US3655476A

US3655476A - Method of making honeycomb core

Info

Publication number: US3655476A
Application number: US827782A
Authority: US
Inventors: Burton L Siegal
Original assignee: Orbitex Inc
Current assignee: Orbitex Inc
Priority date: 1969-05-26
Filing date: 1969-05-26
Publication date: 1972-04-11
Anticipated expiration: 1989-04-11

Abstract

Two webs are imprinted with transverse lines of adhesive, the pattern on one web being staggered with respect to the pattern on the other web, so that if properly cut and stacked, there can be formed a lay-up which may eventually be expanded to produce honeycomb core.

Description

United States Patent Siegal v [73] Assignee:

[54] METHOD OF MAKING HONEYCOMB CORE [72] Inventor: Burton L. Siegal, Skokie, Ill.

Orbitex, Inc., Miami, Fla.

[22] Filed: May 26, 1969 [21] Appl. No.: 827,782

[52] U.S.Cl ..156/197, 156/260, 156/512 [51] Int. Cl ..B3ld 3/02 [58] Field ofSearch ..156/197, 548

[5 6] References Cited UNITED STATES PATENTS 2,649,131 8/1953 Lincoln ..156/548X 6&6

14 1 Apr. 11, 1972 3,114,666 12/1963 Johnson ..156/197 3,242,024 3/1966 Bova et a1. ..156/197 Primary Examiner-Benjamin A. Borchelt Assistant Examiner-G. E. Montone Attorney-Silverman & Cass [57] ABSTRACT Two webs are imprinted with transverse lines of adhesive, the pattern on one web being staggered with respect to the pattern on the other web, so that if properly cut and stacked, there can be formed a lay-up which may eventually be expanded to produce honeycomb core.

15 Claims, 3 Drawing Figures PATENTEDAPR 1 1 m2 SHEET 2 BF 2 0 elvai J' tions applied along one edge thereof, the perforations being applied in pairs, one on each web, while the web is passing a perforating station, for example, without staggering.

If each web has the same length cut therefrom, and the place of cutting is repeated for the next length, the perforations can be used to spindle the lengths and help stack them, providing a proper length is chosen which will produce a cutting point that is thesame for each pair of lengths. This is accomplished by proper choice of length taking into con sideration the pitches of the adhesive lines and the perforations. A length is chosen to be a whole number multiple of minimum distance at which the two pitches will be in phase. The pitch of the perforations need not be changed for different adhesive line pitches. Great flexibility is achieved by choosing the minimum common-in-phase distance to be a whole number, preferably less than ten inches.

A printing roll is constructed to be the same circumference for practically all of the pitches of adhesive lines which will be used, and the pitches are adjusted for the various sizes of honeycomb cells to give a number of lines on the roll which will provide the desired continuous pattern.

BACKGROUND OF THE INVENTION 1 Field of the Invention The invention herein relates to the printing of webs for making lay-ups of lengths of the webs stacked to provide the characteristic staggered node lines on alternate sides of each sheet so that when adhered and pulled apart, the usual sixsized cells will be formed.

The particular aspect of this art which is contemplated by the invention is concerned with transverse printing of the webs, where the problem of registration is more acute. The invention uses perforations as an aid in stacking, the sheets being imprinted with the adhesive lines in a peculiar relation to the perforations to give the advantages and benefits of the invention.

As will be explained, the invention is especially detailed in connection with a double width web passing through a' suitable apparatus which imprints the lines and perforates, slits the web up the center and then laminates the two webs following which the webs are simultaneously cut in pairs and stacked. The stacking is accomplished by means of a spindling pin which engages one of the perforations of each sheet.

The invention is concerned with a method which teaches the application of the printed lines and perforations in a particular way to give rise to certain advantages which will be explained in the discussion concerning the prior art.

2. Description of the Prior Art and Departures Therefrom The following patents disclose transverse printing: Lincoln U.S. Pat. No. 2,649,131; May U.S. Pat. No. 3,074,839; Knoll et 'al. U.S. Pat. No. 2,983,640; and Bova U.S. Pat. No. 3,242,024. Of these the Bova U.S. Pat. No. 3,242,024 discloses placing perforations along the edges of a web that is transversely printed on top and on bottom.

