MXPA97000604A - Method for straightening of enva - Google Patents

Abstract

The present invention relates to a multi-stage matrix forming method for narrowing the open end of a can body so as to form a neck of reduced diameter having a smooth profile comprising the steps of: providing a can body of open ends having a side wall of essentially cylindrical configuration about a longitudinal central axis, the side wall defines an open end having a terminal edge, in the matrix forming station, causing a relative axial movement between the first narrowing matrix and the open end of the side wall for coupling the first die against the side wall so as to form a first neck of reduced diameter having a first contoured portion extending inward from the side wall to a first cylindrical portion terminating in the terminal edge, in a following matrix forming station cause an axial movement rel A second narrowing matrix and the first neck for coupling the second matrix against the first neck so as to form the first neck in a second neck of reduced diameter having a second contoured portion extending inward from the side wall to the second neck. second cylindrical portion terminating on the terminal edge, the diameter of the second cylindrical portion is smaller than the diameter of the first cylindrical portion, the second contoured portion has a first section extending inwardly from the side wall at a minimum entry angle of approximately 26§, a second section of radius joining the first section and curving away from the longitudinal axis by a considerably smaller radius of 22.86 millimeters and a third section of radius that curves away from the longitudinal axis and joins the second section of radius. radius with the second cylindrical portion, the radius of the third section being cons Inerably smaller than the radius of the second section, the angular distance through which the second section extends along the direction of the longitudinal axis, being at least equal to the angular distance through which the third section, the sum of the angular distances being equal to the input angle, and in a subsequent matrix forming station to trigger the relative axial movement between the third narrowing matrix and the second neck to couple the third matrix against the second neck to form the second neck in a third diameter reduced neck having a third contoured portion extending inward from the side wall to the third cylindrical portion terminating at the terminal edge, the diameter of the third cylindrical portion being less than the diameter of the second. cylindrical portion, the third contoured portion has a profile that is essentially the same as the profile l of the second portion contours

Description

"METHOD FOR CONVERSION STRAINING" RELATED REQUESTS This application is a continuation in part of the co-pending application Serial Number 08 / 591,877, filed January 15, 1996, which is a continuation in part of the application Serial Number 08 / 320,999, filed on October 11, 1994, abandoned now.

BACKGROUND OF THE INVENTION This invention relates, generally, to a narrowing method at the open end of a cylindrical package and, more specifically, to a method for matrix tightening the open end of a package that includes a plurality of narrowing steps with matrix forming a smooth neck configuration at the open end of the can. It is common practice to provide a reduced diameter neck portion in the upper part of a thin walled aluminum cylindrical can body in order to receive a separate end cap towards the mouth of the open end of the can body. Typically the diameter of the cylindrical body is approximately 6.83 centimeters (diameter 211) and the open end of the can narrows to a diameter of 6.03 centimeters (diameter 206) or even smaller up to 5.72 centimeters (diameter 204). The various processes employing a plurality of narrowing steps with matrix have been used in trying to form smooth wall necks. The above North American Patents Nos. 3,029,507, 3,964,414, 3,995,572, 4,173,883, 4,403,493, 4,527,412, 4,774,839 and 5,297,414 illustrate the various processes and equipment for forming smooth wall necks. However, as the diameter of the finished neck becomes smaller and smaller, it becomes more difficult to provide a smooth neck profile that is free of folds or wrinkles. We have found that to essentially eliminate wrinkles or creases in the finished neck, it is desirable to maintain contact of the front edge of the can with the profiled forming surface of the die in the axial direction of penetration as long as possible before the Front edge contacts the internal guide block or is centered within the matrix by a stroke. Ideally, the front edge of the can and, therefore, the entire wall of the can must maintain contact with the surface of the die virtually throughout the process of narrowing. In conventional matrix grinding processes, where the matrix forming surface is profiled in a single radius, the wall of the can leaves the surface of the matrix before the front edge comes in contact with the guide block When this occurs, the front edge is no longer compressed and controlled by the matrix. For example, a single-radius array loses control of the front edge of the can wall remotely by approximately 1.16 millimeters before the die exit. This lack of control allows the front edge of the wall to wrinkle and wrinkles become a source of folds in the finished neck. For a number of years, the concessionaire of this invention has used a matrix tapering process, wherein the matrix at certain stations has multiple beams, but different profiles, eg, a large input radius of 22.86 millimeters acting essentially as a flat part and a small exit radius of approximately 2.54 millimeters extending through the exit angle greater than 12 °. Those matrix profiles were a significant improvement in relation to the single-radius array profiles, maintaining control of the front edge of the can up to approximately 0.508 millimeters before the exit of the matrix, and considerably reducing wrinkling problems associated with the profiles of a single radio. In those previous matrix shrinking processes, the configuration of the matrix in one station differed from the configuration of the matrix in each of the other stations, thus adding considerably the cost of the matrices. In addition, it is desirable to minimize the total length or height of the tapered portion of the can so as to maximize the height of the total cylindrical portion in the finished or finished can, thereby providing a larger space in the portion cylindrical for labeling or advertising material. However, unless the tapering matrices are properly designed, it has been found that decreasing the height of the neck portion leads to the formation of an increasingly unacceptable number of wrinkles or creases in the finished or finished can.

