LU82034A1 - ZIGZAG TYPE TRACK DRAWINGS INCLUDING SLOTS ON THE CORDS - Google Patents

Description

~ —'— —A Ο Λ — Ύ— / Grand Duchy of Luxembourg

Patent Ν ° ä J Q ö% of ..... èl - ââcSSÛ) Ve-1979- Mr. Minister, „, Käo of National Economy and the Middle Classes

Title issued: ........................................

LUXEMBOURG Industrial Property Service

Patent Application I. Application ................ (i)

Italy................................................. .................................................. .................................................. .................................................. .................................................. .....

represented by EMeyers & E.Freylinger, · .Jng.cone + en.pvapr + incL, · ........ 46.vue ...... (2) 4ur-ÜÎmtièx ^ Meeei & csiSQ ^ JigiseaxA jen. quaMMÆÆoatâatedre & ................................................ ...........

deposit— this twenty-one..Maenibve ndlneuf.aent 8aixantù..âix..neuf ........... (3) to - "se ........: .. hours, at the Ministry of National Economy and the Middle Classes, in Luxembourg: 1. this request for obtaining a patent for invention concerning: é) essins „„ âe ~ -bcaide ~ de-.vaulenien. t ... jâu ~ -type ~ .jen ·. zigzag eonpartantdeeenizi (4) on the cords .......................................... .................................................. .................................................. .................................................. ...............................

declares, assuming responsibility for this declaration, that the inventor (s) is (are): • é? ^ ulvana -GEITtÄE ^ I-if—: l ^ vale "MareH * —Sesto — Str — Gœoam .i'îr .................... (5) 2. the delegation of power, dated .............. .Milan ..................................... le. .12 ~ & Gexb * C ~ 2 $ ? 9 ......

3. description in French ................. language .......................... ..... of the invention in two copies; 4 ..... two ............ drawing boards, in two copies; 5. the receipt of the taxes paid to the Registration Office in Luxembourg, on the tenth day, ^^^ ^ this ^ ve --- mil --- neuf- ~ cent --- ss> isKsnte --- dix · · new................................................ ........................

claims for the above patent application the priority of one (s) request (s) of (6) ....................... hxevet ... ............................................... filed® in (7) ........... Italy ................................... .................................................. .............

le ~ i) ing.ti ^ ua ^ - Maenbr ^ .- mit ..- neuf ~.-oent. ~ soixûm ^ ~ M ».- lnd ^ ~ eam..lA .. ^ a ..... ................................. (8) .......... Ζ1..Μ1 ..Λ / Ϋ8 ............................................. .................................................. .................................................. .................................................. ........................................

on behalf of .. „Applicant Ig .......................................... .................................................. .................................................. .................................................. ........ (9) elect domicile for him / her and, if appointed, for their proxy, in Luxembourg ..................... ...................

-46 ....... view ~ <m · Cemetery * --hüßembourg ............................... .................................................. .................................................. ...................... WW

requests the grant of a patent for the subject described and represented in the abovementioned appendices, - with postponement of this grant to -— months.

Clients ..................

yf ij Π. Deposit Minutes

The aforementioned patent application has been filed with the Ministry of National Economy and the Middle Classes, Industrial Property Service in Luxembourg, on: Γ7 <19? £ ..... "Pr. Ie Mmistre -, at ................. hours .___ t of the National Economy, and -of the Middle Classes,) / Λ / "S * '-' ** ·"; <"" N,: 'DOOC if' :,% / =>

Case 7822 BP "'700" Λ ί |

! PATENT

S —-, -i * 1! on behalf of: INDUSTRIE PIRELLI S.p.A.

i - fi a "Tread patterns of the zigzag type comprising P notches on the cords I Inventor: Monsieur GHILARDI Giuliano il

i h

»S i I, ------ U · i; · i

It ‘Priority: patent application filed in Italy J on December 22, 1978, under the number 31201 A / 78 I.

3i i i; ’T ί 'i

II

i 4

The present invention relates to tread patterns, and in particular to patterns for large tires suitable for heavy motor transport on smooth roads and at high speed.

