IMPROVEMENTS RELATING TO INJECTION MOULDING MACHINES

Abstract: An injection moulding apparatus producing moulded articles of two or more colours has an injection barrel (13), a distribution cylinder (16) within the barrel (13) and defining an injection chamber (30) and inlets to the barrel through which two or more plastics materials are fed. The distribution cylinder (16) is rotatable and/or axially movable in the barrel (13) and is formed with a plurality of passageways through which the plastics materials pass from the inlets to the injection chamber (30). The movements of the distribution cylinder (16) in the barrel (13) are controlled during feeding of the plastics materials to preform a desired materials distribution within the injection chamber (30). Thereafter the contents of the injection chamber (30) are injected through an injection nozzle (14) into a die cavity to produce the moulded article.

Description: ΏJROVEI-IEΠ S ΉΞLAΣΉΪG- TO H.JSCTIOIT KOU DIUG EACHI T ΞS FIELD OF THE INVENTION This invention relates to improvements in in-jection moulding machines used for the injection -moulding of synthetic plastic articles. BACKGROUND OF THE INVENTION Injection moulding machines are well known for producing moulded plastic articles from synthetic plastic material, such as, for example polypropylene and other thermoplastic materials and certain ther osetting resins. Because of the nature and operation of the known injection moulding machines, moulded synthetic plastic articles have generally only been produced in a single colour. BACKGROUND ART Several forms of injection moulding apparatus have been proposed to produce articles of two or more materials of different nature or two or more colours. French Patent Application No. 72.28131 proposes a form of apparatus which includes a distribution grill to which is fed plastics material of different colours. The grill has grooves or holes through which.the different plastics materials pass into a pot in ' a predetermined manner, and then all are forced through the injection nozzle into a mould. The plastics materials are fed under pressure to the distribution grill by cyclically actuated cam driven pistons which control the timing and amounts of each plastics material fed to the distribution grill. This apparatus is relatively complex requiring the use of separate piston feed means, piston metering means, cams and cam control means for each of the plastics materials fed to the distribution grill. A method and apparatus for producing composite plastics bodies is disclosed in British Patent No. 1,227,775 in which separate streams of plastics materials are extruded into an annular passageway, surfaces of said passageway being rotatable so as to form layers of the plastics materials as they are extruded. The method and apparatus disclosed in this British patent enables the production of a laminated or reinforced article but, again, the apparatus is relatively complex ai _-_≤ *!"" ** • ' the articles produced are restricted to those of a shape which can be formed around a rotatable mandrel. A method and apparatus for producing by injection moulding a moulded body with a sandwich structure, having an inner core of one material and an outer skin of another material, is disclosed in U.S. Patent Specification No. 3,966,372 in'which a first thermoplastic resin for forming the shell of an article is charged into the front portion of an injection cylinder and a second thermoplastic material, for forming the core of the article, is charged into a rear portion of the injection cylinder so as to contact the first resin in only a central area of the cross-sectional plane of the injection cylinder, and injecting in a mass both first and second resins through a nozzle at the front end of the injection cylinder into the mould cavity. The second resin is enveloped by the first resin to form the sandwich structure. The apparatus disclosed may incorporate a movable mandrel in the injection cylinder which acts to divide the injection cylinder into two chambers and maintain the first and second resins separate. Various other prior patent specifications disclose different apparatus for producing, by injection moulding, an article having an outer surface with a core of a different material. Such prior specifications include U.S. Patent No. 3,894,823, German "Offenlegungsschrift" No. 24 40 193 and Australian Patent No. 458,653. An additive feeder for use in an injection moulding machine is disclosed in Australian Patent No. 430,482 in which an additive feeder nozzle is positioned in the throat of a resin hopper adjacent the feed screw. Movement of the screw causes resin particle swirling resulting in a uniform fix of the additive with the resin particles. It is an object of the present invention to provide an improved injection moulding apparatus which produces an injection moulded plastic article which has a highly decorative surface finish provided by a pattern of two or more colours, or two or more tones of colour and wherein O PI the patterns or colour effect can be varied as desired. It is also desirable to be able to mould synthetic plastic articles in an injection moulding machine using various colour or colour tone combinations of the synthetic plastic material to produce a decorative moulded article. It is also desirable to provide an injection moulding machine having means for combining various colours or various tones of colours of synthetic plastic material so as to produce a moulded article having a decorative appearance created by the colours, or tones of colours dispersed in any desired predetermined manner throughout the moulded article. It is also desirable to provide an injection moulding machine which is able to mould synthetic plastic articles using two or more colours of synthetic plastic material whereby the combination of the colours of material are consistently reproduced i subsequent moulded articles. SUMMARY OF THE INVENTION According to one aspect of the present invention there is provided an injection moulding machine having a die cavity, an injection barrel communicating with the die cavity through an injection nozzle, means for feeding two