Patent GB-1036443-A (GB)
Title: Improvements in or relating to braking devices for vehicles
IPC: F16D65/14
Filed: 1963-03-01
Abstract: 1,036,443. Fluid-pressure brakes; hydraulic shock-absorbers. FRANCAISE DU FERUDO S.A. March 1, 1963 [March 2, 1962], No. 8389/63. Headings F2E, F2F and F2S. [Also in Division B7] A brake control system for two of the wheel brakes on a vehicle has the brakes movable relatively to the vehicle chassis on brake application to actuate a mechanical or fluid pressure control system which balances the retarding effects of the two brakes, each brake incorporating a fluid cylinder connected to a conduit and to an adjustable-capacity piston- and-cylinder device having one of its members fast with the brake and the other with the chassis to form an expansion chamber comprising a part of the balance control, the conduits being fed from a driver-operated master cylinder feeding equal volumes into each conduit on depression of the usual pedal. In one form, a master cylinder 10, Fig. 1, has two separate working spaces 11, 12 feeding two lines 24d, 24g connected to slave units 34, 35 in each of the two front wheel brakes 25d, 25g, Fig. 2 (not shown), of a motor vehicle. The master cylinder 10 is so proportioned that actuation of its control pedal 14 pumps equal volumes of liquid through the two lines 24d, 24g. The right and left-hand front wheel brakes 25d, 25g are each mounted at the end of a strut-type suspension unit 50 pivoting at its lower end 50a upon a bar 53a fast with the vehicle chassis, and permitted at its upper end a slight movement lengthwise of the vehicle chassis 53. The upper end of each suspension unit 50 is connected through a ball-and-socket 64 to a piston 66 slidable within a housing 71d, 71g fast with the vehicle chassis 53. A working space 74 at the front end of each piston 66 is connected through a pipe 78g, 78d to a common pipe 80 leading to a pressure space 22 separating two valves 23 in the master cylinder 10. An expansion chamber formed by a working space 72 at the rear end of each of the pistons 66 is connected through a line 76 to the independent main lines 24d, 24g of the associated brakes. When the brakes are disengaged, the two valves 23 are biased apart by a spring, but will be moved by any difference in pressure within the working spaces 11, 12 of the master cylinder 10 to balance the pressures in these two spaces. When the pedal 14 is depressed to engage the brakes, the master cylinder 10 supplies equal volumes of fluid through the two primary lines 24d, 24g to the respective wheel brakes 25d, 25g. The retardation of the brakes relative to the chassis causes the upper ends of the suspension units 50 to move forwardly relatively to the chassis 53, thus sliding both pistons 66 leftwards to increase the pressure in the working spaces 74, and thus increase the pressure in the line 80 and the space 22 between the two valves 23, which are thereby firmly closed. At the same time, the working spaces 72 at the rear ends of the two pistons 66 are increased in size, thus tending to disengage the brakes. If one brake is engaged more strongly than the other, the corresponding working space 72 becomes proportionally bigger than that on the other side of the vehicle, thus reducing the brake engaging force on that side of the vehicle, to balance the two brakes. In the form shown, the two slave units 34, 35 of each brake are connected by a pipe for simultaneous operation by the pressure in the associated pipe 24. In a modification, Fig. 1a (not shown), two oppositely-acting slave units in one cylinder are provided, one unit being connected directly to the primary line 24, and the other being connected to the pipe 80. Thus, one brake shoe is moved to the engaged position by actuation of the primary pressure, and movement of the upper end of the suspension strut 50 causes the associated piston 66 to slide, thus building up pressure in the pipe 80 to render the second slave unit operative and engage the second shoe. In a modification, a similar master cylinder 10, Fig. 4 (not shown), operates the four road wheel brakes of a motor vehicle. In this construction, the front wheel brakes 100d, 100g are of the disc type, while the rear brakes 123d, 123g are drum brakes. Each of the lines 24d, 24g feeding primary pressure to the disc brakes is connected to an expansion chamber 72 formed by a piston 120, Fig. 5 (not shown), fast with the vehicle chassis 53 and sliding within a cylinder 74 rigid with the disc brake housing 104, the disc brake housing moving lengthwise of the vehicle chassis when the brakes are applied. Each expansion chamber 72 is connected via a pipe 112 to slave-cylinders 110 in a brake plate 105 moved against the bias of springs 113 to engage a small friction lining 103 with a disc 101 fast with the associated vehicle wheel, the latter disc also engaging a friction lining 102 fast with the brake support 104. At its front end, each disc brake support 104 is provided with an axially extending spigot 114 slidable within a bracket 116 vertically movable upon a pin 118 upon the chassis 53. The pistons 120 of the expansion chambers 72 mount the rear end of each disc brake support 104 upon the chassis 53 by means of cross-pins 121. Brake reaction between the support 104 and the chassis 53 is taken in part by a spring 122 within a working space 74 and in part by the pressure of liquid within this working space. Pipes 78d, 78g are connected together and through a pipe 80 to the two mastercylinder valves 23, as before, and also through pipes 125d, 125g to slave units 124d, 124g energized to apply the rear wheel brakes 123d, 123g. Thus, when the master cylinder pedal 14 is actuated, the front disc brakes 100d, 100g are engaged, and move the two disc brake supports 104 relatively lengthwise of the chassis 53. The two interconnected working spaces 74 co-ordinate the sliding movements of the two brake disc supports 104, and simultaneously control the expansion chambers 72, which increase in size the further the supports move relatively to the fixed pistons 120. Accordingly, the engaging force applied to each of the friction elements 103 is varied to obtain balanced braking between the two front wheel brakes. In a modification of this construction, Figs. 7, 8 (not shown), two separate slave units are provided for actuating each front disc brake. One slave unit is, as before, directly connected through the expansion chamber to the associated primary fluid pressure line, while the other slave unit is connected to the pipe 80 and to the working spaces 74. Thus, in this construction, after initial energization of the primary line slave unit, movement of the brake supports relatively to the vehicle chassis produces a pressure in the pipe 80 &c. which is then fed into the second slave unit to increase the brake engaging force. In another modification, a lever 130, Fig. 10 (not shown), pivoted at 131 upon the vehicle chassis 53, co-ordinates the sliding movements of the brake disc housings 100d, 100g lengthwise of the vehicle, to control the size of the expansion chambers 72 and hence the braking forces. A modified master cylinder 10 is used, in which two working spaces 11, 12 only are provided, and the valves 23 are omitted. Hydraulic shock - absorbers. -Each vehicle front-wheel 26d, 26g, Fig. 2 (not shown), is mounted upon the vehicle chassis 53 by a strut-type suspension unit comprising a cylinder 50, pivoted at 50a upon a bar 53a carried by the vehicle chassis, and fast at 32 with the back-plate of the associated drum brake. Within each tube 50 slides a damper 57 connected through a rod 56 and the ball-and-socket joint 64 to each piston 66, slidable within the cylinder 71 fast upon the chassis 53, as described above, a helical spring 52 surrounding the rod 56. Movement lengthwise of the upper end of the rod 56 relative to the chassis 53 is permitted by a slot in the chassis and by an oval-shaped washer 61, Fig. 3 (not shown), within a cup 55 secured to the chassis.