Jacquards may be divided into four classes—viz. single-acting, double-acting lift, double acting with double cylinders, and twilling jacquards; and besides these there are several other varieties made for special purposes. The single-acting is the real jacquard, and much the simplest machine. It has the disadvantage which all single-acting shedding motions have—viz. that one shed must be closed before the following one begins to open. This is on account of the same lifter having to open each shed; it must bring down the set of hooks that are raised, and then raise the next set.
This constitutes the true jacquard lift; and while it makes a clear shed, and is desirable for some purposes, it is generally considered the most imperfect form of shedding—that is, so far as the making of a good cloth is concerned. It is not suitable for making a heavy, well-covered cloth, nor for working at a high speed, 120 to 140 picks per minute being a very good speed to drive it.
A single-acting jacquard is a very simple machine, and when properly made should give very little trouble in working, particularly if the motions are properly set in relation to each other, and if such methods of working are adopted as will cause the least wear and tear on it.
In whatever way jacquards are made, the principle of working is much the same. There are a number of upright hooks set in a frame; attached to each hook is a horizontal wire or needle, one end of which is pressed upon by a spring, which keeps both it and the hook steady and in position, while the other end, or point, passes through a perforated plate, beyond which it projects about half an inch (see Fig. 16a). To lift the hooks there is a set of bars or knives arranged in a frame, just below the heads of the hooks; this frame is called the ‘griffe’ or ‘brander,’ and if raised would draw all the hooks up with it. What hooks will be lifted for each shed is regulated by perforated cards being pressed against the points of the needles. A perforation in the card allows the point of a needle to pass through and the hook to be raised; but where there is no perforation the card comes against the point of the needle, pressing it back, and holding the head of the hook clear of the blade of the griffe, so that the griffe will pass without raising the hook. It will thus be seen that any variety of shedding can be made by punching the cards to suit it. [Fig. 17] shows one of the best makes of single-acting jacquards. One of the best methods of driving is shown in this and the following figure. The griffe is raised by means of the lever G, which is sometimes supported on a beam fastened to the roof or pillars of the shed, or it may be supported by an upright fastened on the frame of the loom. A portion of this upright is shown in Fig. 17, and as well as being fastened to the loom frame, it should be stayed to the top of the machine. One end of the lever is fastened by a link connection to the centre of the bar across the griffe frame, care being taken that the connection is so made as to draw up the griffe vertically, and not have any strain on the slide rods or spindles that are used for keeping the griffe horizontal when rising.
Fig. 17
The other end of the lever is connected to a crank on the crank-shaft of the loom by a rod, E ([Fig. 17]); also shown at A ([Fig. 18]), where the crank is also given.
