Fig. 114.
(198) Having thus described the mechanism employed, its method of action can now be explained. The lap, being passed to the feed rollers, is delivered by them intermittently in short lengths corresponding to that of the staple. This intermittent rotation is obtained by the use of a star wheel, which is revolved by a train of gearing from the cylinder shaft. The extent of the forward movement is regulated by the length of the fibre, the roller making such a portion of a revolution as causes its surface to move that distance, usually from 1⁄8th to 1⁄10th of a revolution. The roller being one inch diameter, the relative distance its surface would travel, and the length of fibre delivered in each case, would be ·39 or ·31 inch. The nipper jaw D, while this movement is being made, is open, and the top comb L is dropped. As soon as the rotation of the feed rollers ceases the nipper closes and grips the fibre. The downward movement of the top nipper blade D is, however, continued beyond that point, and the lower jaw H receives a further downward movement which puts the helical springs K into tension. In the ordinary position of the nippers the comb needles in their revolution would pass the cotton, but the recession of the nipper, as described, brings the uncombed end of the lap into the path of the needles, which accordingly pass through and comb it. It may be here explained that after the process of combing the combed and uncombed parts of the lap are separated, and that, after the free end of the latter is combed, a small portion is pulled away from it, and joined to the previously combed portion in the manner about to be described. For convenience it will be as well to refer to the uncombed cotton as the lap, and to the combed cotton as the sliver.
(199) The circular combs having passed, the continued revolution of the nipper cam allows the nipper to again move forward, and to carry the combed end of the lap into a position in which it can be dealt with by the fluted segment N1. The top comb L drops into the lap at a point in advance of the uncombed portion, and the leather roller Q at the same time is moved round the detaching roller S. As the fluted segment N1 comes under the cotton the leather roller engages with it, and the continued revolution of the former causes the two to act as a sort of revolving nipper. The nipper D has been previously opened and a tuft of cotton is drawn away from the lap, partially by the action of the segment and leather roller. To the latter a peculiar motion is given by a cam, which acts through special mechanism. It is not enough that the combed tuft should be detached from the lap, but it must also be attached to the sliver. In order to effect this the detaching roller moves backward to the amount of one-third of a revolution, previously to the engagement of Q with N1. This, of course, carries a corresponding length of the sliver with it, and lays the free end of the combed tuft on to the free end of the sliver, to which it is at once attached by the pressure of the leather roller Q. The backward motion of the detaching roller commences after the combs have passed through the lap end, before which it is stationary. The piecing being complete, the segment N1 and leather roller Q recede from each other, and the detaching roller makes a forward movement of two-thirds of a revolution. This results in the complete attachment of a tuft of cotton, the uncombed part of which is drawn through the top comb, this preventing the passage of short fibres and nep, which are retained in the lap, and removed by the next passage of the rotating combs. The attachment having been accomplished the detaching roller becomes stationary, the top comb is raised, a fresh portion of lap is fed, and the process is recommenced.
(200) There are thus three distinct stages in combing, viz., the feeding, combing, and detaching, and in the course of the operation the tuft of cotton is completely separated from the lap, and joined to the sliver. It is, of course, absolutely necessary in a machine the movements of which are so delicate, to establish and maintain a very accurate setting. For this reason ample provision is made by which the adjustment of the various parts can be accurately effected, as a reference to Fig. [114] will show. Although the motion given by the cams is of necessity a positive one, and its range fixed to suit the material, the timing of the movements of the different portions of the mechanism is secured by the facilities named. The full importance of this power will be appreciated when it it is stated that from 80 to 95 “nips” or beats are made per minute. Without the most delicate setting it would be impossible to ensure successful work, and this explains the reason for the many adjusting screws shown in Fig. [114].
Fig. 117.J.N.
Fig. 118.J.N.
(201) In treating of the carding engine it was explained that the production of an even sliver was of high importance. This is equally so in the combing machine. It has been explained that the cotton is held by the nipper jaws, while the projecting end of the lap is combed, and it will be readily understood that this action will tend to widen or flatten it a little. This result is also produced by the action of the feed and detaching rollers. Thus a sliver is produced with uneven edges, which is very undesirable. In order to remedy this, Messrs. John Hetherington and Sons have adopted the device which is shown in front elevation and section in Figs. [117] and [118]. In this case the lower nipper jaw, or cushion plate A, has attached to it at each side a guide plate, which has two projecting pieces C D, one at the front and the other at the back of the nipper. D is curved so as to allow the jaw B to descend without difficulty. The two guiding portions C and D are coupled by a connecting piece E so as to form one casting. The nipper plate is cut away, as shown at F, to clear the front guide, which is arranged so as to be in contact with the front edge of the cushion plate A. By this arrangement it is practically impossible for the fibres to escape sideways as the lap is nipped. The length of the nipper plate is sufficient to hold all the fibres firmly, thus ensuring their perfect combing. The fibres are prevented from lifting during the descent of the nipper by a small projecting piece and by the back guide D. The cylinder is also formed with a flange to obviate spreading. By these arrangements a wider lap can be used than would otherwise be the case, and the amount of cotton passed is therefore greater. In addition to this the selvedge is much more even, and the sliver produced in better condition for drawing.