Tech Tips - Forget Hydraulics

Sponsored by Page 4 CONTROLLING SPEED & SHOCK Courtesy of Fabco-Air As you know, we must make accommodations for the inertial and impact forces that will be released when our tooling breaks through the work piece. To capture these potentially destructive forces, and prevent damage to the power cylinder and tooling, an air-over-oil tank is incorporated in the circuit between the directional control valve and the cylinder return port. How It Works Fluid in the tank is used for the cylinder’s return media only. (Reference Figure 3, above.) Fluid flow and cylinder speed can be controlled by a needle or flow control valve. In our example we have chosen a flow control valve because we want to control the speed of the “work” stroke while allowing a full speed retract stroke. When the material shears and the cylinder tries to complete the stroke, the non-compressible fluid resists rapid movement. It “catches” the built-up forces, dissipating them before the cylinder can bottom out. Thus the piston cannot “pound” on the piston stop. Standard Hydraulic Shock options are offered on all Multi- Power® Cylinders and Presses. Seals on the piston, piston rod, and cylinder tube are increased in the single-stage retract section (Shown yellow in Figure 4). Dynamic Poly-Pak® seals combine an automatic lip type seal with an O-spring energizer for excellent sealing from zero to 500 psi. Piston thickness is increased. Figure 3 - Air-over-oil shock control circuit Single Tank Air-over- Oil Directional Control 4-Way Air Valve Power Cylinder Air Supply Muffler Flow Control Valve The Multi-Power® Cylinder has multiple pistons attached to a common rod with internal air passages thus allowing much higher forces without having to use a bulky, larger bore cylinder or high pressure hydraulics. Fabco-Air: Multi-Power Principle video Thicker Piston Standard Piston Seal Additional Polypak® Piston Seal Additional Tube Seal Liquid to and from tank Additional Polypak® Rod Seal Bronze Bushing Figure 4 - Beefed up construction