Note: Descriptions are shown in the official language in which they were submitted.
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Description
Tire stud for anchoring in a tire stud hole of a tread of a pneumatic vehicle
tire
The invention relates to a tire stud for anchoring in a tire stud hole of a
tread of a pneumatic
vehicle tire, having a non-metallic tire stud body, and having a tire stud pin
composed of
hard metal anchored in the tire stud body, which tire stud pin projects with
one end portion
thereof beyond the tire stud body and is anchored with its second end portion
within the tire
stud body in a tire stud body part composed of a first, non-metallic material,
wherein that
portion of the tire stud pin which extends within the tire stud body between
the end portions
is held in at least one further tire stud body part composed of a second, non-
metallic
material.
Tire studs are generally held in the tire stud holes of the tread of pneumatic
vehicle tires by
a combination of positive engagement and clamping. Conventional tire studs
consist of a
tire stud body composed of aluminum or steel, in which is held the tire stud
pin, which
projects beyond the tread surface and is composed of hard metal.
It is customary to use gritting material on winter roads to increase traffic
safety. In recent
years, the use of sand has been reduced in favor of grit since sand tends to
be ground up by
tires into dust or fine dust, which should be reduced or avoided to protect
the health of the
population. However, the use of grit leads to increased wear on the
conventional tire studs
used in pneumatic vehicle tires, especially if the tire stud body thereof is
composed of
aluminum.
There has therefore already been a proposal to use tire studs with tire stud
bodies composed
of vulcanized rubber or of plastic. DE 2 202 373 Al discloses a plastic tire
stud which is
composed of a hard metal pin and a plastic casing, wherein the hard metal pin
is embedded
in the plastic stem by means of ultrasonic vibrations. In the case of other
known production
methods for plastic tire studs, the hard metal pin is encapsulated with a
thermoplastic.
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WO 2017/0888995 Al discloses tire studs in which the tire stud pin and/or the
plastic or
aluminum base flange are/is at least partially embedded into a vulcanized
rubber jacket or
into vulcanized rubber material. The particular advantages of these
embodiments consist in
the fundamental material properties of the vulcanized rubber body. Its low
density of
approximately 1 g/cm3 makes vulcanized rubber particularly light in comparison
with
aluminum and steel. Replacing aluminum and steel with vulcanized rubber as a
body
material therefore leads to a reduction in the tire stud weight, which has a
particularly
positive effect on road wear and the formation of fine dust. Road wear is
determined
principally by the impact energy of the tire stud. The flexible material
properties of
vulcanized rubber have even more advantages. On the one hand, the flexible
body material
damps impacts, with the result that smaller forces act on stones in the road
surface or on
particles of gritting material. Thus, road wear and the formation of fine dust
are also
reduced as a consequence. Moreover, tire stud bodies composed of vulcanized
rubber are
superior to those composed of aluminum or steel in terms of abrasion behavior
since they
have completely different wear behavior. If the tire rolls over stones in the
road surface and,
in particular, grit from gritting material in the vicinity of a conventional
tire stud, the profile
in the tread is deformed to a great extent and gives way to the side. The
fixed, rigid tire stud
cannot follow these movements of giving way. As a result, a gap is formed
between the tire
stud and the vulcanized rubber, exposing the upper and lateral surfaces of the
tire stud body
to the abrasive action of stones. Since stones in the road surface and grit
are generally
harder than aluminum and even steel, a tire stud body composed of aluminum or
steel is
abraded heavily, resulting in a reduction in the tire stud body height and the
diameter of the
tire stud body. This leads to the tire stud hole edge regions being subject to
abrasion with a
cutting effect. They erode, as a result of which the gap between the tire stud
and the
surrounding vulcanized rubber matrix is enlarged. This favors the penetration
of sand and
smaller stones, further accelerating tire stud body abrasion. As a
consequence, the lateral
retaining forces on the tire stud are reduced, leading to a reduction in the
winter properties
due to severe tilting and, in the worst case, to loss of the tire stud.
The invention is based on the object, in the case of a tire stud of the type
mentioned in the
introduction, of taking measures by way of which the weight of the tire stud
can be reduced
even further in comparison with the known tire studs, in particular also those
having a tire
3
stud body composed of vulcanized rubber, in order in this way to reduce even
further road
wear and the formation of fine dust, wherein it is sought to maintain at a
high level the grip
characteristics of the tire stud on icy surfaces, its ice performance, and
durable anchoring of
the tire stud in the tread.
