US2699096A - Rectifier roll assembly - Google Patents

Description

Jan. 11, 1955 L. HORNBOSTEL RECTIFIER ROLL ASSEMBLY i invent UP 7 3.9:. yak/71603143! 5 fiii I775 United States Patent RECTIFIER ROLL ASSEMBLY Lloyd Hornbostel, Beloit, Wis., assignor to Beloit Iron Works, Beloit,.Wis., a corporation of Wisconsin Application April 10, 1953, Serial N 0. 348,000 6 Claims. (Cl. 92-44) This invention relates to allow evener type of stock inlet for a paper making machine, and more particularly, to a rectifier roll assembly for such flow evener device.

The use of rectifier rolls to cause uniform stock flow is well understood. Such rectifier rolls comprise a radially perforated cylindrical tube, which usually has a plurality of disks or radial. baflles extending across the interior of the tube and axially spaced along the length thereof. The stock flows transversely of the rotating rolls through the perforations in the tube, and these perforations in cooperation with the radial bafiles reduce cross-velocities and eddy currents in'the stock streams flowing therethrough, so as to obtain more or less rectilinear stock flow exiting from the rectifier roll.

It has also been proposed to use more than one rectifier roll, for example, a stack of superimposed rectifier rolls, so as to provide rectifying means extending from the bottom of the stock conduit to the top level of the stock flowing therethrough. Also, superimposed rectifier rolls have been used to form a bridge of rectifier means immediatelyahead of the slice in the head box so as to obtain a final rectifying of the stock streams just prior to the exit of the stock through the head box slice.

In general, such rectifying means have proved to be unusually satisfactory. However, in spite. of the recognized effectiveness of such rectifying means, and in spite of particularly careful operation of the paper machine, there is oftena tendency for irregularities to appear in the resultingpaper web, particularly when certain types of stock are used. .There are any number of places where onemight look for the source of such irregularities in paper machines.

The instantinvention, however .is .based upon first, an analysis of the nature of the irregularity pattern, secondly, the discovery that one source of such irregularities was in the rectifier rolls (whichwere heretofore considered the ultimate in flow evening devices) and thirdly, the discovery of an improved rectifier roll assembly which cures the defect in question. Actually, the last two aspects of the instant invention were more or less simultaneous incharacter since it could not be definitely established that the rectifier rolls were the source of trouble until the trouble had been removed by the instant alteration of the rectifier roll assembly.

Analysis of one type of irregularity which tended to occur in the web on certain occasions revealed that the natureof the irregularity indicated the formation of fairly well defined light and heavy streaks running in the machine direction and spaced at regular intervals across the width of the machine. This spacing indicated a correlation therebetween and the uniform spacing of the rectifier roll perforations. In generahrectifier rolls of a givensize and made for a specific purpose, such as bridging the head box outlet to the slice are substantially identical in every detail, having been made from the same set of specifications and drawings. Also, the mounting or journalling of such rolls involves substantially identically spaced units, so that each roll presents substantially identical pattern of perforations and radial baffles (all of which are aligned with thecorresponding elements of an adjacent roll) during operation. The instant invention is based upon the discovery that unusually improved stock flow control may be obtained by offsetting these fiow affecting elements such as the perforations and the radial baffles in adjacent rolls.

It is, therefore, an important object of the instant invention to provide an improved stock flow evening device,

and more specifically an improved rectifier roll assembly.

It is another object of the instant invention to provide an improved rectifier roll assembly, wherein the fiow controlling elements such as the perforations and/or the radial baffles in a given rectifier roll are offset from such elements in the immediately adjacent rectifier roll.

Other features, objects and advantages of the instant invention will become apparent to those skilled in the art from the following detailed disclosure thereof and the accompanying drawings made a part hereof.

On the drawings:

Figure l is a sectional elevational view, with some parts shown fragmentarily, of a flow evener for a paper machine embodying the instant invention;

Figure 2 is a fragmentary detail view of a pair of rectifier rolls embodying the instant invention, taken substantially along the line llll of Figure l, and showing parts of the perforated tube portions of the roll broken away;

Figure 3 is a view comparable to Figure 2 showing a different arrangement embodying the instant invention; and.

