particular that for the second derivative of F1 it holds that

over the complete horizontal interval or width (I, E) of the first guiding element (P₁) of the chute (4). This means in particular that for the first derivative of F1 it holds that

In a preferred embodiment of the invention the knot (κ,κ_y) is taken to be (0.0779m, 0.1279m), measured in an XY reference system as depicted in Fig.2.

[0036] Fig.3 illustrates a sorting apparatus (10) according to another preferred embodiment of the present invention. The sorting apparatus comprises a supply system (3), a detection system (6,6'), a removal system (9) and a chute (P) which guides the stream of products, supplied by the supply system (3), towards the detection system (6, 6') and the removal system (8) while moving under influence of gravity. This supply system (3) can be a conveyor belt, a shaker or any transporting means known in the art. After leaving the chute (P) the product granules are individually scanned by a detection system, preferably both from a front (6) and a rear position (6'). The detection system can comprise a laser and a photo multiplier tube, but likewise a CCD camera is suitable as well. In any case the sensed signal will be analysed and lesser quality product or foreign bodies will be detected. When the decision is taken to remove certain products from the product flow, a signal is given to the removal system (8). Typically this removal system (8) is a manifold of air pressure valves which can be opened on command. This allows the rejected element (1") to be blown out of the product stream as soon as it enters the cone of high pressured air produced by such a valve, while the accepted elements (1'") continue their movement. The present invention is however not limited to an air pressure based removal system. Optionally a element (2) can mounted above the supply system (3) at the point where the products (1) are transferred from the supply system (3) to the chute (P). The products (1) when going from the supply system (1) to the chute (P) will be pushed again this element (2) such that products are more uniformly distributed over the product stream and a thinner product stream towards the chute (P) is obtained.

[0037] The chute (P) comprises a first guided element (P₁) as previously discussed, which has a downwardly-curved surface, i.e. the curvature of this surface is concave in the gravitational direction, and further a second guiding element (P₂) having an upwardly-curved surface, i.e. at least a part of its surface is convex in the gravitational direction. The products will fall from the supply system (3) on the first guiding element (P₁) and glide downwards to the second guiding element (P₂). The chute illustrated in Fig.3 thus comprises upstream a first guiding element (P₁) having a downward parabolic surface and downstream a second guiding element (P₂), at least one section (P_2A) thereof has an upward parabolic surface. As can be seen in Fig.3 both guiding elements (P₁, P₂) are positioned with respect to each other, such that when the falling products (1') leave the first guiding element (P₁) they are propelled towards the second guiding element (P₂) to be received thereby (P_2A). At the bottom end (E) of the first guiding element (P₁), each granule normally has a nominal speed of approximately 2^m/_s. At that point E the product goes into free-fall thereby describing a parabolic curve. Following this parabolic path the product will reach the second guiding element (P₁) at a predetermined point (U). From that point onwards the second guiding element (P₂) will guide the product to an essentially vertical downward direction.

[0038] The receiving section (P_2A) of this second guiding element (P₂) is shaped to be initially parallel with the mean velocity vector of the incoming product stream thereby minimising the risk of the products to bounce back upon impact with the second guiding element (P₂). Due to its convex shape the second guiding element (P₂) first receives the products at point (U) and then redirects them in a vertically downward direction. The velocity vector (V) of the propelled products as determined by the curvature of the first guiding element (P₁) is gradually redirected from a more horizontal direction to a vertical direction thanks to the smoothly curved surface of the second guiding element (P₂) resulting in a free fall of the products with well controlled position and speed. Hence the trajectories of the falling products are better controlled thereby reducing the spread thereof. In a chute with two guiding elements (P₁, P₂) according to the present invention, the second guiding element (P₂) will substantially minimise the spinning of the falling products such that shape detection of these products can be done more accurately.

