Tread pattern structure of all-steel truck tubeless radial tire

Abstract

The utility model relates to an all-steel truck tubeless radial tire tread pattern structure which comprises a tire tread and a plurality of pattern blocks arranged on the tire tread at intervals in the circumferential direction of the tire tread, and the pattern blocks comprise a main pattern block and two auxiliary pattern blocks arranged on the two sides of the main pattern block respectively. Grooves are formed in the main pattern blocks and the auxiliary pattern blocks, so that the heat dissipation performance and the water drainage performance of the tire are improved; the pattern grooves are formed between every two adjacent pattern blocks, and each pattern groove comprises a main pattern groove formed in the middle and two auxiliary pattern grooves formed in the two sides of the main pattern groove respectively; wherein the depth of the main pattern grooves is smaller than that of the auxiliary pattern grooves. The utility model provides a tread pattern structure of an all-steel truck tubeless radial tire, which adopts the design of large patterns and full-groove stone discharging, so that the puncture resistance and the cutting resistance are improved; the design of the staggered patterns and the deep grooves provides excellent braking force for the tire.

Description

Technical Field

[0001] The utility model relates to the technical field of tires, in particular to a tread pattern structure of an all-steel load-bearing tubeless radial tire. Background Art

[0002] Tires are donut-shaped elastic rubber products used on various vehicles and machinery for grounded rolling. Typically mounted on metal rims, they support the vehicle's body, cushion external impacts, maintain contact with the road, and ensure vehicle performance. Tires often operate under complex and demanding conditions, enduring deformation, loads, forces, and high and low temperatures. Therefore, they must possess high load-bearing, traction, and cushioning properties. They must also possess high wear and flex resistance, as well as low rolling resistance and heat buildup. Half of the world's rubber consumption is used in tire production, demonstrating the sheer volume of rubber consumed by tires.

[0003] Tire tread designs vary widely, each designed based on suitability for different uses and road conditions. These factors should also be considered when selecting a tire. Tire tread patterns play a crucial role in driving. A well-designed tread not only effectively saves fuel but also reduces noise while driving. It also enhances driving force, braking force, and traction on harsh and slippery roads, thereby improving driving safety.

[0004] There are generally several types of tire patterns:

[0005] (1) Straight groove pattern, also called ordinary pattern, is a pattern design with longitudinal grooves as the main feature.

[0006] Features: excellent operating stability, low rotation resistance, low noise, especially excellent drainage performance, not easy to slip laterally.

[0007] Applicable to: vehicles used on flat roads: cars, trucks, and even airplanes.

[0008] Disadvantages: Poor drive and traction.

[0009] (2) Horizontal groove pattern: A pattern design with horizontal grooves as the main feature.

[0010] Features: The transverse groove pattern has excellent driving force, braking force and traction, and its wear resistance is excellent.

[0011] Applicable to: gravel roads and other harsh road conditions. Vehicle types: mostly used in industrial and short-distance vehicles such as bulldozers, excavators, loaders and other medium and heavy-duty trucks.

[0012] Disadvantages: loud noise.

[0013] (3) Vertical and horizontal groove pattern: Vertical and horizontal groove pattern is also called comprehensive pattern, which is a combination of straight groove and horizontal groove pattern design.

[0014] Features: It combines the advantages of both longitudinal and transverse groove patterns.

[0015] Applicable to: bad road conditions.

[0016] Disadvantages: prone to abnormal wear.

[0017] (4) Block pattern: The pattern is arranged regularly in blocks.

[0018] Features: good driving force and braking force, providing power to drive the car forward.

[0019] Applicable to: snowy, muddy and other roads.

[0020] Disadvantages: poor wear resistance and short mileage life.

[0021] The main driving routes of tubeless tires on the market are roads above paved roads. The main quality defects of tires are shoulder hollow, crown hollow and poor wear resistance. Tires have high requirements for tread patterns and should have good wear resistance and novel appearance. Utility Model Content

[0022] The purpose of the present utility model is to provide a tread pattern structure of an all-steel load-bearing tubeless radial tire in order to overcome at least one of the above-mentioned defects in the prior art.

