US2735626A - trost - Google Patents

Description

Feb. 21, 1956 c TROST 2,735,626

JET GRINDING MILL Filed Jan. 5, 1955 2 Sheets-Sheet 1 INVENTOR. Chm/940M 77e057 BY W Wyn 5y Feb. 21, 1956 G TROST 2,735,626

JET GRINDING MILL Filed Jan. 5, 1955 2 Sheets-Sheet 2 IN VEN TOR. CON/PAD M 779057- A TTO/P/VEY United States Patent JET GRINDING MILL Conrad M. Trost, Moorestown, N. J.

Application January 3, 1955, SerialNo. 479,451

8 Claims. (CL. 241-39) This invention relates to a pulverizing mill of the type wherein the greater part of the comminuting process is eifected by opposed material carrying fluid streams and the classification is carried out by circulatory means. This application is a continuation-in-part of my application Serial No. 229,593, filed June 2, 1951, now Patent No. 2,704,635, issued March 22, 1955.

While the method and apparatus disclosed in the abovementioned application have proved satisfactory for their intended use, experience has shown that certain structural modifications therein are desirable. in order toimprove the efiiciency and operation thereof. For certain types of material, such as laminar or plate like, some acicular and fibrous materials, the apparatus disclosed in the above-mentioned application does not obtain maximum comminution of the material because the pulverizing action caused by the opposed fluid streams is not sufficiently strong to comminute these types ofless friable material. This difiiculty arises from the fact that the streams of fluid material are not sufficiently concentrated to strike each other with maximum pulverizing force.

A further difliculty which has arisen in the operation in the above-mentioned machine is that for some types of materials the larger particles tend toremain in. the radially inward portion of the classification conduit. The centrifugal force developed in the classification conduit is not strong enough to insure that. these larger particles will be directed to the radially outward surface of the classification conduit. This results in a somewhat incomplete classification of the material being. pulverized.

Accordingly, it is an object of 'thisinvention. to provide an improved pulverizing mill wherein the streams of puverizing. fluid will be directed against each other as streams of a restricted cross-sectional. area.

A further object of this invention is to provide a pulverizing mill which has improved means in the classification chamber to separate the larger from the smaller particles.

Other objects and purposes of the invention will become apparent to persons familiar with equipment of this kind upon a reading of the disclosure and study of the accompanying drawings.

In the drawings:

Figure 1 is a central, vertical, sectional view of a preferred embodiment of my apparatus.

Figure 2 is a sectional view taken along the line 11-11 of Figure 1.

Figure 3 is a. sectional view taken along the line IIIIII of Figure 1.

I Figure 4 is a sectional view taken along the line IV-IV of Figure 1.

Figure 5 is a sectional view of my device taken along the line VV of Figure 1.

Figure 6 is a fragmentary sectional view of my device taken along the line VI-VI of Figure 1.

Figure 7 is a side elevational view of a modified shape for the classifier of my improved mill, partially broken away.

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In meeting the objects and purposes above set forth, I have provided. a device wherein the jets. of puverizing fluid are directed through orifices of. restricted crosssectional area just before. the jets enter into the impact chamber. Upon entering the. impact chamber the mate.- rial carrying: jets strike each other as rod-like streams and thereby an improved comminuting action: is obtained. The off-take leg of. the. classifier. is provided with one or more deflectors or restrictors which. are positioned so that any large particles: which do not. move to the radially outer wall of the classifier immediately after leaving the impact. chamber are deflected toward the radially outer wall before or just after the'particles enter into the semicircular classifying section.

The pulverizing mill consists broadly of agrinding compartment 1, a classifier 2,. and an off-takeconduit- 3 for the pulverized material. The grinding compartment in cludes a tubular housing 4 which, may be horizontally split, and it may, as shown in the drawings, be closed on each of its ends by plugs 6 and 9. The plug 6 at the right hand end of the. housing. 4, as seen in Figure 1, fits snugly within the end of the housing4 and has a central opening through which extends the nozzle 7. The plug 6,. together with the nozzle 7, is adjustable longitudinally of the. housing 4 and is held in predetermined position by means of the set screw 8. The primary grinding fluid is admitted through the nozzle. 7. This fluid is so regulated. that. it has a greater kinetic energy than the second'ary grinding fluid admitted through venturi 10.

