US Patent 8641399 Injection molding system having a digital displacement pump

Injection molding system (20, 220, 320, 420) having hydraulic circuit (50, 250, 350, 450) for motivating hydraulic actuator (36, 38) comprising: pump motor (52); and digital displacement pump (54, 354A, 354B, 454A, 454B) having: piston assemblies (102A, 102B, 102C, 102D) actuatable by pump motor (52), piston assembly including: pair of inlet and outlets operable to be individually opened and closed at selective rate independently of actuation of each piston assembly; at least one hydraulic actuator (36, 38) operably coupled on each of rod side (64, 66) and cylinder side (58, 74) to first subset of the plurality of piston assemblies (102B, 102D) and second subset of the plurality of piston assemblies (102A, 102C), respectively.