EP2336489A2 - Pick holder and base section for holding a pick holder - Google Patents

Abstract

The holder has a holding attachment (25) with a bit accommodator, where a supporting section of the holding attachment and/or a storage section of a plug-in attachment (21) have supporting surfaces and/or storage surfaces arranged in an angle to each other. A middle longitudinal axis (11) of the accommodator and a longitudinal axis (L) of the plug-in attachment enclose an obtuse angle. The storage surfaces are oriented against a tool traverse direction (v), and have surface regions arranged sectionally offset to the supporting surfaces towards a longitudinal axis of the plug-in attachment. An independent claim is also included for a base part for accommodating a bit holder.

Description

The invention relates to a bit holder with a plug projection and a holding approach with a chisel holder, wherein the plug approach has a bearing portion and the retaining lug has a support portion.

The invention further relates to a base part for receiving a chisel holder with a plug-in receptacle, a projection and a support lug, wherein the support lug forms a support with at least one support surface and the approach an abutment with at least one support surface.

From the DE 43 22 401 A1 a chisel holder exchange system with a base part and a chisel holder is known. The base part has a support foot, with which it can be welded on the outer circumference of a milling drum. In the base part a plug-in receptacle is introduced. The plug-in receptacle opens in a paragraph. The heel closes at an angle and opposite to the tool feed direction a support surface. In the base part, a bit holder can be mounted. The bit holder has a plug-in approach that can be inserted into the socket of the base part. In the mounted state, the bit holder is supported by a counter surface on the support surface of the base part. For fixing the chisel holder in the base part, a pressure screw is used. This acts on the plug-in approach of the chisel holder and pulls it into the socket. At the same time the direction of action of the insertion force is designed so that the plug-in approach is pressed with a prism-shaped front surface in a prismatic guide of the base part. In this way, a centered alignment of the chisel holder relative to the base part is created.

In the chisel holder, a round shank chisel can be mounted. This absorbs the forces during operation and passes them into the bit holder. From the chisel holder, the forces are then transferred to the base part, wherein the majority of the forces is passed over the stop connection formed between the counter surface and the support surface. A certain proportion of force is also derived in the contact surfaces created by the prism surfaces.

Such chisel holder change systems are used for the removal of road surfaces. Increasingly, chisel holder change systems are also required in surfacemining. There, a high tool rigidity and tool strength is required with high machine performance and high feed rates.

It is an object of the invention to provide a bit holder or a base part for receiving a chisel holder, with a permanent and stiff support of the chisel holder relative to the base part is possible even at high loads.

The chisel holder relating task is solved in that the support portion of the holding lug and / or the bearing portion of the insertion approach have two mutually angular support surfaces or bearing surfaces and wherein the central longitudinal axis of the bit holder and the longitudinal axis of the plug-in approach include an obtuse angle. In this way, a support region is formed with the support section or the bearing section, via which the transverse loads occurring during the use of the tool can be optimally discharged. In addition, defined and clearly statically determined support zones are created by means of the support surface or the support surfaces and the bearing surface or the bearing surfaces, which allow a reproducible backlash-free mounting of the bit holder. The fact that the bit holder and the plug-in approach are at an obtuse angle to each other, an improved power dissipation and a stiffer design is possible.

According to a preferred embodiment variant of the invention, it may be provided that the support section at least partially holds the support surface or the support surfaces in the tool advance direction in front of the insertion lug and / or the bearing surface or the bearing surfaces are oriented substantially counter to the tool feed direction. In this way, the force direction varying in the use of tools is taken into account. While at the beginning of the tool engagement in the material to be removed, the forces are more likely to be absorbed by the front support surface or support surfaces, a force load on the bearing surface or the bearing surfaces, which are oriented counter to the tool feed direction, arises progressively as the tool engages. This orientation of the support and bearing surfaces thus enable a load-optimized design of the bit holder.

When it is provided in a bit holder according to the invention, that the bearing surface or the bearing surfaces has or have areas which in the direction the longitudinal axis of the plug-in approach offset from the support surface or the support surfaces are arranged, then a lever is provided on the spacing over which moments can be safely removed.

