CN109127003B

CN109127003B - Impact strip

Info

Publication number: CN109127003B
Application number: CN201810627984.4A
Authority: CN
Inventors: F·霍根多恩
Original assignee: Keestrack NV
Current assignee: Keestrack NV
Priority date: 2017-06-16
Filing date: 2018-06-19
Publication date: 2020-08-25
Anticipated expiration: 2038-06-19
Also published as: EP3415237B1; DK3415237T3; DE102017113233B4; PL3415237T3; CN109127003A; EP3415237A1; DE102017113233A1

Abstract

The invention relates to an impact strip for lining an impact chamber of an impact crusher, having the following features: a) the impact strip (1) has a front side (2), a rear side (3) spaced apart from the front side (2), and two longitudinal side faces (4, 5) which extend from the front side (2) to the rear side (3); b) the front side (2) does not extend parallel to the rear side (3) but forms an angle (W3) with the rear side (3) which is smaller than 90 DEG and larger than 0 DEG; and c) the two longitudinal sides (4, 5) extend at least partially in longitudinal side planes (E1, E2) that intersect one another.

Description

Impact strip

Technical Field

The invention relates to an impact strip for lining an impact chamber of an impact crusher.

Background

An impact crusher is a machine for crushing material by impact crushing by generating high kinetic energy with which the material impacts on sharp, hard objects, i.e. wear-resistant linings of the impact chamber. The said protective lining of the impact chamber belongs to the impact mechanism of the impact crusher. The grommet may consist of an impact plate or an elongated impact strip. The impact of the mass of material against the impact panel creates a stress peak in the material. The stress peaks lead to selective fragmentation. The regions of the material having less strength are comminuted particularly well. The harder particles escape from the softer environment.

This method results in high wear on the impact strip. The impact slats must be replaced periodically. It should therefore be possible to replace the heavy impact slats as simply and quickly as possible in order to minimize production stoppages. It is known from practice to insert the impact strip in its longitudinal direction into the receptacle of the protective lining. For this purpose, the impact strip has a substantially T-shaped retaining region on its rear side. This T-shaped configuration results in an undercut being formed on the side of the shank of the retention region. The impact strip is held by the undercut. The actual impact slats are arranged substantially rectangular in cross-section. The impact strip has a front face against which the material to be crushed is thrown, a rear face at a distance from the front face, and two longitudinal side faces extending from the front face to the rear face. The front face is at an angle to the back face. Thereby, adjacent longitudinal edges extend different distances, so that a crushing zone is intentionally formed.

In the unworn state, the impact strips are mounted with their longitudinal sides extending parallel to one another in such a way that a gap is present between the longitudinal sides. If the impact changes are designed in the form of arcs, V-shaped or A-shaped gaps are formed between the impact strips. The material is thrown into these gaps and may get stuck there. The material bed thus formed serves as additional protection for the material to be impacted. On the other hand, the material in the gap can lead to a severe clamping, so that the impact strip can only be released at very high expenditure. This can lead to very high workloads and thus to production stalls. Furthermore, the number of crushing zones and thus also the degree of crushing is smaller when the impact slats are arranged convexly. This is disadvantageous when it is desired to crush hard materials with a high degree of crushing.

Disclosure of Invention

Starting from this, the object of the invention is to provide an improved impact strip which can be easily installed and removed even at high levels of wear and which achieves better protection, in particular in the concavely or convexly curved regions of the impact chamber.

To this end, the invention proposes an impact strip for an impact chamber lining of an impact crusher, having the following features: a) the impact strip has a front face, a rear face spaced apart from the front face, and two longitudinal side faces extending from the front face to the rear face; b) the front surface does not extend parallel to the back surface but forms an angle of less than 90 ° and greater than 0 ° with the back surface; c) the two longitudinal sides extend at least partially in longitudinal side planes that intersect one another; d) providing an outer holding region on the rear side, said outer holding region projecting relative to the rear side and having an undercut for the releasable, positive-locking fastening of the impact strip; e) the outer holding region has a widened foot and a shank which is narrower relative to the foot, the foot being connected to the rear face by the shank, the undercuts being located laterally of the shank and being delimited by the foot and the rear face, the undercuts each having, in cross section, a rounded region which extends from the rear face up to the upper side of the foot; characterized in that f) the foot has a longitudinal recess on its sole facing away from the dorsal surface.

