US3071330A - Apparatus for fine grinding - Google Patents

Description

Jan 1, 1963 G. JACKERING APPARATUS FOR FINE GRINDING 2 Sheets-Sheet 1 Filed Nov. 9, 1959 INVENTOR Giher cl'lz'aieb g BY 6llkuobsy gain ATTORNEYS Jan. 1, 1963 G. JACKERING 3,071,330

APPARATUS FOR FINE GRINDING Filed Nov. 9, 1959 2 Sheets-Sheet 2 INVENTOR fizZni/ae zf'eierjh ATTORNEYS Unite Patented Jan. 1, 1963 Fire 3,071,330 APPARATUS FOR FINE GRHQDING Gunther Jaclrering, Harnrn, Westphalia, Germany, as-

signor to Altenhurger Maschinen G.m.h.H., Post Wabern, Bezirk Kassel, Germany, a firm of Germany Filed Nov. 9, 1959, Ser. No. 851,782 Claims priority, appiication Germany Nov. 18, 1958 3 Claims. (Cl. 241-53) This invention relates to a method and an apparatus for fine grinding, and refers more particularly to a grinding apparatus having a regulated feed of the material to be ground and a regulating and sorting withdrawing device for the ground substance.

In recent times, industrial grinding procedures have eliminated to a large extent the standard crushing methods, such as the impact, the throwing of the material, the compression of the material, the friction, the shearing and the press rolling, and instead have placed in the foreground machinery wherein the substance to be ground, usually consisting of individual pieces, is transported pneumatically and is connected through zones of cyclones or eddies. The material is subjected in these cyclone zones to intensive movements, changes in pressure and charges of energy, so that an intensive grinding operation takes place which is also effected by the friction of the particles against each other. This procedure is particularly advantageous for fine grinding or extra fine grinding.

structurally this procedure is carried out through the use of a rotor having radial blades which move past a vertically corrugated stator, whereby the eddies created behind the blades are particularly effective, since in these zones the substance to be ground is subjected alternately to high pressure and low pressure which are produced by the quick movement of these blades past the corrugated stator. These grinding procedures are particularly noticeable in the case of substances, the structure of which has inner tensions and which have the tendency to break up along these inner tension lines.

I have found in the course of my studies of the operation of such machines that it is necessary to pay more attention to the supply of air and to the regulation of the amounts of air than hitherto was considered necessary on the ground of the prior art knowledge of the interrelated procedures. Since air participates in the grinding process and is also partly a carrier of the grinding energy, there must be a predetermined optimal ratio between the amount of air, the amount of the substance to be ground, and the velocity of air in the grinding current.

In some prior art devices, the substance to be ground is transported directly to the level of the first and second rotor blades. It was then found that breaking and increased Wearing out effects were produced, and that there is a substantial drop in the grinding output both qualitively and quantitively. According to another machine known in prior art, the substance to be ground is carried centrally through a high central shaft to the lower rotor blades, but then it must reverse its direction of flow to the extent of 180, with the result that a uniform flow which is so important for the grinding, cannot be attained. Furthermore, the parts wherein the flow of the substance is changed are subjected to increased wear and tear.

Prior art rotors of grinding apparatus were provided with rigid shock plates with a constant spacing between the edge of the stator and the outer edge of the plates. This constant spacing did not take into consideration the different grinding procedures of the individual grinding stages and produced a drop in output. Another drawback was caused by the grinding method which employed pressure variations which followed each other in quick succession. The high oscillation frequencies which were thus produced, caused regularly the breakage of stems of the rotary discharge apparatus located behind the last grinding stages. The result was substantial impediments in operation, particularly since the centrifugal force must be quite high for the required high circumferential velocities.

An object of the present invention is the provision of a grinding method and a grinding apparatus which eliminate the above described drawbacks of prior art constructions and which make it possible to regulate in a most effective manner the relationship of the amount of air to the amount of the substance to be ground.

Other objects will become apparent in the course of the following specification.

The present invention is based in part on the discovery that even the first grinding stage must be charged completely uniformly. Consequently, according to this invention, the substance to be ground is introduced with an air current underneath the rotor, and the material is distributed completely uniformly over the entire cross-section before it reaches the first grinding stage. The supply of air is arranged in such manner that immediately after the mechanical-1y carried out supply of the substance to be ground takes place, an air passage provides the suction of the amount of air which is necessary for the further transportation of the substance to be ground. The amount of air which is necessary for grinding purposes and which is considerably greater than the amount of air required for transportation, is sucked in only in the ventilator zone.

