GB629367A - Improvements in or relating to gripping devices - Google Patents

Abstract

629,367. Lifting-dogs. JAMES, G. E. June 6, 1947, No. 15027. [Class 78 (iv)] Lifting-dogs of the kind including a pivoted linkage in the form of a parallelogram are provided with a latch member which is pivoted to a member of the linkage near one end of the vertical diagonal of the parallelogram and is engageable with another member of the linkage near the other end of the diagonal, means also being provided whereby the tongs are alternately locked open or unlocked on subsequent collapses of the linkage by means varying the angular position of the latch member. The latch member 18, Fig. 1, is pivoted at 17 to link member 14 and is provided at its upper end with a transverse pin 19 adapted to engage a pair of tracks 20 formed on the inward faces of a box 21 secured adjacent the shackle pin 12 to link member 11. The tracks are substantially heart-shaped having recesses 2, 4 in the crests of the lobes, a similar recess 1 between the lobes and an opening 22 having chamfered walls foi directing the pin into the track. The latch member is biased to turn in the direction of the arrow A by gravity or spring loading. When the under edges 13b, 14b of the tongs contact the top of a block to be gripped the linkage collapses slightly bringing pir 19 out of recess 1, where it is shown locking the linkage, until, owing to the biasing, it enters recess 2. On lifting shackle pin 12 pin 19 travels down the right hand track and out through opening 22 allowing the load to be gripped. On lowering the load, further lowering of the shackle pir causes latch member 18 to be guided by its resting on link 14, so that pin 19 re-enters the track when, owing to the inclined edge 31, it travels up the left hand track into recess 4. On raising shackle pin 12 pin 19 falls back, owing to the bias, into recess 1 locking the tongs open. In a modification a different form of latch member is used comprising a bell crank 118, Fig. 8, pivoted on shackle pin 12. The depending arm 118a is provided with a pin 33 for engaging hook 34 formed on link 14 and arm 118b is finned to link 36 whose lower end carries a pin 119 which travels in a heartshaped track 120 similar to that of the previous construction except that opening 22 is replaced by a recess 113. Recesses 111, 112, 114 thus correspond with recesses 1, 2, 4 of the previous construction. Pin 119 is biased to travel clockwise as shown by the arrows. In the locked position pin 119 is in recess 113. On collapse of the linkage pin 33 is forced down the inclined surface 35 to position 33a when pin 119 is in recess 114. On lifting shackle pin 12, pin 119 falls into recess 111 allowing pin 33 to travel back only to 33b where it is clear of hook 34 allowing gripping of the load to take place. On depositing the load, pin 33 describes exactly the same movements on surface 35 in reverse, first forcing pin 119 into recess 112 while moving between 33b and 33a positions and on again raising shackle pin 12 engaging hook 34 as pin 119 travels under gravity or supplementary spring down track 120 into recess 113.