The present invention concerns a mixing device having a wear-resistant lining.
Such mixing devices generally have a container rotatable about a mixer axis for receiving material to be mixed, with a discharge opening arranged in the bottom thereof. In general the discharge opening is arranged in the centre of the bottom. Those mixing devices frequently have a mixing tool arranged in the interior of the container and a closure cover for closing the discharge opening. The mixing container can be for example cylindrical.
A mixer having cylindrical mixing containers which are oriented vertically or slightly inclined in relation to the vertical are usually lined with a wear-resistant lining to at least reduce the wear of the mixing container and the closure cover. Besides small-format ceramic tiles which are glued on to the bottom and the walls of the mixing container, in particular large-format wear-resistant plates of thicker, highly wear-resistant steel sheets, chilled cast iron or hard steel materials or wearing plates with hardfacing thereon are used for that purpose. Those wear-resistant plates are admittedly themselves subjected to wear but they can be easily replaced so that the use of wear-resistant plates provides that the service life of the mixing container and the closure cover can be markedly extended.
In the case of mixing containers with a discharge opening arranged centrally in the container bottom, part-annular wear-resistant plates are releasably fixed on the container bottom between the outside edge of the discharge opening and the container wall or the wear-resistant lining fixed thereto. A circular wear-resistant cover which covers over the entire cross-section of the discharge opening is also releasably fixed on the surface of the closure cover so that, when the closure cover is fitted into the discharge opening, a continuous, flat and wear-resistant surface is formed, which is only interrupted by the gaps which are necessarily formed between adjacent wear-resistant lining elements.
For fixing the wear-resistant plate usually a plurality of round openings are produced by means of a plasma cutter in the plates, into which threaded bushes are then welded. In that way the wear-resistant plates can be fixed in position from below. Particularly in the case of hardfaced wear-resistant plates the particularly wear-resistant wear protection layer has to be removed for that purpose in the region of the opening. Each threaded bush thus represents a point of attack for wearing solids particles. During operation the wear-resistant protective layer is slowly ground away, beginning at the fixing points, until the wear-resistant plates have to be replaced. Each fixing point therefore inevitably results in increased wear of the wear-resistant plate.
In the case of mixtures with a rotating mixing container and a rotating mixing tool blades are generally arranged at the mixing tool bottom, the blades moving over the surface of the container bottom or the wear-resistant surface and thereby keeping the container bottom free from material adhering thereto. The outer region of the container bottom between the container wall and the region over which the bottom blade has just passed is generally cleaned by the rotary movement of the mixing container by way of a stationary bottom scraper which is held in vertically cantilever relationship from above. In that case the bottom blades on the mixing tool are arranged, like the stationary bottom scraper, in such a way that they are at a small spacing relative to the surface of the wear plates and always move over the centre point of the mixing container and keep it free. That results in increased wear in the centre of the discharge opening so that the wear-resistant lining on the closure cover has to be replaced more frequently than the part-annular elements on the container bottom. As the peripheral speed of the bottom blades is generally markedly greater than that of the rotating mixing container the abrasion of the wear-resistant layer increases during operation towards the centre of the mixing container.
As described for example in EP 1 103 492 the closure cover is pivoted into and out of the discharge opening with a circular motion by means of a carrier arm. So that the discharge opening is sealingly closed and the wearing attack by the material to be mixed at the resulting gaps is slight gaps which are as narrow as possible are necessary between the mixing container on the one hand and the wearing cover on the other hand. That means that replacement of the wearing cover is very complicated and expensive. The wearing cover has dimensional tolerances caused by production engineering so that the closure device has to be freshly adjusted in the horizontal and vertical directions by particularly skilled personnel, which is time-consuming.
If the closure cover is pivoted into the discharge opening of the rotating mixing container by way of a circular movement in the closing process then the edge of the closure cover or the wearing cover fixed thereto will hit against the lower edge of the discharge opening. The closure cover can then be deflected slightly out of the circular movement by way of a tilt axis provided in the carrier arm so that the closure cover moves linearly into the discharge opening. Contact of the closure cover with the discharge opening surrounding same ensures that the rotary movement of the mixing container is transmitted to the closure cover which is provided with a mounting arrangement so that in the closed condition the closure cover also rotates with the mixing container in slippage-free relationship. The hooking engagement of the closure cover into the discharge opening provides that the inside of the annular discharge opening becomes worn with time and also has to be replaced. Therefore it is already usual for the edge of the discharge opening which in each closing operation comes into engagement with the closure cover to be provided with a separate wear-resistant and replaceable reinforcing ring.
