The Mechanical Handling and Storing of Material

COMBINED ELEVATORS AND CONVEYORS CHAPTER X GRAVITY BUCKET CONVEYORS The underlying principle of this type of conveyor is utilised for handling material in bulk, as well as for larger independent loads. Conveyors for the former purpose are generally described as :—- Gravity or Tilting Bucket Conveyors-—These conveyors consist of two endless chains or ropes held at fixed distances apart by suitable bars, which are fitted with small rollers at each end. Every link, or sometimes every second link, carries a, bucket, so that the whole is an endless and unbroken chain of buckets, which are not, however, fixed like elevator buckets, but are movable and suspended above their centre of gravity. When this conveyor is at work the buckets will always be in an upright position, whether they are moving horizontally or vertically. Each bucket carries its load to the point at which its delivery is required, and here it is generally met by some adjustable tripping device which tilts each bucket in turn, and thus empties the contents. The gravity bucket conveyor enjoys great popularity, especially in America, and the details of some of the best forms have been most carefully designed. Where coal has to be conveyed to overhead bunkers in boiler-houses, this kind of conveyor certainly has great advantages. Instead of using a separate conveyor to bring the coal from the railway sidings and installing an elevator to raise it to the level of the bunkers, at which point a second conveyor must be used to distribute the coal from the elevator to the different compartments of the bunkers, one travelling bucket conveyor will perform these three operations, while sometimes the returning and therefore empty strand of buckets is used to convey the ashes away from under the boilers. This latter use is, however, bad practice, as an expensive installation used for handling alternately coal and ashes is not economical, since the damp ashes—which by the way only represent 10 to 15 per cent, of the coal—are highly corrosive and will rapidly destroy an equipment which with ordinary care would last for many years if used for coal alone. The driving gear is in some cases not unlike that of the ordinary chain-driven elevator, but more often it is independent of the conveyor, and actuates it by a series of pawls attached to a wheel, each of which pushes the conveyor forward, link by link. Or sometimes there is a wheel, with suitable projections, which are of the same pitch as the buckets, and which gear, as it were, into a portion of the continuous chain of buckets either on the inside or on the outside of the strand. The devices for loading each of the buckets without spilling the material are of great importance in this type of conveyor. They are very numerous, and are fully- detailed later. Figs. 168 and 169 show sections of two distinct types of the travelling bucket conveyor, the “Hunt” and the “Bradley.’’ 122