Patent ID: 7318404

Claim:
A piston engine that mounted on a frame having a mounting bracket protruded out the frame, a gearbox mounted securely with the frame and having a holding bracket, and a swing shaft connecting the frame and the piston engine, and the piston engine comprising a crank assembly adapted to be mounted rotatably between the mounting bracket and the holding bracket and having a central axle having two connecting segments, one of the connecting segments adapted to be attached in the holding bracket and extended into the gearbox, and the other connecting segment adapted to be attached in the mounting bracket of the frame; and two flanges coaxial but eccentric mounted on the connecting segments respectively and one of the flanges abuts with the holding bracket and the other flange abuts with the mounting bracket of the frame and each flange having an eccentricity h with a corresponding connecting segment; two counterweight blocks mounted securely on the central axle and each having an outer surface abutting with one of the flanges; and an inner surface facing to each other; and a crank axle mounted transversely between the inner surfaces of the counterweight blocks; a piston assembly connected with the crank assembly and having a piston rod mounted on the crank axle and having a distal end mounted around the crank axle between the counterweight blocks; and a proximal end; a piston pin mounted transversely on the proximal end of the piston rod; and a piston mounted around the proximal end of the piston rod and attached securely to the piston pin; a crank case assembly attached with the crank assembly and having a body being U shaped, attached to the central axle of the crank assembly and having two side walls formed and protruded up from the body and parallel with each other; two mounting grooves being semicircular and respectively formed on the side walls, facing each other and respectively holding the flanges of the central axle inside; and a chamber formed between the side walls to hold the counterweight blocks inside; and a cylinder head assembly combined with the crank case assembly, adapted to be connected vertically with the swing shaft of the frame and having a cylinder housing combined with the body of the crank case assembly and having two side walls connected to the side walls of the crank case assembly; two mounting grooves respectively formed in the side walls of the cylinder housing, and corresponding respectively to the mounting grooves in the crank case assembly; and a piston channel formed in the cylinder housing between the mounting grooves and the piston of the piston assembly extended slidably into the piston channel; and a cylinder head mounted over the cylinder housing and adapted to be connected with the front end of the swing shaft.