None of the disclosed methods is simple while being applied to high speed machinery, because the difficult problem is maintaining registration, uniformity, economy and efficiency. Most importantly, none of the methods is universally applicable to a machine which can produce honeycomb lay-ups using different cell sizes without requiring radical and substantial changes in the machine. According to the invention, the only change which need be made in the machine of the invention is to change the printing roll and adjust the sheeter for the different pitch size. lines will repeat at the The invention makes possible cutting lengths of web of almost any desired size without concern about registration, so long as the length of web is according to a given factor which will be described hereinafter.

SUMMARY or THE INVENTION According to the invention, the double width web is imprinted with side by side patterns of transverse adhesive lines which are staggered with respect to one another along the length of the web, and each pattern is also provided with a row of perforations along one side edge thereof, the apparatus slitting the web into two single widths, and bringing these widths together in proper face-to-face engagement for enabling cutting into lengths and stacking. The pitch relationship of the adhesive lines and the perforations along the length are chosen to be such that a whole number of Lines will repeat at the same time that a whole number of perforations will occur, the repeat length where this occurs being a whole number, preferably much smaller than 10. Likewise, the circumference of the print roll is chosen so that a whole number of print lines of any of a large number of pitches may be provided thereon, this whole number being divisible by another whole number to give a substantially smaller whole number.

Thus, the length of web cut can be a multiple of the least common denominator of the pitches of the lines and perforations, and if properly chosen, this number can be quite small giving an almost unlimited choice of lengths.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a fragmentary sectional view through a piece of honeycomb core to show its construction;

FIG. 2 is a perspective diagrammatic view showing apparatus constructed using the method of the invention; and

FIG. 3 is a fragmentary top plan view of a double width web showing the application of printing lines and perforations thereto.

DESCRIPTION OF THE PREFERRED EMBODIMENT Prior to describing the preferred embodiment, some understanding should be had of the dimensional relationships involved in the art of honeycomb manufacture.

Honeycomb core material is formed of sheets of flexible web adhered face-to-face on staggered lines. In FIG. 1, the piece of core 10 is shown formed of hexagonal cells. Each cell has the

sides

12, 13, I4, 15, 16 and 17. The

sides

12, 13, and 14 are integral with an upper sheet which is corrugated during the pulling of the sheets apart, as well-known. The

sides

15, 16, and 17 are integral with a lower sheet adhered to the upper sheet along node lines of adhesive at 18. The core 10 is built up out of many cells of identical construction. The dimension across the cell is Sc or cell size, and in modern industry the sizes almost universally specified for Sc are Vs inch, 3/16 inch, A inch, inch and /2 inch. The theoretical pitch P (HO. 3) and theoretical node line width W for these cell sizes is computed on the basis of the formula:

P= 2.31 Sc 1 or, the pitch P of the node lines is equal to 2.3] times the nominal across-the-flats size of a given hexagonal cell of honeycomb. For the universally used sizes mentioned above, the following are the computed theoretical pitches and node line widths: (all dimensions in inches) Several factors modify these dimensions in the practical application of theory. The web material does not bend on a perfect 60 angle and hence it fillets; the adhesive spreads upon application of heat and/or pressure; the pitch must be a whole number to fit the circumference of the print roll and this may require some adjustment; the particular overall characteristics of the machinery and materials used may require variations to provide desired physical properties and appearance.

Accordingly, the following dimensions have been used to obtain practically acceptable results. In each case the width W of the node line is somewhat smaller than those of Table No. 1 above, and is a result of experiment, varying from material to material.

The choice of the actual pitch in each case was dictated by the desire to compromise between the theoretical and choosing a dimension which will give an even multiple on a printing roll of fairly easy manufacture. Obviously, the first three of Table No. l are not too difficult to provide on printing rolls with whole number circumferences, and the last two are applicable to printing rolls which are 22 or 44 inches in circumference.

As thus far described, the disclosure is within the skill of the artisan. Registration is obtainable for any given length of web by carefully choosing the point of cutting, and the prior art teaches this to be the identical point for each sheet or pair of sheets. The difficulty comes in finding the proper point and maintaining it in a high speed machine. Furthermore, even if the machine is capable of accurate cutting, it is suitable only for one size of cell. A change in cell size requires a complete change in the registration characteristics of the machine, introduction of new driving connections and synchronization, etc.

