Seal at the piston for a cylinder. With single-acting cylinders (plunger), the piston is only subjected to pressure on one side so only needs sealing in one direction in most cases. For hydraulic cylinders, a seal from the lip seal group (e.g. grooved ring seal, roof-shaped seal, lip seal) will often be used. In order to provide a piston seal for double-acting cylinders (synchronizing cylinder, differential cylinder), two lip seals will be required. These days, it is becoming increasingly common in hydraulics as well to use compact seals (Figure K 22) that provide a seal at both sides. Featuring vulcanised or inserted guide rings, these form complete sealing-guide elements.
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