Patent Application
20050190642
The invention relates to a dispersing tool with a hollow shaft, which has an open, laterally slotted region at its free end that faces away from a drive and that is at the bottom in the position of use, and with an inner shaft, which can rotate in this hollow shaft and which has a dispersing rotor interacting with this hollow shaft in the region of the slotted end of the hollow shaft, wherein as the inner shaft rotates, it creates a pumping effect directed towards the free end.
A dispersing device of this type is known from U.S. Pat. No. 6,398,402 B1. In this publication, the inner shaft with a helical thread arranged thereon, which has the mentioned pumping effect in the direction towards the working end, is housed in a stationary, rigid hollow shaft, where both of these shafts are aligned with their working ends essentially downwards and arranged especially vertically in the position of use. This should prevent a pumping effect in the opposite direction due to the inner shaft and its formation while the inner shaft rotates. However, at the very high rpm values that are to be made available by such devices, there is the risk that displacements of the inner shaft will cause the thread to come into contact with the inner side of the hollow shaft, which could lead to worn and rubbed-off parts and these in turn could lead to undesired and disruptive fillers in the material to be dispersed. In addition, such an inner shaft can then become heavy if it is to be composed of metal. The thread on the inner shaft produces unbalanced masses, which differ over the profile of the inner shaft and which likewise can lead to undesired deformations and accordingly to contact with the hollow shaft, which is arranged at only a minimal distance.
Therefore, the objective of the invention is to create a dispersing tool of the type mentioned in the introduction, with which the pumping effect of a smooth inner shaft can act opposite the direction towards the drive, wherein eccentricities in the profile of the inner shaft are nonetheless prevented and also manufacturing from metal is be possible in a simple way.
This problem, which at first glance appears to be contradictory, is solved in that the inner shaft features at least one section with a cross section that changes in the axial direction and this cross section increases from the drive side towards the free end.
Tests have shown that when this inner shaft rotates within fluid rising in the stationary hollow shaft, this fluid is drawn outwards due to centrifugal force to the region with the increasing cross section, whereby it is necessary that fluid flows across the increasing cross section from top to bottom, thus the fluid is drawn in the direction towards the free end. Accordingly, the changing cross section produces a motion vector acting on the fluid from the drive towards the free end, so that fluid located in the hollow shaft can be drawn away from the drive without requiring a feeding screw with corresponding eccentricities and resulting unbalanced masses on the outer side of the inner shaft.
In one configuration of the dispersing tool according to the invention that has proven to be effective, the cross section of the section is at least point-symmetric relative to the longitudinal center axis of the inner shaft. This configurations achieves a uniform load on the inner shaft and drawing effect in the relevant region or regions while preventing unbalanced masses, so that the disruptive pumping effect in the direction towards the drive can be optimally compensated and eliminated.
It is especially advantageous when the inner shaft has several, especially several equal sections with increasing cross section. Therefore, the described drawing effect can be increased and better distributed, above all it can be designed or tuned such that just enough fluid is drawn or displaced from the hollow shaft downstream or in the direction towards the free end so that suctioning of air from above into the hollow shaft with corresponding entrance into the fluid is prevented.
Preferably, two to ten, especially three, four, or eight sections with changing cross section are distributed over the length of the inner shaft.
In addition, in the sense of a constant drawing effect in the direction towards the free end, it has proven to be advantageous in one embodiment of the dispersing tool when the sections with increasing cross section are arranged on the inner shaft at least at a predominantly uniform spacing.
Here, configurations have proven to be especially advantageous, in which the open spacing between the individual sections with changing cross section correspond in their axial dimension to approximately one-half, two times, or three times this value or to an intermediate value.
Other configuration of the dispersing tool according to the invention relate to dimensioning and size relationships, especially of the section or sections with changing cross section. Thus, it is advantageous, for example, if the angle enclosed by a meridian line of a section (6) with changing cross section and a line parallel to the longitudinal axis of the inner shaft (3) equals approximately 10° to 60°, preferably approximately 15° to 45°, especially approximately 20° to 30°. In a different configuration, the axial extent of the section (6) with increasing cross section equals between approximately one-half and two times its greatest diameter; in particular, it is approximately the same size as this largest diameter.
One embodiment of the invention, which has an essentially cylindrical projection, whose diameter corresponds to approximately the largest diameter of the section, arranged at the end of one or more sections (6) with changing cross section facing away from the drive side, is advantageous both in terms of manufacturing and also for stabilizing the inner shaft. The projections have the effect that, first, inner shafts manufactured from plastic in an injection-molding method can be removed easily and without disruptive excess from the molds after the manufacturing process. Thus, the finishing work is kept to a minimum as much as possible. Second, the projections can provide an additional support function, especially in the region of strong deflection of the inner shaft.
In another configuration of the invention, the inner shaft features minimal spacing between the regions with changing cross section in a middle region between the drive side and the working end in order to counteract the deflection of the inner shaft, which is strongest at these locations, or to distribute possible contact with the inner side of the hollow shaft to several positions.
