Patent GB-704573-A (GB)
Title: Method and apparatus for attenuating fiber-forming materials to fibers
IPC: D04H1/72
Filed: 1951-11-06
Abstract: Fibres of thermoplastic resins are formed by flowing streams 14 of fibre-forming material and attenuating the streams to fine fibres by moving them at a comparatively high linear speed by directing them into frictional engagement with a pair of moving elements 20, 21 arranged and driven so that the fibre-engaging surfaces of the elements, when out of engagement with the fibres, are moved at a linear speed greater than the speed of the fibres. As shown, material from a heated container 10 flows through apertures in the bushing 12 to form the streams 14 which are attenuated into fibres, a strand s of such fibres being gathered by a grooved roll collector 23 or a V-shaped gathering pad.  A sizing or coating material, e.g. waxes such as microcrystalline wax, <PICT:0704573/IV (a)/1> <PICT:0704573/IV (a)/2> <PICT:0704573/IV (a)/3> <PICT:0704573/IV (a)/4> <PICT:0704573/IV (a)/5> <PICT:0704573/IV (a)/6> amorphous wax such as ozokerite, montan, ceresin, paraffin, carnauba, or bee's waxes, synthetic waxes such as hydrogenated castor oil or other wax-like substances, in a container 24 may be applied to the fibres by contact with roll 26, which is driven at slow speed by motor 27 and gearing 28 and filmed with sizing material by engagement with a second roll 271 immersed in the sizing material, which may be heated by an element 30.  In addition to or in lieu of the sizing, a coating of lubricant may be applied through a tube 32.  A binder, e.g. synthetic or natural resin, rosins, or other heat softenable material, may be p  applied at the roll applicator 24 or at the gatherer 23 to secure the fibres in the strand.  The strand s may be projected from the attenuating means 20, 21 into an offset open container 35 which is mounted on platform 37 and slowly rotated on rollers 39 by means of a belt 42 from pulley 43 driven through gearing by motor 46. Alternatively the fibres may be collected on a movable conveyer which is oscillated to distribute the fibres and provided with a suction chamber beneath the belt at the collection zone.  An apparatus is also shown for severing the fibres into short lengths, comprising a knife rotatable about a vertical axis at an adjustable speed, the lengths of strand being sprayed with a binder if desired.  The rolls 20, 21 secured on shafts 52, 53 by keys 54 are rotated by means of gears and motor 60 at equal speeds of well above 5,000 linear feet per minute.  An oscillating traverse is used to change the path of the fibres between the rolls.  The rolls driven in the direction A, Fig. 3, each include a central body portion 24, preferably of metal, with an annular member 65 of resilient material, e.g. semi-hard rubber or synthetic rubber, secured to the periphery by a bonding cement and preferably by a dovetail groove in the periphery.  The peripheral edges of the rolls are chamfered to facilitate the entry of the fibres into contact with the rolls and to provide a gradual acceleration to the fibres.  The annular members may be slotted, as at 69, to provide spaced fingers 68 about the entire periphery, each slot being angularly arranged with respect to a tangent at the entrance of the slot.  Each finger is of smaller dimension at the junction 73 than at the outer edges 72 and is flexible at 73 so that when the rolls are rotated at high speed each finger, when out of engagement with the strand, assumes a substantially radial position with respect to the axis 52, 53 due to centrifugal force, Fig. 4 showing the normal position and Fig. 3 the position during rotation.  The shafts 52 are spaced as shown so that the fingers, when in maximum contact with the fibres, are distorted so as temporarily substantially to close the slots 69.  Since the radial distance R1 of the tips of fingers 68, under the unrestricted influence of centrifugal force, is greater than the distance R of the strand S, the unrestricted finger tips travel at a greater linear speed than the strands, and this difference prevents the adhesion of fibres to the peripheries of rolls 20, 21.  The radially distended fingers also reach out to grip the fibres and provide a rectilinear gripping zone, and when being restored to this distended position tend to push the strand from the fingers and by agitating the air help to cool the elements 65. Blower or suction means, e.g. jets 70, may be provided for cooling.  In the construction shown in Fig. 6, rotating elements 20a, 21a each include a metal disc 72 having peripheral flanges forming a groove 75, and a series of sheet metal fingers 77 are secured in the groove by pins passing through the flanges and through eyes in the fingers.  Rubber or plastic fibre-engaging elements 80 may be provided on the outer extremities of the fingers, and the action is similar to that described with reference to Fig. 3.  The rotors 20b, 21b, Fig. 9, each include a disc 91 with an annular member 90 of resilient material with a series of spaced openings 93 so that the peripheral surface 95 is joined to the body by webs 94.  The shafts are spaced so that the strand s is gripped by the peripheral surfaces of the rotors over a substantial rectilinear distance established by the distortion of webs 94.  Thus the strand s moves at a lesser linear speed than the peripheral surface of the rotors influenced by centrifugal force and out of contact with the strand, and clinging of the fibres is prevented.  In a further construction, similar in application to that shown in Fig. 9, the rotor discs have concave peripheral portions which receive tyre-like air-filled members which have no webs or thickened base portions.  In a further construction, Fig. 12, a deformable annular band 120 on a metal disc 2411 has an annular row of slits 122 which permit portions 123 to move outwardly under centrifugal force to form raised bands which move at greater linear speed than the normal periphery 124 and prevent adherence of the fibres.  In another construction, similar to Fig. 3, the slots in the annular member are of greater width and spaced further apart and the resulting fingers, being adapted for substantial outward movement due to centrifugal force, are capable of substantial relative movement during rotation and deformation at the gripping zone, and provide effective cooling.