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.
Control of Automatic Changes
Most of the builders have devised means to do this and one of the best methods is the cylinder or drum idea devised by Dubied & Co., which is shown in Fig. 50. To more easily master the explanation of how this cylinder operates, it should be understood that its only function is to count the rounds and start the main chain at the proper point, the chain stopping itself after having caused the automatic changes necessary at that point.
Fig. 50.
Counting Drum for Short Chain Arrangement, Dubied Machines.