Side fork motion or weft fork motion ( an auxiliary loom motion)
The side fork motion is an auxiliary loom motion. The main objective of side fork motion is to stop the machine immediately in case of weft insertion failure during weaving. The side fork motion is mounted at the starting handle side of the loom. Since this mechanism gets mounted at the one side of the loom so that this mechanism is called side fork motion. This side fork motion helps to improve both quality and productivity.
Structure of side fork motion:
A grid is mounted between one end of the reed and the mouth of the shuttle box. The race board has a grove just opposite the prongs of the fork. the prongs of the fork get operated in this grove of the race board. This grid gets parallel to sley and in front of the prongs of fork F. The fork F is fulcrummed at fulcrum point G. The fork is mounted on the weft fork lever K. The fork has prongs at one end and a tail hook H at another end. This fork is made of lightweight material. The weight of the tail hook side is greater than the side of the prongs. Normally, the tail hook H of the fork F rests on the hammer lever notch J just because of the higher weight of the tail hook H. The knock-off lever L is mounted just behind the weft fork lever K. The other end of the knock-off lever gets touched to starting handle M. A cam B is mounted on the bottom shaft A of the loom. The greyhound tail lever D and the hammer lever I are connected to each other and they are fulcrummed at the joint of both levers. A bowl C is mounted at the end of the greyhound tail lever D. Bowl C touches cam B.
When the bottom shaft rotates, the cam B mounted on the bottom shaft also rotates with the bottom shaft. The cam imparts up and down movement to the bowl mounted at the end of the greyhound tail lever. Since the greyhound tail lever and hammer lever are connected to each other and get fulcrummed at the joint of both levers so that the cam imparts to and fro motion to the hammer lever.
The side weft fork motion performs its work when the sley moves to the front dead centre position. The prongs of the fork push the weft yarn present in the shed in a normal running position of the loom. When prongs of fork strike the weft yarn, the tail hook of the fork lifts up and the loom gets to continue to running position. The cam makes one round when the crankshaft makes two rounds.
If the weft yarn gets absent due to any reason during loom working, the tail hook of the fork falls down on the hammer lever. Since the hammer lever makes a to and fro motion, the hammer lever notch carries the weft fork lever with it. The weft fork lever pushes the knock-off lever in this situation. The knock-off lever strikes the starting handle and the starting handle gets disengaged. In this way, the loom is stopped in a weft break situation.