5 It is known that in tires the part of the radially outermost surface, which extends axially from one shoulder to the other of the tire, is provided with a design consisting of a series of grooves made in the 'thickness of the tread and arranged in variable ma-1Q nière to subdivide said strip into cords and / or blocks separated from each other by the above grooves.

There is generally provided, in the thickness of the beads and blocks, what are called lamellae, (j 15 that is to say narrow notches directed from the surface i [towards the interior of the tire, which have a depth more or less equal to that of the grooves and which can also lead to the sides of the cords and blocks.

! The set of grooves and lamellae constitutes precisely the pattern of the tread which forms a characteristic and distinctive element of the tire which mainly depends on the type of use of the latter.

Thus, for example, winter type tires have a tread pattern with strong blocks and 25 with deep grooves in order to increase the traction force on snowy or muddy soils, typical of the winter season, while that the designs for tires intended for road use under normal conditions are usually characterized by large circumferential grooves in a zigzag, low angle, from which branch other transverse grooves more or less inclined and s' extending so as to completely cross the longitudinal cords, the whole being integrated by tight strips.

The main purpose of this type of tread pattern consists in breaking the film of liquid which forms, for example in rainy weather, between the tire and the wet road surface in order to avoid the appearance of the phe-i nomene of aquaplaning. Another object is to contribute significantly to road holding and stability * '' ** _ V * y * l c 2 driving the tire.

Unfortunately, these requirements are contradictory to each other. In fact, in order to guarantee the prevention of the phenomenon of aquaplaning, very subdivided and laminated designs are needed, while to obtain a good behavior of the tire on the road, rather compact designs are necessary since the grooves and the notches, by weakening the resistance of the blocks, allow a notable mobility of these under the contact surface of the matt tire-1Q, which gives rise to a more important and especially irregular wear which makes the tire, and therefore the vehicle, transversely mobile. to the direction of travel and not very sensitive to the action of the direction.

More particularly, for tires 15 intended for heavy motor transport at high speed, there is a need for drawings of the type with cords and continuous circumferential grooves, in zigzag, in which however the continuity of the cords is interrupted by a plurality of transverse notches which can also extend from one 2Q groove to another. In fact, these drawings give optimum results with regard to stability and direction of movement as well as with regard to the prevention of aquaplaning under normal running conditions.

On the other hand, these drawings are not yet completely satisfactory in critical situations, such as for example in the event of braking or in the event of drift when tangential forces of high value act on the surface of the cords.

In fact, if the aforementioned notches close under the effect of these forces, the corresponding portion of the bead stiffens giving an increase in stability of the tire, but also a significant loss of grip in the case of wet ground. because the action of rupture of the liquid film between the tire and the road in the area of reciprocal contact is lacking.

If, on the contrary, the width of the notches is such that they do not close, even under these 4 critical conditions, the phenomenon of aquaplaning is avoided but the cords are subdivided into blocks which have an excessive mobility ί 3 t, this mistletoe reduces the qualities of road behavior of the tire.

This excessive mobility is, moreover, the cause of another drawback, namely a type of wear 5 of the highly irregular tread. In other words, it has always been found that any type of transverse notch gives rise, to a more or less pronounced extent, to a type of wear called "sawtooth" because of the appearance particular that takes the surface 10. of the cords. The aforementioned phenomenon is all the more marked as the notch is wider and that, consequently, the block thus delimited is more mobile and this, more especially, at the places where the notches open into the longitudinal grooves.

Finally, in these drawings, we also normally see another type of irregular “speckled” wear which begins on the edges of the beads by chamfering the edges.

It zigzag in the circumferential direction and on the plane of the contact surface.

2Q All these phenomena, which significantly shorten the life of the tire, give it

In addition, from their appearance an unpleasant and detrimental aspect for the image of product quality, with all the unfavorable commercial consequences which ensue, their | 25 effects being particularly marked in the case already cited | tires for heavy and fast automobile transport.

