Patent ID: 7001162

Claim:
A rotary device comprised of a housing comprising a curved inner surface with a profile equidistant from a trochoidal curve, an eccentric mounted on a shaft disposed within said housing, a first rotor mounted on said eccentric which is comprised of a first side, a second side, and a third side, a first partial bore disposed at the intersection of said first side and said second side, a second partial bore disposed at the intersection of said second side and said third side, a third partial bore disposed at the intersection of said third side and said first side, a first hollow roller disposed and rotatably mounted within said first partial bore, a second hollow roller disposed and rotatably mounted within said second partial bore, and a third hollow roller disposed and rotatably mounted within said third partial bore, wherein each of said first hollow roller, said second hollow roller, and said third hollow roller is comprised of a core, a first hole disposed within said core, and a sheath surrounding and contiguous with said core, and wherein: (a) said sheath is comprised of at least 50 weight percent of a first material with a first coefficient of friction of from about 0.01 to about 0.15, and said core is comprised of at least 50 weight percent of a second material with a second coefficient of friction of from about 0.01 to about 0.15, provided that said second coefficient of friction is at least 1.2 times as great as said first coefficient of friction; (b) said core has a cross-sectional area that is at least about 1.5 times as great as the cross-sectional area of said sleeve; (c) each of said first material and said second material has a coefficient of thermal expansion of from about 1×10 −5 to about 20×10 −5 ; (d) said second material has a moisture absorption of from about 0.1 to about 3.0 percent; (e) said second material has a melting point of from about 200 to about 350 degrees Celsius; and (f) each of said sheath and said core has a notch Izod impact strength of from about 50 Joule-meters −1 to about 100 Joule-meters −1 .