Abstract:
A granulator mill includes a mill housing with an openable part and a fixed part, a rotor which is rotary inside the mill housing and has a number of blades for co-operation with at least one fixed blade mounted in the mill housing and a discharge section whose interior is discrete from the interior of the mill housing by means of a grid through which granulate passes from the mill housing to the discharge section. The openable part of the mill housing is connected to the fixed part by the intermediary of a pivot device with a pivot axis which is substantially vertical in the normal position of use of the granulator mill.

Description:
TECHNICAL FIELD 
     The present invention relates to a granulator mill which comprises a mill housing with an openable section and a fixed section, a rotor which is rotary inside the mill housing and has a number of blades for co-operation with at least one fixed blade mounted in the mill housing, and a discharge section whose interior is discrete from the interior of the mill housing by means of a grid through which granulate passes from the mill housing to the discharge section. 
     BACKGROUND ART 
     In the employment of granulator mills within the plastics industry for recycling or reuse of plastics, it is necessary to carefully clean the interior of the granulator mill before a change can be made to a new plastics quality or plastics colour. This entails demands, on the one hand, that the interior of the mill housing must be accessible, as well as the interior of the receptacle section in which the finished granulate is collected and from which the granulate is conveyed off, as a rule via a conduit. For this reason, mill housings have previously been constructed to be openable so that a part is openable in relation to that part in which the rotor of the granulator mill is journalled. In these prior art constructions, the openable part is pivotal about a horizontal axis and suspended in its lower edge. 
     Constructions of this type entail demands for auxiliary tools on opening and closing the openable part, since this is so heavy that it cannot be handled manually. 
     The openable part further has a very limited opening angle because of the suspension in an area beneath the mill. The reason for this is that the substrate on which the granulator mill stands quite simply prevents opening of the openable part to any larger opening angle. 
     Further, it has often been necessary in these prior art constructions first to dismantle the discharge section in order to be able to get at the openable part at all. 
     Taken as a whole, prior art mills have been difficult to access interiorly so that, as a result, cleaning of a mill has proved to be circumstantial and time-consuming. 
     Problem Structure 
     The present invention has for its object to design the granulator mill intimated by way of introduction so that the drawbacks inherent in prior art technology are obviated. In particular, the present invention has for its object to realise a granulator mill in which the openable part may readily be opened and closed manually without auxiliary tools or aids, where considerably greater access is afforded to the interior of the mill in the open state than has been possible hitherto, and also where the discharge section and grid are readily accessible for cleaning. 
     Solution 
     The object forming the basis of the present invention will be attained if the granulator mill intimated by way of introduction is characterised in that the openable part of the mill housing is connected to the fixed part by the intermediary of a pivot device with a substantially vertical pivot axis in the normal position of use of the granulator mill. 
     As a result of these features, the advantage will be afforded that the openable part may readily be opened manually, since its point of gravity does not undergo any change in height on opening and closing. Further, the pivoting about the vertical axis permits the opening angle to be made considerably greater, for which reason accessibility is correspondingly improved. 
     According to expedient and advantageous embodiments of the present invention, the discharge section and the grid are suitably fixed in and supported by the openable part of the mill housing and are pivotal together therewith. 
     As a result of these features, it is possible, in a simple and convenient manner to gain access also to these components for cleaning. 
    
    
     
       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: 
         FIG. 1  is a perspective view of a granulator mill seen obliquely from above from a first end of the rotor shaft; 
         FIG. 2  is a view corresponding to that of  FIG. 1 , the granulator mill being, however, seen from the opposite end of the rotor shaft; 
         FIG. 3  is a view corresponding to that of  FIG. 1 , the openable part of the mill housing as well as the infeed hopper of the granulator mill being open; 
         FIG. 4  is a vertical cross section through the granulator mill; 
         FIG. 5  is, on a larger scale, a perspective view of the region according to the arrow  1  in  FIG. 1 ; and 
         FIG. 6  shows, in perspective, the openable part of the mill housing seen from the inside. 
     
    
    
