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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C45/1711—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1732—Control circuits therefor
• • 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
  • B29C45/26—Moulds
  • B29C45/34—Moulds having venting means
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C45/1711—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity
  • B29C2045/1712—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity plastic material flowing back into the injection unit
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C45/1711—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity
  • B29C2045/1714—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles and removing excess material from the mould cavity by the introduced fluid, e.g. to an overflow cavity overflow cavities provided with heating means
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C2045/1726—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles moving the fluid through the hollow using a fluid inlet and a fluid outlet
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C2045/1729—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles fluid venting means
• • 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
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76003—Measured parameter
  • B29C2945/76167—Presence, absence of objects
• • 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
  • B29C2945/00—Indexing scheme relating to injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould
  • B29C2945/76—Measuring, controlling or regulating
  • B29C2945/76177—Location of measurement
  • B29C2945/76254—Mould
  • B29C2945/76257—Mould cavity
• • 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
  • B29C45/1703—Introducing an auxiliary fluid into the mould
  • B29C45/1704—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles
  • B29C45/1706—Introducing an auxiliary fluid into the mould the fluid being introduced into the interior of the injected material which is still in a molten state, e.g. for producing hollow articles using particular fluids or fluid generating substances

Definitions

• the present invention operates in the field of industrial processes for injection molding plastic materials. More in detail the present method is aimed for producing plastic elements that are entirely hollow.
• US6713014 describes a process that is deemed the closest prior art.
• the method comprises the following steps: a) injection of thermoplastic melt from an injection unit, along a melt flow path into the cavity of a mold; b) injection of a fluid into the still-liquid plastic material, such that the plastic material is pressed against the walls of the interspace; c) allowing the plastic material to cool up to forming the self-supporting shaped part and d) removing the molded part from the interspace of the mold.
• the fluid used in the second step b) of the method can be water or a pressurized gas, preferably nitrogen.
• DE19505633 describes a process for making hollow pieces of thermoplastic material that provides for the injection of the thermoplastic melt in the interspace of a mold and the simultaneous or subsequent injection of a pressurized fluid through one or more nozzles.
• the pressurized fluid which is preferably nitrogen, is released through one or more pressure release nozzles separated from the fluid injection nozzles, possibly collected in a recipient and reused.
• a first object of the present invention is therefore that of reducing the costs deriving from the use of nitrogen and other materials, recycling them as much as possible.
• a second object of the present invention is to remove any impurity from the interspace within the just-produced hollow object.
• a machinery and a method are proposed for making hollow elements by means of injection molding, which effectively solve the abovementioned problems.
• the machinery comprises a mold constituted by a matrix and a cooperating punch, which in closed configuration describe an interspace having the external form of the object to be attained.
• a secondary space is arranged in which the excess thermoplastic material melt is poured - i.e. that resulting from the internal excavation of the object.
• a valve is present in the connection duct that reversibly opens and closes based on the operating step.
• a perforating element is also arranged which is adapted to perforate the thermoplastic shell in order to allow the outflow of the nitrogen that forms, in one step of the method described in detail hereinbelow, the cavity in the obtained piece.
• a gas introduction tube is connected to the main interspace of the mold and, depending on the current operating step, is adapted to convey nitrogen or compressed air within the interspace, which are coming from respective tanks and whose entrance in the mold is regulated by corresponding valves.
• a first suction valve placed at said perforating element, advantageously adapted to suction the nitrogen from the interior of the interspace and to introduce it into a first recycling duct adapted to transfer the gas from the interspace to the pressurized gas feed tube in order to be advantageously reused in a subsequent molding cycle;
• a second suction valve adapted to suction the air from the interspace and from the secondary space of said mold, creating reduced pressure useful for the first step of the method described hereinbelow.
• the molding of a piece made of thermoplastic material, provided with a cavity, making use of the machinery, object of the present invention, is carried out at least according to the following steps:
