The Mechanical Handling and Storing of Material

WORM OR ARCHIMEDEAN SCREW CONVEYORS 49 An 18 or 20 in. continuous worm will do the work if driven at 60 revs, per minute, and the power required will be 18^- to 19 H.P. To convey cement would absorb some- what more power on account of the greater friction of the worm blades and the box against the cement, and the greater specific gravity of the cement. Table giving the Approximate Horse Power Required to Drive a Worm Conveyor for Heavy Material Length of Conveyor in Feet. Tons per_____________________________________________________________ Hour. 10 20 30 40 50 60 70 80 90 100 5 0-33 0-66 0-99 1-32 1-65 1-98 2-31 2-64 2-97 3-30 10 0’66 1-32 1-98 2-64 3-30 3’96 4-62 5-28 5-94 6-60 15 0-99 1-98 2-97 3-96 4-95 5'94 6'93 7'92 8-91 9-90 20 1-32 2-64 3-96 5-28 6-60 7-92 9’24 10-56 11-88 13-20 25 1-65 3-30 4'95 6-60 8-25 9-90 11-55 12-40 14-85 16’50 30 1-98 3’96 5-94 7-92 9-90 12-28 13-86 15'84 17-82 19'80 35 2-31 4-62 6-93 9-21 11-55 13’86 16-17 18-48 20-79 23-10 40 2-64 5-28 7'92 10-56 13-20 15-84 18-48 21-12 23-76 26-40 45 2-97 5-94 9-81 11-88 14-85 17-82 20-79 23-76 26-73 •29-70 50 3-30 6’60 9-90 13-20 16-50 19-80 23-10 26'40 29-70 33-00 The principal advantages of a worm conveyor consist in its great simplicity and small first cost. The terminals are much less expensive than those of most other types of conveyors. Short worm conveyors can, therefore, be procured at a much smaller cost than short conveyors of other types. Worm conveyors are of great service where a mixing of the material to be conveyed is desired. For example, when cement and sand in a dry state are to be conveyed, they will arrive at the delivery end well mixed. The disadvantages are the large amount of driving power required, the grinding action on the material being conveyed, and the great wear and tear if the conveyor be used for hard and cutting substances. Troughing and Intermediate Bearings of Worm Conveyors.—Worms are fitted into a wooden or iron trough so as to leave a clearance between the revolving and stationary parts of from | to j in. The different lengths are supported at intervals of 8 ft. for 4 in. worms, 8 to 10 ft. for 6 to 10 in. worms, and 10 to 12 ft. for 12 to 18 in. worms. A continuous worm is more rigid than a paddle worm, and may therefore be in slightly longer lengths between the bearings, /.<?., have fewer intermediate supports. A detail of great importance in all worm conveyors is the intermediate bearing ; this, if cumbersome, obstructs the passage of the material, a drawback which must be carefully avoided. As all adjustable bearings are in halves and of necessity bulky, it is preferable to choose whole or bush bearings, although they lack some advantages that the former possess. The best intermediate bearing is a small phosphor-bronze bush, connected by a short piece of pipe to a cast-iron support. The pipe is screwed into the support and secured by means of a lock nut. The bearing can be oiled through the pipe. Fig. 48 shows such a bearing, and Fig. 49 a simple form of adjustable bearing in halves. Fig. 50 illustrates another type of intermediate bearing. It is similar to that illus- trated in Fig. 48, with the exception that the bearing is in halves and the cap held in 4