The invention also relates to a granulation mill comprising the feeding device.

PRIOR ART

When taking care of left-over material, such as remains from industrial production of objects made from plastics, granulation mills are often used in order to disintegrate the material, so that it can be recirculated into the production or be recovered in any other way.

A typical example of such a production process is thermal forming of thin- walled products from a plastic material in sheet or web form. The products are formed and stamped out of the material in an automated method, and a plastic grid remains to be taken care of in the above mentioned way, either in parts or continuous.

In many cases there is a granulation mill arranged as part of the production line. In order to save space said mills are often made small and compact, so that they will be easy to place in between, underneath or consecutively after molding or stamping machines, packaging machines, and conveyors for the manufactured products, depending on the respective production line. The recirculation of the disintegrated material into the production can be completely or partly automatized. In general, the granulation mill has a feeding part, which is provided with two feeding rolls, rotating in mutually opposite directions, so that the material is fed inwardly into the granulation mill between the rolls. Since the feed material is not always completely flat and further, often has a certain thickness, the rolls must be arranged at a distance from each other in order to permit the feeding.

The compact size of the granulation mill has the disadvantage that the feeding part is situated very close to the mill housing, wherein a rotor provided with knives rotates at a high speed and with much power cuts the feed material in cooperation with one or several stationary knives in the mill housing.

The power and the speed of the rotor implies that partly disintegrated material is thrown around in the mill housing, and there is a risk for such fragments to be thrown upwardly towards the feeding part. Because of the short distance between the feeding part and the rotor in the mill housing, there is thus a risk for fragments of the material to pass past the rolls in the feeding device in a direction opposite to the feeding direction. Such fragments, which thereby will get out of the granulation mill, are called "fly-backs", and they will cause littering, but also result in an increased security risk, since they can be sharp, and do have a rather high velocity. Further, there is risk for contamination or defects of the manufactured products, since these "fly-backs" can reach the molding step in the production, and be completely or partly pressed into the products, which will then be defective.

THE PROBLEM

Accordingly there is a need to reduce or completely eliminate the occurrence of "flybacks" and the disadvantages associated therewith.

SOLUTION OF THE PROBLEM

The object of the present invention as achieved when the feeding device defined in the preamble is characterized in that the catcher is yielding and non-locking in order to stay in close contact with the feeding roll and prevent return of disintegrated material past the feeding roll. Further advantages will be achieved if the feeding device is also given one or several of the characterizing features of claims 2 - 8.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described with reference to the attached drawings. In the drawings:

Fig la shows a view in perspective of a granulation mill having a feeding device according to the invention;

Fig lb a cross-sectional view of the granulation mill according to Fig 1;

Fig 2 a simplified cross-sectional view of one embodiment of the feeding device;

Fig 3a-c simplified views in perspective from different angles of the feeding device according to Fig 2;

Fig 4a a view corresponding to Fig. lb of a second embodiment of the feeding device and the granulation mill;

Fig 4b a view corresponding to Fig 2 of a second embodiment of the feeding

device; Fig 4c a view corresponding to Fig 3b of a second embodiment of the feeding device; and

Fig 4d a view corresponding to Fig. 3c of a second embodiment of the feeding device. PREFERRED EMBOIDMENT

Figure la shows a granulation mill 1 according to the invention in a perspective view obliquely from above.

A material 2 in sheet form is on the way to be fed into the feeding device 3 in order to be disintegrated and subsequently to be recovered. The granulation mill 1 has compact dimensions, so that it is not made more bulky than necessary, but still so that the power demand for the disintegration of the material can be obtained without any problems.

A cross section through the granulation mill 1 is shown in Fig. lb. According to the preferred embodiment a rotor 4 is provided with four knives 5. In the walls of the mill housing 6 there are three stationary knives 7. When a movable knife meets a stationary knife, material 2 being between the knives 5, 7 will be disintegrated. Material 2 having been disintegrated and having a sufficiently small size will pass through a grid 8 in the wall of the mill housing 6, and are discharged for recovery (not shown).

Of particular interest in the present embodiment is the feeding device 3, which is shown in a larger scale in Fig. 2. A rotating feeding roll 9 is arranged immediately inside an elongate feeding opening 10. At least one scraping means 11 is arranged along the feeding roll 9, in order to prevent the fed in material 2 from being attached to the feeding roll 9 and from being rolled around it. The scraping means 11 also prevents partly disintegrated material from swirling up from the mill housing 6 to attach to the feeding roll 9 and thereby be fed out through the feeding opening 10.

