Patent ID: 7789815

Claim:
A chest expander comprising: a head having a spring installation part at which a spring is installed and arm connection parts installed at both sides of the spring installation part; a pair of arms pivotally coupled with the arm connection parts of the head at their upper ends; a spring member vertically installed at the spring installation part of the head, and converting movement of the pair of arms approached toward each other into a resilient force generated by compressing the spring to vertically transmit the resilient force to the arms; a pair of links having first ends pivotally connected to each arm and second ends extending between the arms; and a spring operation part having a link connection part pivotally connected to the second ends of the links and compressing the spring member using power added and transmitted to the link connection part through the links by the movement of the arms, wherein the spring member is formed of a compression coil spring, and the spring operation part compresses the coil spring using vertical movement of the link connection part, wherein the spring operation part is configured to adjust the magnitude of a resilient force generated by the coil spring when the arms approach each other, wherein the spring installation part is formed of a hollow cylindrical part having an upper open end, and a lower end of the coil spring is supported by a lower surface of the hollow cylindrical part, wherein the spring operation part includes: (i) a head part for supporting an upper end of the coil spring in a compressible manner and (ii) a connection rod extending downward from a lower end of the head part along the hollow cylindrical part to pass through the lower surface of the hollow cylindrical part, and connected to the link connection part at its lower end, and wherein the second ends of the links connected to the link connection part are disposed lower than the first ends of the links to move the link connection part downward when the arms approach each other so that the head part is moved downward by the connection rod to compress the upper end of the coil spring.