EP0263015B1 - Optical sorting device to separate two categories of particles having different optical transmissivities - Google Patents

Abstract

The particles to be sorted are poured onto a translucent inclined plane (3) beneath which is arranged a light source and above which is placed a camera. At the bottom of the inclined plane (3) there are arranged, side by side, hammers (8) capable of tilting about a pivot (9) between a rest position and a position in which they eject the undesirable particle when the latter is detected by the camera. Each hammer (8) is fixed to a connecting rod (47), the downwards displacement of which places the hammer (9) in the ejection position. The connecting rod (47) is joined to the rod (61) of a double-action pneumatic jack (62) controlled by a distributor (43) which is pilot-controlled by a light-sensitive element of the camera. Applicable for sorting cullet. <IMAGE>

Description

The present invention relates to an optical sorting device for separating two categories of particles having different optical transmissivities, the least opaque particles constituting the first category, and the most opaque particles constituting the second category.

For the purposes of this text, "transmissivity" means the capacity for a particle to be crossed by light. The invention finds in particular an application for the recovery of used glass and it therefore relates in particular to a device for optical sorting of currant, that is to say of a mass of elements of recovery glass having undergone crushing and comprising infusible or refractory elements.

It is known that, for economic reasons, used glass is collected, in particular in the form of empty bottles, with a view to its re-use in glass furnaces. Unfortunately, the collected set includes, next to the glass, various metallic, plastic and ceramic materials and plugs, among others.

Currently, manual sorting is generally carried out in two successive stages separated by grinding:

- in the first step, before grinding, a first sorting is carried out in order to eliminate large undesirable elements (plastic bottles, plates, etc.);

- in the second stage, the product called currant -constituted by the collected mass, freed from part of the undesirable elements of the first phase, then crushed is subjected to a new manual sorting, more careful, in order to eliminate as much as possible 'unwanted elements to obtain a product called "cullet" suitable for being sent to a glass furnace.

The second manual sorting is painful, expensive, and above all, insecure, because it lets through small fragments of refractory or infusible products (porcelain, earthenware, stones), which cause incidents in the oven and lead to the production of quality glass. poor: bottles made with a high percentage of recovered glass may break during filling or once filled.

FR-A-2 576 008 proposes a device for automatically carrying out the second sorting phase. This device is of the type which comprises:

- discharge means for discharging the material to be sorted consisting of a mixture of particles of the two categories;

- An inclined plane of translucent material, at the top of which is poured, by the above-mentioned pouring means, the material to be sorted;

- optical detection means which make it possible to detect, in the spilled material, the particles of the second category and which comprise a light source disposed below the underside of the inclined plane over the entire width thereof and a opto-electronic unit, arranged opposite said source at a certain distance above the upper face of said inclined plane, said opto-electronic unit comprising a photosensitive component with at least N elements, which observes M parallel channels adjacent dummies covering the entire width of said inclined plane;

- Ejection means for ejecting particles of the second category from the spilled material, said ejection means being controlled by said optical detection means, when the latter detect a particle of the second category, and being constituted by N hammers arranged side by side at the bottom of said inclined plane, over the entire width thereof, each mat being assigned to a fictitious channel of the inclined plane and capable of tilting, under the command sent by the corresponding element of the opto-electronic unit of the detection means, between a rest position in which the particles slide on it in the extension of the upper face of said inclined plane, and an active position of ejection, the particles being directed on two separate outlets according to the position of said hammer, each hammer being able to pivot around a hinge pin placed below, but in close proximity to, the upper face of the translucent inclined plane under the action a control member, which is linked to it at a certain distance from said articulation axis.

