(220) The sliver may, however, fail between the drawing rollers and the delivery can, and it is therefore necessary to provide a means whereby the machine can be arrested in this event also. In its passage to the can the sliver is collected by a trumpet-mouthed tube and carried over another spoon lever O, balanced and borne exactly as the lever G. The failure of the sliver is followed by the fall of the inner end of O, which comes in the path of the lever P, to which a lateral reciprocal motion is given from the shaft H, as shown. This results in the stoppage of the machine exactly as in the case of the back stop-motion.
(221) After passing the detector lever, the sliver goes through another tube and is compressed by the calender rolls Q, driven as shown in Fig. [124]. These give the sliver more cohesion, and slightly flatten it, after which it is treated by the coiler head R, which is of the same construction as that employed on the carding engine, and is driven by the gearing indicated in Fig. [123]. Some makers provide a full can stop motion, which operates when the can gets quite filled with cotton. There is a danger, if the attendant is careless, of it becoming jammed under the coiler plate and serious damage occurring. In order to obviate this, a thin plate is fitted below the coiler plate, thus forming a sort of false bottom. This is weighted suitably for various strengths of slivers, it being desirable to press the sliver to a certain degree in order to get as great a length in each can as possible. The amount of this pressure is, of course, variable, and care must be taken not to make it too great. When the loose plate is raised it lifts a vertical stop which comes in front of a lever coupled to the front end of a lever corresponding to P, in Fig. [124], and the motion of the latter is arrested as before, with the same result. This is the arrangement used by Messrs. Platt Brothers and Co., Limited.
(222) It sometimes happens that a sliver in coming out of the can will be formed into a knot, or loop, which, when it comes into the guide plates, F, cannot pass through the holes in the latter. The result is, that the sliver is broken and requires re-piecing. Now, it is desirable to prevent the breakage of the sliver when possible, and the case named is met by Mr. Brooks by the use of the motion shown in detail separately. The bar fixed in L oscillates under a catch lever S, which is balanced by the plate F, so as to be raised above the path of L. When, however, a knot occurs, the plate F is drawn inward, and the catch lever S brought in the way of the bar in L, the oscillatory movement of the latter being arrested. The machine is thus stopped, as in the cases previously named. In order to make this movement more sensitive, the plate F is balanced by the weighted lever fixed on the same rod on which F oscillates, the weight being adjustable to suit different strengths of sliver.
(223) Messrs. Howard and Bullough have for some years made an application of electricity to this machine for the purposes of stop motions. Their arrangement is shown in Fig. [127], in transverse section. The machine is practically divided into two pieces, which are joined together, but have pieces of some insulating material introduced into the joint. One half of the machine thus constitutes one pole, and is connected to the battery, or dynamo, by the rod R; and the other half being the other pole, also coupled to the battery by the rod O. The sliver, as it passes to the back roller, goes between two rollers S T, which are coupled to the positive and negative poles respectively. The lower roller is fluted and is the full length of the machine, while the upper roller is only long enough for two slivers. Failure of an end is followed by the contact of the two rollers, thus establishing the circuit and causing a current to pass through the magnet X, which attracts the catch Z. The latter engages with a constantly revolving cam and thus stops the latter, this being followed by the release of the knocking-off lever. The lapping of a sliver in passing through the drawing rollers causes the top front roller H, which is coupled to one pole, to engage with a pin L, connected to the other, and so stop the machine. The breakage of the sliver before reaching the calender rollers N K, is followed by the establishment of contact between them, with the usual result. Over filling of the can lifts the tube plate in the coiler O, and completes the circuit with the same result. The use of electricity in this connection has greatly simplified the machine, and has proved to be a great success.
Fig. 127.J.N.
(224) It only remains to be said that the diameter of the front roller is from 1 inch to 13⁄8 inches, according to the work required, and the speed at which it is run, from 290 to 450 revolutions per minute.
CHAPTER X.
SLUBBING AND ROVING MACHINES.
(225) The sliver as left by the drawing frame consists of a number of fibres arranged in a parallel order, and contains a little twist introduced by the coiler. It is not practicable to carry the parallelising process much further, as the drawn slivers are so attenuated that very little more draught would pull the fibres asunder. As, however, it is essential, in order to produce a yarn of the requisite fineness, that a further reduction shall be effected, it is the practice to gradually introduce into the sliver a small amount of twist. This is done by stages, and at each stage the partially twisted fibre is subjected to the action of drawing rollers. The machines about to be described, therefore, have a dual action, and, in most cases, are three in number, known respectively as slubbing—second slubbing or intermediate—and roving frames. While this is the rule, it is not the universal practice. In spinning coarse counts, for instance, only the first and third of the series are sometimes employed, while the production of very fine yarns is aided by the use of a fourth machine, known as a “jack” frame. Whatever may be the number of steps by which the process is completed the object is the same—to reduce the sliver to an even round thread of such proportions that it can be readily twisted into yarn of the requisite diameter. The introduction of a slight twist binds the fibres together, and enables them to be drawn as required without breakage. The thread finally produced is technically known as a “roving.” The various machines being practically identical in their details, varying only in correspondence with the increasing fineness of the thread, it is only necessary to give a description of one of the series.