[0023] The purpose of the utility model can be achieved through the following technical solutions:

[0024] A tread pattern structure of an all-steel load-bearing tubeless radial tire comprises a tire tread and:

[0025] A plurality of pattern blocks are arranged on the tire tread at intervals along the circumferential direction of the tire tread, the pattern blocks including a main pattern block and two secondary pattern blocks respectively arranged on either side of the main pattern block; wherein grooves are provided on both the main pattern block and the secondary pattern blocks to improve heat dissipation and drainage of the tire;

[0026] The grooves are arranged between two adjacent tread blocks, and the grooves include a main groove arranged in the middle and two auxiliary grooves respectively arranged on both sides of the main groove; wherein the depth of the main groove is less than the depth of the auxiliary groove.

[0027] Furthermore, a longitudinal oblique groove is provided between the main pattern block and the secondary pattern block;

[0028] Longitudinal inclined groove:

[0029] In the present invention, the width of the longitudinal oblique groove is 17-20 mm;

[0030] In the present invention, the longitudinal oblique groove has a length of 38-39 mm;

[0031] In the present invention, the depth of the longitudinal oblique groove is 10-12 mm;

[0032] In the utility model, the groove bottom inner corner of the longitudinal oblique groove has an arc transition with a radius of 1-2mm.

[0033] Furthermore, the grooves provided on the main pattern blocks are Z-shaped grooves, and the grooves provided on the secondary pattern blocks are straight grooves.

[0034] Z-groove:

[0035] In the present invention, the width of the Z-shaped groove is 2-4 mm;

[0036] In the present invention, the Z-shaped groove has a depth of 2-4 mm;

[0037] In the present invention, a circular arc transition with a radius of 1-2 mm is provided at the bottom of the Z-shaped groove;

[0038] In the present invention, the positive angle surface at the turning point of the Z-shaped groove is provided with an arc transition with a radius of 10-11 mm;

[0039] In the present invention, the inner corner surface at the turning point of the Z-shaped groove is provided with an arc transition with a radius of 9-10 mm.

[0040] Straight groove:

[0041] In the present invention, the width of the linear groove is 2-4 mm;

[0042] In the present invention, the linear groove has a depth of 2-4 mm;

[0043] In the present invention, the length of the linear groove is 30-40 mm;

[0044] In the present invention, both ends of the linear groove have arc transitions with a radius of 1-2 mm;

[0045] In the present invention, the groove bottom of the linear groove has an arc transition with a radius of 1-2 mm.

[0046] Furthermore, the main pattern block is peanut-shaped, and all corners of the main pattern block have arc transitions, wherein the positive corners on both sides farthest from the center of the main pattern block have arc transitions with a radius of 4-5 mm, and the remaining corners have arc transitions with a radius of 10-11 mm.

[0047] Furthermore, the secondary pattern block is pentagonal, and the two secondary pattern blocks are symmetrically distributed along the center of the main pattern block; the secondary pattern block has two vertices on the side near the shoulder, wherein the angle corresponding to one vertex is an obtuse angle, and the angle corresponding to the other vertex is an acute angle; the secondary pattern block has three vertices on the side near the main pattern block, wherein the vertex in the middle has an arc transition with a radius of 5-6mm, and the other two vertices have arc transitions with a radius of 10-11mm.

[0048] Furthermore, a plurality of stone-removing blocks are arranged at intervals on the groove surface of the auxiliary groove.

[0049] Furthermore, a plurality of exhaust holes are distributed at intervals around the main tread blocks, the auxiliary tread blocks and the stone-repelling blocks.

[0050] Furthermore, a shoulder groove connected to the secondary groove is provided on the shoulder of the tire tread.

[0051] Compared with the prior art, the utility model has the following advantages:

[0052] (1) The utility model provides a tread pattern structure of an all-steel load-bearing tubeless radial tire. The structure adopts a large-block pattern and a full-groove stone-removing design to improve puncture resistance and cut resistance. The staggered pattern and deep groove design provide the tire with excellent braking force.

