Opinion ID: 2225574
Heading Depth: 1
Heading Rank: 19

Heading: Hydraulic Basics

Text: As noted, SFAC's disputed trade secret involves a hydraulic valve spool. SFAC and R.K. use hydraulic systems to move their aerial ladders. Oversimplified, the hydraulic systems create power to move the ladders by moving hydraulic fluid through a control valve. The control valves have four openings called ports. A pump moves pressurized hydraulic fluid ÔÇö in this case oil ÔÇö from a reservoir tank through a line connected to the valve's pressure port. The valve directs the pressurized fluid to a work port, A or B. Both work ports have lines connected to a hydraulic cylinder that controls a particular ladder movement. In a hoist cylinder system, for example, if the fluid in the valve is directed to the A work port, it will pass through a line to the part of the cylinder that pushes the fluid against a piston in a way that raises the ladder and holds it up. At the same time, fluid is returning to the valve through the line connected to the B work port. That fluid is directed to the tank port of the valve, which has a return line to the reservoir tank. The returning fluid is redirected to the control valve, creating a circuitry. The flow in the valve is controlled by a hydraulic valve spool, which is a movable, cylinder part in the valve. The valve spools are machined so that depending on how they are moved, they open the pressure and tank ports and direct the flow of hydraulic fluid to the A or B work ports. As we understand the parties' testimony and briefs, they have referred to the part of a valve spool that opens the pressure side (or pump side) of the control valve as the corresponding pump side or pressure side of the valve spool. And they have referred to the part of the valve spool that opens the tank side of the valve as the tank side or return side of the valve spool. For convenience, we shall also refer to the pressure side and tank side of the valve spool to mean the part of the valve spool that opens the corresponding pressure or tank port of the valve. A common problem with hydraulic systems is pressure surges, which occur because there is a burst of fluid through the system when the valve is opened. The surge creates oscillations in the system until the pressure settles back into a constant pressure. In aerial ladders, the oscillations transfer to the ladder, causing jerky movements and making control of the ladder difficult. While Kreikemeier worked for SFAC, SFAC developed a modification for its valve spools to dissipate these pressure surges. With that background, we are asked to decide whether the court correctly found that R.K.'s 1996 modification of the pressure side of its commercially available valve spools violated the 1990 injunction.