| 摘要 |
A combination tow and pressure relief valve for use in a hydraulic fluid circuit used in a hydraulically driven wide area lawn mower. The valve includes a cylindrical valve body having a hexagonal head. A slideable valve tip with a shank and a valve head has its shank slidably mounted within the valve body. The valve tip is biased by a spring to move in a direction away from the hex head. In operation, the valve is inserted into a suitable chamber placed in series with a bypass passage. The valve tends to block the bypass passage under steady state conditions. When a surge in hydraulic pressure occurs, as would occur in response to operator input or at startup, the hydraulic fluid overcomes the bias of the spring and urges the valve tip away from the otherwise blocked orifice which links the bypass passage to the chamber. Opening the orifice tends to diminish the magnitude of the pressure peak and helps eliminate jerky starts of the mower. The spring eventually overcomes the reduced hydraulic fluid pressure and returns the head of the valve tip into a sealed relationship with the bypass passage orifice. A shoulder nut permits the valve to be secured at a fixed position within the chamber. Varying the position of the valve within the chamber permits adjustment of the absolute value of the peak pressure which will be reached within the bypass passage. Loosening the valve further permits its use as a tow valve, so that the associated mower can be moved without skidding of the mower tires or actually starting the mower engine. Closing the valve further permits maximum operating pressure availability for larger and heavier equipment.
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