Patent ID: 6893246
Filing Date: 2005-05-17
Classification: B29C

Abstract:
1. A clamping device for an injection-molding machine, comprising: a movable mold holder having a first side, to which a first mold half is connected; a guiding assembly being mounted on a bed of said injection-molding machine for guiding said movable mold holder mounted thereon to move in linear motion; a first screw rod unit being fixedly connected at an end to a second side of said movable mold holder opposite to said first side and adapted to mesh with internal threads of a nut element for said nut element to screw thereto, such that when said nut element is rotated, said first screw rod unit is brought to move in linear motion in a first lead; and said nut element being provided at a rear outer end facing away from said movable mold holder with external threads; a clamping screw rod unit being screwed to said nut element to mesh with said external threads of said nut element and thereby rotating said nut element for said first screw rod unit meshed with said nut element to move in reciprocating motion; a pre-pressing unit being adjustably tightened to said clamping screw rod unit for the latter to generate a pre-pressure against said nut element; a transmission assembly including a driving source, a driving force produced by which is transmitted to said clamping screw rod unit to rotate the same; and a braking unit being fixedly mounted on said bed of said injection-molding machine in the vicinity of said first screw rod unit for braking said nut element; whereby when said braking unit is actuated to brake said nut element, a driving torsion produced by said driving source continuously increases to concentrate on said clamping screw rod unit; and when said driving torsion becomes larger than said pre-pressure generated by said clamping screw rod unit against said nut element, said clamping screw rod unit is caused to rotate relative to the rear outer end of said nut element in a second lead and thereby generates a linear push force to drive forward said brake nut element, said first screw rod unit meshed with said nut element, and said movable mold holder connected to a front end of said first screw rod unit, enabling closing of mold under a clamping force; and when said driving source is rotated reversely to release said closed mold from said clamping force produced by said clamping screw rod unit and said first screw rod unit and said braking unit is caused to release said nut element, said driving torsion produced by said driving source is transmitted to said first screw rod unit for the same to move backward said movable mold holder and said first mold half connected thereto to complete opening of mold, and wherein the first lead is larger than the second lead.