Double Stage Necking

Abstract

This disclosure relates to the necking-in of can bodies for the purpose of applying smaller diameter or special ends thereon. Previously experienced extreme difficulties in properly necking-in can bodies have been eliminated by first necking-in a larger than normal end portion of a can body to an intermediate diameter and then utilizing tooling for performing the desired necking in operation to further neck-in the extreme end portion only of the previously necked-in longer end portion.

Description

This invention relates in general to new and useful improvements in the manufacture of containers and more particularly to the necking in of end portions of can bodies for either the reception of smaller than usual ends or special ends.

BACKGROUND OF THE INVENTION

Although it has been known for many years that it may be advantageous to neck-in end portions of can bodies for the reception of smaller diameter closures, only recently has there been a true commercial development of can bodies having necked-in end portions for the receipt of smaller diameter closures. However, extreme difficulties have been encountered. It is well known that tubular bodies may have the end portions thereof expanded inasmuch as metal will stretch. On the other hand, it is extremely difficult to compress metal.

It has been found that utilizing conventional necking dies, when extreme end of a tubular member, such as a can body, engages the sloping surface of the die, wrinkling immediately occurs. These wrinkles, when the necked-in end portion of the can body is later outwardly flanged or curled as part of a double seaming operation, are normally stretched, but minute cracks may occur either during the flanging operation or during the double seaming operation.

It has also been found that when the can body side seam construction is such that it must be coated with a side stripe, during the necking operation, the applied side stripe has a tendency to peel, particularly on the inner surface of the can body, with the result that the can body, after being necked-in, has an improper coating.

While diligent efforts have been made, and with a large degree of success, to commerically neck-in can bodies so that after the closures have been applied thereto the double seam between the can body and the closure will be disposed within the axial projection of the main portion of the can body, extreme difficulties have been experienced in further necking-in can bodies for the reception of even smaller closures, particularly closures of the aerosol type.

SUMMARY OF THE INVENTION

In the solution of the problem, dies for necking-in the end portions of can bodies to the desired reduced diameter were first constructed in accordance with prior commercially successful dies for the necking-in of like can bodies to a slightly larger diameter. However, these dies met with immediate failure. These failures were in the form of severe wrinkle formations in the neck and shoulder area of the necked-in end portions.

In view of the difficulties experienced in commercially necking-in can bodies to the larger diameter, it was thought that once the can bodies have been necked-in to the larger diameter, an ultimate necking-in operation had been performed on the particular can body. However, it was discovered that by first necking-in the can bodies to a larger than desired diameter on the order of or slightly greater than one-half the total desired reduction, and necking-in the end portion to a greater length, these necked-in can bodies could then be worked upon by the previously formed dies with a portion only of the previously necked-in end portion being successfully necked-in to the desired smaller diameter.

The net result of the double necking-in operation is one which met with commercial success and wherein the end portion of the can body which was necked-in had an intermediate portion of an intermediate diameter and there being two shoulders formed in the end portion. These shoulders, however, added to the decorative appearance of the can body.

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.

IN THE DRAWINGS

FIG. 1 is a schematic sectional view showing a can body having a previously necked-in end portion about to be further necked-in in accordance with this invention.

FIG. 2 is an enlarged fragmentary sectional view showing the can body entered into the die.

FIG. 3 is an enlarged fragmentary sectional view similar to FIG. 2 and shows the die and the can body fully telescoped with the necking operation completed and the can body and die ready to be separated.

FIG. 4 is a fragmentary sectional view similar to FIG. 3 and shows a modified form of die.

Referring now to the drawings in detail, it will be seen that there is illustrated in FIG. 1 a can body which is generally identified by the numeral 5. While the can body 5 is illustrated as being open at both ends, it is to be understood that as far as this invention is concerned, the can body may be of a drawn construction or may be provided with a side seam. It is envisioned that the can body 5 may possibly be of the type having a welded side seam or of a soldered side seam of the interrupted lock and lap type with an elongated lap, and wherein th side seam has been provided with an internal and external striping so that the coating of the car body, both externally and internally, is complete.

When the car body is to be utilized in the formation of an aerosol can, one end thereof will be more greatly reduced in diameter than normal. This is the primary usage of the can body of this invention. It is to be understood, however, that the can body may have both ends thereof necked-in, and the necking-in at the opposite ends of the can body may be identical or may be to different degrees. This invention has to do solely with the necking-in of at least one end of a can body to an extent greater than that which is normally commercially acceptable.

In accordance with this invention, an end portion 6, at least at one end of the can body 5, is necked-in to be of a reduced diameter. This necking-in is preferably the same as that which is commercially proven for the particular diameter of can body 5, but may be of a different reduction.

The end portion 6 is separated from the remainder of the normal diameter portion 7 of the can body by a shoulder 8. The end portion 6 is also of a greater than normal length inasmuch as normally the length of the necked-in end portion is only sufficient to effect the necessary double seaming operation.

In order to effect the further necking-in of the end portion 6, there is provided a necking die assembly which is generally identified by the numeral 10. The die assembly 10 includes an outer die ring 11 and a centrally located die plug 12. If the can body is the type having a side seam which is thicker than the sheet material from which the can body is formed, the die plug 12 will be mounted for floating movement with respect to the die ring 11 with there being clearance between a base portion 13 of the die plug 12 and a corresponding wall 14 of the die ring 11.

