Scored And Seam Welded Can

Abstract

A metal can is seam welded and opens by means of a key through which is inserted a tab of a tear strip; the tear strip being then rolled about the key as the key is rotated, thereby tearing the tear strip away from the remaining metal portion of the can. The tear strip tears along two parallel circumferential grooves in the can body. A transverse groove extends under the tab at the edge of the weld between the two grooves and is formed in the portion of the body of the can which underlies the tab.

Description

BACKGROUND OF THE INVENTION

This invention relates to sealed metal cans, and more particularly, to cans of the type which are opened by a key and tear strip.

In the prior art, metal cans are formed by producing a flat blank of thin metal in a generally rectangular shape, having two or more continuous parallel grooves extending across the width of the blank from one edge to the opposite edge parallel to and closely adjacent to one of the remaining edges and having a tab extending beyond one edge from the portion bounded by said parallel grooves. The blank is then formed into a cylinder so that the grooves are on the inside and extend circumferentially and the tab overlies the outer surface of the can and the edge from which the tab extends overlies the outer surface so as to be closely adjacent to the underlying edge. The overlapped surfaces are then welded along a seam parallel to these edges as shown generally in FIG. 2 of the drawings at 18.

In the prior art as shown in FIG. 5, that portion of the welded seam 19 designated generally 20 which crossed between the parallel grooves (22 shown in dotted lines) at the tab 23 was not welded. Rather, the weld was interrupted and the overlapped portions were soldered together. Thus, when the tab was lifted backward away from the can body, the solder would give way, leaving some of the solder on the base portion as at 24 and some solder on the overlying portion of the body contiguous with the tab as at 25. The means for lifting the tab backwardly and parting it at its soldered connection and tearing it along the grooves 22 in the prior art was a key with a slot in the end. The tab 23 was inserted into the slot and the key was rotated to fold the tab back upon itself and lock the key to the tab. Then as the key was continued to be rotated, it rolled up the tab, parted the solder, and began rolling a strip of metal in an ever-increasing bundle as the metal tore away from the parent metal of the can. This key has not been shown in the prior art FIG. 5 nor in the remaining figures, since it is old and well-known in the art and would interfere with a clear presentation in the drawings of the action and effect that the prior art and the present invention have on cans of this type. Accordingly, for the sake of clarity, the key will not be shown, but it is to be understood that the tabs and tear strips are being removed by a standard prior art type key. To aid in starting the tearing of the parent metal, the overlying portion was provided with two deep V notches 26 which were formed in the blank. These directed the forces so that the tear started correctly along the two grooves 22.

It is an expensive operation to interrupt the weld and to produce a separate soldered portion in order to complete the seal. Attempts have been made to reduce the weld by reducing the current or pressure necessary to produce a good weld, but these attempts result in an inferior grade of cans from the standpoint of providing an acceptable seal. It is accordingly desirable to provide some means to continually seam weld a can right through the portion embraced by the parallel groves (known generally as the tear strip), so as to provide a uniform and inexpensive weld and a superior seal. Attempts to do this have failed because the tab did not have sufficient strength to destroy the integrity of the weld and was, therefore, torn off when it was rotated about the key before it could effectively begin to tear along the grooves 22.

SUMMARY OF THE INVENTION

I have discovered that a weakening of the metal at the underlying portion of the can body will permit the tab to preserve its integrity long enough to break through the seam so that the tear strip can then be wound about the key. This weakening most preferably comprises a groove parallel to the weld and lying adjacent the edge of the weld which is most remote from the underlying edge of the can body blank. I disclose in this application preferred embodiments of this groove, and its disposition.

Accordingly, it is an object of this invention to provide an improved seam welded can of the key opening type by providing a continuous weld through the tear strip area.

This and other objects of my invention will become apparent from the following description with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a perspective view of a metal blank used in forming a can in accordance with the preferred embodiment of this invention;

FIG. 2 shows a perspective view of the blank of FIG. 1 formed into a cylinder and seam welded;

FIG. 3 is a greatly enlarged plan view of a portion of the can body shown in FIG. 2;

Fig. 4 is a view similar to FIG. 3 showing the parts in an alternate position wherein the tear strip has been partially torn away from the body of the can;

FIG. 5 is a view similar to FIG. 4 showing a prior art can in similar condition;

FIG. 6 is a view taken as indicated by the lines and arrows 6--6 in FIG. 3 with a portion shown in phantom alternate position depicting a condition similar to that shown in FIG. 4;

FIG. 7 is a greatly enlarged section similar to FIG. 6 showing the parts in alternate positions after they have been separated as in FIG. 4, and depicting in phantom lines their original positions as in FIG. 3;

FIG. 8 is greatly enlarged foreshortened section taken as indicated by the lines and arrows 8--8 in FIG. 1;

FIG. 9 is a greatly enlarged section taken as indicated by the lines and arrows 9--9 in FIG. 1;

FIG. 10 is a perspective view on a greatly enlarged scale partially broken away and partially shown in section of a portion of the partially formed blank of the body of a can as viewed from the inside when looking at the left hand edge of the blank shown in FIG. 1; and

FIG. 11 is a section taken as indicated by the lines and arrows 11--11 in FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Although specific forms of the invention have been selected for illustration in the drawings, and the following description is drawn in specific terms for the purpose of describing these forms of the invention, this description is not intended to limit the scope of the invention which is defined in the appended claims.

