Patent GB-234190-A (GB)
Title: New and improved apparatus for grinding wood pulp
IPC: D21B1/06
Filed: 1924-02-26
Abstract: 234,190. Warren, J. J. Feb. 26, 1924. Rasping - apparatus. - In a wood-pulp grinder of the magazine type, the magazine mounted above the grindstone is of substantial height in comparison with the diameter of the grindstone and endless woodgripping feed-chains operate along substantially the entire length of the magazine to grip the wood along its sides and continuously force it against the grindstone, the driving-sprockets of the chains being situated so closely adjacent the grindstone that the wood cannot arch or jam in the lower end of the magazine. The magazine is adjustable relatively to the grindstone, and woodgripping spurs are provided near the forward ends of the links of the feed-chains. The grindstone 21, Figs. 3 and 4, is secured fixed by means of bushings 25 and concave flanges 26 upon a shaft 22 journaled in water-cooled bearings 23, and one end of the pit 27 below the stone forms a dam 28 or overflow of variable height to keep the bottom of the stone immersed in stock to any required depth and over which the ground wood-pulp passes. The wood is fed from a vertical magazine 29, arranged centrally over the stone and adjustably mounted on the housing 24, by means of four endless roller chains 30, two on each side of the magazine, which pass down the inside of the magazine on tracks 31, in guides 32 fastened to the magazine. The chains pass through vertical slots 33, 34 in the guides near the upper and lower ends of the magazine. Beams 35 are riveted to the exterior of the magazine to prevent bulging. The holes in the side links 44, 74, Fig. 6, for the thimble 45 and pin 47 are not located centrally so that the rollers 46 project beyond the backs of the links; and on the face of the chain the links project beyond the face of the rollers to keep the wood away from the rollers. Each link is provided with a long spur or spike 48 at its forward end just ahead of the thimble 45, and with a short spike 50 at the centre of its length, a spike 49 of intermediate length being placed between the spikes 40. 50. The magazine is slightly larger at the top than in its main body. The feed-chains 30 are driven by sprockets 39 mounted upon the lower end of the magazine and close to the grindstone. The sprockets 39 are driven by a variablespeed motor through speed-reducing and worm gears. The idler sprockets 38 at the top of the magazine are journaled in bearings adjustable vertically by means of screws 40 engaging the vokes 41. The grindstone is driven by a motor 59 on the shaft of which is a direct-current generator 64 to excite the field of the motor 59 and supply power to the motor 52. A torque motor 63 is connected in parallel with the motor 59 so that the current transmitted to it is proportional to the current transmitted to the motor 59. The shaft of the motor 63 is connected to the movable contact-arm 64 of a rheostat 58 which controls the resistance in the field of the motor 52. At full load, the torque in the induction motor 63 is balanced by a weight 65. If the load on the motor 59 drops off, the torque of the motor 63 is decreased and the weight 65 overcomes the torque and the arm 63 is moved across the rheostat to insert additional resistance in the field circuit of the motor 52, thereby increasing the load on the motor 59 and producing a balanced system. The magazine is supported on the housings 75, 76 by means of adjusting- screws 67, 68. The shaft 22 is kept cool by means of water forced through cooling-jackets 37 bolted to the housings 75, 76. A swinging board 81 with a toothed design on its lower edge is arrange in front of the grindstone to keep the cold spray water fed to the pulp in the pit 27 from striking the grindstone directly and to give an equal distribution of the water sprayed on the upper part of the board from a spray-pipe 82. A door 83 permits removal of wood from the magazine when required, and peep-holes 102 are provided in the ends 68, 79. An agitator 91 in the pit 27 prevents the accumulation of slivers or heavy stock. For trueing-up the grindstone, a hydraulic stone-trueing lathe 85 is provided' and supported on the inside of the sole-plates 90. In a modification, separate packing-chains in the upper end of the magazine feed the wood to the primary feed-chains in compact form.