CA3014707A1

CA3014707A1 - Stud for a pneumatic vehicle tire, and method for producing a stud

Info

Publication number: CA3014707A1
Application number: CA3014707A
Authority: CA
Inventors: Christoph Berger; Jan Schlittenhard; Friedrich Gassner
Original assignee: Continental Reifen Deutschland GmbH
Current assignee: Continental Reifen Deutschland GmbH
Priority date: 2016-05-17
Filing date: 2017-02-28
Publication date: 2017-11-23
Anticipated expiration: 2037-02-28
Also published as: EP3458286B1; WO2017198352A1; DE102016208386A1; EP3458286A1; CA3014707C; RU2689082C1

Abstract

Spike for a pneumatic vehicle tire, the spike comprising: a spike body which is composed of a plastic comprising strengthening fibers, and a spike pin which is positioned in the spike body and which projects out of the spike body and which is composed of hard metal, wherein the spike body has a main body part and a foot part which projects laterally beyond the main body part. The spike pin extends in the spike body substantially as far as the level of the foot part and has a pin shank with at least one anchoring element which widens the radially inner end region of the pin shank, wherein the strengthening fibers in the central region of the foot part are oriented predominantly and substantially perpendicular to the spike pin.

Description

2 Description Stud for a pneumatic vehicle tyre, and method for producing a stud The invention relates to a spike, and to a method for producing a spike, for a pneumatic vehicle tire, having a spike body which is composed of a plastic comprising strengthening fibers, and having a spike pin which is positioned in the spike body and which projects out of the spike body and which is composed of hard metal, wherein the spike body has a main body part and a foot part which projects laterally beyond the main body part.
It is known and conventional for pneumatic vehicle tires to be equipped with spikes in order, under winter driving conditions, to increase the power transmission from the tire to snow-covered and/or ice-covered roadways. The spikes are made up of a spike body and of a spike pin which is positioned in, and projects out of, said spike body. In particular, the spike body may be manufactured from different materials, wherein, in the material selection, a low spike body weight and low material costs for the spike body are generally primarily sought. In particular, the spike body may be manufactured from a plastic which comprises strengthening fibers which impart high strength to the finished spike body. Such spike bodies have already long been known.
A spike of the type mentioned in the introduction is known, for example, from 682 Al. During the production of the spike, the spike pin is driven into a cutout of the already-produced spike body, wherein the height of that part of the spike pin which is seated in the spike body corresponds at most to half of the pin height. To increase its hardness, the plastic of the spike body may have glass fibers added to it.
Furthermore, in the spike body, there is incorporated a spiral-shaped wire which surrounds the spike pin.
Said wire is intended to continuously firmly hold the spike pin, which is driven deeper into the spike body as the latter wears.

The spike known from DE 26 23 754 A has a spike pin composed of tungsten carbide, which spike pin has a sawtooth profile, and a spike body composed of a metal alloy. The spike body is mounted onto the spike pin by deformation of the metal alloy.
WO 01/032449 Al has disclosed a spike having a spike pin and having a spike body which has a main body part, a substantially cylindrical central part and a foot part composed of plastic. The foot part manufactured by means of injection molding, and the central part, are fixed in a sleeve arranged substantially below the spike pin, and the spike pin is subsequently pressed into the main body part. In the finished spike, the spike pin projects approximately as far as the center of the spike body.
The spike known from DE 1 529 988 Al has a spike pin composed of hard metal, around which there is arranged a support part composed of four ribs which extend radially outward in relation to the spike axis. The support part is in turn surrounded by a spike body and is intended to support and strengthen the spike body and the spike pin, such that a movement of the spike in the tread about its spike axis is prevented. The support part is preferably composed of plastic, and is formed by injection molding around the spike pin.
A spike which is manufactured by casting or pressing methods and which is manufactured from an epoxy resin with added filler materials such as sand and/or glass fibers is known from DE 2 165 744 Al. The spike known from DE 22 48 249 Al has multiple spike pins and a spike body composed of rubber or plastic, which spike body is molded around the spike pins by pressing during the production of the spike. EP 0 037 576 B! has disclosed a spike having a spike body which has a ceramic main body part and a plastics part which surrounds said main body part and which simultaneously forms a foot part. A
further spike having a plastics body and having a metallic spike pin is known from US 3 747 659. On the inner side of the plastic body there is formed a thread-like structure into which the spike pin is pressed in stepwise fashion during driving as a result of the wear of the plastics spike body.
It is therefore basically sought to produce spikes with plastics bodies. Here, the spike body and the spike pin are normally manufactured separate from one another, and the spike pin is =
,

