Brake Actuating Mechanism for Drum Brake

Field of the Invention:

This invention relates generally to drum brake activated by brake cable and more particularly, relates to anchoring of the brake cable.

Background of the Invention:

Generally in a drum brake, the brake cable activates the brake lever by being pulled from a distance. The brake cable is connected to a free end of a brake lever in the drum brake while a base end of the brake lever is pivotally mounted on a brake panel. The brake cable is comprised mainly of an inner cable and an outer casing. At the free end of the brake leveF, there is provided with a cable retaining groove bent into inverted U shape in cross section. One end of the inner cable is connected to a brake application device such as a hand lever and the other end of the inner cable is inserted into the drum brake through an opening in the brake panel and passing through that opening, it gets fit in the cable retaining groove of the brake lever. When an enlarged cable end fixed to the other end of the inner cable engages on an edge surface of the cable retaining groove opposite to a cable pulling direction, the brake cable is completely installed in the cable retaining groove. When the hand lever is operated, the inner cable is pulled accordingly, which rotates the brake lever to open a pair of brake shoes to activate brake.

In a brake device of this kind, the overall force to the brake lever is a multiple of hand lever ratio and hand lever force. The hand lever ratio is equal to the effective hand lever length divided by pitch distance between hand lever pivot and cable abutment.

The hand lever force is the force exerted by the rider on hand lever. During partial braking to panic braking if the overall force to brake lever exceeds the wheel locking force (i.e., the braking force, beyond which the corresponding road wheel intends to slide longitudinally (skid) over road surface) , the said wheel locks, which is not a desirable from safety point of view.

The other component which adds up to the overall force in such brake device brake is brake lever force. Brake lever force is equal to the brake lever length divided by half brake cam width. Increase in brake lever length helps in getting more braking force during partial braking condition, but In the conventional design the brake lever length cannot increased because it will again amplify the overall force on brake lever and thereby will lead to wheel locking.

Therefore, to overcome the problems of the prior art, the present invention has been devised to optimize the hand lever ratio in all condition (partial braking and panic braking) to avoid wheel locking.

Summary of the Invention:

An object of the present invention is to provide a floating anchor for drum brake which will help in optimizing the overall force on the brake lever.

Another object of the present invention is to keep the hand lever force less than wheel locking force in all riding condition (partial to panic braking).

Another object of the present invention is to improve partial brake performance by providing higher hand lever ratio.

Yet another object of the present invention to provide more safety feature by incorporating the floating anchor.

Further object of the present invention is to provide a cost effective way for eliminating wheel locking.

Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to
those skilled in the art from this detailed description.

Brief description of the Drawings:

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein

Figure 1 shows a conventional motorcycle.

Figure 2 shows brake actuating mechanism for drum brake according to the present invention.

Detail Description of the Drawings:

The present invention now will be described more fully hereinafter with different embodiments. This invention may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein; rather those embodiments are provided so that this disclosure will be thorough and complete, and fully convey the scope of the invention to those skilled in the art.

With reference to Figure 1 a motorcycle comprises of a frame (101), front fork (102) attached to a pivot tube (201) of the vehicle frame, a front wheel (103) attached to these front forks (102), a handle bar (104) connected to the front forks (102), a fuel tank (105) attached so as to straddle an upper part of the vehicle frame, a seat (106) attached to the upper rear portion of the vehicle frame, an engine unit (107) attached to the lower front section of the vehicle frame, a swing arm (108) attached to a lower rear section of the vehicle frame, suspended by a rear shock absorber (not shown) from the vehicle frame and a rear wheel attached to a rear end of swing arm (108). The intake system of the engine comprises of a fuel air metering device such as a carburetor (109), intake duct and an air cleaner. The exhaust system of the engine comprises of exhaust pipe and a muffler. The motorcycle is also provided with a side cover for covering a side section of the vehicle frame, a seat cover for covering a rear section of the vehicle frame below the seat, a front fender (110) for covering an upper part of the front wheel (103), and a rear fender (111) for covering an upper part of the rear wheel (112). The drive from the engine (107) is transmitted from the engine to the driven wheel sprocket mounted on the rear wheel hub mounted on the rear wheel assembly.

According to one embodiment of the present invention and referring to Figure 2, a brake actuating mechanism for drum brake for a two wheeler comprises a brake panel 208, a brake lever 206 connected to the brake panel 208 The free end 206 a of the brake lever 206 is adapted to receive one end of brake cable 203. A first stay 202 is provided to hold the brake cable 203 and located on the brake panel 208. A second stay 209 is provided for permitting the brake cable 203 to pass from first stay 202 to the brake lever 206. A floating anchor 201 is arranged between the first 202 and second stay 209 and over the brake cable 203. A return spring 205 is placed between second stay 209 and free end of brake lever 206a and over the brake cable 203. The said brake lever free end 206a is provided with a cable retaining groove preferably in inverted U shape.

The brake cable 203 is routed from the hand lever to the first stay 202 and through the first stay 202 it goes to the second stay 209 and then further gets connected to the brake lever free end 206a. The other end or base end 207 of the brake lever 206 is pivotally mounted to the brake panel 208. The brake cable 203 comprises an inner cable 204 and an outer casing. The outer casing of the brake cable 203 abuts on the first stay 202. Between the first stay 202 and second stay 209 a floating anchor 201 is provided. The said floating anchor 201 is preferably a spring over the inner cable 204. Between the free end 206a of the brake lever 206 and second stay 209 a return spring 205 is provided. The floating anchor 201 helps in limiting the excess rider input force to the brake lever 206. The floating anchor 201 is preferably a spring
anchor.

A cable abutment 203 a is permanently assembled with the outer casing of the brake cable 203 and is made to sit over the floating anchor 201. The floating anchor 201 is supported by the second stay 209. One end of the inner cable 204 is connected to the hand lever and other end is connected to the brake lever 206 to facilitate the transfer of the rider input force to the brake lever 206.

When rider applies the input force to stop or slow down the vehicle the inner cable 204 connected to the brake lever 206 gets pulled and thereby the brake lever 206 rotates. Further, the cam connected to the brake lever 206 rotates and lifts the brake shoe which in turn contacts the brake drum to create the braking action.

After reaching the set input force (decided by the anchor spring stiffness), the floating anchor spring 201 will start moving along with the cable abutment 203a. The cable will move along with the floating anchor 201 so that excess force transfer to brake lever 206 will not take place.

The present invention helps to increase the lever ratio to improve the partial braking without the fear of wheel locking during panic braking.

The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the claims.

We Claim:
1. A brake actuating mechanism for drum brake for a two wheeler comprising:

a brake panel;

a brake lever connected to the brake panel and the free end of the brake lever is adapted to receive one end of brake cable;

a first stay to hold the brake cable and located on the brake panel;

a second stay permitting the brake cable to pass from first stay to the brake lever;

a floating anchor is arranged between the first and second stay and over the brake cable;

a return spring placed between second stay and free end of brake lever and over the brake cable; and

wherein floating anchor absorbs the excess input force from rider.

2. The brake actuating mechanism as claimed in claim 1, wherein the said brake lever free end is provided with a cable retaining groove preferably in inverted U shape.

3. The brake actuating mechanism as claimed in claim 1, wherein the said brake cable comprises a inner cable and outer casing.

4. The brake actuating mechanism as claimed in claim 1, wherein the said floating anchor is preferably a spring and is moved along the pulling of the cable to absorb the excess input force from the rider.