Tire with quadrangular studs

Abstract

The invention relates to a studded air-filled vehicle tire having a rolling direction and comprising a rubber tread with pattern blocks and grooves that separate said blocks. In said tread, there are arranged premade stud holes and in at least part of said stud holes, there are anti-slip studs, having hard cermet pieces of that have a substantially quadrangular shape with diagonal dimensions At least part of the anti-slip studs arranged in the stud holes are orientated so that one of said diagonal dimensions of the hard cermet piece is located in the rolling direction or forms an angle, not larger than the toe-out angle, with respect to the rolling direction.

Description

[0001] The invention relates to a studded air-filled vehicle tire with a rolling direction and a rubber tread with pattern blocks and grooves separating said elements, as well as in the tread anti-slip studs having an inner head and an outer head as well as total length therebetween, each of said anti-slip studs comprising a body provided with a bottom flange and with a shank element extending outwards thereof, the outer head of said anti-slip stud being provided with a polygonal contact surface.

[0002] The publication DE-23 42 743 describes an ice stud designed for winter tires of vehicles, said ice stud comprising an element made of one single material and being rectangular in cross-section. The shape of said ice stud is substantially the same along the whole length of the anti-slip element, and the only exceptions are the narrowing bevels arranged in the inner head inside the tire, the notches made in the stud shank and the short X-shape of the outer stud head. A stud designed in this fashion is by a slight force pressed deeper in the tire and tends to incline excessively in the tire tread during speed changes, for instance during braking or acceleration, as well as during changes in the direction, which results in a weak holding power and hence in a weak grip on a slippery road surface. These kinds of ice studs are easily detached from the tire tread during usage. As the only objective of the invention, the publication mentions a decrease in the wearing of the road surface.

[0003] The publication JP-58-012806 describes a completely ceramic spike for winter tires. The spike is a polygon in cross-section, and particularly the contact surface of the spike tip is polygonal, according to the drawings of the publication either a sharp-angled quadrangle or an octagon, and the spike includes a bottom flange made of the same ceramic material, with the same shape as the respective shape of the contact surface of the tip. According to the publication, this kind of design is chosen primarily because of the manufacturing technique, although it is maintained that also the spike strength and grip are improved in comparison with a spike that is round in cross-section, but otherwise has the same type of structure. In this publication, the spike material is mainly composed of aluminum oxide Al.sub.2O.sub.3, and the durability of this type of material is not sufficient in practice. This type of spike is strongly inclined when driving, particularly if the tire tread is made of a relatively soft rubber as is the trend nowadays, which means that the grip is remarkably reduced, and the spikes may even be detached. If a spike of this type is made of a sufficiently hard, impact-resistant and wear-resistant hard metal, the weight of the anti-slip element becomes remarkably heavy, which means that the wearing of the road surface is intensive, and the rubber tread of the tire is easily damaged. The design according to said publication makes it difficult to install spikes by automatic devices, and what is more, it results in a swift tearing of the tire tread in the vicinity of the spike when driving; as a consequence, the spikes fall off.

[0004] The publication US-2002/0050312 discloses a studded winter tire. According to the publication, the stud has an elongate bottom part with a shape other than round, and said shape has a lengthwise axis and an elongate top part other than round, said shape also having a lengthwise axis, and the lengthwise axes of the bottom part and the top part are mutually reversed, so that the lengthwise axis of the top part and the lengthwise axis of the bottom part together close an angle other than zero, which advantageously is within the range 65.degree.-115.degree.. The shape of the bottom part and top part of the stud is nearly an ellipse, or an oblong shape resembling an ellipse. According to said publication, this type of studs are shot in the tire tread in a non-vulcanized state by injection tubes, the cross-sectional shape of the tubes corresponding to the shape of the studs, so that in the middle of the tire rolling surface, the lengthwise axes of the top parts of the studs are in a position parallel to the tire axis, and the lengthwise axes of the bottom parts of the studs are arranged in the circumferential direction of the tire, whereas at the edges of the tire rolling surface, the lengthwise axes of the top parts of the studs advantageously form an angle of 45.degree. with respect to the circumferential direction of the tire, and the lengthwise axes of the bottom parts of the studs advantageously form an angle of 25.degree. with respect to the circumferential direction of the tire. When the studded tire disclosed in the publication is made ready, it may function relatively well, but the manufacturing is problematic. Studs designed in this way cannot be reliably turned in the right position in automatic installation machines, and the studs may end upside down in the injection tubes. Moreover, studs designed in this way also easily stick to some part of the automatic installation machines. Further, the vulcanization of tires that are already provided with studs is extremely difficult and expensive and results in a large number of discarded tires in the production process.

