GB2184179A - Rim or disc brake for a vehicle - Google Patents

Abstract

Two brake shoes 3, 4 act on a rim 5 or disc between them. In order to achieve equally good braking behaviour in both the dry and the wet, one brake shoe 4 is more suited to dry braking with respect to its friction surface structure and/or its material and the other brake shoe 3 is more suited to wet braking. The rim or disc regions can also be constructed to suit wet and dry braking respectively. <IMAGE>

Description

SPECIFICATION Rim or disc brake for a vehicle The invention relates to rim or disc brake for vehicles, with two brake shoes which act upon the rim or disc provided between them. Such shoes may differ with respect to their material or structure of their friction surface, depending on whetherthey are designed fordry braking orforwetbraking.

In the case of such rimordiscbrakeswhichare generally known, the two brake shoes have hitherto been made of the same material with the same structure of their friction surface. In the same way the two opposite rim or disc surfaces cooperating with the brake shoes have no diference in the structure ofthe friction regions. It has been found, however, that the brake shoes used in vehicle construction and intended for dry weather, i.e. forso-called dry braking, with respect to the choice of materials and theirsur- face structure are not suitable in the same way in wet weather or in the case of so-called wet braking, since a film of liquid which adversely affects the braking action occurs first of all between the friction surface of the brake shoes and the corresponding region of the rim or disc.The pressure of the shoe on the corresponding region mustthen be substantially increased until the film of liquid has been expelled, afterwhich a jerky increase in the braking action occurs, so that an unfavourable or unreliable braking effect is produced. If, on the other hand, the braking shoes were originally produced from a material having a coefficient offriction suitableforwet braking and surface channels or the likeforexpelling the film of water, the optimum braking characteristics would be lost in dry braking, particularly since the special structure does not exert a beneficial effect on the braking action in the dry. Hitherto, therefore, it has only been possible to optimize the rim or disc brakes fordry braking orforwetbraking.

The object of the invention is therefore to mitigate this disadvantage and to improve the brake described above by means of simple steps orwithoutin- creasing the degree of technical outlay, in such a way as to produce a favourable braking action in both wet braking and dry braking.

The invention provides a rim or disc brake in which the brake shoe (and optionally rim or disc region cooperating therewith) on one side is designed for dry braking and the brake shoe (and optionally the rim ordise region) on the other side isdesignedfor wet braking.

In dry braking,the braking action is not adversely affected by the arrangement on one side of a brake shoe or a corresponding rim or disc friction surface intended for wet braking, since the shoe on this side acts in any case as an abutment for the brake shoe acting on the other side and intended originally for dry braking and the full braking force can therefore be applied. If wet braking is involved, on the other hand, a gradual braking action occurs on the side of the brake originally intended therefor, before the film of liquid on the other side of the brake disappears, so that it is unnecessary to increase the braking force excessively in order to achieve a braking effect. In wet braking,therefore, a considerably better response behaviour is achieved, or jerky braking is avoided.This situation can be further improved, of course, if not only the brake shoes but also the rim or disc regions cooperating therewith are constructed accordingly, it being entirely possibleforthe rim or disc regions to be provided with a coating in thefriction zone.

The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure lisa front view of a rim brake of a singletrack vehicle, and Figures2 and 3 are elevations ofthe two brake shoes.

The rim brake comprises two levers 1,2 which cooperate with one another in the manner of tongs and which are each provided with a brake shoe 3, 4.

In the braking procedure these brake shoes 3, 4 are pressed againstthe rim 5 provided between them.

The brake shoe 3 is constructed for wet braking and therefore comprises surface grooves 6 (Figure 2), whereas the other braking shoe 4 is intended for dry braking and is therefore provided with a smooth surface. In addition, the material is also selected to be different, i.e. the material of shoe 3 is softer than that of shoe 4.

Itwould also be possible, of course, to makethe two rim surfaces different.

1. A rim or disc brake for a vehicle, comprising two brake shoes which act upon a rim ordiscbe- tween them, the two brake shoes being different with respect two their material and/orthe structure oftheir friction surface so that one shoe is more suitable for dry braking and the otherforwet braking.

2. A rim or disc brake as claimed in claim 1,in which the rim ordisc region cooperating with the said one shoe is constructed so asto be more suit- able for dry braking and the rim or disc region cooperating with the other shoe is constructed so as to be more suitable for wet braking.