Referring to the figures, the forming of a blank and assembling it into a cylindrical condition whereby one portion is overlapping another and then welding just slightly inwardly from the edges so as to join the two portions and form a can is shown generally in FIGS. 1 and 2 and has been described above in connection with the prior art. The welded seam 18, however, differs from the prior art in that it is continuous. In the present invention I improve upon the prior art cans by providing a weakened area in the underlying portion, which in the embodiment shown comprises a detent 40, FIG. 1, formed in the blank along that surface which is to be the outer surface of the can. This is the surface which is opposite to or on the reverse side of the blank from the two parallel grooves which will normally be inside the can when it is formed. These grooves are shown in greater detail in FIG. 8 and are identified by the same numbers as those in the prior art. They are formed into the metal a distance approximately one-half of the metal thickness. The method of forming is to roll a sharp tool along the blank, thereby forcing the metal out of the way. After the tool has produced these grooves, approximately fifty to sixty percent of the metal remains. This scoring or forming operation does not remove metal, but merely displaces it.

A similar method of scoring is used to produce the transverse groove 40. Thus, the metal again is not removed, but merely displaced, as for example, by a stamping tool complementally configured to the shape of the groove. The groove produced is shown in greater detail in FIGS. 9, 10 and 11. Note that the two parallel grooves have been filled in along the inner surface 42 of the can blank at the points where the transverse groove 40 overlies them. By virtue of the stamping operation displaced metal has been forced into the grooves 22 on the inner surface. The groove 40 extends in both directions most preferably beyond the width of the tear strip as defined by the parallel grooves 22. The metal 43 which has been forced into the parallel grooves is shown in greater detail for the lower groove in FIG. 11. Groove 40 is similar to the other grooves in that it extends into the metal for a distance of about fifty percent of the thickness of the metal (as shown in FIG. 9).

An important feature of the present invention is the positioning of the groove 40 with respect to the weld. Most preferably it is parallel to and adjacent to the weld at the lead edge of the weld when viewed in the direction of advance of the tearing strip during the tearing operation. This is shown clearly in FIGS. 3, 4, 6 and 7, and in actual practice is about 0.086 inches from the edge of the underlying portion when using metal on the order of 0.010 inches thick with a groove 0.005 inches deep. By so positioning the groove 40, I have discovered that the following condition obtains when pulling on the tear strip tab 45. As the tab 45 and tear strip 47 are pulled away from the can body, as from the position shown in FIG. 3 to that shown in FIGS. 4, 6 and 7, the metal on the underlying portion 49 breaks at the groove 40 and the tears along its grooves 22 as the overlying metal is also tearing along its grooves 22. Thus, the metal and the weld is broken at two points along the grooves in the metal. Note that the integrity of the weld insofar as its ability to join two pieces of metal is concerned, is not destroyed as in the case of the prior art soldered joint. The small remaining piece of metal 49 of the underlying portion is, therefore, attached to the tear strip and remains with it as it is separated.

In the preferred embodiment, the groove 40 is positioned as shown in the drawings with at least one edge adjoining the weld. It is possible, within the scope of this invention, to overlap the weld and groove slightly, although care should be taken not to destroy the effectiveness of the weld by undercutting it to any great extent. It is also possible to place the groove further to one side of the weld, thereby leaving a slight space between the groove and the weld, but this may provide less reliable results.

It will be understood that various changes in the details, materials and arrangement of parts which have been herein described and illustrated in order to explain the nature of this invention, may be made by those skilled in the art within the principle and scope of the invention as expressed in the following claims. For example, while I have described the invention as being applicable to a cylindrical can, it will be understood by those skilled in the art that other shapes could be formed from the blank, as for instance, a rectangular can body.

It will further be understood that the "Abstract of the Disclosure" set forth above is intended to provide a nonlegal technical statement of the contents of the disclosure in compliance with the Rules of Practice of the United States Patent Office, and is not intended to limit the scope of the invention described and claimed herein.

Claims

What is claimed is:

1. In a metal can having a body with overlapped portions welded together at a seam, and grooves delineating a tear strip, the improvement comprising:

a. a continuous weldment at said seam across said grooves; and

b. means of weakening the underlying portion of the can in the area adjacent said continuous weldment across said grooves to permit tearing of the tear strip across said seam.

2. The invention of claim 1 wherein said means comprises a groove adjacent said weldment.

3. The invention of claim 2 wherein said groove extends parallel to said weldment.

4. The invention of claim 2 wherein said groove has one edge contiguous with said weldment.

5. The invention of claim 2 wherein said grooves delineating said tear strip extend into said metal a distance of about half the thickness of said metal; snd said groove forming said weakening means extends into said metal a distance of about half the thickness of said metal and in the areas in which it crosses the grooves delineating the tear strip, said last mentioned grooves are filled in with the metal.

6. The invention of claim 2 wherein the groove adjacent said weldment is in the surface of the body opposite to that surface having in it the grooves delineating the tear strip.

7. The invention of claim 2 wherein said groove adjacent said weldment is closest to the edge of said weldment which is most remote from the edge of the underlying portion of said body.