A METHOD AND AN APPARATUS FOR MIXING MATERIALS

Abstract: A method of mixing materials in a container (1) having two or more rotating stirring means (10, 20, 30) and an apparatus for performing the method, in which at least one of these stirring means (10, 20, 30) is caused to rotate with a speed of rotation (1, 2, 3) differing from that of the other or the others by a value not exceeding 25 %.

Description: A method and an apparatus for mixing materials The invention concerns a method of mixing materials. More specifically, it concerns mixing of materials, such as e.g. granulate (stones, gravel, sand, etc. ) and liquids by means of two or more rotating, substan¬ tially functionally uniform sets of stirring means. In known mixers, having two or more substantially func¬ tionally uniform sets of stirring means, the paths of movement of the sets have been overlapping owing to mixing efficiency since it has been believed that this resulted in quicker and better mixing of materials . Therefore, it has also been necessary to have the sets rotate with a synchronous speed of rotation. Such a mixer is known from the German Offenlegungsschrift 2 029 950 where two sets of horizontal, parallel stirring means forcibly mix concrete in a container. However, it has been found that this method is inexpedient since the synchronous stirring, in spite of overlapping paths of movement, causes areas to be formed in the container where the mixing efficiency is poor, which is due to a symmetrical movement in the mixture. The object of the invention is to provide a method which gives a more uniform mixing effect in the entire mixing container. This is achieved, as stated in the characterizing por¬ tion of claim 1, in that the stirring means are caused to rotate with a disunifor speed of rotation. The invention also concerns an apparatus for performing the stated method and of the type defined in the intro- ductory portion of claim 9, and the characteristics of the apparatus of the invention are stated in the characterizing portion of claim 9. The invention will be explained more fully below with reference to the drawing, in which fig. 1 shows the fundamental structure of the mixer of the invention, and fig. 2 shows a preferred embodiment of the invention. Fig. 1 shows how a plurality of rotating stirring means 10, 20 and 30 in a mixing container 1 are mutually secured to a holder 5. The rotating stirring means 10, 20 and 30 are constructed uniformly in princiμ . e and comprise e.g. a plurality of fixed blades 11 and 12, 21, 22 and 23 and 31, 32 and 33. The stirring means rotate individually with respect to the holder 5. The speeds of rotation c l , t 2 and > 3 for the εtirrjng means 10, 20 and 30 are disuniform so that e.g. ιύ = ύ 2 , and cύ 3 is 5% greater than cύ 1. The result s that the mutual movement of the blades will be asy:*: me¬ trical, which has been found to be very expedient wnen uniform and rapid mixing of materials is desired. ' e holder 5 may moreover rotate with a speed of rotati n Cύ 5 about an axis 6 common to the stirring means. This common rotation may instead be established in that the mixing container 1 rotates with respect tc the stirring means 10, 20 and 30. The common speed of rotation tϋ 5 will typically be some orders of magni¬ tude smaller than (ύ 1, tϋ 2 and Cύ 3. Fig. 2 shows a preferred embodiment of the invention where the function is provided by means of a planet gear. A motor wheel M sets a planet wheel carrier PB in rotation with respect to a fixed sun wheel S. Stirring means in a mixing container 50 are provided with a planet wheel PI, P2 or P3, said planet wheel being engaged with the first sun wheel S and rotatably jour- nalled in the planet wheel carrier PB. According to the invention the tooth numbers nl, n2 and n3 for the planet wheel PI, P2 and P3 are mutually different, thereby providing asynchronous rotation of the stirring means. Since the position of blades on the stirring means may. differ, it is necessary in certain cases that the position of the axes of rotation of the stirring means can be selected individually, which may be obtained by inserting an idler gear wheel MT between the sun wheel S and the planet wheel P3. This changes the di¬ rection of rotation of the stirring means, and if this is not desirably, two idler means are to be used. Of course, the invention can be realized with diffci • . z forms of drive mechanisms, e.g. by electrical or hyά * _.- lic operation. The advantageous aspect of the invent .. n can also be obtained in that e.g. each stirring mean.**, is provided with separate drive mechanisms, it being only necessary to establish a disuniform speed of rot - tion for the stirring means. In addition to the subst .- tially uniform stirring means operating with a disuni¬ form speed of rotation, a mixer according to the inve: - tion may also comprise other means for making the mixiri of materials more efficient. This may e.g. be a mixing screew intended for pulverization of the material, said screew rotating with a considerably greater speed of rotation than the stirring means since its function is different.

Claims: P a t e n t C l a i m s 1. A method of mixing materials in a container having two or more sets of rotating, substantially functionally uniform stirring means adapted for uniform working of materials, c h a r a c t e r i z e d in that the paths of movement of the sets are not mutually over¬ lapping, and that at least one of the sets is caused to rotate with a speed of rotation differing from that of the other or the others by a value not exceeding 25%. 2. A method according to claim 1, c h a r a c t e r ¬ i z e d by using a stationary container in which the sets of rotating stirring means rotate as a unit about a common axis. 3. A method according to claim 1, c h a r a c t e r ¬ i z e d by using a rotating container in which the sets of rotating stirring means form a stationary unit. 4. A method according to claim 2, c h a r a c t e r ¬ i z e d by using rotating sets of stirring means po- sitioned with a different radius of rotation with re¬ spect to the common axis. 5. A method according to claims 1-4, c h a r a c ¬ t e r i z e d by using three sets of rotating stirring means. 6. A method according to claims 1-5, c h a r a c ¬ t e r i z e d by using sets of rotating stirring means, each of which comprises three blades. 7. A method according to claims 1-6, c h a r a c ¬ t e r i z e d in that at least one set of the stirring means is caused to rotate with a speed of rotation differing from that of the other or the others by a value of about 5%. 8. An apparatus for performing the method according to any of the preceding claims, comprising a container with two or more substantially functionally uniform sets of stirring means which rotate about a common central axis, each of said stirring means being rotat- able about its axis of rotation, and a planet gear where a motor drives the planet wheel carrier whi*~h rotates about the common central axis, where the sun wheel is stationary, in which planet wheel carrier the axes of rotation for the stirring means are v i- tioned, c h a r a c t e r i z e d in that at lea.it one of the planet wheels has a tooth number differing from that of the other or the others by a tooth nu oer not exceeding 25%. 9. An apparatus according to claim 8, c h a r a c ¬ t e r i z e d in that one or more of the planet wh -els are driven by the sun wheel via an idler gear wheel .

Inventors: GRAU-CHRISTENSEN ARNE, NIELSEN NIELS HOELL, GRAU-CHRISTENSEN, ARNE, NIELSEN, NIELS, HOELL
Applicants: SKAKO AS, SKAKO A/S
Application year: 1989
Main classification: B01F7
IPC codes: B01F7, B28C5