Patent GB-671633-A (GB)
Title: Improvements in or relating to the drafting of textile fibres
Inventor: AMBLER GEOFFREY HILL
IPC: D01H13/04
Filed: 1947-04-11
Abstract: 671,633. Drafting textile fibres. AMBLER SUPERDRAFT, Ltd. April 6, 1948 [April 11, 1947], No. 9678/47. Classes 120(i) and 120(ii) In the singlestage high drafting of textile fibres, twist in a length of roving or the like undergoing drafting is controlled by pressing upon the roving at an urging point close to the drafting nip with forwardmoving surfaces subjected to external loading insufficient to prevent slip of any fibres receiving the high draft and by preventing any sensible rotation of the roving about its axis over a length of the roving forward of the urging point, without producing such frictional drag as would prevent satisfactory drafting. In one modification, the roving is not flattened at the urging point, but in a modification permitting flattening rotation of the roving is prevented rearwardly of the urging . point, thereby avoiding an intermittent: flow of twist. The urging preferably is performed by rollers, which may be 0.3 inch in diameter or less and may press the roving over the whole of its periphery. Preferred means of preventing rotation is a channel-shaped member of substantially rectangular cross-section and provided with a flared end to its channel facing the urging point. It is stated that, when a twisted fibre bundle of varying crosssectional area is freely suspended between a pair of nip points, the rate of twist t, at any cross-sectional area r, is governed by the equation t=T(R/r)<SP>x</SP>, where T is the average rate of twist throughout the bundle and R is the cross sectional area of the bundle. Vaules of x are determined empirically and. for worsted rovings, are stated to be 0.735. The drawings include a number of figures (not shown) illustrating diagrammatically the effect on twist distribution of the use of carrier rollers at different positions and of the employment of twist control means, such as a channel-shaped member, when operating at high drafts. In a described form of apparatus, a roving 31 is passed between feed rollers 32, 33, through a flared roving guide 34, to urging or intermediate rollers 35, 36 and thence through a channel-shaped member 37 to drafting rollers 38. The lower feed roller 33 is provided with flanges 41 within which the upper feed roller 32 fits closely, as described in Specification 671,641. Both intermediate rollers 35, 36 are positively driven, preferably slightly faster, say 10 per cent, than the feed rollers and one or both may be fluted. In addition, the lower roller 36 is flanged. Details of the mounting of and driving arrangements for the intermediate rollers are described in Specification 671,639. Rotation of the roving 31 is prevented by the channel-shaped member 37, which is formed at the top with a slot for threading the rectangular channel. The base of the channel extends between the flanges of roller 36 to act as a scraper, as set forth in Specification 671,644. Leaf springs 59 may be employed to hold the member 37 in position, as disclosed in Specification 671,638. Additional control may be obtained by having more than one channel-shaped member. Instead of the flared roving guide 34 being located immediately behind the intermediate rollers 35, 36, one or more additional channel-shaped members may be provided. The intermediate rollers 35, 36, the channel-shaped member 37 and the roving guide 34 may comprise a unit, as described in Specification 671,643, the unit being mounted for adjustment towards and away from the drafting rollers 38, preferably in association with other units forming a group of, for example, eight units. Specification 671,642 discloses such adjusting means. The units may be traversed by a shaft 64, as described in Specification 671,637. Examples given refer to drafts of 20 to 204 for worsted rovings, of 110 for cotton roving and 70 to 1,000 for rayon staple fibres. Specification 385,739 also is referred to.