EP1633485B1 - Device for grinding up non-metallic pieces - Google Patents

Abstract

The shredder consists of at least one driven rotary shaft (11) with teeth (8), located inside a container holding non-metallic articles to be shredded. The teeth are designed to interact with others (15) on one or more fixed combs (4, 4a, 4b) between upper and lower compartments of the container, and each comb has an electrically-conducting base (41, 42) that is raised to a given potential, and a conducting surface (14) facing the upper part of the container, insulated electrically from the base and raised to a different potential to detect the presence of metallic particles by closing the electrical circuit created. The comb bases and shaft teeth carry the same electrical potential, which can be zero, and the conducting surfaces (14) are in the form of plates attached to the bases by insulated fastenings or by screws passing through layers of self hardening insulating material between the plates and bases. The conducting plates are connected to a control unit that stops the shaft when a metal component closes the circuit.

Description

Technical area

The invention relates to the recycling sector of non-metallic materials. It thus relates to an apparatus for grinding non-metallic parts capable of reducing granules to a piece of plastic material in particular.

It is more particularly a means for detecting the presence of metal material parts inside the device.

Prior art

In general, non-metal part recycling machines comprise a grinding device for generating granules that can be reused to manufacture new parts by injection or extrusion, for example.

It happens however that metal parts can be introduced into the grinding device because serving for example means for securing the parts to grind on a structure, for example automobile bumpers fixed by metal rivets on the frame. However, if the metal parts enter the mill, they may on the one hand to damage the teeth of the mill and on the other hand to plug the injection nozzles or extrusion during the subsequent use of the granules.

The detection of the metal parts is not carried out inside the grinding devices. This operation is done traditionally upstream of the grinding, inside the mechanism of supply of the parts to grind, for example by heavy magnetic means to implement and expensive.

The document FR 2,700,278 thus describes a feed system for a grinding apparatus of non-metallic parts. This system is equipped with a device for detecting metal parts by means of a bar arranged longitudinally in the machine and electrically isolated from the frame of the machine. A circuit is then closed when a metal piece is both in contact with the bar and the frame.

However, this detection device does not detect metal parts embedded in the non-metallic material. In addition, it is located upstream of the mill and therefore, it is common that metal parts reach the grinding apparatus, causing significant damage. Similarly, metal parts can be introduced between the two operations, which can damage the mill and clog the injection or extrusion nozzles.

Presentation of the invention

The invention aims to remedy this disadvantage in a simple, safe and effective manner.

The invention proposes to perform the detection of metal parts located inside a grinding apparatus on the one hand, and then to control the automatic shutdown of the grinding apparatus on the other hand, in particular for grinding apparatus with low rotational speed of the mill shaft.

To solve such a problem, it has been designed and developed a grinding apparatus of non-metallic parts having a motorized rotating shaft within a receptacle. The shaft is provided with a plurality of teeth for shredding and grinding non-metallic parts. The teeth are arranged radially in rows on the periphery of the shaft so. to cooperate, during their rotation, with the teeth of at least one fixed comb, secured to the receptacle and defining the receptacle in an upper portion above the comb and a lower portion located below the comb.

According to the invention, the fixed comb comprises an electrically conductive base, brought to a determined potential, and an electrically conductive surface oriented toward the upper part of the receptacle, electrically isolated from the base, and carried to a potential different from that of the base. This configuration makes it possible to detect the presence of metal parts by closing the electrical circuit between the surface and the base.

In other words, the electrically conductive surface electrically insulated from the base of the comb, is in the area of supply of non-metallic parts of the grinding apparatus. When a metal piece comes into simultaneous contact with this conductive surface and the base of the comb, it then creates "a short circuit", or more simply varies the resistance that can be associated with a particular Wheatstone bridge. It is then deduced from this variation or state change that a metal part is present in the non-metallic material supply zone of such a grinding apparatus.

According to the invention, the grinding apparatus may comprise a plurality of combs capable of detecting the presence of metal parts, which are arranged on either side of the longitudinal median plane of the apparatus. In other words, the combs make it possible to delimit the apparatus in two volumes, the first volume being the volume of supply, also called the upper part of the apparatus when the supply is made by gravity, the second volume receiving the granules of Non-metallic materials, also called the bottom of the device when the supply is done by gravity.

Advantageously, the electric potentials of the base of the comb and the teeth of the motorized rotating shaft are identical. Indeed, the distance between these two elements being very small, a potential difference between these two elements could be at the origin of an electric arc, which would close the circuit and disrupt the effectiveness of the detection.

In practice, the base of the comb and the teeth of the motorized rotating shaft has zero potential. In this case, they are connected to the ground of the device.

According to a first embodiment of the invention, the conductive surface consists of a conductive plate held on the base of the comb by at least one electrically isolated clamping element.

In practice, the electrically isolated clamping element is a screw with the same potential as that of the base. This screw then passes through a hole in the plate and then blocks the plate by means of its head.