In such a system, the reaction time available for the control devices is that which is necessary for the particle to be ejected to cover the distance between the point where it is located on the inclined plane (location point) and the point it will have reached when the hammer is operated to come into its active position (ejection point). It has been found that, in order to have good mechanical efficiency of the hammers, it was unwise to cause the hammer to operate when the particle is in the vicinity of the axis of rotation of said hammer; on the contrary, the maneuver must take place when the particle has traveled a certain fraction of the length of the hammer, advantageously about two-thirds of it, which defines the point of ejection on the device. However, the distance D between the locating point and the ejection point must not be too large, to avoid that the particle to be ejected has time to undergo a deviation from the trajectory with respect to the straight path which is supposes between the locating point and the ejection point and to thus have the certainty that the hammer ejects the particle responsible for the occultation of the beam. The distance D must therefore be shortened as much as possible to improve the ejection reliability.

To define the reaction time of the machine control members, one must not only define the distance D as above indicated, but also define the speed of movement of the particles on the inclined plane: this speed depends, for an inclined plane made of a given material, the angle of inclination of the plane and the sliding length on said plane. It has been found that, if the angle of inclination is too large, the currant is no longer correctly guided in its movement and that if said angle is too small, the friction of the currant on the inclined plane disturbs the regularity of the flow of the curtain of currant. There is therefore an optimum angle of inclination in each case; for an inclined plane made of polymethacrylate, this angle is approximately 45 °. For a given particle and optimum inclination, the speed of movement on the inclined plane increases all the more quickly the lower the friction but, after a sufficient length of sliding, the speed becomes substantially constant for all the particles. We therefore make sure that the distance D is sufficient for the particles to move at a speed which is substantially the same for all the particles and substantially constant; in the case of a polymethacrylate plane inclined at 45 °, the distance D must therefore be at least approximately 20 cm and its optimum value is between 20 and 25 cm. It can therefore be seen that practically no action can be taken on the speed of movement of the particles in the detection zone.

If one chooses a distance D allowing to have a good ejection reliability, one notes, taking into account the imposed speeds of displacement, that the reaction time of the hammers for the ejection of the undesirable particles must be of order of a few milliseconds (3 to 15 milliseconds). It turned out that the choice of electromagnets to carry out this command, as described in FR-A-2 576 008, is not very satisfactory because the power available with an electromagnet, whose volume size is sufficiently reduced to be compatible with its use in the sorting machine, is too limited, which results in too long a response time on the hammers to be controlled due to the inertial forces. This constraint leads to increasing the distance D to the detriment of the ejection reliability and therefore of the selectivity of the sorting performed.

US-A-3 980 181 discloses an optical sorting device in which the hammers are controlled by pneumatic cylinders, the response times of which can be shorter than those of electromagnets. However, the size of the assembly of a jack and of a shutter or hammer is significant, the axis of the jack being substantially orthogonal to the shutter.

US-A-2 927 690 discloses an apparatus for sorting ores of a type different from that of the invention, the elements to be sorted being moved by a horizontal belt conveyor. Ejection means comprising pushers controlled by jacks are provided. The cylinders are oriented orthogonally to the trajectory of the elements to be sorted, in a maximum space requirement.

The object of the invention is, above all, to ensure a reduction in the response time of hammers in a sorting device of the kind defined above, and corresponding to FR-A-2 576 008, in a space that is as small as possible.

According to the invention, an optical sorting device of the kind defined above is characterized in that the control member associated with each hammer comprises an actuator connected to the movable rod of a pneumatic cylinder connected by a distributor to a source of gas compressed under an appropriate pressure, said distributor being controlled by one of the elements of the optoelectronic unit; the jacks are arranged so that their rods are parallel to the line of greatest slope of the inclined outlet plane and the fixing member of a hammer is common to all the hammers of a module of n hammers and consists of a plate fixed under the inclined outlet plane, along its upper edge, this plate carrying n arms capable of being housed each in a slot of a hammer, each arm having, at its free end, an orifice crossed by an axis pivot point common to the n bits of this module.

In the present text, the term "translucent material" means a material which is uniformly traversed by light, which includes transparent materials and those which are opalescent or frosted.

According to a preferred embodiment, the actuator of the control member is a link.

