Jacquard Weaving and Designing

by T. F. Bell

Sometimes glass rollers are used in the silk trade for this purpose, with mountings of the London tie, and while they are very smooth and polish the twines, they get too hot if used in warm power-loom factories working at a high speed. Hecks are not required for very narrow harnesses, as the cords do not diverge much from the vertical, and the friction on the heck being saved, the cords wear much longer.

In a wide harness it is impossible to draw an even shed without a heck, although in some districts they are hardly known, and the more any portion of the harness diverges from the vertical, the more irregular will the shed be.

Fig. 48

Suppose we take an extreme case of a loom having three or four jacquards on it, the harness to be 96 in. wide, and the pattern to be for a table-cover; then, if we deduct 2 ft. from the width of the harness, it is possible some of the border twines may have to slant across 6 ft., or 72 in. Now make a triangle as No. 1, [Fig. 48]. Let the base, A B, be 72 in., and take it as the level of the cumber board. Take the vertical side, A C, as the height of the harness to the heck, viz., 84 in. Now calculate the length of the hypotenuse B C by squaring 84 and 72 and finding the square root of the sum, and it will be found to be 110·63 in. Again: Make another triangle, as No. 2, with base 72 in.; vertical side 3-1/2 in. longer than that of the former triangles, viz., 87·5 in. (this 3-1/2 in. is to represent the draw or lift of the harness). Calculate the length of the hypotenuse as before, and it will be found to be 113·31 in. From this deduct 110·63 in., the length of B C in No. 1, and the remainder, 2·68 in., equals the height that the cord B C has been raised, while the cord A C, which is vertical, has been raised 3-1/2 in.; and if we take into consideration that the side draw of the sloping cords, as B C, will pull the tail cord a little to one side and rise the vertical cords a little higher, while the sloping ones remain proportionately lower, 1 in. may be safely taken as the difference of the height that the two cords, B C and A C, would be raised by the jacquard, and all the other cords in the harness would vary, being less than this in proportion to their divergence from the straight or vertical line. It can thus be seen how the shed would require to be opened to let the shuttle through, and the irregular strain that would be on the yarn; and for any cloth that requires a fine surface, any irregularity of strain on the warp has a deleterious effect, very well known by experienced overlookers.

Some consider that the London style of harness is more suitable for working without a heck than the Norwich style, and adopt it to avoid using one, as it is severe on the harness twines. Some raise the machines very high to avoid using them, but for particular work with border ties they must be used to give a proper working harness. With the London mounting rollers should be, and are, used when there is no heck. These rollers are set as a coarse heck in a frame under the machine, and lie lengthways under it, just as they would do when used above a heck. The heck should be about 3 in. below the knots which fasten the tail cords to the neck twines. Some have the tugs, or tail cords, coming down through the heck; in this case the heck only takes the strain off the hooks of the machine, and has no effect on the shed, though sometimes this is mitigated by having more than one tug or tail cord, and the neck twines that slant in different directions are tied to different tail cords. The only point in favour of this is that it saves some trouble in tying broken harness twines when they begin to wear away by their friction on the heck.

PREPARING THE NECK OF THE HARNESS

The twine for the neck, as well as that for the other portions of the harness, is usually wound on spools, and when the neck is to be prepared it is warped from these spools to the length required, either on a hand warping mill or round two pins fastened in a wall or on a bench, as far apart as the length of the harness; three or four spools are put on pins, and the ends from them are taken and wound round the pins fixed for warping them on. When warped the twines may be cut at one end, and can either be tied in a bunch or stretched on a board and tied down on it, so that they may be kept straight and admit of any number of them being pulled out as they are wanted.

In some methods of mounting the neck twines are first tied to the tail cords; perhaps this is the plan most commonly adopted with double-acting machines. Sometimes they are tied to the sleepers first, and fastening them to the tail cords is the last process. This is called ‘beeting’ the harness. When single-acting machines are made with the hooks resting on a perforated board, they have tugs on the hooks; but when the wire hooks pass down through a perforated grating, tugs are unnecessary, and the neck twines are fastened to the hooks. When fastened to the hooks, or even when fastened to the tail cords, and a heck is not to be used, the neck twines should be formed into heads, either before they are tied up or afterwards, as may be desired. The reason of this is, that when a number of neck twines are tied to a hook or tail cord, and the hook is raised by the machine when working, the twines will be slanting in different directions, and when coming down again would be liable to catch on the knots of those that were not raised; and the head is for the purpose of keeping them together, so that they cannot separate for a short way down. One method of doing this is, after the bunch of neck twines is tied to a tail cord or hook, to take one of the twines and knot it round the others about 3-1/2 in. below the tail cord, and the same may be done with a second twine, if there are many in the parcel.