The feed is thrown on and off by means of a lever. The cut under the coal, 5 to 6 ft. by 3 ft.
6 in., is made and the cutter-bar withdrawn in from four to six minutes. The machine is then moved over the length of the cutter-bar used, and another cut is made in the same man ner. This is continued until the entire width of the room has been undercut, after which the ma chine is loaded on the truck and taken into another room. The makers claim that in some coal veins the machines have cut at the rate of 130 to 150 lineal ft. face in ten hours to a depth of 6 ft.
Harrimn 5 embodies a direct-acting engine mounted upon two wheels, the whole resting upon a board which is inclined toward the face of the coal. A pick shaped like a fish-tail is attached to the piston-rod. The valve is a rotary engine, and moves constantly and uninterrupt edly when the throttle is open, whether the piston is stationary or in motion. Two handles are attached to the mar of the der, which are used by the operator to direct the machine. The operator sits on the board, places his feet against the wheels, and takes hold of the handles. A channel is made under the face of the coal. The machine requires a maximum of 16 cub. ft. of air per minute at 45 lbs. pressure to run it, and an average of 15 cub. ft. each per minute when several machines are being run from one main pipe at the same time, which is fed to the machine through a 1-in. four-ply hose. The projectile weighs from 60 to 90 lbs.—according to the length of the rod—and strikes from 190 to 210 blows per minute. The total weight of the machine is from 570 to 620 lbs.. The makers claim that from 25 to 50 sq. yds. of floor is the ordinary amount undercut by one machine each day. It has often undercut from 6 to 8 sq. yds. of floor per hour. cutting time, but all lost lime for moving and other con tingencies are included in this statement of a day's work.
The Sergeant Machine (Fig. 0) is made in two sizes: the standard machine—weight, 700 lbs. ; length, 7 ft. 0 in. over all—which will undercut to a depth of 4} ft.; and the light mining-machine—weight, 500 lbs.; length, 7 ft. over all—which will undercut to a depth of 5 ft. The light mining-machine is 15 in. high, and will mine coal from a 10-in. vein.
The distinctive features of this machine are as follows: No rotary or reeipmeating engine is used to operate the valve. but a duplex slide-valve system. consisting of two valves in the same chest, independent of the action of the main piston. This valve motion is positive. Having no dead centers, it starts on turning on the air, and has no outside hand-wheels or moving parts. The stroke is made variable both in length and strength. and the force of blow and length of stroke are muter instant control of the operator. The picks are of forged steel, with shanks made square and of full size where they enter the socket. Balancing is effected by loosening one nut and slipping the hub backward or forward in a slot east in the side of the cylinder. The piston is made of forged steel, and is corrugated to prevent rocking or twisting. It is held in place by a composition metal sleeve which is bolted into the front head. The wheels are provided with large hub-bearings-4 in. in diameter—which eases the effect of the blow on the operator, and obviates lost motion. The movement back and forth on the board while running at full speed-190 to 250 double strokes per minnte—is about # in.
The operator can swing the machine and direct the blow with one hand, and can work either right or left handed. The ma chine requires but little space and can be used successfully in narrow veins. around and between props, and wherever a miner can swing a pick.
The Jeffrey Electric Machine is represented in side view with the cutter-bar withdrawn, in Fig. 7. It consists of a bed-frame occupying a space 2 ft. wide by 8 ft. I; in. long. composed of two steel channel bars firmly braced. the top plates on each forming racks with their teeth downward. into which the feed-wheels of the sliding frame engage. :Mounted upon and engaging with this bed-frame is a sliding frame, similarly braced, consisting mainly of two steel bars, upon which are mounted at the rear ends one electric motor, from which power is transmitted through straight gear and worm wheel to the rack, by means of which the slitting frame is fed forward. l'pou the front end of this sliding frame is mounted the entter-bar, held by t urn solid steel shoes, with brass boxes. The cutter-1w contains bits, made of tool-steel, held in place by set screws. When the cutter-bar is revolved. these cut ters or bits rover its entire face. The eutter-bar is revolved by an endless, curved-link, steel chain from the driving-shaft, and, as it is revolved, is talvaneed by the above mechanism into the coal or other teat evict to be malerent to the desired depth. The current required is from 30 to 50 ampi•res at a pres.ure of 220 volts: Nicht motor is wound to develop fully 15 horse power, though frequently in some veins of coal the machine only uses 30 amperes, or 7-.1 horse-power in making Nits. The armature of the motor is ealculated to run at a speed of 1.000 revolutions per minute, from which the speed is reduced, so as to run the eutter-bar 200 rcvolitunits per minute.
The Leehner Machine is represented in Fig.. 8. The machine is operated by either compressed air or electric power. It consists of a stationary frame held to the floor of the mine by two jacks, out of which a sliding frame is advanced and withdrawn by means of a screw feed-rod. Around the front of this sliding frame passes an endless chain provided with steel cutters securely fastened in its solid links, suitable gearing driving the chain around at proper speed. A steadying drill, provided with a long bearing directly back to the cutting bead, passes forward with the sliding frame, and prevents any thrust caused by the side-cutting action of the chain. The standard machine is made to undercut 31 ft. in width, 5 ft. in depth, and 3 in. in height, although these dimensions can be varied to suit special conditions. The size of the machine is 8i ft. in length, 3,1 ft. in width at the front end. 23 ft. at the back end, and 22 in. in height. The weight of the standard machine for rope transmission is 1,050 lbs., with engines for compressed air 1,350 lbs.. and with electric motor on frame of machine 1.800 lbs. It is claimed that in ordinary hard bituminous coal the undercut of 17i sq. ft. is made within four minutes. The cutting chain is provided with 39 bits• or three sets of 13 each, following in the same plane ; these bits are backed tip with metal similar to a lathe or planer tool. The power required to drive the Lochner machine depends entirely on the work to be clone..
Coal-Hoist : see Elevators. Coal-Screens, Coal-Sizing Maehinery, Coal-Washing Machinery : see I Breakers.