Читать книгу The Jacquard Machine Analyzed and Explained - E. A. Posselt - Страница 5

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If a fabric contains a great number of ends of warp bound differently in the filling, the method of guiding the warp by harness frames is too cumbrous and inefficient; in such cases it becomes necessary to use the Jacquard machine for raising the warp-threads separately by means of hook and leash.

The hooks as used for raising leash, mail, lingo, and warp-thread, consist of wires 16 to 17 inches long, with a crook on each end. On the lower crook is fastened the leash by means of the neck-cord.

The cords of each leash are threaded through the holes of the comber-board; the latter are separated from each other according to the texture of the warp in reed.

On the harness-cords are adjusted the heddles, (either twine or wire), on which are fastened the lingoes as weights. In the mails of the heddles are drawn the warp-threads.

Now, from the foregoing explanations, it will be apparent that by raising the hook in the Jacquard machine we raise the leash, and the latter raises every warp-thread throughout the fabric for interlacing with the filling.

The next point required to be known is, which hooks are to be raised, and which are to be lowered? To regulate this, a design (pattern) is prepared in which the floating of the warp over the filling is indicated.

For the warp-threads required to be raised holes are punched in the cards. In these holes the points of the needles extending through the needle-board are pushed by a spring fastened on the rear of each needle. The needles are adjusted in rows of different heights. The arrangements most used are 4, 8, and 12 rows high. Each row as to height in the machine contains a bar (knife) in the griffe. When the griffe is down, or the machine at rest, the upper crooks of the hooks are raised about half an inch above the griffe-bars.

The needles which control the position of the hooks, permitting them to rise or compelling them to remain stationary, are pressed by the springs fastened in the rear towards the cards, which are moved on a quadrilateral and perforated cylinder. This cylinder performs a movement similar to a pendulum towards the points of the needles. Any needle for which a hole was punched in the card will penetrate the cylinder; consequently, the corresponding hook will remain in its natural position, on the crook over the corresponding griffe-bar, and upon lifting the griffe the hook will be raised.

Again, needles for which no holes are punched in the cards will be thrust back by moving the cylinder containing the cards towards the needle-board; this motion forces back the corresponding hooks, pushing them away from the griffe-bars above, and upon raising the griffe they will remain stationary; hence, if a blank card were pressed against all the needles of any machine, the entire number of needles the machine contains would be pushed back, and none of the hooks would come in contact with the griffe-bars, and, consequently, raising the griffe would produce an empty lift. On the other hand, using a card having every hole of the cylinder punched, (or the empty cylinder used), would lift every needle in the machine. Pressing the needles towards the rear compresses the springs; these will again expand as soon as the cylinder leaves the needle-board. The hooks, which were left standing in their position over the griffe-bars are caught by the latter at the raising of the griffe. The elevation of these hooks raises the leashes fastened to them, thus causing the lifted warp-threads to form a shed with those not lifted.

Jacquard machines are made of different sizes and descriptions, some having only a few hooks and others a large number. The sizes most often used are 100, 200, 400, 600, 900, 1200 hooks. The number or size is always indicated by the number of needles and hooks which it contains, without counting the reserve rows, of which there are generally two. These reserve rows are used for various purposes, such as raising the selvedge; raising the front harness; raising the shuttle-boxes on hand-looms; guiding the take-up motion on hand-looms; indicating a certain card through ringing a bell on hand-looms, etc.

Sometimes a few of the needles and hooks from the reserve are added to the main part of the needles and hooks. For example: Take a design in which the ground weave repeats on 12 ends; working a 400 machine, we find:

400 ÷ 12 = 33 repeats of the weave, less 4 hooks;

Consequently, if this ground-weave is repeated all over the width of the fabric, we must use either:

396 hooks, leaving 4 hooks more to be added to the two rows already used; or 408 hooks, requiring us to call upon the reserve rows for eight extra hooks.

Hooks which have no leashes adjusted must be taken out of the machine.

Sometimes two, three, or more, machines are employed on one loom, and may be worked in different manners. In this country Jacquard machines, for power as well as hand-looms, are made of iron, whereas in Europe the machines for hand-looms (comprising the greater part of the Jacquard machines in use) are made of wood; using the iron ones only for power-looms; and even yet, in most cases, the wooden machines are used for the latter.