US3405874A - Apparatus usable in particular for preparing paint and printing ink - Google Patents

Description

Oct. 15, 1968 J. M. A. BRIZON 3,405,874 APPARATUS USABLE IN PARTICULAR FOR PREPARING PAINT AND PRINTING INK 2 Sheets-Sheet l Oct. 15, 1968 J. M. A. BRIZON 3,405,874

APPARATUS USABLE IN PARTICULAR FOR PREPARING PAINT AND PRINTING INK Filed Dec. 17, 1965 2 Sheets-Sheet 2 United States Patent 4 Claims. ci. 241 174 ABSTRACT OF THE DISCLOSURE A crushing apparatus comprising one or more crushing cells each having two substantially vertical and parallel walls and a horizontal rotating shaft perpendicular to said walls, agitating arms on said shaft, and balls substantially filling the available space within the cell, the distance between the two said walls being less than one quarter of the height of the cell and the sum of the dimensions of the agitating arms, parallel to the shaft, being at least half of said distance. The apparatus may comprise several cells mounted vertically one above the other, and the aforesaid walls may be cooled by a circulating medium. The halls employed should be not more than ten millimeters, and preferably about two millimeters, in diameter.

The pigments used in paints and certain printing inks are usually crushed by means of balltype crushers, the partly filled cylinder of which is rotated about a horizontal axis. Friction against the cylinder wall causes the balls to be carried along and to form a sloping pile, with the balls continuously falling from the top to the bottom of this pile.

It is also known to use crushers containing balls of smaller diameter which are forcibly agitated by rotating blades instead of by mere rotation of the cylinder. Crushers of the latter type include a stationary cup which is filled with balls and the vertical axis of which is occupied by a rotating shaft having a plurality of superimposed agitators. Such crushers have the major drawback that the pigments to be crushed, which are relatively dense, naturally tend to deposit at the bottom of the crusher even if a helical impeller is positioned adjacent the bottom to raise the pigments, as is generally the case with paint mixers.

This solution is not very elfective in the case of crushers filled with balls. The crushing achieved tends to be irregular and varies in both the upward and radial senses of the crusher. Further, the impellers or agitators, which must rotate very fast to stir the pigments effectively, tend to wear out rapidly in contact with the balls. Lastly, the larger the crusher, the more powerful must be the agitating effect to ensure uniform crushing. This in turn entails a considerable temperature rise, making the cooling of such crushers both difiicult and irregular.

These drawbacks have naturally limited the maximum size of vertical crushers equipped with agitators and adapted to be filled With balls.

It is accordingly the principal object of the present invention to overcome these drawbacks, especially the unequal crushing and the temperature rise, irrespective of the total capacity of the crusher, and to eliminate the blemishes which may be caused by friction of the balls against the wall and the agitator, notably in the case of light coloured paint. The invention thus enables crushers of greater capacity and crushing speed to be built without difficulty.

A crusher according to the invention consists essentially of a horizontal cylinder having at least substantially vertical end-closures, which is coaxial with a rotatin shaft carrying agitating arms of rounded cross-section (at least two of which revolve adjacent the end-closures) and which is filled with balls. In a first form of embodiment of the invention, the length of the straight horizontal generating lines of the cylinder is preferably less than onequarter of the cylinder diameter. The vertical end-closures of the cylinder are therefore very close to each other, and the distance between them must not exceed twice the aggregate of the axial dimensions of the agitating arms. This being so, only by increasing the cylinder diameter is it possible to augment the capacity of this crushing unit, which will necessarily be shaped as a flat cell formed by a small portion of a horizontal circular cylinder. The agitating arms are small in number in order to avoid heating up, the preferred number being three. The distance between each end-closure and the arms adjacent thereto is less than the axial dimensions of the arms.

The cylinder may be stationary during the crushing operation and be provided with double-walled vertical end-closures cooled by water circulation. The rotating shaft may carry only three agitating arms regularly spaced apart and jointly occupying more than half the length of the cylinder. The walls, arms and shaft may be covered with low-friction plastic, an example being polytetrafluoroethylene which has the added advantage of possessing unusually good abrasion and heat resisting properties.

