Plastic and nonmetallic article shaping or treating: processes – With severing – removing material from preform mechanically,... – Forming continuous work followed by cutting
Patent
1996-11-15
2000-04-04
Silbaugh, Jan H.
Plastic and nonmetallic article shaping or treating: processes
With severing, removing material from preform mechanically,...
Forming continuous work followed by cutting
264319, 264571, 425256, 425297, 425449, B29C 3902
Patent
active
060457368
DESCRIPTION:
BRIEF SUMMARY
The invention relates to a process and devices for producing a molded article from plastic by separating individual portions of material from a vertically downwardly directed flow of material exiting from a sealable dispensing aperture of a material dispenser, said material being plastic plasticized by heat, transferring the separated portions of material into a hollow mold space, and pressing to a molded article by closing of the hollow mold space.
Such a process and such a device are known from DE-C3-30 23 415. According to said process and in said device, ring-shaped blanks are obtained by separating individual material portions and by closing a tubular part of the material dispenser, said part being directed against the hollow space of the mold, by a closing element displaceable against the end of the tubular part in the axial direction, whereby the separated, ring-shaped material portions are transferred by freely falling into the hollow space of the mold. In this connection, the ring-shaped material portions are molded to blanks by controlling the closing element, such blanks having an approximately lentiform cross-sectional profile. Preferably, the ring-shaped blanks are detached from the closing element by a stream of gas directed against the point of separation.
Said process requires a complicated nozzle system which, furthermore, requires a specific closing characteristic in order to obtain the desired cross sectional shape of the ring-shaped blank. Since thermoplastics exhibit strong adhesive or adhesion properties, additional measures are required, as a rule, such as currents of hot air for detaching the produced blank from the closing device.
Another process and another device are known from EP-B1- 328 096. In this connection, a blank is dispensed from a nozzle and separated, whereby the entire heated thermoplastic material required for a blank is deposited on an intermediate carrier, which can be driven under the nozzle, with the surface of said carrier forming a part of the pressing mold. Prior to or during the closing of the mold, the intermediate carrier is lowered and the blank is transferred into the pressing mold in this way. With said device, the pressing mold is more complicated on account of the extendable intermediate carrier, and consequently also more expensive.
According to the process according to DE-C3- 30 23 415, only ring-shaped blanks can be produced. According to EP-B1- 328 096, the blanks also can have a ring-shaped form. In connection with the manufacture of molded articles in the form of a tube that has to have a closed dispensing aperture, for example a pierceable diaphragm, or in the case of so-called "twist off" or "brake off" tubes, in connection with which the dispensing aperture is released only after a suitably designed closing part has been twisted off and/or broken off, the use of ring-shaped blanks poses problems because bubble-shaped air inclusions often occur during pressing, causing rejects.
A device for dispensing a portion of the material is known from U.S. Pat. No. 2,894,285, according to which thermoplastic material is dispensed from an extruder, the latter being arranged inclined, through a dispensing aperture into a duct-like chamber extending inclined, with application of pressure, whereupon the dispensing aperture is closed by a piston and the portion of the material thereby separated is transported through said chamber and finally into a hollow mold space, whereby stripping fingers close around the piston and, as the latter retracts, strip the portion of the material from the piston.
The problem of the invention is to propose a process and a device by which especially closed material portions of a desired size are obtainable in a simple and rapid way without additional measures, as well as to propose a device by which desired material portions and particularly closed portions of material are manufacturable in a simple way, such portions having a simple structure. Furthermore, the process and the device permit the manufacture of flawless tubes with a
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Hanot Dominique
Keller Gerhard
Roeder Ralph
Aisa Automation Industrielle S.A.
Lee Edmund H.
Silbaugh Jan H.
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