The impact strip according to the invention is used for lining the impact chamber of an impact crusher. The impact crusher throws the material in the direction of the impact slats in order to crush the material by impact. The impact strip has a front face configured for impact of a material and a back face spaced from the front face. The front and back faces are interconnected by two longitudinal side faces. The impact slats may wear from the front face to a short distance from the back face. This section of the impact strip which is intended for wear is quadrangular in cross section.

According to the invention, the front surface does not extend parallel to the rear surface but forms an angle of less than 90 ° and more than 0 ° with the rear surface. The angle is preferably in the range of 10 ° to 20 °. Preferably, the angle is 12 ° to 18 °. An angle of 15 deg. is suitable and particularly advantageous for many applications. The front face is disposed obliquely with respect to the rear face.

The impact strip has a holding region for fixing the impact strip on a support of the impact chamber. The holding area does not participate in the wear of the impact strip. This part of the impact strip is used only for anchoring and for fixing the impact strip for easy removal. On the rear side, a retaining region protruding relative to the rear side and having an undercut can be provided for the releasable, positive-locking fastening of the impact strip to the abutment in the impact chamber. Alternatively, the impact strip has an inner retention area for receiving a threaded connection. The impact strip, due to its elongated shape, is secured with a plurality of threaded connections, thereby also providing a plurality of internal retention zones. The inner holding region is in particular a passage for a screw, which is inserted into the impact strip from the front. The bolt head is here embedded deeper into the impact strip.

The impact strip according to the invention has longitudinal sides, which extend in longitudinal side planes. In the prior art, the longitudinal sides or longitudinal side planes extend parallel to one another. The longitudinal side planes do not intersect. According to the invention, it is desirable that the longitudinal side planes in which the longitudinal sides extend at least partially, preferably for the most part (more than 50%) and in particular all intersect one another. This means that the longitudinal sides do not extend parallel to one another, but at an angle. This oblique side shape of the longitudinal sides makes it possible to position the impact slats in the circular section of the impact chamber without V-shaped gaps forming between adjacent impact slats at this time. This generally enables an improved lining of the impact chamber. More material of the impact strip for wear can be installed inside the impact chamber, thereby increasing the service life. There are more fragmentation zones per unit length of the casing. A higher degree of crushing is thereby achieved, which is advantageous in particular for harder materials. Furthermore, the already crushed material clearly cannot easily enter between adjacent impact slats, since the V-shaped gap between the impact slats is avoided. This in turn makes the removal of the impact slats easy when replacement is necessary due to wear. The intersecting longitudinal side planes may be arranged relative to each other such that the impact slats narrow towards the front. In this case, the impact strip is very well suited for mounting in the concave arc section. With the impact strip according to the invention, a smaller radius can also be achieved inside the impact chamber.

Within the scope of the invention, it is possible for only one of the two longitudinal sides to be arranged partially, largely or completely at an angle different from 90 ° to the rear side, so that the other longitudinal side is perpendicular to the rear side. The longitudinal side planes also intersect in this case and intersect at a distance from the front side or at a distance from the rear side of the impact strip.

The intersection line at which the longitudinal side planes intersect preferably lies in the longitudinal mid-plane of the impact strip. The longitudinal mid-plane is perpendicular to the back face. The longitudinal mid-plane is centrally distributed through the holding area. The intersection line running centrally means that the two longitudinal sides are at the same angle to the longitudinal mid-plane. The angle is preferably in the range from 4 ° to 8 °, in particular from 6 ° to 7 °, and the angle may be in particular 6.5 °. Thus, an angle of 8 ° to 16 °, in particular an angle of 13 °, is obtained, viewed in both longitudinal side planes. This angle is independent of whether the impingement plate is a concave or convex region for the impingement cavity.

The upper side (front side) preferably extends at an angle of 12 ° to 17 ° and in particular at an angle of 13 ° to 16 ° relative to the rear side. For many applications an angle of 15 ° has proven to be advantageous and preferred.

The design of the holding region also plays a very important role in order to improve the utilization. The outer holding region preferably has a widened foot and a shank which is narrower relative to the foot. The foot is connected to the rear face of the impact strip by a shank. Undercuts are arranged on two sides of the handle part. The undercut is defined by a foot and a back surface. The undercuts each have a rounded region in cross section, which extends up to the side of the foot. The rounded region preferably extends over the entire contour of the undercut, at least as far as the contour is concerned with the shank. The rounding has in particular a constant radius, and the plate is dimensioned such that it extends tangentially from the rear side as far as the foot. The radius is at least 10mm, preferably 14mm or more.

