EP3225300B1 - Mixing tool, mixing device and mixing tool manufacturing method - Google Patents

Description

The invention relates to a mixing tool, in particular a mixing blade, a mixing device with such a mixing tool and a method for producing such a mixing tool.

Such mixing tools are used to mix building materials, especially coarse-grained material, such as cement, mortar or concrete. For this purpose, the building material is filled into a mixing container in which the mixing tool, in particular designed as a mixing blade, is rotatably mounted on a mixing arm relative to the mixing container. Either the mixing container can be fixed and the mixing arm can be rotatably mounted, or vice versa.

Due to contact with the granular building material, signs of wear on the mixing tool and even minor or major damage to its surface can quickly occur. The mixing tool then needs to be repaired or even replaced. In order to increase the durability of the mixing tool, they are often partially or completely covered with a plastic, for example using polyurethane.

DE19856622A1 discloses a mixing tool according to the preamble of claim 1 and describes, for example, a mixing blade that has a stiffening core in the form of a sheet or casting that is completely covered by a plastic layer. Wearable plates made of ceramic, hard metal or sheet metal can also be embedded in the plastic layer.

Further describes DE7046148U a mixing shovel. The mixing blade has an elastomer layer at its outer end, from which a Carbide hard metal part protrudes, which rests against a surface to be scraped during operation.

DE3152029A1 describes a mixing blade made of plastic, which has slats made of plastic, which optionally have hard metal plates.

DE3149640A1 describes a mixing trough with a mixing blade formed in one piece from a plastic material, which only rests on a trough wall over a narrow area and has a bead at an outer end which projects in the direction of rotation and tapers from a contact point on the trough wall towards the opposite edge.

EP2586522A1 describes a mixing blade with a scraper that consists of an elastomeric plate that can enclose a reinforcing mesh.

When used in the mixing device, the mixing tool not only serves to mix the building material in the mixing container, but also to scrape off or strip off building material that has stuck to the container walls of the mixing container. In particular, a scraping edge of the mixing tool scraping along the container wall is subjected to extreme stress. The plastic is easily damaged and leads to rapid wear of the mixing tool.

It is the object of the invention to provide a mixing tool with a longer shelf life.

The object is achieved according to the invention by a mixing tool with the features of claim 1, by a mixing device with the features of claim 7 and by a mixing tool manufacturing method with the features of claim 8. Advantageous developments of the invention are listed in the subclaims.

The invention is based on the idea of forming the scraper edge of a plastic mixing tool from hard metal. This means that one or more hard metal elements are attached to the mixing tool, which provide or form the scraper edge. The hard metal element is preferably formed from sintered hard metal, in particular from sintered carbide hard metal. It is preferably made as a composite material from tungsten carbide and the binder cobalt.

The scraper edge is arranged on a scraper section of the mixing tool and serves to scrape mixed material from the wall of the mixing container. In order to attach the mixing tool to the mixing arm, it has a fastening section that is rigidly or elastically connected to the stripping section. The fastening section and stripping section together have a metallic core that is surrounded by a plastic jacket.

The mixing tool is manufactured by first connecting the metallic core to the hard metal element. The entire assembly of core and hard metal element is then introduced into a mold, which is then filled with a plastic casting material. The plastic casting material is a preliminary product of the plastic from which the plastic jacket is formed. In particular, it can be a mixture of two or more components, which then solidify into the desired plastic. Only after the plastic casting material has hardened is the finished plastic jacket with the desired hardness available. The curing process can take a few minutes or longer. Furthermore, the curing process can take place at ambient temperature or with the addition of heat.

The finished mixing tool is then removed from the mold and reworked if necessary. For example, it may be necessary to remove plastic that covers the hard metal element(s). Preferably, the arrangement of core and hard metal element is arranged in the mold before filling with the plastic casting material in such a way that that when loading the mold with the plastic casting material, the hard metal element or at least the scraper edge is essentially not covered. This can be achieved in particular by the scraper edge resting on or touching a mold wall of the mold.

In an embodiment not according to the invention, it is provided that a first core section assigned to the fastening section is rigidly connected to a second core section assigned to the stripping section. The connection is preferably a welded connection between the two core sections. Alternatively, the first and second core sections can also be formed in one piece, for example produced as a single metal casting. However, the core is preferably composed of several metallic elements that are welded together. The metallic core can in particular be made of steel, for example tool steel, or have metallic elements made of steel or tool steel.

