US 3734471 A
A method and device for uniformly wetting wood chips with glue in which the wood chips are propelled along a helical path with the glue being applied by centrifugal action concentrically and radially in finely dispersed form.
Description (OCR text may contain errors)
Elite States atent 1 Engeis  DEVICE FOR CONTINUOUS MIXING OF SOLIDS WITI-I LIQUIDS  Inventor: Kaspar Engels, 68 Mannheim 31,
Germany  Assignee: Firma Draiswerke Speckweg, Germany  Filed: Aug. 31, 1971  Appl. N0.: 176,534
 Foreign Application Priority Data Nov. 24, 1970 Germany ..P 20 57 594.4 Mar. 23, 1971 Germany ..P 21 13 960.6
 US. Cl. ..259/6, 118/303, 259/10  Int. Cl. BOB 7/04  Field of Search ..259/6, 9, 10, 25, 259/45, 46; 118/19, 24, 302, 303, 418;
III l 2b 1 .15 2 18217 11 3,734,471 51 May 22,1973
 References Cited UNITED STATES PATENTS 3,163,403 12/1964 Engels ..259/9 3,343,814 9/1967 Mund ..259/6 FOREIGN PATENTS OR APPLICATIONS 1,507,894 4/1969 Germany ..259/l0 Primary Examiner-William 1. Price Assistant ExaminerStuart S. Levy Attorney-Alvin Browdy and Sheridan Neimark  ABSTRACT A method and device for uniformly wetting wood chips with glue in which the wood chips are propelled along a helical path with the glue being applied by centrifugal action concentrically and radially in finely dispersed form.
18 Claims, 10 Drawing Figures PATENTEU M2 3; 734.47 1
' sum 2 [1F 6 PATENTEDHAYZBIQB $734,471
SHEET 3 OF 6 FIG. 4 3 8 39 38a LLA/IIIIIII II III!!! PATENTEU MAY 2 2 I973 SHEET S 0F 6 DEVICE FOR CONTINUOUS MIXING OF SOLIDS WITH LIQUIDS The present invention relates to a method as well as a device for continuous mixing and wetting of solids with liquids, and, more particularly, to a method and apparatus for gluing of chipped, fibrous or powdered material from vegetable raw materials.
In known methods and devices of this type, there is only a relatively low statistical probability that the solids will be mixed with the liquids so as to ensure a complete wetting of the fibrous, chipped and/or powdered particles of material. These problems occur especially in the gluing of wood chips where lump formation occurs, especially in the case of the powdered components which are often present.
In addition, the known methods and devices move the chips in free trajectory parabolas, which call for mixers which are extraordinarily large in comparison to the throughput volume. The chips previously used in such devices were not supposed to be subjected to stress; however, the latter problem no longer exists. It is therefore no longer necessary, either, that the chips used be of uniform length, width and thickness.
It is, accordingly, an object of the present invention to overcome the deficiencies of the prior art, such as indicated above.
Another object of the present invention is to provide a method and a device which will allow good mixing of solids with liquids in a short time, in which a uniform wetting of the solid particles (especially by directed addition of liquid) is achieved, and in which the amount of energy required for mixing and the construction costs for the apparatus can simultaneously be kept low.
The present invention is provided in a method of the type described above by an arrangement in which the material to be mixed, wet or glued, is propelled along a helical path in a roughly cylindrical layer, and the liquid is applied to the material layer primarily concentrically and radially, by centrifugal action.
This method possesses the considerable advantage that the liquid (e.g. glue) is added to the material when such liquid is already in finely dispersed form with a large surface area, and that simultaneously the rapid rolling motions of the individual solid particles (e.g., wood fibers or wood chips including sawdust) produce an extraordinarily intensive wetting of these solid particles by a pronounced frictional effect.
This mixing and wetting action can also be improved by adding to the material, at successive time intervals or in partially overlapping time intervals, individual glue components and/or finely dispersed water or steam. In particular, this acts to prevent the danger of lumping. It is also advantageous if the material layer has added to it, liquid with different depths of penetration in a quantitatively specified amount. On the .one hand, this increases the intensity of the mixing and wetting; at the same time, it reduces the time required for a good wetting or mixing.
