Scroll-type fluid displacement apparatus

A scroll-type fluid displacement apparatus comprising:

• a housing having a fluid inlet port and a fluid outlet port;
• an orbiting scroll member having a first end plate and a first spiral element extending from one side of said first end plate;
• a fixed scroll member having a second end plate and a second spiral element extending from one side of said second end plate, said first spiral element and second spiral element interfitting at an angular and a radial offset to form a plurality of line contacts defining at least one pair of sealed-off fluid pockets;
• a driving mechanism including a drive shaft rotatably supported by said housing to effect the orbital motion of said orbiting scroll member by the rotation of said drive shaft to thereby change the volume of said fluid pockets, and
• an annular boss projecting from a second side of said first end plate, said annular boss having an internal diameter,
• wherein said second side of said first end plate has a recess portion having a diameter less than said internal diameter of said annular boss, and a second side of said second end plate has a recess portion.

A scroll-type fluid displacement apparatus comprising:

• a housing having a fluid inlet port and a fluid outlet port;
• an orbiting scroll member having a first end plate and a first spiral element extending from one side of said first end plate;
• a fixed scroll member having a second end plate and a second spiral element extending from one side of said second plate, said first spiral element and second spiral element interfitting at an angular and a radial offset to form a plurality of line contacts defining at least one pair of sealed-off fluid pockets;
• and
• a driving mechanism including a drive shaft rotatably supported by said housing to effect the orbital motion of said orbiting scroll member by the rotation of said drive shaft to thereby change the volume of said fluid pockets,
• wherein a second side of said second end plate has a recess portion.