1. A backhoe operator controls the speed of the cylinder, which extends the bucket by cracking open the DCV controlling flow of the cylinder. Describe the difference in the “feel” of the controls using the two different relief valves (a) and (b) shown in Fig. 3.31. 2. A 1.79-in3 displacement motor is turning at 804 […]
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A pilot-operated relief valve has the same function as a direct-acting relief valve; however, it has a different pressure vs. flow curve. The performance curves for the two types of relief valve are given in Fig. 3.7. The pilot-operated valve opens completely over a narrow pressure range. This allows the circuit to operate over a […]
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A schematic of a direct-acting relief valve is shown in Fig. 3.4. Pressure acts on the annular area of the valve spool. The hydraulic force is given by The notation Fs will be used for the spring force. When Fh equals Fs , the valve cracks open, meaning that the spool lifts off its seat […]
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ANSI symbols are introduced here as they are needed. The directional control valve symbol is the most intuitive and selfexplanatory of the symbols. Some experience with the directional control valve symbol has already been gained. At this point, it is necessary to review the three most common center configurations (Fig. 3.1) for spool-type directional control […]
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