US 3845940 A
A mixing tool for use with a machine for mixing glue with particulate material such as shavings in which the machine has a drum shaped container in a shaft rotatable on the axis of the container. The mixing of the glue with the particulate material is effected by tools extending radially from the shaft and each consisting of a body cylindrical at the radially inner end adjacent the shaft and a head at the radially outer end of the body. The head has a forwardly protruding nose and the head and body taper inwardly to the juncture thereof when viewed in the circumferential direction. Each tool is tubular and a coolant pipe extends radially outwardly inside each tool and supplies coolant fluid thereto. Each tool preferably has a blade-like element thereon near the radially outer end that is inclined to exert a radially outward force on work material in the drum shaped container of the machine.
Description (OCR text may contain errors)
United States Patent Lodige et a1.
1 1 Nov. 5, 1974 MIXING TOOL FOR MACHINES FOR APPLYING GLUE TO SHAVINGS  Inventors: Wilhelm Lodige, Elsener Strasse 9c; Fritz Lodige, Leuschner Strasse 12; Josef Lucke, lm Lohfeld 13, all of 479 Paderborn, Germany  Filed: Aug. 8, 1973  Appl. No.: 386,781
 Foreign Application Priority Data Aug. 12, 1972 Germany 2239852 52 us. Cl. 259/107, 259/178 A 51 Int. Cl B0lf 7/20 1 58] Field of Search... 259/107, 108, 178 R, 178 A, 259/5, 6, 7, 8, 22, 23,24, 41, 42, 43, 44, 66,
Herfeld 259/107 Primary Examiner-Robert W. Jenkins Attorney, Agent, or FirmWalter Becker 1 1 ABSTRACT A mixing tool for use with a machine for mixing glue with particulate material such as shavings in which the machine has a drum shaped container in a shaft rotatable on the axis of the container. The mixing of the glue with the particulate material is effected by tools extending radially from the shaft and each consisting of a body cylindrical at the radially inner end adjacent the shaft and a head at the radially outer end of the body. The head has a forwardly protruding nose and the head and body taper inwardly to the juncture thereof when viewed in the circumferential direction. Each tool is tubular and a coolant pipe extends radially outwardly inside each tool and supplies coolant fluid thereto. Each tool preferably has a blade-like element thereon near the radially outer end that is inclined to exert a radially outward force on work material in the drum shaped container of the machine.
10 Claims, 6 Drawing Figures SHEET 10F 2 PMENTEDRDV 51974 \xxxxAr PATENTEBNUY 51924 v 3845340 SHE 20$ 2 The present invention relates to a mixing tool for machines for applying glue to shavings, fibers or similar mixing material of wood, bagasse or the like, especially cellulose containing materials. More specifically, the present invention relates to a mixing tool of the above mentioned type which is connected to a mixer shaft arranged centrally in a drum-shaped mixing chamber and which with its head portion rotates at a high speed in the vicinity of the wall of the mixing chamber and immerses into the material to be mixed.
Mixing tools of this type are customarily designed in the manner of a paddle, the narrow side of which is aligned approximately parallel to the axis of rotation of the mixing tool and for obtaining an axial transport of the material to be mixed is slightly inclined with regard to its axis of rotation.
In view of the action of the mixing tools, the shavings are supposed to be rubbed against each other at a certain pressure so that the glue will be uniformly wiped over the surfaces of the shavings. However, the pressure must not become too high because otherwise the shavings will be broken down excessively, and the strength values as well as the quality of the eventually obtained plate will be reduced. When the shavings are primarily whirled by the tools in the interior of the drum, this low friction will not suffice to distribute the glue over the surfaces of the shavings. With heretofore known mixing tools which for purposes of obtaining better sliding conditions for the shavings are rounded at the head range, the shavings are on one hand, when backing up in front of the mixing tool and in the gap between the radial outer head end of the mixing tool and the drum wall pressed excessively so that damage to the shavings and in view of high friction increased wear and increased heat development will occur. On the other hand, only insufficient relative movements of the shavings, especially in the direction of the mixing chamber radials will be generated. Therefore, with heretofore known mixing tools, on one hand only an insufficient distribution of the glue between the shavings is obtained, whereas on the other hand too high a pressure effect is exerted upon the shavings. This causes heat development and at the same time a tendency to form lumps and produces undue wear on the tools and on the wall of the mixing chamber while at the same time the shavings are diminuated with the result that the quality of the shaving material is greatly reduced. Moreover, the paddle shape of customary mixing tools makes an intensive fluid cooling more difficult so that the out- I lined drawbacks of an undue heating up in view of the mixing tools will weigh all the heavier.
