GB2064687A - Braking device for a vehicle and vehicles provided with this device - Google Patents

Abstract

The braking device comprises a drum (5), a plate (10) with (an) axle(s) (11) on which shoes (12, 13) are pivotally mounted at one of their ends, these shoes being pivoted by a control cam (16) via rollers (17, 18) to ensure, during braking, the separation of the shoes and their application against the drum. In Fig. 3 the cam (16) acts via rollers (17, 18) on the free ends of the shoes (12, 13). In Fig. 5, the cam (26) occupies a central position, and the shoes (20, 21) are pivotally mounted on respective axles (22, 23). As shown, rollers are in contact with rectilinear surfaces of the cam and the shoes - alternatively these surfaces may be curved. As shown, rollers are freely mounted, although flanges (12<1>, 13<1>) on the shoes constitute roller displacement limiting stops in Fig. 3. However, flanges may be provided either at the end of the rollers or on the lateral edges of the shoes and/or the cam to ensure lateral positioning of the rollers. <IMAGE>

Description

SPECIFICATION Braking device for a vehicle and vehicles provided with this device The invention relates to a braking device for a vehicle, and the vehicles provided with this device.

Reference is now made to Figs. 1 and 2 of the accompanying drawings, showing in elevation a known braking device in the off and braking positions respectively.

The drum brakes and shoes of the known device generally comprise two shoes 1 and 2 pivotally mounted with one of their ends on an axle 3 integral with a plate or disc 4.

These shoes 1 and 2 are designed to act upon the internal cylindrical wall of a drum 5 when they are separated one from the other during pivoting about the axle 3 with the action of a control cam 6 which is also pivotally mounted at 6, on the plate 4.

The separation of these shoes with the action of the cam 6 is effected counter to the springs 7 and 8 which keep the ends of these shoes acting, on the one hand, upon the common pivoting axle 3 and, on the other hand, upon the control cam 6.

This cam 6 is set in rotation by an appropriate transmission device, such as a lever and cable or rack.

In the case of cycles and motorcycles, the plate 4 is integral with the axle of the wheel, while the drum 5 is integral with the hub of the wheel.

However, in the case of automotive vehicles, the plate, which is always fixed in rotation, is integral with the hub of the wheel, whilst the drum on which the wheel is fixed is integral with the axle which has been set in rotation.

In the operation of a braking device of this type, the springs 7 and 8 have a dual role: on the one hand, they ensure the adjustment of the shoes 1 and 2 on the cam when the effort applied to this cam has ceased, and, on the other hand, they ensure the adjustment of the transmission by causing the cam to turn in the reverse direction.

However, during a braking control, it is clearly apparent that, at the points of contact 9 between the cam 6 and the shoes 1 and 2, friction is produced which is detrimental to the good efficiency of the brake.

Thus, when the braking control has ceased, the springs 7 and 8 must ensure the adjustment of the transmission despite this friction and it is therefore necessary to use more powerful springs 7 and 8 than those which would just be sufficient to ensure the adjustment of the transmission.

However, the consequence of this increase in the force of the springs 7 and 8 is that the operator is forced to develop a greater force to ensure braking, to increase the friction of the cam on the shoe and also to increase the wear on the cam and its shoes.

The particular object of the present invention is to eliminate these disadvantages and, for this purpose, the invention provides a braking device for a vehicle comprising a drum and a plate provided with shoes mounted pivotally at one of their ends, these shoes co-operating also with a control cam which ensures, during braking, the separation of the shoes and their application against the drum, wherein the control cam co-operates with the shoes by means of rollers.

The rollers are preferably mounted freely between the cam and the shoes, and at least one stop flange for the rollers may be provided on the shoes.

The invention is shown, by way of nonlimiting example, in the accompanying drawings, in which: Figures 1 and 2, as indicated, show in elevation, in the off position and in the braking position respectively, a known braking device; Figures 3 and 4 show in elevation, in the off position and in the braking position respectively, a braking device according to the invention; Figure 5 shows in elevation another embodiment of the braking device according to the invention.

As intimated, the object of the present invention is to provide a braking device which does not necessitate a considerable force for its control, which has a progressive action and which is highly reliable with regard to eliminating the wear by friction on the control parts.

