Yarn Take-Up Spring
No matter how close to the edge of the fabric the yarn guide may be stopped, unless the yarn is kept taut the selvage will not be perfect, therefore a very insignificant appearing but quite important adjunct called the yarn take-up spring is provided to do this. There is one provided for each yarn guide and their position in relation to the machine may be seen at the top of the yarn stand in Fig. 45, while one is shown in detail in Fig. 51. The spring is a coil spring turned around the stud, f, and attached at the inner end. The outer end is a part of this spring straightened out as at b, with an eye turned in the end at d.
Fig. 51.
Yarn Stand and Take Up Spring.
By turning the top of the stud f away from you it will put more pull or tension on the spring, and by turning toward you less. The yarn is drawn from the bobbin, e, through an eye directly over the bobbin, then through a hole in the tension stud at a, then through an eye of the spring, then down through another eye in the stand at g, and directly to the yarn guide of the machine. The tension a prevents the spring from drawing any yarn from the bobbin, therefore it will always draw the slack yarn from the yarn guide and keep it taut at all times. There must be a take-up spring for each thread in use and that means that there are sometimes as many as eight or ten on one stand.
We have had a drawing of the double lock in Fig. 40, showing the cam side with an explanation of how it works and its advantages, so now we will show only the top carriage side in Fig. 52, with its appurtenances for the automatic changes. Bear in mind that when slides or plungers are mentioned in the following explanation reference is made to Fig. 52, and when cams are mentioned reference is had to Fig. 40.