Home >> New International Encyclopedia, Volume 16 >> Plague to Polybius >> Pneumatic Gun

Pneumatic Gun

hammers, valve, tool, air, cylinder, hammer and piston

PNEUMATIC GUN. A gun in which the expansive force of air under pressure is employed action is essentially the same in all pneumatic tools of this type, and it will be sufficient to de scribe the mechanism in one of them only. and for this purpose the hammer will perhaps serve best. The pneumatic hammer consists essentially of a cylinder containing a piston which. by means of suitable cylinder inlet and exhaust openings for air under pressure, is made to reciprocate back and forth in the cylinder. A tool is inserted into the front end of the cylinder loosely in such a way that the reciprocating piston or hammer strikes its near end at each forward stroke, the action being exactly analogous to that of a man driving a chisel with a hand hammer. The near end of the cylinder terminates in a handle by which the tool is held by the operator. Com reseed air is conveyed to the cylinder by means of a suitable connection or a flexible hose. The variety of constructions by which the piston -.trek.: is actuated and controlled is large, but generally speaking all pneumatic hammers may It classed either as valveless hammers or valve hammers. one of the former class. the Keller tool, being shown in the diagram and in various appli cation on the accompanying plate. The valveless hammers have no valve beyond the striking pis ton, this being itself a valve to effect the proper admission of air to alternate ends of the work ing cylinder. In the valve hammers a recipro cating valve, working either at right angles to or parallel with the striking piston. acts in com bination with it to regulate the inlet and the exhaust of the compressed air.

There are several constructions of both valve less and valve hammers, each of which is eon trolled by patents owned by the manufacturers of such tools. The general characteristics and comparative merits of the two forms of construe lion may be summarized as follows: V:al•eless hammers have essentially a short stroke, and al though economical in air consumption in relation to the number of blows given, they do not com pare with valve hammers in giving powerful blows, which are necessary in heavy chipping and riveting. Owing, however, to their simple con struction, they have probably a longer life than valve hammers, and for such purposes as beading tines. light calking and chipping, and especially earring in stone, they compare very favorably with their rivals. The speed of the valveless.

hammers is very high, being from 10.000 to 20, 000 strokes per minute. The speed of valve ham mers for ordinary work ranges from 1,500 to 2,000 blows per minute. although they can he driven much faster. Their stroke is ennsider ably longer than that of valveless hammers. and the blow struck is correspondingly greater. These characteristics of valve hammers make them most suitable for general and heavy clip ping. calking. and riveting. This comparison is a fair summary of repent engineering opinion on the subject, but advocates of one or the other form naturally contest the claims of their op ponents. The preceding description leas referred particularly to hammers: by replacing the ham mer tool struck by the piston as above described with sharpened or otherwise specially formed tools we have the hammer converted into a tool for chiseling, chipping, beading, calking, rivet ing, etc. In operation the apparatus is held by the handle so that the tool presses firmly against the work: air pressure is then turned on by pressing a trigger or thumb lever on the handle and the reciprocating piston begins to strike the tool, which is thus caused to cut nr hammer the work in front of its nose. As pre viously stated, the blows are exceedingly rapid, their sound coming to the ear as a continuous buzz, and they depend for their effect upon their great frequency rather than upon their individ ual energy. Pneumatic percussion tools are made in a variety of sizes, but with the exception of riveters their weight and dimensions are kept small enough to permit them to he manipu lated by hand. As specially designed for rivet ing work the percussive pneumatic tool re quires brief special description. Any of the regular hammer tools may be used for riveting in connection with a holder-up for supporting the butt of the rivet, but such work is more effectively accomplished by heavier tools having a longer stroke. The yoke riveter is another common form and consists of a U-shaped yoke having at the end of one arm an inwardly projecting holder-up. The yoke riveter is made in several modifications designed for special purposes aml requires generally to he handled by chain or pneumatie hoists or other power. (For illustration, see METAL-WORKING MA