US 3728980 A
A tool for forming a score in a can end to define an easy-opening tear strip. In lateral cross section, the scoring die comprises a five-sided element having a leading edge with a very narrow planar surface, a pair of highly finished side faces extending outwardly on either side of the leading edge at first, smaller angles relative to the plane of the leading edge, and a second pair of faces extending upwardly from the highly finished faces at second, larger angles relative to the plane of the leading edge.
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Description (OCR text may contain errors)
United States Patent [191 Fraze 1111 3,728,980 451 Apr. 24, 1973 1 1 SCORING DIE  Inventor: Ermal C. Fraze, 355 West Stroop Road, Dayton, Ohio 45429 22 Filed: Feb. 10, 1971 21 Appl.No.: 114,192
 U.S.Cl. ..;.....ll3/l F, 72/325, 83/6, 113/15A,113/121C  Int. Cl ..B2ld 51/26, B26d 3/08  Field of Search ..72/325, 326, 476; 83/6, 7; 113/121 R, 15 A, 15 R, 121 C, 1 F
 References Cited UNITED STATES PATENTS 3,583,348 6/1971 Brown ..1 13/15 A 2,041,912 5/1936 Fabrice ..1 13/15 A 3,359,773 12/1967 Stuchbery ..72/325 Primary ExaminerRichard J. Herbst Assistant Examiner-R. M. Rogers Attorney-Smyth, Roston & Pavitt 57 ABSTRACT A tool for forming a score in a can end to define an easy-opening tear strip. 1n lateral cross section, the scoring die comprises a five-sided element having a leading edge with a very narrow planar surface, a pair of highly finished side faces extending outwardly on either side of the leading edge at first, smaller angles relative to the plane of the leading edge, and a second pair of faces extending upwardly from the highly finished faces at second, larger angles relative to the plane of the leading edge.
9 Claims, 3 Drawing Figures SCORING DIE BACKGROUND OF THE INVENTION Easy-opening can ends have become widely accepted in a variety of applications such as the packaging of beverages, juices, lubricants, etc. In nearly all of these applications, it is very important that the material within the can does not come into direct contact with the metal because the metal would taint the contents, the contents will attack and weaken the metal, or both.
Therefore, in forming an easy-opening can end, the inner surface of the end is coated with a suitable protective coating such as an epoxy which will prevent such metal-contents contact. After being coated, an integral rivet boss is formed in the can end so that a pull tab may later be attached, and a score line is then formed to define a removable tear strip or panel for access to the can contents without requiring an opening tool. 1
Easy-open can ends employed today are usually within a thickness range of from 0.008 to 0.0145 inch. When a score is formed in a can end, the residual, or material between the bottom of the score and the inner surface of the can, is normally approximately 0.004 inch.
Most of the presently available scoring tools comprise, in cross section, a substantially V-shaped tool which is truncated to provide a relatively broad leading edge which coins or extrudes the metal from the score in opposite directions away from the tool. These tools produce relatively large stresses on the can ends, particularly in the area near the inner surface,.and it has been found that these large stresses result in cracking and rupturing or serious thinning of the protective coating in the area immediately below the score. If the can end is to be used with a commodity which will attack the metal, the unprotected metal beneath the score, being very thin, may be eaten away to allow the score line to be ruptured prematurely.
Consequently, it has become the practice to postcoat the can ends or at least those which are to be used with the problem contents, so as to obviate the possibility of damage and loss.
In attempting to relieve the stresses created in the areas of the can end adjacent the protective coating, dies have been manufactured which are V-shaped throughout their entire cross section, each having a leading edge which is, in effect, a knife edge. While these dies have been very effective in achieving the desired result so that the protective coating is not ruptured and post-coating is unnecessary, their useful life has proven to be extremely short sometimes merely a matter of hours since the knife-like leading edge quickly becomes damaged and blunted, resulting in either damaging of the can ends being scored or requiring replacement of the scoring tool.
It has thus become necessary to produce a scoring tool, having a relatively long service life, which does not cause a rupturing of the protective coating on the interior surface of the can end so that post-coating will not be required.
SUMMARY OF THE INVENTION The present invention therefore relates to an improved scoring tool having these advantages. More specifically, the present invention relates to a scoring tool having a very narrow leading edge which, in use, is positioned so as to be substantially perpendicular to the can end which is to be scored.
Symmetrically located on each side of the leading edge, a pair of faces are formed which serve to control the flow of metal. The first face on each side of the leading edge forms a relatively small acute angle with the plane of the leading edge and is highly finished so as to be subject to as little friction as possible during the scoring operation. A second face between each of the first, highly finished faces and the ram, is formed at a relatively large acute angle relative to the plane of the leading edge.
