Plastic article or earthenware shaping or treating: apparatus – Means feeding fluent stock from plural sources to common...
Reexamination Certificate
2001-06-29
2004-08-17
Heitbrink, Tim (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Means feeding fluent stock from plural sources to common...
C425S572000
Reexamination Certificate
active
06776600
ABSTRACT:
BACKGROUND
The invention relates to a process for the manufacture of injection-molded articles, especially toothbrush bodies or toothbrushes, wherein the molding material is conveyed from a supply container by means of an injection unit, in particular a screw-piston extruder or a similar material delivery means to the mold cavities. Beyond this, the invention relates to an injection molding machine for the carrying out of this process.
Toothbrushes, particularly in regard to the toothbrush body, have been produced in a multiplicity of colors, generally limited to five different colors. Production in these colors could be executed by the installation of a corresponding number of injection molding machines. However, setting aside the extreme cost factor, such a measure had disadvantages, in that as a rule, different quantities for the toothbrush body lots for each color resulted in no uniform production quota for each machine. Instead, in practice, color changes were undertaken during the production of toothbrush bodies. This again proved to be a complicated matter, very time consuming and caused a poor result in production, which was seen as anything but trivial.
The various coloring substances were, in one method, mixed dry into the plastic granulate at hand for the toothbrush bodies, and this mixture was then heated in the screw-piston extruder, or a similar delivery system, then liquified and apportioned through a mold-entry and internal cavity connection system for distribution into the individual mold cavities or nests thereof, while the injection procedure was in action. In another method, liquid coloring material was employed, which if a screw-piston extruder was being used, was fed into the entry chamber thereof.
If a color change is to be made, then all traces of previous color must be purged from the screw extruder, as well as the delivery channels. This operation is carried out, so that the new color is brought into the system, without stopping the molding of toothbrush bodies until the last remnants of the previous color have been eradicated. This can take as much as an hour and the toothbrush bodies so made, form an unusable product, since they show both the old and the new coloring. Furthermore, an operator's attention is required to monitor the color change of an otherwise automatically running injection molding machine.
The ensuing costs for such a color change are so great, that this procedure is seldom followed as a matter of practice. On this account, toothbrush bodies of respectively one color are produced on an inventory basis. Where production exceeding the current production needs for toothbrush bodies of one color is concerned, large quantities of toothbrush bodies must therefore be placed in interim inventory, so that, for the subsequent insertion of the bristles, toothbrush bodies of all possible colors are made available in the desired color assortment ratios as called for. For this operation, a corresponding, dedicated area in the factory is necessary. It is also problematic that measures must be taken to avoid, that over a lengthy storage time, a contamination of the toothbrush bodies occurs. This is valid especially in the production of toothbrush bodies from the standpoint of hygienic demands.
In order to avoid this interim inventory storage, it is certainly possible to forward the produced toothbrush bodies immediately to the insertion of the bristles. However, then an even more circumstantial color sorting following either the insertion operation or the packing could be required.
SUMMARY OF THE INVENTION
Thus, the object of the present invention is to create a process, in which, according to immediate need, a change in production to a different variety, at least in regard to the coloring of the injection molded articles, can be carried out in a short time. Also the possibility should be realized, of simultaneously manufacturing different injection molded items with one injection molding machine. Finally, an injection molding machine for carrying out the process is to be provided.
For the achievement of this object, insofar as it concerns the process and in accordance with the invention for the manufacture of injection molded items, the molding material is to be combined with at least one additive which is fed into the distribution path of the molding material as this is being delivered to one or more mold cavities. The introduction of the additive is to be at a point in the direction of flow following the injection unit, behind its entry point, and the additive material and the molding material are to be mixed.
In this way, it becomes possible, with a single injection molding machine, to simultaneously produce different items of injection molding manufacture. This capability substantially reduces the cost and, in many applications, a changeover of the injection molding machine from one item to another becomes a matter of little time and trouble. The basic material issuing from the injection unit on its way to the single or grouped nests of molds receives one or more additives, so that, in accordance with each additive, different items can be simultaneously produced.
As an example, in the case of an injection molding die with, customarily, a multiplicity of mold cavities, it is possible, by the above described advantage, that toothbrush bodies differing in colors can be injection molded entirely on an as needed basis. Then in accordance with the required assortment, these bodies can be suitably color grouped as produced in the injection molding machine.
Additionally, in the case of a possibly foreseen changeover in the production of injection molded items to a different design, such items which may carry the previous additive are essentially smaller and hence a quicker changeover becomes possible. At least the screw-piston type extruder or similar delivery means operation, is isolated from that channel section which contains the additive, for instance coloring material, so the molding material found in the extruder need not purged. With each new position of the entry point of the color, or the like additive, within the transport path of the molding material as it approaches the mold cavities, the zone containing such additive or coloration is less and thereby, for an individual color change, the requirement for purging also is reduced. By means of mixing the molding material and the additive just after their being joined, the feed of the mix can be done even closer to the respective mold cavity.
If a multiplicity additive feed points are foreseen, it is possible that these can be conducted directly into the mold entry opening by means of one feed line. In this case, practically from injection cycle to injection cycle, a change of color could be undertaken, without the necessity of an intermediate purge procedure. Without additional measures for the thorough mixing of color and molding material, it is possible, by direct injection or injection of the color near to the respective mold openings, to bring about desired, colorized formulations, whereby the toothbrush body has no uniform, penetrating color, but exhibits a color pattern. The chromatic or optical appearance can be obtained through the input of several colors or by the addition of color varied in combination with other additives.
Besides colors, other additive materials, possibly in combinations, can also be added, after the injection unit with respect to the direction of the flow to the molding material within the transport distribution system to the molds. Again, this additive input to the molding material can be done directly at the mold entry openings. Advantageously, additives are available as colors, preferably liquid colors, powders, metal platelets, reinforcing or supportive material, deformation preventatives, chemically active additives, such as, for instance, a propelling agent, hardening material, softener, or the like.
Metal platelets can provide a scintillating effect whereby the injection molded product can be varied in its visible appearance, possibly in connection w
Chu Simon
Gellert Jobst Ulrich
Senn Alexander
Zahoransky Ulrich
Anton Zahoransky GmbH & Co.
Heitbrink Tim
Sterne Kessler Goldstein & Fox P.L.L.C.
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