CN109127003B - impact slats - Google Patents

Abstract

The invention relates to an impact strip for lining the impact chamber of an impact crusher, which has the following features: a) the impact strip (1) has a front surface (2) and is spaced apart from the front surface (2). back (3) and two longitudinal sides (4, 5) extending from the front (2) to the back (3); b) the front (2) does not extend parallel to the back (3), but is an angle (W3) less than 90° and greater than 0° with the back (3); and c) the two longitudinal sides (4, 5) are at least partially in longitudinal side planes (E1, E2) that intersect each other extend.

Description

impact slats

technical field

The present invention relates to an impact slat for lining the impact chamber of an impact crusher.

Background technique

An impact crusher is a machine for crushing materials by means of impact crushing by generating high kinetic energy with which the material hits sharp, hard objects, i.e. the wear resistance of the impact chamber lining. The protective lining of the impact chamber belongs to the impact mechanism of the impact crusher. The lining may consist of an impingement plate or an elongated impingement slat. The impact of the block of material against the impact slats produces stress peaks in the material. The stress peaks lead to selective fragmentation. Areas of the material with less strength are comminuted particularly well. Harder particles are released from the softer environment.

The impact slats are subject to high wear due to this method. The impact slats must be replaced periodically. It should therefore be possible to replace heavy impact strips as simply and quickly as possible in order to minimize production stoppages. It is known from practice that the impact strips are inserted into the receptacles of the lining in their longitudinal direction. For this purpose, the impact strip has a substantially T-shaped holding area on its rear side. This T-shaped configuration results in an undercut on the side of the shank of the holding area. The impact strip is held by the undercut. The actual impact strips are arranged substantially rectangular in cross section. The impingement strip has a front face to which the material to be crushed is thrown, the impingement strip has a back face spaced from the front face, and has two longitudinal sides extending from the front face to the back face. The front and back are at an angle. As a result, adjacent longitudinal edges protrude by different distances, so that crushing zones are 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 there is a gap between the longitudinal sides. If the impact wange is designed to be curved, a V-shaped or A-shaped gap is formed between the impact slats. Material is thrown into these gaps and can get stuck here. The material bed thus formed serves as additional protection for the material to be struck. On the other hand, the material in the gap can lead to severe clamping, so that the impact strip can only be loosened at a very high cost. This results in a very high workload and thus a build stall. Furthermore, in the case of the convex arrangement of the impact slats, the number of crushing zones and thus also the degree of crushing is lower. This is disadvantageous when it is desired to crush hard materials with a high degree of crushing.

SUMMARY OF THE INVENTION

Proceeding from this, it is the object of the present invention to provide an improved striker strip which can be easily installed and dismantled even at high levels of wear and in particular in recesses or projections of the strike chamber Better lining is achieved in curved areas.

To this end, the present invention proposes an impingement strip for an impact chamber lining of an impact crusher, having the following features: a) the impingement strip has a front face, a back face spaced from the front face, and two longitudinal sides , the longitudinal sides extend from the front to the back; b) the front does not extend parallel to the back, but forms an angle with the back of less than 90° and greater than 0°; c) the two longitudinal sides are at least partially at each other extending in intersecting longitudinal side planes; d) an outer retaining region protruding relative to the rear surface is provided on the rear surface, the outer retaining region having an undercut for the releasable, form-fit fixing of the strike plate strip; e) the outer holding area has a widened foot and a shank narrower with respect to the foot, the foot is connected to the back by the shank, the undercut is located laterally of the shank and is formed by the foot and The back is delimited, the undercuts each have in cross-section a rounded area which extends from the back all the way to the upper side of the foot; it is characterized by the following features, f) the sole of the foot on which it faces away from the back There are longitudinal recesses on it.

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 panel has a front face configured for material impact and a back face spaced from the front face. The front and back are connected to each other by two longitudinal sides. The impingement slats may wear from the front to a short distance in front of the back. This section of the impact strip, which is intended for wear, is quadrilateral in cross section.

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

The striker strip has a holding area for fixing the striker strip on the support of the strike chamber. The holding zone does not participate in the wear of the impact slats. This part of the striker strip is only used for anchoring and for easily detachable fixing of the striker strip. On the rear side, a holding region with an undercut can be provided which protrudes relative to the rear side for releasably, form-fittingly fixing the striker strip to a seat in the strike chamber. Alternatively, the striker strip has an inner retention area for accommodating the threaded connection. Due to its elongated shape, the impact strip is secured with a plurality of threaded connections, so that it is also provided with a plurality of inner retention areas. The inner holding area is in particular a passage for the bolts which are inserted into the striker strip from the front. The bolt heads are here deeply embedded in the impact battens.

