Patent GB-997700-A (GB)
Title: Hydraulic brake system for motor vehicles
Inventor: MEIER ERNST
IPC: B60T8/26
Filed: 1961-02-01
Abstract: 997,700. Hydraulic brakes. H. TEVES, E. A. TEVES, and M. TAUSEND, [trading as ALFRED TEVES MASCHINEN-UND ARMATURENFABRIK KOMM. GES.]. March 9, 1962 [Feb. 1, 1961], No. 3801/61. Heading F2F. In an hydraulic master cylinder braking system for a vehicle means is provided for controlling the braking pressure applied to the wheel brake cylinders associated with a vehicle axle in accordance with the load on the axle, the means comprises a first piston and cylinder device 3 in which operates a piston 8 for interrupting the flow of fluid from the master cylinder 4 to the wheel brake cylinders associated with the rear axle 23 of the vehicle and a rod member 10 acts on the piston 8 and is controlled by a second piston and cylinder device 1 supplied with fluid from the master cylinder via conduit 14 and mechanically connected to the rod 10 by means of a lever system 25, 23<SP>1</SP>, 20, 21 responsive to deflection of the axle 23. At the commencement of braking, fluid flows from the master cylinder-4 through the first piston and cylinder device 3 via passage 9 in the piston 8 of the device 3, through line 2 and distributer 5 to the line 7 connected to the brake cylinders 6. Fluid also flows through the line 14 to the second piston and cylinder device 1 which, as the pressure builds up therein, swings about its pivot 13 from a substantially vertical position to move the rod 10 to the left and close the passage 9 in the piston 8. The master cylinder pressure then acts on one side of the piston 8 whilst the brake cylinder pressure together with the pressure exerted by the rod 10 acts on the other side of the piston which will move in the cylinder 3 until the opposing pressures are substantially balanced. When the second piston and cylinder device is substantially coaxial with the cylinder 3, the brake pressure will then have fallen to zero since the master cylinder pressure on one face of the piston 8 will be completely balanced by the same pressure exerted through the device 1 on the other face of the piston. As the axle load increases the angle through which the device 1 is permitted to swing is reduced with a consequent reduction of pressure exerted by the rod 10 on the piston 8 and an increase in the brake pressure is achieved until when the axle load reaches a maximum the device 1 returns to a substantially vertical position, thus opening the passage 9 in the piston 8 and permitting free flow of fluid from the master cylinder to the wheel brake cylinders. Rapid changes of axle loading caused by the vehicle travelling over uneven road surfaces is prevented by interposing a shock absorber 26 between the pivot 28 and the vehicle frame and a spring 24 between the axle 23 and the rocker arm 25. An alternative embodiment (Fig. 2, not shown) is designed to increase the force applied to the brakes associated with the rear axle in dependence upon the axle load. Fig. 3 illustrates a variant of the embodiment illustrated in Fig. 1, wherein the connection between the first piston and cylinder device 3 and the second piston and cylinder device 1 takes the form of a lever 29 pivoted to the vehicle frame at 30 and a roller 32 carried by a second rod member 33 acted upon by a leaf spring 34 secured to the axle 23 of the vehicle is adapted to vary the pressure supplied to the wheel brake cylinders 6 in accordance with the vehicle load. As the braking effort increases the spring compression of the axle 23 is reduced since the weight of the vehicle is displaced towards the front axle such that when the rear axle spring compression is reduced the roller 32 moves towards the outermost free end of the lever 29 changing the ratio to enable a greater force to be exerted through the rod 10 which moves the piston 8 to the left in opposition to the master cylinder pressure so that the volume of chamber 50 is increased and the pressure in the wheel brake cylinders 6 is reduced. Other embodiments are disclosed in the Specification including one embodiment in which the connection to the master cylinder from the first piston and cylinder device is controlled by a poppet valve and a further embodiment where a spool-type valve is introduced.