the second cavity 48 the slider 50 comprises a cylindrical first portion 51 and a cylindrical second portion 52 the diameter of the first portion 51 is larger than that of the extending portion 53 and the second portion 52 when the slider 50 is disposed in the hub portion 45 the first portion 51 is received in the first cavity 46 and the second portion 52 is received in the second cavity 48 two leak proof members 70 and 72 such as o rings or teflon rings are disposed around the outer bore of the first and second portions 51 and 52 abutting the inner surface of the hub portion 45 therefore two separated enclosed spaces 47 and 49 are defined between the slider 50 and the hub portion 45 of the non orbiting scroll 41 the non orbiting scroll 41 of this embodiment comprises a plurality of bypasses 471 communicated with the first cavity 46 when the scroll compressor starts work fluid passes through the bypasses 471 filling in the enclosed space 47 and assists in raising the slider 50 to the first position to rapidly establish required operational pressure furthermore when the compression ratio of the scroll compressor.