3 subsequently pressed into a depression which is formed in the spike body and which narrows into the interior. The holding forces of the spike pin in the spike body therefore result only from a non-positively locking connection, therefore by means of an interference fit. Said interference fit can easily loosen as a result of the loads that arise during driving, in particular as a result of the notch action of the spike pin in the spike body, such that the spike pin breaks away from the spike body. Spike bodies composed of plastic furthermore exhibit considerably less wear resistance than metallic spike bodies.
The invention is therefore based on the object of providing a spike which is of simple construction and which has a plastic body and which does not exhibit the disadvantages of known spikes with plastics bodies, in particular exhibits a high level of wear resistance and reliably prevents any loss of the spike pin. The invention is also based on the object of providing a method with which a spike of said type can be produced in a simple and economical manner.
The stated object is achieved according to the invention by means of a spike in which the spike pin extends in the spike body substantially as far as the level of the foot part and has a pin shank with at least one anchoring element which widens the radially inner end region of the pin shank, wherein the strengthening fibers in the central region of the foot part are oriented predominantly and substantially perpendicular to the spike pin, and those in the main body part are arranged predominantly in a random orientation.
As regards the method, the stated object is achieved according to the invention in that a spike pin, which has at least one anchoring element formed on its radially inner end region and projecting laterally beyond the spike pin is positioned in a mold cavity, formed in accordance with the spike body to be produced, of a casting mold, wherein the spike pin positioned in the closed casting mold extends substantially as far as the level of that region of the mold cavity which forms the foot part, wherein, subsequently, a liquid plastics material comprising strengthening fibers is injected, substantially perpendicular to the spike pin, at the center of the edge of the mold cavity region that forms the foot part, wherein the plastics material laminarly flows through and fills that mold cavity region , ,

4 which forms the foot part, and substantially turbulently flows through and fills that region of the mold cavity which forms the main body part.
Spikes according to the invention therefore have, at least at the inner end region of their spike pin, at least one anchoring element which is completely surrounded by the spike body manufactured from fiber-reinforced plastic. Since the anchoring element locally increases the diameter of the spike pin, the spike pin and the spike body are connected to one another by means of a durable positively locking connection. A particularly firm seat of the spike pin in the spike body is therefore ensured, such that a breakaway of the spike pin from the spike body even under intense load is prevented. The strengthening fibers, which in the central region of the foot part are oriented predominately perpendicular to the spike pin, provide the foot part with a maximum compressive strength in relation to the static and dynamic axial forces (compressive forces) that act thereon during driving. The substantially randomly arranged fibers in the main body part provide the latter with isotropic, that is to say non-directional material characteristics, such that the shock and shear loads that act on the main body part from different directions during driving are optimally absorbed. Spikes according to the invention are therefore strengthened in accordance with requirements and optimally.
With the method according to the invention, it is possible to produce such spikes in a particularly simple and economical manner. Here, it is essential that the entire spike body is produced by injection of a plastics material comprising strengthening fibers, such that said spike body is manufactured "in a single casting process" and in its final form directly around the spike pin. In this way, the spike pin and spike body are connected to one another in a positively locking manner. The at least one anchoring element of the spike pin and the specially selected gate point for the plastics material give rise to targeted swirling in the plastic flowing around the spike pin, such that said plastic flows in turbulent fashion around the spike pin and the strengthening fibers in the subsequent main body part assume a random arrangement and provide the finished spike body with the desired characteristics already described above. The region below the spike pin is flowed through laminarly by the plastics material, such that the fibers in the finished foot part are oriented substantially perpendicularly or at acute angles with respect to the spike pin.

