US1762379A - Coal pulverizer - Google Patents

Description

L'MZ 79 2 Sheets-Sheet l June 1U, W30. H. H. BATES COAL PULVERIZER Filed April 25, 1927 ATTORNEY H. H. BATES COAL PULVERIZER June IU, 1930.

Filed April 25, 1927 2 Sheets-Sheet' 2 CL im ATTORNEY WITNESS l Patented JuneV 10, 1930 UNITED STATES PATENT f OFFICE HARRY H. BATES, or RIDLEY PARK, rnNNsYLvANIA'A'ssIGNOR To wEsTINGHOUsE ELECTRIC a MANUFACTURING COMPANY, A CORPORATION OF PENNSYLVANIA oo AL rUIyRRIznR Application med April 25, 1927. Serial No. 186,457.

My invention relates to grinding machines, for example, machines for grinding coal into pulverous form for use in furnaces, and has for its object to provide apparatus of .the

character designated which shall be relatively small and compact and which shall have a Apparatus embodying features of my in- Y vention isillustrated in the-accompanying 20 drawings, in which:

Fig. 1 is a longitudinalsection view of apparatus embodying features of my inven-V tion' V Fig. 2 is a sectional view'taken along the line II-II of Fig. 1 and looking in the direction of the arrows;

Fig. 3 is a perspective view ofthe station-v ary grinding stone employed in my invention;

Fig. 4 is a view, in elevation, showing a modified form of rotating grinding stone; Fig. 5 is a sectional view similar to Fig. 1 but showing a grinding machine embodying a plurality of grinding units; Y

Fig. 6 is a view similar to Fig. 1 and showing a further modified form of my invention; and, Fig. 7 is a fragmentary. sectional view taken along the line VII-VII of Fig. 4.

I-Ieretofore, in the design of grinding machines for` pulverized fuel, among the difculties to be overcome there has been that of producing a machine which is effective to reduce the fuel to a sufficiently finely divided state in one passage through the machine that it might be employed in a pulverized fuel burning furnace and also in providing a machine which hasa relatively high output for the Apower required to drive it. 50 I have discovered that these and other 'element and avcoaxially arrange diiculties may be overcome by providing a machine embodying a stationary indmg rotary grinding element cooperating with the stationary element and in arranging the grinding elements with conjugate working faces. I provide, in the working face of the station# ary element, a feed groove whichforms one of the important features of my invention, and which extends from the periphery in a chordal direction, to one side of the axis of the stone and is so disposed that the action of the working face of therotary element in passing the groove exerts an inward force on the material in the groove thereby producing apacking and crushing action on said material before Vit actually passes between the working faces of the two stones. The

Vfeeding groove is generally wedge-shaped and uniformly decreases in depth from the peripheryinwardly of the stone. Inorder to provide suicient length to the groove, it may be turned arcuately around the axis of the stationary. element as it approaches inwardly of said element.

In order to avoid overheating of the stones in service,'I provide them with hollow retaining members which embrace the stones and provide means for circulating a cooling fluid through the retaining members on theA side opposite the working faces thereof. The stationary member is yieldingly held in a predetermined working relation with respect to the rotary member, and should some foreign material, such as iron or other hard material which would endanger the stones, accidentally pass into the machine, the yielding means permit a separation of the stones and thus prevent danger to the machine. I may also provide means effective upon such 90 relative displacement of the stones to shut oii' the supply of material to be ground to the' machine and thus prevent an undue amount of coarse -material from passing through the machine.

Referring now to the drawings for a better understanding of my invention, I show, in Fig. 1, my improved grinding machine wherein a casing 10 surrounds a rotary grind ing stone 11 and a cooperating stationary 100 grinding stone 12. The rotary grinding stone 11 is secured to a shaft 13 which may be driven by any suitable means as from a pulley 14. The rotary grinding stone 11 is preferably of much coarser texture than the stationary grinding stone 12. The stones are preferably both made of a highly refractory fast cutting grinding material such as silicon carbide.

The opposed working faces of the two stones are conjugate, that is, the opposed working faces are parallel throughout and are not dished as has heretofore been common in the art.

In the working face of the stationary member 12, I provide a wedge-shaped groove 16 which extends from the perimeter inwardly to one side of the axis of the 4stone and which decreases uniformly in depth from the perimeter to the end thereof where it merges into the working face of the stone. In order to provide suiiicient length to this groove, I may also form it with an arcuate portion 17 which bends around the axis of the stone and which is spaced away from the axis. The direction of rotation of the rotary grinding stone 11 is indicated in Fig. 2 by an arrow 18. It will be seen from Fig. 2 that the groove is disposed on that side of the axis of rotation so that the direction of movement of the working face of the rotating stone passing in front of the groove exerts a force giving an inward component of motion to the material in the groove. The coal to be ground is fed into the groove from a conduit 19 and passes thereto by gravity.