The impingement strip according to the invention has longitudinal sides, each of which extends in the longitudinal side plane. In the prior art, the longitudinal sides or longitudinal side planes extend parallel to one another. Therefore the longitudinal side planes do not intersect. It is desired according to the invention 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 each other. This means that the longitudinal sides do not extend parallel to each other, but at an angle. This sloping side shape of the longitudinal sides makes it possible to position the impingement slats in the circular section of the impingement cavity without creating a V-shaped gap between adjacent impingement slats at this time. Overall, the lining of the impingement chamber can thus be improved. More of the wear material of the impact slats can be installed inside the impact chamber, thereby increasing service life. There are more crush zones per unit length of the liner. As a result, a higher degree of fragmentation is achieved, which is advantageous in particular for harder materials. In addition, the crushed material obviously cannot easily enter between adjacent impingement slats, since V-shaped gaps between the impingement slats are avoided. This in turn facilitates the removal of the impact slats when replacement is necessary due to wear. The intersecting longitudinal side planes can be arranged relative to one another in such a way that the impact strip narrows towards the front. In this case, the impact slats are very well adapted to fit in the concave arcuate section. With the impact strip according to the invention, smaller radii can also be achieved inside the impact chamber.

It is possible within the scope of the invention that only one of the two longitudinal sides is arranged partially, mostly or completely at an angle different from 90° to the rear, so that the other longitudinal side is perpendicular to the rear. The longitudinal side planes also intersect in this case, either at a distance from the front face of the impact strip or at a distance from the rear face.

The line of intersection where the longitudinal side planes meet is preferably located in the longitudinal midplane of the impact panel. The longitudinal midplane is perpendicular to the back. The longitudinal midplane is distributed centrally through the retention zone. A line of intersection extending in the center means that the two longitudinal sides are at the same angle to the longitudinal midplane. The angle is preferably in the range of 4° to 8°, in particular 6° to 7°, the angle may in particular be 6.5°. Thus, viewed in two longitudinal side planes, an angle of 8° to 16° is obtained, in particular an angle of 13°. This angle is independent of whether the impact slats are used for the concave or convex regions of the impact chamber.

The upper side (front side) preferably extends in an angular range of 12° to 17° and in particular 13° to 16° with respect to the rear side. An angle of 15° has proven to be advantageous and is preferred for many applications.

In order to improve the utilization rate, the design shape of the maintenance area also plays a very important role. The outer retention area preferably has a widened foot and a narrower shank relative to the foot. The feet are connected to the back of the impact slat through a handle. Undercuts are provided on both sides of the handle. The undercut is defined by the foot and the back. The undercuts each have a rounded area in cross section which extends as far as the side of the foot. The rounded area preferably extends over the entire contour of the undercut, at least as long as the contour relates to the area of the shank. In particular, the rounding has a constant radius, and the plate is dimensioned such that it extends tangentially from the rear all the way to the foot. The radius is at least 10mm, preferably 14mm or more.

The side of the foot facing the rear is formed as a side which is at an angle of 18° to 20°, in particular at an angle of 20°, with the rear. The sides of the foot preferably adjoin the rounded area tangentially. Due to the tangential transitions between the rounded area and the sides and with the backside of the impingement strip, there are no areas where stress concentrations can occur. This continuous transition gently induces possible stresses into the adjoining material regions. The material arranged in the area of the footing is uniformly loaded. This better use of material makes it possible to save material in the area of the footing, which in turn helps to improve the 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 back. The longitudinal recesses are designed to save material in the area of the feet. The longitudinal recess is preferably wider than the shank. The longitudinal recesses should likewise be designed such that no stress peaks occur. Therefore, the longitudinal recesses should not have sharp transitions or edges. The longitudinal recess may have a lowest position which is 20% to 40% of the height of the foot (excluding the sides). Preferably this depth extends in the range of about 30% to 35% of said height.

The longitudinal recess can be rounded in its transverse direction, so that the depth is present centrally, ie in the region of the longitudinal midplane, and decreases continuously towards the edge side of the T-foot.

The entire holding area is preferably designed to be mirror-symmetrical, which makes it possible to extract the impact strip from the support in the longitudinal direction and to turn it over. After a certain degree of wear has been reached, the impact strip can be turned over and/or used in other areas of the impact crusher.

