Patent GB-239535-A (GB)
Title: Improvements in four wheel braking systems for motor vehicles
IPC: B60T8/40
Filed: 1925-09-04
Abstract: 239,535. Studebaker Corporation, (Assignees of Link, V.). Sept. 4, 1924, [Convention date]. Braking; hydraulic transmission; deflectable axle-ends. -In a four-wheel brake system for motor vehicles the front and rear wheel brakes on one side of the vehicle are connected by mechanical means not connected to those on the other side the two sets of mechanical connections being respectively connected to a pair of pistons in a common cylinder, fluid - pressure in which is adapted to be established for operating the brakes bv a pump geared to the road wheels. The fluid-pressure system is of the type comprising a gear - wheel pump normally circulating freely oil or other liquid the circuit being restricted to establish the braking pressure. The rear wheel brakes can be applied by the direct pressure of the driver exerted on the pedal or other control valve operating member. The pressure applied to the front and rear brakes is equalized but a lesser braking action is obtained on the front wheels than on the rear wheels. The fluid-pressure system comprises a casing 46 bolted to the rear of the gear box 38 of the vehicle and enclosing the wheels 49, 50 of a gear-wheel pump, the wheel 49 being keyed on the transmission shaft 44. The pump normally circulates oil supplied from the gear box by a passage 53 and in a circuit comprising passages 52, 54, ports 55, 57 in a control valve cylinder 56, and passage 58. Passages 59, 60, 61 lead from the passage 54 to a transversely disposed cylinder 62 formed in the lower part of the gear box 38 and containing a pair of pistons the rods of which abut against a pair of levers 82. A slide valve 65, Fig. 15, working in the cylinder 56 and connected by a rod 67 to a pedal 66 is adapted gradually to restrict the ports 55, 57 and thus to establish the desired pressure in the brake cylinder 62. A relief-valve 69 with a spring adjustable by a screw 72 is provided and in addition provision is made for a limited amount of leakage from the pressure side of the system to prevent locking of the wheels. The fluidpressure in the system reacts on the valve 65 and the driver thus " feels " this pressure through the pedal. Passages are also provided for the return of oil which escapes past the pistons in the brake cylinder 62. The levers 82 against which the piston rods abut are pivoted to arms 81 and each is connected by rod 90 to one arm 89. Fig. 10, of a three-armed bell-crank pivoted upon an arm 85 mounted at 84 to swing freely on the chassis 34. The other arms of this bell-crank are connected to the brakes on one of the front and rear wheels by rods 121, 108, rock shaft 102 and rod 100. The connections for the front-wheel brakes which are of the internal shoe type comprise a rock shaft 118, Figs. 1 and 19, mounted on the front axle and having arms 120, 117 connected respectively to the rod 121 and to a link 116 which is jointed also to an arm 115 on the cam shaft 114. The ball-joint 117<1> between the members 116. 117 is disposed in the axis of the steering pivot. The cam shaft 114 and pivots 110 of the brake shoes are mounted in a cross-member 111 integral with the steering knuckle. These crossmembers may also carry the steering connections comprising an arm 123 on one member for the attachment of the control rod 124 and an extension 125 on each member for a link 126 connecting the two wheels. By reason of the pivots of the bell-cranks 89 being free to move an equalized force on the connections to the front' and rear brakes is ensured but by the provision of internal and external brakes respectively on the front and rear wheels a less intense braking action is produced on the front wheels. To provide for the direct application of the rear wheel brakes in the event of failure of the fluid-pressure or during backward travel when the fluid system is ineffective, the valve controlling pedal 66, Fig. 4, has connected thereto an additional link 132 extending to an equalizing bar 128 the ball-ends of which are socketed to the ends of arms on the shafts 102. The arrangement is such that the direct pressure is not applied to the brakes until the pedal has been moved sufficiently completely to close the ports of the control valve to give the full fluid-pressure operation.