In an alternative form of embodiment, a large-capacity crusher comprises a plurality of flat crushing cells forming juxtaposed portions of the same cylinder separated by vertical double walls between which circulates a coolant. The cylinder may be caused to rotate, preferably in the opposite direction to the shaft carrying the agitating arms.

Since, in order to be effective, crushing by means of small balls requires that the substance to be crushed be fluid enough, i.e. contain an appreciable proportion of thinner, the apparatus according to the invention could be unsuitable for crushing substances containing little or no thinner, an example being viscous printing inks. This drawback can be overcome by first diluting the paste to be crushed, thereby enabling the crushing to be satisfactorily accomplished in the subject crusher of the invention. The additional solvent can then be extracted, since it was incorporated solely for crushing in a thick-paste mixer similar to a helical paddle type kneader, equipped with a resistance-type heating enclosure and a vacuum pump. The solvent used may be a special solvent which is not included in the formulation for the substance to be crushed but which is particularly volatile.

The invention consequently also relates to a method which includes the steps of diluting a substance to be crushed by means of an additional solvent, and of subjecting the fluid paste obtained thus to a crushing accomplished almost exclusively by balls rolling over one another, affer which part at least of the solvent is evaporated and may be recovered if desired.

The invention includes in its scope a piece of apparatus obtained by superimposing a horizontal-axis crusher as hereinbefore described and a mixer-extractor into which the fluid paste may flow under gravity subsequent to crushing.

in yet another form of embodiment of the invention, both the balls and the internal lining of the crusher cell are made of a very hard steel or metal, with the balls preferably having a diameter of no more than about 2 mm.

This particular constructional form makes it possible to simultaneously achieve:

(i) Very rapid crushing, due to the fact that the density of the steel balls is more than three times that of the glass or steatite balls usually employed in crushers used for quality paints, and also that, for a given total volume, small-diameter balls have a greater total area than larger-diameter balls;

(ii) Very great resistance to wear of the component 3 parts of the apparatus; in this connection it should be noied that the small diameter of the steel balls assists in reducing wear due to shock, since the mass of the balls is relatively low notwithstanding their high density; and

(iii) Complete freedom from pollution or blemishing in the case of white or light coloured paints, irrespective of the grade of steel used for the crusher walls.

The halls, of which the diameter is preferably 2 mm., and the internal lining of the crusher container may be made with advantage of a chromium steel containing for instance 1.5% of chromium and 1% of carbon such as the KS steel produced by the UGINE Company, which after hardening by tempering at 850 C. possesses a Rockwell hardness of 62 to 64.

Since this metal becomes brittle after hardening and consequently has little resiliency, and tends furthermore to distort under hardening, it is preferable for the body of the container to be made of a commonplace steel of good resiliency having a degree of hardness permitting easy fabricaiion, and to line the container internally with hard steel. In providing this lining it will be advantageous to use the hard steel in the form of small adjoining plates secured to the frame in any convenient manner, for instance by means of screws. In order to obtain the same degree of hardness for the horizontal shaft and the agitating arms carried by the same, these parts may be sheathed with the same metal. Further, in order to ensure that the lining posseses equal hardness in its midst as on its surface, its thickness should preferably be small. The plate referred to may have a thickness to 10 mm. and the sheaths a thickness of about to mm.

Alternatively, the hard lining to be provided for the container may be made of nitrogen-hardened steel, the balls being made either of structurally hard steel as precedingly, or of nitrogen-hardened steel.

In yet another form of embodiment, the container may be lined with a l to 3 mm. thick layer of electrolytically deposited hard chromium.

In accordance with a specific feature of this invention, a plurality of flat cylindrical cells may be superimposed and interconnected whereby to produce, by means of this superimposition and a vertical intercommunication between the cells, a column of balls of great height and weight, thereby increasing the effectiveness of the crusher.

According to a simplified embodiment, two flat walls parallel to the horizontal superimposed shafts may be substitute to the cylindric walls of the superimposed cells.

The main advantage of this embodiment, in which the container is essentially bound with flat walls is the possibility to build the highly hard lining with flat sheets, easier to produce than curved ones.

