Patent GB-1341019-A (GB)
Title: Vehicle shoe drum brakes
IPC: F16D65/08
Filed: 1971-04-19
Abstract: 1341019 Internal shoe drum brake shoes GIRLING Ltd 19 April 1971 [10 March 1970 18 April 1970] 11293/70 and 18618/70 Heading F2E A vehicle shoe drum brake has an arcuate shoe platform or support 12, Fig. 1, and at least one correspondingly-curved replaceable shoe lining component 16, Fig. 6, such component comprising a block of friction material 20 rigidly secured to a convex face of an arcuate backing plate 18, and means such as screws 27, Fig. 2, detachably retaining the lining component(s) to the shoe platform; a plurality of apertures and/ or projections are formed at at least one single circumferential position of the shoe platform 12 and are engaged by corresponding projections and/or apertures on the concave face of the backing plate(s) to transmit braking drag to the shoe platform; the projections are wholly or mainly disposed radially inwardly of the convex face of the backing plate, and the retaining means do not extend radially outwardly beyond the projections. As shown, the projections take the form of lugs 24, Fig. 2, each being an interference fit in a hole 22, Fig. 1, in the shoe platform 12, and a close fit in a hole 30, Fig. 6, in the lining component 16. Six lugs, in two sets, each of three, axially aligned, are provided. The screws 27 extend through counter-sunk holes 28 in the lining component 16, Fig. 2, and engage tapped holes 26 in the shoe platform 12. Figs. 15 and 16 show a complete shoe incorporating four lining components each overhanging the side of the shoe platform 12; the linings are parallel-faced and the lining components are identical. The lining components are interchangeable provided their inside edges remain facing each other, and this is ensured by assigning a range of values to each of the angle parameters α 1 -α 4 , #, γ, and # in Fig. 15 and to each of the distance parameters a, b, c, d, in Fig. 16; these angles and distances are concerned with the relative dispositions of the detachable retaining means, each indicated by letter L, Fig. 16, and the drag-transmitting means (or circumferential locating points), each indicated by letter T. For any one lining component, a single value is assigned to each parameter, and certain relationships amongst the angle parameters and amongst the distance parameters, respectively, have to be complied with. Each lining component has only one point T (equivalent to a hole 30), in this embodiment, so manufacturing tolerances are less critical. In Fig. 8 (not shown), two of the lugs 24 are axially offset so that if two lining components are used with it, they may not be interchanged, nor may each be fitted back to front. In Fig. 9 (not shown) the two components may be interchanged but neither may be fitted the wrong way round. In Figs. 10 to 14 (not shown) there are four identical, interchangeable components; in Figs. 17, 18 (not shown) there are two such components. In Figs. 19, 20 (not shown) two lining components are used in which the linings are asymmetrically-tapered, and the components are not interchangeable in any way. In Figs. 21, 22 (not shown) two parallel-faced components are used which are only interchangeable on rotation through 180 degrees. In Figs. 23, 24 (not shown) two identically-tapered lining components are used and these also are interchangeable on rotation through 180 degrees. For Figs. 17 to 24, sets of ranges of values, and sets of values, of the parameters, are provided in the Specification, together with relationships to be complied with. Holes 26, Fig. 1, may be untapped, and a nut provided under shoe platform 12 for each screw, instead.