APPARATUS FOR TREATING AND COOLING FOUNDRY MOULDING SAND

Abstract

The present invention concerns an apparatus for treating and cooling foundry moulding sand, comprising a mixing container and a mixing tool rotatable about a drive shaft, wherein there is provided an air feed for the feed of air into the container interior. To provide an improved apparatus with which a more uniform fluidised layer is produced as far as possible over the entire cross-section of the mixing container, wherein moreover the proportion of the solid particles entrained with the gas flow is to be reduced, it is proposed according to the invention that the mixing tool has at least two mixing vanes spaced from each other in the vertical direction and at least one mixing vane has a mixer blade with a surface which is inclined relative to the horizontal.

Claims

1. Apparatus for treating and cooling foundry moulding sand, comprising a mixing container and a mixing tool rotatable about a drive shaft, wherein there is provided an air feed for the feed of air into the container interior, characterised in that the mixing tool has at least two mixing vanes spaced from each other in the vertical direction and at least one mixing vane has a mixer blade with a surface which is inclined relative to the horizontal wherein the mixing tool has at least two vertically spaced mixing vanes with mixer blades, wherein a mixer blade, preferably the uppermost mixer blade, has a surface inclined upwardly in the direction of rotation of the mixing tool.

2. Apparatus according to claim 1 characterised in that the surface of the mixer blade is inclined downwardly in the direction of rotation of the mixing tool.

3. (canceled)

4. Apparatus according to claim 1 characterised in that the mixer blade extends substantially to the container wall, wherein the spacing between mixer blade and container wall is less than 100 mm.

5. Apparatus according to claim 1 characterised in that there is provided a drive for rotating the mixing tool, wherein the drive is so designed that the mixer blade has a peripheral speed at its radially outer end of between 2 and 75 m/s.

6. Apparatus according to claim 1 characterised in that the container wall is inclined so that the container cross-section becomes larger in an upward direction from the container bottom.

7. Apparatus according to claim 6 characterised in that each mixing vane has a mixer blade, wherein the spacing between mixer blade and container wall is approximately the same for all mixer blades.

8. Apparatus according to claim 1 characterised in that the mixer blade is arranged substantially at the container bottom.

9. Apparatus according to claim 1 characterised in that the mixing container has at least two mixing portions, wherein provided in each mixing portion is a respective mixing tool rotatable about a drive shaft.

10. Apparatus according to claim 9 characterised in that there is provided a drive device with which each mixing tool can be driven with a peripheral speed which is adjustable independently of each other at the mixing vanes.

11. Apparatus according to claim 9 characterised in that each mixing tool has a mixer blade arranged substantially at the container bottom, wherein the two mixing tools are spaced from each other so far that the two mixer blades arranged at the container bottom do not touch each other in any position of the mixing tools.

12. Apparatus according to claim 9 characterised in that each mixing tool has a mixing vane with a mixer blade which is not arranged at the container bottom, wherein the mixer blades which are not arranged at the container bottom are arranged at different axial heights.

13. Apparatus according to claim 9 characterised in that at least one mixing vane of the one mixing tool describes a circular path which in a projection on to a parallel plane intersects with a projection of a circular path described by at least one mixing vane of the other mixing tool on to the same parallel plane.

14. Apparatus according to claim 1 characterised in that the air feed has openings in the container wall, through which air can be blown into the container interior.

15. Apparatus according to claim 1 characterised in that the air feed is effected by way of the mixing tool which has a hollow shaft.

16. Apparatus according to claim 1 characterised in that the mixer blade is of a width which enlarges in the radial direction.

17. Apparatus according to claim 1 characterised in that the mixer blade is in the form of an angled profile, wherein the inner angle is opposite to the direction of rotation of the mixer blade and is preferably between 90? and 180?.

18. Apparatus according to claim 1 characterised in that the mixer blade has air outlet openings on its side oriented in opposite relationship to the direction of rotation.

19. Apparatus according to claim 1 characterised in that a solids separator is arranged above the mixing tool, wherein preferably the solids separator is so designed that by means of a rotor it produces a rotational flow.

20. Apparatus according to claim 1 characterised in that the mixer blade extends substantially to the container wall, wherein tere is provided an attachment which is associated with the mixer blade and which projects in the direction of the container wall beyond the mixer blade and contacts the container wall.

21. Apparatus according to claim 9 wherein each mixing tool has at least two mixing vanes spaced from each other in the vertical direction.

Description

[0038] Further advantages, features and possible uses of the present invention will be apparent from the description hereinafter of preferred embodiments of the invention. In the drawing:

[0039] FIG. 1 shows a sectional view of a first embodiment according to the invention of a cooling apparatus,

[0040] FIG. 2 shows a sectional view of a second embodiment according to the invention,

[0041] FIG. 3 shows a detail view of a mixer with a plurality of different mixer blades, and

[0042] FIGS. 4 to 8 show cross-sectional views of different mixer blades.

