Stirring rod with replaceable, wear-resistant element

Abstract

An element or agitator comprises a main body designed to be operatively connected to a material processing machine and a detachably attached tip. The body and tip define a first lateral side, which includes a leading edge designed to engage a material to be mixed, and a second lateral side opposite the first lateral side. A plurality of fasteners detachably secure the tip to the body. The fasteners extend at least partially from the second lateral side through the body and engage the tip.

Description

AREA OF INVENTION The present disclosure relates to material processing devices and in particular to a material processing element, such as a stirrer, a hammer, a stirring blade or a stirring rod, which has at least one removable element. BACKGROUND Mixing, blending, comminution, and classification processes are common in material processing and manufacturing across a wide range of industries and applications. These processes can be performed manually or mechanically and utilize various types of stirring to blend materials (e.g., rotation, vibration, etc.). For example, mixing machines often employ rotating or otherwise moving elements or agitators, such as stir bars or blades, to mix materials. Due to the often harsh properties of the material(s) being mixed, as well as the operating parameters (e.g., mixing time, speed, etc.), the wear on these elements can be significant. Consequently, the elements must be replaced frequently.The routine replacement of these elements is not only costly, but can also be time-consuming, thus limiting the overall performance and efficiency of the processing. Furthermore, the wear of the elements may not be uniform, as the operating forces acting upon them are highest at their leading edges and distal ends. Therefore, replacing an entire element may be unnecessarily uneconomical. Similarly, the mechanical and physical requirements for certain features or areas of the mixing element may differ from others. Thus, a monolithic element, as found in the prior art, may not be optimal. For strength and corrosion resistance in a primary body and mounting area of ​​the element (e.g., when the element is attached to a rotating spindle of a machine), a material such as stainless steel may be preferred. In contrast, it may be desirable to manufacture a tip, end, and / or leading edge of the element from a harder and / or more wear-resistant material, such as sintered tungsten carbide. Accordingly, improved elements that counteract the aforementioned disadvantages are desirable. SUMMARY According to one embodiment of the present disclosure, an element, for example an agitator or agitator assembly, comprises a main body designed to be operatively connected to a material processing machine and a tip removably attached to the main body. The body and the tip define a first lateral side comprising a leading edge designed to engage a material to be mixed and a second rear lateral side opposite the first lateral side. A plurality of fastening elements removably attach the tip to the body. The fastening elements extend at least partially from the second lateral side through the body and engage the tip. BRIEF DESCRIPTION OF THE DRAWINGS The invention will now be described by way of example with reference to the accompanying figures: Fig. 1 is a top view of an exemplary element, agitator, stirring blade or stirring rod according to one embodiment of the present disclosure; Fig. 2 is a partial top view of the element of Fig. 1, illustrating a main body, a removable and / or replaceable tip therein, and a fastening system or means; Fig. 3 is a partial perspective view of the main body of the element of the preceding figures, with the tip removed; Fig. 4 is a partial perspective view of the tip of the element of the preceding figures; Fig. 5 is a partial top view of an exemplary element comprising a main body and a removable and / or replaceable tip therein, according to another embodiment of the present disclosure; Fig. 6 is a partial perspective view of the main body of the element of Fig. 5; Fig.Figure 7 is a perspective view of the tip of the element of Figure 5; Figure 8 is a partial top view of an exemplary element comprising a main body and a removable and / or replaceable tip thereof, according to another embodiment of the present disclosure; Figure 9 is a partial perspective view of the main body of the element of Figure 8; Figure 10 is a perspective view of the tip of the element of Figure 8; Figure 11 is a partial top view of another exemplary element comprising a main body and a removable and / or replaceable tip thereof, according to one embodiment of the present disclosure; and Figure 12 is a partial top view of another exemplary element comprising a main body and a removable and / or replaceable tip thereof, according to one embodiment of the present disclosure. DETAILED DESCRIPTION OF THE EXECUTION FORMS Exemplary embodiments of the present disclosure are described in detail below with reference to the accompanying drawings, where identical reference numerals refer to identical elements. However, the present disclosure can be embodied in many different forms and should not be understood as limited to the embodiment set