EP1109661A4 - Appareils et procedes pour le thermoformage de feuilles en paire - Google Patents

Appareils et procedes pour le thermoformage de feuilles en paire

Info

Publication number
EP1109661A4
EP1109661A4 EP99928252A EP99928252A EP1109661A4 EP 1109661 A4 EP1109661 A4 EP 1109661A4 EP 99928252 A EP99928252 A EP 99928252A EP 99928252 A EP99928252 A EP 99928252A EP 1109661 A4 EP1109661 A4 EP 1109661A4
Authority
EP
European Patent Office
Prior art keywords
sheet
mould
sheets
support means
heater
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99928252A
Other languages
German (de)
English (en)
Other versions
EP1109661A1 (fr
Inventor
Daniel Witten-Hannah
Stewart Vaughan
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Fischer & Paykel Ltd
Original Assignee
Fischer & Paykel Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Fischer & Paykel Ltd filed Critical Fischer & Paykel Ltd
Publication of EP1109661A1 publication Critical patent/EP1109661A1/fr
Publication of EP1109661A4 publication Critical patent/EP1109661A4/fr
Withdrawn legal-status Critical Current

Links

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
    • 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
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C49/06905—Using combined techniques for making the preform
    • B29C49/0691—Using combined techniques for making the preform using sheet like material, e.g. sheet blow-moulding from joined sheets
    • 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
    • B29C51/262—Clamping means for the sheets, e.g. clamping frames
    • 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
    • B29C2949/00—Indexing scheme relating to blow-moulding
    • B29C2949/30—Preforms or parisons made of several components
    • B29C2949/3086—Interaction between two or more components, e.g. type of or lack of bonding
    • B29C2949/3094—Interaction between two or more components, e.g. type of or lack of bonding preform having at least partially loose components, e.g. at least partially loose layers
    • 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
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • 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
    • B29C49/00—Blow-moulding, i.e. blowing a preform or parison to a desired shape within a mould; Apparatus therefor
    • B29C49/02—Combined blow-moulding and manufacture of the preform or the parison
    • B29C49/06905—Using combined techniques for making the preform
    • B29C49/0691—Using combined techniques for making the preform using sheet like material, e.g. sheet blow-moulding from joined sheets
    • B29C49/06916—Means for avoiding parts of the sheets to stick together, e.g. to provide blow opening
    • 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
    • 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
    • B29C51/14—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 using multilayered preforms or sheets
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29L—INDEXING SCHEME ASSOCIATED WITH SUBCLASS B29C, RELATING TO PARTICULAR ARTICLES
    • B29L2009/00—Layered products
    • B29L2009/001—Layered products the layers being loose

