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
  • B29C51/32—Moulds having cutting 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor
  • B29C48/03—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus therefor characterised by the shape of the extruded material at extrusion
  • B29C48/07—Flat, e.g. panels
• • 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
  • B29C51/02—Combined thermoforming and manufacture of the preform
• • 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
  • B29C51/261—Handling means, e.g. transfer means, feeding 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
  • B29C2791/00—Shaping characteristics in general
  • B29C2791/004—Shaping under special conditions
  • B29C2791/006—Using vacuum
• • 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
  • B29C2793/00—Shaping techniques involving a cutting or machining operation
  • B29C2793/0081—Shaping techniques involving a cutting or machining operation before shaping
• • 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
  • B29C48/00—Extrusion moulding, i.e. expressing the moulding material through a die or nozzle which imparts the desired form; Apparatus 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
  • 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
  • B29C51/10—Forming by pressure difference, e.g. vacuum
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2023/00—Use of polyalkenes or derivatives thereof as moulding material
  • B29K2023/04—Polymers of ethylene
  • B29K2023/06—PE, i.e. polyethylene
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
  • B29K—INDEXING SCHEME ASSOCIATED WITH SUBCLASSES B29B, B29C OR B29D, RELATING TO MOULDING MATERIALS OR TO MATERIALS FOR MOULDS, REINFORCEMENTS, FILLERS OR PREFORMED PARTS, e.g. INSERTS
  • B29K2027/00—Use of polyvinylhalogenides or derivatives thereof as moulding material
  • B29K2027/06—PVC, i.e. polyvinylchloride

