Description:FIELD OF THE INVENTION
[001] The present invention relates to a Brake Assembly.

BACKGROUND OF THE INVENTION
[002] In conventional automobiles, mechanically actuated brakes are used. One such mechanically actuated brake is a drum brake. The drum brake uses friction caused by a set of shoes or pads that press outward against a rotating cylinder-shaped part called a brake drum. Typically, for internally expanding shoe type brakes, a brake cam of circular cam profile is used.
[003] In conventional mechanically actuated brakes, the contact point of the brake cam with the brake shoes slides during a braking operation. Such sliding of the contact point of the brake cam with the brake shoes causes frictional losses which leads to higher effort to achieve brake torque/performance. Further, when the brake cam is actuated, due to rubbing, the effective width of the contact portion from the center of brake cam will keep decreasing. Therefore, the lever ratio increases. As a result, there are instances of an abrupt increase in overall lever ratio and braking will be non-linear or non-progressive control. Hence, braking characteristics changes over the period of shoe life, leading to poor brake feel and performance.
[004] Further in conventional mechanical brake systems, there is excess wear & tear between brake shoe-cam contact which leads to loss on operative life of the brake shoe as well as the brake cam. The wear and tear also cause a jerky feel to braking and occasional excess friction at brake shoe-cam contact. Further, there arises a variation in overall lever ratio during braking and over the period of shoe-life, which leads to poor durability performance and lower life of both the brake shoe and the brake cam.
[005] Thus, there is a need in the art for a brake assembly which addresses at least the aforementioned problems.

SUMMARY OF THE INVENTION
[006] In one aspect, the present invention is directed towards a brake assembly. The brake assembly includes a brake shoe. The brake shoe is being configured to be actuated to come in contact with a brake liner, thereby providing braking force wherein the brake shoe includes a flat mating surface. The brake assembly includes a brake cam. The brake cam is being configured to rotate wherein rotation of the brake cam causes the actuation of the brake shoe. Further, the brake assembly includes a contact member provided on the brake cam. The contact member is being configured to be in contact with the flat mating surface of the brake shoe. The contact member comprises a contact portion which is provided at at-least a first end of the contact member. The contact portion is having a single involute profile.
[007] In an embodiment of the invention, the contact portion is provided on the first end and a second end of the contact member.
[008] In another embodiment of the invention, the contact member comprises a top flat face and a bottom flat face. The contact portion extends between the top flat face and the bottom flat face.
[009] In a further embodiment of the invention, the single involute profile of the contact portion at the first end comprises an involute of a circle extending from the top flat face and a planar portion extending from the involute of the circle to the bottom flat face. The single involute profile of the contact portion at the second end comprises an involute of a circle extending from the bottom flat face and a planar portion extending from the involute of the circle to the top flat face.
[010] In a further embodiment of the invention, on rotation of the brake cam, a locus of the contact point between the contact member and the flat mating surface of the brake shoe, extends in a vertical straight line.
[011] In another aspect, the present invention is directed towards a brake assembly. The brake assembly includes a brake shoe. The brake shoe is being configured to be actuated to come in contact with a brake liner, thereby providing braking force, wherein the brake shoe comprises a flat mating surface. The brake assembly includes a brake cam. The brake cam is being configured to rotate wherein rotation of the brake cam causes the actuation of the brake shoe. A contact member is provided on the brake cam. The contact member is being configured to be in contact with the flat mating surface of the brake shoe. The contact member comprises a contact portion provided at at-least a first end of the contact member. The contact portion is having a double involute profile.
[012] In an embodiment of the invention, the contact portion is provided on the first end and a second end of the contact member.
[013] In another embodiment of the invention, the contact member comprises a top flat face and a bottom flat face. The contact portion extends between the top flat face and the bottom flat face.
[014] In a further embodiment of the invention, the double involute profile of the contact portion at the first end comprises a pair of involutes of a circle extending from the top flat face to the bottom flat face. The double involute profile of the contact portion at the second end comprises a pair of involutes of a circle extending from the bottom flat face to the top flat face.
[015] In a further embodiment of the invention, on rotation of the brake cam, a locus of the contact point between the contact member and the flat mating surface of the brake shoe, extends in a vertical straight line.

