A releasable hook for use with a high-tensile load-bearing object, comprising:
- (a) a frame;
- (b) a hook means rotatably mounted on said frame to move between a first position wherein said hook means is engaged with the load-bearing object and a second position wherein said hook means is disengaged from the load-bearing object;
- (c) means for releasably locking said hook means in said first position, said releasable locking means comprising:
- (i) a shaft slidably mounted on said frame to slide along a longitudinal axis;
- (ii) a toggle linking means having a first end pivotally mounted on said hook means to pivot about a first pivotal axis and a second end pivotally mounted on said slidable shaft to pivot about a second pivotal axis that is substantially parallel to the first pivotal axis, said toggle linking means further including a hinged central portion that rotates about a rotational axis that is substantially parallel to the first and second pivotal axes to enable movement of said central portion, such that as said central portion moves so that the rotational axis is moved into alignment with the first and second pivotal axes, said first and second ends of said toggle linking means are urged away from each other to thereby move said hook means into said first position, and as said central portion moves so that the rotational axis is moved out of alignment with the first and second pivotal axes, said first and second ends of said toggle linking means are urged toward each other to thereby move said hook means into said second position;
- (d) means for stopping movement of said central portion of said toggle linking means, said stopping means being formed to prevent movement in one direction of said central portion such that as said central portion moves the rotational axis in a first direction out of alignment with the first and second pivotal axes, said stopping means prevents further movement of said central portion in said first direction and permits movement of said central portion in an opposite second direction whereby when the rotational axis of said central portion is positioned out of alignment in said first direction and said hook means is subjected to a load exerted by the load-bearing object, the force of the load is transmitted to said central portion of said toggle linking means to urge said central portion to move in said first direction toward and against said stopping means to lock said toggle linking means in position to thereby hold said hook means in said first position, and, when the rotational axis of said central portion is positioned out of alignment with the first and second pivotal axes in said second direction, the force of the load moves away from said stopping means to thereby move said hook means to said second position;
- (e) means for urging said slidable shaft toward said first end of said toggle linking means with a predetermined amount of force such that when said hook means is in said first position and subjected to a load that transmits a force of a greater magnitude and opposing said predetermined amount of force of said urging means, said second end of said toggle link is moved away from said first end such that the second pivotal axis is moved out of alignment with the first pivotal axis and the rotational axis of said central portion of said toggle linking means such that said central portion is urged in said second direction to thereby move said hook means from said first position to said second position and disengage said load-bearing object;
- and
- (f) means for moving said central portion of said toggle-linking means in said second direction away from said stopping means and out of alignment with said first and said second pivotal axes when said central portion is adjacent said stopping means whereby said hook means is moved from said first position to said second position.