US3507745A - Doctor blade mechanism - Google Patents

Description

April 21, 1970 M. J. FUERST DOCTOR BLADE MECHANISM 2 Sheets-Sheet l Filed May 23, 1966 April 21, 1970 M. J. FUERST DOCTOR BLADE MECHANISM 2 Sheets-Sheet 2 Filed May 23, 1966 United States Patent l 3,507,745 DOCTOR BLADE MECHANISM Milton J. Fuerst, New London, Wis., assignor to Kimberly-Clark Corporation, Neenah, Wis., a corporation of Delaware Filed May 23, 1966, Ser. No. 558,536 Int. Cl. B31f 1/12; D21g 3/04 US. Cl. 162-281 1 Claim ABSTRACT OF THE DISCLOSURE My invention relates to papermaking machines and more particularly to apparatus for making differentially creped tissue sheets which are tissue sheets having a series of finely creped strips separated by relatively coarsely creped strips.

It has been proposed to make such differentially creped tissue sheets in Voigtman et a1. Patent No. 3,017,317, by spraying the drier drum for the tissue with spaced jets of liquid release agent, and it has been proposed to make such sheets in Nobbe Patent No. 3,163,575, by means of a creping doctor blade effective on a drier drum. The Nobbe doctor blade has an end surface which extends at an obtuse angle with respect to the trailing end of the tangent to the drier drum at the place of contact of the blade, and notches are cut in the blade to provide surfaces extending at an acute angle with respect to this end of the tangent. The first mentioned blade surfaces finely crepe paper tissue from the drier drum, and the surfaces in the blade formed by the notches flare or coarsely crepe the tissue from the drum so as to provide a composite tissue which has alternate finely creped and coarsely creped longitudinal strips.

It is an object of the present invention to provide an improved, simplified doctor blade of this general type which has alternate creping end surfaces extending at different angles with respect to the surface of the drier drum along a substantial line of contact of the blade with the drum; and more particularly it is an object to provide such a doctor blade which, except for spaced edge portions that have been blunted, has an edge portion extending at an acute angle with respect to the trailing end of the tangent to the drier drum at said substantial line of contact. It is a further object of the invention to provide a simplified method for making such a doctor blade.

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 a preferred form of the invention, illustrated with reference to the accompanying drawings, wherein:

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

FIG. 2 is a fragmentary sectional view of the doctor blade and the doctor blade supporting assembly;

FIG. 3 is a perspective view of the creping edge of the doctor blade prior to run-in of the blade on the surface of the drier drum;

FIG. 4 is a fragmentary cross-sectional view of the doctor blade taken on line 44 of FIG. 3;

FIG. 5 is a sectional view similar to FIG. 4 and taken on line 5-5 of FIG. 3;

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FIG. 6 is a view similar to FIG. 5 after the blade has been run in on the surface of a rotating drier drum to put it into operating condition;

FIG. 7 is a fragmentary end view of the doctor blade in creping position on the Yankee drier drum; and,

FIG. 8 is a side elevational view of the doctor blade showing the manner in which a toothed gear may be run back and forth on the sharpened edge of the blade for the purpose of providing notches in the sharpened edge so as to give the blade its differential creping capability.

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

Referring now to FIG. 1, in particular, the papermaking machine fragmentarily illustrated includes a drier drum 10 which is supported by a frame 11 disposed on a suitable foundation 12. The wet paper web 13, in the operation of the machine, is applied on the outer surface of the drum and is dried by the drum during less than a single revolution thereof.

The drum comprises a cylindrical shell 14 fixed to heads 15, and the heads and shell may be made of cast iron, for example. The drum is mounted for rotation by means of end shafts 16 disposed in bearings 17 secured to the frame 11 and is driven by conventional driving mechanism (not shown) attached to one of the shafts 16, Steam is applied to the drum 10 by conventional connections for heating the drum to dry the web 13, and a heated hood 18 extends around the upper portion of the drum 10 for providing additional heat for drying the web. The hood is provided with suitable hot air inlets and outlets for the entrance and discharge of the heated air or other medium.

