Weft replenishment mechanism (pirn changing):-

Weft replenishment mechanism (pirn changing):-

PIRN CHANGING MECHANISM IN CROMPTON KNOWLES C-7 LOOM.

SPECIAL FEATURES:- 

The Crompton and Knowles C-7 pirn-changing loom has made extensive used of electrical components. The loom has the enclosed motor drive power transmitter, and conveniently placed electrical control cabinet. The model C-7 loom with four-box motion introduced in 1958 , has established a proper balance between electrical and mechanical components and had co-ordinated these in the fundamental design of the new loom. The electrical components, which form the main features, are the following:-

(1) Push-button starting , stopping and reversing motion.

(2) Electric clutch and brake application, and

(3) Electrical operation of the various secondary motions, namely:-

(a) the warp stop motion,

(b) the weft stop motion, and

(c) the replacement of the conventional stop rod warp protector motion by an electro-magnetic system. Through the adoption of these electrical motions , the improvement and simplification of purely mechnical motion have been made possible.

The adoption of each electrical device performs a task more simply and efficiently than its mechanical fore-runner. The device offer definite operational advantages and are suited to the work they are required to perform. In this independent mechnical components have also been developed, some of which have been incorporated in the electrical design. Thus it has been possible in establish a proper balance between the mechanical and the electrical motion in the loom. The adoption of electrical components has also led to the improvement of loom operation, maintenance, performance and effectiency.

Power Transmission System in C-7 Loom.

(i) The basic motion or mechanisms of a loom require periodically large amounts of energy. For opening shed , the shedding mechanism requires more power during this phase of its operation than it requires on the average.

(ii) The heavy reciprocating sley, particularly on a multiple box loom, requires alternately large amounts of power to accelerate and decelarate its movement.

(iii) Moreover , the energy demands of picking motion during the acceleration period of the shuttle are quite substantial.

FLY WHEEL.

To meet all these particularly recurring energy demands , it is necessary to employ some form of energy storage device in the loom. The device, which is frequently employed, is the fly wheel. The fly wheel may be located in any of the following positions —

(a) on the crank-shaft of the loom .

(b) on an intermediate shaft between the loom drive and the motor, and

(c) directly on the motor shaft.

Evidently more energy for a given mass can be stored in a body which is rotating at a high speed than in one which rotates at a slower rate. The transmission should be placed so that it may function more effectively throughout the loom operating cylce.

The benefits of type of fly wheel energy is evident, but any detrimental effect of this added must be removed from the loom during period of rapid starting or stopping; otherwise , abnormal starting and stopping requirements would be encountered. To do this effectively, clutch and braking system are usually made to operate, so that during the time the loom is being started or stopped, the rotation of the fly wheel is undisturbed. With this arrangement, maximum of stored energy is available to the loom during the starting-up of a shuttle. On the first pick a minimum of energy is required to be absorbed by the braking system when the loom is stopped. It is also necessary to incorporate some means of reversal by power in the modern loom design.

POWER TRANSMISSION:-

To meet the various drive requirements a power transmitters, incorporating the mechanical and electrical components, has been developed. Energy storage is obtained in a fly wheel placed on a shaft intermediate between the motor and the crank-shaft of the loom.

(a) To control properly the phases of starting and stopping this loom, electrical clutches and electrical brakes are utilised. The type of electric clutches and electric brakes , used on this transmitter drive, is of the single disc friction type, composed of a metallic armature and an electro-magnet employing frictional material. When the coil is energized, the armature is attracted to the magnet and torque is then transmitted by the frictional coupling between armature and magnet. In operation, both armature and magnet have little air gap between them; and thus rapid energisation can be obtained without moving heavy inertia loads.

(b) The reversal of the loom is obtained by the provision of a simple reversing drive operating through an auxiliary shaft and in turn energised by a similar electro-magnetic cluch.

Image of Crompton and Knowles looms:- courtesy N S University.

ADVANTAGES:-

The power transmitter drive , designed on the C-7 loom, has the following advantages.

(i) It provides adequate energy storage in its fly wheel to ensure proper loom operation, specially at the time of picking.

(ii) It utilises simple loom control and allows the loom to be started or stopped by the operation of an electrical circuit.

(iii) It allows easy reversal through a simple electrically operated unit.

(iv) It allows single-pick, operation either automatically or at will. A loom, which turns one pick and automatically stops , is most useful for picking-out to avoide fabric defects.

Push Button Starting, stopping and reversing in Crompton and Knowle’s C-7 Loom:-

Simple push button are used to start and stop the loom; one button to start , a second button to stopped and third button to reverse or to backup the loom. In case of electrical controls it is necessary to provide wires between the various elements in place of rods, levers and cranks , which constitute the usual form of mechnical connections also eliminates their maintanence their maintenance and adjustments.

In operating an electric push button, the weaver fatigue and power consumptions are reduced to minimum.

(a) By interlocking the push button into the operating system of the loom, action following push button indication only takes place at the proper instant and under proper operating condition.

(b) By interlocking the stop button with a properly adjusted rotary switch , stoppage is delayed until the loom is on a safe stopping position. Actually the stop-button is employed simply as a signalling device, the rotary switch contact stops the loom in safe position. Thus, the danger of shuttle smash is completely eliminated.

(c) The reverse Push-button is interlocked into the circuit in such a manner that a limit switch will prevent reversal operation, whenever the loom is in an unsafe position. If the loom stops with the reed close to the fell of cloth, the reverse-button should be pressed to reverse the movement of the sley and the loom will quickly back up . The reverse limit switch will stop the loom at the back center position. No amount of pressure on reverse limit switch will cause the loom to move beyond this limit.

Electrically operated motions can also be provided for automatically reversing a loom and opening that shed on a weft break , automatically stopping the loom by other types of stop motion, single pick operation and the like.

Ref:-Weaving Mechanism Book Vol. II by Prof. N. N. Banerjee.