The texture of the stationary stone is made ne enough so as to impede as little as possible the iiow of material through the groove and the texture of the rotating stone 11 is made as -coarse as possible, consistent with the degree of iineness sought, so as'to exert Y suiciently linely divided state to pass be-4 tween the stones whereupon it is subject to Y,

the greatest degree of force on the material in the groove in its passage inwardly of the working faces of the stones. Y

y Thus the action of the rotary stone on the material while it remains in the` groove is a packing action or one which causes the material to be crushed against other material and the bounding walls of the groove duringits passage inwardly. By the time it reaches the lower end of the groove 16 it is in a with a remarkable reduction in power required per ton as compared with4 apparatus heretofore known to me, the power required in the test above referred to being in the neighborhood of 2 k. w. hours per ton.

The stationary stone 12 is retained by a hollow member 22 having a ring portion 23 extending entirely around the periphery thereof. The ring portion 23 is joined to the stone by melting lead or other suitable material and-pouring it between the stone and the ring portion as shown at 25. The ririg portion 23 is provided with a suitable number of protuberances or lugs 24-around its periphery which are adapted to engage with complementary stops 26 disposed around the interior of the casing 10 and which hold the stationary member in a predetermined position within the casing.' The hollow member 22 is provided with an annular partition 27 which is joined to the back of the stationary member 12 in a fluid-tight manner. A water main is shown at 28 from which a iexible branch conduit 29 leads into the interior of the hollow member 22 for circulating water therethrough and cooling the stationary stone 12. After passing through the hollow member 22 the water is discharged through a iexible conduit 31.

The rotary member 11 is similarly retained by av hollow member 32 joined to the rotary member as previously described for the stationary member. The member 32 is provided with a hub-like portion 33 having openings 34 therein which, in effect, act as the vanes of a pump. The shaft 13 is provided with a passage 36 so that it is hollow and it is provided, interiorly of the hollow member 32, with a plurality of passages37. Cooling water from the main 28 'isintroduced into the end of the passage 36 of the shaft 13 at 38. Thepassages 37, upon rotation of the shaft 13 act. asvanes of a pump and discharge the water-.from the it is pumped outwardly thereof by action of the passage 34 in the hub portion 33 and is thence discharged through a discharge' conduit 39.

On the outer side of the hollow member 22 there is arranged a spring 41 abutting against the casing 10 and exerting a force for holding the lugs 24 0f the member`22 against the stops 26, so that the stationary member is yieldingly held in a predetermined position with respect to the rotary member. By this yielding means, the stones are relatively dis- The position of the rotary member with re-.

spect to the stationary member is adjustable by means of a thrust bearing 46 which is movable longitudinally of a holding pedestal 48 by means of a screw and nut connection 49 and 51.

In case there should be axial movement of the stationary member 12 such as when iron or other hard foreign material is inadvertently fed into the mill, it will be obvious that a considerable amount of unpulverized material might pass through the mill., In order to obviate this as muchas possi le, I provide a gate or valve 53 in the feed conduit 19 and control the closing of the gate 53 by an electromagnetic device, or solenoid, 54. The gate 53 is normally held in .an open position by means of a spring 56. The solenoid 54 is included in an electrical circuit 57 which is controlled by a switch 58. lThe switch 58 has a sliding stem 59 vbearing against the outside of the member 22 and `held thereagainst by action of a spring 60. Upon axial movement of the stone 12 the-switch 58 is closed, completing the circuit 57, energizing the solenoid 54, and effecting a closing of the gate 53 and thus shutting oi the supply of material to be ground to the machine. As soon as the stationary stone 12 has regained its normal position, the circuit 57 is again opened by the spring 60 and the spring 56 reopens the gate 53, permitting the machine to resume operation. The clearance between the switch points is preferably made'such that the gate 53 is held closed as long as the stationary stone 12 is only slightly displaced axially with re spect to the rotative stone 11.

Referring now to Fig. 5, I show a grinding machine embodying a plurality of grinding units. In this machine, the casing is divided into compartments, such as 61a and 62, each similar to the casing 10 already described. Disposed within the compartment 61a is a rotary grinding stone 63 and a stationary grinding stone 64 similar to the grinding stones already described. Likewise, in the section 62 there is disposed a rotary grinding stone 66 and a stationary grinding stone 67. The rotary grinding stones 63 `and 66 are secured to a common shaft 68 which may be driven by a pulley 69. Material to be ground is admitted to the compartment 61a'through a conduit 71 and to the compartment 62 through a conduit 72. Pulverized, material, after passin through the grinding elements is discharged through discharge conduits 73 and 74, from whence it may be conveyed to points of use. I

The shaft 68 is provided with an interior passage 7 6 which opens through passages 78 and 79 to hollow retaining members 81 and 82,

both similar to the retaining member 32 Ereviously described. The retaining mem ers Sland 82 are provided with hollow hub portions 83 and 84, the hollow hub portions being provided with outlet ports 86 and 87. When the machine is running, water is admitted to the passage 76 from a conduit 89 from whence it is pumped by action of the rotating shaft, as previously described, into the interior of the retaining members and from thence outwardly by the pumping action of the hub portions thereof so as to cool the rotating stones 63 and 66. The stationary stones are cooled in the same manner as described for the single unit.