A conceivable alternative of the invention is such that the plug-in approach has at its facing in the tool feed direction plug projection front side at least one pressure surface for acting on a screw, wherein the pressure surface is at an angle to the longitudinal axis of the plug approach. About the screw, a pull-in force can be introduced into the plug-in approach. Due to the fact that the screw acts on the plug-in projection on the front, the bit holder can be guided counter to the tool feed direction into its mounting position and held there, whereby it is optimally supported on the back.

A preferred embodiment of the invention is such that the support surface or surfaces facing towards the free end of the plug-in approach. Thus, the forces acting at the beginning of the tool engagement, rather in the direction of the free end of the plug-in loading forces can be safely removed. In this case, it can be provided in particular that the support surface or the support surfaces extend substantially parallel to the central longitudinal axis of the bit holder.

If a chisel holder is designed such that the holding lug has a region which projects beyond the insertion lug and that the support surface or the support surfaces is / are arranged on the projecting region, then a load-optimized design of the chisel holder becomes possible. Characterized in that the support surface or the support surfaces are arranged on the projecting portion of the retaining lug, they can support this reliable and they are also arranged close to the caused by the inserted pick shank force application point. This makes it possible to reduce the load moments.

As the tool feed increases, the resulting force direction changes. While at the beginning of the tool engagement the force direction is oriented rather in the radial direction, it will rotate with increasing tool engagement in the direction opposite to the feed direction. In order to reliably absorb the resulting resultant forces, it can be provided according to the invention that the bearing surface / bearing surfaces partially project beyond the support surface or support surfaces in the direction of the longitudinal axis of the insertion projection and / or that the bearing surface / bearing surfaces extend in the direction of the longitudinal axis is in the range of the holding approach is / are.

A simple constructive design results in particular in that the bearing surface / the bearing surfaces runs parallel to the longitudinal axis of the plug-in projection / extend or extends / extend substantially in the direction of this longitudinal axis.

A preferred embodiment of the invention is such that the support surface or the support surfaces and the bearing surface or the bearing surfaces each form sliding guides. When mounting the chisel holder this can be placed with its support surfaces on mating surfaces of a base part. Subsequently, the bit holder is clamped to a base part, wherein it can be displaced continuously in its sliding guide in the determination position. This ensures a clear and reliable installation. The sliding guide thus serves to guide the bit holder in its intended mounting position. In the mounting position of the bit holder is firmly connected to the base part, so that between these components no relative movement is possible.

The chisel holders are removable parts, which can preferably be mounted at different positions of a milling drum on the corresponding base parts. To always cause a reliable power dissipation in the different mounting positions To be able to, it is provided according to an embodiment of the invention that the bearing surfaces and / or the support surfaces are each arranged on both sides of extending in the tool feed direction transverse center plane of the bit holder and / or are arranged symmetrically to this median transverse plane.

A preferred embodiment of the invention is such that the support surface or the support surfaces are substantially parallel to the central longitudinal axis of the bit holder, or that between the central longitudinal axis of the bit holder and the support surface or the support surfaces an obtuse angle in the range between ≥ 0 ° and 20 ° is included. Thus, the support surface or the support surfaces can be performed close to the bit holder, resulting in a compact design.

It has been found that, in particular with deep cutting operations in the material to be removed sufficient rigidity of the chisel holder is then given if it is provided that the obtuse angle between the central longitudinal axis, the bit holder and the longitudinal axis of the plug-in approach in the range between 110 ° and 160 ° is selected.

In order to securely intercept the force directions changing during the cutting engagement, it is preferably provided that the support surface or the support surfaces and the bearing surface or the bearing surfaces are oriented pointing in opposite directions, in particular diametrically opposed to each other.

The object of the invention is also achieved with a base part for receiving a chisel holder, which has a plug-in receptacle, a projection and a support lug. In this case, the support lug forms a support with a support surface or a plurality of support surfaces. The approach creates an abutment having a further support surface or other support surfaces. According to the invention it is provided that the support approach Has two support surfaces and / or the approach has two more support surfaces, and that the support surfaces and / or the other support surfaces are each prismatic angled employed and that the support surface or the support surfaces with the central longitudinal axis of the socket includes an obtuse angle or include. As mentioned above in connection with the bit holder, the upcoming transverse forces can be optimally derived via the prism-shaped support surfaces or prism-shaped further support surfaces. The arrangement of the support surface (-n) at an obtuse angle to the central longitudinal axis of the plug-in receptacle allows optimal power dissipation and compact design.

