EP0203260B1 - Kneading machine - Google Patents

Abstract

A kneading machine with a charging opening leading to a kneading chamber, in which two axially parallel kneading tools can be driven in opposite directions at different rotational speeds, has at least three such kneading chambers which are disposed next to each other and an aperture which connects their internal spaces. The material to be kneaded can be conveyed through this aperture, which extends transversely of the shafts of the kneading tools from one kneading chamber to the next, so that the material is continuously treated until it reaches in the last kneading chamber an evacuating opening and preferably an evacuating worm which is mounted at such location and by means of which the material is ultimately evacuated from the machine. In this manner, the advantages of a kneading machine with shafts for kneading tools which are journalled at both ends are combined with the advantages of continuous treatment of the material to be kneaded. This also renders it possible to vary the shapes of kneading tools in the of kneading chambers.

Description

The invention relates to a kneading machine with a loading opening and mutually adjacent kneading chambers, each of which connects its interior and has an opening which is oriented transversely to the axes of the kneading tools and in which two axially parallel kneading tools can preferably be driven in opposite directions at different speeds.

Kneading machines of this type are known for many applications. A batch introduced into the kneading chamber through the loading opening must always be processed for a certain time, if necessary provided with additives and then removed.

In the plastics and rubber industry, single or twin-screw extrusion mixers have been used for some time, with which solid or liquid additives in plastics or rubber materials can be mixed in homogeneously at elevated temperatures in the thermoplastic or in the solvent phase. Solid fillers and reinforcing agents such as calcium carbonate, silicates, asbestos, talc, kaolin, metal oxides, dyes, glass fibers, synthetic reinforcing fibers, graphite fibers, boron fibers, and liquid additives such as plasticizers may be mentioned as additives.

To a lesser extent, substances such as antioxidants, light stabilizers, stabilizers, crosslinking agents, lubricants, processing aids, fire retardants, antistatic agents or blowing agents have to be incorporated in the polymer materials in an exact concentration in the most homogeneous possible distribution.

The process usually runs in such a way that the additives and the plastic granules are metered in with dosing scales, mixed in a continuously operating mixing extruder, mostly in the thermoplastic state, and extruded as strands at the head end of the extruder, which are then extruded with a cutting machine be granulated.

Mixing and / or plasticizing processes can thus be carried out in the mixing extruder.

For the subsequent shaping, the filled plastic granules can be processed further into molded parts, for example in injection molding machines.

In commercially used plastic or rubber products, the filler content in the majority of cases should be 50% or less in order not to unduly lower the mechanical strength and other important properties of the plastic parts.

Another new area of application for continuously operating mixing extruders is the production of propellants and explosives as well as pyrotechnic articles.

In this area of work, they worked mainly on solid fuels, propellant powder, explosive charges with plastic binders and pyrotechnic articles. In particular, so-called double-base solid fuels were produced using the thermoplastic working process, while other products are processed from a pasty state in the solvent phase or due to a liquid polymeric binder.

In contrast to the filled plastic and rubber articles described at the beginning, these products have high proportions of solid or liquid additives in some cases because of their specific application. B. can be about 70% to 95%. The polymeric binder proportions are then only about 30% to 5% and could actually only be partially processed with the help of solvents.

With many substances in this production area such as B.

Nitrocellulose as a polymer component is impact and friction sensitive materials. The same applies to explosive components. These substances and compounds are often also very thermally sensitive and fizzle out at temperatures between 170 ° C and 250 ° C.

The problem described has hindered and made it more difficult to use continuously operating machines. A number of reasons, which can also be found in the extruder system, were largely responsible for these difficulties. For thorough mixing, mixing screws are required, the length of which is approximately 15 to 30 times their diameter, in order to ensure a sufficient residence time for the required wetting processes in the extruder. Another important requirement is the very exact dosing of the raw materials, since there is hardly any backflow in the extruder, even in the kneading zones, and therefore hardly any mixing with the following materials in order to compensate for any weighing inaccuracies.

Another major difficulty for the processing of fuels and explosives must be seen in the possible wall contact of the extruder screws, which are only supported on one side. Due to the considerable length of the screws, wall contact cannot be ruled out even when the machine is completely full. However, substances sensitive to impact can be ignited under these loads, which can lead to fires, deflagrations or, if confined, even detonation.

Another problem must be seen in the processing of fuels and explosives in particular in the high filler proportions already mentioned. The wetting and homogenization process cannot be optimally ended during the short residence time of a few minutes, so that often several runs with the same material or premixes have to be carried out in batch mixing processes.

