Scroll-type compressor units with minimum housing and scroll plate radii

In a scroll-type fluid compressor unit having a cylindrical compressor housing including a front end plate and a rear end plate, a fixed scroll member fixedly disposed within said compressor housing including first circular end plate means to which first wrap means are affixed, an orbiting scroll member orbitably disposed within said compressor housing including second circular end plate means to which second wrap means are affixed, said second wrap means being similar to said first wrap means in number of turns, pitch and thickness, driving means for effecting orbital motion of said orbiting member, and said first and second wrap means interfitting with an angular phase difference of 180.degree. to make a plurality of line contacts to define at least one pair of sealed off fluid pockets which move with a reduction of volume thereof by the orbital motion of said orbiting scroll member, to thereby compress the fluid in said pockets, the improvement which comprises said second circular end plate means having a radius of X which is expressed by (a+R)>X.gtoreq.(a+R/2), where a is the distance from the center of said second wrap means to the outer terminal end, and R is the radius of said orbital motion, said second wrap means being affixed to said second circular end plate means in a manner so that the center of said second wrap means is offset from the center of said second end plate means towards the outer terminal end of said second wrap means by R/2, said fixed scroll member being fixedly disposed within said compressor housing in a manner so that the center axis of said cylindrical compressor housing is offset from the center of said first wrap means towards the outer terminal end of said first wrap means by R/2, said cylindrical compressor housing having a radius of Y which is expressed by (a+2R)>Y.gtoreq.(X+R), and said first end plate means having a size sufficient to at all times contact the entire axial surface of said second wrap means during the orbital motion of said second orbiting scroll member.