[0005] The publication WO-99/56976 discloses an anti-skid spike with a hard cermet piece that has a geometric cross-sectional shape, a limited number of symmetry levels and a changing cross-sectional area from the outer head to the inner head, particularly so that the hard cermet piece expands towards the bottom flange of the spike. The publication mentions several different cross-sectional shapes of the hard cermet piece, such as a triangle, a rectangle, an ellipse, a semi rectangle, a semicircle and a quadrangle, as well as an octagon, all these particularly equal in significance. As regards the shape of the bottom flange of the anti-skid spike, it is only said that it may be asymmetrical with respect to one lengthwise plane, having a length and a width that are mutually different. According to the drawings attached to said publication, the bottom flange includes two opposite straight sides, either in parallel or at a sharp angle with respect to each other, and neither of the shapes of said sides are quadrangles, which deviates from the definition of the present invention. In particular, the publication recommends the use of a rib in the lengthwise direction of the spike, but without the top bowl. Further, in the drawings it is seen that the longer dimension of the bottom flange can be positioned either in the circumferential direction of the tire, in which case it is according to the specification suited to urban driving, or as perpendicular to the circumferential direction, in which case it is according to the specification suited to driving on country roads. It is also mentioned that intermediate shapes between these two are possible, but the specification does not offer a more detailed description, only a general remark.

[0006] The main objective of the present invention is to realize an air-filled vehicle tire provided with anti-slip studs in order to achieve an excellent grip on a slippery road surface, which studs should not have a tendency to fall off even during intensive acceleration and/or braking. A second objective of the invention is to realize a described tire provided with anti-slip studs, which tire would have an optimal wear resistance. A third objective of the invention is to realize a described tire provided with anti-slip studs, with a studding that could be made by automatic studding machines in a process that is as free of errors as possible. A fourth objective of the invention is to realize a described tire provided with stud holes that could be made to be ready for use as such, among others by conventional and effective production methods, but which tire could thereafter be provided for example with studs that in cross-section are other than round, so that the studs could be orientated according to the needs of the situation, i.e. that certain directions of the cross-sectional shape of the studs could be in certain predetermined positions with respect to the circumferential direction or axial direction of the tire.

[0007] The above described problems are solved and the above defined objectives realized by means of a vehicle tire according to the invention, provided with anti-slip studs, characterized by what is defined in the characterizing part of claim 1.

[0008] It has now been surprisingly found out that by replacing the traditionally cylindrical hard cermet tip of an anti-slip stud by a hard cermet piece that is quadrangular in cross-section, and by replacing the traditionally round bottom flange of the stud by a quadrangular bottom flange, and by arranging this kind of studs in the vehicle tire tread so that one diagonal of the hard cermet piece that is quadrangular in cross-section is substantially arranged in the circumferential direction of the tire; the grip of the studded tire is clearly improved in comparison with tires that are provided with conventional studs having a round hard cermet piece, because the stud tips in that case make a wider adhesion groove in an icy surface or the like. However, the weight of the anti-slip studs is not increased in comparison with prior art studs. Likewise it has surprisingly been discovered that by replacing the traditionally round bottom flange of the stud body by a bottom flange that is quadrangular in the direction perpendicular to the stud length, the studs are easily and without difficulty adjusted in the tire stud holes by automatic installation machines provided with four jaw fingers or even with only three jaw fingers, and at the same time in a desired orientation with respect to the circumferential direction of the tire or with the axial direction of the tire, for instance in the above described diagonal circumferential direction. As additional advantages, there are achieved the following: the inclination of the anti-slip studs is reduced under the holding forces, because the flange, i.e. the diagonal, is longer in the direction of a possible inclination, and the turning of the anti-slip studs is reduced, as well as the wearing of the tire rubber. Further, by using a relatively wide top bowl in the stud shank, which top bowl is preferably separated from the bottom flange by a neck portion, the inclination of the stud is further reduced.

[0009] The invention is described in more detail below with reference to the appended drawings.

[0010] FIGS. 1A and 3A illustrate first embodiments of the orientations of anti-slip studs according to the invention, having a quadrangular hard cermet piece and bottom flange in the vicinity of the first and respectively the second tire shoulder, at points I and III of FIG. 4, but in a larger scale. Here the first embodiments of the orientations are realized by the second installation method according to the invention.

[0011] FIGS. 1B and 3B illustrate first embodiments of the orientations of anti-slip studs according to the invention, having a quadrangular hard cermet piece and bottom flange in the vicinity of the first and respectively the second tire shoulder, at points I and III of FIG. 4, but in a larger scale. Here the first embodiments of the orientations are realized by using the first installation method of the invention.

[0012] FIG. 2 illustrates a first embodiment of the orientations of anti-slip studs according to the invention, having a quadrangular hard cermet piece and bottom flange, nearer to the center regions of the tire width than in FIGS. 1 and 2, at point II of FIG. 4, but in a larger scale. As an alternative, the drawing illustrates a second embodiment of the orientations of anti-slip studs according to the invention, having a quadrangular hard cermet piece and bottom flange, in various regions of the tire width, at points I and II of FIG. 4, but in a larger scale.

