An Improved Grab Crane. 167 



and, second, in a modified construction of crane for working 

 my grab, by which it is made a portable machine." 



The sketch shows the grab crane, which has pivoted jaws, 

 a a, and connecting links, b b, similar to the ordinary grab ; 

 but the crosshead and shaft of the ordinary grab are com- 

 bined in one shaft, n, which is capable of a vertical motion 

 between guides in a frame, also of a rotary motion, and is 

 supplied with a barrel, o, and two smaller warping barrels, 

 pp. The larger barrel has two lifting chains, qq, which are 

 at one end wrapped round and fastened to it, then led over 

 two jib-head sheaves to two chain pulleys, r r (one close to 

 each cheek of the crane), which are capable of being 

 revolved by the hoisting engines, or of being stopped by a 

 brake; thence by a series of guide pulleys to the roling 

 counterbalance barrels, s s, round which they are wrapped 

 and fastened. The main barrel of the grab has also a 

 lowering chain, v, wrapped round it in the opposite direction 

 to that of the lifting chains, and led over a jib sheave to a 

 barrel, t, which is capable of being put into gear and 

 revolved by the hoisting engine, or stopped by a brake by 

 the action of one lever acting on an eccentric and friction 

 wheel. The two warping barrels have each chains, x x, the 

 ends of which are wrapped round and fastened to them and 

 to a fixed point, w, of the framing at the pivots of the jaws 

 in such a manner that when the lifting chains, qq, are pulled 

 by the engine the bucket closes, and when the lowering 

 chain, v, is pulled the bucket opens. Two rolling counter- 

 balance barrels, s s, which have the ends of the lifting 

 chains attached to their circumferences, are fixed to a shaft, 

 having pinions shrouded to their pitch lines, keyed to each 

 end, which are free to roll down or up inclined shrouded 

 racks as the lifting chains are either pulled or let out by the 

 engines, and at the same time coiling or uncoiling the chains 

 on their outer circumferences in a self-acting manner. 



By this new machinery, which I have endeavoured to 

 describe, the various operations of closing, digging, hoisting, 

 opening, lowering, and partly counterbalancing the grab jaws, 

 are effected in a novel and improved manner, as follows: — 



Assuming that the grab is resting in the open position on 

 the material to be lifted, the grab is then closed by putting 

 the chain pulleys, rr, into gear with the engines, and thus 

 pulling the lifting chains, q q, which, being wound round the 

 main barrel of the grab, causes the warping barrels, p p, to 

 revolve and drag down the shaft, n, by the warping chains 



