Mixer for granular material

A mixer for granular materials has a mixing container consisting of a first mixing container portion and a second mixing container portion detachably connected to one another. The mixing container has a longitudinal axis and a transverse axis extending perpendicularly to the longitudinal axis. A support frame is provided in which the mixing container is supported so as to be pivotable about the transverse axis and rotatable about the longitudinal axis. The mixing container has a first position in which mixing is performed and in which the second mixing container portion is positioned above the first mixing container portion. The mixing container has a second position in which the second container portion, after completion of mixing, contains the mixed material and is detachable from the first mixing container portion.

BACKGROUND OF THE INVENTION
 The present invention relates to a mixer for any granular or particulate
 material of any granule or particle size, such a powders, grit-size
 material etc, which optionally may have liquids added thereto, as well as
 pastes, especially PVC paste. The mixer comprises a first mixing container
 portion that is pivotable about an axis positioned at an angle to the
 longitudinal axis of the mixing container portion and a second mixing
 container portion in which the mixed product, after separation from the
 first mixing container portion, is located for further use. The present
 invention also relates to a method for performing a mixing process in the
 inventive mixer.
 Mixers having a mixing container consisting of two mixing container
 portions are known. In such mixers, the bottom mixing container portion
 into which the material to be mixed has been filled is connected to a
 second mixing container portion having a mixing tool and, subsequently,
 the mixing container is rotated by 180.degree. relative to a horizontal
 axis so that the mixing tool is now at the bottom. In this upside down
 position, in which the mixing tool rotates about a vertical rotary axis,
 the mixing process is performed. After completion of the mixing process,
 the mixing container is again rotated about the horizontal axis into its
 initial position in which the mixing container portion containing the
 mixed material can be separated from the other parts of the mixer.
 From European Patent 0 269 799 B1 a mixing device is known in which a
 mixing container is provided comprised of two bowl-shaped mixing container
 portions that are connectable to one another. The mixer comprises a
 stationary holder at which one of the mixing container portions of the
 mixing container is rotatably supported so as to be pivotable about a
 horizontal support axis and wherein the second container portion has a
 mixing tool whose shaft in the mixing position is vertical.
 In such mixers the mixing tool must be rotated at a high rpm in order to
 ensure that the material is sufficiently mixed. The material to be mixed
 is forced upwardly at the inner walls of the mixing container. This causes
 heating of the material to be mixed. This undesirable temperature increase
 is counteracted by cooling measures, for example, cooling of a double wall
 outer mantle of the mixing container. This requires a considerable
 additional expenditure, and may result in an undesirable change of the
 product properties because heating of the mixed material during mixing
 cannot be completely avoided.
 It is therefore an object of the present invention to improve a mixer of
 the aforementioned kind such that an excellent mixing of the material can
 be performed in a short period of time without causing temperature-based
 undesirable changes of the material properties.
 SUMMARY OF THE INVENTION
 The mixer for granular materials according to the present invention is
 primarily characterized by:
 a mixing container comprised of a first mixing container portion and a
 second mixing container portion detachably connected to one another;
 the mixing container having a longitudinal axis and a transverse axis
 extending perpendicularly to the longitudinal axis;
 a support frame in which the mixing container is supported so as to be
 pivotable about the transverse axis and rotatable about the longitudinal
 axis;
 the mixing container having a first position in which mixing is performed
 and the second mixing container portion is positioned above the first
 mixing container portion;
 the mixing container having a second position in which the second mixing
 container portion, after completion of mixing, contains the mixed material
 and is detachable from the first mixing container portion.
 Advantageously, the mixer further comprises a pivot bracket comprising a
 rotary bearing. The mixing container is supported by the rotary bearing in
 the pivot bracket for rotation about the longitudinal axis. A shaft is
 fixedly connected to the pivot bracket and rotatably supported in the
 support frame, wherein the mixing container is connected to the shaft.
 Advantageously, the rotary bearing is a roller bearing.
 Preferably, the first mixing container portion has a rotating mixing tool
 comprising radially extending mixing blades, wherein the mixing blades end
 in direct vicinity of a container wall of a first mixing container
 portion.
