Another advantage claimed for this pump is that clear air inlets are maintained—see Figs. 359 and 360. Under ordinary working conditions, when the bucket descends and the ports open, there is no obstruction between the condenser and the pump; the air has a free entrance while immediately afterward the water is injected into the barrel at a high velocity. Thus, instead of obstructing the entrance of the air, the water tends to compress that already in the barrel, and to entrain or carry in more air with it.
The bucket or piston is a hollow casting with water grooves instead of packing rings.
The valve seat is constructed with a rib between each valve and a lip around the outer edge, so that each valve stands in its own water and is separated from the others. This forms a ready means of testing the relative tightness of each valve.
The cast iron working barrel is lined with brass.
The pump rod is Tobin bronze, and valve plate and valves of composition. These pumps are either single, twin, triplex, and are steam, electric or belt driven, for stationary, marine or sugar plantation service.
The steam driven pumps are built with either single or compound steam cylinders, fitted with new and improved valve gear, and with their arrangement of fly-wheels, insures smooth running, making full strokes free from vibration.
_Compressed air_ is air compressed by mechanical force into a state of more or less increased density. _The power obtained from the expansion_ of greatly compressed air in a cylinder, on being set free is used in many applications as a substitute for steam or other force as in operating drills, shop tools and _engines_ which are driven by the elastic force of compressed air.
_A compressor_ is a machine usually driven by steam by which air is compressed in a receiver so that its expansion may be utilized as a source of power at distances where an ordinary engine could not be conveniently used.
The compressor proper comprises two sets of valves, usually designed to be opened automatically by excess of pressure under them and to be closed by gravity or by the action of springs when the pressures become equal. The inlet valves open just after the piston commences its stroke, when the expansion of the compressed air remaining in the cylinder behind the piston has lowered the pressure above the valves. They close at the end of the intake stroke, just as the piston comes to rest. The outlet valve lifts during the compression stroke, at about the time the rising pressure in the cylinder becomes equal to that in the outlet passage above the valves; and they close when the flow of air ceases as the piston completes its stroke.