US 3555976 A
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 Patented United States Patent  Inventors Charles 1. Carter;
Rupert 0. Rogers, Mobile, Ala.
Jan. 14, 1969 Continuation-impart of Ser. No. 585,175, Oct. 7, 1966, Patent No. 3,428,239
Jan. 19, 1971 International Paper Company New York, N.Y.
a corporation of New York  AppLNo,  Filed  Assignee  METHOD AND APPARATUS FOR PRODUCING SPIRAL WOUND CONTAINER 9 Claims, 19 Drawing Figs.
 US. Cl 93/80, 93/36.9, 93/58, 93/59, 93/94  Int. Cl B31c 3/04,
 Field ofSearch 93/369, 58(ST),59(CEMT),77 (CL),80,94(1V1)  References Cited UNITED STATES PATENTS 2,387,439 10/1945 Grabus 93/59 3,108,516 10/1963 Elam 93/59 3,159,515 12/1964 Dunlap... 93/94 3,196,762 7/1965 Schmeltz... 93/94 3,253,520 5/1966 Cvacho 93/80 3,274,905 9/1966 Demsey 93/94 3,304,844 2/1967 l-losenfeld 93/94 3,400,029 9/1968 Mesrobian 93/94 3,406,614 10/1968 Martin 93/80 3,457,130 7/1969 Morrison... 93/77 3,468,225 9/1969 Pesch 93/94 3,468,733 9/1969 Dunlap 93/80X 3,485,147 12/1969 l-lurst.. 93/80 3,495,507 2/1970 Haas .1: 93/58 Primary Examiner wayne A. Morse, Jr. Atlorney-Charles B. Smith ABSTRACT: A method and apparatus for producing spiral wound containers in which a plurality of plies, coated on at least one surface with a thermoplastic coating, are spirally wound onto a mandrel, heated and adhesively secured with the thermoplastic coatings to form a spirally wound tube and the spirally wound tube is cut into can length units, the ends of the can length units are moistened and flared and can ends are attached.
v l 31555976 SHEET 1 of 6 1 I r z I y I II .nflu-HHFPflL-"F i I A J ll lllli I I'll Ill. m ii! I I Al I I I I I II lvll ll v V k h V PATENTEIDJANISIQYL 3555976 satnanra METHOD AND APPARATUS FOR PRODUCING SPIRAL WOUND CONTAINER This application is a continuation-impart of application Ser. No. 585,l74. filed Oct. 7, I966 now Pat. No. 3.428.239by Thomas M. Wannamaker, Charlesl. Carter and Rupert'O. Rogers. The instant invention relates to a method and paratus for producing spiral wound containers.
There is shown and described. inthe aforementioned application. an improved spiral wound container for malt beverages such as beer and ale and for similar products packaged and sealed, under pressure. In such improved spiral wound container an inner ply. intermediate ply and outer or label ply. suitably coated with a thermoplastic material. are laminated, or wound, one over the other, and adhesively united by the thermoplastic coating material to form a .container body that, when suitably flanged and capped, provides a container to withstand the conditions and abuses normally encountered in handling, shipment. storage and use.
Containers of the type shown and described in the foregoing application are used in large quantities. Hence. to be commercially acceptable, such containers must be produced in large numbers, within close tolerances, inexpensively and uniformly. The instant invention is concemed with the method and apparatus for producing such containers.
In the instant invention, a continuous-strip of foil, coated on its inner surface with a slip and sanitary coating, is spirally wound onto a mandrel simultaneously with a continuous tape, coated on its inner surface with a slip and'sanitary coating and, on its outer surface, with a thermoplastic adhesive. The foil strip and tape are spirally wound simultaneously with the trail ing edge of the foil strip overlapping a" portion of the tape across the tape width. The remaining portion of the tape width projects beyondthe trailing edge of the foil strip so that. as the next following winding is brought into abutment with the trailing edge of the preceding winding, the leading edge of the following winding overlaps the tape. The abutting edges are then heated, softening and activating the thermoplastic coating on the tape. Theedges are then cooled and the tape seals the abutting edges of the foil strip. One or more thermoplastic coated strips of body ply are next spirally wound onto the abutted. tape sealed, foil strips. Prior to being spirally wound, the edges of the body ply strips are skived and the skived edges are overlapped. The body ply is then heated, softening and activating the thermoplastic coating and. is'then cooled, uniting the body ply to the spirally wound foil strip. Finally, an outer or label ply, coated with a'therrnoplastic coating, is spirally wound over the outer body ply, heated to soften and activate the thermoplastic coating and cooled, uniting the outer ply with the inner ply and the spirally wound, sealed, foil strip.
The spirally wound tube. with the tape joined and sealed inner foil strip, body ply and outer or label ply adhesively united. is fed oh of the end of the mandrel, cut into suitable length, the ends are moistened and flared and end closures are attached.
