US2225797A - Colloidal mill - Google Patents

Description

Dec. 24, 1940. H. PLAUSON 2,225,797

' COLLOIDAL MILL Filed Dec. 14, 195B 2 Sheets-Sheet 1 5y J dig Afgar-ney Patented Dec. 24, 1940 UNITED STATES PATENT OFFICE Application December 14, 1938; Serial N0.'245,683 In Germany December 17, 1937 4 Claims. (01. 83-93) Colloidal mills are known in which one or two toothed wheels are mounted within a fixed counter-beater provided with similar teeth. In all these colloid mills the breadth of the teeth is equal or approximately equal to the intermediate spaces between individual teeth.

Such arrangements sufier from the following serious disadvantages:

The mill allows too little or almost too little of the material being treated between the toothed wheels, if the material runs continuously through the mill in the direction of rotation. The through flow capacity is too small even when the rotor teeth lie opposite the intermediate spaces of the i counter-beater, because the breadth of the rotor teeth bridges over the opposite intermediate spaces. To overcome this disadvantage it has already been proposed to employ cross recesses out in the toothed wheels in the direction of ro- 20 tation.

Such a construction does indeed permit large quantities of material to be passed through the mill; but the efficiency is too low because a part of the fluid can pass through the intermediate 25 spaces without being beaten.

A further deficiency of the known construction is that the vibrations occurring during the grinding have too small an amplitude for the principle of the colloid mill to be regarded as a vibration -30 principle.

As a result of many experiments a new kind of colloid mill, forming the primary object of the present invention, has been developed, in which the grinding or dispersing action is produced by 35 a very high rate of vibration or oscillation up to that of ultra sound waves, this amounting to the discovery of an entirely new principle of colloid milling.

On the basis of the experiments it has been established that an entirely new effect in colloid milling is obtained, if the ratio of tooth breadth to the'intermediate spaces cut in the rotor and in the stationary casing serving as counter beater, is'not as hitherto usual 1:1, but is made 5 1:2 or still better in large machines 1:3 (the figures 2 and 3 indicating the ratio of the intermediate spaces cut between the individual teeth) and the material under treatment is carried in and out in the direction of rotation. with such a 50 construction it is possible that the material under treatment at the instant that the rotor teeth are in the centre of the empty spaces between adjacent casing teeth, flows between the rotor and casing in a free zig zag path to the point of out- 55 flow. The feeding of the material from the inlet to the outlet is effected by the rotation of the rotor, and this gives such a powerful pumping effeet that the material can be pumped back from the outlet to the inlet funnel without any additional pump. In this way a multifold uninterrupted automatic circulation of the material through the mill and continuous rhythmic vibration of the material are made possible. The material can be pumped directly into the discharge receiving vessel through a separate pipe. In practice the circulating pipe will always remain more or less open even during discharge, to moderate the internal pressure on the stufling box packing.

The action of the new vibratory colloid mill is based upon the feature that when the proportions of teeth and intermediate spaces are for example 1 cm. and 3 cm. (the depth of the intermediate spaces is about equal to the breadth of the teeth both in the rotor and the casing) two phases occur in each period. The first phase 00- curs when a casing tooth is opposite a rotor tooth. The greatest pressure and milling action then occurs. The flow of the fluid stream is however almost entirely interrupted. The second phase occurs when the tooth surface of the ro- 5 tor is opposite the centre of the intermediate 'space between two tooth surfaces of the casing.

Then the pressure action on the fluid material is least and a passage for the flow of fluid of 1 cm. cross section has been set free. The change from the one to the other phase proceeds in regular succession. The material during these periods must fiow in a zig zag path through the free space opened from period to period between the rotor and casing and is thus subjected to periodic vibrations or oscillations of high rate which are produced by regularly alternating pressure and release.

Even with normal rates' of the periods these colloid mills can work as reaction and dispersion 40 apparatuses with high output.' It is possible however to build machines which eiiect a raised rate of vibration which approaches the rate of ultra sound waves. In such constructions the new effects characteristic of the invention, which are similar to the efiects of ultra sound waves, come into play.

