Knowele's drop box motion:
Structure of Knowle's drop box motion:
This mechanism receives motion from the bottom shaft. Two driving gears fastened on the bottom shaft. These driving gears have half teeth on their periphery. The direction of the teeth of driving gears is just opposite to each other. There are two eccentric shafts used in this drop box motion. Each eccentric shaft gets mounted at both sides of the bottom shaft. The eccentrics are mounted on their respective eccentric shafts as shown in the figure. A sliding dog tooth gear is mounted on each eccentric shaft opposite the driving gear. The engaging and disengaging of sliding dog tooth gears are controlled by sliding dog tooths. The sliding dog tooth gets operated by a selection mechanism through an independent pattern chain and cylinder or dobby. The eccentrics are connected with a box unit lever through intermediate levers. A spring-loaded stud is used to prevent the damage of the shuttle or shuttle box in case of incorrect settings or mishappening.
Working principle of Knowele's drop box motion:
The driving gear is mounted on the bottom shaft. Since it is fastened on the bottom shaft so that it rotates with the bottom shaft. The sliding dog tooth gear is mounted on the eccentric shaft in such a way that the teeth of the sliding dog tooth gears do not touch the teeth of the driving gears in normal conditions. The sliding dog tooth is attached to the sliding dog tooth gear. As the sliding dog tooth receives the motion from the selection mechanism, it pushes the sliding dog tooth gear toward the driving gear. The continuously rotating drive gear gets engaged with the teeth of the sliding dog tooth gear. This sliding dog tooth gear rotates for half a revolution because the driving gear has half teeth on its periphery. Now the sliding dog tooth gear's teeth get disengaged again. The position of the sliding dog tooth gear gets unchanged till the weft pattern does not demand the change in the box position. Since the sliding dog tooth gear is mounted on the eccentric shaft, the eccentric also rotates for the half-round. This motion is transferred to the box unit lever through an intermediate lever. Thus the position of the shuttle box gets changed.
The spring-loaded stud remains engaged with a cut-out on the box unit support shaft to drive the boxes up and down. If the shuttle is projecting from the box so full movement of the box unit is not possible. In this situation, the catch will be forced out of the cut-out so that the drive mechanism will make it a full movement but box unit movement will be limited and damage avoided.
The initial position of the rear eccentric with connection is the up position and the initial position of the front eccentric is the down position.
When the rear eccentric is in the up position and the front eccentric is in the down position, then the first ( top box) box gets leveled with the race board.
If rear and front both the eccentrics go in their up positions, then the second shuttle box gets leveled with the race board.
If the rear and front both eccentric come in the down position, the third shuttle box gets leveled with the race board.
If the rear eccentric is in the down position and the front eccentric is in the up position then the fourth box gets leveled with the race board.