US3549453A - Flash spinning apparatus for nonwoven fibrous sheet making - Google Patents

Description

J. G. SMITH Dec. 22, 1970 FI JASH SPINNING APPARATUS FOR NONWOVEN FIBROUS SHEET MAKING Filed April 6, 1967 6 Sheets5heet 1 Dec. 22, 1970 FLASH SPINNING Filed April 6, 1967 6 Sheets-Sheet 2 n /o4 I I I. n

84 I mi 90 6 Q 56 66 Q s a 6 5 Q Q 4- W an: 5

Dec. 22, 1970 J. G. SMITH Q 3,549,453

FLASH SPINNING APPARATLJS FOR NONWOVEN FIBROUS SHEET MAKING Filed April 6, 1967 -e Sheets-Sheet 3 Dec. 1970 J.- G. SMITH FLASH SPINNING APPARATUS FOR NONWOVEN FIBROUS SHEET MAKING Filed April 6, 1967 6 Sheets-Sheet 4.

Dec. 22, 1970 J. G. SMITH 3,549,453

FLASH SPINNING APPARATUS FOR NONWOVEN FIBRQUS SHEET MAKING Filed April 6, 1967 6 Sheets-Sheet 5 Dec. 22, 1970 J. a SMITH 3,549,453

FLASH SPINNING APPARATUS FOR NONWOVEN FIBROUS SHEET MAKING Filed April 6, 1967 e Sheets-Sheet s United States Patent O 3,549,453 FLASH SPINNING APPARATUS FOR NONWOVEN FIBROUS SHEET MAKING James Gerald Smith, Newark, Del., assignor to E. I. du

Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware Filed Apr. 6, 1967, Ser. No. 628,872 Int. Cl. B29j 5/00 US. Cl. 156-370 8 Claims ABSTRACT OF THE DISCLOSURE A flash-spinning apparatus for use in making nonwoven fibrous sheets including an L-shaped solution supply tube, a spinning orifice and a position-adjustable rotary deflector. Polymer solution under high temperature and pressure is supplied to a vertical arm of the tube and flash-spun through the orifice on a horizontal arm to produce a plexifilamentary strand. The deflector is positioned to receive the strand from the orifice and direct it toward a collection surface while simultaneously spreading it into a web and causing it to oscillate.

BACKGROUND OF THE INVENTION This invention relates to apparatus for use in the preparation of nonwoven fibrous sheets of synthetic organic polymers. It is more particularly directed to apparatus for flash-spinning a polymer solution to make a plexifilamentary strand, spreading the strand into a planar web and directing the web toward a surface where it is collected in the form of a nonwoven fibrous sheet.

In the preparation of fibrous nonwoven sheets various methods and apparatus have been developed for dispersing the filaments from a bundle into a wide band and for directing the strand by oscillating means in a programmed manner to various locations across the width of a moving collecting surface. For example, in Steuber, US. 3,169,- 899, an apparatus is described for spreading and directing a stream of flash-spun polymer and solvent gas by utilizing the combined action of an expanding solvent gas and a curved baflle. The curved baflle serves to spread the web. The oscillating motion serves to direct the web to various areas across the width of a moving collecting belt. A randomly deposited fibrous nonwoven sheet is thereby obtained.

Similarly various baflles have been devised to handle melt spun fibers. For example in Frickert US. 2,736,676 several methods are described for directing glass fibers by the use of wobble plates or by deflection from the perimeter of a cylinder rotating about an axis other than the longitudinal axis of symmetry and oriented at a small angle relative to the axis of symmetry.

The flash-spun strands used in the Steuber sheet are prepared by the method of Blades and White US. 3,081,- 519. The strands exist as three-dimensional networks otherwise known as plexifilaments. The plexifilaments are composed of film-fibril elements which are on the average less than 4 microns thick and which are interconnected at random points along and across the length of the strand. Because of the light weight of the filmfibril elements and because of the high velocity gas flow created by the evaporating solvents, difficulty has been encountered in developing uniform sheets and in making adjustments during spinning. Additional problems have arisen in spinning into a closed chamber, this type of spinning being desirable for recovery of the solvent and re-use. In particular, removal of a spinneret for cleaning 3,549,453 Patented Dec. 22, 1970 p CC or adjustment of the distribution pattern of the web flowing from the bafile has been very time consuming and costly. In addition, opening of the cell by the operator causes disruption of the aerodynamic flow, and allows the solvent to escape or allows air to flow into the cell, thereby diluting the solvent before recovery. Loss of solvent is, of course, expensive, and dilution is undesirable because of the difficulties it causes in recovery of solvent by compression-condensation techniques. In addition precise adjustment was diflicult with the prior art apparatus.

