Hoist safety device

Claim 1

A SAFETY DEVICE FOR A HOIST HAVING A FRAME AND A HOISTING CABLE WITH AN UP DRIVE AND A DOWN DRIVE, SAID DEVICE COMPRISING A CYLINDER PROVIDED AT ONE END WITH A CENTRAL HOLE AND AT THE OTHER END WITH A LATERALLY PROJECTING FLANGE, A BAR EXTENDING THROUGH SAID HOLE AND MOVABLE AXIALLY THEREIN, THE BAR BEING PROVIDED INSIDE THE CYLINDER WITH AN ABUTMENT LARGER IN DIAMETER THAN SAID HOLE, A COLLAR RIGIDLY MOUNTED ON THE BAR BETWEEN SAID ABUTMENT AND THE FLANGE END OF THE CYLINDER, A LIGHT COIL SPRING INSIDE THE CYLINDER ENCIRCLING THE BAR AND COMPRESSED BETWEEN SAID ONE END OF THE CYLINDER AND THE COLLAR, A HEAVY COIL SPRING ENCIRCLING THE CYLINDER AND ENGAGING SAID FLANGE, RIGID MEANS ENGAGING THE OPPOSITE END OF THE HEAVY SPRING, MEANS FOR SECURING SAID RIGID MEANS TO THE HOIST FRAME, THE HEAVY SPRING BEING STRONG ENOUGH TO MAINTAIN SAID FLANGE A SUBSTANTIALLY FIXED DISTANCE FROM SAID RIGID MEANS UNDER NORMAL OPERATING CONDITIONS OF THE HOIST, MEANS AT THE OUTER END OF THE BAR FOR CONNECTING THE HOISTING CABLE THEREWITH TO PULL SAID ABUTMENT AGAINST SAID ONE END OF THE CYLINDER WHEN A NORMAL LOAD IS APPLIED TO THE CABLE AND ALSO TO PULL THE CYLINDER BY MEANS OF THE BAR AND COMPRESS THE HEAVY SPRING WHEN THE CABLE IS OVERLOADED, AN ELECTRIC SWITCH, MEANS MOVABLE WITH THE CYLINDER FOR ACTUATING SAID SWITCH TO STOP THE UP DRIVE OF THE HOIST WHENEVER THE CYLINDER IS MOVED A PREDETERMINED DISTANCE BY MEANS OF THE BAR, AND AN ELECTRIC SWITCH ACTUATED BY THE BAR TO STOP THE DOWN DRIVE OF THE HOIST WHENEVER THE BAR COLLAR IS MOVED TOWARD THE FLANGE END OF THE CYLINDER BY SAID LIGHT SPRING DUE TO SLACK STARTING TO DEVELOP IN SAID CABLE.