Advantageously, the support lug in the tool feed direction and the approach in the tool feed direction is oriented behind the longitudinal axis of the plug receptacle. Thus, the support surface (-n) and the other / n support surface (-n) are held in front of or behind this longitudinal axis. Through this support surface distribution, a lever arm is created, which reduces the upcoming load moments. Advantageously, the further support surface (s) of the attachment have surface regions which are offset at least in regions transversely to the tool feed direction relative to the support surface (s) of the support extension.

A conceivable variant of the invention is such that the support surface or the support surfaces of the support extension run at an obtuse angle to the longitudinal axis of the plug receptacle and / or have opposite to the tool feed direction. This orientation of the support surface (-n) allows an optimal power flow at the beginning of the tool engagement in the material to be removed.

In order to securely hold the bit holder in the base part, it may be provided that the support lug has at least one screw receptacle which opens into the plug receptacle. In the screw receptacles screw elements can be screwed, which act on the bit holder.

Figur 1

eine Werkzeugkombination mit einem Basisteil und einem Meißelhalter in perspektivischer Frontansicht,

Figur 2

die Werkzeugkombination gemäß Figur 1 in perspektivischer Rückansicht,

Figur 3

einen Vertikalschnitt durch die Werkzeugkombination gemäß Figur 1 bzw. 2,

Figur 4

den Meißelhalter gemäß der Werkzeugkombination nach Figur 1 bis 3 in perspektivischer Frontansicht,

Figur 5

den Meißelhalter gemäß Figur 4 in Rückansicht,

Figur 6

einen Vertikalschnitt durch den Meißelhalter gemäß Figur 4 bzw. 5,

Figur 7

eine perspektivische Aufsicht auf den Meißelhalter gemäß den Figuren 1 bis 3, und

Figur 8

einen Vertikalschnitt durch den Meißelhalter gemäß Figur 7.

The invention will be explained in more detail below with reference to an embodiment shown in the drawings. Show it:

FIG. 1

a tool combination with a base part and a chisel holder in a perspective front view,

FIG. 2

the tool combination according to FIG. 1 in perspective rear view,

FIG. 3

a vertical section through the tool combination according to FIG. 1 or 2,

FIG. 4

the chisel holder according to the tool combination Figure 1 to 3 in a perspective front view,

FIG. 5

according to the chisel holder FIG. 4 in rear view,

FIG. 6

a vertical section through the bit holder according to FIG. 4 or 5,

FIG. 7

a perspective view of the bit holder according to the FIGS. 1 to 3 , and

FIG. 8

a vertical section through the bit holder according to FIG. 7 ,

FIG. 1 shows a base member 10 having a bottom 11 with concave top surfaces. By means of this attachment surfaces, the base part can be placed on the cylindrical outer shell of a milling drum and welded firmly. A bit holder 20 is connected to the base part 10.

As the FIG. 3 shows, the base part 10 on a plug-in receptacle 15 which receives a plug 21 of the chisel holder 20. The following is with reference to the FIGS. 4 to 6 the design of the bit holder 20 explained in more detail.

As the FIG. 4 shows, the bit holder 20, the plug approach 21, at the angle of a holding lug 25 is connected. Ideally, an obtuse angle is included between the plug 21 and the retaining lug 25. The plug-in projection 21 forms in the region of its, in the tool feed direction (v) facing plug approach front 22 a front surface 21.1. In this front surface 21.1 two recesses are recessed so that they form pressure surfaces 21.2. The pressure surfaces 21.2 are arranged at an angle to the longitudinal axis of the plug-in projection 21. The pressure surface 21.2 bearing projection of the plug 21 passes through lateral transition sections 21.3 in side surfaces 21.4 over. In this case, the side surfaces 21.4 are aligned in the direction of the tool feed direction (v) and point to the tool sides. As the FIG. 5 can recognize the side surfaces go 21.4 in the area of the plug projection rear side 23 in bearing surfaces 21.5 over. The storage areas 21.5 are at an angle to each other. The bearing surfaces 21.5 in turn are connected by means of a transition surface 21.6 and have opposite to the feed direction v.