A particularly advantageous device for performing the method according to the invention is characterized by the fact that a mixer composed of a mixing shaft and mixing elements, capable of being operated at high speed, is mounted concentrically in a cylindrical mixing trough, such mixing trough having a tangentially mounted material feed pipe at one end and a tangentially mounted material outlet pipe at the other end,
and by the fact that the mixing shaft has provisions for liquid distribution.
In such apparatus, the solids pass through the mixing trough in a very thin layer, with a constant alternation of smooth flow and turbulence. They pass through an area in which finely dispersed liquid is added. By means of the constant acceleration and subsequent deceleration against the mixing trough walls, the average velocity of the solid particles at the mixing trough wall will be about half as great as the peripheral velocity of the mixing apparatus, each solid particle being brought into contact with the liquid with extraordinary intensity. At the same time, a grinding action takes place at the walls of the mixing trough. In addition to the spraying and mixing effect, there is also an impact effect, which improves the intensity of the mixing or wetting.
The practical field of application of the method according to the invention and the apparatus according to the invention lies primarily in the field of gluing wood chips, the collective term chips" being understood to refer to chipped, fibrous, and pulverized as well as dust particles. It will be understood, however, that adaptations may be made without departing from the scope of the invention.
The rotation speed of the mixer is between approximately 600 rpm for large mixers containing coarse material to be mixed and about 5,000 rpm for small mixers containing fine, powdered material. Intermediate sized mixers, as well as large mixers working on fine particles and small mixers working on coarse particles, will optionally operate at intermediate rates. In order to keep the material layer and the ring of material on the trough wall thin, the material inlet (feed) pipe and outlet pipe are mounted tangentially.
In a more advantageous embodiment, the mixing shaft is made in the form of a hollow shaft, and liquid spray nozzles are mounted on such shaft, projecting somewhat radially from the latter and connected to the interior thereof. Through these spray nozzles the fluid (e.g. glue) is sprayed out from the hollow shaft and thereby finely dispersed. By making the liquid spray nozzles of different lengths, the glue (or even individual components of the glue) can be supplied with different degrees of penetration into the outwardly centrifuged layers of material, so that a suitable amount of liquid can be supplied over the entire cross-section of the mixing trough relative to the concentration of solid material in the individual cross-sectional areas.
According to a further advantageous feature of the invention, one or more feed tubes with outlet openings are arranged on the mixing shaft for various liquids. These feed tubes can be used to supply, for example, different glue components, and to spray water at specific points, so that on the one hand the danger of lumping is reduced and on the other hand the directed water supply serves for cooling and also reduces the clogging of the mixer.
Two removable and replaceable feed tubes can be mounted on the mixing shaft so that in the event of clogging one feed tube can be removed and its activity taken over by the other; hence, no'interruption of operation is necessary.
According to another advantageous feature of the invention, the liquid spray nozzles may be used as mixing. If the liquid spray tubes are made so long that they are plunged into the ring of material on the inner wall of the trough, they act as mixing arms at the same time.
On the other hand, however, it is also possible to make the liquid spray nozzles in the form of mixing paddles. In order to keep the danger of contamination at a minimum, the mixing paddles not made in the form of liquid spray nozzles are preferably made hollow and connected to a coolant circuit mounted in the hollow shaft.
According to another advantageous feature, it is also possible to have a coolant circuit in the mixing shaft and to mount the liquid feed tubes with liquid spray nozzles on the exterior of the shaft. To ensure good mixing and wetting of the solids with liquid and especially to have the wood chips well covered with glue, it is necessary that the liquid spray nozzle be mounted on the mixing shaft along an area of at least percent of the length of the mixing trough, so that the solid particles, due to their high rate of throughput in the trough will still pass through a liquid distribution zone in the mixing trough during a sufficiently long period of time.
Advantageously, the mixing paddles are mounted 180 apart and arranged only along half the length of the trough on the mixing shaft.