This process in accordance with the present invention makes it possible to regulate the ratio of the amount of air to the amount of the ground substance in the best possible manner and with very fine precision. The described second supply of air, shortly before the distributing ventilator state, attains by renewed cyclonic mixing, for the first time, a completely uniform mixture of air and of the substance to be ground.

The invention will appear more clearly from the following detailed description when taken in connection with the accompanying drawings showing by way of example, a preferred embodiment of the apparatus of the present invention.

In the drawings:

FIG. 1 is a section through a grinding device of the present invention and illustrates the so-called air lock.

FIG. 2 is a transverse section along the line II-II of FIG. 1.

FIG. 3 is a transverse section along the line IIIIII of FIG. 1.

FIG. 4 is a transverse section along the line 1V-IV of FIG. 1.

FIG. 5 is a top view of the upper discharge device for the ground substance.

FIG. 6 is a plan view of the rotary discharging body.

FIG. 7 is a partial central section through the body shown in FIG. 6 with parts shown in side elevation.

FIG. 8 is a section through one of the shock plates of the rotor.

FIG. 9 is a side view of the PEG. 8.

The grinding apparatus shown in the drawings includes a main substantially cylindrical casing 12. carrying a vertical shaft 4, which is driven by any slidable means; not shown in the drawings, and which carries the rotors consisting of superposed plates 11 forming the different grinding stages. The shaft 4 also carries a rotary body 14 for the discharge of the ground substance.

The device supplying the substance to be ground includes a supply hopper 1 leading to a tubular casing containing a feed screw 2.. A vertical pipe 3 connects the shock plate shown in the supplying device and.

upper discharge chamber of the machine with the feed screw. A short pipe connects the casing of the feed screw with the main casing 12 of the machine and is provided with an opening 5 which will be described hereinafter as an air vent or an air lock.

The casing 12 of the machine which constitutes the stator, may be provided with vertical corrugations if desired.

The lower portion of the casing 12 contains a supplying chamber 6 which is located directly above the bottom of the casing 12. The bottom is provided with openings 7 and 8 for the inflow of the second current of air serving as the carrier of the substance during the grinding operation. As shown in FIG. 2, the openings 7 and 8 may be conveniently closed or only partly opened by shutters 9 and 10, so as to provide the correct amount of air. Air is supplied to the openings 7 and 8 through passages surrounding the shutters.

The rotor discs of the machine carry shock plates 11. According to the present invention, the plates 11 are not located any more, as was the case in prior art, at the same distance from the casing or stator 12 for each rotor stage, but can be shifted closer to or further away from the casing 12 depending on the type of the substance to be ground and the required extent of grinding. In order to attain this, the shock plates 11 are provided with longitudinal slits which make it possible to adjust the plates radially. Obviously, the adjustment must be carried out within such limits that the plates 11 will not contact the casing 12. FIG. 3 shows diagrammatically and in top view the arrangement of the shock plates 11.

The upper portion of the casing 12 contains a discharge chamber 13. A rotary body 14 which is driven by the shaft 4 is located in the chamber 13. The rotary body 14 carries plates 14a provided with milled grooves 15 shown in FIG. 7. Inserts or pieces 16 fit in these grooves and carry ejecting plates 17 which extend at such an angle to the casing 12 that the heavy, large or unground particles of the substance being treated can be ejected tangentially. The chamber 13 communicates with an outlet 18 shown in FIG. 4. A trap 19 is located at the outlet 18 and forms a narrow passage 21 which permits only the specifically heavy particles to pass through the outlet 18 (FIG. 4).

The top of the casing 12 is connected with ventilator 22 (FIG. 1) which creates a suction, by means of which the particles which have been ground to the desired extent of fineness, are sucked into the outflow casing 23. As shown in FIG. 5, the casing 23 has the form of a spiral.

The operation of the described apparatus is as follows:

Particles of the substance to be ground are introduced into the machine through the hopper 1 and reach the feed screw 2. The feed screw 2 which is driven by any suitable means not shown in the drawings, transports the substance to be ground toward the opening 5. Should the feed screw 2 transport a larger amount of substance than can be ground by the machine, the supply of this substance provided by the feed screw 2 will be gradually accumulated at the opening 5 and in time will cover a part of the opening 5. If the supply continues to increase thereafter, the substance will close the opening 5 entirely, so that no more air will be able to flow into the interior of the machine through the opening 5. Then due to insufficient ventilation effect and also since the air current serving as a carrier for the substance to be ground is interrupted, the grinding process will be interrupted completely. Thus, the opening 5 serves not only as an air vent, but also has a self-regulating air lock and as a safety device, in that instead of a flow of air, the substance to be ground may drop downwardly through the openings 7 and 8, thereby avoiding damage to the apparatus.