[0013] FIG. 4 is a general illustration of the tread of an air-filled vehicle tire, showing the positions of the anti-slip studs as seen from the outside, corresponding to the direction V of FIGS. 5, 13A and 12A-12B.

[0014] FIG. 5 illustrates a first embodiment of an anti-slip stud to be used in a studded tire according to the invention, provided with a quadrangular hard cermet piece and bottom flange, seen in an axonometric view.

[0015] FIGS. 6-10 illustrate a second, third, fourth, fifth and sixth embodiment of an anti-slip stud to be used in a studded tire according to the invention, provided with a quadrangular hard cermet piece and bottom flange, seen in the lengthwise direction of the anti-slip stud, in the direction IV of FIG. 5.

[0016] FIGS. 11A and 11B illustrate an oval embodiment of the stud hole arranged in the studded tire according to the invention, as well as the position of the oval with respect to the circumferential direction of the tire: on one hand in the vicinity of the tire shoulders, at points I and III of FIG. 4; and on the other hand respectively nearer to the center regions of the tire width, at points II of FIG. 4, in the same view as in FIG. 4, but in a larger scale.

[0017] FIGS. 12A and 12B illustrate longitudinal cross-sections of the stud hole of FIGS. 11A and 11B, having an oval bottom part and a round top part, seen along the planes VI-VI of FIGS. 11A and 11B and respectively VII-VII.

[0018] FIGS. 13A and 13B illustrate a round embodiment of the stud hole arranged in the studded tire according to the invention, at points I, II and III of FIG. 4, seen in a longitudinal cross-section along the plane IV-IV of FIG. 4, and respectively in the same view as in FIG. 4, but in a larger scale, in the direction V of FIG. 13A.

[0019] FIGS. 14 and 15 illustrate two other embodiments of the oval bottom shape according to the invention, arranged in the studded tire according to the invention, and two other embodiments of the top part, seen in the same view as in FIG. 4, but in a larger scale, corresponding to the direction V of FIGS. 12A-12.

[0020] FIG. 4 illustrates a typical tread pattern of a studded, air filled vehicle tire. This kind of an air-filled vehicle tire comprises, among others, a tire housing (not illustrated), a tread 20 made of rubber and in the tread, stud holes 18 created during the vulcanization of the tire, and in at least part of said stud holes, anti-slip studs 1. As is well known, in the tread 20 that also is called the wear surface, there are further made grooves 16 and pattern blocks 17, in which the anti-slip studs are typically attached, as well as possible fine grooves in the pattern blocks, but because the invention does not relate to the tread as such, the design thereof is not explained in more detail. For an optimal holding capacity of the tire, the hardness of the rubber quality in the tread 20 is relatively low, advantageously of the order 55-60 Shore A. The studded tire illustrated in FIG. 4 has a given rolling direction P, but anti-slip studs according to the invention can also be arranged in tires with a rolling direction that is either one of the opposite circumferential directions, as shall be explained in more detail below. The anti-slip studs 1 arranged in the tread have an inner head 14, i.e. a head that points towards the axial line of the tire and is set deeper in the tread 20, and an outer head 15, i.e. a head that is set in the region of the outer surface of the tire tread or in the vicinity of said region, as well as a total length L1 therebetween. Each of the anti-slip studs comprises a body 3 provided with a bottom flange 4 and a shank element 5 pointing outwards of said body.

[0021] The premade stud holes 18 arranged in the tread 20 for the anti-slip studs can, according to a preferred embodiment of the invention, be substantially circular in cross-section, in which case typically both the bottom part 25 of the stud hole, in which bottom part the bottom flange 4 of the anti-slip stud is set, is round, and also the top part 26 of the stud hole, in which the top bowl 5 of the anti-slip stud is set, is round as is seen in FIGS. 1A-3B and 13A-13B. According to the invention, said premade stud holes 18 of the tread 20 preferably have a bottom part 25 that is oval or elongate in cross-section, said oval shape having a larger transversal dimension W4 and a smaller transversal dimension W3 in directions that are perpendicular to the depthwise direction of the hole, which in turn corresponds to the direction of the stud total length L1. In this case, particularly the larger transversal dimension W4 of the oval bottom parts 25 of the stud holes 18 arranged in the tread for the anti-slip studs 1 belonging to the first group J1.sub.A and/or J1.sub.B is located substantially in parallel with the tire rolling direction P, as is shown in FIG. 11A. Now also, in a preferred embodiment, the larger transversal dimension W4 of the oval bottom parts 25 of the stud holes 18 arranged in the tread for the anti-slip studs 1 belonging to the second group J2 is located as substantially perpendicular to the tire rolling direction P, as is shown in FIG. 11B. In other words, in the vicinity of the tire shoulders, the short transversal dimension W3 of the oval bottom part of the stud holes is substantially parallel with the axial line of the tire, and the long transversal dimension W4 is thus in a direction perpendicular to the rolling direction P, while in the tire regions located in the center parts of the tire width, the short transversal dimension W3 of the oval bottom part of the stud holes is substantially parallel with the rolling direction P, and the long transversal dimension W4 is parallel with the axial line of the tire. The ratio of the longer transversal dimension W4 of the bottom part 25 to the shorter transversal dimension W3, i.e. W4:W3 is at least 1.05 but not more than 2. Said premade stud holes 18 arranged in the tread have a top part 26, with a cross-sectional shape that is either round or other than round. Thus the shape of the top part 26 is relatively insignificant. The cross-sectional area A.sub.H of said stud holes is smaller than the cross-sectional area of the stud holes, i.e. more precisely, the cross-sectional area at the bottom flange or in the region of the bottom flange is smaller than the cross-sectional area A4 of the bottom flange 4 of the anti-slip studs, and the cross-sectional area at the top bowl or in the region of the top bowl is smaller than the cross-sectional area A6 of the top bowl 6 of the anti-slip studs, which means that the anti-slip studs 1 are set tightly in their holes 18.

