WO2014051527A1

WO2014051527A1 - The tire tread and the lamella for a vulcanization mould

Info

Publication number: WO2014051527A1
Application number: PCT/SK2013/050005
Authority: WO
Inventors: Jaroslav HAJDÚCH; Martin RYPÁK
Original assignee: Continental Matador Rubber, S.R.O.
Priority date: 2012-09-25
Filing date: 2013-09-24
Publication date: 2014-04-03
Also published as: EP2900490A1; SK500452012A3

Abstract

The tire tread and the lamella for fixing into a vulcanization form for forming a lamellar cut in the pattern block of the tire tread, wherein the lamellar cut in a pattern block of a tire tread contains in both opposing surfaces three (OA, AB BC) radially arranged axial rows of projections alternately arranged with the depressions in axial and radial directions, into which the projections of the opposite cut surface fits; each projection of the first row adjacent to the tread surface contains two inclined side surfaces, an inclined bottom surface, and a front surface which is parallel with the main plane of the lamella; each projection of the second row arranged radially below the first row contains two inclined side surfaces, a top and a bottom inclined surface (11, 12) and a sloped front surface (15; 16); each projection of the third row arranged radially below the second row contains two inclined side surfaces, a top inclined surface and a sloped front surface; the two planes tangent tangent to the front surfaces of the second and third row and to the bottom edge of the front plane of the first row of the projections form a V, which planes are defined by the front plane of the projections of the right side of the pattern block and the plane defined by the front plane of the projections of the left side of the block.

Description

THE TIRE TREAD AND THE LAMELLA FOR A VULCANIZATION MOULD

Technical field

An invention relates to construction of a vulcanization form for production of winter, summer and/or all- season tires for passenger and cargo vehicles. In particular the invention relates to a lamella, which at pressing forms narrow cuts of a required shape and amount into the pattern blocks in the tread area defined by the tread area of the tire. Tractions thereby formed provide more effective transfer of forces at the contact of the tread with a road surface.

State of the art

Tires designed for use on vehicles in winter period as well as all seasons are characterised in addition to circumferential and transverse tread grooves also by a large number of narrow cuts formed by lamellas positioned in the tread part of a vulcanization mould cavity. The lamellas are made by moulding operations of sheet metal, from materials specified by purpose specified properties (corrosion resistance, strength...). They are unreleasably fastened in the form (milled form by e.g. gluing), secured against extraction during the mould opening phase. They are position in a radial direction with relation to a tire rotation axis. The lamellas may acquire a depth of tread grooves given by the tire profile, or that can vary depending on requirements for the tread. A shape of the lamella when viewed from the radial direction can be composed from known curves (arc, line, parabola...) and form a certain pattern (e.g. function sin, zig-zag...). The size and the shape are given by design, by desired properties and by size of pattern blocks. Lamellas use in one pattern may be identical or different in shape.

Lamellas by their number on winter and all-season tires form a high number of traction edges in order to enhance the efficiency of force transmission in the point of pattern contact with a road surface. The fact can be utilised on wet, snow-covered and/or icy road surfaces. During the tire and road interaction when forces are transferred significant deformations of the tread block occurs. The deformation significantly affects drivability, it has a negative effect on driving stability, it influences a reaction rate of the tread. After decomposition of projection forces into the road plane the size of deformation depends on the nature of the force working at that particular moment. It is apparent that deformation acquires values of all quadrants of the circle. Use of a block having no pattern cuts or grooves is an ideal solution in terms of deformation in the road plane. As this case is undesired from both legal and technical aspects, it is necessary to divide the continuous tread by grooves. In order to increase traction properties it is necessary to divide the block by narrow cuts. That negatively affects the rigidity of the block. Therefore, at present a variety of cut shapes are used: direct ones with variable bottom depth, variously shaped, but most frequently in the shape resembling a course of the goniometric function sin. By shaping the cut, rigidity of the block is increased, in particular in axial direction, partially in the direction tangential to the circumference of the tire. The phenomenon results in the deformation of the pattern block differing in longitudinal and transverse direction as to the cut.

