(259) Now, if it be assumed that a coarser roving requires producing, and that the ratchet wheel =I= is changed for one containing only 20 teeth, it will be seen that while the same necessity exists for the full traverse of the strap guide and diminishing rod, a smaller number of layers of roving will be wound in the same time. In this case 40 layers only will be laid, although the strap makes the same movement. That is, the same reduction of the speed of the bobbin is made while 40 layers are wound that was previously made while 60 were wound. Now, as the diminution of the speed of the bobbin must be exactly proportionate to the increase of its diameter, it follows that the roving in the former case must be correspondingly thicker. It should also be observed that the inward traverse of the diminishing rod =S= is quickened as well as that of the racks =P=, because the time occupied by the ratchet wheel in making a complete revolution is, of course, less than when one with 30 teeth is employed. Thus the speed of the bobbin and the length of its traverse are both decreased at a more rapid rate when a ratchet wheel is employed, which is exactly what is wanted when coarser roving is being produced.
(260) A locking motion is fitted to the machine by which, when the rack =P= is released in the manner described, the stop rod is locked in such a way that until the rack has been wound back by hand into proper position the frame cannot be started. There are two advantages in this motion, viz., that the size of the bobbins is accurately regulated, and damage to the frame is prevented.
[Illustration: FIGS. 143, 144, 145, AND 146.]
(261) In order to avoid the uneven wear of the top rollers, caused by the slubbing or roving passing through them at one point constantly, it has become the practice to give a slight lateral traverse to the guide bar. One of the latest developments of this special treatment is illustrated in Figs. 143 to 147, this being the invention of Mr. George Paley, a spinner, of Preston. It consists of a worm =I= fixed upon the end of the roller spindle, which gears into two wheels =G H=, carried on a pin fixed in a bracket. The number of teeth in the wheels are different, =H= having one more tooth than =G=. In this way =G= is revolved once for every 24 revolutions of the worm, while =H= requires 25 revolutions of the latter before making a complete rotation. The wheel =H= has a boss =J=, the upper part of which =K= is formed eccentrically, and on this portion the eccentric =L= is placed. To the clip of =L= the traverse rod =P= is coupled. =L= is driven from the wheel =G= by means of a pin fastened in =L=, and engaging with a slot in =G=. Thus the rotation of the eccentric =L= is followed by the traverse of the guide bar.