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forces in more than one direction.
DESCRIPTION OF THE DRAWINGS
FIG. 1 is an elevational view of a molded container according to the invention, indicating a cap adapted to be screwed onto the top of the container;
FIG. 2 is a sectional view of the container, taken along the line 2-2 of FIG. 1;
FIG. 3 is a plan view of the container, taken along the line 3-3 of FIG. 2;
FIG. 4 is an exploded view of an injection mold according to the invention, for producing the container of FIGS. 1 and 2;
FIG. 5 is a sectional view of a portion of the mold, taken along the line 5-5 of FIG. 4; and
FIG. 6 is a frontal view of the other mold portion, taken along the line 6-6 of FIG. 4.
DESCRIPTION OF THE PREFERRED EMBODIMENT
In the drawings, FIGS. 1 and 2 show a molded cylindrical article 10, having a helical male thread 11 formed on a neck portion 12 of the article. The thread 11 does not completely encircle the neck portion 12,but rather subtends an angle of less than 3600, with end points 13 and 14 obliquely spaced from one another.The article 10 is molded with a two-piece mold whose part line 15 follows the outer periphery or maximum diameter of the thread 11 and connects the two thread end points 13 and 14. In the portion of the parting line 15 between the thread ends 13 and 14, the part line preferably includes short portions 17 and 18 generally parallel to the helical thread, for reasons of mold design as will be seen below. An oblique line 19 connects the short portions 17 and 18 of the parting line 15.
As FIG. 1 indicates, the thread 11 and neck portion 12 of the container 10 may be adapted to receive a female-threaded cap 20.
The article 10 may be a plastic vial which is preferably formed by injection molding. For the vial 10 shown in the figures, the molten plastic would preferably be injected at 22 (see FIG. 2) to fill the closed mold.
FIGS. 4, 5 and 6 show a mold 25 according to the invention which may be used for producing the neckthreaded molded article 10. Although the mold shown is an injection mold, it should be understood that other types of molds can be employed according to the invention, so long as the neck thread 11 of the molded article 10 is formed in accordance with the above description.
The injection mold 25 includes two mold sections: a"lower" section 26, so denominated herein and in the appended claims because it forms the lower portion of the outside of the vial 10, and an "upper" mold section 27. Of course, in most injection molding presses, the mold 25 would be oriented horizontally. The mold section 26 includes a central mold cavity 28 connected to a gate opening 29 and a fitting 30 for connection to the nozzle of an injection molding press (not shown). As FIGS. 4 and 6 indicate, the upper end of the lower mold section 26 is formed into a helical edge 32 with an oppositely angled bridging portion 33, to define the parting line 15 of the mold 25 as described in reference to the molded article 10 of FIGS. 1, 2 and 3. Around the inside of the helical surface 32 and at the top of the mold cavity 28 is a helical cut out portion 34, which may be, for quarter-round a quarter-round shape as shown in the drawings. The cut out portion 34, which
forms the lower half of a thread projection of groove for the thread 11 of the molded article 10, does not make a complete turn around the mold cavity 28 but rather stops short of both edges of the angled surface 33. "The reason why the thread projection does not reach the interfaces between the surfaces 32 and 33 is to avoid the necessity of sharp points the mold at ends 36 and 37 of the thread projection 34. Of course, the parting line 19 between the thread ends 36 and 37
need not be of the shape shown in FIG. 4 and FIG. 1-it could alternatively follow an oblique reversed curve path.
The upper mold section 27, seen in FIGS. 4 and 5, includes a central core rod 39 which forms the inside surface of the vial 10. Of course, if the molded article 10 is a solid component rather than a hollow vial, the core rod 39 would not be included. Similarly, if blow molding is utilized rather than injection molding as the final step in the formation of a hollow vial article 10, there would be no core rod 39 on the upper mold section 27.