Agitating – Having specified feed means – Impinging jets
Reexamination Certificate
2002-09-25
2003-09-09
Soohoo, Tony G. (Department: 1723)
Agitating
Having specified feed means
Impinging jets
C422S133000
Reexamination Certificate
active
06616321
ABSTRACT:
This application claims the priority of German Patent Application Serial No. 100 14 972.3, filed Mar. 25, 2000, pursuant to 35U.S.C. 119(a)-(d), the content of which is incorporated herein by reference.
FIELD OF THE INVENTION
The present invention relates to a deflector mixing head for a reaction molding machine and in particular to a mixing head configured for improved mixing and homogenization of the mixing components in reaction systems, even for hard-to-mix systems.
BACKGROUND OF THE INVENTION
From DE 32 08 696 A1, a linear mixing head is known, where the reaction components flow in through impact valves which are disposed diametrically above each other and the components flow past damming bodies prior to reaching the mold cavities which are disposed immediately downstream from the mixing chamber in order to realize a throttle effect and an improved mixing effect.
In order to obtain an essentially homogenized component mixture, other deflector mixing heads that are known, for example from DE 40 09 465 A1, are configured such that an overflow chamber which acts as a slowing-down zone is disposed downstream from and positioned at an angle relative to the mixing chamber, where the overflow chamber is divided into two single chambers that are likewise positioned at an angle relative to each other, to thereby realize an additional deflection of the mixture, or alternatively, as in the afore-described deflector mixing head, a reversible cleaning piston is disposed in the overflow chamber in order to attain a reduction of the mixture flow at the mixing chamber side of the inlet opening of the overflow chamber for a simultaneously deflection of the mixture, which can be adjusted. Such deflector mixing heads are generally used and fully sufficient for use with a majority of reaction systems that are utilized. However, it is in the hard-to-mix-systems where localized inhomogeneous mixtures occur that are causing problems and that are also not acceptable on the basis of quality considerations.
From DE 32 13 153 A1, a mixing head is known, where the mixing chamber and the overflow chamber are arranged relative to each other in axis-parallel relationship. Between the mixing chamber and the overflow chamber and transverse to their axes overflow apertures are provided through which the reaction mixture can flow from the mixing chamber to the overflow chamber. An improvement of the mixing degree can be realized when throttle members are driven in and out of the overflow apertures.
From the generic patent U.S. Pat. No. 5,443,797, a deflector mixing head is known in accordance with the preamble of claim 1. This deflector mixing head exhibits drawbacks that are identical to those as stated in connection with DE 4009 465. In systems of hard-to-mix components, localized inhomogeneous mixing condition can occur in the same manner as in with the deflector mixing head of U.S. Pat. No. 5,443,797, which are for reason of quality assurance unacceptable.
It would therefore be desirable and advantageous to provide an improved deflector mixing head to obviate prior art shortcomings and to provide a deflector mixing head of a simple construction and with which highly homogenized mixtures can be realized even in hard-to-mix reaction systems.
SUMMARY OF THE INVENTION
According to one aspect of the present invention, a deflector mixing head is provided capable to achieve a high degree of homogenization of reaction components, in particular also with hard-o-mix reaction systems.
The deflector mixing head according to the present invention comprises a mixing chamber with an inlet valve and a control piston for regulating an inflow of components, an overflow chamber arranged downstream from and in perpendicular position to the mixing chamber, a cleaning piston for controlling an opening and closing of a mixing chamber inlet side of the overflow chamber, a connection chamber in substantially axially parallel position to the overflow chamber and disposed between the mixing chamber and overflow chamber, said connecting chamber is provided with deflector elements positioned in a flow path between the inlet and an outlet side of the connecting chamber and provided with a displacement piston disposed parallel to the cleaning piston to be lifted for allowing emptying the connection chamber.
According to one feature of the invention an additional intensive mixing effect can be realized by means of providing an intermediate connecting chamber of a particular configuration which is positioned between the mixing chamber and the overflow chamber. The disposition of a connecting chamber provides for additional multiple dividing and re-mixing of the mixture flow which takes place at the juncture of the deflecting elements and ensures that even the hard-to-mix reaction components are worked into a homogenized reaction mixture. Furthermore, an essential aspect of the deflector mixing head according to the present invention that after the constant flow of homogenized mixture, the connection chamber is completely emptied by means of the displacement piston at the end of the shot, so that when operating in conjunction with the control piston and the cleaning piston all remaining residue has been cleared from the mixing head.
In a preferred embodiment of the invention and in order to improve the degree and quality of mixing the components, the flow path of the mixture is extended by means of providing a correspondingly enlarged number of deflecting elements and by universally encasing the overflow chamber by the connecting chamber, which is connected to the mixing chamber at an inlet side on the side opposite the side of the overflow chamber.
In a further especially preferred embodiment of the invention, the connecting chamber is so configured as to terminate in an annular gap, which is variably adjustable by means of a cleaning piston and the flow of the reaction components can thus be homogeneously mixed at the deflecting elements positioned in the circumferential direction of the annular gap. This configuration ensures on the one hand a highly stabilized laminar discharge and on the other hand, the possibility to adapt the reduced flow effect of the annular gap individually to a particular mixture.
In another especially preferred embodiment, the shear effect of the deflector mixing head is variably adjustable and thus the flow diameter of the connecting chamber is adjustable by means of a corresponding lifting position of the displacement piston so that the high shear forces necessary for a good mixing effect can be adjusted in correspondence to keeping the size of the diameter of the connecting chamber small by lowering the displacement piston, while on the other hand, when lifting the displacement piston and the flow diameter of the connecting chamber is thus enlarged, the shear effect becomes very small, which ensures that even the very shear-sensitive reaction mixtures can be treated gently but at the same time are subjected to a thorough mixing action.
In yet a further preferred embodiment of the invention and in particularly simple manner, the deflecting elements which are secured with the displacement piston in a fixed manner are received with a bearing and sealing fit in corresponding receiving bores disposed at the delimiting wall of the connection chamber opposite the displacement piston.
In order to allow a most homogeneous flow of the component mixture through the connecting chamber, a number of diverting elements are provided extending from the entry side to the exit side of the connection chamber and which are configured as a number of mixing pins of varying diameters positioned in such a manner, such that the mixing pins are placed offset and in staggered position corresponding to their diminishing diameters.
REFERENCES:
patent: 4773564 (1988-09-01), Wallner
patent: 5277567 (1994-01-01), Bauer et al.
patent: 5443797 (1995-08-01), Proska et al.
patent: 5785422 (1998-07-01), Eidenmuller
patent: 32 08 696 (1983-09-01), None
patent: 32 13 153 (1983-10-01), None
patent: 29 41 975 (1985-12-01), None
patent: 40 09
Day Ursula B.
Feiereisen Henry M.
Krauss-Maffei Kunststofftechnik GmbH
Soohoo Tony G.
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