There are numerous possibilities for forming anchoring elements on the pin shank which, together with the specially oriented strengthening fibers, ensure a particularly firm seat of the spike pin. The design and the arrangement of the anchoring elements also play a roll in the method for producing spikes according to the invention in order to promote the special orientation of the strengthening fibers.
According to one feature of the invention, it is basically possible for multiple anchoring elements to be formed on the pin shank. An embodiment is preferable in which at least one anchoring element is provided which surrounds or encircles the pin shank.
What is particularly advantageous here is a design variant in which at least one anchoring element is provided which surrounds the pin shank and which conically widens over its extent along the pin shank. For good positive locking of the spike pin in the spike body, it is sufficient here for the conically widening anchoring element to have a height of 10% to 15% of the pin height.
In a very simple design variant of the invention, at least one conically widening anchoring element is provided on the pin shank, which anchoring element is of frustoconical form. It is preferable here for a conically widening anchoring element of said type to be provided on the inner end region of the pin shank, wherein the widening takes place in particular in the direction of the inner end of the pin shank. In an alternative embodiment of the invention, multiple anchoring elements formed as projections are provided on the inner end region of the pin shank. Embodiments with anchoring elements formed on the inner end region of the pin shank are expedient for a particular firm seat of the spike pin.
In another embodiment according to the invention, the pin shank has multiple anchoring elements which are elevations and depressions formed on the outer side of the pin shank, which elevations and depressions are provided so as to encircle said pin shank in alternating fashion and are in particular of identical dimensions. In this way, the pin shank is provided with a type of ribbed outer surface or a bellows-like structuring. Here, an embodiment is preferable in which the spacing, measured transversely with respect to the extent of the pin shank, between the lowest point of the depressions and the highest point of the elevations amounts to 0.2 mm to 0.5 mm.
The spike body produced by means of an injection molding process may be produced from a thermoset or a thermoplastic. Several of the conventional thermosets and thermoplastics are suitable for the production process.
As strengthening fibers, the spike body may, according to the invention, comprise organic strengthening fibers, in particular aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers or Plexiglas fibers, or else inorganic strengthening fibers, such as for example basalt fibers, boron fibers, glass fibers, ceramic fibers or silica fibers. All fiber types may also be used in combination with one another.
To increase the compressive strength of the spike body, the latter may additionally have platelet-like or spherical filler bodies or filler substances, for example mineral filler substances such as mica, A1203 or wollastonite.
Further features, advantages and details of the invention will now be described in more detail on the basis of the drawing, which schematically shows exemplary embodiments of the invention. In the drawing:
figure 1 to figure 4 show, in each case schematically, a cross section through a design variant of a spike according to the invention, figure 5 to figure 7 show views of an embodiment of a spike pin, figure 8 schematically shows a cross section through a spike as per figure 2 during the production thereof, and figure 9 schematically shows a cross section through a spike as per figure 4 during the production thereof.

In the following description, expressions such as top, bottom, inside, outside, vertical, horizontal and the like relate to the position of the individual constituent parts of the spike as shown in the figures.
The spikes shown in figure 1 to figure 4 each have a spike body 1 composed of fiber-reinforced plastic, and a spike pin 2 which is embedded in said spike body and which is preferably composed of hard metal. The spike body 1 is made up of a main body part 3 and a foot part 4, wherein, in the simplified exemplary embodiments shown, said parts 3, 4 each have a rotationally symmetrical geometry, and a cylindrical design, with respect to the spike axis ai . The foot part 4 has a greater diameter than the main body part 3 and has an upper or radially outer delimiting surface 4a which encircles the main body part 3. The main body part 3 and the foot part 4 may also be non-rotationally-symmetrical parts, for example parts which are elongate or oval in cross section. Spike bodies which are elongate in plan view are known for example from WO 2012/107305 Al.
The spike pin 2 shown in all of the figures has a pin shank 5 and projects with a shank section 5a beyond the spike body 1. Aside from the regions where the spike pin 2 is equipped with anchoring elements 6, 6', 6", 61", 6, said spike pin may have a circular cross section with a preferably constant diameter D of for example 2.0 mm to 2.4 mm.
The spike pin 2 extends in the main body part 3 substantially from the level of the radially outer delimiting surface 4a of the foot part 4 upward. The spike pin 4 may furthermore have a pin shank 5 of non-rotationally-symmetrical design. For example, spike pins or pin shanks which are elongate in plan view are known from WO 2015/139860 Al.
In the design variant shown in figure 1, the pin shank 5 has a preferably frustoconical anchoring element 6 which is formed on the inner end region of said pin shank and which conically widens the pin shank 5 to the radially inner end thereof The anchoring element 6 has a height hi of 10% to 15% of the pin height H, and the base surface of said anchoring element, situated at the level of the radially outer delimiting surface 4a of the foot part 4, has a diameter di > D of approximately 3.0 mm.

