The air compressor forces the air down the inside pipe, which is 11⁄4″ in diameter. The outside pipe, which is 3″ in diameter, has its lower end submerged in the well. The compressed air forces a rising column of air mingled with water in the outer pipe to the supply tanks, which are situated at the top of the building.
Direct Air Pressure Pumps. This term is applied to that class of pumps in which the liquid is taken into an air tight vessel and then driven out through pipes to a higher level by the application of compressed air directly on the surface of the liquid in the tank, thus dispensing with cylinders, pistons, valves, glands, etc., of the more common class of pumps.
Fig. 387.
Fig. [387] shows the parts of the pump; its operation is as follows: Suppose the compressor to be in operation and the switch set as in the figure; the air will be drawn out of the right tank and forced into the left tank, and in so doing will draw water into the former and force it out of the latter. The charge of air in the system is so adjusted that when one tank is emptied the other is filled, and at that moment the switch will be automatically thrown, reversing the pipe connections and thereby reversing the action in the tanks.
The switch is a simple mechanism placed on the air pipes near the compressor. It can be automatically operated in one of three ways:
First, by means of the suction which occurs in the intake pipe to the compressor, when water is drawn above its outside level in one of the tanks. The details of the mechanism to utilize this suction are very simple.
Second, by a mechanism, that will throw the switch at some assigned number of strokes of the compressor, the proper number being that which will empty one tank and fill the other. This can be closely computed beforehand and can be determined exactly by test when commencing operation and the switch adjusted accordingly.
Third, by an electrically controlled mechanism, the circuit being made and broken by a pressure gauge on the intake of the compressor.