[0039] As shown in Fig.3 the second guiding element (P₂) need only to have a section (P_2A) with an upwardly curved surface from impact point (U) downwards. All trajectories of the propelled product should reach the second guiding element (P₂) at this point (U) or below. However some outlier products may have a deviating trajectory which leads them above this point (U). These products will then be lost. Optionally a second section (P_2B) can be placed in the second guiding element (P₂) at a position above this point (U). This upstream section (P_2B) preferably has a downward parabolic shape as shown in Fig.3. Due to its concave shape this second section (P_2B) will prevent such outliers from travelling beyond the second guiding element (P₂) by either bouncing them back to the first guiding element (P₁) or by guiding them directly to the downstream convex section (P_2A). However as shown in Fig.5 this section (P₂₃) can be designed to have a straight shape which is more or less parallel to the trajectory of the incoming products. The latter alternative might be easier to manufacture as the second guiding element (P₂) can then be constructed from a straight plate only requiring one end of it (P_2A) to be curved according to the required specifications.

[0040] As can be seen in Fig.3 the first guiding element (P₁) is positioned below the product stream to carry the product stream, while the second guiding element (P₂) is positioned downstream and above the product stream to prevent the propelled products to move further in horizontal direction. Due to this configuration one can position the removal system (8) downstream and at the same side as the second guiding element (P₂) as it this second guiding element (P₂) will prevent residues or products being deposited on the removal system (8). The removal system (8) can even be positioned parallel in vertical direction with the second guiding element such that the distance between the removal system (8) and the product stream is minimised. Given the fact that the product stream is more confined the average distance between the removal system (8) and the free-falling products can greatly reduced. Thus if the removal system (8) comprises a manifold of air-pressure valves, which is often the case, the effective removal area of one such valve at this short distance from the falling product is, contrary to prior art sorting apparatus, no more much larger than the size of a typical granule such as a raisin or a peanut. As a result the false reject, i.e. the amount of good product which has been removed, will be considerably reduced.

[0041] Although not shown in Fig.3 optional features can be foreseen to adjust the position of the second guiding element (P₂) in the vertical and/or horizontal direction to allow varying the relative position of the second guiding element (P₂) to the first guiding element (P₁) as will be appreciated by any person skilled in the art.

[0042] To further illustrate the invention, a detailed description is given below to determine the configuration of a chute (P) according to this second aspect of the invention: the shape and the relative position of each guiding element (P₁, P₂) can be selected according to the description given below. Fig.4 illustrates the mathematical modelling of the both elements (P₁,P₂).

[0043] The curvature of the first element (P1) is fully given by a B-spline F1. By convention the origin is placed on the outgoing point of the first plate. The knot sequence describing F1 is given by


where 0 is the origin, κ is a sliding knot with which we the curvature can be controlled and l is the length of the first guiding element (P₁), i.e. its horizontal dimension. The following constraints are further specified: F1(0)=0, F1(1)=h, F1(κ)= κ_y, DF1(1)=tanα, DF1(0)=tanβ. In this set-up it is clear that F1 describes a cubic spline, i.e. the number of knots minus the number of constraints is four. The present invention is however not limited to this particular mathematical formulation.

[0044] The gravitational force, as a function of x, acting on a granule which glides along P₁ is given by


where g is the acceleration due to gravitation. Because one is only interested in the speed of a granule at the point where it leaves P₁, M can be assumed to be one (i.e. the speed is independent of mass).
The work done by a granule following the path P₁ can be expressed as


where s denotes the parameter space in which P₁ and F are described. In a Cartesian system with x- and y-axes this becomes


Finally one can calculate the speed at any position on P₁ as

[0045] In particular applications where products are sticky or have a tendency to deposit dirt on the chute (P), it can be taken into account that not all work is converted into kinetic energy. The speed of such a product is then given by


where λ_p is product specific and indicates the tendency of that product to stick or deposit dirt and hence to increase the friction along P₁.