The side of the foot facing the rear is configured as a side which is at an angle of 18 ° to 20 °, in particular at an angle of 20 °, to the rear. The sides of the foot are preferably connected tangentially to the rounded region. Due to the tangential transitions between the rounded areas and the sides and the back of the impact strip, there are no areas where stress concentrations may occur. This continuous transition gently guides the stresses that may occur into the adjoining material regions. The material arranged in the foot region is uniformly loaded. This better utilization of material makes it possible to save material in the region of the feet, which in turn contributes to an improved utilization of the impact slats.

In an advantageous development of the invention, the foot has a longitudinal recess on its sole facing away from the rear side. The longitudinal recess is provided for saving material in the region of the foot. The longitudinal recess is preferably wider than the shank. The longitudinal recesses should likewise be designed such that no stress peaks occur. Thus, the longitudinal recess should not have sharp transitions or edges. The longitudinal recess may have a lowermost position which is 20% to 40% of the height of the foot (excluding the sides). Preferably, the depth extends in the range of about 30% to 35% of the height.

The longitudinal recess can be rounded in its transverse direction, so that the depth is present in the center, i.e. in the region of the longitudinal mid-plane, and decreases continuously towards the edge side of the T-foot.

The entire holding region is preferably designed mirror-symmetrically, which makes it possible to pull the striking plate out of the holder in the longitudinal direction and to turn it over. After reaching a certain degree of wear, the impact slats may be turned and/or used in other areas of the impact crusher.

This optimized shape of the impact slats improves the utilization. Such an impact strip can be easily mounted and dismounted. The impact strip has a very low notch (stress concentration) effect in the outer holding region, since there are defined lateral angles on the foot and rounded transitions in the region of the shank. Furthermore, an impact strip optimized with respect to the cross-sectional shape, having inclined sides, can be used very advantageously in a concavely or convexly curved impact chamber, but not only in the case where the impact strip can be mounted in a flat and rounded region in order to line the impact chamber. If impact slats with opposite side angles, which are adjacent to each other, are arranged alongside each other, the gap between the impact slats has a constant width. But the impinging material cannot easily enter the region where the gap is deeper because at least one gap extends at an angle to the back surface. Depending on the particular impact direction, the material must first turn over the wall of the gap at an angle to the impact direction. At which time the material loses kinetic energy. The gap is thus only filled by the material without a high degree of densification. This makes the replacement of the impact slats easy.

Drawings

The invention will be described below with reference to an embodiment shown in the schematic drawings. Wherein:

FIG. 1 shows a first embodiment of an impact strip with an outer holding area in a transverse sectional view;

FIG. 2 shows another illustration of the impact strip of FIG. 1, also in a transverse cross-sectional view;

FIG. 3 shows a further embodiment of an impact strip with an outer holding area in a transverse sectional view;

FIG. 4 shows another embodiment of an impact strip with an inner holding area, likewise in a transverse section;

FIG. 5 shows another embodiment of an impact strip with an outer holding area, likewise in a transverse section;

FIG. 6 shows another illustration of the impingement strip of FIG. 5, again in a cross-sectional view;

FIG. 7 shows another embodiment of an impact strip with an outer holding area, likewise in a transverse section;

FIG. 8 shows the impact slats of FIG. 5 in a raised arrangement

FIG. 9 shows the impingement strip of FIG. 1 in a recessed arrangement;

FIG. 10 shows the impact slats of FIGS. 1 and 6 in a flat arrangement; and

FIG. 11 shows a perspective view of an impact slat.

Detailed Description

Fig. 1 shows an impact strip 1 in a transverse sectional view. The impact strip 1 is mounted in an impact chamber of an impact crusher, not shown in detail. The upper part of the (impact slats) in the plane of the drawing is set to withstand the impact of the material to be crushed for as long as possible. This part is the wear zone. The lower region of the impact strip 1 in the plane of the drawing serves for fastening the impact strip 1 to the impact crusher.

The impact strip 1 has a substantially quadrangular cross section in its upper region. The impact strip 1 has a front face 2 for the material to strike. A rear side 3 is arranged at a distance from the front side 2. The rear face 3 is connected to the front face 2 by two longitudinal side faces 4, 5, so that the quadrilateral outline is obtained. On the rear side 3, a retaining region 6 projects rearward. The holding region 6 has a T-shaped contour in cross section and, together with the rear side 3, forms undercuts 7, 8 which flank a shank 9. The shank 9 of the holding region 6 is a connecting element with a widened foot 10 of the holding region 6, by means of which shank and foot the T-shape is formed.