Taking the described state of the art as the basic starting point therefore the object of the present invention is to provide a mixing device having a wear-resistant lining, which wears less severely and which in the event of wear can be replaced more easily and in particular less expensively.
That object is attained by a mixing device of the kind set forth in the opening part of this specification, in which the wear-resistant lining comprises a main lining portion and a wearing element, wherein the wearing element is arranged closer to the container axis than the main lining portion. According to the invention therefore the wear-resistant lining is divided into an element which is loaded more greatly during operation, the so-called wearing element, and an element which is loaded less heavily in operation, the main lining portion. In general, when the wear-resistant lining itself presents wear phenomena, only the wearing element but not the main lining portion has to be replaced.
In a preferred embodiment it is provided that the main lining portion has at least two and preferably at least three fixing bores, arranged on a bolthole circle, the main lining portion has an opening for receiving the wearing element, the wearing element has at least one and preferably at least three fixing bores, wherein the fixing bores of the wearing element are arranged on the bolthole circle when the wearing element is fitted into the opening.
In the case of existing mixing devices with wear-resistant lining it is mostly fixed to the container bottom or the closure cover by means of screws engaging into suitable threaded bushes in the wear-resistant lining.
The described measure makes it possible to use the multi-part wear-resistant lining according to the invention in already existing mixing devices without fresh bores having to be introduced into the container bottom. In addition the bolthole circuit in the existing mixing devices is generally so positioned that optimum fixing of the wear-resistant lining is possible at the fixing locations. In a preferred embodiment therefore it is provided that exactly the same fixing points are used. In addition the use of the usual fixing points enjoys the advantage that the number of fixing bores for the wearing element does not have to be increased, that is to say the number of points exposed to increased wear is not increased.
In a further preferred embodiment it is provided that at its side towards the main lining portion the wearing element is of a concave configuration at least portion-wise, at its side towards the wearing element the main lining portion is of a convex configuration at least portion-wise, wherein the concave portion of the wearing element and the convex portion of the main lining portion are of mutually corresponding configuration. That measure is advantageous in particular when the wearing element and the main lining portion are fixed on the same bolthole circle as then that measure provides that the area covered by the wearing element is reduced so that the costs of manufacture of the wearing element are reduced.
In a further preferred embodiment it is provided that the main lining portion and the wearing portion overlap at least portion-wise at the mutually facing edges, wherein preferably the edges are of such a configuration that the main lining portion and the wearing portion adjoin each other in substantially flush relationship. Thus it is possible for example for the edges to converge conically or to be of a stepped configuration so that both edges engage into each other without the substantially flat surface formed by the wear-resistant lining being interrupted.
Because one of the parts overlaps the other part at the edge, that provides an additional holding action for the part, the edges of which are covered by the edge of the other part. By virtue of that measure, it is possible to save on fixing bores, which in turn increases the service life of the wear-resistant lining since, as already mentioned in the opening part of this specification, each fixing bore represents a point involving increased wear.
In that respect the edges are advantageously of such a configuration that the edge of the wearing element extends over the edge of the lining element so that the main lining portion is held by the wearing element. In an alternative embodiment the two edges can also be of a design configuration in the manner of a groove-and-tongue connection.
In a further preferred embodiment at the side towards the container interior the container bottom is provided with a wear-resistant lining comprising the main lining portion and the wearing element, wherein the wearing element is of a stepped configuration at its side towards the discharge opening so that the wearing element at least portion-wise covers over the inner edge of the discharge opening.
As already mentioned in the opening part of this specification the inner edge of the discharge opening, in some mixing devices, serves at the same time as an abutment and guide for the closure cover held on a carrier arm. Consequently the inner edge of the discharge opening is exposed to increased wear. Because the closure element is of a stepped configuration so that it also at least partially covers the inner edge of the discharge opening, no further measures are necessary to protect the inner edge of the discharge opening.