Figure 4 is an enlarged fragmentary detail view taken substantially along the line lVlV of Figure 2.

As shown on the drawings:

In Figure l, the reference numeral 10 indicates generally an inlet box for a Fourdrinier type paper making machine, the box wardly directed inletvconduit 11 for subsequent introduction. onto the forming wire 12 locked about a breast roll 13 in a conventional Fourdrinier type paper making machine. The stock fiows through the box 10 and then through the slice at 14- and onto the forming wire 12 where the web W is formed.

The inlet box 10 may be a closed box provided with air pressure supply means (not shown) for accelerating the flow of stock through the slice 14, or the inlet box fill may be as showman open topped inlet box which is definedgeneraily by a bottom wall 15 terminating in a forward, arcuate, apron portion 15a, a pair of side walls 16 (only one of which is shown), a rear wall (not shown) and a forward Wall 17 overlying the breast roll 13. The stock flowing in the box Ill is maintained at the level L by suitable fiow control and level control means (not shown). The stock thus flows at the level L fromthe stock inlet 11 to the stock outlet or slice 14 between the side walls 16, in.

A plurality (which may be more than the twolhere shown) of rectifier rolls 1% and 19, in the form of vertically stacked or superimposed rolls 1% and 19 are positioned between theinlet lit and the outlet 14, as here shown near the inlet ll, so as to extend between the side walls 16, 1d and to cooperate with each other in close running relationship to substantially prevent how of stock therebetween except through one of the rolls 1% or 19. The stack of rolls l8 and 19 thus extends from the floor 15 to approximately. the stock level L, and there is-rninirnum clearance between the roll 13 and the floor 15 and the roll 18 and the roll .19. Suitable journalling means indicated at 2 and 21 are provided for rotation of the rolls in the positions indicated. Such journalling means are mounted in the side walls 16, ldand their nature function is well understood in the art and need not be further discussed herein. Generally, a positive drive means (not shown) isemployed to effect the desired rate and direction of rotation of the rolls ls and 19.

It will .alsobe seen from Figure 1 that another plurality (again a pair. as shown, but more may be used) of rectifier rolls22 and 23 are positioned in superimposed bridging relationship with respect to the slice 14, so as to receive allstock flowing through the box 10 and out the slice 14. The rolls 22 and 23 are positioned in their bridging relationship as shown so that they will be spaced a short distance from the slice 14 so as to permit a reasonable amount of additional smoothing out of the flow of stock after it has departed from the rolls 22 and 23 and before it reaches the slice 14. The rolls 22 and 23 are also suitably journalled at 24 and 25 in the same manner that the rolls 18 and 19 are mounted for rotation.

Heretofore, it was thought that the spacing of {the it receiving the stock from an upbridging rectifier rolls 22 and 23 from the slice 14 was more than adequate for the purpose of eliminating completely any irregularity forming stock fiow pattern at the exit of the rectifier rolls. In fact, it was generally understood that the stock flow at the exit of the rectifier rolls was substantially uniform and only a small amount of space was necessary for the minor adjustments in stock flow required as a result of the stock passing through the perforations in the rectifier rolls. It has been found, however, that mere spacing is not enough and that superior results are obtained by offsetting the flow control elements (in a manner which will be described) in adjacent rectifier rolls.

Although it is not desired to limit the instant invention to any particular theory, certain theories have been developed, some of which led to the instant discovery and some of which were arrived at by hindsight after the instant discovery was made. In order to provide a minimum restriction to the stock flow passing through a rectifier roll, it was, of course, advisable to provide the roll with a maximum area of perforations. For this purpose, a uniform perforation pattern was established for perforations or holes of substantially the same size.