[0022] The body 3 of the anti-slip studs also comprises a top bowl 6 that has transversal dimensions D5, D6 perpendicular to said length of the anti-slip stud, and a top bowl cross-sectional area A6 that is perpendicular to the length L1. Between the top bowl and the bottom flange, there is arranged the neck portion 7 that has a cross-sectional area A7 perpendicular to the length L1 of the anti-slip stud, said cross-sectional areas being substantially smaller than the cross-sectional areas A6 of the top bowl and the cross-sectional areas A4 of the bottom flange. Now the neck portion 7 clearly separates the top bowl 6 from the bottom flange 4. The top bowl 6 may have a round shape in perpendicular to said length of the anti-slip stud, in which case said transversal dimensions D5 and D6 are equally large, or an oblong shape, in which case said transversal dimensions D5 and D6 are unequal, or a polygonal shape, in which case said transversal dimensions D5 and D6 are equally large or not equally large.

[0023] According to the invention, each anti-slip stud 1 comprises a hard cermet piece 2 made of a different material than said body, which is placed inside the body 3 and protrudes out of its outer head 15, said hard cermet piece also having an substantially quadrangular shape in the direction perpendicular to the stud length L1. The length L1 of the studs for passenger car tires is typically of the order 10 mm-11 mm, for delivery vans typically of the order 11 mm-13 mm, for trucks typically of the order 14 mm-17 mm and for heavy machinery, such as loaders, road machines etc., typically of the order 17 mm-20 mm. The rubber surrounding the stud body 3 in the tread 20 supports the stud and holds it in the right position, i.e. substantially perpendicular to the tread rolling surface. The quadrangular hard cermet piece has diagonal dimensions D3 and D4 in a direction perpendicular to the stud length L1. At least part of the anti-slip studs 1 inserted in the premade stud holes 18 are orientated so that one of said diagonal dimensions D3 or D4 of the hard cermet piece is located in the tire rolling direction P, as is shown in FIG. 2, or forms an angle that is not larger than the toe-out angle K with said rolling direction P, as is shown in FIGS. 1A-1B and 3A-3B. It should be understood that the studs 1 can, according to the needs of the situation, be installed in either all stud holes 20 arranged in the tread 20, or only in part of said stud holes 18. Likewise, it should be understood that all anti-slip studs 1 installed in the tread 20 are orientated either so that the diagonal dimensions D3, D4 of the hard cermet pieces are located in said rolling direction P, or so that they form, with respect to said direction, an angle that is not larger than the toe-out angle K, or alternatively a part of the installed anti-slip studs are orientated in some other way. According to the invention, said toe-out angle K is smaller than 30.degree., but typically not larger than 20.degree. and advantageously not larger than 15.degree., although in many cases it may be advantageous to use toe-out angles K that are not larger than 10.degree..

[0024] The hard cermet piece 2 is arranged inside the stud body 3, because it has a piece length L2 that is smaller than the total length L1 of the anti-slip stud, and because its cross-sectional area A2 is smaller than the cross-sectional area A7 of the stud neck portion 7, and substantially smaller than the cross-sectional areas A6 and respectively A4 of the stud top bowl 6 and the bottom flange 4. The hard cermet piece is composed of any sufficiently hard and appropriate known or new, generally sintered metal, such as metal carbides, metal nitrides, metal oxides etc. However, advantageously the hard cermet piece 2 is made compounds of known, mainly sintered carbides that are typically, but not necessarily, bound by a metal matrix. As for the stud body 3, it may be made in a known or new way of some suitable metal alloy, such as steel or aluminum, or it may be made of a suitable plastic or composite material. The invention neither relates to the material of the hard cermet piece as such, nor to the material of the body as such, and hence they are not dealt with in more detail here; the materials enlisted above shall be understood as examples only. The hard cermet piece 2 can be attached to the body 3 by a solder joint, by adhesive, by a cast adhesion or by a conical pressure joint depending, among others, on the body material.