According to the invention it is provided that a first core section assigned to the fastening section is connected elastically and/or in an articulated manner to a second core section assigned to the stripping section. The fact that the first core section is assigned to the fastening section means that the fastening section is formed from the first core section and the part of the plastic jacket surrounding or covering the first core section. The same applies to the stripping section and the second core section. An elastic and/or articulated connection between the two core sections means that the connection between the fastening section and the stripping section is also deformable and preferably elastic due to the plastic jacket surrounding both core sections. This means that the stripping section is movable, preferably elastically movable, relative to the fastening section. Since the wiping edge is formed on the wiping section, this means that the wiping edge can give way when it comes into contact with obstacles, for example dents or smaller elevations in the wall of the mixing container, without risking damage to the mixing tool, for example due to splintering of the hard metal element.

In any case, the first core portion has one or more fasteners to attach the mixing tool to the mixing arm. For this purpose, the fastening element can, for example, have an opening, a profile with a groove, for example a C-profile, and/or a threaded element. Furthermore, the plastic jacket is in any case preferably formed from a single casting, and therefore in particular has no seams.

The articulated or elastic connection between the two core sections can be formed exclusively by the plastic jacket. Preferably, however, a mechanical joint is additionally or alternatively formed between the two core sections, which also exists without the plastic jacket. In an expedient embodiment it is provided that one of the two core sections has an extension, in particular a pin-shaped or tongue-shaped extension, which projects into a recess in the other core section. In particular, the extension can be formed on the first core section. Preferably, two or more such extensions are formed on one core section, which are inserted into two or more openings in the other core section when the mixing tool is manufactured. A termination element is then soldered or welded to the ends of the extensions to establish the articulated connection between the core sections.

When producing the mixing tool with an articulated or elastic connection between the two core sections, the two core sections are movable relative to one another, preferably pivotable relative to one another about an oscillation axis. In this case, it is advantageous to fix the two core sections against each other before or during placement in the mold. This is preferably done by changing the mold like this is designed so that the two core sections cannot move against each other.

According to a preferred development, it is provided that the hard metal element is welded or soldered to the metallic core. This is preferably done by brazing. In any case, several hard metal elements are preferably lined up along the scraper edge. The hard metal elements are preferably sickle-shaped. Further hard metal elements can also be arranged on an end face or end edge of the mixing tool in order to protect the mixing tool there from wear.

It is preferably provided that the metallic core is covered or surrounded by more than 70%, 80%, 85%, 90%, 95% or essentially completely by the plastic jacket and/or by the hard metal element. These percentages refer in particular to the surface of the metallic core. Preferably, the metallic core is essentially completely covered except for the end faces and fastening elements, with exposed end faces possibly being present perpendicular to the scraper edge. The aim here is to protect the metallic core from wear using the plastic jacket or the hard metal element.

In a preferred embodiment it is provided that the metallic core is divided into several segments which are fastened to one another. The metallic core is preferably segmented along the stripping edge. The segments of the metallic core can in particular be designed to be essentially identical. Before the plastic jacket is produced, these segments can also be attached to one another by means of joining elements, for example by welding.

Preferably, the hard metal element or the hard metal elements are embedded in the plastic jacket. This means that one, two or more outer surfaces of the hard metal element is/are designed to be aligned with a jacket surface of the plastic jacket.

In an advantageous development it is provided that the plastic jacket is made of polyurethane. The polyurethane preferably has a Shore hardness in a range between 65 and 90 Shore-A.

Fig. 1

ein Segment eines Mischwerkzeugs;

Fig. 2

ein weiteres Segment des Mischwerkzeugs;

Fig. 3

eine Querschnittsansicht des Segmentes aus der Fig. 2;

Fig. 4

eine Querschnittsansicht des Segmentes aus der Fig. 1;

Fig. 5

eine Seitenansicht des metallischen Kerns des Segmentes aus der Fig. 1, mit hieran befestigten Hartmetallelementen;

Fig. 6

ein nicht segmentiertes Mischwerkzeug;

Fig. 7

eine Seitenansicht eines gelenkig aufgebauten metallischen Kerns, mit hieran befestigten Hartmetallelementen;

Fig. 8

eine perspektivische Ansicht des Kerns aus der Fig. 7 mit Kunststoffmantel; und

Fig. 9

eine Explosionszeichnung der Anordnung aus der Fig. 7.

