DESCRIPTION

5 The present invention refers to a scrap shredder (waste, machine scrap, recycling material, etc), which includes:

- a supporting structure carrying a loading compartment;

- a rotor - placed in a seat (open at the bottom for discharging the shredded scrap) made in the bottom wall of the loading compartment - which shreds the scrap falling from the

10 loading compartment due to the gravity;

- a pair of opposed mobile pushers designed to push alternately the scrap to be shredded against the rotor; and

- means (not described herein since they are already known) designed to move the rotor and the pushers.

L5

As known, the rotor normally comprises a cylindrical body that carries multiple protruding tools, which interact with other tools fixed to the two sides of the seat in which the rotor moves.

Known scrap shredders comprise one or more rotors placed at the bottom of a sidewall of 10 the loading compartment and a horizontally mobile pusher that pushes the scrap against the at least one rotor.

Sometimes a second, vertically mobile, pusher is provided, which pushes the scrap against the at least one rotor. .5

These known shredders have some drawbacks, including the fact that:

- a solid body (much) larger than the cutting zone of the rotor rests against the wall of the loading compartment behind the rotor without being able to be shredded further, forcing the shredder to be stopped for repositioning such a solid body and, sometimes, for

50 removing it from the loading compartment; in order to avoid this drawback, it is possible to increase the number of rotors and/or their diameter, but this involves an increase in the power consumed by the rotor (or by the rotors) and often requires the use of expensive coupling means such as, for example, oleodynamic couplings, with a considerable cost increase;

55 - when the pusher has reached the end of its stroke it has to be moved backward to make other scrap to be shredded drop from the loading compartment: each working cycle hence

includes a fairly significant dead time, which reduces the shredder's productivity.

Object of this invention is to develop a scrap shredder designed to remedy the limitations presented by the known shredders; this object is achieved by means of a scrap shredder providing the characterising elements illustrated in claim 1.

Additional advantageous characteristics of the invention are the subject matter of the dependent claims.

The invention will now be described with reference to the purely illustrative (and hence not restrictive) embodiments illustrated in the appended figures, where:

- figure 1 shows schematically a longitudinal section view of a scrap shredder according to the invention;

- figures 2a-2m show schematically, in sequence, some phases of the work cycle of the shredder of figure 1 ;

- figure 3 shows very schematically a longitudinal section view of another possible embodiment of the shredder of figure 1.

The corresponding elements will be identified in the appended figures using the same numerical references.

Figure 1 shows schematically a longitudinal section view of a scrap shredder 1 according to the invention, which includes at least a loading compartment 3, a rotor 4 located in a seat open underneath (not visible in the appended figures because it is occupied by rotor 4) provided in the bottom wall of the loading compartment 3 and a pair of opposed mobile pushers (5, 6), cooperating each other, designed to push towards the rotor 4 the scrap dropping from the loading compartment 3 due to the gravity.

The front ends of the pushers (5, 6) are facing one another and each pusher (5, 6) has an alternate movement opposite to that of the other pusher (6, 5).

It is an important characterising feature of a scrap shredder according to the invention the fact that the pushers move the scrap so that the scrap path is tangent to the rotor and the scrap is "milled" by the rotor, without being pressed against the rotor as occurs in scrap shredders of the prior art.

As will be better disclosed with reference to the appended drawings 2a-2m, it is a further important characterising feature of a scrap shedder according to the invention the fact that, when the material included between the pushers (5, 6) and pushed towards the rotor 4 by a pusher cannot be (further) compressed, said pusher continues its stroke and the other pusher moves back, maintaining a preset pressure on the material included between the pushers (5, 6).

Preferably, the pushers (5, 6) are operated by means (such as, for example, oleodynamic means) whose action can be controlled.

Preferably, the seat in which the rotor 4 is placed is made in the centre of the bottom wall of the loading compartment 3.

The shredded scrap drops (arrow S) through the aperture of the seat containing the rotor 4 and is collected in a manner already known.

The shredder 1 also includes a supporting structure 2 which carries the loading compartment 3, the rotor 4, the additional tools (not shown in the appended figures for simplicity of graphical representation) located in the sides of the seat containing the rotor 4 and means designed to move the rotor 4 and the pushers (5, 6); these moving means and the rotor 4 will not be described herein because they are already known and in any case they are extraneous to this invention.

It can be seen from figure 1 that the ends of the pushers (5, 6) facing one another have an arched shape, which substantially prevents the scrap located in the loading compartment 3 from coming into contact with the rotor 4 when the rotor 4 starts to turn (figures 1 and 2a) or when it inverts its direction of rotation (figures 2f and 2m); in both cases the arched form of the pushers (5, 6) reduces the amount of energy consumed by the rotor 4 on starting, respectively when it inverts its direction of rotation.

