US3163575A

US3163575A - Doctor blade for differentially creping sheets from a drum

Info

Publication number: US3163575A
Application number: US175737A
Authority: US
Inventors: Bernard D Nobbe
Original assignee: Kimberly Clark Corp
Current assignee: Kimberly Clark Corp
Priority date: 1962-02-26
Filing date: 1962-02-26
Publication date: 1964-12-29
Anticipated expiration: 1981-12-29

Description

B. D. NOBBE Dec. 29, 1964 DOCTOR BLADE FOR DIFFERENTIALLY CREPING SHEETS FROM A DRUM 4 Sheets-Sheet 1 Filed Feb. 26, 1962 a G Lt? it:

DOCTOR BLADE FOR DIFFERENTIALLY CREPING SHEETS FROM A DRUM Filed Feb. 26, 1962 B. D. NOBBE Dec. 29, 1964 4 Sheets-Sheet 2 DOCTOR BLADE FOR DIFFERENTIALLY CREPING SHEETS FROM A DRUM B. D. NOBBE Dec. 29, 1964 4 Sheets-Sheet 3 Filed Feb. 26, 1962 &+ E S awna B. D. NOBBE 3,163,575

DOCTOR BLADE FOR DIFFERENTIALLY CREPING SHEETS FROM A DRUM Dec. 29, 1964 4 Sheets-Sheet 4 Filed Feb. 26, 1962 3,lh3,575 Patented Dec. 29, 1%64 3,163,575 DOCTOR BLADE FGR DIFFERENTIALLY CREPING SHEETS FROM A DRUM Bernard D. Nohbe, Neenah, Wis, assignor to Kimberly- Clark @orporation, Neenah, Wis., a corporation of Delaware 7 1 Filed Feb. 26, 1962, Ser. N 175,737

3 Claims. (Cl. 162-281) My invention relates to papermaking machines and, more particularly, to methods and apparatus for making differentially creped tissue sheets, that is, tissue sheets that have a series of finely creped strips separated by relatively coarsely creped strips.

It has been proposed, in accordance with the teachings of Patent 3,017,317, issued January 16, 1962, to make differentially creped tissue sheets, which may be superposed to make multi-ply pads of such sheets, by utilizing spaced jets of chemical solution applied onto the surface of a papermaking machine drier drum used in conjunction with a creping doctor for creping the tissue from the drum. The chemical solution is such that the paper tissue readily releases from the surface of the drum and it therefore is not substantially creped along the paths provided by these jets, so as to provide the sheets that are finely creped between these paths and relatively coarsely creped along the paths.

It is an object of the present invention to provide an improved method and apparatus for differentially creping paper tissue from a drier drum that do not require the use of such chemical drier release agents. More particularly, it is an object of the invention to provide an improved doctor blade for such a drier drum that has a plurality of spaced notches in it so that the unnotched portions of the blade crepe the tissue from the drum in a certain manner and the notched portions of the blade crepes the tissue from the drum in still another manner to provide the series of alternate finely and coarsely creped strips in the tissue.

The invention consists of the novel constructions and methods to be hereinafter described and claimed, for carrying out the above stated objects, and such other objects, as will be apparent from the following description of preferred embodiments of the invention, illustrated with reference to the accompanying drawings, wherein:

FIG. 1 is an elevational view of the dry end of a papermaking machine of the Yankee type, including a Yankee drier drum and a doctor blade for creping paper from the drum;

FIG. 2 is a fragmentary end elevational view of the papermaking machine;

FIG. 3 is a fragmentary sectional view on an enlarged scale of the blade andthe associated assembly;

FIG. 4 is a fragmentary end view of the doctor blade on a still further enlarged scale;

FIG. 5 is a fragmentary side view of the doctor blade taken from the line 5-5 of FIG. 4;

FIG. 6 is a fragmentary cross sectional view, on a still further enlarged scale, of the doctor blade taken on line 66 of FIG. 5;.

FIG. 7 is a view similar to FIG. 6 and taken on line 77 of FIG. 5;

FIG. 8 is a perspective view of the crepedtissue sheets produced by the doctor blade assembly with the sheets being superposed one on another to form a pad;

FIG. 9 is a view similar to FIG. 4 of a modified form of doctor blade; and,

FIG. 10 is a fragmentary side view of the FIG. 9 form of blade taken from the line 1ti1ti of FIG. 9.

Like characters of reference designate like parts in the several views.

