US 3,940,930 AGranted

Hydraulic system for injection molding machine

AssigneePackage Machinery Company

InventorRussell B. Rosander

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Abstract

A fixed platen is supported in the machine frame, and a movable platen is connected to two parallel rods which project rearwardly through the fixed platen. Each rod carries a first piston and each piston is slidably received in a first cylinder. These cylinders are slidably received on the rods and each cylinder has a forward end defining a second larger piston slidably received in a fixed second cylinder. The front and rear faces of the smaller pistons are selectively connected to fluid from a first pump through a synchronizing valve, and a paralleling pump supplements the flow from the first pump during synchronization, that is during the major part of the mold opening and closing movement. Slower movement is provided for just prior to the platen reaching the mold open and closed positions. The larger piston is fed high pressure fluid from still another pump at the mold closed position to clamp the molds closed, a power check valve being provided to seal fluid between the first piston and the second during such clamping action.

Claims16

Dependent claims

In an injection molding machine of the type having a fixed frame supporting a stationary mold part and a movable platen which supports a mating mold part, and a hydraulic system for the movable platen, said system comprising:

a. parallel rods slidably received in the fixed frame and connected to the movable platen for closing movement toward and opening movement away from the stationary mold part,
b. at least one of said rods having a portion which projects rearwardly through the fixed frame generally opposite the movable platen and a first piston on said projecting portion,
c. means defining a first cylinder for slidably receiving said first piston, and a first fluid conduit for providing a first fluid to a front face of said first piston to close said mold parts,
d. a second piston defined on said first cylinder defining means, said first cylinder defining means being slidably received on said rods, said second piston having a forward limit position wherein a forwardly facing stop surface abuts the fixed frame,
e. second cylinder defining means fixed in the machine frame and slidably receiving said second piston, and a second fluid conduit for providing a second fluid to the front face of said second piston to bias said first cylinder rearwardly, and
f. valve means for selectively closing said first fluid conduit when second fluid is provided at said second fluid conduit.

3 more elements

Dependencies are inferred from the claim text.