At this point, attention may be invited to FIG. 2 which shows in diagrammatic form a structure for practicing the invention.

The machine is designated generally by the reference character 20. The double width web 22 is stripped off a roll 24 by in-feeding rolls 25 and passes through a printing station 26 and a perforating station 28. The perforating station 28 may be before the printing station, depending upon the type of adhesive used and the type of web-driving equipment. Likewise, the roll 24 may be preperforated. The web 22 is then passed through a drying station 30, a cooling station 32 and .a slitting station 34 at which point it is divided into two half webs 22A and 22B. These are turned at 36 and after adjustment of one for registration at 38 are laminated together at the roll 40 and together pass into the sheeter 42. The sheeter 42 cuts the sheets simultaneously by means of the rotary knife 44 whose speed is controlled by some variable speed drive (not shown) to provide pairs of cut sheets 46 of any desired length. The sheeter discharges the cut sheets at 46 into a bin 48 which, when filled, is rolled to the station 50 after which the sheets are removed and turned over onto a jogger 52. The jogger 52 has a board 53 with a single spindling pin 54, and the sheets are all spindled through the same perforation on this pin, and after jogging provide the stack 56 which is ready for further processing. There are alternative methods for receiving the sheets from the sheeter and forming the stack 56.

The perforations are shown at 60A and 608 corresponding to the two half widths into which the web 22 will be cut. The

two patterns of transverse adhesive lines 18 are best shown in FIG. 3, and these are designated 62A and 628. Note that the perforations are spaced to the left of the patterns and that each pattern and its line of perforations is disposed on opposite sides of the center or slitting line 66. As previously mentioned, the perforations are located at identical places along the web length. Thus, the perforations are aligned as indicated by the lines 68. The pitch of the perforations is the distance between perforation centers along the length of the web, and this is indicated as R. The same pitch R is maintained unifomily along the length of the web and is kept at the same value for all cell sizes which will be printed. Perforations will not necessarily occur alongside of individual adhesive lines 18, but as will be seen, will repeat at some rate that can be synchronized with the rate of repetition of the adhesive node lines 18, considering that both are passing a single point.

The pitch Pa of the printed adhesive node lines 18 is shown in FIG. 3, being the same for both patterns 62A and 628.

It was determined that a convenient circumference for the print roll 72 was a value that is divisible by the maximum number of whole integers. This was 24 inches, the circumference being divisible by 2, 3, 4, 6, 8, 12. Likewise, this number is divisible by the pitches that can be chosen quite closely to the theoretical for all of the commercial sizes of cells. Accordingly, for a 24-inch circumference print roll, the following pitch sizes were used to achieve substantially all of the commercial size honeycomb cells:

It will be seen that the choice of perforation pitch R is a matter of finding a repeat grouping that will be in phase with the printed lines a desirable number of times per revolution. In the case of a pitch R of l inch, a maximum flexibility is achieved. In the case of a pitch R of 2 inches, a good result is obtained.

The length of the cut sheets 46 must be chosen as a multiple of the least number of node line pitch distances which corresponds to a whole number factor of the number of perforation pitch distances for the same circumferential length C as the printing cylinder. This may be expressed generally as follows:

L M (2) where L is the total length of the cut sheet,

M is any whole number multiple, chosen and maintained throughout any given run,

X is a distance which is a whole number factor of the circumference of the print cylinder and also,

X= nPc= mR C/u where n, m and u are whole numbers,

Pc is the chosen pitch of node lines, and R is the perforation pitch.