forth herein; rather, these embodiments are provided to ensure that the present disclosure is thorough and complete and that the concept of the disclosure is fully conveyed to the person skilled in the art. The following detailed description presents numerous specific details for explanatory purposes, in order to enable a comprehensive understanding of the disclosed embodiments. However, it will be clear that one or more embodiments can also be realized without these specific details. In other cases, known structures and devices are shown schematically to simplify the drawing. Embodiments of the present disclosure include a rotating element, agitator, stirring rod, or stirring blade designed to be attached to a machine (e.g., at its rotating outlet). The element comprises a main body made of a first material, such as stainless steel, and at least one replaceable end or removable tip attached thereto. The replaceable end may be formed of a second material different from the first material, e.g., sintered tungsten carbide. The end defines at least a section of a leading edge or working surface of the element, designed to be in contact with the material(s) during operation (e.g., mixing, dispersing, grinding, etc.).In an exemplary embodiment, the end is attached to the main body by means of a further fastening means, or multiple fastening means, or a fastening means system with multiple fastening means. In particular, the main body defines a fastening means opening extending through it. The fastening means opening comprises an open first end, distal to the replaceable end and designed to receive a fastening means, and an open second end, formed by or opening toward a mating surface of the body. The fastening means opening of the main body is aligned with a corresponding opening or bore formed in the replaceable end (e.g., a threaded opening formed in an insert embedded in the replaceable end).The fastener is designed to be inserted into the first end of the fastener opening of the main body and to engage with the opening of the replaceable end. The engagement (e.g., thread engagement) of the fastener with the replaceable end is designed to draw the end into contact with the main body, thereby selectively fastening it to the main body. With general reference to Fig. 1, a simplified example of an element, a stirrer, a stirring rod, or a stirring blade 10 is shown. The element 10 comprises a main body 12 and a pair of removable and / or replaceable ends or tips 50. The element 10 can be described as having two sides 13, 15 arranged opposite each other longitudinally relative to a center of the element. It is understood that the longitudinal ends or sides 13, 15 of the element 10 may be identical to each other except for their different orientation about a longitudinal axis. The relevant descriptions given herein therefore apply equally to both sides 13, 15. The sides 13, 15 may be separate elements, each having a body 12 operatively connected to each other, or the sides 13, 15 may be designed as a single element having a common body 12.Although the exemplary embodiment comprises two interchangeable ends 50, it is understood that the number of interchangeable ends can be varied (e.g., 1, 3, etc.) without deviating from the scope of this disclosure. While the exemplary ends 50 are each removable, in other embodiments one or more ends or tips may be permanently connected to the main body 12 (e.g., integrally formed or bonded to it). The main body 12 defines a centrally located, generally circular opening or drive feature 14 designed to accommodate, for example, a drive spindle of a material processing machine. The opening 14 may include one or more keyways or keyways for engagement with corresponding drive keys or keyways of the machine's spindle to rotate the element 10. The main body 12 further comprises tapered surfaces 11 that define sections of leading edges or working surfaces of the element 10. Likewise, the replaceable ends 50 may each include tapered surfaces 51 that define a remaining section of a respective leading edge of the element 10. In particular, the tapered surfaces 51, 11 of each end 50 and of the main body 12 define a continuous, uniform leading edge of the element 10, with the ends attached to the main body.In this way, the element 10 can be direction-dependent (i.e., it is designed to rotate in a specific direction during operation). As illustrated, the tapered surfaces 11 are formed only at each distal end of the exemplary main body 12. In other embodiments, the tapered surfaces 11 can extend over the entire length of each side 13, 15 of the element 10 (i.e., over half the total length of the element). In still other embodiments, no section of the leading edges of the element 10 may be defined by the main body 12; instead, they may be defined only by the ends 50. As shown in Fig. 1, the lateral sides of the element 10, which are opposite the leading edges in a width direction W, can include rear sides or edges 17 that are generally aligned vertically between the upper and lower surfaces of the main body 12 and / or the ends 50 and may not define a taper. In other embodiments, the tapered leading edges of the element 10 can be formed on each lateral side thereof. In this embodiment, the element 