Kneading machines of the type mentioned at the outset are also known from US Pat. No. 2,698,962 and DE-AS 11 31 389, in which two kneading chambers are arranged one above the other, but in which kneading screws are also provided are arranged. Especially in the case of wholly or partially powdery and / or granular starting material, there is a risk that the kneaded material can get too quickly from one kneading chamber to the other and from there to its discharge opening before gravity achieves the desired consistency. In addition, even with other kneaded material, gravity ensures that the kneaded material is transported relatively quickly, so that the dwell time of the kneaded material is relatively short.

The invention is therefore based on the object to provide a kneading machine of the type mentioned, with which a longer residence time of the kneaded material can be achieved, with sensitive fuels and explosives as well as other filled plastics being able to be continuously mixed and kneaded in great homogeneity without that there is a risk that the mixing and kneading tools touch the wall of the kneading chamber. At the same time, a good compression of the kneaded product should be achieved when leaving the kneading machine, so that any air influences or the like that may have been incorporated during the kneading are avoided as far as possible.

The solution to this problem is that at least three. Kneading chambers arranged in an approximately horizontal row next to each other and that at the end of the row of kneading chambers, a discharge screw is attached to the discharge opening of the last kneading chamber.

The horizontal row of more than two kneading chambers results on the one hand in an intensification of the processing of the kneading material, on the other hand the influence of gravity which accelerates the feeding of the kneading material is switched off, so that the combination of these measures can increase the dwell time of the kneading material in the kneading machine. In addition, the discharge screw located at the end can compact the kneaded material again and, depending on the selected speed, can also influence the dwell time.

A development of the invention can consist in that the speed of the discharge screw can be changed and / or the direction of rotation and conveying can be reversed. This also allows the dwell time of the kneaded material to be changed as desired. In addition, between the reversal of the direction of rotation and conveyance, there is also the speed O of the discharge screw, which likewise largely prevents the kneaded material from escaping and thus can increase its dwell time.

The measures described above can be supported in that the mouth of the housing of the discharge screw is narrowed, preferably in the form of an extrusion nozzle. In this way, there is above all a certain back pressure within the discharge screw, which can bring about the desired compaction of the kneaded material after it has been kneaded during discharge.

The advantages of a kneading machine, each with two axially parallel kneading tools and a plurality of kneading chambers, are retained, namely the kneading tools can be mounted on both sides and carry out thorough mixing and kneading. At the same time, a sufficiently long dwell time of the kneading material is ensured in the kneading machine, since three or more kneading chambers of this type are arranged horizontally next to one another, so that the material to be kneaded can gradually move from chamber to chamber without being moved too quickly by gravity, and this enables continuous work over a sufficiently long dwell time. The mixing and kneading can be influenced and extended by the choice of the number of kneading chambers, but it can also be influenced by the discharge screw in a finished machine with a fixed number of kneading chambers. In view of the continuous operation, new kneading material can be refilled at the loading opening, while the processed material can be drawn off at the last of the kneading chambers located next to one another at the discharge opening and the mouth of the discharge screw.

Continuous processing that can be adapted to the needs of the respective kneading material is therefore possible.

The kneading paddle shafts generally used in such kneading machines can cause high compressive, tensile and shear forces and thus strong friction in the kneaded material, which leads to excellent dispersion and homogeneity. Because of the connection opening from one kneading chamber to the next, these kneading tools and kneading blades have an additional function because they gradually convey the kneaded material to this opening and finally to the next kneading chamber. Depending on the desired residence time, the number of kneading chambers can be selected next to one another.

The speed of the kneading tools of one chamber can be different from that of at least one other chamber. Thus, not only can the two kneading tools be driven in a chamber at different speeds, but these speeds can also differ from chamber to chamber if the kneading material makes this necessary. For example, the speed of the tools of the chamber next in the feed direction for the kneaded material could be lower than that of the tools in at least one of the previous kneading chambers. As a result, a certain back pressure and thus a sufficiently long dwell time of the kneaded material can be achieved in the course of time. Such deviating speeds can also be used to determine whether the kneaded material changes its viscosity during processing.

An embodiment of the invention of considerable importance and great advantages can consist in that inlet openings for liquid and / or solid additives are provided between and / or on the kneading chambers. Thereby the kneaded material can be gradually provided with further additives during its continuous processing, which are then mixed and kneaded in the subsequent chambers. In such a case, it may then be expedient that the speed of the kneading tools in a kneading chamber at or behind openings for metering in is greater than that of the kneading tools in a kneading chamber before metering in, for example to take into account the increase in kneading substance and this now a larger amount of kneaded material to be conveyed correspondingly faster.

