Textiles: spinning – twisting – and twining – Apparatus and processes – Open end spinning
Patent
1987-01-20
1989-04-18
Petrakes, John
Textiles: spinning, twisting, and twining
Apparatus and processes
Open end spinning
57408, 57411, 57413, D01H 7898, D01H 1135
Patent
active
048215058
DESCRIPTION:
BRIEF SUMMARY
This invention relates to a method and apparatus for spinning yarn made from natural, artificial, or snythetic fibres.
In the practice of open-end rotor spinning, a collector groove in the rotor is employed for the collection and condensing of the fibres carried to it by means of an airstream. The deposited assembly of fibres is withdrawn from the collector groove to the central point of the rotor adjacent the axis thereof, the assembly of fibres thus being in the form of a crank. The crank action achieved as the rotor rotates is instrumental in inserting one twist in the forming yarn for each revolution of the rotor. In this rotor system, there is naturally a weakness in the assembly of fibres constituting the crank, as there is a lack of twist in that portion of the assembly of fibres unless specific measures are taken.
The rotor spinning system also has certain limitations mainly to do with the high rotor speeds required for economic production, and the difficulties in providing economically the high levels of twist as required for the production of fine counts of yarn.
The development of friction spinning, whereby the yarn is formed by drawing the assembly of fibres over a rotating friction surface, and caused to roll thereon, overcomes the limitations of the rotor spinning technique in respect to its restriction to one twist of the forming yarn for each revolution of the rotor. Thus the rate of twist insertion is greatly enhanced with the added advantage of comparatively low mechanical speeds.
Australian Pat. No. 501999 relates to one form of friction spinning wherein a yarn is spun by delivering a flow of fibres in an airstream to form an open-ended, cohering fibre assembly, which is drawn through a gap between two surfaces of revolution provided by two rings situated one within the other, so that the fibre assembly during its passage from one end of the friction surfaces to the other, is acted on by the frictional content with each surface, and twist inserted, while the yarn product is gripped and drawn off by the withdrawal rollers.
The effective operation of spinning machines in accordance with the beforementioned patent is largely dependent upon the positive rolling action in twisting and backtwisting the fibre assembly, which is characteristic of the system so long as an `open-end` exists upstream of the friction surfaces. The convex surface of the inner friction ring fitting within the concave surface of the outer friction ring presents a more extensive and more efficient friction contact with the intervening fibre formation than is obtainable with the employment of two convex surfaces in juxtaposition as proposed in other friction spinning systems. Also the gradual taper of the concave and convex surfaces fitting one within the other, when the inner ring has a lesser diameter than the outer ring and is not coaxial with it, enables the position of the intervening fibre formation to be precisely adjusted according to the thickness of the fibre formation. Thus the inner ring may be rotatably re-located to present a wider or narrower gap as appropriate for the particular width of the fibre formation. A firm and satisfactory `nip` is thus formed for the passage of the forming yarn therethrough, with advantageous frictional effect in comparison to the alternative method of employing two juxtaposed convex surfaces of revolution.
The method of delivery and the assembling of the delivered longitudinally orientated fibres into a condensed and cohering form for presentation to the appropriate gap between the friction surfaces, and the maintaining of an open-end condition with free rotation of the fibre assembly, are essential to achieving a satisfactory friction spun yarn of required strength and evenness.
For high speed friction spinning maximum twisting efficiency is necessary without an excess of slippage of the rolling fibre assembly between the friction sufaces apart from that involved in the longitudinal withdrawal. The effect of the friction rolling should be so far as possible to roll the fibre a
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