| 摘要 |
1,144,349. Combined external and internal shoe drum brakes. SOC. ANON. FRANCAISE DU FERODO. 5 May, 1966 [6 May, 1965; 12 Nov.. 1965], No. 19872/66. Heading F2E. A combined external and internal shoe drum brake comprises a floating U-shaped stirrup 12, which both surrounds the drum 10 and an assembly consisting of outer and inner shoes 13, 14, and a cylinder 19 formed in a support 11 which is fixed by its legs 15 to an axle journal within the drum, the stirrup being slidable in a radial direction so that when fluid is supplied to the cylinder between a pair of pistons 20, 21, shoe 14 is applied directly by the piston 20 and shoe 13 by the reaction transmitted through the stirrup by the piston 21. In the embodiment shown, the stirrup is guided by a U-shaped rod 30 which is passed through apertures in a pair of U-shaped extensions (17, Figs. 1 and 2, not shown) of the support 11 on opposite sides of the stirrup and through a slot 31 in the stirrup. The extensions (17) are arranged to engage the ends of both shoes to absorb the braking force. Shoe 14 has a locating recess to engage the piston 20, while shoe 13 is pivotally mounted at 28 to the stirrup. The drum is formed with a number of apertures 35 which both ventilate the drum and also enable removal of the shoe 14 through any one of them. The drum is also provided with an aperture (36, Fig. 4, not shown) for access to the fluid inlet connection (22) to the cylinder. In a second embodiment (Figs. 5-8, not shown), a radially arranged shaft (54) is used to mount the stirrup (12) on the support (11), the shaft being in the form of a long bolt which is passed through an aperture in the outer arm (27) of the stirrup, through apertures in lugs (50) of backing plates (53) of the pads (13), (14), through a bore (61) drilled in the support (11), and is screwed into a tapped aperture in the inner arm (25) of the stirrup. As a result, the pads can be replaced without the need for openings in the drum, since the stirrup is dismantled at the same time as the pads are freed by removing the shaft (54). The apertures in the lugs (50) of the pad backing plates are sufficiently large to enable the whole of the braking torque to be absorbed by the support (11). The arms (25), (27) are preferably set at an angle to each other of about 30-45 to allow for conicity of the drum during heavy braking. The piston and cylinder assembly is made more compact by fitting the sealing rings (23) for the pistons in grooves in the pistons instead of in grooves in the cylinder. The drum is secured to a plate (33) which is in turn secured to a hub (41) which carries a clamp (43) to which the support (11) is secured. The disc (33) carries wheel studs (60) at an intermediate radius. A flexible plastic rod (70) having a magnetic powder core is arranged to wipe the drum surface as the drum rotates to pick up iron dust. Lining dust can escape through apertures (62) in the drum. |
