2 however these gaps are not important in understanding the present invention and are omitted from these figures further the radius of orbit r actually includes halves of the respective bearing gaps which are very small and negligible the eccentric ring 27 is rotatable about the center o 5 within the eccentric hole 26 the distance between o 2 and o 4 which is substantially equal to r is changed cyclically with the rotation of the eccentric ring 27 about the point o 5 an important feature of this embodiment is that when the center of rotation o 2 of the crankshaft 14 the center o 4 of the orbiting scroll 2 and the center of rotation o 5 of the eccentric ring 27 are arranged in that order along a straight line the distance between o 2 and o 4 is substantially equal to the crank radius in the operation of the compressor thus constructed the compression of gas is performed according to the principles illustrated in fig1 a to 1d the load arising due to gas compression is transmitted from the shaft 4 of the orbiting scroll 2 to the eccentric ring 27 with the loading conditions being as shown in fig8 the load includes two components one being a radial load mainly the centrifugal force f c and the other being a gas compression load f g in a direction orthogonal to the radial load f c these load components act on the center o 4 of the shaft 4 of the orbiting scroll 2 as shown in fig8 since the center of rotation of the eccentric ring 27 is o 5 the gas compression load component f g produces a moment about o 5 which causes the eccentric ring 27 to be rotated about.