These curved sheets are only used to build the bottom of the container, which will be shaped as an half-cylinder, corresponding to the circles swept by the agitating arms of the lower shaft, to avoid any deposit of pigments lining on the bottom of the cell.

The description which follows with reference to the accompanying non-limitative exemplary drawings will give a clear understanding of the different features of the invention and of the art of carrying them into practice, such additional features as emerge either from the description or the drawings obviously falling within the scope of the invention.

In the drawings,

FIGURES 1 and 2 are elevation views of an improved crusher according to the invention, shown in diametrical section and in cross-section, respectively;

FIGURE 3 shows in diametrical section an alternative constructional form of said crusher, comprising a plurality of juxtaposed crushing cells;

FIGURE 4 shows schematically in elevation an improved machine comprising a crusher having a juxtaposedcells, type crusher superimposed upon a mixer-extractor;

FIGURE 5 shows schematically in elevation an arrangement of three superimposed cylindrical cells interconnected in series, the front end-closure being assumed to be cut away in its centre and the casing of the middle cell to be cut open to show the agitating arms;

FIGURE 6 is a sectional view of this apparatus taken through the vertical plane containing the axes of the three shafts; and

FIGURE 7 shows on an enlarged scale the cross-sectional form of an agitating arm;

FIGURE 8 shows schematically in elevation another embodiment.

FIGURES 1 and 2 show a flat" crusher according to the invention, comprising a stand 1, a cylindrical container for receiving the paste to be crushed (generally designated by reference numeral 2) and a rotating shaft 3 for agitating balls 15 which fill container 2 almost entirely.

Said container is formed by a cylindrical wall 2a, the length of the straight generating lines of which is less than one-quarter of the cylinder radius, and two end-closures which may be flat and consist in each case of two walls 212, 20 with a small axial gap 9 therebetween. The endclosures are respectively rigid with two axial bushes 5, 6 supporting the container. Bush 5 is provided with a seal 4 and has shaft 3 extending through it. The other bush 6 carries a mechanism for rotating the container about its axis to permit loading and unloading, an example being a worm screw 7 rotated by a crank 8. Loading and unloading is made possible by the provision, on cylindrical wall 2a, of a plug 14 (which may be replaced by a grill of sufficiently fine mesh to retain the balls 15) and by mounting a receiving hopper 16 (which may form an integral part of stand 1) beneath container 2.

The end-closures are cooled by means of flexible pipes 10, 11 which cause a coolant such as water to circulate through the gap 9 between walls 2b, 2c. A connecting pipe 12 permits where necessary of spacing the inlet and outlet points for the coolant. It goes without saying that additional connecting pipes or the like (not shown in detail in FIGURE 1 but exemplified in FIGURE 3) are provided to cool the end-closure remote from bush 6.

Shaft 3 carries for example three staggered agitating arms 3a of rounded cross-section. These arms are spaced from one another and from the walls, by possibly equal gaps. Preferably, the cross-section of the agitating arms is circular and their tips are rounded. Shaft 3 is driven by a motor 13, through the medium for instance of a pulley 3b and a V-belt.

By way of example, the cylinder may have a diameter included between 60 and cm. and a length of 15 cm. The arms 3a may have a diameter of 3 cm. These arms are located at equal distances from the end-closures and are 1.5 cm. apart axially. Shaft 3 rotates at approximately 60 to 70 r.p.m., a speed less than one-third that of a conventional vertical-axis crusher.

The apparatus hereinbefore described functions as follows: crank 8 is used to first position cylindrical container 2 with plug 14 at the top, the container being filled with balls 15 and with material to be crushed, an example being a suitably diluted pigment. Motor 13 and the cooling system are then started.

The rotating arms 3a cause the substance filling the container to be very uniformly crushed, due chiefly to the friction between balls 15 and also to the fact that the arms are located immediately adjacent the end-closures, the balls being thrust against the latter by the transit of each arm. Hydrostatic pressure causes the friction between the balls to increase with decreasing distance from the bottom of the container, thus increasing the effectiveness of the crushing in the lower part of the crusher and offsetting the tendency of dense substances to deposit.