This optimized shape of the impact slats improves utilization. Such impact slats can be easily installed and removed. The impact strips have a small notch (stress concentration) effect in the outer holding area, because of the defined side corners on the foot and the rounded transition in the region of the shank. Furthermore, impact strips with sloping sides optimized in terms of cross-sectional shape can be used very advantageously in concavely or convexly curved impact chambers, but not only when impact strips can be installed in flat as well as inverted In a rounded area for lining the impact chamber. If adjacent impingement strips with opposite side angles are arranged next to each other, the gap between the impingement strips has a constant width. But the impinging material cannot easily enter the deeper areas of the gap because at least one of the gaps extends at an angle to the backside. Depending on the specific impact direction, the material must first be turned on the walls of the gap angled to the impact direction. At this point the material loses kinetic energy. The gaps are thus filled only with material that is not highly densified. This makes replacement of the impact slats easy.

Description of drawings

The invention is explained below with reference to the embodiments shown in the schematic drawings. in:

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

FIG. 2 shows another illustration of the impact panel of FIG. 1 , also in transverse section;

FIG. 3 shows another embodiment of an impact strip with an outer holding area in a transverse section;

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

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

FIG. 6 shows another illustration of the impact panel of FIG. 5, also in transverse section;

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

Figure 8 shows the strike slat of Figure 5 in a protruding arrangement

Figure 9 shows the strike slat of Figure 1 in a recessed arrangement;

Figure 10 shows the strike slat of Figures 1 and 6 in a flat arrangement; and

Figure 11 shows a perspective view of the impact panel.

Detailed ways

FIG. 1 shows an impingement strip 1 in a transverse section. The impact strip 1 is installed 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 broken for as long as possible. This part is the wear area. The lower region of the impact strip 1 in the plane of the drawing serves to fasten 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 impacting the material. A rear surface 3 is provided at a distance from the front surface 2 . The rear face 3 is connected to the front face 2 by two longitudinal sides 4 , 5 , resulting in the quadrilateral contour. On the rear face 3 there is a holding area 6 which protrudes rearwards. The holding area 6 has a T-shaped profile in cross-section and, together with the back face 3 , forms undercuts 7 , 8 which are flanked by the shank 9 . The shank 9 of the holding area 6 is the connecting element with the feet 10 widened by the holding area 6 , by means of which the shank and the feet form the T-shape.

The holding area 6 is significantly smaller than the area above the back face 3 which is provided for wear to occur. The holding area 6 need only be constructed with the necessary dimensions. After the impingement strip 1 has worn away, the holding area is discarded. 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 primarily compressive and less torque-loaded by the impact of the material, the requirements for the holding zone 6 are lower, and therefore there is still room for improvement in the profile of the foot 10 and shank 9 . Most of the undercuts 7 , 8 are formed as rounded regions 11 , 12 . The rounded areas 11 , 12 transition tangentially from the flat back 3 to the shank 9 and from there to the inclined sides 13 , 14 of the foot 10 which face the back 3 . The angle of the sides 13, 14 is 20° in this embodiment.

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

FIG. 2 shows again the impact strip 1 of FIG. 1 in a sectional view, with the reference numerals for angles and lengths supplemented. The impact strip 1 is formed below its rear face 3 , that is to say in the region of the holding region 6 , mirror-symmetrical with respect to the longitudinal midplane MLE. This symmetry is known to continue up to the height H1 of the left longitudinal side 4 in the plane of the drawing. Due to the inclined position of the front 3 angle W3 of 15°, the front area beyond H1 is asymmetrical. The angle W1 between the longitudinal midplane MLE and the left longitudinal side 4 in the plane of the drawing is 6.5°. On the opposite side, the angle between the longitudinal midplane 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 that is greater than the height H1 of the opposite longitudinal side 4 . The ratio (of the heights) 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 on the intersection S, which is visible as a point in the selected sectional view. The line of intersection S is above the front face 2 at a distance therefrom. 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 midplane MLE. This makes it possible to turn the impact strip 1 by 180° (use).

Since the impingement strip 1 tapers upwards, the width B1 of the rear face 3 is greater than the width B2 of the front face 2 perpendicular to the longitudinal midplane MLE. The width difference is about 15%. Such an impingement strip 1 has a height H2 of approximately 101 mm.

The height H3 represents the height of the holding area 6 measured from the back surface 3 . This height is approximately 50 mm, so that the ratio of the height H2 of the longer longitudinal side 5 to the height H3 of the holding area 6 is approximately 2:1.

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

The height H5 represents the height of the foot 10 excluding the sides 13 , 14 . The height H5 is about 40% of the height H3 of the entire holding area 6 . The transition between the wider foot 10 and the significantly narrower shank 9 is achieved by sloping sides 13 , 14 , which in each case transition at an angle W2 of 20° (relative to the back) to rounded in areas 11 and 12. 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 with R3 on the sole 15 of the foot 10 . Said longitudinal recess 16 is rounded as a whole. The radius R3 is 35 mm in this example, while the overall width B4 is 70 mm. The maximum depth H4 of the longitudinal recess 16 (measured in the longitudinal mid-plane) is 7 mm. The depth H4 of the longitudinal recess 16 thus extends over one third of the height H5 of the foot 10 .

