Safety grapple

A grapple unit for releasably engaging an object to be moved thereby, such grapple adapted to prevent inadvertent release of such object, which comprises:

• a hollow cylindrical frame housing having a central axis, said frame housing closed by an end plate at a first end and open at a second end, said end plate provided with a centrally disposed aperture;
• a guide housing carried in said aperture of said end plate, said guide housing attached to said end plate and having a central passageway, said passageway provided with an axial keyway;
• a shaft positioned along said central axis adapted for axial movement in said passageway, said shaft provided with a key engaged in said keyway to prevent rotation of said shaft relative to said guide housing, said shaft having a first end disposed exterior to said frame housing and a further end disposed within said frame housing;
• a substantially cylindrical sleeve, having a first end disposed toward said end plate and a further end, rotatably mounted within said frame housing, said sleeve provided with a radially extending centering guide rail intermediate said first and further ends;
• a plurality of guide rollers rotatably mounted from said frame housing engaged with a periphery of said centering guide rail for maintaining said sleeve concentric with said frame housing;
• a bearing member disposed within said sleeve intermediate said first end and said further end of said sleeve, and surrounding said shaft, said bearing member providing for axial and rotational movement between said shaft and said sleeve;
• first and further cylindrical indexing cams fixedly attached to said further end of said sleeve, said indexing cams being concentric with said central axis, said cams having toothed surfaces directed toward each other, said toothed surfaces being mirror images, with said teeth being equally spaced around said indexing cams at selected angular positions, and said teeth of said first indexing cam equally spaced between said teeth of said further indexing cam;
• a rotatable indexing cam follower disposed between said first and further indexing cams, said indexing cam follower projecting radially from said further end of said shaft, whereby axial movement of said shaft moves said indexing cam follower into a succession of said teeth of said indexing cams and results in unidirectional rotation of said sleeve, the amount of rotation of said sleeve due to each axial movement of said shaft corresponding to said selected angular spacing of said teeth of said indexing cams;
• an actuating cam plate fixedly carried by said sleeve at said first end thereof oriented perpendicularly to said central axis and adapted to rotate with said sleeve about said central axis, said cam plate being provided on a periphery thereof with a selected plurality of substantially flat lobes and valleys, said lobes and valleys having selected dwell times;
• a plurality of lifting lugs, said plurality of lugs equal in number to said plurality of lobes, each of said lugs having a first end disposed within said frame housing, and a further end for releasable engagement with such object extending from said open end of said frame housing, each of said lugs being provided with a pivot aperture;
• guide legs on each side of each of said lifting lugs, said guide legs having a first end fixedly mounted to said frame housing and a further end extending proximate said further end of said lugs, said further end of said legs contoured to guide said grapple into engagement with such objects, each of said legs provided with a pivot aperture;
• pivot pins for each of said lugs, said pivot pin of each lug passing through said pivot aperture of said lug and said pivot aperture of each leg on opposite sides of each lug, for releasably mounting said lugs to said frame housing for radial pivotal movement of said lugs relative to said central axis, said pivot pins adapted for removal from said lugs and said legs to release said lugs from said frame housing;
• a rotatable lug cam follower attached to said first end of each of said lugs, said lug cam follower engaged with said periphery of said actuating cam plate whereby said lobes and valleys of said cam plate produce said pivotal movement of said lugs;
• a coil spring mounted between said frame housing and said first end of each of said lugs for maintianing said lug cam followers in contact with said periphery of said cam plate;
• and
• wherein said selected angular positions of said teeth of said indexing cams and said selected dwell times of said lobes and valleys of said cam plate prevent removal of said lugs from such object until said shaft has completed three axial reciprocations.