Applying formula (2) to the information from Table No. 3,

we can derive the following:

TABLE NO. 4

Assuming a print roll of 24 inches; C 24 Cell Size Cs Pc R X=Clu u n 1/8 0.300 1 3 8 l 3 3/ l 6 0.400 1 2 l2 2 1/4 0.500 1 l 24 2 l 318 0.800 1 4 6 5 4 1/2 L000 1 l 24 l 1 From Table No. 4, it will be seen that for the chosen pitches Fe and a perforation pitch R of 1 inch and a 24-inch print roll, the sheet lengths can be anymultiple of 3 inches, 2 inches, 1

inch, 4 inches and 1 inch for the respective cell sizes listed. A

TABLE NO. 5

Assuming a print roll of 24 inches; C 24 Cell Size Cs Pc R X=Clu u n m 1/8 0.300 2 6 4 20 3 3/16 0.400 2 2 l2 5 1 1/4 0.500 2 2 l2 4 1 3/8 0.800 2 4 6 5 2 1/2 1.000 2 2 l2 2 1 in making a lay-up, the operator of the apparatus is given the factor X and told to make the length of the cut sheets 46 in every case a multiple of this factor. If there is a nominal registration at the sheeter, say of the order of plus or minus Va inch, the spindling of the sheets on the pin 54 and their jogging on the board 53 will provide the registration desired for proper stacking. It is understood that registration as usedherein is intended to mean the stacking of the sheets on top of one another alternating from the A and B side so that the lines of adhesive will be staggered.

ln stacking, it will be appreciated that the stacking or spindling pin 54 is at one end and at the top of the board 53. Thus, the sheets will rotate by gravity during the jogging and will lay against the bottom guide 74. Side drift of the web is taken care of by using two cutting knives in the slitting station 34, one of which establishes a trimmed edge for purposes of assuring a minimum of variation in the width of the two webs 22A and The advantages of printing two patterns side by side on the same web and perforating the web before slitting are, among others, the establishment of perfect relationships between perforations and lines, uniformity of the printing, and the great economy and efficiency of handling only one web with a minimum of waste until the web passes the slitting station 34.

The inventions principles may be applied to other systems and methods in which two webs are printed and perforated separately and it is desired to stack the same. In such cases, the situation is identical from just before the laminating roll to the end of the process. The two half webs 22A and 22B are printed and perforated independently but having the printline-to-perforation relationship which they would have if the entire web were printed and perforated. There is an important additional factor which must be taken account of. In such cases, the perforating must be done with the identical spaced relation along the length of the web with respect to both patterns, but of course, considering one pattern staggered with respect to the other.

In the case of the unitary double web, it is immaterial where the perforations occur with respect to the patterns, because they will always maintain the same relation to both patterns.

This emphasizes another important benefit of printing and perforating the double web.

Spindling on any one or more of the perforations of the sheets, so long as the identical ones of each sheet are used, for achieving proper arrangement of sheets for stacking is an attribute of both methods. Multiple pin stacking eliminates the need for referencing on sheet edges.

It is also possible to print and perforate a single web with the printing on both sides, staggered with respect to one another, laminate the same with a blank web of a width to cover the transverse lines but not the edge perforations, and use the method of the invention to cut and stack. The system will operate the same, that is, so long as the distance X is based upon the formula (2) above, the length of the cut sheet will give registration irrespective of where the cutting is done with respect to the pattern. This obtains because the chosen factor X assures that the repeat pattern of perforations and printed lines will be in phase every time a cut is made.

Considerable variations are possible within the scope of the invention as defined in the appended claims.

What it is desired to secure by Letters Patent of the United States is:

1. In a method of making honeycomb core structure in a stack suitable for further processing by at least expanding the same and in which a pair of webs is laminated face-to-back, each web having a pattern of transversely printed adhesive node lines thereon, the pattern of one web being staggered along its length with respect to theother, and in which the laminated web is cut into a plurality of equal lengths that are stacked one upon the other to form a lay-up, the steps of:

A. printing the patterns of node lines side-by-side along the length of a double width web, on one face thereof, with the patterns staggered along the length of the web, each pattern occupying somewhat less than half of the web, respectively,

' B. perforating the web along its length on two transversely spaced rows, one row being in a clear path between the side edge of one pattern and one edge of the double width web, the other being in-a clear path between patterns, the perforation pitch of each row being equal along the row and each perforation of one row being transversely aligned with an identical perforation in the other row normally to the rows irrespective of the staggered arrangement of the patterns relative one another,

' C. dividing the web along its center to provide a pair of half webs each having a pattern and a row of perforations,

D. bringing together the half webs with their perforations in register and without changing their lengthwise relative orientation substantially, to form a two-ply web prior to cutting, the cut length dimension being chosen as a multiple of a minimum dimension at which one pattern of adhesive lines has a whole number of node pitches and the row of perforations has a whole number of perforation pitches, both numbers being repetitive for each of said minimum dimension occurring.