.The substance to be ground carried by air supplied through the opening 5 reaches the chamber 6 and there receives the second current of air which carries the substance through the grinding stages provided by the rotors 11. The amount of this second current of air which is introduced into the machine through the openings 7 and 8, is regulated by adjusting the size of the openings 7 and 8 by means of the shutters 9 and 10 which move in the direction of arrows shown in FIG. 2. This regulation provides the correct mixture of air and the substance to be ground required for the specific grinding operation.

Furthermore, the operator before the grinding oper' ation can conveniently adjust the position of the shock plates 11 relatively to the casing 12 depending on the type of the substance to be ground and the required extent of grinding. As already stated, this is possible through the provision of longitudinal slits in the shock plates 11 of the rotors.

The plates 11 provides air cyclones which quickly follow each other and which result in the grinding of the substance which passes upwardly through the rotors. When the substance has left all the individual grinding zones of the rotor, it reaches the upper ejecting chamber 13 containing the rotary body 14. As already stated, the ejecting plates 17 of the body 14 are located at such an angle to the inner surfaces of the casing 12, that they will convey the heavy or large particles, or such particles which have not been sufliciently ground, tangentially toward the outlet 18. Due to the provision of the trap 19, only the specifically heavy particles which were driven against the inner walls of the casing 12, will be able to pass through the outflow passage 18. Obviously, it is possible to change the position of the trap 19 so as to adjust the amount or the size of the particles which will reach the passage 18.

if the ejected particles which pass through the passage 18 are not to be treated any more. they can be easily collected by an suitable means (not shown), or placed in sacks.

However, as shown in FIG. 1, the outflow passage can be connected with a vertical tube 3 so that the particles will be resubmitted to the feed screw 2 and reintroduced into the machine for rpnewed grinding.

FIGURE 4 illustrates by arrows the process of removing the particles, while the chamber 13 is illustrated in FIG. 4. F168. 6 and 7 show the construction of the rotary body 14 provided with the supports 16 and the ejecting plates 17.

The substance which has been ground to the desired extent, is sucked in from the chamber 13 through the upper ventilator 22 and reaches the outflow casing 23 which is of spiral form, as shown in FIG. 5. The spiral widens toward the exit so that here the ground particles have only small velocities.

Any suitable separator, not shown in the drawings, can be used to receive the particles leaving the casing 23.

Extensive experimentations with apparatus constructed in accordance with the above described principles of the present invention, have produced the surprising effeet that the described method of introducing the substance to be ground and of moving it by air currents in the described manner, results in an output which is many times greater than that of prior art machines. While heretofore there was always the danger that the machine would be operated with an insufficient amount of air and that the machine may be overheated to an extent which will endanger its further operation, the novel feed methods of the present invention have not only eliminated this danger, but have also made possible grinding operations which heretofore could be carried out by prior art machinery either with considerably greater expenditure or not at all.

Furthermore, in accordance with the present invention, the described process makes it possible to combine to some extent the grinding step with the step of drying the ground substance. It will be noted in this connection that the temperature in the described machine can be technically regulated by a regulation of the air supplied through the openings 5, 7 and 8. Thus, these openings can be connected with suitable heaters (not shown) so that even warm air with gradually increasing temperatures can be introduced into the machine. Practical experimentation with machines constructed in accordance with the principles of the present invention, has shown that in this manner it is possible to introduce air during continuous operation at a temperature of up to 200 C., with the result that the final temperature of the ground substance will drop to the extent of 10%. This makes it even possible to introduce viscous substances for grinding purposes into the grinding apparatus.

Obviously, heated air can be introduced into the ap paratus at such locations at which cold or cooled air can be also introduced into the apparatus.

It will be noted that described methods and apparatus follow the general development of the art which requires breaking up procedures, grain fineness and sorting which must be always more precise and have greater fineness. An important advantage of the present invention is that it makes it possible to carry out grinding processes in a single grinding apparatus which heretofore were not considered possible for continuous operation. A further advantage is that the described grinding method was found to be considerably less expensive and much more etfective in actual operation than methods known in prior art.

It is apparent that the example shown above has been described solely for the purposes of illustration and not for the purposes of limitation and that it is capable of many variations and modifications within the scope of the present invention. All such variations and modifications are to be included within the scope of the present invention.