BRIEF DESCRIPTION OF THE DRAWINGS
[016] Reference will be made to embodiments of the invention, examples of which may be illustrated in accompanying figures. These figures are intended to be illustrative, not limiting. Although the invention is generally described in context of these embodiments, it should be understood that it is not intended to limit the scope of the invention to these particular embodiments.
Figure 1 illustrates a perspective view of a brake cam of a brake assembly, in accordance with an embodiment of the present invention.
Figure 2 illustrates a perspective view of a contact portion of the brake cam having a single involute profile, in accordance with an embodiment of the present invention.
Figure 3 illustrates a front view of the single involute profile of the contact member, in accordance with an embodiment of the invention.
Figure 4 illustrates a perspective view of the brake cam, in accordance with an embodiment of the invention.
Figure 5 illustrates a perspective view of the contact portion having a double involute profile, in accordance with an embodiment of the invention.
Figure 6 illustrates a front view of the double involute profile of the contact member, in accordance with an embodiment of the invention.
Figure 7 illustrates a locus of the contact point between the contact member and a flat mating surface of a brake shoe, in accordance with an embodiment of the invention.
Figure 8 illustrates a graph depicting effective width variation of prior art from the present invention, in accordance with an embodiment of the invention.
Figure 9 illustrates a graph depicting shoe lift variation of prior art from the present invention, in accordance with an embodiment of the invention.