The: plug 9 at the left hand end of the grinding chamher 5, as seen in Figure 1, fits snugly within the end of the housing 4. Concentrically throughthe center of the plug 9, is formed a venturi opening 1.0. A guide block 16 is positioned in the housing 4 between the off-take and return legs 19 and 21, respectively, of the classifier. The guide block 16 has an opening 20 of restricted crosssectional. area therethrough. The opening 20 flares at the end. of the block closer to the nozzle 7.. The opening through the guide. block 16 communicates with the impact chamber 5 which is located in housing 4 between block 16 and the block 9.. Externally of the. housing ad.- jacent the block 9 is a material hopper 11 communicating at. its lower end with. the venturi opening 10. Coaxial with the venturi opening and extending through the material at the bottom of the hopper 11 is a press'urized: fluidv supply tube 12 terminating at the junction of the hopper 11 and. the venturi opening It The diameter of the; tube 12 is substantially less than that of the venturi opening 14) where the. venturi opening communicates with the hopper 11 to permit aspiration of material from the hopper into the venturiopening by the fluid discharged from the tube 12. Thus, the secondary grinding fluid and the unground material is admitted to the impact chamber 5 through the venturi opening it The classifier 2. is preferably a somewhat horseshoeshaped tube 3t! extending upwardly from the housing 4 and having. its off-take and inlet legs in open communication with the housing; The off-take leg 19 of the classifier communicates with the impact chamber 5 while the return leg 21 of the classifier communicates with the return chamber 18.

The. cross-sectional shape and size of the tube 30'vary appreciably throughout its length. In the preferred embodiment illustrated, the interior passage 33 of the offtake end 31 of the tube 30, at the point where it communicates with the grinding chamber 5, can be substantially rectangular as shown in Figure 2 of the drawings or it may be trapezoidal similar to the shape shown in Figure 5. As the tube 30 extends upwardly, in said preferred embodiment, the cross-section of the passageway 33 within the tube changes from a rectangle to a trapezoid with the inward wall 34 of the tube 30 (Figure 3') being the base of the trapezoid and the altitude of the trapezoid extending radially of the classifier 2. Positioned between the side walls 28 and 29 of the passageway 33 is a deflector or restrictor 22. The restrictor merges with the radially inward wall 34 of the classifier adjacent the off-take end 31 of the classifier. The restrictor diverges with respect to the wall 34 as the semicircular portion of the classifier is approached and presents a planar surface projecting into the passageway 33. The restrictor is provided with a flange 23 which engages the wall 34 adjacent the semi-circular portion of the classifier. The trapezoidal cross-sectional area of the passageway 33 is gradually reduced by the restrictor until a point adjacent the horizontal reference line X (Figure 1) is reached. The reference line X represents the base of the 180 degrees arcuate segment forming the top of the classifier 2. At this point, and above the flange 23 the radial altitude of the trapezoidal passageway 33 is substantially greater than the width of its base or inward wall 34.

At a point approximately 45 degrees to the right of the vertical reference line Y, as appearing in Figure 1, an off-take opening 36 is provided through the inward wall of the tube 30 (Figures 4 and 6). The reference line Y represents the center line of the arcuate portion at the top of the classifier 2. The opening 36 provides the means through which the fine, pulverized material from the classifier is withdrawn. As the tube 30 extends beyond the opening 36, the size of the passageway 33 rapidly decreases. This reduction in size continues until, and at a point below the horizontal reference line X, the tube takes on a constant shape and area which continue down to the return chamber 18, as shown. Although the size of the passageway 33 is reduced, the trapezoidal shape is retained, and the inward wall and outward wall remain approximately the same size as shown in Figure 5. In the reduction of the cross-sectional size of the passageway 33, the outward wall 35 continues to trace a circular path and the inward wall traces a path of increasing radius. Thus, the reduction in size is effected by the inward wall 34 approaching the outward wall 35. The inlet end 31 and the discharge end 32 of the classifier 2 converge toward each other as they approach the housing 4.