Referring to Figure 2, wherein the perforations are shown partially, for example, in the cylindrical tube 26 of the upper roll A, it will be seen that the perforations or holes 27, 28 and 29 are axially aligned in a row and are axially spaced from each other the minimum distance which strength specifications will permit. The immediately adjacent rows of holes 30, 31, 32 etc. is also an axially aligned row wherein the holes 30, 31 and 32 are axially spaced from each other the minimum permitted distance. As a specific example, the distance between the centerline 320 of the hole 32 and the centerline 31c of the hole 31 is 1 /2 inches and the holes 31 and 32 are each 1%. inches in diameter. The distance 0 between the centerline 270 of the hole 27 and the centerline 280 of the hole 28 is, of course, the same. In addition, the holes 27, 28, 29 etc. of the one row are centered in their axial alignment intermediate the centers of the holes 30, 31, 32, etc. of the second row; so that the distance between the centerline 320 of the hole 32 and the centerline 280 of the hole 28 is c/ 2. This pattern provides for maximum perforation area in the roll shell or tube 26, and the holes or perforations thus form a perforation pattern which is that of alternate peripherally spaced axially aligned rows of perforations, wherein the perforations in one row are axially aligned intermediate the perforations in both immediately adjacent row, and this pattern covers the entire surface of the tube 16 (although many of the perforations have been omitted from the drawings to avoid undue confusion). It was expected that such a perforation pattern would surely eliminate all possible irregular flow patterns, but as has been pointed out, it has now been found that when a plurality of such rolls are operated in close running relationship using identical perforation pattern alignments therebetween flow irregularities may be developed. One possible explanation whv the instant perforation pattern in each roll is not sufi'icient in and of itself to avoid the creation of an irregular fl w pattern is that adjacent rolls may tend to cooperate with each other during rotation so as to cause more or less stock flow at a given (angular) location at the periphery of the tubes so that the irregularities in the exit fiow patterns for each are multiplied instead of neutralized.

Referring now to the lower roll B in Figure 2, it will be seen that the cylindrical tube 33 is radially perforated with a perforation pattern that is the same as that described in connection with the upper roll A, and radial baffles 34, 35, 36, etc. extend across the interior of the tube 33 and are axially spaced (a distance s) along the length of the tube 33. For example, the distance s between the centerline 340 of the bafile 34 and the centerline 35c of the bafile 35 is 3 inches in the embodiment here shown. It will be seen that the baffles 34, 35, 36, etc. are aligned with some of the perforations and are positioned between others of the perforations. Referring briefly to the right-hand portion of the lower roll B, and to the detailed showing in Figure 4, it will be seen that in the case of a hole 37 which is directly aligned with a baffle 38 a notch 39 is cut in the disk-shaped baflle 38 immediately adjacent the hole 37, so as to permit free flow of stock into the hole 37 from either side of the bafile 38. This is a typical feature of the construction of each of the disk-shaped baffles employed in the instant rectifier rolls; but the peripheral notches, such as the notch 39, are not otherwise shown on the drawings in order to avoid undue confusion. The radial baffles or disks 34, 35, 36, 38, etc. serve to channel the stock flow through the roll and to eliminate cross-velocities and eddy currents in the stock streams flowing therethrough. Again, in view of the very substantial amount of perforated area in the tube shell 33 and the relatively large space between each of the baffles, it was expected that no appreciable irregularities in stock flow should be created by stock passing through such a roll; and the instant discovery leads to the conclusion that there was some sort of cooperation between adjacent rolls during their operation, if the baffles and/or perforation patterns are identically aligned, which results in magnification instead of neutralization of flow pattern irregularities.

As shown in Figure 2, the bafiles 34, 35 and 36 of the lower roll B are offset axially from the bafiles 39, 40 and 41 of the upper roll A. In other words, the centerline 40c of the upper roll baffle 40 is not aligned with the centerline 350 of the lower roll baffle 35, but is axially offset the distance x, although the distance s of the axial spacing of the bafiles in each of the rolls A and B is the same. Although it is preferred, as will be explained, to have the offset distance x equal to approximately s/2, this is not absolutely necessary in order to obtain some of the advantages in flow evening of the instant invention.

