Briefly Description of Ball Warping Machine Different Parts (Part-2)

Tensioners

The individual yarn from each package loaded in the warping creel are passes through a tensioner.There are different types of tensioners available for ball warping machines. The different types of tensioners are as below:

Fig.:Typical Yarn delivery to the warp preparation machines

Post and disk tensioners: This type of tensioner unit two or three posts fitted onto a flat base. Two round disks are placed onto each post. The yarn is passes between the disks and wrapped around the posts. Out of the two or three post, one is movable. This varies the angle of wrap, which apply different levels of tensions to the yarn. The tension on the yarn can be increased by adding weights onto the op weights. This type of tensioners is inexpensive, simple to thread up, require less maintenance. However the yarn has a tendency to jump up out from between the disk, it is very labour intensive to change the tension levels to the yarn.

Driven disk tensioners: This type of tensioners has a twin-disk arrangement. The disks are supported from below and the tension is applied from above the disk through weights or a spring loaded device. A gear under each pair of disk is matched to another gear. This gear is mounted on a continuous shaft which is connected to a motor to rotate the disk. In some latest machinery manufacturer incorporates 4 RPM motor per post for disk drive. The rotation of the disk prevents thread cutting and dampens due to ballooning of the yarn. This type of tensioners requires less effort to change tension levels. However it requires more maintenance due to maintenance of the electric motor.tension to the yarn, as the yarn already has higher tension. However, at the front of the creel, the yarn tension is less. The balls exert higher pressure to the yarn as it passes between them. Hence the tension across the yarn sheet remains equal.

The advantages of this type of tensioners are minimum maintenance required and no adjustments required in this system. However, there is a limit of how much tension can be applied to the yarn. It is difficult for threading and it is relatively expensive.

Electronic Tensioner: 

The electronic tensioners are of two types, such as: Capastan Type and Rotating Disc Type.

In the Capastan type of tensioner, a round capastan fitted on a precision shaft. The capastan is fitted onto the bearings located inside of a round DC coil. The yarn is wrapped around the outer surface of the capastan and when the yarn is pulled out, the capastan rotates. An EM field is created under the capastan if no voltage is applied to the DC coil. A hysterisis ring attached to the inside of the capastan, reacts with the EM field and a resistance is created against the free rotation of the capastan. This resistance incorporates tension to the yarn. In order to achieve equal tension to each yarn, varying levels of DC voltages are applied to each tensioner. The advantages of this type of the tensioners are less maintenance required, no use of electric motor.

In the Rotating Disc type on the same principle, but it applies tension in different way. Two disks are fitted in the vertical position onto a ceramic shaft. Inside disk, there is a DC coil. An electromagnetic field is generated when voltage is applied to the DC coil. The outside disk is attached to the magnetic field and pulls tightly against inner disk. It applied tension to the yarn threaded between the two disks. The amount of tension depends upon the strength of the EM field created by the DC coil. A 4 RPM AC motor fitted on each tensioner turn the disks to avoid thread cutting.

Stop motion devices

A stop motion device is fitted in the creel to stop the machine at the event of any end breakages. There are different types of stop motion devices available. However each of them having their own advantages and disadvantages. Some of stop motion devices are as below:

Drop wire stopmotion : It is fitted on each vertical row at the front of the creel bands. This is the simplest type of stop motions. A drop wire is placed onto each yarn end. There is an exposed electric contact bar beneath the drop wires. An open electric circuit is maintaining in the electric contact bar in normal running condition. However at the time of any end breakages, the drop wire falls onto the contact bar and shorts out the circuit. This system is very inexpensive and very fast reacting. However, the system is exposed to dust, lint and short fibers. If the contact bar is accumulated with fluff, the drop wire will not be in contact with the bar and the system remains open.

Photoelectric stopmotion : This type of stop motion works on almost in same principle as the drop wire type, but there is some difference. The photoelectric system uses a faller which is attached to a shutter inside of an airtight housing of the housing. Inside the housing, there is a photocell having a transmitter at one end and a receiver at the other end of the housing. A light beam is emitted to the receiver which maintains an open electric circuit. At the time of an end breaks, the faller drops. This causes the attached shutter passes through the light beam, which ultimately initiating the stop signal to the warper. The system is reliable, inexpensive as compared to drop wire. It is easy to thread and maintenance free. However, the system having disadvantages of residual tension on the yarn which preventing the shutter to drop.

Electric Motion Sensor : In this system an electric motion sensor is fitted in the balloon shield at the yarn cone. The system measures the motion of the yarn when it exits from the cone. The yarn balloons housed in the balloon shield through a light beam. The system remains open as long as the light beam is broken by the ballooning motion. At the event of end breakages, the ballooning action immediately stops and the sensor signals the warper to stop. This system is reliable, fast acting and self cleaning. But the system is expensive.

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