• thermoplastic material melt in the interspace by means of said nozzle, upon closure of the second air suction valve.
• the second valve which places the interspace in communication with said secondary space, is closed;
• the cavity is created which is provided within the piece under production.
• the nitrogen is introduced at a pressure such to also reach the secondary space;
• the impurities possibly present in the cavity of the piece are removed and the solidification of the thermoplastic melt is accelerated;
• a compressed air treatment device is advantageously also used, before such compressed air is introduced into the interspace of the mold.
• the air can be introduced at the desired temperature and pressure and possibly also dried and purified.
• a second recycling duct which, from the air suction valve, conveys the suctioned air into the treatment device and then into the duct for feeding the compressed air into the interspace of the mold.
• thermoplastic melt can also be advantageously arranged by means of the following devices:
• thermoplastic material melt - a system of heating elements, organized on the internal walls of the secondary space in order to maintain the thermoplastic material melt at the fluid state during the entire molding process; - a third suction valve adapted to remove the thermoplastic melt at the fluid state from said secondary space and to convey it into a recycling duct which leads it back towards the introduction nozzle;
• FIGURE 1 shows a moment of the second step B of the present method
• FIGURE 2 shows a moment of the third step C of the present method
• FIGURE 3 shows a moment of the fourth step D of the present method
• FIGURE 4 shows a moment of the fifth step E of the present method
• FIGURE 5 shows a moment of the sixth step F of the present method
• FIGURE 6 shows a moment of the seventh step G of the present method.
• a mold is shown that constitutes the central and essential part of the machinery of the present invention.
• this too is provided with a matrix 1 and with a punch 2 which, when arranged in a closed configuration, define an interspace 3 and a secondary space 8 connected by a connection duct 7.
• Said interspace 3 is communicating on one side with a nozzle 4 for introducing thermoplastic material melt 100.
• the interspace 3 is connected with a tube 5 for feeding pressurized gas which, due to a first valve 6, controls the introduction of nitrogen 300 into the interspace 3 of the mold.
• the mold is provided with a second valve 9 which opens or closes the communication between the interspace 3 and the secondary space 8, and with a perforating element 10 which is adapted to perforate the piece 200 being molded up to attaining the cavity 20 thereof.
• an air treatment device 16 that regulates pressure, temperature, drying and purification of the pressurized air 400 to be fed within the mold;
• a second suction valve 14 that suctions the air from the interspace 3 and from the secondary space 8 of the mold and introduces it into a second recycling duct 14’, which leads it back to the air treatment device 16 and hence to be newly introduced into the interspace 3 in the subsequent molding cycle;
• thermoplastic material melt 100 at the fluid state
• thermoplastic melt 100 at the fluid state from the secondary space 8 itself, before the solidification and extraction of the piece 200 from the mold.
• the collected thermoplastic melt 100 is conveyed into a recycling duct 15’ adapted to lead it back from secondary space 8 once again towards the introduction nozzle 4;
• the second step of the method object of the patent, is shown.
• the first step A due to the second air suction valve 14, slight reduced pressure was created in the interspace 3 of the mold which facilitates, in the second step of injecting the melt B, the entrance of the thermoplastic melt 100 from the nozzle 4 and its uniform and quick dispersion in the interspace 3.
• valve 9 is open and also the secondary space 8 is filled with thermoplastic melt 100 at the fluid state.
• the fourth step D is shown for introducing the nitrogen 300 by means of the stopping of the injection of the melt 100 and the opening of the first valve 6 in the pressurized gas feed duct 5.
• the cavity 20 is created in the piece 200 under production and the nitrogen 300 opens a passage in the thermoplastic melt 100 up to attaining the secondary space 8.
• the feeding of nitrogen 300 is interrupted and, simultaneously, the piece 200 is perforated in the section corresponding to the connection duct 7, by means of the perforating element 10. This allows the outflow of the nitrogen 300 towards the first suction valve 13 and its subsequent conveyance into the first recycling duct 13’ for the reuse of the gas in the following molding cycle.
• the sixth step F shown in FIG. 5, provides for opening the second valve 12 in the feed duct 11 for feeding compressed air 400 and introducing the latter in the cavity 20 of the piece 200 for the removal of impurities therefrom and for accelerating the solidification of the thermoplastic melt 100.
• the seventh and last step G (FIG. 6) consists of opening the mold and extracting the molded piece 200, by now solidified with the cavity 20 thereof.

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Citations (7)

• 2018
  • 2018-02-06 IT IT201800002428A patent/IT201800002428A1/it unknown
• 2019
  • 2019-02-04 WO PCT/IB2019/050863 patent/WO2019155341A1/en active Application Filing

Patent Citations (7)

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