Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Plural orifices
Patent
1994-12-16
1996-07-02
Davis, Robert
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Plural orifices
425464, B29C 4712
Patent
active
055315879
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention concerns a closable extrusion nozzle for thermoplastic materials with a nozzle plate containing nozzles that permit extrusion of the plastic material from a hopper, and with a perforated plate arranged upstream of the nozzle plate, whose apertures can be brought in and out of alignment with the nozzles by displacing the perforated plate relative to the nozzle plate.
Such an extrusion nozzle is known from the European Patent 0 093 358. There, the design described in the patent consists of the perforated plate that is located downstream of a flat nozzle plate. The perforated plate is pressed against the nozzle plate by recesses in the nozzle plate and a spring assembly resulting in a seal between the nozzle plate and the perforated plate when the nozzles are not aligned with the apertures of the perforated plate. The nozzles and the apertures are brought in and out of alignment by a sliding mechanism that allows to open and close the extrusion nozzle. The recesses of the nozzle plate grip the rims of the perforated plate like U-channels that result in protrusions on the exit side of the perforated plate that interfere with the access to the entire width and length of the perforated plate. The patent also mentions that the perforated plate can be located above the nozzle plate, but it does not provide any details.
SUMMARY OF THE INVENTION
The objective of the invention is to improve the known extrusion nozzle in such a way that a more compact design is achieved that allows access to the entire exit surface of the nozzle plate. The invention achieves this by a nozzle plate design featuring a U-shaped cross section perpendicular to the sliding direction that encloses the perforated plate like a housing, and by a perforated plate design featuring a sealing surface that rests against the flat housing bottom in which the nozzles are located, and by restricting the sealing contact of the sealing surface to a narrow area around the nozzles and leaving a gap between the perforated plate and the housing at least in the curved areas of the housing.
By placing the perforated plate into the U-shaped housing formed by the nozzle plate, a suitable support is obtained for the perforated plate within the nozzle plate that eliminates any protrusions for attaching the perforated plate. The exit side of the nozzle plate, which is the housing bottom, presents a free surface that can easily be scraped for example with a knife or similar tool. The extrusion nozzle may also be mounted at an angle, depending on the hopper layout, because the extrusions that exit the nozzles at an angle can separate freely from the housing bottom.
A useful design feature of the sealing surface of the perforated plate is a slightly convex shape perpendicular to the sliding direction. This will ensure a good seal between the surfaces of the perforated plate and the housing bottom by allowing the housing bottom to adjust to the convex shape under load. In addition, the housing bottom will be slightly curved when the extrusion nozzle is mounted, providing a snug fit around the convex shape of the perforated plate and thereby providing a good seal.
A suitable extrusion nozzle design with respect to the accommodation of the perforated plate in the housing features projecting housing flanges that are bolted to a flat hopper base plate with a cutout, and provides the proper fit of the perforated plate between the housing bottom and the base plate through elastic contact of the bottom to its sealing surface that allows the perforated plate to slide.
This design defines a space between the base plate and the inside of the housing to accommodate a properly fitted perforated plate and provides for its support by the base plate on one side and by the housing bottom on the other side in a manner that allows the perforated plate to slide.
BRIEF DESCRIPTION OF THE DRAWINGS
Examples of the invention are shown in the figures. They show:
FIG. 1 a sectioned extrusion nozzle with two rows of nozzles (3-dimensional view),
F
REFERENCES:
patent: 3245112 (1966-04-01), Williamson
patent: 3336633 (1967-08-01), Curran, Jr.
patent: 3397426 (1968-08-01), Fujita et al.
patent: 3480995 (1969-12-01), Lenk
patent: 3912439 (1975-10-01), Newman, Jr.
patent: 4479768 (1984-10-01), Kube et al.
patent: 5147197 (1992-09-01), Hodan et al.
Davis Robert
Rieter Automatik GmbH
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