DE3920422A1 - Mixer for synthetic resin reagents - by feed reagents to tapered screws revolving in equal or opposite directions in tapered chamber - Google Patents

Abstract

Apparatus for mixing synthetic resin reagents has a mixing chamber with inlets for the reagents and an outlet for the mixture produced, and a stirrer in the chamber which has a tapered screw and forms a variable shear gap to the wall of the chamber. This stirrer consists of two meshing screws which revolve in the same or opposite directions and which can be moved together longitudinally. ADVANTAGE - The mixer is efficient even under critical conditions. It is self-cleaning when used for prolonged periods.

Description

The invention relates to a mixing device for multicomponent plastics according to the preamble of claim 1.

Such mixing devices, so-called. Low pressure mixing devices, at which are mixed mechanically by a stirrer known in a wide variety of embodiments. The ones to be mixed Components are passed through the mixing chamber containing the stirrer appropriate lines and supplied via valves. The valves are controlled synchronously, often in the closed position a return for the individual components is provided.

Low pressure mixers are generally replaced by a detergent cleaned, the fully reacted mixture and non-fully reacted components leftovers washed out through the outlet opening. Such a rinse or Cleaning is essential so that the mixing chamber does not "grows" and always a clean, recipe-based mixture is created. As Detergent is often used methylene chloride. After exiting this methylene chloride evaporates in the outlet of the mixing chamber the atmosphere. This procedure is "simple", but it can be questionable from a health point of view.

From DE-PS 20 62 008 is a device for mixing and conveying at least two liquid bodies which react to form solid bodies Known substances in which it is no longer necessary to leave material residues in the mixing chamber with the help of special tools or with the help of solutions detergents or detergents. For this there is a Conveyor or stirring screw used, which has a conical section has, so that between the mixing screw and the inner wall of the mixer chamber creates a gap, which is briefly replaced by a corresponding one Movement of the stirring screw can be reduced. That in the worm gear after the end of a mixing process, material left over from the high speed of the mixing screw on the inner wall of the mixing chamber flung and then scraped off the mixing screw and through the Exit opening promoted. However, this material can be used for manufacturing of molded parts are often not used, because the stirring screw in this phase, i.e. with already closed valves, is only partially filled and thus not knocking air into the mixture of components  is to be avoided. In addition, the mixing effect of the stirring screw is a consequence their lack of pressure build-up capacity, especially in the case of short mixing phase, inadequate.

With the invention, a mixing device of the type mentioned be created, which has an agitator and also under critical Conditions always ensures good mixing of the components, and the also cleans itself in continuous operation.

To solve this task, the measures according to the indicator of Claim 1 proposed.

As a result, the components are mixed so intensively that a homogeneous Mixture is formed and the component mixture adheres to the screws waves and housing walls is prevented. There is not just one Shear between the screw shafts and the inner wall of the mixing chamber, but also due to the intermeshing to closely intermeshing arrangement of Worm shafts between these themselves in the respective worm channels. This leads to significantly better product qualities.

The mixing device according to the invention also ensures good and stable funding conditions, since those located in the screw channels Components or the mixture of components through the web of the other Worm shaft are forced to move. This particularly contributes to reaction plastics to ensure that the mixture of components does not last too long Snail channel remains and thus a product structure in the channels is counteracted. Due to the good promotional effect of the one another gripping worm shafts will also be used to fill molds necessary pressure build-up is achieved faster and can take much longer be maintained so that air is driven into the Component mixture is prevented.

For the worm shafts, both the same and the opposite can be used Direction of rotation can be selected. Counter-rotating worm shafts are recommended, for example, for the catalysis of resins because relatively low demands on mixed and self-cleaning ability of the device. To generate a chemical reactive mixture, especially for the production of polyurethane on the other hand have worm shafts rotating in the same direction as proven useful.  

