Fig. 47 is a common lift-pump. In the up-stroke of the piston or bucket, the lower valve opens and the valve in the piston shuts; air is exhausted out of the suction-pipe, and water rushes up to fill the vacuum. In the down-stroke, the lower valve is shut, the valve in the piston opens, and the water simply passes through the piston. The water above the piston is lifted up, and runs over nut of the spout at each upstroke. This pump cannot raise water over 30 ft. high.
Fig. 48 is an ordinary force-pump with 2 valves. The cylinder is above water and is fitted with a solid piston; one valve closes the outlet-pipe and the other the suction-pipe. When the piston is rising, the suction-valve is open, and water rushes into the cylinder, the outlet-valve being closed. On the descent of the piston, the suction-valve closes, and water is forced up through the outlet-valve to any distance or elevation.
Fig 49 is a modern lift-pump operating in the same manner as that shown in Fig. 48, except that the piston-rod passes through the stuffing-box, and the outlet is closed by a flap-valve opening upwards. Water can be lifted to any height above this pump.
Fig. 50 is a force-pump similar to that in Fig. 48, with the addition of an air-chamber to the outlet, to produce a constant flow. The outlet from the air-chamber is shown at 2 places, from either of which water may be taken. The air is compressed by the water during the downward stroke of the piston, and expands and presses out the water from the chambers during the up-stroke.
Fig. 51 is a double-acting pump. The cylinder ia closed at each end, and the piston-rod passes through the stuff-ing-box on one end; the cylinder has 4 openings covered by valves, 2 for admitting water and 2 for its discharge. A is the suction-pipe; B, discharge-pipe. When the piston moves down, water rushes in at suction-valve 1 on the upper end of the,cylinder, and that below the piston is forced through valve 3 and discharge-pipe B. On the piston ascending again, water is forced through discharge-valve 4 on the upper end of the cylinder, and water enters the lower suction-valve 2.
Fig. 52 is a double lantern-bellows pump. As one bellows is distended by the lever, air is rarefied within it, and water passes up the suction-pipe to fill the space; at the same time the other bellows is compressed, and expels its contents through the discharge-pipe, the valves working the same as in the ordinary force-pump.
Fig. 53 is an old rotary pump. The lower aperture is the entrance for water, and the upper for its exit. The central part revolves with its valves, which fit accurately to the inner surface of the outer cylinder. The projection shown in the lower side of the cylinder is an abutment to close the valves when they reach that point.
The drum causes sliding pistons c to move In and out, in obedience to the form of the cam. Water enters and is removed from the chambers through the porta I- M, as indicated by arrows. The cam is so placed that each piston is, in succession, forced back to its seat when opposite E, and at the same time the other piston is forced fully against the inner side of the chamber, then driving before it the water already there into the exit-pipe H, and drawing after it through the suction-pipe the stream of supply.
In Fig. 55 a flexible diaphragm is H employed instead of bellows, the valves being arranged as usual.
Having described the best known means of raising water under various circumstnuces, there remains to eater with more detail into the construction, capacity, and working of the 3 kinds of Common pump in everyday use - i. e. (1) the lift-pump for wells not over 30 ft. deep, (2) the lift and force for wells under 30 ft. deep, but forcing the water to the top of the house, and (3) the lift and force for wells 30-300 ft. deep.
The working capacity of a pump is governed by the atmospheric pressure, which roughly averages 15 lb. per sq. in. It is also necessary to remember that 1 gal. of water weighs 10 lb. The quantity of water a pump will deliver per hour depends on the size of the working barrel, the number of strokes, and the length of the stroke. Thus if the barrel is 4 in. diam., with a 10-in. stroke, piston working 30 times a minute, then the rule is - square the diameter of the barrel and multiply it by the length of stroke, the number of strokes per minute, and the number of minutes per hour, and divide by 353, 42 in. x 10in. stroke x 30 strokes _________X 60 minutes_______ 353 = 815 gal. per hoar. About 10 per cent. is deducted for loss. The horse-power required is the number of lb. of water delivered per minute, multiplied.
Fig. 56 shows a vertical section of the simple lift-pump, a is the working barrel, bored true, to enable the piston or bucket b to more up and down, airtight. The usual length of barrel in a common pump is 10 in. and the diameters are 3, 2 1/2, 3, 3 1/2 , 4, 5, and 6 in.; a 3-in. barrel is culled a 3-in. pump. The stroke is the length of the barrel; but a crank, 5-in. projection from the centre of a shaft, will give a 10-in. stroke at one revolution; but in the common pump shown, use is made of a lever pump-handle, whose short arm c d is about 6 in. long, and the long arm or handle d e is usually 36 in., making the power as 6 to 1; f is the fulcrum or prop. Improved pumps have a joint at f, which causes the piston to work in a perpendicular line, instead of grinding against the side of the barrel. The head g of the pump is made a little larger than the barrel, to enable the piston to pass freely to the barrel cylinder; in wrought-iron pumps, the nozzle is riveted to the heads, and unless the head is larger than the barrel these rivets would prevent the piston from passing, and injure the leather packing on the bucket. The nozzle A, fixed at the lower part of head, is to run off the water at each rise of the piston.