US1673483A - Pulverizing mill - Google Patents

Description

June 12, 1928.

W. M. BARKER ET AL glwuen row WE M 195m .m/

June 12, 1928. 1,673,483

W. M. BARKER ET AL PULVERIZING MILL Filed July 23. 1924 4 Sheets-Sheet 2 gwve'ntm M M 361%9/ am/ A (Baa/20% June 12, 1928.

W. M. BARKER ET AL PULVERIZING MILL Filed July 25, 1924 4 Sheets-Sheet a Fu Q MUN I w n M auto: "e414 June 12, 1928.

W. M. BARKER ET AL PULVERI Z ING MILL Filed July 25, 1924 4 Sheets-Sheet gwoe'ntow IVE! Bar/Few .y/zd

Z. 6750/2/20! 55% %W ix 4 4 Patented June 12, 1928.

' UNITED STATES 1,673,483 PATENT OFFICE.

WILLIAM i. BARKER, OF CANTON, AND LOUIS C. BONNOT, OF LOUISVILLE, OHIO.

t PULVEBIZIN G HILL.

Application filed July 28,

The invention relates to a rotary drum grindin or ulverizing mill partly filled with ba ls, pe bles or the like, and the ob ject of the improvement is to provide a machine which can be operated at slow speed and will. continuously deliver a predetermined unvarying powdered product, without any adjustments or changes in the machine, and without the use of screens or other separating or grading apparatus.

The improved-mill is well adapted for pulverizing small lump or slack coa for supplying powdered fuel directly in a furnace or a fuel feeding system, and the invention is illustrated and described with reference to such a use of the mill, without intending to limit it thereto.

In mills of this type, an axial tube extending into and sometimes through the mill has been used for withdrawing the powdered product from the drum by suction through.

one end of the tube; and in the rotation of the drum, the grinding balls have been carried by frictional engagement with each other and with the peripheral wall of the drum supplemented by the action of centrifugal force, upward on the rear side of the axial tube and thence'forward over and above the same, so as to fall freely throu h space downward, either against the perip eral wall of the drum or'upon the grinding balls in front of the tube.

Such a movement of the balls is ineffective for grinding purposes insubstantially all of the forward and downward portion of their orbits, and is also objectionable for the reason that the impinging action upon the forward peri heral wall of the drum, wears the same wit out accomplishing any grinding action upon the material to e powdered.

The present invention involves the use of a stationary deflecting wall extending directly upward from the rear side of the axial tube to the peripheral wall of the drum, and filling the entire distance between the endwalls thereof, which serves as a baflle or abutment for the grinding balls and ground materials moving upward in the rear side of the drum, to deflect the same when falling forward so as to shower downward upon the ascending body of balls and raw material in rear of the axial tube. for a direct grind ing action therewith.

When a fixed axial suction tube is used for 1924. Serial No. 727,699.

ward from the rear side and thence forward under and upward in front of the axial tube.

It is also preferred to further define the dust removing openin in the axial tube by providing upri ht wa ls at each end and at the back thereo and to secure thereon aroof plate inclined downward and forward from the deflecting wall a substantial distance to overhang the mouth in the forward side of the exhaust box thus formed so as to shed forward any ground material which finds its way into the upper ortion of the drum, and prevent anything at finely powdered material from finding its way into the mouth of the exhaust box.

A further feature of the present improvement relates to the admission of air into the drum through an annular opening in each end thereof around the axial tube; so as to carry powdered material into the mouth of the exhaust box from both ends of the drum, and also from both sides of as well as from below the axial tube. 7

These annular .openings are referably formed lar e enough so as to ren er the in terior of te drum visible from each end thereof, and enable an attendant to properly regulate the supply of material to be ground. The same annular openings also permit the material to overflow from one or both ends of the drum, whenever it is overfed, thereby rendering it impossible to choke the drum by overfeeding the same.

A final feature of the present improvement involvesthe location of a feed chute downward and inward through the axial tube at one end annular opening of the drum, so as to deliver the raw material to the middle of the drum immediately below the axial tube, where it is at once subjected to the intensive grinding action of the shower of balls falling at the'rear thereof.

Apparatus embodying the present invention is illustrated in the accompanying drawin s, forming part hereof, in which-- igure-l is a side elevation of the pulverizing mill showing the rinding drum, the feed chute and the discl arge tube in axial section;

Fi 2, an end elevation of the drum, lookin om cross section line 2-2, Fig. 1;

ig. 3, a cross section elevation of the mill, on line 3-3, Fig. 1;

Fig. 4, a cross section elevation of the mill on line 4-4, Fig. 1;

Fig. 5, a detached perspective view of the exhaust box forming the exhaust mouth; and

Fig. 6, a detached perspective view of the roof plate thereof.

