AIR-HOIST. Fig. 1 shows a pneumatic hoist that has recently been introduced by Pedrick & Ayer, of Philadelphia, as a substitute for the commonly used chain hoists and blocks. The cylinder is made of extra strong wrought-iron pipe, which is carehilly reamed out ; to the upper head is fastened an ordinary pipe cap, to which there is attached a hook by which the hoists can be readily hung to the overhead trolley, and, if desired, the hoist can be transferred to different parts of the shop. The lower head is made of two castings, one of which is screwed to the end of the cylinder and has a lug to re ceive a screw-end of the valve which supplies the air for lifting. By this construction the piston can not travel below the air-opening, which would interfere with the proper operation of the hoist. To this lower ring is attached a head, which is held in place by four small studs and nuts; this head also contains the stuffing-box for packing around the piston-rod; by this construction the lower head e2111 be readily removed for an examination of the piston and its packing without in any way disturbing the hoist. The piston is of simple design, consisting of a cast-iron head, follower-plate, and a leather cup-ring, which adjusts it self to the cylinder and prevents leakage. The lower end of the piston
rod hits a swivel, which allows the ring to be turned to any desired po sition in the rod. The piston acts but one way, as it has been found that the weight of the load, or even the piston-roll and head, is sufficient to allow it to drop when the pressure from the lower end is relieved. The valve consists of but four parts: a body, valve-stem, cap, and small spring to keep the valve-stein in place, which, with the air pressure, keeps the stein in con stant pressure against the body. One side of the valve is provided with a lug, by which it is attached to the lower ring of the hoist. The power is supplied by nn air-compressor, one of which is 6" to 8" in diameter, with a storage tank of about 3' in diameter and 5 long, which will supply sutheient compressed air fur 12 to 18 hoists having average use. For special purposes, such as where the hoist is used constantly. a less number can be supplied by a compressor of the above size. Hose is attached to the upper entl of the wrought-iron pipe, the length of the hose depending upon the floor area which it is desired the hoist should cover.
About 80 lbs. air pressure is generally used.