Patent GB-992643-A (GB)
Title: Improvements in or relating to braking systems for tractor-trailer vehicle combinations
Inventor: RODWAY JOHN
IPC: B60T13/58
Filed: 1962-03-08
Abstract: 992,643. Fluid-pressure brakes; valves. AUTOMOTIVE PRODUCTS CO. Ltd. March 6, 1963 [March 8, 1962], No. 9021/62. Headings F2F and F2V. A braking system for a tractor-trailer vehicle combination having drum or disc brakes on both vehicles controlled from the tractor vehicle and an independently controllable hydro-kinetic brake on the tractor vehicle, includes a control by which actuation of the hydro-kinetic brake to provide a retarding torque exceeding a predetermined value causes application of the trailer vehicle brakes. Thus " jack-knifing " is less likely to occur. In one form, depression of the usual pedal on a tractor to open a valve 11, Fig. 1, admits compressed air from a tank 10 to a pipe 12 to apply the tractor brakes, and simultaneously to a pipe 13 and a shuttle-valve 14 which opens to a pipe 22, compressed air then acting on a relay valve 23 on the trailer which opens to admit compressed air from a tank 24 to a pipe 25 for application of the trailer brakes. If, however, an hydro-kinetic brake 15 on the tractor is operated by means not described to absorb a torque greater than a predetermined value, the reaction element of the hydro-kinetic brake acts through a master cylinder 16 to apply a liquid pressure to a relay valve 18, which is thereby opened to connect the tank 10 through pipes 19, 20 to the shuttle valve 14, and thence to the relay valve 23 for application of the trailer brakes. In a modification, depression of the usual pedal opens a valve 58, Fig. 4, to admit compressed air from a tank 52 on the tractor to a pipe 59 for engagement of the tractor brakes, and simultaneously to a pipe 61 leading through a shuttle-valve 56 to a relay valve 63 on the trailer, the latter valve then opening to admit compressed air from a tank 64 to a pipe 65 for application of the trailer brakes. An hydro-kinetic brake 45 on the tractor is controlled by hand operation of a selfcapping valve 53 to admit compressed air from the tractor tank 52 through a pipe 57 to an hydraulic accumulator 51, which forces oil into a work circuit 46, 47 of the hydro-kinetic brake, the work circuit including a cooler 48. If the self-lapping valve 53 is opened so far that the hydro-kinetic brake 45 absorbs a torque which exceeds a predetermined value, then the pressure of the air in a pipe 54 connected to the pipe 57 increases so much that a valve 55 is opened to pass air to the shuttle valve 56, and thence to the relay valve 63 for application of the trailer brakes. In a variation of this form, Fig. 6 (not shown), the valve 55 is omitted and a second self-lapping valve, operated simultaneously with the self-lapping valve 53, opens to connect the tractor tank 52 to the shuttle valve 56 &c. Valves.-The relay valve 14, Fig. 1, comprises a cylinder 32, Fig. 2, containing a piston 31 biased by a spring 35 away from a valve spool 29 in turn biased by a spring 38 so that its end closes a port 26, to shut-off an inlet 27 connected to the compressed air pipe 19 from an outlet 28 connected to the pipe 20. The spring 35 separates the piston 31 from the valve spool 29, so that the outlet 28 is vented through a passage 34 in the piston and through a port 37 to the ambient atmosphere. When liquid pressure is developed in the master cylinder 16 due to the reaction torque produced by the hydrokinetic brake 16, it is transmitted through the pipe 17 to act upon a piston 33, which forces the piston 31 downwards against the bias of its spring 35, first to engage the end 36 of the valve spool 29, so that the passage 34 leading to atmosphere is closed, and then to move the other end of the spool away from the port 26, thus connecting the inlet 27 to the outlet 28. The pressure developed in the outlet 28 acts back upon the piston 31 in the same direction as the bias of the spring 35 and in opposition to the force of the liquid acting upon the piston 33, to close the valve 26 &c. when a position of equilibrium has been reached. The valve 55, Fig. 4, comprises a cylinder containing a piston 72, Fig. 5, biased by a spring 76 against the pressure of compressed air supplied through the pipe 17 to an inlet 67, a valve disc 75 within a passage through the piston being biased by a spring 77 to abut a shoulder 74 in the piston stem. In the absence of air pressure acting upon the piston 72, the spring 76 biases the latter so that the valve disc 75, held against the shoulder 74 by its spring 77, is withdrawn from a port 71, through which an outlet 68 connected to the pipe 62 is vented to the ambient atmosphere. When air under pressure is supplied to the inlet 67, first the piston 72 moves downwards against the bias of its spring 76 until the disc 75 closes the vent port 71, further movement of the piston then separating the valve disc 75 from the shoulder 74 in the piston stem, to connect the inlet 67 to the outlet 68. The pressure of the compressed air in the outlet 68 acts back upon the piston 72 in the direction of the bias of the spring 76, to shut off the flow of air when equilibrium is reached.