Cotton Weaving and Designing / 6th Edition

by John T. Taylor

FIG. 132.

FIG. 133.

In the pressure harness a number of warp threads are placed in each mail, the number of threads varying from five to sixteen; but in the twilling Jacquard only one end is drawn in each mail, and a separate hook is required for every end. The advantage comes in making each needle serve for several hooks and in making one card serve for several picks. One of the first inventors of this kind of Jacquard was Mr. Barcroft, of Newry, Ireland, and it has been improved since by him and others. The principle is illustrated at Figs. [132] and [133]. There may be any number of hooks to each needle. In the illustration there are three. The machine is necessarily a single-lift, the griffe goes up and down every pick. Only two needles are shown, operating six hooks. When the top needle is pressed back it will press back the hooks 1, 2, and 3, and when the bottom needle is pressed back it will press back the hooks 4, 5, and 6. These hooks are bent at the bottom as in the diagram, and a bar or rod A is passed through each row of hooks the full length of the machine. These bars A are lifted by the twilling hooks, shown in the diagram in dotted line. These hooks are placed at the sides of the machine: two hooks for each long row of the ordinary hooks, or one for each end of every bar, A. The blades of the griffe are movable about the centres EE, and at each end of the blades and immediately behind each twilling hook (dotted) there is a projecting piece, P, also shown in a dotted line in the diagram.

Now, when the griffe is at the bottom, the blades are operated by a pegged barrel, and by turning the blades one at a time out of the way of the hooks as the blade M is turned, it is obvious that a whole row of hooks can be left down which would otherwise be lifted.

Turning the blade has also another effect. On the front of the blade at each end, as previously pointed out, is a projecting piece, P, and when the blade is turned, this projection pushes the twilling hook in front of it (dotted) on to the next blade of the griffe, and the twilling hook is lifted. The bottom of the twilling hook is fastened to the end of a bar, A, and the bar is lifted, thus lifting a whole row of hooks which would otherwise be left down. In this manner it is obvious that by operating the blades of the griffe in regular order, the figure can be woven warp twill and the ground weft twill, or vice versâ. At [Fig. 133] the position of the six hooks is shown after the griffe is lifted. It will be seen that the blank opposite the top needle pressed the first, second, and third hooks back, and they would all three have been left down but for the bar A being lifted. The hole opposite the bottom needle leaves the fourth, fifth, and sixth hooks over the griffe, and they would all have been lifted but for the blade M being turned, which also caused the bar A to be lifted. It will be obvious that the twill must repeat on the number of bars A, or on the number of rows of hooks, in the machine, exactly as in a split harness the ground weave must repeat on the number of shafts or rods used under the comber board. In these machines, as in the pressure harness, the same card is pressed against the needles two, three, or more times in succession, so as to give a great extent of pattern with a small number of cards. The number of times a card is pressed against the needles depends on the number of hooks there are to each needle, and on the relative amount of warp and weft in the fabric. If there are three hooks to a needle and the same number of picks as ends per inch, the card should be used three times in succession, but sometimes there are more picks per inch than ends, in which case each card should be used oftener; and sometimes, as in silk damasks, there are 400 or more warp threads per inch and 100 picks, and supposing there were eight threads in a mail, it would make a step of eight ends in the warp; therefore, to make the steps in the weft balance it would be necessary to bring the same card against the needles only twice in succession.

[Fig. 134] is another arrangement for weaving damask. It is called a damask attachment, and was patented by Tschorner and Wein. Its construction differs from ordinary twilling Jacquards, but the principle is much the same.

Each needle is twisted round several hooks, and the knives are operated separately by cams at the side of the machine. The illustration shows one of the knives left down, leaving down a row of hooks which would in the ordinary course have been lifted, and one of the bottom lifters is taking up a row of hooks which would in the ordinary course have been left down.