The holding region 6 is significantly smaller than the region above the rear side 3 which is provided for wear to occur. The holding section 6 need only be configured to have the necessary dimensions. After the impact strip 1 has worn away, the holding zone is disposed of. It is important for the operational safety of the impact strip 1 that the impact strip 1 does not break or split during operation. Since the impact strip 1 is loaded mainly by pressure and less by torque by the impact of the material, the requirements on the retaining zone 6 are lower, and therefore there is still room for improvement in the profile of the foot 10 and the shank 9. The major part of the

undercuts

7, 8 is designed as

rounded regions

11, 12. The

rounded areas

11, 12 run tangentially from the flat rear side 3 to the shank 9 and from there to the

inclined sides

13, 14 of the foot 10, which are directed toward the rear side 3. The angle of the

side portions

13, 14 is 20 deg. in this embodiment.

The foot 10 also has a longitudinal recess 16 on its sole 15 facing away from the dorsal face 3. The longitudinal recess 16 is concave and is completely rounded. The longitudinal recess 16 is wider than the shank 19. Said longitudinal recess extends over more than 50% of the width of the foot 10. The longitudinal recess 6 serves to save material in the region of the foot 10. Since the longitudinal recesses 16 at the same time should not produce a notch stress concentration effect, they are rounded with a very large radius, like flat pits.

Fig. 2 shows the impact strip 1 of fig. 1 again in a sectional view, with angle and length reference numerals being supplemented. The impact strip 1 is formed mirror-symmetrically with respect to the longitudinal mid-plane MLE below its rear side 3, i.e. in the region of the retaining region 6. This symmetry is known to continue to the height H1 of the longitudinal side 4 on the left in the plane of the drawing. The front region beyond H1 is asymmetrical due to the 15 ° angled position of the front 3 angle W3. The angle W1 between the longitudinal mid-plane MLE and the longitudinal side 4 on the left in the plane of the drawing is 6.5 °. On the opposite side, the angle between the longitudinal mid-plane MLE and the second longitudinal side 5 is likewise 6.5 degrees. The second longitudinal side 5 is correspondingly higher and has a height H2 which is greater than the height H1 of the opposite longitudinal side 4. The ratio (of the height) is about 2: 1.

The straight

longitudinal sides

4, 5 extend completely in the longitudinal side planes E1, E2. The longitudinal side planes E1, E2 intersect at an intersection line S, which is visible as a point in the selected sectional view. The intersection line S is spaced above the front side 2. Since the angle W1 is the same for both

longitudinal sides

4, 5, the intersection S of the longitudinal side planes E1, E2 lies in the longitudinal mid-plane MLE. This makes it possible to turn the impact slats 1 through 180 ° (use).

Due to the upward tapering of the impact strip 1, the width B1 of the rear face 3 is greater than the width B2 of the front face 2 perpendicular to the longitudinal mid-plane MLE. The width difference is about 15%. Such an impact strip 1 has a height H2 of approximately 101 mm.

The height H3 represents the height of the holding section 6 measured from the rear face 3. This height is approximately 50mm, so that the ratio of the height H2 of the longer longitudinal side 5 to the height H3 of the retaining zone 6 is approximately 2: 1.

The width B3 represents the width of the handle 6. The shank 9 is the narrowest region of the impact strip 1. The shank 9 is narrower than the adjoining foot 10. The ratio between the width B4 of the foot 10 and the width B3 of the shank 9 is about 2: 1.

Height H5 indicates that foot 10 does not include the height of

sides

13, 14. Height H5 is about 40% of height H3 of the entire retention zone 6. The transition between the wider foot 10 and the significantly narrower shank 9 is realized by

inclined flanks

13, 14, which each merge into the

rounded regions

11, 12 at an angle W2 of 20 ° (with respect to the rear side). In this case, the radius R2 of the rounded portion is 14 mm. All other corners of the impact strip 1 are rounded with a radius R1 of 5 mm.

The radius of the longitudinal recess 16 is marked R3 on the sole 15 of the foot 10. The longitudinal recess 16 is entirely rounded. The radius R3 is 35mm in this embodiment, while the total width B4 is 70 mm. The maximum depth H4 (measured in the longitudinal mid-plane) of the longitudinal recess 16 is 7 mm. The depth H4 of the longitudinal recess 16 thus extends over a third of the height H5 of the foot 10.

