Agitating – Having specified feed means – Impinging jets
Patent
1998-12-30
2000-05-23
Cooley, Charles E.
Agitating
Having specified feed means
Impinging jets
422133, B01F 504, B01F 1502
Patent
active
060658622
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a high-pressure mixing head for mixing at least two reactive plastic components, in the case of which components the mixture emerges from the mixing head in the form of a curtain.
BACKGROUND OF THE INVENTION
Mixing heads for two-component plastics are known in which the components are injected under high pressure through injection nozzles located opposite one another into a cylindrical mixing chamber, the mixture is transferred from the mixing chamber into a settling chamber arranged at a right angle to the mixing chamber and is subsequently charged, for example in free-flowing manner, into open molds (see DE-A 29 07 938). In this case axially displaceable cleaning pistons and ejection pistons are provided both in the mixing chamber and in the settling chamber, which, after the filling of a mold has been concluded--ie, at the end of the shot, are axially displaced so that they fill out the respective chambers. The mixing-chamber cleaning piston comprises longitudinal grooves located opposite one another which in the piston position sealing the mixing chamber cover the injection nozzles and establish a connection to return lines for the components.
A reduction in the turbulence prevailing in the mixture is intended to take place in the settling chamber, so that emission of the mixture from the settling chamber takes place in laminar manner.
Now, it has been shown that, particularly in the case of mixing heads for relatively large throughputs of the two-component mixture, in the case of which the diameter ot the settling chamber is designed to be correspondingly large, only an inadequate reduction of turbulence takes place, so that the stream of the mixture flowing out has a tendency to fan out. With a view to avoiding a fanned outflow stream the settling chamber has to be disproportionately extended in the axial direction.
SUMMARY OF THE INVENTION
In accordance with the invention it is now proposed to provide the outflow chamber with a substantially rectangular cross-section.
The present invention provides a high-pressure mixing head for mixing at least two reactive plastic components in particular the components of a polyurethane reactive mixture, said mixing head containing a mixing chamber with proportioning piston, into which there lead two injection nozzles arranged opposite one another for the components, said mixing chamber leading into a settling chamber with cleaning slide, said settling chamber extending in substantially rectangular manner in relation to the axis of the mixing chamber, said mixing head being characterized in that the settling chamber and the cleaning slide have a substantially rectangular cross-section with an axial ratio from 10 to 100. The axial ratio is defined as the ratio of the width of the settling chamber and the cleaning slide to the thickness of the settling chamber and the cleaning slide.
The component mixture accordingly emerges from the mixing head in the form of a curtain with a breadth or width that is 10 to 100 times greater than its thickness.
The settling chamber and the cleaning slide should preferably have a substantially rectangular cross-section with an axial ratio from 15 to 80, in particularly preferred manner from 25 to 60.
The settling chamber is accordingly formed by two parallel boundary surfaces with a small spacing, whereby the spacing may amount to approximately 1 to 10 mm. By reason of the small spacing of the boundary surfaces a rapid and effective reduction of turbulence takes place in the flowing component mixture.
The mixing chamber opens, preferably in perpendicularly centric manner, through one of the large boundary surfaces of the settling chamber. The large lateral dimension of the settling chamber may amount to 2 to 8 times, in particularly preferred manner at least 3 times, the diameter of the mixing chamber.
The high-pressure mixing head according to the invention not only guarantees excellent settling of the component mixture but furthermore permits the rate of flow of the mi
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Althausen Ferdinand
Thiebes Florian
Wirth Jurgen
Cheung Noland J.
Cooley Charles E.
Gil Joseph C.
Hennecke GmbH
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