With those mixing tools which in particular with one shaft gluing machines are arranged in the discharge zone, additional drawbacks are encountered. The tools in the discharge zone are intended to increase the pressure of the shaving ring onto the drum wall which pressure is brought about by centrifugal forces, so that a flap which is held closed due to a preload will open in order to permit the material to be freely discharge. Due to the shape and the angle of attack of the customary paddle-shaped tools, however, an excessive pressure is built up radially outside the head range and in the short running ahead range encountered in the direction of rotation da so that the flap will very suddenly open up and will then as suddenly and strongly close. Thus, the withdrawal flap carries out strongly pulsating opening and closingmovements which permit no uniformly flowing discharge of the product. The finish glued material rather escapes stepwise and in a shock-like manner and when the flap subsequently slams shut it jams. Moreover, a paddle-shaped mixing tool pushes a comparatively large quantity of the product in front of the mixing tool and the mass, already prior to the opening of the flap, frequently jams at the confinement of the openings of the drum. A further grave disadvantage of the paddle-shaped tools in the discharge area is seen in the fact that in spite of different filling height and in spite of a differently thick ring of material always pushes the same quantity of the product out of the discharge flap. An adaptation of the emptying or discharging quantity to the thickness of the respective product ring obtained in the mixing chamber can be effected only by mechanically adjusting the angle of attack of the paddle-shaped mixing tool relative to the axis of rotation when the machine is at a standstill.
It is, therefore, an object of the present invention to provide a mixing tool which treats very carefully the shavings and the machine parts and which simultaneously when employing a mixing zone brings about a uniform application of glue to the shavings and, when employed in the discharge range, brings about discharge quantities depending on the filling and also brings about a dampened pulsating discharge.
These and other objects and advantages of the invention will appear more clearly from the following specification, in connection with the accompanying drawings, in which:
FIG. 1 shows a section through a mixing tool according to the invention, said section being taken along the line l-l of FIG. 5.
FIG. 2 shows a section through the mixing tool of the invention, said section being taken along the line ll-ll of FIG. 5.
FIG. 3 illustrates a section through the mixing tool according to the invention, said section being taken along the line lll-Ill of FIG. 5.
FIG. 4 shows a section through the mixing tool of the invention, said section being taken along the line lV-lV of FIG. 5.
FIG. 5 represents a section through the mixing tool,
said section being taken along a plane perpendicular to the axis of rotation of the mixing tool.
HO. 6 is an axis normal section through a mixing chamber where two mixing tools, according to the invention, are located opposite to each other on the mixer shaft.
A mixing tool according to the present invention is characterized primarily in that the head range, when viewed in the direction of rotation of the body of the mixing tool is divided by a narrow section which while forming surfaces inclined toward the interior of the mixing chamber and the mixing chamber wall gradually widens towards the head range and toward the body. The mixing tool according to the invention is furthermore characterized in that the cross sectional dimensions on the mixing tool when viewed in a direction perpendicularto the direction of rotation at least to no material extent drop below the maximum cross sectional dimension when viewed in the direction of rotation.
ln view of the thus relatively narrow design of the mixing tool, a carrying along of pressed material in the region directly ahead of the mixing tool with the above mentioned disadvantageous effects is prevented on one hand with regard to too high a pressure load on the shavings and on the other hand with regard to the discharge operation, while at the same time the inclined design of the lateral walls in the head range imparts upon the ring of the mixing material a speed component toward the interior of the mixing chamber. As a result thereof, the shavings are for purposes of the distribution of glue divided in the direction of the radials toward the mixing chamber, and the surfaces of the body of the mixing tool which are inclined toward the mixing chamber wall are with a rather high filling of the mixing chamber exerting a pressure in the ring of the mixing material in the direction toward the mixing chamber wall and thereby upon the discharging or emptying flap so that with a rather high filling of the mixing chamber, an accelerated emptying is effected so that a tendency for forming a uniform and optimum strong ring of mixing material will be generated.