Definitions

  • This invention relates to apparatus and methods for twin sheet thermoforming and in particular to improve methods and apparatus which do not require a sheet supporting framework.
  • Twin sheet thermoforming is becoming increasingly popular in formation of large articles. Applications such as refrigerator cabinets and other large appliance cabinets have been envisaged, see for example US patent 5374118. That specification describes a process wherein twin extruded sheets are fed directly between opposed mould halves which are then brought together to form the panels of a cabinet. Such a method creates significant material handling problems and material wastage problems with the material being continuously extruded while the moulding process is a non continuous process. Consequently it is considered more appropriate in this area to cool thermoplastic sheets which can be heated immediately before moulding.
  • the invention consists in apparatus for twin sheet thermoforming comprising: a pair of opposed mould halves relatively movable between an open position and a closed position during the thermoforming process, sheet support means associated with each said mould half, each mould sheet support means connected to its respective mould half and configured to hold a thermoplastic sheet around its edge, the sheet support means configured to hold the respective sheet apart from one another with said mould halves in their open position, each said mould half, its respective support means, and a sheet held in place by said support means together defining a pressurised volume, and means associated with each said mould half which can create a controlled pressure differential between its respective defined volume and the outside thereof.
  • the invention consists in a method of twin sheet thermoforming comprising: holding a heated thermoplastic sheet on each of a pair of mould halves, in a manner to provide a sealed volume between said sheet and said mould half, while controlling the air pressure differential between each space enclosed between a respective sheet and its respective mould half to guard against sagging of either said sheet, altering said pressure differentials to ensure that the narrowest space between the sheets occurs at, and only at, portions thereof intended to become in contact and form seams therebetween, moving said mould halves toward one another while increasing the effect of the pressure differentials, and causing each said sheet to seat itself against an annular weld region, and continuing to bring said mould halves together to bring together said weld regions and cause a seam to be created between said weld regions.
  • each mould half incorporates a sheet support means which can hold a sheet by its edge and support the sheet during heating and wherein at least one said sheet support means can retract during thermoforming.
  • Figure 1 is a cross sectional elevation of a twin sheet thermoformer with sheets and heater in place according to the embodiment of the present invention wherein the secured sheet edges remain separated
  • FIG 2 is a perspective view of a part of the thermoformer of Figure 1 showing the sheet support means, an abutment member and a section of the mould cavity,
  • FIG. 3 is a cross sectional elevation of a part of the thermoformer of Figure 1 with the heater now removed and the thermoforming process partly progressed,
  • Figure 4 is a cross sectional elevation as in Figure 3 with the thermoforming process further progressed
  • Figure 5 is a cross sectional elevation as in Figure 4 with the thermoforming operation substantially completed and the twin sheets seamed together,
  • Figure 6 is a cross sectional elevation of twin sheet thermoforming apparatus according to an alternative embodiment of the present invention wherein the seam forming mould edges are incorporated in the sheet support means and in-mould trimming of the finished product can be achieved,
  • Figure 7 is a cross sectional elevation of part of the apparatus of Figure 6 with the thermoforming operation partly progressed
  • Figure 8 is a cross sectional elevation as in Figure 7 with the thermoforming operation further progressed with the sheets just joined,
  • Figure 9 is a cross sectional elevation as in Figure 8 with the thermoforming operation almost complete.
  • Figure 10 is a cross sectional elevation as in Figure 9 wherein the thermoforming operation has been completed and in-mould trimming has been accomplished by the guillotining effect between the upper sheet support means and the lower mould half,
  • Figure 11 is a cross sectional elevation through a sheet support member accoding to one embodiment of the present invention
  • Figure 12 is a cross sectional elevation through twin sheet forming apparatus according to a further alternative embodiment of the present invention.
  • Figure 13 is a cross sectional view through twin sheet forming apparatus according to Figure 1 and a sheet carrying heater assembly according to a further aspect of the present invention
  • Figure 14 is a cross sectional elevation through a region of twin sheet forming apparatus and associated sheet carrying heater assembly depicting clamps used in sheet transfer and including some hidden detail in shown in broken line,
  • Figure 15 is a perspective view of one embodiment of heater apparatus adapted to accommodate sheets of differing sizes
  • Figure 16 is a perspective view of an alternative embodiment of heater apparatus adapted to accommodate sheets of differing sizes.
  • apparatus for twin sheet thermoforming is shown in cross section having a lower mould half 1 and an upper mould half 2.
  • the thermoformer is shown with a pair of thermoplastic sheets 5,6 in place.
  • Each sheet 5 or 6 is supported on its respective mould half 1 or 2 by a sheet support means 11 movably connected to a general body 10 of the mould half.
