Patent ID: 7611344

Claim:
A positive fluid displacement apparatus, comprising: a) a back plate; b) at least one orbiting scroll member having a first end plate with a first side and a second side, and a first involute wrap affixed to the first side; c) at least one stationary scroll member with a second end plate having a second involute wrap affixed thereto, the second involute wrap being engaged with the first involute wrap of the orbiting scroll member; d) a rotatable shaft arranged to drive the orbiting scroll member in orbiting motion with respect to the stationary scroll member; e) inner and outer sealing tabs fixed to the at least one orbiting scroll member on the second side thereof so that the inner and outer sealing tabs orbit with the at least one orbiting scroll member, the sealing tabs are spaced from each other in a radial direction and extend away from the first end plate toward the back plate; f) the back plate includes a sealing piston disposed thereon; a plurality of springs engaged with the sealing piston and biasing the sealing piston toward the orbiting scroll member so that the sealing piston is engaged with the sealing tabs; and a bleeding hole formed through the sealing piston providing fluid communication between a front side of the sealing piston and a back side thereof.