[0043] FIG. 1 shows a sectional view of a first apparatus according to the invention. The apparatus 1 for treating and cooling foundry moulding sand has a mixing container 2 arranged in a housing 3. The mixing container 2 has two mixing portions, in the centre of which is arranged a respective drive shaft 4. The drive shafts 4 in turn each have a plurality of mixing vanes with corresponding mixer blades. The apparatus 1 has an inlet 5 and an outlet 5, by way of which hot foundry moulding sand can be introduced into the mixing container 2 for example by means of a conveyor belt 6 and the treated sand can be discharged from the mixing container 2 again. Provided in the inclined container wall 2 are a series of cooling air openings 7 by way of which cooling air can be introduced into the mixing container 2. Near the bottom the two drive shafts 4 respectively have mixing vanes which extend in opposite directions and to which a respective mixer blade 8 is mounted. The two drive shafts 4 are arranged spaced from each other in such a way that the mixer blades 8 which are arranged near the bottom cannot collide with each other in any rotational position. Arranged spaced in a vertical direction relative to the mixing vanes near the bottom are further pairs of mixing vanes which are also equipped with respective corresponding mixer blades. In the illustrated embodiment all mixer blades are inclined downwardly so that, when the drive shaft is rotated in the intended direction, the foundry moulding sand in the mixing container 2 is lifted and flows over the inclined mixer blade surface. The mixer blades of the second and third planes are arranged at a height corresponding to the vertical height of the air inlet openings 7 in the container wall 2. In addition the mixer blades in the planes 2 and 3 are so arranged that they extend almost to the air inlet openings 7. The two drive shafts 4 are driven by means of the drive motors 9. Arranged in the cover of the housing 3 is a solids separator 11 comprising a wheel which is provided with fins and which can be rotated by means of the drive motor 10. The cooling air which is supplied by way of the air inlet openings 7 is then sucked away by way of the intermediate spaces between the fins of the solids separator 11. The driven wheel of the solids separator 11 generates a turbulent flow in which the solid body components contained in the air to be sucked away are deposited and drop back into the mixing container.

[0044] FIG. 2 shows a diagrammatic sectional view of an alternative embodiment of the invention. In this case the same references are used to denote the same components. In the FIG. 2 embodiment the feed of cooling air is effected on the one hand by way of a drive shaft 4 which is in the form of a hollow shaft and in which air flows by means of the feed 12 into the passage 15 and by way of the passage into corresponding openings within the mixer blades 8, 8, 8 and 8, into the material to be mixed. In addition or alternatively thereto air can be introduced into the housing by way of the air feed 13 and into the material to be mixed by way of the air inlet openings 7. It will be clearly seen in this embodiment that the mixer blades of the upper planes are of a longer radial extent than the mixer blades in the lower plane.

[0045] The mixer blades 8, 8, 8 and 8 extend substantially to the container wall. To avoid damage to the mixer blades however a small gap must remain. By way of example therefore the drawing shows in relation to a mixer blade that the mixer blades can have an extension portion 14 of plastic, which can also be pressed by means of springs against the container wall in order to reduce the proportion of the cooling air feed, which flows directly vertically upwardly.

[0046] FIG. 3 shows by way of example different embodiments of mixer blades. In principle, as shown in the embodiment denoted by reference 17, the mixer blade can extend uniformly from the drive shaft to the container wall. It will be appreciated however that curved shapes would also be possible, as in the case of the embodiment denoted by reference 15, or shapes which are enlarged fan-like, as with the embodiment denoted by reference 16.

[0047] In the embodiment denoted by reference 18 ploughshare-like attachments 19 are provided on the mixing vanes.

[0048] FIG. 4 shows a cross-sectional view through a mixer blade 20 which here comprises a single inclined surface. Upon movement of the mixer blade 20, there is formed behind the mixer blade a zone which is kept substantially free of material to be mixed and into which the cooling air introduced into the mixing container through the air feed openings 7 can flow radially inwardly along the mixer blades. In that case the contour of the air outlet opening 7 is ideally so selected that, in combination with the geometry of the mixer blade, it is possible to provide for an intake flow of air which is as uniform and as long-lasting as possible, into the zone which is kept free of material to be mixed, behind the mixer blade.

[0049] FIG. 5 shows a cross-sectional view of a second embodiment of a mixer blade 21. Here the mixer blade comprises an inclined surface and a surface which is angled relative thereto and which extends substantially horizontally.

[0050] FIG. 6 shows a cross-section through a third embodiment of a mixer blade 2. In this case also there is an inclined surface which is adjoined in one direction by a substantially vertically extending portion and in the other direction by an oppositely inclined portion.

[0051] FIG. 7 shows a cross-section through a further embodiment of a mixer blade 23. The mixer blade 23 again has an inclined surface. Here it is mounted to a substantially tubular element, through which cooling air can also be introduced into the mixing container.

[0052] FIG. 8 shows by way of example an embodiment in which different mixer blades 24 to 26 are mounted to the drive shaft in three different planes. The mixer blade arranged in the lowermost plane has a downwardly inclined blade surface and a portion extending substantially perpendicularly thereto. In the central plane a mixer blade 25 is used, involving a cross-section forming a kind of cavity, through which cooling air can be transported from the drive shaft radially outwardly. Used in the uppermost plane is a mixer blade 26 which is inclined upwardly to prevent the material being mixed from being swirled up excessively. It is self-evident that further geometries are possible for the design configuration of the mixer blade.

LIST OF REFERENCES

[0053] 1 apparatus [0054] 2 mixer blade [0055] 3 housing [0056] 4 drive shaft [0057] 5, 5 inlet, outlet [0058] 6 conveyor belt [0059] 7 air inlet openings [0060] 8, 8, 8 mixer blades [0061] 9 drive motors [0062] 10 drive motor [0063] 11 solids separator [0064] 12 feed [0065] 13 air feed [0066] 14 extension portion [0067] 15-18 mixer blades [0068] 19 attachments [0069] 20-26 mixer blades