Alternatively or in combination thereof at the side towards the container interior the closure cover can be provided with a wear-resistant lining comprising the main lining portion and the wearing element, wherein the main lining portion is of a stepped configuration at its side towards the edge of the closure cover so that the main lining portion at least portion-wise covers over the edge of the closure cover.
With that feature the edge of the closure cover can also be protected and in the event of wear the wearing element can be easily replaced.
It is further advantageous if at the side towards the container interior the container bottom is provided with a wear-resistant lining comprising the main lining portion and the wearing element and the container wall is provided with a wear-resistant lining which does not extend to the container bottom so that a gap remains at least portion-wise between the wear-resistant lining of the container wall and the container bottom, into which gap the main lining portion projects at least partially.
The main lining portion is thus inserted between the wear-resistant lining of the container wall and the container bottom so that the wall lining holds the main lining portion in the region of the container wall. It is now therefore only still necessary to fix the main lining portion at the opposite side, that is to say the side towards the wearing element. If for example the wearing element and the main lining portion are of a corresponding stepped configuration at the mutually facing edges, as was described hereinbefore, it is then possible to completely dispense with an additional screw fixing for the main lining portion, and that markedly increases the service life of the main lining portion, especially as it is in any case according to the invention arranged in a region exposed to only slight wear. In addition it is possible for the container wall to have at least one aperture and for the main lining portion to be of such a configuration that it extends through the aperture in the container wall. That feature can also provide that the main lining portion is fixed in the region of the container wall.
As however the thickness of the wear-resistant lining is subjected to certain tolerances, optimum dimensioning of the container wall aperture is not possible. If the aperture is too small, then depending on the wear-resistant lining production tolerance, the main lining portion can possibly no longer extend through the aperture. If in contrast the aperture is too large the aperture or the container wall can no longer securely support the main lining portion.
In a preferred embodiment it is therefore provided that a clamping device is arranged outside the container in such a way that the clamping device can come into engagement with the portion of the main lining portion, that projects through the aperture in the container wall, and can press the main lining portion on to the container bottom. With this embodiment the container wall aperture can be larger as it is now no longer intended for holding the main lining portion.
The main lining portion may also be of a multi-part nature, wherein the parts of the main lining portion are arranged in the peripheral direction, wherein preferably the mutually adjoining edges of two adjacently arranged parts of the main lining portion are not arranged exactly radially. Frequently the described mixing devices more specifically use a bottom scraper arranged exactly radially relative to the container axis. If the gaps between adjacent parts of the main lining portion are also arranged exactly radially that leads to periodic increases in the resistance that the scraper has to overcome, and that leads to increased wear of the scraper. The fact that the gaps between mutually adjoining parts of the main lining portion do not extend radially but for example in angled or rounded relationship provides that such periodically occurring shock forces can be avoided.
Further advantages, features and possible uses of the present invention will be clearly apparent from the description hereinafter of preferred embodiments and the accompanying Figures in which:
The cylindrical mixing container 1 has a mixing tool 2 which is arranged eccentrically in the mixing container and which is supported in cantilever relationship, on a central shaft 3, with laterally arranged mixing vanes 4, and a stationary wall/bottom scraper 5 which is held in cantilever relationship vertically from above. Fixed to the lowermost vane plane of the mixing tool 2 are vertically downwardly projecting bottom blades 6 which operate at a small spacing relative to the surface of the wearing plate 7 or the wearing cover 8 of the closure device 9. Curved wearing surfaces 11 with incorporated threaded bores 12 are releasably fixed by way of screws 13 to the inside wall 10 of the container 1.
The discharge opening 14 is in the centre of the mixing container 1. The discharge opening 14 can be closed with the closure cover 15 mounted on the closure device 9. The closure cover 15 is connected to a carrier arm 17 by way of a mounting fork and the mounting journal 16 and is thus pivotable about the tilt axis of the mounting journal 16. The carrier arm 17 is rotatably mounted by way of a pivotal shaft 18. A return element (not shown) provides that, without the actions of external forces, the closure cover 15 assumes a given position relative to the carrier arm 17.
