GB2062147A - Drum brake assembly for automotive vehicles - Google Patents

Abstract

In the assembly, the one or two webs (24) of each brake shoe (11, 12) have apertures (34) in the ends (13, 14) to engage rotational anchor pins (16, 17) the apertures and the pins having co-operating flats (38, 40). In the embodiment of Figures 1-3 the apertures have section (36) and lateral flats (38, 39) to engage sections (42) and lateral flats (40, 41) on the ends of the anchor pins (16, 17). The apertures form slidable, but not rotational, connections with anchor pins (16, 17) to support brake shoes (11, 12) and to allow a pivoting movement of brake shoes (11, 12) by means of anchor pins (16, 17) which rotate in bushings 22 when an actuation and release of the brake is effected by a cam (26). The apertures are directed in such a way with respect to a line passing through the centers C1 of the brake assembly and C2 of the rotational pins (16, 17), that the ends of the brake shoes form hooks preventing the ends of the shoes, having the apertures, from being moved away from the anchor pins (16, 17) whenever a brake actuation is effected. In the embodiment of Figure 4 (not shown) the apertures are semi- circular with an acuate section (54) and a lateral flat (56). <IMAGE>

Description

SPECIFICATION Drum brake assembly for automotive vehicles This invention relates to a drum brake assembly for automotive vehicles consisting of a brake spider, on which is mounted a pair of brake shoes, pivotably mounted on one of its ends and actuated by a rotatable cam, disposed between the opposite brake shoes ends. The cam rotation will cause a pivoting movement of each shoe around its respective anchor pin, moving them away from the brake assembly center, to force them into engagement with the internal friction face of the brake drum. The shoes employed in this type of brake are fabricated or cast with one or two webs, as required, and according to the characteristics of the vehicle where said shoes will be used.

In the end of the shoe, actuated by a cam, a cam follower roller is mounted. The opposite end of said shoe is mounted on an anchor pin. There are two anchor pins, one for each shoe.

In the present state of the art, the shoes are mounted by inserting an anchor pin through a hole located in the brake spider and hole(s) provided in the web(s) of each shoe. Normally, pins and shoes are held in place by snap rings at the ends of the anchor pins, thus, preventing any displacement of either shoes or pins, except for pivoting movement of the shoes, necessary to obtain the braking action of the brake assembly.

The above described system presents some disadvantages, well known to those skilled in the art. The main disadvantages being is the difficulty to remove the anchor pin when friction material needs to be changed (brake lining) or when the shoe should be replaced. Due to vehicle usage, and environmental conditions it is impossible to prevent penetration of humidity and/or contaminants in the bearing area between the anchor pin and the anchor pin hole, and said contamination and/or humidity often causes seizing and corrosion of the pins creating difficulty in removal in order to remove said shoe.

Sometimes seizing and corrosion are so bad that the user is compelled to change the entire brake assembly.

This invention presents a brake shoe, with one or two webs, having, in the end opposite to that actuated by the cam, an aperture slidably engaging the anchor pin. In one option, said pin has, on both ends, lateral flats parallel to each other and equidistant from the center of said pin.

The web(s) of said shoe present(s) a U-shaped aperture having a radial section, which abuts the radial section of the pin, between two lateral and parallel flats that intersect with the radius of the radial section and that, in the assembled brake, engage with the lateral flats of the anchor pin.

The two parallel flats of the aperture in the end of said shoe are directed in such a way in the web, that, when said shoes are mounted, said parallel flats will form an angle with a line passing through the anchor pin center and brake assembly center.

The purpose of this angle in to prevent, that during a brake application, when by a tangential force one shoe is urged into engagement with its anchor pin, and the other shoe tends to move away from its respective anchor pin, said angle maintains the parallel flats in a position, such, that then will form a gripping hook, which prevents that said shoe moves away or disengages from the anchor pin.

In another option of this invention the pin has one lateral flat on each end, both flats to be in the same plane. The shoe web(s) show(s) an aperture substantially semi-circular, having a radial section which engages the radial section of the anchor pin and a flat, that intersects with the radius of said radial section, and that, in the brake assembly engages said lateral flat of said anchor pin. The lateral flat of said aperture in the end of said shoe is directed in such a way in the web, that, when said shoes are mounted, said lateral flat will form an angle with a line that passes through the center of the anchor pin and the center of the brake assembly.The purpose of this angle is to prevent, that during a brake application, when by a tangential force said shoe is urged into engagement with an anchor pin and the other shoe tends to move away from the anchor pin, said angle sets the lateral plane in such position, that it will form a gripping hook which prevents said shoe from moving away from the anchor pin.

