Picker : see Cotton-spinning- Machines. Also Harvester, Cotton.
Picking. Table : see Ore-dressing Machinery.
PILE DRIVING.—Drop hammers are now made to weigh from 75 to 4,200 lbs. They are much longer for a given weight than the older forms, Hills avoiding the sidewise throw when the hammer strikes near one edge, Wear is thus dimin ished and the effect of the blow increased. The bottoms of the hammers are made concave, while the sides are cored, as shown in Fig. 1. Dies are of hammered steel, triangular in form, fitted in the hammer and stationary, or are arranged to rotate on a turned pin which is keyed in the ham mer. These forms of die are used with nippers. Where driving is clone by friction, the hoisting line is attached directly to a turned steel pin.
In the operation of pile driv ing it frequently happens that the piles are either split or " ',roomed" on their tops by the concussion of the hammer. To overcome this difficulty, re course has been had to metal bands around the upper ends of the piles. This is expensive and wastes time. Casgrain's cap. illustrated in Fig. 2, is intended to overcome the trouble. It consists of a cast-iron cap with tapered recesses above and below, the chamfered head of the pile fitting the lower one, and the wooden block, D, fitting the upper one. Suitable jaws, similar to those on the hammer, engage the leaders and form a movable toggle iron, the pile as it is being driven. As the ham mer descends, it strikes the timber or cushion block set in the upper cavity, and the pile is forced down by the blows. When the pile is driven, the short chains on either side of the hammer are connected to the caps by means of pins, and both hammer and cap are hoisted up and secured for an other operation.
In order to prevent the grinding action of the drop hammer on the leaders. it is usual to protect them with iron wearing pieces known as "liner irons." The most modern form of these consists of a channel-iron liner protecting the entire face and corners of the leaders. They are made in full lengths to avoid joints and to add to the strength of the leaders.
Pile Dricers.—Fig. 3 represents a pile driver intended for township work. It is provided with leaders 25 ft. high, and with a 1, a min e r weighing from SOO to 1,200 lbs. The hammer is handled by horse power, one end of the line being fastened to a suitable post, while the other end is passed through a pulley block, which is fastened to the main hoisting line and leads to the whiffle tree direct. Fig. 4 resents a pile saw arbor made to cut off piles 16 to 24 ft. under water. The shaft is 3± in, in diameter, and counter- :•: balanced. A 42-in. saw, at a speed of about 600 revolutions, is usually em ploy-ed. The arbor works on a spline over its entire length, and is easily ad justable to any dept It within its range. The belt runs on side rollers and frames fastened to the inner side of the leaders. The hoisting gear for steam pile drivers is usually an engine of simple construction, provided with means for sustaining and lowering the load. Friction-drum engines, the drums being cones of wood and iron brought into contact while hoisting by means of thrust screws, are employed. The following table shows the dimensions of engines, boilers, etc., of the Vulcan Iron Works pile drivers Steam Pile hammers are raised by the engine in the leaders and allowed to rest full weight on the pile. Steam is then the hammer cylinder, causing the piston carrying the hammer head to reciprocate so that the hammer pounds automatically until the pile is driven as far as may he required. The Vulean-Nasmyth hammer, represented in Fig. 5, has the novel feature of a positive valve gear capable of adjustment for long or short strokes, operated by the movement of the hammer, and deliver ing either an elastic or non-elastic blow at will. A rigid connection between the steam cylinder and lower bonnet is obtained by four turned steel columns fitting into reamed holes in the cylinder and bonnet, and secured by heavy keys.