A very interesting system of driving gear for lift hammers was applied in an apparatus exhibited at Frankfort in 1881 by Mr. Meier of Herzen. The arrangement of the mechanism is shown in Figs. 1 and 2. In the upper part of the hammer-frame there is a shaft which is possessed of a continuous rotary motion, and, with it, there is connected by a friction coupling a drum that receives the belt from which is suspended the hammer. In the apparatus exhibited, the mechanism is so arranged that the hammer must always follow the motion of the controlling lever in the same direction; but a system may likewise be adopted such that the hammer shall continue to operate automatically, when and so long as a lever prepared for such purpose is lowered.

ab is the shaft having a continuous rotary motion, and upon which are fixed the pulley, c, the fly-wheel, d, and the friction-disk, e. Upon one of the extremities of the driving shaft is fixed an elongated sleeve, formed of the drum, g, and of the screw, f, carried by the nut, h. This latter is supported in the frame in such a way that it cannot turn, but can move easily in the direction of the axis. Such motion may be produced by the spring, i, and its extent is such that the drum, g, is brought in contact with the friction-disk, e.

The hand-lever, k, rod, l, and bent lever, m, serve to bring about a motion in the opposite direction, and which disengages the drum, g, from the disk, e, and lets the hammer fall; the drum being then able to turn freely. If the lever, k, be afterward raised again, the spring, i, will act anew and couple the drum with the driving-shaft, so that the hammer will be lifted. In this rotary motion the screw, f, turns or re-enters into its nut, which it displaces toward the left, since it cannot itself move in that direction until the rectilinear motion be wiped out, and the power of the spring be thus overcome. At the same moment, the screw should naturally also make this rectilinear movement forward, that is to say, the coupling would be disengaged, if, at the least lateral motion toward the right, the spring, i, did not push the system toward the left. There is thus produced a state of equilibrium such that there is just enough friction between the disk, e, and the drum, g, to keep the hammer at rest and suspended.

Through the action of an external force which lowers the lever, K, the hammer at once falls, and the screw issues anew from its nut and brings the parts into their former positions.