Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/17—Component parts, details or accessories; Auxiliary operations
  • B29C45/46—Means for plasticising or homogenising the moulding material or forcing it into the mould
  • B29C45/58—Details
  • B29C45/581—Devices for influencing the material flow, e.g. "torpedo constructions" or mixing devices
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/16—Making multilayered or multicoloured articles
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
  • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
  • B29C45/16—Making multilayered or multicoloured articles
  • B29C45/1634—Making multilayered or multicoloured articles with a non-uniform dispersion of the moulding material in the article, e.g. resulting in a marble effect

Definitions

• This invention relates to improvements in injection 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, for example polypropylene. 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.
• 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 housing, an inner surface of said housing being rotatable to form layers of the plastics materials.
• a method and apparatus for producing a moulded body with a sandwich structure by injection moulding is disclosed in German Patent Specification No. 2,425,627 in which first and second plastics materials are fed to an injection cylinder having an injection nozzle at one end thereof communicating with a mould cavity, an inner cylinder, which divides the injection cylinder into front and rear chambers, and a conventional injection screw.
• the first and second plastics materials are injected as a . single mass into the mould cavity in such a manner that • the second plastics material is enveloped by the firs plastics material to produce the moulded sandwich structure.
• an injection moulding machine having an injection head arranged for at least reciprocal movement in a. barrel, first means feeding plasticized plastics material to be moulded to said injection head, at-least second means feeding further plasticized plastics material to the injection head, said injection head having passage means to distribute said first and second plasticized plastics materials in a predetermined manner for injection into said injection moulding machine, said injection head being reciprocal in said barrel to inject the said plastics materials into the moulding machine die cavity.
• the invention also provides an injection moulding machine having a die cavity, a barrel communicating with said die cavity, plasticizing and feed means wherein plastics material to be moulded is heated, plasticized and fed to said barrel to be injected in predetermined quantities into the die cavity, characterized in that an injection plunger is provided in said barrel between said feed means and said die cavity, said plunger being at least reciprocal in said barrel, and possibly also rotatable, said plunger having a predetermined number and array of generally axially extending passageways and/or grooves through which a first plastics material may be fed from said plasticizing and feed means, a second feed and plasticizing means mounted on the barrel and arranged to feed a second plastics material to the barrel, the array of grooves and/or passageways in the plunger providing a predetermined distribution of the first and second plastics material when injected into said die cavity.
• the plunger is mounted coaxially with a rotatable feed screw which operates to plasticize and feed the plasticized plastics material to the die cavity.
• a second barrel is mounted on the first barrel and a further rotatable screw in the second barrel is selectively operated to feed the second plasticized material to the plunger.
• the plunger is preferably formed with an annular channel or groove into which the second plasticized material is fed. Axially extending grooves on the surface of the plunger convey t second plasticized material to the front end of the plung the arrangement of the axially extending grooves providin a predetermined distribution of the second plasticized material.
• the array of grooves and/or passageways may include a passageway extending axially from the rear end of the plunger towards the forward end thereof.
• the axial passa way communicates with one or more further passageways at the forward end of the plunger which open out on the fron end surface of the plunger to distribute the first plasti material fed to the axial passageway.
• the invention also includes a method of producing multi-coloured injection moulded plastic article comprisi the steps of feeding a first plasticized plastics materia to an injection chamber, feeding a second plasticized plastics material of a different colour to that of the fi plastics material to the injection chamber, controlling t feed and distribution of said first and second plastics material to provide a predetermined distribution of the materials in the injection cavity, and injecting the firs and second plastics material into a die cavity.
• Figure 1 is a cross-sectional side elevational view of one form of the apparatus of the invention
• Figure 2 is a cross-sectional side elevational view of the apparatus of Figure 1 but showing the plunger in a rearward position
• Figure 3 is a cross-sectional view taken along t lines 3-3 of Figure 1,
• Figure 4 is an enlarged perspective view of a portion of a mould die formed in accordance with a featur of the invention.
• Figure 5 is a perspective view of a container mad in accordance with the invention.
• the apparatus of the embodiment of the invention illustrated comprises a barrel extension 32 which is mounted coaxially on the forward end of the barrel 11 of a conventional injection moulding machine.
• the feed screw 12 is rotatable and axially movable relative to the barrel 11 so as to plasticize synthetic plastics material supplied to the barrel and to convey the plastic- ized material to the forward end of the barrel 11 whereat a plunger head 13 injects the plasticized material into a die cavity 15.
