| 摘要 |
<p>A valve block for hydraulic systems of advancing support frames of underground mining equipment comprises a block 1 provided with coaxial accepting 2 and connecting 7 borings for different sized load connections 6, 7. The accepting borings accommodate directional control valves comprising pilot 4 and main valve 3 cartridges. Pressure P, return T lines and a separate pilot line Pst extend through the block perpendicularly to the accepting borings. Shown closed to open: a solenoid plunger moves pilot pin 51 rightward to supply (60 (70 Fig. 6)) pilot pressure to chamber 50 to firstly shift sleeve 42 to engage seats 44, 45 and isolate return passages 48, T from main valve through boring 32; pilot pressure then shifts control piston 34 rightward separating seats 36, 38 to allow fluid to flow from the pressure line trough radial bores 39, 41 to piston blind bore 33 and then to load.</p> |
