GB2041120A

GB2041120A - Improvements in or relating to vehicle brake assembly

Info

Publication number: GB2041120A
Application number: GB7942161A
Authority: GB
Original assignee: Volkswagen AG
Current assignee: Volkswagen AG
Priority date: 1978-12-08
Filing date: 1979-12-06
Publication date: 1980-09-03
Also published as: GB2041120B; FR2443358A1; FR2443358B3; DE2853111A1

Abstract

In a cable operated, vehicle parking brake assembly having a pair of parking brakes operated by the ends of a single cable (3) which passes around an arcuate balancing link or lever (4) mounted on a manually displaceable transmission member (2), a guide member (6) is also mounted on the transmission member (2) the guide member (6) having arcuately convergent, inturned ends (61, 62) constituting guides for cable portions (31, 32), brake cable adjustment to compensate for cable elongation being effected by axial displacement of a nut (5) to displace the link (4) along transmission member (2) while the guide member (6) remains stationary. The adjustment does not alter angle alpha . As shown, cable portions (31, 32) are also guided by fixed guide means e.g. guide blocks (9) - in the case of the end regions of the cable having an external sleeve the guide blocks are replaced by abutment or stop members to abut against sleeve ends. During fitting of cable position of member (6) may be effected by nut (7). <IMAGE>

Description

SPECIFICATION Improvements in or relating to vehicle brakes This invention concerns vehicle parking brakes and relates more particularly to a device for adjusting the operating cable of the parking brakes of a motor vehicle.

One such device is described, for example, in J. Reimpell's "Fahrwerktechnik", Volume 1, third edition, 1976, page 104, Fig.

3.2/12b and is intended for use in a vehicle parking brake assembly of the type (hereinafter referred to as "the type described") comprising a transmission member having a transmission member which is actuable by a hand-brake lever or the like and which extends at least approximately in the longitudinal direction of the vehicle in the centre thereof and transmits tractive forces, a brake operating cable-whose two ends act upon two parking brakes disposed externally of the vehicle, the central region of said cable being connected to the transmission member by way of a balancing link or lever which in plan view is bent rearwardly in an at least approximately crescent-shaped manner and is arcuately embraced by the operating cable, and a nut mounted on the transmission member for axially adjusting the link to compensate for elongation of the brake cable.

In these known devices, when the balancing or equalizing lever or linkage is axially displaced on the transmission member, that is to say, is displaced further forwardly of the vehicle by actuating the nut for the purpose of compensating for elongation of the cable, there is necessarily a change in the angle at which the portions of the cable coming from the two parking brakes act upon the balancing linkage or at which they extend from such components as guide blocks, abutments or stop members disposed externally of the vehicle.Apart from the fact that the resulting spatial displacement of the cable portions concerned can be difficult to accommodate, such a change in the angle can also result in an undesirable change in the travel/transmission ratio, that is to say, in the relationship between the increasing force with which the parking brakes are applied responsive to successive increases in displacement of the handbrake operating lever or the like.

Devices for adjusting the operating cables of parking brakes of motor vehicles are known (for example, German Utility Model 71 33 923 J. Reimpell's "Fahrwerktechnik", Volume 1, third edition, 1976, Page 109, Fig.

3.2/24) in which these difficulties do not arise owing to the fact that, even when adjusting to compensate for elongation of the cable, the balancing linkage maintains its spatial position, apart from the displacement occurring during operation of the hand-brake. However, two separate brake-operating cables are used in these known devices, one end of each cable cc operating with the balancing linkage and the other end with the parking brake to be actuated, in order to be able to compensate for elongation of the two brake-operating cables, each of their ends co-operating with the balancing linkage is provided with a separate screw device.

The invention seeks to provide a vehicle parking brake assembly of the type described, in which, despite the use of a single brake operating cable, there is no substantial change in the above-mentioned cable angles when adjustment of the cable itself is effected.

According to the present invention, a parking brake assembly of the type described is characterized in that a cable guide member is mounted on the transmission member in spaced relation to the balancing link or lever and extends transversely of the transmission member in the plane of said link, the guide member having two ends which, in plan view, are inwardly curved or arcuately convergent and are bent over towards the centre of the vehicle such that they embrace lateraily spaced and rearwardly extending portions of the brake operating cable to form a rearwardly widening, rounded guide for the said portions of the operating cable, and that the balancing link alone is axially adjustable to increase the spacing between the link and the guide member for the purpose of compensating for elongation of the brake cable.

The invention will be described further, by way of example with reference to the accompanying generally diagrammatic drawings, in which Figure 1 is a plan view of a part of a parking brake device embodying the invention, and Figure 2 is an elevation taken in the direction of the arrow II in Fig. 1.