  • the sheet support means in the preferred form is configured as an annular support member 11 fitted within an annular groove 12 which surrounds the mould cavity 16 of the mould half.
  • the sheet support member 11 holds the sheet along its edge 51 , for example by use of an annular vacuum seal 20.
  • Other means of securing the sheet around its edge may be used instead.
  • a series of hinged and locked down clamps which could be manually or automatically operated, for example by solenoid or pneumatic means, could be used.
  • Figures 11, 12 and 14 illustrate means for securing the sheet of this type and will be described in detail further on.
  • the support member 11 is shown in what is preferably a substantially fully extended position, which for example may be limited by a series of dowels and slotted holes or any other suitable means, and is able to be depressed into the channel 12 so that the mould half bodies 10 may be brought together until opposed seam regions 17 of the mould halves are substantially abutting.
  • a series of springs 13 are disposed within the channel 12, between the bottom face 13 of the support member 11 and the base 15 of the channel 12 to provide graduating and increasing resistance to the depression of the support member 11.
  • Clearly means other than springs may be provided such as carefully controlled mechanical actuators, hydraulic or pneumatic actuators or any other suitable devices, springs merely being among the least complex options.
  • abutting members 19 may be provided extending from the opposed surfaces 18 of the support members 11 to provide an abutment 28 therebetween.
  • the abutting members 19 also allow reasonable access between the sheets, for example, for insertion of radiant heaters 9 to heat the thermoplastic sheets 5, 6. Where insertion of the heater, for example, may require additional separation this may be achieved by controlling the platen separation or by having one or more of the abutting members 19 proportionally longer and being resiliently depressible into a cavity by that amount of its length.
  • thermoforming method accomplished by the apparatus of Figure 1 is demonstrated.
  • the sheets are shown with the heater 9 disposed therebetween.
  • the heater 9 may for example comprise a simple electric radiant heater, and is used to raise the thermoplastic sheets 5, 6 to an appropriate thermoforming temperature before proceeding. The heater 9 is subsequently withdrawn.
  • each of cavities 24 and 25, defined by each sheet 5, 6 and its respective mould half 1, 2 can be controlled as appropriate to support the sheets.
  • each mould half for thermoforming and the mould cavities themselves are not shown, including the small access channels and air holes provided into the mould cavity 16 which are used in the thermoforming process to control the pressure in the mould cavity. These same holes may be used in supporting each of the sheets against sagging.
  • the pressure in cavity 25 will be kept below the ambient pressure and the pressure in cavity 24 should be kept above the ambient pressure.
  • Pressure based sheet support systems of various types are known in the thermoforming art.
  • An example practical in the present application uses a light beam level sensor on one side of the sheet to detect whether the "bubble" of the sheet is presently interrupting the beam.
  • the controller controls the pressure in the support cavity to bring the sheet into a favorable condition.
  • An improved version of this incorporates a controlled leak between the support cavity and the ambient room and a minimum pressure (positive or negative) application time, so that the "bubble" is caused to continually oscillate across the boundary of the light beam in accordance with the hysterisis of the system.
  • thermoforming temperature For ABS plastics typically this will be above 140C. Other considerations such as the complexity of the shape to be formed may dictate a higher forming temperature.
  • the total heating time for a sheet will depend on the material, thickness and heater power. Typical total times for the heating process when using ABS sheet from 2-3mm thick, and heating at a rate giving efficient production without sacrificing sheet quality, would be 120 seconds, with the sheet benefiting from active support for at least the last half of the total time.
  • the mould halves 1 and 2 have now been completely brought together, fully compressing the springs 13 such that the support members 11 are now fully depressed into their respective cavities 12.
  • the continued application of vacuum in the mould cavities 16 causes the respective sheets 5, 6 to be drawn fully into the cavities to thereby conform to the cavity shape.
  • the seam regions 17 of the mould halves 1 and 2 have come substantially into abutment forming a seam 55 between the two sheets 5, 6 of thermoplastic material.
  • the mould halves 1 and 2 have been brought together closer than the combined thickness of the two sheets in the region of seam forming regions 17, so that material has been forced away from the seam 55, so as to form for example a reinforcing bead 56 on the inside of the thermoformed part.
  • thermoforming process is thus basically complete. Now the part may be allowed to cool, foam may be injected, the part may be removed and trimming may take place as appropriate.
  • an in-mould trimming type device may be provided, for example, a knife or cutting blade, or a guillotine adaptation such as will be described with reference to Figures 6 to 10 may be incorporated into the mould design, at the seam region 17, for example as depicted in Figure 12.
  • FIG. 6 an alternative embodiment is depicted which achieves the same goal of eliminating the support frame and allowing heating of the thermoplastic sheets from a single heater disposed therebetween, but which also achieves the objective of in-mould trimming by a guillotining type approach using the depressible support members in the guillotining process.
  • the upper sheet support member 41 may be fixed without substantially altering the operation of the machine.