One of the advantages of the shoe constructed as described herein is that, whenever necessary, said shoes may be removed without any problem or aid of special tools.

Still another advantage of said shoes constructed as described herein is that there is no rotational movement of the shoe web(s) on the anchor pins. Thus, wear of shoe web(s) will be avoided.

Figure 1 is a front view of the brake assembly, according to the present invention; Figure 2 is a view of the lower part of the brake spider of the brake of Figure 1, with one end of the shoe showing the U-Shaped aperture; Figure 3 is a view of a section cut along line A-AofFigure 1; and Figure 4 is a view of the lower part of the brake spider, with one end of the shoe showing a substantially semi-circular shaped aperture.

Referring now to the drawings, a brake assembly, actuated by a cam is indicated by the numeral 10. The assembly 10 is supported by a brake spider 20, which is rigidly secured to the vehicle axle flange (not shown).

The brake assembly 10 includes a pair of brake shoes 11, 12 each being pivotally mounted by one fits end 13, 14 on an anchor pin 16, 17 which in turn is secured to the brake spider 20. Anchor pins 16, 17 are individually mounted in cylindrical holes 21 formed in hubs 18, where guide bushings 22 are pressed in, which rotatably receive anchor pins 16, 17; the assembly is clearer in Figure 3. Hubs 1 8 are integral parts of the brake spider 20, and are axially off-set so as to support a pair of webs 24 of the brake shoes 14, 1 5.

A cam 26 is provided between the brake shoe ends, opposite to the anchor pins 16, 17, having a rotary movement. Each brake shoe 11, 12 is provided with a roller 28, 29 which functions as a follower of cam 26. The cam 26 is rotated by means that are not shown in the drawings but are well known to those skilled in the art. When brake 10 is actuated, cam 26 rotates, urging the shoes 11, 12 outward by means of rollers 28. The shoes are pivoted around the axis of the bushings 22, by means of anchor pins 16, 1 7. This displacement expanding the brake shoes 11, 12 forces the brake lining 30 into engagement with the internal face of a brake drum (not shown) fastened to the wheel of vehicle.

When the brake 10 is released, the brake shoes 11, 12 and brake linings 30, bonded to the brake shoes, move away from the internal surface of the brake drum by action of a return spring 32, held conveniently between the webs 24 of the two shoes.

In the end opposite to the followers 28, 29 of cam 26, each shoe web 24, shows a U-shaped aperture 34, formed by a radial portion 36, and two parallel flats 38, 39, which intersect with the radius of said radial section.

Anchor pins 16, 17, in turn, have on both ends two parallel flats 40, 41 , to engage with parallel flats 38. 39 of aperture 34 of brake shoes 11, 12, while the radial section 36 of aperture 34, engages radial section 42 on both ends of anchor pin 16, 1 7. Apertures 34 are oriented in such a way in shoe ends 13, 14, that, when mounted in brake assembly 10, the plane perpendicular to the parallel flats 38, 39 of apertures 34 will form an angle varying between 100 and 400 in relation to a line that passes through the centers C1 of brake assembly 10 and C2 of anchor pins 16, 17 as illustrated in Figure 2.This angle causes ends 13, to act as hooks that hold shoes 11, 12 in contact with anchor pins 16, 1 7 preventing shoes 11, 12 from being separated from anchor pins 16, 1 7 when, during a brake application, the friction force developed between the brake linings 30 and the internal surface of the brake drum generates a tangential force that tends to separate the brake shoes 11, 12 from anchor pins 16, 17. It should be understood that, when a wheel and brake drum rotate counter-clockwise, as indicated by the arrow in Figure 1 , this hook action occurs with shoe 12, shown at the right in Figure 1.

Should the wheel rotate clockwise, then this action occurs with the shoe 11 shown at the left in Figure 1.

Bushings 22 are pressed in the holes 20 of hubs 18, of brake spider 20. The anchor pins 1 6, 1 7 are slidably mounted in the bushings 22, so as to allow a free rotary movement. Webs 24 of brakes shoes 11, 12, show holes 46, close to apertures 34, where springs 48 are hooked, which hold the radial sections 36 of apertures 34, in contact with radial sections 42 of anchor pins 1 6.

Another embodiment of the invention is represented in Figure 4.

In the end opposite to the followers 28, 29 of cam 26, each shoe web 24 shows a semicircular shaped aperture 52 formed by a radial section 54 and a lateral flat 56 which interesect with the radius of said radial section 54 to slidably engage anchor pins 16, 17 which in turn have on both ends a radial section 60 and a lateral flat 58. The radial section 54 ends in an extension 50 parallel to the lateral flat 56 and tangential to the radius of the radial section 54.