In the extension of the translucent inclined plane of the sorting device according to the invention, there is advantageously, downward, an inclined outlet plane carrying the fixing members of the hammers and jacks, which are associated with them.

Advantageously, the distributor is a distributor with a movable drawer, the movement of said drawer being controlled by at least one electromagnetic coil.

In accordance with an embodiment of the present invention, each hammer is a stirrup crossed by a hole allowing the insertion of a pin, the associated link hanging on the part of said pin located in the tent, which separates the two wings of the stirrup that constitutes said hammer.

One has noted, moreover, that, to obtain a satisfactory detection of the opaque particles which slide on the inclined plane of the sorting device according to the invention, it was necessary that the lighting of the zone observed by the various elements of the unit opto-electronics is as intense and as uniform as possible. It was therefore necessary to use lighting tubes which extend over the entire width of the optical sorting machine; to have a significant lighting power, preferably, tubular lamps with incandescent filament are chosen. Given the length of the commercially available tubular lamps and the width required for an optical sorting machine according to the invention of the industrial type, provision has been made for placing end to end, along the same axis, a plurality of lamps. incandescent filament tubes and to concentrate the light power provided by this alignment on a narrow strip of the inclined plane made of translucent material, said strip being arranged just above the area occupied by the hammers. Unfortunately, such lighting sent directly on the translucent inclined plane did not give a satisfactory result due to the non-uniformity of the lighting thus obtained in the illuminated strip, the part corresponding to the image of the incandescent filament being of course brighter than the neighboring parts.

It has therefore been imagined according to the invention to concentrate the light emitted by the tubular lamps on a strip playing the role of reflector-diffuser, said strip returning the light which it receives towards an optical concentrator disposed at the rear of the illuminated area of the translucent inclined plane. According to the invention, the light source arranged below the inner face of the translucent inclined plane, over the entire width of the latter, is therefore advantageously constituted by a plurality of tubular lamps arranged side by side. said tubular lamps being associated with a reflector-concentrator, which sends the light onto a strip forming a reflector-diffuser and arranged in line with the tubular lamps over the entire width of the translucent inclined plane, said reflector-diffuser standardizing the illuminations in the illuminated field and returning the light towards an optical concentrator arranged parallel to the axis of the light source, over the entire width of the translucent inclined plane, said optical concentrator defining a transverse light strip on the translucent inclined plane. The reflector-concentrator associated with the light source is advantageously a parabolic reflector, for example made of steel stainless. The reflector-diffuser is advantageously a flat strip painted white and oriented around its longitudinal axis to return a maximum of light in the median plane of the optical concentrator. The optical concentrator is advantageously a cylindrical diopter whose cross section is substantially a semicircle. The lighting strip which is obtained on the translucent inclined plane is situated just on the edge of said inclined plane, upstream of the zone occupied by the hammers; this strip can advantageously have a width, measured in the direction of movement of the particles on the inclined plane, of approximately 1 to 5 cm depending on the nature of the particles to be sorted.

It has been found, moreover, that the device according to the invention, in particular when it operates with wet materials capable of causing sludge and dust, had a tendency to fouling by penetration of sludge and dust into the interstices existing in the area occupied by the hammers, interstices which communicate with each other the two parts of space separated by the inclined plane along which the particles to be sorted slide. This tendency to fouling is troublesome when one wants to ensure continuous operation of the sorting device because the dust and sludge will settle on the hammer control members and quickly cause equipment to be taken out of service. To avoid this drawback, it has been proposed, according to the invention, to place the entire zone, which contains the hammers and its control members, in a box where an air overpressure is created; the overpressure air flows through the interstices, which exist at the level of the hammers, in the direction of the half-space, where the particles to be sorted are located, and this exhaust avoids any possibility of entry of dust or sludge in the opposite direction of the exhaust.