SUMMARY OF THE INVENTION Accordingly, the main object of the invention is to provide a process of tapering with novel matrix to form a smooth neck of reduced diameter at the open end of a can, so as to eliminate wrinkling or folding, but without However, maximize the available height of the billboard in the finished can. Another object of the invention is to provide a tapering process with a novel matrix in which the tapering array has a multiple radius forming profile wherein each successive radius from the entry to the exit of the matrix is smaller than the previous radius. Still another object of the invention is to provide the novel matrix tapering process wherein the tapering array has a double radius profile and the input radius is substantially less than 22.86 millimeters. Another object of the invention is to provide the aforementioned novel matrix tapering process, wherein the exit radius extends through an exit angle of less than 12 °. Still another object of the invention is to provide the aforementioned novel matrix tapering process which includes a step in which a tapering array moves axially with respect to the open end of the cylindrical side wall of a can body, engaging the wall lateral to form a reduced diameter first neck having a contoured portion extending inward from the side wall to a first cylindrical portion terminating at a terminal edge. The first neck of reduced diameter has an axial length corresponding to the desired length of the finished neck in the can. The process further includes subsequent forming steps in which each of the narrowing matrices preferably of essentially multiple radius configuration, eg, a double radius profile, so that the contoured portion of each neck diameter The reduced profile has essentially the same double radius profile, leading to the cylindrical portion of each neck. This feature eliminates folding and considerably reduces the cost of narrowing matrices. Yet another object of the invention is to provide the novel process described above, wherein the contoured portion of each neck is formed at a more intense angle with respect to the cylindrical wall, thereby reducing the axial length of the neck finished in a can, and maximizing the available height of the billboard in the finished can. Other objects and advantages of the invention will become apparent upon reading the following detailed description of the invention, with reference to the accompanying drawings, wherein like numbers indicate like elements.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 schematically illustrates a step of a narrowing process with novel multi-end cap of the invention, whereby a first neck of reduced diameter is formed, the neck having an axial length corresponding essentially to the desired length of the finished neck in the tin; Figure 2 illustrates the next step of the matrix tapering process of the invention forming a second neck of reduced diameter having a novel double radius profile configured in accordance with the invention; Figure 3 schematically illustrates the profile of the narrowing matrix employed in the second step illustrated in Figure 2 and preferably in each subsequent forming step of the multi-step process; Figure 4 is a schematic scaled illustration of about 4.5 to 1 of the neck profiles that are formed by each of the six steps used to produce, for example, a neck of diameter 206. Figure 5 is a schematic illustration amplified of the double radius forming surface profile of the matrix of Figure 3; Figure 6 is an enlarged schematic illustration of a triple radius forming surface profile of a matrix constructed in accordance with the invention; Figure 7 is an enlarged schematic illustration of a constricting passage illustrating the front edge of the can wall leaving the matrix forming surface and axially penetrating in an uncontrolled manner towards the outlet of the matrix and the block as guide; Figure 8 is an enlarged schematic illustration of a can wall engaging a surface of the matrix illustrating the phenomenon of differential reduction by which contact can be maintained; Figure 9 is a graph showing the ratio of differential reduction versus the distance from the outlet or throat of the matrix for a conventional single-radius array, the previous multiple-radius array of the concessionaire described above and the matrix double radius constructed in accordance with the invention. Figure 10 is a graph similar to Figure 9, illustrating computer modeling graphs for 3 or 4 spoke arrays constructed in accordance with the invention.