10 can be used to act on material or to process material in both directions of rotation without the need to reorient the element relative to the machine. With continued reference to Fig. 1, in some embodiments the width of the main body 12 and the ends 50 in the lateral direction W can generally be constant along the length of the element 10. In other embodiments, however, the width of the element 10 can taper outwards from the center or opening 14 along its length in any radial direction. The same can be true for the thickness of the element 10 (i.e., it can be constant, tapered, or vary in some other way). In the exemplary embodiment illustrated, each end 50 simply defines a section of the tip or free end of the element 10 in the lateral direction W.This embodiment can be mechanically advantageous because forces acting generally perpendicular to the tapered surface 51 of the end 50 are directly counteracted by the main body 12, thereby reducing stresses or strains on the mounting elements with which the end is attached to the main body. In other embodiments, however, each end 50 can form the entire tip of the distal end of the element 10 in the lateral direction W. With reference to Figures 2-4, an exemplary assembly system or assembly arrangement 100 for attaching each end 50 to the main body 12 of an element 10 according to a first embodiment is shown. In particular, the system 100 comprises a plurality of fastening elements, including a first fastening element 102 (e.g., a socket head cap screw or a cap screw), a second fastening element 104 (e.g., a second socket head cap screw), a pair of inserts 106, 107 (e.g., threaded Invar plugs), and a pair of positioning pins 108 (e.g., slotted dowel pins) arranged between the first and second fastening elements 102, 104. The main body 12 defines two through holes 110, 111 formed in the rear edge 17. As shown, each through hole 110, 111 can be countersunk or countersunk to accommodate the head of each of the fasteners 102, 104. End 50 has a pair of corresponding openings 151, 152, which are aligned coaxially with the through-holes 110, 111. The inserts 106, 107 are arranged in the respective openings 151, 152 and are designed to receive the ends of each of the fasteners 102, 104 and engage with them in a threaded connection. The use of the metal inserts 106, 107, and in particular Invar inserts, provides temperature-stable, high-strength threaded components with which the fasteners 102, 104 can be repeatedly and removably (i.e., threaded) engaged. In one embodiment, the first fastener 102 is larger (e.g., longer or larger in diameter) than the second fastener 104. This can be achieved by tapering the thickness and / or width of the element 10 towards its ends. The pair of pins 108 is arranged in the openings 112, 113 formed in the body 12 and corresponding coaxially aligned openings 153, 154 formed in the element 50. The pins 108 serve to position the end 50 appropriately relative to the body 12 and to provide the fastening system 100 with additional strength and stability. Furthermore, the pins 108 allow the end 50 to be attached to the body 12 in an appropriate position before the threaded fasteners are inserted and engaged. This improves the ease of assembly of the element 10 (e.g., during replacement). As explained in more detail herein, it is apparent to those skilled in the art that only one pin 108 can be used instead of two pins, or in other embodiments, no pin can be used at all. As shown in Figures 3 and 4, the through-holes 110, 111 and the openings 112, 113 open onto a generally vertical side wall or counter surface 121 of the body 12. The side wall 121 extends substantially in a longitudinal direction of the body 12. A second vertical side wall or counter surface 122 is oriented substantially perpendicular to the side wall 121 and extends substantially in the width direction W of the body 12. It is apparent to those skilled in the art that the angle between the side walls 121 and 122 could also be acute or obtuse. The first and second side walls 121, 122 define a cavity 125, which is dimensioned to accommodate or be complementary to the end 50. Likewise, the end 50 defines corresponding vertical side walls or counter surfaces 155, 157, each opposite one of the side walls 121, 122.As shown, each of the openings 151, 152, 153, 154 opens to the side wall 155 for coaxial alignment with the through holes 110, 11 and the openings 112, 113 of the body 12. With reference to Figures 5-7, another embodiment of a mounting system or assembly arrangement 200 for attaching the end 50 to the main body 12 of the element 10 is shown. Like the embodiment of Figures 2, 3 to 4, the system 200 comprises a plurality of fastening elements, which have the threaded fastening element 102, the pair of positioning pins 108, and the same associated through holes 110 and openings 112, 113, 151, 153, 154 described above. The second threaded fastening element 104 and the associated insert 107 of the previous embodiment are replaced by an adjusting screw 201. In particular, the countersunk through hole 111 of the previous embodiment is replaced by a threaded through hole 211 in which the adjusting screw 201 engages. The end 50 defines a corresponding coaxially aligned opening 