' United States Patent Ufihce Referring now'to the drawings and, in particular, to FIGS. 1 and 2, there is illustrated fragmentarily a typical Yankee type paper machine, particularly the dry end of the machine which includes a drier drum It). The drum is supported by a supporting frame 11 resting on a suitable foundation 12. The wet paper web 13 is adapted to be applied to the outer surface of the drum having its edges 14 spaced a few inches, such as about 6 or 7 inches, from the edges of the drum and being dried by the drum during a single revolution thereof.

The drum includes a generally cylindrical shell 15 Which is fixed to heads 16. The shell 15, as well as the heads 16, may be made of cast iron which is a conventional material for Yankee driers. The drum is mounted for rotation by means of end shafts 17 disposed in bearings 18 secured tothe frame 11. The drum is rotated by a conventional driving mechanism (not shown) which is attached to one of the shafts 17.

The drum it? has steam supplied to it byv conventional connections for heating the drum to dry the web 13, and additional heat for drying the web on the surface of the drum is provided by a heated hood 19 secured to the frame 11 and extending around the upper portion of the drum 1t Suitable hot air inlets and outlets are provided in the hood forthe entrance and discharge of the air or other heating medium.

The wet paper web to be dried is carried by a felt web 2% which travels around

rolls

21 and 22. The paper web is forced against the surface of the drum 1th by a pressure roller 23 which is rotatably mounted in brackets 24 attached to arms 25. The arms 25 are pivoted at 26 to the frame 11, and the pressure roller is forced against the surface of the drum 10 by rams 27 of hydraulic cylinders 28 which bear against the arms 25. The dried paper web is removed from the surface'of the drier shell by a creping doctor 29 which includes a creping blade 35% secured within a doctor blade holder 31. The ends of the holder 31 are provided with shafts 32 which are rotatably mounted within guide blocks 33. The blocks 33 in turn are each mounted within a slide assembly 34 attached to a pivot frame 35 pivotally carried by the frame 11. The doctor blade holder 31 and the blade 31' are pivoted by a toggle mechanism 36 which is attached through a lever arm 37 to one of the shafts 32.

In addition, a spring loading mechanism 33 of any suitable detailed construction is connected through the toggle mechanism 36 to provide a resilient contact for the doctor blade 3% against the surface of the drier drum 10.

In addition to the vertical and pivotable adjustment for the doctor blade 30, the doctor blade is adapted to oscillate in a direction parallelv to the axis of the drum 10. The oscillating motion is provided by an eccentric drive which is shown generally at 39 connected tonne of the shafts 32.. The oscillating motion is permitted by a loose fit between the pivot frame 35 and the frame 11 which permits the doctor blade to move back and forth across the surface of the drum 10, as the drum 10 rotates, to prevent uneven Wear of the blade 30.

Referring to FIG. 3, the doctor blade holder maybe posite sides of the blades 30. A doctor blade support 'bar 42 is disposed between the bars 413 and 41, and the

parts

40, 41 and 42 are fastened together at their bases by any suitable means (not shown) to act as a single assembly. The doctor blade 30 extends slightly beyond the ends of the drum 1t) and is substantially coincidental in the length with the

parts

40, 41 and 42.

Three

backing blades

43, 44' and 45 are provided behind the doctor blade 3th for supporting the doctor blade and causing it to forcefully bear on the outer surface of the drum 10. The backing blades are fixed at their bases with respect to the parts 40 and 41 by any suitable means (not shown). The bar 40 has a guard portion 46 fixed to it, and the end 46a is disposed somewhat downwardly with respect to the ends of the

parts

43, 44 and 45. As will be observed, the

backing blades

43, 44 and 45 are progressively longer in length and extend closer to the doctoring edge 35a of the blade 39. The'backing blade 45 is preferably provided with a chamfered surface 45a adjacent the doctor blade 39 so as to allow flexing of the doctor blade due to forceful contact of the latter with the drum 10. As will be apparent, the backing blade 45 is in contact and supports the doctor blade 30 and the

blades

43 and 44 respectively are shorter than and bear on the

blades

45 and 44 to support the latter.

The

backing blades

43, 44 and 45 are supported on their inner edges by a shoulder 41b on the bar 41. The support bar 42 has a plurality of square buttons 47 fixed to it for supporting the lower edge of the doctor blade 30.

Appropriate slots

49 and 50 are provided in the

backing blades

44 and 45 receiving the buttons 47.

The blade 30 may be made of a variety of different materials; however, spring steel has been found suitable. The thickness of the blade 30 may vary considerably-- the thickness for very satisfactory operation may well be between .025 inch to .050 inch. In order to provide the differentially creped tissue, the blade 30 is provided with a plurality of notches 51 on its edge. The Width of the notches and the distance of separation between them will, of course, vary with the character of the differential creping desired; however, the notches may be approximately /8 inch wide, and they may be separated by inch, for example.