In order to ensure sufficient impact effects and hence adequate wetting of very easily wet solids, which tend toward a peripheral velocity approximately the same as that of the mixer, it is advantageous to mount two or more mixing troughs with their mixers arranged axially parallel to each other and connected together with an axially parallel connecting pipe, the distance between the mixer axes being less than the sum of the diameters of the adjacent mixers. In particular, twin-shaft machines are useful in practice.
In order to inhibit clogging, which has heretofore always occurred in wood-chip gluing machines, it is advantageous if the mixing trough is divided axially into an upper and lower section, with the upper section made to be swung opened and having the material outlets both mounted on only one section; preferably the operable one. To clear up blockage in the material inlets, a safety conveyor belt is provided at the impact area of the material feed pipe, said belt arranged to feed into the mixing trough. This conveyor belt serves to carry away the material thrown against the impact area so that a tangential feed for the solid matter into the apparatus is ensured.
In order to reduce bubble formation at this RPM and with thin layers of material, a throttle valve is mounted in or in front of the material outlet pipe, its operation depending on the load on the electric drive motor of the apparatus and/or the temperature of the material at the outlet, such valve opening the material outlet pipe depending on the actual mixing or wetting effect in existence, and also keeping the device from acting as a sort of fan. In order to prevent liquid (and glue in particular) from running out of the glue spray tubes when the device is stopped, thereby leading to severe clogging of the apparatus, the liquid spray tubes are advantageously provided with a valve that allows liquid to pass through only during operation.
It is also advantageous if the mixing paddles, especially in the area of the liquid spraying tubes, are made to provide zero axial feed at their outer ends of the mixed material, near the wall of the mixing trough, with the axial feeding effect increasing steadily toward the mixing shaft. This measure serves to ensure uniform wetting of the solid material with liquid during variations in throughput. At normal loads, almost no additional propulsive force is necessary to maintain the thin, flowing, stirred-up ring of material, (e.g. chips) and keep it moving axially through the mixing trough. Hence, the mixing paddles are made with a zero feeding effect, especially in the area of the material-ring coating. To keep the apparatus from clogging in the event of intentional or accidental overloads, the mixing paddles are mounted so that the pitch increases steadily toward the mixing shaft, so that an increased axial propulsion occurs automatically when the thickness of the material coating increases. This allows automatic adjustment of the mixer to various throughput loads. Hence, no special adjustment of the mixer is required, even at relatively high variations in throughput.
It has been shown that low-volume, high-speed mixers are especially sensitive to throughput. The especially advantageous feed arrangement using intermittent addition of preweighed amounts of chips is not possible. To avoid additional control processes, such as are required, for example, in equalizing bunkers, it is proposed to install a slow-speed equalizing premixer with overflow to provide uniform, and therefore clogfree, loading of the apparatus. In such an equalizing premixer, the individual batches of chips of different size and different quality of wood are mixed completely uniformly.
Further advantages and features of the invention will be more apparent from the following detailed description of sample embodiments taken in conjunction with the drawings, wherein:
FIG. 1 is a lengthwise side view of an apparatus according to the invention for gluing wood chips, in partial cross section;
FIG. 2 is a section through the apparatus, along line 11-11 in FIG. 1;
FIG. 3 is a cross-section through the apparatus, along line III-III in FIG. 1;
FIG. 4 is a cross-section through a twin-shaft apparatus;
FIG. 5 is a cross-section through a mixing shaft with several feed tubes;
FIG. 6 is another embodiment of an apparatus according to the invention, shown partly in lengthwise cross section;
FIG. 7 is a partial lengthwise cross-section, top view, through an apparatus in accordance with the present invention with two glue feed tubes, mounted in the hollow shaft, with provision for alternate use;
FIG. 8 is a partial lengthwise section through an apparatus with glue feed tubes located externally and cooled mixing paddles along the entire hollow shaft;
FIG. 9 is a cross-section through a hollow shaft with valve-controlled liquid-spraying tube, and
FIG. 10 is an apparatus according to the invention, showing an equalizing premixer with overflow (connected ahead of the mixer) in schematic lengthwise section.
