| 摘要 |
An electrically controlled, proportional, pressure relief valve (100/200) used to control the maximum allowable pressure in a hydraulic line (3), whose pressure is used to control, for example, the relative up-and-down positioning and speed of movement of a combine header (1) on an agricultural combine, in which the effective maximum pressure of the pilot valve of the relief valve is controlled by a solenoid (113/213). The distal tip of the armature (114/214) of the solenoid bears against a movement and force translating drive pin (112/212), which in turn bears against a ball (110; FIG. 2) or a poppet pin (210; FIG. 3). The effective maximum pressure permitted by the relief valve is linearly varied by the applied voltage/current to the solenoid coil (115/215). Such an arrangement allows the electrically controlled pressure relief valve to be easily interfaced and controlled by, for example, a computer (20) with a condition responsive input/output section (21), greatly expanding the possible applications for the pressure relief valve system of the invention. In the preferred application (FIG. 1 ), the movement of a ground contacting ski sled (22) carried by the combine ("C") is monitored by the computer, which then sends electrical signals to the pressure relief valve, which in response to the electrical signals controls the pressure level in the hydraulic line to the ram moving the combine header, determining its vertical position and the speed with which the header moves, as it goes from one vertical position to the other with respect to the ground.
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