According to one aspect of the present invention, there is provided a tire
stud for anchoring
in a tire stud hole of a tread of a pneumatic vehicle tire, having a non-
metallic tire stud body
with a base flange, and having a tire stud pin composed of hard metal anchored
in the tire
stud body, which tire stud pin projects with a first end portion thereof
beyond the tire stud
body and is anchored with a second end portion within the tire stud body in a
first tire stud
body part composed of a first, non-metallic material, wherein a portion of the
tire stud pin
which extends within the tire stud body between the end portions is held in at
least a second
tire stud body part composed of a second, non-metallic material, characterized
in that the
first tire stud body part, in which the second end portion of the tire stud
pin is anchored,
consists of thermoplastic or thermosetting plastic or of hard vulcanized
rubber, wherein the
second tire stud body part in which the portion of the tire stud pin which
extends within the
tire stud body between the end portions of the tire stud pin is held consists
of abrasion-
resistant and cut-resistant vulcanized rubber material or of a thermoplastic
vulcanizate.
The stated object is achieved according to the invention in that the first
tire stud body part,
in which the end portion of the tire stud pin is anchored, consists of
thermoplastic or
thermosetting plastic or of hard vulcanized rubber, wherein the tire stud body
part in which
that portion of the tire stud pin which extends within the tire stud body
between the end
portions of the tire stud pin is held consists of abrasion-resistant and cut-
resistant
vulcanized rubber material or of a thermoplastic vulcanizate.
Therefore, a tire stud designed according to the invention contains no
metallic components
apart from the pin composed of hard metal. That end portion of the tire stud
pin which is
situated in the tire stud body is anchored in a material of high hardness with
a low specific
weight and in a durable manner. The material of the tire stud body in that
region which,
with a tire stud inserted in a tread, adjoins the tread periphery
advantageously consists of an
abrasion-resistant and cut-resistant vulcanized rubber material or of a
thermoplastic
Date Recue/Date Received 2021-08-31
3a
vulcanizate. A tire stud according to the invention therefore has a low
weight, which is
advantageous for low road wear and a low level of fine dust formation. Due to
the
vulcanized rubber material or the thermoplastic vulcanizate, which is very
similar to
vulcanized rubber material, in the upper tire stud body region, the abrasion
of the tire stud
body is substantially a good match for that of the surrounding vulcanized
rubber matrix of
the tread. No gaps are formed between the tire stud body and the tread
material, as a result
of which the tire stud retains its winter characteristics or its ice
performance over the
lifetime of the tire.
.. In a preferred embodiment variant of the invention, the tire stud body part
in which the end
portion of the tire stud pin is anchored is an insert in the tire stud body,
which insert is
encased by vulcanized rubber material or by thermoplastic vulcanizate. In said
embodiment
variant, the tire stud pin can be anchored in the tire stud body in a
particularly durable
manner.
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In said embodiment variant, the insert preferably has a base part and a pin
holder, wherein
the base part forms, together with its casing, the base flange of the tire
stud body.
In order for the insert to be anchored in the tire stud body in a particularly
durable manner,
it is advantageous if the pin holder is provided with at least one undercut
and/or if the pin
holder is of mushroom head-like form and has a groove-like transition region
to the base
part.
In a further embodiment variant, the tire stud body consists of an upper part
and a lower
part, wherein the lower part is formed in one piece with the base flange and
is that tire stud
body part in which the end portion of the tire stud pin is anchored. Said
embodiment variant
is distinguished by a particularly simple construction.
In said embodiment variant, the tire stud body part in which that portion of
the tire stud pin
which extends between the end portions of the tire stud pin is held is
preferably the upper
part of the tire stud body. Also preferred are embodiment variants in which
the upper part
of the tire stud body consists either of a single material or of at least two
layers, arranged
one above the other, of different materials. The type of force transmission
from the tire stud
pin to the tire stud body can be influenced by layers of different materials.
In one preferred embodiment, the parting surface between the upper and lower
parts
extends perpendicular to the tire stud pin. Also possible, however, are
embodiment variants
in which the parting surface between the upper and lower parts extends
obliquely with
respect to the extent of the tire stud pin, in particular at an angle of 5 to
30 to the
horizontal.
In the case of a parting surface between the upper and lower parts that
extends
perpendicular to the tire stud pin, the lower part preferably has a height of
30% to 40% of
the tire stud height.
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In order to ensure optimum anchoring of the tire stud pin in the tire stud
body, it is
furthermore advantageous if that end portion of the tire stud pin which is
anchored in the
tire stud body is provided with at least one anchoring element.
5 The thermoplastic material in the tire stud body is preferably at least a
thermoplastic from
the group comprising acrylonitrile butadiene styrene copolymer, polyethylene,
polypropylene, polystyrene and polyamide.