[0046] If the product enters the chute (P) having a given speed v₀, the resulting speed is calculated as


Once the product leaves P₁ it enters a free-fall curve described by


where v(E) is the speed of a granule when it leaves P₁.

[0047] The tangent line at a certain point X is then given by


To determine the shape of the second guiding element (P₂), a suitable point (U) is chosen for which the following holds


Typically U=l₂/2, where l₂ is the length of the second plate along the x-axis.
Finally, the control points of the spline function F2, fully describing the shape of the second guiding element (P₂,), are defined as follows


Here

and

are the rightmost (n) and leftmost (m) points on the second plate (P₂), respectively. The control points CP_p2 ensure that the outgoing direction of granules along P₂ is vertical.

[0048] The vertical distance between point (I) and point (m), i.e. the height of the chute (P), can vary between 0.1m and 1.2m. The height of the first guiding element (P₁), measured between point (I) and point (E), is preferably between 0.3m and 0.8m and the height of the second guiding element (P₂), measured between point (n) and point (m), is preferably between 0.05m and 0.4m.

[0049] The horizontal distance between point (I) and point (m), i.e. the width of the chute (P), can vary between 0.15m and 0.7m. The width of the first guiding element (P1), measured between point (I) and point (E), is preferably between 0.05m and 0.4m and the width of the second guiding element (P2), measured between point (n) and point (m), is preferably between 0.02m and 0.3m.

[0050] In one embodiment of the present invention n_y=d_y= T_U(n_x), in other words the points (n) and (d) coincide. This produces a guiding element (P₂), which is shaped completely convex in the downward direction of gravitation. This selection of parameters thus results in a second guiding element (P₂) of the chute (P) having only the downstream section (P_2A) curved. This embodiment is illustrated in Fig.5.

[0051] In a preferred embodiment of the present invention, the speed of a product at point (E) is

The angle α, indicative for the slope of the first guiding element (P₁) near the supply system (3) and measured counter clockwise relative to the horizontal axis, should preferably be between 70 and 90 degrees and more preferably about 80 degrees. The angle β, indicative for the slope of the first guiding element (P₁) at the end remote from the supply system (3) and measured clockwise relative to the horizontal axis, is preferably between 20 and 80 degrees and more preferably about 50 degrees.

[0052] The knot (κ, κ_y) is varied to such an extent that the first guiding element (P₁) of the chute (P) is concave in the downward direction. This means in particular that for the second derivative of P₁ it holds that

over the complete horizontal interval or width (I, E) of the first guiding element (P₁) of the chute (4). This means in particular that for the first derivative of P1 it holds that

In a preferred embodiment the knot (κ,κ_y) is taken to be (0.0799m, 0.1279m), measured in an XY reference system such as depicted in Fig.4.

Claims

1. A sorting apparatus for sorting products (10), comprising a supply system (3) for providing products (1) in a continuous stream to a chute (P), said chute comprising a first guiding element (P₁) having a curved surface, characterized in that the curvature of said surface is shaped concave in the gravitational direction such that, in use, said products (1) leave said first guiding element (P₁) in a direction which is equal to or below the horizontal direction, wherein said chute guides said supplied products (1') while moving under gravity, towards a detection system (6,6') and at least one removal system (8), said detection system being configured to detect lesser quality products or foreign bodies, and said removal system being configured to remove said lesser quality products or foreign bodies, said detection system (6,6') being positioned such as to analyse said products (1') when propagating in an essentially vertical direction, after said products have left the chute (P).

2. Sorting apparatus as in claim 1, wherein said concave surface, when expressed by a function F1, has a second derivative of function F1 which is equal to or greater than zero.

