Pump system for use with dialysis and like apparatus

A pumping system for pumping the blood of a patient comprising:

• a rigid casing and a flexible diaphragm within the casing, the diaphragm defining and separating a working chamber and a blood chamber which is expandable and contractable for pumping blood said blood chamber having blood inlet means and blood outlet means in fluid communication therewith;
• means including a displaceable chamber for supplying the working chamber with a working fluid for expanding and contracting the working chamber so that the blood chamber is contracted and expanded;
• low pressure limiting valve means in fluid communication with the working chamber responsive to pressure within the working chamber for preventing pressure below a predetermined low pressure in the working chamber by venting the working chamber, and high pressure limiting valve means in fluid communication with the working chamber responsive to pressure within the working chamber for preventing pressure above a predetermined high pressure in the working chamber by venting the working chamber, whereby the supplying means and the blood pumping means operate in phase at pressures between the predetermined low and high pressures within completion of one cycle of expansion and contraction after start up regardless of phase differences at start up.

A pumping system for pumping the blood of a patient comprising:

• a rigid casing and a flexible diaphragm within the casing, the diaphragm defining and separating a working chamber and a blood chamber which is expandable and contractable for pumping blood said blood chamber having blood inlet means and blood outlet means in fluid communication therewith;
• means for alternately creating a pressure above ambient pressure and a pressure below ambient pressure in the working chamber so that the blood chamber is alternately contracted and expanded;
• low pressure limiting valve means in fluid communication with the working chamber responsive to pressure within the working chamber for preventing pressure below a predetermined low pressure in the working chamber by venting the working chamber to the ambient, and high pressure limiting valve means in fluid communication with the working chamber responsive to pressure within the working chamber for preventing pressure above a predetermined high pressure in the working chamber by venting the working chamber to the ambient, whereby the supplying means and the blood pumping means operate in phase at pressures between the predetermined low and high pressures within completion of one cycle of expansion and contraction after start up regardless of phase differences at start up.