OPEN-SHED JACQUARDS
To obviate the vibration of the harness as much as possible, as well as to economise the wear and tear of it and to minimise the friction on the warp threads, especially in weaving patterns requiring heavy lifts, such as warp-faced patterns, Messrs. Priestley & Co., of Bradford, patented an open-shed jacquard, the principle of which is shown in [Fig. 104]. It did not, however, prove successful, as the tacklers found some difficulty in working it.
The machine is an ordinary double-lift jacquard with one cylinder, and works in the ordinary way. The hooks are made as in [Fig. 104], where it may be observed there is a turn or catch on the lower portion of the hook, at A. Above these catches is a set of bars, b, like a stationary griffe, and when the hooks are raised by the upper griffe, in the ordinary way, they spring over these lower bars and rest on them when the griffe begins to fall. All the hooks raised would thus remain up, were it not that the cylinder, pressing in for the second griffe (the machine being double-acting), which begins to rise as the upper one begins to fall, presses back those hooks that are not to be raised for the following shot, and as they are held by the griffe above, they spring back at the bottom, and, clearing the bars b, come down with the falling griffe. In this way the hooks, when once raised, remain up till pressed off by the card, so that in the case of working a warp stripe with an 8-leaf satin binding the hooks would only fall for every seventh pick.
Fig. 104
Fig. 105
Another machine has since been tried, but did not work satisfactorily. In this machine the lifting hooks are formed with loops or hooks, in addition to the top hooks. The hooks are lifted in the ordinary way by the griffes; and upper knives, made to reciprocate horizontally, catch the raised hooks and support them. By suitably timing the motions of the card cylinder the hooks may be kept up as long as required by being transferred from one set of knives to the other. The shape of the hooks and needles is shown in [Fig. 105]. The needles may be as at b or b1. This machine acts as an ordinary double-lift jacquard, but has only one set of needles, which pass through needle boards at each side of the machine, and are acted upon by two card cylinders. No springs are required, the hooks acting as springs to keep the needles in position. The cylinders are driven by a tappet, and can be held against the needles as long as required; one cylinder must press on them when the griffes are passing, so as to prevent those hooks which are descending from being taken up by the ascending griffe. There are two griffes; three of the knives of the one are shown at 1, 3, 5, and three of the other at 2, 4, 6. When these knives lift the hooks by the lower loops or hooks on them, they deposit them on to a set of knives, a, a, a, a, in an upper grid or grating, which has a lateral or horizontal motion.
The lower knives raise the tops of the hooks slightly above these upper knives, so as to clear them, and the upper grid is then moved sideways, taking the knives from under one set of heads of the hooks and placing them under another set. Each time the griffe rises all the hooks not acted upon by the cards will be deposited on the upper grating, and will be transferred from one knife to another at each lift, till the card acting upon the needles keeps them clear of the upper grating and allows them to fall with the descending griffe. In this machine the tugs or tail cords, as used with double-lift machines, are not required, the double hooks serving for two single ones. Other efforts have been made in this direction, but the plan of using small pulleys on the tail cords, between the pairs of hooks, to which the neck twines are hung, is the only one worth mention. The same principle will be found for working the shafts in [Fig. 115], and is more suitable for a few shafts than for 400 to 600 hooks, or pairs of hooks.