| 摘要 |
<p>905,608. Hydraulic apparatus. CESSNA AIRCRAFT CO. Jan. 18, 1960 [Feb. 19, 1959], No. 1753/60. Class 69 (2). A pressure-fluid control system for a double-acting fluid motor 19 comprises fluid supply means 16, fluid return means 24, 25, means forming two circuit control passages 26, 27 connectible to opposite sides of the motor, valve means 18 for selectively connecting either control passage 26 or 27 to the supply means while connecting the other control passage to the return means and in one position blocking flow to and from both control passages, two separate by-pass passages 28, 29 each associated with and connectible to a respective one of the passages independent of the valve means, and means 30, 31 responsive to an increase in pressure in one control passage and a decrease in pressure in the other control passage to by-pass excess fluid from the higher pressure control passage into the lower pressure control passage. The motor 19, which may operate the boom 41 of a power shovel, is connected by lines 22, 23 to ports 20, 21 leading from the circuit control passages 26, 27. The control passages are connected to a bore 32 receiving a reversing valve spool 18 which when moved to the left from its neutral position shown connects the passage 27 through a check valve 35 and the supply means 16 to a relief valve 15 and pump 12, and connects the passage 26 to a transfer passage 36 leading to the return line 24, 25 connected to a reservoir 13, the boom 41, in this position of the spool 18, being lowered. When the spool is returned to its neutral position, to which it is urged by a device 60, the inertia of the boom causes an increase in pressure in the side of the motor connected to the passage 26. The increase in pressure acts through an orifice 61 in the relief valve 30 to open a needle valve 51 dropping the pressure in a chamber 63 so that fluid in a chamber 43 connected by ports 45 to the control passage 26 moves a member 47 to the right against a spring 48 to allow fluid to pass through a seating 44 to the by-pass passage 28, transfer passage 36 and return line 24, 25. The passing of fluid through the valve 31 causes a drop in pressure on the side of the motor connected to the passage 27, which drop in pressure permits fluid in the return line 24 to pass through the by-pass passage 29 and passages 55, 58 in the one-way ball valve 31 into the passage 27 to prevent cavitation in the motor. The valve housing 17 is formed with passages 10, 11, whereby it may be used in association with other valves in a multiple valve bank. The housing may be modified by replacing the transfer passage 36 by a passage 39 connected to the return line 25.</p> |