As the scoring tool is moved toward the can end, the narrow leading edge places a high compression force on the end which causes a very localized severing. Continued movement of the tool causes the first set of faces to contact the end, resulting in a flow of metal both toward the inner surface of the can end and in a direction perpendicular to the movement of the scoring tool, in approximately equal amounts. Since the first faces are highly finished, very little friction force occurs between the tool and the can end along these faces, allowing the metal to flow in a relatively free fashion. These faces therefore impose relatively small stretching stresses on the inner surface of the end so that the coating is undamaged thereby.
As the second set of faces come into contact with the can end, they force metal at the outer surface of the end to move in a direction such that mostof this metal flows perpendicularly to the'direction of movement of the scoring tool. The high stresses placed on the outer surface of the can end by these faces are not transmitted to the inner surface so that the protective coating is .uneffe'cted.
It is expected that the width of the leading edge and the acute angle formed therewith by the first pair of faces may vary according to the thickness and type of material which is to be scored, but a scoring tool formed in accordance with this invention will produce ,an entirely satisfactory rupturable score line in easyopen can ends without creating such stresses in the metal in the area of the score residual that the protective coating applied to the inner surface of the can becomes so disturbed that any danger of reaction between the metal and the can contents exists.
Other advantages and objects of the present invention will be understood by those skilled in the art when the following description of the preferred embodiment of the invention is read and understood. Those skilled in the art will realize, of course, that only a preferred embodiment of this invention is now to be described and that the full measure of the invention is set forth in the claims.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a partial sectional view of a scoring tool formed in accordance with the present art, shown acting on a can end to produce a rupturable score therein;
FIG. 2 is a partial sectional view of another scoring tool which has been formed in the prior art to produce a rupturable score; and
FIG. 3 is a partial sectional view of a scoring tool formed in accordance with the present invention.
DETAILED DESCRIPTION As shown in FIG. 1, a scoring tool 11 which is suitably mounted on a ram 13 acts upon a can end 15 which is supported by a suitable surface (not shown).
Prior to the time that the can end 15 is acted upon by the scoring tool, the surface thereon which will be inside the can is provided with a protective coating 17 which will prevent the contents of the can and the metal of the can end from coming into contact. This protection is necessary to prevent the metal from altering the taste or other properties of the contents and also to prevent the contents from attacking and possibly weakening the metal.
The scoring tool 11 is provided with a leading edge 19 and a pair of angularly related faces 21. In a typical example, in scoring a can end 15 having a thickness of 0.0145 inch, the width of the leading edge 19 is usually between 0.007 and 0.008 inch. An angle A between the plane of surface 19 and either of the faces 21, is normally formed to be approximately 60.
The scoring tool is normally used in such a way that the penetration is sufficiently deep to leave approximately 0.0040.006 inch of residual, i.e., the metal between the lowest point of the score andthe inner metallic surface of the can end.
When scoring tools of this type act against can ends, very large stresses are created in a direction perpendicular to tool movement within the area about the score and the metal is effectively stretched in that direction. This often causes the protective coating 17 to rupture, or become seriously thinned, as shown in the area designated at in the figure. As a result, the metal of the can end and the contents are able to contact one another and, in some cases, the above described undesirable effects may occur. It is readily apparent that if the contents are under pressure and are ablev to attack the metal in the can end, they will do so in the area of the residual, causing at least an eventual loss of pressure when the residual is eaten away and, possibly, a dangerous situation in which the weakening of the residual could result in an explosive release of the tear strip.
Referring now to FIG. 2, a scoring tool 31, having a leading knife edge 33, is mounted on a suitable ram or other device 35 such that the scoring tool may be brought into penetrating contact with the can end (not shown). Scoring tools of this type have been found to provide very satisfactory scoring characteristics in that the stresses generated adjacent the internal surface are insufficient to cause rupturing or thinning of the protective coating. However, experience has shown that these scoring tools do not have long service lives since the leading edge 31 quickly becomes dulled due to contact with the can ends. In particular, tests have shown that the leading edge become knicked over a large portion thereof so that after a very short time the scoring tool actually does not have a continuous leading edge but becomes ratherjagged.
When this occurs, the scoring tool is no longer capable of properly scoring a can end'since, at best, the residual is no longer uniform throughout the score. At worst, the tool begins to actually damage the can ends, causing a wastage of material and/or possible damage to the machine, and resulting in a shutting down of the entire production line while the scoring tool is replaced. In some cases, it has been found that such scoring tools may have a useful life which can be measured in minutes orjust a few hours.
