Webb, Burden, Robinson & Webb
Two-stage pump assembly
 An accurately controllable two-stage pump assembly comprising two plunger pumps connected in series. The suction port of the outlet pump A is connected to the discharge port of the inlet pump B, so that the discharge port of the outlet pump A and the suction port of the inlet pump B act as the discharge port and the suction port, respectively, of the whole pump assembly. While the inlet pump B is delivering fluid from the whole pump assembly, the outlet pump A completes the filling stroke of the whole pump assembly and fully increases the pressure inside the chamber of the outlet pump A. While the inlet pump B is filling, the outlet pump A is in the stage of displacement stroke and delivers fluid from the whole pump assembly. The plungers of the pumps are moved via cams by stepper motors which swing or rotate back and forth within a certain angular range. 
Jeol Ltd.
F F G G G
F04B F04B G01N G01N G01N
inventional inventional additional additional additional
Makoto Toshinori
Takeuchi Saito