Fail-safe device for raising/lowering articles

摘要

A failsafe device for raising/lowering articles includes a frame and a fastener for attaching the frame to a ceiling or wall to elevate an article above the floor. A pulley or sheave is mounted on the frame about a substantially horizontal axis when the frame is mounted on the ceiling or wall. A cable is entrained over the pulley and has a substantially vertical lifting cable portion attachable to the article to the lifted and a substantially vertical pulling cable portion arranged to be pulled downwardly by a user to elevate the article and raised upwardly to lower the article. A cam is mounted on the frame on one side of the pulling cable portion and has a cable engaging surface. The cam is movable between a cable releasing position and a cable locking position, the cable engaging surface including a first engaging portion normally spaced a fixed distance from the pulling cable portion to form a clearance gap in the cable releasing position and a second engaging portion bridging the clearance gap a distance equal to least the fixed distance for substantially instantaneously arresting the cable and preventing movement of the pulling cable portion upwardly toward the pulley and corresponding downward movement of the article. A pusher is mounted on the frame for always applying a force on the pulling cable portion in the direction of the cam for urging it across the clearance gap into contact with the first engaging portion only when tension in the pulling cable portion is decreased relative to the tension in the lifting cable portion, continued contact between the pulling cable portion causing the second engaging portion to bridge the clearance gap as it moves from the releasing to the locking positions until a tension is applied by the user to the pulling cable portion with a force that substantially corresponds to the weight of the article.