The present disclosure concerns tires and a rim brake system for a wheel fitted with such tires.
References considered to be relevant as background to the presently disclosed subject matter are listed below:
WO 2011/067742
U.S. Pat. No. 3,921,764
U.S. Pat. No. 3,114,434
FR 1141172
EP 2743095
US 2014/015307
GB 191009830
GB 191107930
DE 2157076
GB 940062
Acknowledgement of the above references herein is not to be inferred as meaning that these are in any way relevant to the patentability of the presently disclosed subject matter.
Rim brakes are inexpensive, light, mechanically simple, easy to maintain, and generally powerful. However, they suffer from some drawbacks. For one, the braking power directly correlates to the force the rider applies to the braking lever. In addition, brake pads wear down and have to be replaced regularly. Some types of rim brakes, e.g. dual pivot, require that the rim be relatively straight; if the rim has a pronounced wobble, then either the brake pads rub against it when the brakes are released, or apply insufficient or uneven pressure to the rim.
In use, the brake pads also heat because the brake functions by friction, which results in converting kinetic energy into thermal energy. In normal use this is not a problem, as the brakes are applied with limited force and for a short time, so the heat quickly dissipates into the surrounding air. However, on a heavily-laden bike on a long descent, heat energy is added more quickly than it can dissipate and temperature of the pad may increase to cause accelerated wear; and in the event of excessive heat the pads may fail to brake which may be a cause of accidents.
The present disclosure provides, by a first of its aspects, a rim brake system for a wheel. The system comprises a frame, positioned adjacent an upper portion of the wheel (namely a portion that is upward the wheel's axle) and holding at least one brake element, preferably at least one pair of brake elements. Each of the elements has a rim-bearing face that faces the wheel's rim. Where the rim brake system comprises a pair of elements, each member of the pair is opposite one another and faces an opposite rim of the wheel than that of the other element of the pair. Each of the elements can move in opposite forward and rearward directions and hence reciprocate between a front position and a rear position. Each of the elements is biased by at least one urging element to move in the forward direction into its front position. Each of the elements is configured such that, in its rear position, the rim-bearing face is distanced from the rim, while this distance is gradually diminished with the forward movement of the brake element, said face comes to bear onto the rim in said element's front position. The rim brake system also comprises an actuation element associated with a second urging element, the actuation element can be displaced between first and second states and is biased into its first state in which it forces the braking elements to be in their rear position against the bias of the first urging element. The actuation element is coupled to a user-operable actuation mechanism, for example one comprising a brake lever, and through user actuation thereby switches the actuation element into its second state; whereby the brake element is free to move into its front position.
The configuration of the rim brake system of this first aspect permits the build-up of a braking force in a manner independent of the force applied by a user. In the system of this disclosure, the main effect of user actuation is to release the brake element and permit it to move forward by the biasing force of the first urging member (or members). This forward movement is accompanied by a gradual diminishing of the lateral distance between the rim-bearing face and the wheel's rim until said face bears onto said rim. This bearing induces a braking force, while the on-going forward rotation of the wheel drags the brake element a further distance forward, causing it to bear stronger onto the rim. Thus, the braking force is amplified by the forward movement of the wheel.
In some embodiments, the system may be configured to function in an “all or none” manner, namely, that upon user actuation and consequent release of the arresting force of the braking element, a braking force is exerted which is completely user-independent. This may be useful, for example, in slow moving vehicles, such as a wheelchair. In other embodiments, the system may be configured to permit gradual actuation, namely, such that partial actuation may permit forward displacement of the brake element up to a certain point and further actuation may permit it to advance a little further, etc.; and thereby gradual or stepwise user-controlled braking force may be exerted. However, as distinct from existing rim brake systems, even in such a case the braking force is not dependent on the force applied by the user.
The frame of a system of said first aspect is typically fitted on or attached to an upper end of the wheels' fork.
The brake element in said first aspect, according to some embodiments, comprises a brake pad with the rim-bearing face defined by it. The rim-bearing face is generally parallel to the rim's side face. The brake pad may be hinged to a pivot arrangement configured to permit the forward-rearward reciprocation, while maintaining the general parallel orientation of the rim-bearing face. By one embodiment, the brake pad is a generally planar element.
The pivot arrangement may comprise a front pivot unit that is hinged to a front portion of a brake pad and a rear pivot unit hinged to a rear position of said brake pad. The two pivot units have a generally parallel orientation to one another. This arrangement provides for a fixed spatial orientation of the brake pad during its forward-rearward reciprocation. By an embodiment, each of the two pivot units is associated with a respective first urging member.
By an embodiment of the first aspect of this disclosure, each of the brake elements has an arm member connected to or integral with the brake pad which is configured to engage said actuation element. The actuation element may be hinged to the frame and is displaceable between its first and second states in a hinged manner
By a second aspect, this disclosure provides a rim brake system that comprises a frame holding at least one brake element with a rim-bearing face that faces the wheel's rim. Each of the elements is capable of displacement between a rim engaging state in which its rim-bearing face bears against the rim, and a rim disengaging state in which its rim-bearing face is distanced from the rim. The system is characterized in that (i) the rim-bearing face is devoid of an elastomeric material; and in that (ii) the brake element is configured so as to cause the rim-bearing face to bear against a portion of the rim that comprises or is fitted with an elastomeric material. In this manner, rather than generating brake-causing friction between the elastomeric surface of a brake pad and a non-elastomeric rim portion, as in known rim brake systems, the rim-bearing face (being typically part of a brake pad) generates brake-causing friction with an elastomeric surface of the wheel's rim. Thus, for example, the heat that may be generated owing to such friction is distributed over a large surface of elastomeric material and is quicker to dissipate. Hence, the risk of excessive heating that induces wear, and in extreme cases loss of braking efficiency, is considerably reduced.
