| 摘要 |
<p>The valve unit comprises a body (51) in which are defined: a supply chamber (C) intended to be connected to a pressure source through a supply connector (11) and to a line for supplying pressure to the braking system of a towed vehicle through an outlet connector (12); a discharge chamber (E) which communicates with the atmosphere through a venting aperture (3); at least one control chamber (F) provided with an inlet connector (41) for the introduction of a brake-operating pressure, and an outlet chamber (D) connected to a line for supplying the brake-operating pressure to the braking system of the towed vehicle. A relay valve (73c, 90, 92) is provided in the body (51) and is controlled by the pressure in the control chamber (F). This valve comprises an obturator unit (90) cooperating with two valve seats (73c, 92) to control communication between the outlet chamber (D) and the discharge chamber (E) and between the outlet chamber (D) and the supply chamber (C). This obturator unit (90) is controlled by a movable control element (71, 73, 100) which is sealingly slidably mounted between the control chamber (F) and the outlet chamber (D). A stop valve (servo-diverter valve) (90b, 66) including a seat (66) formed in the supply chamber (C) is also provided in the body (51) and is adapted to disconnect the outlet chamber (D) from the supply chamber (C) when the pressure difference between the control ohamber (F) and the outlet chamber (D) exceeds a predetermined value during service braking. The obturator of the stop valve is constituted by the obturator (90) of the relay valve (73c, 90, 92) and the relay valve control element (71, 73, 100) comprises a piston (100) which thrusts this obturator unit (90) into a position in which it closes the seat (66) of the stop valve (90b, 66) when the pressure difference between the control chamber (F) and the outlet chamber (D) exceeds the predetermined value.</p> |
