Safety clamp device and apparatus utilizing same

A safety clamp device adapted to be slidably mounted on an upright hoist cable for raising and lowering a movable platform and adapted to be slidably mounted on an upright safety cable and further adapted to grip said safety cable when said hoist cable is subjected to less than a predetermined tension, said device comprising:

• a body member having a cable receiving cradle adapted to receive said safety cable;
• a lever arm shiftably mounted on said body member for movement about an axis transverse to the slidable movement of said body member relative to said safety cable, said lever arm shiftable between a safety cable engaging position and a safety cable release position;
• safety cable engaging means for engaging said safety cable when said lever arm is in said engaging position;
• an elongate member pivotally connected to said lever arm;
• means for coupling said elongate member to said movable platform;
• tension sensing means for shifting said elongate member to a first upright position to urge said lever arm to said release position when said hoist cable is subjected to greater than a predetermined tension and for shifting said elongate member to a second upright position to urge said lever arm to said engaging position when said hoist cable is subjected to less than said predetermined tension;
• said tension sensing means comprising a first roller means rotatably mounted at one end of said elongate member for engaging said hoist cable, a second roller means rotatably mounted at the other end of said elongate member for engaging said hoist cable, and a control arm having a first pivotal connection at one end portion to said body member and carrying a third rotatably mounted roller means at another end portion, said control arm including a second pivotal connection to said elongate member intermediate said first pivotal connection and said third roller means;
• and
• said hoist cable being threaded over said first, second and third roller means such that when said hoist cable is subjected to greater than said predetermined tension, said other end portion is urged toward said body member and said control arm urges said elongate member to said first upright position.

Platform apparatus for ascending or descending a hoist cable and for engaging a safety cable to prevent sudden downward movement thereof, said apparatus comprising:

• a movable platform;
• a platform lifting device;
• a safety clamp device slidably mounted on said safety cable, said safety clamp device comprising:
• a body member having a cable receiving cradle adapted to receive said safety cable;
• a lever arm shiftably mounted on said body member for movement about an axis transverse to the slidable movement of said body member relative to said safety cable, said lever arm shiftable between a safety cable engaging position and a safety cable release position;
• safety cable engaging means for engaging said safety cable when said lever arm is in said engaging position;
• an elongate member pivotally attached to said lever arm and coupled to said movable platform, said elongate member carrying a first roller at one end and a second roller at the other end, said first and second rollers being adapted to engage said hoist cable;
• a control arm pivotally attached at one end to said body member, carrying a third roller at the other end, and pivotally attached to said elongate member intermediate said first pivot means and said third roller, said first roller being adapted to engage said hoist cable and said control arm;
• said hoist cable being threaded over said first, second, and third rollers;
• said control arm operating to maintain said elongate member in a first upright position to, in turn, maintain said lever arm in said release position in response to said cable being tensioned;
• said elongate member adapted to shift to a second upright position to urge said lever arm to said engaging position in response to said cable having less than a predetermined tension;
• and
• said lever arm and said control arm cooperatively acting to maintain said cradle in parallel relationship to said elongate member when said elongate member is in said first upright position.

Platform apparatus for ascending or descending a hoist cable and for engaging a safety cable to prevent sudden downward movement thereof, said apparatus comprising:

• a movable platform;
• a platform lifting device;
• a safety clamp device connected to said movable platform and adapted to be slidably mounted on said hoist cable and said safety cable and further adapted to grip said safety cable when said hoist cable is subjected to less than a predetermined tension, said device comprising:
• a body member having a cable receiving cradle adapted to receive said safety cable;
• a lever arm shiftably mounted on said body member for movement about an axis transverse to the slidable movement of said body member relative to said safety cable, said lever arm shiftable between a safety cable engaging position and a safety cable release position;
• safety cable engaging means for engaging said safety cable when said lever arm is in said engaging position;
• an elongate member pivotally connected to said lever arm;
• means for coupling said elongate member to said movable platform;
• tension sensing means for shifting said elongate member to a first upright position to urge said lever arm to said release position when said hoist cable is subjected to greater than a predetermined tension and for shifting said elongate member to a second upright position to urge said lever arm to said engaging position when said hoist cable is subjected to less than said predetermined tension;
• said tension sensing means comprising a first roller means rotatably mounted at one end of said elongate member for engaging said hoist cable, a second roller means rotatably mounted at the other end of said elongate member for engaging said hoist cable, and a control arm having a first pivotal connection at one end portion to said body member and carrying a third rotatably mounted roller means at another end portion, said control arm including a second pivotal connection to said elongate member intermediate said first pivotal connection and said third roller means;
• and
• said hoist cable being threaded over said first, second and third roller means such that when said hoist cable is subjected to greater than said predetermined tension, said other end portion is urged toward said body member and said control arm urges said elongate member to said first upright position.