Speed of Flat Machines
As a general rule, where the machine is in good condition and the yarn of fairly good quality, a flat machine with a crank drive should be operated at from 100 to 125 lineal feet per minute, and a chain drive may be operated at from 125 to 150 lineal feet per minute. The reason for this difference between the chain drive and the crank drive is that with the crank drive the movement of the carriage across the machine is not uniform throughout, its movement being faster in the center than at either end, therefore we must regulate our speed so it will not be too high at this point. On the other hand, the chain drive carries uniformly throughout the movement of the carriage except for two or three inches at the ends.
To explain what is meant by lineal feet per minute, let us assume that we have a 20-inch machine, that is, there are 20 inches of needles. In this case the carriage would have to travel about 30 inches on account of the locks having to clear the needles at both ends, therefore a movement of the carriage across and back, or one complete round, would cover twice 30 inches or 60 inches, or 5 feet. Now if we intend to run this machine at a speed of 120 lineal feet per minute, we would divide 120 feet by 5 feet, which would give us 24 rounds per minute, the speed the machine should run.
I do not wish to be understood as giving this as a hard and fast rule for the speed of machines, for there are many factors which enter into the operation of knitting machinery which might make it desirable to vary this speed. Some of these factors are the condition of the machine, the experience of the operator, the character of the yarn, the class of fabric, and sometimes the skill of the mechanic in charge of the machines.
Going back to the two-faced fabric, this must be made on one of the two cardigans. The “cotton backs” are usually made on the half cardigan, while the fabrics with two different colored faces are made on the full cardigan as a rule.
Fig. 40.
Dubied System of Double Locks.
Fig. 40 shows a type of double lock used in a Dubied machine made in Switzerland. The reader will understand from what has gone before that this illustration shows the locks turned upside down, that is, if they were in operation on a machine they would be turned over with the cams close to the needle plates. It will be noted that the fundamentals are the same as in the Lamb system previously described, but the method used to change from the plain rib to the full or half cardigan, or vice versa, is different.
In making a plain rib fabric the needle butts would follow the camway as in the Lamb system, that is, if the carriage were being moved from left to right the needle butts would follow the course up with cams 1a, 1b and 1c below, and 1, 1s, 8s and 8 above. This explanation would of course apply to all four sets of cams. The cams 1b, 2b, 3b and 4b have studs which project through the cam plate and there are means provided to draw any one or all of these cams back through the cam plate by these studs far enough so that the faces of the cams are flush with the cam plate, and entirely out of operation.
The cams 1c, 2c, 3c and 4c are made to swing on the pivots, aa, and are held down on cams, 1a to 4a, in the position shown, by springs. It should be particularly noticed that the cams just mentioned, 1b to 4b, and 1c to 4c, are exactly alike in the four sets of locks, but their positions are reversed in the sets opposite. They are placed in this way in order to facilitate the making of the cardigan stitches.