[0025] The side surfaces 10a, 10b, 10c, 10d of the quadrangular hard cermet piece can be convex, as is shown in FIG. 10, or concave, as is shown in FIG. 8, in which cases the side surfaces have a curvature R4, or they are straight, as in FIGS. 1A-3B, 5-7 and 9. The above mentioned diagonal dimensions D3, D4 of the hard cermet piece 2 are typically equally large or nearly equally large as in FIGS. 1A-3B, 5 and 7-10, in which case the shape of the quadrangular hard cermet piece is mainly a square or a rectangle, but the diagonal dimensions D3, D4 may also be mutually different, as is shown in FIG. 6, so that the shape of the quadrangular hard cermet piece is mainly a lozenge or a parallelepiped. Said shape definitions--square, rectangle, lozenge and parallelepiped--are also applied to shapes provided with sides 10a, 10b, 10c, 10d having curvature R4, as long as the side curvature or radius of curvature R4 is substantially larger than the radius of the circle drawn via the edges 11a, 11b, 11c, 11d of the hard cermet piece. Thus both of said diagonal dimensions D3 and D4, passing from an edge of the hard cermet piece to the opposite edge, are larger than all other such connecting lines between the opposite sides 10a and 10c or 10b and 10d of the hard cermet piece that pass via the intersection of the diagonal dimensions D3, D4. The edges 11a, 11b, 11c, 11d between the side surfaces of the quadrangular hard cermet piece have a rounding R3 that is substantially smaller than said curvature R4, and typically said rounding R3 is at least 0.1 mm but no more than 0.2 mm, said rounding preventing the hard cermet piece from splitting. Moreover, the side surfaces 10a, 10b, 10c, 10d of the quadrangular hard cermet piece have widths W1, W2 with a mutual difference that is at the most the ratio 1.5, in other words W1:W2.ltoreq.1.5. Typically in the anti-slip studs 1 of the tires of passenger cars and delivery vans, the cross-sectional area A2 of the hard cermet piece is within the range 4.5 mm.sup.2-6 mm.sup.2, in which case the widths W1, W2 are respectively of the order 2.1 mm-2.5 mm, and the diagonals are of the order 2.9 mm-3.6 mm in a quadrangular or corresponding shape, and a rectangular shape has extreme values that somewhat deviate from these. In the tires of trucks, the cross-sectional area A2 of the hard cermet piece of the anti-slip studs 1 is typically within the range 7 mm.sup.2-9 mm.sup.2, and in heavy machinery typically within the range 9 mm.sup.2-13 mm.sup.2. By applying this shape and orientation of the hard cermet piece in the tire according to the invention, there is achieved an excellent holding capacity for, the studded tire in the desired way.

[0026] Moreover, according to the invention the bottom flange 4 of the anti-slip stud has a substantially quadrangular shape in a direction perpendicular to said length, and diagonal dimensions D1 and D2 as well as a cross-sectional area A4 in a direction perpendicular to the stud length L1. Said diagonal dimensions D1, D2 of the bottom flange 4 can be equally large, as is shown in FIGS. 1A-3B and 5-9, or they can be different in length, as is shown in FIG. 10. Thus the bottom flange is mainly and for the major features quadrangular or a lozenge, but it may also be mainly a rectangle. The diagonal dimensions D1, D2 of the bottom flange 4 are either substantially parallel with the diagonal dimensions D3, D4 of the hard cermet piece that is separate from the bottom flange, in a way shown in FIGS, 1A, 2, 3A, 5-6 and 8, or they form a toe-out angle K with respect to the diagonal dimensions D3, D4 of the hard cermet piece, as is seen in FIGS. 1B, 3B, 7 and 9-10. The bottom flange sides 9a, 9b, 9c, 9d can be convex, as is shown in FIGS. 5, 6 and 10, or concave, as is shown in FIG. 9, in which cases the sides have a curvature R2. As an alternative, the bottom flange sides 9a, 9b, 9c, 9d can be straight in a way illustrated in FIGS. 1A-3B and 7-8. The above given shape definitions square, rectangle and lozenge also apply to shapes provided with sides 9a, 9b, 9c, 9d that have a curvature R2, as long as the curvature or radius of curvature R2 of the sides is substantially larger than the radius of the circle drawn via the bottom flange edges 8a, 8b, 8c, 8d. Thus both of the above mentioned diagonal dimensions D1 and D2, passing from the bottom flange edge to the opposite edge, are larger than all other such connecting lines of the opposite sides 9a and 9c or 9b and 9d of the bottom flange that pass via the intersection of the diagonal dimensions D1, D2. In addition, the edges 8a, 8b, 8c, 8d left between said sides of the bottom flange have a rounding R1 that is substantially smaller than said curvature R2. By means of this shape according to the invention of the bottom flange, the anti-slip studs are orientated in a desired fashion in the stud holes 18 arranged in the tire tread, and there is thus obtained a desired and excellent holding capacity for the studded tire.