Apertures 52 are oriented in such a way in shoe ends 1 3, 14 that when mounted in brake assembly 10, the plane perpendicular to the flat 56 of aperture 52 will form an angle varying between 100 and 400 in relation to a line passing through the centers Cr of brake assembly 10 and C'2 of anchor pin 17.

Claims (12)

1. A drum brake assembly for auotomotive vehicles, characterized in that the brake shoe comprises one or two web(s) (24), having an aperture (34), in one end, to slidably engage an anchor pin (16), said aperture (34), containing a radial section (36), and two parallel flats (38) to engage one radial section (42) and two parallel flats (40) of said anchor pin (16).

2. A drum brake assembly for automotive vehicles, as claimed in claim 1, characterized in that said anchor pin has, at each end, two radial sections (42) and two parallel flats (40), the two said parallel flats (40) being equidistant from the center of said anchor pin (16), and intersecting with the two said radial sections (48), the distance between the two said parallel flats (4) being smaller than the anchor pin diameter (1 6), being said pin slidably mounted in a bushing (22), which in turn is pressed in the hole (20), of hub (18), of spider (12).

3. A drum brake assembly for automotive vehicles, as claimed in claim 1, characterized in that the two webs (24) of the brake shoe are formed in one end with equal and laterally aligned apertures (34), each of which consisting of a radial section (36), and two parallel flats (38), forming an extremity (44).

4. A drum brake assembly for automotive vehicles, as claimed in claim 1, characterized in that, when the brake shoe is mounted on the brake assembly (10), said aperture (34), is oriented at an angle of 100 to 400 formed by the plane perpendicular to the parallel flat (38), and by a line, passing through the centers of brake assembly (10), and of the respective anchor pin (1 6), such that the extremity (44), of the brake shoe acts as hook, to prevent the displacement of said extremity (44) from said pin (16), in response to the tangential force that tends to displace the said brake shoe (14) toward the opposite end of said brake shoe.

5. A drum brake assembly for automotive vehicles, as claimed in claim 1, characterized in that the two parallel flats (38), of aperture (34) are equidistant from the center of the radius of the radial section, such that the distance between said two parallel flats (28) is smaller than the diameter of said anchor pin (16).

6. A drum brake assembly for automotive vehicles, as claimed in claim 1, characterized in that the said aperture (34) of said brake shoe (14) engage slidably, but not rotatably, said anchor pin (1 6), which, for this engagement has a radial section (42), and two parallel flats (40), the said anchor pin (16) being rotatably mounted in a bushing (22), and said bushing (22) pressed in the hole (20) of hub (18) of brake spider (12).

7. A drum brake assembly for automotive vehicles, characterized in that the brake shoe has one or two web(s) (24) with an aperture (52) in one end, to slidably engage an anchor pin (16), the said aperture consisting of a radial section (54) and a lateral flat (56), to engage with a radial section (60), and lateral flat (58) of said anchor pin (16), the radial section ending in an extension (50), parallel to said lateral flat (56), and tangential to the radius of the radial section (54).

8. A drum brake assembly for automotive vehicles, as claimed in claim 7, characterized in that the anchor pin has, on each end, a radial section (60) and lateral flat (58), the two said lateral flats (58) being parallel to each other and equidistant from the center of said anchor pin (16), and intersecting with the two said radial sections (60), being said pin slidably mounted in a bushing (22) which in-turn is pressed in to the hole (20) of hub (18) of brake spider 2).

9. A drum brake assembly for automotive vehicles, as claimed in claim 7, characterized in that the webs (24) are formed in one end with apertures (52), equal, and laterally aligned, each of which consisting of a radial section (54), end one lateral flat (56) forming an extremity (44).

10. A drum brake assembly for automotive vehicles, as claimed in claim 7, characterized in that, when the brake shoe is mounted on the brake assembly (10), said aperture (52) is oriented at an angle of 100 to 40 formed by the plane perpendicular to the lateral flat (56) and by a line passing through the center of the brake assembly (10) and of the respective anchor pin (1 6), such that the extremity (44) of the brake shoe acts as a hook to prevent the dislodging of said extremity (44) from said pin (16), in response to the tangential force that tends to displace the said brake shoe (44) toward the opposite end of said brake shoe.

11. A drum brake assembly for automotive vehicles, as claimed in claim 7, characterized in that the said aperture (52), of the said brake shoe (14), engages slidably, but not rotatably with said anchor pin (16), that, for this engagement, has radial section (60), and lateral flats (58), the said anchor pin (16) being rotatably mounted in a bushing (22), and said bushing !22) being pressed in the hole (20) of hub (18) of brake spider (12).

12. A drum brake assembly substantially as described and as shown in the accompanying drawings.