Definitions

• the traditional method ermo- t ormage uses a cycle f roid for performing pieces formed of a thin wall; an e :: extruder comprising a flat die continuously manufactures a strip of plastic material, with a thickness ranging from a fraction of a millimeter. ten millimeters and a width determined by that of the sector; this strip of thermo-plastic material is generally calendered between rollers :: at the outlet of the machine, to adjust the thickness thereof, while it is still plastic then it is cooled and cut into standard size sheets.
• these plates are optionally cut again according to the characteristics of the shape to be coated; they are reheated, generally by panels :: radiant radiant in 1 î nf ra-r ouge then introduced ua ⁇ s the mold; the mold generally consists of a horizontal joint plane placed at its upper part, the shape to be molded being in a cavity placed below the joint plane; the plate is pinched on the joint plane of the mold so as to create a sealed volume with the mold cavity; the molding is generally done by placing the cavity thus closed in depression, while the plate comes to marry by creep, under the action of atmospheric pressure, the shape of the bottom of the oule cavity.
• thermoforming When it comes to manufacturing large series of small parts, such as small Swiss jars, skin-formed from thin sheets, a hot cycle thermoforming is used; the sheet is continuously extruded slipped on a horizontal carpet; the leaf is pinched laterally by pins which connect it to two: lateral drive chains which accompany it throughout the cycle; it is conditonnée temperature while the side chains on the lead a chain î mobile did horizontal multiple molds where it is molded as indicated here above pre; the separation of thermoformed objects only takes place on the finished part.
• Large series of large parts are
• SUBSTITUTE SHEET ⁇ RULE 26 made, in the hot cycle from an extruded sheet held laterally by a raiting chain as in the previous example; the mold is moved back and forth accompanying the movement of the sheet in the molding phase and, after demolding, returning to position upstream at a new portion of thermoform sheet; part separation is only done at the end of the cycle.
• blowing extrusion technique for the manufacture of hollow bodies: in thin walls such as bottles using a hot tube; it consists in extruding a tube ically. forming what is called a free parison the length of which is pinched in the joint plane of a mold and separated from the upstream part of the parison; the mold is retracted and the tube is then inflated with compressed air to allow the tube to marry, by creep under air pressure, the shape of each half mold in order to thus form a hollow body with thin wall; during this time the extruder extrudes the free parison length necessary for molding the next part.
• thermoforming technique which uses a cold cycle requires heavy means of extruding the plates which must be of great precision to allow the calendering which is itself imposed to allow uniform heating of the plate.
• the handling of the plates, their cutting and their reheating generate additional processing costs which generally lead to the abandonment of this technique for large series.
• Large series using the hot cycle require heavy mobile molding equipment.
• the ob j e and the invention is to combine the advantages of both techniques, extrusion blow molding and thermoforming, to produce parts the mo-formed wall thin in hot cycle.
• Fig.1 shows an exploded perspective view of the device according to the invention open molding device.
• the F ⁇ g.2 represents a perspective view of the device of the F ⁇ g.1 with the closed and retracted molding device.
• Fig.3 shows a perspective view of the mold part of the molding device according to a preferred version of the invention.
• the F ⁇ g.4 represents a perspective view of the part against the mold of the molding device.
• the F ⁇ g.5 to 9 show in section of the molding device the various phases of the thermoforming cycle according to a preferred version of the invention.
• the F ⁇ .10 rep és n e an erspective view of the extrusion device of the flat parison according to a preferred version of the invention.
• FIG. 16 represents an exploded perspective view of a device for cutting the thermoformed part during cycle.
• the invention consists in extruding vertically from a flat die (1) a length of a strip of thin plastic material, which will be called hereinafter "flat parison ( 2) ", to condition it at temperature, and to introduce it into a thermoforming device (7) formed by a mold ( 3 ) and a counter mold (4) which clamps a length of flat parison ( 2) in its joint plane (5) which is in a vertical position, to separate it from the upstream part ( 6 ) of the flat parison (2) located between the molding device ( 7 ) and the die ⁇ 1>, to retract the molding device ( 7 ) F ⁇ g.2 in order to carry out the thermoforming of the part; meanwhile the flat die (1) extrudes a flat parison length (2) sufficient for the rmo-f form the next part.
• the thermoforming device comprises a mold f ⁇ g.3 which is composed of two. parts; the first part consists of a frame (10) supporting the joint plane (13) and the second part constitutes the impression (11) of the form (14 ) to be molded; the frame (10) and the imprint (11) slide relative to each other by means of guide columns (12).
• a blade ( 21 ) F ⁇ g.3 is fixed on the imprint so • _.
• the counter mold F ⁇ g.4 and (4) F ⁇ g.5 comprises a cavity (19) bordered by a joint plane (20) which comes to apply F ⁇ g.6 on the joint plane (13) of the frame (10) of the mold (3) in order to pinch the flat parison (16); this cavity (19) is deep enough to contain the volumes which exceed the joint plane when the molding device is closed: in a preferred version of the invention, the cavity (11) is provided with vents for evacuation air contained between the flat parison (16) and the cavity (11); when the molding device is closed on a flat parison (16) F ⁇ g.7 compressed air is injected into the cavity (19) F ⁇ g.8 of the counter mold (4) as we do to blow a bottle and we plate the flat parison ( 16 ) on the form (18) the imprint (11); the mold carriers having closing pressures of several tonnes, this makes it possible to use compressed air pressures of several bars and to obtain a very good surface quality of the part ( 24 ) F ⁇ g.9 thus the mo- formed.
• the version of the invention which we have just described can be suitable for amorphous thermo-plastic materials such as polyethylenes or ⁇ o lych 1 o rural vinyls; it can allow the use of existing blow molding machines without major modifications; however, the process is not suitable for thermoforming of so-called crystalline thermoplastic materials, the viscosity of which drops very rapidly as a function of the temperature in the temperature zone co res undulating at the extrusion temperature.
• this problem is solved by extruding the material continuously on a movable belt (preferably 25 ⁇ horizontal which moves at substantially constant speed relative to the die).
• the material is conditioned in temperature, by a temperature conditioning device (28). to bring it to a temperature where the internal friction between the molecules is sufficient to slow the creep.
• a temperature conditioning device 28
• the material can be extruded between 200 and 300 degrees centigrade and brought to the moving belt ( 25 ) at a temperature of the order of 80 to 100 degrees centigrade which may correspond to what is called for certain materials the caout zone chout i que and which reduces the time of cycle.
• the flat parison (27 ) At the end of the moving belt, the flat parison (27 )
• Fig. 11 hangs in a vacuum to be able to be taken between the mold ( 3 ) and the counter mold (4) when it has reached a sufficient length as described above.
• One way of achieving synchronization between the movements of the moving belt (25) and the movements of the extruder ( 30 ) is to use a synchronous motor to drive the drum motor (32) of the moving belt (25); a link chain ( 33 ) in closed loop is driven by a pinion ( 34 ) , integral with the motor drum (32) of the moving belt ( 25 ) , at the same
• the speed of the motorized wheels (35) can be slightly modulated during the cycle to vary the thickness of the flat parison (27 ⁇
• a molding device which remains in place once it is closed since the e - 1 seamer ( 30 ) deposits the material on the movable belt (25) which is immobilized then introduces it between the mold (3) Fj.13 and the con r - oule (4; lo sque the molding device ( "is open and the previous part (36) F ⁇ g.11 gée.
• the counter mold (3) F ⁇ g.4 has a cavity (19) inside which it is possible to place one or more cutting devices F ⁇ g.16 allowing the cutting of elements of the thermoformed part and working in the atmosphere of the thermoforming air pressure; a cutting device comprises a cutting tool (37) and an operating device (38) thereof; without this example being limiting, the operating device (38) can be made up of one or more preferably hydraulic jacks which apply the cutting tool (37) to the area to be cut at the same time as the material is applied to the shape of the impression by air pressure.
• the force necessary to ensure a good cut is several 1- lonewtons per centimeter of cut added to the gas pressure in the counter-mold which can be of the order of 8 to 10 bars can impose closing forces.
• the temperature of the material can be regulated by natural cooling and or by forced convection with the aid of a temperature conditioning device (28); when using fans it is preferable to fix the temperature conditioning device (28) to the frame (31) of the extruder so that whatever the movements of the moving belt (25) are cooling in forced convection remains essentially the same.

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• Engineering & Computer Science (AREA)
• Mechanical Engineering (AREA)
• Manufacturing & Machinery (AREA)
• Blow-Moulding Or Thermoforming Of Plastics Or The Like (AREA)

Applications Claiming Priority (3)

Publications (1)

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• 1996
  • 1996-07-19 FR FR9609344A patent/FR2751266B1/fr not_active Expired - Fee Related
• 1997
  • 1997-07-16 AU AU37730/97A patent/AU3773097A/en not_active Abandoned
  • 1997-07-16 WO PCT/FR1997/001319 patent/WO1998003325A1/fr not_active Ceased
  • 1997-07-16 EP EP97934572A patent/EP0920372A1/de not_active Withdrawn

Non-Patent Citations (1)

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