A method of making pairs of thread splits inserts used to injection mold bottle preforms. Machining a hollow outer part of the pair of thread split inserts with an opening therethrough and outer portions of two cooling conduits extending from the opening therethrough to respective inlets and outlets. Making an inner part of the pair of thread split inserts by injection molding a ceramic core with the required shape and investment casting the inner part around the ceramic core. The outer surface of the inner part having grooves to partially form inner portions of the two cooling fluid conduits. Then machining the cast inner part to fit in the opening through the outer part. Mounting the outer part around the inner part with the inner and outer portions of the two cooling fluid conduits aligned. Applying brazing material between the inner and outer parts and heating them in a vacuum furnace to integrally braze them together. Finally, cutting the integral inner and outer parts in half to form the pair of thread split inserts with each of the thread split inserts having one of the cooling fluid conduits therein.
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0. 5. A method of making a pair of split inserts for use in injection molding, comprising the steps of:
(a) casting a hollow inner part; (b) machining a hollow outer part; (c) integrally brazing the hollow inner part and the hollow outer part together; and (d) cutting the integral hollow inner and outer parts to form the pair of split inserts.
1. A method of making a pair of thread split inserts used in injection molding elongated hollow bottle preforms, each preform having a neck portion with an outer surface forming a ring collar and threads extending between an open end and the ring collar , each thread split insert having a front end, a rear end and first and second flat inner aligned faces extending on opposite sides of a curved inner surface, the thread split inserts to be mounted together in a mold with the respective flat inner faces of the thread split inserts abutting, wherein the curved inner surfaces of the thread split inserts combine to form an opening therethrough shaped to mold the outer surface of the neck portion of the preform, the curved inner surfaces of the thread split inserts each have a semicircular groove to form the ring collar and a threaded portion extending between the semicircular groove and the rear end to form the threads, comprising the steps of;
(a) injection molding a ceramic core having a predetermined shape, (b) casting wax around the ceramic core in the shape of an inner part of the pair of thread split inserts, (c) investment : (a) casting a suitable metal in a mold to replace the wax around the ceramic core to form a hollow inner part of the pair of thread split inserts extending around a central longitudinal axis, said inner part having a generally cylindrical outer surface with grooves therein to partially form inner portions of two cooling fluid conduits, each cooling fluid conduit to extend around the curved inner surface of one of the thread split inserts, (d) machining the cast inner part to make the outer surface a predetermined size, (e) ; (b) making a hollow outer part of the pair of thread split inserts of a suitable metal having a predetermined shape with an opening therethrough having an inner surface which fits around the outer surface of the inner part and outer portions of the two cooling conduits extending from the opening therethrough to respective inlets and outlets, (f) (c) mounting the outer part around the inner part with the inner and outer portions of the two cooling fluid conduits aligned, applying brazing material between the inner part and the outer part, and heating the assembled inner part and outer part in a vacuum furnace to integrally braze the inner part and the outer part together, and (g) (d) cutting the integral inner and outer parts in half along the central longitudinal axis to form the pair of thread split inserts, each of the thread split inserts having one of the cooling fluid conduits therein.
2. A The method of making a pair of thread split inserts as claimed in
3. A The method of making a pair of thread split inserts as claimed in
4. A The method of making a pair of thread split inserts as claimed in
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This invention relates a method of making pairs of cooled thread split inserts used to injection mold bottle preforms.
As seen in the applicant's U.S. Pat. No. 5,599,567 which issued Feb. 4, 1997, it is well known to use a pair of thread split inserts in a mold to form the threaded neck portion of a PET bottled preform. The neck portion of the preform also has a ring collar which is used to eject the preform from the mold. The thread split inserts have conduits through which cooling fluid is circulated to cool the neck portion of the preform prior to ejection.
In the past, thread split inserts have been made by machining steel upper and lower parts and then integrally brazing them together. This method has the disadvantage that both parts must be machined to provide cooling fluid conduits and threads and this is time consuming and therefore relatively costly.
Accordingly, it is an object of the present invention to at least partially overcome the disadvantages of the prior art by providing a method of making cooled thread split inserts wherein an inner part which fits in an outer part is made by casting rather than machining.