  • the two mould halves are no longer substantially the same.
  • the upper mould half 4 has an annular sheet support member 41 depressible into a channel 42, with springs 45 disposed between the opposed faces 44 and 43 to provide a resilience and opposition to such depression.
  • a sheet 8 is retained by the vacuum channel seal 48, which is evacuated through tubes 47, much as in the embodiments of Figures 1 to 5.
  • the internal face of the depressible member 41 itself forms a part of the mould cavity.
  • the member 41 in Figure 6 could equally be formed integral and as a complete part of the non movable part of the mould body 40 without significantly affecting the performance of the thermoformer.
  • the sheet support member 41 has a small seam forming region 49 protruding at the lower face thereof, adjacent the vacuum seal 48 which retains the edge 80 of the sheet 8. The effect of this protruding edge is demonstrated in the later figures.
  • the lower mould half 3 has mould half body 30, with the sheet support member 31 retained within a channel 32.
  • First springs 35 are provided in the cavity 32 to act between the opposed faces 34 and 33 of the support member 31 and the main body 30 respectively.
  • Further springs 36 are provided in the base of the channel 32, which will act between the faces 34 and 33 only once the support member 31 is sufficiently depressed within the channel.
  • the depth of channel and height of support member 31 are such that the further springs 36 will be encountered once the support member 31 has been sufficiently depressed that the seam forming region on the upper face thereof is at the level of the mould surface 26.
  • the reasons for this will be shown with respect to Figures 7 - 10.
  • the edge 70 of the sheet 7 is secured by vacuum seal 38, evacuated through tubes 37.
  • a rebate is provided in the mould body 30 to allow for the depression of the support member 31.
  • a heater may be inserted between the thermoplastic sheets and used to heat the thermoplastic sheets to a thermoforming temperature in substantially the same manner as in Figure 1. Further preferred methods of loading and heating the sheets will be described below with reference to Figures 13 to 16.
  • the mould halves 3, 4 are slowly brought towards one another, while the cavities 22, 23 previously used to support the sheets 7, 8 against sagging, are evacuated to separate the sheets as depicted by the region 71 and 81 of the sheets in Figure 7.
  • neither member 31 or 41 has begun to be depressed into its respective cavity as the support members are not yet abutting to cause compression in the respective springs 35, 45.
  • thermoforming process is shown advanced still further, with the mould halves 3, 4 brought together to such an extent that the sheet support members 31 and 41 are now in abutment with the edges 70, 80 of the respective sheets 7, 8 contacted therebetween, and now in contact with the seam regions 39, 49 of the support members 31, 41.
  • Continued evacuation of the cavities 22, 23 has led to the more advanced formation of the respective sheets, with for example portion 72 of the lower thermoplastic sheet now contacting the mould surface 26.
  • the final stage of the process is depicted in Figure 10.
  • the mould halves have been further brought together.
  • the upper support member 41 was already fully depressed into its respective channel.
  • the lower support member 31 has been subject to further depression into its channel by further compression of the springs 35 and by compression of the springs 36 between the face 34 of the support member 31 and the face 33 of its respective channel 32.
  • the resistance of the springs 35 and 36 has meant that significant pressure has been placed in the abutment between seam regions 39 and 49, to displace plastic material from the weld region 76, and form a bead 75 on the inside cavity of the formed component in the weld region, this bead will provide substantial reinforcement to the weld.
  • the present invention provides a method whereby the sheets may be supported in association with each of the mould halves without the use of a separate supporting frame, and that the thermoforming process may be conducted in a simple operation by bringing the mould halves together.
  • an in-mould trimming operation without the need for additional knives and parts, and which accomplishes a reinforcing bead in the finished component is also achieved.
  • FIG 11 depicts an alternative arrangement for securing a thermoplastic sheet 90 to a support member 91.
  • a clamping toggle 92 is mounted for pivotal movement about a pivot axis 93. This may involve supporting the toggle 92 off a lug 94 extending from the support member.
  • the toggle 92 includes a clamping arm 95 which has a clamping surface 96 adapted to bear against the surface of the sheet 90.
  • An actuator 98 is connected to the clamping toggle 92 to operate it through a pivotal movement typically of at least 90 degrees.
  • the actuator 98 may comprise a solenoid which has the advantage of controllable bearing pressure.
  • a resilient strip seal 99 is provided in a channel 100 in the surface of the support member 91.
  • the resilient strip may be formed for example from silicone rubber, and has a sealing edge 101 raised substantially from the surface 102 of the support member.
  • the clamping surface 96 presses the sheet against the resilient strip seal 99. It is preferred that a number of these clamps are provided, and that they are at sufficient spacing to ensure an adequate seal of the sheet 90 against the seal 99 around the entire periphery of the sheet. For a 3mm ABS sheet a typical arrangement would have 45mm width toggles separated by 50mm spaces.
  • the spaced apart clamps may at some points be interspersed with abutments 103, and the toggles 107,108 may be provided at alternate positions on the upper (105) and lower (106) mould halves respectively so that the movement envelope of the toggles of each mould half is not impeded by the toggles of the other mould half.