SUMMARY OF THE INVENTION In accordance with the present invention, there is provided an apparatus for use in making nonwoven fibrous sheet of organic synthetic polymers, including a spinneret pack and a web deflecting unit. The spinneret pack comprises an L-shaped solution supply tube adapted to fit in the ceiling of a spinning chamber or cell in a generally upright position. That is, the supply tube fits in the cell with its long arm in a generally vertical position and its short arm in a generally horizontal position. The tube is adapted to receive a supply of polymer solution under pressure in the upper portion of its vertical long arm. At the outer most end of the said arm is an extrusion orifice through which the solution is flash-spun to form a plexifilamentary strand.

The web deflecting unit comprises a rotary webdeflector, means for rotating the webdeflector, and structure for supporting the web-deflector. The web-deflector is disposed so as to receive the plexifilamentary strand directly as spun in a horizontal direction from the orifice. The axis of rotation of the deflector is generally parallel to but spaced from the axis of the orifice. The surface of the web-deflector is contoured so as to simultaneously spread the strand into a planar web, direct the web into a generally vertical plane downward toward a collecting surface, and cause the web to oscillate in said plane as the deflector rotates. The structure for supporting the web-deflector includes positioning means for establishing the transverse distance between the axis of rotation of the deflector and the axis of the spinneret orifice.

In the preferred embodiment of the invention the transverse positioning means is remotely actuated. Thus the position of the deflector relative to the orifice and consequently the laydown pattern of the web can be varied during spinning. Also in the preferred embodiment the support structure for the web deflector also includes positioning means for establishing the vertical distance between the axis of rotation of the deflector and the axis of the spinneret orifice, as well as positioning means for establishing the longitudinal distance between the orifice and the deflector.

Further, in the preferred embodiment, the support structure for the web deflector is rigidly attached to the long vertical arm of the L-shaped solution supply tube. This provides a modular assembly which can be placed in and removed from .the ceiling of a spinning cell as a unit. As will be seen from the discussion which follows, this permits removal of the apparatus for cleaning or other servicing or for adjustment of the laydown pattern of the webs without greatly disrupting the flow of gases within the cell and without allowing solvent to escape or air to flow into the cell. It is sometimes desirable, however, to remove the spinneret pack from the modular assembly without dismantling the web deflecting unit. For this reason, in one embodiment, means are provided for separately supporting the web-deflecting unit while the spinneret pack is dismantled.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an elevation showing one of the flash-spinning units of the invention including a rigid support plate, a spinneret pack assembly and a rotary web deflector assembly. The ceiling of the spinning chamber is shown in cross-section.

FIG. 2 is the side view of the flash-spinning unit as seen from the right side of FIG. 1.

FIG. 3 is a top view of the flash-spinning unit of FIG. 1 shown partially in cross-section.

FIG. 4 is an elevational view in cross-section showing the rotary deflector assembly, the center line adjustment mechanism, part of the spinneret pack assembly and a multi-needled ion gun.

FIG. 5 is a side view, partially in cross-section of that portion of the spinning unit shown in FIG. 4. In the left hand portion of the figure the pitch circles for gears and pinions in the drive mechanism for a rotating annular target plate are shown.

FIG. 6 is a drawing showing a U-shaped ion gun used to apply an electrostatic charge to the plexifilamentary strand.

FIG. 7 shows a support plate for one of the integral flash-spinning units.

DESCRIPTION OF THE PREFERRED EMBODIMENT A general view of the apparatus is shown in FIGS. 1, 2, and 3. The apparatus shown is an integral flash-spinning unit, including a spinneret pack and a web deflecting assembly. The spinneret pack comprises L-shaped solution supply tube 10 and spinneret orifice 12. The web deflecting assembly comprises rotary web deflector 14, vertical positioning means 16, longitudinal positioning means 18, and transverse positioning means 20.

The unit fits in a hole 99 in ceiling structure 28 of a closed spinning cell. Principal support and alignment of the unit are provided through attachment block 110 which is mounted on the upper end of the supply tube 10 and which is connected by means of bolts through holes 107 to a fixed mounting block, not shown. Hole 99 is closed and sealed by means of plate 26 and gasket 30.

The spinneret pack fits in hole 101 in plate 26. Welded to the upper end of L-shaped solution supply tube 10 is a flange 22. Flange 22 and gasket 24 seal hole 101 in plate 26. Other holes in plate 26 are provided for auxiliary equipment, to be described, and these holes likewise are closed by flanges and sealed by gaskets.

