US3230747A

US3230747A - Cascade washing apparatus

Info

Publication number: US3230747A
Application number: US308883A
Authority: US
Inventors: Richard L Leonard; Thomas B Truscott; Thomas M Veazey
Original assignee: Monsanto Co
Current assignee: Monsanto Co
Priority date: 1963-09-13
Filing date: 1963-09-13
Publication date: 1966-01-25
Anticipated expiration: 1983-01-25
Also published as: GB1076418A; IL22025A

Description

1966 R. LEONARD ETAL 3, 30,747

CASCADE WASHING APPARATUS Filed Sept. 15, 1963 FIG.|

INVENTORS R.L. LEONARD T. B. TRUSCOTT T. M. VEAZEY 32mg MA ATTORNE.

United States Patent F 3,230,747 CASCADE WASHING APPARATUS Richard L. Leona d; Thomas B. Truscott, and-Thomas M.

Veazey, Decatur, Ala., assignors t0 Monsanto Company, a corporation of Delaware Eiled'Sept. 1 3, 1963, Ser. No. 398,883 1 Claim. (l. 68-43) The present invention relates to the washing of synthetic fibers and more specifically to the stripping of a tow as it pases along a cascade.

In the wet spinning process of making synthetic fiber, a dope which consists of a polymer and a solvent is extruded through spinnerettes intoa coagulation bath to form a filamentary tow. The two is then wash relatively free of solvent by hot water traveling down a cascade as the tow is being drawn up the cascade. In order for the tow to be of an acceptable qua-ilty, it must be washed until it is almost completely free of solvent. The wash water clings to the tow forming a boundary layer of water which impedes the rinsing process. This boundary layer is removed in the present invention by stripping the tow. The tow can be stripped by being sharply bent or by being nipped. When the tow is being drawn up the cascade, it is impractical to bend it, therefore a method of nipping the tow is employed. Accordingly, a primary object of this invention is to provide a cascade with a stripper which will effectively remove the boundary layer of wash water from the tow and permit fresh wash water to rinse the tow thereby removing the undesirable solvent.

Another object of this invention is to provide a cascade with a stripper which has a pivotally mounted depressor bar.

A further object of this invention is to provide a cascade with a stripper which forms a weir.

A still further object of this invention is to provide a cascade with a stripper which removes the boundary layer of water from the tow and also guides and aligns the tow.

FIGURE 1 of the drawings isometrically shows a section of the cascade in which a stripper is employed.

FIGURE 2 is a sectional view of the apparatus demonstrating particularly the pivoting movement of the depressor bar and the boundary layer wash water being stripped from the tow.

One embodiment of the present invention contemplates using a depressor bar to force the tow against a stripper bar which removes the boundary layer of wash water from tow thereby more eificiently rinsing the solvent from the tow. After the dope is extruded from the spinnerette and coagulates forming the tow, it is then drawn up the cascade where the wash water removes the undesirable solvent. The tow is drawn between a stationary stripper bar and a pivotally mounted depressor bar. The depressor bar pivots through an arc and forces the tow against the stripper bar. The tow is put under a slight compression and by the friction which is produced between the tow and the stripper bar and the tow and the depressor bar, the boundary layer of water clinging to the tow is stripped. By removing the water forming the boundary layer, the tow can proceed to the next section of the cascade with a reduced solvent concentration. The tow after proceeding between the depressor bar and the stripper bar comes in contact with water backed up by a weir which is formed by the depressor bar and the stripper bar. This backup water through its turbulence swirls around the tow and continues to wash the sol-vent therefrom. This method of nipping the tow is repeated a sufficient number of times along the length of the cascade to reduce the solvent content in the tow to an acceptable level.

The stripper bar is not an absolutely necessary element of the invention and the boundary layer wash water can 3,23%,747 Patentedv Jan. 25', 1966:

be nipped without it but to properly align the tow and to keep the tow from rubbing against the bottom of the cascade, the stripper bar is a very desirable element;

Referring now to the drawings, the wet spinning apparatus and coagulating hath (not shown) have prepared the tow 10, which is the fiber to be washed, to be drawn up the cascade 11'. The cascade 11 extends from the coagulating bath to the drying apparatus (not shown). Relatively pure wash water 12 is supplied .at the upper end of-th-e cascade 11 and is gravity forced down the length of the cascade 11 where it is then drained off. The cascade 11 is in the shape of a trough having a bottom panel 13 and sides 14 and 15' parallel to each other and perpendicular to the bottom panel 13.