The object of the present invention consists in ij a drawing of a tread of the cord type and with circumferential grooves having transverse notches on the cords capable of eliminating all the drawbacks described but even, on the other hand, of maintaining and even to increase the qualities of driving stability and handling on wet surfaces of tires manufactured according to the prior J technique.

fl - 35 To this end, the object of the present invention i! consists of a tire for vehicle wheels, the part of which forms the crown, which extends axially from one side to the other, presents towards the outside a strip of elastomeric material called tread, the radially external “1> * r” t / · 4 surface is provided with a design, hollowed out in the thickness of said strip, comprising a plurality of circumferential zigzag grooves which delimit a plurality of circumferential zigzag cords, one of which at the 5 less has a plurality of transverse notches extending from one groove to another, characterized in that said notches comprise three contiguous sections, two lateral near the edges of said bead and open on the corresponding groove and a section median, interposed 10 to join the two lateral sections and having a minimum width greater, at least in the circumferential direction, than the maximum width of the said lateral sections.

It is very expedient that the lateral sections mentioned are straight segments, inclined with respect to the circumferential direction of the tire with angles between 50 ° and 90 °. In particular, according to a first embodiment of the invention, the aforementioned sections are arranged in a substantially transverse position and are offset between them so that the straight line 20 te which joins their axially internal ends is inclined relative to the circumferential direction cited from an angle between 10 ° and 60 °, and preferably between 20 ° and 40th.

The middle section may coincide with this junction line, thus representing its practical embodiment, or it may on the contrary deviate from it in order to have only its ends in common with this line. In particular, according to another suitable embodiment of the invention, the aforementioned median section consists of three contiguous segments, the two outer segments being inclined relative to the circumferential direction by a value angle included in the mentioned area , the internal segment being on the contrary oriented in the above circumferential direction and lying in the equatorial plane of the tire. 35 Whatever the shape of the notches, it is preferable, however, for the ratio between the projection in the transverse direction of the single median section and that of the entire notch to be between 0.3 and 0.8.

/ s 5 I Finally, the ratio between the maximum width of the lateral sections and the minimum width of the middle section is preferably between 0.2 and 0.7. In any case, the present invention will be better understood with the aid of the description which follows and of the appended figures, given simply by way of non-limiting examples, in which: - Figure 1 gives a plan view of a circumferential part of the drawing according to the invention, in a first embodiment, and 1 - FIG. 2 shows, according to the same methods as in FIG. 1, a second embodiment of the drawing of 1 ' invention.

The tread pattern shown in Figure 1 includes four circumferential grooves 1, zigzag developing, which delimit a large circumferential bead 2 and two similar side cords 3 narrower, also zigzag; the two lateral grooves also delimit with the shoulder of the tire two other shoulder cords 4 of which only the axially internal sidewalls; are zigzagging.

The surface of the median cord is generally laminated by a plurality of notches 5 each consisting of three contiguous sections of different width, at least i in the circumferential direction, that is to say in the direction i | parallel to the equatorial plane m - m of the tire.

! It should be made immediately clear that the word I "section" should not be understood here as a segment J of rectilinear notch but as a segment of whatever shape! 30 conch, the point of separation between the contiguous sections! being determined by the value of the ratio between the respective widths, as already mentioned, and which will be moreover detailed in more detail in the following; description.

35 Of course, the other cords can also be lamellas and are usually even, but in! within the framework of the present description it suffices to take into consideration only the strips of the median cord 2.

! / • fi 6

Among the contiguous sections mentioned above, the lateral sections - which are offset towards the edge of the cord - are the narrowest. In addition, they open on the sides of the corresponding groove in order to allow the water collected by the notch to be unloaded during the running of the tire on wet ground.

The aforementioned lateral sections may be broken sections, but it is preferable that they be straight and inclined relative to the circumferential direction of the tire at an angle "b" varying between 50 ° and 90th.

In view of what has been specified, it can in fact be observed that in the particular embodiment illustrated in FIG. 1 the aforementioned notches 5 extend 15 from one side to the other of the cord by opening onto the two zigzag grooves and thus dividing the cord into a circumferential succession of blocks. Each notch is constituted by three contiguous sections, the two lateral 6 and 8 being arranged transversely, that is to say inclined 2Q with respect to the circumferential direction of the angle "b" substantially equal to 90 °, and offset between them so that the straight line joining the axially internal ends of the said sections is inclined relative to the circumferential direction by an angle "a" of approximately 35 °. The middle section 25 7, which joins the two lateral sections, coincides in this case with the junction line cited and is therefore also inclined by an angle "a" of about 35 °.

