Agitating – Stationary deflector in flow-through mixing chamber
Patent
1995-04-27
1996-10-15
Jenkins, Robert W.
Agitating
Stationary deflector in flow-through mixing chamber
366340, B01F 506
Patent
active
055648274
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a device for the homogenization of high-viscosity fluids and also to uses of such a device.
During the extrusion and injection molding of thermoplastic materials, homogenous--particularly thermally homogenous--melts are produced using static mixers. Without special provisions plastics melts in plastification machines on leaving the screw exhibit considerable temperature differences; when coloring agents and/or additives are added, their distribution can also be irregular. In injection molding machines the necessary homogeneity of the plastics melt is obtained by the provision of a mixing head in the nozzle (see e.g. G. Schneider and R. Maurer, Osterr Kunststoff-Zeitschrift, 1985, pages 86-89).
A mixing head or melt mixer comprises a sleeve in which are situated several mixing elements. Due to the high viscosity of plastics melts large forces act on the mixing elements and also between the mixing elements and the sleeve. In a preferred embodiment of the mixing head, the mixing elements are in the form of a casting which is monolithic (i.e. cohesive without joints) and is soldered into the sleeve. Such a mixing head has the disadvantage that under extreme conditions the soldered joint may not survive. Such extreme conditions which may arise during faulty operation are, for instance: cold start (with a peak pressure of around 2000 bar), fast heating, cleaning with a naked flame, or quenching at an annealing temperature with water.
SUMMARY OF THE INVENTION
An aim of the invention is to provide a device for the homogenization of high-viscosity fluids--for instance a mixing head or a melt mixer--which remains, as far as possible, indestructible even under extreme conditions. Such device should be also able to be readily cleaned. The device should comprise, in addition to static mixing elements, possibly also a filter element, for instance a rib filter.
The term "monolithic structural member" as used in this application is intended to mean a structural element which has no weaknesses caused by joints--for instance soldered joints (although a structural member with weld joints may be monolithic). The sleeve parts referred to herein comprise in an extreme case only the flange-like parts which are, in this case, tubular.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is a cross-section of the nozzle of an injection molding machine having a mixing head of a known design,
FIG. 2 shows a mixing head made according to the invention,
FIG. 3 shows a mixing element of a device made according to the invention,
FIG. 4 shows a second embodiment of a mixing element made according to the invention,
FIG. 5 is a cross-section shown in the mixing element of FIG. 4,
FIGS. 6 and 7 illustrate are further variants of mixing elements,
FIG. 8 shows a rib filter element for a device made according to the invention, and
FIG. 9 shows a monolithic structural member of a device made according to the invention with two mixing elements.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
The nozzle 2 shown in FIG. 1 has the following components: a mixing head 1 with mixing elements 11, 12 and a sleeve 13; a nozzle head 21 with a nozzle orifice 22 and a bore 23 for the mixing head 1; by chain lines is indicated a strip heater 24; and finally the tip of an extruder screw 3. FIG. 2 shows a side elevation of a mixing head 1 according to the invention which does not have a one-piece sleeve 13, as in the known design, but has a composite sleeve comprising parts 4 and 5. The part 4 forms, together with the mixing element 11, a monolithic structural member 10. FIG. 3 shows a first embodiment: The part 4 is a flange-like part of the structural member 10 by means of which this part is anchored between the sleeve parts 5. The part 4 is ring-shaped and situated perpendicularly to a sleeve axis 15; in the illustrated example the part 4 is situated in the middle of the mixing element 11. The mixing element 11 is composed of layers 101 of pleated lamellae between which are situated, due to often pleating, channel
REFERENCES:
patent: 2584827 (1952-02-01), Bailey
patent: 3860217 (1975-01-01), Grout
patent: 4207202 (1980-06-01), Cole
patent: 4731229 (1988-03-01), Sperandio
patent: 4747697 (1988-05-01), Kojima
Jenkins Robert W.
Sulzer Chemtech AG
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