Fig. 40
The only drawback to this machine is, except what may be said against the method of shedding, the liability of one cylinder to be turned out of time, or get a shot or two before the other, so as to put the cards off their proper rotation; but this is only a difficulty in the hands of inexperienced weavers; nevertheless it exists. The effect will be to spoil the pattern on the cloth, giving the twill a mixed or broken-up appearance. There are motions in use for stopping the loom, unless the cards come in rotation, but many prefer to work without them. [Fig. 40] is a view of a two-cylinder machine made by Messrs. Devoge & Co., with swing-motion cylinders, which are, perhaps, the best motions for these machines, as they do not require to travel quickly. A very good speed for the machines to work at is 160 to 180 or 200 picks per minute, and the cylinders would only travel at half this speed. The cylinders should be driven by an eccentric, same as given for the single-acting machines, but instead of being on the crank shaft, it should be on the tappet shaft, which runs at half the speed; and as the two cylinder frames are connected together, when the one is going out the other is coming in, so that one eccentric making a revolution for two beats of the slay will drive both cylinders. Sometimes the eccentric is on the tappet shaft, inside the framing of the loom, and is connected with the top lever, as shown in [Fig. 34] (B). C is the eccentric, D the fulcrum of a short lever attached to it, and E the upright rod attached to an arm or lever on a horizontal shaft supported by the machine, or on the top of the loom. A lever from this shaft on each side of the machine drives the cylinders. The eccentric may be on the end of the tappet shaft, same as it is shown on the crank shaft in [Fig. 18]; but it might not always be convenient to have it here, and perhaps the most desirable way to have it at any time is to have a pinion on the crank shaft with, say, twenty teeth in it, and a stud wheel alongside with forty teeth gearing into it. On this stud the eccentric can be fixed, and will give a very steady and convenient method of driving. The griffes are raised in the same way as for the double-lift jacquard with one cylinder. (See [Fig. 34] (A)).
Fig. 41
Fig. 42