Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or...
Patent
1989-02-14
1990-08-21
Woo, Jay H.
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
26432811, 425155, 425171, 425569, 425574, B29C 4507
Patent
active
049501445
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a nozzle touch apparatus in an injection molding machine, in which a spring is compressed to generate a nozzle touch force, and more particularly to a nozzle touch apparatus arranged to change the nozzle touch force with progress of the injection molding cycle so as to prevent deformation of a stationary half of a mold.
BACKGROUND ART
Typically, in a conventional nozzle touch apparatus for use in an electrically-operated injection molding machine, a ball screw coupled to a motor via a speed-reducing gear is rotated to axially move a ball nut threadedly engaged therewith. A spring which is interposed between a spring seat member, arranged for movement in unison with an injection unit, and a movable spring sat member, arranged for movement in unison with the ball nut, is compressed. The rotation of the motor is then stopped and at the same time a brake is actuated when a predetermined compressed amount of the spring is reached, to hold the spring in the compressed state so as to maintain the spring force, or the nozzle touch force, to be applied to the injection unit.
In this case, the nozzle touch force is kept constant during the injection molding cycle. Thus, the nozzle touch force sometimes becomes excessive in magnitude for some kinds of molds used for injection molding.
More specifically, when the mold is in its lockup state in injection and hold processes of the injection molding cycle, a stationary mold half 100 mounted on stationary platen and a movable mold half 101 are urged in contact with each other, as shown in FIG. 2. Thus, the stationary mold half 100 is not deformed even if a rather excessive nozzle touch force f is applied thereto. On the other hand, during metering and eject processes and up to completion of the mold clamping process (that is, during a section of the injection molding cycle where the mold lockup state is released), the movable mold half 101 provides the stationary mold half 100 with no substantial urging force, or is disposed out of contact with the stationary mold half, as shown in FIG. 3. In this mold lockup released state, the stationary mold half 100 is urged towards the movable mold half 101 when an excessive nozzle touch force f is applied thereto. Thus, the stationary mold half 100 can be deformed. Actually, in the case of using a hot runner type mold in an electrically-operated injection molding machine, since the mold of this kind is formed with a number of cavities for prevention of heat transfer from a heated manifold to its peripheral parts and is liable to be deformed, in particular, at the manifold, this mold can be deformed by virtue of an excessive urging force, i.e., nozzle touch force generated by the nozzle in the lockup released section in the injection molding cycle such as the mold-opening process.
With regard to this point, a hydraulic injection molding machine has mold clamping and injection apparatuses whose respective hydraulic cylinders are connected to a common hydraulic pressure source, so that a force applied to the movable mold half is balanced with a force applied to the nozzle. That is, during the injection process, for instance, on one hand, the nozzle is urged in contact with the stationary mold half with a great nozzle touch force, and on the other hand, the movable mold half is urged in contact with the stationary mold half with a mold clamping force which is exerted in an opposite direction to a direction along which the nozzle touch force is exerted. Further, during metering and eject processes, both of the nozzle and the movable mold half never apply a force to the stationary mold half. At any rate, an equilibrium-of-force relationship is always established between the both sides of the stationary mold half.
However, in the electrically-operated injection molding machine where the clamping apparatus and the nozzle touch apparatus are separately driven by independent motors, it is difficult to balance forces applied from these apparatuses to the stationary mold half.
SUMMARY OF TH
REFERENCES:
patent: 3538549 (1970-11-01), Hehl
patent: 3888388 (1975-06-01), Mahoney
patent: 4299791 (1981-11-01), Aoki
patent: 4676730 (1987-06-01), Yamasaki
patent: 4836962 (1989-06-01), Aoki
Muranaka Masaki
Watanabe Kikuo
Fanuc Ltd
Mackey James P.
Woo Jay H.
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