The invention therefore also relates to a sorting device of the aforementioned type, characterized in that the hammers, their actuators, the cylinder rods connected to the actuators and the corresponding pneumatic cylinder heads are placed inside a gaseous overpressure box. Preferably, said box is supplied with compressed air at a pressure of between 2 and 4 bars absolute; the walls of the box are supported by seals, on the one hand, on the face of the translucent inclined plane which receives the illumination from the light source, downstream of the light strip, and, on the other hand, on a element integral with the inclined outlet plane, which extends the translucent inclined plane.

To better understand the object of the present invention, there will be described below, by way of purely illustrative and nonlimiting example, an embodiment shown in the accompanying drawing and intended for sorting currant.

On this drawing :

- Figure 1 is a schematic overview illustrating the principle of optical sorting on which the device of the invention is based;

FIG. 2 is a diagram illustrating the system for detecting the particles to be ejected;

- Figure 3 shows, in section along III-III of Figure 5, the part of the device of the invention comprising the lower region of the inclined plane receiving spilled particles, the region of the hammers and that of the inclined outlet plane, which is located in the extension of the hammers, when they are in the rest position;

- Figure 4 shows, on a larger scale, the detail of Figure 3, which corresponds to the region of the hammer;

FIG. 5 is a view along V-V of FIG. 3 showing the rear of the hammers and of the inclined outlet plane as well as all the members of the device for controlling the tilting of the hammers, which are carried by said inclined outlet plane:

- Figure 6 is an exploded perspective view a hammer and the element which allows it to be mounted on the inclined exit plane, said element, common to the eight hammers of the same module, being represented only for its part associated with the hammer illustrated, the associated actuator with the hammer being partially figured;

- Figure 7 is a view along VII-VII of fig] ure 5 showing the fixing of the cylinders of the same module.

We will first refer to Figure 1. In this figure, we see that the currant 1, for example from a distributing hopper itself supplied by a conveyor belt, pours on a vibrating table 2, arranged horizontally .

The optical currant sorting device, which is shown in the drawing, comprises an inclined plane 3, consisting of a glass plate; the upper edge 4 of this inclined plane is under the discharge end 5 of the vibrating table 2, to collect the pieces of currant, such as the fragment 1 a ; the pieces of currant received, such as 1 b , slide on the upper surface 3 a of the inclined plane 3.

A light source 6 illuminates in white light the lower face 3b of the inclined plane 3, over its entire width; the light passes through the inclined plane 3. The inclined plane 3, initially transparent, is quickly scratched by the sliding of the currant and becomes frosted.

A camera 7, or detection unit, advantageously of the type linear photosensitive device to charge transfer, comprising many elementary photosensitive cells is set to a sharp focus on the surface 3a of the plane 3. The photosensitive cells of the camera 7 therefore receive the light, which was emitted by the source 6 and which has passed through the inclined plane 3 and, possibly, pieces of currant 1 b transparent. On the contrary, if pieces of currant 1 b , constituted by opaque materials, such as refractory or infusible fragments, stop the light emitted by the source 6 in the direction of the camera 7, the photosensitive cells associated with this area of the inclined plane are not lit. The photosensitive cells are grouped to form N sensor elements, for example eight, each corresponding to a channel of the inclined plane 3, that is to say a strip of plane arranged along the line of greatest slope of the plane 3. Each channel of the plane is thus observed by a sensor element of the camera 7; all the channels cover the entire width of the plane 3. According to a line perpendicular to the line of greatest slope of the plane 3, as many hammers 8 have been placed as there are adjacent channels in said plane. Each hammer 8 is therefore associated with a sensor element of the detection unit; this sensor element controls or not the tilting of its hammer 8 depending on whether or not the light from the source reaches said sensor element.

The hammers 8 are elongated pieces, placed side by side in the direction of the width of the inclined plane 3; they can tilt around an axis 9, between two positions, namely a first rest position 8 a , illustrated in solid lines, and a second active position 8 b , illustrated in broken lines, position 8 b which it comes to occupy under the control of the camera 7, when the latter has detected, in the channel corresponding to this hammer 8, a non-transparent piece. The structure of each hammer 8 will be described in detail below.

