Patent Application
20140062054
This invention relates to a tire rim for use in spoked wheels, which are mounted to wheelchairs or tricycles with a camber.
Spoked wheels mounted with a camber to a rolling apparatus, such as a wheelchair or a tricycle, are known. For the use in sports such as for example wheelchair basketball, wheelchair rugby and/or wheelchair tennis, the wheelchair is propelled by the seated occupant turning the rear wheels by hand and the rear wheels are mounted at an angle between 3 and 25 degrees with normal. The camber enhances the stability, improves the pivot speed and protects the hands during collision with another wheelchair.
Spoked wheels, with a size also used for bicycles, are preferred by wheelchair athletes, because these wheels are light and relatively strong compared to solid wheels made of carbon composite. Spoked wheels can resist high impact, especially when athletes use a so called “boxing technique” to move forward. Besides, the rim of a spoked wheel normally has relatively high shoulders compared to the relatively low shoulders of common tubular rims of carbon wheels. Also, such a rim may include retaining ridges at the free ends of the shoulders. The relatively high shoulders and the retaining ridges at the free ends of the shoulders can make a spoked wheel particularly suitable for use with occasional lateral forces on the wheel, which for instance occur during skidding or when performing a bouncing technique such as a “boxing technique”.
It is an object of the invention to provide a tire rim for spoked wheels that improves the performance of the wheels when mounted to a human powered rolling apparatus with a camber.
It was observed that self-propelled wheelchairs with wheels mounted with a negative camber have higher rolling friction than wheelchairs with wheels mounted perpendicular to the floor. The asymmetrical force on the tire of the wheel in the inclined position results in particular side-way deformation of the tire and consequently extra loss of energy.
When a regular wheel, comprising a regular symmetrical tire rim with a first shoulder and a second shoulder supporting a regular symmetrical tire with a first side wall and a second side wall, is mounted perpendicular to the floor, the tire is supported opposite to the floor. The position of the support area between the two shoulders of the tire rim is in the middle above the contact patch, i.e. the area of the tread of the tire during use actually being in contact with the floor. Furthermore, both shoulders of the tire rim have the same distance to the floor and the first shoulder supports the first side wall of the tire the same as the second shoulder supports the second side wall of the tire.
When this regular wheel is mounted with a camber the tire rim is not supporting the tire as opposite to the floor as when the regular wheel is mounted perpendicular to the floor. The support area between the two shoulders of the tire rim has been dislocated and rotated by turning the regular wheel to the inclined position of the camber. The dislocated position of the support area between the two shoulders of the tire rim is not anymore in the middle above the contact patch. Furthermore, the rotated position of the support area, with the first shoulder having a larger distance to the floor than the second shoulder, provides a different support of the first shoulder for the first side wall than of the second shoulder for the second side wall. The restrains of the first shoulder are too little, providing for the first side wall of the tire to deform outward and the restrains of the second shoulder are too strong, providing for the second side wall of the tire to prevent deformation outward. The particular restrains on the tire by the tire rim and the asymmetrical force at the contact patch provide for a support not opposite to the floor and for particular side-way deformation of the tire.
Thereto, the invention provides a tire rim for a rolling apparatus with wheels mounted with a camber, the rim comprising a first shoulder having a first diameter, a second shoulder having a second diameter, and a main body arranged for connecting spoke elements, wherein the first diameter is larger than the second diameter.
By having the first diameter of the first shoulder larger than the second diameter of the second shoulder the restrains of the tire at the first shoulder will be different than the restrains of the tire at the second shoulder. By mounting a wheel, comprising the tire rim according to the invention, with a camber, wherein the first and second shoulder have a substantially similar distance to the floor, the position of the support area between the first shoulder and the second shoulder is substantially in the middle above the contact patch. Furthermore, the restrains of the first shoulder and the second shoulder on the tire are balanced to provide for less side-way deformation. Therefore, the tire is opposite to the floor substantially more evenly supported by the tire rim.
It is noted that a rolling apparatus with wheels mounted with a camber may be a human powered rolling apparatus, which may be but not necessarily limited to a manually powered, preferably a manually propelled apparatus. Advantageously, the apparatus can be powered by manually propelling one or more pushrims attached to one or more wheels, preferably rear wheels. Alternatively or additionally, the apparatus, for instance being a handcycle such as a tricycle, may be drivable in other ways, for instance by driving hand cranks or by driving pedal cranks.
Further, it is noted that the apparatus may for instance be a device having at least three wheels. Preferably at least two wheels, more preferably two rear wheels, are spoked wheels. Besides, the apparatus may comprise other wheels, for instance caster wheels such as swivel casters, which may form front wheels of the apparatus. It is noted that, in embodiments, not all wheels of the rolling apparatus need to be, but nevertheless can be, mounted with a camber.
In particular embodiments of the invention the tire rim may have specific dimensions that provide particular advantages for a rolling apparatus with wheels mounted with a camber. Wheels for such rolling apparatus, often being a human powered rolling apparatus, like bicycles, tricycles and wheelchairs, regularly have different dimensions than wheels for a motor powered rolling apparatus, like automobiles and motorcycles. Wheels for a human powered rolling apparatus mostly have a relatively large diameter for a good transmission combined with a relatively narrow tire rim for low weight and low friction. A tire rim, wherein the first and second diameter is between 400 mm and 660 mm and the distance between the first and second shoulder is between 18 mm and 54 mm are most advantageous for wheels for a rolling apparatus with wheels mounted with a camber.