It is especially advantageous when the section with increasing cross section next to the free end is offset approximately into the middle of a lateral outlet opening of the hollow shaft or relative to this in the direction towards the drive, especially completely outside the outlet opening in this direction. Therefore, the drawing effect in the region of the free end can be deflected outwards, so that the fluid to be treated remains in the region from the bottom side up to this opening due to hydrostatic pressure and air entry into this fluid can be prevented as much as possible.
In the various embodiments of the dispersing tool, different spatial configurations are conceivable. Especially advantageous are those, in which the meridian line of the sections with changing cross section has a constant profile up to its greatest radial extent, especially with a straight line, convex curve and/or concave curve.
Configurations of the dispersing tool, in which the meridian line of the sections with changing cross section leads back in a simple way from the point of greatest extent in the direction towards the inner shaft, are advantageous in terms of manufacturing. Here, the meridian line preferably runs from the point of its greatest radial extent in a curved or straight line, especially in a plane perpendicular to the axis of the inner shaft, to its end facing the free end of the inner shaft.
In one preferred embodiment, the sections with changing cross section extend out relative to the surface of the inner shaft at least in the region of the greatest cross section. In this way, an inner shaft of greater stability can be created relative to an arrangement, in which these sections are worked into the profile of the inner shaft. Here it is also especially favorable also for manufacturing when the smallest cross section of the section with changing cross section corresponds to the cross section of the inner shaft and thus the entire section projects from the inner shaft. On the other hand, however, it is also conceivable that the largest cross section of the section with changing cross section corresponds to the cross section of the inner shaft and the sections are worked into or inserted into the inner shaft arranged relative to each other in this way. Depending on the profile of the meridian line of each section, more or less long axis-parallel surface parts of the inner shaft are produced.
For a good drawing effect with simultaneously the best possible circulation, it is preferable when the section with changing cross section is rotationally symmetric relative to the longitudinal middle axis of the inner shaft at least region-by-region and/or has circular cross sections.
Finally, to be able to manufacture the dispersing tool simply and favorably, it is advantageous when the inner shaft is manufactured from one or more metallic materials and/or plastics. Manufacturing with composites of the mentioned materials or assembling the inner shaft from several pieces of the same and/or different materials is also possible.
In the following, embodiments of the invention are described in more detail with reference to the figures of the drawing. Shown in partially schematic representation are:
All of the figures show a dispersing tool designated as a whole with 1. The dispersing tool 1 has a hollow shaft 2, which has an open, laterally slotted region on its free end 4, which faces away from a not shown drive and which is at the bottom in the position of use. In
In a continuation of the inner shaft 3 towards the free end 4, four sections 6 with increasing cross section can be seen, which in the present case are each embodied the same and are spaced uniformly, wherein the open spacing between the sections 6 corresponds to approximately two times an axial dimension of the shaft. Starting from the surface of the inner shaft 3, the meridian line of the sections 6 with changing cross section extends continuously up to its greatest radial extent in a straight line, so that the smallest cross section of the sections 6 with changing cross section corresponds to the cross section of inner shaft 3. The meridian line then runs from the point of its greatest radial extent at its end facing the free end of the inner shaft back to the inner shaft in a plane perpendicular to the inner shaft axis.
Likewise, it can be taken from
The embodiment of the dispersing tool 1 shown in
Therefore, FIGS. 1 to 3 show a dispersing tool 1 with a hollow shaft 2, which has an open, laterally slotted region at its free end 4 that faces away from a drive and that is at the bottom in the position of use, and with an inner shaft 3, which can rotate in this hollow shaft 2 and which has in the region of the slotted end of the hollow shaft 2 a dispersing rotor 5 interacting with this hollow shaft, wherein when it rotates, the inner shaft 3 causes a pumping effect directed towards the free end. To counteract the pumping effect of a smooth inner shaft in the direction towards the drive and simultaneously to prevent eccentricities in the profile of the inner shaft 3 and to guarantee simple manufacturing, the inner shaft 3 is provided with at least one section 6 with an increasing cross section and the cross section increases from the drive side toward the free end.
The embodiments show dispersing tools 1 with a hollow shaft 2, which has an open, laterally slotted region on its free end 4 that faces away from a drive and that is at the bottom in the position of use, and with an inner shaft 3, which can rotate in this hollow shaft 2 and which has a dispersing rotor 5 interacting with this hollow shaft in the region of the slotted end of the hollow shaft 2, wherein when it rotates, the inner shaft causes a pumping effect directed towards the free end 4. To counteract the pumping effect of a smooth inner shaft in the direction towards the drive and simultaneously to prevent eccentricities in the profile of the inner shaft 3 and to guarantee simple manufacturing, it is proposed that the inner shaft 3 has at least one section 6 with an increasing cross section and the cross section increases from the drive side toward the free end 4.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2004 009 708.9 | Feb 2004 | DE | national |