[0027] According to the invention, the earlier described location of the diagonal dimensions D3, D4 of the hard cermet pieces in the rolling direction P or at an angle with respect to said rolling direction, which angle is not larger than the toe-out angle K, is arranged so that one of the diagonal dimensions D1 or D2 of the bottom flange is located in said rolling direction P or forms said toe-out angle K with respect to the rolling direction P. First of all it is maintained that in principle, the number of different orientations in the tire may be nearly infinite, which is understandable when there is taken into account the toe-out angle K=0.degree., i.e. D3 or D4 is parallel with the rolling direction P, as well as other possible toe-out angles that are used simultaneously, for example K=1.degree., 2.degree., 3.degree., 4.degree. . . . etc. These different orientations of the anti-slip stud with respect to the rolling direction can be realized in many different ways by using a quadrangular shape of the anti-slip stud bottom flange 4 in adjusting the stud position. According to a first embodiment of the installation method, all anti-slip studs used in a given tire are--at least as regards the mutual directions or positions of the diagonal dimensions D3, D4 of the hard cermet piece and the diagonal dimensions D1, D2 of the bottom flange 4--of the same type, preferably for example of a type where at least one of the diagonal dimensions D3 or D4 of the hard cermet piece is parallel with at least one diagonal dimension D1 or D2 of the bottom flange, typically so that both of the diagonal dimensions D3 and D4 of the hard cermet piece are parallel with the corresponding diagonal dimensions D1 and D2 of the bottom flange. In this case the control elements of the installation machine--not illustrated in the drawings--are always arranged in such a position with respect to the tire tread under operation that the studs 1 are set in a desired orientation. This installation method is apparent from FIGS. 1A, 2, 3A; in the case of FIG. 2, the mutually parallel diagonals D3 and D1 of the studs are located in the tire rolling direction P, and in the case of FIGS. 1A and 3A, both of said mutually parallel diagonals D3 and D1 are turned to opposite toe-out angles K with respect to the rolling direction P. It should be understood that these positions can be achieved by turning the jaws of the installation machine in three different positions, wherebetween there is formed said toe-out angle. According to a second embodiment of the installation method, the anti-slip studs used in a given tire are at least of two different types with respect to the mutual directions or positions of the diagonal dimensions D3, D4 of the hard cermet piece, and the diagonal dimensions D1, D2 of the bottom flange, of which two types in at least one type the diagonal dimension D3 and/or D4 of the hard cermet piece forms a toe-out angle K with a predetermined size with the diagonal dimension D1 and/or D2 of the bottom flange. In this case the control elements of the installation machine can be arranged in a standard position, presupposing that in said anti-slip studs of different types, the angle differences between the diagonals of the hard cermet piece and the diagonals of the bottom flange correspond to the desired toe-out angles K in a finished studded tire, in which case in the various regions of the tire tread, there is in each case obtained the desired orientation of the hard cermet piece by changing the type of the studs to be inserted. This method of installation can be understood from FIGS. 1B and 3B; the studding is carried out for instance by using studs according to FIG. 5, as is shown in FIG. 2, and the toe-out angle K is formed by means of studs illustrated in FIGS. 1B and 3B and installed according to FIGS. 1B and 3B, in which studs the diagonal dimensions D1 and/or D2 of the bottom flange are set in a way illustrated in FIG. 2 in the rolling direction P, but where the diagonals D3 and/or D4 of the hard cermet piece are turned to opposite toe-out angles K with respect to the rolling direction P.