From the description thus far it will be seen that the entire flash-spinning unit can be removed from hole 99 of the spinning cell merely by removing the bolts in holes 107 and lifting by a hoist connected to a hook (not shown) bolted to plate 26. Thereafter the deflecting assembly can be separately supported from plate 26 and detached from the spinneret pack; the spinneret pack can then be removed separately through hole 101 in plate 26. The operations involved in removing the unit from the spinning cell will be described in subsequent paragraphs.

L-shaped solution supply tube 10 comprises a vertical mounting arm and a tapered horizontal spinning arm 34. Inside the supply tube 10 is an L-shaped central passageway which teminates in single spinneret orifice 12 at the outermost end of spinning arm 34. Solution is supplied to the upper end of the central passageway through port 32 in attachment block 110. The central passageway in the vertical arm carries a tubular screen filter which may be removed through cover 102. The vertical mounting arm also has an annular passageway for steam or other heating fluid which communicates at the upper end with port 106 in attachment block 110.

Horizontal axis 36 of orifice 12 coincides with the axes of two generally conical bodies which are part of arm 34 and are aligned end-to-end, becoming progressively smaller from left to the extreme right where the orifice 12 is situated. The tapered design of arm 34 is provided to give minimum resistance to the flow of gases in the spinning cell which are entrained by the expanding solvent gases at the spinneret orifice. The conical bodies referred to above, besides the central passageway for polymer solution, also have ports for heating fluid communicating at one end with the annular passageway in the vertical mounting block and at the other end with heating fluid return line 104.

Return line 104 in turn communicates with a port 108 in attachment block 110. Ports 32, 106, and 108 terminate in a common surface of block 110. This surface is machined to mate precisely with a similar machined surface of a mounting block, not shown.

A pressure transducer 94 for indicating pressure in the spinning arm 34 is supported in hole 96 in plane 26 (FIG. 3). The lower end of this device is a pressure transmitting tube 98 attached to a fitting 100 which is attached to a pressure let-down chamber in the spinning arm 34 just ahead of orifice 12, this being shown in FIG. 1.

The spinneret pack is described in greater detail in US. application of James G. Smith, Ser. No. 628,888, filed simultaneously herewith. The entire disclosure of said Smith application is hereby incorporated by reference.

Directly beneath the flange 22, are vertical plates 38 which are welded to the outside of the L-shaped solution supply tube 10; the face 40 of the plate 42 is generally at right angles to the axis 36 and forms a mounting surface for a bracket 44 which is secured to the face 40 by means of screws. On its right side, the bracket 44 has two horizontal lugs 46, 48 which project to the right and support two vertical cylindrical rods 50 which are part of the vertical adjustment device 16. Slidably mounted on the rods is a vertically sliding head 52 which is positioned by means of opposed screws 54 located midway between the two rods 50 (FIG. 3), running through vertical holes in the lugs 46, 48 and threaded into head 52. Bolted to the head 52 is a right-angle bracket 56 (FIG. 1) the lower face of which is provided with lugs, rods, and screws which form the longitudinal adjustment device 18, carrying the crosshead 58 in a direction parallel to the axis 36.

Housing 60 contains the drive mechanisms for the transverse positioning device 20, the rotating web deflector 14, and rotating annular target plate 62. As shown, axis 64 of web deflector 14 is parallel to but offset from axis 36 of spinneret orifice 12 so that the stream of polymer and fluid issuing from the orifice impinges on the lower portion of the deflector and is diverted downward. Attached to housing 60 by means of bolts 66 are insulated support arms 68 for U-shaped ion gun 70. Housing 60 supports a scraper device 109; the blade of the scraper device contacts the front surface of the target plate 62, preferably at the top of the plate, and keeps the plate free of any polymer residue build-up. A vacuum system or other device (not shown) is provided to remove any debris scraped from the target plate 62.

Target plate 62, ion gun 70, and associated equipment are described in greater detail by reference to FIGS. 4, 5 and 6. Aluminum housing 72 for ion gun resistors is provided with a threaded hole 74 to receive a jack for supplying high voltage direct current to the gun 70. The current is supplied through cable 76 and porcelain insulated connector 78 as shown in FIG. 2. Connector 78 is supported in round hole 80 in plate 26. Rectangular hole 82 in plate 26 is used for various insulated electrical input and output lines, the plugs for these being supported by plate 84. The plugs and corresponding cables are shown in FIGS. 2 and 3. Power for target plate motor 71 is carried in plug and cable 86, power for web deflector motor 33 is carried in plug and cable 88, and power for motor 43 driving the transverse positioning device 20 is carried in plug and cable 90. The output signal for a differential transformer (see discussion below of FlGS. 4 and 5) is carried through cable and plug 92.