252, which is designed to receive the end of the adjusting screw 201.In one embodiment, the adjusting screw 201 defines a conical head and the opening 252 defines a correspondingly tapered opposite surface or bottom wall 252', as shown in Figs. 5 and 7. As in the embodiment of Figs. 2, 3 to 4, each of the openings and through-holes is formed in and / or opens to the same opposite side walls 121, 155 of the main body 12 and the end 50. Figures 8-10 illustrate another embodiment of a mounting system or assembly arrangement 300 for attaching the end 50 to the main body 12 of the element 10. The system 300 comprises a plurality of fastening elements, including the same second threaded fastening element 104 and a corresponding through-hole 111, as well as the opening 152 and the insert 107 according to the embodiment of Figures 2-4. Similarly, the pins 108 and corresponding openings 112, 113, 153, and 154 of the main body 12 and the end 50 are also provided. The first fastening element of the embodiment of Figures 2-4 has been replaced by a fastening element 302. The fastening element 302 extends obliquely or at an angle to the width and / or length of the element 10. In one embodiment, a countersunk through-hole 310 is formed through the body 12 from the rear edge 17 towards the end 50 at an angle δ of approximately 45 degrees to a longitudinal axis of the element 10. A corresponding coaxially oriented opening 351 is formed in the element 50, which is also provided with an Invar or metal insert 306 such that it engages the threads of the fastening element 302. The fact that the fastening element 302 is angled provides additional tensile force on the end 50, which draws the side walls 122, 157 into contact in a manner not achieved by the embodiments of Figures 2-7. Thus, the embodiment of Figure 2-7 represents a different solution.8-10 a means of generating a compressive force between each of the pairs of opposing side walls 121, 122, 155, 157, thereby improving the strength and stability of the connection between the end 50 and the body 12. Similarly, the embodiment of Fig. 12 has features similar to those described above with reference to Figs. 8-10, namely a plurality of fastening elements comprising the threaded fastening element 104 and the obliquely oriented fastening element 302. However, unlike the pair of pins 108 used in the embodiment of Figs. 8-10, only a single pin 108 is provided between the fastening elements 104 and 302. As in the previous embodiments, the pin 108 is arranged between the opposing side walls 121 and 155 and offers similar strength, stability, and positioning advantages. This design, however, simplifies manufacturing, assembly, and replacement operations and reduces overall component and manufacturing costs. A further improved embodiment of a mounting system or assembly arrangement 400 for attaching the end 50 to the main body 12 of the element 10 is shown in Fig. 11. Like the embodiment of Figs. 8-10, the system 400 comprises a plurality of fastening elements, including the second threaded fastening element 104 and a corresponding through-hole 111, the opening 152, and the insert 107. The system 400 also includes one of the pins 108 and its corresponding openings 113, 154, each formed in the body 12 and the end 50, respectively. As in the previous embodiment, system 400 has a fastening element 402 that is oriented obliquely (e.g., at an angle δ of approximately 45 degrees) relative to the width and / or length direction of the element 10. However, in contrast to system 300, where the through-hole 310 and the opening 351 each open towards the vertical side walls 122, 157, a countersunk through-hole 410 and a coaxially oriented opening 451 each open towards the opposite side walls 121, 155 of the body 12 and the end 50. In this way, all openings and through-holes are formed in or open towards the same side wall 121, 155 of the body 12 and the end 50. This simplifies the manufacturing process of the system 400, while retaining the advantages of applying a tensile force to the end 50, which pulls it into contact with each of the opposing pairs of side walls 121, 155 and 122, 157.As shown, the opening 451 of the end 50 can also be provided with a metal insert 406, for example an Invar insert, which is designed to thread and receive one end of the fastening element 402. With regard to the individual embodiments listed above, it is understood that the through-holes of the fastener and corresponding threaded fasteners can define a complementary shoulder or head, respectively, thus limiting the insertion depth of the fastener into the body 12. In this way, tightening or screwing the fastener into the insertion of the end 50 effectively pulls the end 50 in at least one direction (i.e., the width direction) of the element 10, and in the embodiments of Figures 8, 9, 10 to 11, in two directions (i.e., the width direction and the length direction) of the element 10. Since the end 50 is attached to the main body 12 by a threaded connection, embodiments of the present disclosure provide means for adjusting the locking force with which the end is attached to the main body.This has the advantage that, depending on the different coefficients of thermal expansion between the ends 50 and the main body 12 