To simplify construction and reduce the overall cost of the mill, the tube 30 is divided into detachable sections. These sections are joined at their ends along lines X and Y by means of conventional flanges 37 and bolts 38. It will be understood that for convenience in fabrication, the tube 30 may be divided into a greater or a lesser number of component sections and the joints between these sections need not lie in the reference planes X and Y.

The ofi-take opening 36 is an elongated slot (Figure 6) through the inward wall 34 having its longitudinal axis aligned with the central axis of the passageway 33 and its ends either pointed or rounded. In the embodiment shown, the opening 36 comes to a tapered point at each end and has a central width constituting a major portion of the width of the inward wall 34. The opening 36 communicates with an off-take conduit 40, of any convenient cross-sectional shape, and leads to a collector. The collector is neither shown nor described in detail since it is of conventional design and may be any one of the commercial designs currently available on the market.

Modification In some instances it is desirable to provide more than one restrictor in the off-take leg of the classifier in order to improve the separation of the larger from the smaller particles. As shown in Figure 7, the off-take leg 19 of the classifier 2 is divided into a plurality of sections 51, 52 and 53. In each of the sections is provided a restrictor 55 of generally similar construction to that of the restrictor 22. Each restrictor extends from the side walls of the passageway 33 and merges with the radially inward wall 34 of the passageway adjacent one end thereof and diverges with respect to the wall as the restrictor approaches the next higher section of the offtake leg. In this embodiment, the surfaces of the restrictors projecting into the passageway 33 are not planar surfaces as is the surface of the restrictor 22 but are formed with a slightly concave shape which shape has been found to be beneficial in classifying some types of material. The lowermost restrictor projects only slightly into the passageway 33 while the next adjacent restrictor projects a little further into the passageway 33 and so on until the uppermost restrictor is reached, the uppermost restrictor projecting into the passageway the greatest distance. Thus, the minimum cross-sectional area of the conduit preferably occurs adjacent the top edge of the top restrictor and adjacent the semi-circular portion of the classifier. It will be recognized that the number of restrictors in the off-take conduit can be varied depending upon the characteristics of the material being worked on. Therefore, the invention is not limited to the precise number shown. It will also be recognized that the restrictor shown in Figure 1 can be made concave, if desired.

