Patent GB-1157222-A (GB)
Title: Servo Assisted Motor Vehicle Braking System
IPC: B60T13/52
Filed: 1966-12-07
Abstract: 1,157,222. Fluid-pressure brakes; handbrake mechanism. FORD MOTOR CO. Ltd. 7 Dec., 1966 [21 Dec., 1965], No. 54659/66. Headings F2E and F2F. In an hydraulic braking system for a vehicle of the kind having a servo-operated master cylinder (28, Fig. 1, not shown), the servo being of the vacuum suspended type and being controlled by a manually operated valve of the follow-up type, the movable valve plunger 64<SP>1</SP>, which is slidable within the power piston (54, Fig. 1), is operated by a linkage which is so arranged that initial movement of the linkage causes plunger 64<SP>1</SP> to be moved to a position relative to the servo piston such that air is admitted to the power chamber (50, Fig. 1) to cause the servo piston to move, after which the plunger and servo piston move together so as to maintain their relative positions, without further movement of the manually operated member controlling the linkage being necessary. In the embodiment of Fig. 2 (Fig. 1, does not disclose the invention), the linkage comprises a first lever 78<SP>1</SP>, which is pivoted at 80<SP>1</SP>, is connected conventionally by a link 82<SP>1</SP> to a pedal, not shown, and has a lost-motion connection 90, 98 with a rod 66<SP>1</SP> engaging the plunger 64<SP>1</SP>, and a second lever 100, which is pivoted to the lever 78<SP>1</SP> on the pin 101 by which the link 821 is connected, the lower end of the lever 100 being connected by a rod 104 to a pull type control knob on the dashboard of the vehicle, and the upper end having an arcuate surface 102 which engages the slotted end 98 of the rod 66<SP>1</SP>. A sleeve 92 surrounds the rod 66<SP>1</SP>, is pivoted to the pin 90, and has spaced circumferential fingers 94 arranged to engage an insert 96 in a sleeve-like extension 56<SP>1</SP> of the power piston when pressure is not being applied to the pedal. In pedal operation, the initial movement moves plunger 64<SP>1</SP> to the position in which air is admitted to the power chamber and the consequent movement of the servo piston causes follow-up movement of the pedal as usual, the fingers 94 moving away from the insert 96 and only re-engaging the latter when pressure is removed from the pedal. If, however, the dashboard control is operated, the resulting relative pivotal movement of the levers 78<SP>1</SP>, 100 causes the clearance 106 in the lost-motion connection 90, 98 to be taken up simultaneously with movement of the plunger 64<SP>1</SP> to the position in which air is admitted to the power chamber, so that the " feel " which reacts on the plunger 64<SP>1</SP> as a result of the provision of a conventional resilient reaction disc (62, Fig. 1) is absorbed by the insert 96 and does not react on the pedal linkage, whilst further movement of the dashboard control to maintain servo operation during subsequent follow-up movement of the plunger 64<SP>1</SP> is substantially eliminated by the location of the point at which rod 104 is connected to the lever 100 being close to the pivot 80<SP>1</SP>, since during follow-up movement the two levers 78<SP>1</SP>, 100 pivot together about the pivot 80<SP>1</SP>. In a second embodiment, Fig. 3, the dashboard control is eliminated and the second lever 100<SP>11</SP> is operated, through link 82<SP>11</SP>, by the pedal 84<SP>11</SP> so that follow-up movement of the pedal is substantially eliminated as a result of pivoting of the two levers about pivot 80<SP>11</SP> during follow-up movement of the valve plunger. In this embodiment the two levers are pivoted together at 110 and an arcuate edge 112 of lever 100<SP>11</SP> engages a corresponding surface on the slotted end 114 of the rod 66<SP>11</SP>, since the direction of rotation of lever 100<SP>11</SP> is reversed, operation otherwise being similar to that for dashboard operation in the first embodiment with the exception that, should a vacuum failure occur, the lower end portion of the lever 100<SP>1</SP> is able to contact a stop 113 to enable direct pedal operation of the master cylinder without excessive pedal movement in that event.