Referring to FIGS. 4 and 5, the longitudinal positioning device :18 comprises two lugs 11 and 13, two horizontal cylindrical rods 15, opposing screws 17, and crosshead 58. Lugs 11 and 13 are integral with a plate welded to the bottom of brackets 56. Rods 15 and screws 17 are supported in lugs 11 and 13. Crosshead 58 is free to slide on rods 15 in a direction parallel to axis 36, but is positioned by means of screws 17.

Lugs -19 are integral with the crosshead 58 and carry parallel, horizontal rods 21 which, in turn, support yet another crosshead 23 on a plurality of commercial ball bushings 25 all of which comprise a part of the transverse positioning device 20. The ball bushings 25 provide for essentially frictionless motion of the crosshead 23, and members are supported therefrom, in a direction at 90 to the axis 36. This device differs from the other two positioning means in that a motor drive (to be described) is provided.

Crosshead 23 is made of a massive block of metal on the underside of which is secured the upper flat plate 27 of housing 60. One end of the housing is closed with a plate 29 having a large circular opening in its lower portion, which plate is adapted to receive the flange 31 of a motor 33 which is secured to the plate with screws 35. From this it may be seen that the axis of rotation of the motor is parallel to the axis 36 of the spinneret. The shaft of the motor extends outwardly of the housing 60 and carries a shaft extension 37, on which is mounted the rotary deflector 14. Part of the shaft extension 37 passes through two seal members 39, preventing any ingress of fluids to the motor 33 or to the interior of the housing 60. Similarly, an O ring seal 41 is provided under the flange 31.

In the upper part of the housing 60 is a small motor 43 which is flange'mounted and coupled to a worm and worm wheel type speed reducer 45, the output shaft 47 of which extends vertically through the plate 27 where two seal members 49 are provided. The shaft 47 is joined to another shaft 51 which is journalled in the crosshead 23; at its upper end the shaft 51 carries a disc 53 on which is a crankpin 55. The crankpin 55 carries a connecting rod 57 the opposite end of which is anchored or pivotally mounted on a vertical pin 59 in the underside of the crosshead 58. From the foregoing it will be seen that rotation of the motor 43, transmitted through the speed reducer 45, will result in slow speed rotation of the shafts 47 and 51, and crankpin 55 which, being anchored by the connecting rod 57, will cause the crosshead 23 to move horizontally on the ball bushings thereby causing the entire housing 60, the motor 33 and rotary web deflector 14 to move slowly back and forth from side-toside (as viewed in FIG. 5) Le. transversely whenever the motor 43 is energized. In practice the motor is energized only for a brief moment while the assembly is moved either to the left or right.

For purposes of remote indication and control of the position of the above-described housing 60, motor 33, rotary deflector 14 as well as other apparatus on the housing a position sensing device 61a and 61b comprising a linear variable differential transformer is provided; the body 61a of this, comprising an electrical coil, is secured to the top of the crosshead 23 by means of the clip 63; slidable endwise within the coil is a metal core 6112 which extends outwardly from one end of the body 61a, which is secured to the lug 19' on the crosshead 23. Thus, the core 611: stands still while the body 61a is moved whenever the crosshead 23 is moved by the position device 20. Electrical leads (not shown) from the coil in body 61a are connected to external circuits through plug and cable 92 (FIGS. 1, 2., and 3). The position is determined by use of a calibrated chart for transformer output versus transverse distance between axis 36 and axis 64.

The target plate 62 is rotatably mounted on a tubular shaft 67 which is carried in ball bearing 65 which, in turn, are mounted inside the stationary ring 69. The ring 69 extends outwardly from the housing 60 and is secured to the plate 29 by bolts not shown. Inside the housing 60 is a small slow-speed motor 71, which is secured to the plate 29; the motor body and the shaft are sealed in the housing 60 in the same manner as the motor 33; the motor 71 carries a small pinion 73 which meshes with a gear 75 on stationary jackshaft 77. Secured to the gear 75 is a small pinion 79, which meshes with a large gear 81 secured to the rearward end of the tubular shaft 67. From this it will be seen that the motor 71 will drive the target plate 62 at a very low rate, for example at 2 revolutions per minute. To assure electrical grounding of the target plate 62 a carbon brush 83 is urged against the back of the plate 62 by a spring 85 and both are mounted in a hole in the stationary ring 69. A sheet metal guard 87 covers the gear train. As may be seen in FIG. 4, the target plate 62 is threadedly engaged in the tubular shaft 67 and consequently may be removed without the necessity for disassembling any other members.

