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
  • B29C51/008—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 without using a mould, e.g. ballooning
• • 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
  • B29C51/26—Component parts, details or accessories; Auxiliary operations
  • B29C51/30—Moulds
  • B29C51/34—Moulds for undercut articles

Definitions

• the invention is based on a method for producing molded parts from thermoplastic sheets according to the preamble of the main claim and on an apparatus for producing such molded parts according to the preamble of claim 6.
• one side of the corresponding section of the already heated plastic plate is pressurized with working air for the deformation and the other side of the plate section is pressurized with air under vacuum ⁇ strikes.
• spaces are arranged above each of the two outer surfaces of the plate section, of which an air overpressure is directed into one and an air underpressure into the other.
• the shaping is determined by a shaping tool in that channels are arranged for the negative pressure transmission, in order thus to allow the plate section to be deformed to rest well against the shaping tool.
• This method uses the existing overpressure in addition to the underpressure of the working air for the deformation, but with the disadvantage that largely airtight spaces must be present on both outer surfaces of the plate section to be deformed. As a result, the production is relatively cumbersome and also sluggish. Awkward because, for the insertion of the plastic plate and for the heating of the same, one of the two rooms must be removed in order to be put back on afterwards and to be removed again after the deformation in order to take out the finished part.
• the tool which is built on a table, is moved into the working position with the latter, the plastic plate being bulged out accordingly, after which by producing a Air vacuum, the soft plastic plate is pulled to the mold.
• the molded part has undercuts and the tool has movable parts in order to be able to pull the tool out of the undercuts after the molded part has cooled.
• the heated plate section is not only to be adapted to a specific tool shape from one side (DE-PS 11 68 055), but if a deformation of a part of the part is independent of it deforming plate section is provided.
• DE-OS 34 13 714 the heated plastic plate is first sucked onto a molding tool which has been moved in front of one of the outer surfaces of the heated plastic plate, and then another area of the heated plate section is turned into one deformed in another direction by moving up a second tool on the opposite side of the plastic plate, after which the plastic plate is subjected to negative pressure on this opposite side.
• thermoplastic plastic sheets can only be optimally deformed in a relatively narrow temperature range and this temperature range cannot be maintained due to cooling in the case of several deformation steps required in succession.
• a process becomes particularly difficult to handle if partial solidifications, for example in the first process step, are desired during the processing of the warm plastic. Subsequent or partial heating of the workpiece during the overall deformation can lead to tensions within the plastic material and thus to cracks. In addition, there is a risk that already formed sections deform again.
• the inventive method with the characteristic Process steps of the main claim and the device according to the invention with the characterizing features of claim 5 have the advantage that the combined use of pressurized air and pressurized air in one operation and from only one surface of the plastic plate not only complicated parts can be produced, but this production also takes place quickly and with little effort.
• the plastic plate can be pulled onto a molding tool on the one hand by vacuum and on the other hand can be cambered by overpressure.
• the working air spaces, which are on the one hand under pressure and on the other hand under pressure, can be separated in the most varied of ways. The separation can thus be achieved by the molding tool forming a circumferential sealing point with the plastic plate, one part of the surface being subjected to the negative pressure and the other part being subjected to the excess pressure.
• the shaping takes place by overpressure and placing the plastic plate on the mold, or that the crowning is carried out by underpressure by the plastic plate being sucked away from the mold in the corresponding area.
• the degree of crowning can be measured without contact, regardless of whether it is generated by overpressure or by underpressure of the working air, via a proximity sensor that operates a switch.
• the plastic plate is drawn to the shape of the mold in a corresponding plate section delimited by the lines of contact of the vacuum chamber with the plastic plate, and the plastic plate in another area of the plastic plate is drawn by the excess pressure of the working air cambered in the opposite direction, this area being limited by the line of contact of the overpressure space with the plastic plate.
• parts can also be produced with a circumferential frame which has an undercut, the surface of the plastic plate spanning the frame being cambered.
• a workpiece is achieved with a large area that is stiffened by the crowning, so that such a molded part can be exposed to significant wind forces in later use.
• the mold can serve as an airtight room divider between the two rooms of completely different pressure types and thus the retraction and extension of the molding tool is possible, according to the invention, such molds consist of several pieces which can be moved next to one another, with a seal between the pieces in the working position.
• Fig. 1 shows a vertical section through part of a
• a plastic plate 1 made of thermoplastic is stretched over a bar 2 to a housing 3, namely as a circumferential frame, of which only the left corner is shown here.
• a table 4 can be moved up and down, on which molds 5 and 6 can be moved horizontally. These molds are transported by appropriate devices 7, only one of which is indicated.
• the usual manufacturing steps take place during the production of the deep-drawn workpiece.
• the plastic plate 1 is clamped by the bar 2 to the housing 3 and heated in a known manner from one or both sides of the surface. The heating can of course also take place before the fixed voltage.
• the heating is then removed and the table 4, including the locked molds 5 and 6, is moved from the lower position shown in broken lines to the upper position shown in broken lines.
• the plastic plate 1 is deformed upwards by the tools 5 and 6 and thus undergoes its first plastic deformation.
• the molds 5 are thus in the working position, with an air seal at points 8.
• a sealing strip 14 can also be provided, as shown in dashed lines in FIG. 1.
• the tools are retracted or extended, and after releasing the locking, the mold 6 is first retracted so far that the mold 5 can assume the position shown in broken lines in FIG. 5, and then with the table 4 -in the lower starting position closed. after which the tools are moved back into the outer position.

Landscapes

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

Applications Claiming Priority (2)

Publications (1)

Family

ID=6371675

Family Applications (1)

Country Status (2)

Citations (6)

Family Cites Families (2)

• 1989
  • 1989-01-07 DE DE19893900305 patent/DE3900305C1/de not_active Expired - Lifetime
  • 1989-12-22 WO PCT/DE1989/000791 patent/WO1990007416A1/de not_active Ceased

Patent Citations (6)

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