Patent Application
20240092123
The present invention relates generally to non-pneumatic tires and, more particularly, to reinforced-rubber spokes for a non-pneumatic tires.
In recent years, non-pneumatic tires are seen to gain traction since they provide advantages in tire performance without relying on inflation for supporting the load applied to the tire by the car. One of the challenges of non-pneumatic tires is providing an adequate connecting structure for connecting the annular tread to the wheel hub, in particular one of the challenges is to provide adequate reinforcement structure to the spokes of the connecting structure without overly complicating the manufacture process thereof.
EP3368335A1 relates to a spoke for a non-pneumatic wheel. The spoke may be manufactured with a reinforcement structure having reinforcement elements and one or more layers of material. The spoke can also be provided in various shapes and configurations. The spoke includes anchors that allow the spoke to be more readily incorporated into, or removed from, a non-pneumatic wheel. More particularly, the anchors also allow the spoke to be joined as one-piece with the non-pneumatic wheel or releasably connected on one or both ends with the non-pneumatic wheel.
EP3519204A1 relates to a spoke for a wheel attaching an outer tread to a hub, the spoke having a first and second spoke elements joined by a joint body comprised of an elastomer connecting the first spoke element to a second spoke element.
WO2019050547A1 relates to a non-pneumatic wheel comprising a plurality of spokes attaching an outer tread band to a hub, each spoke having first and second spoke elements joined by a body comprised of an elastomer connecting the first spoke element to the second spoke element.
In a first aspect, the invention relates to a reinforced-rubber spoke for a non-pneumatic tire, comprising
According to an embodiment, the serpentining reinforcement cord is embedded between a first and a second layer of rubber.
According to an embodiment, the serpentining reinforcement cord may be located in a median surface of the web.
According to an embodiment, the serpentining reinforcement cord may be located in an off-median inner surface of the web.
According to an embodiment, the serpentining reinforcement cord may comprise first U-turns at the radially outer end and second U-turns at the radially inner end of the spoke.
According to an embodiment, the spoke may comprise an array of first holes at the radially outer end, the first U-turns being centered on the first holes, and an array of second holes at the radially inner end, the second U-turns being centered on the second holes.
According to an embodiment, at least one of the first and second holes may be through-holes extending through the spoke.
According to an embodiment, the spoke may comprise a tube arranged between each U-turn and the corresponding hole.
According to an embodiment, the web may be planar.
According to an embodiment, the web may be curved.
According to an embodiment, the radially outer end may comprise a flange for connecting the spoke to a shearband.
According to an embodiment, the radially inner end may comprise a flange for connecting the spoke to a hub.
In a second aspect, the invention relates to a non-pneumatic tire, comprising
According to an embodiment, the first and second layers of rubber may be symmetric, so that the serpentining reinforcement cord is located in a median surface of the web.
According to an embodiment, the first and second layers of rubber may have different thickness, so that the serpentining reinforcement cord is located in an off-median surface of the web.
According to an embodiment, the serpentining reinforcement cord may comprise U-turns at the radially outer end and oppositely oriented U-turns at the radially inner end of the spoke.
According to an embodiment, the spoke may comprise an array of first holes at the radially outer end, the U-turns at the radially outer end being centered each on a respective one of the first holes, and an array of second holes at the radially inner end, the U-turns at the radially inner end being centered each on a respective one of the second holes.
According to an embodiment, the first holes or the second holes, or both, may be through-holes extending through the spoke.
According to an embodiment, the spoke may comprise a tube arranged between each U-turn and the respective hole.
According to an embodiment, the web of each spoke may be essentially planar, or planar.
According to an embodiment, the webs of the spokes may be curved.
According to an embodiment, the webs of the spokes may all be curved in the same angular direction about a tire axis.
According to an embodiment, each of the radially outer ends of the spokes may comprise a flange for connecting the spoke to the shearband.
According to an embodiment, each of the radially inner ends of the spokes may comprise a flange for connecting the spoke to a hub.