The instant invention will be more. fully understood from the following description and appended drawings of a preferred embodimentof the inventionin which:
FIG. I is a top plan view, partly diagrammatic, illustrating a methodarid apparatus in accordance with the invention for making spiral wound can bodies;
FIG. 2 is a vertical sectional view taken along the line 2-2 of FIG. I;
FIG. 3 is a vertical sectional view taken along the line 3-3 of FIG. I;
FIG. 4 is a cross-sectional view of an outside laminate layer for a can body fabricated in accordance with the invention;
FIG. 5 is a cross sectional view ofan intermediate laminate layer or body ply for a can body fabricated in accordance with the invention;
FIG. 6 is a cross-sectional view of another intermediate laminate layer or body ply;
FIG. 7 is a cross-sectional view of an internal laminate layer or barrier ply for a can body embodying the invention;
FIG. 7A is a cross-sectional view of a tape for a can body embodying the invention; FIGS. 47 and 7A being intended to be generally to practical scale as to width but being substantially enlarged as to thickness to better illustrate the construction of the various plies; 7
FIG. 8 is a side elevational view of a can body as produced by the method and apparatus of FIG. I;
FIG. 9 is an enlarged cross-sectional view of the can body wall taken along the line 9-9 of FIG. 8;
FIG. 10 is a cross-sectional view ola typical can end closure element constructed in accordance with the invention;
FIG. II is a partial longitudinal sectional view ofa can body showing the flared edge provided prior to-assembly of the end closure element to the can body;
FIG. 12 is an enlarged partial cross-sectional view of the end closure element of FIG. 10 processed so as to have a rolled in edge and an annular layer of calking FIG. I3 is an enlarged partial sectional view illustrating an intermediate point in the operation of assembling the can body and end closure;
FIG. 14 is a view similar to FIG. 13 at a more advanced point in the operation;
FIG. 15 is a view similar to FIG. l4'at a still more advanced point in the operation;
FIG. 16 is a view similar to FIG. 15 at a still more advanced point in the operation;
FIG. I7 is a view similar to FIG. 16 but showing the completely assembled can body and end closure;
FIG. 18 is a partial vertical sectional view showing the end construction of a modified can body embodying the invention; and
FIG. 19 is a view similar to FIG. 17 but embodying the construction of FIG. 18.
While the invention will be described primarily in connec tion with cans for packaging beer and ale, it should be un' derstood that the principles of the invention may be applied to cans for packaging other products.
Referring now to the drawings and more particularly to FIG. 1, there is shown a spiral tube winding machine basically of ordinary construction but with certain modifications in accordance with the invention.
In FIG. I a four ply or layer tube 10 is wound on a cylindrical mandrel 11 by a winding belt 12. Motion is imparted to belt 12 by winding belt pulleys l3 and 14 which are suitably driven in a conventional manner. In FIG. 1 the tube 10 advances along mandrel 11 toward the left, as shown by the ar' row. Successive lengths of the tube 10 are cutoff at predetermined locations by a suitable saw or knife, indicated diagrammatically at 16, to provide individual can bodies 17. One tube length or a plurality of tube lengths may be cut off simultaneously. and the cutting operation will be effected so that the usual printed matter on the outside ply of each can will be in proper registry, as is well known in the art.
The tape and four plies which make up the tube 10 are designated I5, 18, I9, 20, 21, respectively. The tape and plies are fed from conventional rolls (not shown). The tape 15 and ply 18 are the first to be wound on the mandrel I1 and serves as the barrier ply of the can bodies. The ply I9 is the second to be wound and, as shown, overlies the barrier ply I8. The ply 20 is the third to be wound and, as shown, overlies the ply 19. The plies I9 and 20 are the can body plies and provide the principal structural strength for the can bodies. The ply 21 is the final ply to be wound and overlies the body ply 20. The ply 21 serves as the outside of the can bodies and usually will be provided with decorative or advertising matter on its outer surface, as is customary. The ply 21 thus forms the can label and will be referred to as the outer or label ply.
The construction of the barrier ply I8 is best shown in FIG. 7. The barrier ply I8 is formed as a laminate of two layers, inner layer 18A being a slip and sanitary coating and outer layer 183 being a metal foil, preferably aluminum foil.
The construction of tape 15 is best shown in FIG. 7A. Tape 15 is formed as a laminate of three layers, inner layer 15A being a slip of sanitary coating. intermediate layer B being a metal foil. preferably aluminum foil. and outer layer 15C being a heat scalable thermoplastic. preferably a low density polyethylene. By low density polyethylene is meant polyethylene having a density in the range of about .910 to .925 grams per cubic centimeter. A medium density polyethylene would have a density in the range of about .925 to .945. while a larger density polyethylene would have a density above about .945. The term "sanitary" as used herein. is intended to mean not only clean but also tasteless and odor less; in other words a coating which will not impart a flavor or odor to the packaged product and is inert to such product.
While polyethylene has been found to be particularly well suited for use as the heat scalable thermoplastic material for the layer 15C and similar layers of the various plies. as later described. other materials can be used. The most practical extrusion coatings at the present time are polystyrene and polymers or copolymers of the lower olefins (ethylene. propylene and butylene High melt coatings of low molecular weight polymers. ethylene-vinyl acetate or wax blends of either resin would be suitable.
The tape 1513 should be a self-supporting foil free of pinholes. Tape 15B should be thin. but not so thin that wrinkling problems will interfere with winding and adhesion of the tape. An aluminum foil thickness of .001 inches and. preferably. .0015 inches has been found to be well suited for the purpose.