This inclination can naturally vary depending on the measurement of the tire and other characteristics of the tread pattern, but it must however be between 10 ° and 60 °, preferably between 20 ° and 40 °.

According to another embodiment, illustrated in FIG. 2 using the same modalities and the same references as for FIG. 1, the above-mentioned median section is constituted by three contiguous segments 9, 10 and 11, the two axially external segments 9 and 11 being inclined by: relative to the circumferential direction at angles / larger than that which would have in the drawing for a • il * il pneumatic identical a median section corresponding to single segment (see the broken line of figure 2) but which will always be between 10 ° and 60 °. On the contrary, the internal segment 10 is always placed at 0 °, that is to say exactly 5 in the said circumferential direction of the tire.

When said sections (both the median and the lateral ones) are constituted by a plurality of segments, as in the particular case of FIG. 2, the segments which belong to the same section may also not (have the same width, but in this case, as will be explained better below, there is a range of preferential values to be observed for the ratio between the maximum width of the lateral sections and the minimum width of the middle section.

The same condition also applies when said sections are formed not by a broken line of segments but by a single segment having a variable width along its axial development.

2Q One factor rather much more important than the above-mentioned implication of the median section consists, on the other hand, in the relationship between the transverse dimensions, that is to say | say axial, of the respective interested parts of the cord! by the narrow lateral sections and by the wide median section of the notch.

1 As can be seen in Figure 1 (a condition which is however easily verifiable also in ί j the drawing of Figure 2) the narrow sections of the notch i concern a circumferential lateral part of the cord 3Q 2 which can be delimited on one side by two meridian planes, "p" and "r", perpendicular to the axis of the tire, including! the line of the intersection with the plane of the drawing, respectively p-p and r-r, is indicated in the figure. Likewise, on the other side of the cord, the planes "s" and "q" have been delimited by the respective lines s-s and q-q.

! Obviously this is the circumferential part. median part of the cord between the planes "r" and i "s" which is interested in the broad median section 7 of the! / cut.

P7 8

If we now designate by "L '' the projection in the transverse direction of the development of the entire notch, that is to say the axial width of the part of the bead between the planes" p "and" q " , which passes prë-5 precisely through the points at which the notches 5 open into the circumferential zigzag grooves, and if we designate by "%" the transverse part of the development of the median section 7, that is to say the axial width of the part of the cord between the planes "r" and "s" and Ψ IG interested in the notch section of greater width, the ratio £ / L must be between 0.3 and 0.8.

It is good to specify here that when the aforementioned points, which in the drawing of FIG. 1 identify with the planes p, q, r, s, are not found - in another drawing - respectively on a single plane , it is then necessary to consider as planes p, q, r, s the median planes of the circumferential parts of the cord interested in the series of corresponding points.

Finally, with regard to the different width 20 of the two notch sections (6.8 and 7 in FIG. 1 and 9.10 and 11 in FIG. 2), if these widths are designated by "d" and "D "(see Figure 1), it is preferable that the d / D ratio is between 0.2 and 0.7.

The notches described here have proved to be able to solve the problem posed in a very satisfactory manner and the Applicant will now give the explanation which seems to him the most valid but by making it clear however that intends in no way to be bound by this explanation which may not adequately correspond to the reality of the phenomenon.

It has already been recalled that in the presence of tangent forces of high value, for example during braking, the notches on the cords tend to close. In fact, the blocks delimited by these notches, which can be schematized in a very approximate manner as being inserted beams and projecting in a cantilever fashion in a surface placed at the level of the base of the notches-i the, tend - under the action of the tangential / aforementioned forces - to bend while carrying one against the other, TÎ "" I 9; which is accompanied by the closure of the notch if it is not wide enough or excessive mobility of the! block otherwise, causing all the disadvantages-1 nients mentioned.

| 5 With the notches according to the invention j (see. In particular FIG. 1), the sections 6 and 8 are i! will close first; as the rubber is noticeably resistant to compression, the circumferential parts of the cord delimited between the pairs of planes p - r 10 and q - s then absorb and oppose the largest (part of the tangential forces which act on the surface of the block, as a result of which the part of the cord lying between the r - s planes is less stressed.