A one-piece round wearing cover 8 is releasably connected on the top side of the closure cover 15 to at least three threaded bores 19 arranged on at least one bolthole circle by means of screws 20.
Wearing plates 7 are provided in the form of ring segments on the container bottom. There is a small annular gap between the wearing cover 8 on the one hand and the inside edge of the wearing plates 7 on the other hand. The part-annular wearing plates 7 are provided, similarly to the wearing cover 8, with incorporated threaded bores 23 which are disposed on an inner and an outer bolthole circle, and are releasably fixed from below by way of screws 24. The radially outer edge of the wearing plate 7 is of a smaller radius than the inside radius of the wearing surface 11 fixed to the container wall 10. The mixing container 1 is mounted rotatably on the machine frame 22 by way of a rotational connection 21 and is caused to rotate by way of a drive (not shown).
It will be seen that the wear is at its greatest in the centre of the container and decreases, in relation to moving further outwardly. While the wear in the radially outer region of the mixing container 1 due to the rotational movement in conjunction with the stationary wall/bottom scraper 5 is more or less uniform the wear increases progressively towards the container centre. The highest wear is then observed in the centre of the discharge opening 14.
Here the container wall 10 is lined with curved and releasably connected wearing surfaces 11 of known kind. It will be noted however that the lower edge of the wearing surface 11 is no longer on the mixing container bottom but is arranged above the bottom by at least the height of the wearing plate 27. Here the wearing plates comprise the main lining portions 27 and the wearing element 28. The main lining portion 27 does not have any opening or threaded bore and is bevelled at the radially inner edge. In the same manner at its radially outer edge the wearing element 28 has an oppositely extending edge. The square wearing element 28 shown in
A variant of this embodiment is shown in the lower half of
As it has been found that in operation the greatest wear of the wear-resistant lining occurs in the proximity of the discharge opening it is sufficient, with an embodiment according to the invention, to replace only the wearing element 28 while the main lining portions 27 can initially continue to be used further. While in the configurations in the state of the art, the complete wear-resistant lining would have to be replaced in the event of any wear, the invention provides that the main lining portions 27 can be re-used at least once but preferably a number of times before they have to be replaced.
The wear-resistant lining of the closure cover is also of a multi-part nature and comprises a main lining portion 31 and a wearing element 33, wherein the wearing element 33 embraces the inner region of the wear-resistant lining of the closure cover. Thus in this case also the region which is most severely affected by wear is provided at the centre with a separate wearing element 33 which in a wear situation can be replaced while the main lining portion 31 can remain on the closure cover. That has the advantage in particular that no re-adjustment of the carrier arm or the wearing system is involved, which is absolutely necessary when replacing also the main lining portion 31.
In the embodiment shown in
A third embodiment of the invention is shown in
Here the main lining portions 39 have an outer edge 40 of a curved configuration. A particular advantage of this embodiment is that the main lining portions only have to involve a single geometry and this is the case even with segment angles of <90°. In addition, the curved butting edge assists with material entrainment of the material to be mixed which is disposed in the mixing container, particularly upon rotation of the mixing container in the clockwise direction. A further advantage of this geometry is that for example a bottom scraper 41 which is mounted in cantilever relationship and which extends radially from the outside inwardly only has a point contact at its outer edge with the gap and no longer a line contact so that this avoids hooking engagement of jammed solids particles in the gap and thus increased wear.
Disposed at the radially outer edges of the main lining portions 39 are tongues 42 which can be passed through suitable openings 43 in the container wall 10. In this case the lower edge of the wall wearing plates 11 is arranged so far above the mixing container bottom that the main lining portions 39 can be pushed through with the tongues 42. The main lining portions 39 are then held in the vertical direction by the openings 43 in the container wall 10. It is also possible, as shown in
The advantage with this structure is that the opening 43 can be of generous dimensions in its vertical extent and even in the event of manufacture-induced fluctuations in the thickness of the hardfaced main lining portions 39 the latter can be firmly held down in the vertical direction on the surface of the container bottom.