A particularly expedient compromise between a good dwell time for the kneaded material and a not too great mechanical outlay can consist in the fact that four kneading chambers can be provided side by side. This results in intensive kneading and mixing, which far exceeds processing in two kneading chambers one above the other, but the overall height remains low despite the large number of kneading chambers and the desired intensive processing is achieved by four kneading points.

A further embodiment of the kneading machine according to the invention to improve the kneaded products and in particular to avoid air pockets in these products - which is particularly important in the production of propellants and explosives - can consist in at least one kneading chamber and / or the connection of two kneading chambers a connection for generating a negative pressure is provided. It is particularly expedient if a connection for generating a negative pressure is provided on the last and / or penultimate kneading chamber and / or the housing of the discharge screw, so that the kneaded material is freed or kept free of unfavorable air pockets at the end of its processing.

It has already been mentioned that kneading blades can be provided as kneading tools, which lead to a correspondingly intensive processing of the kneaded material and can also ensure the feed from kneading chamber to kneading chamber, that is to say they have a double function.

However, it is also possible for individual kneading chambers to have rollers and / or polygonal disks as kneading tools instead of kneading blades. This configuration is possible because of the arrangement according to the invention of a plurality of kneading chambers next to one another and thus allows the kneading material to be processed in different ways within the individual chambers. While the kneading blades have above all a good mixing effect, larger kneading effects can be achieved with such rollers and polygonal disks. By arranging several kneading chambers next to one another with different kneading tools, it is therefore possible to act differently on the kneaded material in a targeted manner.

It is particularly expedient if at least two kneading chambers with kneading blades are arranged in a row after the loading opening of the kneading machine before kneading chambers with rollers and / or polygonal disks are connected. This ensures that the kneaded material is first mixed as well as possible and is already pre-kneaded before it is exposed to the rollers or polygonal disks, which predominantly carry out shredding and plasticizing work, especially when they are heated.

Sieves or baffles for division and / or slides for stowing the material flow can be arranged between at least two kneading chambers. This in turn can be used to control and influence the residence time of the material in the individual chambers. The screens, baffles and / or slides can be adjustable with regard to their position and the passage opening they can open, and with regard to their orientation for directing the material flow. This configuration is also possible due to the series arrangement of several kneading chambers and allows a targeted change in the material flow and the dwell time of the kneaded material in individual kneading chambers.

It is useful if each pair of kneading tools in a kneading chamber has its own drive, for. B. has an oil motor. This enables the desired speeds and speed differences to be set individually from chamber to chamber. Nevertheless, the overall construction is simple in terms of mechanical complexity.

In order to be able to change the number of kneading chambers lined up, it is advantageous if a connection for the inlet opening of a subsequent adjacent chamber or the discharge screw is provided at the discharge opening of a kneading chamber.

Overall, there is a kneading machine with which a kneadable material can be processed continuously and in a targeted manner depending on the requirements, and the dwell time can also be adapted to the respective requirements. In an advantageous manner, the kneading tools can nevertheless be stored outside the kneading chambers, so that even substances sensitive to friction and impact can be processed without any problems, especially since the kneading tools can be stored on both sides. Dangers for explosive materials caused by wall friction are completely avoided by this selected arrangement. Since the kneading machine can be constructed practically according to the modular principle, it is very versatile and can be used and adapted to a wide variety of mixing, kneading, crushing and plasticizing work for a wide variety of kneaded materials. If an extrusion nozzle or similar constriction is arranged at the outer mouth of the discharge screw or from its housing, there is the further advantage that the kneaded material is shaped into a strand and thus particularly well from the Machine out and then transported on.

• Fig. 1 einen Längsschnitt durch eine erfindungsgemäße Knetmaschine, mit mehreren nebeneinander befindlichen Knetkammern, wobei diese jeweils im Querschnitt zu sehen sind und jede Knetkammer Knetschaufeln enthält,
• Fig. 2 eine der Fig. 1 entsprechende Darstellung, wobei jedoch in der dritten Knetkammer gegenläufig umlaufende Walzen als Knetwerkzeuge vorgesehen sind, sowie
• Fig. 3 eine den Fig. 1 und 2 entsprechende Darstellung, wobei jedoch in der dritten und vierten Knetkammer Polygonscheiben als Knetwerkzeuge vorgesehen sind.

The invention is described in more detail below with its details that are essential to it, using the drawing in three exemplary embodiments. It shows in a schematic representation:

• 1 shows a longitudinal section through a kneading machine according to the invention, with a plurality of kneading chambers located next to one another, each of which can be seen in cross section and each kneading chamber contains kneading blades,
• Fig. 2 is a representation corresponding to Fig. 1, but in the third kneading chamber counter-rotating rollers are provided as kneading tools, and
• 3 shows a representation corresponding to FIGS. 1 and 2, but polygonal disks are provided as kneading tools in the third and fourth kneading chambers.

