The injector and the pulsometer are also classified as pumps, though operating on prin steam from the chamber (a) and admittting it to the chamber (b), from which the water is gradually forced out. In the meantime the condensation of the steam in the chamber (a) creates a partial vacuum, and the pressure of the atmosphere on the external water forces it through the valve (f) into the chamber, so that when it is nearly full, the air it contains will be sufficiently compressed to force the valve (d) over to the right, thus producing a continu ous action. The efficiency of . pulsometers is equal to that of small direct-acting feed pumps, and they are extensively used on account of their simple construction and great durability. Nearly allied to the injector and pulsometer in point of the physical action involved is the ((explosion?) or combustion)) pump a typical example of which ig the so-called Humphrey gas pump. It consists of a chamber ciples quite different from those exhibited in the machines more familiarly known under the title of ((pump?) The injector is described in detail in a special article (see INIncroit). The pulsometer consists of two bottle-shaped chambers (a) and (b), the tapering necks of which incline toward each other in a com mon passage at (c). At the lower end of this passage is a valve (d), which when moved slightly will simultaneously close the opening of the neck of one chamber, and open that of the other.
Water is admitted into the chambers through the passage (e), and valves (f) (g) and forced out through the valves (h) (i), and passage (j) into the air chamber (k). The device oper ates as follows: Suppose both chambers are full of water and the valve (d) to the right. When steam is admitted to the chamber (a) the water is forced out by direct pressure through the valve (h) into the air chamber (k), so that when the chamber (a) is nearly or quite empty, the valve (d) moves to the left, cutting off the (A) in which an explosive mixture of air and vaporized gasoline is admitted through the valve (V). This mixture is exploded by an electric spark, and the expanding gases press downward upon the water in the chamber (B). forcing it out through the pipe-line (P), and into the reservoir (R) and up the standpipe (D). When the force of the gas has expended itself the escape valve (E) drops in the reduced pres sure, and the burned gases pass out before the return surge of the water standing in the stand pipe(D). Meanwhile, in the low pressure prevailing, the inlet valves (I) open and admit water from the basin (K), which pours into chamber (B) until the returning water from the pipe-line brings pressure enough to close them, and also the exhiust valve (E), and opens the gas valve in by a float. A backward surge of the water, in coming to an equilibrium, sucks in a charge of gas through (G), and the vibrating water comes back once more and compresses the gas, at which juncture it is fired; and the cycle is repeated indefinitely. It will be seen that one delivery of water covers four vibrations in the pump. This leisurely action has been reduced to half the time by connecting two pairs of chambers to the suction pipe, so that the first resurge after firing com presses the gas charge in the second gas cham ber, and fires it, each resurge thus being sent forward as a discharge. The largest of these
gas pumps in America is a 66-inch pump in irrigation service at Del Rio, Texas, delivering 28,000 gallons per minute at a height of 38 feet.
lImpulse pumpsD are those operated by the impact of a falling column of water or by the force of a moving column of water suddenly arrested, or by jets of steam, compressed air, or water under high pressure. The hydraulic ram is an example of the first group. It was originally designed by Whitehurst, a watch maker of Derby, England, in 1772, and subse quently perfected by Montgolfier, the famous French balloonist, in 1796. It consists of a supply pipe (a) • an air-chamber (b) attached to the upper side of the pipe (a), and fitted with a valve (c) at the pipe opening; a valve (d) at the end of the supply pipe, and a vertical pipe (e), opening freely into the air-chamber, through which the water is raised to the de sired elevation. The device operates as fol lows: The valve (d) is made just heavy enough to drop and open the lower end of the pipe (a) when the water filling the pipe is at rest. Now assume that this valve opens, allowing the water in (a) to run out. This water gradually acquires an increasing momen tum, which finally carries the valve up against its seat and closes the outlet. The water in (a) is thus brought suddenly to a state of rest and a part of it rushes into the air-chamber (b) through the valve (c). But, the instant the water in (a) is again in a state of rest, the valve (d) drops again, opens the outlet, al lows the water to run out, and is again dosed when the increasing pressure is strong enough, bringing the water again to a sudden halt and forcing some more of it into the air-chamber, thence by the elasticity of the air cushion (b) to be pushed upward through the pipe (e) to the point of delivery — and thus the cycle is continued. The action of the valve (c) pre vents the return of the water from the air chamber to the pipe (o). This device is adapted to numerous locations and will operate auto matically and continuously, without any atten tion whatever, so long as the surface of the water at the source of supply is kept at the same elevation so as to insure a uniform pres sure against the valve (d). When the per pendicular distance from the source of supply to the valve (d) is small, and the water is re quired, to be raised to a comparatively great height, pipe (a) must not only have a con siderable fall but must be of larger diameter, and be of sufficient length to prevent the water from being thrown back into the source of supply by the shock when the valve (d) closes. It is also necessary to maintain the supply of air in the air-chamber, which in time, under the great becomes depleted by being dissolved in the water. In small rams a suffi cient amount of air enters through the valve (d), but in rams of considerable size a small (sniffing valve,* attached to another chamber immediately below the air chamber, automatic ally supplies the additional air whenever it is necessary.