According to the embodiment shown in Figs. 3 and 4, a plate 10 comprises an axle 11 which pivotally receives one of the ends of the brake shoes 1 2 and 13, between which there are disposed restoring springs 14 and 15.

A control cam 16, which is set pivoting on the plate 10 in accordance with its axis 16,, is in contact with the free end of the plates 1 2 and 1 3 by means of two rollers 1 7 and 1 8.

In this embodiment, these rollers 1 7 and 1 8 are applied to plane surfaces of the cam 16 and ends of the shoes 1 2 and 13, flanges 12, and 13, being, however, provided, on the one hand, at the outer end of the shoe 1 2 and, on the other hand, at the inner end of the shoe 13.

The object of these flanges 12, and 13, is to constitute stops limiting the displacement of the rollers for the position of rest of the cam 16.

However, it will be noted that, if desirable, other flanges may be provided at the ends of the shoes 1 2 and 1 3 so as to stop the rollers 1 7 and 1 8 in the rotated position (Fig. 4) of the cam 1 6 or at any rate to limit the possible displacement of these rollers.

As the brake is shown in Fig. 3, it is ascertained that, in the position of rest of the cam 16, the rollers 1 7 and 1 8 are applied to the opposed rectilinear faces of the cam 1 6 at some distance from the ends of these rectilinear surfaces, whilst, on the contrary, these rollers 1 7 and 1 8 are being supported by the flanges 12i and 1 31 When the cam 1 6 is set pivoting in the direction of the arrow F1 about its axis 16,, the rollers 1 7 and 1 8 roll without friction towards the end of the rectilinear surfaces of the cam 1 6 whilst rotating in a clockwise direction, so that the pivoting of this cam 16 in the direction of the arrow F1 causes the separation of the shoes 1 2 and 1 3 simultaneously with the rolling without friction of the rollers 1 7 and 1 8 on the ends of these shoes.

During the course of this braking operation, the rollers 1 7 and 18, which are brought by rolling close to the end of the rectilinear surfaces of the cam 16, are displaced by rolling on the shoes 1 2 and 1 3 whilst being in line with the flanges 12, and 13,.

Because of the elimination of friction during the braking control, the required control force is reduced and the wear on the parts is reduced, whilst the progression of this braking control is improved.

Also, when the braking effort has ceased, the springs 14 and 1 5 only need to overcome a rolling effort and not a friction effort to bring the cam 1 6 and its control transmission to the position of rest. The adjustment of this cam will thus be more effective whilst the force of the springs 1 4 and 1 5 may be weaker.

In the embodiment shown in Fig. 5, a plate 1 9 supports two shoes 20 and 21 which are pivotally mounted on the independent axles 22 and 23 integral with the plate 19.

The free end of each of these shoes is connected to a spring 24 and 25, and their other end is connected to the axles 22 and 23.

In this example, the control cam 26 occupies a central position on the plate 1 9 and it is set in rotation on the axle 27.

The opposed rectilinear surfaces of this cam 26 are in rolling contact with two rollers 28 and 29 which are also in rolling contact with the internal edge of the shoes 20 and 21.

Also in this example, the pivoting of the cam 26 about the axle 27 causes the rotation of the rollers 28 and 29 in a clockwise direction, whilst these rollers are displaced by rolling against the cam 26 and the shoes 20 and 21.

In the examples shown in Figs. 3, 4 and 5, the rollers are in contact with rectilinear surfaces of the cam and the shoes.

However, other arrangements may be adopted.

Thus, it will in fact be possible to give these supporting surfaces a curved shape.

Also, in these examples, the rollers are free and are simply held between the shoes and the cam by the force of application of the adjusting springs.

However, in order to ensure their lateral position between these shoes and the cam, flanges may be provided either at the ends of the rollers or on the lateral edges of the shoes and/or the cam.

Claims (4)

1. Braking device for a vehicle, comprising a drum and a plate provided with shoes mounted pivotally at one of their ends, these shoes co-operating also with a control cam which ensures, during braking the separation of the shoes and their application against the drum, wherein the control cam co-operates with the shoes by means of rollers.

2. Device according to claim 1, wherein the rollers are mounted freely between the cam and the shoes.

3. Device according to either of the preceding claims, wherein at least one stop flange for the rollers is provided on the shoes.

4. A braking device substantially as hereinbefore described with reference to Figs. 3 and 4 or to Fig. 5 of the accompanying drawings.