The optical sorting device according to the invention is completed by:

- Two inclined planes 10 a , 10 b , arranged to receive respectively the fragments 11 a discharged by a hammer in the rest position 8 a and the fragments 11 b overturned by a hammer in the active position 8 b ; the inclined plane 10 a adjacent to the hammers 8 is designated hereinafter "output inclined plane":

evacuation means, constituted, for example, by a conveyor belt 12 driven by a drum 13, for the pieces 12 b spilled on the inclined plane 10 b , these pieces being essentially made up of opaque ceramic or infusible products;

- discharge means, simply schematized by arrow 14 for pieces 11a discharged by the inclined plane 10a, and consist essentially of transparent pieces of glass, these means 14 may also be constituted by a conveyor belt.

The hammers 8 will now be described with reference in particular to FIGS. 3, 4 and 6.

Each hammer 8 comprises, when viewed while being placed on the side of the camera 7, front and rear walls, respectively 16 and 17, of planar shape and parallel to each other, two opposite side walls 8, perpendicular to the previous ones, a upper transverse wall 19, of flat shape, perpendicular to the walls 16, 17 and 18, and a lower transverse wall 20, having the shape of a cylindrical sector of axis perpendicular to the walls 18 and of concavity turned towards the outside. Each hammer 8 has, in a median plane parallel to the side walls 18, a relatively deep slot 2 formed from its rear wall 17; in this way, the hammer has the shape of a stirrup. This slot 21 is delimited by two parallel planar facing walls 22 and by a relatively narrow bottom wall 23.

Furthermore, each hammer 8 has two bores 30 and 31 formed perpendicular to its side walls 18, the first 30 being located in the vicinity of the front walls 16 and transverse 19, the second 31, in the vicinity of the rear walls 17 and transverse 19. The front hole 30 is crossed by the axis 9 around which pivots or rocks the hammer 8. The rear hole 31 is crossed by a pin 32, the role of which is indicated below. The axis 9 is common to the eight hammers of the same module corresponding to eight channels of the plane 3; there is a pin 32 per hammer.

The hammers 8 are arranged between the inclined plane translucent 3 and the inclined outlet plane 10 a . The latter is formed by a metal plate, which extends the translucent inclined plane 3; in the hammers 8 rest position, their front walls 16 are located in the extension of the upper faces of the two inclined planes 3 and 10 a , over which the currant slides.

The eight hammers 8 of the same module are mounted using an elongated plate 33, which comprises, along one of its longitudinal edges, eight arms 34, the end region 35 of which has an orifice 36. The plate 33 has threaded bores 37 aligned with openings 38 of the inclined plane 10 a for the passage of fixing screws 39. In the fixing position, the arms 34 are each placed in a slot 21 of a hammer, so that all the holes 36 are in alignment with the bore 30, which allows the introduction of the axis 9 common to all the hammers 8 of the same module.

Each hammer 8 is associated with an actuator which is constituted by a link 47 comprising a bore at each of its ends. The link 47 is placed in the slot 21 of the hammer 8 with which it is associated; the bore of one of its ends is crossed by the pin 32 of said hammer; the bore of its other end is traversed by a pin 46, which is supported by the two wings of a stirrup 45. The stirrup 45 forms a connecting yoke between the link 47 and the movable rod 61 associated with the piston of the jack tire 62 which cooperates with the hammer 8 described. The connection between the stirrup 45 and the rod 61 is effected by screwing the threaded end of said rod 61 in a threaded bore formed in the rear face of the core of the stirrup 45. A lock nut 44 allows to block the assembly 45/61.

