EP3250788B2 - Pick, in particular a round-shank pick - Google Patents

Description

The invention relates to a chisel, in particular a round shank chisel, with a chisel head and a chisel shank, wherein the chisel head is formed at least from a base part and a cutting element made of a hard material, in particular hard metal, which is connected to the base part, wherein the base part has a wear-resistant layer on its outer surface adjacent to the cutting element, which layer covers at least a section of the outer surface of the base part facing the cutting element, and wherein an end face of the wear-resistant layer facing the cutting element is covered by the cutting element.

From the DE 90 16 655 U1 A chisel is known. The chisel described in the document has a base body with a hard metal tip. A wear-resistant layer made of a hard material (hard metal or ceramic) is arranged on an outer surface of the base body adjacent to the tip. The outer surface of the tip merges seamlessly into the surface of the wear-resistant layer. The base body has a circumferential recess into which the hard material is applied. The hard material can, for example, be sprayed onto the chisel. The base body is truncated cone-shaped at its front end. The tip has a corresponding truncated cone-shaped, axial recess in which the truncated cone-shaped end of the base body is received, thereby positioning the tip and guiding it laterally. In practical use, the axial recess leads to disadvantages, since the wall thickness of the tip is reduced in the area of the axial recess. At the end of the axial recess, a comparatively sharp edge is formed between the conical surface and the bottom surface of the recess. In this area, high stress peaks develop, especially when mechanical loads are applied laterally to the tip. Due to the relatively thin wall thickness of the tip in this area, these stress peaks increasingly lead to fracture of the tip, which is made of a brittle hard material, and thus to Failure of the chisel. A further disadvantage arises from the possible manufacturing process for such an arrangement. In order to avoid damage or destruction of the tip, especially if thermal treatment is required when applying the wear-resistant layer, the tip is attached to the base body, preferably by soldering, only after the wear-resistant layer has been applied to the base body. The tip then sits on a surface of the base body arranged circumferentially to the truncated cone-shaped end. Due to manufacturing reasons, the end face of the wear-resistant layer does not evenly line up with the circumferential surface on which the tip rests, but is recessed or protruding from it within the framework of manufacturing tolerances. Thus, no even soldering gap is formed between the contact surface of the tip, the circumferential surface of the base body, and the end face of the wear-resistant layer, as is the case in the exemplary embodiment shown. DE 90 16 655 U1 The uneven solder gap results in insufficient soldering, which can loosen during use and lead to tip loss.

DE 35 19 101 U1 discloses a chisel for a road milling machine, comprising a chisel shank. A chisel head made of hard metal is connected to the chisel shank. Several hard metal sleeves are arranged in the area of the chisel head, which are inserted into one another and surround the chisel shank.

EP 0 412 287 A2 discloses a round-shank chisel with a chisel head and a chisel shank. A receptacle is arranged in the area of the chisel head, in which a hard metal chisel tip is secured. The chisel head is surrounded by a wear-resistant coating applied using a plasma powder deposition welding process.

Another round shank chisel is made of DE 40 39 217 A1 This round-shank chisel also features a chisel head with a one-piece chisel shank. The chisel head is equipped with a carbide tip.

Following the carbide tip, a wear-resistant layer of hard material is applied to the chisel head.

WO 2009/072958 A1 discloses a chisel that carries a chisel tip in the area of its chisel head. A receptacle is incorporated into the chisel head, extending in the direction of the central longitudinal axis of the chisel. A shoulder of the chisel tip is held in this receptacle. The shoulder has a cylindrical outer surface onto which a carbide ring is slid.

DE 35 31 787 C1 discloses a tooth for a digging device, for example an excavator bucket.

It is therefore an object of the invention to provide a chisel of the type mentioned at the outset with improved mechanical strength.

The object of the invention is achieved in that the base part has an axially aligned recess for receiving a fastening section of the cutting element, in that the base part has a counter surface facing the cutting element around the recess, and in that the counter surface and the end face of the wear-resistant layer form a continuous flat surface or in that the end face of the wear-resistant layer is brought close to the counter surface. Since the fastening section of the cutting element is held in the recess of the base part, thin-walled sections of the cutting element, which are exposed to strong external forces, are avoided. This significantly reduces the risk of breakage for the tip. The flat surface formed by the counter surface and the end face enables the formation of a uniform brazing gap between this flat surface and the cutting element. This makes it possible to achieve an optimized brazing between the cutting element and the base part of the chisel, which does not separate even under strong mechanical stress. Because the base part has a recess instead of a shoulder for connection to the cutting element, the continuous flat surface between the counter surface and the The front surface of the wear-resistant layer can be easily manufactured.

Preferably, the wear-resistant layer is brought close to the opposing surface, effectively protecting the transition area from erosion. For example, the wear-resistant layer can be brought to within less than 1 mm of the opposing surface.

For connection to a chisel holder, the chisel head is preferably connected in one piece to a chisel shank. The chisel shank can be designed as a round shank.

Preferably, the wear-resistant layer is accommodated in a recess in the base part. The recess is provided circumferentially relative to the counter surface on the outer surface of the base part. Advantageously, the applied wear-resistant layer can be radially flush with the cutting element on one side and with the outer surface of the base part on the opposite side, adjacent to the recess.

The wear-resistant layer can be formed by a coating applied to the base part. The wear-resistant layer can also be formed by a separate hard material element that is, for example, firmly bonded to the base part. The use of a soldered hard metal ring or individual hard metal segments adapted to the base part, arranged in a regular or irregular arrangement, is conceivable here.

According to a particularly preferred embodiment of the invention, it can be provided that the counter surface and the end face are designed as separating surfaces created in one operation, in particular as cut surfaces or as ground surfaces or as milled surfaces, or that the end face is designed as a parting surface created during an application process, in particular during a During the welding process, the wear-resistant layer forms a receptacle surface of an auxiliary tool base resting on the counter surface and projecting radially beyond the counter surface. In both cases, a continuous, flat surface is formed between the counter surface and the end face. This creates a uniform brazing gap and thus an optimized, resilient brazing connection between the surface formed by the counter surface and the end face and the cutting element.