The layer 188 should be a self-supporting film free of pinholes. This layer serves as a principal moisture and gas seal for the can body and affords the structural basis for the barrier ply 18 as it is wound on mandrel 11. The layer 188 should be thin. but not so thin that wrinkling problems will interfere with winding. An aluminum foil thickness of 1 mil (.001 inches) has been found well suited for the purpose. From the stand point of a pinhole free layer. aluminum foil down to about .5 mil could be used. but wrinkling problems make a somewhat thicker foil more desirable with present handling techniques.
While aluminum foil has been found preferable. other foils could be used. e.g. a 2 mil tin-plated steel foil. It is believed that the layer 1813 could be made of plastic provided it was compatible with the rest of the can. would hold gas under pressure and would not cause sticking to the mandrel. So far no suitable plastic has been found.
The slip and sanitary coating forming layer 15A and 18A has three principal functions. These are facilitating sliding relative to the mandrel surface, i.c., reducing friction and avoiding sticking of tape 15 and ply 18 to the mandrel 11. a sanitary coating preventing direct contact between the metal tape 15B and 18B and the contents of the can and the sealing of such tiny holes as may exist or may be formed in tape 15B and 18B. In this regard. while tape 15B and 188 should be pin hole free. as a practical matter complete avoidance of pinholes is not reasonably possible in a practical commercial operation with equipment and materials available so that it is desirable to afford a sealing layer which will seal such tiny holes as may exist.
The coating forming tape 15A and 18A will be quite thin. Typically it may be applied in a weight of about 0.5 to 2.5 pounds per ream. a ream being 3000 square feet. The material used for the coating might be. for example, one of the commercially available vinyl materials in a nontoxic solvent system. The vinyl polymer material sold by Adcote Chemical Company under the name of Adcote 501 is a specific example of a suitable slip coating. The coating may be applied in any convenient manner. as by spraying. rolling or brushing.
As shown in FIGS. 1 and 2. tape 15 and barrier ply 18 are simultaneously wound onto mandrel ll. Tape 15 is fed over guide 15' into contact with inner layer 18A of barrier ply 18 along the trailing marginal edge of barrier ply 18 with outer layer 15C of tape 15 in contact with inner layer 18A of barrier ply 18. Substantially half of the width of tape 15 is under tape 18 along the marginal trailing edge of layer 18 as tape 15 and layer 18 are wound onto mandrel 11. The remaining approximate half width of tape 15 projects outwardly from the marginal edge of layer 18.
The leading edge of ply 18. first contacting mandrel 11 at any instant (the left edge in FIG. 1) abuts the trailing edge of the preceding barrier ply 18 turn and overlays the projecting half width of tape 15. tape 15 forming a taped joint between the abutting edges of adjoining barrier ply convolutions. At the point where the leading edge of ply 18 first contacts mundrel l1. abuts the trailing edge of the preceding barrier ply and overlaps the projecting half width of tape 15. the abutting marginal edges ofply l8 and tape 15 are heated by flame 22 of burner 23. Flame 22 heats and softens the polyethylene outer surface outer layer 15C of tape 15. adhesively securing tape 15 to the inner surface of adjoining and abutting spirally wound convolutions of ply 18 thereby forming an adhesive tape secured and liquidtight joint between the trailing and leading edges of abutting convolutions of layer 18.
The barrier ply and tape supply or web are maintained under substantial tension so that the tape and barrier ply drums will be tightly wound and so that the contacting polyethylene tape surface and marginal edges ofthe ply will be forced together under substantial pressure to form a firm. liquidtight taped seam. The webs for the other plies are likewise maintained under substantial tension.
The construction of the two body plies l9 and 20 are preferably identical and comprise can stock layers. designated 19A and 20A. respectively. and polyethylene layers. designated 19B and 208. respectively. extrusion coated to the can stock layers.
The can stock layers of the body plies afford the principal structural strength for the can bodies and hence should be made from relatively strong materials. kraft paper can stock having been found particularly well suited for this purpose. The minimum usable paper weight for the can stock layers is dependent. in part. on the paper tensile strength. Thus is has been found that to resist failure of the cans by creeping under long term loading. the can stock paper in the finished can should not be subjected to a long term load exceeding about 40 to 50 percent ofits ultimate tensile strength.
Another factor which influences the can stock paper weight is the winding angle of the body plies. The winding angle is measured. as is customary in the tube winding an. between the longitudinal axis of the ply in question as it approaches the mandrel and a line normal to the axis of the mandrel. This angle is shown for ply 19 as the angle in FIG. 1. The winding angle is important with respect to strength because most Fourdrinier board has more strength in the direction in which it is made than in a cross direction. Hence it is desirable to take advantage of the greater machine direction strength of the paper by using as small a winding angle as practical. For a pressure can. a winding angle of about 27 has been found most advantageous. It should be noted that the circumferential (hoop) stress in a cylindrical vessel such as a beer can is twice that of the longitudinal stress and hence it is desirable to maximize the can body strength around the circumference of the can. It is desirable that the same winding angle be used for the barrier and label plies. e.g. 27.
For a pressure can expected to have to withstand a pressure of -95 p.s.i., which would be expected when beer is pasteurized at F., the can stock layers for the body plies may conveniently be about 210 pounds per ream, assuming a winding angle of 27. Such a board would have a thickness of about 17 mils.