Particularly when the head range has its greatest width in the direct vicinity of the mixing chamber wall, the generation of a dead zone of pressed and only slowly moving mixing material in the vicinity of the wall is avoided because the here present shavings are grasped by the inclined lateral surfaces of the head range and are moved toward the center of the ring of shaving material. This effect is advantageously aided by the fact that the head range has a front nose when looking in the direction of rotation, which grasps the shaving material near the wall and deviates the same addi tionally toward the center. When the nose in this connection ends in a rounded tip, it will act like a plow and will lift the shaving material near the wall from the wall without undue increase in pressure and will convey the saidshaving material in the direction toward the center of the ring of shaving material. The thus further reduced friction of the tool in the shaving material results in a further decrease in wear and in the development of heat with the disadvantageous effects inherent thereto.
Advantageously, the body of the mixing tool is, in its radial inner range, designed as a tube of round cross section which is provided with a thread and may thus be connected by screws to the mixer shaft. Experience has shown that an optimum influence of the inclined lateral surfaces of the mixing tool upon the mixing ma terial will occur particularly when the distance of the smallest width of the mixing tool, at the narrow area from the radial outer end of the mixing tool will amount to approximately one-third of its distance from the nearest nondeformed cross section of the body. The maximum width of head range advantageously amounts to about 0.5 l.5 times, preferably, however, to 0.6 times the outer diameter of the round tube.
ln contrast to the heretofore known mixing tools, a more intensive liquid cooling of the tool according to the invention encounters no difficulties. Therefore, advantageously, in a manner known per se. cooling liquid is passed through a hollow mixer shaft by means of a feeding pipe arranged in the interior of the tool and is conveyed to a radially outer range of the mixing tool and is discharged in a gap between the feeding tube and the inner wall of the tool. From a cooling technical angle, the tool mantle has a particularly favorable uniform wall thickness.
According to a preferred embodiment of the invention, a suitable impact surface is arranged in the extension of thefeeding tube for the cooling liquid in the rear head range of the tool (with regard to the direction of rotation of the tool). This impact surface deviates the impacting cooling liquid in the direction toward the interior of the nose. Particularly advantageously in this connection, a-portion of the inner surface of the tool mantle acts as impact surface, which tool mantle in its outer contour, as viewed in the direction perpenducular to the direction of rotation has a slanted end. lf, in this connection, the tool, at least in the radial outer range of the impact surface which when viewed in the direction of rotation has a lateral outer confinement of the head range, tearing off edges inclined to the relative movement of the mixing material occur in the rear head range (when viewed in the direction of rotation), which tearing off edges will cause an additional whirling or agitation of the shavings.
Referring now to the drawings in detail, the embodiment illustrated therein comprises a body 10 with a head section 11. Between the body 10 and the head section 11, when viewing in the direction of rotation indicated by the arrows 12, there is provided a constric tion 13. From this constriction 13 in the direction of the head section 11 toward the interior of the mixing chamber there extend inclined lateral surfaces 14 whereas toward the outer mixing wall 15 there extend inclined lateral surfaces 16.
The body 10 is within its radial inner range designed as a round pipe 17 which has an outer thread 18 for connection to a mixer shaft 19. This screw connection is secured by a counter nut 20 (HO. 6).
As will be evident from the sequence of the sections of FIGS. 2, 3 and 4, the round pipe 17 is within the region of the inclined lateral walls 16 flattened on both sides so that an approximately elliptical shape is obtained. The head section (see FIG. 2) has starting from the constriction 13 approximately the shape of a shoe with a nose extending forwardly in the direction of rotation.
Cooling fluid is conveyed through an inner pipe 22 of the hollow mixer shaft 19. This cooling fluid passes from the mixer shaft 19 due to a pumping or centrifugal effect into a feeding pipe 23 which extends up to and into a radial outer range of each mixing tool. The cooling fluid which flows in the direction of the arrows 24 in FIG. 5 will, when leaving the feeding pipe 23, along an extension thereof impart upon an impact surface 25 which is designed as a portion of the mantle of the mixing tool and which impact surface is arranged in the rear head section 11 and is inclined in such a way that the impacting fluid is in the direction of the arrows 24 sprayed into the interior of the nose 21 in order intensively to cool the nose 2! which runs ahead and is subjected to the greatest thermal stresses. Subsequently, the cooling fluid is discharged through the space between the mantle of the mixing tool and the feeding pipe 23 and is conveyed in the annular space 26 toward the mixer shaft.
