A pulley comprising a first pulley wheel and a second pulley wheel and a
ratchet acting between the two pulley wheels. When substantially equal
force is applied to each pulley wheel in use on a rope tail side causing
the pulley wheels to rotate, a low gear ratio is achieved through a rope,
chain or the like acting on a load through a block. When one pulley wheel
is prevented from rotating and a force is applied to the other pulley
wheel in use on a rope tail side causing it to rotate, then a higher gear
ratio is achieved through a rope or chain or the like acting on a load
through a block. When force is applied to the first wheel on a rope tail
side and the second pulley wheel is allowed to rotate, then a still
higher ratio is achieved in use through a rope, chain or the like acting
on a load through a block. In another embodiment, the pulley comprises a
first pulley wheel, a second pulley wheel and means to prevent relative
rotation of the pulley wheels in one direction, the pulley wheels being
able to rotate relative to each other in the other direction. In another
embodiment, the pulley comprises a first pulley wheel, a second pulley
wheel and means acting between the pulley wheels such that, a force
acting to rotate the first pulley wheel in a first direction imparts a
corresponding force to rotate the second pulley wheel in a second,
opposite direction.