Container Body Side Seam Construction

This invention relates in general to containers and more particularly to metal containers having interlocking side seams and to methods for forming such side seams.

Cans and like containers having locked side seams are well known and where seams of improved gas or liquid holding ability are needed, these side seams are treated with adhesives or solders. When solders are used, the cans are usually heated, and the solder is drawn into the interlocking side seams by capillary attraction. When organic materials, known as side seam cements, are used, they are usually applied to the body hooks prior to body-forming and are expected to flow. There is a further type of side seam in which the body material overlaps to form a lap joint with the bond between the lapping portions of the joint having been made by means of solder or by means of organic resinous adhesives such as nylon applied in the form of tape. It is to be understood that when the side seam is in the form of a lap joint, the overlapping edges of the body blank must be mechanically held in place until the bonding of the lapped portions has been completed. This presents particular difficulties and time delays when the bonding means is an organic resinous adhesive.

According to the present invention, it is proposed to bond the side seam by means of an organic resinous material but to form the side seam as a lock seam wherein the interlocked parts of the body blank firmly hold themselves together until such time as the organic resinous material can be heated and flowed to form the necessary bond.

In a method of manufacturing an interlocking side seam of a container in accordance with this invention, an organic resinous material in the form of tape is applied to the seam margins of a container body blank, which is then passed through a known lock seam body-maker in which the seam margins are folded to form body hooks and the blank is then formed around a mandrel to engage the hooks with each other to form a seam which is next hammered flat. The resultant container body is then passed over heaters so that the side seam is raised to a temperature at which the organic resin tape layers can fuse to each other and bond to the adjacent metal to improve the integrity of the side seam.

An advantage of this invention is that the lock seam supports the adhesive during the prolonged setting times needed and allows ordinary body-makers to be used.

In a preferred embodiment of the invention, the two tape margins are both disposed on the same side of the body blank so that when the container body is formed and resin fusion has been carried out, a continuous layer of organic resin material covers the side seam and bridges from one side of the side seam to the other.

With the above and other objects in view that will hereinafter appear, the nature of the invention will be more clearly understood by reference to the following detailed description, the appended claims and the several views illustrated in the accompanying drawings:

FIG. 1 is a cross sectional view of a lap joint formed in accordance with the prior art.

FIG. 2 is a cross sectional view of a container body blank, shown diagrammatically, in which the organic resinous material is placed at each end of the body blank on one side thereof.

FIG. 3 is a sectional view of the body blank of FIG. 2, but after body hooks have been formed thereon.

FIG. 4 is a fragmentary sectional view through the seam of a container body formed with the body blank of FIG. 2.

FIG. 5 is another fragmentary sectional view of a side seam showing an alternative adhesive placement.

FIG. 6 is still another fragmentary sectional view of a side seam showing a further form of adhesive placement.

Referring now to the drawings, it will be seen that there is illustrated in FIG. 1 a known form of container side seam. The container is formed from a body blank 1 which is coated with a lacquer coating 2 on the inside surface thereof and another coating material 3 on the outside surface thereof. Organic resinous joint material 4 is applied to a margin parallel to one edge of the body blank 1 and like material is applied to the other joint margin 5. The two margins are brought into overlapping relation and are heated at 180.degree. C. for up to one minute during which time the organic resinous material fuses, forming a joint such that the organic material not only provides adhesive qualities, but also corrosion protection on the inside of the container. In this method adhesives which do not flow freely can be used, although the time required for forming the bonded side seam is comparatively long with respect to other methods of forming container body side seams.

In FIG. 2 there is shown a generally rectangular flat body blank 6 which, like the body blank 1, has the inner surface thereof coated with a lacquer coating 2 and the outer surface thereof coated with another coating material 3. An organic resinous joint material is applied to two parallel strips 4a and 4b at the respective opposite ends of the body blank 6 and on the same side of the blank.

In FIG. 3 the body blank 6 is shown after body hooks 7 and 8 have been formed thereon with the strips 4a and 4b being shown in their bent configurations diagrammatically. In FIG. 4 there has been illustrated the side seam of a container formed utilizing the body blank 6 of FIG. 3 after the body hooks 7 and 8 have been engaged with one another and the resultant seam has been flattened in a conventional bodymaker. It is to be understood that the container body formed from the body blank 6 is generally cylindrical.

In order to more fully identify the portions of the side seam of FIG. 4, it is to be noted that the body hook 8 is the inside hook and is connected to the body 10 of the container body by means of an inside hook radius 8a, an inside hook panel 8b, an inside hook panel radius 8c, an inside hook panel step 8d and an inside hook panel step radius 8e in that sequence. Further, it is to be noted that the outside body hook 7 is connected to the body wall 10 by an outside hook radius 7a. It is further to be noted that the adhesive strip 4a overlies the inner surface of the outside hook, the outside hook radius and an adjacent portion of the body wall with one part of the strip 4a being disposed directly between the outside hook 7 and the inside hook 8, and another portion of the strip 4a being disposed between the inside hook 8 and the adjacent part of the body wall 10. Further, it is to be noted that the strip 4b extends from the body wall 10 on the inner surface of the container body entirely over all portions of the inside hook and terminates in an end portion disposed between the inside hook and the adjacent portion of the body wall 10 and in face-to-face engagement with an adjacent portion of the strip 4a.

