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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/38—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process
  • B29C33/3821—Moulds or cores; Details thereof or accessories therefor characterised by the material or the manufacturing process composed of particles enclosed in a bag
• • 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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
  • B29C33/48—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling
  • B29C33/50—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible
  • B29C33/505—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling elastic or flexible cores or mandrels, e.g. inflatable
• • 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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/44—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles
  • B29C33/48—Moulds or cores; Details thereof or accessories therefor with means for, or specially constructed to facilitate, the removal of articles, e.g. of undercut articles with means for collapsing or disassembling
• • 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
  • B29C33/00—Moulds or cores; Details thereof or accessories therefor
  • B29C33/76—Cores

Definitions

• This invention relates to a method of fabricating an inner core tool for casting, an inner core tool fabricated by the method, a moulding method using such an inner core tool and the products resulting from such use. It is particularly concerned with the casting of hollow items in plastics material such as a glass reinforced polymer.
• a moulding is made in one piece using a foam core which is slightly smaller than the required outside dimension of the finished component.
• This foam core is wrapped with glass fibre and placed in a two piece mould. The mould is closed and resin injected to flow between the foam core and the inner mould faces so impregnating the glass fibre. Once the resin has cured the two piece mould is then split apart and the hollow moulding removed.
• a problem with this process is the cost of manufacturing the foam core and the weight of the core which adds to the weight of the finished product.
• the method of fabricating an inner core tool is characterised by the further step of incorporating within the mould bag an expanding device so that in use as an inner mould tool for a lost core moulding process the rigidified inner mould tool can be subjected to internal pressurisation by way of the expansion device so as to urge the mould bag outwardly into contact with material juxtaposed with the mould bag.
• the expansion device comprises a subsidiary inflatable bag; or a capsule containing a pressurised gas, the capsule having a closure adapted to vent the capsule within the mould bag in a controlled manner.
• the step of causing the mould bag to be drawn into contact with the working surface the or each raised region provides for the creation of a channel in an outer surface of the mould bag by incorporating at least one raised region on the working surface.
• the step of causing the bag to be drawn into contact with the working surface is achieved by the application of a sub-atmospheric pressure to the working surface by way of ducts through the walls of the mould.
• the step of filling the interior of the mould bag is undertaken with the interior at substantially atmospheric pressure.
• the step of filling the interior of the mould bag at least in part with particles involves particles of a substantially similar size.
• the step of filling the interior of the mould bag at least in part with particles involves the use of particles which vary in size so that the largest are at least twice the size of the smallest.
• the filling step includes the introduction of non-particulate material which is in filamentary or sheet form.
• an inner core tool characterised in that it is fabricated according to the method of the first aspect or any preceding preferred version thereof.
• the inner core tool includes a flexible heater element adapted for heating so as to supply heat as preliminary step of a moulding process in which the inner core tool is to be used.
• the moulding method for producing a moulded component is characterised by an intermediate step, during or following the step of introducing into the plenum volume polymerisable material, wherein the inner core tool is caused to inflate to enhance contact pressure between particles and the inner side of the mould bag and so between the exterior of the mould bag and material located in the plenum volume.
• a moulded component fabricated by the use of a lost core inner tool according to the second aspect or the first preferred version thereof.
• a moulded component fabricated by way of the moulding method of the first aspect.
• the inner core tool of the present invention is accurately located in a mould.
• the bag and its filling are separately removed from a cured moulded component through a small aperture provided in the hollow component: the particulate material, being very free flowing, can be poured out and the bag, which can be of thin film, is also readily removed through the aperture.