DETAILED DESCRIPTION OF THE INVENTION The can manufacturing process of the invention can be carried out by known conventional equipment having a plurality of tapering stations which correspond in number to the number of tapering steps required to provide the diameter of the finished neck, for example, six steps of narrowing to produce a diameter 206. These steps operate at the open end of a cylindrical can 20 to form a smooth narrowed portion 22 (Figure 4) which is ready after proper beading to accept an end cap of a desired diameter, eg, a diameter 206. Each station includes a turret mechanism mounted for rotation about a horizontal axis and adapted to receive from a suitable feeding mechanism, a plurality of cans 20 and to hold each of those cans in a horizontal position with the lower part of the cans coupled against a rotating base 26. In one station, associated with each can, there is a narrowing array assembly 27 that includes an internal guide block 28 that enters the open end of the can 20 and an external matrix 32 that engages against the outer surface of the wall. 21 cylindrical of the can 20, in order to form the desired reduced neck configuration. The base 26 and the array 27 rotate together with the turret mechanism, but the guide block 28 and the forming die 32 are operated by a cam for axial movement towards and away from the open end of the can 20 so as to carry out the narrowing operation in each of the narrowing stations with matrix. Except for the specific configuration and movement of the dies, the apparatus used to carry out the invention is conventional. The drawings illustrate the successive steps of matrix shrinkage involved to reduce the open end of a can 211 to an appropriate neck to receive, for example, an end cap 206. The thickness of the cylindrical wall of the aluminum can 20 can be within the area of .127 millimeter to .191 millimeter. The process can be operated at a speed to produce approximately 1,500 to 2,400 narrow cans per minute. Referring to Figure 4, it is typically desirable to provide a can 20 with a neck 22 of reduced diameter extending from the upper terminal edge 23 of the can, axially downward to a length L where it joins a circular line 2a of the cylindrical lateral wall of the can. The neck 22 includes a smooth inwardly tapering portion 24 extending from the line 2a of the cylindrical side wall 21 to a terminal cylindrical portion 25 that forms the open mouth of the can, it is desirable that the axial length L of the finished neck be reduce to a minimum to bring the maximum height of the cylindrical wall from the bottom of the can to line 2a. This maximizes the amount of billboard space in the cylindrical wall of the can for labeling and advertising purposes. At the same time, the length a must be sufficient to avoid excessively stressing the metal during the forming process of the neck that would cause the formation of cracks and folds in the finished neck.