What is claimed is:

1. An apparatus for fine grinding, said apparatus comprising a casing, a vertical row of blade-carrying rotors in said casing, another casing connected with the firstmentioned casing below said row of rotors, and a mechanical feed device located in the second-mentioned casing for feeding a substance to be ground to the firstmentioned casing below said rotors, said mechanical feed device having an inner end spaced .from the interior of the first-mentioned casing, the second-mentioned casing having an air vent opening located between said inner end of the mechanical feed device and the interior of the first-mentioned casing, whereby the operative size of said opening is regulated by an accumulation of said substance in the space between said inner end of the mechanical feed device and the interior of the first-mentioned casing, the first-mentioned casing having at least one other air vent opening for feeding the substance to be ground from the space below said rotors to said rotors.

2. An apparatus for fine grinding, said apparatus comprising a vertical casing having a bottom, a plurality of blade-carrying rotors located one above the other and above said bottom in said casing, means feeding a substance to be ground along with air into said casing and to the lowermost rotor, said bottom having at least two openings for introducing air into said casing, said openings being spaced in the direction of said feed, the air introduced through said openings forming a separate current of air transporting said substance upwardly through said rotors, said rotors producing a quickly following sequence of air cyclones for grinding said substance, and shutters carried by said bottom for varying the size of said openings.

3. An apparatus for fine grinding, said apparatus comprising a vertical casing having a top and bottom, a plurality of blade-carrying rotors located one above the other in said casing, another casing connected with the first-mentioned casing below said rotors, a feed screw located in the second-mentioned casing for feeding a substance to be ground to the first-mentioned casing below said rotors, said feed screw having an inner end spaced from the interior of the first-mentioned casing, the secoud-metioned casing having an air vent opening located between said inner end of the feed screw and the interior of the first-mentioned casing, said bottom having at least two openings forming a separate current of air transporting said substance upwardly through said rotors, shutters carried by said bottom for varying the size of the lastmentioned openings, said rotors producing a quickly following sequence of air cyclones for grinding said substance, said casing having a space between said top and the uppermost rotor for unground particles of said substance, a separate rotary body located in said space and operatively connected with said rotors, supporting pieces carried by said rotary body, ejecting plates carried by said supporting pieces and extending at an angle to the radial direction for projecting said unground particles against the walls of said casing, a hopper carried by the second-mentioned casing adjacent the outer end of said feed screw and a vertical pipe having an upper end connected with the first-mentioned casing adjacent said ejecting plates and a lower end connected with the secondmentioned casing between said hopper and the first-mentioned air vent opening.

References Cited in the file of this patent UNITED STATES PATENTS 1,748,050 Harrington Feb. 18, 1930 2,075,506 Crites Mar. 30, 1937 2,092,307 Gaflney Sept. 7, 1937 2,200,822 Crites May 14, 1940 2,294,920 Lykken Sept. 8, 1942 2,552,565 Les Veaux May 15, 1951 2,709,552 Lecher May 31, 1955 2,712,416 Beushausen et al. July 5, 1955 2,752,097 Lecher June 26, 1956 FOREIGN PATENTS 1,003,288 France Nov. 15, 1951

Claims (1)

1. AN APPARATUS FOR FINE GRINDING, SAID APPARATUS COMPRISING A CASING, A VERTICAL ROW OF BLADE-CARRYING ROTORS IN SAID CASING, ANOTHER CASING CONNECTED WITH THE FIRSTMENTIONED CASING BELOW SAID ROW OF ROTORS, AND A MECHANICAL FEED DEVICE LOCATED IN THE SECOND-MENTIONED CASING FOR FEEDING A SUBSTANCE TO BE GROUND TO THE FIRSTMENTIONED CASING BELOW SAID ROTORS, SAID MECHANICAL FEED DEVICE HAVING AN INNER END SPACED FROM THE INTERIOR OF THE FIRST-MENTIONED CASING, THE SECOND-MENTIONED CASING HAVING AN AIR VENT OPENING LOCATED BETWEEN SAID INNER END OF THE MECHANICAL FEED DEVICE AND THE INTERIOR OF THE FIRST-MENTIONED CASING, WHEREBY THE OPERATIVE SIZE OF SAID OPENING IS REGULATED BY AN ACCUMULATION OF SAID SUBSTANCE IN THE SPACE BETWEEN SAID INNER END OF THE MECHANICAL FEED DEVICE AND THE INTERIOR OF THE FIRST-MENTIONED CASING, THE FIRST-MENTIONED CASING HAVING AT LEAST ONE OTHER AIR VENT OPENING FOR FEEDING THE SUBSTANCE TO BE GROUND FROM THE SPACE BELOW SAID ROTORS TO SAID ROTORS.

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