of the element 10, a loosening of the ends relative to the housing can be compensated for by regularly tightening or retightening the fastening element(s). In each embodiment, a first end of each through-hole is designed to receive a tool for rotating or otherwise engaging the fastener with the end 50. The first end of each through-hole exits on the second lateral or rear side 17 of the main body 12 opposite the front edge. In this way, the materials to be processed by the element 10 are not forcibly inserted into the opening or through-hole during operation, and the element 10 does not need to be removed from the machine to access the fastener in order to remove the end(s) 50. This improves reliability and cleanliness and increases operational efficiency, as the ends 50 can be replaced more easily. In the embodiments of Figs. 8-11, the lateral side exit of the through-hole is achieved by offsetting a central axis of the through-holes 310, 410 relative to a central extension axis of the main body 12 by an exemplary non-zero angle δ (i.e., they are inclined or not parallel to each other), for example by a 45-degree angle. This ensures that a relatively uniform and / or consistent clamping or pressing force is generated between the bearing side walls of the opposing surfaces of the end 50 and the main body 12. As described above, the end 50 may be formed from a first monolithic material, such as cemented carbide, while the inserts may be formed from, for example, stainless steel, Invar, or another metallic material. The inserts may be secured in the end 50 by suitable means, including bonding or brazing. In some embodiments, a threaded insert (e.g., a helical insert or HELI-COIL®) may be provided in the openings or inserts to form and / or reinforce the threaded connection between the end 50 and the threaded fasteners. In other embodiments, a separate threaded insert may not be required, as the inherent strength of the insert material may be sufficient to provide a strong, reliable connection (i.e., sufficient resistance to pull-out forces) with the fastener. In some embodiments, the positioning pins can be fitted into one of the corresponding openings formed in the body 12 and the end 50 by interference fit, friction fit, sliding fit, or threaded fit. The pins can be straight or taper along their length (or in any direction from their center). Furthermore, it is understood that the overall shape of the element 10 shown in the figures is only exemplary and can be varied without departing from the scope of this disclosure. For example, the distal or free end faces of the individual removable ends or tips 50 can be rounded (as shown), or they can be squared or linearly angled. Likewise, the replaceable ends or tips 50 can generally be flat or planar with respect to the main body 12 (as illustrated) or at least bent either vertically upwards or downwards (i.e., in a direction parallel to an axis of rotation of the element). In still other embodiments, the ends can extend obliquely upwards and / or downwards from the main body. Elements according to the embodiments of this disclosure are generally designed for use in material processing plants, in particular mixing, dispersing, cutting, grinding, hammering and / or stirring processes with one or more materials (e.g., solid, liquid and / or semi-liquid materials). Although the elements described herein (e.g., mixing elements) may generally be referred to as agitators, this term is to be understood as also including agitator blades, stirring rods, hammers, knives or other similar elements or tools designed for processing (e.g., mixing) one or more materials. Furthermore, those areas that would likely be known to those skilled in the art in this field have not been described herein in order to avoid unnecessarily obscuring the described invention. Accordingly, it should be understood that the invention is not limited by the illustrated embodiments, but only by the scope of the appended claims. It is evident to those skilled in the art that the embodiments mentioned above are merely illustrative and not limiting. For example, experts in the field can make numerous modifications to the embodiments described above, and various features described in different embodiments can be freely combined without conflicting the configuration or the underlying principle. Although several exemplary embodiments have been presented and described, a person skilled in the art should understand that various changes or modifications can be made to these embodiments without departing from the principles and spirit of the disclosure, the scope of which is defined in the claims and their equivalents. As used herein, an element listed in the singular and followed by the word "one" or "a" is to be understood as not excluding the plural of the elements or steps unless such exclusion is expressly stated. Furthermore, references to "an embodiment" of the present disclosure are not to be understood as excluding the existence of other embodiments that also have the aforementioned features. Moreover, unless expressly stated otherwise, embodiments that "comprise" or "have" an element or a plurality of elements with a particular property may include additional elements that do not have that property.

