Patent ID: 7175162

Claim:
A hoist for accurately drawing a load comprising: a housing providing a main frame for the hoist, an elongated load screw having external threads and mounted for rotation within the housing, a fitting on a first end of the load screw, accessible from outside of the housing and configured to receive a rotational driving input without longitudinal translation of the screw gear within the housing, a load nut having internal threads engaged with the external threads of the load screw so that rotation of the load screw causes the load nut to move longitudinally along the axis of rotation of the load screw, with the direction of movement of the load nut being dependent on the direction of rotation of the load screw, two wire cables, each having an inner end connected to the load nut within the housing and each having an outer end extending outside the housing, the two wire cables extending in opposite directions from the housing each for connection to a load, two idler pulleys connected in the housing for rotation and each in the path of one of the wire cables, the two idler pulleys having axes of rotation perpendicular to a plane containing the load screw and inner ends of the wire cables, each pulley having a peripheral groove for guiding a wire cable in tension, such that tension in the cables and motion of the cables in one direction due to rotation of the load screw is converted into said oppositely-directed motion and tension of the two cables outside the housing, cable guide means in the housing and positioned adjacent to the inner ends of the wire cables, for guiding and partially confining the wire cables as they move within the housing, and stationary pulley guides closely adjacent to an outer periphery of each of the idler pulleys to guide the wire cables in their passage around the pulleys and to generally retain the wire cables within the peripheral grooves of the idler pulleys even when not in tension.