US 4,230,442 AGranted

Mold-clamping mechanism for injection-molding machine

AssigneeHusky Injection Molding Systems Ltd.

InventorsHerbert Rees, Allan H. Robinson

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Abstract

A thrust member on column secured to a movable platen of an injection-molding machine, surrounded by a mounting frame with laterally withdrawable shutters which enter behind the thrust member in the terminal phase of a mold-closing stroke for transmitting to the thrust member a supplemental clamping force, is linked with a hydraulically actuated plunger or driving piston via a lost-motion coupling. The clamping force is supplied through one or more annular pistons received in respective cylinder chambers of a stationary housing linked via tie rods with a fixed platen. Upon the release of the clamping force, a counter-vailing hydraulic force is developed between the column and the driving piston, whose forward displacement is limited by a fixed abutment, to break open the mold with a larger hydraulic force. The annular clamping pistons remain spaced from the adjoining housing walls in their retracted positions to allow for an extra rearward shift if, through a malfunction, the shutters are trapped between their mounting frame and the column.

Claims5

Dependent claims

In an injection-molding machine provided with a fixed platen, a movable platen and actuating means for reciprocating said movable platen along an axis with reference to said fixed platen between a mold-open and a mold-closed position,

the improvement wherein said actuating means comprises:
a stationary cylinder provided with a driving piston reciprocable under pressure of a hydraulic liquid admitted into said cylinder;
a thrust member rigid with said movable platen and connected with said driving piston by a lost-motion coupling;
clamping means operable in an advanced position of said driving piston, with said movable platen approaching said mold-closed position, to impart an extra forward motion to said thrust member independently of said driving piston within the limits of relative displaceability provided by said lost-motion coupling to complete the establishment of said mold-closed position;
and
unclamping means hydraulically operable in said mold-closed position for subjecting said thrust member to a rearward displacement relative to said driving piston while forcing the latter against a fixed stop, thereby separating said mold portions from each other preparatorily to a retraction of said driving piston together with said thrust member by said hydraulic liquid.

3 more elements

Dependencies are inferred from the claim text.