Patent GB-1343314-A (GB)
Title: Brake actuating mechanism
IPC: B60T13/10
Filed: 1971-04-19
Abstract: 1343314 Brake transmission mechanisms BENDIX CORP 19 April 1971 [30 March 1970] 24096/71 Headings F2E and F2F A variable leverage brake activating mechanism connected to a power booster for a master cylinder comprises a pedal operated lever 10, pivoted at 12, to which are pivoted first and second force transmitting means 14, 18 comprising rods 22, 26 at leverage points 16, 20 means being provided such that when power is supplied to the booster the latter is actuated through the rod 26 but if the power is not available the booster is actuated through rod 22 thereby increasing the leverage on the output rod 44 connected to the booster. In the embodiment shown rod 22 is located with an end clearance 54 within a sleeve 48 rigid with rod 44 and passing through a plate 50 with rod 26 and a spring 30 extending between the plate 50 and a retainer 32. In normal operation when lever 10 pivots about pivot 12 rod 26 moves faster than rod 2 due to it being further from pivot 12 and the force exerted on lever 10 is transmitted to rod 44 through rod 26 and spring 30. If no power is available the applied force is transmitted through the spring until the pressure required to actuate the master cylinder is greater than the spring resilience whereupon the latter collapses and permits rod 22 to close gap 54 and abut rod 44, actuation then taking place through rod 22 about leverage point 16. In a further embodiment the lever 10 is pivoted to a bracket 58, Fig. 2 (not shown), coupled to a vacuum operated servo (56) for the lever 26 so that during normal operation servo 56 is moved as a unit when lever 10 is rotated, the force applied to lever 10 being transmitted to the actuating rod 44 through a rod (88). When no vacuum is available a sleeve (78) in which rod 88 is slidable, moves away from diaphragm (80) of the servo carrying the shell (74) thereof with it. The applied force is then transmitted through the first force transmitting means (14<SP>1</SP>). In a further construction Fig. 5 (not shown) the second force transmitting means (191) is responsive to the movement of an hydraulic piston (98) operated by a vacuum control unit (92) attached to a yoke (58<SP>1</SP>) which is pivotally connected to the lever 10. In a final embodiment Fig. 6 (not shown) the two force transmitting means are connected to the actuating rod via a housing (130) having cylindrical chambers 136, 152 in which are respectively located the first force transmitting means and the actuating rod. A further chamber (132) contains hydraulic fluid and a piston (134) connected to the second force transmitting means is located therein, chamber (132) communicating via a central chamber (148) and a ball valve (140) with a reservoir (138). In normal operation the second force transmitting means acts on piston (134) which causes the hydraulic fluid to maintain ball valve (140) closed and maintain piston (134) in its original position, the apply force being transmitted to the actuating rod through the second force transmitting means until the force required to move the latter is greater than that of a spring (154) acting thereon. Spring (154) then collapses so that the actuating rod starts to move thereby pushing ball valve (140) off its seat permitting fluid to escape into the reservoir. A spring (160) biasing the piston (134) in a direction opposite to the apply direction then collapses so that the push rod 22 of the first transmitting means closes a gap between itself and the bottom of the bore 136 so that the apply force is transmitted through the first force transmitting means.