DETAILED DESCRIPTION OF THE INVENTION
[017] The present invention relates to a brake assembly. The brake assembly of the present invention is typically used in a vehicle such as a two wheeled vehicle, or a three wheeled vehicle, or a four wheeled vehicle, or a multi-wheeled vehicle as required. However, it should be understood that the brake assembly as illustrated may find its application in any non-automotive application using a brake assembly.
[018] In one aspect, the present invention relates to a brake assembly 100. Generally, in a drum brake assembly, brake shoes are crescent shaped with a rough friction material on one side. The brake shoes are mounted inside of a brake drum. When the brake pedal is pressed, the brake shoes are forced outward, pushing against the inside of the brake drum and slowing down the wheel.
[019] A brake assembly 100 has the brake shoe. The brake shoe is configured to be actuated by a brake pedal to come in contact with a brake liner, thereby providing braking force. The brake shoe has a flat mating surface. Further, as illustrated in Figure 1, the brake assembly 100 includes a brake cam 110. The brake cam 110 is configured to rotate wherein rotation of the brake cam 110 causes the actuation of the brake shoe. As shown in Figure 2, a contact member 120 is provided on the brake cam 110. The contact member 120 is configured to be in contact with the flat mating surface of the brake shoe. The contact member 120 comprises a contact portion 130 provided at at-least a first end 120A of the contact member 120. The contact portion 130 has a single involute profile. As shown in Figure 3, in an embodiment, the contact member 120 comprises a top flat face 122 and a bottom flat face 124. The contact portion 130 extends between the top flat face 122 and the bottom flat face 124. In an embodiment, the contact portion 130 is provided on the first end 120A and a second end 120B of the contact member 120.
[020] In an embodiment, the single involute profile of the contact portion 130 at the first end 120A comprises an involute 132A of a circle extending from the top flat face 122 and a planar portion 132B extending from the involute 132A of the circle to the bottom flat face 124. The single involute profile of the contact portion 130 at the second end 120B comprises an involute 134A of a circle extending from the bottom flat face 124 and a planar portion 134B extending from the involute 134A of the circle to the top flat face 122.
[021] In another aspect, as shown in Figure 4, the present invention relates to the brake assembly 100. The brake assembly 100 include a brake shoe. The brake shoe is configured to be actuated to come in contact with a brake liner, thereby providing braking force. The brake shoe has a flat mating surface. Further, as shown in Figure 5, the brake assembly 100 includes a brake cam 110. The brake cam 110 is configured to rotate wherein rotation of the brake cam 110 causes the actuation of the brake shoe. A contact member 120 is provided on the brake cam 110. The contact member 120 is configured to be in contact with the flat mating surface of the brake shoe. The contact member 120 comprises a contact portion 130 provided at at-least a first end 120A of the contact member 120. The contact portion 130 has a double involute profile.
[022] As shown in Figure 6, In an embodiment, the contact member 120 comprises a top flat face 122 and a bottom flat face 124. The contact portion 130 extends between the top flat face 122 and the bottom flat face 124. In an embodiment, the contact portion 130 is provided on the first end 120A and a second end 120B of the contact member 120.
[023] In an embodiment, the double involute profile of the contact portion 130 at the first end 120A comprises a pair of involutes 136A, 136B of a circle extending from the top flat face 122 to the bottom flat face 124. The double involute profile of the contact portion 130 at the second end comprises a pair of involutes 138A, 138B of a circle extending from the bottom flat face 124 to the top flat face 122.
[024] In an embodiment, on rotation of the brake cam 110, a locus of the contact point between the contact member 120 and the flat mating surface of the brake shoe, extends in a vertical straight line (shown in figure 7). In Figure 7, dotted lines represent the locus of the contact point between the contact member 120 and the flat mating surface of the brake shoe as per prior arts while solid lines represent the locus of the contact point between the contact member 120 and the flat mating surface of the brake shoe which extends in a vertical straight line as per present invention. In the present invention, as the brake shoe has the flat mating surface and the contact portion 130 of the contact member 120 is has a single or a double involute profile, the locus of the contact point between the contact member 120 and the flat mating surface of the brake shoe extends in a vertical straight line. This is in contrast to conventional systems wherein if the locus of the contact portion is traced, the locus has an almost sinusoidal curved profile. Thus, in the conventional systems, there is rubbing of the contact portion over the flat mating surface of the brake shoe. Further, the effective width of the contact portion from the center of brake cam keeps decreasing due to rubbing. As a result, there is be an abrupt increase in overall lever ratio. But as per present invention, the point of contact remains in straight line. As a result of this, the rubbing and sliding of the contact portion 130 of the brake cam 110 with the flat mating surface of the brake shoe is minimized, and hence wear and tear due to frictional losses is minimised. Due to this, and the effective width remain constant till entire life of brake shoe. Hence, the constant lever ratio is also maintained leading to consistent braking feel and consistent braking lift.
[025] As a result of the configuration as explained hereinbefore, the present invention provides a stable effective width of the contact portion 130 from the center of brake cam 110 (shown by Curve A) as illustrate in Figure 8. The effective width of the contact portion 130 remains constant over a very large range of the cam angle. The Curve B as illustrated in Figure 8 represents the effective width of the contact portion from the center of brake cam for the existing prior art systems. For existing prior arts, as illustrated, when the brake cam is actuated, the effective width of the contact portion decreases as the cam angle increased, thus the lever ratio keeps on increasing with the cam angle. As a result of this, the braking in conventional system is non-linear or has non-progressive control. In conventional systems, there always remains a risk of wheel locking as the cam angle increases. This risk is reduced in the present invention, since the effective width of the contact portion 130 does not reduce significantly even for very high cam angles.
[026] Similarly, as shown in figure 9, Curve C represents the cam angle vs shoe lift curve for a leading edge of the brake cam in the prior art systems, and Curve C’ represents the cam angle vs shoe lift curve for a trailing edge of the brake cam in the prior art systems. As is clear from Curve C and Curve C’, which are non-linear, meaning that variation in the lift ratio is non-linear. Further, only a predetermined range of cam angle is permissible for actuating the brake cam. Beyond the predetermined actuating range, the contact of the brake shoe with the brake cam is worn out, and the service limit is reached. On the other hand, Curve D represents the cam angle vs shoe lift curve for a leading edge of the brake cam 110 in the present invention, and Curve D’ represents the cam angle vs shoe lift curve for a trailing edge of the brake cam 110 in the present invention. As is clear from Figure 9, in the present invention, for a certain cam angle a higher lift can be obtained. As a result, in the present invention, the lift which is achieved at larger cam angle by the prior art, the same lift can be achieved at a smaller cam angle by the present invention. Hence effectively, with lesser rotation of the brake cam 110, a larger lift, and thus greater braking effect can be obtained.
[027] Advantageously, in the present invention provides a braking assembly which can minimise the rubbing of the contact portion to the flat mating surface of brake shoe. Thus, reducing the sliding of contact portion by providing a single involute profile and a double involute profile to the contact portion.
[028] Also, as per present invention, the effective width remains constant till entire life of brake shoe. Hence, the constant lever ratio is also maintained. The present invention provides a braking assembly which can enhance the braking characteristics over the period of shoe life which as a result lead to better brake feel and performance. In the present invention, with lesser rotation of the brake cam 110, the same lift can be obtained.
[029] While the present invention has been described with respect to certain embodiments, it will be apparent to those skilled in the art that various changes and modification may be made without departing from the scope of the invention as defined in the following claims.

