US3206129A - Rod-mills used especially for the manufacture of inks and paints - Google Patents

Description

Sept. 14, 1965 J. M. A. BRIZON ROD-MILLS USED ESPECIALLY FOR THE MANUFACTURE OF INKS AND PAINTS 2 Sheets-Sheet 1 Filed April 17, 1962 INVENTOR Q we AT ORNEYS Sept. 14, 1965 J. M. A. BRIZON 3,206,129

ROD-MILLS USED ESPECIALLY FOR THE MANUFACTURE OF INKS AND PAINTS Filed April 17, 1962 2 Shaets-fiheet 2 JEAN MARIE ANNIE BRIZON INVENTOR United States Patent 7 Claims. or. 241-241 Various devices have already been proposed in order to improve the effectiveness of rod-mills employed in the preparation of paints and printing inks, in particular of the mills of the so-called single cylinder type. For example, it is known to cool the rod by water circulation, to employ a single or double rod and to support the rod against the cylinder by a mechanical or hydraulic clamping device. In this way, it is sought to improve the fineness of the grinding without deterioration of the pig ment by heating, and without substantially reducing the output.

Two major preoccupations have in fact up to the present time influenced the manufacturers and users of grinding mills. On the one hand, the rod must be clamped against the cylinder with a sufiicient degree of pressure to obtain the desired fineness of grinding (fineness of division and of dispersion of the solid particles), this fineness depending in fact on the compression force to which the pulp is subjected when it passes into the space between the rod and the cylinder. On the other hand, an economic use of the machines requires that the output of pulp treated should be as high as possible.

These two considerations are quite obviously contradictory, since an increase in the application pressure of the rod against the cylinder results in a reduction of output. Furthermore, a strong pressure of the rod on the cylinder causes certain drawbacks: prevention of the entry of large particles, which tend to collect at the entrance under the rod, the strongly-pressed rod applying a filtering action and keeping back the large particles instead of breaking them up, heating the rod and of the cylinder and in consequence of the pulp which may be soiled, soiling of the pulp by metallic particles resulting from the frictional wear between the cylinder and the rod, this latter being particularly troublesome during the preparation of light-coloured paints, etc.

The present invention has for its object to improve the fineness of grinding, but at the same time it permits the output to be increased.

It consists essentially in providing the rod with a longitudinal cavity, the edges of which bear on the cylinder, the latter being closed at its extremities and supplied with a fiuid under pressure, which may be the pulp itself, one of its constituents, or even any fluid compatible with the said pulp. In this way, the pulp must be crushed between the cylinder and the rod, even when the latter is under high pressure.

It has been found that the application of a suitable high pressure to the longitudinal cavity of the rod, which creates especially on the rod 21 force which opposes the elastic force pressing the said rod against the cylinder, results in a considerable increase simultaneously of the fineness of grinding and of the output of the machine, characteristics which have been considered as contradictory up to the present time.

These results are very probably due to the fact that the pressure maintained in the cavity of the rod tends to move the later away from the cylinder, acting in opposition to the elastic pressure force, thus permitting the increase in output and the engagement of the large particles under the rod, in the same way as would be obtained in an ordinary machine in which the rod was "ice only partly pressed against the cylinder, but applying at the same time to the pulp brought under the rod by the cylinder, a high fluid pressure which ensures the grinding action. In short, the compression and the grinding of the pulp between the cylinder and the rod, that is to say only between solid surfaces, such as was the practice up to the present time, are replaced, at least partially, by a grinding action of the pulp brought forward by the cylin der, against the liquid or pulpy mass under pressure which fills the cavity in the rod.

In accordance with a first form of embodiment of the rod-mill, the usual hopper is provided, at the lower portion of which is fixed the supply conduit of a pump, which is thus put on load by gravity and which feeds the groove in the rod with pulp under pressure; the delivery conduit of the pump is divided up before reaching the rod so as to distribute the pressure uniformly along the said rod.

It is however not essential that the fluid under pressure supplied to the rod should be the pulp from the hopper. In accordance with a second form of embodiment of the invention, a liquid or pulp under pressure derived from a tank separate from the hopper is delivered into the cavity of the rod at an adequate pressure by a pump intended to create and to maintain in the said cavity a constant value of the pressure selected, which depends on the clamping pressure on the rod and which is necessarily higher when the clamping pressure itself is higher. The liquid delivered by this pump into the cavity may be the same pulp as that contained in the hopper, but it may also be any other consistent liquid or pulp compatible with the said pulp, so that its mixture with the first pulp does not cause any difficulties. For example, in the case of a paint containing liquid resin, this resin can be injected into the cavity of the rod either as it is or as a mixture with a loading material.