The embodiment of FIG. 3 differs from the embodiment of FIGS. 1 and 2 in that the longitudinal sides 4 , 5 do not extend completely inside the intersecting longitudinal side planes (not shown in detail). The longitudinal flanks 4 , 5 each have upper longitudinal flank sections 17 , 18 and lower longitudinal flank sections 19 , 20 , which are inclined in the manner described above, and the lower longitudinal flank sections 19 , 20 . The segment is perpendicular to the back 3. The dashed line shows the boundary 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 heights H1 , H2 of the longitudinal sides 4 , 5 .

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

The embodiment of FIG. 5 differs from the embodiment of FIGS. 1 and 2 only in that the longitudinal sides 4 , 5 are in opposite directions, and here are inclined outwards. Thereby, the front surface 2 is wider than the back surface 3 . The outer shape of the holding area 6, ie the outer shape of the shank 9 and the foot 10, is the same. Reference may therefore be made to the description of FIGS. 1 and 2 .

Figure 6 again shows the proportional relationship with reference to dimensions and angles, wherein to avoid repetition, the differences are mainly explained. The angle W1 of the longitudinal flanks 4 is likewise 6.5°. The longitudinal flanks 4 are only inclined in opposite directions, so that the impact strip 1 does not narrow but widens towards its front face 2 . The width B1 of the back face 3 is essentially unchanged, while the width B2 of the front face 2 is now greater than the width of the back face 3 . Since the heights H2 and H1 of the front side 2 are basically the same, the angle W3 between the front side 2 and the back side 3 is also basically kept constant at 15°. Considering the absolute value, the difference between B1 and B2 remains the same size, just the sign on the contrary. The longitudinal side planes E1 and E2 also intersect on the intersection S, which is located in the longitudinal midplane MLE and is arranged at a distance from the rear face 3 .

FIG. 7 shows a variant of FIGS. 5 and 6 , in which the longitudinal sides 4 , 5 do not extend completely in the longitudinal side plane, but only for the most part, as in the exemplary embodiment. The longitudinal flanks 4 , 5 each have upper longitudinal flank sections 17 , 18 and lower longitudinal flank sections 19 , 20 , which are inclined in the manner described above, and the lower longitudinal flank sections 19 , 20 . The segment is perpendicular to the back 3. The dashed line shows the boundary 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 heights H1 , H2 of the longitudinal sides 4 , 5 .

Figures 8 to 10 show three different installation states. FIG. 8 shows, by way of example, three impact strips 1 according to the embodiments of FIGS. 5 and 6 . The impact strips 1 are arranged in an arc. Adjacent impact strips 1 (between) are respectively deflected by an angle of 13°. Adjacent impingement slats form a gap between them that remains the same width. The impingement strip 1 is suitable for lining the convex section of the impingement cavity.

The embodiment of FIG. 9 shows three impact strips 1 with the same construction as according to FIGS. 1 and 2 . The adjacent impact slats 1 are also deflected by an angular setting of 13°. Adjacent impingement slats form a gap between them that remains the same width. The impingement strip 1 is suitable for lining the concave section of the impingement cavity.

The embodiment of FIG. 10 shows two outer impingement strips 1 according to the embodiment of FIG. 5 and a middle impingement strip 1 according to the embodiment of FIG. 1 . Due to the adapted side angle, the gap between adjacent impingement strips 1 remains constant in width. This arrangement of impingement strips 1 is suitable for lining straight sections of the impingement chamber. In this case, impingement strips 1 of different designs are arranged alternately. The impingement strips according to the invention can be made of metal cast materials, ceramic materials or hybrid materials comprising steel with a ceramic component. The present invention is not limited to certain materials, as long as said materials are capable of breaking up mineral materials with a sufficient service life.

FIG. 11 shows that the impact strip has a cross section that remains the same over its entire length, as shown in FIGS. 1 to 10 .

List of reference signs

1 impact slat

2 front

3 back

4 Longitudinal sides

5 Longitudinal sides

6 outer holding area

Holding area within 6a

7 undercut

8 undercut

9 handle

10 feet

11 Rounded area

12 Rounded area

13 side

14 side

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

H1 height

H2 height

H3 height

H4 height

H5 height

MLE longitudinal midplane

R1 radius

R2 radius

R3 radius

S intersection

W1 angle

W2 angle

W3 angle

Claims (16)

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.

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