Pulsation free pump

A pulsation free pump comprising:

• a plurality of hydraulic diaphragm pumps;
• a plurality of plungers provided to correspond to said hydraulic diaphragm pumps, each of said plungers performing a reciprocal movement which provides a pumping cycle operation corresponding to one of said plurality of hydraulic diaphragm pumps, each of the pumping cycles comprising a discharge process and a subsequent suction process;
• and
• means for controlling reciprocal movements of said plungers in association with each other at a predetermined difference in phase of the pumping cycle,
• said diaphragm pump comprising a hydraulic diaphragm pump provided with an air exhaust differential pressure regulating valve which operates in accordance with a difference in pressure between an external atmospheric pressure and a liquid in a pump chamber of said hydraulic pump so that in said discharge process not on said liquid but also an air in said sump chamber are exhausted from said pump chamber by a large pressure difference through said air exhaust differential pressure regulating valve whilst in said subsequent suction process only said liquid is returned in said pump chamber so as to exhaust the air in said pump chamber,
• said air exhaust differential pressure regulating valve comprising a ball valve movable between an upstream valve seat positioned near said pump chamber at an upstream side and a downstream valve seat positioned far from said pump chamber so that in said discharge process said ball valve is made to securely contact with said downstream valve seat whilst in said subsequent suction process said ball valve is made to securely contact with said upstream valve seat,
• a distance between said upstream valve seat and said downstream valve seat being adjustable to adjust an amount of said liquid exhausted from said pump chamber in said discharge process,
• wherein said means for controlling reciprocal movements of said plungers controls said reciprocal movement of each of said plungers so as to set a preliminary pressure-rising process just before said discharge process so that a discharge flow rate of each of said diaphragm pumps is initiated to increase without any time delay when said pumping cycle enters into said discharge process whereby a total discharge flow rate defined by the sum of said discharge flow rates of all of said plungers is kept constant and free of any substantial pulsation.