Cable slack detector

A cable slack detection and compensation apparatus for connecting a cable to an object for lifting and lowering of the object, said apparatus comprising:

• a first body part having a portion connectable to the cable;
• a second body part having a portion connectable to the object;
• means for connecting said first body part and said second body part for movement of said body parts relative to each other, said body parts being relatively moveable to and from a position in which said apparatus is fully extended, and a position in which said apparatus is fully retracted, said fully extended position and said fully retracted position and positions therebetween defining a range of movement of said body parts;
• biasing means for biasing said body parts in a direction from said fully extended position toward said fully retracted position, whereby said biasing means moves said body parts from said fully extended position towards said fully retracted position along said movement range in response to a presence of slack in the cable;
• and
• means responsive to said relative positions of said body parts for indicating when said biasing means retracts said body parts from said fully extended position to a predetermined position along said movement range, a portion of said movement range from said fully extended position to said predetermined position providing slack compensation prior to indicting by said responsive means and, wherein
• one of said body parts has a slot extending longitudinally therein, and the other of said body parts has a member projecting into said slot for defining said relative movement with said slot, said slot and said member providing said connecting means;
• said body parts each have a flat portion, and said relative movement is relative sliding movement of said flat portions;
• and
• one of said body parts has a stop, and the other of said body parts has a shoulder facing in opposition to said stop, said stop and said shoulder cooperating to prevent extending movement beyond said fully extended position.

A cable slack control apparatus for a door operator having a jack shaft, drum means mounted on the jack shaft, a cable windable on the drum means, and drive means for turning the jack shaft, said apparatus comprising:

• cable slack condition detection and compensation means for connecting the cable to the door, said detection and compensation means including means for adding tension to the cable to maintain the cable at a minimum acceptable tension, and means for providing a slack detection signal when said means for adding tension to the cable is incapable of tensioning the cable to said minimum tension;
• and
• drive control means for causing the drive means selectively to turn the jack shaft in a first direction to unwind the cable and lower a door, and a second direction to wind the cable and lift the door, said drive control means including means responsive to a slack detection signal from said compensation means for stopping the drive means, and wherein said means for adding tension includes
• a first body part,
• a second body part,
• means for connecting said first body part and said second body part for movement of said body parts relative to each other, said body parts being relatively movable to and from a position in which said apparatus is fully extended, and a position in which said apparatus is fully retracted, said fully extended position and said fully retracted position and positions therebetween defining a range of movement of said body parts, and
• biasing means for biasing said body parts in a direction from said fully extended position toward said fully retracted position along said movement range in response to a presence of slack in the cable, and wherein
• one of said body parts has a slot extending longitudinally therein, and the other of said body parts has a member protecting into said slot for providing said relative movement;
• one of said body parts has a stop for preventing said relative movement beyond said fully extended position, and the other of said body parts has a shoulder facing in opposition to said stop;
• and
• each of said body portions has a protruding arm, and said biasing means includes a spring with one end thereof connected to said protruding arm of one of said body portions and an opposite end thereof connected to said arm of the other body portion.

A cable slack condition detection and compensation apparatus for connecting a cable to an object for lifting and lowering of the object, said apparatus comprising:

• a first body part having a portion connectable to the cable and a first planar portion;
• a second body part having a portion connectable to the object and a second planar portion;
• means for connecting said first body part and said second body part for sliding movement of said body parts relative to each other along said planar portions thereof, said body parts being relatively movable to and from a position in which said apparatus is fully extended, and a position in which said apparatus is fully retracted, said fully extended position and said fully retracted position and positions therebetween defining a range of movement of said body parts;
• biasing means for biasing said body parts in a direction from said fully extended position toward said fully retracted position along said movement range in response to a presence of slack in the cable;
• and
• means responsive to said relative positions of said body parts for indicating when said biasing means moves said body parts from said fully extended position to a predetermined position along said movement range.

A method of detecting and compensating for slack in a cable used for lifting and lowering an object, said method comprising the steps of:

• providing an apparatus including a first body portion having a first planar portion, and a second body portion having a second planar portion, and means for connecting said two body portions to each other so that they are movable relative along said planar portions thereof to each other to and from a first position in which said body portions are fully extended with respect to each other, and a second position in which said body portions are fully retracted with respect to each other, said first and second positions and positions therebetween defining a range of movement of said body portions, and means for generating a warning signal when said body portions retract from said first position toward said second position to a predetermined position;
• connecting one of said body portions to said cable and the other of said body portions to said object;
• biasing said body portions toward said second position against tension in said cable, whereby when said cable becomes slack, said biasing means moves said body portions from said first position toward said second position in order to take up slack in said cable;
• sensing when said body portions retract from said first position to said predetermined position;
• and
• causing said generating means to generate said warning signal upon sensing that said body portions have retracted to said predetermined position.