An electrically insulating curable material is then interposed between the base, the plate and the screw, so as to electrically isolate the base plate.

According to another embodiment of the invention, the conductive surface consists of a conductive metal profile, inserted into a groove etched within the base, and coated with an insulating resin. This profile is inserted into the groove previously filled with glue, the upper surface thus produced undergoing a grinding step, removing the resin on the conductive surface to ensure conduction.

According to the invention, the conductive plate is electrically connected to a control unit of the apparatus. Thus, when the circuit is closed by a metal piece astride the conductive plate and the base of the comb, the control unit then stops the rotation of the motorized shaft and sends information to a display. This display then allows the operator of the device to know the origin of the shutdown of the device. This display can be according to the chosen embodiment, a light or a message on a device type screen. The operator must then remove the metal part forming the short circuit, then reactivate the start of the device.

Brief description of the figures

• la figure 1 est une vue en coupe transversale du broyeur, conformément à l'invention;
• la figure 2 est une vue en perspective de deux peignes aptes à détecter la présence de pièces métalliques conformément à l'invention;
• la figure 3 est une vue en coupe d'un peigne conforme à une première forme de réalisation de l'invention:

• la figure 4 est une représentation schématique vue du dessus d'un peigne conformément à une seconde forme de réalisation de l'invention:

• la figure 5 est une vue en section réalisée selon la ligne V - V de la figure 4.
• la figure 6 est une représentation schématique d'une pluralité de peignes juxtaposés, et réalisés selon la seconde forme de réalisation de l'invention.

The manner of carrying out the invention as well as the advantages which result therefrom, will emerge from the description of the embodiments which follow, given by way of indication and not by way of limitation, in support of the appended figures in which:

• Figure 1 is a cross-sectional view of the mill according to the invention;
• Figure 2 is a perspective view of two combs adapted to detect the presence of metal parts according to the invention;
• FIG. 3 is a sectional view of a comb according to a first embodiment of the invention:

• FIG. 4 is a diagrammatic representation seen from above of a comb according to a second embodiment of the invention:

• FIG. 5 is a sectional view taken along the line V - V of FIG. 4.
• Figure 6 is a schematic representation of a plurality of juxtaposed combs, and made according to the second embodiment of the invention.

Embodiments of the invention

As already mentioned, the invention relates to an apparatus for grinding non-metallic parts comprising at least one fixed comb capable of detecting the presence of metal parts inside said grinding apparatus.

As illustrated in Figure 1, the grinding apparatus (1) comprises a receptacle within which is delimited an upper portion (5), wherein the non-metallic parts (2) to be ground are introduced. A motorized rotating shaft (11) is disposed in the lower part (6) of the grinding apparatus (1). The shaft (11) is provided with a plurality of teeth (8) arranged radially in rows on the periphery of the shaft. It also comprises one or more large knives (9), extending radially relative to the shaft and capable of splitting the large non-metallic parts (2) introduced into the apparatus.

The teeth (8, 9) cooperate, when rotating, with the teeth (15) of at least one fixed comb (4). This zone then delimits the boundary between the upper part (5) and the lower part (6) of the grinding apparatus (1).

When the non-metallic parts (2) fall into the grinding apparatus (1), they are first pressed onto the comb (4) and then shredded progressively to form granules (7). non-metallic materials inside the lower part (6).

As shown in Figure 2, the comb (4) can decompose into two portions (4a, 4b) with a central clearance to let the knives (9). It also has teeth (15) allowing the teeth (8) of the motor shaft to rotate freely while generating granules from the cooperation of the teeth (8) and (15) between them. According to the invention, the comb comprises an electrically conductive base (41, 42), and raised to a determined potential, and an electrically conductive surface (14) oriented towards the upper part (5). ) of the mill (1), and brought to a potential different from that of the base (41, 42), so as to detect the presence of metal parts by closing the electrical circuit thus formed.

Advantageously, the potential for the base (41, 42) is the mass of the apparatus (1).

According to a first embodiment of the invention, the surface (14) of the comb (4) is made by means of conductive plates (43, 44) electrically insulated from the base (41, 42) of the comb (4). . Each conductive plate (43, 44) is held relative to the comb (4) by means of two screws (47). Each of the screws (47) passes through a bore (48) formed in the plate (43, 44) and blocks the plate (43, 44) by means of its head.

As shown in Figure 3, the screw (47) is electrically insulated from the plate (43). In this way, the potential of the screw is that of the base (41) of the comb (4a).

According to another embodiment of the invention (FIGS. 4 and 5), a groove (50) is produced on the upper face of the base, in particular by machining, extending substantially over all or part of its periphery, in addition to its median. This groove is intended to receive the upper conductive surface (14), which in this case is constituted by a metal conductive section (51) of shape corresponding to said groove.