In the parking brake shown in the drawings, the pivoting movement of a conventional hand-brake lever 1 or the like is converted in a conventional manner to a movement, directed longitudinally of the vehicle, of a transmission member 2 which is articulated to the hand-brake lever and which transmits tractive forces. The transmission member 2 extends in the longitudinal direction of the vehicle at least approximately in the centre of the vehicle and its other end is connected to a conventional compensating lever or link 4 which in plan view is curved rearwardly in an at least approximately crescent-shaped manner.

The curved balancing link 4 can be adjusted axially along the transmission member 2, particularly forwardly, that is to say, to the right in the plane of the drawing, by means of a nut 5. A one-piece brake-operating cable 3 is looped around the balancing link 4 to follow the arcuate contour thereof, and two outwardly inclined and rearwardly extending portions 31 and 32 of the brake-operating cable are connected to the normal vehicle parking brakes (not shown). For spatial and other reasons, it is frequently impossible to guide the rearwardly extending regions of the brake-operating cable linearly, that is to say, on a direct path to the parking brakes.Therefore, the portions of the cable emerging from the parking brakes are in the first instance frequently arranged externally of the vehicle, for example extending along longitudinal guides and are only then directed by means such as guide blocks to the transmission member arranged centrally of the vehicle.

Guide blocks of this type are indicated diagrammatically in Fig. 1 and are designated 9.

In many cases, the end regions of the brakeoperating cable acting upon the parking brakes are, like a Bowden cable, provided with an external sleeve which transmits compressive or reaction forces. In these cases, the guide blocks shown in Fig. 1 are replaced by some form of abutment or stop member against which the ends of the sleeves abut.

In accordance with the invention, a cable guide member 6 is mounted on the transmission member 2 at a distance from the balancing link 4 and is located between the link and the two guide blocks 9 to extend transversely of the transmission member 2 in the plane of the balancing link. As shown in Fig. 2, the two ends 61 and 62 of the guide member 6 are arcuately convergent in a direction forwardly of the vehicle and are inwardly turned over so that they embrace and thus can guide the portions 31 and 32 of the brake-operating cable which extend laterally rearwardly.

By virtue of their inwardly curved contour, as seen in plan view, the two ends 61 and 62 of the guide member provide a rearwardly widening, rounded guide for the divergent portions 31 and 32 of the operating cable.

Taking into account the spacing provided on initial installation between the balancing link 4 and the guide member 6, the curvature of the two ends 61 and 62 of the latter and the curvature of the link 4 are matched to one another to minimise the frictional resistance experienced by the cable 3 during its operation. The guide member 6 is fixed axially on the transmission member 2 by a second nut 7 and by the divergence of the cable portions 31 and 32. The two cable portions 31 and 32 emerge from the guide blocks 9 at an angle a measured relative to the longitudinal direction of the vehicle. In order to compensate for elongation of the cable, the balancing link 4 is adjusted further forwardly on the transmission member 2, that is to say, to the right when viewed in the drawing, by actuating the nut 5.The position of the guide member 6 on the transmission member 2 does not change, so that only the distance between the guide member 6 and the link 4 is increased. As is clearly shown in Fig. 1, in contrast to the known arrangements, axial adjustment of the balancing link 4 for the purpose of compensating for elongation of the cable does not result in a change in the angle a, since the guide member 6 provided by the invention maintains its local position and thus maintains the course of the cable portions 31 and 32 between the guide blocks 9 and the guide member 6. Thus, adjustment of the brake-operating cable does not have any effect on the transmission ratio co-determined by the structurally fixed position of the guide blocks 9 or equivalent support means and of the guide member 6.

Accurate positioning of the guide member 6 corresponding to requirements can be varied by means of the second nut 7 whilst fitting the brake cables.

Claims

1. A cable operated vehicle parking brake assembly of the type described, comprising a cable adjusting device which is characterized in that a cable guide member is mounted on the transmission member in spaced relation to the balancing link or lever and extends transversely of the transmission member in the plane of said link, the guide member having two ends which, in plan view, are inwardly curved or arcuately convergent and are bent over towards the centre of the vehicle such that they embrace laterally spaced and rearwardly extending portions of the brake operating cable to form a rearwardly widening, rounded guide for the said portions of the operating cable, and that the balancing link alone is axially adjustable to increase the spacing between the link and the guide member for the purpose of compensating for elongation of the brake cable.

2. A parking brake assembly as claimed in claim 1, in which the guide member is likewise axially adjustably mounted on the transmission member.

3. A parking brake assembly as claimed in claim 1 or claim 2 and constructed, arranged and adapted to operate substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.