2. The method as claimed in claim 1 in which the step of dividing is accomplished by slitting the web along two lines, each of which is spaced the same lateral distance from a row of perforations and in which the stacking is accomplished by spindling.

3. The method as claimed in claim 1 and the additional steps of cutting the two-ply web into double sheets of equal length and stacking the double sheets with the perforations in register and the ends of said sheets in vertical alignment.

4. The method as claimed in claim 3 in which the stacking is performed by spindling on at least one selected matched perforation of each sheet.

5. The method as claimed in claim 2 in which the stacking is accomplished by spindling on an end perforation of each sheet and using the side edge opposite the row of perforations as an alignment reference.

6. The method as claimed in claim 1 in which the node lines are applied by a printing cylinder of circumference C, in

which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression:

X=nPc=mR=C/u where n, m, and u are whole numbers.

7. The method as claimed in claim 6 and the additional step of changing the cell size of the resultant honeycomb core structure solely by substituting for said printing cylinder, another printing cylinder having the same circumference but a different node line pitch.

8. The method of making honeycomb core structures of different cell sizes on the same machine in different runs with a minimum modification of the machine for each cell size, comprising the steps of:

A. printing, with a print roller of circumference C, a pattern of node lines of pitch Pc on the halves of a double width web;

B. staggering the node lines in one pattern relative to the other;

C. applying perforations of pitch R along an edge of each pattern in identical transverse location along the length of the web;

D. slitting the double web in half after printing and applying the perforations;

E. registering the two half webs in face to back engagement with the perforations of one half registered with those of the other half;

F. cutting simultaneously the engaged half webs in equal lengths L of any multiple M of a whole number X;

G. said steps of printing, applying perforations, and cutting in combination determining the dimensional requirements of X= nPc mR C/u where n, m, and u are whole numbers and;

H. changing only the print roller pitch P to a different value for said printing step for each respective cell size.

9. In a method of making honeycomb core structure in a stack suitable for further processing by at least expanding the same and in which a pair of webs is laminated face-to-back, each web having a pattern of transversely printed adhesive node lines thereon, the pattern of one web being staggered along its length with respect to the other, and in which the laminated web is cut into a plurality of equal lengths that are stacked one upon the other to form a lay-up, the steps of:

A. printing node lines and perforating each web in accordance with the following arrangements:

1. perforating both webs along the same edge thereof at an equal pitch in rows of perforations equally spaced from said respective edges, and extending along the lengths of said webs,

2. printing a pattern of node lines on each web in the same imperforate area, identically spaced from the respective rows, of identical node pitch, but with one pattern displaced from the other by half a node pitch, relative to the identical transverse alignment of perforations,

B. bringing the webs together alternately in face-to-back engagement with their perforations registered to form a two-ply web prior to cutting, and

C. cutting the two-ply web at a length chosen as a multiple of a minimum dimension at which one pattern of adhesive lines has a whole number of node pitches and the row of perforations alongside said pattern has a whole number of perforation pitches, both numbers being repetitive for each of said minimum dimension occurring.

10. The method as claimed in claim 9 in which the printing is done before the perforating. I

11. The method as claime in claim 9 In which the two webs comprise halves of a double web and the printing and perforating are performed on said double web, and which includes the further step of slitting said double web along its center to form the said two webs prior to bringing them together.

12. The method as claimed in claim 9 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L=MX where L is the length of the sheet and M is any whole number multipleand X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression: X=nPc=mR=C/u where n, m, and u are whole numbers.

13. The method as claimed in claim 10 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Fe, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression:

X=nPc=mR=C/u where n, m, and u are whole numbers.

14. The method as claimed in claim 10 in which the two webs comprise halves of a double web and the printing and perforating are performed on said double web, and which includes the further step of slitting said double web along its center to form the said two webs prior to bringing them together.

15. The method as claimed in claim 14 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pa, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression:

X=nPc=mR=C/u where n, m, and u are whole numbers.