3. Sorting apparatus as in claim 2, wherein the curvature of said first guiding element (P₁) can be described by a B-spline function F1 having a knot sequence given by K₁=[0 0 0 0 κ l l l l], where 0 is the origin, κ is a sliding knot controlling the curvature, and l is the horizontal dimension of said first guiding element (P₁), further specified by the following constraints: F1(0)=0, F1(1)=h, F1(κ)= κ_y, DF1(1)=tanα, DF1(0)=tanβ, with F1(0)=0 corresponding to the end of said first guiding element (P₁) where said products (1) leave said first guiding element, F1(1)=h corresponding to the end of said first guiding element (P₁) where said products (1) enter the first guiding element, F1(κ)= κ_y corresponding to the position of the sliding knot controlling the curvature of said first guiding element, DF1(1)=tanα being the first derivative of the function F1 at the entering end of said first guiding element and the angle α being indicative for the slope of the first guiding element (P₁) at this end, and DF1(0)=tanβ being the first derivative of F1 at the leaving end of said first guiding element and β, indicative for the slope of said first guiding element (P₁) at this end.

4. Sorting apparatus as in claim 3, wherein the second derivative of said B-spline function F1 is equal to or greater than zero.

5. Sorting apparatus as in any of the previous claims, wherein the dimensions of said first guiding element (P₁) of the chute (P) are selected from the following ranges :

the height of said first guiding element (P₁) is selected from the range 0.1m to 1.2m,

the width of said first guiding element (P₁) is selected from the range 0.05m to 0.4m,

the angle α, indicative for the slope of said first guiding element (P₁) at the end where said products (1) enter said first guiding element (P₁), is selected from the range 70 to 90 degrees, and;

the angle β, indicative for the slope of said first guiding element (P₁) at the end where said products (1) leave said first guiding element (P₁), is selected from the range 20 to 85 degrees.

6. Sorting apparatus as in any of the foregoing claims, further comprising a second guiding element (P₂), said second guiding element (P₂) having a surface adapted for redirecting products (1') which are propelled by said first guiding element (P₁) towards said second guiding element (P₂) in an essentially vertically downward direction.

7. Sorting apparatus as in claim 6, wherein the surface of said second guiding element (P₂) is is convex in the gravitational direction over at least a certain section (P_2A) along the movement of the product stream such that products (1') propelled towards said convex section (P_2A) are redirected by said convex section (P_2A) in an essentially vertical downward direction.

8. Sorting apparatus as in claim 7, wherein said stream of products (1') when being propelled towards said convex section (P_2A) is characterised by a mean velocity vector (V), and said surface of the second guiding element (P_2A) is shaped to be initially tangential to said mean velocity vector (V).

9. Sorting apparatus as in any of claims 6 to 8, wherein said second guiding element (P₂) is convex over its entire length.

10. Sorting apparatus as in any of claims 6 to 8, wherein said second guiding element (P₂) further comprises a concave section (P_2B) upstream the convex section (P_2A).

11. Sorting apparatus according to any of claims 6 to 10, wherein the dimensions of said chute (P) are selected from the following ranges :

the height of said chute (P) is selected from the range 0.1m to 1.2m, whereby the height of said first guiding element (P₁) is selected from the range 0.3m to 0.8m, and the height of said second guiding element (P₂) is selected from the range 0.05m to 0.4m,

the width of said chute (P) is selected from the range 0.15m to 0.7m, whereby the width of said first guiding element (P₁) is selected from the range 0.05m to 0.4m, and the width of said second guiding element (P₂) is selected from the range 0.02m and 0.3m,

the angle α, indicative for the slope of said first guiding element (P₁) at the end where said products (1) enter said first guiding element (P₁), is selected from the range 70 to 90 degrees and;

the angle β, indicative for the slope of said first element (P₁) at the end where said products (1) leave said first guiding element (P₁), is selected from the range 20 to 80 degrees.

12. Sorting apparatus as in any of the foregoing claims, wherein said first guiding element (P₁) of said chute (P) is positioned on one side of said product stream (1') and one of said at least one removal system (8) is positioned at the opposite side of said product stream (1').