  • Figure 13 depicts the general method as applied to forming apparatus such as that of Figure 1.
  • a moveable heater box 115 is provided which can move into a position between the upper and lower mould halves.
  • the heater box includes upper and lower heater supports 117, 118 which support each of the upper and lower sheets for loading onto the mould halves 119,120 respectively.
  • a heater 121 is provided between the sheets 122,123.
  • both upper and lower heaters are provided so that heating of the upper and lower sheets can be independently controlled in accordance with the influence of sheet thickness. This arrangement allows preheating of the sheets on the heater box prior to introduction between the mould halves.
  • the heater box acts as both the heater and the sheet carrier so the time required for heating the sheets is effectively overlapped with time that would otherwise be expended in sheet transport.
  • the sheets are preheated on the heater box to a temperature which is ensured to be below the glass transition temperature (for example 70C). This preheating may be conducted more slowly than would be done if the sheets were already in place, which is preferable as it ensures an even heat distribution and penetration, facilitating later further heating.
  • the heater box, carrying the sheets is subsequently moved into position between the mould halves. Up until this time the mould halves may have been completing an earlier thermoforming sequence or cycle.
  • the sheets are then transferred to the sheet support members of the respective mould halves. Once transferred to the respective mould halves, support of the sheets through the controlled pressure systems already described is initiated and maintained.
  • the heater applies further heating to bring the sheets up to the thermoforming temperature before being removed from between the mould halves. In the typical example using 3mm thickness ABS sheet referred to earlier this further heating may take 60 seconds.
  • the heater is then removed and thermoforming begins as already described.
  • the heater box itself incorporates an upper 124 and a lower 125 controlled pressure cavity, each incorporating a peripheral sheet seal 126, 127 and supporting means which are sufficient to hold the sheet in a sealed condition against the seal.
  • the heater is thus enabled to provide support to both the upper and lower sheets prior to transfer and the sheet may be raised to the thermoforming temperature before the heater box is shuttled into position between the moulds for transfer. This reduces the time that the set of mould halves are required in each cycle allowing an increased number of cycles in a given production time. During transfer there is a transition time as support of the sheet is transferred from the pressure cavity of the heater box to the pressure cavity of the mould half.
  • a clamping toggle based support and transfer system is depicted in Figure 14 which is readily suited to either heating and transfer method described above.
  • This arrangement uses actuator controlled toggles 130 largely as depicted in and described with reference to Figure 11.
  • the toggles 130 preferably grasp the sheet not directly on the seal member 131 but slightly to the outer side thereof .
  • This allows the toggles 130 to operate in cavities 132,133 formed in the support members of the mould half 134 and the heater box 135 respectively without interference with the sheet 136 or with the seals 131.
  • Secondary clamps (not shown) may be provided which disengage prior to the transfer process for additional security if higher thermoforming temperatures are used which will reduce the integrity of the sheet in the peripheral area.
  • a further cavity 137 may be provided for any abutment(s) of the respective mould half . It will also be appreciated that this clamping arrangement can be applied to the sheet support members of the mould halves in the thermoforming method of Figure 6, as it overcomes the interference difficulties that might otherwise be associated with use of a mechanical sheet clamping
  • the heater box 140 includes a plurality of suction support posts 141 spaced evenly throughout the heater box to support a sheet at a plurality of locations on its undersurface irrespective of the sheet size or shape.
  • the number and spacing of the support posts would need to be set in accordance with the strength characteristics of the sheet material at the intended transfer temperature.
  • a heater box 145 includes a plurality of automatically moveable toggle clamps 142 which are adapted to automatically reposition along a series of tracks 143 on walls 144 reaching inwards across the heater box. Movement of the toggles may be effected by known means of linear actuation, and the toggles may be substantially in accordance with the arrangement shown in Figure 14.
  • the heater is controllable in sections so that only regions of the heater in direct juxtaposition with the sheet that is presently held above the heater are activated. This reduces wasted energy, and also ensures that free edges of held sheets are not subjected to additional radiant heating from heater elements not directly below the sheet.
  • the heater may be formed from a large number of arbitrary zones, for example a grid of rectangular zones, which can be individually controlled, otherwise the shape and configuration of the zones may be specifically adapted to the range of sheets that will be used.
  • the present invention eliminates the need for adjustable or different fixed clamp assemblies which are required in conventional forming processes, and whose prescence is required during the entire forming process. It allows for moulds to be quickly changed and producing parts, introducing significant flexibility in the vacuum forming process over a large product range.