The flow behavior of the solder can be improved by designing the counter surface and/or the end face as smooth surfaces or as surfaces with a specified roughness in a range of Rz = 4 µm to Rz = 280 µm, or as surfaces with grooves with a groove depth in a range of 2 µm to 500 µm. The roughness or grooves can be created, for example, during the cutting process when creating the cutting surfaces or as an imprint of the base according to the desired specification.

The cutting element is exposed to high mechanical stresses during use. In order to achieve a secure connection between the cutting element and the base part, the invention provides that the cutting element forms a bearing surface surrounding its fastening section, that the bearing surface covers the counter surface and the end face at least in regions, and that a first soldering joint is formed between the bearing surface and the continuous surface formed by the counter surface and the end face. In addition, it can also be provided that a second soldering joint is formed between an outer surface of the fastening section and an inner surface of the recess and/or that a third soldering joint is formed between an end surface of the fastening section and a bottom surface of the recess. The soldering joints preferably merge into one another, so that a continuous soldering connection is present over the entire interface between the cutting element and the base part and between the cutting element and the end face of the wear-resistant layer.

The abrasive load acting on the base part is greatest adjacent to the cutting element and decreases toward the end of the chisel head facing the chisel shank. At the same time, the cutting element is held by its mounting section in the recess at the front end of the base part.

In order to protect the area of the cutting element holder and thus to avoid loss of the cutting element, it is provided that the wear-resistant layer encloses in axial alignment at least the section of the chisel head in which the recess is made.

According to two alternative variants of the invention, the wear-resistant layer can be provided with a uniform layer thickness or with a varying layer thickness. A wear-resistant layer with a uniform layer thickness is easy and cost-effective to produce. By varying the layer thickness, the wear-resistant layer can be adapted to the actual loads in the various areas of the chisel head.

In order to adapt the layer thickness to the local loads, it can be provided that the layer thickness of the wear-resistant layer decreases, starting from its end face facing the cutting element, towards its end facing the chisel shank, or that the layer thickness of the wear-resistant layer increases, starting from its end face facing the cutting element, towards its end facing the chisel shank. By increasing the layer thickness towards the chisel shank, a conical outer contour of the chisel head can be achieved with a constant diameter of the base part in the area of the coating, through which removed material is guided away from a chisel holder in which the chisel is arranged. With a layer thickness decreasing towards the chisel shank, the greatest layer thickness is arranged in the area of maximum abrasive load directly after the cutting element. This Layer thickness is adapted to the respective abrasion so that comparable service lives are achieved for the different areas of the wear-resistant layer.

Another way to adapt the layer thickness of the wear-resistant layer to the local loads is to have an outer surface of the wear-resistant layer with a convex curvature along its longitudinal extent, or to have the outer surface with a concave curvature along its longitudinal extent, or to have the outer surface with alternating concave and convex curvature sections along its longitudinal extent. In addition, the material flow of the excavated material can be influenced by the shape of the outer surface. For example, a convex surface of the wear-resistant layer directs the excavated material outwards immediately after the cutting element. With appropriate adaptation of the outer contour of the cutting element and the convex shape of the outer surface of the wear-resistant layer, the excavated material can be deflected in approximately the same direction by the cutting element and the wear-resistant layer, thus creating a uniform material flow in which areas of the bit head further away from the cutting element are relieved. The convex shape of the outer surface allows the front coated area facing the cutting element to offer less resistance to the excavated material, while the rear area deflects it more outward. This allows for even loading of the wear-resistant layer along the flow direction of the excavated material. Alternating concave and convex areas allow excavated material to settle in the concave areas. This provides additional wear protection, as the moving excavated material in these areas does not slide directly past the wear-resistant layer.

Furthermore, it can be provided that an internal angle is formed between the surface of the cutting element and the outer surface of the wear-resistant layer at their transition. A brazing joint ending in this transition area is thus protected from the main flow of the passing The brazing joint is recessed from the waste material and thus protected. This protective effect is enhanced by the fact that waste material can settle in the inner angle and additionally shield the brazing joint from the abrasive attack of the passing waste material.

A further embodiment of the invention may comprise a segment-like coating or individual segments formed from one or more hard metals, wherein the arrangement is carried out by means of fastening methods known from the prior art, such as soldering, gluing, build-up welding or the like.

According to a further development of the invention, it can be provided that the wear-resistant layer covers at least one surface section of the cutting element adjacent to the support surface. The wear-resistant layer thus covers the adjacent outer surfaces of both the base part and the cutting element. As a result, both the cutting element and the base part are protected from abrasive wear in the particularly stressed transition area from the cutting element to the base part. In particular, the solder joint formed between the support surface of the cutting element and the base part is also arranged in a protected manner, so that no hard materials can force their way into the solder joint from the outside and separate the cutting element from the base part.

The strength of the connection between the cutting element and the base part can be further improved by forming a brazing joint (fourth brazing joint) between the wear-resistant layer and the surface portion of the cutting element. The cutting element is thus connected to the base part by brazing along its contact surface and along its surface portion adjacent to the contact surface.

Advantageously, it can be provided that the wear-resistant layer protrudes beyond the counter surface in the direction of a central longitudinal axis of the chisel head and/or that the wear-resistant layer and the counter surface form a cup-shaped receptacle for form the cutting element. Preferably, the wear-resistant layer is applied to the base part, and the cutting element is then soldered on. The protruding wear-resistant layer or the cup-shaped receptacle allows the cutting element to be easily and precisely positioned on the base part and soldered to it. During the soldering process, the cutting element remains held in position by the wear-resistant layer, which surrounds the cutting element in the area facing the base part.