A kneading machine designated as a whole by 1 has a loading opening 2 through which the kneaded material according to the arrow Pf 1 is introduced and reaches a first kneading chamber 3. In the kneading chamber 3, two kneading tools 4 are arranged, the axes 5 of which are parallel to one another and which according to FIG. the arrows Pf 2 and Pf 3 are driven in opposite directions and at different speeds. It can be seen that a plurality of kneading chambers 3 are adjacent to one another in a horizontal row and each have an opening 6 connecting their interior spaces, which is oriented transversely to the axes 5 of the kneading tools 4 and through which the kneaded material according to the arrow Pf 4 from a kneading chamber 3 in the next one is being promoted. The last of the kneading chambers 3 located next to each other in a row has a discharge opening 7 from which the finished kneaded material is drawn off.

The speeds of the kneading tools 4 of the one chamber 3 can be different from those of at least one other kneading chamber 3. For example, the speed of the tools 4 according to the feed direction. Chamber 3 following arrow Pf 4 may be smaller than that of tools 4 in at least one of the previous kneading chambers 3 in order to generate a certain jam at the openings 6 and thus increase the dwell time in the previous kneading chamber 3.

In all embodiments, it is also indicated that 3 input openings 8 can be provided between two kneading chambers, through which according to. the arrows Pf 5 liquid or solid additives can be added to the kneaded material and added. It is then expedient if the speed of the kneading tools 4 in a kneading chamber 3 behind an opening 8 for metering in is greater than that of the kneading tools 4 in a kneading chamber 3 in front of the metering opening 8, because the amount of kneaded material increases as a result of the metering in of material and therefore it can be arranged for a somewhat faster onward transport, so as not to cause excessive congestion.

At the end of the row of kneading chambers 3, in the exemplary embodiment, a discharge screw 9 is attached to the discharge opening 7 of the last chamber 3. This can have, for example, a nozzle or the like. End, so that the kneaded material is obtained in a continuous strand and is discharged from the kneading machine 1, so that it can be further processed accordingly. The above-mentioned nozzle or similar constriction at the outlet of the discharge screw 9 also ensures a certain jam in the interior of the screw, so that the kneaded material is additionally compressed again during discharge. The speed of the discharge screw 9 can be changed and it may even be possible to reverse the direction of rotation and thus the conveying direction of the discharge screw 9, whereby discharge of the kneaded material can be prevented for a while, so that the residence time can be influenced and extended.

In a manner not shown, the kneading chambers 3 and in particular in the feed direction according to FIG. the arrows Pf 4 last kneading chambers 3, one or more connections for generating a negative pressure within the kneading chambers 3 may be provided in order to avoid or eliminate air pockets.

In the exemplary embodiment according to FIG. 1, only kneading blades are provided as kneading tools 4.

In the exemplary embodiment according to FIG. 2, rollers 10 are provided in a kneading chamber 3 instead of kneading blades, while in the exemplary embodiment according to FIG. 3, polygonal disks 11 are provided as kneading tools in the third and fourth kneading chambers 3. First, two kneading chambers 3 with kneading blades are arranged in series after the loading opening 2, before these kneading chambers 3 connect either with the rollers 10 or the polygonal discs 11. The arrangement of a plurality of kneading chambers 3 next to one another thus not only permits continuous processing, but also enables the mechanical action on the kneaded material to be influenced by different kneading tools 4.

It can be clearly seen that at the respective discharge opening 6 or 7 of a kneading chamber 3, a connection 12 is provided for the entry opening of a subsequent adjacent chamber 3 or the discharge screw 9, so that the passage openings 6 are formed by coupling these connections 12 together. Furthermore, this makes it possible to enlarge or reduce the number of kneading chambers 3, depending on the type of material or kneaded material to be processed, if these connections 12 can be detachably coupled.

Overall, there is a kneading machine 1 with a simple structure, two kneading chambers 3 each being carried by a common support foot 13. In this case, two kneading chambers 3 can also be firmly connected and coupled to two further such chambers be, as these examples show. As a result, both the number of these kneading chambers and the kneading tools 4 used in each case can be adapted almost arbitrarily to the respective kneading material, the advantages of the previously known batch kneading machines with two axially parallel kneading tools 4 being retained in a single kneading trough, but nevertheless continuous processing of the kneaded material is possible by simultaneously transporting it from the kneading chamber 3 to the kneading chamber 3 and removing it with the aid of a discharge screw 9. The dangers of wall friction of the kneading tools and the like which occur in previous continuous kneading processes with the aid of extrusion screws are avoided, so that the kneading machine 1 according to the invention is also suitable for highly flammable, flammable or explosive substances, but also for other substances which are to be mixed and kneaded as intensively as possible is. Each pair of kneading tools 4 can have its own drive, for example with the help of an oil motor. As shown, six kneading chambers 3, or possibly only three kneading chambers, can lie side by side. A good compromise between machine effort and residence time can be the use of four, possibly five kneading chambers 3 side by side. Seven or more kneading chambers 3 would even be conceivable.