The retaining lug 25 is provided with a bit holder 26 in the form of a cylindrical bore. The central longitudinal axis M of the bit receptacle 26 and the longitudinal axis L of the plug-in projection 21 ideally include an angle in the range between 100 ° and 160 °, preferably 130 °. The bit receptacle 26 merges via an introducer extension 27 into a bearing surface 25.3. In this case, the support surface 25.3 extends radially to the chisel receiver 26. The chisel holder 26 faces away from the support surface 25.3 in a cross-sectional taper 25.1. The cross-sectional taper 25.1 is in the form of a truncated cone and conducts the lateral surface 25.2 of the bit holder 20 in the bearing surface 25.3 on. The retaining lug 25 has in the region below the bit holder 26 two support surfaces 29, which are employed in an angle to each other in a V-shape. Show how the FIG. 6 can recognize the support surfaces 29 due to their oblique position in the direction of the free end of the plug-in approach and at the same time in the feed direction (v) and run, as in FIG. 3 represented, parallel or substantially parallel to the central longitudinal axis M of the bit holder 26. Like the FIG. 5 can recognize, has the retaining lug 25 lateral widening 28 in which the support surfaces 29 expire. The support surfaces 29 and the bearing surfaces 21.5 are oriented pointing in opposite directions.

The following is with reference to the FIGS. 7 and 8 the design of the base part 10 explained in more detail.

The base part 10 has a plug-in receptacle 15 which is adapted in its cross-section to the outer contour of the plug-in projection 21 of the bit holder 20. Front side, the plug-in receptacle 15 is limited by means of a support projection 12. In the support lug 12, a screw 13 is incorporated as a thread. The screw receptacle 13 opens into the plug-in receptacle 15. The plug receptacle 15 faces away from the screw receptacle 13 in a bore enlargement 13.1. The support lug 12 has in its upper, radially outer region on a support 18 which is formed by two support surfaces 18.1. The two support surfaces 18.1 are employed at an angle to each other. The angular orientation of the support surfaces 18.1 is adapted to the orientation of the support surfaces 29 of the chisel holder 20, so that the support surfaces 29 of the chisel holder 20 can rest plane-parallel on the support surfaces 18.1 of the base member 10. The support surfaces 18.1 are for the purpose of the defined investment of the bit holder 20 via a recessed paragraph 18.4 connected to each other.

On the rear side, the plug-in receptacle 15 is delimited by an abutment 16. The anvil 16 is part of a rear projection 17 which protrudes counter to the feed direction (v) via the plug-in receptacle 15. The anvil 16 is formed by two further support surfaces 16.1, which are at an angle to each other. These further support surfaces 16.1 are again adapted in their design and spatial arrangement adapted to the bearing surfaces 21.5 of the bit holder 20, so that a plane-parallel contact the other bearing surfaces 21.5 on the support surfaces 16.1 is possible. Opposite the support surfaces 18.1, the plug-in receptacle 15 is bounded by an open space 18.2. In the tool feed direction (v), the plug-in receptacle 15 is bounded by two lateral connecting sections 19. The inner surfaces formed by the connecting sections 19 and facing the plug-in receptacle 15 pass over open spaces 18.5 into walls 18.6, which in turn are oriented in the tool feed direction (v). The walls 18.6 turn out in the open space 18.2. As the FIG. 7 can be clearly seen, is recessed into the projection 17 a recess 17.1.

The mounting of the bit holder 20 on the base part 10 is carried out as follows.

First, the bit holder 20 is inserted with its plug 21 in the socket 15 of the base member 10. As the FIG. 3 can recognize, is then screwed as a fastener 14, a threaded pin in the screw 13. The fastening element 14 has a pressure surface oriented at right angles to the screw axis, which abuts the pressure surface 21. 2 of the chisel holder 20. The pressure surface does not have to be a flat surface, but can also be a spherical surface. The FIG. 1 shows that two fastening elements 14 are used for fastening the chisel holder 20, thus also two screw receptacles 13 are incorporated into the base part 10. When the fastening elements 14 are braced, the fastening element 14 presses against the pressure surface 21.2. Due to the angular position of the pressure surface 21.2 to the central longitudinal axis of the plug-in projection 21, the fastening element 14 exerts a pull-in force on the plug-in projection 21. At the same time a force component is generated, which is opposite to the feed direction (v) and presses the plug 21 in the counter-bearing 16. The force component running in the direction of the longitudinal axis of the plug-in projection 21 brings the support surfaces 18.1 of the support 18 with the support surfaces 29 of the bit holder 20 to the plant. A tension of the fasteners 14 now causes, as in particular from FIG. 3 clearly recognizable that the bit holder 20 experiences a support on both sides of the central longitudinal axis of the plug-in projection 21. On the one hand, the support on the anvil 16 is made on the rear side of the central longitudinal axis on the plug-in end of the bit holder 20 and on the other on the support 18 on the front side of the central longitudinal axis of the holder approach end of the chisel holder. Thus, the support surfaces 29 and the bearing surfaces 21.5 are diametrically opposed to the bit holder 20. The fastening screw 14 now acts on the insertion projection 21 such that a tensioning of the bit holder 20 takes place on the support 18 and the abutment 16. In this way, a secure and captive attachment of the chisel holder 20 is guaranteed.