The self-cleaning ability of the mixing device according to the invention also results from the fact that the worm shafts in the direction of their longitudinal axes can be moved together. The shift can be mechanical, hydraulically or electrically. During the mixing phase they are Worm shafts are generally interdigitated, i.e. the Worm ridges of a worm shaft only partially engage in the The other worm shaft. At the end of a dosing both worm shafts are shifted, i.e. against the inner wall the mixing chamber and moved against each other at the same time. The worm shafts are then closely intermeshed. Clean this way the screw flights of the screw shafts not only the inner wall of the mixer chamber but also the worm threads of the other worm shaft from. Disassembly of the mixing device for cleaning purposes is when at all, only required at large intervals of several weeks.

According to a further feature of the invention, a worm shaft is against drivable above the other with different angular speeds. For this, the diameter, thread pitch are given the same screw profile and coordinate the number of turns of the worm shafts accordingly.

In a particularly advantageous embodiment of the mixing device are the cylindrical shaft sections of the worm shafts in themselves divided and the parts can be moved against each other. It can be done Realize mixing devices with very small dimensions. In particular the worm shaft bearings can be easily designed. Besides, can the drive for the worm shafts can be stored permanently.

The invention is described below with reference to the drawing of an embodiment explained in more detail.

In the drawing, the mixing device is shown schematically in longitudinal section. It consists of a housing, which is composed of sections ( 1 ), ( 2 ) and ( 3 ). A conical mixing chamber ( 4 ) is formed in the lower housing section ( 1 ). Into the mixing chamber lead an inlet openings ( 5 ) and ( 6 ), to which via rotary plug ( 7 ) and ( 8 ) supply lines ( 10 , 11 ) are connected for the supply of the components. If the rotary plug is in the appropriate position, ie if the components are not to be mixed, they are returned to the storage containers through the lines ( 12 , 13 ). With ( 9 ) the outlet opening of the mixing chamber is designated.

In the mixing chamber ( 4 ) a stirrer formed from the worm shafts ( 14 ) and ( 15 ) is inserted. The worm shafts are also conical, so that a shear gap ( 16 ) in the form of two intersecting truncated cones is formed between them and the inner wall of the mixing chamber. They enclose an angle of approximately 5 ° to approximately 20 ° between them. With a relatively short cone of the worm shafts, a larger angle is necessary and vice versa, so that the overall size of the mixing device remains in reasonable relation overall.

At the conical worm shafts ( 14 , 15 ) connect cylindrical shaft sections ( 17 ) and ( 18 ) which are mounted in the housing sections ( 2 ) and ( 3 ). In the illustrated embodiment, only the worm shaft ( 14 ) is driven. The power transmission to the second worm shaft ( 15 ) takes place with the help of the gear wheels or bevel gears ( 19 ) and ( 20 ).

For the displacement of the worm shafts ( 14 , 15 ) in the direction of their longitudinal axes, the bearing units ( 21 ) and ( 22 ) are moved hydraulically in the housing section ( 3 ). The connections ( 23 , 24 , 25 , 26 ) for the hydraulic pressure medium are indicated. A corresponding lifting movement of the worm shafts increases or decreases the shear gap ( 16 ) and the distance between the worm shafts themselves.

Claims (3)

1. Mixing device for multi-component plastics, has a mixing chamber, the inlet openings for the individual components and an outlet opening for the component mixture, as well as with a stirrer in the mixing chamber, which has a conical screw section and forms a variable shearing gap with the inner wall of the mixing chamber, characterized characterized in that the stirrer consists of two intermeshing, co-rotating or counter-rotating worm shafts ( 14 ) and ( 15 ) and the worm shafts are jointly displaceable in the direction of their longitudinal axes. 2. Mixing devices according to claim 1, characterized in that one of the worm shafts ( 14 , 15 ) can be driven at different angular speeds compared to the other. 3. Mixing devices according to claim 1, characterized in that the cylindrical shaft sections ( 17 , 18 ) of the worm shafts ( 14 , 15 ) divided into themselves and the parts are displaceable against each other.