13. Sorting apparatus according to claim 12, further comprising a second guiding element (P₂) according to any of the claims 6-11 , said second guiding element (P₂) being positioned at the opposite side of said product stream (1').

Ansprüche

1. Sortiervorrichtung zum Sortieren von Produkten (10), ein Zuführsystem (3) zum Zuführen von Produkten (1) in einem kontinuierlichen Strom zu einer Rutsche (P) umfassend, wobei die Rutsche ein erstes Führungselement (P₁) mit einer gebogenen Oberfläche umfasst, dadurch gekennzeichnet, dass die Biegung der Oberfläche in der Schwerkraftrichtung konkav ist, so dass bei Gebrauch die Produkte (1) das erste Führungselement (P₁) in eine Richtung verlassen, die der horizontalen Richtung gleich ist oder darunter liegt, wobei die Rutsche die zugeführten Produkte (1'), während sie sich unter Schwerkraft bewegen, hin zu einem Erkennungssystem (6, 6') und zumindest einem Entfernungssystem (8) führt, wobei das Erkennungssystem eingerichtet ist, um qualitativ minderwertigere Produkte oder Fremdkörper zu erkennen, und wobei das Entfernungssystem eingerichtet ist, um die qualitativ minderwertigeren Produkte oder Fremdkörper zu entfernen, wobei das Erkennungssystem (6, 6') positioniert ist, um die Produkte (1') zu analysieren, wenn sie sich in eine im Wesentlichen vertikale Richtung verbreiten, nachdem die Produkte die Rutsche (P) verlassen haben.

2. Sortiervorrichtung nach Anspruch 1, wobei die konkave Oberfläche, wenn sie durch eine Funktion Fldargestellt wird, eine zweite Ableitung der Funktion F1 aufweist, die gleich oder größer als Null ist.

3. Sortiervorrichtung nach Anspruch 2, wobei die Biegung des ersten Führungselements (P₁) durch eine B-Spline-Funktion F1 mit einer Knotenfolge, gegeben durch K₁ = [0 0 0 0 κ 1 1 1 1], beschrieben werden kann, wobei 0 der Ursprung ist, κ ein Gleitknoten ist, der die Biegung kontrolliert, und 1 die horizontale Dimension des ersten Führungselements (P₁) ist, ferner spezifiziert durch die folgenden Einschränkungen: F1(0) = 0, F1(1)= h, F1(κ) = κ_y, DF1(1) = tanα, DF1(0) = tanβ, wobei F1(0) = 0 dem Ende des ersten Führungselements (P₁), an dem die Produkte (1) das erste Führungselement verlassen, entspricht, wobei F1(1) = h dem Ende des ersten Führungselements (P₁), an dem die Produkte (1) in das erste Führungselement eintreten, entspricht, wobei F1(κ) = κ_y der Position des Gleitknotens, der die Biegung des ersten Führungselements kontrolliert, entspricht, wobei DF1(1) = tanα die erste Ableitung der Funktion F1 am Eintrittsende des ersten Führungselements ist und der Winkel α für die Neigung des ersten Führungselements (P₁) an diesem Ende bezeichnend ist, und DF1(0) = tanβ die erste Ableitung von F1 am Austrittsende des ersten Führungselements ist und β für die Neigung des ersten Führungselements (P₁) an diesem Ende bezeichnend ist.

4. Sortiervorrichtung nach Anspruch 3, wobei die zweite Ableitung der B-Spline-Funktion F1 gleich oder größer als Null ist.

5. Sortiervorrichtung nach einem der vorherigen Ansprüche, wobei die Dimensionen des ersten Führungselements (P₁) der Rutsche (P) aus den folgenden Bereichen ausgewählt sind:

die Höhe des ersten Führungselements (P₁) ist aus dem Bereich 0,1 m bis 1,2 m ausgewählt,

die Breite des ersten Führungselements (P₁) ist aus dem Bereich 0,05 m bis 0,4 m ausgewählt,

der Winkel α, der für die Neigung des ersten Führungselements (P₁) an dem Ende, an dem die Produkte (1) in das erste Führungselement (P₁) eintreten, bezeichnend ist, ist aus dem Bereich 70 bis 90 Grad ausgewählt, und

der Winkel β, der für die Neigung des ersten Führungselements (P₁) an dem Ende, an dem die Produkte (1) das erste Führungselement (P₁) verlassen, bezeichnend ist, ist aus dem Bereich 20 bis 85 Grad ausgewählt.