Referring to FIG. 4, a multi-needle ion gun 70 is situated in proximity to the spinneret orifice 12 and the target plate 62. As shown in FIG. 6 the ion gun is U-shaped. It carries a number of needles 89 with pointed ends as shown in FIG. 4. The needles are each connected to a high voltage power supply to promate corona discharge between the points and the annular target plate 62.

The ion gun 70 (FIG. 6) comprises a tabular conductive sheath 91 with numerous ports 95 along its length. At each end of the tubular U-shaped portion is a cylindrical sheathed resistor housing 72 made of electroconductive material. The entire structure is supported and electrically insulated by means of a pair of arms 68 and 93 which are made of insulating material. The arms 93 are each secured to the ion gun sheath 91 by means of epoxy cement; the arms 68 are at to the respective arms 93 being secured thereto by means of screws in holes 97. The arms 68 are thus parallel to each other and straddle the housing 60 being secured to brackets on each side of the housing (FIG. 5) by means of bolts 66.

The lower portion of the U-shaped sheath 91 is fabricated from aluminum having an oval cross-section as shown in FIG. 4.

As shown in FIG. 6, in the lower portion of the sheath 91, spaced from each other with a chordal distance of about 0.965 cm. (or 710 angular spacing) are holes or ports 95 each occupied by an insulative tubular insert. Extending through the center of each insulative insert is a corona generating point (needles 89 in FIG. 4) which is connected to a separate insulated wire conductor. Each wire conductor is connected to a separate resistor located in resistor housing 72. The axes of the points 89 are generally at right angles to a plane running through the left hand face of the tubular sheath 91 as seen in FIG. 4. The axes of the points are also perpendicular to the planar surface of the target plate 62. The points 89 are adjusted, so that they are sharp, conical ends are equi-distant from the surface of the target plate 62, being spaced therefrom by about 1.3 cm. The ion gun is oriented so that the points are aimed at an imaginary curve (a semi-circle) situated about 1.3 cm. from the edge of the target plate. The entire interior of the sheath 91 is filled with epoxy resin (Armstrong EG-OOl, R. Hardener) to retain the inserts and for other purposes described further below.

Each wire conductor is insulated along its length from the corona generating point to the resistor. The wires pass upwardly through the legs of the tube 91 into the confines of one of the aluminum resistor housings 72 where each wire is joined to one terminal of its respective resistor, the resistance of these being substantially equal and being in the range of 10 to 1000 megohm. The resistor housing 72 is provided with a threaded hole 74 to receive a jack for supplying high voltage direct current to the gun. The conductive sheath 91 is electrically connected to the power source and in addition each needle is connected through a resistor to this source.

The ion gun is supported and electrically insulated from the remaining parts of the apparatus by insulative support arm 93, which are in turn attached to the ion gun by an epoxy cement. Bolts through holes 97 are used to attach insulated support arms 93 to insulative rigid supports 68. One insulative support 68 is shown in FIG. 1. These supports are attached to housing 60.

In operation the annular target plate 62 is grounded and the distance between the points 89 and the target 62 together with the voltage are adjusted to promote corona discharge, this being readily apparent from a glow in the dark. The voltage between the power source at jack hole 74 and the grounded target electrodes is usually between 25 and 150 kilovolts, preferably about 45 kilovolts.

The protective tubular sheath 91 on the ion gun has a beneficial effect in extending the life of the ion gun. The voltage drop from the bus bar in the resistor housing 72 to the corona generation points 89 is only 3 to 5 kilovolts. The voltage drop between the tubular shield 91 and the wires leading to the corona generating points 89 is likewise only 3 to 5 kilovolts. The ion gun is more fully described in US. application of Rapp Wallace Crook III, Ser. No. 628,983, filed simultaneously herewith.

In operation of the flash-spinning unit a spinning solution is continuously provided at constant temperature and pressure through a valve (not shown) located to the right of attachment block 110 as shown in FIG. 2. Integral with the valve is a rigid mounting block (not shown) which is adapted to mate precisely with the machined surface 103 of attachment block 110. A conduit for polymer solution in the valve mounting block communicates with port 32 in attachment block 110. Passageways are provided in the body of the valve and also in the mounting block for circulation of heating fluid and these communicate with ports 106 and 108 in attachment block 110. The entire flash-spinning unit is supported principally by bolts in holes 107 as shown in FIG. 1. These bolts pass through the attachment block 110 and screw into the mounting block (not shown). Proper alignment of the flash-spinning unit is assured by mating of guides provided in attachment block 110 and the mounting block, the latter being an integral part of a valve which is accurately positioned on ceiling structure 28.