Because of the slight increase in tube diameter caused by the presence of the first body ply 19, the second body ply 20 should be slightly wider than the first ply. For example. a 21 1- size can (12 ounce) might have a ply 19 with a width of 4 5/32 inches while the ply 20 might have a width of4 3/16 inches.
In general it is desirable that the can stock layers 19A and 198 have relatively smooth surfaces. One reason for this is that a smooth paper surface reduces the weight of polyethylene coating required for heat sealing the body plies. Another reason is that on the outside body ply 20 a smooth surface provides a smooth base for the label ply which greatly improves the appearance of the cans.
. each layer typically might be about I0.8 pounds per ream.
While it is preferable to provide both of the polyethylene layers 19B and 208. so long as polyethylene layer 18C is provided on barrier ply 18. the polyethylene'laycr 198 on inner body ply 19 could be eliminated.
An important feature of the pressure can of the invention has been the use of skived joint'sinforniing the body plies.
Skiving contributes to the strength of thebody plies by affording large contact areas at the joints'..If-butt.joints were to be used. a gap of.several thousandths of'aninch would occur in commercial winding. Such a gap would allow. a crevice to form and the high pressure in the canwould force the barrier ply into this crevice. eventually causing a leakat the end seam.
In order to provide a skivedjoint for each of the body plies.
each of the body ply webs supplied to the-mandrel II is passed through a skivingunit 24 which tapers the body ply edges as shown at 19C. 19D. 20C and 20D. The skiving unit 24 may contain sanding wheels or other suitable devices .for skiving the body, ply edges. The polyethylene coating on the body plies join the skivetl ply edges to form respective tubes on the mandrel 11. l j a The can body ply.webs I9 and 20 are passed under mandrel 11 from the opposite side. shown for barrier ply web 18 and are wound on the mandrel in the usual way with the respective plies each forming complete tubes. Theply l9 overlies ply 18. while ply 20 overlies ply 19. The polyethylene layers 198 face upward in FIG. 1. causing these plies to be wound with the polyethylene layers facing the inside of the can body.
A series of burners 25, 26. .27 and 28 is positioned over the can stock ply web 19 just prior to the. web 19 reaching mandrel 11. Each of the burners 25-28 directs a gas flame downwardly onto the polyethylenelayer 19B and completely across the width of the layer to heat the entire polyethylene surface to a heatsealing temperature. The'last one of the butners. designated 28. preferably directs its flame onto the polyethylene surface at the point of contact of that layer and the barrier ply 18 on mandrel 11. The flame from burner 28 will thus heat the polyethylene layer 195 and barrier ply l8. affording a maximum heat sealing action. As shown at 198' in FIG. 9. softened polyethylene from layer l9Bwill enter the tiny space at the lap of ply I8. r I
A set of burners 29. 30. 31 and 32. which may be identical to the burners25-28. is similarly positioned over can body ply web 20 so that the latter forms a tube as described in connection with ply 'l9. ln 'this case the polyethylene layer 205 will be heat sealed to the can stock paper layer 19A.
The skived joint between the trailing edge of one turn of ply l9 and the leading edge of the next turn of ply 19 on mandrel 11 is shown at 19F in FIG. 9. The corresponding skived joint 20F for ply 20 is similarly formed. his important that the entire inner surface of each of the body plies be adhesively attached to the underlying ply so that the entire can body will act as a unit. This adhesive attachment occurs by heat sealing polyethylene.
The label ply 21 is shown in detail in FIG. 4. The label ply is formed from four layers laminated together. These are an inner polyethylene layer 2IA. a kraft paper layer 218. a polyethylene layer 21C and a metal foil layer 21D. The principal strength for ply 21 is provided by layer 218 which might be. for example. a 25 pound (per ream) natural machineglazed kraft paper. The kraft paper weight preferably lies in the range of about 25 to pounds. The polyethylene layers 21A and 21C maybe laminated or coated on the opposite sides of the paper 218 in the usual way. The outer layer of metal foil may also be laminated to the polyethylene as is well known in the art.
The foil layer 21D is preferably aluminum foil and may be as thin as desired so long as it is strong enough to be laminated to the paper. Typically the foil layer 21D might be 0.00035 inches. although satisfactory results have been achieved with 0.000285 inches aluminum foil.
The polyethylene layers" 21A and 21C might each be coated. for example. at a weight of I08 pounds per ream. The outer polyethylene layer 21C is preferably medium density to make the label more resistant to wrinkling on the can line. The inner polyethylene layer 21A is preferably low density to facilitate heat scaling to the outer body ply 20.
The label ply web 21 is fed to the tube on mandrel II from the same side as is barrier ply web .18. but at an advanced or downstream location relative to the previous plies l8. l9 and 20. It is desirable that the label ply 21 be wound on the mandrel after the tube has been contacted by the belt 12 so that the latter will not mar the appearance of the label. The web 21 is fed over the mandrel 11. as shown'in FIGS. 1 and 3. A burner 33 is positioned under web.2l .in advance ofthc web 21 contactingthe tube on mandrel I1. Burner 33 directs a gas flame onto polyethylene layer 21A toheat the entire width of the layer 21A to a heat sealing temperature.
