BLOWERS. (See Air Compressors, Boilers, Steam, and Engines, Blowing.) Fan-Blow ers.—Fig. 1 shows a type of fan which has come into extensive use for ventilating, dry ing, and similar purposes where a large volume of air is to be moved at a slight press ure. The shapes of the blades vary in the fans made by dif ferent makers. The accompany ing the speed, horse power used, and cubic feet of air exhausted per minute when there is no obstruction, according to the catalogue of the L. J. Wing Co., makers of the fah shown in the cut : The Smith Double-Discharge Fan-Blower.—Fig. 2 is a diagram showing the principle of the doub le-discharge fan -blower in con trast with that of the ordinary fan shown in Fig. 3. To secure the double discharge the case is extended on the rear and a second outlet provided, which is led around under the first to the front, to the two outlets uniting in one at the discharge. The construction is common to both pressure and exhaust fans. The principle is thus described by the makers: It is experimentally demonstrated that the vane of a fan, operating normally, becomes loaded with air in one third of a revolution. In Fig. 3, representing the ordinary single-discharge blower, the compartment a is partly loaded, b near ly so, and c fully loaded. This air it seeks to deliver ; but, as there is no outlet, the wheel must drag the accumulated pressure with its accompanying friction around half the circum ference of the shell before it can be relieved at A. The double-discharge blower is claimed to unload the air at A as soon as the full pressure is accumulated, and immediately picks up and discharges another full load at 13 in the same revolution.
Tilghman'.s Stearn-.Jet Exhauster.—The ordinary steam-jet exhauster is such a simple and convenient apparatus that it would be used much more largely than it is—were it not for its wastefulness of steam. It has, however, been noticed that small jets are more ellicient than large ones, showing that the surface of contact of the jet with the air is of importance rather than time cross-section of the jet. With the object of increasing this surface of contact, in a new steam-jet exhauster the steam issues radially between two disks fixed at the end of the steam-pipe. Openings through these disks lead into branches connected with the suction pipe through which the air is drawn. The thin, radial stream of steam in flowing over these openings lakes up its full quota of air, and the mannfaetnrers claim that a very considerable saving of steam is effected. The thickness of the jet is regulated by the hand-wheel, the spindle of which is attached to the lower disk. The hest distance between these disks is fOund to be -nju in. to in. The exhauster works with a complete absence of noise. Though primarily designed for exhausting air for sand-blast purposes, the apparatus is evidently applicable elsewhere.
Boats, Fire: see Engines, Steam Fire.
Bobbin-Holder : see Cotton-Spinning Machinery.