To this end, in one of its aspects, the invention provides a method of making a pair of thread split inserts used in injection molding elongated hollow bottle preforms. Each preform has a neck portion with an outer surface forming a ring collar and threads extending between an open end and the ring collar. Each thread split insert has a front end, a rear end and first and second flat inner aligned faces extending on opposite sides of a curved inner surface. The thread split inserts are mounted together in a mold with the respective flat inner faces of the thread split inserts abutting, wherein the curved inner surfaces of the thread split inserts combine to form an opening therethrough shaped to mold the outer surface of the neck portion of the preform. The curved inner surfaces of the thread split inserts each have a semicircular groove to form the ring collar and a threaded portion extending between the semicircular groove and the rear end to form the threads. The method comprises the steps of injection molding a ceramic core having a predetermined shape and then casting wax around the ceramic core in the shape of an inner part of the pair of thread split inserts. Then investment casting a suitable metal in a mold to replace the wax around the ceramic core to form a hollow inner part of the pair of thread split inserts extending around a central longitudinal axis. The inner part has a generally cylindrical outer surface with grooves therein to partially form inner portions of two cooling fluid conduits. Each cooling fluid conduit extends around the curved inner surface of one of the thread split inserts. Then machining the cast inner part to make the outer surface a predetermined size. Making a hollow outer part of the pair of thread split inserts of a suitable metal having a predetermined shape with an opening therethrough having an inner surface which fits around the outer surface of the inner part and outer portions of the two cooling conduits extending from the opening therethrough to respective inlets and outlets. Mounting the outer part around the inner part with the inner and outer portions of the two cooling fluid conduits aligned. Then applying brazing material between the inner part the outer part and heating the assembled inner part and outer part in a vacuum furnace to integrally braze the inner part and the outer part together. Cutting the integral inner and outer parts in half along the central longitudinal axis to form the pair of thread split inserts, with each of the thread split inserts having one of the cooling fluid conduits therein.
Further objects and advantages of the invention will appear from the following description taken together with the accompanying drawings.
Reference is first made to
Each thread split insert 12, 14 has a front end 26, a rear end 28 and flat inner aligned faces 30, 32 extending on opposite sides of a curved inner surface 34. During molding of the bottled preforms 10, the thread split inserts 12, 14 are mounted in a mold with the respective flat inner faces 30, 32 of the thread split inserts 12, 14 abutting, whereby as seen in
The bottle preform 10 has an elongated cylindrical portion 40 and may include a slightly tapered portion 42 extending from the neck portion 16. As is well known, the cylindrical portion 40 and tapered portion 42 are later enlarged by stretching and then blow molding to form a beverage bottle. After the preform 10 is stretch-blow molded and the resulting bottle is filled with a suitable beverage, a removable threaded cap (not shown) is screwed on to the threads 22 to close the bottle. The ring collar 20 is used in the stretch-blow molding process, but is also used to assist in ejecting the preform 10.
Reference will now be made to the rest of the drawings in describing the method of making the pair of thread split inserts 12, 14 by casting a hollow inner part 44, machining a hollow outer part 46, integrally brazing the hollow inner part 44 and the hollow outer part 46 together, and then cutting the integral hollow inner and outer parts 44, 46 in half to form the pair of thread split inserts 12, 14.
Reference will first be made to
As seen in
Reference is now made to
Nickel brazing paste 94 is applied to the inner portions 84 of the cooling conduits and the hollow inner part 44 is inserted into the central opening 106 through the hollow outer part 46 to form the pair of thread split inserts 12, 14. As can be seen in
After removal of the integral pair of thread split inserts 12, 14 from the vacuum furnace, they are cut in half along the longitudinal axis 96 in an electrical wire-cut machine to form the two separate thread split inserts 12, 14 shown in FIG. 12. As shown, they are cut in the correct plane to have one of the cooling conduits 112 in each of the thread split inserts 12, 14. The pair of thread split inserts 12, 14 are then machined to provide a good outer finish and the tapered portions 120, 122 at their front and rear ends 26, 28. During molding the pair of thread split inserts 12, 14 are secured tightly together by the tapered flange portions 120, 122 being engaged by the rest of the mold (not shown). In this position, the matching flat inner surfaces 30, 32 abut and the curved inner surfaces 34 of the pair of thread split inserts 12, 14 combine to form the opening 35 therethrough shaped to mold the outer surface 18 of the neck portion 16 of the preform 10. Of course, during molding an elongated cylindrical core (not shown) extends through this opening 35 to form the inner surface 124 of the preform 10.
In use in a multi-cavity mold, a number of pairs of thread split inserts 12, 14 made according to the invention are mounted in a conventional mold. A supply of cooling water or other suitable cooling fluid is connected to the inlet 116 of the cooling fluid conduit 112 in each thread split insert 12, 14 to circulate through each cooling fluid conduit 112. Pressurized melt from a molding machine is then injected into the cavity in the opening 35 through each pair of thread split inserts 12, 14 according to a predetermined injection cycle. After the cavities are full, injection pressure is held momentarily to pack and then released. After a short cooling period, the mold is opened to eject each preform 10. This is done by the preform 10 first being ejected from the core and the two thread split inserts 12, 14 then separated to drop the preform 10 onto a conveyor belt or cooling plate. Of course, this requires that the two thread split inserts 12, 14 be separated enough to release the ring collar 20 and threads 22 of the preform 10. After ejection, the mold is closed and injection pressure is reapplied to refill the cavity and the injection cycle is repeated continuously.
While the description of the method of making the pair of thread split inserts 12, 14 has been given, with respect to a preferred embodiment, it will be evident that various other modifications are possible without departing from the scope of the invention as understood by those skilled in the art and as defined in the following claims.
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