Recent findings evidence that various manufacturers have started using differently shaped cuts in order to achieve increase of rigidity in all directions and of even stress distribution in the tread block. By that, minimal deformations in the force transmission are achieved, response reaction speed to the input of the driver is increased, and so is the operation safety. Findings from currently known models of closed cuts are as follows:

3-D cuts by Continental, described in European Patent Application EP 1 223 054 Al of January 12, 2001 shaped of a wave consisting of alternately spaced radii of different diameters positioned against each other. A lamella in its lower part transforms into opposite shape, where the curves of a small diameter are replaced by larger curves and vice verse. Modifications of the shape of such distribution can have a triangular shape or a rectangular quadrangle shape, or their combination. Variations in locking features will depend on use of individual shapes. The time lag in locking will occur.

A solution of Semperit described in patent document US 5 350 001 dated September 27, 1994 depicts a function sin shaped cut changing into the shape shifted by ¼ of the wave length. A repetition in the radial direction depends on the shape and can take values of 2 or more. At value 2 a cut area is radially oriented at the point of intersecting the tire surface, at higher values there is an angular deviation from the radial direction. Solutions of compound triangular groove shapes have differently oriented edges.

Patent EP 0 131 246 of Continental describes a zig-zag groove smoothly running from an upper curve into an identical one positioned in its lower part, shifted by ¼ of its length.

Document WO 99/48707 of Goodyear describes a cut formed by a planar area having alternately positioned hemispherical recesses on one side and hemispherical protrusions on the other side, fitting into each other and alternately oriented to the cut axis. The solution caused strengthening of the tread pattern block in all direction of the lamellar plane. The locking occurred with a certain time lag as to the shape of the protrusions.

The said document serves as a basis for another solution of Goodyear' s patent EP 1 533 141 Al, in which projections form the cut plane and fluently following openings are regularly spaced. Their shape may be triangular, rectangular, ... up to x-angular in their section. By the solution Goodyear partially eliminates the lag and the locking has a sharper start.

Definitions

Axial direction is the direction given by the automobile tire rotation axis

Radial direction - is the direction given by the normal axis to the tire circumferential circle and to the rotation axis thereby simultaneously intersected

Tangential direction - is the direction given by a tangent to the circumferential circle

Lamella - is a part pressed from a sheet metal, a material of required properties, of a defined thickness, firmly, unreleasably connected with a mould cavity in the tread part giving the shape and dimensions of narrow cuts in tread blocks In order to simplify the description, the body of the lamella will be described merely as a surface consisting of neutral axis during the bending process of the lamella. Radii essential for thin-walled extract production technologies will not be considered. The body of the lamella is then formed by a layer of evenly coated material given the neutral surface in the direction of each side of the surface (wall thinning due to the forming process is not considered).

Recognised in the art and in the geometry of the element it is obvious that lamellas of periodically repeating elements type are capable of providing a suitable transfer of forces in axial direction. When transferring forces in tangential direction a higher block deformation occurs. The shaped lamellas have a more favourable effect on rigidity in tangential direction when compared to flat lamellas. The flat lamella is formed merely by the bending process technology.

Subject-matter of the invention

The above mentioned deficiencies are largely eliminated by the present invention, which is based on a combination of a flat lamella and a periodically repeated element lamella, where in the radial direction the shape is discontinued and replaced by the shape of the identical periodically repeated element shifted by a period. That prevents long mutual movement between the individual parts of the pattern block as well as transmission of braking and traction forces, and of movement in curves. Having regarded the block deformation character, which can be considered as the clamped beam, the area defining the size and the shape of the projections, indented from the central plane, will have the shape of the resulting curve of the bending of the beam. By that the locking function of the unworn tread is provided and equally the possibility to bend depending on the degree of wear is not lost.

A tire tread contains at minimum one row of blocks arranged in the circumferential direction of the tire, while at minimum one of the blocks is equipped with one or more 3D shaped lamellar cuts in radial direction, and this shaped lamellar cut is defined by two mutually fitting shaped surfaces formed by the lamella during vulcanization. Its subject-matter is that the lamellar cut contains three radially arranged axial rows of projections having dimensions OA, AB, and BC in radial direction, which projections are placed on the opposing surfaces and alternate with the depressions in axial and radial directions; while these depressions fit the projections of the opposite cut surface, whereas each projection of the first row contains two inclined side surfaces, the inclined bottom surface, and the front surface being parallel with the axis surface; each projection of the second row contains two inclined side surfaces, the top and bottom inclined surfaces and a sloped front surface, each projection of the third row contains two side inclined surfaces, the top inclined surface and the sloped front surface, whereas the planes defined by the front surfaces of the projections of the second and third rows and by the bottom edge of the front plane of the first row of the projections form a letter V, which arms are formed by the curves having the shape of the course of the clamped beam deformation reflecting the deformation of individual parts of the pattern block.

