Plastic article or earthenware shaping or treating: apparatus – With apparatus assembly or dismantling means or with idle part – Means permitting removal or substitution of elements during...
Patent
1992-12-28
1994-07-05
Chiesa, Richard L.
Plastic article or earthenware shaping or treating: apparatus
With apparatus assembly or dismantling means or with idle part
Means permitting removal or substitution of elements during...
425190, 425381, 425467, B29C 4766
Patent
active
053262476
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a paste extruder for making hollow articles (profiles), for example, plastic pipes or tubes, particularly of polytetrafluorethylene (PTFE). The extruder includes a machine stand to which are attached an extrusion cylinder having an extrusion mouthpiece to receive a preform composed of the plastic to be extruded; and an extrusion drive for an extrusion piston that can be driven into the extrusion cylinder and thus effects the extrusion of the plastic material. The extruder further includes a mandrel pulling rod that is axially displaceably mounted within the extrusion piston and is movable by a mandrel positioning drive for positioning a mandrel that is fixed to the rod end and cooperates with the extrusion mouthpiece to form the hollow article.
Because of their structural length, such paste extruders require a significant amount of space. A substantial structural length for the paste extruder is needed, because the preforms may have a length of up to 2 m, and the stroke of the extrusion piston must correspond to this length. If additionally the extrusion cylinder is to be charged in the advantageous manner of a breechloader, the extrusion piston must be pulled out of the extrusion cylinder to such an extent during the charging process that sufficient space for the introduction of the preform exists between its pressure face and the extrusion cylinder. This space must generally be significantly larger than the length of the preform because in preferred configurations of such extruders the mandrel shaping the interior profile of the article projects beyond the pressure face of the extrusion piston.
Because of the resulting structural lengths of such extruders, they are frequently designed for a vertical extrusion direction. This, however, requires a correspondingly tall operating space which is in part inconsistent with the multi-purpose use of such extruders.
Such extruders require considerable pressures of up to, for example, 1000 bar to drive the extrusion piston. The drives for the extrusion piston must be dimensioned correspondingly large. It is thus customary to have several cooperating drive assemblies act jointly on the extrusion piston. Furthermore, a drive assembly required to axially position the mandrel must be added to the drive assemblies. Thus, the prior art paste extruders of the above-mentioned type, in addition to the significant great structural length, also have a considerable structural width and height.
SUMMARY OF THE INVENTION
It is an object of the invention to provide an improved paste extruder of the above-discussed type which has reduced spatial requirements compared to prior art structures.
This object and others to become apparent as the specification progresses, are accomplished by the invention, according to which, briefly stated, the mandrel positioning drive is surrounded (encapsulated) by the extrusion drive and both drives are disposed in a common housing.
The compact configuration according to the invention is of increased significance if additional drive and positioning means are present. It is generally important that the paste extruder does not project far radially with respect to its longitudinal axis extending in the extrusion direction.
According to a further feature of the invention, if the extrusion piston is retracted from the extrusion cylinder, the common housing together with its drives is pivotal about a pivot axis that is disposed approximately at a right angle to the longitudinal axis of the extrusion piston. Such an arrangement additionally provides for a short structural length in spite of the fact that the extrusion cylinder is recharged as a breechloader. The small structural width or height also favorably affects the space requirement of the paste extruder if its components, when pivoted out, do not project significantly beyond the dimensions in the operating position. In order to make available the axially effective space required to reload the preform from the rear into the extrusion cylinder, t
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patent: 2734226 (1956-02-01), Willert
patent: 2941240 (1960-06-01), Distler
patent: 3898831 (1975-08-01), Kahlefeld
patent: 4360332 (1982-11-01), Cyin
patent: 4565512 (1986-01-01), Wills et al.
patent: 4714422 (1987-12-01), Meeker et al.
patent: 4731006 (1988-03-01), Freda et al.
Bergner Heinrich
Prenzel Karl
Chiesa Richard L.
WK Worek Kunststofftechnik GmbH
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