Patent ID: 6508639
Filing Date: 2003-01-21
Classification: F01C,F04C

Abstract:
A combination double screw rotor assembly, comprising:a casing, said casing comprising an inside wall defining a receiving chamber, an inlet, and an outlet; a first screw rotor, said first screw rotor comprising a shaft pivoted in said casing, a low pressure screw rotor element and a high pressure screw rotor element respectively and separately mounted on the shaft of said first screw rotor in a direction from said inlet toward said outlet, and a spiral thread raised around the periphery thereof and extended over the low pressure screw rotor element and high pressure screw rotor element of said first screw rotor, the spiral thread of said first screw rotor being comprised of a first spiral thread segment raised around the periphery of the low pressure screw rotor element of said first screw rotor and defining a uniform long pitch, and a second spiral thread segment raised around the periphery of the high pressure screw rotor element of said first screw rotor and defining a uniform short pitch; a second screw rotor, said second screw rotor comprising a shaft pivoted in said casing and disposed in parallel to the shaft of said first screw rotor, a low pressure screw rotor element and a high pressure screw rotor element respectively and separately mounted on the shaft of said second screw rotor in a direction from said inlet toward said outlet, and a spiral thread raised around the periphery thereof and extended over the low pressure screw rotor element and high pressure screw rotor element of said second screw rotor, the spiral thread of said second screw rotor being comprised of a first spiral thread segment raised around the periphery of the low pressure screw rotor element of said second screw rotor and defining a uniform long pitch, and a second spiral thread segment raised around the periphery of the high pressure screw rotor element of said second screw rotor and defining a uniform short pitch, the first spiral thread segment and second spiral thread segment of the spiral thread of said second screw rotor being respectively meshed with the first spiral thread segment and second spiral thread segment of said first screw rotor; two sets of bearings respectively mounted in said casing near said outlet to support the shaft of said first screw rotor and the shaft of said second screw rotor; a plurality of keyless axle bushes, each being disposed near said inlet, and each being respectively fastened to the shaft of said first screw rotor and the shaft of said second screw rotor to secure the respective low pressure screw rotor elements of said first screw rotor and said second screw rotor to the respective shafts, said keyless axle bushes allowing a region near said inlet to be maintained free of axle bearing grease; connection means for connecting the respective high pressure screw rotor elements of said first screw rotor and said second screw rotor to the respective shafts; and a set of timing gears adapted to transmit the rotary power between the shaft of said first screw rotor and the shaft of second screw rotor, while preventing friction contact between the spiral thread of said first screw rotor and the spiral thread of said second screw rotor.