Patent ID: 7628739

Claim:
A variable resistance device incorporated in an exercise machine for providing selectively-variable resistance including: an exercise machine; a primary fluid chamber adapted to receive fluid therein, the primary fluid chamber having a primary fluid flow region; a rotation mechanism having a plurality of fixed vanes, the rotation mechanism being positioned and adapted to rotate within the primary fluid flow region such that upon rotation the vanes encounter a degree of resistance dependent on the amount of liquid in the primary fluid chamber, the rotation mechanism being adapted to be rotated by rotational input from the exercise machine, a gap being defined between the vanes and an inner surface of the primary fluid chamber such that the vanes can rotate without obstruction by the inner surface; a secondary mechanism adapted to achieve and maintain an appropriate amount of liquid in the primary fluid chamber to provide a selected degree of resistance for the exercise machine, the secondary mechanism including a secondary fluid chamber adapted to receive fluid therein, the secondary fluid chamber having a secondary fluid flow region, a wall of the secondary fluid chamber being provided with an inlet leading from the primary fluid chamber to thereby allow liquid to flow from the primary fluid chamber into the secondary fluid chamber, the secondary mechanism being provided with an outlet spaced from the inlet to allow liquid to flow out of the secondary fluid chamber and into the primary fluid chamber; a fluid flow circuit, which includes said primary and secondary fluid flow regions, through which circuit the liquid flows to establish a circuit-flow condition that repetitively cycles around the circuit from the primary fluid chamber into the secondary fluid chamber via the inlet and then back into the primary fluid chamber via the outlet, the circuit-flow condition being adapted to establish and maintain said appropriate amount of liquid in the primary fluid chamber during use; a controller for variably controlling flow of liquid through the outlet to selectively establish different circuit-flow conditions each corresponding to a different appropriate amount of the liquid in the primary fluid chamber to provide a different degree of resistance; the secondary fluid chamber is positioned internally within the primary fluid chamber, the primary fluid flow region of the primary fluid chamber is defined by inner surfaces of the primary fluid chamber and by outer surfaces of the secondary fluid chamber, the inner surfaces of the primary fluid chamber form a first circle, the outer surfaces of the secondary fluid chamber form a second circle which is concentric and coaxial with the first circle, the primary fluid flow region being generally between the two; the primary fluid chamber and the secondary fluid chamber are arranged such that the amount of liquid contained in the device remains substantially constant.