This fact, added to the greater width of the section 7 of the notch, ensures that this part of the notch remains open below the contact surface and that the design of the tread retains all its effectiveness for the purpose of the tread. prevent the phenomenon of aguaplaning, even in con! Very difficult editions.

! 2Q In addition, the less significant stresses imposed on the part of the block which is at the level of the open section of the notch improves in an extremely substantial manner the irregular stepped wear, common in the current state of the art, in the green or 25 notch area.

At the same time, the closing of the notch sections 6 and the subsequent stiffening of the corresponding part of the bead substantially promote the behavior characteristics of the tire in service.

But, surprisingly and completely unpredictable, the drawing of the invention has shown itself capable of also solving the problem of irregular wear along the edges of the cords, which thereby acquire! a marked improvement in appearance.

I 35 Although it is not clear how this can happen, it is possible to think that on the one hand the concentration of the efforts in the part of the cord at the level of the sections 6.8 of the notch also stiffens the part of the 5 -bi 71_ * 10 cord axially external to the planes "p" and "q" and that, on the other hand, the open notch section 7 allows an axial expansion of the block, logical consequence of a compression in the circumferential direction, also discharging the edges of the bead in this direction. In tires according to the prior art, on the contrary, this possibility of expansion inside the block is absent and the aforementioned edges must curl a lot, which gives rise to serious irregularity in wear.

10 The considerations set out so far are general in nature. It is clear, however, that the practical results will vary depending on the variable values assigned to the characteristic parameters involved. Furthermore, for many of these parameters, it will be necessary to determine the range of values within which the best is achieved. trade-off between positive and negative aspects. From this angle, all the fields of variables mentioned by the Applicant in the present description are those which have made it possible to obtain a significant and indisputable improvement in the overall characteristics of the tires of the invention compared with tires similar to the prior art.

It is understood that the present description is given only by way of nonlimiting example and that 25 are also included within the scope of the invention all modifications or variants which are not expressly mentioned but that a technician in the sector can easily be deduced from the present inventive idea.

/

Claims (8)

1. A tire for vehicle wheels of which the part forming the crown, which extends axially from one sidewall to the other, presents towards the outside a band of elastomer material called tread, the radially outer surface of which is provided with a design, hollowed out in the thickness of said strip, comprising a plurality of I "circumferential zigzag grooves which delimit a plurality of circumferential zigzag cords of which one at least 1Q has a plurality of transverse notches s extending from one groove to another, characterized in that the said notches comprise three contiguous sections, two lateral near the edges of said bead and open on the corresponding groove and a median section, interposed; 15 to join the two lateral sections and having a minimum width greater, at least in the circumferential direction, than the maximum width of the abovementioned lateral sections. 2. A tire according to claim 1 characterized in that said lateral sections are rectili-20 genes and inclined relative to the circumferential direction of the tire at an angle between 50 ° and 90th. 3. A tire according to claim 2 characterized in that said lateral sections are disposed in a substantially transverse position and are offset from one another so that the line which joins their axially internal ends is inclined with respect to the circumferential direction by an angle included between 10 ° and 60 °. 4. A tire according to claim 3 characterized in that said angle is preferably 3Q between 20 ° and 40 °. 5. A tire according to claim 3 characterized in that said median section coincides with said junction line. 6. A tire according to claim 3 ca-35 characterized in that said median section is constituted by three contiguous segments, the two outer segments being inclined relative to the circumferential direction at angles between 10 ° and 60 °, the inner segment I being disposed in the equatorial plane of the tire and oriented% 12 in the circumferential direction. 7. A tire according to any one of the preceding claims, characterized in that the ratio between the projection in the transverse direction of the development of said median section and that of the entire notch is between 0.3 and 0.8. 8. Tire according to any one of the preceding claims, characterized in that the ratio between the maximum width of the lateral sections and the minimum width 11 of the middle section of the middle section is between 0.2 and 0.7. /