From the example shown, it will be apparent that my improved, grinding apparatus may comprise any desired number of units, all driven from a common shaft. Thus it may be designed for any desired capacity by selecting the required number of units.

In Figs. 4 and 7, I show a modified form of a rotating grinding stone which may be capable of more edectively causing the fuel in the `feed groove 16 to pass between the relatively rotating faces of the stones. In these figures the rotating stone is indicated at 91.

InV its working face there is provided a series of pockets 92. The pockets 92 are of such radial depth that their outer boundaries are conjugate with the outer boundary of the feed groove 16 of the stationary stone. The effect of these pockets 92 passing before the feed groove is to draw the material near the lower end of the groove and further inwardly of the groove and thus increase the rate of grinding of the unit.

Referring now to Fig. 6 of the drawing, I show a further modified form of my invention, wherein a grinding machine embodying two grinding units of the general character rheretofore described, are embodied within a single casing. In this figure, a casing 101 encloses a pair of stationary grinding elements 102 and 103. Both of these stationary grinding elements are similar to those heretofore described and do not require further description. The working faces of the stationarystones 102 and 103 are arranged facing toward each other, and between the two is located a two-faced rotating element 104, with its two faces cooperating with the stationary stones 102 and 103. The rotating element 104 is provided with a hollow retaining member 106 mounted on a shaft 107. The shaft 107 has a passage 108 extending therethrough and terminating in the interior of the retaining member 106. A second passage 109 also extends through the shaft from the in terior of the retaining member 106 and termioperation, water under ressure is admitted from a conduit 114 into t e passage 108 from whence it is dischar ed into the interior of the member 106. A er passing into the interior of the member 106 and cooling it, it is pumped outwardly thereof by the action of the pump 112.

The stationary grinding stones 102 and 103 are arranged to be cooled in the same manner as previously described and need not be again.

repeated.

From the foregoing, it will be, apparent that I have devised an improved grinding machine which is compact, eiflcient, and which requires the minimum of power for its operation. f

While I have shown my invention in several forms, it will be obvious to those skilled in the art that it is not so limited, but is susceptible ofvvarious other changes and modifications, without departing from the spirit thereof, and I desire, therefore, that only such limitations shall, be placed thereupon as are imposed by the prior art or as are s pecically set forth in `the appended claims.

1. Ina grinding machine, a rotary grinding stone, a hollow retaining member having a ring portion embracing and retaining the stone and a hollow hub-like portion with openings in said hub-like portion, a hollow `rotary shaft secured to the rotary member and having passages from the hollow thereof opening into the hollow of the retaining member, and means for introducing a cooling fluid into the hollow shaft whereby it is pumped into the hollow retaining member by rotation of the shaft and outwardly thereof by the rotation of the hub portion of the retaining member.

2. In a grinding machine, means for feeding materialtobeground to the machine, a

pair of coaxially' arranged relatively rotatable grinding members having conjugate working faces, means for iixedly holding one of the members against movement longitudinally of its axis, yielding means for holding the other member against movement longitudinally of its axis, means for shutting ofi' the supply of materiall to the machine, an electro-magnetic `device for controlling the shutting off means, an electric circuit for the electro-magnetic device, and means effective material to be ground to the deeper portion of said groove.

n 4. In a grinding machine, a rotary grinding stone, a stationary grinding stone cooperating with the rotary grinding stone and having its working face` conjugate with the working face of the rotary stone, said stationaryA stone being rovided with a Wedge-shaped feed groove 1n its working face extendlng parallel to and spaced from a radius of the stone and extending from the outer periphery inwardly and being curved in the direction of rotation of the rotar stone as it approaches the inner area o the stationary stone, said groove being so arran ed with respect to the rotating stone and to 1ts direction of rotation that the action of the rotating stone draws the material to be ground inwardly from the periphery of the stationary stone, said vrotary stone being of coarser texture than the stationary stone.

5. In a grinding machine, the combination of a pair of relatively-movable grinding elements having cooperating working faces, one of said grinding elements having an elongate feed groove in the working face thereof, said groove extending in the general direction of relative movement ofthe other grinding ele- "ment and being of decreasing depth in said direction, the other of said grlnding elements being of a coarser texture than the one grinding element, and means for feeding the material to be ground to the deeper portion of said groove.

In testimony whereof, I have hereunto subscribed my name this nineteenth day of April,

HARRY H. BATES.

upon longitudinal'movement of the yielding means for completing the electric circuit and closing oif'the supply of material.

3. In a grinding machine, the combination of a stationary grinding element, a rotary grinding element of relatively coarser texture

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