To coat a chisel head of a chisel according to the invention, it can be provided that an auxiliary tool is fixed to the base part of the chisel head in such a way that at least a portion of its contact surface rests on the counter surface, that in a first method step the outer surface is coated with the wear-resistant layer and that the auxiliary tool is then removed. The wear-resistant layer is thus applied to the outer surface of the base part of the chisel head, thereby protecting it from mechanical damage and abrasion during later use. The auxiliary tool prevents the counter surface, to which the cutting element is soldered in the second manufacturing process, from also being coated during the coating process. This thus maintains a defined surface for soldering the cutting element. Furthermore, the auxiliary tool predetermines the outer shape of the wear-resistant layer in its transition region to the cutting tool, so that here too a predetermined soldering surface to the cutting tool is produced.

According to a preferred method variant, it can be provided that the wear-resistant layer is applied to the outer surface of the chisel in such a way that its end face rests against at least a portion of the contact surface of the auxiliary tool and/or that it rests against a surface area of the auxiliary tool adjacent to the contact surface with a spatial orientation different from the contact surface. Depending on the design of the auxiliary tool, a different contour of the surface of the wear-resistant layer that will later adjoin the cutting element can be produced. This allows the contour of the surface facing the cutting element the wear-resistant layer is adapted to the contour of the cutting element. The contour of the auxiliary tool and thus the contour of the surface of the wear-resistant layer are specified in such a way that, when the cutting element is soldered on, it follows the contour of the cutting element. This ensures that a uniform brazing gap is formed along the interface between the cutting element and the wear-resistant layer. If, for example, the auxiliary tool protrudes radially over the mating surface of the base part with its contact surface, the wear-resistant layer can be brought up to the contact surface. This creates an end face of the wear-resistant layer which is arranged radially to the mating surface of the base part and forms a flat surface with it. In a subsequent manufacturing step, the cutting element can be placed with its contact surface against the mating surface and the end face and connected to them by soldering. Alternatively or additionally, it can be provided that the wear-resistant layer is applied to a surface adjacent to the contact surface of the auxiliary tool. This adjacent surface is aligned such that it follows the contour of the cutting element surface adjacent to the support surface. If the cutting element is placed with its support surface against the mating surface of the base part in a subsequent manufacturing step, its surface adjacent to the support surface faces the wear-resistant layer, spaced apart by a defined wide brazing gap. The wear-resistant layer thus encloses part of the outer surface of the cutting element. The cutting element can be connected to the base part by brazing, with the brazing gap being formed along the interface between the cutting element on one side and the mating surface and the wear-resistant layer on the other side.

To produce a chisel according to the invention, it can be provided that the base part of the chisel head is produced in a size that is extended to its final dimension in the direction of the cutting element, that the wear-resistant layer is applied to the outer surface of the extended base part, and that the base part is subsequently shortened along a parting line together with the wear-resistant layer. The parting surface thus formed represents a continuous, flat Area between a formed counter surface as the front end of the base part and the formed end face of the wear-resistant layer. The flat surface enables the formation of a uniform soldering gap to the cutting element covering the counter surface and the end face, which is soldered onto the base part in a subsequent process step.

Preferably, the wear-resistant layer can be applied to the outer surface of the chisel head by a welding process. This welding process enables the production of a cost-effective and durable wear-resistant layer. The disadvantage of the welding process, namely that an open end surface of the resulting coating can only be determined imprecisely in its position and therefore a continuous, flat surface cannot be produced with an adjacent counter surface, is eliminated by the described separation process.

A resistant wear-resistant layer and thus a long-lasting chisel can be obtained by applying a layer of a hard material, in particular of hard metal, and/or an iron alloy and/or a nickel alloy and/or a cobalt alloy and/or a titanium alloy and/or of tungsten carbide and/or of titanium carbide as the wear-resistant layer.

Figur 1

in einer perspektivischen Seitenansicht einen Meißel mit einem Meißelschaft und einem Meißelkopf mit einer verschleißfesten Schicht,

Figur 2

den in Figur 1 gezeigten Meißel in einer seitlichen, zum Teil als Schnitt ausgeführten Darstellung,

Figur 3

einen Ausschnitt des in Figur 2 gezeigten Meißels,

Figur 4a-4i

in seitlicher Schnittdarstellung einen Ausschnitt des Meißelkopfs mit unterschiedlichen Ausführungsformen der verschleißfesten Schicht,

Figur 5

in einer weiteren seitlichen Schnittdarstellung einen Ausschnitt des Meißelkopfs mit einem Hilfswerkzeug,

Figur 6

in einer weiteren seitlichen Schnittdarstellung einen Ausschnitt eines Meißelkopfes in einer zu seiner Endabmessung in Richtung zum Schneidelement verlängerten Größe,

Figur 7

in einer seitlichen Schnittdarstellung einen Ausschnitt einer in axialer Richtung überstehenden verschleißfesten Schicht,

Figur 8

in einer seitlichen Schnittdarstellung einen Ausschnitt eines Meißelkopfes in einer weiteren Ausführung einer in axialer Richtung überstehenden verschleißfesten Schicht und

Figur 9

in einer seitlichen Schnittdarstellung einen Ausschnitt des Meißelkopfs mit einem Hilfswerkzeug,

The invention will be explained in more detail below with reference to an embodiment illustrated in the drawings. In the drawings:

Figure 1

in a perspective side view a chisel with a chisel shank and a chisel head with a wear-resistant layer,

Figure 2

the in Figure 1 shown chisel in a side view, partly in section,

Figure 3

an excerpt from Figure 2 shown chisel,

Figure 4a-4i

in side sectional view a section of the chisel head with different designs of the wear-resistant layer,

Figure 5

in another side sectional view a section of the chisel head with an auxiliary tool,

Figure 6

in a further lateral sectional view, a section of a chisel head in a size extended to its final dimension in the direction of the cutting element,

Figure 7

in a lateral sectional view a section of a wear-resistant layer projecting in the axial direction,