or more plasticized plastics materials to the injection barrel and means for injecting plastics material in the injection barrel through the injection nozzle into the die cavity, characterized in that a material distribution cylinder is disposed within the injection barrel and defines one end of an injection chamber, said distribution cylinder having a plurality of passageways and/or grooves, said means for feeding the plastics material to the injection barrel include at least some of said passageways and/or grooves whereby the plastics material are conveyed to the injection chamber by the distribution cylinder, and means for moving said distribution cylinder axially and/or rotatively within said injection barrel to provide a predetermined distribution of said plastics material within said injection chamber prior to injection thereof into said die cavity. Preferably, the distribution cylinder has two sets of passageways for feeding first and second plastics OMPI materials to the injection barrel. The first and/or second plastics material are supplied to the distribution cylinder through inlet ports in the sides of the injection barrel which communicate with manifolds formed as circumferential grooves in the surface of the distribution cylinder. With the apparatus of this invention, the distribution cylinder is rotated and/or axially movable within the injection barrel during feeding of the plastics materials to the injection chamber through the plurality of passageways or grooves. The movements of the cylinder are controlled so as to pre-form a desired materials distribution within the injection chamber, which desired distribution can be repeated continuously or varied as desired. Variations in the amounts of the respective materials fed to the chamber may also be used to produce further variations in the pre¬ formed distribution in the injection chamber prior to injection of the materials into the die cavity. Any number of different plastics materials, or materials of different colours, may be fed to the injection chamber through the distribution cylinder. The invention also includes a method of producing an injection moulded plastic article of two or more plastics materials which are different in colour tones, colour or composition comprising the steps of feeding a first plasticized plastics material to an injection chamber through a distribution cylinder located in an injection barrel, feeding a second plasticized plastics material to the injection chamber through the distribution cylinder, controlling the feed and relative movement of the distribution cylinder to thereby control distribution of the first and second plasticized plastics material within the injection chamber, and injecting the dispersed first and second plasticized plastics material in the injection chamber into a die cavity. The invention will be more fully understood by reference to the accompanying drawings. DESCRIPTION OF THE DRAWINGS Figure 1 is a cross sectional side elevational O PI view of one form of the apparatus of the invention, Figure 2 is a cross-sectional view taken along the lines 2-2 of Figure 1, Figure 3 is a cross-sectional view taken along the lines 3-3 of Figure 1, Figure 4 is a cross-sectional side elevational view of a second form of the invention, and Figure 5 is a cross-sectional side elevational view of a further form of the invention. * DESCRIPTION OF PREFERRED EMBODIMENTS Referring to the drawings. Figure 1 illustrates the apparatus of one form of the invention wherein an injection plunger 12 is reciprocally mounted in an injection barrel 13 which terminates at an injection nozzle 14. The nozzle 14 communicates with the interior of a mould cavity 14A which defines the shape of the article to be moulded. A distribution cylinder 16 is disposed in the barrel 13 between the forward end of the plunger 12 and the nozzle 14. The distributor 16 has at its forward end a shoulder 15 provided with radially extending gear teeth 15A. An electric motor 20 is mounted externally of the barrel 13 and has a drive gear 25 which engages with the teeth 15A to rotate the distribution cylinder 16 within the injection barrel 13. The motor 20 may be controlled by a predetermined program to provide a predetermined distribution of plastics material to be injected into the die mould. The forward end of the plunger 12 is formed asa core and the rear end of the distributor 16 has a corresponding shape to closely receive the plunger 12 thereby enabling a close tolerance to be maintained on the material injected into the die cavity 14A. As shown in Figure 1, the distributor 16 has two distribution manifolds 17 and 18 which communicate with the interior of the barrel 13 between the plunger 12 and therear end of the distributor 16 by means of the plurality of passageways 19 and 21 (see Fig.3) . The arrangementofpassage¬ ways 19 and 21 through the distributor 16 is such as to en-_ble a predetermined distribution of plastics material from the • TQRE OMPI two distribution manifolds 17 and 18 so that the "shot" of material which is subsequently injected into the die mould produces a predetermined and repeatable distribution of the plastics materials in the finished moulded product. In the embodiment illustrated in Figures 1, 2 and 3, two plasticized plastics material are fed to an injection chamber 30, comprising part of the interior of the barrel 13 between the rear end of the distributor 16 and the plunger 12, for injection into the mould. It will be appreciated, however, that the plunger 12 may also be provided with additional slots or passageways to enable additional plastics material to be fed to the chamber between the forward end of the plunger 12 and the distributor 16. Thus, the injection plunger 12 may be located on the forward end of a screw feeder in a screw fed injection moulding machine. Referring to Figure 4, the distribution manifolds 17 and 18 may be formed as a pair of circumferentially extending axially spaced grooves in the surface of the distributor 16. The distribution cylinder 16 in both embodiments of the invention illustrated in Figures 1 and 4 is provided with an axially extending passageway 22 which communicates