BACKGROUND ART Granulators are manufactured in a range of various sizes and configurations. A feature common to these granulators is that they have an infeed section or hopper which, on the one hand, diverges outwards for infeed of the material to be granulated, and, on the other hand, discharges inwards towards the mill housing, where the actual granulation takes place. In order to reduce or obviate the risk of injury, the two openings are placed in such spaced apart relationship to one another that the person feeding in the material to be granulated cannot reach into the mill housing during operation. The infeed section has a fixed size, both as regards the distance between the two openings and the cross sectional areas of the two openings.

Typically, the infeed section is relatively large in relation to the dimensions of the granulator and the mill housing as well as the material which is to be granulated. The reason for this is that it must be possible to make maximum use of the capacity of the granulator, and also that the need for pre-grinding or comminution of the material before it can be granulated is eliminated.

The granulator must be able to be used for different types of materials. Occasionally, it may be relevant to granulate bulky and relatively thin-walled material, such as for example plastic cans and beer crates. On other occasions, the same machine must be capable of granulating solid plastic lumps, for example plastic material which, on cleaning, has been emptied out of sprayers for injection moulding.

The different properties of the various types of materials require different geometries in the mill housing. For the bulky and thin-walled material, a relatively roomy mill housing is required, in order that the material can be accommodated at all in the mill housing. Moreover, the granulation will be more rapid and efficient if the material can be compacted or crushed in connection with the granulation. On the other hand, the hard, solid material should not fall too far down in the mill housing before it has had time to be processed, but should remain in the upper area of the mill housing during a gradual processing.

Thus, configuration, material properties and material thickness in the material which is to be granulated can in certain cases entail that the cutter in the mill housing stops. What happens then is thus that material of an excessively hard and compact nature has fallen so far down in the mill housing that the cutter and the blades do have not sufficient force to complete the comminution operation. The result will be operational stoppage with consequential time-and work-consuming cleaning of the machine. One possibility of reducing the risk of this type of operational stoppage is that the material is first divided into smaller pieces of suitable dimensions, but this requires an additional working phase and machinery. Another method of counteracting operational stoppage is to restrict the size of the mill housing so that large sized material does not entirely fall down into the mill housing, but that it gradually sinks down according as the cutter and the blades have granulated the lower area of the material.

Granulators with a large infeed section or hopper and small mill housing constitute, however, no ideal solution, since this implies an inflexible design and construction. Moreover, this construction entails an unnecessary time wastage when easily processed material is to be granulated, since such material does not need to be processed a little at a time.

A better method of solving the problem is to provide an existing mill housing with different types of rear sides which each imparts to the mill housing different sizes and configurations.

In such instance, the size of the mill housing is thus reduced within the framework of the maximum possible mill housing. For example, a thicker rear side or a rear side projecting into the mill housing can be mounted. In this instance, one or more fixed blades are placed on the inside of the rear side. The position of the blade or blades is dictated by the geometry of the rear side and the desired properties of the granulation.

This mode of approach has achieved a certain improvement of the above-described problematical situation. However, one problem is that an upper region of the rear side may be

of such shape that a"shelf'occurs inside the mill housing and that material or partly processed granulate is accumulated on this"shelf'. Another problem is that the material which is to be granulated and which is placed in the upper infeed opening is not fed in in a suitable manner into the inlet of the mill housing, since this has been made smaller than originally.

PROBLEM STRUCTURE There is thus a need in the art to realise an adaptation of the size and configuration of the inlet to the mill housing. This adaptation must be capable of being carried into effect in a simple and readily manageable method for different types of materials.

SOLUTION The object forming the basis of the present invention will be attained if the granulator intimated by way of introduction is characterised in that the infeed section is movable on the mill housing for adaptation to the replaceable rear side so that a substantially smooth transition is formed between the inside of the mill housing and the inside of the infeed section.

BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS The present invention will now be described in greater detail hereinbelow, with particular reference to the accompanying Drawings. In the accompanying Drawings: I Fig. 1 is a perspective view of a granulator according to the present invention; Fig. 2 is a perspective view of a part of the granulator of Fig. 1 with the mill housing in the open position and the infeed section tilted rearwardly; Fig. 3a is a schematic view of the mill housing with the fixed blades and a replaceable rear side; Fig. 3b is a view according to Fig. 3 a with a second rear side;

Fig. 3c is a view according to Figs. 3a and 3b with a third rear side; Fig. 4 is a straight side elevation of the granulator; and Fig. 5 is a straight side elevation of a part of the granulator with the mill housing in the open position and the infeed section tilted rearwardly.