The outer paper layer 20A of the tube on mandrel prior to contact with ply 21 is heated by a gas flame directed thereon from a burner 34. Itis desirable that burner 34 heat the entire outersurface of layer 20A to facilitate heat sealing thereto of the heated polyethylene layer 21A. For this purpose the length of burner 34 should be correlated with the speed of rotation of the tube on mandrel 11. If desired. additional burners may be provided peripherally spaced to heat the entire surface of layer 20A. The tension maintained on label ply web 21 should be sufficient to cause thesame to be tightly bonded to the paper surface 20A of ply 20. a
The leading edge of web 21 (left in FIG. I) overlaps the trailing edge of the preceding turn of web 21 to provide a simple lap seam. as shown in FIG. 9. Polyethylene from layer 21A fills this lap seam, as shown at 21A. affording a good sealing action similar to that of the polyethylene at 198' in the barrier layer lap seam.
It should be remembered that the thickness dimension in FIG. 9 is tremendously exaggerated. Hence while the label ply lap seam looks large in FIG. 9. actually this lap seam is so thin as to be hardly noticeable in the final can body.
Each of the plies of the can body of the invention with the exception of barrier ply 18 has been described as having one or more layers or coatings of polyethylene. So far as is presently known. polyethylene is thejmost suitable material for this purpose in view offactors such as cost. heat scalability. moisture vapor barrier properties and ease of extrusion lamination. Other plastics may. however, be found to have suitable qualities for these purposes and polyethylene could be replaced in one or more of the layers with such a plastic. In general. the polymers and copolymers of the lower olefins (propylene. ethylene and butylene) which can be extruded in molten form and laminated to paper or metal and which can be heat sealed would be usable in place of polyethylene. However. at the present time it is not believed that any such material would be as desirable as polyethylene.
It is desirable that the moisture-vapor barrier propertiesof the various polyethylene layers be as high as possible. Attention is directed in this regard to the, processes and products of U. S. Pat. Nos. 3.161.560 and 3,196,063 issued Dec. l5, I964 and Jul. 20. I965, respectively. to Leon J. Paquin et al.
An important advantage of the can body of the invention is the low moisture content which results from the absence of moisture containing adhesives commonly used in making spiral wound cans. Because of this. lowmoisture content the can bodies may be made in an in-line operation with the can filling and closing equipment without the need for any intermediate drying period.
The individual can body 17 (FIGS. 1 and 8) cut off from the tube 10 is a simple cylinder in shape. It is desirable that both ends of the can body be flared outwardly. as shown at 35 in FIG. 11. before end closures are applied to the can body ends. The can end flare may be producedwith any convenient apparatus as is well known in the art. Typically. if the internal diameter of the can body were 2.488 inches. the internal diameter of the flared ends might be 2.506 inches. In the usual operation. one end closure will be applied at the time the can is made and the other end closure will be applied at some later time. e.g.. at a brewery after the can is filled with the product.
Prior to flaring the ends of the can body. it has been found preferable to steam the ends to be flared or to coat such ends with a wetting solution. Such wetting of the ends. before flaring. prevents the barrier from rupturing during flanging. Excess wetting should be avoided because. if excessively moist. the flange will crush during seaming. The addition of from about l to 41) mg. of water per can. depending upon the inirial moisture content of the can body has been found acceptable. The can may be steamed in a condensing steam chamber for from one to three minutes. depending upon the moisture addition required. or the ends of the can may be dipped or roll coated with water containing about one-half percent solution of a wetting agent. such as. lgepal. Where steamed. the can is immediately flanged. Where dipped or roll coated. flanging is preferably delayed 20 to 30 seconds to allow the moisture to penetrate into the can body.
The types of can end closure and end seam construction usually adopted for metal cans have been used with satisfactory results in nonpressure spiral wound cans. However. such end closures and seam constructions have not yielded a pressure tight can suitable for products such as beer. Accordingly, a further aspect of the invention has been concerned with the provision of an end closure and end seam construction espe cially adapted for retention ofpressure.
Proper design and attachment of the end closure is a very important aspect of the invention. particularly with respect to overcoming two major problems. One of these problems is a tendency for the can body end hook to and allow the can end to blow off. The other problem is a tendency for the can end to deform permanently or peak under load. allowing the end to buckle outwardly and either blow off or lose pressure.
The techniques and constructions used with metal cans are not suitable for a spiral wound paper can intended to hold pressure. In this regard. it is common in metal cans to use a simple double seam with the end closure skirt held in a hook at the can end. This works well with metal cans because the metal can body wall is highly ductile and relatively thin. typically 6.6 to mils. allowing formation of a good book section and a tight seam. Also the shear strength ofa metal can body is extremely high so that there is little or no tendency for the end hook to cut through the can wall. Also a metal can body is essentially incompressible and will not spring back. resulting in a tight. mechanically strong scam.
In the case of a spiral wound can, the sidewall is relatively thick. being ofthe order of 40 mils. making formation ofa true body hook difficult. so that with a high pressure the body hook will tend to unroll. The principal structural features of the end closure of the invention which overcome this tendency to unroll are the use of an extended flat and an extended skirt on the end closure. The tendency of the end closure of the invention to peak is controlled primarily by deep drawing ofthe end closure. as will be described.