The planes defined by the front surfaces of the projections of the second and the third rows form an acute angle.

The V-shape is formed by two curves having the shape of the clamped beam deformation course, which reflects deformation of individual parts of the pattern block that are deformed according to the said curve in order to achieve more even locking and the course of deformation forces and stresses during operation with respect to the wearing out tread, when at a reduced depth the locking ability of the lamella is not required to such an extend as for the new tread. Local maxima in tensile and compression forces at a lamella root are reduced because of the direct cut, decreasing formation of increased thermal stress in a given place.

After the preferred embodiment interval OA, AB, BC may be in proportion 1/3 / 1/3 / 1/3, but it may also be irregular with respect to the required properties, such as ½ / ¼ / ¼ , or ½ Ι\β 1 1/6.

The nature of the lamella suitable for fixing inside the vulcanization mould in order to form the lamellar cut in the tire tread block is that it contains three radially arranged axial rows OA, AB, and BC alternately arranged with the depressions in axial and radial directions; while each projection of the first row contains two inclined side surfaces, the inclined bottom surface, and the front surface being parallel with the neutral surface; each projection of the second row contains two inclined side surfaces, the top and the bottom inclined surfaces and the sloped front surface, each projection of the third row contains two side inclined surfaces, the top inclined surface and the sloped front surface, whereas the planes defined by the front surfaces of the projections of the second and third rows and by the bottom edge of the front plane of the first row of the projections form a letter V.

The planes defined by the front surfaces of the projections of the second and the third rows of the lamella form an acute angle.

After the preferred embodiment the V-shape is the shape formed by two curves having the shape of the clamped beam deformation course, which reflects deformation of individual parts of the pattern block, which are deformed according to the said curve in order to achieve more even locking and course of deformation forces and stresses during the operation with respect to the wearing out of the tread, when at a reduced depth the locking ability of the lamella is not required to such an extend as for the new tread.

By the shape more even effect of lamellas on the road between individual states of tread wear is achieved, which was unfavourable for worn tread and decreased traction ability and pattern block deformation when using sin shaped lamellas. Another advantage compared to previously used lamellas is reduction of locking time caused by the horizontal - sloped surface of projections, so is the increased solidity of the tire tread pattern block, substantial start of locking, more favourable course of pattern block wearing-off, better transfer of forces when changing motion conditions due to limitation of mutual shifting of individual parts of the tire tread pattern blocks in radial and axial directions resulting in enhanced safety as well as driving comfort.

In order to simplify the description, the body of the lamella will be described merely as a surface consisting of neutral axis during the lamella bending process. Radii and slopes essential for thin-walled extract production technologies will not be considered. The body of the lamella is then formed by a layer of evenly coated material given the neutral surface in the direction of each side of the surface.

Brief description of drawings Figure 1 shows a lamella under the invention suitable for connection to a vulcanization mould in a tire tread. Figure 2 depicts a dependence of deformation of a tire tread pattern block on a depth of a lamella cut corresponding to a course of a clamped beam bending. Figures 3-1 and 3-2 depicts cuts 3-1 and 3-2 from Fig. 1. Figure 4 show a tread pattern block with one cut in a disassembled state (for illustration) and a lamella. Figures 5-1 to 5-3 depict lamellar cuts visible on the tire tread pattern block at various stages of tread wear.

Exemplary embodiment of the invention

A lamella is formed by moulding of sheet material. Three-dimensional pressed part designed for placing in the mould cavity is formed, helping to create a cut in the pattern block of the tread. The lamella axis is identical with the neutral axis of the pressed part. A shape of the lamella is depicted on Fig. 1, Fig. 1-1 is formed as an extension of a periodically repeated shape to a distance equal to the length of interval OA (Fig. 1), at interval AB the shape is replaced by an identical periodically repeated function shifted by one half of the period. At interval BC the lamella regains its original shape.