On the other hand, it is also possible to obtain flow evening advantages provided by the instant invention merely by offsetting the perforations (as will be described) without offsetting the baffles; but most preferably both the baffles and the perforation patterns are offset, as shown in Figure 3.

Referring to Figure 3, which shows the most preferred embodiment of the instant invention, whereby superior results are obtained, it will be seen that the baffles 42 and 43 in the upper roll A and the bafiles 44 and 45 in the lower roll B are spaced the distance s which is the same as the distance s of Figure 2; but the bafile 43 is offset axially from the bafile 45 the preferred distance s/2, so that the bafiles 44 and 45 of the lower roll B are axially aligned intermediate the battles 42 and 43 of the upper roll A.

It will also be seen that the roll holes 46, 47, 48, etc. and the roll holes 49, 50, 51, etc. shown in the upper roll A are positioned in accordance with the pattern described previously in connection with Figure 2. The perforation pattern in the lower roll B is, likewise, the same pattern, as indicated by the roll holes 52, 53, 54, etc. and the adjacent roll holes 55, 56, 57, etc. However, it will be noted that the centers of each of the holes of the upper roll A are axially offset from the centers of each of the holes in the lower roll B. This will be apparent from a consideration of the centerlines 46c, 53c, 50c, 57c, and 470 of the holes having the corresponding reference numerals. The distance between centerlines 46c and 470 for holes in the same roll is c, which is the same as c disclosed in Figure 2. The distance between centerline 500 and 470 for holes in adjacent rows in the same roll A is c'/ 2. The distance between the centerlines 46c and 530, representing holes in different rolls A and B. respectively, is c/4, thereby indicating that the perforations in the two rolls are axially aligned intermediately.

Because of the particular dimensions here used, the baffles are not positioned so as to be exactly in intermediate alignment, but only substantially so, so that the distance of baffie offset, s/2, represents substantially the amount of ofiset.

By the use of the arrangement shown in Figure 3, it has been found that an unusually superior result is obtained in uniform web formation particularly in connection with those operations and those specific types of stock which heretofore caused the particular defects herein described.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention.

I claim as my invention:

1. In a flow evener for a paper machine having members defining a stock flow conduit from a stock inlet to a stock outlet between side walls, the improvements which comprise a plurality of rectifier rolls, each of said rolls having a radially perforated cylindrical tube, means journaling the tube for rotation in position interposed between the inlet and the outlet to extend between the side walls and cooperating with an adjacent roll in close running relationship to stock therebetween except so as to effect different stock flow patterns in the stock streams existing from adjacent rolls.

2. In a flow evener for a paper machine having members defining a stock flow conduit from a stock inlet to a stock outlet between side walls, the rniprovements which comprise a plurality of rectifier rolls, each of said rolls having a radially perforated cylindrical tube, the radial perforations therein being axially spaced in axially extending rows, and means journalling the tube for rotation in position interposed between the inlet and the outlet to extend between the side walls and cooperating with an adjacent roll in close running relationship to substantially prevent flow of stock therebetween except through one of said adjacent rolls, the perforations in one of said adjacent rolls being axially aligned intermediate the perforations in the other so as to efiFect different stock flow patterns in the stock streams existing from adjacent rolls.

radial baffles extending and axially spaced along the length thereof to channel stock flow therethrough rolls having a radially perforated cylindrical tube, means journalling the tube for rotation in position interposed between the inlet and the outlet to extend between the ties and eddy currents in the stock streams flowing through adjacent rolls being substantially half way intermediate the which comprise a plurality of rectifier rolls, each of said rolls having a radially perforated cylindrical tube, the radial perforations therein being axially spaced in axially extendi g rows, means journalling the tube for rotation in position interposed between the inlet and the outlet across the interior of said tube and axially spaced along the length thereof to channel stock flow therethrough and to eliminate cross-velocities and eddy currents in the stock streams flowing through said tube, the perforations OTHER REFERENCES Bearce, Tech. Assn. Papers Series 18, p. 314 (1935).

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