[0053] (2) The utility model provides a tread pattern structure of an all-steel load-bearing tubeless radial tire. The tire tread pattern is designed as a transverse pattern. The arrangement of Z-shaped grooves and straight grooves provides excellent heat dissipation and drainage performance.

[0054] (3) The utility model provides a tread pattern structure of an all-steel load-bearing tubeless radial tire, wherein a plurality of stone-removing blocks are arranged at intervals on the groove surface of the secondary groove of the tire tread, thereby improving the stone-removing and water-removing performance of the tire;

[0055] (4) The utility model provides a tread pattern structure of an all-steel load-bearing tubeless radial tire, in which the longitudinal oblique grooves on the tire surface have arc transitions at the inner corners of the groove bottom, which effectively prevents cracks at the groove bottom. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] Figure 1 This is a schematic structural diagram of the tire tread pattern in the present invention;

[0057] Figure 2 This is a schematic structural diagram of one pitch of the tire tread pattern in the present invention;

[0058] Figure 3This is a structural rendering of the tire tread pattern in the present utility model;

[0059] The numbers in the figure show:

[0060] 1- Tire tread;

[0061] 2-pattern block; 21-main pattern block; 22-secondary pattern block; 23-Z-shaped groove: 24-straight groove:

[0062] 3-groove; 31-main groove; 32-secondary groove; 33-stone removal;

[0063] 4-longitudinal oblique groove;

[0064] 5-groove under the shoulder;

[0065] 6- Exhaust hole. DETAILED DESCRIPTION

[0066] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process, but the protection scope of the present invention is not limited to the following embodiments.

[0067] Any features such as component models, material names, connection structures, control methods, etc. that are not clearly stated in this technical solution shall be deemed as common technical features disclosed in the prior art.

[0068] In the description of the present invention, it should be understood that the terms "upper", "lower", "vertical", "horizontal", "top", "bottom", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0069] In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined. Furthermore, the terms "mounted," "connected," and "connected" should be interpreted broadly, encompassing, for example, fixed, removable, or integral connections; bolted or welded; directly or indirectly through an intermediary; and internal communication between two components. Those skilled in the art will understand the specific meanings of these terms in this utility model on a case-by-case basis.

[0070] Example 1

[0071] Tubeless tires have high requirements for road driving. Common tire quality defects are shoulder hollow, crown hollow and poor wear resistance. Therefore, the tire has high requirements for the pattern and should have good wear resistance and novel appearance. However, straight groove patterns, transverse groove patterns, longitudinal and transverse groove patterns, and block patterns cannot simultaneously have good guidance, drainage, grip, puncture resistance and side slip resistance, and the tire's traction or lateral force is not high. Based on this, this embodiment provides a tread pattern structure of an all-steel load-bearing tubeless radial tire. The specific structure is shown in Figure 1-3 , including tire tread, and:

[0072] A plurality of pattern blocks are arranged on the tire tread at intervals along the circumferential direction of the tire tread, the pattern blocks including a main pattern block 21 and two secondary pattern blocks 22 respectively arranged on either side of the main pattern block 21; wherein grooves are provided on both the main pattern block 21 and the secondary pattern blocks 22 to improve the heat dissipation and drainage of the tire;

[0073] The grooves 3 are arranged between two adjacent tread blocks, and the grooves 3 include a main groove 31 arranged in the middle and two auxiliary grooves 32 respectively arranged on both sides of the main groove 31; wherein the depth of the main groove 31 is less than the depth of the auxiliary groove 32.

[0074] Please see again Figure 1 In the present invention, a longitudinal oblique groove 4 is provided between the main pattern block 21 and the secondary pattern block 22; the longitudinal oblique groove 4 meets the requirements of groove width 17-20 mm, groove length 38-39 mm, groove depth 10-12 mm, and a circular arc transition with a radius of 1-2 mm at the groove bottom corner.

[0075] Please see again Figure 1 In the present invention, the grooves provided on the main tread block 21 are Z-shaped grooves 23 , and the grooves provided on the auxiliary tread block 22 are linear grooves 24 .