In the process of the invention, in a matrix forming step, the material at the open end of the can is deformed through the entire length L to form a first neck of reduced diameter. In the next step and in each subsequent step, each neck of reduced diameter previously formed is preferably deformed by coupling with a respective tapering die having the same profile, but if desired for some object one of those steps can be used matrix that has a different profile. Referring to Figure 1, the upper half of the figure illustrates the guide block 28 and the array 32 placed in its initial non-working positions, while the lower half of the figure illustrates the block and the array driven towards the internal operative neck forming positions. The same is the case for the positions of the guide block and the in Figure 2. In the initial step of Figure 1, the guide block 28 first enters into the open end of the wall 21, followed by an inward movement. of the matrix 32. The matrix forming surface engages against the terminal 23 edge of the cylindrical lateral wall 21 in a circular line 2a, and the continuous inward movement of the matrix 32 deforms the metal along a portion 32a of surface contoured inwards, and from there between the outer diameter of the guide block 28 and the internal diameter of the cylindrical portion 32b of the The axial stroke of the 32 is adjusted so that the open end of the can penetrates axially between the external diameter of the block 28 and the internal diameter of the cylindrical surface 32b at a sufficient distance up to, from a first neck 40 of reduced diameter that it has an inwardly contoured portion 40a extending from the circular line 2a to a cylindrical terminal portion 40b having an internal diameter of approximately 1.91 millimeters smaller than the diameter of the cylindrical wall 21. The axial length of the first neck 40 of reduced diameter from the terminal edge 23 downwards to the circular line 2a corresponds to the desired length L of the finished neck. It should be understood that the narrowing step with matrix illustrated in Figure 1 may be preceded by one or more preliminary forming steps, for example, the preliminary step disclosed in Patent Number 5,297,414 to prepare the open end of the can for the forming step of Figure 1. Referring now to Figures 2 to 4, at the next taper station, the neck 40 of reduced diameter is actuated by a second matrix assembly 50 which includes a guide block 52 and a matrix 54 to form a second neck 60 of reduced diameter at the open end of the can 20. The configuration and profile of the 54 is illustrated in Figure 3 and in the amplified schematic illustration of Figure 5 includes a contoured portion 66 that it has a tapered section 68 tapering inward at the entry angle A within the range of 26 ° to 30 ° with respect to the cylindrical wall 21. The tapered section 68 is fused with the first radius section 70 which curves away from the longitudinal axis of the at a radius R ^ of approximately 6.99 millimeters. The section 70 is then fused with a second radius section 72 that curves away from the longitudinal axis of the array at a much smaller radius R2 within the range of 2.03 millimeters to 3.56 millimeters, preferably of about 3.05 millimeters. The section 72 at the outlet or throat 76 of the then joins a section 74 of straight cylindrical matrix having an internal diameter of approximately 1.40 millimeters less than the outer diameter of the first cylindrical portion 40b of the neck 40. The section 72 radius extends outward through an angular distance C from the intersection point 76 with section 74, the central point X of R2 being placed on a line perpendicular to the axis of the array and passing through point 76 of output . The radius section 70 extends outwardly from the point of intersection 78 with the section 72 through an angular distance B to an intersection point 80 with the tapered straight section 68. The central point Y of R ^ lies on a line that passes through point 78 and the central point X. It has been found that the sum of the angles B and C must be equal to the tangency angle D of the contact point 90 of the front edge of the can wall in the section 70, which is axially and radially inward from the point of intersection 80 of sections 68 and 70, being in this way the angle D slightly smaller than the angle A. The angle C can not exceed 12 °. In a prototype of the invention, with the angle of entry A at 27 °, the angle D at 26.5 °, the radius R2 at 3.05 millimeters, it was determined that the matrix worked best when the angle B was 18.5 ° and the angle C It was 8 °. Referring again to Figure 2, as the turret assembly rotates, the guide block 52 enters centrally into the open mouth of the first reduced diameter neck 40 and the matrix 54 then moves inward so that the first radio section 70 comes into contact with bank 23 on a circular line 3a (Figure 4). As the die 54 continues to move inwardly, the neck portions 40a and 40b constituting the metal are reformed by engagement with the die sections 70 and 72 and by axial penetration between the outer diameter of the guide block 52 and the diameter internal surface 74 of cylindrical matrix. The axial stroke of the die 54 is adjusted so that the open end of the can penetrates a sufficient distance between the external diameter of the block 52 and the internal diameter of the cylindrical die surface 74 so as to form a second neck 60 in diameter reduced as illustrated in Figure 4. The second neck 60 of reduced diameter will then have an inwardly contoured portion 60a conforming to the contoured portion 66 of the die 54 and extending from the cylindrical wall 21 on the circular line 3a to a second reduced cylindrical portion 60b having a diameter of approximately 1.40 millimeters smaller than the diameter of the cylindrical portion 40b of the neck 40. At each subsequent forming step where respectively the neck 84, 86, 88 and 22 are formed reduced (Figure 4) the profile of the matrix of preference is the same as that shown in Figure 3, but of course, the internal diameter of the supe The cylindrical surface of each successive hue is approximately 1.40 millimeters smaller than that of the previous matrix. In those subsequent steps where the necks 84, 86, 88 and 22 are formed, the part of the anterior neck in contact with a die 54 is the axial length from the terminal edge 23 down to lines 4a, 5a, 6a and 7a circular, respectively. As mentioned above, the tapered angle A can be within the range of 26 ° to 30 °. Of course, the greater the shortest angle will be the axial length L of the finished neck and, therefore, there will be more space available on the billboard of the can for publication or advertising purposes. In the prototype mentioned above, where the entry angle A was 27 °, the axial length of the finished neck was approximately 16.26 millimeters and virtually no folding problems occurred. In more conventional processes, where smooth necks are produced with acceptable folding levels, the length of the neck is more within the 19.05 millimeter scale. It is significant that all matrices used in the training steps subsequent to the initial step of Figure 1, preferably have the same profile. This greatly simplifies the construction of the matrices and reduces their cost.

