Power loom are driven by the following types of drives :
a. Individual drive
b. Group drive
In this method, each power loom is driven by an individual motor. The power required to drive a plain power loom is 0.75 HP. Figure 1.2 shows a simple driving arrangement commonly found in mills. A single motor is used to drive the loom. Motor A, via motor pulley B and loom pulley or fast and loose pulley C and D, drives the top shaft or crank shaft E. A crank shaft gear wheel F and a bottom shaft gear wheel G drive the bottom shaft H. By means of a starting handle, a belt fork can be used to change the position of the belt on the fast-and-loose pulley arrangement. When the belt is on the loose pulley D the pulley will rotate but the crank shaft will not rotate. Therefore the machine can be stopped. By moving the belt to the fast pulley C the loom can be started or stopped at any time. In the latest looms, a motor with an electro-magnetic clutch drive is used. This is more reliable and stops the loom instantaneously by a push-button control system.
1. The ratio of the number of teeth on the gear wheels i.e. the ratio of the number of teeth on the crank shaft gear wheel to that on the bottom shaft gear wheel is 1:2. The actual number of teeth in the two gear wheels could be 36:72, 45:90, etc.
2. Since the ratio of the number of teeth on the gear wheels is 1:2, the ratio of the speeds of the crank shaft and the bottom shaft will be 2:1. If the crank shaft has a speed of 50 rpm, the bottom shaft will have a speed of 25 rpm.
3. When the crank shaft makes one revolution, one pick is inserted. If it has a speed of 75 rpm, 75 picks will be inserted in a minute. Therefore the crank shaft speed in rpm also indicates the picks per minute (ppm), i.e. a crank shaft speed of 75 rpm indicates a pick insertion rate of 75 ppm.
4. Crank shaft speed indicates the loom speed.
- The advantages of individual drive are listed below :
1. In case the motor of any particular loom fails, that loom alone will stop running, while all the other loom keep running.
2. Power losses in individual loom drive are much less than the losses in a group drive system. There is therefore a considerable saving in power.
3. The life of the transmission belt is comparatively greater in individual drive.
4. In the individual drive system, there will be a clear view of all the looms in the shed. Due to the absence of a overhead shafts and moving belts, the lighting in the shed will be brighter and more uniform.
5. The possibility of accidents is considerably minimised in the individual drive system as each loom and its drive is compactly arranged, without any interloom connection.
6. The shed plan and layout of looms is neat and easy.
- The disadvantages of individual drive are :
1. Initial cost is high.
2. High maintenance cost.
In the de-centralised weaving sectors, a group of looms is driven by means of a common motor and an overhead shaft and belt-drive arrangement.
This method of driving power looms is found in the de-centralised weaving sectors, It can be seen in Figure 1.3 that in this system, a common motor A drives an overhead shaft D via pulleys B and C, which is in fact the main shaft of the system. The main shaft runs from one end of the loom shed to the other. A number of pulleys E, are fixed on this shaft, one for each loom. Each loom has a fast-and-loose pulley G which is connected to the corresponding main shaft pulley by means of a belt F. The belts can be shifted on the corresponding fast-and-loose pulley, either to run the loom or to stop it.
- Advantages of group drive :
1. Initial cost is low.
2. High maintenance cost.
- Disadvantages of group drive ;
1. Higher power consumption.
2. One motor drives a number of looms. So, if it fails, all the looms it drives are affected. This results in poor loom-shed efficiency.
3. There are greater chances of accidents due to the overhead and other interloom connections
4. The large number of pulleys and belts in the loom shed will reduce the effective amount of light in the loom shed.
5. The layout for a group-drive system is complicated and presents a clumsy overall appearance.