FIG. I0 show-s a can end closure 36 embodying the invention with certain dimensions marked for ready reference. The end closure 36 has a skirt 3'7. a flat 38. a shoulder 39. a panel draw 40 and an end panel 4 The shoulder. flat and skirt form the end closure chime area. The skirt 37 corresponds to dimension D. and should be longer than conventional ends. typically l5 to mils longer.
The dimension referred to herein will. of course. vary with can sizes. wall thicknesses and other factors. The dimensions are intended as typical examples for a can having an internal diameter of about 2.5 88 inches (which corresponds to a mandrel diameter of 2.585 inches). a height of 4.875 inches. a body wall thickness of approximately 40 mils and a maximum internal gas pressure of 85 p.s.i. The can body height will. of course. be reduced by the flanging operation. cg. to 4.860 inches. A typical value for the can body internal diameter at the flanged end would be 2.687 inches. The end closure 36 might typically be made from 12.3 mil tinplate. which is thicker than customary for can ends.
The flat 38 corresponds to dimension B and typically might be 30 mils longer than a customary flat length. The shoulder 39 corresponds to the difference between the chime height (dimension C t and the skirt height. dimension I). The shoulder 39 should be quite steep. the shoulder angle (I typi cally being about 4 to 6. which is approximately one-half the usual value. The height of panel draw 40 is dimension E and is substantially greater than usual. e.g. 50 mils greater.
Typical values for the dimensions shown in FIG. II) for a nominal can body internal diameter of 2.588 inches are as follows:
2.603 inches B 0.221 inches 0.245 inches 0.087 inches E 0.152 inches 6 4 to 6 degrees.
Before the can end 36 is joined to the can body the skirt 37 is rolled to have a rounded cross section and an inturned edge 42. as shown in FIG. 12. An annular layer of calking material 43. which may be of any suitable type. is also applied to the inner surface of the can end. It is desirable that as much of the calking as possible. preferably the entire quantity. be confined to the can end area high on shoulder 39.
lnjoining the can end 36 to the can body 17. the can end. in the condition shown in FIG. 12. and the flared open end of the can body. as shown in FIG. 11. are forced together. The interrial diameter of can body 17 is smaller than dimension A of the can end so that the can body must be stressed substantially in forcing the can end onto the can body. For the typical dimensions given above this difference in diameter would be 2.603 inches -2.588 inches or 0.015 inches. This stressing occurs before the seam is started. The flame sealing to which the can body has been subjected during tube winding. particularly the flame sealing actions directly affecting the body plies. result in a can body which is substantially stiffer than is usual in spiral wound cans and this stiffness permits the can to withstand the stressing to which it is subjected when the can body and can end are forced together. FIG. 13 illustrates the can body and can end forced together. the can body being stressed so as to contact not only the shoulder surface 39 but also a portion of the flat 38.
In FIG. 13. and also in FIGS. 14-l7. the actual seam area extends outwardly from about the middle of shoulder 39. the start of the seam area being approximately at the point designated 44.
Since the chime height (dimension C) is relatively great and the shoulder is steep (small angle 9). there is a substantial area of contact between shoulder 39 and the inner surface of can body 17 inwardly of the end seam. i.e.. inwardly of point 44. The extent of this contact. which is from about point 44 to point 45 might typically be about 50 mils. And since the can body is stressed in this region of contact. the frictional force between the can body and the shoulder below the seam area assists in retaining the can end 36 in place and in pressure tight relationship with the can body.
FIG. 14 shows a further rolling in of the can end rim and a slight separation of the can wall body plies l9 and 20. This separation occurs primarily because the respective body ply ends travel through different length paths in the rolling and seaming operation. FIG. 15 shows a continued rolling in of the can end rim and a reverse turning of the separated end of outer body wall ply 20. In FIG. 16 the rolling of the can end rim is almost complete. FIG. 16 also shows a tight lapping over of the separated ends of body wall plies l9 and 20.
Finally in FIG. 17 there hook shown the completely rolled can end with all of the layers of the can wall tightly compressed between the skirt 37 and shoulder 39 and between skirt 37 and flat 38. It will be observed in FIG. 17 that skirt 37 and flat 38 form a smooth curved hook without a sharp angle at the juncture of the skirt and flat. Also the can body end completely fills the space between skirt 37 and flat 38. The smooth curved metal hook configuration and the complete filling of the metal hook with the can body material greatly decrease the tendency for the metal hook to unroll under pressure and hence increase the internal gas pressure which can be retained and also increase the period of time during which such high pressures can be maintained. This construction also reduces the tendency for the sharp metal hook to damage or shear off the can body wall hook which extends into the seam. The extended flat and skirt sections referred to previously are important in obtaining the good seam construction referred to. Careful rolling of the can end rim to achieve the seam of FIG. 17 is also important in obtaining a good seam.
