Patent GB-696882-A (GB)
Title: Improvements in or relating to the drafting of textile fibres
Inventor: AMBLER GEOFFREY HILL
IPC: D01H13/04
Filed: 1949-06-29
Abstract: 696,882. Drafting textile fibres. AMBLER SUPERDRAFT, Ltd. June 26, 1950 [June 29, 1949; March 30, 1950], Nos. 17154/49 and 7918/50. Addition to 671,633. Classes 120(i) and 120(ii) The process of high drafting textile fibres disclosed in the parent Specification is modified in that drafts of at least 50 are applied by a nip offering soft resilience to one side of the roving under a pressure adjusted to maintain the drafting nip point substantially fixed. When drafting wool fibres, drafts exceeding 100, e.g. 250, may be used and drafts exceeding 500 may be employed with rayon fibres The first Provisional Specification refers to a draft of 1,500. Because rovings undergoing such high drafts taper sharply, the angle at which the drafting rollers approach each other at the nip must be greater than the angle of taper of the roving and the resilient drafting roller must not distort in a manner reducing the angle at which the rollers approach each other. 'Satisfactory resilient rollers have a cover of cellular material, such as cork, having a hardness in the range of 55 to 80 as measured on a Shore Durometer: In preferred apparatus, the roving 1 is fed through feed rollers 2, 3, such as are disclosed in Specification 671,641, through a "twist stabilizer" 3A that may have a deep V-shaped channel with an included angle of about 30 degrees, a roving guide 4, intermediate rollers 5, 6, such as are described in Specifications 671,633 or 678,763, and through a channel member or "flume" 7, that may have a similar V-channel to the "twist stabilizer" 3, to the nip of a pair of drafting rollers 8, from which it passes to the spinning spindle. The upper drafting roller 8 may be mounted as described in Specification 685,528. In order to compress the roving 1 into a rectangular crosssection, the rollers 5, 6 are flanged and weighted through a pivoted bracket 21, as described in Specification 671,639, and the intermediate unit comprising the rollers 5, 6, bracket 21, the guide 4 and members 3A and 7 are detachably mounted on a traversing bracket 31, as described in Specification 671,637. Adjustment of the intermediate unit relatively to the drafting rollers 8 may be as described in Specification 671.643. A method of calculating the correct intermediate settings relatively to the drafting rollers and with or without a "flume" is given. With the apparatus described, including a "flume," the most forward intermediate roller setting is 1.25 inches from the drafting nip. When employing 64/70s wool, drafts may be about 70 per cent greater when using a  "flume" than without. For drafts between 50 and 100 upon worsted rovings. the intermediate rollers 5, 6 may be 0.25 inch diameter, mav be driven about 8 per cent faster than the roving is fed and a weight of about 7.25 ounces may be applied to the upper roller 5. This loading corresponds to a pressure of about 70 lbs. per square inch upon the roving. In order to prevent rotation of the roving behind the intermediate rollers 5, 6, the "twist stabilizer" 3A is arranged to enclose the roving for about 1.5 inches, which ensures the maintenance of the initial twist rate, e.g. 0.6 turns per inch, throughout this length. Theoretical considerations indicating the advantages of employing a "twist stabilizer" are set out. Satisfactory "flume" lengths are stated to be between 0.5 and 0.75 inches. A method of calculating suitable cross-sectonal areas for the "flume" channel is given and an example provides for an entry width of 0.075 inch with a depth of 0.25 inch, corresponding exit figures being 0.065 and 0.075 inches. A method of calculating roving thickness in drams per 40 yards is disclosed and formulae for obtaining appropriate drafts for particular conditions are provided. According to the first Provisional Specification, the rollers 5, 6 may be replaced by belts.