DESCRIPTION OF PREFERRED EMBODIMENT Fig. 1 shows a granulator 1 in perspective obliquely from above. The granulator 1 has uppermost an infeed section 2 which is disposed above a mill housing 6 beneath which there is disposed a receptacle device 7 for finished granulate. The infeed section 2 has, in turn, a front section 3 and a main section 4. The front section 3 has an opening 5 for the infeed of the material that is to be granulated. The front section 3 of the infeed section is open through- going towards the main section 4 of the infeed section. The main section 4 is, in turn, open downwards so that infed material is passed down into the mill housing 6.

The mill housing 6 is accessible for cleaning and maintenance.

The receptacle device 7 receives the finished granulate when the particles in the granulate have assumed such size that they can pass through a grid or sieve above the receptacle device 7.

Fig. 2 shows the main section 4 of the infeed section, the mill housing 6 and the receptacle device 7. The main section 4 of the infeed section is tilted rearwards, at the same time as a front region of the mill housing 6 is opened so that the inside of the mill housing 6 is accessible.

The mill housing 6 displays a rotary cutter 8 with a number of blades uniformly distributed around the cutter 8. Further, there is a number of fixed blades 9 disposed in spaced apart relationship around the rotary cutter 8. The positioning of the fixed blades 9 may be varied above all in the construction, but also depending on the type of material that is to be granulated. The mill housing 6 has a replaceable rear side 11 by means of which the size and configuration of the mill housing 6 may be varied. The replaceable rear sides 11 also permit a

variation of the positioning of the fixed blades 9. In such instance, optimum granulation conditions will be realised for different material types.

Figs. 3a-c schematically show cross sectional views of the mill housing 6. A number of fixed blades 9 are disposed around the cutter 8 which is disposed between a pair of similarly rotary side walls 10. The positioning of the blades 9 is merely to be viewed as one of many examples of positioning. The Figures show three different examples of rear sides 11 la, 1 lb, lie which may be employed, but in practice only one rear side is provided at a time. Some of the fixed blades 9 are disposed on or in association with the replaceable rear sides 1 la, 1 lb, lie.

The substantially planar and slightly inclining rear side 11 a is particularly suitable in the granulation of the hard and compact material. The size of the mill housing 6 is considerably limited and the position and angle of the fixed blade 16 permit granulation of the material to take place high up in the mill housing. The fixed blade 16 is disposed at the periphery of the cutter 8 at a position around"one o'clock". Each time the material is struck by one of the moving blades 17 of the cutter 8, possibly in a scissors-like engagement with one of the fixed blades 9,16, a small piece of the material will be cut, knocked or torn off. At the same time, an impulse is imparted to the material which counteracts gravitational forces which cause the material to move downwards. Before the material piece is totally granulated, it will, during a certain period of time, move in the area above the rotary cuter 8 in such a manner that it appears as if the material"bounces".

The rear side lib in Fig. 3b extends downwards so far that a fixed blade 16 disposed at its lower edge is disposed approximately at position"three o'clock". The upper end 18b of the rear side 1 lb is disposed further away from the cutter 8 than the corresponding end 18a of the rear side lla. The inclinations of the two rear sides lla and llb are, in the preferred embodiment, substantially the same, but the different positionings of the ends of the rear sides 1 la, 1 lb realise differences in the volume and configuration in the mill housing 6. The rear side lib is suitable for material where the demand is not as stringent on a gradual comminution, but it is possible to accept moderately large pieces of the material being cut up in engagement between the fixed blades 9,16 and the moving blades 17. The exact configuration and inclination of the rear sides 1 la and lib may be varied, provided that the granulate does not accumulate in any given area thereof.

The rear side lie in Fig. 3c has its lower end and the fixed blade 16 mounted thereon disposed at position"five o'clock". At the same time, the rear side lie is not substantially planar but has a cross section which approximately corresponds to a part of an x2 curve.