Claims

A stirrer comprising: a body designed to be operatively connected to a material processing machine; a tip removably attached to the body, wherein the body and the tip define: a first lateral side comprising a leading edge designed to strike a material to be mixed; and a second lateral side opposite the first lateral side; and a plurality of fastening elements removably attaching the tip to the body, wherein at least a section of the fastening elements extends from the second lateral side through the body and engages with the tip. Agitator according to claim 1, wherein the plurality of fastening elements comprises: a first threaded fastening element arranged in a first through-hole formed through the body and engaging with a corresponding first fastening element opening defined in the tip; and a first positioning pin arranged between the body and the tip, wherein the pin is arranged in respective coaxially aligned first pin openings formed in the body and the tip. Stirrer according to claim 1 or 2, wherein the body defines a first counter surface and the tip defines an opposing second counter surface. Stirrer according to claim 2 or claims 2 and 3, wherein: the first through-bore and the first pin opening formed in the body open to the first counter surface; and the first fastening opening and the first pin opening formed in the tip open to the second counter surface. Agitator according to one of the preceding claims, wherein the plurality of fastening elements further comprises a second threaded fastening means which is arranged in a second through-bore formed through the body and engages with a corresponding second fastening opening defined in the tip. Stirrer according to claim 5, wherein: the body defines a third counter surface oriented transversely to the first counter surface, and the tip defines an opposing fourth counter surface oriented transversely to the second counter surface; and the second through-hole opens towards the third counter surface and the second fastening opening opens towards the fourth counter surface. Stirrer according to claim 6, wherein the first and second counter surfaces are aligned perpendicular to the third and fourth opposing counter surfaces. Stirrer according to claim 6 or 7, wherein the second threaded fastening means, the second through-hole and the second fastening means opening are inclined relative to the first and second opposing counter-surfaces and the third and fourth opposing counter-surfaces and extend inclined to them. Stirrer according to claim 8, wherein the second threaded fastening means, the second through-hole and the second fastening means opening are aligned at an angle of approximately 45 degrees relative to the third and fourth opposing counter-surface. Stirrer according to one of claims 5 to 9, wherein the first positioning pin and the coaxially aligned first pin openings formed in the body and the tip are generally aligned perpendicular to the first and second opposing counter surfaces and generally extend perpendicular to them. Stirrer according to one of claims 5 to 10, wherein the first and second threaded fastening means, the first and second through-holes, the first positioning pin and the first pin opening generally extend perpendicular to the first and second opposing counter-surface. Stirrer according to one of claims 5 to 11, wherein: the second through-bore formed in the body opens towards the first counter surface; and the second fastening opening opens towards the second counter surface. Agitator according to one of claims 5 to 12, wherein the plurality of fastening elements further comprises an insert which is arranged in both the first and the second fastening opening of the tip, wherein both the first and the second fastening means engage in threaded engagement with one of the respective inserts. Stirrer according to claim 13, wherein the inserts are made of Invar. Agitator according to one of claims 5 to 14, wherein the first and second threaded fastening means are cap screws and the first and second through-holes define countersunk holes which accommodate a head of the individual cap screws. Stirrer according to one of the preceding claims, wherein the tip is formed from at least one of tungsten carbide or ceramic. A stirring arrangement comprising: a metal body designed to be operatively connected to a material processing machine; a carbide or ceramic tip removably attached to the body, the body and tip defining: a first lateral side comprising a leading edge designed to engage a material to be processed; and a second lateral side opposite the first lateral side; and a plurality of fastening elements removably securing the tip to the body, comprising: a first threaded fastening element extending from the second lateral side through the body and engaging with the tip; and a second threaded fastening element extending from the second lateral side through the body and engaging with the tip. The arrangement according to claim 17, further comprising a positioning pin arranged between the body and the tip, wherein: the body defines a first counter surface and a second counter surface; the tip defines a third counter surface and a fourth counter surface, which are opposite a respective first counter surface and second counter surface of the body; the first threaded fastening element is arranged in a first through-hole formed through the body and engages with a corresponding first fastening element opening defined in the tip; the second threaded fastening element is arranged in a second through-hole formed through the body and engages with a corresponding second fastening element opening defined in the tip;and the positioning pin is arranged in the respective coaxially aligned first pin openings formed in the body and the tip. Arrangement according to claim 18, wherein: the first through-hole opens to the first counter-surface of the body; the second through-hole opens to the second counter-surface of the body; the first fastening opening opens to the third counter-surface of the tip; and the second fastening opening opens to the fourth counter-surface of the tip. Arrangement according to claim 18 or 19, wherein: the first counter surface of the body and the third counter surface of the tip are aligned transversely to the second counter surface of the body and the fourth counter surface of the tip; and the first fastening means is aligned obliquely relative to the second fastening means.

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