All features and construction details shown in the description, the summary and the claims and the drawing can have significant meaning both individually and in any combination with one another.

Claims (19)

1. A kneading machine (1) including a charging opening (2) and kneading chambers (3) adjacent to one another in each case having an opening (6) which connects their interiors and is oriented transversely to the shafts (5) of kneading tools (4), in which kneading chambers in each case two axially parallel kneading tools are adapted to be driven in opposite directions, preferably at a different speed, characterized in that at least three kneading chambers (3) are arranged side by side in an approximately horizontal row and that at the end of the row of kneading chambers (3) there is a discharge screw (9) fitted at the discharge opening (7) of the last kneading chamber (3).

2. The kneading machine as claimed in claim 1, characterized in that the speed of the discharge screw (9) is variable and/or the direction of rotation and conveyance is reversible.

3. The kneading machine as claimed in claim 1 or claim 2, characterized in that the opening of the housing of the discharge screw (9) is constricted, preferably taking the form of an extrusion nozzle or the like.

4. The kneading machine as claimed in any one of claims 1 to 3, characterized in that four kneading chambers,43)- are provided side by side.

5. The kneading machine as claimed in any one of claims 1 to 4, characterized in that the speeds of the kneading tools (4) of the one chamber (3) are different from those of at least one further kneading chamber (3).

6. The kneading machine as claimed in any one of claims 1 to 5, characterized in that the speed of the tools (4) of the next following chamber (3) in the direction of feed is lower than that of the tools (4) in at least one of the preceding kneading chambers (3).

7. The kneading machine as claimed in any one of claims 1 to 6, characterized in that between and/or at the kneading chambers (3) openings (8) are provided for feeding liquid and/or solid admixtures.

8. The kneading machine as claimed in any one of claims 1 to 7, characterized in that the speed of the kneading tools (4) in a kneading chamber (3) at or behind an opening (8) for batched infeed is higher than that of the kneading tools (4) in a kneading chamber (3) before the batched infeed.

9. The kneading machine as claimed in any one of claims 1 to 8, characterized in that at least one attachment to generate a vacuum is provided at at least one kneading chamber (3) and/or at the connection of two kneading chambers (3).

10. The kneading machine as claimed in any one of claims 1 to 9, characterized in that an attachment to generate a vacuum is provided at the last and/or last but one kneading chamber (3) and/or at the housing of the discharge screw (9).

11. The kneading machine as claimed in any one of claims 1 to 10, characterized in that kneading paddles are provided as kneading tools.

12. The kneading machine as claimed in any one of claims 1 to 11, characterized in that individual kneading chambers have rollers (10) and/or polygonal discs (11) as kneading tools, instead of kneading paddles.

13. The kneading machine as claimed in claim 12, characterized in that at least two kneading chambers (3) with kneading paddles are arranged in a row one behind the other after the charging opening (2) of the kneading machine, before being adjoined by kneading chambers with rollers (10) and/or polygonal discs (11).

14. The kneading machine as claimed in any one of claims 1 to 13, characterized in that screens or baffles for dividing the flow of material and/or slide plates for causing the flow of material to accumulate are arranged between at least two kneading chambers (3).

15. The kneading machine as claimed in claim 14, characterized in that the screens, baffles and/ or slide plates are adjustable with respect to their position and the opening they can clear as well as with respect to their orientation for conducting the flow of material.

16. The kneading machine as claimed in any one of claims 1 to 15, characterized in that each pair of kneading tools (4) in a kneading chamber (3) has its own drive, e.g. an oil engine.

17. The kneading machine as claimed in any one of the preceding claims, characterized in that at the discharge opening (6, 7) of a kneading chamber (3) there is in each case a connection (12) provided for the intake opening of a following, adjacent chamber (3) or the discharge screw (9).

18. The kneading machine as claimed in claim 17, characterized in that the connections (12) are adapted to be detachably coupled.

19. The kneading machine as claimed in any one of the preceding claims, characterized in that in each case two kneading chambers (3) are joined and are adapted to be coupled to further kneading chambers (3) or groups of kneading chambers (3).

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