Figure 8

in a lateral sectional view a section of a chisel head in a further embodiment of a wear-resistant layer projecting in the axial direction and

Figure 9

in a side sectional view a section of the chisel head with an auxiliary tool,

Figure 1 shows a perspective side view of a chisel 10 with a chisel shank 50 and a chisel head 40 with a wear-resistant layer 30. The chisel 10 is designed as a round-shank chisel. A cutting element 20 consisting of a hard material, for example, hard metal, is assigned to the chisel head 13. This cutting element is connected to a base part 41 of the chisel head 13, which tapers conically towards the cutting element 20, in the present embodiment by soldering. In an area facing the cutting element 20, the base part 41 is coated with the wear-resistant layer 30 all the way around the cutting element 20. The wear-resistant layer 30 consists of a hard material and is welded to the base part applied. In the illustrated embodiment, the wear-resistant layer 30 is formed from hard metal. It can also be made from an iron alloy, a nickel alloy, a cobalt alloy, a titanium alloy, tungsten carbide, or titanium carbide.

Starting from the base part 41, the chisel head 40 widens via a transition area 41.2 to a collar 41.3 with a constant outer diameter. The collar merges into the chisel shaft 50. A fastening sleeve 51 is arranged around the chisel shaft 50. The fastening sleeve 51 is designed as a clamping sleeve made of a spring-elastic material, for example, sheet steel. As shown in Figure 2 As shown, it has a longitudinal slot that is delimited by sleeve edges. Due to the longitudinal slot, the fastening sleeve diameter can be varied, with the sleeve edges moving towards one another (small diameter) or being further apart from one another (large sleeve diameter). In this way, different clamping states can be achieved. A support element 52 designed as a wear protection disk is mounted on the fastening sleeve. This support element 52 has a circular cross-section and is penetrated by a bore. The bore is dimensioned such that the fastening sleeve is held in a pre-tensioned state with a reduced outer diameter compared to its relaxed state. The outer diameter thus created is selected such that the fastening sleeve 51 can be inserted into a chisel receptacle of a chisel holder (not shown) with little or no force. The insertion movement is limited by the support element 52. As the chisel shank 50 is further inserted into the bore, the support element 52 is moved into an area of the chisel shank 50 not encompassed by the fastening sleeve 51. The fastening sleeve 51 then springs open radially and clamps itself in the bore of the chisel holder. In this way, the chisel 10 is held axially captive, yet freely rotatable in the circumferential direction. Figure 1 As further shown, the support element 52 forms a support surface 52.1, oriented toward the chisel head 40, surrounded by an edge 52.2 for supporting the collar 41.3 of the chisel head 40. The edge 52.2 is pierced by edge recesses 52.3.

The cutting element 20 has, starting from a front cutting tip 21, a convex-shaped cutting surface 22 which merges into a base 23 which terminates radially with the wear-resistant layer 30.

The chisel 10 is used to turn its Figure 2 The tool is rotatably mounted on a bit holder on a rotating roller carrier along the central longitudinal axis M shown. Due to the rotation of the roller carrier, the cutting element 20 penetrates the material to be removed, for example, asphalt or soil, and crushes it. The excavated material slides past the bit head 40 and is diverted outwards through the base part 41 with the circumferential, wear-resistant layer 30 and the transition region 41.2. A bit carrier in which the bit 10 is held is thus optimally protected from abrasion by the excavated material.

The mechanical stress on the chisel head 40 is greatest in the area of the cutting element 20. Therefore, the cutting element 20 is made of a hard material, resulting in a long service life of the chisel 10. To increase the service life of the base part, in particular, in its mechanically highly stressed area adjacent to the cutting element 20, the wear-resistant layer 20 is applied there.

Figure 2 shows the Figure 1 shown chisel 10 in a lateral view, partly in section. The section reveals part of the base part 41 of the chisel head 40. As can be seen there, a recess 44 is provided in the base part 41 at the end of the base part 41 facing the cutting element 20. The recess 44 has a cylindrical contour and is axially aligned along the central longitudinal axis M of the chisel 10. The cutting element 20 forms a fastening section 24 opposite the cutting tip 21, which is also cylindrical and is held in the recess 44 in the base part. The cutting element 20 is soldered to the base part 41 and is thus securely and resiliently connected to the base part 41.

The wear-resistant layer 30 encompasses the area of the recess 44. A comparatively thin-walled web 45 of the base part 41, which surrounds the recess 44, is thereby protected from abrasive wear. This prevents the web 45 from being prematurely abraded by sliding debris, which would lead to the loss of the cutting element 20 and thus to the premature failure of the entire chisel 10.

Figure 3 shows a section of the Figure 2 shown chisel 10 in the region of the cutting element 20. As can be seen in the enlarged view, a recess 42 is provided circumferentially around the base part 41 in a region facing the cutting element 20, into which recess the wear-resistant layer 30 is introduced. An outer surface 33 of the wear-resistant layer 30 thus terminates with the base 23 and with the surface of the base part 41 running alongside the recess 42. An inner surface 32 of the wear-resistant layer 30 forms a firm connection to an outer surface 41.1 of the base part 41, to which it is applied. An end face 31 of the wear-resistant layer 30 facing the cutting element 20 is covered by a radially aligned bearing surface 25 of the cutting element 20, which closes off the base 23 towards the base part 41. The web 45 of the base part 41 is closed off from the cutting element 20 by a counter surface 43. The counter surface 43 and the end face 31 of the wear-resistant layer 30 form a continuous, flat surface. In the illustrated embodiment, this surface is arranged radially and is covered by the support surface 25 of the cutting element 20.

The support surface 25 of the cutting element 20 merges into the fastening section 24 via a rounded connecting area 28. The rounding of the connecting area 28 lies opposite a rounded surface 43.1 of the base part 41, via which the counter surface 43 is transferred into an inner surface 44.1 of the recess 44. An outer surface 26 of the fastening section 24 is arranged opposite the inner surface 44.1 of the recess 44. An end surface 27 closing the fastening section 24 lies spaced from a bottom surface 44.2 of the recess 44 of the base part 41.

