Plastic article or earthenware shaping or treating: apparatus – Control means responsive to or actuated by means sensing or... – Temperature control
Patent
1988-06-15
1993-04-27
Heitbrink, Jill L.
Plastic article or earthenware shaping or treating: apparatus
Control means responsive to or actuated by means sensing or...
Temperature control
425182R, 425547, 425548, B29C 4578
Patent
active
052060330
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention is a device for producing injection molded parts having a mold including supply conduits, such as passages, nozzles or the like, for molten material and heating means and/or cooling means with temperature measuring means, which means are interconnected via regulating means. The injection molded parts consist preferably of synthetic plastic material but can also be produced from metals suitable for the injection molding process.
It is already known to produce injection molded parts by a continuous injection molding process which assures a rapid operation sequence and which avoids, to a great extent, the formation of coupons which must be comminuted when reusing the material. In such a continuous injection molding process, the passages, nozzles or the like for supplying the molten material therethrough into the mold cavity must, for the purpose of obtaining an acceptable product, be heated such that the molten material has a definite temperature at predetermined locations. If the temperature is below the predetermined value, the molten material will not have the viscosity required for obtaining an acceptable product, while, if the temperature is too high, the molten material is decomposed and, for example, emits toxic constituents. For the purpose of maintaining a constant temperature within a predetermined temperature interval at definite locations in the conduits for supplying molten material, it has already been proposed to provide temperature measuring devices at the respective locations, noting that the temperature measured in each temperature measuring device is transmitted via an electric conduit to a regulating means assigned to each temperature measuring device which is arranged separately from the mold. An associated heating device is controlled via a further conduit by the regulating means. Such an arrangement permits reliable maintenance, during normal operation, of constant temperatures at the individual measuring points within a predetermined temperature interval, but has numerous drawbacks. Because of the necessity of providing an electrical conduit leading from each measuring device out of the mold to the associated regulating means and of providing a further electrical conduit from the regulating means to the associated heating or cooling device in the mold, numerous electrical conduits are arranged outside the mold. Accordingly, there is the risk of damaging the conduits or of interrupting the connecting points of the conduits when they are performing or monitoring the injection molding process, so that no unobjectionable operation is possible with respect to the temperature control. A further drawback of this known arrangement is that the temperatures are maintained constant at predetermined measuring points but that no dialogue is established between the individual measuring points. If, for example, the temperature changes at a definite measuring point due to external influences, the temperatures measured at adjacent measuring points are not automatically adjusted to another value. This also occurs when there is a change in, for example, the temperature of the molten material. Finally, it is necessary that, for the purpose of compensating a temperature rise due to friction phenomena, a higher temperature exists at the individual measuring points when starting the injection molding process than after a certain start-up time. In the known arrangement, the temperature changes required in case of these events can only be effected by an operator optically monitoring the temperature values. The operator, which, as a rule, has to attend to a plurality of injection molding devices, is frequently overcharged, so that rejects are produced due to false temperatures at the individual measuring points or incorrect temperature relations between the individual measuring points, and individual parts of the injection molding device may become damaged. If a failure occurs, it may be necessary to shut down the plant so that the defect may be located and eliminated.
REFERENCES:
patent: 4707310 (1987-11-01), Debeaud
Plastics Engineering, vol. 40, No. 4, Apr. 1984, "Streamlined mold changing: a key to profitability" by Ruhl, pp. 39-42.
Heitbrink Jill L.
VanOphem Remy J.
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