By an embodiment of this second aspect, the brake element is configured to cause the rim-bearing face to bear against the rim of a ground-bearing elastomeric element of the wheel, for example, against the rim of the wheel's tire. By another embodiment, the wheel's rim is fitted with a dedicated elastomeric sheet serving as a brake-forming surface, and the brake element is configured to cause the rim-bearing face to bear against said sheet.
As can be appreciated, the rim brake system of the first aspect and that of the second aspect are independent aspects one from the other. However, the rim brake system of this disclosure may also be configured to embody features of both of these aspects. This means, that (i) the rim-bearing face of the system of the first aspect may be fitted with an elastomeric material and hence the brake element may be configured to cause it to bear against the non-elastomeric portion of a wheel's rim, or alternatively, (ii) the rim-bearing face is not fitted with an elastomeric material and hence the brake element is configured to bring it to bear against an elastomeric portion of the rim.
Provided by a third aspect of this disclosure is a tire and a wheel that is fitted with such a tire. The tire comprises a circumferential tire body with a circumferential sealed compartment that is defined between a tire base and a circumferential ground-bearing portion, and two flanking portions integral with tire body generally parallel one to the other. The tire of this aspect may be employed in a rim brake system of this disclosure.
The tire is, typically, made of an elastomeric material; for example vulcanized rubber. The circumferential compartment may be filled with a gas (e.g. air), optionally pressurized, or a shock-absorbing material or an elastomeric material softer than the tire material.
As the compartment is of deforming (due to its filling with gas or a softer material), the circumferential sealed compartment may function as a shock absorber when a rider rides a vehicle (such as a bicycle) over a bumpy surface. When filled with non-compressed air or another elastomeric material, the tire functions as a non-pneumatic, tubeless (and/or airless) tire, thereby circumventing the need to maintain a suitable air-pressure in the tire and/or risking a flat-tire.
A wheel that is fitted with such a tire comprises a wheel body, a rim portion and a circumferential surface, and a tire of the kind specified above. In the wheel the tire base is associated with the circumferential surface and the two flanking portions are fitted over the wheel's rim portion. The association between the tire base and the circumferential surface or between the flanking portions and the rim portions may be by adhering (e.g. by gluing) or by pressure fitting.
When utilizing the tire and/or wheel of this disclosure, the rim brake system comprises a frame holding at least one brake element with a rim-bearing face that faces the wheel's rim, each of the elements being capable of displacement between a rim engaging state in which its rim-bearing face bears against the rim and a rim disengaging state in which its rim-bearing face is distanced from the rim; and being characterized in that the rim-bearing face being devoid of an elastomeric material, and in that the brake element is configured so as cause the rim-bearing face to bear against the flanking portions of the tire fitted over the wheel's rim.
In order to better understand the subject matter that is disclosed herein and to exemplify how it may be carried out in practice, embodiments will now be described, by way of non-limiting example only, with reference to the accompanying drawings, in which:
In the following description, the rim break system of this disclosure will be described with reference to an exemplary implementation, according to an embodiment of this disclosure, in which it is fitted onto a fork of a bicycle. The illustrated bicycle which comprises cardboard as its main building block is disclosed in WO 2011/067742. As can be appreciated, the rim brake system of this disclosure may be implemented in a variety of different embodiments that may implemented in bicycles of different kinds, on wheelchairs, on a variety of other wheeled devices.
In addition, as will also be clarified from the description below, the disclosed embodiments combine features of the first and second aspects of this disclosure, as described above. In other words, the rim-bearing face of the brake element is devoid of elastomeric material and bears against an elastomeric layered surface of the rim. However, as can be appreciated, the general configuration of the brake system of this embodiment is applicable also in the case of a braking surface fitted with an elastomeric material. Furthermore, as can also be appreciated, the illustrated rim brake system is but an exemplary embodiment of a rim brake system with a rim-bearing face which is devoid of elastomeric material that bears against an elastomeric surface on the wheel's rim so as to yield a braking force and there may be different configurations of different embodiments of a rim brake system with such a characteristic. For example, rim brake system of a general conventional design in which the brake power is proportional to the braking force applied by the user on the brake lever, but with a rim-bearing face of a brake element that is devoid of an elastomeric material and that bears against an elastomer-covered surface of the rim.
With all this in mind, reference is now being made to
Also seen in
Frame 118 and its elements may be better seen in
As can best be seen in
Each of the brake elements 122 includes an arm 136 integrally formed with and extending upwardly from brake pad 126. In the position seen in
As seen in
Reference is now made to
The circumferential compartment 204 may be filled with a gas, which may air or any other (typically inert gas), which may be at atmospheric pressure or may be pressurized to a higher pressure. The compartment is sealed, which ensures that the gas will not leak out. Compartment 204 may also be, in addition or in the alternative, filled with an elastomeric material softer than the tire material. An example of such a material is a solid foam or spongy material.
Once fitted onto a bicycle equipped with the braking system as described herein, in operation, the rim-bearing face of the brake pad (that bears no elastomeric material) is brought into contact with the tire's flanking portion. The friction between the brake pad and the flanking portion of the tire causes braking of the wheel's movement.
Number | Date | Country | Kind |
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242631 | Nov 2015 | IL | national |
242632 | Nov 2015 | IL | national |
1605731.7 | Apr 2016 | GB | national |
Filing Document | Filing Date | Country | Kind |
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PCT/IL2016/051143 | 10/20/2016 | WO | 00 |