As is evident from FIG. 17, the can body end is distorted in the rolling or crimping operation in which the can body and end are sealed. This distortion includes a separation of the ends of the two body plies l9 and 20. There is a tendency for the end of the outer body ply to push the end of the inner body ply 19 out of thevmetal hook. In some cases this tendency may make it difficult to obtain the most desirable seam construction. To minimizethis problem the can body end may be cut or skived. as shown at 46 in FlG..l8,-so that the ends of the body plies will be at the same elevation in the completed seam. as shown in FIG. 19 The skiving referred to should be effected before the can body end is flanged and may conveniently be done in a sanding or grinding device. It is desirable that the, skiving be done so as to leave an uncut shoulder 47 at the inner surface of the inner body ply 19. This shoulder may have a width of approximately one-half the thickness of the inner body ply. i
With the skived can body end, as in FIG. 18, the ends of the body plies come to the same level in the can end seam because their initial lengths are different. This difference in length should as closely as possible equal the difference in the length of the paths through which the respective body ply ends travel. It is desirable that each ply fills an equal amount of space in the end hook.
For a can having the typical dimensions described above the difference in length of the body ply paths might be typically about 0.031 inches Hence the vertical height between shoulder 47 and the middle of body ply 20 (at surface 46) should be about 0.031 inches. The corresponding angle between the skived surface 46 and the horizontal will be approximately 55".
The various dimensions referred to herein are given only by way of example and should not be considered as limitations on the can construction of the invention.
While the invention ha sbeen described in connection with the specific embodiments thereof and in specific uses, various modifications thereof will occur to those skilled in the art without departing from the spirit and scope of the invention as set forth in the appended claims.
1. The method of making spirally wound can bodies having an inner barrier ply formed as a laminateof a self-supporting. substantially pinhole free, thin metal foil, a thin continuous layer of a slip and sanitary coating ,on the inner surface of said foil, at least one body ply overlying said barrier ply and comprising a first outer paper can stock layer and a continuous layer of a heat sealable thermoplastic material coated on the inner surface of said first outer paper can stock layer, and a label ply formed as a laminate having an inner heat sealable thermoplastic layer; said method comprising the steps of:
a. winding a strip of said barrier ply on a mandrel to form a first continuous tube with said slip and sanitary coating contacting said mandrel and with a leading edge portion of each turn butting a trailing edge portion of the previous turn;
b. winding a strip of said body ply on said mandrel and over said barrier ply tube to form a second continuous tube, said thermoplastic coating of said body ply being disposed to contact said barrier ply;
c. skiving the said edges of said body ply prior to winding thereof on said mandrel to provide tapered paper surfaces at each edge of said body ply. the winding ol'said body ply being conducted so that the thermoplastic coating at the leading edge portion of said body ply overlies the tapered paper surface at the trailing edge portion of the preceding turn of said body ply;
d. heating the entire width of said thermoplastic layer of said body ply to a heat sealing temperature just prior to contact thereof with the underlying tube on said mandrel thereby to heat seal substantially the entire width of said body ply to said barrier ply and to heat seal said leading edge portion of said thermoplastic coating of said body ply to said underlying tapered paper surface;
e. winding a strip of said label ply on said mandrel to form a third continuous tube as the outermost ply of said can body, said label ply being disposed with said inner heat sealablc layer thereof disposed toward said mandrel; and
f. heating substantially the entire width of said inner thermoplastic layer of said label ply to a heat sealing temperature just prior to contact thereof with the immediately un derlying tube on said mandrel thereby to heat seal said label ply to said immediately underlying tube across substantially the entire width of said label ply.
2. The method of making spirally wound can bodies having an inner barrier ply formed as a laminate of a self-supporting, substantially pinhole free, thin metal foil. a thin. continuous layer of a slip and sanitary coating on the inner surface of said foil, at least first and second body plies overlying said barrier ply and each comprising a first outer paper can stock layer and a continuous layer of a heat scalable thermoplastic material coated on the inner surface of said first outer paper can stock layer, and a label ply formed as a laminate having an inner heat scalable thermoplastic layer; said method comprising the steps of:
a. winding a strip of said barrier ply on a mandrel to form a first continuous tube with said slip and sanitary coating contacting said mandrel and with a leading edge portion of each turn butting a trailing edge portion of the previous turn;
b. winding a strip of said first body' ply on said mandrel and over said barrier ply tube to form-a second continuous tube, said thermoplastic coating of said first body ply being disposed to contact said barrier ply;
c. winding a strip of said second body ply on said mandrel and over said second tube to form a third continuous tube, said thermoplastic coating on said second body ply being disposed to contact said second tube;
d. skiving the side edges of said body plies prior to winding thereof on said mandrel to provide tapered paper surfaces at each edge of said body plies, the winding of said body plies being conducted so that the thermoplastic coating at the leading edge portion of each of said body plies overlies the tapered paper surface at the trailing edge portion of the preceding turn of the corresponding body ply;
e. heating the entire width of said thermoplastic layer of each of said body plies to a heat sealing temperature just prior to contact thereof with the underlying tube on said mandrel thereby to heat seal substantially the entire width of said first body ply to said barrier ply, to heat seal substantially the entire width of said second body ply to said first body ply and to heat seal said leading edge portions of said thermoplastic coatings of said body plies to the corresponding underlying tapered paper surfaces;
winding a strip of said label ply on said mandrel to form a fourth continuous tube as the outermost ply of said can body, said label ply being disposed with said inner heat scalable layer thereof disposed toward said mandrel, a
leading edge portion of said label ply being arranged to overlap a trailing edge portion of the preceding turn of said label ply; and
heating substantially the entire width of said inner thermoplastic layer of said label ply to a heat sealing temperature just prior to contact thereofwith the immediately underlying tube on said mandrel thereby to heat seal said label ply to said immediately underlying tube across substantially the entire width of said label ply, said heating of said inner thermoplastic layer of said label ply also serving to heat seal together said overlapping edge portions of said label ply.
