Instead of the metal plate, Paulstra offers a rubberised cover which has the following advantages:
– only a simple shape needs to be machined in the crankcase.
– only one part needs to be fitted to ensure the closure of the crankcase with a perfect seal.
In a crankcase, it is sometimes necessary to have temporary access in order to:
– machine an internal shape which is otherwise inaccessible.
– carry out a mechanical adjustment at the time of assembly.
This type of temporary passage is usually closed by a screwed plate with a flat seal or an O-ring.
The seal is assured by a beading of elastomer fitted to the inside or the outside of the sheet. The shape of the beading and its attachment to the sheet are designed in such a way that the compression of the elastomer absorbs the faults in the flatness and deformation due to expansion while remaining within acceptable stress constraints.
This type of seal has its own friction track.
Its main advantages are:
-reduces the need to grind the shaft,
-treatment of only one part,
-no shaft wear,
– protection of the lip in storage and handling,
– in a bearing, it can serve as a supporting element until it is fitted in the unit.
The efficiency of the ridge increases with its size.
In an automatic gearbox, the setting in motion and the changing of gears are done by clutches on which pistons, moved by oil pressure, act.
Up to the present, these pistons were in moulded aluminium alloy or steel. The sealing for aluminium pistons was done by elastomer seals of various shapes fitted into the grooves or, for steel pistons, kept in position by outer rings.