The paper web to be dried is carried by an endless felt 19 which extends around a pressure roll 20 suitably mounted so as to force the felt 19 against the outer surface of the drum 10, whereby the web 13 transfers from the felt to the drum.

A creping doctor assembly 21 is utilized for creping the paper web from the surface of the drum 10. The assembly comprises a doctor blade holder 22 suitably carried and fixed within the assembly 21 and a creping doctor blade 23 secured in the holder.

The doctor blade holder, referring particularly to FIG. 2, may be seen to comprise side support bars 24 and 25 on opposite sides of the blade 23. A support bar 26 is disposed between the bars 24 and 25; and the bars 24, 25 and 26 are fastened together at their bases by any suitable means (not shown) to act as a single assembly. The doctor blade 23 extends slightly beyond the ends of the drum 10 and is substantially coincidental in length with the bars 24, 25 and 26.

Three backing blades 27, 28 and 29 are provided behind the doctor blade 23 for supporting the blade. The backing blades are fixed at their bases with respect to the bars 24 and 25 by any suitable means (not shown). The bar 24 has a guard portion 30 fixed to it, and the end 30a of the guard portion is disposed somewhat downwardly with respect to the edges of the backing blades 27, 28 and 29.

Prior to run-in on the moving peripheral surface of the drum 10, the doctor blade 23 appears in the condition shown in FIGS. 3, 4 and 5. The blade is ground or otherwise formed with a surface or side 23a that is at an acute angle a with respect to the side or base surface 23b of the blade. Thin notches 31 are provided on the edge of the blade at which the surfaces 23a and 23b meet, and the bottoms of the notches 31 are formed by surfaces 230 each of which extends at a larger angle b with respect to the face or base surface 23b of the blade.

Spring steel, for example, which is flexible has been found suitable as material for the blade 23. The blade 23 may vary in thickness considerably; for example, the thickness for very satisfactory operation may well be between .025 inch to .050 inch. The blade is initially formed so that the surface 23a extends for the complete length of the blade and intersects the surface 23b in a knife edge 23d for the complete length of the blade. As the blade is actually used, it is provided with the notches 31, and these may be formed by filing them in the blade, for example, or they may also be formed simply by rolling a gear 32 having teeth 33 (see FIG. 8) on its periphery back and forth along the sharp edge 23d until the notches 31 are formed to the desired depth. The notches may, for example, have a width on their base surfaces 23c of about .005 inch, and the depth of the notches may also be about .005 inch but may Well vary from about .0015 inch to .007 inch. The teeth 33 havea rolling contact wiith spaced portions of the edge 23d and dull the edge in the portions thereof contacted by the teeth 33 in order to provide the notches 31. I have found that creping is facilitated if the surfaces 23c are somewhat rough. This roughness may be attained if the ends of the teeth 33 are provided with surfaces which are like the abrading surfaces of a file; and, in fact, file segments may be fixed on the end of the teeth 33 for this purpose. Such file segments may, for example, be parts of fine files of the type used for dressing the distributor contacts of the ignition system for an internal combustion engine and may, for example, have about 80 ridges and grooves per inch of file length.

In order to put the blade 23 in condition for differential creping, it should first be run in and preferably dressed before running in. Dressing is done by moving a stone or file along the blade surface 23b to remove any burrs protruding on this surface due to the dulling action of the gear teeth 33 on the sharpened edge of the blade 23. The blade 23 is run in by running it on the surface of the drier, preferably without a sheet 13 being provided on the felt 19 and drier. This has the effect of wearing the edge surfaces of the blade 23 in contacts with the drum so that the edge surfaces now appear as seen in FIG. 6. After such running in, the end of the blade 23 is in the shape of a short are 23 corresponding to the cylindrical shape of the drum 13, and this arc terminates at an edge 23 on the surface 23a and at edges 23g on the surfaces 230. Thus, after such run-in, the surface 23a, which is at an acute angle a with respect to the base surface 23b of the blade 23 and also the surface 230, which is at a larger angle b with respect to the base surface 2317, are both in contact and thus in creping relation with respect to the outer surface of the drum 13.