The temperature rise can easily be controlled because of the relatively large expanse of the walls, and particularly the end-closures, of container 2. The rounded arms 3a wear very little, and in any case problems of heating up and wear are of only secondary importance since the homogeneous crushing achieved enables low rotation speeds to be used, thereby lowering the power needed to drive shaft 3 and simplifying the mechanical design of the crusher.

Preferably, the balls are very small, their diameter being advantangeously less than 1 cm. They may be made of any of the usual materials, examples being steatite, or hardened glass in the case of light coloured paints. Friction of these balls against the walls of container 2, the shaft 3 and the arms 3a can be considerably reduced by covering these parts with a substance having a low coefiicient of friction, such such as polytetrafluorethylene, which likewise has a great capacity for withstanding heat and abrasion.

Once the crushing has been completed, the plug 14 is replaced by a grill adapted to retain the balls 15 and container 2 positioned so that its opening is at the bottom, whereupon the crushed material will flow out under gravity into receiving hopper 16.

FIGURE 3 illustrates an alternative constructional form for a large-size crusher having five juxtaposed cells separated by partition Walls cooled in the same way as the end-closures. Container 2 may if desired be contiuously rotated by a motor 18 which drives it through the agency of a worm screw 17 and bush 5, preferably in the opposite direction to shaft 3. Cooling liquid is admitted and discharged via rotary unions 21, 22 carried by bush 6 and fed through pipes and 11. Interconnecting pipes 19, 20 distribute the cooling liquid between the various walls to be cooled. This particular design completely eliminates any tendency for the substance being crushed to deposit.

Reference to FIGURE 4 shows a machine formed by positioning, beneath a crusher 25 of the type just described, a mixer 26 for thick pastes which comprises a leaktight casing 27, a vacuum extraction pump 28 and a heating system which may either be electrical or operate by steam circulated through casing 27, which casing would in that case be double-walled and provided with inlet and outlet conduits 31, 32. Preferably, mixer 26 is of any convenient known type comprising a helical paddle 29, with the paste from crusher 25 passing therethrough subsequent to opening of a leaktight plug 30.

The procedure for preparing a synthetic ink or 'a glycerophthalic paste, comprising only a small proportion of dense and barely volatile solvent such as white spirit, is to fill the flat crusher according to the invention with a mixture containing all the pigment, part only possibly of the binding agent entering into the ultimate composition of the ink or paste to be prepared, and an auxiliary solvent which is preferably more volatile than the former solvent.

The crusher is sealed leaktightly after having been possibly drained of air by causing an inert gas (nitrogen or or carbon dioxide) to blow through it, in order to avoid any risk of explosion. The crushing can then be effected and lasts for a relatively short time.

The fluid paste resulting from this crushing is transferred into the mixer, preferably under gravity, after which the vacuum pump and the heating system are started up and the paste is ground long enough to extract the auxiliary solvent incorporated solely for the crushing operation. The substances required to complete the definitive formulation for the paste can be added before or after extraction.

Alternatively, in cases where the formulation for the material to be crushed included a fairly volatile solvent, a surplus amount of this solvent may be placed in the crusher and evaporated subsequent to crushing.

For a given degree of fineness, the efiiciency of the apparatus and method described hereinabove are greatly superior to that obtainable with conventional cylindertype crushers, while the use of an auxiliary solventwhich may be recovered and used several times over-enables products covering a wide viscosity range to be obtained. Foremost among the solvents suitable for use are the aromatic or aliphatic (light gasoline) solvents, and methanol, which has a very low boiling point, or even the chlorinated volatile solvents, which are non-inflammable.

The apparatus shown in FIGURES 5 through 7 comprises three crushing containers or cells 40, 41, 42 placed one above the other. Each of these cells is of flat cylindrical shape as hereinbefore described, i.e. its diameter is greater than the distance between its end-closures. By

way of example, each cell may have a width of 15 cm.'

for a diameter of 35 cm. Each cell is made up of a cylindrical shell or cylindrical shell portion 40a, 41a, 42a, clamped between two side- plates 49, 50 of rectangular shape say, forming the end-closures common to the three cells.