     DESCRIPTION OF PREFERRED EMBODIMENT 
     In  FIGS. 1 and 2 , which show a granulator mill in perspective seen from different directions, reference numeral  1  relates to a fixed part of a mill housing in which the rotor of the granulator mill is journalled. Correspondingly, reference numeral  2  relates to an openable part of the mill housing, while reference numeral  3  relates to the removable rear side of the mill housing and reference numeral  4  relates to the infeed hopper of the granulator mill. The infeed hopper  4  is openable in relation to the mill housing by pivoting about the pivot axis shown by the broken line  5 . Since the infeed hopper is of considerable weight and size, auxiliary equipment is required for opening and closing, in the form of a motor  6 , a toothed gear  7  and a screw device  8  connected thereto. 
     In order to avoid the use of mechanical aids on opening and closing the openable part  2  of the mill housing, this is arranged in such a manner that it substantially does not undergo any vertical displacement during an opening and closing cycle. This is realised in that the openable part  2  is secured in the fixed part  1  of the mill housing by means of a pivot device which is disposed, in the vertical direction, to keep the point of gravity of the openable part  2  substantially constant and which, to this end, is provided with a substantially vertical pivot axis  9  illustrated by broken lines in  FIGS. 1 to 3  and  6 . 
     The pivot device with the substantially vertical pivot axis  9  has mutually pairwise engaging guide surfaces, on the one hand on the fixed part  1  of the mill housing and, on the other hand on its openable part  2 . These guide surfaces are at right angles to the pivot axis  9  and are disposed, on the one hand on projecting lugs  10  on the fixed part  1  of the mill housing and, on the other hand on projecting lugs  11  on the openable part  2  of the mill housing. In the illustrated embodiment ( FIG. 2 ), it is apparent that the fixed part  1  of the mill housing has four such guide surfaces, which also applies to the openable part  2 . 
     The pivot axis  9  is defined by a cylindrical pin which constitutes the physical pivot shaft between the fixed part  1  and the openable part  2 . This implies that the pivot shaft (not shown on the Drawings) guides the openable part  2  in a direction towards and away from the rotor of the granulator mill of which only one stub shaft  12  is shown in  FIG. 2 . 
     It will be apparent from  FIGS. 3 and 4  taken together that the rotor is provided with a number of blades  13  at its periphery, in the illustrated embodiment three in number. Correspondingly, there are fixed blades  14  in the mill housing, both in the fixed part  1  and in the openable part  2 , of which blades the openable part has at least one. The fixed blades  14  are disposed closely adjacent to and co-operate with the blades  13  on the rotor and are, therefore, distributed around the peripheral surface of the rotor. 
     Internally in the rotor, but also internally in the mill housing, there is a space in which the comminution proper of the plastic material into granulate takes place. Where this comminution has proceeded sufficiently, the finely-divided particles or granulate pass through a grid  15  which may have varying mesh size. This grid  15  surrounds the rotor along a part of its periphery. On the underside or outside of the grid, there is a receptacle section  16  in which the granulate is collected and from which the granulate is conveyed off via an outlet  17 . The receptacle section  16  has, in the axial direction of the rotor, approximately the same extent as the blades  13  and  14 . 
     According to the present invention, both the grid and the receptacle section  16  are secured in and carried by the openable part  2  of the mill housing and they are, therefore, pivotal together with it. However, it is also conceivable that the receptacle  16  may be arranged on the fixed part  1  of the mill housing. 
     The grid  15  extends about the periphery of the rotor and in under it and at least up to a vertical line through the centre of the rotor shaft, but preferably also a short distance past this vertical line. In order not to impede the opening capability of the openable part  2 , the part  18  of the grid  15  located under the rotor is disposed in a tangential plane to the circumference of the rotor, this tangential plane being at right angles to the pivot axis  9 . This part  18  of the grid  15  may, therefore, suitably be substantially planar. 
     As is apparent from  FIGS. 3 and 4 , the openable part  2  of the mill housing surrounds approximately 140°-180°, preferably approximately 160° of the circumference of the rotor. 
     In  FIG. 4 , reference numeral  19  relates to a number of plates which are disposed with spacing in the longitudinal direction of the rotor shaft and which have edges facing towards the rotor which support the grid  15 . These plates  19  lie in the diameter plane to the rotor at right angles to its centre axis. Since the grid  15  enjoys good support from the arcuate edge surfaces of the plates  19  facing towards the rotor, the grid  15  is quite simply placed in a recess  31  in the openable part ( FIG. 6 ). As was intimated above, the grid is guided in the radial direction by the above-mentioned plates  19 , while, in the axial direction and in the circumferential direction, it is guided and positionally fixed by the edges of the recess  31  in the openable part  2 . 
     It will also be apparent from the Figures that the receptacle section  16  is placed beneath the openable part  2  of the mill housing. Suitably, the receptacle section  16  may be guided in a pair of sliding rails or grooves  32  on the underside of the openable part  2  so that the receptacle section  16  may thereby readily be drawn out from or slid into position again beneath the openable part  2 . 
     In the open state of the openable part  2 , approximately ¾ of the periphery of the rotor is free and readily accessible for cleaning. Further, after lifting off the grid  15 , it is simple to gain access to the inside of the openable part  2  in the plates  19  but also the interior of the receptacle section  16 . 
     In  FIG. 3 , the openable part  2  is shown in only the partly open state. If the space around the granulator mill permits, the openable part may be opened to up to circa 180° about its pivot axis  9 , which implies extraordinarily good access to the interior parts of the mill. For positioning the openable part in the correct position when this is located in the closed position, both it and the fixed part  1  of the mill housing have mutually engaging guide members. 
       FIGS. 3 and 5  show the one journal box  20  for the shaft of the rotor. The journal box  20  has a projecting flange  21  ( FIG. 3 ) by means of which the journal box  20  is secured in the fixed part  1  of the mill housing with the aid of a number of bolts  22  ( FIG. 5 ). The peripheral edge of the flange  21  serves the purpose of guide surface which is accommodated in a corresponding seat or recess  33  on the openable part  2  of the mill housing. As a result, the openable part of the mill housing will accurately be positioned in relation to the rotor. 
     In order to realise reliable engagement between the guide surface and the seat use is made of bolts  23  which, with their one end, are secured in the fixed part  1  of the mill housing and which, with their other end, extend through a projecting edge portion  24  of the openable part  2 . The bolts  23  may be secured in the fixed part  1  of the mill housing and may, therefore, also be designated pin bolts which extend through apertures  25  in the projecting edge portion  24 . On the outside of this edge portion, use is made of a locking rail  26  which has keyway-shaped apertures  27 . After release of the nuts  28  on the bolts  23 , the locking rail  26  may be moved downwards so that it can be removed from the nuts in that these pass through the greater part of the apertures  27 . 
     Reference numeral  29  ( FIG. 5 ) relates to a safety switch which is secured in the infeed hopper  4  and which fixedly locks a key  30  which is secured on the locking rail  26  when the granulator mill is in operation and at least during as a long a time as is required for the rotor to have time reliably to have parked once the drive motor of the rotor has been turned off. Only when this has taken place can the locking rail  26  and the key secured therein thus be removed and thereby the openable part  2  of the mill housing be opened. In a corresponding manner, the rotor cannot be restarted until the infeed hopper  4  is closed so that the safety switch  29  is located in the correct position for inserting the key  30  when the locking rail  26  has been put in place. 
     The present invention may be further modified without departing from the scope of the appended claims.