GB2265329A

GB2265329A - Method and apparatus for applying a layer of dissimilar material to the inside or outside of a molded part

Info

Publication number: GB2265329A
Application number: GB9205698A
Authority: GB
Inventors: Gary V Montgomery
Original assignee: Sunbeam Plastics Corp
Current assignee: Silgan Plastic Food Containers Corp
Priority date: 1991-03-05
Filing date: 1992-03-16
Publication date: 1993-09-29
Also published as: GB9205698D0; FR2673567A1; DE4208276A1

Description

t 1 2265329 METHOD AND APPARATUS FOR APPLYING A LAYER OF DISSIMILAR

MATERIAL TO THE INSIDE OR OUTSIDE OF A MOLDED PART

BACKGROUND OF THE INVENTION

Field of the Invention

This invention relates to apparatus for and a method of applying a layer of dissimilar material to the inside or outside of a molded part. More particularly, this invention relates to coating a closure such as a standard threaded cap.

Description of the Related Art

There are various methods of applying a layer of a different material to a molded part. In the f ield of container closures, the problem of supplying a softer or more resilient sealing material to the inside of a cap of harder material has existed since the application of cork liners to metal bottle caps.

More recently, it has been found desirable to fuse the softer sealing material to the harder cap. This has been generally accomplished in a multiple step compression molding process. Usually the harder cap is first compression molded, and then the softer sealing material is introduced into the cap and formed by well known compression molding techniques. Variations of this procedure include forming the softer or more resilient sealing material in an end cavity of a core followed by molding the harder cap material in the mold cavity surrounding the core.

2 Application of dissimilar materials to closures for purposes other than providing a sealing surface have been largely undeveloped.

SUMMARY OF THE INVENTION

The present invention provides a means for applying a dissimilar material to the inside or outside of a closure during the injection molding of the closure itself. The method and apparatus can be used for coating the inside of a parison being injection molded so that when the parison is blow molded into a container, the inside or outside of the container is coated. The method and apparatus of this invention also permits the selective coating of the inside or outside of the top only of a closure cap. The primary purpose of applying such a fused coating is to provide a gas impervious or chemical resistant surface to protect the product packaged in the container. For example, it is known that Vinyliden Chloride copolymers, known by the trademark SARAN, have low permability to gases and liquids and thus are useful for gas barriers and for chemical resistance. In application to a closure, this can furnish an oxygen barrier to reduce spoilage or deterioration of a pharmaceutical or food product. Other materials such as a polypropylene copolymer can be used for a barrier to avoid contact or resist penetration by various gases and liquids. Also the fused coating may be desirable to present a different color or pattern effect for the cap.

The method in its broader aspects furnishes a means for applying a dissimilar material to the surface of a closed end tubular part being injection molded. The die set of the molding machine has opposed and 3 aligned mold parts, and the method includes the following steps:

A) opening the molding machine.

B) Passing a film of the dissimilar material between mold parts.

C) Closing the molding machine, and trapping the film between the mold parts.

D) Injecting a plastic into the mold and forming the part with a coating of the dissimilar material fused to a surface of the part.

A finished, coated part, is ejected in the opening step A), and in step B), the film is advanced from a supply roll to a take up roll.

The mold has a cavity side and a core side so that when the plastic is injected into the mold in step D) through the cavity side, the dissimilar material fuses to the inside surface of the part. When the plastic material is injected into the mold through the core side, the dissimilar material fuses to the outside surface of the part. Preferably, the portion of the film which will coat the part is cut during the closing of the molding machine in step C). Preferably a peripheral cutting edge on the cavity side presses the film towards the core side, which also preferably has a peripheral cutting edge or blade which squeezes the film and extrudes it as it is brought against the peripheral cutting edge on the cavity side.