In the lower portion of the drum-shaped mixing chamber there is provided an emptying or discharging flap 27 which, when the machine is at a standstill, is kept closed by a preload, for instance a counter weight 28. The ring formed by the shavings (not shown) which rotates together with the mixing tools in the head section 11 exerts, however, by the centrifugal force of its forces which eventually cause an opening of flap 27 against the returning force exerted by the weight 28 so that a discharge gap 29 will be freed through which the mixing material can be discharged from the mixing chamber.
During the rotation of the mixingtools, the head section 11 together with the nose 21 loosens up the ring formed by the mixing material and lifts the ring off the drum wall and throws it on both sides uniformly toward the side. The mixing tool does not exert a direct pressure upon the drum wall so that the shavingswill not be pressed and damaged but will rather be intermixed with the material therebelow and radially further toward the interior. As soon as the ring of material to be mixed be comes thicker than the spacing between the constriction 13 and the wall 15 of the mixing chamber, also the inclined side surfaces 16 of the body move in the material to be mixed and in contrast to the side surfaces 14 of the head section 11 exert upon the material to be mixed a pressure in the direction toward the wall of themixing chamber. This pressure increases with the thickness of the ring of the material to be mixed and with the degree of filling of the machine because the surface which is located within the material to be mixed and pushes laterally toward the wall 15 of the mixing drum likewise increases.
Inasmuch as in this phase of operation, which means with a higher degree of filling, a higher pressure is exerted upon the discharge flap 27 which is journalled in the manner of a pendulum, a correspondingly larger quantity of mixing material is pushed through the discharge gap 29 so that a greater quantity of mixing material is discharged in conformity with the respective filling of the machine. The pressure exerted by the side walls 16 of the body 10 upon the mixing material in the direction radially outwardly builds up only laterally and in view of the rotation offset relative to the mixing tool in a direction laterally toward the rear and in contrast to heretofore known mixing tools does not generate in the region in front of the mixing tool a strong pressure which is anyhow independent of the degree of filling. Such building up of pressure ahead of the mixing tool is also avoided by the running ahead nose which in the manner of a plow by means of its running ahead and V- shaped adjusted lateral surfaces 30 and 31 pushes the material toward the side in the direction toward the constriction 13. The back 32 of the nose tangentially merges with a front mantle line of the pipe so that as total result a disadvantageous jamming and squeezing of the material to be mixed in front of the tool will be avoided. In addition to subjecting the machine parts to less stresses and adverse forces, also the strong pulsating shock-like pressing-open and relieving of the discharge flap will be prevented which is encountered with heretofore known tools of the type involved. Quite to the contrary, when using the tool according to the invention, the pressure exerted by the mixing material upon the walls of the mixing chamber and thereby upon the discharge flap 27 will slightly drop in the direct head section ll of the mixing tool because the lateral surfaces 30 and 31 of the nose will push the material in the direction toward the center of the mixing chamber. With a corresponding filling, the tool passing by the discharge flap 27 is followed by the soft pressure of the shavings which with a corresponding filling height is in particular by the lateral surfaces 16 of the body 10 6 pressed toward the outside,-which pressure permits a highly dampened pulsating withdrawal of the mixing material.
'Glue applying machines must frequently be operated with greatly varying throughputs depending on the type of shavingsand of the plates or boards to be made and the thickness ofthe plates to be made. The throughput quantities may vary, for instance, from between 2 to 6 tons per hour. The thickness of the ring of the mixing material in the glue applying machine must, however, remain substantially constant so that the higher throughput has to be realized by causing the shavings to pass through the machine at a higher rate of speed. The design of the tool according to the present invention will in the manner described above assure that with all throughputs a ring of shavings will be obtained which has substantially the same thickness. In practical operation, particularly at higher throughputs, disorders are sometimes encountered which cause a rapid increase in the filling of the glue applying machine. This results in a faulty gluing in view of too little movement of the shavings. The machine will then clog up and the drive will be choked off.
According to a preferred embodiment of the invention, the tools arranged in the discharge elements, in other words the discharge flap 27, are provided with conveying elements 35 which in response to the intended maximum thickness of the ring of shavings being exceeded will immerse into the mixing material and by means of the working surfaces 36 adjusted toward the wall 15 of the mixing chamber will exert an additional pressure in outward direction upon the shavings. When in this connection the ring of shavings becomes thicker than the radial distance between the inner wall of the drum and the outer margin of the conveying elements, the latter will exert upon the excessive thickness of the ring of shavings stronger conveying impulses in the direction toward the discharge. An increasing overfilling is thus counteracted automatically.