A first solder joint 11.1 is formed between the end face 31 of the wear-resistant layer 30 and the counter surface 43 of the base part 41 on one side and the support surface 25 of the cutting element 20 on the opposite side. A second solder joint 11.2, arranged between the inner surface 44.1 of the recess 44 and the outer surface 26 of the fastening section 24 of the cutting element 20, continuously adjoins the first solder joint 11.1. Following the second solder joint 11.2, a third solder joint 11.3 is formed between the bottom surface 44.2 of the recess 44 and the end surface 27 of the fastening section 24.

The surface formed by the end face 31 and the counter surface 43 is continuous and flat. This creates a first solder joint 11.1 with a uniform thickness between this surface and the opposite support surface 25. A uniform thickness of the solder joints 11.1, 11.2, 11.3 is a prerequisite for a stable and resilient soldered connection. The flat surface formed by the end face 31 and the counter surface 43 can be produced by a separating or machining production step or by a forming process during the application of the wear-resistant layer 30, as is the case with the Figures 5 and 6 is explained in more detail. It is advantageous that the counter surface 43 and the end face 31 form the front end of the base part 41, so that, for example, machining processes can be applied over the front end of the base part 41 after the wear-resistant layer 30 has been applied and before the cutting element is soldered on.

The cutting element 20 is securely held in the base part 41 of the chisel head 40 by the formed solder joints 11.1, 11.2, 11.3. By designing the cutting element 20 with a fastening section 24 held in the recess 44 of the base part 41, thin-walled areas of the comparatively brittle cutting element 20 can be avoided. Furthermore, the rounded transition from the support surface 25 to the outer surface 26 of the Stress peaks are avoided by the fastening section 24. Both measures significantly reduce the risk of breakage for the cutting tip 20.

The wear-resistant layer 30 is introduced into the recess 42. This prevents protruding edges at the transition of the wear-resistant layer 30 to the base 23 and to the outer surface 41.1 of the base part 41 outside the recess 42, thereby reducing both the abrasive wear of the chisel head 40 and the energy consumption during use of the chisel 10. The end face 31 of the wear-resistant layer 30 is covered by the cutting element 20 and the first solder joint 11.1 filled with solder. This prevents waste material from getting between the outer surface 41.1 of the base part 41 and the inner surface 32 of the wear-resistant layer 30 and causing it to break off.

An interior angle is formed between the base 23 and the outer surface 33 of the wear-resistant layer 30, at the apex of which the first solder joint 11.1 ends. The first solder joint 11.1, with the comparatively soft solder material, is thus recessed from the developing main stream of the passing waste material and is thus additionally protected against wear.

The Figures 4a to 4i show a section of the chisel head 40 with different designs of the wear-resistant layer 30 in a side sectional view.

In the execution according to Figure 4a The outer surface 41.1 of the base part 41 is initially cylindrical in the area of the web 45 and then transitions into a conically widening area. The outer surface 33 of the wear-resistant layer 30 is continuously conical. This design ensures that the web 45 has a uniform thickness with a consistently comparatively high material thickness. As a result, high transverse forces acting via the cutting element 20 can be safely absorbed. The formed wide counter surface 43 results in a secure fit of the cutting element 20 on the Base part 41 and a large-area soldered connection between the support surface 25 of the cutting element 20 and the counter surface 43.

According to Figure 4b The wear-resistant layer 30 has its greatest layer thickness in the area facing the cutting element 20, which layer thickness continuously decreases towards its opposite end. The mechanical stress and thus the abrasive wear of the wear-resistant layer 30 is greatest immediately adjacent to the cutting element 20 and decreases in the direction of the collar 41.3 of the chisel head 40. The distribution of the layer thickness shown achieves a uniform service life of the wear-resistant layer 30 over its entire extent. By adjusting the layer thickness in the direction of the collar 41.3, the material consumption during the production of the wear-resistant layer 30 is optimized, taking into account the expected mechanical stress on the wear-resistant layer 30 in the various areas along the chisel head 40.

Accordingly Figure 4c The wear-resistant layer 30 has its smallest layer thickness in the area facing the cutting element 20, which increases continuously towards its opposite end. This also results in a web 45 with a uniform, comparatively large material thickness with the already Figure 4a The outer surface 41.1 of the base part 41 can be cylindrical in the region of the recess 42 with a uniform distance from the central longitudinal axis M of the chisel 10 and thus easy to manufacture, while the conical outer contour of the chisel head 40 is retained.

Figure 4d shows a variant in which the outer surface 33 of the wear-resistant layer 30 is convexly shaped. This shape creates a transition between the cutting element 20 and the wear-resistant layer 30, as well as between the wear-resistant layer 30 and the outer surface 41.1 of the base part 41 adjoining the recess 42, without protruding edges, which lead to increased abrasion. At the same time, the wear-resistant layer 30 is given a high material thickness, whereby long service life of the chisel head 40 and thus of the chisel 10 can be achieved. The outer surface 33 of the wear-resistant layer 30 is aligned approximately the same as the surface profile of the cutting surface 22 of the cutting element 20, resulting in a uniform material flow of the waste material. The internal angle between the base 23 and the outer surface 22 tapers comparatively sharply, so that the first solder joint 11.1 is clearly set back from the main material flow of the waste material and is thus protected. An internal angle is also formed in the transition of the outer surface 33 into the outer surface 41.1 to the side of the recess 42, so that this connection area between the material of the wear-resistant layer 30 and the material of the base part 41 is also set back from the material flow of the waste material and is thus protected.