The thermosetting plastic is preferably phenol resin, epoxy resin or polyester
resin.
The thermoplastic(s) of the thermoplastic vulcanizate preferably comes/come
from the
group comprising polyurethane, polypropylene, polystyrene, polyamide and
acrylonitrile
butadiene styrene copolymer. Preferably, it is furthermore the case that the
elastomer of the
thermoplastic vulcanizate is based on an unvulcanized rubber mixture which, as
the
unvulcanized rubber(s), contains at least one of the unvulcanized rubbers from
the group
comprising natural rubber, synthetic polyisoprene, polybutadiene, styrene
butadiene rubber
and nitrile butadiene rubber.
Further features, advantages and details of the invention will now be
described in more
detail on the basis of the drawing, which illustrates exemplary embodiments.
In the
drawing,
figure 1 and figure 2 show side views of a first embodiment of a tire stud,
figure 3 shows a plan view of the tire stud according to the first embodiment,
figure 4 and figure 5 show sectional illustrations along the lines IV-IV and V-
V in figure 3,
figure 6 shows a section along the line VI-VI in figure 4,
figure 7 and figure 8 show side views of a second embodiment of a tire stud
according to
the invention,
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figure 9 shows a plan view of the tire stud according to the second
embodiment,
figure 10 and figure 11 show sectional illustrations along the lines X-X and
XI-XI in figure
9,
figure 12 shows a section along the line XII-XII in figure 10, and
figures 13 to 16 show views of a tire stud pin,
figure 13 showing an oblique view,
figure 14 and figure 15 showing side views, and
figure 16 showing a plan view.
The tire studs 1 (figure 1 to figure 6) and l' (figure 7 to figure 12) shown
in the figures
consist fundamentally of a tire stud body 2, 2' and a tire stud pin 3. In the
exemplary
embodiments shown in the figures, the tire stud body 2, 2' consists of a
circular-cylindrical
or approximately circular-cylindrical body part 2a, 2'a, which is seated on a
base flange 4,
4' which, in plan view, has an approximately oval shape with two side surfaces
extending
along the longer extent of the oval and parallel to one another. The body part
2a, 2a' is
arranged centrally on the base flange 4, 4', its diameter corresponding
substantially to the
width of the base flange 4, 4'.
A preferred configuration of the tire stud pin 3 as is contained in both tire
studs 1, l', said
tire stud pin consisting in particular of hard metal, will now be described in
more detail on
the basis of figures 13 to 16. The tire stud pin 3 consists of a base 5 and an
elongate pin
portion 6. In the embodiment shown, the pin portion 6 has a cross section
which is constant
over its extent. The cross-sectional surface and the top surface 7 at the free
end of the pin
portion 6 are approximately quadrangular with two longer sides 7a of identical
form which
extend substantially straight and parallel to one another and which, via
roundings, merge
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into two shorter sides 7b which are curved inward. As a consequence of the
inwardly
curved short sides 7b, the pin portion 6 has narrower side surfaces 6b, which
are likewise
curved slightly inward. The wider side surfaces 6a of the pin portion 6 are
largely planar
surfaces but may likewise be of inwardly curved form. The base 5 of the tire
stud pin 3 has
four base elements 5a, which project at the corner regions and between the
side surfaces 6a,
6b and serve as anchoring elements for secure anchoring in the material of the
tire stud
body 2, 2'. In the embodiment shown, the base elements 5a have obliquely
rising transition
surfaces to the pin portion 6 of the tire stud pin 3. The illustrated
embodiment is merely one
of many possible embodiments of base elements. Additionally or alternatively,
the tire stud
.. pin 3 may be provided with undercuts, for example at peripheral grooves.
In the embodiment shown in figures 1 to 5, an insert 8 is contained in the
tire stud body 2,
said insert having a base part 8a jointly forming the base flange 4 and having
a pin holder
8b which, in the embodiment shown, is of mushroom head-like form and in the
middle of
which the tire stud pin 3 is anchored. The tire stud pin 3 projects with an
end portion
beyond the tire stud body 2. The base part 8a of the insert 8 is encased by a
layer of the
material of the body part 2a and forms, together with this casing 9, the base
flange 4. At its
transition region to the base part 8a, the pin holder 8b shaped like a
mushroom head forms
an undercut 10 at a depression which is peripheral in a groove-like manner.
The insert 8 consists of a plastic, specifically either a thermoset - a cured
plastic resin - or a
thermoplastic. From the group of thermosets, for example phenol resin, epoxy
resin or
polyester resin is suitable. From the group of thermoplastics, for example ABS
(acrylonitrile butadiene styrene copolymer), PA (polyamides), PE
(polyethylene) and PP
(polyproylene) are suitable.