[0028] In the tread 20 of a vehicle tire, the anti-slip studs 1 may be arranged in one position only, in which case all studs are arranged in a position illustrated in FIG. 2, where one of the diagonals D3 or D4 of the hard cermet piece 2 is substantially in parallel with the rolling direction P. However, it is more advantageous to arrange the anti-slip studs 1 in the tire tread 20 in various positions, generally in at least two different positions, but advantageously in three or more positions in the way described in FIGS. 1A-4. Thus the anti-slip studs typically constitute at least two first groups J1.sub.A and J1.sub.B nearer to the tire shoulders, and at least one second group J2 nearer to the center regions of the tire, so that in the width direction of the tread, the studded tire is made symmetrical, when so desired. It also is possible to use only one first group J1.sub.A or J1.sub.B nearer to one of the tire shoulders, and at least one second group J2 nearer to the center regions of the tire and to the opposite shoulder, so that in the width direction of the tread, the studded tire is made asymmetrical, when so desired. It is known in the prior art that the tread pattern proper of the tread 20 may, independent of the studding, be either symmetrical or asymmetrical. According to the invention, in the first groups J1.sub.A and J1.sub.B, one set of the diagonal dimensions D3 or D4 the hard cermet pieces of the anti-slip studs are located at said toe-out angle K with respect to the rolling direction P, as can bee seen from FIGS. 1A-1B, 3A-3B and 4, and in the second group J2, one set of the diagonal dimensions D3 or D4 of the hard cermet pieces of the anti-slip studs are located substantially in parallel with the rolling direction P, as is seen from FIGS. 2 and 4. In any case, the toe-out angles are in the second group J2 smaller than in the first group or groups J1.sub.A, J1.sub.B. In the first groups J1.sub.A, J1.sub.B, the toe-out angle K is thus smaller than the earlier mentioned 30.degree., but typically not larger than 20.degree. and preferably not larger than 15.degree.. There are, however, situations where there are applied toe-out angles K that are not larger than 10.degree.. In the second groups, the toe-out angles K are smaller than 15.degree. and typically smaller than 10.degree., advantageously approaching the value 0.degree. of the toe-out angle. In case in between said first and second groups the tire includes third groups--not illustrated in the drawings--that can naturally be interlaced with one or both of the above described groups, there are advantageously used intermediate toe-out angles K, for instance angles within the range of 10.degree.-15.degree.. In the first groups or group, the toe-out angles K can be pointed in any of the two directions, i.e. outwardly from the center line 21 of the tread 20, or inwardly in a case where the tread pattern represents a type that can in the vehicle be arranged to rotate in any direction, i.e. that can have a rolling direction that is either one of the two opposite circumferential directions. On the other hand, in a case where the tread pattern represents a type that requires a given, predetermined rolling direction, i.e. the tire must be arranged in the vehicle so that the rolling direction is always the same when driving forward, there can be applied an even more effective method of forming the toe-out angle. In that case in the first groups J1.sub.A and J1.sub.B, the toe-out angles K of one set of the diagonal dimensions D3 or D4 of the hard cermet pieces are pointed, when seen in the rolling direction P, outwardly from the center line 21 of the width of the tread 20. In FIGS. 1A-1B and 3A-3B, the rolling direction P points downwards, and now the toe-out angles K opening in the rolling direction, which toe-out angles thus are angles between the diagonal D3 or D4 of the hard cermet piece and the rolling direction, are always located outside the rolling-direction line 22 proceeding via the center line 23 of the anti-slip stud 1, in the group J1.sub.A in one direction and in the group J1.sub.B in the opposite direction. There may be several of such groups, for example five, in which case the studs 1 belonging to the group that is located nearest to the shoulders can have the widest toe-out angle, the middle group does not have any toe-out angle at all, exactly as was explained above, and the studs 1 belonging to the group therebetween have a toe-out angle that is smaller than with the studs located near the shoulders. It also is possible to arrange such additional groups of the anti-slip studs 1 where the toe-out angles of the studs are pointed in different directions than what was explained above. Said first stud groups J1.sub.A, J1.sub.B and second stud group J2, i.e. those regions of the tire tread that are provided with studs fulfilling said conditions, can be mutually fully detached, or the regions can be exactly bordered by each other. In practice it should be most feasible that for instance the first groups J1.sub.A, J1.sub.B were interlaced with respect to the second groups J2, when these groups are observed in the way indicated in FIG. 4, as zones in the width direction, bordered in the width direction by the outermost studs 1 that fulfill the toe-out condition of the studs of said group, i.e. the toe-out angle K has either a given, predetermined value, or the toe-out angle K is within a given, predetermined angle range.

Claims

1-23. (cancelled)

24. A studded air-filled vehicle tire, having a rolling direction, and comprising a rubber tread with pattern blocks, grooves separating said blocks and premade stud holes in said tread, said tire being provided with anti-slip studs with an inner head and an outer head, and a total length therebetween, said studs being inserted in at least some of said stud holes, said studs comprising: a body with a bottom flange and a shank, said bottom flange having a substantially quadrangular shape with diagonal dimensions perpendicular to said length, and a hard cermet piece of a different material than said body, and protruding out of said outer head, said hard cermet piece having a substantially quadrangular shape with diagonal dimensions perpendicular to said length; and said diagonal dimensions of the bottom flange being substantially parallel to the diagonal dimensions of the hard cermet piece separate from the bottom flange or forming a toe-out angle with respect to the diagonal dimensions of the hard cermet piece; wherein at least some of the anti-slip studs inserted in the stud holes are orientated so that one of said diagonal dimensions of the hard cermet piece is in said rolling direction, or from a toe-out angle that is smaller than 30, .degree.with respect to the rolling direction.

25. A studded tire according to claim 24, wherein said diagonal dimensions of the bottom flange are equally large.

26. A studded tire according to claim 24, wherein said diagonal dimensions of the bottom flange are different from each other.

27. A studded tire according to claim 24, wherein said inserted anti-slip studs have said diagonal dimensions of the bottom flange in said rolling direction, or at said toe-out angle with respect to the rolling direction.

