Agitating – With heating or cooling – Electrical heating
Patent
1987-06-30
1990-05-01
Coe, Philip R.
Agitating
With heating or cooling
Electrical heating
165181, 366 79, B29C 4782, B01F 708, B01F 1506, F28F 130
Patent
active
049213555
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a heating and cooling arrangement for an extrusion cylinder, as well as to an extrusion cylinder with at least one heating and cooling arrangement.
In plastic-extrusion machines, it is important for the extrusion process that the whole extrusion cylinder can be heated or cooled. It is known, for heating an extrusion cylinder, to provide for a casting with integrally cast heating at the periphery thereof. This arrangement has the disadvantage that it has a great time lag as regards heating and cooling and does not make possible any individual heating and cooling of a cylinder section.
The heating and cooling unit according to U.S. Pat. No. 3,730,262 has the disadvantage that it comprises a rigid pipe which cannot well be adapted with optimum heat trasnfer to an extrusion cylinder. The result is poor heat distribution since air for cooling is conducted over a pipe around the extrusion cylinder. The heat distribution is not homogenous over the surface of the cylinder.
The device for increasing the heat exchange according to U.S. Pat. No. 4,236,578 has no heating elements. The heating elements would have to be disposed next to the cooling elements. Thus, at a specific location of the pipe, merely heating or cooling can take place. The arrangement according to this disclosure is likewise not flexible and cannot be optimally adpated to a given cylinder. With the rigid design according to this patent and the one mentioned above, a small space is possibly produced between jacket and tube, and this makes the heat transfer much poorer. Very precise machining of the jacket is necessary in order to ensure good heat transfer. The conduction of heat would not be ensured, for instance, if the heating elements were disposed under the cooling elements since the heating wires must be insulated.
The air-cooled extruder according to U.S. Pat. No. 3,743,252 likewise has the disadvantage that the cooling arrangement is not flexible. The cooling plates must be very precisely machined.
The heating and cooling unit for extruders according to U.S. Pat. No. 3,285,329 yields the same problems as the device according to U.S. Pat. No. 3,730,262. The device is likewise rigid, which makes optimum adaptation to the extruder pipe impossible. Good heat transfer is not ensured. The air cooling with pipes also results in poor heat distribution on the surface of the cylinder.
It is a task of the present invention to provide a heating and cooling arrangement by means of which individual cylinder sections can be both cooled and heated. The heating and cooling arrangement should be able to be adapted in a simple manner to any desired diameter of the extrusion cylinder.
This is achieved, according to the invention, by means of at least one cooling element and at least one heating element, the arrangement being formed flexible.
Furthermore, it should be possible to bring about an optimum adaptation of the temperature profile along the extrusion cylinder to each extrusion process individually.
This is achieved in an extrusion cylinder with a heating-cooling arrangement according to the invention in that in each case on one section of the extrusion cylinder, at least on a great part of its periphery, cooling elements are fastened, and at least one heating element is provided over the cooling elements on the surface of the extrusion cylinder. By means of the arrangement according to the invention, the temperature profile can be adapted to the respective process speed. A dynamic heating and cooling system is provided, which is also suitable for very rapid extrusion processes. The heating-up and cooling processes take place much more quickly than with the rigid arrangements of the prior art.
An embodiment of the invention, as well as its use, is described in detail below with the aid of the appended drawing.
FIG. 1 shows a schematic representation of an extruder with heating and cooling elements provided thereon,
FIG. 2A shows a section of a cooling element and FIG. 2B shows a top plan view of the cooling element,
FIG. 3 shows
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Coe Philip R.
Gruter Elektroapparate AG.
Haugland Scott J.
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