In operation, the doctor blade may be disposed at various angles with respect to a tangent 34 (see FIG. 7) to the drum 10 at the edge 23 in contact with the drum. The angle c of the blade 23, noting the direction of drum rotation A and measuring from the trailing end of the tangent 34, for satisfactory operation may be, for example, from 20 to 45.

The surface 23a is a flaring or coarsely creping surface and the surfaces 230 are finely creping surfaces with respect to the surface of the drum 10 after run-in. The surface 23a extends at an acute angle d (which is the sum of the angles a and c) with respect to the trailing end of the tangent 34, and the angle a. is preferably 40 to 75. The surface 230 extends at a larger angle e (which is the sum of the angles b and c) with respect to the trailing end of the tangent 34, and the angle e is preferably 85 to 150. It will be noted that the angle e can thus be a. relatively large acute angle or an obtuse angle, as desired. Assuming that the angle 0 is 30", for example, the angle a defining the angle of the surfaces 23a with respect to the base surface 23b of the doctor blade 23 thus is an acute angle of 10 to 45, and the angle b between the surfaces 230 and the base surface 23b of the blade 23 is an angle of to The surfaces 23a and their creping edges 23 will strip or flare off the tissue web 13 from the surface of the drier drum 10 with very little or coarse creping, while the surfaces 230 with their edges 23g will finely crepe the web 13 from the drier drum due to the fact that the web tends to double back on itself and become crinkled as the web strikes the surfaces 230 that either lean toward the leading end of the tangent 34 or else extend substantially directly outwardly, or nearly at right angles, with respect to the tangent 34. Thus, the creping blade of the invention produces a differentially or unevenly creped product or tissue, such as the product described in No-bbe Patent No. 3,163,575, and also, incidentally, described in Voigtman et al. Patent No. 3,017,317. The advantageous and usages of these differentially creped Webs or sheets are very suitable for these patents, and, as it set forth in these patents, such differenttially creped webs or sheets are very suitable for cushioning and insulating purposes.

It will be apparent that the length and spacing of the notches 31 may be varied as desired in order to change the differential creping action. The notches 31 may, for example, be about inch long, and the spacing between the notches may also be approximately the same.

The creping doctor blade above described affords an economical mechanism for producing the differentially creped tissue disclosed in the above mentioned Patents 3,017,317 and 3,163,575, without the necessity of using relatively expensive chemical solutions or without the relatively costly necessity of grinding notches in a doctor blade. Inasmuch as the doctor blade disclosed herein is simply one that initially has its complete side sharpened with the acutely extending surface 23a and sharp edge 23d, and with the edge 23d subsequently being blunted and dulled in selected spaced portions, the blade may be constructed very economically while yet obtaining the desired differential creping results.

What is claimed is:

1. A doctor blade for differentially creping a flexible web from a moving surface and comprising a flexible sheet material doctor blade strip having one longitudinal and continuous sharpened edge and a series of notches spaced apart on said longitudinal edge extending through the thickness of the sharpened edge, wherein the angle b formed by the bottom of said notches with respect to the base surface (23d) of said blade strip (as illustrated in FIG. 6 of the drawings) is between about 55 and 120, and the angle formed by blade surface (23a) and base surface (232]) is an acute angle between about 10 to 45.

References Cited UNITED STATES PATENTS 670,401 3/1901 Greth 162281 1,588,732 6/1926 Hoberg 162281 2,995,180 8/1961 Klenk 264283 HOWARD R. CAINE, Primary Examiner US. Cl. X.R.

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