GB1393529A - Tandem fluid-pressure servo boosters - Google Patents

Abstract

1393529 Tandem servo-boosters GIRLING Ltd 8 June 1972 [17 June 1971 21 Oct 1971] 28365/71 and 48882/71 Heading F2F A fluid pressure servo-booster having an output rod 41 connected to a piston of a master cylinder of a vehicle braking system comprises a housing 11 comprising two shells 12, 13 and incorporating a rigid internal wall 37 and movable diaphragms 31, 39 on either side of the wall 37 to thereby form four axially spaced chambers 67, 68, 69, 70 within the housing 11, the chambers 67, 69 and the chambers 68, 70 being in respective fluid communication for common pressure conditions. In the embodiment of Figs. 1, 3, the chambers 67, 69 are connected by tubular ducts 71 arranged in three groups, each of two ducts 71, housed in three angularly spaced ribs 72 on a wall 16 of shell 12. The ducts 71 extend through shaped slots 73 in an enlarged peripheral portion 40 of the diaphragm 39 and into passageways 74 in an axially extending flange portion 38 of rigid wall 37. This flange portion 38 also abuts an enlarged peripheral portion 32 of diaphragm 31 which is seated in a ring 28, and the chambers 68, 70 are connected by fluid pressure passages between the ring 28 and six ribs 26 formed on shell 13 and slots (75) cut in three angularly spaced regions of the flange portion 38. The booster also has an input rod 64 located in a valve body 24 and a flange 58 of an annular sealing member 55 is co-operable with valve seats 77, 78 on the body 24 to control the fluid operation of the booster. The member 55 is a double lip seal and the maximum internal diameter 56 between the lips is less than the minimum diameter of a recess 57 in the member 55 in which a spring register 54 is engaged. The flange 58 lies between a finger plate 44 and the valve body 24, and the finger plate 44 is engaged by a fulcrum plate 43. In a normal inoperative condition shown in Fig. 1, flange 58 is seated on seat 77 and unseated from seat 78, all the chambers 67-70 are interconnected, and a connection 76 from chamber 67 to a low pressure source thereby maintains all the chambers 67-70 at low pressure. To actuate the booster, the input rod 64 is moved towards the left and with it valve body 24; the movement of body 24 is resisted by compression springs 81, 82 and initial movement of body 24 causes the fingers of finger plate 44 to bend about the annulus of contact with fulcrum plate 43 and thereby seat flange 58 on both seats 77, 78. Thereafter flange 58 lifts from seat 77 to admit atmosphere to chambers 70 and 68 and urge diaphragms 31, 39 to the left, diaphragm 31 acting via finger plate 44, fulcrum plate 43 and a sleeve 47 and diaphragm 39 via a plate 42 and spring ring 48 on the rod 41 which is thereby urged leftwards to operate the master cylinder. When the actuating rod 64 is moved to the right the servo-booster is restored to its original position. In the embodiment of Figs. 7, 8, 9 the slots 75 are replaced by one or more holes 110 extending through a solid portion 112 of wall 37 and communicating with one or more passageways 114. The peripheral portion 40 of diaphragm 39 seals with wall 37 as seen in Fig. 9, and the peripheral portion 118 of diaphragm 31 co-operates with flange 38 and annular retaining band 138 as seen in Fig. 8. The servo-booster is assembled by mounting the partition 37 and diaphragms 31, 39 on an axial assembly, inserting the assembly into the split housing and then crimping the shells 12, 13 of the housing in the peripheral region 14.