The intensive cooling of the tool greatly contributes to the fact that no disorders in the glue applying process will occur due to the formation of lumps in the mixing zone and that also no disorders will occur in the discharge operation. Also in this respect, the tool according to the present invention has great advantages over paddle-shaped tools because the last mentioned tools will not permit any favorable structural design of the hollow chamber for receiving the necessary cooling means. Such hollow chamber design brings about that the paddle-shaped mixing tool would become too great in width and thickness while on the other hand a controlled guiding of the cooling medium to the outer head section which is most subjected to frictional heat will hardly be possible. The formation of deposits on the poorly or not at all cooled surfaces of the mixing tool are inevitable. In view of the geometry of the paddleshaped mixing tool, a self-cleaning effect by friction of the shavings on the tool cannot be expected while the approximate flow line shape, especially in the head sec tion 11 of the tool according to the invention, favors a self-cleaning effect so that in particular the surfaces l4,
16, 30 and 31 which are especially important for pro- 1 ducing the intended effect are kept clean. This action is also aided by the tear-off edges 33, 34 in the rear portion of the head section which edges separate the outside of the impact surface 25 located transverse to the 7 axial direction of the toolsfrom the lateral surfaces 14, 16 of the head section 11. Experience has shown that the lateral surfaces l4, 16 in view of the self-cleaning effect of the shavings friction remain clean up to the edges 33, 34. Past the tearoff edges 33, 34, the whirling effect aids the mixing operation.
Thus, the present invention creates a tool which in addition to having a highly satisfactory mixing effect reduces the wear of the machine and the tool to a minimum, permits an optimum cooling in spite of a simple construction and at the same time exerts a substantially uniform dampened pulsating pressure upon the discharge flap 27 and discharges a quantity of mixing material which corresponds to the respective degree of filling.
It is, of course, to be understood that the present invention is, by no means, limited to the specific showing in the drawings but also comprises any modifications within the scope of the appended claims.
What is claimed is:
l. A mixing tool for a machine for applying glue or the like to particulate material such as wood shavings in a vertical drum-shaped mixing container having a shaft rotatable on the axis thereof, said tool being fixed to the shaft and extending, radially therefrom to near the peripheral wall of the container, said tool comprising; a head section on the radially outer end, a body having the radially inner end adapted for fixed connection to said shaft and the'radially outer end being connected to said head, said head and body tapering inwardly toward one another adjacent the juncture thereof and forming surfaces on the tool which are inclined radially inwardly and radially outwardly respectively, said tool when viewed in the direction of the axis of rotation thereof presenting substantially the same maximum cross sectional dimension as when viewed at right angles to the said axis. 7
I 2. A mixing tool according to claim 1 in which said head when viewed at right angles to the direction of rotation has the greatest dimension adjacent the container wall and when viewed in the direction of said axis has a forwardly protruding nose.
' 3. A mixing tool according to claim 1 in which the radially inner end of said body is circular in transverse cross section and has a thread formed thereon for connection of the body to the shaft.
4. A mixing tool according to claim 1 in which said body is circular in cross section at the radially inner end and the width of said tool at the juncture of said head and body when viewed in the circumferentialdirection is about one-third of the length of the tapered region of said body, the greatest width of said head when viewed in the circumferential direction amounting to from about one-half up to about equal to the diameter of the radially inner end of said body.
5. A mixing tool according to claim 1 in which said head has a forwardly protruding nose formed thereon terminating in a rounded tip, said head comprising plow-shaped surfaces extending rearwardly from said tip on the radially inner sideof said nose.
6. A mixing tool according to claim 1 in which said tool is tubular and has substantially uniform wall thickness, and a coolant pipe extending radially inside said tool for supplying coolant to the inside thereof near said head.
7. A mixing tool according to claim 6 in which said head has a forwardly protruding hollow nose portion and on the inside has a surface disposed in front of the discharge end of said coolant pipe and inclined to direct coolant fluid from the pipe toward the forward part of said nose portion.
8. A mixing tool according to claim 1 which includes a conveying element mounted on the tool in a radial region thereof near the radially inner limit of work material in the container, said element having a surface inclined toward the peripheral wall of the container and operable during rotation of the tool to develop a radially outward pressure on the work material.
9. A mixing tool according to claim 1 which includes at least two said tools mounted on said shaft in uniformly circumferentially distributed relation.
10. A mixing tool according to claim 9 in which the container is circular in cross section and said tools are threadedly connected to the shaft for radial adjustability thereon.