Figure 4e shows an embodiment in which the outer surface 33 of the wear-resistant layer is designed to be conical. The outer surface 41.1 of the base part 41 is designed to be concave in the area of the recess 42, so that the inner surface 32 of the wear-resistant layer 30 is convex. This results in a large layer thickness of the wear-resistant layer 30 with a correspondingly long service life. The web 45 with the formed counter surface 43 is correspondingly thick-walled or large-area with the associated, already to Figure 1 The conical outer surface 33 provides edge-free transitions at the edges of the wear-resistant layer 30 and thus the previously described reduced abrasion and energy consumption.

According to Figure 4f Both the inner surface 32 and the outer surface 33 of the wear-resistant layer 30 are convex. This allows the advantages of the Figure 4d shown embodiment of a convex outer surface 33 with the Figure 4e advantages of a convex inner surface 32.

In the version according to Figure 4g the outer surface 41.1 of the base part 41 is cylindrical in the area of the web 45 and conical in the connection to the web 45 The outer surface 33 of the wear-resistant layer 33 follows this shape, with the conical region of the outer surface 33 being steeper than the conical region of the outer surface 41.1. The layer thickness of the wear-resistant layer 30 is selected to be greatest in the region of the web 45 and thus of the highest mechanical load on the base part 41 and decreases within the conical regions. Due to the outer surface 33 of the wear-resistant layer 30 being cylindrical in the region of the web 45, it is set back from the main flow direction of the excavated material predetermined by the shape of the cutting element 20, so that abrasion in this area is reduced compared to a conical or concave design of the outer surface 33. As a result of this and the high layer thickness of the wear-resistant layer 30, the comparatively thin-walled web is optimally protected against wear.

A similar effect is shown by the Figure 4h shown design of the wear-resistant layer 30 with a concave outer surface 33 and a conically extending inner surface 32. Here, too, a great layer thickness is achieved in the area of the web 45 and thus in the heavily loaded, immediate vicinity of the cutting element 20. The outer surface 33 runs in the area of the web 45, within the scope of the deviation due to the concave shape, approximately in the direction of the surface of the base 23. As a result, this area offers the excavated material sliding past only a small contact surface, whereby the abrasion in the area of the comparatively thin-walled web is kept to a minimum. In the continuing concave course of the outer surface 33, the excavated material is diverted away from the chisel 10 to the outside, thereby protecting the uncoated area of the chisel head 40. Due to the conical shape of the coated outer surface 41.1 of the base part 41, the material thickness of the web 45 increases towards its base, so that even high transverse forces introduced via the cutting element 20 can be absorbed without damaging the web 45.

Figure 4i shows a section of the chisel head 40 with a wear-resistant layer 30, whose outer surface 33 has alternating concave and convex areas. Excavated material can settle in the concave areas, so that the excavated material sliding past the outside is not in direct contact with the outer surface 33 of the wear-resistant layer 30, at least in the concave areas. This simple measure can significantly reduce the abrasion of the wear-resistant layer 30.

Figure 5 shows in a further lateral sectional view a section of the chisel head 40 with an auxiliary tool 60. The chisel head 40 is still in the form of a semi-finished product without the soldered cutting element 20. Figure 5 shows a possibility for coating the base part 41 of the chisel head 40 with the wear-resistant layer 30, so that a continuous, flat surface is formed between the end face 31 of the wear-resistant layer 30 and the counter surface 43 of the base part 41.

Shown is a chisel head 40 with a wear-resistant layer 30 having a uniform layer thickness. However, the method can be used for any other design of the wear-resistant layer 30, as shown by way of example in the Figures 4a to 4i shown.

The auxiliary tool 60 is formed from a base 61, in the center of which an axially aligned positioning pin 63 is arranged. The diameter of the base 61 is selected such that it projects radially beyond the wear-resistant layer 30. The positioning pin 63 is designed such that it can be inserted into the recess 44 of the chisel head 40 with minimal lateral play. It ends at a distance from the end of the recess 44 by a gap 44.3. In the present embodiment, the auxiliary tool 60 is made of a metal, preferably copper.

Before applying the wear-resistant layer 30, the auxiliary tool 60 is fixed with its positioning pin 63 in the recess 44 in such a way that it a shaping contact surface 62 extending around the positioning pin 63 rests on the counter surface 43 of the base part 41. The wear-resistant layer 30 is then introduced into the recess 42. The wear-resistant layer 30 is applied by means of a welding process such that it rests against the contact surface 62 of the base 61. This forms an end face 31 of the wear-resistant layer 30, which merges flatly and continuously into the counter surface 43 of the base part 41. After the coating process, the auxiliary tool 60 is removed.

By appropriately structuring the shaping surface 63, the end face 31 of the wear-resistant layer 30 can be smooth or provided with a predetermined roughness or with another structure, for example, with grooves. Advantageously, a roughness in a range of Rz = 4 µm to 280 µm or groove depths in a range of 2 µm to 500 µm is provided. The surface structure of the end face 31 can thus be optimized for good solder flow.

Figure 6 shows, in another side sectional view, a section of a chisel head 40 in a size extended to its final dimension in the direction of the cutting element 20. This is also a semi-finished product to which the cutting element 20 has not yet been applied. The later final dimension of the base part 41 is marked by a dividing line T. The base part 41 is extended by the length of a projection 12. The recess 42 of the base part 41 continues at the projection 12. The axial recess 44 is also formed in the base part 41 and the projection 12. The projection 12 ends in a radially aligned end surface 13.

Shown is a chisel head 40 with a wear-resistant layer 30 having a uniform layer thickness. However, the method can be used for any other design of the wear-resistant layer 30, as shown by way of example in the Figures 4a to 4i shown.

The wear-resistant layer 30 is introduced into the recess 42 of the extended chisel head 40 by a welding process. The illustration schematically shows the rough outer surface 33 of the wear-resistant layer 30 caused by the welding process.