 Advantageously, the mixing blades, in the direction of rotation of the
 mixing tool, are downwardly and forwardly slanted at least in a radially
 outer portion of the mixing tool.
 Preferably, the first mixing container portion has a rotating mixing tool
 comprising mixing blades spaced from a container wall of the mixing
 container portion. The mixing blades, in a direction of rotation of the
 mixing tool, are preferably downwardly and forwardly slanted at least in a
 radially outer portion of the mixing tool.
 Preferably, the first mixing container portion comprises a cover closing of
 the interior of first mixing container portion for enclosing in the
 interior a granular cleaning substance.
 The present invention also relates to a method for mixing granular
 material, wherein the method is primarily characterized by the steps of:
 providing a mixing container comprised of a first mixing container portion
 and a second mixing container portion detachably connected to one another,
 wherein the mixing container has a longitudinal axis and a transverse axis
 extending perpendicularly to the longitudinal axis;
 supporting the mixing container on a support frame such that the mixing
 container is pivotable above the transverse axis and rotatable about the
 longitudinal axis;
 filling a granular material into the second mixing container portion and
 connecting the second mixing container portion to the first mixing
 container portion; pivoting the mixing container into a first position in
 which the longitudinal axis is slanted relative to a vertical position and
 in which the second mixing container portion is positioned above the first
 mixing container portion;
 rotating the mixing container positioned in the first position for mixing
 the granular material;
 after completion of mixing, positioning the mixing container in a second
 position such that the second mixing container portion contains the mixed
 material and detaching the second mixing container portion from the first
 mixing container portion.
 The invention also relates to a method for mixing granular material
 characterized by the steps of:
 providing a mixing container comprised of the first mixing container
 portion and a second mixing container portion detachably connected to one
 another, wherein the mixing container has a longitudinal axis and a
 transverse axis extending perpendicularly to the longitudinal axis;
 equipping the first mixing container portion with a mixing tool comprising
 radially extending mixing blades ending in direct vicinity of the
 container wall of the first mixing container portion;
 supporting the mixing container on a support frame such that the mixing
 container is pivotable about the transverse axis and rotatable about the
 longitudinal axis;
 filling a granular material into the second mixing container portion and
 connection the second mixing container portion to the first mixing
 container portion;
 pivoting the mixing container into a first position in which the
 longitudinal axis is vertical and in which the second mixing container
 portion is positioned above the first mixing container portion;
 rotating the mixing container positioned in the first position and the
 mixing tool for mixing the granular material;
 after completion of mixing, positioning the mixing container in a second
 position in such that the second container portion contains the mixed
 material and detaching the second mixing container portion from the first
 mixing container portion.
 Preferably, in the step of rotating, the mixing container and the mixing
 tool are rotated in opposite directions.
 The mixing tool is preferably rotated at a higher speed than the mixing
 container.
 According to the present invention, the mixing container comprised of a
 first and a second mixing container portion is supported at a support
 frame such that is rotatable about its longitudinal axis and is pivotable
 from a mixing position, in which the second mixing container portion is
 above the first mixing container portion, into a second position, in which
 the second container portion containing the mixed product can be separated
 (detached) from the first mixing container portion.
 In the inventive design the inner container wall causes the movement of the
 material to be mixed so that, in comparison to an agitating mixer, a
 relatively large slowly rotating surface is provided for entraining the
 material to be mixed. This results in a much more intensive mixing of the
 material. The heat development within the material to be mixed is
 negligibly small so that cooling of the mixing container is no longer
 needed.
 In a preferred embodiment of the invention the support frame has connected
 thereto a shaft which is rotatable within the support frame and fixedly
 connected to a pivot bracket. The pivot bracket comprises a rotary bearing
 in which the mixing container, comprised of the two mixing container
 portions, is guided so as to be rotatable about its longitudinal axis.
 A suitable rotary bearing can be in the form of a ball bearing or roller
 bearing. The forces and moments resulting from the rotation of the mixing
 container can be safely received by such a bearing and by the pivot
 bracket.
