THE BURNLEY DOBBY (dobby shedding):-

THE BURNLEY DOBBY :-

During the years 1888 to 1893 Messrs. Lupton and Place developed a dobby of original design and action . The frame work is triangular in shape, and support at its apex A Fig. 71 . This shaft carries two lever B, and also two fulcrum pins C, D for a series of cast-iron arms E, F.

The working parts are actuated by a crank and connecting rod from the bottom shaft of the loom . The pendent arm E, F are vibrated alternately and give motion to the Heald shafts through jack levers G. These levers are fulcrumed at H, and bent almost at right angles to place their notched ends J in line with E, F , while their outer ends are united by links L to the heald levers I.

Fig.71 the Burnley dobby.

Two pendents arms E, F serve, instead of draw hooks, to lift one shaft . This occurs whenever the lower end of E or F is pushed by a peg O over one of the notches J. On the next oscillation of the levers B , the bent end of jack lever is forced down by either E or F, and the levers I and I in rising carry a shaft up with them. 

To protect the pegs from injury a flat spring K is fixed upon stationary bar T, T, to face each arm , E, F, and the lower end of each spring is passed through a slotted slide U, which also governs a pendant. Immediately an unpegged portion of a lag faces a spring , the latter moves out with its slide and draws a pendant out of contact with the notched end of J. But when a peg O faces a spring, that spring gives way, and at the proper moment, carries back its slide and pendant until latter is over a notch in J.

A lattice is made in two parts; off picks from the design form one chain , and even picks the other. The chains are passed round separate octagonal barrels M , N, and an intermittent rotary motion is imparted to them by s pushing catch P , centred upon an arm Q , on the top shaft A. Consequently P,Q partak of the rocking of A , and as P acts upon a ratchet wheel on the shaft of N, the barrels ate turned for alternate picks. Both lag barrels M, N are connected by spur wheels R, S , hence both ate moved simultaneously. 

A reversing motion is applied to the dobby to assists a weaver to find the proper starting place after unweaving , or after the weft has been broken. A lever W has for its fulcrum the shaft of barrel N, and mounted upon W is a pawl that may engage the inside of an inverted ratchet wheel on the shaft of N . By drawing down a cord attached to W, the pawl P is lifted , and the lever W reverse both barrels, while the loom is stationary.

A cross-bar X limits the upward movement of the jack lever G; it can be fixed nearer to, or farther from, the fulcrum of G, and so regulate the depth of shed , but when parallel to H the lift of all the shafts is equal. An unequal lift will be obtained by fixing the forward end of X farther from H than its rear end , fir the front notched J will thereby be pushed farther down , and the pendants E, F will move through a greater space before disturbing the front healds. S stout spiral spring V is attached to the inner end of B, to balance the lifting tackle, and two flat spring Z bear upon star wheels to steady the barrels M, N.

Ref:- The Mechanism of Weaving Book . By Thomas W. Fox.