6. Sortiervorrichtung nach einem der vorherigen Ansprüche, ferner umfassend ein zweites Führungselement (P₂), wobei das zweite Führungselement (P₂) eine Oberfläche aufweist, die für das Umleiten von Produkten (1'), die vom ersten Führungselement (P₁) hin zum zweiten Führungselement (P₂) getrieben werden, in eine im Wesentlichen vertikale Abwärtsrichtung ausgerichtet ist.

7. Sortiervorrichtung nach Anspruch 6, wobei die Oberfläche des zweiten Führungselements (P₂) in der Schwerkraftrichtung über zumindest einen gewissen Abschnitt (P_2A) entlang der Bewegung des Produktstroms konvex ist, so dass Produkte (1'), die hin zum konvexen Abschnitt (P_2A) getrieben werden, vom konvexen Abschnitt (P_2A) in eine im Wesentlichen vertikale Abwärtsrichtung umgeleitet werden.

8. Sortiervorrichtung nach Anspruch 7, wobei der Strom von Produkten (1'), wenn er hin zum konvexen Abschnitt (P_2A) getrieben wird, durch einen mittleren Geschwindigkeitsvektor (v) gekennzeichnet ist, und wobei die Oberfläche des zweiten Führungselements (P_2A) geformt ist, um anfänglich tangential zum mittleren Geschwindigkeitsvektor (V) zu sein.

9. Sortiervorrichtung nach einem der Ansprüche 6 bis 8, wobei das zweite Führungselement (P₂) über seine gesamte Länge konvex ist.

10. Sortiervorrichtung nach einem der Ansprüche 6 bis 8, wobei das zweite Führungselement (P₂) ferner einen konkaven Abschnitt (P_2B), dem konvexen Abschnitt (P_2A) vorgeschaltet, umfasst.

11. Sortiervorrichtung nach einem der Ansprüche 6 bis 10, wobei die Abmessungen der Rutsche (P) aus den folgenden Bereichen ausgewählt sind:

die Höhe der Rutsche (P) ist aus dem Bereich 0,1 m bis 1,2 m ausgewählt, wobei die Höhe des ersten Führungselements (P₁) aus dem Bereich 0,3 m bis 0,8 m ausgewählt ist, und die Höhe des zweiten Führungselements (P₂) ist aus dem Bereich 0,05 m bis 0,4 m ausgewählt,

die Breite der Rutsche (P) ist aus dem Bereich 0,15 m bis 0,7 m ausgewählt, wobei die Breite des ersten Führungselements (P₁) aus dem Bereich 0,05 m bis 0,4 m ausgewählt ist, und die Breite des zweiten Führungselements (P₂) ist aus dem Bereich 0,02 m bis 0,3 m ausgewählt,

der Winkel α, der für die Neigung des ersten Führungselements (P₁) an dem Ende, an dem die Produkte (1) in das erste Führungselement (P₁) eintreten, bezeichnend ist, ist aus dem Bereich 70 bis 90 Grad ausgewählt, und

der Winkel β, der für die Neigung des ersten Führungselements (P₁) an dem Ende, an dem die Produkte (1) das erste Führungselement (P₁) verlassen, bezeichnend ist, ist aus dem Bereich 20 bis 80 Grad ausgewählt.

