US1796542A - Corrugated paperboard and method of making the same - Google Patents

Description

March 17, 1931. v SCHQO 1,796,542

CORRUGATED PAPER BOARD AND METHOD OF MAKING THE SAME Filed 001.. 7, 1930 IN V EN TOR.

, CZARf/VCZJ S0700 l I I I I p c b c D q i I I a ATTORNEYS.

Patented Mar. 17, 1931 UNITED STATES 1 .'rr.1-rr OFFICE CLARENCE J. SCHOO, 0F SPRINGFIELD, MASSACHUSETTS, ASSIGNOR T0 GENERAL FIBRE BOX 00., OF WEST SPRINGFIELD, MASSACHUSETTS, A CORPORATION OF MASSA- GHUSETTS CORRUGATED PAPERBOARD AND METHOD OF MAKING THE SAME Application filed October 7, 1930. Serial No. 486,931.

In the manufacture of corrugated paper board the general procedure followed is to pass a Web of suitable heavy paper, which in past practice has generally been formed of a straw base, between heated meshing fluted rolls. F or the proper control of the paper the paper web is supplied to the rolls under tension and is forced into corrugated form by the action of the alternating ridges and valleys on the two rolls. These rolls are generally held in meshing relation under a heavy spring pressure which permits the rolls to yield and thus to accommodate themselves to irregularities in the thickness of the paper web. In order to set the paper in its corrugated form it is generally steamed before passing between the rolls, and the rolls are heated to dry out the moisture and to give an ironing action which causes the paper to retain the shape given to it by the corrugations.

While the Web thus corrugated is still supported by one of the rolls, an adhesive is applied to the crests of its corrugations on one side. A separate web, called a lining sheet, is applied to the adhesive coated side of the corrugated web, being bridged across the crests of the corrugations and imparting a truss-like rigidity to the two-ply laminated product. This material is sometimes used in its two-ply form, being known as singlefaced corrugated board but in order to make a stronger product a lining sheet is usually added upon the other side, the crests of the corrugations on the second side of the corrugated web being previously coated with adhesive. This product is known as double .faced corrugated board.

While my invention, as will appear from the description below, has with beneficial results been applied to the single faced prodnot, its full advantage is felt only with double faced board. The latter product will therefore be considered chiefly in pointing out the diiiiculties inherent in former methods of manufacture and overcome by the use of my invention. The two lining sheets of the double faced board lie parallel ,to each other and are adhesively secured to opposite sides of the corrugations, giving a double trussing action which impartsgreat rigidity to the composite board. Variations in the height of the corrugations, or failure of the corrugations to reach the height at which maximum rigidity is obtained, affect the strength of the product seriously. If some corrugations are lower than others, they may not receive any adhesive or may fail to make contact with the lining sheet. If some corrugations are higher than the average, they may be crushed down in applying the second lining sheet. fective and is easily bent along the line of each improperly formed corrugation.

In past practice, attempts to corrugate the central web uniformly to the proper height by using a high pressure between the rolls have not been uniformly successful. While some grades of paper, such as the relatively low-strengthstraw paper, have been corrugated commercially, attempts to secure equivalent corrugating efi'ect with papers of higher strength have met with diliiculties of considerable magnitude. Among these difficulties may be mentioned the weakening or actual rupture of the paper during corrugation when a pressure was employed sufiiciently high tomake corrugations of uniformly fullv height; the failure to force the paper all the way into the flutings of the corrugating rolls; irregularities in the height of the corrugations produced; and sticking of the paper to the rolls with a consequent tearing ofi of a portion of the paper fibers. It is the object of my invention to avoid these dimculties, to improve the speed of production and the quality of the product, and to render possible the corrugation with substantially equal facility of a wide variety of papers.

one important step in my improved process, I apply a very thin film of a lubricant such as melted paraflin to the tops of the ridges or corrugation on the 'corrugating rolls. As a result all of desirable results above referred to may be secured. More particularly a-kraft paper may be used successfully as the corrugated sheet in a high speed machine, something which as far as I In either event, the board is deknow has never heretofore been accomnot entirely understood by me. It is not believed to be merely a case of reducing friction of the paper in moving over the corrugations of the rollers because these corrugations are of smooth and polished steel, offering very little friction and tests have demonstrated that some papers may be successfully used in my improved method, which could not be satisfactorily used heretofore even though they gave every indication of being smoother and offering less friction than the straw paper which has in the past offered less objection than most other types of paper.

I am aware that paper has been coated or saturated with paratlin to facilitate bending into predetermined shapes or to assist in the retaining of such shapes but such prior practice is not to be confused with my improved method.

It is important that in my improved process the paper shall not be coated to any such extent as will prevent the steam or moisture in the paper from being rapidly driven out by the heat of the corrugating rollers. Silicate of soda is the adhesive most commonly employed for securing the liners to the crowns of the corrugations of the intermediate sheet. The amount of paraffin added must also be so slight that it does not interfere in any way with application of the adhesive, whatever its kind, or the prompt efficient and lasting action of the adhesive in connecting the sheets together along the narrow lines of tangeney of the corrugation crowns with the parallel lines to form a rigid structure.