Claims

1. In a method of making honeycomb core structure in a stack suitable for further processing by at least expanding the same and in which a pair of webs is laminated face-to-back, each web having a pattern of transversely printed adhesive node lines thereon, the pattern of one web being staggered along its length with respect to the other, and in which the laminated web is cut into a plurality of equal lengths that are stacked one upon the other to form a lay-up, the steps of: A. printing the patterns of node lines side-by-side along the length of a double width web, on one face thereof, with the patterns staggered along the length of the web, each pattern occupying somewhat less than half of the web, respectively, B. perforating the web along its length on two transversely spaced rows, one row being in a clear path between the side edge of one pattern and one edge of the double width web, the other being in a clear path between patterns, the perforation pitch of each row being equal along the row and each perforation of one row being transversely aligned with an identical perforation in the other row normally to the rows irrespective of the staggered arrangement of the patterns relative one another, C. dividing the web along its centeR to provide a pair of half webs each having a pattern and a row of perforations, D. bringing together the half webs with their perforations in register and without changing their lengthwise relative orientation substantially, to form a two-ply web prior to cutting, the cut length dimension being chosen as a multiple of a minimum dimension at which one pattern of adhesive lines has a whole number of node pitches and the row of perforations has a whole number of perforation pitches, both numbers being repetitive for each of said minimum dimension occurring.

2. printing a pattern of node lines on each web in the same imperforate area, identically spaced from the respective rows, of identical node pitch, but with one pattern displaced from the other by half a node pitch, relative to the identical transverse alignment of perforations, B. bringing the webs together alternately in face-to-back engagement with their perforations registered to form a two-ply web prior to cutting, and C. cutting the two-ply web at a length chosen as a multiple of a minimum dimension at which one pattern of adhesive lines has a whole number of node pitches and the row of perforations alongside said pattern has a whole number of perforation pitches, both numbers being repetitive for each of said minimum dimension occurring.

6. The method as claimed in claim 1 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression: X nPc mR C/u where n, m, and u are whole numbers.

8. The method of making honeycomb core structures of different cell sizes on the same machine in different runs with a minimum modification of the machine for each cell size, comprising the steps of: A. printing, with a print roller of circumference C, a pattern of node lines of pitch Pc on the halves of a double width web; B. staggering the node lines in one pattern relative to the other; C. applying perforations of pitch R along an edge of each pattern in identical transverse location along the length of the web; D. slitting the double web in half after printing and applying the perforations; E. registering the two half webs in face to back engagement with the perforations of one half registered with those of the other half; F. cutting simultaneously the engaged half webs in equal lengths L of any multiple M of a whole number X; G. said steps of printing, applying perforations, and cutting in combination determining the dimensional requirements of X nPc mR C/u where n, m, and u are whole numbers and; H. changing only the print roller pitch Pc to a different value for said printing step for each respective cell size.

9. In a method of making honeycomb core structure in a stack suitable for further processing by at least expanding the same and in which a pair of webs is laminated face-to-back, each web having a pattern of transversely printed adhesive node lines thereon, the pattern of one web being staggered along its length with respect to the other, and in which the laminated web is cut into a plurality of equal lengths that are staCked one upon the other to form a lay-up, the steps of: A. printing node lines and perforating each web in accordance with the following arrangements:

10. The method as claimed in claim 9 in which the printing is done before the perforating.

11. The method as claimed in claim 9 in which the two webs comprise halves of a double web and the printing and perforating are performed on said double web, and which includes the further step of slitting said double web along its center to form the said two webs prior to bringing them together.

12. The method as claimed in claim 9 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression: X nPc mR C/u where n, m, and u are whole numbers.

13. The method as claimed in claim 10 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression: X nPc mR C/u where n, m, and u are whole numbers.

15. The method as claimed in claim 14 in which the node lines are applied by a printing cylinder of circumference C, in which the node line pitch is Pc, and in which the perforation pitch is R and the relationship between these factors is defined by the formula L MX where L is the length of the sheet and M is any whole number multiple and X is said minimum dimension and is a whole number factor of the circumference of the print roll and also satisfies the expression: X nPc mR C/u where n, m, and u are whole numbers.