12. Sortiervorrichtung nach einem der vorherigen Ansprüche, wobei das erste Führungselement (P₁) der Rutsche (P) auf einer Seite des Produktstroms (1') positioniert ist, und wobei zumindest eines des zumindest einen Entfernungssystems (8) auf der gegenüberliegenden Seite des Produktstroms (1') positioniert ist.

13. Sortiervorrichtung nach Anspruch 12, ferner umfassend ein zweites Führungselement (P₂) nach einem der Ansprüche 6 bis 11, wobei das zweite Führungselement (P₂) an der gegenüberliegenden Seite des Produktstroms (1') positioniert ist.

Revendications

1. Appareil de tri pour trier des produits (10), comprenant un système de fourniture (3) pour fournir des produits (1) en un flux continu à une goulotte (P), ladite goulotte comprenant un premier élément de guidage (P₁) comportant une surface incurvée, caractérisé en ce que la courbure de ladite surface a une forme concave dans la direction gravitationnelle de sorte que, en utilisation, lesdits produits (1) quittent ledit premier élément de guidage (P₁) dans une direction qui est égale à la direction horizontale ou au-dessous de celle-ci, dans lequel ladite goulotte guide lesdits produits fournis (1'), alors qu'ils se déplacent par gravité, vers un système de détection (6, 6') et au moins un système de retrait (8), ledit système de détection étant configuré pour détecter des produits de moindre qualité ou des corps étrangers, et ledit système de retrait étant configuré pour retirer lesdits produits de moindre qualité ou corps étrangers, ledit système de détection (6, 6') étant positionné de manière à analyser lesdits produits (1') lorsqu'ils se propagent dans une direction essentiellement verticale, après que lesdits produits ont quitté la goulotte (P).

2. Appareil de tri selon la revendication 1, dans lequel ladite surface concave, lorsqu'elle est exprimée par une fonction F1, a une dérivée seconde de la fonction F1 qui est égale ou supérieure à zéro.

3. Appareil de tri selon la revendication 2, dans lequel la courbure dudit premier élément de guidage (P₁) peut être décrite par une fonction B-spline F1 ayant une séquence de noeuds donnée par K₁ = [0 0 0 0 κ l l l l], où 0 est l'origine, κ est un noeud glissant commandant la courbure, et l est la dimension horizontale dudit premier élément de guidage (P₁), spécifiée en outre par les contraintes suivantes : F1(0) = 0, F1(l) = h, F1(κ) = κ_y, DF1(l) = tgα, DF1(0) = tgβ, avec F1(0) = 0 correspondant à l'extrémité dudit premier élément de guidage (P₁) où lesdits produits (1) quittent ledit premier élément de guidage, F1(l) = h correspondant à l'extrémité dudit premier élément de guidage (P₁) où lesdits produits (1) entrent dans le premier élément de guidage, F1(κ) = κ_y correspondant à la position du noeud glissant commandant la courbure dudit premier élément de guidage, DF1(l) = tgα étant la dérivée première de la fonction F1 à l'extrémité d'entrée dudit premier élément de guidage et l'angle α étant indicatif de la pente du premier élément de guidage (P₁) à cette extrémité, et DF1(0) = tgα étant la dérivée première de F1 à l'extrémité de sortie dudit premier élément de guidage et β étant indicatif de la pente dudit premier élément de guidage (P₁) à cette extrémité.

4. Appareil de tri selon la revendication 3, dans lequel la dérivée seconde de ladite fonction B-spline F1 est égale ou supérieure à zéro.

5. Appareil de tri selon l'une quelconque des revendications précédentes, dans lequel les dimensions dudit premier élément de guidage (P₁) de la goulotte (P) sont sélectionnées dans les plages suivantes :

- la hauteur dudit premier élément de guidage (P₁) est sélectionnée dans la plage de 0,1 m à 1,2 m,

- la largeur dudit premier élément de guidage (P₁) est sélectionnée dans la plage de 0,05 m à 0,4 m,

- l'angle α, indicatif de la pente dudit premier élément de guidage (P₁) à l'extrémité où lesdits produits (1) entrent dans ledit premier élément de guidage (P₁), est sélectionné dans la plage de 70 à 90 degrés, et

- l'angle β, indicatif de la pente dudit premier élément de guidage (P₁) à l'extrémité où lesdits produits (1) quittent ledit premier élément de guidage (P₁), est sélectionné dans la plage de 20 à 85 degrés.