It is to be noted that the die ring 11, at the free end thereof, is provided with a tapered entrance portion 15, which leads into a cylindrical wall portion 16 which conforms generally to the external diameter of the intermediate portion 7 of the can body 5 so as to function as a guide for the same during the second necking-in operation. The die ring 11 further includes a tapered necking-in portion 17 which leads into the cylindrical portion 14.

It will be seen that when there is relative axial movement between the can body 5 and the necking die assembly 10, as is best shown in FIG. 3, the leading portion of the reduced diameter portion 6 of the partially necked-in can body 5, upon engagement with the tapered die portion 17, will be deflected inwardly into engagement with the die plug 12 and a second necking-in operation will be performed on the can body 5. As a result, the can body 5, in addition to being provided with the shoulder 8 will have an intermediate portion, which is formed by that part of the necked-in portion 6 which has not been further acted upon, a second shoulder 18 and a terminal portion 20 of the desired necked-in diameter. It will be understood that the terminal portion 20 will be of a sufficient length to receive the desired end (not shown).

In order that there may be set forth here a practical example of the invention, a typical example of the can body 5 is one having a nominal diameter of 2 11/16 inches. In order that the can body 5 may have secured to one end thereof a special end closure, such as an aerosol end, it is necessary that the diameter of the can body be reduced in the end portion thereof to 2 and 7.5/16 inches. After such experimentation it has been found possible to commercially neck-in can bodies having a diameter of 2 and 11/16 inches to have a diameter of 2 and 9/16 inches. Since it is known that this necking-in can be commercially accomplished, it was decided, in accordance with this invention, to in a like manner neck-in the end of the can body 5, but to a much greater extent than that which is necessary for the receipt of an end closure. This is the can body shown in FIG. 1. Thereafter, the necked-in can body 5 was subjected to the necking die assembly 10 in the manner described above so as to reduce the end portion 20 thereof to the required diameter of 2 and 7.5/16 inches. The axial extent of the end portion 20 is much shorter than the axial extent of the intermediate portion 6 and is of only such length as is required to effect the necessary application of the end closure for which the can body is intended.

With particular reference to FIG. 4, it will be seen that there is illustrated a modified form of necking-in die which is generally identified by the numeral 21. The die 21 is specifically configurated to produce the same necking-in operation as does the die 10 but provides more support for the previously necked-in end portion during the necking-in of the extreme end portion to the desired degree.

The die assembly 21 includes an outer die ring 22 which corresponds to the outer die ring 11, but it is of a modified construction. The die assembly 21 also utilizes a die plug which is identical with the die plug 12 and will be so identified.

With reference to FIG. 3, it will be seen that the end portion 6 is substantially unsupported between the cylindrical wall portion 16 and the tapered necking-in portion 17. As a result, during the second necking-in operation, the end portion may be unduly distorted in this unsupported area. For this reason, the die ring 22 has been provided.

The die ring 22, like the die ring 11, is provided at the free end thereof with a tapered entrance portion 23 which leads into a cylindrical wall portion 24. The die ring 22 also includes a tapered necking-in portion 25 which leads into a cylindrical portion 26 which cooperates with the die plug 12. It is also to be noted that there will be the same clearance between the base portion 13 of the die plug 12 and the cylindrical wall 26 so that limited shifting of the die plug 12 relative to the die ring 22 may occur when the can body being necked-in is provided with a side seam of a thickness greater than the nominal thickness of the metal from which the can body is formed.

It is to be noted that the die ring 22 differs from the die ring 11 in that intermediate the cylindrical wall portion 24 and the tapered necking-in portion 25 there is provided a tapered guide wall portion 27 and a cylindrical wall portion 28. The cylindrical wall portion 28 has a diameter generally corresponding to the external diameter of the reduced diameter portion 6 of the can body 5.

It will be readily apparent from FIG. 4 that when the can body 5 enters into the die ring 22, the can body will be guided by both the tapered entrance portion 23 and the tapered wall portion 27 to a centered relationship and will be supported by both the cylindrical wall portion 24 and the cylindrical wall portion 28 during the necking-in operation performed by the die assembly 21.

It will also be apparent that the die assembly 21 will function to neck-in the already necked-in end portion 6 of the can body 5 to form thereon a second shoulder 18 and a terminal portion 20 of the desired necked-in diameter.

Although only a preferred embodiment of the invention has been specifically illustrated and described herein, it is to be understood that minor variations may be made in the necking-in operation without departing from the spirit and scope of the invention, as defined by the appended claims.

Claims

I claim:

1. A one-piece conventionally formed can body of the type including a side seam and particularly constructed for the reception of an end of a diameter materially less than a normally provided end for a like diameter can body, said can body being a double necked-in can body including a main body portion of a normal diameter and forming a major portion of the length of said can body, an extreme end portion of a greatly reduced diameter and having an open terminal end of a diameter at least as great as the remainder of said extreme end portion, said open terminal end being at the extreme end of said can body for directly receiving thereon an end of a diameter materially less than a normally provided end for a can body of the diameter of said main body portion, and an intermediate portion of an intermediate diameter, the combined lengths of said extreme end portion and said intermediate portion being greatly less than the length of said main body portion, and a frustoconical shoulder portion disposed between adjacent ones of said can body portions.

2. The can body of claim 1 wherein the difference in diameters of said normal diameter and said intermediate portion is on the order of 50 percent of the difference in diameters of said normal diameter and said extreme end portion.