Each hammer 8 is thus associated with a double-acting pneumatic cylinder 62, which is supplied by a distributor with movable drawer 43. A machine according to the invention contains a plurality of identical modules arranged side by side. side. In this embodiment, each module consists of eight hammers and therefore comprises eight pneumatic cylinders and eight distributors; each hammer corresponds to an element of the photosensitive component of the opto-electronic unit; each module corresponds to a group of photosensitive cells. If the machine has six modules arranged side by side, the camera will include six groups of photosensitive cells arranged side by side for the observation of the entire width of the translucent inclined plane, which faces it. The complete machine consists of the juxtaposition side by side of six modules which gives an overall width of 1.3 meters. The axes of the jacks 62 are perpendicular to the axis 9 of the hammers 8 and parallel to the inclined outlet plane 10 a . All the jacks 62 of the same module are therefore placed side by side and their cylinders are sandwiched between a jaw 42 carried by the inclined outlet plane 10 a and an associated jaw 41 which is secured to the previous one by screws 40 The jaws 41 and 42 have recesses in the shape of a semicircle to allow the cylinders of the jacks 62 to be accommodated.

Each cylinder 62 communicates with its distributor 43 associated by means of two tubes 24 connected to the two outputs of the distributor. The dispenser comprises a movable drawer controlled by an electromagnet; it is supplied by two pipes, one connected to the open air and the other to a source of compressed air. For a position of the distributor drawer, one of the chambers of the actuator is supplied and the other is moved to the free area; the opposite occurs for the other position of the dispenser drawer. The eight distributors 43 associated with the eight jacks 62 of the same module are arranged on either side of the core 25 a of a stirrup 25 whose two wings have their lower part bolted by bolts 26 on a return in bracket 27 integral with the output inclined plane 10a and, therefore, the module frame described.

When all the modules of the same machine are assembled side by side, a box is placed over the whole width of the machine, which is positioned behind the inclined plane on which the particles slide, at the level of the hammers 8, the rods 47 and the cylinder rods 61. This box is integral with the lateral wings which border the two transverse ends of the machine according to the invention and it consists of two parts connected to each other by a hinge 80; the first part 81 comes to bear by a seal against the translucent inclined plane 3 and this part 81 includes a right angle, which is parallel to the translucent inclined plane 3; the hinge 80 is carried by this return square and connects it to a flat cover 82, which comes to bear by a seal on the jaws 41 for fixing the jacks 62; on the two transverse ends of the box 80, 81, 82, compressed air inlets 83 are brought to 3 bar absolute. In this way, the interior of the box can be pressurized, the overpressure air escaping in the direction of the particles to be sorted through the interstices which exist at the level of the hammers 8. This exhaust of compressed air prevents any entry of dust and sludge inside the box and therefore maintains the hammer actuator 8 in perfect working order.

The set of juxtaposed modules, which constitutes the machine according to the invention, is also associated with a lighting device which extends over the entire width of the machine. This device comprises seven tubular lamps 84 of 500 watts each arranged along the same axis. The incandescent filaments of these lamps are placed at the focal point of a parabolic cylindrical mirror 85 made of stainless steel sheet. The mirror 85 is a reflector-concentrator which sends all the light energy produced by the lamps 84 onto a reflector-diffuser 86 consisting of a strip of flat sheet metal painted white. This reflector-diffuser 86 returns the light while standardizing the illumination in the light beam. The beam is sent to an optical concentrator constituted by a cylindrical diopter 87 whose cross section is a semicircle. The plane of symmetry of the diopter 87 makes an angle of 45 ° with the plane of the reflector-diffuser 86 which itself makes an angle of 45 ° with the plane of symmetry of the parabolic reflector-concentrator 85. The tubular lamps 84 are retained by supports 88 relative to the reflector-concentrator 85 which is itself carried at its ends by the lateral wings of the machine; the reflector-concentrator 85 is placed in a casing 89, part of which constitutes the white reflector-diffuser 86; this casing 89 is connected to part 81 of the pressurized box. A window has been provided in the casing 89 inside which the cylindrical diopter 87 has been put in place, the edges of the window penetrating into grooves provided for this purpose in the diopter 87. The diopter 87 can be produced by transparent plastic.