Furthermore, tests have shown that it is possible to dispense with any pump for supplying the cavity of the rod, this cavity being automatically filled with liquid or with the pulp contained in the hopper, by the action of the grinding-mill itself and With the production of a high pressure in the said cavity, so that in this case also there is formed a real liquid grinding rod which enables the fineness of grinding to be improved to a very considerable extent.

It is probable that this creation of a high pressure inside the cavity of the rod during the operation of the machine is due to the drawing along of the liquid viscosity or surface tension between the cylinder and the rod.

By means of a suitable shaping of the rod, it is possible to arrange that the resistance offered to the passage of the liquid under the lip of the rod which precedes the cavity is less than the resistance to its passage under the lip which follows the cavity, which naturally favours the increase of pressure in the interior of the said cavity. As the rod is pressed against the cylinder by an appropriate device, most frequently by hydraulic jacks distributed along the said rod or its support, it is preferable that the intake lip should have a greater width than the outlip, which makes it possible for the inlet lip to have a lower application pressure than the outlet lip.

The description which follows below with reference to the accompanying drawings, given by way of example only and not in any limitative sense, will explain quite clearly the various particular features of the invention and the manner in which they are carried into effect, any arrangement brought out either in the text or in the drawings being understood to fall within the scope of the present invention.

FIG. 1 shows diagrammatically in section at right angles to the axis, a single cylinder grinding machine in accordance with a first form of embodiment of the invention;

FIG. 2 shows also in section, but to a larger scale, the rod, the cylinder and the bottom of the hopper;

FIG. 3 is a perspective view of a rod according to the invention, turned over so as to show the pipes by which it is supplied;

FIG. 4 shows diagrammatically a single-cylinder mill in accordance with a second form of embodiment of the invention, in cross-section in a plane perpendicular to the axis of the cylinder;

In the same way, FIG. 5 shows an alternative form of construction, in which the pump is eliminated;

FIG. 6 is a transverse section to a larger scale of a rod with unequal lips, carrying a pressure gauge.

Referring now to FIG. 1, there is shown in diagrammatic cross-section a grinding mill with a single cylinder. This mill comprises a rotating cylinder 1, a hopper 2 receiving the pulp 3 being treated, a rod 4a of metal or plastic material and a scraper 22 serving to evacuate the product after working. A usual clamping device is constituted by at least one cylinder 5a carried by the frame, in which slides a piston 6, subjected at 7 to a suitable hydraulic pressure and rigidly fixed to a member 8 supported on the rod 4a proper. This pressure device could also be mechanical.

The supply device is composed of pipes 12 which may be deformable and which couple the central groove 9 of the rod to a pump 16. Other pipes such as 11 also connect the said pump to a reservoir or tank receiving the pulp to be treated.

The pump 14) shown is of the gear type, but it is quite obvious that other types could equally well be employed. In the same way, the pulp to be treated may be contained in an independent tank and not in the hopper 2.

An arrangement of this kind is however advantageous because of the operation of a rod-mill thus equipped. In fact, whereas one of the constant considerations of manufacturers of single cylinder mills is to facilitate the engagement of the pulp carried along by the cylinder under the forward portion 13 of the single or double rod, and to ensure an adequate output in spite of the high pressure applied on the rod to force it against the cylinder, which determines the fineness of grinding, the existence of a substantial over-pressure in the groove 9 of a rod according to the invention eliminates this difficulty of engagement at 13. The latter is no longer necessary and has no influence on the output. Only the lubrication of the edge 13 must be ensured. In this lat- .ter zone, the action on the pulp of the internal pressure and of the friction on the cylinder have opposite directions, but the height of the pulp in the hopper ensures sulficient lubrication. In addition, the operator can thus see directly at what moment the operation is completed. As the point of connection of the pipe 11 to the hopper may form a small reserve h, the mill may continue to function for a few moments as a conventional single cylinder when the pump is no longer working, without risk of seizure.

As all the pulp is compelled to pass through, a machine according to the invention acts like a true grinding machine, although the grinding takes place against the liquid .or pasty mass which fills the cavity in the rod.

FIG. '3 shows a rod 40 in 'the inverted position so as to show .its supply conduits.

It is therefore ,easy to modify a conventional mill in order to make it in conformity with the invention and even to manufacture a special mill comprising a separate a new parameter of adjustment which is capable of increasing considerably the output of the grinding mill for a given pressure and fineness. A value of about 10 kg. per square centimeter would appear desirable for the pressure in question, but this value may be higher if the pressure of the rod on the cylinder is modified in an appropriate manner. The usual method of cooling the rod by means of a water jacket may be retained.

