Pin Slider Disc Brake

In general a pin slider disc brake, such as illustrated in U.S. Pat. Nos. 3,375,906 and 3,628,639, provides a pair of pins which extend from a torque member to slidably carry a caliper. Each pin forms a slidable connection on both sides of the disc with the caliper so that the caliper requires a pair of coaxial openings for receiving each pin. Consequently, the caliper of the prior art pin slider disc brake includes a pair of radially outwardly extending flanges so as to form the pair of coaxial openings. As a result the outwardly extending flanges take up space so that the construction is not compatible with the small space available for many small cars, especially those cars with front wheel drive.

In addition, the pin slider disc brake of the prior art utilizes a resilient ring or grommet to form a sliding connection between the pair of pins and the caliper so that the metal pins slidably engage the resilient rings.

The invention herein discloses a caliper which forms a single sliding connection with each pin in a pin slider disc brake. In particular, the caliper slidably engages at least one pin on the side of the disc which also includes a hydraulic actuator carried by the caliper and referred to as the inner side. The one pin extends to the outer side to slidably engage an outer friction element while remaining spaced from the caliper on the outer side. The outer friction element includes projections which cooperate with the caliper to transfer torque developed by the outer friction element to the caliper.

Moreover, the one pin includes a thermo-plastic sleeve and the caliper carries a resilient bushing with an opening for receiving the thermo-plastic sleeve. The outer friction element also carries a resilient bushing with an opening for receiving the one pin. The thermo-plastic sleeve cooperates with the resilient bushing to form the slidable engagement between the caliper and the one pin. In order to carry the thermo-plastic sleeve on the one pin, there is a recess on the pin and the thermo-plastic sleeve is disposed therein. A head on the pin forms one end of the recess while a shoulder on the pin forms the other end of the recess. The shoulder also engages the torque member so that when the one pin is secured thereto, the thermo-plastic sleeve remains spaced from the torque member in an unlocked condition.

It is an object of the present invention to provide a pin slider disc brake which is compactly structured to fit between a small car frame and wheel assembly.

It is an additional object of the present invention to provide a disc brake assembly which accommodates manufacturing tolerances by providing an opening in the outer friction element to receive a pin slider disc brake.

FIG. 1 is an end view of a disc brake assembly;

FIG. 2 is a top view of the disc brake assembly of FIG. 1 with the portion along line 2--2 of FIG. 1 being cut away; and

FIG. 3 is a cross-sectional view of FIG. 1 taken along line 3--3 of FIG. 1.

A disc brake assembly 10 includes a torque member 12 which is secured to a non-rotatable portion of a frame 14 via bolts 16. The torque member is substantially U-shaped to form a pair of radially extending arms 18 and 20. The arms form bores at 22 and 24 and the left arm 18 includes an axially extending flange 26; however, it is possible to also provide an axially extending flange for the right arm 20. The bore 22 is disposed in the flange 26 to receive a pin 28 while the bore 24 receives a pin 30. A caliper assembly 32 is slidably carried by the pins and a hydraulic actuator 34 carried by the caliper assembly 32 cooperates with a pair of brake shoes 36 and 38 to urge the latter into frictional engagement with a disc or rotor 40.

Turning to FIG. 2, the caliper assembly 32 includes a pair of radially extending flanges at 42 and 44 which form openings 46 and 48. Viewing the left radial flange 42, as the right flange 44 is constructed similarly, the opening 46 receives a resilient bushing 50, such as a rubber grommet, and the pin 28 may optionally carry a thermo-plastic sleeve 52 to enhance sliding with the resilient bushing 50. The thermo-plastic sleeve 52 extends through an opening on the resilient bushing 50 and cooperates with the latter to form a sliding connection between the pin 28 and the caliper 32.

The pin 28 forms a head 54 and an adjoining recess 56 to receive the thermo-plastic sleeve 52. A threaded portion of the pin 28 at 58 is engageable with a threaded portion of the bore 22 at 60. In addition, a second portion 62 of the pin 28 forms a close fit with a second portion 64 of the bore 22. A small clearance between portions 62 and 64 is provided to accommodate manufacturing tolerances upon insertion of the pin 28 into the bore 22. A shoulder 55 on the pin 28 is engageable with the torque member arm 18 when the pin 28 is threadably engaged with the bore at 60. The shoulder 55 separates the recess 56 from the torque member so that the thermo-plastic sleeve 52 is always spaced from the torque member. Therefore, the thermo-plastic sleeve is not subjected to compressive axial loading when the pin is attached to the torque member. As shown in FIG. 2, the inner diameter of bushing 50 is greater than the diameter of the shoulder 55 so that the bushing 50 is free to slide on the pin 62 between the head 54 and the torque member arm 18.