Material which is to be granulated has every possibility of falling down completely or partly outside the periphery of the cutter 8. The material tends more or less rapidly to be drawn in inside the periphery of the cutter 8, where the cutter 8 contributes in compacting or crushing the material. Moreover, the volume and configuration of the mill housing 6 are suitable for bulky material.

Thus, Figs. 3a, b and c illustrate that the size and configuration of the mill housing 6 are varied when the rear sides 1 la, 1 lb, 1 c are replaced and there is thereby obtained a certain adaptation to the material that is fed in. Large and compact material pieces will, by means of a suitable rear side lla, l lb, llc, be held in place in a relatively high position so that only small chips of the material are released and a blocking of the cutter 8 is prevented. A comminution or fine division of the material takes place every time a blade in the cutter 8 enters into scissors-like engagement with one of the fixed blades 9. Besides, the blades 9 are slightly angled for realising an optimum engagement with the cutter 8.

Figs. 3a-c show also that the upper region 18a, 18b, 18c of the rear sides lla, llb, llc assume different positions. The upper region 18a of the rear side 1 la is, for example, located further to the left in Fig. 3 than the other regions 18b, 18c of the rear sides lib, lie. In order that the different rear sides l la, l lb, l lc function in practice, an adaptation is needed of the infeed section 2.

As was mentioned by way of introduction, it is vital to avoid that"shelves"occur inside the granulator 1 at the transition between the infeed section 2 and the mill housing 6. In order that the above-described rear sides lla, 1 lb, l lc function for the different granulation cases, it is of the utmost importance that the position of the infeed section co-operate with and be adapted to the volume and configuration of the mill housing 6. Otherwise, the sought-for effects may be counteracted and, in the worst case, not materialise at all.

In Fig. 4, which shows the granulator straight from the side, it is shown how the infeed section 2 is pivotal around a front pivot axis 13 for opening, closing and cleaning. However, there is also a rear position for the infeed section 2 so that it becomes pivotal around a rear

pivot axis 14. The infeed section 2 is thus movable in a forward/rearward direction, seen from a position centrally of the infeed opening 5. Hereby, the position may be selected for the infeed section 2 in which the best adaptation to the pertinent rear side 11 is achieved. Thus, an adaptation of the infeed section 2 is obtained to the material which is to be processed in the granulator 1. In this context, it should be observed that the borderline between the infeed section and the mill housing 6 need not necessarily lie in a horizontal plane, but could juste as well lie in an inclining plane.

The two different positions for the infeed section 2 thus have two different pivot axes 13,14.

In the preferred embodiment, the pivot axes 13,14 are realised by cylindrical pins 19. The pins 19 are inserted in holes in the infeed section 2 and the upper area of the mill housing 6.

The outer ends of the pins 19 are provided with threading so that a removal tool with corresponding threading is applicable when the pins are to be removed on switching between the two different positions. A long series of other methods of concretely realising the pivot axes 13,14 is possible.

Moreover, the infeed section 2 is reversible so that the infeed opening 5 faces in the directly opposite direction. This gives an adaptation to different external environments and configurations of neighbouring machinery. On reversal, the holed parts of the infeed section 2 are moved to that side which was previously turned to face away from the pivot axes 13,14, so that the pins 19 are once again insertible in holes in the infeed section 2 and the upper area of the mill housing 6. A corresponding movement of parts on the opposite side also takes place.

Fig. 5 shows a straight side elevation of those parts of the granulator 1 which were shown in Fig. 2. However, in Fig. 5 it is more clearly visible how the main section 4 of the infeed section 2 is pivotal around an axis 13 when it is tilted upwards and rearwards. The alternative axis 14 is also shown. In order to make possible a simple opening of the granulator 1, there is provided at least one support device 15 in the form of a screw jack or a gas spring at the side of the granulator for supporting the main section 4 of the infeed section 2. The support device 15 is, at its upper end, secured at the side edge of the infeed section 2. The anchorage point in the infeed section is displaced on switching between the two positions, and the angle of the support device is also changed to a vertical axis, as well as the stroke length of the support device 15. Magnet switches at the upper anchorage point permit the angle and stroke length of the support device 15 to be altered.

The granulator 1 may be varied without departing from the scope of the appended Claims.