Experience has demonstrated that one pound of paraffin is all that is needed for making at least 17,000 square feet of double faced paper from which it will be seen that the film of paraffin on any portion of the surface of the paper is so thin that it is immeasurable; can have no waterproofing or coating effect; does not fill the interstitial spaces in the paper: does not change the appearance or feel of the product; and does not interfere with the aste from being re-treated for further manufacture into paper products.

So far as T am aware, the low percentage of paraffin which is used in my paraffin treating process and is incorporated into my improved double faced corrugated board would have no effect whatever in any other art where it has been customary to use paraffin coated or saturated paper. Furthermore such paraffin treated papers as are commonly used in other arts have entirely too high a percentage of paraffin to permit of their satisfactory use in securing the results accomplished by my improved method of making double faced corrugation paper.

The paraffin is advantageously applied in liquid form by means of wicks having wiping engagement with the outer edges only of the successive ridges or corrugations of the rollers. The rollers being heated may serve weasee to keep the paraffin melted in the supply re ceptacle or it may be kept melted in other ways but it is important that the paraffin be kept from solidifying in and closing the pores of the wicking. As the wicking contacts with the heated rollers, the heat of the rollers serves this function.

The invention will now be described with particular reference to the accompanying drawings, in which:

Fig. 1. is a diagrammatic representation of mechanism by which my improved process may be practiced; and

Fig. 2 is a perspective detail of a fragment of corrugated board.

The web a of material to be corrugated passes over guide rolls 10 and a steaming device 11 to the surface of a corrugating roll 12. This roll has teeth 13 meshing with similar teeth 1% on a second corrugating roll 15. The roll 12 is mounted on a bracket 16 pivoted at 17 to a stationary part of the machine and is pressed towards the roll 15 by a compression spring 18. As the paper Web passes between the two corrugating rolls, it is forced into its final corrugated condition, and is set in this condition by the heat of the rolls, generally kept at over 300 F. This heat is generally supplied by steam circulated through the hollow interior of the rolls. An adhesive applying roll 19 runs in contact with the corrugated paper on roll 15 and applies a film of adhesive such as sodium sili- 'ate to the high points of the corrugations. This roll receives adhesive from a supply roll 20 dipping into a tank 21. A lining web b is passed over a roll 22 running adjacent to the surface of roll 15, and is pressed thereby into adhering contact with the corrugated paper. The composite web then passes an adhesive applying roll 23, which receives adhesive from a roll 24 and a tank 25 and applies adhesive to the second side of the corrugated web. The second lining sheet 0 is passed around a roll 26 and is pressed against the corrugated web by this roll and a mating roll 27.

This arrangement of apparatus has been described rather briefly, as it is common in the art. It does, however, illustrate the environment with which the mechanism now to be described is combined to produce the novel results referred to above. According to my invention the lubricant is preferably applied to the crests only of the flutings on the corrugating rolls, being allowed to spread over the remainder of the roll surface. This spreading takes place with considerable rapidity on account of the heat of the rolls, and I have found this method of application to have several features of advantage. In the first place, the portions of the roll flutings which required the maximum lubrication are the crest and the sides. It is the crest which ICLEIYCS the maximum frictional contact of the paper during the drawing of the paper around the roll into corrugated form. It is the sides to which maximum pressure is applied during the actual corrugating, and to which the paper is most likely to stick. The bottom of the groove gives comparatively little trouble during the corrugating operation, and requires little if any lubrication. The bottom of the roll flutings, moreover, corresponds to the crest of the corrugation which is formed in the paper, and it is to this point that the adhesive is subsequently applied. Any appreciable quantity of lubricant will harmfully aifect the sticking of the adhesive to the paper, and it is thus of importanceto prevent the accumulation of an excess of lubricant at the bottoms of the roll flutings. My preferred manner of applying lubricant to the roll surface consists in permitting the outer portions of the flutings to wipe against a wick saturated with the lubricant. This has certain advantages over other methods of application such for example as spraying, for in the latter case the force of the spray would tend to cause an accumulation of lubricant at the bottom of the flutings with a minimum at the top and sides, the reverse of the condition desired.

Referring now to the mechanical details of the apparatus which forms the preferred embodiment of my invention, a tube 30, closed at its ends, is located adjacent the roll 12. Flanges 31 are secured in parallel relation along this roll, leaving between them a space communicating with the interior of the tube. A wick 32 fills this space and is subject to compression to any de ree desired by one or more adjusting screws. %3y tightening the screws the wick will be compressed and the amount of lubricant delivered from the interior of the tube 30 will be lessened. The tube is positioned close to the roll 13, conveniently between it and the steaming device 11, so thatwhen paraflin is used as a lubricant the normal heat of the surrounding parts will be sufiicient to preserve the parafiin in molten condition without the use of special means for heating the tube. The wick 32 is positioned so that it drags upon the periphery of the corrugated roll 12, spreading a thin layer of the lubricant upon the crest of the flutings. As the tube is limited in size on account of its position and is for the same reason rather difficult to fill with lubricant, it is preferably kept filled from an external source. For this purpose it is con- 'nected by a flexible conduit 34 to a steam jacketed tank 35 which may be positioned wherever convenient.

