Abstract: A ratchet block comprised of a frame, movable sheave assembly, ratchet assembly, ratchet assembly and cam wherein the ratchet automatically engages under load permitting rotation of the sheave in only one direction, and disengages when the load is removed permitting rotation in both directions. This automatic engagement and disengagement of the ratchet to increase or reduce friction when a rope or wire is run through the sheave does not require the user to disengage the ratchet mechanism with a conventional switch.

Abstract: A precision, high load capacity linear actuator apparatus incorporating a rotary-actuated cam is disclosed. A moveable load carriage assembly containing a cam member mounted on bearings therein is free to ride linearly on stationary tracks. The cam member engages stationary cam followers mounted on the stationary tracks' support. In the preferred embodiment, a linear ball-slide mechanism supported in bearings at each end of the stationary track passes through the cam member, with its linear slide member attached to the cam's center bore. Rotary actuation of the linear ball-slide shaft causes rotation of the cam member which is converted into a linear motion of the load carriage along the stationary track. Thus, linear positioning of the load carriage is effected through rotary positioning of the ball-slide shaft through associated motor means.