The Mechanical Handling and Storing of Material

TRANSPORTERS, BRIDGE OR CANTILEVER CRANES 429 in a prominent position who can communicate with the men in the hold and the operator in the winch cabin. These minor disadvantages have, however, not materially checked the progress of this type of crane, as its quicker unloading speed, easier manipulation, and smaller first cost have opened up a large field for it. The illustrations, Figs. 600 to 610, show, in diagrams, the most usual forms of manipulating the traveller, with its load, from the winch or winches. Transporters of this type are by no means new, but have been used for a number of years on a small scale on the principle shown in Fig. 600, where the rope which lifts the load is fixed at one end of the structure, and at the other to the drum a, and supports the skip after passing over the fall-block. If the position of the running head is changed by the drum b, the load remains at the same distance from the ground. A represents the drum for raising and lowering the load, whilst B is the winch for moving it horizontally. The constant bending of the steel rope over the two pulleys on 'the traveller and over the fall-block offers considerable resistance to the movement of the load; yet over short distances such transporters do satisfactory work. For long lengths and for a quick rate of travel this construction is unsuitable. It can, however, be used to advantage when the load is so held as to relieve the rope during the lateral movement of the running head, as shown in dotted lines, when the fall-block is held in its topmost position by a catch suspended from the running head. In such a position, and with the load supported by the head itself, the rope will bend freely and without much wear and tear during the horizontal movement of the load. The position of the load close to the running head is also an advantage, as it checks the swinging, pendulum fashion, and admits therefore of a quicker starting and stopping, but it must be raised to its fullest extent and locked before the horizontal movement can take place. It also entails a small loss of time for the locking and unlocking of the load in its raised position. AV hen ore or other material that does not deteriorate by being dropped is being conveyed, it will be unnecessary to disengage the fall-block, and lower the load down the pile before tipping the bucket. Such difficulties as are met with in the plan shown in Fig. 600 are obviated in the scheme illustrated in Fig. 601. In this both conveying and elevating ropes are under the same tension. The two drums a and B are loose on their spindles, which are, however, coupled together by spur wheels, the drums being connected to the spindles by friction clutches, either separately or jointly. The drum a is for elevating only, but both drums a and b must be in motion when the traveller is moved in either direction. 1 his construction enables the operator by simply pulling the hauling ropes to raise or lower the loads in an oblique direction, as is indicated by the dotted line in Fig. 601. 1 he angle is 2 :1 to the horizontal. The side movement of the load is, therefore, twice as great as the up-and-down movement, but the proportion can be altered by using different fall-blocks, or to meet cases where the motor speed varies according to the load, (or short chains used in conjunction with a grab, this oblique movement of the load is most convenient. The principal advantage is that the horizontal and vertical movements of the load are independent of each other, and that the traveller may be moved horizontally with the load in any position. For transporters with high speeds it might be an advantage to convey the skip in as high a position as possible, to avoid the pendulum movement of the load. With this construction both winches a and b must be of the same power, as both ropes are under the same tension. A similar design is shown in Fig. 602. Both winches a and b can be turned either in the same or in opposite directions, this being accomplished by the use of a pair