The tire rim can be made from any desired material regularly in use for making tire rims. Particular embodiments of the invention, however, advantageously, may use metal for the tire rim. The material is strong and tough, and ultimately suitable for making arrangements for connecting spoke elements. Furthermore, in particular embodiments of the invention the metal may be aluminum or an aluminum alloy and optionally the rim may be manufactured using extrusion. Each of these details provides particular advantages and can be implemented independently of the other.
The tire rim may be formed as a separate component. This is, the tire rim can be manufactured and supplied as an independent and/or separate part of a spoked wheel, and is not integrally formed with the rest of the wheel. For example, the tire rim and the hub of such a spoked wheel are built up of two different, independent components, which can be connected to each other by means of spokes.
In particular embodiments the tire rim may have an integrated pushrim, which may be advantageous when used in a wheel for a wheelchair, especially in a rear wheel of a hand propelled wheelchair.
The invention also comprises a wheel including an independent tire rim discussed above and laid down in the appended claims. This wheel may comprise a standard tire, for instance a tubular tire or a tubed tire having an outer tire and a separate inner tube.
The invention further comprises a tire specially designed to a tire rim discussed above and laid down in the appended claims.
In particular embodiments of the invention, the tire comprises a first bead, a first side wall, a tread, a second side wall and a second bead, and the length of the first side wall is substantially equal to the length of the second side wall, wherein the first bead has a larger circumferential diameter than the second bead.
Furthermore, in particular embodiments of the invention the tire is a tubular tire comprising constructional elements, such as reinforcements such as a carcass of fabric plies, a gluing strip, a puncture resistant strip and a tread, wherein at least one of these structural elements is asymmetrically positioned over the cross section of the tire. The tubular element may extend in circumferential direction of an air chamber of the tubular tire over the substantially entire circumference of said air chamber. Further, the tubular element may widthwise extent over a part of the substantially circular cross section of a tube of the tubular tire. It is noted that asymmetrically positioned over the cross section may at least mean that said constructional element is widthwise extending from a central plane of the tubular tire further to one side than it is extending to the other side of said central plane, wherein the central plane may extend substantially through the center of the tube of the tire and/or substantially lateral to a central axis or so called center line of the tire. In particular embodiment of the invention the tire advantageously is used in combination with a tire rim according to the invention. The tire may be supported by the tire rim in an advantageous way according to the invention. Furthermore, the tread of the tire will wear in the middle.
The invention further comprises a rolling apparatus with a wheel discussed above and laid down in the appended claims. In particular embodiments of the invention this rolling apparatus may have a wheel with its center line mounted at any angle to the floor other than parallel to the floor. Between three degrees and twenty five degrees have proven to be the most advantageous, however. In particular embodiments of the invention the rolling apparatus is a wheelchair.
The invention further relates to a method of supporting tires of spoked wheels mounted with a camber substantially more opposite to the floor.
Further advantageous embodiments are in the dependent claims.
With reference to the exemplary embodiments shown in the drawings the invention will now be specified, although only by way of example. In the drawings:
It is noted that the drawings are only diagrammatic and schematic representations of exemplary embodiments of the invention. The embodiments are given by way of non-limiting examples. In the figures, the same or corresponding parts are represented with the same reference numerals.
The wheel 2 further comprises a pushrim 6 to manually propel the wheelchair 1 by the person 11 sitting in the wheelchair 1.
A second embodiment of the invention is shown in
The wheel is positioned with a camber in such a way that the distance between the first shoulder 12a and the floor 5 is substantially similar to the distance between the second shoulder 12b and the floor 5. The area of the tire rim between the shoulders 12a to 12b may support the tire more equally divided above the contact patch 22 than a conventional wheel mounted with a camber. The contact patch 22 may be substantially in the middle below the area between 12a and 12b and supporting the tire substantially more opposite to the floor.
The standard tubular tire 19 may be twisted during mounting and may be glued in a twisted position in such a way that the gluing strip 34 fits better in the tire rim 7, i.e. a larger part of the gluing strip makes contact with the support surfaces 20, 21 of the rim, and in such way that the contact patch 22 is substantially more in the middle of the tread 33. A disadvantage of using a standard tubular tire in a twisted position is that the mounting is very cumbersome and a lot of force is needed. Furthermore, it is a disadvantage that the valve 17 comes in a twisted position as well.
Standard tubular tires are known with a symmetrically positioned tread where the shape of the tread is asymmetrical with respect to a central plane of the tire. This particular tubular tire still has to be twisted relative to the center of its air chamber for best performance.
In
Therefore, the invention further provides for a tire, for instance a tubeless tire or an outer tire for accommodating an inner tube, having two beads having a substantially equal circumferential diameter, two side walls extending from the respective bead to the tread, wherein a first of the two side walls is higher than a second one. Such a tire may for instance be mounted to the rim shown in
Tire 31 comprising a first bead 28, a first side wall 32, a tread 33, a second side wall 321 and a second bead 281. The width of the first side wall 32 is substantially equal to the width of the second side wall 321, wherein the first bead 28 has a larger circumferential diameter than the second bead 281. However, in embodiments, two side walls can have different widths. For instance, a side wall 32 extending from the bead having the larger diameter may have a wider side wall than the second side wall 321.
In accordance with an advantageous feature of the invention and as can be seen in
Many variants will be clear to the person skilled in the art. For example, although the illustrated embodiments of the tire rim have cross sections of equal wall thickness, it may be possible to have variable wall thickness for optimal design. Also, arrangements for connecting spoke elements may be screw joints or hooks. All variants are understood to fall within the scope of the invention as set forth in the appended claims.