Also due to manufacturing reasons, the wear-resistant layer 30 does not end flush and level with the front end surface 13 of the projection 12. In the illustrated embodiment, the wear-resistant layer 30 forms a protruding bead 34 opposite the end surface 13 on one side of the projection 12 and a recessed bead on the opposite side. Both are unsuitable for forming a resilient soldered connection with a uniform solder joint 11.1, 11.2, 11.2 to a rectilinear surface, such as that provided by the support surface 25 of the cutting element 20.

To form the required flat surface between the counter surface 43 of the base part 41 and the end face 31 of the wear-resistant layer 30, the overhang 12 is separated from the base part 41 along the parting line T. This can be done by a parting process, for example by sawing, or a machining process, such as milling. The parting surface can also be further machined in a subsequent processing step. In this way, a defined roughness of the parting surface can be created, or grooves or other structures can be incorporated into the parting surface to improve the flow behavior of a solder used to solder the cutting element 20. The roughness can be set in a range between RZ = 4 µm and 280 µm, or grooves with a groove depth in a range between 2 µm and 500 µm can be introduced.

Both after the Figure 5 as well as to Figure 6 The manufacturing process described above produces a continuous and flat surface formed by the counter surface 43 and the end face 31, against which the support surface 25 of the cutting element 20 can be positioned and soldered. a uniform and therefore resilient first solder joint 11.1 is formed, as shown in the Figures 1 to 4 is shown.

Figure 7 shows a lateral sectional view of a section of a wear-resistant layer 30 projecting in the axial direction.

The cutting element 20 is formed from the cutting tip 21, the cutting surface 22, which is concave in the illustrated embodiment, and the base 23. The base 23 forms a continuous and flat support surface 25 oriented toward the base part 41 of the chisel head 40.

The wear-resistant layer 30 is introduced into the recess 44 arranged circumferentially around the base part 41. A radially inner part of the wear-resistant layer terminates with the counter surface 43 of the base part 41 towards the cutting element 20 and forms the end face 31 there. The cutting element 20 rests with its support surface 25 on the counter surface 43 and the end face 31 via a soldered connection. It covers a centering notch 43.2 introduced into the counter surface 43 along the central longitudinal axis M of the chisel head 40.

Laterally of the end face 31, the wear-resistant layer 30 projects axially beyond the counter surface 43 and the end face 31. It thereby forms a centering collar 36, which encloses the base 23 of the cutting element 20 in its region facing the base part 41. The wear-resistant layer 30 thus covers a surface portion 29 of the cutting element 20 adjacent to the support surface 25. A fourth solder joint 11.4 is formed between the surface portion 29 and the centering collar 36.

The wear-resistant layer 30, together with the counter surface 43 of the base part 41, forms a cup-shaped receptacle 46 into which the cutting element 20 is soldered with its base 23. The cup-shaped receptacle 46 correctly aligns the cutting element 20 during the soldering process and holds it in position. Between the counter surface 43, the end face 31, and the centering collar 36 A soldered connection is formed between the cutting element 20 on one side and the cutting element 20 on the other side. The cutting element 20 is thus securely connected to the base part 41 of the chisel head 40. The section of the soldered connection formed between the support surface 25 and the counter surface 43 or the end face 31 is protected by the circumferential centering collar 36 of the wear-resistant layer 30. This results in a permanent, wear-protected connection between the cutting tip 20 and the base part 41.

Figure 8 shows a side sectional view of a section of a chisel head 40 in a further embodiment of a wear-resistant layer 30 projecting in the axial direction.

The cutting element 20 essentially corresponds to the Figure 7 illustrated cutting element 20, wherein a base extension 23.1 is formed on the base 23 in the area facing the base part 41 of the chisel head 40. The base extension 23.1 has a cross-section that tapers conically towards the base part 41.

The centering collar 36 of the wear-resistant layer 30 follows the conically extending surface section 29 of the base 23, which is located in the region of the base extension 23.1. The base extension 23.1, as the section of the cutting element 20 facing the base part 41, is thus covered by the wear-resistant layer 30.

Here, too, the base extension 23.1 and the counter surface 43 of the base part form a cup-shaped receptacle 46 into which the cutting element 20 is soldered. The soldering joint area formed between the support surface 25 and the counter surface is thus circumferentially surrounded by the wear-resistant layer 30 and thus protected. The fourth soldering joint 11.4 enlarges the formed soldering surface between the base part 41 and the cutting tip 20, so that a firm connection is formed between the cutting tip 20 and the base part 41.

Figure 9 shows a side sectional view of a section of the chisel head 40 with an auxiliary tool 60.

The base part 41 and the wear-resistant layer 30 of the chisel head 40 have the same shape as already Figure 7 , but there with the cutting element 20 inserted.

The auxiliary tool 60 is formed from a base 61 to which a projection 64 is integrally formed. The auxiliary tool 60 is rotationally symmetrical about the central longitudinal axis M. The projection 64 has a smaller diameter than the base 61. The projection 64 rests with its contact surface 62 against the counter surface 43 of the base part 41 and against the end face 31 of the wear-resistant layer 31. A centering mandrel 64.1 is integrally formed in the center of the contact surface 62, which engages in the centering notch 43.2 of the base part 41.

Before the wear-resistant layer 30 is applied, the auxiliary tool 60 is placed with its contact surface 62 onto the counter surface 43 of the base part 41. The centering mandrel 64.1 engages the centering notch 43.2 so that the auxiliary tool 60 is aligned with the base part 41. The wear-resistant layer 30 is then applied, preferably by welding. The wear-resistant layer 30 is applied such that it fills the recess 44. On the side of the auxiliary tool 60, the wear-resistant layer 30 is applied up to the area of the contact surface 62 of the auxiliary tool 60 that protrudes beyond the counter surface 43 of the base part 41, as well as to the outer surface of the extension 64 of the auxiliary tool 60. This forms the end face 31 and the centering collar 36, which protrudes axially beyond the counter surface 43 and, in the present embodiment, beyond the end face 31 of the wear-resistant layer 30. The centering collar 36 is delimited by the base 61 of the auxiliary tool 60.