It may not be necessary to coat the cap skirt, so that coating can be restricted to the cap top. In this instance, the cavity side of the mold is split into a cavity base and cavity insert so that the cavity insert is axially separated from the cavity base during the t 4 opening step A), and the film is passed between the cavity base and cavity insert in step B). When the cavity base and cavity insert is closed during the closing of the machine in step C), a portion of the film is cut to coat only the closed end of the closure.

The apparatus of the invention combines coating apparatus with a die set for use in an injection molding machine. The die set includes a cavity mold having at least one cavity and a core mold having at least one core opposed to the cavity. Means including registerings posts and bearings are provided for moving the core mold relative to the cavity mold from an open position in which a molded part is ejected to a closed position in which the part is molded. The coating apparatus includes advancing means for passing a film of dissimilar material between the molds when they are in their open position. Scoring means is provided for cutting a portion of the film adjacent the peripheries of the core and cavity. Thus when the part is molded it is simultaneously coated with the dissimilar material which fuses to a surface of the part. Advancing means includes a suitable supply roll and take up roll with a drive on the take up roll. Preferably, the film is cut by blades projecting from the cavity mold and core mold which scores the f ilm by extrusion. Shearing action can also be used to perform the cutting operation. When only the top of a closure is to be coated, the cavity mold includes a cavity base and cavity insert which separate along a radial plane when the cavity mold and core mold are moved into their open position. The film of dissimilar material is located between the cavity base and cavity insert with the cutting action taking place between the cavity base and cavity insert members.

1 BRIEF DESCRIPTION OF THE DRAWING

The preferred embodiments of the invention are illustrated in the drawing in which:

Fiqure 1 is a perspective view showing the die set installed in a conventional injection molding machine equipped with coating apparatus which includes means for advancing a film of dissimilar material between the open mold parts; Fiqure 2 is a plan view partially in cross section showing a single mold cavity and core of the apparatus of Figure 1 with means for injecting the plastic through the cavity side of the mold die set; the film of dissimilar material is advanced in this open position; Fiqure 3 is a view similar to Figure 2 showing the die set in its closed position with the film of dissimilar material trapped between the cavity and core sides having been scored or cut in the closing operation; Figure 4 is a view similar to Figure 3 after plastic has been injected into the mold from the cavity side so as to fuse to the inside surface of the closure cap being formed.

Figure 5 is a partial cross sectional view taken in the encircled area of Figure 4 showing a preferred form of the invention for cutting the film of dissimilar material by opposed knife members which act to score and extrude the film into the clearance between adjacent knife surfaces; Figure 6 is a view similar to Figure 4 showing the closure cap being formed with the plastic injected through the core side of the mod so that the film of dissimilar material coats by fusion to the exterior surface of the cap;' 1 6 Fiqure 7 is a view similar to Figure 2 showing a split cavity mold of the die set with its base portion and insert portion moved apart in the open position of the die set to permit the film of dissimilar material to pass between the two parts of the cavity mold so that the film is cut to coat only the top of the closure cap; Figure 8 is a view similar to Figure 7 with the cavity mold closed having cut the film during the closing of the die set; Fiqure 9 is a view similar to Figure 8 showing the cap having been extruded from the cavity side of the mold so as to coat the inside of the cap top; Fiqure 10 is a view similar to Figure 9 showing the cap being formed by injection of the plastic through the core side of the mold to coat the outside surface of the cap top; Fiqure 11 is a view similar to Figure 2 with the mold parts of the die set open and configured to mold a parison with the film of dissimilar material being held for positioning during the closing action of the die set; Fiqure 12 is a view similar to Figure 11 showing the die set in its closed position with the film having been cut and stretched to conform to the core; Fiqure 13 is a enlargement of the encircled portion 13 of Figure 12 showing the parison to have been formed by injection of plastic through the cavity side of the mold with the film being fused to the inside surface of the parison; and Figure 14 is a fragmentary view of a blow mold into which the core of Figures 11-13 has been inserted with the container having been blown showing the coating extending over the inside surface of the container.

