Patent GB-635573-A (GB)
Title: Improvements in or relating to a sedimentation device
IPC: B01D21/06
Filed: 1947-03-27
Abstract: 635,573. Gravity-separation apparatus. GENERAL AMERICAN TRANSPORTATION CORPORATION. March 27, 1947, No. 8305. Convention date, Feb. 16, 1946. [Class 111] [Also in Group XXIV] A sedimentation tank includes rotary rake means suspended by a vertical shaft and fluid pressure means for raising and lowering the shaft to adjust the operating height of the rake means. The apparatus may include means for discharging settled matter from the bottom of the tank, and the fluid pressure means may raise and lower the rake means with respect to the bottom of the tank. As shown in Fig. 3, the mechanism comprises a cylinder structure 21 centrally supported on girders 19 which span a circular tank, and a piston member 24 to which is attached a scraper shaft 13, and on which is supported a motor 37 and gearing for rotating the shaft and piston. The shaft 13 is welded to the bottom 24a of the piston 24 and braced by web-plates 24c. Secured to the top of the piston is a gear-ring 33 in a housing comprising upper and lower plates 28, 30, and a further gear-ring 29. A pinion 38 driven by the motor 37 drives two pairs of planetary gears 39, 40 round the inside of the gear-ring 29, the housing being prevented from rotating by rods 31 bearing against stops 32 on the cylinder member 21. The lower members 39b, 40b, of the gears 39, 40, having a different number of teeth from the upper members 39a, 40a, drive the gear-ring 33 and with it the piston 24 and shaft 13 at a rate depending on this difference. Pressure fluid can be supplied through pipe 26a to a space 160 below the piston whereby the scrapers, shaft, piston, housing and motor rise as a unit, the rotational motion not being affected. In a modification the'pinion 38 drives two diametrically opposite gears mounted on bearings in a central flange in the housing, the gears having pinions secured to them beneath the flange which drive an externally-toothed gear-ring mounted on top of the piston. In the modification shown in Fig. 5 the piston member is fixed, the scraper shaft being secured to, and rotating with, the cylinder member. A piston 92 is secured to a framework 91 mounted on the girder 19 and has an axial space within which a shaft 90 is free to slide vertically and rotate in bearings 134, 134a. A cylinder 104 is secured by keys 115, 116, 117, Fig. 6, in slots 118, 119, 120 in the hub 93b of a worm gear 93 driven in a circular bearing 96 by three motors one of which is shown at 100 mounted on top of the housing 91c, the cylinder being thus constrained to rotate with the gear 93 but free to slide vertically with respect to it. The shaft 90 is secured to an extension 105a of the cylinder 104 by a key 110, and supported on top of the extension by a nut 112 and washer 111. In its lowermost position the cylinder rotates on a thrust-bearing 133. Pressure fluid for raising the rakes attached to the shaft 90 is supplied via an annular space 132 in the piston, and holes 127a to the region 131. As the cylinder rises a sleeve 145 adjustably clamped to a rod 143 fixed to the cylinder head comes in contact with a switch 146a by which the pressure fluid supply is automatically cut off. The switch 146a may be shunted so that the automatic cut-off is actuated by switch 146b. , In order to drive the rake arms into the sludge the driving shaft in each case may be divided into two sections one section threading into the other, and the thread on the upper section spiralling reversely to the direction of drive. A limit stop is provided to prevent the two sections of the shaft from separating and to prevent the rake arms from striking the bottom of the tank.