28. A studded tire according to claim 24, wherein said inserted anti-slip studs comprise at least one first group nearer to the tire shoulders, and at least one second group nearer to the tire center regions, wherein the studs in said first group have said diagonal dimensions of the hard cermet pieces located at said toe-out angle, and the studs in the second group have said diagonal dimensions of the hard cermet pieces substantially parallel with the rolling direction.

29. A studded tire according to claim 28, wherein said toe-out angles of the diagonal dimensions of the hard cermet pieces in said first group are pointed outwardly from the center line of the width of the tread, when observed in said rolling direction.

30. A studded tire according to claim 24, wherein said toe-out angle is not larger than 20.degree..

31. A studded tire according to claim 24, wherein said toe-out angle is not larger than 15.degree..

32. A studded tire according to claim 28, wherein said at least one first group and said at least one second group are arranged in an interlacing fashion.

33. A studded tire according to claim 24, wherein the body of the anti-slip studs comprises a top bowl having transverse dimensions, and a neck portion between said top bowl and said bottom flange, the neck portion having a cross-sectional area that is substantially smaller than the cross-sectional areas of the top bowl and the bottom flange.

34. A studded tire according to claim 24, wherein the sides of the bottom flange are straight, convex or concave, and wherein if the sides of the bottom flange are convex or concave, said sides have a first curvature larger than a rounding formed between said sides.

35. A studded tire according to claim 33, wherein the top bowl comprises a round shape in the direction perpendicular to said length of the anti-slip stud, wherein said transverse dimensions are equally large.

36. A studded tire according to claim 33, wherein the top bowl comprises an oblong shape in the direction perpendicular to said length of the anti-slip stud, wherein said transverse dimensions are different from each other.

37. A studded tire according to claim 33, wherein the top bowl comprises a polygonal shape in the direction perpendicular to said length of the anti-slip stud, wherein said transverse dimensions are different from each other.

38. A studded tire according to claim 24, wherein the side surfaces of the quadrangular hard cermet piece are straight, convex or concave, and wherein if the side surfaces of the quadrangular hard cermet piece are convex or concave, said side surfaces have a second curvature.

39. A studded tire according to claim 24, wherein said diagonal dimensions of the hard cermet piece are substantially equally large.

40. A studded tire according to claim 38, wherein edges between the side surfaces of the quadrangular hard cermet piece have a rounding that is substantially smaller than said second curvature.

41. A studded tire according to claim 40, wherein said rounding is between about 0.1 mm and about 0.2 mm.

42. A studded tire according to claim 38, wherein the side surfaces of the quadrangular hard cermet piece have widths that differ from each other no more than by the ratio 1.5.

43. A studded tire according to claim 24, wherein said hard cermet piece has a piece length that is smaller than the total length of the anti-slip stud.

44. A studded tire according to claim 24, wherein the body of the anti-slip stud is made of plastic or metal, and the hard cermet piece is attached to the body by a solder joint, an adhesive, a cast adhesion of the body, or a conical pressure joint.

45. A studded tire according to claim 24, wherein substantially all of the anti-slip studs installed in the tread are orientated so that said diagonal dimensions of the hard cermet pieces are located in said rolling direction or form with said rolling direction an angle that is not larger than the toe-out angle.

46. A studded tire according to claim 24, wherein the material of the hard cermet pieces is sintered carbide.

47. A studded tire according to claim 24, wherein said premade stud holes in the tread are substantially round in cross-section.

48. A studded tire according to claim 24, wherein said premade stud holes in the tread have a bottom part that is an oval in cross-section, the oval having a larger transverse dimension and a smaller transverse dimension.

49. A studded tire according to claim 48, wherein the larger transversal dimension of the oval is intended for the anti-slip studs belonging to said first group, the larger transversal dimension being located substantially in the tire rolling direction.

50. A studded tire according to claim 48, wherein the larger transversal dimension of the oval is intended for the anti-slip studs belonging to said second group, the larger transversal dimension being located in an substantially perpendicular direction to the tire rolling direction.

51. A studded tire according to claim 48, wherein the ratio of the larger transversal dimension to the smaller transversal dimension is at least about 1.05 but not greater than about 2.

52. A studded tire according to claim 48, wherein said premade stud holes in the tread have a top part with a cross-sectional shape that is round.

53. A studded tire according to claim 48, wherein said premade stud holes in the tread have a top part with a cross-sectional shape that is not round.

54. A studded tire according to claim 47, wherein a cross-sectional area of the stud holes in a bottom flange area is smaller than a cross-sectional area of said bottom flange.

55. A studded tire according to claim 48, wherein a cross-sectional area of the stud holes in the bottom flange area is smaller than a cross-sectional area of said bottom flange.

56. A studded tire according to claim 47, wherein a cross-sectional area of the stud holes in a top bowl area is smaller than a cross-sectional area of a top bowl of the studs.

57. A studded tire according to claim 48, wherein a cross-sectional area of the stud holes in a top bowl area is smaller than a cross-sectional area of a top bowl of the studs.