Abstract: A trolley wheel for a load lifting apparatus that is movable along a rail having a horizontal supporting surface. The wheel includes a crowned tread surface for rolling contact with the rail and a flange for stabilizing the tread surface in position on the rail. The flange includes a substantially crowned realigning portion for realignment of the wheels on the rail with minimal contact or binding. The flange also includes an undercut portion for added clearance between the flange and the rail. Preferably, the crowned tread surface and crowned realigning portions are heat treated for improved wear resistance. The undercut may also be heat treated for added toughness.

Abstract: A load lifting apparatus comprising: a frame; a load engaging mechanism for engaging a load having a weight; a hoist mechanism for raising the load engaging mechanism, the hoist mechanism being mounted on the frame and including a member supporting the load engaging mechanism during lifting of the load, the member having therein an aperture; a sensor disposed in the aperture for detecting a force exerted by the load engaging mechanism on the member, the sensor providing a variable output indicative of the magnitude of the force; and a control for disabling the hoist mechanism when the output reaches a first predetermined value corresponding to the maximum load of the load lifting apparatus.