Tech Tips - Forget Hydraulics

Sponsored by Page 14 MORE USEFUL IDEAS For Using Air/Oil Tanks Two-Speed Work Stroke with Shock Control With a slight modification to the circuit in Figure 3, using a sequence valve, a needle valve and a shut-off valve, our single air/oil tank provides us with 2-speed work stroke operation shown in Figure 11 below. The sequence is as follows: 1. Rapid “extend” stroke to approach the work. 2. Automatic switch to controlled rate when resistance is met and pressure builds up to the point where a Fabco-Air RV “Sequence Valve," (refer to Figure 6 on page 6) actuates the 2-way shut-off valve forcing fluid flow through the speed controlling needle valve. 3. Fluid catches the cylinder motion, thus controlling the shock that could otherwise occur. 4. Automatic return to rapid rate on the “Cylinder Retract” stroke. Double Air-Oil Tanks Earlier we discussed controlling cylinder speed in one direction only. When control is required in both directions, two air-oil tanks are needed. As you can see from the circuit shown below, double Air-Oil Tanks used in conjunction with two flow control valves enables hydraulic control with one speed in each direction. Figure 11 - Two-Speed work stroke with shock control Figure 12 - Controlling speed in two (2) directions