The Art of Inventing

by Edwin J. Prindle

Fig. 10.

Continuing their circular motion, the fingers approach the strands of the cord between the twisted portion and a part of the machine which holds the ends of the cord, and the fingers spread apart as shown in Fig. 13, so that they can pass over and grasp the strands thus approached, as shown in Fig. 14.

The fingers then draw back through the loop which has been formed about them, the fingers holding the grasped portion of the strands, as shown in Fig. 15.

The knot is finished by the completion of the retracting movement of the fingers through the loop, thus forming the bow of the knot as shown in Fig. 16.

Fig. 11.

The inventor found that one finger could have a purely rotary movement, as if it were fixed on the arm and unable to move independently of the arm, and the movement being as if the arm rotated like a shaft, but the second finger must be further capable of moving toward and from the first finger to perform the opening movement of Fig. 13, and the closing movement of Fig. 14 by which it grasps the cord. The inventor accordingly, from his exhaustive analysis of his problem, and his invention or discovery of the proper finger motions, had further only to devise the very simple mechanical device illustrated in Fig. 17 to replace his fingers.

The index finger of the hand is represented by the finger S, which is integral with the shaft V. The second finger of the hand is represented by the finger U, which is pivoted to the first finger by the pin s. The grasping movement of the finger U is accomplished by a spring V' bearing on the shank U', and its opening movement is caused by the travel of an anti-friction roll U", on the rear end of the pivoted finger, over a cam V", on the bearing of the shaft. The shaft is rotated by the turning of a bevel pinion W on the shaft through the action of an intermittent gear. The necessity of drawing the fingers backward to accomplish the movement between Figs. 14 and 16 was avoided by causing the tied bundle to have a motion away from the fingers as it is expelled from the machine, the relative motion between the fingers and the knot being the same as if the fingers drew back.