3. A rim or disc brake substantially as described with reference to and as shown in the accompanying drawings.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims (3)

**WARNING** start of CLMS field may overlap end of DESC **. SPECIFICATION Rim or disc brake for a vehicle The invention relates to rim or disc brake for vehicles, with two brake shoes which act upon the rim or disc provided between them. Such shoes may differ with respect to their material or structure of their friction surface, depending on whetherthey are designed fordry braking orforwetbraking. In the case of such rimordiscbrakeswhichare generally known, the two brake shoes have hitherto been made of the same material with the same structure of their friction surface. In the same way the two opposite rim or disc surfaces cooperating with the brake shoes have no diference in the structure ofthe friction regions. It has been found, however, that the brake shoes used in vehicle construction and intended for dry weather, i.e. forso-called dry braking, with respect to the choice of materials and theirsur- face structure are not suitable in the same way in wet weather or in the case of so-called wet braking, since a film of liquid which adversely affects the braking action occurs first of all between the friction surface of the brake shoes and the corresponding region of the rim or disc.The pressure of the shoe on the corresponding region mustthen be substantially increased until the film of liquid has been expelled, afterwhich a jerky increase in the braking action occurs, so that an unfavourable or unreliable braking effect is produced. If, on the other hand, the braking shoes were originally produced from a material having a coefficient offriction suitableforwet braking and surface channels or the likeforexpelling the film of water, the optimum braking characteristics would be lost in dry braking, particularly since the special structure does not exert a beneficial effect on the braking action in the dry. Hitherto, therefore, it has only been possible to optimize the rim or disc brakes fordry braking orforwetbraking. The object of the invention is therefore to mitigate this disadvantage and to improve the brake described above by means of simple steps orwithoutin- creasing the degree of technical outlay, in such a way as to produce a favourable braking action in both wet braking and dry braking. The invention provides a rim or disc brake in which the brake shoe (and optionally rim or disc region cooperating therewith) on one side is designed for dry braking and the brake shoe (and optionally the rim ordise region) on the other side isdesignedfor wet braking. In dry braking,the braking action is not adversely affected by the arrangement on one side of a brake shoe or a corresponding rim or disc friction surface intended for wet braking, since the shoe on this side acts in any case as an abutment for the brake shoe acting on the other side and intended originally for dry braking and the full braking force can therefore be applied. If wet braking is involved, on the other hand, a gradual braking action occurs on the side of the brake originally intended therefor, before the film of liquid on the other side of the brake disappears, so that it is unnecessary to increase the braking force excessively in order to achieve a braking effect. In wet braking,therefore, a considerably better response behaviour is achieved, or jerky braking is avoided.This situation can be further improved, of course, if not only the brake shoes but also the rim or disc regions cooperating therewith are constructed accordingly, it being entirely possibleforthe rim or disc regions to be provided with a coating in thefriction zone. The invention will be described further, by way of example, with reference to the accompanying drawings, in which: Figure lisa front view of a rim brake of a singletrack vehicle, and Figures2 and 3 are elevations ofthe two brake shoes. The rim brake comprises two levers 1,2 which cooperate with one another in the manner of tongs and which are each provided with a brake shoe 3, 4. In the braking procedure these brake shoes 3, 4 are pressed againstthe rim 5 provided between them. The brake shoe 3 is constructed for wet braking and therefore comprises surface grooves 6 (Figure 2), whereas the other braking shoe 4 is intended for dry braking and is therefore provided with a smooth surface. In addition, the material is also selected to be different, i.e. the material of shoe 3 is softer than that of shoe 4. Itwould also be possible, of course, to makethe two rim surfaces different. CLAIMS

1. A rim or disc brake for a vehicle, comprising two brake shoes which act upon a rim ordiscbe- tween them, the two brake shoes being different with respect two their material and/orthe structure oftheir friction surface so that one shoe is more suitable for dry braking and the otherforwet braking.

2. A rim or disc brake as claimed in claim 1,in which the rim ordisc region cooperating with the said one shoe is constructed so asto be more suit- able for dry braking and the rim or disc region cooperating with the other shoe is constructed so as to be more suitable for wet braking.

3. A rim or disc brake substantially as described with reference to and as shown in the accompanying drawings.