The doctor blade may be disposed at various angles with respect to a tangent 52 (see FIG. 4) to the drum 10 at the edge 30a of the blade in contact with the drum. The angle a of the blade 30, measuring from the trailing end of the tangent 52, noting the direction of drum rotation A, for satisfactory operation may be, for example, 30 to 35 degrees. For satisfactory creping, the angle b between the leading end of the tangent 52 and the end surfaces 30b of the blade 30 between the notches 51 is preferably less than a right angle, and this angle b for satisfactory operation can well vary from 40 degrees to 90 degrees. The angle 0, at which the end surfaces 30b of the blade extend with respect to one of the sides of the blade, with the edge 30a of the blade in contact with the drum 10 constituting the apex of the angle 0, may accordingly vary between 55 and 110 degrees, although the angle is preferably an obtuse angle greater than 90 degrees, as illustrated. The angle of the end surfaces 30b with respect to the trailing end of the tangent 52 (angles c+a) should also preferably be an obtuse angle.

The length of the notches 51, transversely of the blade 30 is not critical; however, they have been found in actual practice to provide satisfactory operation if they are about inch long, measured between the blade edge 30a in contact with the drum and the edges 51a (see FIG. 7). It is important, however, that the base surfaces 51b of the notches 51 shall extend at an acute angle d with respect to the trailing end of the tangent 52. The angle e between the base surfaces 51b of the notches and the side of the blade 30 adjacent the drum' 10, for satisfactory operation, for example, may be to degrees, and the angle d, therefore, may well vary from 45 to 55 degrees, considerably less than a right angle. Thus the creping end surfaces b and 51b both extend in directions less than right angles with respect to the tangent 52, the surfaces 30!; being at an acute angle with respect to the leading end of the tangent 52 and the surfaces 51b being at an acute angle with respect to the trailing end of the tangent 52, corresponding respectively to the acute angles b and d.

The wadding material produced by the blade 30 is a differentially or unevenly creped sheetof paper or tissue 53 (see FIG. 8), such as is described in Patent 3,017,317,

issued January 16, 1962, which incidentally discloses another method for making the differentially creped sheet material including the use of spaced sprays of chemical solution applied onto the surface of a Yankee drier drum for causing uneven release of the material from the drum surface. The details of such an unevenly creped sheet material are disclosed in this Patent 3,017,317, and, therefore, specific details will not be set forth here. Suffice it to say, the individual sheets 53 are formed tissue webs having a basis weight, for example, on a bone dry basis before differential creping, of about 3.5 pounds to 15 pounds per ream of 3000 square feet. For cushioning and insulating purposes, however, the preferred basis weight range is about 4.5 pounds to 7.5 pounds per ream of 3000 square feet on a bone dry basis before differential creping.

Each of the tissue webs or sheets 53 has a series of alternating coarsely creped strips 54 and more finely creped strips 55' extending in the direction indicated by the arrow B in'FlG. 8, and constituting alternating puffed and fiat areas Which give the product unique properties. For general usage, the sheets 53 are superposed one on another so as to form a blanket or pad of substantial thickness, the sheets 53 being shown in such superposed relation in FIG. 8.

The finely creped strips 55 function as stabilizers in each of the sheets 53 holding the arches of the coarsely creped areas 54 in place and enabling the latter to act as structural members to provide the product, which comprises the plurality of superposed plies, with high, stable bulk characteristics. As an example, the coarsely creped reas 54 of the individual plies of the product may have between about 5 and about 30 crepes per inch and preferably between 10 and 20 crepes per inch. The more finely creped areas 55 of the respective plies may have be- .tween about 20 and 200 crepes per inch and preferably between about 30 and 50 crepes per inch. These numbers refer to a sheet 53 as it is wound onto the reel at the end of the papermaking machine, and generally some stretching takes place as the sheets 53 are plied up into multi-ply product. to the extent of about 10 percent of their length.

The papermaking machine illustrated in FIGS. 1 and 2, with the exception of the blade 30, is of conventional construction and operates in accordance with Well known principles of operation. The paper web 13 is carried on the lower surface of the lower pass of the felt 20 passing about the roll 22, and the web 13 transfers onto the drier drum 1t) beneath the pressure roll 23. The pressure roll 23 functions not only to cause transfer of the web 13 onto the drum, but also cooperates with the drum 10, as is well known, to dewater the web 13 to a certain extent at the nip of the pressure roll and drum. 7

The web 13 is dried in passing about the drum 10, and the web is removed from the drum 10 by the doctor blade 30, which functions to crepe it, reducing its length substantially from its length as it exists on the surface of the drum 10. This creping increases the softness and bulk of the tissue, so that the tissue is useful in situations requiring high bulk characteristics.