There is shown in FIG. 4 a second form of embodiment of the invention, characterized in that the rod 4d, arranged at the outlet of a conventional hopper 2 filled with pulp 3 to be treated, is supplied from a tank 16 separate from the hopper, by means of a piston pump 15, preferably actuated by a compressed-air motor 18.

The fluid brought under pressure into the cavity 9 of th od n b e ame. pu a h n he h pp bu it can also be any fluid compatible with the said pulp, in particular a liquid of a pulp of a different nature and viscosity and adhesive power of appropriate values which may be higher than those of the pulp itself.

The piston 19 of the compressed-air motor 18 which can form a single mechanical unit with the pump 15, 17 of the type utilized for the delivery of thick grease, has a surface area which is greater than that of the piston 17. The pressure of the fluid delivered into the cavity 9 is therefore a multiple of that of the compressed-air acting on the piston 19. The usual distribution mechanism of the motor has not been shown, but the pump is provided with two single-.direetion clapper valves 21 arranged respectively on the admission and delivery conduit systems.

A hydraulic fluid under pressure of a type similar to that utilized for the brakes of automobile vehicles is delivered into the cylinders 54 by a master cylinder, the piston of which has an elastic sealing joint and is moved by a screw-adjustment hand-wheel. This master cylinder (not shown) is coupled to the cylinders 5d by pipes '7 which are generally of copper and of a certain length, the expansion and elastic elongation of these pipes under the effect of the pressure, contributing, at the same time as the compressibility of the oil itself, in giving a certain lasticity to the pressure applied to the rod 4d. A pres sure gauge coupled to the delivery of the master cylinder enables the pressure admitted to the cylinders 5 to be checked when the hand-wheel is turned.

The rod-mill above described is utilized in the usual manner.

The hopper is filled and supplied with the pulp or the liquid to be treated, and the mill is started-up with the rod released, that is to say with a slight pressure in the j k afte whi h th s ja ks a e p o re s ve y P vunder pressure in order to force the rod against the cylinder, while at the same time compressed-air is admitted ,to the motor 18 to put the cavity 9 of the rod under pressure, which corresponds to the injection of a small quantity of liquid or pulp into the said cavity, the dimensions of which in vwidth and depth may be relatively small (of the order of a few millimeters).

The satisfatCQry working of the machine requires a suitable correspondence betweenthe pressure in the cavity 9 and the pressure in the cylinders 5d. This relation is that for which the pressure tends to become stable in the cavity'9 ofthe rod, at the same time as the compressedvair motor 18 stops of its own accord by equilibrium of the force of the air pressure on the piston 19 of large section and the pressure of the liquid on the piston 17 of smaller section. This stabization of the pressure is probably due to the fairly viscous nature of the pulp to be ground contained in the hopper and of the pulp .or the liquid delivered by the pump into-the cavity 9.

the pressure. In practice however, the total stoppage of the piston and stability of the pressure in the cavity 9 is observed almost immediately, as long as the hopper is supplied with pulp to be ground, which shows that the liquid injected under pressure in the cavity 9 is retained there. For this reason, because of the existence of a non-return valve on the delivery of the piston 17 of the pump, it is possible, if so desired, to stop the supply of compressed-air to the motor as soon as the pressure in the cavity 9 of the rod has become stable.

The applicant has made comparative tests on a commercial grinder having a cylinder of 300 mm. in diameter with a length of generator line of 600 mm. and a system of pressure on the rod using six hydraulic jacks of such section that a pressure of 160 kg./sq. cm. of the hydraulic fluid admitted to these jacks produces a pressure force on the cylinder by the rod equal to 3 tons.

The machine was built to operate normally with this pressure, but it then had various drawbacks: low output of pulp treated, rapid overheating, soiling of the pulp, rejection of the large particles of pigment, etc.

If the pressure force was reduced by about 40% by bringing the pressure in the jacks down to 60 kg./sq. cm., the output became two or three times as great, the overheating disappeared, but the large particles passed under the rod without being ground.

If now the ordinary rod is replaced by a rod provided with a groove and supplied under pressure according to the invention, it is found that there can be obtained in the groove a stabilized pressure of the order of 30 to 60 kg./sq. cm. for an opposing pressure in the jacks of the order of 100 kg./sq. cm., and that under these conditions, the output increases and becomes of the order of the quantity of output of an ordinary machine in which the pressure force on the rod has been reduced by about 40%, whereas-and this was an absolutely unexpected result-the fineness of grinding and the brilliance of the pulp become quite remarkable. The fineness of grinding attains, in a single pass on the single-cylinder machine the same degree which could only be obtained up to the present time by a number of successive passes on a machine with three cylinders. In addition, there is no longer any rejection of the large particles, which pass through and are ground. Finally, the covering power increases in a remarkable manner in the case of paints, in consequence of the division and of the dispersion of the pigments in the binder, which makes possible a reduction in expenditure of expensive dye pigments. And all these results are obtained without overheating and without soiling the pulp, the wear on the rod and the cylinder being considerably reduced.