3. The method set forth in claim 2 comprising the additional steps of applying a continuous tape, having a continuous layer of a slip and sanitary coating on the inner surface and a continuous layer ofa heat sealable thermoplastic material coated on the outer surface. to the inner surface of said barrier ply along the marginal trailing edge of said barrier ply. as said barrier ply is wound on said mandrel. with a portion of said outer surface of said tape in contact with the inner surface of said barrier ply and the remaining portion of said outer surface of said tape extending outwardly from said trailing edge for receiving the leading edge of the following turn of said barrier ply wound on said mandrel.
4. The method set forth in claim 3 in which the winding angle for each of said body plies is about 27.
5. The method set forth in claim 3 comprising heating substantially the entire outer paper surface of the outermost one of said body plies just prior to contacting thereof by said label ply strip thereby to improve the bonding of said inner thermoplastic layer of said label ply to said outer body ply and to reduce substantially the moisture content of the paper in said outer body ply.
6. The method set forth in claim in which said step of heating substantially the entire outer paper surface of the outermost one of said body plies is effected by contacting said outer paper surface with a gas flame.
7. The method set forth in claim 3 in which each of said heating steps is effected by contacting the surface to be heated with a gas flame.
8. Apparatus for making spirally wound can bodies having an inner barrier ply formed as a laminate of a selfsupporting, substantially pinhole free, thin metal foil, a thin. continuous layer of a slip and sanitary coating on the inner surface of said foil. at least one body ply overlying said barrier ply and comprising a first outer paper can stock layer and a continuous layer of a heat sealable thermoplastic material coated on the inner surface of said first outer paper can stock layer. and a label ply formed as a laminate having an inner heat sealable thermoplastic layer; said apparatus comprising:
a. a tube winding mandrel;
b. means for winding a strip of said barrier ply on said mandrel to form a first continuous tube with said slip and sanitary coating contacting said mandrel and with a leading edge portion of each turn butting a trailing edge portion of the previous turn;
c. means for applying a continuous tape, having a continuous layer of a slip and sanitary coating on the inner surface and a continuous layer of a heat sealable thermoplastic material on the outer surface, to the trailing edge of said barrier ply as said barrier ply is wound onto said mandrel and for bringing the leading edge of the following turn into contact with said tape for forming a tape seal across said butting edges;
d. first flame burner means arranged to direct a flame onto the leading and trailing edge portions of butting windings of said barrier ply strips to heat the same to a heat sealing temperature after said strip contacts said mandrel and to heat seal said tape to said butting windings across said butting edges;
e. means for winding a strip of said body ply on said mandrel and over said barrier ply tube to form a second continuous tube and with said thermoplastic coating of said body ply being disposed to contact said barrier ply:
f. means for skiving the side edges of said body ply prior to winding thereof on said mandrel to provide tapered paper surfaces at each edge of said body ply. said body ply. when wound, being arranged so that the thermoplastic coating at the leading edge portion of said body ply overlies the tapered paper surface at the trailing edge portion of the preceding turn of said body ply;
g. second flame burner means for heating the entire width of said thermoplastic layer of said body ply to a heat sealing temperature just prior to contact thereof with the underlying tube on said mandrel thereby to heat seal substantially the entire width of said body ply to said barrier ply and to heat seal said leading edge portion of said ther moplastic coating of said body ply to said underlying tapered paper surface. said second flame burner means comprising a plurality of individual burners each disposed transversely across said body ply strip adjacent the point of contact thereof with the underlying tube on said mandrel;
h. means for winding a strip of said label ply on said mandrel to form a third continuous tube as the outermost ply of said can body, said label ply being disposed with said inner heat sealable layer thereof disposed toward said mandrel and with a leading edge portion of said label ply being arranged to overlap a trailing edge portion of the preceding turn of said label ply; and
i. third flame burner means for heating substantially the entire width of said inner thermoplastic layer of said label ply to a heat sealing temperature just prior to Contact thereof with the immediately underlying tube on said mandrel thereby to heat seal said label ply to said immediately underlying tube across substantially the entire width of said label ply. said heating of said inner thermoplastic layer of said label ply also serving to heat seal together said overlapping edge portion of said label ply.
9. Apparatus as set forth in claim 8 comprising fourth flame burner means arranged to direct an axially extending flame onto the outer body ply surface at a point just prior to contact thereof by said label ply. the axial length of said axially extending flame being sufficient that substantially the entire outer body ply surface is heated thereby.
Patent No. 3,555,97 Dated an ary 19, 1971 Inventor) Charles I. Carter et a1,
It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:
Title sheet, line 5, "Ser. No. 585,175" should be Ser. No. 585, 7
col. 2, line 17, insert semi-colon after "calking" 4, line 3'4 'is" should be it 7, line 3 4, after "to" insert unroll line 7 4 1,860" should be 4.860
8, line 71, "hook" should be is Signed and sealed this 10th day of August 1 971 (SEAL) Attest:
EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissionerof Patents
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