ABSTRACT
As a general rule, it is not good design to connect cylinders in series. It is better to use a stacked directional control valve to provide a separate circuit for each cylinder. When two or more cylinders are connected in parallel, it is very difficult to get synchronized extension and retraction. Of the three methods commonly used (orifice-type flow divider, gear-type flow divider, and mechanical coupling), the mechanical coupling is the most satisfactory.
Load analysis is a key requirement for the proper selection of a cylinder to develop a given force and achieve a given cycle time. The force versus time function will typically have three sections: breakaway, inertial, and constant velocity. A number of factors interact to produce a given load acceleration, valve dynamics, oil compressibility, line compliance, relief valve performance, pump volumetric efficiency, and leakage [in directional control valve (DCV) and past cylinder seals]. Actual acceleration is always less than the acceleration calculated using the maximum force at the relief valve setting.