The spike pin 2 of the design variant shown in figure 2 has, on its radially inner end section, a doubly frustoconical anchoring element 6', the height h2 of which amounts to 20% to 30%
of the pin height H. The anchoring element 6' is composed for example of two frustoconical parts 6 of preferably corresponding design and with top surfaces lying one on top of the other, the diameter of which top surfaces corresponds to the diameter D of the pin shank 5.
The two parts 6 are preferably each designed analogously to the anchoring element 6 of figure 1.
In the design variant shown in figure 3, the pin shank 5 has two frustoconical anchoring elements 6" which are arranged with a spacing ai to one another. The spacing ai amounts to for example 20% to 35% of the pin height H. The two anchoring elements 6" are preferably oriented such that their "shell surfaces" face toward one another, and may each be designed correspondingly to the frustoconical anchoring element 6 shown in figure 1.
Figure 4 shows a spike with a spike pin 2 whose section of the pin shank 5 situated in the spike body 1 has anchoring elements 61", which anchoring elements are elevations and depressions which are formed on the outer side of the pin shank 5 and which are of rounded form and which are arranged alternately and which are formed at right angles with respect to the extent of the pin shank 5 and which, in a preferred embodiment, form circular arcs which adjoin one another in the longitudinal section of the pin shank 5. Said circular arcs may have equal or different radii. Alternatively, the outer side of the pin shank 5 may have a zigzag-shaped or sawtooth-like structuring. At the lowest point of the depressions, the diameter d2 of the spike pin 2 is slightly smaller than the diameter D of the pin shank 5, and at the highest points of the elevations, the anchoring elements 6" each have a diameter d3 slightly larger than the diameter D of the pin shank 5. The spacing a2, measured transversely with respect to the extent of the pin shank 5, between the lowest point of the depressions and the highest point of the elevations amounts to 0.2 mm to 0.5 mm.
Figures 5 to 7 show views of a spike pin 2 whose pin shank 5 is of elongate design in cross section. The pin shank 5 has, in cross section, two mutually oppositely situated sides which have a greater extent than the two other opposite sides. Figure 6 shows a view of one of the relatively wide sides, and figure 7 shows a view of one of the relatively narrow sides, of the spike pin. In the embodiment shown, it is furthermore the case that those delimiting walls of the pin shank 5 that are assigned to the relatively narrow sides are arched inwardly. At the lower end of the pin shank 5, four anchoring elements 6' are formed as projections which project from the corner regions of the pin shank 5, preferably such that the spike pin 2 has a planar base surface.
To produce a spike according to the invention, the respective spike pin 2 is inserted into a mold cavity, formed in accordance with the spike body 1 that is to be produced, of a casting mold. Such casting molds are made up of multiple, in particular two, mold parts, wherein the spike pins are in each case held with their shank section 5a, which projects beyond the spike body 1, on a mold part. The spike pin 2 positioned in the closed casting mold extends substantially as far as the level of that region of the mold cavity which forms the foot part 4.
The spike pin 2 is encapsulated with liquid plastic comprising strengthening fibers, which plastic, in the cured state, forms the spike body I. Suitable plastics are thermosets or plastics melts composed of thermoplastics. Use may therefore be made for example of epoxy resin, unsaturated polyester resin, vinyl ester resin, phenol formaldehyde resin, diallylphtalate resin, methyl acrylate resin, polyurethane, amino resins, melamine resin or urea resin, and, as thermoplastics materials, of polyvinyl chloride (PVC), polyethylene (PE), polypropylene (PP), polyamide (PA), polyoxymethylene (POM), polyethylene terephthalate (PET), polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVDF), ethylene chlorotrifluoroethylene (ECTFE), perfluoralkoxy polymer (PFA), polyfluoroethylene propylene (FEP), tetrafluoroethylene-perfluoro-methylvinylether (MFA), polyether ether ketone (PEEK), polyetherimide (PEI), polyether sulfone (PES), polysulfone (PSU), polyphenylene sulfide (PPS), polycarbonate (PC) or acrylonitrile butadiene styrene (ABS). As strengthening fibers, use is preferably made of organic strengthening fibers such as in particular aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers or Plexiglas fibers. Use may furthermore also be made of inorganic strengthening fibers, such as for example basalt fibers, boron fibers, glass fibers, ceramic fibers or silica fibers, which are distinguished in particular by their high temperature resistance. The fibers are short fibers with an average length of for example 0.5 mm.