The fineness of grinding increases with the pressure that it is possible to maintain in the groove of the rod, an increase in this pressure necessitating a corresponding increase of the pressure applied to the rod. With the single-cylinder machine, the numerical characteristics of which have been given above, and a rod provided with a groove of 5 mm. in width, having on each side lips of the same width, the total width of the rod at its contact with the cylinder being therefore mm., the applicant has been able to obtain in the groove a stabilized pressure of 36 kg./sq. cm. for a pressure in the hydraulic jacks of 100 kg./sq. cm., giving a pressure force of 3 tons on the rod. The output is high and the fineness of grinding is excellent.

On the same machine, a rod provided with a groove of 2 mm. in width, leaving on each side a width of lip of 4 mm. (total width of the rod 10 mm. at its contact on the cylin er), the stabilized pressure in the groove increased to 100 kg./sq. cm. approximately for a pressure of 160 kg./sq. cm. in the hydraulic jacks, giving a pressure force on the rod of 4.3 tons. The output remained substantially the same as previously, but the fineness of grinding was still further improved.

The foregoing indications are furthermore only given by way of non-limitative examples.

The fact that the compressed-air motor can be stopped has made it possible to consider its replacement by a small pump, hand or motor operated, serving to fill the cavity at the beginning of the operation of the rod-mill and thus to ensure the starting-up of the machine without risk of seizure.

A machine thus modified is shown in FlGS. 5 and 6, with the exception of the starting pump which could be dispensed with if certain precautions are taken.

In FIG. 5, the rod 4e of substantially rectangular section is provided with a longitudinal cavity 9 described above and pressed against the cylinder 1 by the pistons 6 of powerful hydraulic jacks 5 spaced apart along the length of the rod.

The rod is preferably mounted vertically, the hopper 2 being displaced sideways which enables the best arrangement to be obtained of the portion of the frame of the machine intended to carry it and to receive the reaction of the high pressure force applied by the jacks. The intake lip 9a is wider than the outlet lip 9b in order to reduce the resistance oltered to the passage of the pulp under the said intake lip (see FIG. 6 showing the transverse section of the rod to a larger scale).

It would also be possible to machine and guide the rod in such manner that only the outlet lip 91) is pressed against the cylinder, the intake lip 9a leaving a very small clearance of the order of one-tenth of a millimeter between it and the cylinder.

Tests have been made with a rod-mill having a cylinder of 300 mm. in diameter and 600 mm. in length, the rod being pressed vertically on the cylinder by five powerful hydraulic jacks. The cavity 9 of the rod used for the test was 8 mm. in width with a width of 5.5 mm. for the intake lip 9a and 2.5 mm. for the outlet lip 9b. For a pressure force of 9 (nine) tons applied by the hydraulic jacks on the rod, the ressure of the liquid read on a pressure gauge coupled to the interior of the cavity 9 (this pressure gauge 29 can be directly fixed on the rod), increased at the beginning of operation of the machine to kg. per sq. cm. of the interior of the cavity and became stable at that value. Nevertheless, the output of the machine was considerable: of the order of 209 kg. per hour for a paste of glycerophthalic paint containing 40% of pure rutile titanium with a fineness of grinding of about 8.5 on the north guage, which represents an absolutely remarkable result.

The machine does not become hot since the friction takes place essentially on the rod of liquid, and for this reason the pulp does not become soiled.

If the pressure of the hydraulic jacks 5 is increased until a pressure force of 12 (twelve) tons is obtained on the rod, the pressure-gauge 20 shows that the pressure in the cavity increases and becomes stable at 160 kg. per sq. cm., the output being reduced to kg. per hour, but with a fineness of grinding of 9 with the north gauge.

The adjustment of the pressure force applied to the rod as a function of the various products to be ground is effected by observing the pressure read on the pressure gauge 20 of the rod, since it is this pressure which determines the action of the liquid rod contained in the cavity 9, and in consequence determines the fineness of grinding and also the output of the machine.

