(295) The compound strap guide lever is placed almost vertically, as shown in Fig. [158], being hinged upon a pin in the headstock frame. The part G carries a short pin on which a small runner or bowl can freely revolve. While the carriage is running out, the bowl is at the point of the cam Y, but when the half revolution of the cam shaft is made it assumes a position at the base of the cam. These two positions are very clearly shown in the right hand bottom corner of Fig. [156]. This allows the strap to move, in a manner more particularly described afterwards, on to the loose pulley, so that the backing off friction can be engaged.
Fig. 156.J.N.
Fig. 157.J.N.
(296) It has thus been shown that the half revolution of the cam shaft causes the stoppage of the motion of the carriage, rollers, and spindles. This is the second stage or period, and it is at once followed by the third. Before passing on it is worth while reiterating that there is a decided advantage in the constant rotation of the loose half of the clutches X and A1, their engagement being made more rapidly and with less strain. The power derived from the portion of the strap upon the loose pulley is sufficient to rotate the cam shaft, and cause it to make the changes. It is also capable of maintaining the steady rotation of the backing-off and taking-in friction clutches, so long as these are not in gear, or communicating motion to the spindles or carriages.
(297) The strap guide arrangement is shown in detail in Fig. [158]. The guider is fixed at the upper end of a lever F, which is hinged, as shown, at its lower end to the heel of the lever G. F has also an arm F1, which is coupled to a horizontal limb of the lever G by the spring S. The two or compound levers are therefore constantly drawn towards each other. The lever G is secured on a short shaft, and has a second spring Q attached, which pulls it in the direction of the arrow, when it is freed by the rotation of the cam Y. A short stud bowl is fixed in G, and the pull of the spring presses it constantly against the cam. Coupled to a short arm, fixed on the shaft to which G is secured, but at the other side of the headstock, is the horizontal lever H, the outer end of which is drawn upwards by the spring P, fastened to the framing. A shoulder or recess is formed in H, which ordinarily engages with the fixed catch L, by which the strap guide lever is locked in position when the strap is on the fast pulley. On the inner end of the rim shaft a worm K is formed, which gears with a worm wheel compounded with a spur pinion, which, in turn, gears with the spur wheel shown. On the spindle of the last-named wheel a small crank O is keyed, the outer end of which has a pin, carrying a bowl, fixed in it.
(298) The action of this mechanism is as follows: The revolution of the rim shaft causes the crank O, which is, at the commencement of the outward run, just clear of the nose of the lever H, to revolve. By the time the outward run is completed, the crank will have made almost a complete revolution. When the necessary twist has been put in the yarn, the crank O comes in contact with the front end of the lever H and releases the catch L. Immediately this happens the spring Q acts, and the strap guide lever oscillates, causing the strap to glide upon the loose pulley.
(299) This step having been accomplished, the next operation is to engage the backing-off friction. As shown in Fig. [158], the boss of the wheel A1 is formed with a ring groove, into which a claw fastened on a short stud fits. The lever D is also fixed on the same stud, so that any movement given to it is communicated to the claw and backing-off friction. The lower end of the lever is forked and passes over a rod X extending along the side of the headstock. This rod is guided by a bracket fixed to the side of the frame, and has the two stop hoops X1 X2 fastened on it. Between the stop hoops a spiral spring, always in compression, is threaded upon the shaft, one end pressing against the lever D, and the other against the hoop X2. It will be readily understood that the compression of the spring will tend to push the lever D in the direction of the arrow, until its motion is stopped by a link connected with the slide in the arm, to which is fastened the lever H. It is essential that the engagement of the backing-off clutch should be practically simultaneous with the transferring of the strap from the fast to the loose pulley, and it is therefore desirable that the spring on X should be put in compression a little before the actual traverse of the strap.
(300) This is accomplished by means of the swinging lever V shown in Fig. [162]. This is hinged upon the square, and is formed, as shown, with an open mouth, at the upper part of which is an angular projection or lip. Pivoted on the framing is the lever L, the horizontal arm of which carries a small runner, which engages with the incline of V as the carriage runs out. The lever V cannot, until the termination of the stretch, be swung upon its pivot by reason of its connection with the faller locking lever A. When, therefore, the bowl in the lever L engages with the incline of V, the lever L is oscillated, so that the spring on X is further compressed. The spring is, therefore, in a position to push the backing-off lever forward, as soon as the latter is freed. The engagement of the lever L with the lever V takes place a few inches before the carriage arrives at the end of its outward run.