It is conventional for the plastics matrix to be filled not only with the strengthening fibers mentioned above but also with additional filler bodies which have an order of magnitude several times smaller and are composed of different substances. These include for example mineral filler substances such as mica, A1203 and wollastonite, which are commonly used in platelet form and which in terms of their orientation during the crosslinking or solidification of the plastics matrix, behave similarly to the strengthening fibers. Use may however also be made, in smaller fractions, of spherical strengthening bodies for the purposes of increasing compressive strength, such as for example glass beads.
Figure 8 shows the process of the encapsulation by way of example for a spike pin 2 designed as per figure 2. Figure 9 shows an illustration analogous to figure 8, with a spike pin 2 designed as per figure 4. The gate point situated at the center of the edge of that mold cavity region which forms the foot part 4, the gate point being the point at which the plastics material is injected into the mold cavity, is denoted in each of figure 8 and figure 9 by an arrow P. As the arrow P also indicates, the plastics material is injected substantially perpendicularly with respect to the spike pin 2. The streamlines that illustrate the flow of the plastics material in the mold cavity are indicated by a multiplicity of short lines, which after the curing of the plastics material correspond at least substantially to the orientation of the strengthening fibers in the spike body 1 of the finished spike.
Owing to the special geometry and the position of the anchoring elements 6, 6', 6", 6-, 6`v, the plastics material is swirled as it flows in, such that said plastic material flows turbulently through that region of the mold cavity which forms the main body part. 3, whereby the strengthening fibers present in the plastic are arranged stochastically ¨ that is to say arbitrarily and randomly ¨ in said region. The central region ¨
substantially the region below the main body part 3 ¨ of that mold cavity region which forms the foot part 4 is flowed through substantially laminarly, that is to say without turbulence, by the plastics material, such that the majority of the strengthening fibers are aligned substantially perpendicularly, or at an acute angle, with respect to the spike pin 2. The radially outer edge region of that mold cavity region which forms the foot part 4 is flowed through turbulently by the plastics material, such that the strengthening fibers in said edge region are arranged substantially randomly.
The strengthening fibers oriented substantially perpendicular to the spike pin 2 in the central region of the foot part 4 provide the foot part 4 with anisotropic, that is to say direction-dependent, material characteristics, and permit a maximum compressive strength with respect to the static and dynamic axial forces acting on the spike.
Shock and shear loads act on the main body part 3 from different directions, which loads can be optimally absorbed by the main body part 3 owing to the strengthening fibers arranged randomly in the main body part 3, and the associated isotropic, that is to say direction-independent, material characteristics.
Owing to the special alignment of the fibers, spikes according to the invention are strengthened in accordance with requirements.
It is additionally possible for adhesion promoters, for example comprising chromium compounds, to be applied to the outer side of the spike pin 2 before the casting process in order to yet further improve the purchase of the spike pin 2 in the spike body 1.
Furthermore, the spike body 1 may have some other external contour, in particular an external contour that is conventional in the case of spike bodies.