As mentioned above, for a double radius array, the value of the radius R2 is within the range of 2.03 millimeters to 3.56 millimeters, and is preferably approximately 3.05 millimeters. It has been found that a radius R2 less than 2.03 millimeters frequently produces circumferential lines or ribs within the finished neck and that a radius R2 greater than 3.56 millimeters increases the possibility of creases forming in the neck. Even when the exact limitations of the value of Rl have not been clearly known, the prototype works best when R ^ was about 6.99 millimeters. It is believed that any radius considerably less than 6.99 millimeters may cause work hardening of the metal, while a radius R ^ considerably greater than that value will cause an unacceptable amount of bending. For example, a radius R ^ of approximately 20.32 millimeters or 22.86 millimeters is considered as being too large and can act as a flat stretch creating problems. Computer modeling predicts that the radius R ^ must be less than 12.7 millimeters. Table I presents several combinations of radii Ri and R2 and angles B and C that are expected to work well together for the double radius matrix of Figure 5. The values are presented for three different tangency angles used with a reduction X of .699 mm (diameter reduction of 1.40 mm). TABLE I 1. X = .699 mm, D = 26.5 R2 C Rl B 2.03 4 ° 6.76 22.5 ° 2.54 6 ° 6.88 20.5 ° 3.05 8 ° 7.01 18.5 ° 3.56 10 ° 7.16 16.5 ° 2. X = .699 mm, D = 28.5 'R2 C Rl B 2.03 4 ° 6.76 24.5 ° 2.54 6 ° 6.88 22.5 ° 3.05 8 ° 7.01 20.5 ° 3.56 10 ° 7.16 18.5 ° X = .699 mm, D = 30.5' R2 C l B 2.03 4 ° 5.11 26.5 ° 2.54 6 ° 5.16 24.5 ° 3.05 8 ° 5.21 22.5 ° 3.56 10 ° 5.23 20.5 ° Table II presents the different combinations of radii R ^, R2 and R3 and angles B, C and E that are expected to work well together for the triple radius profile matrix of Figure 6. The values are presented for an angle of tangency D of 27 ° and a reduction X of .699 mm.