• the barrel 11 is normally heated by suitable heating means such as steam, hot water or electrical heating elements (not illustrated) .
• the barrel extension 32 is mounted on the barrel 11 and communicates with a die cavity 15 through injection nozzle 36.
• a second conventional extruder having a second barrel 14 housing a plasticizing feed screw 16 is mounted to the barrel extension 32 by bolts 22 and communicates with the interior of the barrel extension 3 ' 2 through a non ⁇ return valve 18 which permit plastics material to enter the barrel extension 32 through passageway 17, but prevent the material flowing back into the extrusion chamber of the second extruder.
• a plunger 31 in the barrel extension 32 extends substantially axially forwardly of the feed screw 12.
• the plunger 31 is connected to the feed screw 12 by a collar 10 which permits relative rotation of the plunger 31 with respect to the feed screw 12 but causes the plunger 31 to move axially in the barrel extension 32 during reciprocal ' ⁇ movement of the feed screw 12.
• the plunger 31 is formed with an axial passageway 33 which communicates at its rearward end with the interior of the barrel 11 through passageways 34.
• the forward end of the axial passageway 33 opens into an injection chamber 35 in the barrel extension 32 through an array of passage ⁇ wa s 37.
• the outer surface of the plunger 31 has a substan ially annular channel 38 which communicates with the interior of the second barrel 14 through the passageway 1 to receive second plastics material therefrom.
• the annul channel 38 also opens into the injection chamber 35 throu a further predetermined arrangement of substantially axially extending grooves or slots 39 in the forward end of the plunger 31.
• the plunger may be permitted to rotate wit the feed screw. If desired the rotation may be controlle by guide means on the plunger 31 and the barrel 11, or by external rotating means connected through a wall of the barrel 11 or barrel extension to drivingly engage with th plunger 31.
• the material in the injection chamber 35 is injec into the die cavity 15 through nozzle 36 by forward movem of the screw 12 and plunger 31 to produce a predetermined dispersion of the first and second plastics material throughout the article which is moulded therefrom.
• the plastics material in the mould cavity 15 cools and the moulded article is removed from the die, whereupon the moulding cycle is repeated.
• 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 plunger 31, by varying the degree of rotation (if any) of the plunger, by varying the amount of second plastics material fed into the injection chamber 35 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 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.
• articles may be produced using two different but compatible thermoplastic materials.
• 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 utilized for producing more practical effects.
• a moulded thin-walled plastics article such as a container, pot or the like, having an external layer of one plastics material or- a plastics material of one colour and an internal layer of either a different plastics material or a plastics material of a different colour to that of the outer layer.
• one of the dies 46 forming the die cavi 15 is formed with raised, stepped up or embossed letterin 48 or designs, patterns or the like, as shown in Figure 4.
• lettering 48 will be described although the invention is not so limited.
• the article 47 to be formed is then produced by injection into the die cavity of a two colour plastics material in the manner previously described with the two colours having a distribution so as to produce tw layers of the plastics material each layer being of a different colour.
• the distribution of the two coloured plastics material injected into the die cavity 15 is controlled, a above described, so that layers of the plastics material occur at at least that part of the die cavity 15 adjacent the raised lettering 48.
• the thickness of the layer of plastics material adjacent the die 46 having the lettering 48 is arranged t be equal to or less than.the height h of the lettering 48. Therefore the outermost surface 49 of the lettering 48 contacts the other layer of plastic material in the mould.
• the finished moulded article 47 therefore, exhibits an outer surface of the layer of plastics materi which was adjacent the embossed die 46 which is dis ⁇ continuous at the areas produced by the embossed or raise lettering 48 on the die 46 to expose the other plastics material, which is of a second colour.
• the impression given is one of the outer surface being engraved or cut away to expose the different colour of the underneath plastics layer.
• the plunger 31 may be formed with circumferential shoulders to restri ⁇
• the second plastics material may be caused to be fed intermittently to the injection chamber 35 to thereby provide layers, rings, circles or other varying amounts of the second plastics material dispersed throughout the first plastics material.

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• Engineering & Computer Science (AREA)
• Manufacturing & Machinery (AREA)
• Mechanical Engineering (AREA)
• Chemical & Material Sciences (AREA)
• Dispersion Chemistry (AREA)
• Injection Moulding Of Plastics Or The Like (AREA)

Applications Claiming Priority (4)

Publications (2)

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Family Applications (1)

Country Status (3)

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Citations (2)

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• 1981
  • 1981-02-27 WO PCT/AU1981/000029 patent/WO1981002407A1/en not_active Application Discontinuation
  • 1981-02-27 EP EP19810900509 patent/EP0052607A4/de not_active Withdrawn
  • 1981-02-27 JP JP50072081A patent/JPS57500277A/ja active Pending

Patent Citations (2)

Non-Patent Citations (1)

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