After the coating process, the auxiliary tool 60 is removed. What remains is the stepped wear-resistant layer 30 as an imprint of the auxiliary tool 60. In The cutting element 20 can be soldered into the cup-shaped receptacle 46 thus formed, as shown in Figure 7 is shown.

The contour of the auxiliary tool 60 is designed to follow the contour of the intended cutting element 20. To produce the Figure 8 For example, an auxiliary tool 60 can be provided for the chisel 10 shown, the projection 64 of which tapers conically from the base 61. This creates a centering collar 36 corresponding to the Figure 8 shown, which follows the conical shape of the base extension 23.1 of the cutting element 20 shown there.

The Figures 5 and 9 The auxiliary tool shown is preferably made of a material that does not form a metallurgical bond with the wear-resistant layer. The auxiliary tool can be made of copper, for example.

To produce the cup-shaped receptacle 46, an alternative manufacturing process can also be used to first coat an extended base part 41 and then shorten it, as is the case with Figure 6 The cup-shaped receptacle 46 can then be introduced into the base part 41 and the wear-resistant layer 30 by a subsequent machining step, in particular by milling or drilling.

Claims (12)

1. A pick (10), in particular round-shank pick, comprising a pick head (40) and a pick shank (50), wherein the pick head (40) is formed at least from a base part (41) and a cutting element (20) made of a hard material, in particular of hard metal, connected to the base part (41),

   wherein the base part (41), following the cutting element (20), has a wear-resistant layer (30) on the outer surface (41.1) thereof, said wear-resistant layer covering at least one section of the outer surface (41.1) of the base part (41) facing the cutting element (20), wherein an end surface (31) of the wear-resistant layer (30) facing the cutting element (20) is covered by the cutting element (20),

   wherein the base part (41) has an axially oriented recess (44) for receiving a fastening section (24) of the cutting element (20),

   wherein circumferentially with respect to the recess (44), the base part (41) has a mating surface (43) facing the cutting element (20),

   wherein the mating surface (43) and the end surface (31) of the wear-resistant layer (30) form a continuous planar surface, or the end surface (31) of the wear-resistant layer is brought to the mating surface (43),

   and wherein the cutting element (20), circumferentially with respect to the fastening section (24) thereof, forms a supporting surface (25),

   characterised in that

   the supporting surface (25) covers the mating surface (43) and the end surface (31) at least in regions,

   and that a first soldered joint (11.1) is configured between the supporting surface (25) and the continuous surface formed by the mating surface (43) and the end surface (31),

   and the wear-resistant layer (30) encloses in axial orientation at least the section of the pick head (40) in which the recess (44) is introduced.
2. The pick (10) according to claim 1,
   characterised in that
   the wear-resistant layer (30) is received in a depression (42) of the base part (41).
3. The pick (10) according to claim 1 or 2,
   characterised in that
   the mating surface (43) and the end surface (31) are designed as separating surfaces created in a process step, in particular as cut surfaces or as ground surfaces or as milled surfaces, or in that the end surface (31) is designed as an impression surface of a base (61) of an auxiliary tool (70), said base lying on the mating surface (43) and protruding radially beyond the mating surface (43), said impression surface formed during an application process, in particular during a welding process, of the wear-resistant layer (30).
4. The pick (10) according to one of claims 1 through 3,
   characterised in that
   the mating surface (43) and/or the end surface (31) are designed as smooth surfaces or as surfaces having a predetermined roughness in a range of Rz = 4 µm to Rz = 280 µm or as surfaces comprising introduced grooves which have a groove depth in a range of 2 µm to 500 µm.
5. The pick (10) according to one of claims 1 through 4,
   characterised in that
   a second soldered joint (11.2) is configured between an outer surface (26) of the fastening section (24) and an inner surface (44.1) of the recess (44) and/or that a third soldered joint (11.3) is configured between an end surface (27) of the fastening section (24) and a bottom surface (44.2) of the recess (44).
6. The pick (10) according to one of claims 1 through 5,
   characterised in that
   the wear-resistant layer (30) has a uniform layer thickness or that the wear-resistant layer (30) has a varying layer thickness.
7. The pick (10) according to claim 6,
   characterised in that
   the layer thickness of the wear-resistant layer (30), proceeding from the end surface (31) thereof facing the cutting element (20), decreases in the direction of the end thereof facing the pick shank (50), or that the layer thickness of the wear-resistant layer (30), proceeding from the end surface (31) thereof facing the cutting element (20), increases in the direction of the end thereof facing the pick shank (50).
8. The pick (10) according to one of claims 1 to 7,
   characterised in that an outer surface (33) of the wear-resistant layer (30) is convexly curved along the longitudinal extension thereof, or that the outer surface (33) is concavely curved along the longitudinal extension thereof, or that the outer surface (33) has concavely and convexly curved sections along the longitudinal extension thereof.
9. The pick (10) according to one of claims 1 to 8,
   characterised in that
   an internal angle is configured between the surface of the cutting element (20) and the outer surface (33) of the wear-resistant layer (30) in the transition thereof.
10. The pick (10) according to one of claims 1 to 9,
    characterised in that

    the cutting element (20) with the supporting surface (25) rests directly or indirectly at least in regions on the base part (41), and

    in that the wear-resistant layer (30) covers at least one surface section (29) of the cutting element (20) which adjoins the supporting surface (25).
11. The pick (10) according to one of claims 1 to 10,
    characterised in that
    a soldered joint (fourth soldered joint, 11.4) is configured between the wear-resistant layer (30) and the surface section (29) of the cutting element (20).
12. The pick (10) according to one of claims 1 through 11,
    characterised in that
    the wear-resistant layer (30) protrudes beyond the mating surface (43) in the direction of a central longitudinal axis (M) of the pick head (40) and/or that the wear-resistant layer (30) and the mating surface (43) form a bowl-shaped receptacle (46) for the cutting element (20).

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