The embodiment of fig. 3 differs from the embodiment of fig. 1 and 2 in that the

longitudinal sides

4, 5 do not extend completely within the intersecting longitudinal side planes (not shown in detail). The

longitudinal sides

4, 5 have upper

longitudinal side sections

17, 18, respectively, which are inclined in the manner described above, and lower

longitudinal side sections

19, 20, respectively, which are perpendicular to the back 3. The dashed lines show the borderlines between the upper and lower longitudinal side sections 17 to 20. The upper

longitudinal side sections

17, 18 extend over more than 50% of the height H1, H2 of the

longitudinal sides

4, 5.

The embodiment of fig. 4 differs from the embodiment of fig. 1 and 2 in that there is no outer holding zone, but rather an inner holding zone 6 a. The inner holding section 6a is shown in dashed lines. This is a through hole that is circular in cross section and stepped in diameter for receiving a threaded connection. The diametrical steps are positioned in such a way that the screw head, not shown in detail, is completely retracted behind the front face 3. The through-hole is plugged with material during operation above the thread head. The material protects the bolt head.

The embodiment of fig. 5 differs from the embodiment of fig. 1 and 2 only in that the

longitudinal sides

4, 5 are inclined in opposite directions, and here outwardly. The front face 2 is thus wider than the rear face 3. The shape of the retaining region 6, i.e. the shape of the shank 9 and the foot 10, is identical. Reference is therefore made to the description of fig. 1 and 2.

Fig. 6 again shows the scaling relationships with reference to dimensions and angles, wherein the differences are mainly explained in order to avoid repetitions. The angle W1 of the longitudinal side 4 is likewise 6.5 °. The longitudinal sides 4 are merely inclined in opposite directions, so that the impact slats 1 do not narrow but widen toward their front faces 2. The width B1 of the back side 3 is substantially constant, while the width B2 of the front side 2 is now larger than the width of the back side 3. Since the heights H2 and H1 of the front side 2 remain substantially the same, the angle W3 between the front side 2 and the rear side 3 also remains substantially constant at 15 °, the difference between B1 and B2 remaining the same, but of opposite sign, when viewed in absolute terms. The longitudinal side planes E1 and E2 also intersect at an intersection line S which lies in the longitudinal mid-plane MLE and is arranged at a distance from the rear face 3.

Fig. 7 shows a variant of fig. 5 and 6, in which, like the exemplary embodiment, the

longitudinal sides

4, 5 do not extend completely in the longitudinal side plane, but only for the most part in the longitudinal side plane. The

longitudinal sides

4, 5 have upper

longitudinal side sections

17, 18 extend over more than 50% of the height H1, H2 of the

longitudinal sides

4, 5.

Fig. 8 to 10 show three different installation states. Fig. 8 shows by way of example three impact slats 1 according to the embodiment of fig. 5 and 6. The impact slats 1 are arranged arcuately. Adjacent impact slats 1 are each (between) offset by an angle of 13 °. Adjacent impingement strips form a gap between them having a width that remains the same. The impact strip 1 is adapted to line the convex section of the impact chamber.

The embodiment of fig. 9 shows three impact slats 1 having the same structural form as according to fig. 1 and 2. The adjacent impact slats 1 are also set at an angle of 13 °. Adjacent impingement strips form a gap between them having a width that remains the same. The impact slats 1 are adapted to line the concave section of the impact chamber.

The embodiment of fig. 10 shows two outer impact slats 1 according to the embodiment of fig. 5 and one intermediate impact slat 1 according to the embodiment of fig. 1. By means of the adapted side angle, the gap between adjacent impact slats 1 remains constant in width. This arrangement of the impact strip 1 is suitable for lining a straight section of the impact chamber. In this case, the impact slats 1 of different design are arranged alternately. The impact strip according to the invention can be made of a metallic casting material, a ceramic material or a hybrid material comprising steel with a ceramic composition. The invention is not limited to a specific material as long as the material is capable of breaking mineral material with a sufficient service life.

Fig. 11 shows that the impact slats have a cross section which remains the same over their entire length, as is shown in fig. 1 to 10.

