FR2772643A1 - MULTI-KNIFE GRINDER FOR THE FOOD INDUSTRY - Google Patents

Abstract

The object of the invention is a multi-knife mill, in particular used in the food industry, provided with means (12, 16, 18) for supplying material, comprising in the direction of flow of the material, a counter-grid (28) provided with at least one orifice (44), a knife holder (30) provided with at least one knife (52), and a grid (22), characterized in that the knife ( 52) comprises at least one ridge of wavy shape.

Description

MULTI-KNIFE GRINDER FOR THE FOOD INDUSTRY

  The present invention relates to a multi-knife mill for

the food industry.

  The grinders used in the food industry are generally placed in production lines for reconstituted products. They allow in particular to grind different products which will be introduced later

  in agri-food preparations.

  They generally consist of a feed hopper, a sheath in which a coaxial worm rotates. The downstream end of the sheath is obstructed by a grid, the diameter of the through holes determines the fineness of the grinding, and the end of the worm is equipped with a knife

  which allows you to cut the product before it passes through the grid.

  This knife made in one piece generally comprises several branches arranged radially which are machined to form sharp blades. The wire of these blades wears very quickly so that it is necessary to stop the shredder regularly to disassemble the knife in order to sharpen the blades. This sharpening, which requires a certain time, can only be carried out a limited number of times on the same knife because at each operation we

removes material.

  To limit the stopping of the machine, one solution consists in having a pair of knives for each grinder. Thus, as soon as the knife in place no longer cuts, it is replaced by the second. But this solution, even if it limits the downtime, does not slow down the wear of the knives which must be changed inevitably. This rapid wear of knives which have a relatively high cost price, greatly increases maintenance costs

grinders.

  In addition, the rapid wear of the knives also affects the throughput of the crusher, since a backflow phenomenon tends to appear when the

blades are poorly sharpened.

  The present invention aims to overcome these drawbacks by proposing a grinder which comprises a counter-grid whose shapes facilitate the grinding action, and knives, arranged in a removable or permanent manner on a knife holder, whose geometric shapes and their provisions make it possible to slow down their wear. This shredder reduces maintenance costs and increases the throughput of crushed products, in particular by improving the

resistance of the thread over time.

  To this end, the present invention relates to a multi-mill

  knives, in particular used in the food industry, provided with material supply means, comprising in the direction of the flow of material, a counter-grid provided with at least one orifice, a knife holder provided with minus a knife, and a grid, characterized in that the knife

  includes at least one edge of wavy shape.

  Preferably, each knife comprises two cutting edges, a first adjacent to the grid and a second adjacent to the counter-grid, which have a wavy shape whose radius at a point considered from the edge is proportional to the distance separating the point considered from the axis of rotation of the knife holder. According to one embodiment, the knife comprises a cutting face

  which has a rectilinear shape in the transverse direction.

  According to another embodiment, the knife comprises a cutting face provided with fragmentation means produced by a double shape curved in the transverse direction, the first being attached to the first

  edge and the second to the second edge.

  Advantageously, the assembly constituted by the counter-grid and the holder

  knife comprises means for shifting the cutting attack of each knife. Preferably, each knife has a toothing profile which is alternated from one knife to another. Preferably, the knives are removably attached to the knife holder. According to another characteristic, the peripheral surface of the orifices of the counter-grid comprises at least one substantially projecting edge

  perpendicular to the surface of the counter grid.

  Other characteristics and advantages will emerge from the description which

  will follow of the device according to a preferred embodiment, description given

  by way of example only, with reference to the accompanying drawings in which: - Figure 1 is a cross section of a mill,

  - Figure 2 is an elevational view of the knife holder and the counter

  grid, - Figure 3A is a perspective view of a first example of a knife profile, - Figure 3B is a cross section of the knife illustrated in Figure 3A, - Figure 4A is a perspective view of a second example of profile knife, and - Figure 4B is a cross section of the knife illustrated by the

Figure 4A.

  In Figure 1, there is shown a cross section of a crusher 10 which comprises in known manner a hopper 12 for feeding, a barrel 14, and a worm 16 driven by a motor 18 at its first end and provided with 'a shaft 20 at its second end. The downstream end of the sheath 14 is obstructed by a grid 22 which includes through holes 24 whose diameter determines the fineness of the grinding, and a bore 26 coaxial with the axis 27

scabbard.

  According to the invention, between the worm 16 and the grid 22, there is placed from upstream to downstream, a counter-grid 28 whose outline is similar to that of the grid 22, and a knife holder 30. This counter-grid 28 which comprises a coaxial bore 32 and of diameter slightly greater than the shaft 20, bears against a shoulder 34 of the bore of said sleeve 14. It is immobilized in rotation, like the grid 22, by means 36 for stopping rotation, for example a notch 37 on its periphery (visible in FIG. 2)

  in which is housed a lug secured to the sheath 14.

