Plastic article or earthenware shaping or treating: apparatus – Stock pressurizing means operably associated with downstream... – Plural orifices
Reexamination Certificate
2001-05-18
2003-04-22
Silbaugh, Jan H. (Department: 1722)
Plastic article or earthenware shaping or treating: apparatus
Stock pressurizing means operably associated with downstream...
Plural orifices
C425S311000, C425S331000, C425SDIG002
Reexamination Certificate
active
06551090
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to an apparatus for the agglomeration of feed material with thermoplastic properties, comprising a radially symmetrical chamber delimited peripherally by a perforated die and at its end faces by a front wall element and a rear wall element, and comprising an agglomerating vane supported in the hollow chamber so as to be rotatable about the longitudinal axis of the hollow chamber and forming with its leading side in the rotational direction together with the two wall elements and the perforated die at least one revolving agglomeration chamber.
The invention further relates to a disc-shaped or ring-shaped wear element suitable for use with an apparatus of the aforementioned kind for delimiting a hollow chamber of radial symmetry.
2. Description of the Related Art
In the course of reutilization of waste material, the recycling of thermoplastic materials, e.g., films, fibers, filaments etc. made of plastic materials, gains more and more importance. In this connection, the thermoplastic waste material is transformed into an intermediate product in the form of granules which are then returned into the production process as starting material for use in extruders, injection molding machines and similar equipment.
During the expert treatment of thermoplastic waste material in an apparatus of the aforementioned kind, the feed material is always subjected to high agglomeration and shearing forces causing a great heat development within the agglomerator. This effect is desired within a temperature range below the type-specific melting point of the feed material since only by means of this heat development agglomeration is made possible. If during agglomeration the material-specific melting point is exceeded, there will be an irreversible alteration of the mechanical properties of the feed material which makes the valuable starting material unusable for further processing.
An apparatus for the agglomeration of thermoplastic wastes of the aforementioned kind is described in German Patent Specifications 26 14 730 C2 and 197 06 371 A1. These references disclose a disc-shaped annular chamber which is enclosed by a perforated die and into which the feed material is fed in the axial direction. A coaxially arranged agglomerating vane rotates in this chamber and forms with its effective flanks two revolving agglomeration chambers. The heat generated during compaction or agglomeration leads to a plasticizing of the feed material which, in turn, effects the passage of the feed material through the perforations of the die. To avoid thermal damage of the feed material, the agglomerator is equipped with a cooling system for dissipating the excess heat developed during the agglomeration and, in this way, the working temperature of the agglomerator is maintained within a range which is not critical to the feed material.
From the German Patent Specification 38 42 072 C1 an agglomerator is already known which differs from the already mentioned agglomerators insofar as the radially symmetrical chamber narrows radially towards the perforated die. This effects a three-dimensional processing of the feed material thus intensifying the compacting and plasticizing of the feed material and increasing in this way the specific throughput efficiency.
SUMMARY OF THE INVENTION
It is an object of the present invention to improve the known agglomerators so that the efficiency of the apparatus is increased without affecting negatively the heat generated in the agglomerator.
In accordance with the present invention, this is achieved in connection with the apparatus in that the surfaces of the front and/or rear wall elements facing the radially symmetrical chamber have profiles running from the inside to the outside for the transport of the feed material.
In accordance with the present invention, this is further achieved in connection with the wear element in that the wear element is configured to confine a radially symmetrical chamber wherein the wear element has profiles running from the inside to the outside.
The arrangement of the profiles on the inner surface of the wall elements according to the invention leads to a mostly defined flow of the feed material within the radially symmetrical chamber. In this connection, the feed material is moved on the shortest possible path along the profiles to the peripheral area of the hollow chamber where the actual plasticization and agglomeration takes place. In this way it is prevented that parts of the feed material reside too long in the central area of the hollow chamber where, even though they are entrained by the agglomerating vane, reach the plasticization area of the compacting chamber too slowly and are thus exposed to the high temperatures longer than necessary.
The configuration of the circular disc-shaped hollow chamber according to the invention achieves a forced material flow resulting in a shorter residence time of the feed material in the radially symmetrical hollow chamber. This provides, on the one hand, the advantage that, due to the shortened exposure time, the thermal stress is reduced and, accordingly, the danger of thermal damage to the feed material is minimized. On the other hand, the shortened residence time of the feed material in the agglomerator leads to a higher material throughput and thus to an increase of the efficiency of the agglomerator over all.
According to the invention, the profiles are preferably grooves worked into the inner surface of the wall elements. In this connection, the efficiency and thus the suitability of the grooves for the material transport depend mostly on their configuration details to be explained in the following.
The configuration of the grooves according to the invention provides the advantage of interacting with the rotating agglomerating vane which effects the advance of the feed material within the grooves during its rotation. Accordingly, the grooves according to a preferred embodiment have a longitudinal, plane guiding surface which acts counter to the rotating direction of the agglomerating vane such that the feed material being rotated by the agglomerating vane reaches the grooves and comes into contact with the guiding surface thereat. This prevents the feed material from continuously rotating and forces the feed material to change its direction of movement so that movement is parallel to the orientation of the grooves. The advance of the feed material is effected by the outer edges of the agglomerating vane; the outer edges define an intersecting point with the grooves, which point moves outwardly during rotation.
Compared to other configurations, the groove with a plane guiding surface has the advantage that its efficiency is not much impaired even after the first signs of wear are detected. In contrast to this, in the case of grooves having, for example, a concave cross-section, wear very quickly leads to small intersection angles &agr; of the groove with the inner surface of the wall elements, and the efficiency of the guiding surface is thus lost in this way.
Good results are obtained with grooves having a guiding surface which forms with the inner surface of the wall elements an angle &agr; of 60 to 90°, wherein the optimum angle &agr; always depends on the type of feed material and the specific configuration of the agglomerator.
In a further embodiment of the invention, the guiding surface forms with only one further plane surface the groove according to the invention, so that the groove has a triangular cross-section. The surfaces constituting the groove form preferably an angle &bgr; of 70 to 110°. The preferred angle &bgr; of 90° provides, in addition to a good material flow, further advantages with regard to a simple manufacture of such a groove.
Another embodiment of the invention is moreover preferred, in which the outer border of the groove is formed by a concave surface which is a continuous extension of the guiding surface. This measure offers the advantage that the outwardly directed material flow, when leaving the groo
Friedrich Kueffner
Heckenberg Donald
Pallman Maschinenfabrik GmbH & Co. KG
Silbaugh Jan H.
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