The solution typically is to 14% linear polyethylene in trichlorofluoromethane (Freon 11). It is provided at a temperature of about 185 C. and a pressure of about 1600 p.s.i.g. Within the central passageway of the L- shaped solution supply tube 10 the solution is filtered and passed through a first orifice into a pressure let-down chamber where the pressure is about 800 to 1100 p.s.i.g. The pressure in this chamber is measured by means of a pressure sensing unit in fitting 100. The pressure is transmitted through a flexible mercury capillary tube 98 to a pressure transducer 94. The solution supply tube is steam heated throughout its length using saturated steam at about 185 C. which passes through separate chambers throughout the length of both arms of the L-shaped solution supply tube 10.

The flash spinning unit which has been described is of course intended for use with other similar or identical units positioned above a moving collection surface. The webs from the individual units are deposited on the surface in multi-directional, overlapping layers to form a fibrous nonwoven sheet.

The collection surface is preferably an endless conductive belt trained to run about conductive rolls mounted in a conductive frame. The frame, rolls and belt are all electrostatically charged, the charge being opposite to the charge on the webs, whereby the webs are pinned to the belt surface. The preferred charged frame laydown machine is described in greater detail in US. application of Owens and Scheinberg, Ser. No. 628,870, filed simultaneously herewith. The entire disclosure of the Owens and Scheinberg application is incorporated by reference.

As described in the Owens et a1. application the laydown machine and the flash-spinning units are preferably enclosed in a chamber or cell having an atmosphere consisting essentially of the solvent (e.g. trichlorofluoromethane) used for spinning. The flash spinning units are disposed in two parallel rows, extending diagonally substantially the full length of the laydown belt and one-half the width of the belt. The direction of spinning, i.e. the direction of flow of freshly spun polymer at orifice 12, is parallel to the longitudinal axis of the laydown belt, but opposite to the direction of movement of the belt. In each row successive units are offset slightly so that each row extends diagonally across one-half the surface of the laydown belt; the first unit in one row is located in approximately the rear center of the laydown machine and the last unit of the other row is located in approximately the front center of the machine, considering the direction of belt travel to be from the rear to the front of the machine. In FIG. 1 the rear of the machine is to the right. The longitudinal and transverse distances between successive spinneret orifices in a given row can of course vary greatly depending upon the sizes of the units, the amount of overlap desired, and numerous other variables; typically, however, these distances can be on the order of one yard and four inches, respectively. The transverse distance between orifices in adjacent rows will also of course depend on numerous variables, but will typically be on the order of one to 1% yards. The total number of units employed will of course depend on the width of sheet and the amount of overlap desired, as well as on other factors.

Because of the close spacing between the two rows of flash spinning units it is necessary to have the supply valves, mounting blocks, and attachment blocks on the left hand side of the unit for the left hand row and on the right hand side for the right hand row. The unit shown in FIGS. 1-3 is termed a right hand unit because the attachment and mounting blocks are on the right of the unit as viewed from the rear of the laydown machine. FIG. 7 shows a support plate 26 for a left hand unit. As will be observed from the position of holes 96 and 80, the auxiliary equipment, i.e. pressure transducer 94 and insulator 78, as well as the attachment block 110, are located on the left side of the unit for a left hand unit.

After the webs are deposited, the belt passes under a cold consolidation roll which lightly compacts the sheet. It is important for most applications that the sheet be as uniform as possible in basis weight, thickness, and opacity. The positioning devices in the support structure for the web deflecting assembly are provided so that uniformity of the sheet can be maximized, as described below.

Prior to start-up of the unit, positioning devices 16 and 18 are used. While these could be remotely operated during spinning, this is not usually necessary. The vertical positioning device 16 is adjusted to place the web deflector hub rim just above spinning orifice 12. The edges of the orifice must not overlap the hub rim, or deposits and fouling will occur. On the other hand, the web deflector hub rim should not be too far above the orifice, or insufficient spreading of the network will occur.

The longitudinal positioning device 18 is fixed before the unit is inserted into the cell so that the face of the deflector hub clears the face of the spinneret at the orifice 12. The deflector hub should be as close as possible to the spinneret orifice to promote optimum spreading without scraping the spinneret.

