The technological solution to these more complex circuits has been the development of proportional valves. These revolutionary valves allow infinite positioning of spools, thus providing infinitely adjustable flow volumes. Either stroke-controlled or force-controlled solenoids are used to achieve the infinite positioning of spools.
This variable positioning allows spools to be designed with metering notches to provide flow/speed control as well as directional control functions all in one valve, instead of requiring separate valves for direction and speed. The other major benefit is when the circuit requires more than one speed. The various speeds are achieved by changing the electrical signal level to deliver the flow/speed required. No additional hydraulic components are required! These proportional directional valves are controlled by DC power.
The proportional controls, used with their associated electronic controls, also add the desirable features of acceleration and deceleration. This offers a variety of machine cycles, safely operated at greater speeds, yet with controlled start and stop characteristics. Regulated acceleration and deceleration result in improved machine overall cycle times and production rates.