GB866491A - Improvements relating to the treatment of textile fibres - Google Patents

Abstract

866,491. Control of textile drafting-machines. JACKSON, S. W., ROBINSON, S., and HOWDEN, J. M., [trading as BRITISH NORTHERN ELECTRICAL APPLIANCES]. July 18, 1957 [July 18, 1956], No. 22315/56. Class 40 (1). [Also in Groups IX and XXIV] The drafting of a textile sliver is controlled by a variable-speed device coupling two drafting elements (e.g. pairs of rollers), this device operating in accordance with electrical signals which have been obtained from a detector responding to the instantaneous thickness or weight per unit length of the sliver as it approaches the drafting mechanism, the signals having been delayed by storage in a bank of capacitors for a time equal to that taken by the sliver to travel from the measuring point to the drafting point. In Fig. 2 the sliver 2 is drawn forward by the back rollers. 1 and the faster moving front rollers 4, and is intermediately operated upon by the faller pins 3. Power is taken from a prime mover 9 via suitable gearing 8, 7, 10, the last having a variable ratio. Electrical signals obtained from the detector 11 are delayed at 12 (as shown below) for a time dependent on the speed of rotation of the rollers 1 (i.e. on the linear speed of the sliver) and also on the distance between the points 3 and 11. The delayed signals are passed into a controller 13 which varies the gear ratio in 10 according to the thickness or density of the sliver at 11, thus ensuring constant thickness of the emergent sliver. Fig. 3 shows a preferred detector comprising a weight-loaded lever 16 pressing the sliver 2 between a roller 15 and a flanged pulley 14. The instantaneous thickness controls the position of the rack 19 and thus the magnitude of the signal from the potentiometer slider 21. Alternatively a radio-active source and detector can be used to measure the quantity of material in the sliver. The delay means for the signals (Fig. 4) comprises a bank of condensers connected successively to three wipers 26, 27, 28 by a rotating commutator; the first wiper charges each condenser to a value depending on the instantaneous value of the signal, the second extracts the signal later and the third removes any residual charge. The delay time depends on the angular separation of the first two wipers (adjustable in accordance with the distance between the points 3 and 11, Fig. 2) and the rotational speed of the commutator (proportional to the speed of rotation of the back rollers 1). The arrangement can be modified by joining the condensers between corresponding segments of two commutators and rotating the whole relative to fixed brushes. The delayed signals are passed through a cathode follower and D.C. amplifier (Fig. 5, not shown) to the field winding of a servomotor which is mechanically coupled to a tachogenerator supplying feed-back to the input of the D.C. amplifier. The speed of the servomotor is thus proportional to the instantaneous thickness of the sliver, and the motor controls the gear ratio of the device 10 (Fig. 2). The control can be direct on a differential between the input and output shafts (Fig. 6, not shown) or via a differential 44 (Fig. 7) whose input is obtained from the driven shaft 43 and compared with the speed of the servomotor 33. Any difference in speed moves the lever 46 to effect a mechanical change of the gear ratio. In another arrangement (Fig. 8, not shown) an electronic device produces a signal which is the difference between the outputs of the cathode follower and of a tachogenerator coupled to the driven shaft of the device 10. The signal then controls the eddy-current coupling of a magnetic clutch. More than one sliver can be fed in to the apparatus, measurement being made of the thickness of each sliver separately, with electrical combination of the signals, or the combined thickness can be measured. The system of the invention may be added to existing textile machinery. According to the Provisional Specification the signals can be delayed on a magnetic tape or drum, in an acoustic line or by storage tubes where the information resides in the charged state of dielectric material.