516,307. Agitating-apparatus. TRIGGS, W. W., (Dorr-Oliver, N. V.). July 7, 1938, No. 20200. [Class 86] [Also in Group I] Rotary stirrers or scrapers such as used in settling apparatus are driven through engaging members formed to permit relative rotation and displacement of the members upon an increase in the driving resistance to raise and permit the lowering of the stirrers or scrapers as the relative rotation continues. Fig. 1 shows a settling-tank with scrapers 4 on a shaft 2 to which a spider 18, Fig. 2, provided with rollers 19 is attached. The rollers engage an annular cam track 12 fixed to a worm-wheel 8 driven from a motor 7a by a worm 11. The cam track, as shown in developed form in Fig. 4, is provided with one or more humps and engagement of the rollers 19 with inclined portions 20 of the track causes rotation of the shaft 2. When the scrapers encounter increased resistance the rollers move up the inclines and the shaft and scrapers are raised to fall again as the rollers pass down slopes 22. To ensure a balanced drive the spider 18 is pivoted on the shaft 2. Fig. 6 shows one form of pivotal connection. A sleeve 24 surrounding the shaft has semi-cylindrical bearing surfaces which rest in trough-like recesses 29 in the spider. The shaft 2 can be raised manually relatively to the spider by means of a nut 32 on a threaded spindle 33 secured to the shaft by a pin 34, which normally rests on the top of the sleeve 24. Adjustable stops limiting the lifting movement may be fitted on the slopes 20 of the cam. Fig 9 shows an arrangement in which the drive stops when the torque exceeds a maximum. In this arrangement the hub of the spider is loose on the shaft and forms one half 38 of a clutch, the other half being formed on a sleeve 40, which rotates with the shaft. The shaft, is supported by a spring 43 which, at maximum torque is compressed so that the spider rises and the clutch is disengaged. In another arrangement the cam track is free to rotate relatively to the gear wheel but is normally moved therewith by spring-controlled pawls on the gear-wheel which are disengaged when the torque exceeds a maximum. The invention may be applied to apparatus in which the rotating blades or scrapers are supported by a cage surrounding a central pier in the tank. The pier 51, Fig. 13 supports a gear wheel 54 driven by a pinion 55 and carrying a cam track 12b. The cage carrying the blades or scrapers is supported by links 56 having rollers 19b moving on the track 12b. Cylindrical guide surfaces 57, 58 on the cage prevent the cage from tilting. The devices described may be provided with means to cushion the descent of the revolving parts. These may take the form of hydraulic rams arranged below the spider 18 and moving in cylinders formed on the gear wheel 8. The scraping blades may be of triangular section with an inclined face, so that, when permitted to descend freely into accumulated solid matter, they tend to move in the direction of their normal travel. Specifications 417,595 and 460,021 are referred to.
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