J 7 DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION

Referring to Figure 1, the apparatus 10 of the invention includes the combination of a die set 12 adapted to be used in a conventional injection molding machine 14 and coating apparatus 16.

The die set 12 includes a mold having a cavity side 18 and a core side 20.

The die set has conventional means including posts and bearings, not shown, for aligning and moving the cavity side and core side relative to each other form an open part ejection position shown in Figures 1 and 2 to a closed molding position shown in Figures 3 and 4 that act in cooperation with elements of the injection molding machine 14 for opening and closing the machine, injecting molten plastic into the mold, etc. The number of cavities 22 in the cavity side 18 and cooperating cores 24 in the core side 20 is varied from machine to machine and by the product being molded. Typically, with a closed end tubular part being molded there will be several vertically spaced horizontal rows of cooperating cavities and cores. When container closures are being molded, matrixes of 32-64 cavities and cores are common., Coating apparatus 16 includes a supply roll 26 of dissimilar material in the form of a continuous web or film 28. The term dissimilar is used to denote a material different than the plastic forming the part being molded, which is shown as a container closure or cap 30 in Figures 4 and 6. The dissimilar material is fused to the surface of the part being molded to impart a particular property to the part. As previously 1 8 mentioned, a SARAN copolymer acts as a gas, normallyoxygen, barrier to prevent deterioration of the product in the container to which the cap is applied. Other materials such as metalic foils can be used as heat barriers or transmitters. Papers and laminated combinations can be used for marking, decoration, coloration and the like.

The film 28 is payed out from the supply roll 26 and successively passes over upper and lower guide rolls 32 and 34 to be taken up on roll 36 driven by motor 38. The supply roll 26, guide rolls 32 and 34 and take up roll 36 are conveniently journaled on the support brackets 40 mounted on a face of the injection-blow molding machine. It will be appreciated that while the brackets 40 are shown as being mounted on the cavity mold side of the die set or molding machine, they can be mounted to the core side or have suitable independent mounting means.

Referring to Figure 2, the die set 12 is shown in an open position in which a previously molded part would be ejected. The film 28 passes between the cavity side 18 and core side 20 of the mold and can be advanced by motor 38 on take up roll 36 to present an unused portion of the film for coating in the next molding cycle. A peripheral cutting edge 42 is provided on the cavity side 18 for cutting or scoring the film 28 when the die set 12 is closed as the molding machine is closed.

Referring to Figure.3, the die set has been closed bringing the cavity side 18 of the mold into contact with the core side 20 of the mold with the film 28 interposed between the sides and having been stretched over the core 24.

J 9 Figure 4 shows the plastic material from which the. part is to be made having been injected through the sprue 44 in the direction of the arrow and gate 46 to mold the cap 30. In the process the film 28 has been pushed into conformity with the core 24 and becomes fused to the inside of the closed end tubular closure 30. The peripheral cutting edge 42 will have cut through or scored it by extrusion so that the when the molding machine is opened to the position of Figures 1 and 2, the part 30 is ejected clear from the continuous web.

In a preferred embodiment of the invention shown in Figure 5, the peripheral cutting edge 42 not only extends from the cavity side 18 but also from the core side 20 so that as the injection molding machine and die set are moved into the closed position the cutting edges 42 extrude the film 28 into the adjacent recesses 48 to perform the cutting action. A series of scoring surfaces or lands 42' will have a similar extrusion action on the film 28 forcing it into succeeding recesses 481, with the primary purpose of the series of lands 421 being to support the molding pressure between the cavity mold 18 and core mold 20.

Figure 6 shows the die set in the as molded position similar to Figure 4 except that the sprue and gate 461 has injected the plastic through the core side 20 so that the film 28 has been pushed into conformity with the cavity so as to coat or fuse to the exterior surface of the closure 30 being formed.

