(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.
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.
(262) It will be noticed that the outer eccentric L is not only out of centre with the pin S, but also with the inner eccentric K. Thus the rotation of the latter perpetually establishes a new condition of eccentricity. At one point the throw of the combined eccentrics is smaller than at another, and there are fixed limits within which many positions are assumed. If the throw of K is 3⁄8 inch, and of L 5⁄8 inch, it is obvious that if they are both at the front centre their combined throw will be 1 inch. But if K is at its back centre and L at its front one the combined throw is only 1\4 inch. Now owing to the fact that the wheels G and H are made with one tooth more or less, it happens that 25 complete revolutions of the eccentrics are needed before they are brought with their centres coinciding after that position had been abandoned. The result is, that during every one of the 25 traverses a different throw occurs, and the length of the traverse is varied, as shown diagramatically in Fig. [147]. By altering the size of the wheels G H any number of variations desired can be obtained.
DIAGRAM SHOWING VARIATIONS OF TRAVERSE
Fig. 147.
(263) Messrs. Howard and Bullough fit to their intermediate frame an electric stop motion. It should be explained that it is customary to pass two slubbings through the rollers at once, twisting them together to form one thread. If from any cause one of these ends breaks, the other may go on twisting, and a thin defective place would result. To obviate this, the arrangement named is applied. The slubbing bobbins are placed in a creel, and are passed between the surface of a metallic spring, and a roller placed at the back part of the machine. The drawing rollers are fixed in their usual position, and the spring is held by a bracket attached to one pole of an electro magnet and battery, the back roller being connected to the other pole. When the thread of slubbing breaks, contact between the spring and the roller occurs, and the circuit is closed. Thereupon a current is passed through the magnet, and one end of a lever is attracted so as to bring its other end in the path of a constantly rotating ratchet wheel. This arrests the motion of the latter, and so releases a catch on the stop rod, allowing it to be drawn along by the action of a helical spring. In this way the machine is rapidly stopped.