Operation The material to be pulverized is introduced into the hopper 11 from which it works down by gravity to a point adjacent the end of the fluid supply tube 12 where it is aspirated by the secondary grinding fluid through the venturi opening into the grinding chamber 5. At the same time the primary grinding fluid is introduced through nozzle 7 into the return chamber 18 and picks up and accelerates any of the material returning through the return opening 32 from the classifier 2. The primary grinding fluid and the returned materials are then directed through the opening 20 in the guide block 16 and from there into the impact chamber 5. Two substantially rodlike streams of fluid material are thereby formed and meet in head-on collision in the impact chamber. The comminuting action is carried out by both the direct action of the fluid streams on the particles and .by the resulting impact of the particles entrained in the grinding fluid. The grinding fluid with its entrained particles then enters the classifier 2. As the particles enter the classifier the larger of the particles will tend to migrate toward the radially outer wall passageway 33. This is the result of the centrifugal force acting upon the particles as the grinding fluid transits the horseshoe-shaped classification chamber. The finer particles of material will not materially change their position within the stream by reason of this centrifugal force because of the absence of sufiicient mass. As the shape of the passageway 33 changes to trapezoidal, the larger particles will crowd into the narrow outer portion of the trapezoidal passageway. As the larger particles crowd into this narrow, restricted portion of the passageway, they will force a similar volume of grinding fluid radially inwardly to occupy the broader path on the radially inward side of the trapezoidal passageway. Because of the decreasing cross-sectional area of the passageway and the constant volume of material and fluid passing therethrough, the particles will be moving at a high rate of speed as they pass the flange 23 on the restrictor. Any larger particles which may be in the radially inner portion of thepassageway will tend to travel in a straight line as they pass the flange 23 of the restrictor because of inertia forces and the centrifugal forces that act upon them in the classifying chamber. The smaller particles on the other hand, because of their light mass will not tend to travel as far in a straight line because the forces acting upon them are less. Therefore, the larger particles will tend to strike against the radially outward wall of the classifier 2 and be carried along said wall by the grinding fluid. Because of the centrifugal force acting upon them, there will be no tendency for the larger particles to drift back down against the radially inward wall of the passageway. Thus, the larger particles will all accumulate and travel along the radially outer wall. The result is a very exact and precise separation of the larger particles from the fine particles. By the time a given segment. of the grinding fluid reaches the off-take opening 36, the inward portion of the grinding fluid is. substantially purged of the larger particles. Thus, that portion of grinding fluid which exits from the classifier to the ofi take opening 36 will have in it only particles of a relatively closely controlled, preselected fineness. The relatively large particles returning to the return chamber 18' are accelerated by the aspirating action of nozzle 7. The dual action of forcing the grinding fluid into the oil-take leg of the classifier 2 plus the aspirating action acting at the discharge end 32 of the classifier 2 maintains an even, high velocity circulatory flow through the classifier 2.

The operation of the embodiment of Figure 7 is substantially the same as that previously described. In this instance, however, the material as it travels up the offtake leg of the classifier is subject to a series of deflecting actions caused by the restrictors. Thus, any particles which might manage to slip by the first restrictor without being thrown into engagement with the radially outer wall are subject to a second deflection, a third deflection and so on until all of the larger particles are thrown into engagement with the outer wall. In this embodiment, the arcuate shape of the restrictors will tend to throw the larger particles, as they approach the edge of the restrictors, along an arcuate path rather than in the straight line path through which the particles move in the previously described embodiment. However, in each instance the particles are thrown outwardly into engagement with the radially outer wall.

These and other modifications of my invention may be made without departing from the principle of my invention and each of these modifications is to be considered as included in the hereinafter appended claims unless these claims by their language expressly provide otherwise.

I claim:

1. In a pulverizing apparatus of the fluid jet type, the combination comprising: a housing; means in said housing defining within said housing an impact chamber and a return chamber, said last-named means including also a pair of spaced, coaxial passageways, one of said passageways leading from one end of said housing to said impact chamber and the other of said passageways leading from said return chamber to said impact chamber, said passageways being of substantially less cross-sectional area than said chambers; a first nozzle mounted at the other end of said housing, said first nozzle extending into said return chamber and being adapted for directing grinding fluid into said impact chamber through said other of said passageways; a second nozzle mounted in said one end of said housing and adapted to direct grinding fluid into said impact chamber through said one of said passageways; a classifying chamber having one end in communication with said impact chamber and another end in communication with said returned chamber, said classifying chamber having a curvilinear portion intermediate its two ends; an ofi-take opening in the radially inward wall of said curvilinear conduit adjacent to said another end of said classifying chamber.

2. In a pulverizing apparatus of the fluid jet type, the combination comprising: a housing defining a grinding chamber, a classifying chamber having a pair of legs and a curvilinear section therebetween, one of said legs communicating with said grinding chamber, a primary jet for directing grinding fluid into said housing, said jet being mounted at one end of said housing, a block having a passageway of restricted cross-sectional area therein, said block being positioned within said housing and spaced from said primary jet, the other leg of said classifying chamber communicating with the space between said block and said jet, a secondary jet for directing. grinding fluid into said'housing, said secondary jet being mounted in the other of the ends of said housing co-axially of said primary jet; a second block having a passageway of re.- strictedcross-sectional area, said second block being positioned within said housing adjacent said secondary jet, said blocks being spaced from each other to provide an impact chamber therebetween; means for introducing comminuted material into the grinding fluid of said secondary jet, said primary jet being adapted to admit a stream of grinding fluid into said housinghaving greater kinetic energy than the stream admitted by said secondary jet.