The invention is explained below using exemplary embodiments with reference to the figures. Show here:

Fig. 1

a segment of a mixing tool;

Fig. 2

another segment of the mixing tool;

Fig. 3

a cross-sectional view of the segment from the Fig. 2 ;

Fig. 4

a cross-sectional view of the segment from the Fig. 1 ;

Fig. 5

a side view of the metallic core of the segment from the Fig. 1 , with hard metal elements attached to it;

Fig. 6

a non-segmented mixing tool;

Fig. 7

a side view of an articulated metallic core with hard metal elements attached thereto;

Fig. 8

a perspective view of the core from the Fig. 7 with plastic jacket; and

Fig. 9

an exploded view of the arrangement from the Fig. 7 .

In the Fig. 1 a segment of a mixing tool not according to the invention is shown schematically. It has a fastening section 2 and a stripping section 4, the division into fastening section 2 and stripping section 4 not taking place strictly along a dividing line. The fastening section 2 serves to fasten the mixing tool to a mixing arm, while the stripping section 4 has a stripping edge 41, by means of which mixed material can be stripped or scraped off a wall of a mixing container (not shown in the figures). The scraper edge 41 is formed by means of hard metal elements 5, which are lined up along the mixing tool in the direction of the scraper edge 41.

On an end face 11 of the mixing tool segment it can be seen that the segment is formed from a metallic core 6 and a plastic jacket 7 made of polyurethane surrounding this core 6. The metallic core 6 made of tool metal is composed of several parts that are welded together. These include a first core section 62, which is designed as a C-profile and thus has a groove. This groove forms a fastening element with which the mixing tool is attached to the mixing arm. Furthermore, the core 6 has a two core section 64 to which the hard metal elements 5 are attached by means of brazing. Further parts of the metallic core 6 also form a connecting piece 63, which rigidly connects the first core section 62 to the second core section 64, and a stiffening piece 65, which is attached to the first core section 62 and serves to ensure that the plastic jacket 7 maintains its stable shape as shown here keeps.

At the in Fig. 1 The segment shown can be an end segment or a middle segment of the mixing tool. In certain embodiments, the entire mixing tool can only consist of one segment as in the Fig. 1 shown exist. The mixing tool preferably has the in Fig. 1 shown segment another in the Fig. 2 shown segment, which can also serve as an independent mixing tool. In addition to the hard metal elements 5 arranged along the scraper edge 41, it has two further hard metal elements 51, which are arranged on the end face 11 and protect an end edge of the mixing tool there against wear.

In the Fig. 3 becomes a cross-sectional view of the segment from the Fig. 2 shown parallel to the end face 11. Here it can be seen that the further hard metal elements 51 are soldered onto carrier elements 66, which, as part of the metallic core 6, are also fastened to the first core section 62 and the second core section 64 by means of welding.

The Fig. 4 shows a cross section of the segment from the Fig. 1 and/or also the segment from the Fig. 2 , but further away from the end face 11, to which the further hard metal elements 51 are attached. Therefore, the other hard metal elements 51 are not visible here. Instead, joining elements 8 are shown, which serve to join several such segments together to form a mixing tool. For this purpose, the joining elements 8 are welded to the metallic cores 6 of two or more mixing tool segments before the plastic jacket 7 is formed around them.

In the Fig. 4 It is clearly visible that on the hard metal element 5 both a front surface 12 and a lower surface 13 are flush with associated surfaces of the plastic jacket 7 or merge into them. This ensures that the mixing tool has a flat front surface 12 and a flat lower surface 13 without recesses or elevations, which could be contact surfaces for the formation of wear.

In the Fig. 5 is the metallic core 6 of the segment from the Fig. 1 with the soldered hard metal element 5 shown. For the subsequent production of the plastic jacket 7, the arrangement from the Fig. 5 preferably introduced into a mold in the direction perpendicular to the image plane, which in cross section has the shape of the plastic jacket from the Fig. 4 having. The mold is then filled or filled with a plastic casting material. When the plastic casting material hardens, the plastic jacket 7 is created.

The Fig. 6 shows a mixing tool that is not manufactured in a segment design. Here only the plastic jacket 7 and the hard metal elements 5, which form the scraper edge 41, are visible. The metallic core 6, which is also present in this embodiment and to which the hard metal elements 5 are soldered, is not visible because it is completely covered or surrounded by the plastic jacket 7 and the hard metal elements 5. Additionally you can see in the Fig. 6 Fasteners 621 in Form of holes used to attach the mixing tool to a mixing arm.

An embodiment according to the invention for a mixing tool will now be based on Fig. 7, 8 and 9 explained. This is a mixing tool that is also developed in the form of a segment, which can be combined with one or more other similar segments to form a mixing tool with a larger scraper edge 41. Unlike those in the Fig. 1 to 5 The mixing tool segments shown have the mixing tool from the Fig. 7 to 9 an elastic connection between the fastening section 2 and the stripping section 4. This is achieved in that the metallic core 6 forms a joint between the first core section 62 and the second core section 64. If the metallic core 6 is then provided with a plastic jacket 7, the elastic connection is created.

