Patent GB-427188-A (GB)
Abstract: 427,188. Disc mills; impact pulverizers. HOLBECK, H. F., 11846, Lake Avenue, Lakewood, Ohio, U.S.A. Oct. 17, 1933, No. 28717. [Class 59] In rotary grinding - apparatus having relatively - rotatable annular grinding surfaces between which material is fed from the outer periphery, means are provided, for creating a flow of air inwardly between the grinding surfaces so as to remove in opposition to centrifugal force, fine material from the chamber or chambers enclosing the surfaces. In the machine shown in Figs. 1, 2 the material is fed from a hopper 44 into a compartment 45 from which it passes through holes 46 to three annular grinding chambers 20, 21, 22 wherein it is first beaten by hammers 37 on the peripheries of grinding discs 28, 29, 30 fixed to a shaft 27 driven by an electric motor or other means. The hammers co-operate with corrugated ring-members 39, 40, 41, which form liners for the grinding chambers and are integral with, or connected by radial arms 43 to the partition walls 23, 24, 25, thereof. Each disc consists of an annular web portion 31 connected to a hub 32 by spokes 34, the opposite sides of the web-portion having grinding means comprising a grid arrangement of radiallyextending ribs 35 which co-operates with similar or other grinding means on the partition walls. Air drawn into the grinding - chambers through the holes 46 by a fan 50 fixed on the shaft 27 passes inwardly through the chambers 20, 21, 22 on both sides of the discs and carries the finely-ground material laterally through aligned openings 26 in the partition walls and discs into the fan-chamber 14 from which it is discharged through a pipe 51. Any tramp metal in the material supplied to the hopper settles downwardly through the material in the chamber 45 and collects in the pocket 47. In the modification shown in Fig. 3 material is fed into the machine through a passage 83 in the removable cover 66 and passes around the periphery of an imperforate end disc 71 to the peripheral portion of an annular chamber 60 and from thence between annular grinding portions of discs 71, 72 and partitions 63, 64 to hub passages, the fine material being carried by a draught of air caused by a fan 70 through the central opening of a wall 64 into a second annular chamber where it is ground by devices similar to those in the chamber 60. The ground material is finally carried by the air into the discharge chamber 57. In the construction shown in Fig. 5 material fed through a passage 114 in the cover 95 of the machine passes around the periphery of,an imperforate end disc 105 having peripheral hammers 110, the fine material being drawn by a current of air between co-operating grinding-surfaces 108, 109 on the disc and fixed wall 96, through a central opening in the wall 96 and into an annular chamber 99. The grinding disc 106 in this chamber has circumferentially-spaced openings 111, Fig. 8, partly covered by rearwardly-inclined blades 112 which co-operate with radially-extending teeth or corrugations in the wall 96, the fine material being then carried by the air current through the openings 111 into another chamber 100 enclosing a disc and grinding means similar to those in the chamber 99. Fig. 9 shows a further construction having a single grinding disc 128 fixed to a driven shaft 120 slidable axially in bearings so that the disc may be moved towards or away from a co-operating grinding surface 130 on a partition wall 118. The disc is urged normally towards the wall by a spring 141 compressed between a fixed housing 123 and an extension 142 of a casing 143 which is movable relatively to the housing 123. A cam 146 supported by the casing 143 co-operates with the stem of a plunger 144 engaging the bearing 126 to make the spring 141 operative. When the cam is rotated through 90‹ the spring is inoperative. A second weaker spring 148 urges the disc away from the wall to prevent the grinding portions contacting when the machine is running idle. Material is fed peripherally to the grinding-chamber 117 through a passage the material being drawn by a flow of air caused by a fan 133 past the grinding elements and into the discharge chamber 116. An additional supply of air may be admitted to the fan chamber through an opening 149 manually-controllable by a shutter 150.