FIG. 3 can further recognize that in the bore extension 13.1 of the screw 13, a cover 14.1 can be used, which covers the tool holder of the fastener 14.

Both the base part 10 and the bit holder 20 are formed substantially mirror-symmetrically to the transverse direction of the medium (in the transverse direction) of these respective components. This promotes a uniform load transfer.

During operational use engages a used in the bit holder 26 round shank chisel conventional construction in the material to be removed, for example, a coal seam. In this intervention mainly the support, consisting of Support 18 and support surfaces 29 claimed. During the tool engagement, the bit holder 20 is also pressed into the counter bearing 16 as a result of the advance (v). The large area of the chisel holder 20 there guarantees a safe power dissipation.

As FIG. 3 can recognize a unique assignment of the bit holder 20 to the base part 10 in particular guaranteed by the fact that only one edition of these two above-mentioned central support points takes place (support 18 and thrust bearing 16). In the area of paragraph 18.4, the free space 18.2, the walls 18.6 of the open spaces 18.5 and the connecting portion 19 of the plug 21 is released from the socket 15. If, for example, a wear of the support surfaces 18.1 takes place in the course of the use of the base part 10, the paragraph 18.4 forms a reset space. The spacing of the bit holder 20 from the paragraph 18.4 guarantees a repositioning of the bit holder 20 in case of wear. In this case, a wear compensation in particular take place because the support surfaces 18.1 and the other support surfaces 16.1 form sliding guides on which the bit holder 20 can slide along during retightening. This embodiment is particularly advantageous if the base part 10, as is usually required, has a service life that lasts several life cycles of bit holders 20. Unworn bit holder 20 can then always be securely clamped and held even on a partially worn base part 10.

During the operational use of the built-in round shank chisel material is degraded, which slides on the bit holder 20 in the region of the lateral surface 25.2. This space material is passed through the spacers 28 to the outside, whereby a protection of the base member 10 is effected before the abrasive attack of this space material.

If a pick has worn out, it can be easily replaced. This is possible because the recesses 17.1 in the base part 10 together with the recess 24 in the bit holder 20 form a tool holder. In this a Ausdrückwerkzeug can be used, which acts on the back of the round shank chisel and this pushes out of the bit holder 26. As FIG. 5 can be seen, the bit holder 26 is in spatial communication with the recess 24th

Claims (21)

