This pump has pistons in a stationary block,
and a rotating wobble plate. There might be 4, 5, or more pistons (usually an
odd number are used) -- only two shown here. |
Each piston has a valve within it and another valve behind it. Fluid comes in on the wobble plate side (on the bottom left in this drawing) and exits under pressure in the back (on the right here).
The pistons are pushed against the wobble plate with large springs. A pair of smaller springs force the valves (small metal balls) closed. The spring inside the piston is fairly weak, since only suction is used to force it open.
This type of pump can develop incredible pressure -- 10,000 P.S.I. or more. It is commonly used for low-volume applications. Hand-operated wobble pumps were used as emergency fuel pumps on some early aircraft.
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