Above the second corrugating roll 15 is a funnel-shaped trough 36 having a wick 37 clamped between its lower edges by one or more adjusting screws 38. This trou h is also so located relative to the normally eated machine parts that in practice para will be kept melted in it due to the heat of the corrugating rolls, and a separate steam jacket will be unnecessary, The wick 37 drags over the crests of the flutings on the roll 15 in the same manner as has been described with relation to the wick 32.

It will be noted that the wick 32 applies its lubricant to the crests of the flutings on roll 13 prior to the contact of the web a with it. The web travels at a speed higher than the surface speed of the roll, on account of the surplus material required for the formation of the corrugations. The lubrication greatly decreases the frictional resistance necessary to be overcome in drawing to the corrugating point the amount of paper required. It also facilitates the actual corrugating operation and prevents stickin of the paper to the roll. The valleys of the utings on roll 12, which preferably receive the lubricant only through spreading and not directly from the wick, and which therefore receive the minimum amount, correspond to the crests of the corrugations which later contact with the adhesive-applying roll 19 and with the lining sheet b. While the total amount of lubricant applied is'preferably very small (it may be on the order of onethousandth of an ounce of paraflin per square foot of paper), this gives added insurance that on the crests of the corrugations there will not be a quantity of lubricant sufiicient to prevent the later applied adhesive from adhering. Similar remarks of course apply to the wick 37.

Claims:

1. Double faced corrugated paper board comprising a central corrugatedweb'and a pair of lining webs, one adhesively secured to the crests of the corrugations on each side of the central web, said central web carrying paraffin in suificient quantity to permit its uniform corrugation to full height without undue strain but insuficient in quantity to affect the sticking theretoof the adhesive joining it to the lining webs, to produce an appreciable waterproofing effect in the central web, or to produce any commercially perceptible change in the natural properties of the paper out of which the central corrugated web is formed, the paraflinbeing carried by the central web in maximum amount on the inside of the crests of the corrugations and in minimum amount on the outside of said crests.

2. Double faced corrugated paper board comprising a central corrugated web and a pair of lining Webs, one adhesively secured to the crests of the corrugations on each side of the central web, said central web carrying parafiin distributed thereon in a concentration of the order of one thousandth of an ounce per square foot, the paratfin being present on the inside surfaces of the crests of the corrugations of the central web in sufii- 4 messes cient quantity to insure uniform full corrugation of the Web to full height Without undue strain and present on the outside surfaces of the crests of said corrugations in insufiicient quantity to prevent sticking E thereto of the adhesive joining it to the lining Webs.

3. Double faced corrugated paper board comprising a central corrugated Web and a lining Web adhesively secured to the crests w of the corrugations on each side of the-central web, said central web being corrugated uniformly and fully and carrying a lubricant suiiicient in quantity to permit its uniform corrugation to full height Without undue 15 strain but insufiicient in quantity to produce any commercially perceptible effect upon the natural properties of the paper or upon the sticking thereto of the adhesive joining it to the lining Webs.

4. A method of corrugating paper which comprises subjecting the paper to corrugating pressure between preformed surfaces in the presence of an intervening lubricant suf- F ficient in amount to cause the paper to be fully and uniformly corrugated but insufiicient to be commercially perceptible in. the corrugated product.

5. A method of corrugating paper which comprises subjecting the paper to corrugatimp pressiuie between heated preformed surfaces in. the presence oi? an intervening film of molten paraiiin. sui'licient in amount to cause the paper to be fully and uniiorrnly 35 out insui' cient to he commercially ceptioie in the corrugated prodmzt, said pciailin. neing o "inuted in a concentration of the order or one thousandth oi en ounce per square foot or the pap-er.

ii. method of corrugating paper which. comprises steaming bhe paper, subjecting the moist paper to con n aring pressure between. ueforincd su faces in the presence of vening film. of molten paraiiin sufiicient in amount to cause the paper to be fully and uniformly corrugated but suiiicient to be commercially perceptible in the corrugated product,

'7. method oi? corriigating paper by heat 50 ano pressure between preformed surfaces 1 "\in lubricant to the oi the surface pressing the paper xetner the surfaces siinultancwsly subjecting it to the action eii heat. applying an adhesive to the crests the corrugations in the paper, so that the adhesive contacts with portions of the paper aiiected only by such lubricant as has migrated over the tinted surfaces and presseo inn lining; sheets upon. the adhesive coated corrugations.

in t LllnOIlj whcreoi i have attired my signature.

CE J. SGHQG C

Images