[0076] Among them, the Z-shaped groove 23 meets the requirements of groove width 2-4mm and groove depth 2-4mm; a circular arc transition with a radius of 1-2mm is provided at the bottom of the Z-shaped groove 23; a circular arc transition with a radius of 10-11mm is provided at the positive angle surface at the turning point of the Z-shaped groove 23; and a circular arc transition with a radius of 9-10mm is provided at the negative angle surface at the turning point of the Z-shaped groove 23.

[0077] The linear groove 24 has a groove width of 2-4 mm, a groove depth of 2-4 mm, and a groove length of 30-40 mm. Both ends of the linear groove 24 have an arc transition with a radius of 1-2 mm. The bottom of the linear groove 24 has an arc transition with a radius of 1-2 mm.

[0078] Please see again Figure 1In the present invention, the main pattern block 21 is peanut-shaped, and all corners of the main pattern block 21 have arc transitions, among which the positive corners on both sides farthest from the center of the main pattern block 21 have arc transitions with a radius of 4-5 mm, and the remaining corners have arc transitions with a radius of 10-11 mm.

[0079] Please see again Figure 1 In the present invention, the secondary pattern block 22 is pentagonal, and the two secondary pattern blocks 22 are symmetrically distributed along the center of the main pattern block 21; the secondary pattern block 22 has two vertices on the side near the shoulder, wherein the angle corresponding to one vertex is an obtuse angle, and the angle corresponding to the other vertex is an acute angle; the secondary pattern block 22 has three vertices on the side near the main pattern block 21, wherein the vertex in the middle has an arc transition with a radius of 5-6 mm, and the other two vertices have arc transitions with a radius of 10-11 mm.

[0080] Please see again Figure 1 In the present invention, a plurality of stone-removing blocks 33 are arranged at intervals on the groove surface of the auxiliary groove 32 .

[0081] Please see again Figure 1 In the present invention, a plurality of exhaust holes 6 are distributed at intervals around the main tread block 21 , the auxiliary tread block 22 and the stone-removing block 33 .

[0082] Please see again Figure 1 In the present invention, a shoulder groove 5 communicating with the auxiliary groove 32 is further provided on the shoulder of the tire tread.

[0083] Example 2

[0084] like Figure 1 As shown, this embodiment proposes a tread pattern structure of an all-steel load-bearing tubeless radial tire, including a main pattern block 21, which is peanut-shaped and arranged in the center; and auxiliary pattern blocks 22 arranged on both sides of the main pattern block 21, which are pentagonal; Z-shaped grooves 23 on the pattern block 21; straight grooves 24 on the pattern block 22; pattern grooves 3 between the main pattern blocks 2 in the circumferential direction, a main groove 31 in the center of the pattern groove 3, and auxiliary pattern grooves 32 on both sides of the main groove 31; stone removal blocks 33 on the auxiliary groove 32; and under-shoulder pattern grooves 5 and exhaust holes 6.

[0085] The tire tread pattern is designed as a transverse pattern, providing excellent heat dissipation and drainage performance. The tire is composed of nine equally divided active molds evenly arranged in the direction of the upper and lower side plates. The center of the tread is a row of peanut-shaped main pattern blocks 21, and the two sides of the tread are two rows of pentagonal auxiliary pattern blocks 22. All pattern blocks have decorative shallow grooves with a width of 2mm and a depth of 2mm, which play a role in heat dissipation during tire driving. Longitudinal oblique grooves 4 are distributed between the pattern blocks in the horizontal direction. Z-shaped pattern grooves 3 are evenly distributed between the pattern blocks along the circumferential distance. The pattern groove 3 is divided into two auxiliary pattern grooves 32 on the left and right sides in opposite directions with the main groove 31 of 39.8mm in length in the middle. The auxiliary grooves 32 on both sides are staggered according to the shape of the pattern block. Each auxiliary groove 32 is distributed with five stone removal block designs 33 to improve the stone removal and drainage performance of the tire.