TABLE II R2 C l B R3 E 2.03 4 ° 5.08 6 ° 6.99 17 ° 2.03 4 ° 5.54 9 ° 7.09 14 ° 2. 03 5. 74 11 .5 ° 7.21 11. 5 ° R2 C Rl B R3 E 2. 54 4 ° 4.60 6 ° 7.04 17 ° 2. 54 4 ° 5.18 9 ° 7.16 14 ° 2. 54 4 ° 5.46 11.5 ° 7.34 11.5 ° 2. 54 6th 6.27 7th 7.01 14th 2. 54 6th 6.38 9th 7.04 12th 2. 54 6th 6.43 10.5th 7.09 10.5th R2 C Rl B 3 E 3. 05 4th 4.11 6th 7.09 17th 3. 05 4 ° 4.85 9 ° 7.24 14 ° 3. 05 4 ° 5.16 11. .5 ° 7.47 11.5 ° 3. 05 6 ° 5.56 7 ° 7.14 14 ° 3.05 5.79 7.24 12 '3.05 5.92 10.5 ° 7.32 10.5 ° 3. 05 6.96 7.01 10 ° R2 C Rl 'B R3 E 3.56 4 ° 3.63 6 ° 7.14 17 ° 3.56 4 ° 4.50 9 ° 7.34 14 ° 3.56 4 ° 4.88 11.5 7.57 11.5 3.56 6 ° 4.88 7 ° 7.26 14 ° 3.56 6 ° 5.23 9 ° 7.42 12 ° 3.56 6 ° 5.41 10.5 ° 7.54 10.5 ° 3. 56 8th 6.12 9th 7.37 10th 3.56 9th 6.63 9th 7.29 9th As mentioned initially above, it is desirable to maintain contact of the front edge of the can with the profiled forming surface of the die through the entire constriction operation from the entrance to the die to the outlet. Figure 7 illustrates schematically the front edge 23 of the can that leaves the surface of the die at a point Pa axially spaced at a distance in the direction of penetration from the outlet or groove 76 of the die. To reduce wrinkles on the front edge, this distance should be reduced to a minimum and ideally it should be zero. When the front edge comes out of the surface of the matrix, it loses the three-dimensional cuvartura and becomes a cone. The cone is much weaker than the shape of "bulls" and it is easier to wrinkle. As the can continues to penetrate the matrix, the length of the cone increases until it hits the internal guide block. The resistance of the cone to wrinkling is either a quadratic or cubic relation with respect to the length ie a length that is twice as long could be wrinkled more easily eight times more. This is analogous to the known cubic ratio of the thickness of the can wall for resistance to wrinkling. The length of the unsupported cone is essentially the same as the amount of penetration that remains after the edge leaves the matrix. EvidentlyBy retarding the point where the edge leaves the matrix, the unsupported cone length is reduced and, therefore, the wrinkles at the front edge are reduced. When the front edge is brought into contact with the guide block, the leading edge is again pushed into contact with the surfaces of the matrix. Any small wrinkles are removed but large ones will permeate and create a crease in the terminal can. The best way to see the ability of a narrowing matrix to restrict the leading edge is to compare a point some distance back from the front edge with the front edge. Figure 8 defines the methodology used to compare the bank with a point further back in the matrix. Point P] _ is the front edge and point P2 is placed at a distance of 2.54 mm (penetration distance) behind the front edge. Point P3 is the distance of .0254 millimeter behind (penetration distance) from point P2. The amount of reduction that occurs at the front edge is defined by R ^ and the reduction of 2.54 mm behind the front edge is Rh. The diagram shows that Rh is always larger than R ^. As the can is pushed further into the matrix, R ^ becomes smaller and eventually reaches zero. If Rh is considerably larger than Ri then the reduction behind the leading edge forces the leading edge away from the matrix as shown in Figure 7. Tests have shown that a further reduction of more than 30 percent greater than the reduction of the front edge will cause this front edge to leave the surface of the matrix. In other words, a differential reduction ratio (Rh / R) of more than 1.3 causes the leading edge to leave the matrix. Figure 9 is a graph showing the ratio of differential reduction versus the distance from the throat of the matrix for a narrowing matrix of a single conventional radio, for the former multiple radio matrix of the dealership, using a large input radius of 22.86 millimeters and a double radius array of this invention. The double radius narrowing matrix of Figures 3 and 5 does not reach the critical ratio of 1.3 until the can is much closer to the throat of the matrix compared to the other processes (approximately .330 millimeter). Computer modeling predicts that 3 and 4-spoke arrays will work even better. For example, a 3-spoke array has a contact tangency angle of 27 °, an input radius of 12.7 millimeters through 18 °, an intermediate radius of 3.05 millimeters through 5 ° and an output radius of 2.03 millimeters through 4 ° that will not reach the critical ratio of 1.3 until the front edge of the can is approximately 2.54 millimeters from the outlet or throat (Figure 10). Similarly, a 4-spoke array having a contact tangency angle of 27 °, an input radius of 15.24 millimeters through 16 °, a following radius of 3.81 millimeters through 4 °, a following radius of 2.03 millimeters through 4 ° and an output radius of 1.10 millimeters through 3 ° will not reach the critical ratio of 1.3 until the front edge of the can is at a distance of approximately .203 millimeter from the outlet (Figure 10 ). A theoretical profile "Best Profile" will be generated if the profile of the narrowing matrix varies constantly, constantly decreasing the radius in such a way that the reduction ratio is kept lower than 1.3 for as long a period as possible. One way to produce this profile would be to generate the perfirl of the matrix using a parabolic function or even more extreme, an Archimedean spiral. It should be noted that in all the above-mentioned multi-radius forming profiles of the invention, each successive radius from the entrance to the exit of the matrix is smaller than the previous radius and the angle through which each successive radius extends is equal ao less than the angle of the previous radius. The angle of the exit radius must not exceed 12 °. It is anticipated that the novel multi-radius array configurations of the invention will also result in a reduction in the number of stations required in the matrix narrowing process., since the dies are expected to produce a greater reduction in neck diameter at each station than was previously possible. The invention may be encompassed in other specific forms without deviating from the spirit or essential characteristics thereof. The present embodiments, therefore, should be considered in all respects as illustrative and not restrictive, the scope of the invention having been indicated by the appended claims rather than by the foregoing description, and all changes remaining within the scope of the invention. meaning and scale of equivalence of the claims, therefore, are intended to be covered in this.