Similar numerals refer to similar parts throughout the drawings.

The grinding drum 6 may be provided on each end with a peripheral track band 7 riding upon flanged wheels 7 mounted on shafts 8, and the drum may be rotated b a central annular girt gear 9 meshing wit a pinion 10 mounted on one of the shafts 8, which may be driven from any suitable source of power.

An axial tube comprising end sections 11 and 11" and an intervening exhaust box 11" extends through enlarged central openings in the ends of the drum, and may be supported on standards 12 at each end thereof. One end 11 of this tube may communicate directly with the inlet orifice of an exhaust fan 13 operated by an electric motor 14 and having its discharge pipe 15 communicating with the combustion chamber of a furnace or other place for delivering powdered material; and the other end 11 of the tube preferabl carries a downward and inwardly incline chute 16, for feeding coal slack or other raw material to be ground from a supply tube 17 through one end opening of the drtum to the middle thereof below the axial tu e.

The middle portion 11 of the axial tube may be in the form of a box with upright walls 18 and 18 on each end, one of which forms a partition transversely shutting off one end 11 of the tube, and the other one being provided with an opening 18 communicating with the exhaust end section 11 of the tube; and with an upright back wall 19 which closes the opening between the rear edges of the walls 18 and 18.

A roof plate 20 is secured across the top of the end walls, and the forward wall of the box 11 terminates in a lip 21 directly in front of the axis of the tube, so as to form a dust receiving mouth 22 between the end walls of the box immediately above the plane of the axis of the tube, and under the overhanging forward end of the roof plate.

The roof plate 20 extends endwise each way close to the end walls of the drum so as to overhang the end walls of the exhaust box; and to the rear of the back wall 19 is secured a stationary deflecting wall 23 extending upward close to the peripheral wall of the drum, and also extending each way close to the end walls of the drum, so as to form sheltered spaces 24 above the axial tube, between the end walls of the box and end walls of the drum.

The central openings in the end walls of the drum are prefcrabl' defined by ontwardly flared collars 25,0 such diameter as to form annular openings 26 around the axial tube for the admission of air at each end of the drum. The diameter of one opening is preferably larger than that of the other, so that overfed material will ordinarily cscape from one end only of the drum.

The described apparatus having a drum some four and one-half feet in diameter and two feet long, and an axial tube about twelve inches in diameter, may be used with ood results for producing powdered fuel rom slack coal, by rotating the drum at the rate of some twenty-eight or twenty-nine R.P.M., in conjunction with a centrifugal fan producing a suction pressure of some three and one-half inches of water.

When the drum is stopped after a rotation in the direction of the arrow, the grinding balls assume a position somewhat as shown in Fig. 2, but when the drum is rotated in the direction of the arrow for a grinding operation, the balls move somewhat in the manner shown in Fi 3: and when a supply of slack coal or t e like is fed into the rotating drum through the chute 16, the same is received and acted upon immediately and directly, somewhat as shown in Figure 4. The air currents produced by the suction pressure of the centrifugal fan, take the course as shown by the broken line arrows in Figs. 1 and 4, which winnows out the line powder which has been produced by the grinding operation, and carries the same into the receiving mouth of the exhaust box.

By these means, the grinding balls and the coarser particles of the raw material an kept constantly at work with each other, in the lower and rear part of the drum, without any of the balls moving into the upper and left part thereof; and without any of the ground material passing by rotating or centrifu al force into the upper or left part of the rum, excepting only the very small portion of the finer particles which may find their way between the upper and end edges of the deflecting plate and the peripheral and end walls of the drum.

Aside from this small portion of the ground material, which is again deflected forward by the roof plate overhanging the discharge mouth of the exhaust tube, the only material which can find its way to the mouth lit) of the exhaust box is the finely pulverized material which is winnowed from the mass of grinding balls and the coarser particles of the raw material, in the lower portion of the drum; whence the fine powder is carried though the annular zone immediately surrounding the axial tube 11, which by reason of the action of the centrifugal force upon the larger particles, is substantially free of all materia excepting only the floating powder and excepting only the slender stream of raw material flowing into the middle of the drum.