with the nozzle 14. The passageway 22 enables the plastics material within the injection chamber 30 to be injected into the mould cavity by forward movement of the plunger 12. It will be appreciated that the dimensions of the distributor 16 and the interior of the barrel 13 are such as to prevent leakage of plasticized plastics material along the outer surface of the .distributor. Alternatively, appropriate sealing means may be provided to seal the manifolds 17 and 18. Plasticized plastics material is fed to each of the distribution manifolds 17 and 18 through ports 23 and 24 located in the wall of the barrel 13. Each port 23 and 24 communicates with an appropriate plasticizing and feeding screw 34 mounted on the wall of the barrel 13. Such feed £fRE OMPI WIPO apparatus is known in the art and will not be described herein in any detail. A non-return valve 35 is located in each of the ports 23 and 24 to prevent plastics material being forced back into the feed system. The invention herein provides significant advances in the art in being able to feed two separate plasticized plastics materials to the injection chamber 30 located between the forward end of the plunger 12 and the rear end of the distributor 16 with only minor modifications, if any, to existing injection moulding machine apparatus. Thus, the barrel 13 containing the distributor 16 and the associated inlet ports 23 and 24 may be constructed as a discrete unit adapted to be connected to an existing • injection moulding machine in between the normal injection barrel and the die cavity of the machine. In a further modification of the invention as illustrated in Figure 5, the distribution cylinder.is integral with the injection plunger 12 and is provided with one or more distribution manifolds 26 and 27 which communicate with an injection chamber 28 *Ln advance of the plunger 12. Passageways 29 and 31 communicate between the manifolds 26 and 27 and the chamber 28, in a predetermined arrangement, to provide a predetermined distribution of plastics material into the chamber 28. The plunger 12 is rotated by an electric motor 36 mounted externally of the barrel 13 and driving through gears 37 and 38 to gear teeth 39 on the plunger 12. The teeth 39 are separated from the manifolds 26 and 27 by annular shoulder 41. The plunger is reciprocated by hydraulic, mechanical or pneumatic means • known in the art whereby the plastics material within the injection chamber 28 is injected into the mould cavity 14A through the nozzle 34. The manifolds 26 and 27 communicate with ports 32 and 33 in the barrel 13. The ports 32 and 33 receive plastics material from feed apparatus, preferably similar to that shown in Figs. 1 and 4, located externally of the barrel 13, said feed apparatus being arranged to supply plasticized plastics material of the desired colour, colour OM tone or composition to the chamber 28. The passageways 29 and 31 are arranged to provide, with a predetermined rotation of the plunger 12, a predetermined distribution of the plastics material fed to the barrel through the ports 32 and 33. The plunger 12 may be rotated and/or rotationally reciprocated on either the forward injecting stroke or the rearward return stroke, or both, depending on the desired effect to be produced. Further the feed of the various plastics material may be controlled to vary the quantities of the separate materials fed to the injection chamber 28. Control apparatus for controlling movement of the plunger and feed can be programmed to provide constantly repeatable movements and quantities of materials to produce substantially identical moulded articles. The decorative appearance produced in an article by the apparatus of the invention can be varied, as desired, by varying the number, shape and/or location of the grooves and/or passageways in the distributor 16 or plunger 12, by varying the degree of rotation (if any) of the distributor 16 or plunger 12 by varying the amount of second plastics material fed into the injection chamber and by varying the time when the second material is introduced into the ' injection chamber. It has been found that by using two tones of a brown coloured synthetic plastic material a thin walled injection moulded article, i.e. a pot for plants, may be produced having a reproducible tortoise shell appearance. The apparatus of the invention may be used for injection moulding of any suitable mouldable thermoplastic material such as polypropylene, polyethylene, polystyrene, polymethyl methacrylate, and the like. In addition, articles may be produced using two different but compatible thermoplastic materials. While the present invention enables highly decorative plastic articles to be made by injection moulding, such articles having reproducable, predetermined multi¬ coloured effects controlled by the feed and distribution of two or more plastics material, the invention may also be OMPI utilized for producing more practical effects. Thus, it is possible to produce "printing" on an injection moulded plastic article made in accordance with the invention. The method of producing such printing is particularly disclosed in our copending application referred to above. It will be appreciated that the term "different plastic materials" used throughout this specification is meant to indicate plastic materials having different colours, colour tones and/or compositions. Thus, the invention is not limited to the injection moulding of articles from one type of synthetic plastics material having desired colour pigmentation but extends to the method and use of the apparatus for injection: moulding of articles having two or more diverse synthetic resinous materials present therein in distinct and separate phases. It will also be appreciated that a feature of this invention is that the material to be injected into the die cavity to form the moulded product is " conveyed to the injection chamber and interdispersed therein in a pre- determined manner prior-to injection into the die cavity. In the prior apparatus most if not all dispersion of materials takes place during the actual injection of the material into the die cavity. • "rCfR-EATj O PI j, WIPO .