The lamella suitable for the vulcanization mould depicted on Fig. 1 is formed by three rows OA, AB and BC of projections alternately arranged with depressions in axial and radial directions, while each projection of the first row contains two inclined side surfaces, the inclined bottom surface 11 and the front surface being parallel with the neutral surface; each projection of the second row contains two inclined side surfaces, top and bottom inclined surfaces 11, 12 and sloped front surface 15, 16, each projection of the third row BC contains two side inclined surfaces, top inclined surface 12 and sloped front surface, while the planes defined by the front surfaces of the projections 15, 16 of the second and third rows and the bottom edge of the front plane of the first row of the projections form letter V. At the place of surface discontinuance (points A and B) the lamella surfaces are limited in the radial direction and closed by surfaces 11, 12 (visible on Fig. 3-1), intersecting points A and B and in points D and E they are under angle alpha and beta towards the side surface 13, 14. Side surfaces 15, 16 bordering the lamella surface in perpendicular direction to the lamellar axis are formed by the surface, which shape is derived from the course of bending of the clamped beam. Figure 4 depicts the axonometric view of two halves of one block of the tire tread pattern block in an open state and the lamella forming such lamellar cut.

Figure 5-1 shows an unworn tire tread pattern block, i.e. at point 0.

Figure 5-2 a view of the pattern block of a partially worn tire tread, i.e. between points A and B is shown.

Figure 5-3 depicts a completely worn tire tread pattern block, i.e. at point C.

Claims

PATENT CLAIMS

1. Tire tread comprising at least one row of pattern blocks arranged in the circumferential direction of the tread, while at least one of these blocks is equipped with one or more 3D shaped lamellar cuts in radial direction, and this shaped lamellar cut is defined by mutually fitting shaped surfaces formed by lamella during the vulcanization, characterized in that, the lamellar cut contains three radially arranged axial rows of projections having dimensions (OA, AB, and BC) in radial direction, which projections are placed on the opposing surfaces and alternate with the depressions in axial and radial directions; while these depressions fit the projections of the opposite cut surface, and each projection of the first row (OA) contains two inclined side surfaces, the inclined bottom surface, and the front surface being parallel with the axis surface; each projection of the second row (AB) contains two inclined side surfaces, top and bottom inclined surfaces (11, 12), and sloped front surface (15); each projection of the third row contains two side inclined surfaces, top inclined surface (12), and sloped front surface (15), while the planes defined by the front surfaces of the projections of the second and third rows and the bottom edge of the front plane of the first row of the projections form letter V, which arms are formed by the curves having the shape of the course of the clamped beam deformation reflecting the deformation of the individual parts of the pattern block.

2. Tire tread according to claim 1, characterized in that, the planes defined by the front surfaces (15, 16) of the projections of the second and third rows form acute angle.

3. Tire tread according to claim 1 or 2, characterized in that, the plane defined by the front surface of the projections of the right side of the block forms the left arm of V letter and the plane defined by the front plane of the projections of the left side of the block forms the right arm of V letter.

4. Tire tread according to claims 1, 2, or 3, characterized in that, the proportion of the size of the individual projection rows in the radial direction - 0A:AB:BC, is 1/3:1/3:1/3.

5. Lamella suitable for fixing into the vulcanization form for forming of the lamellar cut in the pattern block of the tire tread according to claims 1 to 4, characterized in that it contains three radially arranged axial rows (OA, AB, and BC) of projections, which alternate with the depressions in axial and radial directions; while each projection of the first row contains two inclined side surfaces, the inclined bottom surface, and the front surface being parallel with the neutral surface; each projection of the second row contains two inclined side surfaces, top and bottom inclined surfaces (11, 12), and sloped front surface (15, 16); each projection of the third row contains two side inclined surfaces, top inclined surface (12), and sloped front surface, while the planes defined by the front surfaces of the projections of the second and third rows and the bottom edge of the front plane of the first row of the projections form letter V, which arms are formed by the curves having the shape of the course of the clamped beam deformation.

6. The lamella according to claim 5, c h ar ac te ri z e d i n th a t , the planes defined by the front surfaces (15, 16) of the projections of the second and third rows form acute angle.

7. The lamella according to claim 5, c h ar a c t eri z e d i n th at , the proportion of the size of the individual projection rows in the radial direction - 0A:AB:BC, is 1/3:1/3:1/3.