| 摘要 |
<p>1,034,108. Hydraulic apparatus. APPLIED POWER INDUSTRIES, Inc. Nov. 22, 1962 [Nov. 22, 1961], No. 44224/62. Heading F1P. An hydraulic piston 2 Fig. 1 (not shown) is held in any position under load by closing exhaust valves 32, 44 and supply valves 46, 48 in lines 50, 54 connected to opposite ends 51, 52 of the cylinder 3, and during such holding period delivery from a continuously running pump 4 is by-passed to an exhaust reservoir 5 past a valve 16 held open by the stem 20 of a downwardly biased piston 18 and past an open solenoid valve 8. Valves 32, 48 are held closed by a spring 39 surrounding the stem of a plunger 88 Figs. 2, 3 (not shown) of such length as to allow limited axial play whereby valve 48 can be opened by high supply pressure and valve 32 opened by downward displacement of the stem 38 of a piston 36 when the latter is urged downwardly against a spring 37 by hydraulic pressure build-up in a pilot line 26. Valves 44, 46 are of similar construction but the piston stem 42 serving to open valve 44 is biased to the open position by its spring 41 and is displaced to the valve-closing position by pressure build up in a pilot line 30 leading to the underside of piston 40. During holding periods solenoid valves 8, 12 are open and valve 10 is closed, during a piston advance period against load valves 8, 12 are closed and valve 10 is open whereas during return under load valves 8, 10 are closed, and valve 12 is open. At the start of piston advance, pressure from a line 6 builds up in pilot line 24 sufficient to lift piston 18 and allow valve 16 to close. Fluid pressure then opens a check valve 14 and supply valve 48 to enter line 50; line 54 being connected to exhaust 5 past valve 44 which is held open by piston stem 42 since the space below piston 40 is connected to exhaust 5 through pilot line 30 and open valve 10. On opening valve 12 and closing valves 8, 10 to effect piston return under load valve 32 becomes unseated by pilot pressure in line 26, valve 48 is held on its seat, valve 44 is allowed to be seated by spring 86 since piston 40 is lifted by pilot pressure build-up in line 30 whereupon full hydraulic pressure then opens valve 46 and is admitted through line 54 to the return side of the piston 2. High pressure relief valves 17, 62, 64 and low pressure relief valves 66, 68 are provided. In a modification for use with a single acting piston cylinder 3a, Fig. 1a (not shown) the union connecting valves 48, 32 to the line leading to the load end of the cylinder is permanently blocked, solenoid valve 12 is maintained always open. Piston advance is effected by the solenoid valve settings for retracting a double acting piston whilst piston return is effected by opening valves 8, 10. The various valves are assembled in a common block 70 as are fluid flow lines and pressure relief valves.</p> |