[0086] The tire's tread has a pitch of 40 sections and a running surface width of 260mm. The overall pattern features a mixed design, providing excellent braking and driving force. A row of peanut-shaped blocks 21 are evenly spaced from the nine equally spaced active molds to the upper and lower side panels. All corners of the blocks are rounded. The leftmost and rightmost external corners have a 5mm radius, while all other corners have a 10mm radius. A Z-shaped groove 23 is located on the main block 21, with a width of 2mm, a depth of 2mm, and a bottom with a 1mm radius. The Z-shaped groove 23 has a 1mm radius at both ends, an 11mm radius at the external corner, and a 9mm radius at the internal corner. Two rows of pentagonal secondary blocks 22 flank the main block 21. These secondary blocks 22 have two corners on their outer sides, near the shoulder, with a larger angle of 110° and a smaller angle of 74°. The three inner corners of the secondary tread block 22 feature rounded transitions. The upper and lower corners each have a 10mm radius, while the innermost corner has a 5mm radius. A linear groove 24 runs through the tread block 22, measuring 36mm long and 2mm deep. Both ends and the bottom of the groove feature 1mm radius arc transitions. The tread blocks are well-proportioned and smoothly connect with the grooves, creating an aesthetically pleasing transverse pattern block that also provides excellent drainage.

[0087] The tire tread main pattern blocks 21 and the auxiliary pattern blocks 22 are distributed with longitudinal oblique grooves 4 in the horizontal direction. The groove width is 17 mm, the groove length is 38.7 mm, and the groove depth is 12 mm. The groove slopes downward in the vertical direction. The corner of the groove bottom is an arc transition with a radius of 2 mm, which effectively prevents cracks at the groove bottom.

[0088] The tire's tread blocks 2 are evenly spaced along the circumference, with Z-shaped grooves 3 distributed evenly between them. The grooves 3 are divided by a central 39.8mm-long main groove 31, which splits into two oppositely oriented secondary grooves 32 on either side. The main groove 31 is 39.8mm long, 17mm wide, and 12mm deep. The secondary grooves 32 on either side are staggered to follow the shape of the block, varying in width from 23.5mm at its narrowest point to 29.55mm at its widest point, with a depth of 24mm.

[0089] Each groove bottom of the tire tread secondary groove 32 is distributed with five stone-removing blocks 33. The stone-removing blocks 33 are 4 mm wide and 4 mm deep, and have an arc transition with a radius of 0.5 mm at the positive corner. The two stone-removing blocks 33 at both ends are 15 mm long, and the middle stone-removing block is 8 mm long. The two middle stone-removing blocks 33 make L-shaped arc transitions along the trend of the tread groove. The positive corner of the turning point is an arc transition with a radius of 12 mm, and the negative corner is an arc transition with a radius of 8 mm. The overall lines are smooth and the transition is smooth, which effectively improves the stone-removing and water-draining performance of the tire.

[0090] The tire tread blocks 2 and the tire grooves 3 are alternately arranged in sequence along the circumference of the tire, providing excellent traction and braking performance for the tire during driving.

[0091] The tire tread is connected to the transverse pattern groove 3 and extends downwards from both sides of the shoulder, and is evenly distributed with an open block-shaped structure, namely, the shoulder pattern groove 5, with a groove depth of 5mm. The positive corner transition adopts an arc transition with a radius of 5mm, and the negative corner of the groove bottom adopts an arc transition with a radius of 2mm, so as to improve the heat dissipation of the shoulder and avoid shoulder cracks.

[0092] The tire tread pattern blocks are surrounded by multiple exhaust holes 6 with a diameter of 0.8 mm that penetrate the mold to facilitate exhaust during vulcanization, prevent air pockets from causing rounded corners in the pattern and rubber deficiency on the sidewalls, promote rubber flow, and make rubber vulcanization more uniform.

[0093] The tire of this embodiment adopts a large-block pattern and a full-groove stone-removing design to improve puncture resistance and cut resistance; the staggered pattern and deep groove design provide the tire with excellent braking force; the special tread formula gives the tire good wear resistance and heat dissipation capacity, making it suitable for mixed road surfaces in mining areas.