Chisel holder having a plug projection (21) and a holding lug (25) with a chisel receiver (26), wherein the plug lug (21) has a bearing portion and the holding lug (25) has a support portion,
wherein the support section and / or the bearing section have two support surfaces (29) or bearing surfaces (21.5) arranged at an angle to one another, and
wherein the central longitudinal axis (11) of the bit receptacle (26) and the longitudinal axis (L) of the plug-in extension (21) form an obtuse angle. Chisel holder according to claim 1,
characterized,
that the support portion, the support surface (29) or the support surfaces (29) in the tool feed direction (v) at least partially in front of the plug-in projection (21) holds. Chisel holder according to claim 1 or 2,
characterized,
that the bearing surface (21.5) or the bearing surfaces (21.5) substantially opposite to the tool feed direction (v) are oriented. Chisel holder according to one of claims 1 to 3,
characterized,
includes that the bearing surface (21.5) or the bearing surfaces (21.5) surface areas respectively have, in the direction of the longitudinal axis of the insertion projection (21) offset at least in sections to the support surface (29) or the support surfaces (29) are arranged. Chisel holder according to one of claims 1 to 4,
characterized,
in that the insertion projection (21) has at least one pressure surface (21.2) for acting on it with a screw on its insertion projection (22) facing in the tool advance direction (v), the pressure surface (21.2) or the pressure surfaces (21.2) being at an angle to the longitudinal axis of the insertion projection (21.2). 21) stands or stands. Chisel holder according to one of claims 1 to 5,
characterized,
that the support surface (29) or the support surfaces (29) point in the direction of the free end of the plug-in extension (21). Chisel holder according to one of claims 1 to 6,
characterized,
in that the holding lug (25) has a region which projects beyond the insertion projection (21), and in that the support surface (29) or the support surfaces (29) are arranged on the projecting region. Chisel holder according to one of claims 1 to 7,
characterized,
that the bearing surface (21.5) or the bearing surfaces (21.5) in the direction of the longitudinal axis of the plug projection (21) partially extend beyond the support surface (29) or the support surfaces (29) and / or that the bearing surface (21.5) or the bearing surfaces (21.5) to are guided in the region of the holding approach (25). Chisel holder according to one of claims 1 to 8,
characterized,
that the bearing surface (21.5) or the bearing surfaces (21.5) running parallel to the longitudinal axis of the insertion projection (21) or extend substantially in the direction of the longitudinal axis. Chisel holder according to one of claims 1 to 9,
characterized,
that the support surface (29) or the support surfaces (29) and the bearing surface (21.5) or the bearing surfaces (21.5) each form sliding guides. Chisel holder according to one of claims 1 to 10,
characterized,
in that the bearing surfaces (21.5) and / or the support surfaces (29) are respectively arranged on both sides of the central transverse plane of the bit holder (20) in the tool advance direction (v) and / or are arranged symmetrically to this median transverse plane. Chisel holder according to one of claims 1 to 11,
characterized,
that the support surface (29) or the support surfaces (29) extend substantially parallel to the central longitudinal axis (M) of the bit holder (26), or that between the central longitudinal axis (M) of the bit holder (26) and the support surface (29) or the support surfaces (29) an angle in the range between -20 ° and + 20 ° is included. Chisel holder according to claim 12,
characterized,
that the obtuse angle between the central longitudinal axis (M), the pick receptacle (26) and the longitudinal axis (L) of the plug-in projection (21) in the range between 110 ° and selected 160th Chisel holder according to one of claims 1 to 13,
characterized,
that the support surface (29) or the support surfaces (29) and the bearing surface (21.5) or the bearing surfaces (21.5) in opposite directions are oriented facing, in particular diametrically opposite to each other. Base part for receiving a chisel holder (20) with a plug-in receptacle (15), a projection (17) and a support lug (12), wherein the support lug (12) has a support (18) with one or more support surfaces (18.1) and the projection (18). 17) forms an abutment (16) with one or more further support surfaces (16.1),
characterized,
in that the support projection (12) has two support surfaces (18.1), and / or the projection (17) has two further support surfaces (16.1), and that the support surfaces (18.1) and / or the further support surfaces (16.1) make an angle to each other in a prism shape are and that the support surface (18.1) with the central longitudinal axis of the plug receptacle (15) forms an obtuse angle. Base part according to claim 15,
characterized,
in that the support projection (12) in the tool feed direction (v) the support surface (18.1) or the support surfaces (18.1) before and the approach (17) the further support surface (16.1) or the further support surfaces (16.1) behind the longitudinal axis of the plug receptacle (15) holds. Base part according to one of claims 15 or 16,
characterized,
that the further supporting surface (16.1) or the further support surfaces (16.1) of the extension (17) has surface regions which at least partially transversely to the tool feed direction (v) relative to the support surface (18.1) or the support surfaces (18.1) of the support lug (12) arranged offset are. Base part according to one of claims 15 to 17,
characterized,
in that the support surface (18.1) or the support surfaces (18.1) of the support extension run at an obtuse angle to the longitudinal axis of the plug receptacle (15) and / or point substantially opposite to the tool feed direction (v). Base part according to one of claims 15 to 18,
characterized,
that the support connecting portion (12) has at least one screw receptacle (13), which opens into the plug receptacle (15). Base part according to one of claims 15 to 19,
characterized,
that said further supporting surfaces (16.1) in the tool feed direction (v) have. Tool assembly comprising a bit holder (20) according to one of claims 1 to 14 and a base part (20) according to one of claims 15 to 20.

Images