  The knife holder 30 is driven in rotation by the worm 16 by means of drive means 38, and comprises guide means, produced by a bearing 40 which is housed in the bore 26 of the grid, and by a coaxial bore 42 with a diameter slightly greater than the shaft 20 of the screw

unending.

  These drive means 38 are produced by virtue of the combined shapes of the end of the worm 16 which comprises two flats, and

  of the bore 42 of the knife holder 30 visible in FIG. 2.

  A nut 43, screwed to the end of the sheath 14, makes it possible to immobilize in translation from upstream to downstream, the counter-grid 28, the knife holder 30

and grid 22.

  According to a preferred embodiment, illustrated in FIG. 2, the counter

  grid 28, of cylindrical shape, comprises an even number of orifices, arranged symmetrically on its surface, for example six orifices referenced from 44 to 49, uniformly distributed, including the scalloped edges with projecting shapes

pre-cut products.

  The peripheral edge of the orifices 44 to 49 comprises edges 50 projecting over the entire thickness, substantially parallel to the axis 27 of the sheath, which

facilitate pre-cutting.

  Preferably, the counter-grid 28 is made of hardened steel, and undergoes a surface treatment, for example nitriding, in order to give it

  high mechanical characteristics.

  In Figure 2, there is also shown an embodiment

  preferred knife holder 30 according to the invention.

  It comprises five branches 51, 53, 55, 57, 59 which are arranged radially, on which knives 52, 54 are removably fixed,

56, 58, 60.

  These removable knives are fixed, on one of the faces of the branches, perpendicular to the plane of rotation of the knife holder, by means 62 of fixing, for example two screws embedded in housings 64

  of each branch as illustrated on branch 51.

  According to another embodiment not shown, the knife holder 30 and the knives 52, 54, 56, 58, 60 can be made in one piece,

  said knives having the same features as removable knives.

  These knives 52, 54, 56, 58, 60 have teeth profiles 66 adapted to the different types of products, which allow better grinding with a

  high flow and slow wear.

  In order to improve the grinding and limit vibrations, the assembly constituted by the counter-grid 28 and the knife holder 30, comprises means 67 for shifting the cutting attack of the knives, and the profile 66 is shifted from one branch to another. The means 67 for shifting can be produced by taking a number of branches of the knife holder 30 different from the number of orifices of the counter-grid 28, and / or by having an angular distance formed between two consecutive knives and / or two orifices different counter grid. Thus, with such an arrangement, the cutting attack of

  each knife is offset and the cutting forces are better distributed.

  Furthermore, these profiles 66, which have a substantially wavy shape which reduces the cutting forces, vary depending in particular on the hardness of the

product to be ground.

  A first example of profile 66, intended for extremely hard materials, for example frozen products, is illustrated by the

Figures 3A and 3B.

  Each knife, of substantially parallelepiped shape, comprises a bearing face 68 pressed against the branch, a cutting face 70, a first cutting edge 72 adjacent to the grid 22 and a second cutting edge 74 adjacent to the counter-grid 28. These edges are respectively associated with a first face 76 of main draft oriented towards the

  grid 22, with a second face 78 of main draft oriented towards the counter

  grid 28 and a side 80 of secondary draft facing outwards,

common to both edges.

  Each cutting edge has an undulating shape whose radius of curvature at a point considered is proportional to the distance separating said point from the axis 27 of rotation of the knife holder (shown in phantom). Thus, in FIG. 3A, the radius of curvature R2 is less than R1, R2 being closer to

the axis 27 of rotation as R1.

  Preferably, the first and second edges have the same wavy shape. In order to define the characteristic angles of the knife, it is first necessary to determine the reference plane Pr, the edge plane Ps, and the

Pf work plan.

  At a point considered A of the first edge 72, the plane Pr is the plane parallel to the bearing face 68 passing through A, the plane Ps is the plane perpendicular to Pr passing through the point A, and the plane Pf is the plan

  perpendicular to Pr and Ps in this case.

  Thus, for the first edge 72, the cutting angle y1 is the angle separating the reference plane Pr and the cutting face 70, the cutting angle P is the angle separating the cutting face 70 and the first face 76 of main draft, the main draft angle ca1 is the angle separating the first face 76 of main draft and the edge plane Ps, the angle of inclination of edge I1 is the angle separating the mean direction of the edge 72 and the plane Pr, and the angle of secondary draft ('1 is the angle separating the face 80 of secondary draft

  and a plan parallel to the Pf work plan.

