Scroll-type, positive fluid displacement apparatus with diverse clearances between scroll elements

An improved, scroll-type, positive fluid displacement apparatus, having means defining a curved and walled, fluid-working chamber, said chamber having a radial center and an outer peripheral area circumscribing said center, a pair of scroll-shaped, fluid-working elements within said chamber and extending from an adjacency to said radial center into said peripheral area, a first port opening into, and substantially centrally of, said chamber, a second port opening into said chamber radially outwardly-spaced from said first port, and means mounting at least one of said scroll-shaped, fluid-working elements for movement of the latter in an orbit, within said chamber, relative to, and inter-fittingly with, the other of said elements, to effect moving and close, substantially sealing, minimum clearances, between said elements, which define inter-element, walled, variable-volume pockets which, during orbit of said one element, close off, and move progressively and circularly, from one of said ports toward the second of said ports for opening of said pockets onto, and for communication of said pockets with, said second port, wherein the improvement is comprised by:

• said elements having prescribed configurations which cooperate with said mounting means to cause said minimum clearances, between said elements, to be of a given clearance therebetween in said peripheral area of said chamber, of a clearance other than said given clearance in adjacency to said radial center, and of a family of clearances, which differ from said given and other clearances, intermediate said given and other clearances.