The operation of the device which has just been described is as follows:

The pieces of currant 1 arrive, thanks to the vibrating table 2, as pieces 1 a on the translucent inclined plane 3. In fact, the hopper, which is upstream of the vibrating table 2, serves as a reservoir for the currant and allows a regular flow on the vibrating table 2 which, for its part, makes it possible to give the threeil bed, which leaves the end 5 of this table, as pieces 1 a , a regular and adjustable flow without overlapping of the pieces on the inclined plane 3.

The inclined plane 3 serves by its slope, to accelerate the movement of the pieces of currant 1 b thanks to gravity, by ensuring a separation between the different pieces. Moreover, due to gravity, the pieces 1 b bear against the upper face 3a of the inclined plane 3, which is the camera's focal plane 7, which allows the camera to examine the pieces 1 b with sharpness.

Finally, thanks to its translucency, the inclined plane 3 allows regular lighting from below pieces of currant 1 b and, therefore, a correct examination by transparency of these pieces, the photosensitive elements of camera 7 easily distinguishing the transparent pieces made of glass, on the one hand, and opaque (especially ceramic), or infusible, pieces on the other hand.

When the photosensitive element of the camera 7 corresponding to a hammer 8 is fully lit, that is to say when there is no opaque piece in this channel in the area 3 c of intersection of the axis 7 a of the photosensitive element and of the inclined plane 3, the corresponding hammer 8 occupies the rest position 8 a and, consequently, the transparent fragments passing through the zone 3 c arrive as fragments 11 a on the plane 10 has to be evacuated according to arrow 14. On the other hand, when said photosensitive element of the camera 7 receives less light, due to the presence of a non-transparent piece in the zone 3c of this channel, the photosensitive element controls actuation of the corresponding hammer 8 to bring it into position 8 b . The reaction time of the system and the speed of sliding of the pieces of currant on the plane 3 are such that the hammer 8 switches to the ejection position when the opaque piece of currant has reached approximately two thirds of the length of the hammer . This piece is thus deflected towards the plane 11 b and is therefore evacuated by the conveyor belt 12, as piece 12 b .

The hammer 8 control indicated above is carried out from the hammer rest position. For this rest position, the actuator 62 is in the position shown in FIG. 3, the lower chamber of the actuator being under pressure and the rod 61 of the actuator 62 being fully extended. When a photodetector element of the camera 7 receives less light, it emits a signal, which triggers the supply of the electromagnetic coil of the distributor 43 which is associated with it. The dispenser drawer is moved; the supply of the jack 62 is reversed; the rod 61 enters the cylinder of the jack, which makes the hammer 8 pivot about its axis 9 and brings said hammer into the ejection position.

When the photodetector element associated with the jack is again normally lit, the supply to the distributor coil 43 is cut, the distributor returns to its rest position and the hammer 8 returns to its rest position.

Claims (9)