In the Fig. 7 Only the metallic core 6 with a hard metal element 5 soldered to the second core section 64 is shown in a side view. The Fig. 8 shows the metallic core 6 surrounded by the plastic core 7 made of polyurethane Fig. 7 . And the Fig. 9 shows an exploded view of each in the Fig. 7 parts shown.

Unlike the mixing tool with a rigid connection between the first core portion 62 and the second core portion 64, in the present embodiment, the connecting member 63 is replaced by a first joint member 631 and a second joint member 632 which engage with each other. For this purpose, tongue-shaped joint element extensions 634 are formed on the first joint element 631, which engage in the joint element recess 635 of the second joint element 632. After inserting the joint element extensions 634 into the joint element recess 635, a pin-shaped end element 633 is welded to the ends of the joint element extensions 634 in order to hold the second joint element 632. As a result, the two joint elements 631, 632 are against each other to a certain degree movable. Depending on the strength and elasticity of the plastic jacket 7, this leads to a more or less elastic mobility in the finished mixing tool between the first core section 62, which is designed as a fastening element, and the hard metal elements 5, so that the mixing tool touches an elevation on the mixing container wall on the scraper edge is designed to be more or less yielding.

In a modified embodiment, the pin-shaped end element 633 and/or the first joint element 631 is missing. At least in this embodiment, the second joint element 632 is not coupled to the first core section 62 without the plastic jacket 7. In this case, the second joint element 632 is connected to the first core section 62 exclusively by means of the plastic jacket 7.

The other elements of the mixing tool according to Fig. 7 to 9 correspond to the elements of the mixing tool according to the Fig. 1 to 5 , if they have the same reference numbers. In addition, the mixing tool according to the Fig. 7 to 9 Further hard metal elements 51 may be provided on the end face 11 of a segment.

List of reference symbols:

11

face

12

Front surface

13

subsurface

2

Fastening section

4

stripping section

41

scraper edge

5

Carbide element

51

another hard metal element

6

metallic core

62

first core section

621

fastener

63

connector

631

first joint element

632

second joint element

633

Closing element

634

Articular element extension

635

Joint element recess

64

two core sections

65

stiffening piece

66

Support element

7

Plastic jacket

8th

joining element

Claims (8)

1. A mixing tool, in particular a mixing shovel, having a fastening section (2) for fastening to a mixing arm of a mixing device and a scraper section (4) connected to the fastening section (2), on which a scraper edge (41) is arranged for stripping the mixture from a wall of a mixing tank of the mixing device, wherein the fastening section (2) and the scraper section (4) are formed by a metallic core (6) surrounded by a plastic sheath (7) and wherein the scraper edge (41) is formed by at least one hard metal element (5), characterized in that a first core section (62) assigned to the fastening section (2) is connected elastically and/or articulated to a second core section (64) assigned to the scraper section (4).
2. The mixing tool according to claim 1, characterized in that one of the two core sections (62; 64) has a pin-shaped or tongue-shaped appendage (634) protruding into a recess (635) in the other core section (64; 62).
3. The mixing tool according to one of the preceding claims, characterized in that the hard metal element (5) is welded or soldered to the metallic core (6).
4. The mixing tool according to one of the preceding claims, characterized in that the metallic core (6) is covered by more than 70%, 80%, 85%, 90%, 95% or substantially completely by the plastic sheath (7) and/or by the hard metal element (5).
5. The mixing tool according to one of the preceding claims, characterized in that the metallic core (6) is divided into several segments attached to each other.
6. The mixing tool according to one of the preceding claims, characterized in that the plastic sheath (7) is made of polyurethane.
7. A mixing device having a mixing tank, a mixing arm, wherein the mixing tank and the mixing arm are mounted in a rotatable manner relative to each other, and a mixing tool attached to the mixing arm according to any of the preceding claims.
8. A mixing tool manufacturing process for manufacturing a mixing tool according to any one of claims 1 to 6, having the following steps:

   - providing a metallic core (6);

   - attaching at least one hard metal element (5) to the metallic core (6);

   - fastening the metallic core (6) with the hard metal element (5) into a mold;

   - filling the mold with a plastic casting material; and

   - curing the plastic casting material to a plastic sheath (7) surrounding the metallic core (6).

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