3. In a pulverizing apparatus of the fluid jet type, the combination comprising: a housing defining an elongated chamber; a primary jet for discharging grinding fluid under pressure mounted in one of the ends of said chamber; a secondary jet for discharging grinding fluid under pressure mounted in the other of the ends of said chamber coaxially of said primary jet, a classifying chamber including an off-take leg communicating with the elongated chamber, said classifying chamber including a curvilinear portion adjacent to said off-take leg, means mounted on and projecting from the radially inner portion of said leg for decreasing the cross-sectional area of said off-take leg, said classifying conduit having a second leg which engages said curvilinear portion and communicates with the housing.

4. In a pulverizing apparatus of the fluid jet type, the combination comprising: a housing defining an elongated chamber; a primary jet for discharging grinding fluid under pressure mounted in one of the ends of said chamber; a secondary jet for discharging grinding fluid under pressure mounted in the other of the ends of said chamber coaxially of said primary jet, a classifying chamber including an off-take leg communicating with the elongated chamber, a curvilinear conduit communicating with said off-take leg, means mounted on the radially inner portion of said leg, said means extending into said oiltake leg at an angle with respect to the axis of the leg and progressively decreasing the cross-sectional area of said oil-take leg, the minimum cross-sectional area of said cit-take leg being formed where said leg and the curvilinear conduit meet, said last-named means being so positioned that heavier particles adjacent thereto will be directed against the radially outer wall of said curvilinear conduit, said curvilinear conduit having an off-take opening in the radially inner wall thereof.

5. The apparatus of claim 4 wherein said means extending into the off-take leg is formed with a concave surface.

6. In a pulverizing apparatus of the fluid jet type, the combination comprising, a housing defining an elongated chamber; a primary jet for discharging grinding fluid under pressure mounted in one end of said chamber; a secondary jet for discharging grinding fluid under pressure mounted in the other of the ends of said grinding chamber coaxially of said primary jet, a classifying chamber including an offtake leg communicating with the grinding chamber, a curvilinear conduit communicating with said off-take leg, a plurality of deflectors mounted in said off-take leg, said deflectors extending into said offtake leg and decreasing the cross-sectional area thereof, each successive deflector extending into said off-take leg a greater distance, said curvilinear conduit having an offtake opening in the radially inner wall thereof.

7. In a pulverizing apparatus of the fluid jet type, the combination comprising: a housing defining an elongated chamber; a primary jet for discharging grinding fluid under pressure mounted in one end of said chamber, a secondary jet for discharging grinding fluid under pressure mounted in the other of the ends of said chamber coaxially of said primary jet; block means having openings of restricted cross-sectional area therethrough positioned in close proximity to each of said jets and adapted 7 4 l l to control the cross-sectional area of the jets of grinding fluid, an impact chamber being defined by and between said block means, a classifying chamber including an off-take leg leading from said impact chamber, means mounted on the radially inner wall of said leg for progressively decreasing the cross-sectional area of the leg, said classifying chamber also including a curvilinear conduit communicating with said off-take leg, said curvilinear conduit having an ofi-take opening in the radially inner wall thereof.

8. The combination of claim 7 wherein said means for a 8 l a r progressively decreasing the cross-sectional area of the leg includes a plate extending into said ofi-take leg at an angle with respect to the axis of said leg.

References Cited in the file of this patent 9 UNITED STATES PATENTS 1,756,254 Lykken Apr. 29, 1930 2,391,723 Mann Dec. 25, 1945 2,672,296 Venable Mar. 16, 1954 2,704,635 Trost Mar. 22, 1955

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