  For the second edge 74, the angles are defined in the same way, the index 1 of the angles being replaced by the index 2, with X2 equal to Es, and (X'2

equal to (a'1.

  For hard materials, the cutting face 70 is generated by the set of straight lines located in a plane Pf, which connect the first edge 72 and the

second edge 74.

  Preferably, for the first edge 72, the main draft angle e1 is between 1 and 8 and is preferably 3, the cutting angle y, is between 0 and 35, the angle of inclination of edge k1 is approximately 2 and the secondary draft angle cc'1 is approximately 5. For the second edge 74, the angles a2, 92, 72, X2 and (X'2 have values

  substantially identical to cl, Pl, y1, k1 and a'1.

  Another knife profile, used for soft materials, is

  shown in Figures 4A and 4B.

  In this case, the cutting face 70 is not generated by straight lines as before. It is generated by a first set of curves 84 which pass through a point A located on the first edge 72 and by a point C describing a curve, similar and parallel to the first edge 72, located approximately in the middle of the cutting face 70 , and by a second set of curves 86 which pass through a point B located on the second edge 74 and through point C. Curves 84 and 86 are characterized by their

  radius of curvature and by the distance e separating point C from the straight line (AB).

  This curved shape of the cutting face 70 constitutes means 88 for fragmentation, and allows in the case of soft materials to

  fragment to reduce friction and therefore wear.

  Thus, the distance e is inversely proportional to the hardness of the

  crushed material, its value increasing for soft materials.

  In an extreme case, for hard materials of the frozen type, the distance e is zero, the radii of curvature are infinite, and we then find the

  knife shape illustrated in Figures 3A and 3B.

  The other characteristic angles of this knife profile have values identical to the characteristic angles of the knife profile illustrated by

Figures 3A and 3B.

  In all cases, as for the counter-grid 26, these knives are made of hardened steel, and undergo a surface treatment, for example

  nitriding, in order to give them high mechanical properties.

  The crusher of the invention is obviously not limited to the embodiments shown and described above but covers all the variants thereof.

  in particular as regards the number and the shapes of the orifices 44 of the counter-grid 26, the number of branches and the shapes of the knife holder 28.5 as well as the shapes of the knives, the counter-grid 26 and the holder knives 28 can be adapted to all grinder sizes.

Claims (10)

  1. Multi-knife mill, especially used in the food industry, provided with material supply means (12, 16, 18), comprising in the direction of flow of the material, a counter-grid (28) provided with at least one orifice (44), a knife holder (30) provided with at least one knife (52), and a grid (22), characterized in that the knife (52)   includes at least one edge of wavy shape.   2. Multi-knife mill according to claim 1, characterized in that each knife (52, 54, 56, 58, 60) comprises two cutting edges, a first (72) adjacent to the grid (22) and a second (74 ) adjacent to the counter-grid (28), which have an undulating shape whose radius at a considered point of the edge is proportional to the distance separating the point considered   of the axis (27) of rotation of the knife holder (30).   3. Multi-knife mill according to one of claims 1 or 2,   characterized in that each knife (52, 54, 56, 58, 60) has one side   (70) cutting which has a rectilinear shape in the transverse direction.   4. Multi-knife mill according to one of claims 1 or 2,   characterized in that each knife (52, 54, 56, 58, 60) comprises a cutting face (70) provided with means (88) of fragmentation produced by a double shape curved in the transverse direction, the first (84) being attached to the   first edge (72) and the second (86) to the second edge (74).   5. Multi-knife mill according to any one of claims   above, characterized in that the assembly constituted by the counter-grid (28) and the knife holder (30) comprises means (67) for shifting   the cutting attack of each knife (52).   6. Multi-knife mill according to claim 5, characterized in that the means (67) for shifting the cutting attack are constituted by a choice of the number of knives (52), different from the number of orifices (44) of the counter grille (28).   7. Multi-knife mill according to claim 5 or 6, characterized in that the means (67) for shifting consist of an angular distance formed between two consecutive knives and / or two consecutive orifices of the different counter-grid (28).   8. Multi-knife shredder according to any one of claims   previous, characterized in that each knife (52, 54, 56, 58, 60) has a   profile (66) of toothing which is alternated from one knife to another.   9. Multi-knife mill according to any one of claims   previous, characterized in that the knives (52, 54, 56, 58, 60) are   removably attached to the knife holder (30).   10. Multi-knife mill according to any one of claims   previous, characterized in that the peripheral edge of the orifices (44) of the counter-grid (28) has a scalloped shape, and comprises at least one edge (50) protruding, over the entire thickness.