The Mechanical Handling and Storing of Material

TR ANSPOR TER S, BRIDGE OR CANTILEVER CRANES 431 allow of a slight return of the traveller on its support, whereupon the catch will engage with one of the notches, and lock it in position. At the same time this releases the load, and by slackening the rope the load will be lowered. In order to accelerate the return of the traveller, the incline of the girder is placed at about 1 :4. This is necessary, as the weight of the rope has to be drawn along with the head. If such an incline be prohibitive on account of local conditions, or if the transporter be of sufficient length to cause the weight of the rope to hold the traveller back, or to prevent it moving at a sufficient speed, a balance weight, is used to accelerate the downward movement as shown. Another and frequently used method, which is practicable for working with one rope, is illustrated in Fig. 605. The skip is here suspended from the fall-block in the usual manner, and the supporting girder for the traveller is fixed at an angle of about 30°, which angle is sufficient to prevent the running head with its load from moving upward when the winch is at a standstill. In fact, if the angle be made steeper, the load is inclined to run downwards, so that it is necessary to provide a stop block in order to prevent it from running too low. In the position shown, the load can be raised or lowered while the traveller remains stationary, but when raising the load beyond the topmost limit, so that it touches the traveller, the latter with its load will ascend the girder, and the load can then be discharged. The empty skip can only be lowered when the running head comes against an adjustable stop, as shown. The fact.that this system requires such a very steep rail girder will account for its use being confined to comparatively short reaches, and to its mostly being used for unloading ships in connection with other methods of conveying, the transporter in this case only being used to transfer the material from the ship’s hold to a conveyor which takes it to its destination; whereas transporters with horizontal or slightly inclined rail girders are more generally used to convey the material from the ship to its final destination without the intervention of an auxiliary conveyor. Transporter of the Brown Hoisting Machinery Co.—The transporter of the Brown Hoisting Machinery Co., Cleveland, Ohio, is one of a popular type. It is usually made so narrow that three or four can be placed close together to unload from the same ship, or at least one can be set to work over each hatchway. The general construction of the iron trussed bridge depends upon the span of the crane, but the supports are usually made in such a way that the transporters can be moved obliquely across the rails which carry them. Either the support on the quay or that further inland can be moved independently as circumstances may permit. This is accomplished by one support moving on a double track of rails whilst the other moves on a single track, both being connected with the bridge by a swivel joint which allows of this oblique position. The unloading is usually effected by means of a grab, which holds 1 to 2 cub. yds., whilst ordinary skips are also sometimes used. A weighing machine is sometimes fitted, by means of which each load can be weighed independently as it passes a certain portion of the track. Some of the earlier appliances of this firm were erected at one of Krupp’s establishments; four were erected on the Rhine near Duisburg, for unloading ore, which is the chief material imported. Each transporter is driven by a 45 H.P. electro-motor, running at a speed of 200 to 500 revs, per minute. This has been geared to the winding drum by wheels in the proportion of 1 to 4'6. The manner in which the rope is connected from the winding drum to the traveller or running head is shown in Fig. 606, whilst Figs. 607 and 608 show the details of the traveller itself. As long as the load is being elevated, the traveller is mechanically fixed, and is therefore prevented from following the direction of the hoisting rope. As soon as the load is lifted sufficiently high for the fall-block to touch the traveller, the latter is