It is further to be understood that the side seam has all of the components thereof tightly clamped together during the flattening of the side seam with the result that there is pressure engagement on that portion of the strip 4a disposed between the inside hook 8 and the outside hook 7. There is like pressure engagement on those portions of the strips 4a and 4b disposed between the inside hook 8 and the adjacent portion of the body wall 10 so that the strips 4a and 4b are held in place for bonding by the application of heat without the use of any external clamping mechanism.

It is also pointed out at this time that for purposes of clarity the lacquer coating 2 and the layer of coating material 3 have been omitted from FIGS. 4, 5 and 6. In practice, the lacquer coating 2 may not be needed, but if, for some reason, it is needed, care must be taken in its selection. For example, a particular epoxy-phenolic lacquer may be chosen.

Returning now to FIG. 4, it will be seen that the organic resinous layers 4a and 4b meet at a point of juncture 9 between the inside hook 8 and the adjacent portion of the body wall 10 so that upon fusion of the strips 4a and 4b along an interface or juncture, a continuous layer of organic resinous adhesives seals the side seam and covers the adjacent margins to protect the seam region from corrosive influence of any product contained in the resultant container. It is to be understood that normally there is an inner entrance slot into the side seam from the interior at the point of juncture 9 between the adhesive strips 4a, 4b and this entrance slot is sealed by the bonding together of adhesive strips 4a, 4b. The adhesive strips 4a, 4b extend from the entrance slot in diverging relation.

As shown in FIG. 4, the adhesive strips 4a and 4b, combined, extend entirely across the side seam from point c to point e, thus covering all the heavily worked portions of the side seam. However, if for reasons of economy it may be useful to terminate the strip 4b sooner, the strips 4b may be terminated at point e which is generally at the intersection of the inside hook radius 8a and the inside hook panel 8b.

Referring now to FIG. 5, it will be seen that there is illustrated a container side seam formed from the body blank 6 wherein edge portions thereof are formed with hooks 7 and 8 in the same manner as shown in FIG. 3 and then formed into a seam in the same manner as described with respect to FIG. 4. However, the adhesive strips 4a and 4b are applied to the outer surface of the body blank 6 instead of the inner surface thereof, as shown in FIG. 2. In the side seam of FIG. 5, it will be seen that the adhesive strip 4a extends from the body wall 10 around the outside hook radius 7a and into the space between the outside hook 7 and the inside hook panel 8b. On the other hand, the adhesive strip 4b extends from the body wall 10 into the side seam in overlying relation to all portions of the inside hook with an intermediate portion of the adhesive strip b being clamped in face-to-face engagement with a portion of the strip 4a between the outside hook 7 and the inside hook panel 8b. Further, a portion of the adhesive strip 4b is clamped between the outside hook 7 and the inside hook 8.

In addition to forming a bonded interlock between the portions of the hooks 7 and 8, and forming a seal between the hooks 7 and 8, the strips 4a, 4b are joined together along an interface or juncture beginning at the outside entrance slot into the seam, identified by the numeral 11, and extend in opposite directions therefrom on the exterior surface of the body wall 10.

Referring now to FIG. 6, it will be seen that the placement of the adhesive strip 4b may be restricted, for the purposes of economy, or to specifically protect and adhere together only certain parts of the side seam. As shown in FIG. 6, the strip 4b terminates at the end of the inside hook panel 8b adjacent the inside hook radius 8a. The side seam of FIG. 6 is otherwise identical to the side seam of FIG. 5.

It is to be understood that after the side seams of FIGS. 4, 5 and 6 have been formed by a conventional body-maker, heat is applied to the side seam so as to effect fusing of the organic resinous joint material of the adhesive strips 4a, 4b. This heat may be applied in any desired manner and the heater 12 is schematically illustrated in FIG. 6 for this purpose. It is to be understood that a like heater 12 may be utilized in conjunction with the side seams of FIGS. 4 and 5.

It has been found that a suitable organic resinous adhesive which may be utilized for forming adhesive strips 4a, 4b and that marketed under the Trade Mark "Kuroplast 2306", which is a terpolymer of ethylene, acrylic acid and acrylic ester. This organic resinuous adhesive adheres well to tinplate and other container forming metals, and softens at 180.degree. C, which is within the temperature range of current body-maker heaters, such as the heater 12; and stays in place without the risk of the adhesive material fouling the body-maker tooling. The body blank may be preheated so as to obtain initial bonding of the heated strips 4a, 4b to the body blank.

While the method of carrying out the invention, as hereinbefore described, starts with the use of adhesive strips 4a, 4b in the form of tape, it is quite possible to apply adhesive strips to the body blank in some other form such as an extrudate from resinous nozzle. In this case, the extrudate may have sufficient heat to promote adhesion without the body blank being preheated, although preheating of the body blank is not precluded.

It is also to be understood that the organic resinous material of the strips 4a, 4b may, alternatively, be applied to the body blank as a powder. The powder may be applied to the body blank as a spray, with or without electrostatic directional control. If the powder is sprayed hot, then the body blank may not need preheating. If, however, the powder is sprayed cold, the body blank is preferably heated to encourage the organic resinous material to adhere to the body blank.

Although only several preferred embodiments of the invention have been specifically illustrated and described herein, it is to be understood that minor variations may be made in the side seam construction and method of forming the same without departing from the spirit and scope of the invention, as defined by the appended claims.