Wednesday, March 31, 2021

Mechanical warp break stop motion

          Mechanical warp break stop motion:

The warp stop motion is an auxiliary loom motion. The main objective of a warp stop motion is to stop the loom immediately when an end breakage occurs during loom operation. The warp break stop motion plays a very important role to improve the quality of the fabric and the productivity of the loom. If an end breakage occurs and the loom gets continued to run, the broken end coming from the warp beam gets accumulated behind the eye of the heald wire. This yarn deposition causes multiple end breakages and this multiple ends breakage takes a long time to redraw these broken ends. Thus loom efficiency gets decreased. When the loom gets continues to run in case of end breakage, the fabric getting produced becomes defective. Thus the quality of the fabric gets affected. The warp break stop motion helps to increase productivity and improve the quality of the fabric getting woven on the loom.

Types of warp break stop motions:

The types of warp break stop motions are given below:

1 - Mechanical warp break stop motion

2 - Electrical warp break stop motion

3 - Electronic warp break stop motion

Structure of mechanical warp break stop motion

This mechanism consists of a reciprocating bar, oscillating device knock-off device, and drop wire. 

The complete reciprocating bar made of three components. The fixed outer bar consists of two plates. 

The reciprocating bar slides between these two plates of fixed outer bar. The top edge of the outer bar and reciprocating bar gets castillated. 

In order to ensure that the drop wire will fall into the lowest cut-out point of both bars, it is necessary for the reciprocating bar to be slightly higher than the two fixed outer bars. 

The number of castillated bars depends upon the number of ends per inch used in the warp beam. 4 - 8 castillated bars are normally used. 

The one end of each castillated bar gets connected with the drive mechanism through a pin. 

The castillated bars pass through the slot in the drop wire. The reciprocating bar is connected with the forked bracket. 

This forked bracket is attached with a fulcrum lever. This fulcrum lever held in the bottom of the rocking diamond-shaped cut out of the cam lever. 

The lower end of the fulcrum lever gets spring-loaded. The one end of release trip lever rests upon the spring-loaded lever. 

The release catch trip lever gets fulcrummed as shown in the below figure. 

The other end of the release catch trip lever rests in front of the lower end of the lifting catch.  

The oscillating mechanism is connected to the crankshaft through the sprocket wheel and chain. 

The one end of the cam lever is connected to the eccentric.



Working principle of mechanical warp stop motion:

The cam lever and eccentric are connected through the connecting rod. When the eccentric rotates, it imparts oscillating motion to the cam lever.  

The fulcrum lever is connected to the cam lever in the middle. A forked bracket is attached at the top of the fulcrum lever.

When the cam lever oscillates, the forked bracket also oscillates. Since the one end of the reciprocating bar is connected with a forked bracket so that the reciprocating bar also makes back and forth movement

When the loom operates, the drop wire rests upon the warp end due to warp tension. 

Enough clearance between the top edge of the reciprocating bar and the slot of drop wire. 

This clearance makes a free passage for back and forth movement of the reciprocating bar between two fixed outer bars. 

The position of the release catch trip lever doesn't change in this situation and the loom gets continues to run. 

When the end breakage occurs, the drop wire falls immediately in the cut-out of the reciprocating bar. 

The drop wire creates a hurdle in the back and forth motion of the reciprocating bar. 

The spring-loaded end of the fulcrum lever rises in this situation because it cannot be rock side-wise. 

The release catch trip lever also rises. Now the outside end of this lever falls and allows the lifting catch to slip over the outside end of the cam lever. 

As this end of cam lever rises, it raises the lifting catch, and thus the knock off lever slides and through a wire further catch attached to sley at the front end of the loom is raised into line with a projection of the starting handle unit for the loom to be knocked off. 

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