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

Abstract

L'invention concerne des appareils de thermoformage pour paire de feuilles. Ce type d'appareil est équipé d'un moule dont chaque moitié comporte un support de feuille capable de tenir une feuille par son bord et de soutenir cette feuille pendant l'opération d'échauffement. Au moins un des supports de feuille peut se rétracter pendant le thermoformage. Les feuilles sont soutenues à distance de chaque moitié de moule par lesdits supports, mais elles sont chauffées depuis l'intérieur entre les deux moitiés de ce moule. Un dispositif chauffant mobile peut transporter les feuilles pendant l'échauffement et le transfert simultané des feuilles ainsi chauffées, vers les moitiés de moule de l'appareil de thermoformage.
EP99928252A 1998-06-10 1999-06-10 Appareils et procedes pour le thermoformage de feuilles en paire Withdrawn EP1109661A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
NZ33064898 1998-06-10
NZ33064898 1998-06-10
PCT/NZ1999/000079 WO1999064221A1 (fr) 1998-06-10 1999-06-10 Appareils et procedes pour le thermoformage de feuilles en paire

Publications (2)

Publication Number Publication Date
EP1109661A1 EP1109661A1 (fr) 2001-06-27
EP1109661A4 true EP1109661A4 (fr) 2002-08-21

Family

ID=19926765

Family Applications (1)

Application Number Title Priority Date Filing Date
EP99928252A Withdrawn EP1109661A4 (fr) 1998-06-10 1999-06-10 Appareils et procedes pour le thermoformage de feuilles en paire

Country Status (9)

Country Link
EP (1) EP1109661A4 (fr)
JP (1) JP2002517333A (fr)
KR (1) KR20010052725A (fr)
CN (1) CN1107583C (fr)
AU (1) AU744880B2 (fr)
BR (1) BR9911139A (fr)
CA (1) CA2334663A1 (fr)
TW (1) TW407105B (fr)
WO (1) WO1999064221A1 (fr)

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US8077040B2 (en) 2000-01-24 2011-12-13 Nextreme, Llc RF-enabled pallet
GB2374830A (en) * 2001-04-20 2002-10-30 Reckitt Benckiser Improvements in or relating to compositions/components including a thermoforming step
ITMI20031520A1 (it) * 2003-07-24 2005-01-25 Tecnos Spa Metodo ed apparecchiatura per la termoformatura di corpi in materiale plastico
EP1799429B1 (fr) * 2004-09-18 2009-02-18 Faurecia Innenraum Systeme GmbH Outil de moulage par pression et procede pour fabriquer une piece par moulage par pression
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AU4535499A (en) 1999-12-30
CN1304351A (zh) 2001-07-18
JP2002517333A (ja) 2002-06-18
AU744880B2 (en) 2002-03-07
WO1999064221A8 (fr) 2000-03-16
WO1999064221A1 (fr) 1999-12-16
TW407105B (en) 2000-10-01
CN1107583C (zh) 2003-05-07
EP1109661A1 (fr) 2001-06-27
CA2334663A1 (fr) 1999-12-16
KR20010052725A (ko) 2001-06-25

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