Air mass control for diaphragm pumps

A pre-charging system for use with a double diaphragm pump that comprises a first diaphragm that separates a first cavity into a first motive fluid chamber and a first pumped media chamber, a second diaphragm that separates a second cavity into a second motive fluid chamber and a second pumped media chamber, a compressed fluid inlet, and a main valve movable between (i) a first main valve position in which the main valve fluidly couples the compressed fluid inlet to the first motive fluid chamber and (ii) a second main valve position in which the main valve fluidly couples the compressed fluid inlet to the second motive fluid chamber, the pre-charging system comprising:

• a charge unit comprising a first charge chamber having a first controlled volume and a second charge chamber having a second controlled volume, wherein the first controlled volume is adjustable to vary a first controlled mass of compressed fluid capable of being stored in the first charge chamber and the second controlled volume is adjustable to vary a second controlled mass of compressed fluid capable of being stored in the second charge chamber;
• a charge valve configured to be fluidly coupled to a compressed fluid source, the first charge chamber, the second charge chamber, and the compressed fluid inlet of the double diaphragm pump, wherein the charge valve is movable between (i) a first charge valve position in which the charge valve is configured to communicate compressed fluid from the first charge chamber to the compressed fluid inlet and to communicate compressed fluid from the compressed fluid source to the second charge chamber and (ii) a second charge valve position in which the charge valve is configured to communicate compressed fluid from the second charge chamber to the compressed fluid inlet and to communicate compressed fluid from the compressed fluid source to the first charge chamber;
• and
• a controller configured to (i) receive a sensor signal indicative of the first and second diaphragms of the double diaphragm pump reaching an end-of-stroke position and (ii) transmit a first control signal to the charge valve that causes the charge valve to shift between the first and second charge valve positions in response to receiving the sensor signal;
• (iii) determine a stroke speed of the double diaphragm pump using the sensor signal and (iv) transmit a second control signal that causes an actuator to adjust at least one of the first and second controlled volumes in response to the determined stroke speed being outside a desired range.