Claims: Claims . 1. An injection moulding machine having a die cavity, an injection.barrel communicating with the die cavity through an injection nozzle, means for feeding two or more plasticized plastics materials to the injection barrell and means for injecting plastics material in the injection barrel through the injection nozzle into the die cavity, characterised in that a material distribution cylinder is disposed within the injection barrel and defines one end of an injection chamber, said distribution cylinder having a plurality of passageways and/or grooves, said means for feeding the plastics material to the injection barrel include at least some of said passageways and/or grooves whereby the plastics materials are conveyed to the injection chamber by the distribution cylinder, and means for moving said distribution cylinder axially and/or rotatively within said injection barrel to provide a predetermined distribution of said plastics material within said injection chamber prior to injection thereof into said die cavity. 2. Apparatus according to claim 1, characterized in that said distribution cylinder is disposed in the injection barrel between said injection nozzle and said means for injecting plastics material into the die cavity and said cylinder is provided with an axially extending passageway communicating said injection chamber with said injection nozzle. 3. Apparatus according to claim 1 or 2, characterized in that said means for injecting plastics material into the die cavity comprises an injection plunger mounted for reciprocal movement within said injection barrel. 4. Apparatus according to claim 1, 2 or 3, characterized in that said distribution cylinder is provided with means enabling the cylinder to be selectively rotated about its axis by drive means located externally of the barrel. 5. Apparatus according to claim 4, characterized in that said drive means comprises an electric motor which selectively rotates said distribution cylinder by inter- OMPI engaging gears. 6. Apparatus according to any one of claims 1 to 4, characterized in that said distribution cylinder is provided with a circumferentially extending groove forming an inlet manifold for said two or more plastics materials, said passageways and/or grooves extending between the manifold and-said injection chamber. 7. Apparatus according to any one of claims 1 to 4 characterized in that said distribution cylinder is provided with two circumferentially extending axially spaced grooves, one groove constituting an inlet manifold for one of said plastics materials and the other groove constituting an inlet manifold for the other of said plastics materials, each manifold communicating with said injection chamber through a plurality of passageways. 8. Apparatus according to claim 3 characterized in that the injection plunger is provided with a conical forward end and said distribution cylinder has a correspondingly shaped rear end to closely receive said conical forward end. 9. Apparatus according to claim 2 characterized in that said distribution cylinder is formed with a circumferential shoulder adjacent its forward end to cooperate with a corresponding shoulder in the injection barrel to prevent rearward movement of the cylinder in the barrel whilst permitting rotational movement thereof. 10. Apparatus according to claim 1 characterized in that said distribution cylinder is formed as an integral . part of an injection plunger which is movable axially in the injection barrel to inject plastics materials in the injection chamber into the die cavity. 11. Apparatus according to claim 10 characterized in that said plunger is provided with a circumferentially extending recess forming a manifold for the two or more plastics materials, said manifold communicating with said injection chamber through said plurality of passageways. 12. Apparatus according to claim 10 or 11 characterized in that said plunger is provided with means O PI enabling it to be rotated about its axis within the barrel by drive means located externally of the barrel. * 13. A method of producing an injection moulded article of two or more plastics materials comprising the steps of feeding a first plasticized plastics material to an injection chamber through a distribution cylinder located in an injection barrel, feeding a second plasticized plastics material to the injection chamber through the injection cylinder, controlling the relative rates of feed and the relative movement of the distribution cylinder to thereby control distribution of the first and second plasticized plastics materials within the injection chamber, and injecting the dispersed materials into a die cavity. 14. A method according to claim 13 including the step of controlling the relative rotation of the distribution cylinder within the barrel. OMPI /.. IPO

Inventors: PROSKE T
Applicants: GARDEN CONTAINERS PTY, PROSKE T
Application year: 1981
Main classification: B29F1
IPC codes: B29C45