Types of Multiple Box Motion in Power Looms (semi automatic and automatic):-

POSITIVE MULTIPLE BOX MOTION:-

(i) Wrightshaw’s Positive Drop box motion:-

Wrightshaw’s positive drop box motion is different from the other box motion, as there are no chain , star wheels, clutches or eccentric. The main features of this motion are illustrated in figs 162 A, 162 B and 162 C.

Fig. 162A, 162B and 162C, Wrightshaw's positive drop box motion.

(1) In fig. 162 A , a forked rack G is suspended from the free of a treadle lever E, fulcrumed at F. The treadle lever E carries a bowl D, near the center, At one end of the bottom shaft A of the loom are two cam B and C. Either of the two cams may be brought underneath the treadle bowl at will, so as to raise the treadle and forked rack once during the each revolution of the bottom shaft, corresponding to two picks.

(2) Passing midway between the two prongs H, and H' of the fork is a short shaft, upon which are secured two toothed wheels I and J. Wheels I is so placed that the teeth on either side of the rack may be put into engagement with its teeth just before the fork rises , so as to turn the wheel in either direction. The rack may also occupy a neutral position when rising , in which event the wheel I remains stationary. In any case, the rack are always clear of the wheel when descending.

Immediately in front of wheel I is another similar wheel J , whose teeth are permanent engagement with those of a rack K. An extension L of the rack K supports the shuttle boxes M . Thus, if rack H' is put into gear with wheel I, boxes will be depressed as the rack rises ; but if rack H operated, boxed will be raised. One box or two boxes , only may be either raised or dropped at one change , according to which rack and which cam is put into operation. The smaller cam B moves one box , and the larger can C moves two boxes , either up or down.

(3) It is shown that the Wrightshaw’s box motion is positive in action. Additional mechanism are also provided with this motion to stop the pattern chain when a weft breaks. Again if the picker is not clear of the boxes or if a shuttle is imperfectly boxed at the time of a change of boxes , a rod disconnects itself from the driving pinion to prevent smashes of warp threads.

(4). The selection of racks H or H' and cam B or C are made by pattern cards, shown detached, which pass over an octagonal cylinder N. This card cylinder is mounted on an elbow lever, and derives its oscillating movement from a cam on the bottom shaft. The cards are presented separately, once in two picks, to three selecting needles 1, 2, 3 (fig.162 B). The two outer needles 1, 3 are attached one end at each end of a double arm secured at the top of a long vertical shaft O . The bottom of shaft O communicates with the forked rack G. Thus, a depression of boxes is effected by a blank part of a card pressing against needle 1, and an elevation of boxes by pressing back needle 3.

Shaft O is loosely contained within a long tube or sleeve P. Sleeve P carries short arm R, at the top of forked clutch Q, which acts upon the boxes of cam B and C. If it is desired to move two boxes needle 2 is pressed back, thereby causing an inclined piece S, secured to it to act upon arm R so as to slightly turn the sleeve P, and to move the large cam C under the treadle bowl at a time when the short side of the cam is uppermost, ad shown in the figure 162 A. At one point, the larger and outer cam is slightly lower than the smaller cam and can be really moved under the bowl.

PATTERN CARDS:-

In figure 162 C , the various changes which can be made be seen by referring to the pattern cards.

(i) When there is a blank opposite the first needle only , the rack H' is pushed to the left and the boxes are moved 'down one’.

(ii) When there is a blank opposite the third needle only, rack H is moved to the right and the boxes are forced 'up one’.

(iii) When there are blanks opposite the first and second needles , they are pushed backward , thus moving rack H' to the left, and also forcing the larger cam under the treadle bowl , in which case the boxes will be moved 'down two’.

(iv) When there are blanks opposite the second and third needles, they are pushed backward, and the boxes are 'raised two’.

(v) When there are three holes in the card , the racks, when lifted , miss the wheel , and there is 'no change ' in the boxes , that is the racks H and H' occupy a neutral position, when rising . It is seen that the boxes may be made either up or down , a space of only one or two boxes at a time , only one box of the series can be skipped at any one movement. The greatest change which can be made is from the first to the third, from the fourth to the second, and so on , even when give or six boxes were used.