This arched shape also helps to push the scrap toward the rotor 4.

The working cycle of the shredder 1 will now by described with reference to figure 2 (figures 2a-2m), which shows schematically, in sequence, some of the steps of this working cycle.

In figure 2 the direction of rotation of the rotor 4 and the directions of displacement of the pushers 5 and 6 are indicated thought arrows.

After loading the scrap to be treated in the loading compartment 3 with the two pushers 5 and 6 in contact with one another in order to prevent the scrap from coming into contact with the rotor 4 (figures 1 and 2a), the rotor 4 starts to turn.

Then a first pusher (the pusher 5 in figure 2) is moved backward (figure 2b), away from the second pusher (the pusher 6 in figure 2), so that the scrap can drop from the loading compartment 3 in front of the rotor 4; when the first pusher 5 has reached the end of its backward stroke, it changes direction (figure 2c) and the scrap is pushed towards the rotor 4 and the second pusher 6 (figure 2d).

When the material (the compressed scrap or a rigid body) included between the pushers (5, 6) cannot be (further) compressed in between them, the first pusher 5 continues its stroke and the second pusher 6 is moved back by the material that cannot be (further) compressed (figure 2e) maintaining on the material a pressure, opposite to that of the first pusher 5, which controls the material moving towards the rotor.

When the first pusher 5 has reached the end of its stroke (figure 2f), the second pusher 6 continues its backward stroke until it reaches the end of such backward stroke (figure 2g); during this further backward stroke the scrap to be treated drops due to the gravity from the loading compartment 3 between the first pusher 5 and the second pusher 6 substantially without coming into contact with the rotor 4 which, when the second pusher 6 has completed its backward stroke, inverts its direction of rotation without being substantially impeded by the scrap.

The second pusher 6, when it has reached the end of its backward stroke, reverses its motion direction (figure 2h) and pushes the scrap towards the rotor 4 and the first pusher 5 (figure 2i).

When the material (the compressed scrap or a rigid body) included between the pushers (5, 6) cannot be (further) compressed, the second pusher 6 continues its stroke and the first pusher 5 is moved back by the material that cannot be (further) compressed (figure 21).

Finally, when the second pusher 6 has reached the end of its stroke (figure 2m), the first pusher 5 continues its stroke until it reaches the end of the backward stroke, when the rotor 4 once again inverts its direction of rotation.

Therefore rotor 4 inverts its direction of rotation cyclically.

At this point the motion of the first pusher 5 is inverted once more for pushing the scrap towards the rotor 4 and the second pusher 6. The work cycle described previously (figures 2c-2m) is repeated.

During the additional backward stroke of the first pusher 5, the scrap to be treated drops down due to the gravity from the loading compartment 3 between the first pusher 5 and the second pusher 6, without coming into contact with the rotor 4 and without impeding the further inversion of the direction of rotation.

The working cycle described above may be managed by a logic unit, the operating program of which may be prepared by a skilled person without having to perform an inventive step; the logic unit and the peripherals (sensors and actuators) with which it is interfaced have been omitted in the appended figures for simplicity of graphical representation.

If compared with a known shredder, a shredder 1 according to the invention offers numerous advantages, including:

- it does not have dead times (or it has absolutely negligible dead times) since there is always one pusher (5 or 6) pushing the scrap to be treated toward the rotor 4;

- the rotor 4 is positioned in the bottom wall of the loading compartment 3 and it is hence able to treat body of any size, even in several "sweeps";

- this means that the shredder does not have to be stopped in order to reposition or to remove large solid bodies; - the rotor 4 may have a reduced diameter and, hence, with the same power consumption it can exert a greater force on its tools; in addition, the rotor 4 has a lower inertia, which allows it to be turned and to have its direction of rotation inverted with lower electrical overloads;

- if the logic unit is present, it is possible to optimise the operation of the shredder 1 by adjusting, in relation to the characteristics of the scrap being treated and of the pressure made by the pushers, the movement speed of the pushers, which is related to the energy

consumed by the rotor 4.

Figure 3 shows very schematically a longitudinal section view of another possible embodiment of a shredder according to the invention, which differs from that shown in figures 1 and 2 essentially due to the fact that the planes 11 and 12 on which the pushers 5 and 6 slide, rather than being horizontal, are inclined relative to the horizontal by an angle of about 20 degrees (and in any event falling between about 0 and about 40 degrees) and converge toward the rotor 4.

Figure 3 shows the shredder 1 and its supporting structure 2 which carries the planes 11 and 12 on which the pushers 5 and 6 slide.

Without diverting from the scope of the invention, a skilled person may make to the previously described scrap shredder all the modifications and the enhancements suggested by the normal experience and/or by the natural technological development.