This profile is coated for example by dipping an insulating resin, such as polyamide, to a thickness of about three tenths of a millimeter. Once the resin dries, the groove (50) is filled with glue, for example cyanoacrylate, and then said profile (51) is pressed into the groove (50). When the glue has set, the upper surface of the comb is subjected to a rectification, allowing it to be flattened, and especially to reveal the upper conductive face of the profile (51).

Such an embodiment avoids using a mechanical connection between the conductive surface and the base of the comb.

The plate (43, 44) or the profile (51) is connected by a wire element (45, 46) to the control unit of the apparatus (1). When a metal piece comes into contact with both the plate (43, 44) or the profile (51) and the base (41, 42) of the comb (4), an electric circuit is then closed, and the control unit automatically stops the rotation of the motorized shaft (11). It then sends information to a display to allow the operator to see the cause of the shutdown of the device (1).

In order to avoid the multiplication of the wire links in the case of the implementation of a plurality of combs, the profiles (51) are brought into contact with one another by means of a set screw (52) or provided with at both ends of a ball, and coated with an outer shell (53) made of a non-electrically conductive material and having a thread. This screw is received in a bore (54) formed at the side face of each of the combs and opening at the groove (50) which they are provided, so as to be in contact with the conductive section (51). .

In doing so, all the profiles are brought to the same potential, without being short-circuited with the base of the combs.

• il permet de réduire de façon considérable les risques engendrés par la présence de pièces métalliques à l'intérieur d'un appareil de broyage de ce type;
• il s'adapte très facilement sur les appareils de broyage utilisés dans l'industrie ;
• sa simplicité de fonctionnement en fait un instrument sûr et bon marché.

It follows from the foregoing description that an apparatus according to the invention has many advantages, in particular:

• it considerably reduces the risks caused by the presence of metal parts inside a crushing apparatus of this type;
• it adapts very easily to grinding machines used in industry;
• its simplicity of operation makes it a safe and inexpensive instrument.

Claims (10)

1. A device for grinding (1) non-metal parts (2) comprising at least one motor-driven rotating shaft (11) inside a receptacle that receives non-metal parts that are to be ground, said shaft (11) having a plurality of teeth (8) intended to shred and grind said non-metal parts (2), said teeth (8) being arranged radially in rows around the periphery of shaft (11) so as to cooperate, when they rotate, with teeth (15) of at least one fixed comb (4, 4a, 4b) attached to the receptacle and dividing the receptacle into an upper part (5) located above comb (4, 4a, 4b) and a lower part (6) located underneath comb (4, 4a, 4b) characterised in that said fixed comb (4, 4a, 4b) comprises an electrically conducting base (41, 42) held at a specific potential and an electrically conducting surface (14) that faces the upper part (5) of the receptacle and is electrically insulated from said base (41, 42) and held at a potential that is different to that of base (41, 42) so as to detect the presence of metal parts by making the electrical circuit thus produced.
2. A grinding device as claimed in claim 1, characterised in that it comprises a plurality of combs (3, 4) capable of detecting the presence of metal parts either side of the longitudinal median plane of the grinding device (1).
3. A grinding device as claimed in one of claims 1 and 2, characterised in that the electrical potentials of the base (41, 42) and the teeth (8) of the motor-driven rotating shaft (11) are identical.
4. A grinding device as claimed in claim 3, characterised in that the base (41, 42) and teeth (8) of motor-driven rotating shaft (11) are held at zero potential.
5. A grinding device as claimed in any of claims 1 to 4, characterised in that conducting surface (14) consists of a conducting sheet (43, 44) secured on base (41, 42) by at least one electrically insulated fastener.
6. A grinding device as claimed in claim 5, characterised in that the electrically insulated fastener consists of a screw (47) held at the same potential as that of base (41, 42), said screw (47) passing through a hole (48) in sheet (43, 44) and securing sheet (43, 44) by means of its head.
7. A grinding device as claimed in claim 6, characterised in that an electrically insulating hardenable material (10) is inserted between base (41, 42), sheet (43, 44) and screw (47) so as to electrically insulate sheet (43, 44) from base (41, 42).
8. A grinding device as claimed in any of claims 1 to 4, characterised in that the conducting surface (14) consists of an electrically conducting section (51) accommodated in a groove (50) of matching shape made in the upper surface of the comb and extending substantially along all or part of its periphery and also along its median plane, aid section being coated in an insulating resin before being bonded into said groove.
9. A grinding device as claimed in claim 8, characterised in that said sections (51) of a single row of combs are electrically connected to each other by means of cone-point set screws or screws with a ball at both their ends and housed in an outer enclosure made of an electrically non-conducting material having a thread, each of said screws being intended to be accommodated in a bore in the lateral surface of each of the combs and opening out into groove (50) which they have, so as to be in contact with conducting section (51).
10. A grinding device as claimed in any of claims 1 to 9, characterised in that conducting sheet (43, 44) or section (51) is electrically connected to a control unit of device (1) intended to stop rotation of motor-driven shaft (11) when the circuit is made by a metal part.

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