The inner brake shoe 36 includes a backing plate 66 which fits within the opening formed by the U-shaped torque member 12. Consequently, braking torque developed by the inner brake shoe 36 is transmitted directly to the torque member 12. Moreover, the inner brake shoe 36 releasably carries a spring 68 to retain the inner brake shoe in abutment with the underside of the caliper assembly via tabs 67 and 69 extending from the backing plate 66 so as to eliminate rattle generated by the inner brake shoe. The outer brake shoe 38 also includes a backing plate 70 which is formed with projections 72. The projections extend into apertures 74 which are provided on a radially inwardly extending leg 76 of the caliper assembly 32. The projections extend into apertures 74 which are provided on a radially inwardly extending leg 76 of the caliper assembly 32. As a result braking torque developed by the outer brake shoe 38 is transmitted to the caliper assembly 32 which in turn transmits braking torque to the axially extending flange 26 via an abutment interface between the caliper assembly and the axially extending flange at 77. Consequently, substantially no braking torque is transmitted to the pins 28 and 30, even though the resilient bushings 50, 81, and 84 may be deformed during braking. A pair of radially outwardly extending ears at 78 and 80 on the friction element 38 carry the resilient bushings 81 and 84 within openings 83 and 85 for receiving the pins 28 and 30, respectively. The resilient bushings form a spacing between the pin and the wall of the openings 83 to permit slight movement of the brake shoe 38 without transferring any torque to the pin portion 62. The opening on the bushing 81 or the opening on the bushing 84, or both, may be elliptical to accommodate manufacturing eccentricities between the pins 28 and 30. The outer brake shoe 38 releasably couples to a spring 82 for retaining the outer brake shoe in abutment with the radially inwardly extending leg 76 of the caliper.

If the disc or rotor 40 is rotating in a reverse direction, such as when a vehicle is backing up, the torque member 12 includes a second abutment interface at 79 with the caliper assembly 32 to absorb braking torque generated through the caliper assembly during braking. The abutment interface at 77 is partially formed by at least two projections on the axially extending flange 26 while the abutment interface at 79 is formed by only one projection on the arm 20 as more braking torque will be developed during forward rotation of the disc 40 than reverse rotation of the latter.

In accordance with the invention, it is seen, viewing FIG. 2, that the caliper assembly 32 forms a single sliding connection with each pin 28 and 30 via the radially extending flanges 42 and 44 and the pins 28 and 30 are spaced from the caliper 32 on the axially outer side of the torque member 12. Consequently, the transverse width A, of the caliper 32 is substantially uniform from the radially extending flanges 42 and 44, but not inclusive thereof, to and including the radially inwardly extending leg 76. In other words, the caliper transverse width A is less than the transverse distance between the pins 28 and 30, provided the transverse width A is measured axially outside of the flanges 42 and 44.

In addition, the outer friction element 38 includes openings 83 and 85 for receiving the pins 28 and 30. These openings are provided in the radially outwardly extending ears 78 and 80 on the outer friction element, so that the concentricity between the openings 46, 48, and 83, 85, respectively, is maintained in the absence of openings being required in the caliper assembly leg 76. In contrast thereto, the prior art generally requires two sliding connections between the caliper and each pin so that two openings on the caliper assembly are required to be concentric for receiving the pin. As a result, the disc brake assembly of the present invention is believed to be easier to manufacture with respect to accommodating manufacturing tolerances, in comparison to the prior art pin slider disc brakes.

Furthermore, if the thermo-plastic sleeve is provided, the resilient bushing cooperates with the thermo-plastic sleeve to form a sliding connection between the caliper and pin to accomodate axial movement of the caliper as the hydraulic actuator is operated to urge the pair of brake shoes into frictional engagement with the rotor. Otherwise, the resilient bushing forms a single sliding connection with the pin 28. The disc brake 10 operates in a conventional manner to retard rotation of the rotor.

The foregoing description is directed to the left pin 28 and flange 42; however, the right pin 30 may carry a thermo-plastic sleeve which cooperates with a resilient bushing on the flange 44 in the same manner as the sleeve and bushing, 52 and 50, respectively.

Many variations of the present invention are feasible by one skilled in the art and, as such, these variations are intended to fall within the scope of the appended claims.