A scroll type fluid displacement apparatus comprising:
- a housing having a fluid inlet port and fluid outlet port, said housing divided into a first housing portion and a second housing portion, said second housing portion having a hollow portion formed therein, said hollow portion defining a first radial length and being radially surrounded by an end portion of said second housing portion;
- a fixed scroll fixedly disposed relative to said first housing portion and having an end plate from which a first wrap extends;
- an orbiting scroll having an end plate from which a second wrap extends, said first and second wraps interfitting at an angular and radial offset to form a plurality of line contacts to define at least one pair of sealed off fluid pockets;
- a driving mechanism including a drive shaft rotatably supported by said housing and a drive pin eccentrically extending from an inner end of said drive shaft;
- a balance weight member operatively coupled to and swingable about said drive pin, said balance weight member located in said hollow portion of said second housing portion, said balance weight member including a radial end portion which when said balance weight member swings about said drive pin describes a second radial length, said first radial length being greater than said second radial length;
- rotation preventing means for preventing the rotation of said orbiting scroll during orbital motion thereof, said rotation prevention means including a fixed ring member attached to an inner surface of said second housing portion and an orbital ring attached to an axial end surface of said orbiting scroll, said fixed and orbital rings having a plurality of facing pockets within which a plurality of balls are disposed;
- and
- at least one recessed portion formed in said second housing portion adjacent said hollow portion, said recessed portion being at least large enough to accommodate one of said balls so that when one of said balls is disposed within said recessed portion, said ball protrudes inside of said second radial length and said radial end portion of said balance weight member strikes said ball and prevents the further rotation of said balance weight member.