The tire stud body 2 together with casing 9 consists of a cut-resistant and
abrasion-resistant
vulcanized rubber material or of a thermoplastic vulcanizate which likewise
has these
properties.
During the production of the tire stud 1, the tire stud pin 3 is encapsulated
with the plastic
material for the insert 8 in a mold. After the insert 8 has cured, the insert
8 and the tire stud
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pin 3 are coated on the outside with an adhesion promoter for vulcanized
rubber, for
example with Chemosil 0, and are subsequently encapsulated with an
unvulcanized rubber
mixture or with a thermoplastic vulcanizate, and in this way the formation of
the tire stud
body 2 together with the casing 9 is realized, wherein an unvulcanized rubber
mixture is
subsequently vulcanized. Here, it is also possible, as the sectional
illustrations in figure 4
and figure 5 show, for that end portion of the tire stud pin 3 which projects
beyond the tire
stud body 2 to be jointly encased, at least on the outside.
Mixture compositions for the production of cut-resistant and abrasion-
resistant vulcanized
rubber materials are sufficiently well known to tire specialists.
A thermoplastic vulcanizate is a blend composed of at least one thermoplastic
and one
elastomer, wherein the thermoplastic forms a continuous phase and the
elastomer forms a
disperse phase finely distributed in said thermoplastic. In a thermoplastic
vulcanizate,
elastomer particles are therefore surrounded by the thermoplastic. During the
production of
thermoplastic vulcanizates, at least one unvulcanized rubber is reactively
compounded with
at least one thermoplastic, wherein the unvulcanized rubber mixture which
forms is
crosslinked in a phase-selective manner so that the elastomer is formed
therefrom. The
production is preferably realized in a shear field ("dynamic vulcanization").
The
thermoplastic forming the continuous phase is meltable, and so thermoplastic
vulcanizate
can be processed for example by means of injection molding.
The thermoplastic is or contains in particular at least one thermoplastic from
the group
comprising polyurethane (PU), polypropylene (PP), polystyrene (PS), polyamide
(PA) or
acrylonitrile butadiene styrene copolymer (ABS). As the unvulcanized rubber,
the
unvulcanized rubber mixture of the elastomer contains at least one of the
unvulcanized
rubbers from the group comprising natural rubber (NR), synthetic polyisoprene
(IR),
polybutadiene (BR), styrene butadiene rubber (SBR) and nitrile butadiene
rubber (NBR).
A tire stud body 2 which, together with the encasing layers, consists of a
thermoplastic
vulcanizate therefore consists of an abrasion-resistant material which, in
this respect, has
very similar properties to vulcanized rubber material of treads.
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In the embodiment shown in figures 7 to 12, the body part 2'a of the tire stud
body 2' of the
tire stud l' consists of an upper part lla and a lower part 11 b, wherein the
latter is formed
in one piece with the base flange 4' and has a height hi of 35 % to 50 % of
the tire stud
height H. In the example shown, the parting surface between the upper part lla
and the
lower part 11 b extends horizontally, and therefore at right angles to the
extent of the tire
stud pin 3. The tire stud pin 3, which is formed according to figures 13 to
16, is anchored in
the lower part llb with the end portion thereof which has the base 5. The
lower part llb
consists of hard vulcanized rubber with a Shore D hardness according to DIN
ISO 7619-1
of at least 50, or of a plastic material, for example a material which is
described as material
for the insert 8 of the first embodiment. The upper part 11 a consists of an
abrasion- and cut-
resistant vulcanized rubber material or of a thermoplastic vulcanizate. For
the production of
the tire stud I', the tire stud pin 3 composed of hard metal, which is coated
with an adhesion
promoter, is encapsulated with the flowable heated materials for the upper
part lla and for
the lower part llb in a corresponding mold, and the materials are cured or
vulcanized.
In an alternative embodiment variant of the invention (not shown separately),
the tire stud
body 2' may consist of more than two different materials, for example three
different
vulcanized rubber materials.
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List of reference numerals
5 1,1' ... Tire stud
2, 2 ......... Tire stud body
2a, 2'a ...... Body part
3 ............ Tire stud pin
4, 4' ........ Base flange
10 5 ......... Base
5a ........... Base element
6 ............ Pin portion
6a, 6b ....... Side surface
7 ............ Top surface
7a, 7b .. Sides
8 ............ Insert
8a ........... Base part
8b ........... Pin holder
9 ............ Casing
10 ..... Undercut
1 I a ........ Upper part
lib .......... Lower part
H, hi ........ Height
............. Tire stud height
