IL242632A - Rim brake system - Google Patents

Description

Rim Brake System TECHNOLOGICAL FIELD The present disclosure concerns a rim brake system for a wheel.

BACKGROUND 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.

GENERAL DESCRIPTION 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 rimbearing 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 buildup 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 userindependent. 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 forwardrearward 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 BRIEF DESCRIPTION OF THE DRAWINGS 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: Fig. 1 is a schematic illustration of an exemplary bicycle with its front wheel fitted with a brake system according to an embodiment of this disclosure.

Fig. 2 is a schematic close-up, isometric rear view illustration of the brake system.

Fig. 3 is a schematic isometric front view illustration of the brake system of Fig. 2 in isolation.

Fig. 4 is an enlarged isometric rear view, showing a large view of the frame with its associated elements.

Figs. 5 A and SB are respective rear view and schematic upper view of a portion of the brake system with the brake element being in the rear position in which the rim bearing face is distanced from the wheel's rim.

Figs. 6A and 6B are the same views as in Figs. 5A and 5B, respectively, with the brake elements in its front position in which the rim-bearing face bears against the wheel's rim.

DETAILED DESCRIPTION OF EMBODIMENTS 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 201 1/067742. 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 Fig. 1 showing the bicycle 100 with a front wheel 102, coupled to the bicycle's frame via fork 104, which is part of a steering assembly 106 including handlebar 108 and a stem held within a head tube 110. The wheel is fitted with a tire and the wheel's rim is layered with an elastomeric material 112. As can be appreciated, in some embodiments, the elastomeric material 112 may be independent of the tire; in other embodiments it may be integrally formed with the tire and a lateral extension thereof.

Also seen in Fig. 1 is a general view of the rim brake system designated 114 that includes a brake lever 116 and frame 118 holding system's elements to be described below, coupled to one another by a coupling link 120. The frame is fixed at an upper end of the fork and is, hence, positioned adjacent an upper portion of the wheel. This portion of the wheel rotates in a general forward direction during forward movement of the bicycle.

Frame 118 and its elements may be better seen in Figs. 2-4. The frame 118 has a generally horseshoe shape and holds the main functional elements of the brake system, which includes a pair of brake elements 122 opposite one another and facing each an opposite rim of the wheel than that of the other. The frame also holds an actuation element 124 which is coupled through coupling link 120 to the user actuation mechanism, being, in the exemplary embodiment, in the form of a brake lever 116. It should be noted that a user operable actuation mechanism in the form of a brake lever is but one example of many different embodiments of user actuation mechanisms, which may be configured in a manner different than a hand-operated brake lever, such that actuation by a pedal, may be electrically, mechanically, pneumatically, hydraulically actuated, etc. Thus, for example, where the user actuated mechanism is electrically, hydraulically or pneumatically operable, coupling link 120 may be configured accordingly. By way of example, where the actuation is electrical, the frame may also hold a solenoid coupled to a user actuated button configured to actuate the actuation element.

As can best be seen in Fig, 4, each of the brake elements 122 includes a brake pad 126 that defines a rim-bearing face 128. Each brake pad 126 is connected to the frame via two pivot units 130 A and 13 OB which are essentially parallel to one another. Of these, one pivot unit 130 A is hinged to a front portion of the brake pad and the other pivot unit 130B is hinged to a rear portion of the brake pad. The pivot units 130A and 130B are in turn pivoted to the frame about respective axles 132A and 132B. Each of the pivot units is associated with a first urging element in the form of a spring 134 which exerts a biasing force on the brake element to urge its displacement from its rear position, seen in Fig. 4 (and also seen in Figs. 5A-5B, to be described below) into a front position (as seen in Figs. 6A-6B to be described below).