The Mechanical Handling and Storing of Material

3io THE MECHANICAL HANDLING OF MATERIAL 1'ig 446. Discharge of. the Skip of a Travelling Electrically Driven Bleichert Cable-Crane with Man-Trolley into,a Portable Hopper for Loading Trains of Trucks. cairying the hoisting line up around a sheave in the bucket block, over a second sheave in the carriage, and on to the tower opposite the engine, in the manner well known in crane practice. I his permits of hoisting or lowering the bucket simultaneously with traversing the carriage. The varying strain of the load upon the hoisting line, with the varying sag resulting, is counteracted in one of several ways. 1 he most usual method is to hold up the horizontal part of the hoisting rope by a series of idler pulleys in carriers running on the main cable. One method of spacing them is by connecting them at equal distances along a chain: The ’tendency of the slack chains to foul each other, and the heavy strain on the traversing rope, as they are stretched out behind the ad- vancing carriage, limit the use of this system to slow speeds. Another method provides an extra wire rope carrying knobs or bosses attached at intervals, known as the button rope. The carriers ride on a steel horn projecting from the end of the carriage, and embrace the button rope by jaws or loops of varying width. The buttons are made of regularly increasing size, beginning from the tower across the span. The first carrier to be dropped has the narrowest slot, and is caught by the smallest button, which has passed through the wider jaws of the other carriers without interference. In this way each carrier is taken off by the button corresponding, and the hoisting rope is held up at equal dis- tances by suitable sheaves pro- vided in the carriers. In order to avoid the striking of the buttons by the carriers, the patented differential rope system of spacing has been devised. I he button rope is replaced by two smaller lines suspended side by side, and spreading like the sides of a wedge, being held apart by suitably graduated blocks fastened between the ropes. The carriers are partly supported by long rollers resting on both ropes. As the carriage runs out from the tower the diverging differential ropes pick each carrier successively off the carriage. This affords a smooth-running carrier system suited to the highest speeds. Another system employs trolley carriers running on the main cable and propelled by the traversing rope so that they proceed at some definite fraction of the speed of traverse. The simplest is the half-speed carrier, in which a single sheave in contact with the main cable sheave and with the traversing rope below propels the carrier frame so