Abstract:
A refiner including a rotor and a stator defining a cylindrical or conical refining gap therebetween. A pulp feed channel extends in a radial direction from an inlet pipe to the refining gap.

Description:
BACKGROUND OF THE INVENTION 
     This invention relates generally to refining apparatus. More particularly, the present invention relates to refining apparatus having a rotor and a stator forming a cylindrical or conical refining gap between rotor and stator. 
     Nowadays most of the refiners built are of twin disc or conical design. The disadvantages of the twin disc refiner are the changing relative speed along the length of the refining zone, a relatively high idle running rating and problems with centering the rotor, particularly at low throughputs. A significant disadvantage of the conical refiner known is the poor pumping effect. This leads to throughput difficulties and, as a result, the need to enlarge the grooves in the refining zone, which reduces the edge length. Possible other disadvantages are the relative displacement of the knives when being set in relation to one another, the need for a sturdy design as a result of the bearing forces occurring, and the difficulties in changing the refiner plates, which lead to high manufacturing costs. With a cylindrical refiner, as known from U.S. Pat. No. 5,813,618, for example, many of these disadvantages can be avoided, however there may be problems with the throughput, similar to those occurring with the conical refiner. 
     SUMMARY OF THE INVENTION 
     The aim of the invention is, therefore, to circumvent the disadvantages of the cylindrical and conical refiners known, in order to also permit higher throughputs. 
     The invention is thus characterized by the pulp feed channel extending in radial direction from the inlet pipe up to the refining gap. The pulp fed in is accelerated here by the rotating movement of the rotor in circumferential direction, which causes a pressure increase in the liquid. On the one hand, this pressure build-up eliminates the need for a feed pump and on the other, it provides good rotationally symmetrical inflow. 
     An advantageous configuration of the invention is characterized by the pulp feed channel having a rotationally symmetrical design. This results in even and rotationally symmetrical inflow to the refining flaps. 
     An advantageous further development of the invention is characterized by the inlet pipe connected to the pulp feed channel being on an axis which coincides with the axis of the rotor. In this way the pulp is fed directly into the axis of the refiner, which causes the pulp to be accelerated partially in the pipe before entering the pulp feed channel on the one hand and provides even more uniform pulp distribution on the other hand. 
     A favorable farther development of the invention is characterized by a disc being provided between the inlet pipe and the refining gap which limits the pulp feed channel. If the pulp is fed in outside the axis, the disc deflects the pulp at the shaft and directs it in rotational symmetry outwards, where the liquid is accelerated radially outwards between disc and front face of the rotor and subsequently flows evenly distributed into the refining gap. 
     A favorable configuration of the invention is characterized by a cylindrical rotor being provided. The rotor can also be conical, widening in the flow direction of the pulp or, as an alternative, a conical rotor narrowing in the flow direction of the pulp. Thus, the shape of refining gap suitable for the given requirements can be used. 
     An advantageous further development of the invention is characterized by a twin rotor being provided. With a twin rotor, where the rotor can be cylindrical as well as conical (widening cone or narrowing cone), it is possible to achieve a high throughput, also with even inflow to the refining gaps in rotational symmetry. 
     A favorable further development of the invention is characterized by the pulp feed channel being located between the two rotors. In particular, if an inlet pipe positioned in the axis of a rotor is used, the pulp can be fed into the center of the refiner and then directed outwards by the rotating movement, which leads to a corresponding rise in pressure. Further downstream the pulp is fed into the center of the corresponding refining gap, which achieves further evening out of the pulp feed. 
     An advantageous configuration of the invention is characterized by a cylindrical and a conical refining gap being arranged in series. This arrangement of a cylindrical and a conical refining gap in series can be achieved either on one rotor or using two different rotors positioned one behind the other. In both cases, the sequence of the series is arbitrary and depends only on the pulp characteristics to be obtained. 
     A favorable further development of the invention is characterized by internals, particularly paddles, being mounted in the pulp feed channel and/or inlet pipe. Internals of this kind in the inlet pipe or the pulp feed channel can significantly increase acceleration of the liquid even further in addition to the effects of wall friction. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The present invention may be better understood and its numerous objects and advantages will become apparent to those skilled in the art by reference to the accompanying drawings in which: 
     FIG. 1 is a schematic view of a first embodiment of a refiner in accordance with the invention; 
     FIG. 2 is a schematic view of a second embodiment of a refiner in accordance with the invention; 
     FIG. 3 is a schematic view of a third embodiment of a refiner in accordance with the invention; 
     FIG. 4 is a schematic view of a fourth embodiment of a refiner in accordance with the invention; 
     FIG. 5 is a schematic view of a fifth embodiment of a refiner in accordance with the invention; 
     FIG. 6 is a schematic view of a sixth embodiment of a refiner in accordance with the invention; 
     FIG. 7 is a schematic view of a seventh embodiment of a refiner in accordance with the invention; 
     FIG. 8 is a schematic view of an eighth embodiment of a refiner in accordance with the invention; 
     FIG. 9 is a schematic view of a ninth embodiment of a refiner in accordance with the invention; 
     FIG. 10 is a schematic view of a tenth embodiment of a refiner in accordance with the invention; 
     FIG. 11 is a schematic view of an eleventh embodiment of a refiner in accordance with the invention; 
     FIG. 12 is a schematic view of a twelfth embodiment of a refiner in accordance with the invention; 
     FIG. 13 is a schematic view of a thirteenth embodiment of a refiner in accordance with the invention; and 
     FIG. 14 is a cross section view taken along line A—A of FIG.  5 . 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     FIG. 1 shows a refiner according to the invention, with inlet  1 , pulp feed channel  7 , refining zone  3 , outlet  4 , rotor  5  and stator  6 . The pulp here flows into the refiner centrally through the inlet  1 , positioned in the axis of the rotor  5 . In the pulp feed channel  7  between rotor  5  and stator  6 , the pulp is accelerated in circumferential direction due to wall friction or special internals (see FIG.  14 ), thus causing a pressure build-up. The pulp flows subsequently through the refining zone  3  and leaves the refiner through the outlet  4 . The stator  6  comprises a ring movable in axial direction and on which a wedge  10  is mounted. The refiner plates are connected to a further wedge  11 , with the refining gap  3  being set by moving the ring  9 . 
