Scroll type fluid displacement compressor with spiral wrap elements of varying thickness

Claim 1

In a scroll type fluid displacement compressor including a housing having a fluid inlet port and fluid outlet port, a fixed scroll fixedly disposed within said housing and having a circular end plate from which a first wrap extends, an orbiting scroll having a circular end plate from which a second wrap extends, said first and second wraps interfitting at an angular and radial offset to make a plurality of line contacts to define at least one pair of sealed off fluid pockets, a driving mechanism operatively connected to said orbiting scroll to effect the orbital motion of said orbiting scroll and a rotation prevention device to prevent the rotation of said orbiting scroll during orbital motion so that the volume of the fluid pockets changes, the improvement comprising said second wrap of said orbiting scroll having a thickness which is gradually reduced along its entire length from the inner end portion to the outer end portion thereof to strengthen the inner portion of said second wrap without increasing the centrifugal force generated by said orbiting scroll during its orbital motion, an inner wall surface and outer wall surface of said second wrap being formed by involute curves generated from generating circles having different radii, and said first wrap of said fixed scroll having a thickness which is gradually increased along its entire length from the inner end portion of the outer end portion to compensate for the reduction in thickness of said second wrap to thereby achieve proper line contacts between said first and second wraps to improve radial sealing.