In many instances coating the top of the part, particularly in the case of a closure, is sufficient to accomplish the intended purpose, for examplet of acting as a gas permeation or liquid corrosion barrier, or for 1 supplying a particular type of indicia to the closure. In Figures 7-11, a die set 12 having a split cavity mold 18 with a separate base section 50 and separate insert section 52 is shown. With this arrangement, as shown in Figure 7, when the injection molding machine and die set is in its open position, cavity insert section 52 is axially separated from the cavity base section 50 so that the web of dissimilar material 28 is fed between the separate sections. As the molding machine and die set is closed the cavity mold parts come together so that a peripheral cutting edge on the cavity base portion 50 coacts with the cavity insert section to cut the f ilm This cutting arrangement can take the form shown in Figures 2-4 or the form of opposed peripheral cutting edges shown in Figure 5. In Figure 7 a shearing type of inwardly directed knife edge 54 is shown on the base cavity section 50 which coacts with a cylindrical portion 56 on the cavity insert section 52 to perform a shearing type of cutting action. As seen in Figure 8, when the molding machine has been completely closed, the shearing action of the complimentary cutting surfaces 54 and 56 have separated the portion which will be fused to the closure 30 being molded from the continuous film portion of the dissimilar material 28. Figure 9 like Figure 4 shows the plastic material having been injected into the cavity portion of the mold 18 through the sprue 44 and gate 46 so that the fill 28 has been fused to the Alternately, the film 28 can be fused to the exterior of the top of closure 30 as shown in Figure 10 by injection of the molten plastic through the gate 461 in core 24.

inside of the top of closure 30 The present apparatus and method permit the application of a dissimilar material to a closed end cylindrical part in the form of a coating to a parison 11 being injection molds so that the parison can be blownin a subsequent step to produce a container having an external or internal coating. Figures 11-14 shown the sequence of forming the parison and blowing it into a coated container. Figure 11 shows the molding machine in its open position with the elements of the die set and coating apparatus being the same as in former embodiments except that since the parison presents a cylindrical part having a greater height than previously discussed closed end cylindrical parts, an additional film guide plate 58 has been introduced as part of the coating apparatus between the core and cavity sides of the die set. The film 28 of dissimilar material is threaded in the coating apparatus 16 on the core side 20 of the guide plate 58 to aid in directing the film to envelop the parison core 241 as the die set 12 is closed in the injection molding machine from the open position of Figure 11 to the closed molding position of Figure 12. Any of the cutting elements or similar devices of the previous embodiments may be used to sever a portion of the film from its web in this process.

As the molten plastic is injected through gate 46 on the cavity side of the mold, the parison 301 is formed with an internally fused coating 28 as shown in Figure 13. As is common in conventional injection-blow molding machines, the core 241 is removed from the cavity side 18 of the injection mold during the next opening cycle to the position in Figure 11 and is moved in alignment with a blow mold 60 to from a blown container 62 in the next molding cycle as shown in Figure 14. The container 62 thus has a fused coated inner surface 28 as shown.

12 The coating of an injection molded closure cap. shown in Figures 2-10 and in injection molded parision shown in Figures 11-14 illustrate the variety of closed end cylindrical parts that can be coated by the method and combined die set and coating apparatus of the present invention.

1 13

Claims

A method of applying a dissimilar material to the surface of a part being molded, said part having a closed end generally tubular configuration and being molded in an injection molding machine having opposed aligned mold parts, the method comprising the following steps:

A) opening said molding machine; B) passing a film of said dissimilar material between said mold parts; C) closing the molding machine, and trapping said film between said mold parts; and D) injecting a plastics into said mold and forming said part with a coating of said dissimilar material fused to a surface thereof.
2. The method according to claim 1 wherein in step A) a part is ejected and in step B) said film is advanced from a supply roll to take up roll.
3. The method according to claim 1 or claim 2 wherein the mold parts include a cavity side and a core side and in step D) the plastic is injected into the mold through the cavity side and said dissimilar material fuses to the inside surface of said part.
4. The method according to any of claims 1-3 wherein said part formed in step D) is a parison and said parison is ejected on a core rod and said core rod and parison are introduced into a blow mold where a container is blown having its internal surface coated with said dissimilar material.

