PDA U-Cup
PDA (Double U-Rings)
Double U-rings are predominantly used as piston seals in pneumatic equipment. They perform a dual function: sealing and guidance. Double U-rings require hardly more space in the radial direction than is the case with O-rings and are thus particularly suitable for installation conditions where space is at a premium.
In principle, this seal combination consists of two U-rings connected to eachother by means of a ridge. The U-rings and the ridge priduce an all-round goove inside the sealing ring. This serves, in conjunction with a corresponding collar on the piston body, to retain the double U-ring. The advantage is as follows: Simple piston bodies without undercuts which can be manufactured cheaply with either cutting or non-cutting methods e.g. using extrusion tools of injection molding tools.
The piston itself does not come into contact with the cylinder wall. This largely avoids scoring, above all if using plastic or light metal cylinders.
In order to minimize the stick and slip frictional forces, double U-rings have completely molded sealing lips with a rounded sealing edge. In conjunction with the retained vulcanization skin of the elastomeric material, this produces a very favorable influence on friction, stick-slip behavior and wear. Modern pneumatics sealing lips achieve an average of 50% reduction in frictional force as compared with the preciously conventional sharp sealing edges.
Operating Conditions:
Maximum Speed: 1 m/s
Temperature: -30°C to 100°C (-22°F to 212°F)
Maximum Pressure: 16 bar