     FIG. 2 shows a refiner of analogous design, where the pulp is fed in from the side. The pulp flows here through the lateral inlet  1  into the refiner and is deflected towards the shaft by a disc  8 . Here it is accelerated due to wall friction or special internals and enters the pulp feed channel  7  between disc  8  and rotor  5 , where channel  7  acts as acceleration zone. In this acceleration zone the pulp is further accelerated in circumferential direction, thus causing the necessary pressure build-up. The pressure build-up here is in the region of 1.5 to 2 bar. Subsequently the pulp flows through the refining zone  3  and leaves the refiner through the outlet  4  located opposite the inlet  1 . Here, too, the refining gap  3  is set by means of the adjustable wedges  10  and  11 . 
     FIG.  3  and FIG. 4 show analogous refiners to FIG. 2, with the same pulp feed, but where FIG. 3 contains a conical refiner with a widening cone and FIG. 4 a conical or tapered refiner with a narrowing cone. 
     FIG. 5 illustrates how a twin rotor refiner functions. In the design showed here the pulp flows through the inlet  1 , formed as a hollow shaft, and through the rotor  5  to the pulp feed channel  2  located in the center. Due to acceleration of the pulp in circumferential direction in the hollow shaft of the inlet  1  and in the pulp feed channel  2 , the pressure builds up here. The pulp flows subsequently through the refining zone outwards and leaves the refiner through the two outlets  4   a  and  4   b , respectively. The refining gap  3  is adjusted here again using an axially adjustable ring  9 . In addition to the facility of a wedge  10  acting over the entire length and a counterpart  11  connected to the refining plates, the present illustration shows a wedge  10  divided wedge  10   a  and wedge  10   b . The surfaces of the counterpart  11  have corresponding wedge shaping. This permits a better and more even distribution of energy. 
     FIGS. 6 and 7 show an analogous refiner to FIG. 5 with twin cone, where the conical shaping in FIG. 6 widens towards the outlets  4   a  and  4   b , respectively, when viewed from the pulp feed channel  2 , and narrows in FIG.  7 . These refiners function in the same way as the twin cylinder refiner shown in FIG.  5 . 
     A further possibility is illustrated in FIG. 8, where the pulp is fed in on both sides through the inlet  1   a  and  1   b , respectively, towards the shaft and deflected into the pulp feed channel  7  by the disc  8 . From there the pulp enters the refining gap  3  on both sides and is discharged centrally through the outlet  4 . The same pulp routing is also possible with a twin cone, which can be designed as a widening or a narrowing cone from the outer inlet to the center outlet. 
     Taking the example of a refiner with twin rotor and axial inlet  1  designed as a hollow shaft, FIG. 9 shows a combination of cylindrical and conical refining zones. In addition to the variant shown, the pulp can also flow in on two sides through the inlet, with deflection by a disc, and the outlet can be located centrally. 
     FIGS. 10 to  13  illustrate the combination of cylindrical and conical refining zones on one rotor. In this case the pulp can either flow through the cylindrical part (FIG. 11, FIG. 12) or through a conical part (FIG. 10, FIG. 13) first, where the cone has either a widening (FIG. 10, FIG. 12) or narrowing (FIG. 11, FIG. 13) shape. The definition of widening or narrowing for the shape of the cone is always determined by the flow direction of the pulp. 
     FIG. 14 shows a section according to line A—A in FIG.  5 . Here the internals  12 , also known as vane or blade can be seen. These internals  12  divide the pulp feed cannel  2  into separate pulp feed channels  2 ′ through which the pulp suspension is led from the centrally arranged feed  1  to the refining gap  3  on the outside. By these internals  12 , which are manufactured as a filled wedge, the pulp suspension is accelerated additionally and a pressure increase builds up. The internals  12  however nary also be hollow or rounded on its surface, i.e. manufactured as blades. Such internals also may be used in the pulp feed channel  7  of e.g. FIGS. 1-4 or  8 ,  10 - 13  as also in the analogous variants to FIG. 5 in FIGS. 6,  7  or  9 . 
     While preferred embodiments have been shown and described, various modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustration and not limitation.