14
5. The method according to claim 1 or claim 2wherein said mold parts include a cavity side and a core side, and in step D) the plastic is injected into the mold through the core side, and said dissimilar material fuses to the outside surface of said part.
6. The method according to claim 5 wherein said part formed in step D) is a parison and said parison is ejected on a core rod and said core rod and parison are introduced into a blow-mold where a container is blown having its external surface coated with said dissimilar material.
7. The method according to any preceding claim, wherein a portion of said film for coating said part is cut in step C).
8. The method according to claim 7 wherein said mold parts include a cavity side and a core side and the portion of said film is cut in step C) by a peripheral cutting edge on said cavity side pressing said film against said core side.
9. The method according to claim 8 wherein the portion of said film is cut by opposed and aligned cutting edges on said cavity and core sides.
10. The method according to claim 7 where said mold parts include a cavity side and a core side and said cavity side is split into a cavity base and a cavity insert, said cavity insert being axially separated from said cavity base during step A), said film passing between said cavity base and cavity insert in step B), said cavity base and cavity insert being closed in step C) cutting a portion of said film to coat only the closed end of said part in step D).

1 is
11. The method according to claim 10 wherein the. portion of said film is cut by a peripheral cutting edge on said cavity base pressing said film against said cavity insert.
12. The method according to claim 11 wherein said portion of the film is cut by opposed and aligned cutting edges on said cavity and core sides.
13. The method according to any preceding claim wherein said cavity mold and core mold are configured to form a closure for a container, said closure including a cap having a top, an annular skirt depending from the periphery of said top with container engaging means on said skirt, and wherein the part formed in step D) is a closure having a coating of dissimilar material fused to a surface of said cap.
14. A combination of a die set for use in an injection molding machine and coating apparatus for applying a coating of a dissimilar material to a closed end generally tubular part being molded in said die set, said die set including:

cavity mold having at least one cavity; core mold having at least one core opposed to said one cavity; and means for moving said core mold relative to the cavity mold from an open position in which a molded part is ejected to a closed position in which said part is molded; said coating apparatus including:

advancing means for passing a film of dissimilar material between said molds when they are in said open position; and scoring means for cutting a portion of said film adjacent the peripheries of said core and cavity; 16 whereby said closed and generally tubular part is molded in said molds with a coating of dissimilar material fused to a surface of said part.
15. The combination according to claim 14 wherein said advancing means includes a supply roll, a take up roll and means for driving said take up roll when said molds are in an open position.
16. The combination according to claim 13 or claim 14 wherein said scoring means includes an annular blade projecting outwardly from said cavity mold for contacting said core mold when said molds are in their closed position.
17. The combination according to claim 16 including an annular blade projecting outwardly from said core mold for pushing said film into contact with said annular cavity mold position.

blade projecting outwardly from said when said molds are in their closed
18. The combination according to any of claims 14-17 wherein said cavity mold includes a cavity base and a cavity insert which separate along a radial plane when said cavity mold and core mold are in their open position and said advancing means locates the film of dissimilar material between said cavity base and cavity insert.
19. The combination according to any of claims 14-18 wherein said cavity mold and core mold are configured to form a closure for a container, said closure including a cap having a top, an annular skirt depending from the periphery of said top with container engaging means on said skirt,, whereby said closed and 1 17 generally tubular part molded is a closure havipg a. coating of dissimilar material fused to a surface of said cap.
20. A method of applying a dissimilar material to the surface of a part being molded substantially as described herein with reference to and as illustrated in the accompanying drawings.
21. A combination of a die set for use in an injection molding apparatus and coating apparatus for applying a coating of a dissimilar material to a closed end generally tubular part being molded in the die set substantially as described herein with reference to and as illustrated in the accompanying drawings.