List of reference numerals

1 impact strip

2 front side

3 back side of

4 longitudinal side

5 longitudinal side

6 outer holding zone

6a inner holding zone

7 side concave

8 side concave

9 handle part

10 feet

11 rounded region

12 radius region

13 side part

14 side part

15 soles

16 longitudinal recess

17 upper longitudinal side section

18 upper longitudinal side section

19 lower longitudinal side section

20 lower longitudinal side section

B1 width

B2 width

B3 width

B4 width

E1 longitudinal side plane

E2 longitudinal side plane

Height H1

Height H2

Height H3

Height H4

Height H5

MLE longitudinal midplane

Radius R1

Radius R2

Radius R3

S line of intersection

Angle W1

Angle W2

Angle W3

Claims

1. An impact strip for an impact chamber liner of an impact crusher, having the following features:

a) the impact strip (1) has a front side (2), a rear side (3) spaced apart from the front side (2), and two longitudinal side faces (4, 5) which extend from the front side (2) to the rear side (3);

b) the front side (2) does not extend parallel to the rear side (3) but forms an angle (W3) with the rear side (3) which is smaller than 90 DEG and larger than 0 DEG;

c) the two longitudinal sides (4, 5) extending at least partially in longitudinal side planes (E1, E2) intersecting each other;

d) an outer holding region (6) which protrudes relative to the rear side (3) and has undercuts (7, 8) for the releasable, positive-locking fastening of the impact strip (1) is provided on the rear side (3);

e) the outer holding region (6) has a widened foot (10) and a shank (9) which is narrower relative to the foot (10), the foot (10) being connected to the rear side (3) via the shank (9), the undercuts (7, 8) being located laterally of the shank (9) and being defined by the foot (10) and the rear side (3), the undercuts (7, 8) each having, in cross section, a rounded region (11, 12) which extends from the rear side (3) up to an upper side (13, 14) of the foot (10);

which is characterized in that the method is characterized in that,

f) the foot (10) has a longitudinal recess (16) on the sole (15) thereof facing away from the rear side (3).

2. The impact strip according to claim 1, characterized in that a majority of the longitudinal sides (4, 5) extend in the longitudinal side planes (E1, E2) intersecting each other.

3. An impact strip according to claim 1 or 2, characterised in that it has an inner retaining zone (6a) for accommodating a threaded connection.

4. The impact strip according to claim 3, characterized in that the longitudinal side planes (E1, E2) intersect on an intersection line (S) which lies in a longitudinal mid-plane (MLE) of the impact strip (1), which is perpendicular to the rear face (3) and centrally extends through the inner holding zone (6a) or the outer holding zone (6).

5. The impact strip according to claim 4, characterized in that the intersection (S) of the longitudinal side planes (E1, E2) extends at a distance from the front face (2), each longitudinal side plane (E1, E2) making an angle (W1) of 4 ° to 8 ° with the longitudinal mid-plane (MLE).

6. The impact strip according to claim 4, characterized in that the intersection (S) of the longitudinal side planes (E1, E2) extends at a distance from the rear face (3), each longitudinal side plane (E1, E2) making an angle (W1) of 4 ° to 8 ° with the longitudinal mid-plane (MLE).

7. The impact strip according to claim 4, characterized in that the angle (W1) between the longitudinal side planes (E1, E2) and the longitudinal mid-plane (MLE) is 6 ° to 7 °.

8. The impact strip according to claim 1 or 2, characterized in that the angle (W3) between the front face (2) and the back face (3) is 12 ° to 17 °.

9. An impact strip according to claim 1, characterised in that the upper side (13, 14) of the foot (10) is arranged at an angle (W2) of 18 ° to 22 ° to the back face (3).

10. The impact strip according to claim 1 or 2, characterized in that the rounded areas (11, 12) transition tangentially into the back face (3) of the impact strip (1) and into the upper side (13, 14) of the foot (10).

11. An impact strip according to claim 1 or 2, characterised in that said longitudinal recess (16) is wider than the shank (9).

12. The impact strip according to claim 1 or 2, characterized in that the foot (10) has a height (H5) measured perpendicular to the back face (3) and the longitudinal recess (16) has a depth (H4) measured perpendicular to the back face (3), said depth (H4) at the lowest point being 20-40% of said height (H5).

13. The impact strip according to claim 1 or 2, characterized in that the longitudinal recess (16) is rounded in the transverse direction.

14. The impact strip according to claim 4, characterized in that the outer retaining zone (6) is constructed mirror-symmetrically with respect to the longitudinal mid-plane (MLE).

15. The impact strip according to claim 4, characterized in that the inner retaining zone (6a) is constructed mirror-symmetrically with respect to the longitudinal mid-plane (MLE).

16. The impact strip according to claim 1 or 2, characterized in that the rounded areas (11, 12) each have a radius of at least 10 mm.