Patent GB-241585-A (GB)
Title: Improvements in and relating to braking apparatus
IPC: F16D51/56
Filed: 1925-10-19
Abstract: 241,585. Hydraulic Brake Co., (Assignees of Loughead, M.). Oct. 20, 1924, [Convention date]. Shoes acting on drums; compensating for wear. -In a drum brake, more particularly for automobiles, comprising a floating shoe adapted, when engaged with the brake drum, to move therewith, the floating shoe is provided with connections for multiplying the force imparted to it by the drum and applying is to a second brake shoe, which is thereby also engaged with the drum, and a third independently-pivoted shoe is provided which is applied to the drum directly by the means acting on the floating shoe. In the form shown in Fig. 1, the brake comprises three interchangeable shoes 17 - - 19 of channel section, the first one of which are mounted on fixed pivots 20, 21 carried by a bracket 22, whilst the pivot 24 of the third shoe is carried by a lever 25 mounted on a fixed pivot 26. To permit initial adjustment of the shoes, the pins 20, 21, 24 are of the form shown in Fig. 5, the eccentric portions 43, 44 being received in the shoe flanges, and the portion 45 by ,the bracket 22 or the lever 25. A stud 29 having a ball head 30 is screwed into a member 27 provided near the free end of each shoe and may be adjusted therein to compensate for wear of the shoes and be locked in adjusted position by a cap screw 31. Toggle links 32, connected by a link 33 to an arm 34 on a brakeoperating shaft 35, have recessed ends to engage the heads 30 cf the shoes 17, 19, and a link 32<1>, identical with the links 32, engages the head 30 of the shoe 18 and is pivoted on a pin 38 carried by the lever 25. The links 32, 32<1> are held in engagement with the ball heads by brake release springs 36, 39, the spring 39 serving also to position the pivot 24, when the brake is released, by holding the lever 25 against a fixed stop 41. When the shaft 35 is rocked to apply the brakes, the shoes 17, 19 are engaged with the drum by the links 32, and when the drum votates in the direction of the arrow, the force imparted to the shoe 19 by the drum is multiplied by the lever 25 and link 32<1> and transmitted to the shoe 18, the line joining the axes of the pins 24, 26 being radial to the drum, so that the movement of the pin 24 is almost tangential, and the link 32<1> being parallel to the radius bisecting the arc formed by the shoe 18, so that this shoe is firmly engaged with the drum. When the drum rotates in the opposite direction, the shoe 13 is ineffective, but both shoes 17, 19 are effective, since the pivot 24 of the latter becomes fixed by the engagement of the lever 25 with the stop 41. Guide plates 42, attached to the drum cover 14, are provided to prevent rattling of the brake shoes, and a small normally closed aperture in the cover plate is provided to permit access to the pivot 24 for adjustment purposes without dismantling the brake. The diameter of the cover plate is substantially equal to that of the interior of the brake drum, so that when the latter is removed with the wheel to permit adjustment of the shoes. the cover plate serves as a guide by means of which the shoes may be positioned correctly.