 In another embodiment of the invention the first mixing container portion
 comprises a rotating mixing tool having mixing blades which extend
 substantially radially outwardly into direct vicinity of the container
 wall of the first mixing container portion. The term mixing tool includes
 tools for mixing and/or dispersion.
 In the alternative, the first mixing container portion may have a rotary
 (rotating) mixing or dispersion tool having mixing blades that are spaced
 from the container wall of the first mixing container portion.
 When using such mixing or dispersion tools, the movement of the material to
 be mixed resulting from the container wall has a further movement
 superimposed thereon which results from the rotation of the mixing or
 dispersion tool. Since the superimposed gravitational forces and
 centrifigal forces act in different directions, in a very short period of
 time a very homogeneous mixed material will result.
 When the mixing blades of the mixing or dispersion tool are at least in
 their radially outer portions slanted forwardly and downwardly in the
 direction of rotation, a pressure difference will result between the top
 and the bottom side of the mixing blade which causes turbulence without
 significant increase of friction of the particles of the material to be
 mixed and favors a fast mixing of the material.
 For cleaning the mixer, the first mixing container portion can be provided
 with a cover that together with the first mixing container portion
 provides a closed interior for receiving a flowable or granular cleaning
 substance. If it is desired to also clean the second mixing container
 portion, a cover is not required. In such a case, the cleaning of the
 mixing container is performed in a position in which the longitudinal axis
 of the container is substantially horizontally positioned.
 For an expedient mixing process the mixing container is pivoted into a
 mixing position and is rotated in this mixing position. The longitudinal
 axis of the container is slanted relative to a vertical position in this
 mixing position. Such a method can be modified so as to provide an
 especially efficient mixing of the material by slanting the mixing
 container with its longitudinal axis relative to a vertical position by 10
 to 35.degree..
 In another preferred method, the mixing container is pivoted into a mixing
 position in which the longitudinal axis of the container coincides with a
 vertical position and in this position the mixing container is rotated. In
 addition, in the mixing container has a mixing tool that is also rotated.
 It has mixing blades which extend into the direct vicinity of the
 container wall of the mixing container.
 Another expedient method includes the steps of rotating the mixing
 container and the mixing or dispersion tool in opposite rotary directions.
 The resulting increase of relative movement of the colliding particles
 results in improved distribution, (dispersion) optionally also in a size
 reduction and mixing of the material.
 The speed of the mixing container can be relatively small in comparison to
 the speed of the mixing or dispersion tool by taking advantage of the
 effect of gravity, and this results in prevention of undesirable heating
 of the material to be mixed. An especially short mixing time can be
 achieved when the speed of the mixing tool is greater by 40 to 80 times
 than the speed of the mixing container.
 Such a method can be modified with respect to an especially efficient
 mixing of the material by performing rotation of the mixing container when
 it is positioned with its longitudinal axis pivoted by about to 10.degree.
 to 70.degree. relative to the vertical position.
 When the mixer is provided with a dispersion tool, it is possible, by
 rotating the mixing container and the dispersion tool in opposite
 directions, to increase the relative velocity of the colliding particles
 so that an accelerated distribution, optionally size reduction and mixing
 of the material is achieved.
 The speed of the mixing container, when taking advantage of the effect of
 gravity, can be small in comparison to the speed of the dispersion tool
 which avoids undesirable heating of the material to be mixed. An
 especially favorable result can be achieved when the speed of the
 dispersion tool is by 40 to 100 times greater than the speed of the mixing
 container.

DESCRIPTION OF THE PREFERRED EMBODIMENTS
 The present invention will now be described in detail with the aid of
 several specific embodiments utilizing FIGS. 1 through 8.
 The mixer represented in FIG. 1 comprises a cylindrical mixing container
 portion 1 and a mixing container portion 2 having a basic cylindrical
 portion and a truncated cone-shaped portion attached thereto. The two
 container portions are connected by a clamping device 3 to form the mixing
 container 4. The clamping device 3 can be pneumatically actuated rotary
 closure members.
 The mixing container portion 1 is connected to the pivot bracket 5 which is
 connected to a shaft 6 in a fixed manner. A pivot drive 7 engages the
 shaft 6 for pivoting the mixing container 4 relative to a support frame 8
 in which the shaft 6 is rotatably supported.
