Keighley double acting negative dobby for shedding mechanism:-

Keighley double acting negative dobby for shedding mechanism:-

Another type of dobby used in textile industry most common is KEIGHLEY DOBBY. It is a double lift negative dobby .

When loom makes two revolutions of crank shaft , the dobby make one revolution .

The loom rpm gets increased if the loom is equipped with double acting dobby.

This a very simple dobby mechanism.

Structure of a Keighley dobby:-

The T-shape lever I is mounted on the dobby shaft O. The T-shape lever gets freely mounted on the dobby shaft . An upper knife A is mounted on the X-side of the T-shape lever I . The lever knife B is mounted on the Y-side of the T-shape lever. The knives are pivoted and get free to make free partial angular displacement. The upper hook C rests upon the upper connecting rod E and the lower connecting rod F. These hooks are connected with the jack lever H through the link . The jack lever fulcrummed at point O. The heald shaft J is connected with the jack lever through two leather straps L . One spiral spring K gets mounted at each side of the heald shaft. The lower ends of the spring are connected with the two side frame. The feelers are mounted under the upper and lower connecting rod rests upon the feeler T. A pattern cylinder G is mounted under the feeler. The lattice is mounted over the pattern cylinder G. The peg R is inserted in the hole of the legs Q. An L-shape crank N is fastened on the bottom shaft P. The T-shape crank N are connected to each other with the help of connecting rod M .

Digram of Keighley Double Acting dobby.

Working principle of Keighley dobby:-

When the L-shape crank is mounted on the bottom shaft rotates, it transfer motion to the T-shape lever I . The T-shape lever I makes a reciprocating motion when the L-shape cranks rotates. The pattern cylinder G rotates with the help of a ratchet wheel and pawl. The peg R mounted on the leg Q presses the corresponding feeler S & T. As one end of the feeler goes upwards the other end of the feeler comes downward at the same time . The bottom end of either the upper or lower connecting rod comes downward. Since the upper and lower hooks rests upon corresponding connecting rods. So that the hook falls on the knife while the corresponding connecting rod comes downward . Now the reciprocating knives pull the hook towards the right hand side. The hook pulls the jack lever and heald shaft goes upward with the jack lever . In this way , the shaft makes up and down movement. The pulley spring helps the heald shaft in a lower position.

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