The apparatus shown in FIG. 1, for gluing of wood chips, consists of an inner trough l of cylindrical shape and a cooling jacket 2 thereabout forming a cylindrical mixing chamber, closed at the ends by bulkheads 3. At one end (the right end, in the drawing) is a material feed pipe 4, emptying into the trough 3, from above at a tangent; at the other end (at the left in the drawing) is a material outlet pipe 5, likewiseattached to the trough at a tangent. The mixing trough is divided along its axially perpendicular lengthwise plane, so that its bottom part 2a and its top part 2b are held together by toggle levers 6 along the lengthwise flanges.
A mixing shaft 7 is mounted coaxially in the mixing trough 2, such shaft 7 being supported in bearings 8, 8a and driven by a motor 9 through suitable means; such as a belt 9a, and V-belt pulley 9b mounted on the mixing shaft 7. A housing 10 is mounted over the V-belt pulley 9b as a belt guard. A pair of driven plates 11, 1 1a are mounted on the mixing shaft 7 near the bearings 8 and 8a, to compensate for varying loads on the mixing shaft 7 during operation.
In the left half of the drawing, a cooling-water tube 12 is shown in the hollow mixing shaft 7, rotating with the latter. Threaded sockets 13 are mounted on the mixing shaft 7, into which mixing paddles 14 are screwed, such paddles 14 being mounted at an angle to their rotational plane and being bent at their outer ends in the propulsion direction of the mixer, so that they remove material adhering to the inner wall of the trough. In the area of the material outlet pipe 5, some of the mixing paddles (shown schematically) are made shorter than those described above. A cooling-water pipe 15 branches off the cooling-water tube and is connected to the hollow mixing paddle 14, so that the cooling water flows through the main cooling water tube 12, into and through the additional cooling water pipe 15, through the interior of mixing paddle 14 and then into the annular space between the cooling water tube 12 and the mixing shaft 7, as shown in FIG. 1 by the appropriate arrows indicating direction of flow. The fresh cooling water a enters the mixing shaft through a pipe coupling 19 that serves as the cooling water connection, the coupling 19 being non-rotary with respect to the mixing shaft 7; the old cooling water b drain is drained from the stationary coupling 19.
At the other end of the mixing shaft 7 (at the right in the drawing) is a pipe coupling 16, which also does not revolve with the shaft, into which a glue mixture feed pipe 16a empties. From this pipe 16, glue flows into the interior of the hollow mixing shaft 7, from which it is sprayed out through liquid spray tubes 17, shown in phantom, into the gluing area 18.
As shown in FIG. 2, the bottom part 2a of the mixing trough is mounted on a base 20. The funnel-shaped material feed pipe 4 is connected only to the top section 2b. The entire top section 2b of the mixing trough, including the material feed pipe 4, pivots on a shaft 23 running parallel to mixing shaft 7 and is balanced by a counterweight 24. The material feed pipe 4 is provided with a sloping surface 22 at its upper end, so that the top section 2b can be tipped to the position indicated by the dot-dashed lines without removing intermediate sections or elastic connections.
An outlet stub 25 for cooling water is mounted in the top section 2b of the trough, so that the cooling water supplied through an inlet stub (not shown) leaves the annular space between the inner trough 1 and the cooling jacket 2 through this outlet stub 25. In order that cooling water can also reach the lower part 2a of the mixing trough, through holes are provided in flanges 2c.
An impact area 29 is provided between the trough 1 and 29 the funnel-shaped material feed pipe 4, against which the material is thrown by the mixing paddles 14 according to the direction of rotation of the mixing shaft 7 (indicated by the arrow). Passing about such impactarea 29 is a protective belt 26 made in the form of a conveyor belt, driven over suitable drive rollers 27, 28 or the like in the direction indicated by the arrows shown on these rollers, so that the material thrown against the impact area 29 is carried downward and scraped off such scraping action can be reinforced by providing a scraping knife 21 or a brush.