 A rotary drive 10 is provided that engages with friction wheel 9 the mixing
 container portion 1 and rotates the mixing container 4 about its
 longitudinal axis. The mixing container 4 can also be driven by a hollow
 shaft 14 supported in ball bearings 13 within the pivot bracket 5. This
 hollow shaft is driven by the rotary drive 10 as shown in FIG. 4. Within
 the hollow space of the hollow shaft 14 a shaft 15 guided in bearing 16 is
 provided and rotatable relative to the hollow shaft 14. The shaft 15
 supports the mixing or dispersion tool 11 arranged within the first mixing
 container portion 1 and driven by a motor 12 in rotation. The relative
 arrangement of hollow shaft 14 and shaft 15 can be seen in the
 representation of FIG. 5. The mixing or dispersion tool (11) can have
 different designs. A basic design is that the mixing blades 18 have a
 slant relative to the horizontal position so that between the upper and
 lower edges of the mixing blades 18 a pressure difference results which
 causes an intensive mixing of the material to be mixed. An embodiment of
 this kind is shown in FIG. 6.
 Furthermore, the contour of the forward or leading edge of the mixing blade
 18 can be adapted to any specific application. FIG. 7 shows such a mixing
 or dispersion tool having crescent-shaped mixing blades 18 that at the
 forward or leading edge are continuously curved with a substantially
 uniform radius of curvatures.
 Since a complete emptying of the first mixing container portion is
 impossible due to adhesion of particles at the mixing or dispersion tool
 and at the container wall, it is necessary to clean the mixing container
 portion when the composition of the material to be mixed or of the type of
 material to be mixed is changed. For this purpose, as shown in FIG. 8, a
 cone-shaped cover 17 is arranged between the two mixing container
 portions. At the outer circumference of the cover 17 an annular attachment
 is provided which, when fastening the second mixing container portion 2 at
 the first mixing container portion 1, is clamped between the respective
 connecting flanges of the two container portions 1, 2 and is fastened
 thereat by the clamping device 3.
 In preparation of the mixing process, the second mixing container portion 2
 which can travel, is filled with the material to be mixed in a position
 detached from the first mixing container portion 1 arranged at the support
 frame 8. Subsequently, the second mixing container portion 2 is centered
 below the first mixing container portion 1, lifted, and connected by the
 pneumatically actuated rotary clamping members 3 to the first mixing
 container portion 1.
 For performing the mixing process, the mixing container 4 is moved by the
 pivot drive 7 into the mixing position, as shown, for example, in dashed
 lines FIG. 2.
 In this position, the mixing container 4 is rotated When a mixing or
 dispersion tool 11 is used, the speed of the tool 11 in comparison to the
 mixing container 4 is selected to be relatively high. The slant of the
 mixing container 4 relative to the vertical position is determined by the
 separation of the material to be mixed in the upper portion of the inner
 container wall of the mixing container 4. It is selected to be such that
 the downwardly oriented flow of material to be mixed can reach the area of
 the mixing or dispersion tool 11.
 In practice, a slant of the mixing container 4 relative to the vertical
 position by 10.degree. to 70.degree. has been proven to be expedient with
 respect to an excellent mixing of the material. When a mixing or
 dispersion tool 11 is used, for the aforementioned slant the speed of the
 mixing or dispersion tool 11 and of the mixing container 4 should be
 different by a factor of approximately 100 and the direction of rotation
 should be opposite (FIG. 3).
 After completion of the mixing process, the container 4 is pivoted into its
 initial position in which is longitudinal axis coincides with the vertical
 position and the second mixing container portion 2 is the lower part of
 the mixing container 4. After separation of the mixing container portions
 1 and 2, the second mixing container portion 2 can be moved to any desired
 location for emptying the mixed material.
 The specification incorporates by reference the disclosure of German
 priority document 197 08 075.8-23 of Feb. 28, 1997.
 The present invention is, of course, in no way restricted to the specific
 disclosure of the specification and drawings, but also encompasses any
 modifications within the scope of the appended claims.