Speed and Production
This point leads up to another advantage of the double-lock machine, that is, increased production on account of putting on two courses with each movement of the carriage across, as against one course with the single-lock machine. The production would not be twice as much, as might be supposed at first thought, for comparing two machines of the same size, the single lock could be operated at a greater speed than the double lock, but not approaching twice the speed. The reason for this is that the locks of the double-lock machine must, of course, be practically twice the length of the locks of the single-lock machine, and inasmuch as the locks must move far enough at each end to be clear of or past the needles, it is quite obvious that the double-lock carriage must have a longer travel. Therefore, it takes longer to complete one round of the carriage than the single-lock machine, to maintain the same needle speed.
This brings us to another point that may as well be disposed of here, and that is the speed of latch needle machines. Generally speaking, the maximum speed of a latch needle machine, either flat or circular, is governed by the needle speed; that is, the speed at which the cams raise and lower the needles, and the thread velocity, which is of course dependent on the needle speed.