Depressor bar guides

16 and 17 are rigidly secured to the top of

sides

14 and 15 respectively, the

depressor bar guides

14 and 15 being provided with slots 18- and 19 which are adapted to receive a pivoting bar 20. The pivoting bar 20 is integrally connected with a depressor bar shaft 21 which is perpendicular to pivoting bar 20 and the depressor bar shaft 2 1 is integrally connected with a depressor bar nipper 22' which is perpendicular to the depressor bar shaft 21 and parallel to pivoting bar 20. The

depressor bar guides

16 and 17 permit the pivoting bar 20 to freely rotate thereby permitting the depressor bar nipper 22 to pivot about an axis which is parallel to its longitudinal dimension.

The stripper bar 23 is rigidly secured to and is per-pendicular to cascade

sides

14 and 15. The depressor bar nipper 22 is parallel to and rests on the stripper bar in the absence of tow 10. When the tow 10 is drawn up the cascade 11 and between the stripper bar 23 and the depressor bar nipper 22 depressor bar nipper 22 contacts the tow 1t) and impinges it against the stripper bar. When the tow 10 touches the stripper bar 23 and the depressor bar nipper 22, the water forming the boundary layer 25 around the tow 10 is broken and is thereby dissipated allowing the wash water 12 to make new contact with the tow 10. For every set of stripper bars and depressor bar nippers, this method of stripping the boundary layer water is repeated thereby permitting the wash water to properly rinse the tow and remove the solvent contained therein.

The stripper bar 23 and the depressor bar nipper 22 form a weir which backs up the wash water 12. As the wash water 12 spills over the depressor bar nipper 22, it produces a turbulence in the back water 24 which helps circulate the wash water 12 around the tow 10 and thereby aids in the rinse.

It is to be noted that the stripper bar 23 and the depressor bar nipper 22 also aid in effecting a better rinse by reducing the concentration of the wash water that forms the boundary layer. By stripping the tow 10, the boundary layer wash water 25 with its high concentration of solvent is prohibited from mixing with the back water 24- which has a lower concentration of solvent. The amount of solvent removed from the tow 11 by each strip-per can be mathematically illustrated by letting X representing the concentration of the solvent in the tow 10 before entering the stripper and letting X represent the concentration of the solvent in the tow 10 after it has been nipped, therefore, X, the quantity of solvent removed by each stripper, can be determined by the formula X =X X The value of X is the quantity of solvent that each stripper prevents from mixing with the wash water on the back water side of the weir. Since the wash water 12 has less solvent intermixed therein, the solvent can be more effectively removed from the tow 10.

The depressor bar nipper 22 by pressing the tow 10 against the stripper bar 23 aligns the tow 10 and keeps it from floating to the surface of the wash water 12. This alignment assures a proper rinse by keeping the tow submerged and by uniformly collimating the tow 10 as it travels up the cascade 11.

While a preferred embodiment of the invention has been disclosed, it is to be understood that changes and variations may be made without departing from the spirit and scope of the invention as defined by the appended claim.

We claim:

Apparatus for continuously stripping the washing fluid forming a boundary layer on the surface of a tow consisting of a bundle of filaments of synthetic material comprising:

(a) a cascade having a bottom portion and side portions secured thereto to thereby form a trough for a Washing fluid;

(b) an elongated smooth surface cylindrical stripper bar mounted in said cascade and extending between said side portions;

(0) a pair of oppositely disposed, slotted bar guides each mounted on a side portion above said stripper bar;

(d) an elongated bar rotatably and removably mounted in said slots with its axis of rotation passing through said slots and extending across said trough;

(e) a depressor bar shaft secured to and revolvable with said elongated bar about said axis;

(f) a smooth surfaced nipper bar secured to and revolvable about said axis with said depressor bar shaft and said elongated bar;

(g) said bar guides and said stripper bar being so related to one another that an arc passing through a point on said nipper bar and having its center coincident vvith said axis of rotation of said elongated bar will also pass through said stripper bar whereby pressure will be applied to a tow moving between and contacting the stripper bar and nipper bar, and the boundary layer of washing fluid thereby stripped therefrom.

References Cited by the Examiner UNITED STATES PATENTS 2,133,535 10/1938 Campolunghi. 2,516,268 7/1950 Spalding 68175 2,665,189 1/1954 Cox 68205 X 2,782,623 2/1957 Coe 68-181 FOREIGN PATENTS 661,941 4/1963 Canada.

25 IRVING BUNEVICH, Primary Examiner.