An exercise apparatus capable of generating harmonic resistance to an exercising user, comprising:
- a base;
- a guiding screw rod journalled on the base for reversible rotation about its own longitudinal axis;
- said guiding screw rod having two ends and a mid-section disposed intermediate said ends;
- a first bevel gear secured on one said end of said guiding screw rod;
- a compression coil spring encircling said mid-section of said guiding screw rod and having one end axially fixed in relation of the other said end of said guiding screw rod;
- an axially movable block mounted on an opposite end of said compression coil spring and threadedly mounted on said guiding screw rod so as to be axially reversibly advanced along said longitudinal axis as said guiding screw rod is correspondingly reversibly rotated, whereby said compression coil spring is correspondingly variably compressed as said guiding screw rod is reversingly rotated;
- a straight rod axially movably arranged on said base so as to be parallel to said guiding screw rod, said axially movable block being fixed on said straight rod at an intermediate location between two opposite ends of said straight rod;
- two collision elements, including one mounted on said straight rod between said block and a forward end of said straight rod and the other mounted on said straight rod between said block and a rear end of said straight rod;
- a transverse shaft journalled on said base for rotation about its own longitudinal axis, which is arranged perpendicularly to said longitudinal axis of said guiding screw rod;
- spline sleeve means mounted on said transverse shaft for rotation therewith;
- second and third bevel gears journalled on said transverse shaft, each having a respective clutch means;
- first and second clutch members axially shiftably mounted on said spline sleeve means for rotation with said transverse shaft;
- first and second shifting means respectively operatively associated with said first and second clutch members, respectively for shifting said first clutch member into and out of operative engagement with said clutch means of said second bevel gear, and said second clutch member into and out of operative engagement with said clutch means of said third bevel gear;
- first and second rocking levers arranged to be engaged and rocked by said other collision element upon rearward axial travel of said straight rod due to rotation of said guiding screw rod in one direction;
- third and fourth rocking levers arranged to be engaged and rocked by said one collision element upon forward axial travel of said straight rod due to rotation of said guiding screw rod in a direction opposite to said one direction;
- cable means operatively associating said first shifting means with said first and third rocking levers and said second shifting means with said second and fourth rocking levers, so that as said first and second rocking levers are engaged and rocked by said other collision element said third bevel gear is operatively engaged with said first bevel gear, and said fourth bevel gear is disengaged from said first bevel gear, and, as said third and fourth rocking levers are engaged and rocked by said one collision element said fourth bevel gear is operatively engaged with said first bevel gear, and said third bevel gear is disengaged from said first bevel gear;
- and
- means actuable by an exercising user for rotating said transverse shaft, so that as said user continues to exercise and thereby rotate said transverse shaft, said guiding screw rod is rotated in said one direction thereby causing said spring to become progressively more compressed and thus offer progressively greater resistance to further rotation of said transverse shaft, until said first and second rocking levers are rocked by said other collision element, and then said guiding screw is rotated in said other direction thereby causing said spring to become progressively less compressed and thus offer progressively less resistance to further rotation of said transverse shaft, until said third and fourth rocking levers are rocked by said one collision element, so that as exercising time progresses simple harmonic resistance is provided to the user as the user uses the actuable means to rotate the transverse shaft.