During operation, the transverse positioning device can be remotely actuated to move the axis 64 of deflector 14 to the right or left of the axis 36 of spinneret orifice 12. Considering FIG. 1, if the web deflector 14 is moved to the left of orifice 12 (upward out of the plane of the paper as viewed from the rear as seen in FIG. 2 of the laydown machine) the web will be directed more to the right as it passes to the collection surface; movement of the web deflector 14 to the right (downward beyond the 9 plane of the paper as viewed from the rear of the laydown machine), will of course have the opposite effect, i.e. the web will be directed more to the left. It should be understood that in each case the web is continuously oscillating and it is the center of oscillation that is changed by this maneuver.

After the sheet is compacted by passage under the cold roll, it is passed through a beam of radiation. A radiation receptor, which is located on the opposite side of the sheet from a radiation source, transmits a signal proportional to the weight per square area. Measurements are made for several longitudinal strips of sheet located in succession across the entire width of the sheet. The output of the scanning device is fed to a computer which integrates the information received over a period of time from side-by-side strips of the same length. Information is also fed to the computer from sensing device 61 concerning the location of the crosshead 23 on horizontal rods 21 for each flash spinning unit. The computer then determines what adjustment, if any, should be made in the distance between the centerline of the rotary deflector 14 and spinneret orifice 12 for each unit in order to obtain a maximum area of nonwoven sheet with uniform weight per unit area. Adjustments in the deflector positions prescribed by the computer are then carried out by an operator or optionally by automatic controls activated by the computer.

As pointed out in previous paragraphs, the modular construction of the apparatus of the invention permits rapid removal and/or replacement of an entire integral flash spinning unit. For example, if deposits have accuulated in the spinneret pack assembly or if the orifice has become fouled by deposits, the unit may be replaced rapidly by a refurbished unit. Likewise, problems with the deflector-positioning assembly, ion gun, target plate, pressure sensor, or any other part may be serviced by removal of the entire unit.

In order to remove the entire integral flash-spinning unit from the ceiling of the spinning cell, the solution supply is shut off at a valve not shown and the steam supply is likewise shut off. In addition, electrical connectors are removed from each of the connections 86, 88, 90, and .92 shown in FIGS. 1, 2, and 3. The high voltage is shut off and the high voltage cap is disconnected from insulated connector 78. The electric cable is disconnected from pressure transducer 94. All of these operations can be completed in a few minutes.

Next a chimney having the shape of supporting plate 26 is fitted around the integral flash-spinning unit. The chimney is attached to the upper surface of the ceiling prior to removal of the unit to minimize the entrance of air. The chimney is high enough to contain the entire lower part of the integral flash-spinning unit, i.e. the portion hanging below support plate 26. It fits closely to plate 26 but still permits free movement up and down. Since the trichlorofluoromethane gas in the spinning cell is denser than air and since the pressure at the top of the cell is kept at atmospheric pressure, very little of the gas can escape during removal or replacement of the flashspinning unit. A crane is attached through an eye bolt or hook (not shown) bolted to plate 26 with the eye of the bolt or hook located above the center of gravity of the unit. For the unit depicted in the drawings the center of gravity is located approximately above and between vertical shafts 50 shown in FIG. 3. After a crane has been activated to lightly support the weight of the integral unit, bolts in holes 107 are removed. After making certain that all complex and connecting equipment have been disconnected the integral flash-spinning unit is lifted up through the chimney. As the bottom of the unit clears the ceiling of the spinning chamber a limit switch is activated and the resulting signal causes a sliding door to move automatically over the opening in the ceiling to 10 close the opening. Similar sliding doors are provided for each of the openings.

The operations are simply reversed for inserting a new unit into the spinning chamber. If the new unit is lowered through the shaped chimney it activates a limit switch which opens the sliding door. The unit comes to rest on gaskets 30, which seal the entire port in the ceiling. The crane lightly supports the unit while bolts through holes 107 are attached to the mounting block. After all of the electrical and other attachments have been replaced the unit is started up by opening valves upstream to permit entry of saturated steam. Valves upstream may be provided also to permit use of fluids other than the solution to pressurize the solution supply 10. After starting fluids have been pressurized, solution may be started through the solution supply tube 10.

The rapid removal of the unit is greatly facilitated by the unit constructionof the attachment block and by the matching fittings of the mounting block. The flat face 103 on attachment block 110 matches a similar face on the mounting block (not shown). The face carries grooves for O-ring gaskets all of which are compressed when the mounting bolts are tightened.

