Fig. 168.J.N.
(331) The screw has fixed upon it, at its lower extremity, a small bevel pinion, gearing with a similar one placed loosely on the short shaft forming the centre for the arm. During the oscillation of the arm the pinion moves with it, and it is clear that if both remained in this position only this alternate action would occur, and no rotation of the screw would be made. If, however, the pinion on the short shaft be rotated it communicates its motion to the screw P, and thus traverses the nut. This is what takes place, and the precise method of effecting it will be described in detail at a little later period. The nut engages with the screw and originally had an eye or hook formed in it, to which the end of the winding chain or band C was fastened. The attachment is now made in a different manner, a frame A being fixed to the nut along with which it can slide. At the upper end of the frame a small drum is carried, round which the winding chain is wrapped, passing over a small bowl D at the lower end of the frame. The other end of the chain or band C is fastened to the drum or scroll X1 which is mounted on a shaft X carried in suitable bearings in the square. On the same shaft a spur wheel is geared which engages with a pinion loose upon the tin roller shaft, which it revolves by special mechanism afterwards described in detail. The use of a scroll is intended to accelerate the revolutions of the spindles during the latter part of the fallen traverse. This, like the winding arm, is a modified application of the fusee, and it will be easily understood that when the chain is being unwound from the larger diameter of the scroll, the number of revolutions given to the scroll will be less than when it is being taken off the smaller diameter.
(332) It has been previously shown that the diminishing diameter of the spindle causes it to be necessary that, as the cop is built higher upon it, a correspondingly higher rotary velocity shall be given to it, in addition to the increased terminal velocity produced in the manner described. The most usual method of doing this has been to provide at the end of the quadrant arm a bracket carrying a pin known as the “nosing peg.” The object of this device is to shorten the chain by deflecting it from a straight line about the time when the carriage nears the end of its inward run. This is equivalent to a sudden shortening of the chain, and gives a sudden acceleration to the winding drum. In some cases an automatic arrangement is fitted by which the peg is brought into contact with the chain at an earlier point every stretch, so that the acceleration of the spindle takes place sooner, as the nose of the cop is formed higher up the spindle. It is not difficult to obtain a clear notion of the action of the nose peg if a short length of string be held at one end and attached to a sliding piece at the other. If then the string be pressed down by a rod at the same point, but a little further every time, it will be seen that the sliding piece is moved to a greater extent with each depression.
(333) The arrangement used in the Platt mule is shown in detail in Fig. [169]. It consists of the sliding bracket A, carrying, as described, at its upper part, a small drum on which the winding chain C is fastened. On the spindle of the winding drum a ratchet wheel E is fixed, with which the detent pawls E1 engage, thus ensuring that E is held in any position assumed by it. Also fastened on the spindle of the drum is the curved sector arm F, to which a chain G is secured. By means of the guide pulleys shown the chain G is conducted over the arm or lever K, and is attached to the bracket I. The lever K is hung from its upper end, and has a projecting short arm K1 attached to it, which can move upwards in the direction of the arrow. The outer end of K1 presses against a bracket K2 attached to the quadrant, so shaped that the backward movement of the quadrant pushes the lever K back at its lower end. In the bracket I a finger I1 engaging with the copping nut is fixed. The parts having been adjusted to their proper position the slide A is at the bottom end of the quadrant M, as shown, and the curved arm F is in such a position that it has wound upon it a certain length of the chain G. The latter is a little slack at first, but as the nut moves out this is rapidly taken up until the chain G is in tension. As soon as this happens, each of the forward oscillations of the arm M leads to the chain being drawn, and causes the lower end of the lever K to be swung forward. The return movement of the quadrant leads to the bracket K2 pressing upon the arm K1, so as to push back the end of the arm or lever K. In this way the chain G is pulled and the curved arm F is drawn a little forward, thus causing the drum and ratchet wheel E to revolve. As the winding chain is wound on the barrel, every rotary movement of the latter in a forward direction takes up a little more chain and shortens its length. The amount of this shortening is not great up to the time of the completion of the cop bottom and the arrival of the slide A at the end of its traverse along the arm. The position of the parts at this period is shown in the detached view at the right hand top corner of Fig. [169]. Up to this time only about the same length of chain is taken up which is needed by the increased distance of the slide A from the centre, and the greater forward traverse of the quadrant arm, which, in a sense, releases a certain length of winding chain. When this point is reached the finger I1 begins to be pressed against by the nut S1 of the shaper screw, and the bracket I commences to be drawn inward. To facilitate the correct action of this mechanism the finger I1 is adjustable, and the exact moment of its contact with the nut S1 is thus regulated. The forward movement of the shaper nut which follows gives a similar motion to the bracket I, and the chain G is thus drawn forward. In this way the drum and ratchet wheel E are rotated, and the winding chain gradually shortened. Thus more of it is unwound from the scrolls at each traverse of the carriage, and as it is drawn from the smaller diameter of the scroll towards the end of the run in, the velocity of the spindles is considerably accelerated. The position of the various parts when the carriage is at the back stops is shown in Figs. [170] and [171].
(334) These represent respectively the places occupied by the different portions of the mechanism immediately at the completion of the cop bottom, and at the finish of building a set of cops. The positions of the various parts connected with the slide A when winding is complete are shown also in Fig. [169], at the top end of the quadrant arm. Referring to Fig. [170], it will be noticed that the winding chain C is unwound from the large part of the scroll only, while Fig. [171] shows it almost entirely unwound from the smaller portion. As was shown, this implies a high terminal velocity of the winding scroll and spindles.
(335) It has been previously mentioned that the rotation of the quadrant screw is obtained by means of the engagement of two bevel wheels, one on the foot of the screw and the other upon the spindle, forming the centre of the quadrant. It was also stated that the last-named wheel was held so as to move round the centre with the quadrant. This is effected by means of a brake spring P2 which clips the boss of the wheel and holds it. The resistance thus created causes the bevel wheel to move with the quadrant, and prevents it from rotating on its axis. The wheel is compounded with a grooved cord pulley P1, over which an endless band Q passes. The band Q fits the groove in the pulley, and is afterwards guided by the various carrier pulleys shown. Two of these, S S1, are borne by brackets fixed to the carriage, and S is formed with teeth so as to allow of the engagement of the vertical detent catch on the lever Y. If the whole of the pulleys over which the band Q passes are free to revolve, except that on the quadrant centre, the inward run of the carriage gives no motion to the cord or band. No effect is produced beyond the rotation of the carrier pulleys, and the forward stroke of the quadrant is made without any effect being produced upon the position of the nut.
(336) It was shown that the gradual accretion of yarn by the cop results in the necessity for a graduation of the velocity of the spindle in winding. This takes place during the whole period of building, and it follows that the traverse of the nut must be governed during the whole period. After a layer of yarn has been wound the nut remains in the position occupied by it during the preceding inward run, until the carriage has made another outward run, and is again commencing to run in. At the commencement of the run in of the carriage the spindles revolve at the same speed as that at which they rotated in the preceding period of winding. If the yarn is a coarse one this is sure to be too fast, because of the increase in the diameter of the cop, owing to the yarn wound during the last inward run. The initial velocity of the spindles is, therefore, such that they take up the yarn too rapidly, and put an extra amount of tension upon it. As was shown in paragraph 303, this causes a depression of the counter faller wire. This is utilised to revolve the quadrant screw and traverse the nut and slide. In other words, the winding is said to be “governed,” and the motion is known as the “governing” or “strapping” motion.