As used herein, the term “rubber” is intended to include both natural rubber compositions and synthetic rubber compositions. Unless otherwise specified, “rubber” designates a cured rubber (typically obtained from unsaturated rubber by sulfur or non-sulfur vulcanization). The rubber need not be completely cured, i.e., its molecular chains may contain residual cure sites (e.g., allylic positions) available for crosslinking with other molecular chains. The expression “rubber composition” “compounded rubber” and “rubber compound” may be used interchangeably to refer to rubber (elastomer) which has been blended or mixed with various ingredients and materials, e.g., reinforcing fillers, such as carbon black, precipitated amorphous silica, or the like, and then cured. Specific examples of rubbers include neoprene (polychloroprene), polybutadiene (e.g., cis-1,4-polybutadiene), polyisoprene (e.g., cis-1,4-polyisoprene), butyl rubber, halobutyl rubber (such as, e.g., chlorobutyl rubber or bromobutyl rubber), styrene/isoprene/butadiene rubber, copolymers of 1,3-butadiene or isoprene with monomers such as, e.g., styrene, acrylonitrile and methyl methacrylate. Other types of rubber include carboxylated rubber, silicon-coupled rubber, or tin-coupled star-branched polymers.
In the present document, the term “serpentining” refers to an element, in particular the reinforcement cord, lying in a winding path.
The expression “wheel hub” or “hub” are used herein to refer to the central part of the non-pneumatic tire for receiving the axle from a car and enabling the non-pneumatic tire to spin around the axle.
As used herein, an “annular tread” is the outermost part of the non-pneumatic tire for contacting the ground.
As used herein, “spokes” is a part of a connecting structure for connecting the annular tread (or, possibly, a shearband supporting the tread) to the wheel hub.
As used herein, a “flange” is a projecting edge on the spoke, e.g. for strengthening and/or for attaching to another element.
As used herein, a “web” connects the radially inner end and the radially outer end of the spoke.
The expressions “axial” and “axially” are used herein to refer to lines or directions that are parallel to the axis of rotation of the tire.
The expressions “radial” and “radially” are used to mean the direction of a line intersecting the tire's axis of rotation at right angle.
In the present document, the verb “to comprise” and the expression “to be comprised of” are used as open transitional phrases meaning “to include” or “to consist at least of”. Unless otherwise implied by context, the use of singular word form is intended to encompass the plural, except when the cardinal number “one” is used: “one” herein means “exactly one”. Ordinal numbers (“first”, “second”, etc.) are used herein to differentiate between different instances of a generic object; no particular order, importance or hierarchy is intended to be implied by the use of these expressions. Furthermore, when plural instances of an object are referred to by ordinal numbers, this does not necessarily mean that no other instances of that object are present (unless this follows clearly from context). When reference is made to “an embodiment”, “one embodiment”, “embodiments”, etc., this means that these embodiments may be combined with one another. Furthermore, the features of those embodiments can be used in the combination explicitly presented but also that the features can be combined across embodiments without departing from the invention, unless it follows from context that features cannot be combined.
The invention will be described by way of example and with reference to the accompanying drawings in which:
The reader's attention is drawn to the fact that the drawings are not to scale. Furthermore, for the sake of clarity, proportions between height, length and/or width may not have been represented correctly.
The connecting structure comprises a plurality of a reinforced-rubber spokes 18. For the sake of clarity, only a subset of the spokes are represented.
A radially inner shearband 16 may be provided between the wheel hub 17 and the connecting structure. The spokes 18 may be in direct contact with the radially inner shearband 16. In an embodiment, the radially inner shearband 16 may be dispensed with. In another embodiment, the radially inner shearband 16 may be replaced by (reinforced) plastic. In that case, the spokes 18 may be in direct contact with the (reinforced) plastic.
In particular, the rubber spokes 18 comprise a radially outer end 20 for connecting the spoke 18 to the radially outer shearband 14 and a radially inner end 22 for connecting the spoke to the wheel hub 17 (or the radially inner shearband 16 as depicted in
The radially outer end 20 of the rubber spokes 18 may comprise a flange for connecting the spoke to the shearband 14. The radially inner end 22 rubber spokes 18 may comprise a flange for connecting the spoke to the wheel hub 17 (or the radially inner shearband 16 as depicted in
The rubber spokes 18 may comprise a web 24 extending between the radially inner end 22 and the radially outer end 20. The web may comprise a reinforcement cord in its core. In particular, as will be further described below, the reinforcement cord may be sandwiched between first and second layers of rubber. The reinforcement cord may be serpentining between the radially outer end 20 and the radially inner end 22.
In the following, different steps, according to several embodiments, for producing the spokes 18 and the NPT 10 will be described for illustrating the structure of the spokes 18 and their integration in the NPT 10.
