Abstract: An internal combustion engine having ring shaped cylinder is disclosed herein. In one embodiment, an internal combustion engine includes an engine body and a ring-shaped cylinder in the engine body. The ring-shaped cylinder has a center and an outer circumference spaced radially apart from the center. The internal combustion engine further includes a plurality of synchronizing valves at least proximate the outer circumference of the ring-shaped cylinder so that the ring-shaped cylinder is divided into a plurality of cylinder portions. The synchronizing valve has a valve shaft and a valve opening. The internal combustion engine further includes a rotor at the center of the ring-shaped cylinder, and the rotor has isolation blocks extending from the rotor toward the outer circumference of the ring-shaped chamber. The valve openings are configured to receive the isolation blocks and to form seals in the ring-shaped cylinder.

Abstract: A two directional multi-speed shifting sear of middle axle is made of outer ring, bearings ring, starwheel, freewheel screw cup, freewheel plate, core teeth, inner and outer pawls, and chainwheel etc. The chainwheel is fixed on the outer ring through thread or thread hole. The starwheel is geared with inner teeth of the outer ring and the core teeth. The outer pawl is mounted on pawl hub, the later is fixed on the bottom bracket case of the cycle frame. The middle axle is passed through and fixed with the freewheel plate, the core teeth and the right crank, and then inserted into the bottom bracket case. With such a shifting gear, a pedal cycle may be given a unique function that when the cycle is moving forward, the changing of it's moving speed in the very moving direction may be in-situ realized by variating the shifting gear through pedalling to enable the crank to be rotating in either positive or inversive directions.

Abstract: Disclosed is a two-way-driven 3-speed free wheel which provides a multi-gear-changing mechanism for use with various kinds of pedal cycles. The disclosed device has four kinds of catches: pawl, hook-pawl, backward pawl and forward pawl. The backward and forward pawls respectively are hinged on the opposed sides of a sprocket wheel by small spindles mounted on the opposed sides of the sprocket wheel. On one side of the sprocket wheel are the backward pawls and an outer ring; on the other side are forward pawls, a ratchet cone and a bearing collar. Between the outer ring and a central gear are two or more planet pinions. As compared with prior art structures, this invention has the following advantages: the structure is simple, the cost is lower, and it is facile to operate and to change speed. Also disclosed are one-way-driven 2-speed free wheels and two-way-driven 2-speed free wheels, using two or three kinds of catches, of the above-described four kinds of catches.