In this mechanism the card saving appliance is useless where two picks of one color are required, and also where the picks of any color are not 4, 6, 8, 12, 24 or multiple of these number .

(ii) Whitesmith’s Drop box motion:-

The working of drop boxes by means of eccentric and eccentric ring was introduced by ‘Whitesmith’. This principle is probably the best and the change in boxes may be made positively from any box to any box . The arrangement of four boxes in loom is illustrated at fig. 163, 164, and 165.

Fig .164 white Smith drop box motion.

(1) At fig 165, four different position of the boxes are shown. The box rod connected to the eccentric ring at E. Turning the eccentric F half way round , a lift or a depression of one box is obtained. By turning the eccentric ring E half way round a lift or a depression of two boxes are obtained. Again by turning both ring and eccentric, a lift or a depression of three boxes are obtained. Thus by causing the eccentric or the eccentric ring or both to make half a revolution intermittently every two picks we can make changes from one box to any other .

Fig. 163 of white Smith drop box motion.

(2) (i) At fig. 165 A , the first box is in line with the sley board , the eccentric F being at the top and the eccentric ringE at the bottom. (ii) By turning the eccentric half way round, as at 165 B , the second box is placed in line with the sley race, both eccentric and ring being at the bottom.

(iii) Starting from the first position, by turning the eccentric ring half way round, as at 165 C and ring being top .

(iv) Starting again from the first position, by turning both eccentric F and eccentric ring E half way round, as at 165 D , the fourth box is placed in line with the slay race , the eccentric being at the bottom and the ring at the top .

(v) Now turning both eccentric and eccentric ring next half way round at the same time in the same direction, a depression of three boxes may be obtained.

(vi) Again, if we are at box no. 3 and like to reach box no. 2 by turning the eccentric half way round and the eccentric ring half a revolution we get box no. 2.

Image 165 of eccentric and eccentric ring for white Smith drop motion.

(3) Another view of the eccentric and the eccentric ring may be seen at fig 164. The wheel H is keyed to the shaft T on which the eccentric F is fixed. Another wheel I, of the same size, riding loosely upon the shaft T. A fork K is attached to the wheel I and fits on to a pin st the back of the ring E. Thus by turning the wheel I, the ring can be moved independently of the eccentric. The wheel H , therefore moves the eccentric and the wheel I the eccentric ring.

(4) Now , the wheel H is driven by a wheel L , twice it’s size shown in fig. 163. On the face of the wheel L there are four pins. If the lever OP is lifted at O by a blank in the pattern card again the needle N the pulling hook M is dropped round one of the pins. The pulling hook M is moved forward by s crank Q on the bottom shaft, thereby , causing the wheel L to make a quarter revolution, and the wheel H to make half revolution. Therefore the eccentric F is moved half a revolution to lift or depress one box only . The pattern card cylinder S is presented again the needles N every two picks.

(5) In fig. 163, on the same shaft as the wheel L, there is another wheel of the same size and with four pins. This wheel gears with wheel I. There is second pulling hook M, a second lever OP, a second needle lever X and a second needle N. When this second needle is pressed back by the pattern card cylinder, the second pulling hook drops on to the second wheel, causing wheel I and the eccentric ring to rotate half a revolution. Thus any or both wheels I or H may be turned half way to lift or to depress boxes, but always in the same direction. The wheel L is prevented from turning too far by a strong frictional arrangement. Again by suitably manipulating two eccentrics any of the four shuttles could be moved to face a picker instantly and steadily. In fig. 163, the needles are moved by cards, but they may be worked from a dobby or a Jacquard, in which event the barrel and it’s driving wheel is removed.

(6) To work six boxes on Whitesmith’s principle, another eccentric inside the first eccentric F should be used. This second eccentric will also require a third pulling hook M

ADVANTAGES:-

The Whitesmith’s box motion is positive in action. The advantage of using eccentric F is that the boxes begins to move slowly, the speed increase at center and again slow down at the speed increases at the center and again slows downs at end of the journey. This causes less vibration of the boxes at rest and higher speed of the loom.

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