As shown in FIG. 3, a throttle valve 30 is swingmounted on the funnel-shaped material outlet pipe 5 in the bottom part 2a of the mixing trough 1, such throttle valve being pivotally mounted on a shaft 31. A lever 32, also pivoting on the shaft 31, is attached to throttle valve 30; iron core 33 of a solenoid 34 is connected to the lever 32. The solenoid 34 is activated depending on the current drawn by motor 9 and/or the temperature of the emerging processed material, so that the throttle valve opens further as the load on the motor grows and- /or the temperature of the emerging processed material increases. With a small load on the apparatus and when starting up, the throttle valve serves the damp the air stream generated by the mixing paddles 14.
The processed material, eg glued wood chips, emerges from the mixing trough l in the direction of the arrow c into the material outlet pipe 5 bounded by the walls 35 and 36, and is carried away to other machines for further processing by way of the connecting conduit 37.
FIG. 4 shows an apparatus according to the invention, with two cylindrical inner troughs 38, 38a mounted axially parallel to each other, surrounded by a common cooling jacket 33. The mixing chamber formed by the inner troughs 38, 38a and the cooling jacket 39 are again divided along the plane of the two mixing shafts 7, with flanges 20 being held together by toggle clamps (not shown). The upper part 3% can be lifted off the bottom part 39a in accordance with the system shown in FIGS. 1 to 3.
FIG. 5 shows a section through a mixing shaft 7, as might be provided, for example, in an arrangement such as shown in the right half of FIG. 1. The mixing shaft 7 consists of a tube 40, on which liquid spraying tubes 17 are mounted by means of threaded sockets 41 to extend outward radially, so that they extend inwardly into the wall of tube 40 as well. In addition, mixing paddles 14 are mounted on the tube 40 by means of threaded sockets 13. The tube 40 contains four feed pipes 42, 43, 44, 45, which do not revolve with it, through which, for example, glue, setting agent, emulsion and water could be fed. These glue components enter the tube 40 through outlets 46, and are well mixed with one another in the tube 40 due to the latters rotating movement at high speed; the glue mixture then sprayed out through liquid spraying tubes 17. Preferably there is also an outlet opening in the vicinity of one of the liquid spraying tubes 17.
In the embodiment of the invention according to FIG. 6, a mixing shaft 7 is mounted to rotate at high speed ina mixing trough consisting of an inner trough 1 and cooling jacket 2 and material feed pipe 4. In this and the following examples of the embodiment of the invention, those parts that correspond to embodiment No. 1 are labelled with the same reference numbers, while the altered parts are shown and described.
In the interior space of the hollow mixing shaft 7 there are four feed pipes of different lengths which do not revolve together with the shaft 7; tube 47 is for water, 48 for setting agent, 4.9 for raw glue and 50 for emulsion. These pipes are mounted rigidly in a holder 51 outside the mixing shaft 7. Such feed pipes 47, 48, 49, 50 have nozzle-shaped outlets 52 only along certain lengthwise areas, so that liquid from each of these feed pipes is sprayed against the inner wall of hollow mixing shaft 7 only within this area. Thus, water is sprayed from feed pipe 47 only in area a, and reaches the mixing trough with simultaneous cooling of the corresponding area. Setting agent comes out of feed pipe 48 in area b, i.e., at the end of the mixing trough, while raw glue comes out of feed pipe 49 in area c and emulsion comes out of feed pipe 50 in area d. If these areas a, b, c, d overlap in some selected fashion, a precisely controlled mixing of the individual glue components can be achieved.
If too many liquid spraying tubes 17 become clogged, the ring of liquid inside the mixing shaft 7 increases so sharply that it can no longer be held back by a flexible overflow seal 53 provided for this purpose, and the liquid flows to the open end 54 of mixing shaft 7 and is sprayed out tangentially there. This liquid is caught in a safety tank 55 which contains a float switch 56, connected to a signal light (not shown); when the light goes on, it indicates that the safety tank contains a certain amount of liquid. From this it may be concluded that a number of liquid spraying tubes 17 are clogged and that the system must therefore be cleaned. As long as only a small number of liquid spraying tubes 17 are clogged, all the liquid components being supplied can still issue from these liquid spraying tubes 17, so that no liquid enters the safety tank 55 and no alarm signal is given.
