Die closing unit for injection molding machine

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination:

• a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis;
• a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom;
• a movable die carrier member to which the movable half of the injection molding die is attachable and which is arranged axially between the stationary die carrier plate and the stationary head plate;
• means for guiding the movable die carrier member and attached die half in relation to the stationary die carrier plate and head plate for opening and closing movements along the unit center axis between a forward closed position and a rearward open position;
• and
• a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the unit center axis and being rigidly connected to the movable die carrier member for the transmission thereto of opening and closing forces, including elevated closing pressures;
• and wherein:
• the hydraulic linear actuator includes:
• a power cylinder rearwardly adjoining the stationary head plate, a smaller-diameter auxiliary cylinder coaxially adjoining the rear extremity of the power cylinder, and a mounting flange connecting and centering the two cylindrs;
• the piston rod extends through the power cylinder and into the auxiliary cylinder, carrying a matching double-acting power piston inside the former and a matching single-acting auxiliary piston inside the latter;
• the piston rod portion between the power piston and auxiliary piston extends sealingly through the mounting flange between the two cylinders with a diameter which is smaller than the diameter of the piston rod portion extending forwardly from the power piston;
• the piston rod further has a hollow forward end portion for the accommodation therein of a drive for an accessory device, said drive being an accessory hydraulic linear actuator;
• and
• the power piston includes at least one bypass channel extending from one axial side thereof to the other side, and hydraulically operated valve means for selectively opening and closing the bypass channel, so that the piston rod in the power cylinder acts as a differential piston, producing a rapid die closing motion, when the power cylinder is pressurized with the bypass channel held open, and the auxiliary piston produces a rapid die opening motion, when the forward side of the auxiliary piston is pressurized with the power piston bypass channel held open, while the power piston produces an elevated closing pressure, when its rear side is pressurized with the bypass channel closed.

A push-type die closing unit for an injection molding machine, serving to open and close the die halves of an injection molding die in a reciprocating motion along the longitudinal center axis of the unit, the die closing unit comprising in combination:

• a stationary die carrier plate to which the stationary half of the injection molding die is attachable and which extends transversely to the unit center axis;
• a stationary head plate likewise extending transversely to the unit center axis, on the other side of the emplacement of the injection molding die and at a distance therefrom;
• a plurality of tie rods extending between the two plates, parallel to and radially spaced from the unit center axis, and connected to said stationary plates so as to define with them a rigid elongated guide frame;
• a rigid movable die carrier frame to which the movable half of the injection molding die is attachable, the die carrier frame being engaged by the tie rods for guided movement therealong between a forward closed position and a rearward open position;
• and
• a hydraulic linear actuator mounted axially behind the stationary head plate, said actuator having a piston rod extending in the center axis of the die closing unit and connected to the movable die carrier frame for the transmission thereto of opening and closing forces, including elevated closing pressures;
• and wherein
• the movable die carrier frame includes:
• a die mounting wall on the forward axial side thereof;
• a pressure transfer wall which is substantially continuous in the transverse direction and spaced axially to the rear of said die mounting wall, and to which is connected the forward extremity of the piston rod;
• a plurality of tie rod embracing guide sockets defined by said die mounting and pressure transfer walls;
• and pressure transfer ribs extending between and rigidly connecting said two walls in the area located radially inside the guide sockets, while leaving free a central space between said walls, for the accommodation therein of an accessory device;
• the piston rod of the hydraulic linear actuator includes, at its connected forward extremity, a thrust plate with which it engages the rear side of the pressure transfer wall in a central area whose radial extent is greater than the minimum radial distance of the pressure transfer ribs on the opposite side of the pressure transfer wall;
• and
• the hydraulic linear actuator further includes:
• a power cylinder enclosing a power piston seated on the piston rod;
• valve means associated with the power piston for selectively hydraulically bypassing the power piston;
• and an auxiliary cylinder extending coaxially to the rear of the power cylinder and enclosing an auxiliary piston seated on the same piston rod.