Respectively concentric with these three cylindrical cells are rotating shafts 43, 44, 45 arranged one above the other in the same vertical plane. Each shaft carries a plurality of agitating arms, for instance three arms 46, 46a, 46b mutually spaced at angularly, and by equal distances along the length of the shaft. The three shafts are'interconnected by a system of pulleys 47 and belts 48 (or chains and sprockets), whereby the rotation imparted to any one of these shafts by an appropriate motor, and preferably via a speed variator, is transmitted to the other two shafts.

The three cylindrical containers are interconnected in series, the bottom of the middle cell 41 communicating with the top of the lower cell 40 via a wide slot 51 parallel to the cylinder generating lines, and the bottom of the upper cell 42 communicating with the top of the middle cell 41 via a wide slot 52. Thus, a tall column of balls is formed from the bottom to the top of the container, and the pressure exerted by one ball on another at the bottom of the lower cell 40 is very high. In effect, the three cells jointly act as a single cell the height of which is six to eight times the Width.

This bottom of the lower cell includes a pipe 53 for admitting the substance to be crushed, which is delivered under pressure by a suitable pump, and the top of the upper cell 42 is fitted with a pipe 54 for discharging the crushed substance. Pipes '53 and 54 are fitted with wire gauze or the like to prevent the escape of the balls which fill the major part of the volume of the three cells.

For a given capacity, such as a crusher having multiple superimposed cells can be designed with unit cells of relatively small diameter. The agitating arms 46, 46a, 46b of each cell will then be relatively short and thereby permit much higher rotation speeds than with longer arms.

Preferably, as shown in FIGURE 3, the arms are diamond shaped in cross-section, thereby making it easier for them to cut through the mass of balls, which they set in rapid horizontal agitation.

It goes without saying that the continuously operating apparatus described with reference to FIGURES 5 to 7 could also be operated intermittently.

Like the end-closures, the cylindrical shells are lined with a very hard metal, as indicated precedingly. In FIGURE 6, this lining is designated by the reference letter r, while the letter 0 designates a metal of lesser quality and good resiliency used for the body of the end-closures and the cylindrical shells.

In FIGURE 5, the middle cell, which is shown cut away, has the lining represented as being formed of small plates which, in the case of the end-closures, are flat and juxtaposed vertically (plates p and which, in the case of the shells, are formed as cylinder portions cut out along the generating lines (plates p These plates can be secured in position in any convenient way, for example by means of screws, their preferred thickness being about 10 mm. Alternatively, juxtaposed rods or bars could be used in lieu of the plates.

FIGURE 5 shows a cylindrical sheath f of the same very hard metal threaded over shaft 44. One of the arms 46b is shown as being cut longitudinally to reveal the sheath f covering it, this sheath being also shown on FIGURE 7. These sheaths may have a thickness of 10 mm. in the case of the shaft and a little less in the case of the arms.

' The apparatus may additionally include Water jackets to cool the end-closures and shells.

In the embodiment of FIGURE 8, vertical walls 60 and 61 are substitute to the cylindrical walls shown in FIGURE 5, so that the inner hard lining may be made, in major put, of plate sheets 17 p It goes without saying that the invention is by no means limited to the specific forms of the embodiment hereinbefore described, and that many changes and substitutions of parts may be made without departing from the spirit and scope of the invention.

What is claimed is:

1. A crusher having at least one crushing cell, said crushing cell comprising a container having two substantially vertical and parallel Walls, at least one horizontal rotating shaft perpendicular to said two walls, agitating arms fixed to said shaft, and balls filling almost the whole of the space available in said container, the distance between said two vertical walls being less than one quarter of the height of said container, and the sum of the dimensions of said agitating arms parallel to the shaft being not less than one half of said distance.

2. A crusher as claimed in claim 1, wherein the balls have a diameter not greater than 10 mm.

3. A crusher as claimed in claim 2, wherein the balls have a diameter equal to about 2 mm.

4. A crusher as claimed in claim 1, wherein the number of the agitating arms in said crushing cell is not higher than 3.

' References Cited UNITED STATES PATENTS 2,292,275 8/1942 Kiesskalt 24l'172 2,621,859 12/1952 Phillips 241--174 X 3,149,789 9/1964 Szegvari 241-172 X WILLIAM W. DYER, JR., Primary Examiner.

F. T. YOST, Assistant'Examiner.

Images