Racking Chains
We will leave the slides and levers for the present and give our attention to the two racking chains shown in Fig. 49 at figures 1 and 2. Inasmuch as the rack stitch is made by a part of the machine entirely separate and distinct from the locks and carriage, that is, the needle plate, obviously it is necessary to arrange means other than the levers and slides on the top of the machine to do this automatically. The mechanism used to do the actual racking is illustrated in Fig. 32. The illustration is accompanied by an explanation of the required movements. This racking cam may be seen in Fig. 49 at letter R. Having in mind the former explanation it is evident that to control the racking it is necessary to control the pawls only which actuate the ratchet. This is done by the racking chains shown in Fig. 49. They of themselves do no actual racking, but simply put the pawls into action or out of action, as the case may be, at the proper time. These chains hang on a sprocket roller and are moved two links at each round of the machine by the same means as the main chain, and are started and stopped automatically by studs on the main chain at any predetermined time. There are also two levers over the top of each, and it is by means of these levers that they control the pawls which actuate the racking cam ratchet through small rocker shafts.
Fig. 49.
Racking Chains and Cam, Dubied Automatic Single Lock Machine.
It will be noted that the chains have studs attached, similar to the main chain, which are staggered or attached alternately near both sides of the chain. As these studs pass under and raise a lever at the top of the chain they cause a pawl to act on the racking cam ratchet, thereby making one rack.
When the carriage makes the next round the chain would have moved forward so the lever just mentioned would have dropped off its stud and the stud on the other side of the chain would move up to and under the second lever, which would cause the other pawl to act in the opposite way and therefore would rack the plate back to its starting point. If two or more racks in the same direction are desired, it would only be necessary to put two or more studs in line on the same side, but remembering that where this is done it is imperative that later the same number be placed on the other side so as to return the racking plate to its original position.
Both of these chains do the same work and in the same manner, and either one may be selected to do the racking at any time or place, but both should not and cannot be operated at the same time for there is a very ingenious arrangement which will stop the one automatically, if working, immediately when the other one starts.
The reason for providing two chains instead of one is to enable the operator to make two different kinds of rack in one garment by setting the studs on one chain for let us say a one-needle rack, and on the other for a two-needle rack. This arrangement permits the use of very short chains, as the racked pattern may repeat itself on the chain any number of times, where if a single chain were used it would be necessary to have a chain long enough to have a stud for each time the plate racked, when two patterns are required, and this would necessitate the use of a very long chain at times.
Some few years ago, when automatic machines were first brought out, all automatic functions were operated from a single chain. This meant the use of very long and unwieldy chains many times, as it was necessary to have a link in the chain for each round. It was soon realized that by stopping the chain during the time the machine was making one kind of fabric without a change, which on most work is by far the greater part, and operating it only when needed, not only much time and material in making up the chain would be saved, but also much annoyance and trouble in providing means to keep the chain from getting twisted or out of place while running would be eliminated.