List of Reference Numerals
100 – Brake Assembly
110 – Brake cam
120 – Contact member
120A – First end
120B– Second end
122 – Top flat face
124 – Bottom flat face
130 – Contact portion
132A – Involute at the first end
132B – Planar portion
134A – Involute at the second end
134B – Planar portion
136A, 136B – Pair of Involutes at the first end
138A, 138B – Pair of Involutes at the second end
, Claims:1. A brake assembly (100), comprising:
a brake shoe, the brake shoe being configured to be actuated to come in contact with a brake liner, thereby providing braking force, wherein the brake shoe comprises a flat mating surface;
a brake cam (110), the brake cam (110) being configured to rotate wherein rotation of the brake cam (110) causes the actuation of the brake shoe; and
a contact member (120) provided on the brake cam (110), the contact member (120) being configured to be in contact with the flat mating surface of the brake shoe, wherein the contact member (120) comprises a contact portion (130) provided at at-least a first end (120A) of the contact member (120), the contact portion (130) having a single involute profile.

2. The brake assembly (100) as claimed in claim 1, wherein the contact portion (130) is provided on the first end (120A) and a second end (120B) of the contact member (120).

3. The brake assembly (100) as claimed in claim 1, wherein the contact member (120) comprises a top flat face (122) and a bottom flat face (124), wherein the contact portion (130) extends between the top flat face (122) and the bottom flat face (124).

4. The brake assembly (100) as claimed in claim 3, wherein the single involute profile of the contact portion (130) at the first end (120A) comprises an involute (132A) of a circle extending from the top flat face (122) and a planar portion (132B) extending from the involute (132A) of the circle to the bottom flat face (124); and the single involute profile of the contact portion (130) at the second end (120B) comprises an involute (134A) of a circle extending from the bottom flat face (124) and a planar portion (134B) extending from the involute (134A) of the circle to the top flat face (122).

5. The brake assembly (100) as claimed in claim 1, wherein on rotation of the brake cam (110), a locus of the contact point between the contact member (120) and the flat mating surface of the brake shoe, extends in a vertical straight line.

6. A brake assembly (100), comprising:
a brake shoe, the brake shoe being configured to be actuated to come in contact with a brake liner, thereby providing braking force, wherein the brake shoe comprises a flat mating surface;
a brake cam (110), the brake cam (110) being configured to rotate wherein rotation of the brake cam (110) causes the actuation of the brake shoe; and
a contact member (120) provided on the brake cam (110), the contact member (120) being configured to be in contact with the flat mating surface of the brake shoe, wherein the contact member (120) comprises a contact portion (130) provided at at-least a first end (120A) of the contact member (120), the contact portion (130) having a double involute profile.

7. The brake assembly (100) as claimed in claim 6, wherein the contact portion (130) is provided on the first end (120A) and a second end (120B) of the contact member (120).

8. The brake assembly (100) as claimed in claim 6, wherein the contact member (120) comprises a top flat face (122) and a bottom flat face (124), wherein the contact portion (130) extends between the top flat face (122) and the bottom flat face (124).

9. The brake assembly (100) as claimed in claim 8, wherein the double involute profile of the contact portion (130) at the first end (120A) comprises a pair of involutes (136A, 136B) of a circle extending from the top flat face (122) to the bottom flat face (124); and the double involute profile of the contact portion (130) at the second end comprises a pair of involutes (138A, 138B) of a circle extending from the bottom flat face (124) to the top flat face (122).

10. The brake assembly (100) as claimed in claim 6, wherein on rotation of the brake cam (110), a locus of the contact point between the contact member (120) and the flat mating surface of the brake shoe, extends in a vertical straight line.