The double hydraulic ram is shown in Fig. 151. A sectional view of the same device is shown in Fig. 152, the cuts represent the Rife hydraulic engine, or ram,—a so-called double acting or double supply type of the water ram. It is more clearly described by considering it, first, as a single machine by disregarding its double supply feature.
First, suppose the opening at H, Fig. 152, to be closed, the valve B being open, the water from the source of supply from more or less elevation above the machine flows down the drive pipe, A, and escapes through the opening at B until the pressure due to the increasing velocity of the water is sufficient to close the valve, B. When the flow through this valve ceases, the inertia of the moving column of water produces a reaction, called the ramming stroke, which opens the valve at C, and compresses the air in the air chamber, D, until the pressure of the air plus the pressure due to the head of the water in the main, is sufficient to overcome the inertia of the moving column of water in the drive pipe. This motion may be likened to the oscillation of water in a U shaped tube. The instant the column of water in the drive pipe comes to rest, and the air pressure being greater than the static head alone, the motion of the moving column is reversed, and the valve, C, closes. The water in the drive pipe then moves backward, and with the closing of valve C a partial vacuum is formed at the base of the drive pipe. This negative pressure causes the valve, B, to open again, and completes the cycle of operations. At the moment negative pressure appears the little snifting valve, E, admits a small quantity of air, and at the following stroke this air rises into the air chamber D, which would otherwise gradually fill with water, or the air is gradually absorbed by the water.
In this machine the valve, B, is made as light as is consistent with the necessary strength, and the negative pressure at the completion of the stroke opens the valve. In the largest size of these machines this valve is 18 inches in diameter, with a head of 8 feet, which is a common head for use with hydraulic rams; the static pressure on the under side of this valve is 883 pounds; it is seen that so great a shock in a valve of this weight would rapidly destroy both valve and seat.
Fig. 152.
The waste in a mechanism of the Rife engine consists of a large port with ample opening and a large rubber valve or overflow with a balance counterweight and spring seat, which removes almost entirely the jar of closing. The valve, C, in the air chamber consists of a rubber disc with gridiron ports and convex seats fastened at the center and lips around its circumference. The object of this arrangement is to transfer the shock from the power of the driving water to the air cushion with the smallest possible friction and vibration.
After the valve, C, closes, the pressure in the air chamber forces the water in the air chamber out into the delivery pipes. The Rife engine is claimed to elevate water 30 feet for each foot of fall in the driving head; the machine is built in sizes to elevate as much as 150,000 gallons per day, the efficiency being about 82 per cent.
When a water supply pipe is attached to H, the engine is called double acting; spring water, or that which is purer than the water used to drive the engine, may then be supplied through the supplemental drive pipe I, and by a proper adjustment of the relative flow of the impure driving water, and that of the pure supply, the engine may be made to deliver only the pure water into the mains. This method is employed where the supply of pure water is limited.
The most important detail in which the Rife engine differs from the ordinary hydraulic ram is the waste valve. It will be seen in the engraving that the counterweight on the projecting arm of this valve permits the adjustment of this valve to suit varying heads and lengths of drive pipe. By adjusting the counterweight so that the valve is nearly balanced, the valve comes to its seat very quickly after the flow past it begins. The result is that the ram makes a great number of short, quick strokes, which are much easier on the valves and seats than slower and heavier strokes. The stroke must be sufficiently powerful to act efficiently in overcoming the head in the delivery pipe. The adjustable weight permits this to be effected with great nicety.
Note.—The engine illustrated weighs approximately 2,800 pounds; the capacity of the air chamber is 203⁄4 cubic feet; diameter of drive pipe, 8 inches; diameter of the waste valve, 18 inches; weight of waste valve, 50 pounds; diameter of delivery pipe, 4 inches; height to top of air chamber, 71⁄2 feet.