Thus, with the tools presently known in the art, it has not been possible to produce can ends over an extended period of time without either rupturing or thinning the protective coating on at least enough of the can ends that they must be post-coated with another layer of the protective coating after the scoring has been completed.
Referring now to FIG. 3, there is illustrated a scoring die formed in accordance with the present invention which has a relatively long service life but which does not cause a rupturing or thinning of the protective coating due to its configuration. In fact, it is expected that the service life of this scoring tool will be at least as good as the service life of the type of tool shown in FIG. 1, which has proven to be relatively long.
As shown, the scoring tool 51 is provided with a leading edge 53, a pair of first faces 55, and a pair of second faces 57.
The first faces 55 each form an angle B with the plane of surface 53 which is substantially smaller than the angle A of tool 11. On the other hand, the faces 57 form an angle C with the plane of that surface which is approximately equal to the angle A of tool 1 1.
The first set of faces 55 are finished so as to be as smooth as possible in order to minimize the friction forces generated between those faces and the metal of the can ends during the scoring operation. These faces allow a sufficient quantity of the metal displaced during scoring to be moved toward the internal face of the can end to prevent the buildup of large outwardly directed stretching, or stress forces in the metal so that the protective coating does not become ruptured or seriously thinned. On the other hand, the surfaces 57 do produce sufficient stresses at the external surface of the can end to allow a clean opening of the score.
Since the leading edge 53 is much narrower than the leading edge 15 of the presently used tool, the width of the score at the upper surface of the residual will be correspondingly less. This reduction in score width does not reduce the severability of the score when the tear strip is removed from the can end 115, but does reduce the amount of stretching which occurs in the can end immediately adjacent the protective coating 117 so that the coating is not greatly affected during the operation. On the other hand, the size of the tool is larger than that shown in FIG. 2 so that the same force is distributed over a somewhat larger leading edge which is supported by the mass of the tool between the faces 55 and does not become jagged.
In a typical case, it has been found that the leading edge 53 could be manufactured so as to be 0.00l-0.002 inch, the angle between the faces 55 and the plane of edge 53 approximately 45 and the angle between the faces 57 and the plane of edge 53, approximately 60. These dimensions have proven to be satisfactory for scoring aluminum can ends having a thickness 0.0145 inch and a residual of 0.006 inch, but it will be realized that if these dimensions or the specific can end material are altered, some alteration of the tool dimensions may also be required. In any event, use of the tool 51 will provide a very suitable scoring of the can end 115, without rupturing or thinning the protective coating 117 such that post-coating would be required, while still having a long service life.
Thus, the applicant has provided an embodiment of a new and improved concept in the can end scoring art which yields a true advance in that art. Modifications and alterations of the embodiment will now be evident to those skilled in the art, without exceeding the scope of the invention as defined in the claims.
What is claimed is:
l. A tool for scoring can ends to provide a tear strip therein comprising:
a movable press member a tool fastened to said press member having a relatively narrow leading edge defining a flat surface,
a first set of side faces extending outwardly and upwardly from said leading edge toward said movable press member, and
a second set of side faces extending outwardly and upwardly from said first set of side faces toward said movable press member.
2. The tool of claim 1 wherein said first set of side faces are formed at smaller angles, relative to a plane including said leading edge, than are said second set of side faces.
3. The tool of claim 1 wherein said first set of side faces are provided with relatively friction'free surfaces.
4. A tool for scoring can ends to produce a removable tear strip therein comprising in cross section,
a narrow leading edge extending for initial contact with a can end to commence penetration thereof in forming the score,
a first side face extending from said leading edge for secondary contact with a can end to move metal therein away from the score being formed by the penetration of said leading edge, and
a second side face extending from said first side face for tertiary contact with a can end to move metal therein away from the score being formed, in a vector direction different from that in which metal is moved by said first side face.
5. The tool of claim 4 wherein said narrow leading edge presents a flat surface to a can end being scored,
said first side face is formed at a first angle relative to a plane including said flat surface,
said second side face is formed at a second angle relative to a plane including said flat surface, and
said first angle is smaller than said second angle.
6. The tool of claim 5 wherein said first angle is approximately 45 7. The tool of claim 5 wherein said second angle is approximately 60 8. The tool of claim 5 wherein said flat surface is approximately 0.001 to 0.002 inch wide.
9. The method of scoring a can end so as to create a severable residual therein comprising the steps of penetrating said can end across a relatively narrow dimension a distance sufficient to leave the desired residual,
enlarging the penetration above the residue by forcing metal away therefrom at an angle of about 45, and enlarging the penetration above the first enlargement y forcing metal away therefrom at an angle of about