GB722043A - Improvements in or relating to internal shoe drum brakes for vehicles - Google Patents

Abstract

722,043. Internal shoe-drum brakes. MANLEY, G. E., and FAZEKAS, G. A. G. June 1, 1953 [April 10, 1952]. No. 9153/52. Class 103 (1). In an internal shoe-drum brake of the type in which one or both shoes are arranged to be in light rubbing contact with the brake drum, as described in Specification 519,787, when the brakes are released, the leading shoe 30 and trailing shoe 31, Fig. 3, are coupled by links 34 and 35 to a balance lever 36 pivoted on the backplate, such that when the brake is inoperative the trailing shoe 31 is in light contact with the drum, but the leading shoe 30 is held just clear of the drum. This effect may be obtained by making the arms of the lever 36 of different length or by arranging the links 34, 35 at different angles to the lever 36. A spring 41 between abutment 42 on the back plate and shoe 30 provides the necessary bias to hold the trailing shoe 31 in light contact with the drum. Alternatively this may be produced by locating the main retraction spring 42 radially outwardly of the abutment pins 32, 33 as in Fig. 5. Instead of a fluid pressure actuator, a bell crank lever 60 pressing against the web of a shoe through a steel insert 65 in a slide 62 and operated by a cable attached to a lever'66 may be used, the crank 60 and lever 66 being coupled by an adjustment mechanism comprising a threaded tappet 69 with ratchet and pawl detent. Two further forms of lever operating mechanism are described. The arrangement of the anchor pins may be as described in Specification 675,579.