• the proposed system provides a number of advantages over existing systems. There is no sacrificial component in the method (except possibly the mould bag which in any event is inherently cheap); no heating is required to remove the core; accurate reproduction of the finished product is facilitated as no significant shrinkage takes place during the evacuating step; an evacuated core is readily obtained at room temperature using low cost tooling; there is no limitation on the size of the evacuated core that can be fabricated and used; and due to the low density of the particulate materials available (such a micro balloons) the weight of the evacuated core is significantly lower than that of the previously known wax or low melt point metal.
• Figures 1 to 4 is a rigid mould being used to form a rigidified mould bag
• Figure 5 shows a completed rigidified mould bag located in a working mould for the manufacture of a hollow component
• Figure 6 shows a moulded hollow component resulting from the working mould of Figure 5.
• FIGs 1 to 4 variously show the preparation and use of a rigidified mould to produce a hollow moulded component.
• Split case mould 11 is made up of sections 12, 13 hinged along one side to enable the sections 12, 13 to be hinged apart to give access to interior 14 of the mould 11.
• Port 15 provides for access to the interior 14 of the mould.
• Seal 16 bounds moulding surfaces 12 A, 13A once the sections 12, 13 are hinged shut as shown in Figure 1.
• the moulding surfaces 12A. 13A serve to provide an accurate reproduction of an external surface of a hollow component to be manufactured by way of the mould 11.
• a number of vacuum ports 16 are provided through the walls of the sections 12, 13 to enable a sub-atmospheric pressure to be applied to the interior 14.
• Mould 11 is shown closed with a thin walled mould bag 17 hanging in interior 14 of the mould. Interior 18 of the bag 17 communicates with the outside of the mould 13 by way of filling neck 19.
• Ports 16 in walls of the mould 11 provide for a sub-atmospheric pressure to be applied to cause the outer surfaces of mould bag 17 to be drawn into contact with, and so conform closely to, the moulding surfaces 12A, 13 A. If necessary this effect can be enhanced by provision of a slight overpressure to the interior 18 by way of the neck 19.
• Figure 3
• the micro spheres form a mass M which during the filling operation behaves in the manner of a liquid.
• the mass M is shown filling the interior 18 of the bag 17 to the extent that the bag 17 is fully supported in the vicinity of the mould surface 12 A, 13.
• a vacuum is applied to the interior 18 of the bag 17 to withdraw air to a sufficient extent to cause the micro balloons forming the mass M to agglomerate to cause the mass M, and so the mould bag 17, to cohere into a rigid component.
• the filling neck 19 in then sealed off as shown in Figure 4 to preserve low pressure in the interior of the bag 17.
• the rigidified bag 17 obtained as described in connection with Figure 4 is removed from the mould 11 and has pre-formed glass fibre reinforcement 60 wrapped around it and is then located in the interior 61 of a working mould 62 and aligned to provide a casting plenum 63 between the outside of the bag 17 and inside moulding surface 64. Resin is then injected into the casting plenum 63 to immerse the reinforcement 60 and thereafter having cured form the required hollow fabrication F.
• the fabrication F is removed from the working mould 62 and aperture 65 is prepared at one end.
• the bag 17 is cut to vent the interior of the mould bag 17 to atmosphere by way of the atmosphere. This serves to allow the micro balloons making up the mass M to separate slightly from one another and revert to a liquid like behaviour. Consequently the small micro-balloons are readily poured out of the bag 17 by way of aperture 65. Once the micro-balloons have been removed the bag 17 can be withdrawn also. As a result the fabrication F is left hollow. If necessary a filling cap or other closure can be provided for the aperture 65.
• the exemplary embodiment represents a cheap and readily undertaken method of manufacturing hollow fabrications.
• the method is readily undertaken without a need for highly trained manufacturing staff and lends itself to production line use and readily provides for both small and large scale production requirements.
• the exemplary embodiment makes use of a filling of particles of substantially uniform size.
• the filling can comprise other elements.
• it can be of particulate material of different sizes.
• smaller particles can be used for the outer layer of the tool to provided for particularly close conformity of the inner tool surface with the surface to be moulded from when manufacturing the inner core tool and so providing for a high definition of surface for the inner tool in that region.
• the inner part of the filling is then taken up by particles of larger or much larger size.
• the filling can include other forms of material such as filamentary or sheetlike material. The only requirement is that whatever filling material is used it must be capable of being withdrawn form the inner core tool through the aperture.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Moulds For Moulding Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (1)

Family

ID=10745752

Family Applications (1)

Country Status (4)

Families Citing this family (11)

Family Cites Families (6)

• 1994
  • 1994-11-28 WO PCT/GB1994/002599 patent/WO1995014563A1/en not_active Application Discontinuation
  • 1994-11-28 BR BR9408141A patent/BR9408141A/pt not_active Application Discontinuation
  • 1994-11-28 EP EP95902848A patent/EP0730519A1/de not_active Withdrawn
  • 1994-11-28 AU AU11945/95A patent/AU1194595A/en not_active Abandoned

Non-Patent Citations (1)

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