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
  • B29C51/00—Shaping by thermoforming, i.e. shaping sheets or sheet like preforms after heating, e.g. shaping sheets in matched moulds or by deep-drawing; Apparatus therefor
  • B29C51/26—Component parts, details or accessories; Auxiliary operations
  • B29C51/30—Moulds
  • B29C51/36—Moulds specially adapted for vacuum forming, Manufacture thereof
  • B29C51/365—Porous moulds

Definitions

• the invention concerns both a mould and a method for the manufacture of moulded objects of plastic.
• the mould is of the kind permeable for a gaseous work ⁇ ing medium in order to let that medium affect a sheet or a layer of plasticified plastic material through the mate ⁇ rial of the mould in order to bring the material to lie a- gainst the exterior surface of the out-line forming mould surface by suction.
• the plastic material is pre-heated to a suitable plas- ticifying temperature and placed on the mould surface in such a way that it can be brought to lie against the con ⁇ tour of the mould surface by suction, whereafter the object thereby formed is removed from the mould, e.g. by de-suc ⁇ tion or by blowing.
• the object of the invention is to state how this pro ⁇ cessing technique can be performed by means of a mould which is simple and thus cheap to manufacture so that the processing technique mentioned will be advantageous to use also for the manufacture of relatively small series of ob ⁇ jects.
• the mould in accordance with the in ⁇ vention is characteristic thereby that at least the mould surface consists of a particular composite material whose particles are bound together for the formation of an out ⁇ line form stable contour and at the same time defining open passages which extend through the mould material to the ex ⁇ terior of the mould surface.
• Such a mould can be manufactured from a both cheap, inorganic raw material such as sand, and by a processing technique which is simple, of short duration and thus cheap.
• the composite material may ij e composed of particles of different particle size, the particle size being small in the mould forming surface part.
• the mould strength necessary for the carrying out of the processing process can in a simple way be achieved by mixing the particles with suitable binding agents, which may include adhesion improving agents, and that the mould manufactured from such mixture is hardened e.g. by means of heat. Also a wedging between the particles may be ap ⁇ plied in order to give strength to the mould.
• suitable binding agents which may include adhesion improving agents
• a suitable composition of the mould consists according to the invention in that the mould has a basis part below in which the particles are bound together by a real fusion, while the particles in the rest of the mould are bound to ⁇ gether by a hardening fusion compound.
• Such a form presents a good strength and thus will also be able to sustain sub ⁇ stantial working load.
• the method according to the invention is that prior to the suction of a sheet or a layer of plasticified plas ⁇ tic material lying against the contour shaping mould sur ⁇ face, which is permeable for a gaseous working medium, a mould is manufactured with the characteristics stated a- bove, in that at least the mould surface is formed by a particular composite material whose particles are bound to ⁇ gether for the formation of an open stable structure ' with air passages extending to the outer mould surface, and that the suction may then be carried out on the mould thus form ⁇ ed.
• the total manufacturing process, counting from the start of the manufacturing of the mould to the de ⁇ livery of the object manufactured may be substantially cheaper, as it is no longer necessary to manufacture an " ex- pensive metal mould. Therefore it will be possible to apply the suction technique mentioned above in an economically attractive way for the production of also small series of objects, and/or for the manufacture of specially formed ob- jects.
• a particular composite material whose particles are of such size and form that they may be wedged together it will at least partly be possible to avoid using a binding agent.
• the particular composite material is linked to ⁇ gether before the start of the suction by the use of a bin ⁇ ding agent having such surface tension that it seeks to a- chieve the smallest possible surface size.
• the permeability aimed at of the mould can be controlled and adjusted by a suitable selec ⁇ tion of the grain size of the particle material, and di ⁇ - tribution of the grains both in order to achieve favourable conditions for the adhesion connection between the particl ⁇ es, and for an appropriate dimensioning of the porosity, in order to avoid undesired pressure drop across a building material being unnecessarily compact.
• the particular composite material may according to the invention before the start of the influence at the gaseous working medium be linked together by the application of a binding agent which after the compound of the particles leaves a free surface which has been smoothed. This method ensures an adequate surface slip also in cases where the contour shaping surface due to the already mentioned sur-
• the particular com ⁇ posite material particles before the start of the influence at the gaseous working medium be bound together by the ap ⁇ plication of a binding agent which is thermo hardening.
• a binding agent which is thermo hardening.
• the hardened mould may have a good slip effect towards the model which the contour shap ⁇ ing surface of the mould has been moulded against.
• the final mould may thereby become temperature stable to such an extent as to achieve a high degree of freedom for the cleaning of the mould by the application of heat.
• a thermo-hardening binding agent may be applied containing a fusible smoothing agent.
• the mould may e.g. be subjected to a treatment with wax, oil or a teflon product.
• the fusible smoothing agent may counter an undesired depositing or detention of e.g. dust on the outside mould surface. Furthermore, by the application of heat and suction to a fusible smoothing a- gent this may contribute to a cleaning of the porosity of the mould.
• the particular com ⁇ posite material particles before the start of the influence by the gaseous working medium may be linked together by the application of a binding agent, which before the final com ⁇ pound of the particles, presents wedging compound proper ⁇ ties. This may facilitate an easier contour shaping of the mould surface.
• thermo-hardening binding agent re- ference can be given to phenol resin and the wedging com ⁇ pound properties aimed at may e.g. be provided by also ap ⁇ plying silane.
• the removal of an ob ⁇ ject formed by depositing a plasticified plastic material on the outline-forming outside of the mould by suction may be performed in practice by affecting the object by com ⁇ pressed air through the air passages of the mould thus lifting the object free of the mould.
• a transfer mould is usually employed which is adap ⁇ ted for interaction with the side of the object pointing away from the above-mentioned outline-forming outside for the removal of the object from this outside and for the subsequent placing of the object on for instance a conveyer belt.
• a mould used in accordance with the invention can also be produced in such-a way that it may, after use or in case of heavy wear, be regenerated as the particle-shaped build ⁇ ing material of the mould may be recycled.

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Citations (5)

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• 1989
  • 1989-10-24 CA CA 2001294 patent/CA2001294A1/en not_active Abandoned
  • 1989-10-25 CH CH221090A patent/CH677750A5/de not_active IP Right Cessation
  • 1989-10-25 PT PT9209589A patent/PT92095A/pt not_active Application Discontinuation
  • 1989-10-25 ES ES8903595A patent/ES2017054A6/es not_active Expired - Lifetime
  • 1989-10-25 CN CN 89108945 patent/CN1042507A/zh active Pending
  • 1989-10-25 BR BR8905452A patent/BR8905452A/pt not_active Application Discontinuation
  • 1989-10-25 MX MX1809789A patent/MX169789B/es unknown
  • 1989-10-25 GR GR890100688A patent/GR1001026B/el unknown
  • 1989-10-25 AU AU45137/89A patent/AU4513789A/en not_active Abandoned
  • 1989-10-25 WO PCT/DK1989/000252 patent/WO1990004509A1/en unknown

Patent Citations (5)

Non-Patent Citations (1)

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