| 主权项 |
1. A ratchet pulley comprising:
a housing composed of two side plates, the housing having two openings for a rope to go into and go out of the housing, a first slide section being disposed on inner face of at least one of the side plates; a hub formed of two half hubs, the hub being received in the housing with two end faces respectively facing the inner faces of the side plates, the hub having an internal space, a lateral opening being formed on a circumference of the hub, a first position, a second position and a third position being disposed in the internal space, a second slide section being disposed on at least one of the half hubs corresponding to the first slide section, the second slide section being slidably disposed on the first slide section, whereby the hub is reciprocally movable between an upper position and a lower position, a first elastic body being disposed between the first and second slide sections, when no pull force is applied to the hub, the first elastic body making the hub move to the upper position; an annular pulley received in the housing, each of two end faces of the annular pulley having an annular bearing rotational face rotatable on the circumference of the hub, the annular pulley having an outer circumference with a groove for receiving the rope, a first engagement section being disposed on an inner circumference of the annular pulley; a selection device disposed in the internal space of the hub, the selection device including a rotatable rod, a rock block, a guide slope and an activation section, at least one end of the rotatable rod passing through an end face of the hub and the side plate corresponding to the end face, the rotatable rod including a locating section and a protrusion section, the locating section serving to at least locate the rotatable rod in a position selected from a group consisting of the first, second and third position, one end of the rock block being pivotally fitted on the rotatable rod, the other end of the rock block being formed with a second engagement section, a second elastic body being disposed between the rock block and the rotatable rod for making the second engagement section move toward the lateral opening of the hub and locating the second engagement section as follows:
(1) when the rotatable rod is positioned in the first position, the second engagement section is engaged with the first engagement section to limit the rotational direction of the annular pulley;(2) when the rotatable rod is positioned between the first and second positions, the second engagement section is engaged with the first engagement section to limit the rotational direction of the annular pulley; and(3) when the rotatable rod is positioned in the second and third positions, the second engagement section is disengaged from the first engagement section, whereby the rotational direction of the annular pulley is not limited; the guide slope being disposed between the first position and the second position; and the activation section being disposed at one end of the first slide section, when the rotatable rod is positioned in the second position and an external force is applied to the annular pulley and the hub to move the annular pulley and the hub to the lower position, the activation section abutting against and pushing the protrusion section of the rotatable rod to drive the locating section, whereby the rotatable rod is positioned between the first and second positions, when the external force disappears, the protrusion section of the rotatable rod being released from the activation section and the guide slope guiding the locating section to make the rotatable rod restore to the second position. |
