Types of multiple box motion in power loom (semi-automatic and automatic):-

NEGATIVE MULTIPLE BOX MOTION:-

(iii) Diggle’s pick-at-will motion:-

(1) For pick-at-will motion the lever or treadle pick is made to act independently from one side or the other, as required by the colour or weave pattern.

(2) One method of picking with wide slow running looms is to run the bottom shaft at the same speed as the crank-shaft, and slide the arm and bowl along the bottom shaft so that they may hit or miss the treadles as desired. An added advantage why this form of picking is used on wide and slow running looms, where great force is needed to drive the heavy shuttles, is the fact that a blow delivered by the same length of arm is four times as powerful if the speed is doubled. This increase in speed is obtained by driving the bottom shaft at the same speed as the crank-shaft.

(3) Another method of picking is to double the striking arms and bowls , so that they are effective at both sides of the loom with every pick, and swivel the striking plates on their treadles so that they can receive the stroke of the bowls or allow them to pass without moving the treadles.

A pick-at-will under-pick motion where the striking plates are swivelled on their treadles is out lined at fig. 161.

The picking treadle A fulcrumed at B, carries a swivelling striking plate C, fulcrumed at D. A long rod E extends across the loom to link up with the striking plate of the other treadle. This rod is so set that as one swings out from under the picking bowl, the other plate swings into the position parallel with the picking treadle and takes the blow for that pick.

Fig. 161 Diggle's pick-at-will drop box motion.

The selection is made from the pattern barrel F , which is moved one link every pick by the pegged wheel G, mounted on the bottom shaft of the loom. The selection lever H, fulcrumed at J, rises or falls according to the pattern of the links , thus moving the bell crank lever K through the link L. The lower leg of the bell crank lever K is attached to the striker plate connecting rod E, and moves the rod laterally, thus controlling the picking from either treadle according to the weft pattern chain.

As in the figure, the star wheel S is compounded with the pattern barrel F that rotates the pattern chain one link every pick. The chain is composed of deep and shallow links to suit the required order of picking. The lever H carries a bowl T, which is pulled upon the pattern chain F by the spiral spring V, but rises or falls as the link beneath is deep or shallow.

When a Jacquard is used on the loom is sometimes necessary to work the pattern from the Jacquard cards. This can be done in a very simple manner by covering the hole in the barrel carrying the cards with a metal plate, which is held over the hole by a spring.

The picking mechanism is pick-at-will loom may also be over-pick. In that the picking tappets are sometimes moved on the shaft by a clutch arrangement.

Pick and Pick Loom:-

(i) It is desirable in many fabrics to use single pick of colour or count or quality of weft. In such cases there must be movable boxes are both sides of the loom.

(ii) In such looms it is usual to have picking mechanism which will allow of several picks being made in succession from either side of the loom, in order to allow of all the boxes being emptied at one side if required.

(iii) Several types of pick and pick looms are now in use in the industry, some of them have elaborate mechanism. But the treadle under-pick for pick-at-will motion is most simple and easy to operate. The drop box or the pick and pick loom, when mounted with a Jacquard, may have the weft pattern barrel worked from the Jacquard hooks and cards . The over pick loom sometimes have pick-at-will motion.

Ref:-Weaving Mechanism Book Vol.I by Prof. N. N. Banerjee.