List of reference numerals 1 ............ Spike body 2 ............ Spike pin 3 ............ Main body part 4 ............ Foot part 4a ........... Delimiting surface ............ Pin shank 5a ........... Shank section 6, 6, 6", 6", 6' Anchoring element al .......... Spike axis az .......... Spacing D, di, dz, d3 .. Diameter H ............ Pin height h1, h2 ....... Height

Claims

claims

1. A spike for a pneumatic vehicle tire, having a spike body (1) which is composed of a plastic comprising strengthening fibers, and having a spike pin (2) which is positioned in the spike body (1) and which projects out of the spike body (1) and which is composed of hard metal, wherein the spike body (1) has a main body part (3) and a foot part (4) which projects laterally beyond the main body part (3), characterized in that the spike pin (2) extends in the spike body (1) substantially as far as the level of the foot part (4) and has a pin shank (5) with at least one anchoring element (6, 6', 6", 6'", 6IV) which widens the radially inner end region of the pin shank (5), wherein the strengthening fibers in the central region of the foot part (4) are oriented predominantly and substantially perpendicular to the spike pin (2), and those in the main body part (3) are arranged predominantly in a random orientation.

2. The spike as claimed in claim 1, characterized in that the pin shank (5) has multiple anchoring elements (6', 6", 6"' 6IV).

3. The spike as claimed in claim 1 or 2, characterized in that at least one anchoring element (6, 6', 6", 6") surrounds the pin shank (5).

4. The spike as claimed in one of claims 1 to 3, characterized in that the pin shank (5) has at least one anchoring element (6, 6', 6") which surrounds the pin shank (5) and which conically widens over its extent along the pin shank (5).

5. The spike as claimed in claim 4, characterized in that the conically widening anchoring element (6, 6', 6") has a height (hi) of 10% to 15% of the pin height (H).

6. The spike as claimed in claim 4 or 5, characterized in that the conically widening anchoring element (6, 6', 6") is of frustoconical form.

7. The spike as claimed in one of claims 4 to 6, characterized in that a conically widening anchoring element (6) is formed on the inner end region of the pin shank (5).

8. The spike as claimed in claim 1 or 2, characterized in that multiple anchoring elements (6') formed as projections are provided on the inner end region of the pin shank (5).

9. The spike as claimed in one of claims 1 to 3, characterized in that the pin shank (5) has multiple anchoring elements (6") which are elevations and depressions formed on the outer side of the pin shank (5), which elevations and depressions are provided so as to transversely encircle said pin shank and in alternating fashion and are in particular of identical dimensions.

10. The spike as claimed in claim 9, characterized in that the spacing (a2), measured transversely with respect to the extent of the pin shank (5), between the lowest point of the depressions and the highest point of the elevations amounts to 0.2 mm to 0.5 mm.

11. The spike as claimed in one of claims 1 to 10, characterized in that the central region of the foot part (4), in which the strengthening fibers are oriented predominantly at right angles with respect to the spike pin (2), extends substantially over the region below the main body part (3).

12. The spike as claimed in one of claims 1 to 11, characterized in that the spike body (1) is produced from a thermoset or a thermoplastic.

13. The spike as claimed in one of claims 1 to 12, characterized in that, as strengthening fibers, the spike body comprises organic strengthening fibers, in particular aramid fibers, carbon fibers, polyester fibers, nylon fibers, polyethylene fibers or Plexiglas fibers.

14. The spike as claimed in one of claims 1 to 13, characterized in that the spike body (1) additionally comprises platelet-like or spherical filler bodies or filler substances, for example mineral filler substances such as mica, Al2O3 or wollastonite.

15. The spike as claimed in one of claims 1 to 13, characterized in that the spike body (1) additionally comprises spherical strengthening bodies, for example glass beads.

16. A method for producing a spike for a pneumatic vehicle tire, having a spike body (1) which is composed of a plastic comprising strengthening fibers, and having a spike pin (2) which is positioned in the spike body (1) and which projects out of the spike body (1) and which is composed of hard metal, wherein the spike body (1) has a main body part (3) and a foot part (4) which projects laterally beyond the main body part (3), characterized in that a spike pin (2), which has at least one anchoring element (6, 6', 6", 6m) formed on its radially inner end region and projecting laterally beyond the spike pin (2) is positioned in a mold cavity, formed in accordance with the spike body (1) to be produced, of a casting mold, wherein the spike pin (2) positioned in the closed casting mold extends substantially as far as the level of that region of the mold cavity which forms the foot part (4), wherein, subsequently, a liquid plastics material comprising strengthening fibers is injected, substantially perpendicular to the spike pin (2), at the center of the edge of the mold cavity region that forms the foot part (4), wherein the plastics material laminarly flows through and fills that mold cavity region which forms the foot part (4), and substantially turbulently flows through and fills that region of the mold cavity which forms the main body part (3).

17. The method as claimed in claim 16, characterized in that the liquid plastics material is a thermoset or a thermoplastic.