[0094] The above description is merely a preferred embodiment of the present invention and does not constitute any limitation thereto. Any person skilled in the art may utilize the above disclosure to modify or remodel the present invention into equivalent embodiments. However, any simple modification, equivalent variation, or modification of the above embodiment that does not depart from the technical content of the present invention and is based on the technical essence of the present invention shall still fall within the scope of protection of the present invention.

Claims

1. A tread pattern structure of an all-steel load-bearing tubeless radial tire, characterized in that: Includes tire tread, as well as: A plurality of pattern blocks are arranged on a tire tread at intervals along the circumferential direction of the tire tread, the pattern blocks comprising a main pattern block (21) and two auxiliary pattern blocks (22) respectively arranged on both sides of the main pattern block (21); wherein grooves are provided on both the main pattern block (21) and the auxiliary pattern blocks (22) to improve the heat dissipation and drainage of the tire; A tread groove (3) is provided between two adjacent tread blocks, wherein the tread groove (3) comprises a main tread groove (31) provided in the middle, and two auxiliary tread grooves (32) provided on both sides of the main tread groove (31); wherein the depth of the main tread groove (31) is less than the depth of the auxiliary tread groove (32).

2. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: A longitudinal oblique groove (4) is provided between the main pattern block (21) and the secondary pattern block (22); The longitudinal oblique groove (4) satisfies at least one of the following conditions: ① The width of the longitudinal oblique groove (4) is 17-20 mm; ② The longitudinal oblique groove (4) has a groove length of 38-39 mm; ③ The depth of the longitudinal oblique groove (4) is 10-12 mm; ④ The bottom inner corner of the longitudinal oblique groove (4) has an arc transition with a radius of 1-2 mm.

3. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: The grooves provided on the main pattern block (21) are Z-shaped grooves (23), and the grooves provided on the auxiliary pattern block (22) are linear grooves (24).

4. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 3, characterized in that: The Z-shaped groove (23) satisfies at least one of the following conditions: ① The width of the Z-shaped groove (23) is 2-4 mm; ② The Z-shaped groove (23) has a depth of 2-4 mm; ③ The bottom of the Z-shaped groove (23) is provided with an arc transition with a radius of 1-2 mm; ④ The positive angle surface at the turning point of the Z-shaped groove (23) is provided with an arc transition with a radius of 10-11 mm; ⑤ The inner corner surface at the turning point of the Z-shaped groove (23) is provided with an arc transition with a radius of 9-10 mm.

5. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 3, characterized in that: The linear groove (24) satisfies at least one of the following conditions: ① The width of the linear groove (24) is 2-4 mm; ② The linear groove (24) has a depth of 2-4 mm; ③ The length of the linear groove (24) is 30-40 mm; ④ Both ends of the linear groove (24) have arc transitions with a radius of 1-2 mm; ⑤ The bottom of the linear groove (24) has an arc transition with a radius of 1-2 mm.

6. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: The main pattern block (21) is peanut-shaped, and all corners of the main pattern block (21) have arc transitions, wherein the positive corners on both sides farthest from the center of the main pattern block (21) have arc transitions with a radius of 4-5 mm, and the remaining corners have arc transitions with a radius of 10-11 mm.

7. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: The secondary pattern block (22) is pentagonal in shape, and the two secondary pattern blocks (22) are symmetrically distributed along the center of the main pattern block (21); The auxiliary pattern block (22) has two vertices on one side near the shoulder, wherein the angle corresponding to one vertex is an obtuse angle, and the angle corresponding to the other vertex is an acute angle; The auxiliary pattern block (22) has three vertices on one side close to the main pattern block (21), wherein the vertex in the middle has an arc transition with a radius of 5-6 mm, and the remaining two vertices have arc transitions with a radius of 10-11 mm.

8. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: A plurality of stone removal blocks (33) are arranged at intervals on the groove surface of the secondary groove (32).

9. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 8, characterized in that: A plurality of exhaust holes (6) are distributed at intervals around the main tread block (21), the auxiliary tread block (22) and the stone removal block (33).

10. The tread pattern structure of the all-steel load-bearing tubeless radial tire according to claim 1, characterized in that: The shoulder of the tire tread is also provided with a shoulder groove (5) connected to the auxiliary groove (32).

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