6. Appareil de tri selon l'une quelconque des revendications précédentes, comprenant en outre un deuxième élément de guidage (P₂), ledit deuxième élément de guidage (P₂) comportant une surface conçue pour rediriger les produits (1') qui sont propulsés par ledit premier élément de guidage (P₁) vers ledit deuxième élément de guidage (P₂) dans une direction essentiellement verticalement vers le bas.

7. Appareil de tri selon la revendication 6, dans lequel la surface dudit deuxième élément de guidage (P₂) est convexe dans la direction gravitationnelle sur au moins une certaine section (P_2A) le long du déplacement du flux de produits de sorte que les produits (1') propulsés vers ladite section convexe (P_2A) sont redirigés par ladite section convexe (P_2A) dans une direction essentiellement verticalement vers le bas.

8. Appareil d e tri selon la revendication 7, dans lequel ledit flux de produits (1'), lorsqu'il est propulsé vers ladite section convexe (P_2A), est caractérisé par un vecteur de vitesse moyenne (V), et ladite surface du deuxième élément de guidage (P_2A) est formée de manière à être initialement tangente audit vecteur de vitesse moyenne (V).

9. Appareil de tri selon l'une quelconque des revendications 6 à 8, dans lequel ledit deuxième élément de guidage (P₂) est convexe sur toute sa longueur.

10. Appareil de tri selon l'une quelconque des revendications 6 à 8, dans lequel ledit deuxième élément de guidage (P₂) comprend en outre une section concave (P_2B) en amont de la section convexe (P_2A).

11. Appareil de tri selon l'une quelconque des revendications 6 à 10, dans lequel les dimensions de ladite goulotte (P) sont sélectionnées dans les plages suivantes :

- la hauteur de ladite goulotte (P) est sélectionnée dans la plage de 0,1 m à 1,2 m, moyennant quoi la hauteur dudit premier élément de guidage (P₁) est sélectionnée dans la plage de 0,3 m à 0,8 m, et la hauteur dudit deuxième élément de guidage (P₂) est sélectionnée dans la plage de 0,05 m à 0,4 m,

- la largeur de ladite goulotte (P) est sélectionnée dans la plage de 0,15 m à 0,7 m, moyennant quoi la largeur dudit premier élément de guidage (P₁) est sélectionnée dans la plage de 0,05 m à 0,4 m, et la largeur dudit deuxième élément de guidage (P₂) est sélectionnée dans la plage de 0,02 m à 0,3 m,

- l'angle α, indicatif de la pente dudit premier élément de guidage (P₁) à l'extrémité où lesdits produits (1) entrent dans ledit premier élément de guidage (P₁), est sélectionné dans la plage de 70 à 90 degrés, et

- l'angle β, indicatif de la pente dudit premier élément (P₁) à l'extrémité où lesdits produits (1) quittent ledit premier élément de guidage (P₁), est sélectionné dans la plage de 20 à 80 degrés.

12. Appareil de tri selon l'une quelconque des revendications précédentes, dans lequel ledit premier élément de guidage (P₁) de ladite goulotte (P) est positionné d'un côté dudit flux de produits (1') et l'un dudit au moins un système de retrait (8) est positionné du côté opposé dudit flux de produits (1').

13. Appareil d e tri selon la revendication 12, comprenant en outre un deuxième élément de guidage (P₂) selon l'une quelconque des revendications 6 à 11, ledit deuxième élément de guidage (P₂) étant positionné du côté opposé dudit flux de produits (1').

Drawing