The blade 30, due to its notched construction, provides the differentially creped sheets 53 above described which are particularly useful in multi-ply blankets for insulating or packing purposes.

The end surfaces 30b of the doctor blade 30 that extend at the acute angle b with respect to the leading end of the tangent52 function to provide the finely creped strips 55 of the sheets 53 (see FIG. 6). The end surfaces 30b force the web 13, as it travels on and is fixed to the dium 10, back on itself in very closely spaced folds in scraping the web from the drum to thus provide the multitude of fine folds in thesheet in the finely creped strips 55. The surfaces 51b of the notches 51 extend at the acute angle d with respect to the trailing end of the tangent 52, and these surfaces do not cause any substantial folding back of the web on itself as the Web is scraped oit the drum at the blade edge 30 and thus cause substantially no creping of the tissue (see FIG. 7). The multitude of tissue crepes in the areas 55, however, cause a shirring of the material between the strips 55 so as to in eliect provide relatively coarse crepes in the areas 54. The sheets 53, which are in effect differentially creped, thus result.

The doctor blade 56 shown in FIG. 9, provides differentially creped sheets similar to the sheets 53 and may be substituted for the blade 30 in the doctor blade assembly above described. The blade 56 is a composite blade and is made up of a very thin blade part 57 located adjacent to the drum 10 and a much thicker blade part 58 in contact with the blade part 57. The

blade parts

57 and 58 are ground on a bias on their ends so as to provide edges 57a and 58a that extend at the same angle With respect to a tangent to the drum as the blade edge 30b in the first described embodiment. The blade part 58 is provided with notches 59 in its edge which correspond to the notches 51 in the first described embodiment. The blade 56 functions to finely crepe tissue from the drum 10 by means of its edge made up of the edges 57a and 58a of the

blade parts

57 and 58 and to more coarse- 1y crepe portions of the tissue passing through the notches 59.

The notched oreping blades above described constitute relatively economical constructions for providing the differentially creped tissues, which in themselves have numerous advantages particularly for forming multi-ply pads for insulating and packaging. In order to form the blade 3%), it is simply necessary to grind the scalloped edge including the notches 51 into a strip of sheet steel, and the second form of blade 56 may be made by obvious and easy grinding and blanking operations.

I wish it to be understood that the invention is not to be limited to the specific constructions and methods shown and described, except only insofar as [the claims may be so limited, as it will be understood to those skilled in the art that changes may be made without departing from the principles of the invention.

I claim:

1. A doctor blade for creping flexible sheet material from the surface of a drier drum and comprising a strip of sheet material having a straight, continuous longitudinal edge on one side of the strip adapted to contact the surface of the drier drum, said sheet material strip being provided with a flat end surface which extends at an obtuse angle with respect to said side about said edge as the apex, said strip having notches indented into the other side of the strip and extending from said edge toward the middle of the strip with said notches having flat base portions that extend at an acute angle with respect to said side about said edge as the apex and having flat sides that are normal to said base portions.

2. A doctor blade for creping flexible Web from the surface of a drier drum and comprising a sheet material strip having a straight continuous longitudinal edge on one side of the strip adapted to contact the surface of the drier drum, said strip being provided with a plurality of spaced notches indented into the strip from the other side thereof and extending only partially through the strip to have base surfaces extending from said edge toward the middle of the strip, said base surfaces being flat in section longitudinally of the strip.

3. A doctor blade for creping flexible web from the surface of a drier drum and comprising a sheet material strip having a straight continuous longitudinal edge on one side of the strip adapted to contact the surface of the drier drum, said strip being provided with a plurality of spaced notches indented into the strip from the other side thereof and extending only partially through the strip to have base surfaces extending from said edge toward the middle of the strip and sides normal to said base surfaces, said base surfaces and sides being flat in section longitudinally of the strip.

References Cited in the file of this patent UNITED STATES PATENTS 1,588,732 Hoberg June 15, 1926 1,764,676 Campbell June 17, 1930 2,995,180 Klenk Aug. 8, 1961 FOREIGN PATENTS 456,032 Great Britain Nov. 2, 1936 150,549 Germany Apr. 14, 1904