Patent ID: 6234454
Filing Date: 2001-05-22
Classification: B66D,Y10T

Abstract:
A failsafe device for raising/lowering articles comprising a frame; attaching means for attaching said frame to a support surface above a predetermined height to which the article is to be selectively elevated; low friction deflection means mounted on said frame about a substantially horizontal axis when said frame is mounted on the support surface; a cable entrained over said low friction deflection means which 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 released upwardly to lower the article; cam means on said frame on one side of said pulling cable portion and having a cable engaging surface, said cam means being movable between a cable releasing position and a cable locking position, said cable engaging surface including a first engaging portion normally spaced a distance .DELTA. from said pulling cable portion to form a clearance gap in said cable releasing position and a second engaging portion bridging said clearance gap a distance equal to least .DELTA. for substantially instantaneously arresting said cable and preventing movement of said pulling cable portion upwardly toward said low friction deflection means and corresponding downward movement of the article; and pushing means on said frame on an opposing side of said pulling cable portion in relation to said cam means for continuously applying a force on said pulling cable portion in the direction of said cam and for urging said pulling cable portion across said clearance gap said distance .DELTA. into contact with said first engaging portion only when tension in said pulling cable portion is decreased relative to the tension in said lifting cable portion, continued contact between said pulling cable portion and said cable engaging surface causing said second engaging portion to bridge said distance .DELTA. while said cam means moves from said releasing to said locking positions until a tension is applied by the user to said pulling cable portion that substantially corresponds to the weight of the article.