Along the feeding roll 9, and substantially in parallel therewith, there is a catcher 12, which is in contact with the feeding roll 9, and closes the lower part 16 of the feeding opening 10, so that material from the inside of the mill housing 6 cannot escape therefrom. The lower part 16 of the feeding opening is thus wedge-formed. In order to make it possible to feed in material 2 having a certain thickness, the catcher 12 is spring- mounted, and thereby allows the thickness to vary within an interval from 0 (i.e. the catcher is in contact with the feeding roll) to a thickness so large that the catcher 12 is turned back into the very back. The thickness variation is mostly a question of dimensioning, and is adapted after the maximum thickness of the material 2 to be processed by the granulation mill. In the embodiment shown in Fig. 2 the catcher is pivoted on a pivot axle 13, which is substantially in parallel with the feeding roll 9. Accordingly, the catcher 12 is pivoting to and from the feeding roll 9 around this axle. A spring means 14 is arranged at that end of the catcher 12, which is opposite to the pivot axle 13, in a direction across the plane of extension of the catcher 12. In the preferred embodiment, the spring means 14 is a compression spring, so that the catcher 12 normally is urged into contact with the feeding roll 9, or to a position with a strictly controlled minimum slot between the roll 9 and the catcher 12, but yields under the action of the material 2, which is dragged in by the feeding roll 9. The spring rate of the compression spring 14 is fixed purely as a dimensioning action depending of the expected field of applications, the dimensions of other inherent components, and factors such as the power used for making the feeding roll 9 to rotate. One variant is that the spring rate of the compression spring 14 is variable or adjustable as desired, according to the skills of the man skilled in art.

Since the supplied material 2 often does not have the same thickness over the whole width, it is advantageous if the catcher 12 is divided into a number of sections 12a, 12b, 12c, etc., such as is shown from different angles in Figs. 3a - 3c. The different sections 12a, 12b, 12c are individually pivotable around the pivot axle 13, and are each provided with a separate spring means 14. Only those sections 12a, 12b, 12c that are affected by a force from the supplied material 2 are therefore pivoted away from the feeding roll 9, and only to the extent necessary for the material 2 to be able to pass through. In Figs. 3b and 3c are shown that only one of the sections 12a, 12b, 12c of the catcher has yielded away a distance from the feeding roll, while the other sections 12a, 12b, 12c are in contact with the feeding roll 9. Accordingly it is possible to feed material 2 having a thickness which varies along its width, without having to open the catcher 12 completely according to the largest thickness of the material 12. The probability for that disintegrated material 2 from the mill housing 6 could pass past the feeding roll 9 and the catcher 12 is therefore minimized.

ALTERNATIVE EMBODIMENT

In Figs. 4a - 4d an alternative embodiment of the invention is shown. The catcher 12 is divided into sections 12a, 12b, 12c being individually movable to and from the feeding roll 9, and which are biased towards the feeding roll 9. In these aspects the feeding device 1 corresponds to the above described embodiment. In the alternative embodiment the sections 12a, 12b, 12c of the catcher 12 have been given an oblique abutment surface 15 to be in contact with the feeding roll 9. At the end of the respective sections 12a, 12b, 12c being opposite the abutment surface 15, a spring means 14 is arranged, so that the respective section 12, 12b, 12c yield in a non- locking fashion in relation to the feeding roll 9, in a way which resembles the yielding in a non-locking fashion according to the above described embodiment. When feeding material 2 with the aid of the feeding roll 9, the oblique abutment surface will imply that the fed in material 2 exert a force on the sections 12a, 12b, 12c of the catcher 12, substantially in the longitudinal direction of the spring means 14, so that this will be compressed and the sections 12a, 12b, 12b of the catcher 12 will yield.

Still another embodiment comprises a series of catcher rolls arranged substantially in parallel with the feeding roll 9. The catcher rolls are arranged in a line with small or negligible gaps in between, similar to the above described catcher sections 12a, 12b, 12c. The catcher rolls are arranged to be individually yielding and non- locking, also similar to the above described catcher sections. Since the catcher rolls are individually pivotable, they will be set in motion by the feeding roll 9, either in direct contact therewith, or through contact with supplied material 21, which is set in motion into the granulation mill 1 by the feeding roll 9. The force which must be exerted by the feeding roll 9 in order to feed the material 2 will typically be less in comparison with the embodiments with the catcher sections 12a, 112b, 12c, since the roll friction between the material 2 and the catcher rolls in general is smaller than the sliding friction between the material 2 and the catcher sections 12a, 12b, 12c. The illustrated embodiments are only examples of the different constructions which the skilled artisan could use in order to vary the invention according to the principles, which are common for the embodiments and within the scope of the attached claims.