The Mechanical Handling and Storing of Material

ROPE WA YS 213 a little vibration, unless an automatic catch is provided to prevent this, and that is the plan adopted by Otto. His device is shown in Fig. 396 ; a shows the portion of the carrier to which the apparatus is attached, which consists of the disc b with pin c upon which latter is a second disc which can revolve on the same, and which is controlled by the thread d. When the handle e is turned, the loose disc is pressed against the fixed one and thus holds rope f as in a vice, the catch g snaps into position and keeps the grip tight. The coupling operation is performed by hand, whilst the uncoupling is effected automa- tically by tripper h. If the clearance men- tioned above is somewhat reduced, so that a lesser movement of the lever is sufficient for the grip, the catch can be dispensed with as the thread of the grip- ping screw is shallower. Fig. 397 shows such a coupling; the arrangement is similar to the foregoing but more like a vice. In order to intensify the gripping power the gripping portion has a slight bend in it (see illustration). This coupling is used by hand only, and the tendency to bend the rope cannot be looked upon as advisable, at least from the economic point of view. In the meantime Obach experimented, independently of Otto, with a coupling on the vice principle, but realised that the rope mus tbe gripped in its central position in order to get the tightest grip, and at the same time cause the least injury to the rope. This prompted him to abandon the vice principle with a single screw and substitute Fig. 398. Werner Coupling. for it a gripping device with a right and left handed thread, which has the advantage that both the gripping plates move towards each other, and that, without making the thread of the screw too steep, the arc described by the coupling lever is not more than 180°. This principle was further developed by Alexander Werner in 1885, who improved on the idea by using different threads on the two halves of the grip, the one with a fast pitch, whilst the other was fitted with a fine thread, so that each half of the coupling had to perform a different kind of movement, and altogether they exercised a very powerful grip on the rope. One of these devices is shown in Fig. 398 18