In the embodiment of the invention shown in FIG. 6, the mixing paddles are made to provide zero propulsion at their outer ends, starting behind the material feed pipe 4, i.e., they exert no propulsive force in the lengthwise direction of the mixing trough upon the material to be processed. On the other hand, their pitch increases toward the mixing shaft 7, i.e., they increase their propulsive force on the material to be processed, inward toward the mixing shaft. The liquid spraying tubes 17 increase in length as seen in the throughput direction of the mixing trough, so that different layers and different areas of the material are treated with the individual liquid components. The order in which the lengths of the liquid spraying tubes 17 change depends on the desired gluing conditions.
The mixing shaft 7 is divided by a plug 57, so that the glue feed chamber for example is separated from a cooling chamber, as shown in FIG. 1 at the left.
In the embodiment according to FIG. 7, two feed tubes 58, 58a are mounted in the hollow mixing shaft 7 and connected by flexible lines 60, 60a and a 3-way valve 59 to a glue-supply line 61. By using 3-way valve 59, feed pipe 58 or 58a can be used as desired. Likewise, one of the two feed tubes 58 or 58a can be removed during operation. For this purpose, sufficient play is allowed in mountings 62, 62a for feed tubes 58, 581: so that the tubes can be withdrawn axially without significant change of angle; such mountings on 62, 62a, made in the form of clamps, are fastened to the frame of the machine.
In the embodiment according to FIG. 8, plug 57 is located rather far to the right, so that the cooling water tube 12 extends nearly through the entire mixing shaft 7a. This means that all mixing paddles 14 can be cooled. Liquid spraying tubes 170 are supplied with liquid, particularly glue, via axially parallel feed tube 63 which in turn is connected by a connecting stub 64 to the right side of hollow mixing shaft 70, the glue being fed through a supply pipe 65 that does not revolve with the shaft.
FIG. 9 shows a hollow mixing shaft 7, consisting of a tube 40 to which spray tube 17b is connected in the manner and fashion described above. The glue is fed through a feed tube 66 via one or more outlets 67. After the glue has been sprayed against the inner wall of tube 40, it passes through a hole 68 into the liquid spraying tube 17b, whose outer end has a ball valve operated by a spring 69. The spring presses at its other end against a spray nozzle 71, screwed into the liquid spraying tube 17b. The force of spring 69 is such that ball 70 opens the passageway 68 at approximately half the rated speed of the mixer.
As indicated above, both the quality of the gluing and especially the clogging are highly dependent on the concentrated charging with chips and glue. Feeding solid materials (e.g. wood chips) at intervals, which is the outstanding and extremely precise method most independent of the amount of clogging, is not practical for the high-speed, small material volume operation according to the invention. However, in order to be able to take advantage of the desirable features of intermittent feed, a so-called equalizer mixer with automatic control and overflow is installed ahead of an apparatus according to the invention. By means of a scale, consisting of weighing pan 72, housing 73 and indicator 74, the chips enter funnel 75 of an equalizer mixer mounted beneath, consisting of a trough 76 and a mixer 77 driven by a 'motor (not shown). The RPM of the mixer 77 lies in the range of (0.3 1.2) X n where the critical RPM n 42.3 VD. Here D is equal to the diameter of the mixer in meters. The critical RPM ri (measured in revolutions per minute) develops when (D /4) W g, where W is the angular velocity of the mixer and g is the acceleration due to gravity.
The intermittently supplied chips are then fluidized by the mixer 77, so that no inhomogeneities exist in the glue composition at the outlet 78 of the equalizing mixer that could disrupt practical operation. For this purpose, an overflow barrier 79 is provided in trough 76, as is known in mixers. In order that the batches of chips falling down from the scale do not create a puff of air that could extend to outlet 78, a barrier 80 is located beneath inlet funnel 75 so that its lower edge extends down into the layer of chips in the trough. The glue feed at g in the arrangement according to the invention and the chip feed via the batch scale can also be connected in a known manner.