A colloid mill is known in which a grooved cylindrical or slightly coned grinding rotor runs concentrically within a stator having the same number of grooves. An uninterrupted rhythmic vibratory action on the material under treatment as is obtained in the present construction of vibratory colloid mill by the arrangement of the inlet and outlet openings, is not possible in the known mill even if the grooves are wider than the ribs because the feed direction for the material in this known mill is axial, so that the material is kneaded between the grooves and ribs in a helical path but a continuous rhythmic vibratory eflect on the material is prevented by interference phenomena. In contradistinction the major advantage of 'the present vibratory colloid mill lies in theemployment of continuous rhythmic vibration of the material. By the entry of the material, according to the invention, in the direction of rotation and its outflow after traversing say of the periphery of the casing before a final, smooth quarter, the vibratory colloid mill is at the same time given the ability to pump, which is of great importance for its technical employment and is unattainable with the known colloid mills.

One of the known colloid mills in addition has diiferent numbers or pitches of tooth surfaces on the rotor and casing so that rhythmic vibrations as are obtained according to the present invention, are interrupted by interference phenomena.

The new colloid mill will be further described by the aid of examples.

Example 1 rhythmically occurring vibration, namely 2500 single amplitudes of vibration or'1250 periods per second, is by this mechanical force, given a highvalue impetus and acceleration so that the apparatus according to the invention can render valuable service both as an excellent dispersing giachine and for'carrying out chemical .reacons.

toothedgearing at 6,000 B. P. M., then 150,000 periods or 300,000 single amplitudes per minute are obtained, equalling 2500 periods or. 5000 single amplitudes per second. I

This does not represent the limits of possibility however, The colloid mill can be driven at 9000 R. P. M. or, by the use of a high speed tur blue, at 12.000 R. P. M.: in the latter case 25X 12,000=300,000 periods or 800,000 amplitudes per minute are obtained; representing an extremely high periodicity per second. Phenomena similar to those on the boundaries of ultrasounds now come into play and with them entirely new. possibilities and new actions in the production of dispersions and the forwarding of chemical reactions by mechanical power.

Example 2 In order to achievemtri-sound-like eifects for particular purposes with the new. vibration principle, colloid mill, the tooth surfaces of the rotor and the casing are made with a breadth of but 5 1 mm. and the intermediate spaces between them of a breadth of 1 cm. and a depth ofabout 1 cm. If a rotor diameter of 800 mm. is used, which corresponds to a periphery of approximately 943 mm., then 63 periods are obtained per revolution. with a speed of only 6.000 R. P. M. accordingly If this colloid mill is. driven by the aid of 378,000 periods per minute are obtained, equalling 6,300 periods or 12,600 single amplitudes per second. Using a speed of 18,000 R. P. M. which is technically quite feasible and has alreadybeen employed, 63x18,000=1,134,000 periods and 5 2,268,000 amplitudes per minute are obtained equalling 37,800 amplitudes per second.

If the diameter is increased to 500 mm. and a driving speed of 18,000 R. P. M. is used, 104 -l8,000=1,892,000 periods or 3,744,000 amplitudes per minute, i. e. 62,400 amplitudes per second, are obtained. The working range of ultra sound waves is thereby attained. .But in practical use excellent technical results are already obtained with considerably lower rates of vibration. It is desired to point out however that it is possible within the scope of the invention to obtain vibrations akin to ultra sound waves by means of the present vibratory colloid mill.

The present colloid mill is best constructed wi h a funnel having a regulating valve, arranged over the casing which itself is provided with a cooling or heating jacket. After starting the machine the material under treatment flows through the regulating valve and over /4 of the periphery of the counter-beater casing, over the beater teeth and intermediate spaces, to the outlet. In a construction according to Example 1 the material in this time undergoes pressure and release actions, that is 25 periods in unbroken succession. Shortly before the last quarter of the casing periphery the material is forced out by the pumping action of the toothed wheel and is returned thrc"'!h a pipe to the filling funnel, as long as the procedure is to be repeated. For discharge a suitable discharge fitting, is provided in the return pipe. The interior of the casing is toothed to correspond with the rotor only over of its periphery. The quarter of the casing beyond the outlet is made smooth to permit pumping out or increase the pumping effect.

A heating or cooling Jacket is provided in the casing of the vibratory colloid mill, through which for example in the treatment of pasty material steam or hot water can be led.

Colloid mills the action of which rests upon the principle of vibration were unknown hitherto. That vibration efiects akin to ultra sound waves could be produced on liquids, gases or vapours by mechanical action was not know. and above all how such effects were to be obtained in practice was not to be foreseen.