Claims (22)

R E I V I N D I C A C I O N E S;

1. A multi-cap die forming method for narrowing the open end of a can body to form a reduced diameter neck having a smooth profile comprising the steps of: providing an open ended can body having a wall laterally of essentially cylindrical configuration about a longitudinal central axis, the lateral wall defines an open end having a terminal edge; in the matrix forming station, causing a relative axial movement between the first nip matrix and the open end of the side wall to couple the first nip against the side wall so as to form a reduced diameter first neck having a first portion contoured extending inward from the side wall to a first cylindrical portion terminating at the terminal edge; in a next matrix forming station causing a relative axial movement between a second nip matrix and the first neck to couple the second nip against the first neck so as to form the first neck in a second neck of reduced diameter having a second portion contoured extending inward from the side wall to the second cylindrical portion terminating at the terminal edge, the diameter of the second cylindrical portion is smaller than the diameter of the first cylindrical portion; the second contoured portion has a first section extending inwardly from the side wall at a minimum entry angle of approximately 26 °, a second section of radius joining the first section and curving away from the longitudinal axis at a considerably smaller radius of 22.86 millimeters and a third section of radius that curves away from the longitudinal axis and joins the second section of radius with the second cylindrical portion, the radius of the third section being considerably smaller than the radius of the second section, the angular distance through which the second section extends along the direction of the longitudinal axis, being at least equal to the angular distance through which the third section extends, the sum of the angular distances being equal to the angle of entry; and in a subsequent matrix forming station or causing relative axial movement between the third nip matrix and the second neck to couple the third nip against the second neck to form the second neck in a third diameter reduced neck having a third contoured portion extending inward from the side wall to the third cylindrical portion terminating at the terminal edge, the diameter of the third cylindrical portion is smaller than the diameter of the second cylindrical portion, the third contoured portion has a profile that is essentially the same than the profile of the second contoured portion.

2. The matrix-forming method of Figure 1, wherein the radius of the third section is within the range of 2.03 millimeters to 3.56 millimeters.

