| 摘要 |
<p>1,199,428. Air brake systems; valves. BERG MFG. & SALES CO. 5 Dec., 1967 [9 Dec., 1966], No. 55366/67. Headings F2F and F2V. A protecting valve for air brake systems comprises a reciprocable shuttle member carrying a plurality of seals which co-operate with ports in a chamber, the shuttle being biased by a single spring to one position where it connects a first port to a second port, but moved by the pressure at the second port to a second position in which it connects the first port to a third port. The Figure shows the valve used to prevent loss of pressure in a tractor compressed-air braking system if the trailer line should be broken. The valve is biased into the position shown by a spring 25, when connection is shut off between the service inlet 3 and outlet 4, and between the emergency inlet 5 and outlet 6, the last-named being connected through passage 15, the hollow centre of the valve 16, aperture 26 and dust-excluding check valve 27 to the atmosphere. When pressure is applied from the reservoir to inlet 5 through a manually or pressure-operated control valve, the piston 8 is driven to the right against the spring, and at a certain value of pressure a seal 9 will come opposite the lands between grooves 11 in the valve casing. Air can then flow from inlet 5 to outlet 6 and thence to the emergency system of the trailer (not shown). At the same time, a seal 13 moves beyond the conical portion 14 of the valve casing to shut off the outlet 6 from the passage 15 and hence from the atmosphere. Also, a third seal 19 comes opposite the lands between grooves 30 and establishes a connection between inlet 3 and outlet 4 to supply air to the service braking system of the trailer. The pressure required to hold the valve to the right is lower than that required to move the valve since the seal 13 is of lesser diameter than seal 9. If the pressure in the reservoir drops to this lower level, the valve will move back to the left, sealing the inlets 3 and 5 to prevent any further loss of pressure, and venting the outlet 6 through the check valve 27 to trigger the emergency application of the trailer brakes.</p> |
