Fig. 142.
(253) In consequence of the sudden release so effected, the lever L1 assumes the position shown in Fig. [140], and at the same time the pin E1 strikes one side of the hole in the lever E (see Fig. [141]), and causes the latter to turn rapidly on the pin F. This is followed by three things. The head of the lever E strikes the catch G1 and throws it out of gear with the ratchet wheel. The latter at once makes a rotary movement to the extent of half a tooth, but is then arrested and retained by the catch G. As the catch levers G G1 are coupled by the spring H it will be easily understood how the movement of one of them to the right or left is accompanied by a corresponding movement of the other. By this release of the ratchet wheel and its partial revolution, the upright shaft K also moves and causes the rack P to travel inwards and so move the strap on the cones. This is the first effect of the movement of the lever E.
(254) As shown in Fig. [134], and also in Fig. [141], the lower end of the lever E is attached to the rod R, which is connected at its other extremity by a forked lever to the double bevel or “striking” wheel T T1. The latter engage alternately with the small bevel pinion fixed on the lower end of the upright or “change” shaft M and slide upon a short shaft U, which they drive by means of a feather key. On U is also fixed a spur pinion V which drives, by the intervention of suitable gearing, a shaft running longitudinally and placed just behind the spindles. This shaft has a number of spur pinions fixed on it, which engage with vertical racks or “pokers” fastened to the bobbin frame. In this way the rotation of the pinion V in either direction is followed by the traverse of the bobbins either upwards or downwards. When, therefore, the rod R is traversed by the oscillation of the lever E and the bevel wheels T T1 are respectively thrown into gear with the pinion on M, the bobbin traverse in a corresponding direction is obtained.
(255) A further effect which arises from the rotation of the ratchet wheel is found in the fact that the wheel T (Fig. [140]) also moves, and as it engages with the rack on the underside of the rod S draws the latter inward. As will be readily understood, the position of the pin O plays an important part in the oscillation of the cradle A. If, for instance, the pin were at the extreme point of Q furthest from A, the motion of the latter would be made much more slowly than if O were at the other end of the slide, when, owing to the shorter radius, A would make its oscillatory movement more quickly, and, if Q made the same vertical traverse, A would move through a greater arc. Thus, if O is drawn inwards, it is followed by a more rapid movement of the cradle A, and, as a consequence, the change of the position of the lever E occurs at an earlier moment. This causes the reversal of the traverse of the bobbin rail to take place sooner, and, in this way, each succeeding layer of roving occupies a shorter portion of the bobbin surface longitudinally than its predecessor. Thus the bobbin is built accurately in the double conical shape required, and the shortening of the lift, the necessity for which has been previously demonstrated, is properly effected.
(256) A reference to Fig. [134] will show that the weight attached to the rack P is fastened to the latter by a chain, which passes over a pulley at the lower end of the lever W, which is sustained in position by a catch placed at X. When the rack P has made its extreme inward traverse the catch is released, and the lever W is caused to strike the collar on the rod Y, so as to cause the latter to move longitudinally. As the rod is connected with the driving strap fork, the strap is thrown over on to the loose pulley, and the frame is stopped. Attached to the bobbin frame are chains, to the other end of which balance weights are fastened so as to relieve the work of the lifting pinions. These chains are passed over pulleys fixed to the framing as shown in Fig. [134].
(257) Recurring now to the action of the building and winding motions, it is necessary to note that the number of the releases of the ratchet wheel I correspond to those of the reversals of the bobbin rail, and consequently to the number of the layers of roving. It therefore becomes necessary to alter the wheel I whenever a change in the roving which is being produced is made. As the ratchet wheel is the governing factor in the regulation alike of the speed of the strap traverse and of that of the inward movement of the rod S, the reason for changing it is easily seen. Thus the increase in the diameter of a bobbin on which a roving 1⁄16th inch diameter is being spun would be less than that which occurs when a roving 3⁄32nd inch diameter is made. It follows, therefore, that the rate at which the strap is moved along the cones would in the first case be only two-thirds of that at which it moves in the last case. Again, the lessened increase in diameter involves, as was shown, the winding on of a shorter length of roving during the “lift” of the bobbin, and consequently the latter does not require to be diminished in the same ratio. Therefore, it is desirable to substitute for the ratchet wheel one with more teeth, the number of which must be in direct ratio to the number of coils it is intended to wind on the full bobbin.
(258) Let it be assumed that the pitch of the teeth of the rack P and of that in S is one-quarter inch; that the ratchet wheel I has 30 teeth, the pinion engaging with P 31 teeth, and the pinion T 19 teeth. As was shown, the wheel I moves to the extent of half the pitch of the tooth every time the traverse of the bobbin rail takes place. In this case 60 such reversions would take place during the time that the ratchet wheel made a complete revolution. During that time the wheel engaging with P would also have made a complete revolution, and P would have moved in 73⁄4 inches, giving a corresponding traverse to the strap. In the same time the pinion T would have made a revolution, and the “diminishing rod” S would move in 43⁄4 inches. Assuming—a purely hypothetical assumption—that the distance from the centre A1 of the cradle A to the outermost point of the slide Q to which the pin O can be pushed is 15 inches, and that the lift of the bobbin be 7 inches, it will follow that the above reduction of the distance of O from A1 will cause a more rapid oscillation of the cradle A. A simple calculation will show that this would cause the change of the direction of the lift to take place when 43⁄4 inches was covered. This example will serve to illustrate the principle involved, but does not necessarily represent any actually existing case. It is only intended to show that the reduction of the lift takes place in exact accordance with the period occupied by the ratchet wheel I in its rotation. During the time the traverse has been shortened the speed of the bobbin, owing to the traverse of the strap along the cones, has also been diminished in the exact proportion required to compensate for the increased diameter.
(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.