1. Field of the Invention
The invention relates to a sealing means between a pressurized chamber and a lubricated chamber.
2. Description of the Related Art
Numerous bearings, particularly of aircraft gas turbine engines, have bearings lubricated by a jet or mist of oil and it is necessary to ensure that it is not spread to other parts through the clearance made necessary by the passage of the rotary shafts out of the bearings. For this purpose use is made of various seal types combined with a pressurization of the chambers located on the other side of the seal and which must be protected. The pressurized gas is taken from the engine compressor. The inflow of gases entering the lubricated chamber after passing round the seal therefore reinforces the action of the latter. However, the blown gas flow rate is often too low at low engine r.p.m.'s, where the pressurization is low, in order to be effective.
Therefore, the invention aims at obviating this disadvantage and ensuring a satisfactory flow of gases towards the lubricated chamber in all circumstances. The invention achieves this by giving a variable permeability to the seal, i.e. it is fitted with flexibility enabling it to assume two stable positions as a function of the extent of the pressurization and where the sealing controlled by it differs.
European Patent 387,122 of the present Applicant describes a sealing means forced back by a spring towards an invariable abutment position. U.S. Pat. No. 4,426,090 describes a mobile seal so that the waste lubricant can escape to the outside on forcing it back, which opens a pipe. However, neither of these patents describes the lubrication by an oil mist or the like associated with a permanent flow back into the lubricated chamber by a gas intake through the seal means. The seals are fitted without clearance on the rotary shaft, so that they ensure the necessary sealing. Consequently, they are exposed to friction and a greater wear.