The first layer of rubber 26 is deposited between the pins 30, i.e. between the radially inner end and the radially outer end of the spoke being manufactured. A reinforcement cord 32 is provided on top of the first layer 26 of rubber. The reinforcement cord 32 serpentines between the radially inner end and the radially outer end. The reinforcement cord 32 comprise first U-turns at the radially outer end, around the (first) pins 30, and second U-turns, around the (second) pins 30, at the radially inner end. In an embodiment, as depicted, the reinforcement cord 32 alternates between the radially inner end and the radially outer end. The reinforcement cord 32 may regularly (periodically) alternate between the radially inner end and the radially outer end.
It is worthwhile noting that a tube 31 may be arranged between each U-turn and the corresponding pin, as depicted in
It may be beneficial to fix the reinforcement cord 32 to one or more pins 30, e.g. the extremal pins in order to keep the reinforcement cord 32 under tension and mitigate the risk of movement of the reinforcement cord 32 during a subsequent step of curing. The fixing may be carried out by making a knot around the extremal pins. Alternatively or additionally, the fixing may be effected by making a knot and stapling the knot to the first layer 26 of uncured rubber with one or more (metal or polymer) staples. The knot may thus act as a stopping knot. Also, alternatively or additionally, the knot may be pushed into the uncured rubber.
In an embodiment, the extremal pins may be additional pins, i.e. different from the pins 30. The extremal pins may be off centered with respect to the first and/or second arrays of pins. This allows for leaving more space for making the knot.
The knot may be a Marlinspike Hitch. Of course, other knots are equally possible. The reinforcement cord 32 may be is cut on the outer ends of the knots.
The reinforcement cord 32 may be made of steel cords and/or cords formed from nylon fiber, polyester fiber, fiber glass, carbon fiber, aramid fiber, glass fiber, polyethylene fiber, polyethylene terephthalate fiber, or other reinforcement materials. Different reinforcement materials could be combined. It is worthwhile noting that a “cord” may include one or plural strands.
In a further step, as schematically depicted in
The thickness of the first layer 26 may be the same as the thickness of the second layer 34. In that case, the reinforcement cord 32 is located in a median surface of the web 24. In another embodiment, the thickness of the first layer 26 may be the different than the thickness of the second layer 34. In that case, the reinforcement cord 32 is located in an off-median inner surface of the web.
As depicted in
Mold cap elements 38, 40 are also provided on top of each of the flanges 20, 22 and are also in (direct) contact with the mold elements 28, 36 so as to seal the uncured rubber in the mold comprising the mold elements 28, 36 and the mold cap elements 38, 40.
The mold may then be heated to an elevated temperature sufficient to cure partially the rubber. When the rubber is partially cured, the mold is disassembled, and the spoke, comprising the merged first and second layers 26, 34, flanges 20, 22, in embodiments also the tubes 31, and reinforcement cord 32, is removed from it. The spoke is thus a monolith. Of course, when the mold is disassembled, the pins 30 are also removed, leaving holes 39 in the spoke. In other words, the pins 30 are placeholders so that the spoke comprises holes 39 where the pins were located. In embodiments, (at least some of) the holes 39 are through holes.
The spoke may comprise an array of first holes at the radially outer end, with the first U-turns being centered on the first holes, and an array of second holes at the radially inner end, with the second U-turns being centered on the second holes.
With reference to
In more details, the inner shearband 16 may be wrapped around the inner mold element 42, the spokes 18 and interstitial mold elements 41, 43 may then be placed. The outer shearband 14 may then be wrapped around the spokes 18 and covered by the outer mold element 44.
The mold may then be heated to an elevated temperature, sufficient to (fully) cure the rubber. It should be noted that, in case of green rubber, the combination of elevated temperatures and high pressure causes vulcanization of the rubber. When the rubber is cured, the mold is disassembled and the cured (monolithic) product, comprising the shearbands merged with the spokes, is removed from it.
The annular tread 12 (see
In embodiments (e.g. as depicted in the present document) the web of the spokes is planar, or at least essentially planar. In other embodiments, the web of the spokes is curved. In that case, the mold elements 28, 38 and/or the mold elements 41, 43 may be modified for providing the spokes with a web having curved outer surfaces. For examples, the web of the spokes may all be curved in the same angular direction about a tire axis.
It will be appreciated that embodiments of the present inventions allow for a lightweight, high tensile, highly compressible and highly flexible connecting structures, in particular spokes, with a high yield point/domain.
Variations in the present invention are possible in light of the description of it provided herein. While certain representative embodiments and details have been shown for the purpose of illustrating the subject invention, it will be apparent to those skilled in this art that various changes and modifications can be made therein without departing from the scope of the subject invention. It is, therefore, to be understood that changes can be made in the particular embodiments described which will be within the full intended scope of the invention as defined by the following appended claims.