Withthe-use of high periodicities,.it is not necessary to extend the casing teethaccording to the invention over the whole distancefrom inlet to outlet. On the contrary only say a half of this part of the casing or separate portions of it can be provided with teeth. For example closely after the inlet of a group of say 10 teeth can be provided and closely before the outlet another group of 10 teeth. Groups of teeth could however be provided at 3 or 4 places. Such a construction is necessary with very high periodicities to regulate the through flow rate.

In the accompanying drawin s one construc- 05 tion according to the invention is shown by way of example.

In this drawing:

Fig. 1 is a cross section and Fig. 2 is a longitudinal section through a colsential to obtain the rhythmic vibratory actionof uniform nature upon the liquid material to be treated.

Only of the circumference of thestationary casing is provided with the above mentioned toothing. No teeth are provided between the discharge or pumping out point 'I and the supply point 3, but these intermediate spaces are metallically filled. Due to this construction, the

automatic pumping necessary for the vibratory colloidal mill is obtained and thereby a'longer vibratory action of uniform and continuous character is possible on the material to betreated.

From the discharge point I a conduit 8 havin a discharge valve or cook 9 leads back to the funnel I so that the material to be treated may con+ tinuously be acted upon until the desired state of quality is obtained.

The machine is provided with a cooling space It, having inlet and outlet connections II and I2, and its lower frame I! rests upon a foundation plate It.

F18. 2 illustrates the colloidal mill in an axial section showing the funnel I. the feed control valve or cock 2 and the supply pipe 3. The spaces between the teeth 8 on the rotating inner toothed wheel and on the stationary casing are designated 6. The edges of the teeth are indicated on the drawing. The body of the toothed wheel and the axis are designated l5 and It respectively. The water cooling or heating space and the feed connection are again designated l0 and II respectively.

The shaft I6 is, at the points where it passes through the wall of the vibratory space, sealed by means of a metal-graphite-packing II. .The shaft Ii ends on the one hand behind a pressure oil bearing separated from the machine and on the other hand is passed through a pressure oil bearing and ends in a'coupling projection 2|. The pressure oil bearings aredesignated ll and i9 and are connected to pumps (not shown) through III. The oil pump constantly and automatlcally .eflects lubrication under pressure. By

means of the coupling projection 2| the machineisconnectedtothemotoseitherdirectlyor by way of a gear changing the speed of revolution. 1

What I claim is:

l. A colloid mill comprising a casing, internal teeth in said casing over about three quarters of its periphery, the remainder being smooth and at the height of said teeth, an inlet to said cas- 5. ing located at one end of said smooth remainder and directed peripherally away therefrom, an outlet from said casing at the other end of said smooth remainder, a rotor journalled in said casing, and teeth on said rotor running with small clearance past said' casing teeth, the casing teeth and rotor teeth being equally pitched'and their thickness being substantially less than the spaces between adjacent teeth.

2. A colloid mill comprising an internally 15 toothed casing and a toothed rotor therein, the

teeth of said casing and rotor being equally pitched but having a thickness substantially less than the spaces between adjacent teeth, the casing only. being toothed in groups over a fraction of its periphery and provided with an inlet in front of said fraction to direct suppliedfluid material in the peripheral direction and; with an outlet beyond said fraction and the imtoothed portion of said casing between said inlet and outlet embracing a substantial angle and lying close to the teeth of said rotor.

3. A peripheral flow colloid mill comprising a rotating toothed rotor and an internally toothed casing surrounding said rotor, the rotor and casing having equally pitched teeth, the tooth width of the rotor and easing being in a ratio of about 1:2 to 1:3 tothe spaces betweentheteethand the casing only having teethover of its periphery and being smooth and close to said rotor teeth 85 over the remaining quarter, an inlet for the material being provided immediately after the smooth quarter of the periphery of the casing, and an outlet for the material being provided immediately before said smooth quarter.

4. A 'colloid mill comprising a casing having smooth arcs of substantial length and tooth groups alternating. the tops of the teeth being level with said smooth arcs, an inletto said casing located at one end of one of 'said smooth arcs and directed peripherally away therefrom,

an outlet from said casing located at the other end of said last mentioned smooth are, a rotor iournalled in said casing. and teeth on said rotor running with small clearance past said'cas- 50.

ingteetmthecasingteethandrotorteethbeing equallypitchedandtheirthicknessbdhtsubstantialiy lessthanthespacesbetweenadiacent PLAUBON.

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