1. An optical sifting device for separating two categories of particles having different optical transmissivities, the less opaque particles constituting the first category and the more opaque particles constituting the second category, this device comprising;
   - dumping means (2) for dumping the material to be sifted constituted by a mixture of particles of two categories;
   - an inclined plane (3) made of a translucent material, onto the upper part (4) whereof the material to be sifted is dumped by the above mentioned dumping means;
   - optical detection means (6, 7) which allow the particles of the second category to be detected in the dumped material and which comprise a light source (6) disposed below the bottom side of the inclined plane over the whole width of the latter, and an opto-electronic unit (7) disposed opposite the said source at a certain distance above the upper side (3a) of the said inclined plane (3), the said opto-electronic unit comprising a photosensitive component with at least N elements that observes N imaginary parallel and adjacent channels covering the whole width of the said inclined plane (3);
   - ejection means (8) for ejecting the particles of the second category from the dumped material, the said ejection means (8) being controlled by the said optical detection means (6, 7) when these latter detect a particle of the second category and being constituted by N hammers (8) disposed side by side at the bottom of the said inclined plane (3) over the whole width of the latter, each hammer (8) being allocated to an imaginary channel of the inclined plane (3) and being capable of rocking under the actuation sent by the corresponding element of the opto-electronic unit of the detection means (6, 7) between a rest position wherein the particles slide thereon in the extension of the upper side (3a) of the said inclined plane (3), and an active ejection position, the particles being directed to two separate outlets (10a, 10b) according to the position of the said hammer (8), each hammer (8) being capable of pivoting round an articulation pin (9) placed below, but in the immediate vicinity of the upper side (3a) of the translucent inclined plane (3) under the action of a control device connected thereto at a certain distance from the said articulation pin (9), characterized in that the control element associated with each hammer (8) comprises an actuator (47) connected to the movable rod (61) of a pneumatic jack (62) connected by a distributor (43) to a source of compressed gas at an appropriate pressure, the said distributor (43) being controlled by one of the elements of the opto-electronic unit (7); the jacks (62) are disposed so that their rods (61) are parallel to the line of steepest slope of the inclined outlet plane (10a) and the device for the fixing of a hammer (8) is common to all the hammers of a module of n hammers and consists of a plate (33) fixed under the inclined outlet plane (10a) along its upper edge, this plate carrying n arms (34) capable of being each accommodated in a slot (21) of a hammer, each arm (34) having at its free end an opening (36) traversed by an articulation pin (9) common to n hammers (8) of this module.
2. A device according to claim 1, characterized in that the actuator of the control device is a link rod (47).
3. A device according to one of claims 1 or 2, characterized in that in the extension of the translucent inclined plane (3), there is disposed towards the bottom, an inclined outlet plane (10a) carrying the elements (33, 34; 41, 42) for fixing the hammers (8) and the jacks (62) associated therewith.
4. A device acoording to one of claims 1 to 3, characterized in that the distributor (43) is a distributor with a movable slide, the displacement ot the said slide being controlled by at least one electromagnetic coil.
5. A device according to one of claims 1 to 4, characterized in that each hammer (8) is a stirrup traversed by a bore (31) allowing a pin (32) to be inserted, the link rod (47) associated with the said hammer (8) being fastened onto the portion of the said pin (32) situated in the slot (21) separating the two sides of the stirrup constituting the said hammer (8).
6. A device according to one of claims 1 to 5, characterized in that the light source is constituted by a plurality of tubular incandescent lamps (84) disposed end to end, the said lamps being associated with a concentrating reflector (85) which passes the light to a band forming a diffuser reflector (86) and which is disposed opposite tubular lamps (84) over the whole width of the translucent inclined plane (3), the said diffuser reflector (86) providing uniform lighting in the lighted field and returning the light towards an optical concentrator (87) disposed parallel to the axis of the light source over the whole width of the translucent inclined plane (3) so as to form transversely on the said translucent inclined plane, a narrow strip of light.
7. A device according to claim 6, characterized in that the concentrating reflector (85) is a mirror in the form of a parabolic cylinder, and in that the diffuser reflector (86) is a plane strip painted white and orientated so as to send the maximum amount of light into the median plane of the cylindrical diopter constituting the optical concentrator (87), the cross section of the said diopter substantially forming a half circle.
8. A device according to one of claims 1 to 7, characterized in that the hammers (8), their actuators (47) and the jack rods (61) connected to the actuators (47) and the corresponding pneumatic jack heads are placed inside a casing (80, 81, 82) at a gaseous overpressure.
9. A device according to claim 8, characterized in that the walls (81, 82) of the casing bear via joints, on the one hand, on the side of the translucent inclined plane (3) receiving the illumination from the light source down the line from the illuminated strip, and, on the other hand, on an element (41) fixed to the inclined outlet plane (10a) that extends the translucent inclined plane (3).

Images