It is furthermore possible to dispense with any pump if, in order to avoid all risk of seizure during starting-up, the machine is arranged so that, before starting up, the cylinder can be rotated very slowly through a fraction of a revolution. The part of the cylinder which has passed under the rod during this rotation is covered, on the downstream side of the rod, with a film of pulp which can be controlled visually and which proves the existence of this same film under the rod. It is thereby known that the normal driving power can then be applied to the machine without fear of seizure. This prior slow start can be carried out either by .hand or by meansof a small electric motor which will preferably by provided with an automatic limit-switch restricting the drive 'of the cylinder through the desired angle.

It will also be understood that the invention is not limited to the form of embodiment described. It may be applied to rod-mills comprising a number of cylinders, for example three. In this case, the rod referred to can be mounted on the cylinder on which the scraper blade is fitted, on the upstream side of this latter. It can be an advantage to associatethis rod with a hopper or with side cheeks permitting the retention, on the upstream side of the rod, of a small quantity of pulp. In addition, a plurality of rods provided with longitudinal grooves or cavities could be combined with a single machine or even with a single cylinder, the pulp passing successively under the grooves which are put under pressure or alternatively a number of parallel grooves or cavities can be provided on the same rod. Finally, the invention is extended to cover forms of construction which are equivalent to those which have been described above.

What I claim is:

1. A grinding mill for paint and printing ink materials comprising a rotary cylinder, a fixed rod urged by pressure means against and longitudinally along said cylinder, a distributing hopper for the material to be ground closed at its lower extremity by said cylinder and rod, said rod being provided with a longitudinally blind groove closed at each extremity by a solid wall facing said cylinder, and said mill further comprising hydraulic pressure exerting means apart from the pressure exerted by the material in said hopper in communication with a fluid compatible with the material to be ground and with said groove for supplying said fluid under pressure to said groove.

2. A grinding mill according to claim 1, wherein the hydraulic pressure exerting means is a pump connected by supplying conduit means to the lower part of said distributing hopper and thence by delivery conduit means to said groove.

3. A grinding mill according to claim 1, comprising liydraulic means for applying pressure to said rod and urging it against said cylinder at a predetermined pressure and pump means for supplying said groove in the rod with and in correspondence with said hydraulic means so that the pressure in the groove stabilizes, whereby the yield at least equalsthat with grooveles rods at apressure 40% less than said predetermined pressure and the tintorial qualities of the pigments are enhanced.

4. A grinding mill according to claim 1, wherein said blind groove has a width in the vicinity of one third the overall width of said rod.

5. A grinding mill according to claim 1, wherein said hydraulic pressure exerting means comprises a reciprocating piston-pump actuated by a compressed-air pistonmotor, the whole assembly forming a motor-pump set of the type which automatically starts and stops to maintain a pressure within predetermined limits, said piston pump being connected by supply conduit means to ,a tank distinct from said hopper.

6. A grinding mill according to claim 1, wherein means are provided to rotate the cylinder before application of the pressure fluid to said groove.

7. A grinding mill according to claim 1, wherein said hopper has a wall against which said rod is applied, said wall being substantially radial and vertical with respect to the cylinder.

References Cited by the Examiner UNITED STATES PATENTS 1,523,632 1/25 China 241-21 1,713,270 5/29 Drysdale 241-241 1,926,907 9/33 Lehmann et al 241-241 2,024,073 12/ 35 Sonsthagen 241-241 2,361,059 10/44 Robertson 241-21 2,687,852 8/54 Midgette et al 241-241 FOREIGN PATENTS 1,146,480 5/57 France.

606,994 12/34 Germany.

636,852 10/ 36 Germany.

883,225 7/ 5 3 Germany.

ANDREW R. JUHASZ, Primary Examiner.

EVERETTE W. KIRBY, Examiner.

Claims (1)

1. A GRINDING MILL FOR PAINT AND PRINTING INK MATERIALS COMPRISING A ROTARY CYLINDER, A FIXED ROD URGED BY PRESSURE MEANS AGAINST AND LONGITUDINALLY ALONG SAID CYLINDER, A DISTRIBUTING HOPPER FOR THE MATERIAL TO BE GROUND CLOSED AT ITS LOWER EXTREMITY BY SAID CYLINDER AND ROD, SAID ROD BEING PROVIDED WITH A LONGITUDINALLY BLIND GROOVE CLOSED AT EACH EXTREMITY BY A SOLID WALL FACING SAID CYLINDER, AND SAID MILL FURTHER COMPRISING HYDRAULIC PRESSURE EXERTING MEANS APART FROM THE PRESSURE EXERTED BY THE MATERIAL IN SAID HOPPER IN COMMUNICATION WITH A FLUID COMPATIBLE WITH THE MATERIAL TO BE GROUND AND WITH SAID GROOVE FOR SUPPLYING SAID FLUID UNDER PRESSURE TO SAID GROOVE.

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