The wearing element 28 is of an annular configuration in this variant. Depending on the respective machine size, it can be of a single-part or multi-part nature. At its radially outer edge the wearing element 28 has a stepped recess 46 which overlaps with the correspondingly designed stepped recess 46a at the radially inward edge of the main lining portion 39. Arranged on a bolthole circle in the wearing element 28 are conical openings 47 through which screws with a conical screw head 47a can be fitted without a gap and can be releasably clamped by way of nuts to the container bottom from below the mixing container. The main lining portion is held fast at the inner edge by the overlap at the butting edge between the wearing element 28 and the main lining portion 39. In this variant, no openings at all are required for fixing purposes in the outer bottom region of the mixing container, that is to say for the main lining portions, so that here an uninterrupted wearing layer is exposed to wearing attack and is therefore markedly more wear-resistant. In addition, depending on the respective geometrical configuration, with for example a one-piece configuration, with a total of only three releasable connections, the wearing element 28 can be fixed with a minimum number of fixing points over the entire periphery.
The circular wear-resistant lining of the closure opening comprises a circular main lining portion 31 in which a cross-shaped opening 48 with angular or rounded-off corners is provided, into which a corresponding cross-shaped wearing element 49 is inserted in accurately fitting relationship and releasably fixed there. In that case the bores for fixing the wearing element 49 are preferably disposed on the same bolthole circle as the bores for fixing the main lining portion 31, but can also be arranged at any other desired point.
A variant of the
As an alternative thereto for fixing a wearing element a threaded bush could be fitted on the rear side of the wearing element and welded thereto, brazed thereto or bonded thereto, without in that case an aperture having to be provided in the wearing element. The threaded bush is smaller in its outside diameter than the diameter of the bore in the bottom of the mixing container 1 or the holding plate of the closure cover 15 and upon assembly projects into same. The wearing element can thus be releasably connected from the rear side of the mixing container or the closure cover by way of screws without the wearing surface in the container interior being damaged.
A comparable fixing method could equally be used for the main lining portions. In this particularly preferred variant for fixing the wearing element and the main lining portions no opening whatsoever would be necessary in the entire surface of the wear-resistant lining and that would entail an uninterrupted wearing layer.
The main lining portion 31 is also releasably fixed on the closure device by way of three fixing points 54 preferably arranged on a bolthole circle.
As can also be seen from
In principle no limits are placed on the geometrical configuration of both the outer edge of the wearing element and also the radially inner edge of the main lining portion. In a further configuration of the invention the inside edge of the discharge opening, that is exposed to wear, is integrated into the wearing element 67 which lies on the mixing container bottom so that additional fitment operations when replacing the reinforcing ring can be eliminated. In addition the outer edge of the wearing cover of the closure device can be adapted by way of a particular geometrical configuration to resist wearing attack upon closure of the closure device.
For illustration purposes
At its radially outward end the wearing element 65 has an edge 68 which is angled in a L-shape and which covers over the radially outer part of the closure cover 15. The surface of the edge which is angled in a L-shape, like the flat surface of the main lining portion, can comprise the same or a different wear-resistant material or a hardfaced surface. The closure cover 15 is reduced in diameter to correspond to the thickness of the L-shaped edges. On its outer periphery the closure cover 15 has a stepped recess 60 into which an annular rubber seal 61 is releasably introduced by means of screws 62 distributed over the periphery. The radially outer end of the rubber seal 61 projects beyond the edge and is bevelled. Fixed on the mixing container bottom 1 is a wearing element 67 which also has at its radially inner end an edge 69 which is angled in a L-shape. The outer end of the angled edge 70 is bevelled to correspond to the rubber seal so that in the closed condition of the closure device the rubber seal sealingly closes the gap between the closure device and the mixing container. That arrangement according to the invention provides that the inside edge of the reinforcing ring, that is particularly loaded in the closing operation, is also replaced upon replacement of the worn wearing element 67. As fixing is effected together with the wearing element 67 additional fitment of a reinforcing ring is eliminated.
List of references
Number | Date | Country | Kind |
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10 2010 027 885.8 | Apr 2010 | DE | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/EP11/56005 | 4/15/2011 | WO | 00 | 9/28/2012 |