3. The matrix forming method of Figure 2, wherein the radius of the third section is 3.05 millimeters.

4. The matrix forming method according to claim 2, wherein the angular distance through which the third section extends does not exceed 12 °. The matrix forming method according to claim 2, wherein the radius of the second section does not exceed 12.7 millimeters. 6. The trust matrix forming method of claim 5, wherein the radius of the second section is about 6.99 millimeters. The multi-stage matrix forming method for narrowing the open end of a can body to form a reduced diameter neck having a smooth profile comprising the steps of: providing an open ended can body having a wall laterally of essentially cylindrical configuration about a longitudinal central axis, the lateral wall defines an open end having a terminal edge; a matrix forming station, which causes relative axial movement between a first nip matrix and the open end of the side wall to couple the first nip against the side wall so as to form a reduced diameter first neck having a first portion contoured extending inward from the side wall to a first cylindrical portion terminating at the terminal edge; in a next matrix forming station, providing a second nip matrix having a contoured surface including a first section extending inwardly from the side wall at a minimum entry angle of about 26 °, a second radio forming section which joins the first section and which is curved away from the longitudinal axis by an essentially smaller radius of 22.86 millimeters, and a third radius forming section which is bent away from the longitudinal axis and which joins the second radius section with a cylindrical section, the The radius of the third section is smaller than the radius of the second section, the angular distance through which the second section extends along the direction of the longitudinal axis is at least equal to the angular distance through the which extends the third section, the sum of the angular distances being equal to the angle of entry and causing a movement relative axial between the second nip matrix and the first neck for coupling the first neck against the radius forming sections of the second nip matrix to form the first neck in a second neck of reduced diameter having a second contoured portion that is extends inward from the side wall to a second cylindrical portion terminating at the terminal edge, the diameter of the second cylindrical portion being less than the diameter of the first cylindrical portion; in a subsequent matrix forming station, providing a third narrowing matrix including a contoured surface having a profile that is essentially the same as the profile of the contoured surface of the second matrix and causing relative axial movement between the third narrowing matrix and the second neck for coupling the second neck against the contoured surface of the third die so as to form the second neck on a third reduced diameter neck having a third contoured portion extending inward from the side wall to a third cylindrical portion ending at the terminal edge, the diameter of the third cylindrical portion is smaller than the diameter of the second cylindrical portion. The matrix forming method according to claim 7, wherein the radius of the third section is within the range of 2.03 millimeters to 3.56 millimeters. 9. The matrix forming method according to claim 8, wherein the radius of the third section is 3.05 millimeters. The matrix forming method according to claim 8, wherein the angular distance through which the third section extends does not exceed 12 °. The matrix forming method according to claim 8, wherein the radius of the second section does not exceed 12.7 millimeters. The matrix forming method according to claim 11, wherein the radius of the second section is approximately 6.99 millimeters. 13. A die forming method for tapering the open end of a can body to form a reduced diameter neck having a smooth profile comprising the steps of: providing an open ended can body having a side wall configuration essentially cylindrical about a longitudinal central axis, the side wall defines an open end having a terminal edge; in a matrix forming station providing a narrowing matrix having a contoured surface including a first section extending inwardly from the side wall at an inlet angle, a second radius forming section and curving away from the longitudinal axis by an essentially smaller radius of 22.86 millimeters and a third radius forming section that curves away from the longitudinal axis and joins the second radius section with a cylindrical section, the radius of the third section is smaller than the radius of the second section, the angular distance through which the second section extends along the direction of the longitudinal axis is at least equal to the angular distance through which extends the third section, the sum of the angular distances being equal to the entrance angle; and causing a relative axial movement between the nip matrix and the open end of the side wall to couple the side wall against the die forming surfaces of the die so as to form a neck of reduced diameter having a contoured portion extending inward from the side wall to a cylindrical portion that ends at the terminal edge. The matrix forming method according to claim 13, comprising a subsequent matrix forming station that provides a second narrowing matrix including a contoured surface having a profile that is essentially the same as the profile of the contoured surface of the matrix. the first die, and cause relative axial movement between the second narrowing die and the first neck to engage the first neck against the contoured surface of the second die so as to form the first neck in a second neck of reduced diameter having a second contoured portion extending inward from the side wall to a second cylindrical portion terminating at the terminal edge, the diameter of the second cylindrical portion is less than the diameter of the first cylindrical portion. The matrix forming method according to claim 14, wherein the radius of the third section is within the range of 2.03 to 3.56 millimeters. 16. The matrix forming method according to claim 15, wherein the radius of the third section is 3.05 millimeters. 17. The matrix forming method according to claim 15, wherein the angular distance through which the third section extends does not exceed 12 °. 18. The matrix forming method according to claim 15, wherein the radius of the second section does not exceed 12.7 millimeters. 19. The matrix forming method according to claim 18, wherein the radius of the second section is approximately 6.99 millimeters. 20. A die forming method for narrowing the open end of a can body to form a neck of reduced diameter having a smooth profile comprising the steps of: providing an open-ended can body having a side wall essentially of cylindrical configuration about a longitudinal central axis, the side wall defines an open end having a terminal edge; a matrix forming station that provides a narrowing matrix having a multi-radius forming surface, each successive radius from the entry to the exit of the matrix is smaller than the anterior radius and the angle through which each successive radius is When the extension is equal to or less than the angle of the anterior radius, the sum of the angular distances through which the radii extend is essentially equal to the angle of tangency with which the front edge of the can wall engages the radius of entry of the matrix; and causing a relative axial movement between the nip matrix and the open end of the side wall to couple the side wall against the multi-radius forming surface of the die so as to form a reduced diameter neck having a contoured portion that is extends inward from the side wall to a cylindrical portion that terminates at the terminal edge. 21. The matrix forming method according to claim 20, wherein the angle of the exit radius does not exceed 12 °. The matrix forming method according to claim 20, comprising a subsequent matrix forming station, which provides a second narrowing matrix including a multi-radius forming surface having a profile that is essentially the same as the profile the forming surface of the first die, and causing the relative axial movement between the second nip matrix and the first neck to engage the first neck against the forming surface of the second die so as to form the first neck in a second neck of reduced diameter having a second contoured portion extending inward from the side wall to a second cylindrical portion terminating at the terminal edge, the diameter of the second cylindrical portion being less than the diameter of the first cylindrical portion.