Once the flash-spinning unit has been removed from the spinning chamber, it may be serviced in any way needed. It should be pointed out that after removal from the chamber the pack assembly may be serviced without dismantling the deflector assembly. A suitable attachment may be provided between bracket 56 and supporting plate 26 to hold the deflector assembly in place during the oper ation. Supporting pins may be provided, for example, to be inserted during the servicing operation. After properly supporting the web deflecting assembly it is separated from the spinneret pack by removing bolts 111 (FIG. 4) between plate 42 and a plate attached to bracket 44. After removal of bolts 111 the solution supply tube 10 may be lifted away from the deflector assembly by a crane attached to an eye bolt screwed into a threaded socket in cap 102. When the L-shaped tube is replaced, it rests on gaskets 24 (FIG.'1). The bolts 105 are used only during installation of the entire unit in the spinning cell. They act as clamps during this operation but are later released so that the plate 22 rests on gaskets 24 without clamping during operation of the unit. The exact level and orientation of the spinneret pack assembly is of course governed by the accurate positioning of attachment block to the valve (not shown).

The web deflector 14 and target plate 62 which are preferred for use in this invention are described in detail in, respectively, Pollock and Smith US. application Ser. No. 628,871 and Kilby and Smith US. application Ser. No. 628,868 and now US. Patent No. 3,456,156, both filed simultaneously herewith. The entire disclosures of both of these applications is hereby incorporated into this disclosure. 1

While only one form of the apparatus has been shown in the drawings it is obvious that numerous variations are possible using the principles of the invention. Each of the adjustments may be automated. As a minimum, the apparatus should be provided with remote control for adjusting the amount of network deflection to the left or right as it is deposited on the collecting belt. Numerous methods are available for cleaning the rotating annular target plate during operation. If a scraper is provided, the scrapings may be removed by use of a vacuum tube. The scraper obviously can be pressurized by means of a gas pressure, fluid pressure or by springs.

I claim:

1. An apparatus for use in making nonwoven fibrous sheets of organic synthetic polymers including a spinneret pack and a web deflecting assembly;

the spinneret pack comprising an L-shaped solution supply tube (10) adapted to fit in the ceiling (28) of a spinning chamber and to receive a supply of polymer solution under pressure through its generally vertical long arm and fitted withia horizontally oriented extrusion orifice at the outermost end of its generally horizontal short arm through which the polymer solution is flash spun to form a plexifilamentary strand;

the web deflecting assembly comprising (A) a rotary web deflector (14) disposed so as to receive the plexifilamentary strand directly as spun in a horizontal direction from the orifice (12), the'axis of rotation of saiddeflector (14) being generally parallel to but spaced from the axis (36) of said orifice (12), the surface of said web' deflector (14) being contoured so as to simultaneously spread said strand into a planar web, direct the web into a generally vertical plane downward toward a collecting surface, and cause the web to oscillate in said plane as said deflector rotates, (B) means for rotating said web deflector (14), and (C) structure for supporting said web deflector (14) includingpositioning means (20) for varying the transverse distance between said two axes (36 and 64).

2. An apparatus as defined in claim 1 wherein the support structure for said web deflector (14) also includes positioning means (16) for establishing the vertical distance between said two axes (36 and 64) and positioning means (18) for establishing the longitudinal distance between the orifice (12) and the deflector 14).

3. An apparatus as defined in claim 1 wherein said transverse positioning means (20) is remotely actuated whereby the position of said deflector 14) relative to said orifice (12) can be varied during spinning.

4. An apparatus as defined in claim 2 wherein said transverse positioning means (20) is remotely actuated 12 whereby the position of said deflector (14) relative to said orifice (12) can be varied during spinning.

5. An apparatus as defined in claim 1 wherein the support structure for said web deflector (14) is rigidly attached to the long arm of the L-shaped solution supply tube, thereby providing a modular assembly which can be placed in and removed from the ceiling (28) of a spinning cell as a unit. 7

' 6. An apparatus as defined in claim 5 wherein the web deflecting assembly includes means for separately supporting said web deflector 14) and wherein the web deflecting assembly is separable from the spinneret pack.

7. An apparatus as defined in claim 4 wherein the support structure for said Web deflector (14) is rigidly attached to the long arm of the L-shaped solution supply tube, thereby providing a modular assembly which can be placed in and removed from the ceiling (28) of a spinning cell as a unit.

8. An apparatus as defined in claim 7 wherein the web deflecting assembly includes means for separately supporting said web deflector (14) and wherein the web defleeting assembly is separable from the spinneret pack.

References Cited UNITED STATES PATENTS SAMUEL FEINBERG, Primary Examiner US. Cl. X.R. l56-380

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