Finally, one more example of the method of operation of a device according to the invention is given. The diameter of the mixer is 500 mm., the mixer rotational speed is 1,200 RPM and the throughput of the apparatus is 8 tons/hour. Fine top-layer chips are glued, with the following composition: 15 percent of the chips are larger than 1 mm., 30 percent are between 1.0 and 0.63 mm., 30 percent are between 0.63 and 0.4 mm. and 25 percent are smaller than 0.4 mm. The size data for the chips are based on screen fractions, i.e., the amounts correspond to screens with mesh sizes of the given dimensions. The chips are treated with a 15 percent (by weight) glue mixture, 7.5 percent (i.e., half) being solid resin lumps.
It will be obvious to those skilled in the art that various changes may be made without departing from the scope of the invention and the invention is not to be considered limited to what is shown in the drawings and described in the specification.
What is claimed is:
1. Apparatus for the continuous mixing of solids with liquids, preferably for the application of glue to chips, fibers or powdered materials, comprising:
a cylindrical mixing trough, a material-feed funnel at one end of said mixing trough and a material outlet at the other end of said mixing trough;
said mixing trough having mounted coaxially therein at least one mixing shaft, means to drive said mixing shaft, said shaft being provided with mixing arms for the axial propulsion of the material through said trough in the form of a ring of material contiguous with the trough wall;
wherein the mixer shaft has a hollow inner space and carries at least one fluid feed tube, and means to spray liquid into the ring of material contiguous with the trough wall and being propelled through said trough, said spraying means comprising liquid spray tubes mounted on said mixing shaft and projecting therefrom, aid spray tubes having a liquid receiving end for receiving fluid from said fluid feed tube, said spray tubes being sufficiently long to project into the ring of material contiguous with the trough wall.
2. Apparatus according to claim 1, wherein said liquid spraying tubes are different lengths.
3. Apparatus according to claim 1, wherein more than one said feed tube is present and said tubes have outlets in said shaft only at specified locations along the length of said shaft.
4. Apparatus according to claim 1, wherein two removable and replaceable feed tubes are mounted on the mixing shaft.
5. Apparatus according to claim 1, wherein said mixing elements are in the form of liquid spraying tubes.
6. Apparatus according to claim 1, wherein said mixing elements are hollow paddles, connected to a cooling circuit enclosed in said hollow shaft.
7. Apparatus according to claim 1, comprising a cooling circuit mounted on the mixing shaft and wherein said at least one liquid feed tube with liquid spraying tubes are mounted on the exterior of said mixing shaft.
8. Apparatus according to claim 1, wherein said liquid spraying tubes are arranged along an area of at least 20 percent of the mixing trough length, on the mixing shaft.
Apparatus according to claim 1 wherein the mixing elements arms are displaced relative to each other and are arranged only along approximately half the length of the trough, on the mixing shaft.
10. Apparatus according to claim 1, comprising a second trough with mixers is arranged axially parallel to said first trough and connected thereto by an axially parallel connection, so that the distance between the mixer axes is less than the sum of the diameters of the adjacent mixers.
11. Apparatus according to claim 1 wherein: the mixing trough is divided axially into an upper part and a lower part; a portion of the lower part of said mixing trough is removable; and the material feed pipes and material outlet pipes are tangentially attached to said lower parts.
12. Apparatus according to claim 1, further comprising an impact area adjacent said material feed pipe and a protective conveyor belt covering said impact area of the material feed pipe, with the direction of travel of said belt being toward said mixing trough.
13. Apparatus according to claim 1, comprising an operable throttle valve at the material outlet pipe, said valve being operable by said driving means.
14. Apparatus according to claim 1, wherein said liquid spraying tubes are each provided with a valve that opens to allow liquid to flow only during operation.
15. Apparatus according to claim 1 wherein said mixing arms, especially in the area of the liquid spraying tubes, are pitched to provide zero propulsion at their outer ends, located in the vicinity of the mixing trough wall, while their propulsive effect increases steadily toward the mixing shaft.
16. Apparatus according to claim 1, further comprising a slower-running equalizer premixer with overflow means connected ahead of said inlet pipe.
17. An apparatus in accordance with claim 1 wherein said fluid feed tube is carried within saidhollow inner space of said mixer shaft.
18. Apparatus in accordance with claim 1 wherein said hollow mixer shaft carries said fluid feed tube on the exterior thereof.