Thus the air currents which are drawn inward through the annular openin s in the ends of the drum are free to act se ectively upon the pulverized powder, more particularly in the lower and forward parts of the drum, and to carry the same into the centrally located mouth of the exhaust box, while all the coarser particles in the bottom, lower and rear portions of the drum are being ground by abrading contact with each other and with and between the grinding balls. At the same time the coarser particles of the small portion of the ground material which finds its way around the edges of the deflecting plate into the forward side of the drum, are carried by rotary and centrifugal force, and by the action of gravity, downward in front of the exhaust mouth, and are deflected by the roofplate so far forward that they are not drawn into the same, but drop on downward into the mass of grinding balls and raw material in the bottom of the drum.

The deflecting wall 23 may be and preferably is provided with a thick layer or facing of resilient material 23 on its rear side, for receiving the impinging action of the grinding balls and raw material; and the same serves not only to accelerate the rebound and increase the activity of the grinding balls, but to deaden or soften the sound of the machine when in operation.

When properly fed with raw material, the machine reduces the same to a fine powder and continuously delivers a powdered product of uniform predetermined fineness, depending upon the movement of air as controlled by the suction pressure, which may be varied by a damper 27 in the exhaust tube or by the speed of the exhaust fan.

Although the mill is intended for grinding dry materials, it can be successfully operated for pulverizing substances carrying a considerable amount of moisture without materially affecting its grinding capacity; and if desired, a heating and drying medium may be drawn into the mill, either through the feed chute 16 or through the end section 11 of the axial tube, WhlCh for that purpose may be provided with openings 28 within the drum, and to control the amount of air which may be thus received,

a damper 29 is referably provided in this section of the tube.

We claim:

1. A mill for pulverizing raw material, including a rotary drum with grinding media therein, an axial exhaust tube having an upwardly opening receiving mouth within the drum, and stationary means above the receiving mouth and extending substantially contiguous to the inner wall of the drum for deflecting all the grinding media and ground material downward in the rear of the axial tube.

2. A mill for pulverizing raw material, including a rotary drum with grinding balls or the like therein, an axial exhaust tube having an upwardly opening receiving mouth within the drum, and stationary means above the receivin mouth and extendin substantially contiguous to the inner wal of the drum for deflecting all the grinding balls and ground material downward in the rear of the axial tube.

3. A mill for pulverizing raw material, including a rotary drum with grinding balls or the like within, an axial exhaust tube having an upwardly opening receiving mouth within the drum, and a stationary angled partition wall in the rear of the receiving mouth extending upward from the tube substantially contiguous to the inner wall of the drum and endwise to the end walls thereof, for deflecting all of the grinding balls and ground material downward in rear of the axial tube.

4. A mill for pulverizing raw material, including a rotary drum with grinding balls or the like therein, an axial exhaust tube. having a receiving mouth within the drum, and a stationary partition wall faced with resilient material in the rear of the receiving mouth and extending upward from the tube to the peripheral Wall of the drum and endwise to the end walls thereof for deflecting all of the grinding balls and ground material downward in rear of the axial tube.

5. A pulverizing mill including a rotary drum with grinding balls or the like therein, an axial exhaust tube having a receiving mouth within the drum, there being an annular opening in each end wall of the drum.

6. A pulverizing mill including a rotary drum with grinding balls or the like therein, an axial exhaust tube having a receiving mouth Within the drum, there being an annular opening in each end wall of the drum around the axial tube.

7. A pulverizing mill including a rotary drum with grinding balls or the like therein, an axial tube having a central receiving mouth opening directly in its upper wall, upright walls at each end and in rear of the mouth and a downward, forward inclined roof plate thereon, forwardly overhanging the exhaust receiving mouth.

8. A pulverizing mill including a rotary drum with grinding balls or the like therein, an axial exhaust tube with a. receiving mouth opening directly in its upper wall and shielding means for the receiving mouth openin only in front thereof with a. roof plate i orwardly overhanging the receiving mouth.

9. A ulverizing mill including a rotary drum wlth grinding ball or the like therein, an axial exhaust tube with a receiving mouth opening directly in its upper wall, and shielding means for the receiving mouth opening only in front thereof.

10. A pulverizing mill including a rotary drum with grinding balls or the like therein. an axial exhaust tube having an exhaust receiving mouth openin directly in its upper wall, a chute extending through one end of the tube for feeding raw material into the middle of the drum below the axial tube.

11. A pulverizing mill including a rotary drum with rinding balls or the like therein, an axial to e having an exhaust receivin month opening directly in its upper walfi and a way for feeding raw material into the middle of the drum below the axial tube.

1:2. A pulverizing mill including a rotary drum with grinding balls or the like therein, an axial tube having an exhaust receiving month opening directly in its upper wall, and a way for directing a heating medium into the drum.

In testimony that we claim the above, we have hereunto subscribed our names.

\VILLIAM M. BARKER. LOUIS BONNOT.

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