GB1379501A - Spring-loaded braking devices for motor vehicles - Google Patents

Abstract

1379501 Spring-loaded pneumatic braking devices ROBERT BOSCH GmbH 19 April 1972 [24 April 1971] 18061/72 Heading F2F A spring-loaded braking device for motor vehicles comprises a parking brake valve 1, 1<SP>1</SP>, for controlling air pressure in a spring-loaded brake cylinder 6 and a check valve unit 5 connected upstream of the cylinder 6 for controlling a brake line 4 and a locking and bypass line 28, in which, in the check valve unit 5, a valve closure member 11 of a non-return valve 10, 11 controlling the return flow of air from the brake line 4 to a supply line 3 is coupled with axial lost motion 17, 19 to an operating piston 15, 16 upon which a first spring 27 acts in a direction to close the non- return valve through a second spring 12 acting between the valve closure member 11 and the operating piston 15, 16 whereby the non-return valve can be urged to the closed position whether or not cylinder 6 contains air under pressure, the non-return valve can be opened in response to pressure difference between the supply line 3 and the cylinder 6 to permit flow of air from the supply line 3 to the cylinder 6, and movement of the operating piston 16 against the action of the first spring 27 in response to pressure difference between the cylinder 6 and the locking and by-pass line 28 moves the valve closure member to open the non-return valve 10, 11 and place the spring-loaded brake cylinder 6 in communication with the supply line 3. Construction.-Line 3 from parking brake valve 1 leads to valve seat 10 of non-return valve 11, 10, closure member 11 of which is separated from a tubular member 15 by a spring 12. Tubular member 15 carries the piston 16 extends with radial clearance through a fixed wall 14 forming one wall of a chamber 13, and has a transverse pin 17 secured to it, the pin passing through a transverse bore 19 (of larger diameter than the pin), in an extension 18 of closure member 11 to provide the axial lost motion. A pin 18<SP>1</SP> surmounting extension 18 extends with radial clearance through a partition 15<SP>1</SP> across tubular member 15. Piston 16 is urged downwards by spring 27, has a packing washer with sealing lip 24 inclined towards the non-return valve 11, 10, and is movable between stops 21, 22, the lower one, 22 having radial openings 23. The locking and by-pass line 28 is connected to a valve 1<SP>1</SP> operated in conjunction with parking brake valve 1 (see below), and to a branch line 32, an emergency release valve 31 and a separate reservoir 30. Brake cylinder 6 connected at 4 to chamber 13 has piston 7 urged to the left by spring 8 to apply the brake (not shown), and to the right by compressed air to release the brake. In operation, to release the brake when the vehicle has been started, parking brake valve 1 is moved to connect line 2 with line 3; valve 1<SP>1</SP> is closed. Non-return valve 11, 10 now opens, admitting air to cylinder 6, releasing the brake. Pressure builds up in chamber 13 and, through clearance 18<SP>1</SP>, 15<SP>1</SP>, in chamber 26 and line 28, so eventually valve 11, 10 closes. To apply the brake, operation of parking brake valve 1 results first in valve 1<SP>1</SP> being opened to exhaust, so chamber 26 is exhausted. The pressure in cylinder 6 now raises piston 16 against its spring 27 until piston 16 through lost-motion connection 17, 19, raises valve closure 11, thereby connecting cylinder 6 with valve 1. When valve 1 is operated further, it connects line 3 with exhaust, whereupon spring 8 applies the brake. When the pressure in chamber 13 has dropped to about 0À3 atmospheres, spring 27 pushes piston 16 against stop 22, so valve 11, 10 is closed and cylinder 6 is finally exhsusted through clearance 18<SP>1</SP>, 15<SP>1</SP>, and line 28. If line 3 breaks while the vehicle is running, valve 11, 10 remains closed so no leakage through line 3 occurs and the brake remains off. Line 4 may be eliminated to avoid breakage. If line 28 breaks, leakage, only through clearance 18<SP>1</SP>, 15<SP>1</SP>, is made up from compressor 29 through reservoir 2<SP>1</SP> and line 2, the discharge warning the driver. For emergency release of the brake (e.g. when line 3 is broken), the emergency release valve 31 is operated to pressurize line 28 from reservoir 30; the compressed air displaces sealing lip 24 and flows around it and then through openings 23 and clearance 15, 14 to cylinder 6; air flows also through clerance 18<SP>1</SP>, 15<SP>1</SP>. For re-application of the brake after such emergency release, line 28 is exhausted through valve 1<SP>1</SP> by manipulation of the parking brake valve.