Title: Method for molding composite articles

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Abstract: A molding apparatus to provide composite plastic articles within the mold is provided. The apparatus includes upper and lower sections which when in a closed position, form a mold cavity divided into two separated chambers by partitions in the upper section. Elements of a desired configuration are formed in the chambers by injecting molten plastic therein and cooling. After formation of the elements, the upper section of the mold is removed and with it, the partitions separating the cavity into chambers. The elements, which are now at opposite ends of an unblocked cavity, are then driven into engagement with each other by a driving means while still in the mold. The joined elements are then ejected from the mold as a composite article. In the preferred embodiment, the elements are interlocked "E" shaped devices which form a solid cube when joined. These elements are molded with protrusions placed on the surfaces thereof and when coated with a plastic coating, the cube forms a game die with the protrusions functioning as the "numbers" thereon. FIELD OF INVENTION This invention relates to a method for molding parts and more specifically, to a method for molding a composite plastic article. DESCRIPTION OF THE PRIOR ART There are presently many varied techniques employed for molding plastic parts. Injection molding is one example of a process typically employed. In this process, a mold having a cavity in the form of the article to be produced is selected, a molten plastic is then injected into the cavity, the plastic is cooled until it sets, and the formed article is formed from the mold. Of course, as in any commercial process, the time required to form an article by injection molding is quite significant in determining whether or not the process is sufficiently economical for the manufacture of certain products. One of the difficulties in such a process is that the thicker the object being formed, the longer is the time required to cool and set the object. Therefore, if it is desired to set up a fast running production line, usually only thin walled objects such as plastic bottles and the like may be economically produced with such a process. Yet there are many kinds of articles which are quite susceptible to being formed by injection molding procedures but because of the thickness of such articles, the process is not as useful as it could be. Items such as gaming dice, marjohng pieces, pool balls and the like require much time to be produced by molding techniques. One possible solution to the problem of how to reduce process time for articles of this type is to form thin walled parts and join them together to complete by building up thin walled sections to form a cube and then coating the cube with the customary coating material. However, present apparatus and methods still prevent this approach from gaining commercial acceptance. The manufacture of a composite plastic object using presently available equipment is quite expensive and time consuming. For example, a mold having two sections forming a mold cavity in the shape of part of the article to be produced is filled with a molding material which is allowed to set. After the part has formed, one section of the mold is removed while the part remains in place and another or third section is moved into the original position of the first section. The third section has a second cavity which is configured to form the other part of the article. The second cavity is filled with plastic and the second part of the article is formed. In some manner, the second part is joined to the first part and a composite article results. This may be repeated with any number of mold sections to build up an article, but obviously it is a very time consuming and expensive process. DESCRIPTION OF THE INVENTION It is the primary object of this invention to provide a method which is capable of manufacturing composite articles quickly and economically by molding techniques. It is another object of this invention to provide a method which molds several parts of an article simultaneously and then joins those parts to form a composite article. It is still another object of this invention to provide a simple and economical method of forming gaming dice and other such objects. Broadly, the apparatus comprises a novel mold or tool for producing a composite article. This mold includes two sections or mold halves which are adapted to join together in a closed position and to separate when the mold is open. When these sections are joined together they define a cavity which is divided into several chambers. Each chamber is intended to be used to form one element of the composite article. While these chambers are blocked from one another during the molding step so as to form individual elements, they are in communication with each other after the mold sections are separated. Since the newly formed elements have no obstacle between them when the mold is open, they may be joined together right in the mold. The elements are joined by a driving means which is operatively connected to a mold section and which, when actuated, drives one element into engagement with the other element to thereby form a unitary composite article. The article is then ejected or removed as a unitary piece. The elements which are formed in the chambers may be joined in any desired manner when driven into engagement. Preferably, however, each element when molded is provided with a part which is adapted to mate with a complimentary part on another element. Typically, one element may have one or more projections while the corresponding element is provided with one or more mating grooves. To provide properly positioned mating parts, the apparatus is provided with an appropriately shaped forming means which extends into the chambers and is effective to define the mating parts so that when the molding material fills the chambers, the defined mating parts are formed. Thus if projections are to be formed on the elements, a plurality of spaced members extend from the mold section into the chamber and the spaces between adjacent members define the projections which are to be formed. In one embodiment, two substantially "E" shaped elements are in this manner formed in separate chambers and when driven together, the flags of the elements interlockingly engage to form a solid cube. In many cases, it is desired that final composite article so formed have one or more portrusions extending outwardly from its surfaces. The apparatus may include for this purpose a number of depressions in the walls of the mold sections. These depressions are located at the place where the mold walls define the chambers so that when the chambers are filled with molding material, the depressions are also filled. Thus the protrusions are molded as an integral part of the element. In such a case, movement of the elements in the mold to join with each other is difficult since the protrusions which are formed on the surface of the element extend into the depressions in the walls. For the same reason, removal of the final article may also be difficult. To avoid this difficulty, one mold section is provided with adjustably positioned walls. That is, one or more of the walls of the mold section which retains the molded elements are movable toward or away from the chambers. By moving the walls away from the chambers, the protrusions are released from the depressions in these movable walls and the elements are free to move toward each other to a mating position. This also enables the final article to be easily ejected from the mold cavity. Ejection may be accomplished by one or more pins or other forcing means movably positioned in the mold section and effective to drive the article out of the cavity. The method of the invention includes the steps of injecting a molding material into a mold apparatus having at least two chambers therein, filling the chambers with molding material to form molded elements, providing during the formation of such elements, a mating part on each of such elements, the mating part on one element being adapted to join with a mating part on another element, and after formation of the elements, driving one part into mating relationship with the other part thereby joining the elements to form a single composite article. The method of the invention are particularly suited to the manufacture of gaming dice. For example, each chamber of the mold may be employed to form an E-shaped element which is driven into mating relationship with another E-shaped element to form a cube. During formation of the E-shaped elements, small protrusions representing the "numbers" on the faces of the die are formed by filling depressions in the walls of the mold. After the cube is ejected, it is coated with the conventional coating and a die is quickly formed. Any number of die cubes may be formed simultaneously in a plurality of mold sections and thus mass production of dice at a very low cost is achieved.


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