GB2202777A

GB2202777A - Method of producing a neck-in can

Info

Publication number: GB2202777A
Application number: GB08721428A
Authority: GB
Inventors: Kazuhiro Sawada; Chusei Kato
Original assignee: Toyo Seikan Kaisha Ltd
Current assignee: Toyo Seikan Group Holdings Ltd
Priority date: 1987-03-30
Filing date: 1987-09-11
Publication date: 1988-10-05
Anticipated expiration: 2007-09-11
Also published as: JPH0316207B2; GB2202777B; JPS63242430A; GB8721428D0; KR880010837A

Abstract

A method of producing a neck-in can by necking simultaneously with double seaming, wherein a can cover 1 and a can body 2 are formed so that a difference between a diameter of a curl opening of the can cover and an outside diameter of a flange of the can body is in the range from 0.2 mm to 3.2 mm, and a neck-in portion is formed by lower jaws of a first seaming roll (5, Fig. 5(a)) and a second seaming roll (6, Fig. 5(c)), respectively, so that the amount of reduction in diameter B of the neck-in portion is within 5% with respect to the outside diameter A of the can body, and the amount of reduction in diameter is less than 3.5 mm. The width of a flange of the can body is formed within the range from 1.2 mm to 2.6 mm. The radius of curvature of the lower jaws of the first seaming roll and the second seaming roll, respectively, is formed to be above 0.8 mm, and the lower jaw of the first seaming roll and the lower jaw of the second seaming roll come into contact with the same height-position of the can body when a can is seamed. <IMAGE>

Description

METHOD OF PRODUCING A NECK-IN CAN This invention relates to a method of producing a neck-in can in which an end of a can body is reduced in diameter.

So-called neck-in cans the body end of which is reduced in diameter and a cover thereof having a smaller outside diameter of a chuck wall than an inside diameter of the can body is subjected to double seaming provide advantages in that material cost for the cover is saved to lower the cost, that since the rolled portion is not inflated outwardly of the can body, an encasing space can be saved; and that close stacking can be achieved, and the like. They have been very often employed.

The above-described neck-in can has been produced by applying before-hand to a can body necking using rolls or dies of a necking device, then applying flanging thereto; and thereafter subjecting a can cover to double seaming in a conventional manner. Therefore, the production line for the neck-in cans requires an extra necking device as compared with the normal can production line, thus posing problems that the cost of equipment increases, the process of manufacture is extended, and the like.

In order to solve these problems, proposals have been made to obtain neck-in cans by applying necking to a can cover simultaneously with seaming of the cover by rolls in a double seaming process, without pre-necking a can body by a necking device. (See for example, U.S.

Patent No. 4,270,475 Specification, Japanese Patent Application Laid-Open No. 35027/1963, etc.) The method proposed as described above for carrying out the necking simultaneously with seaming is advantageous in that the particular necking device is not needed. However, when the neck-in can is produced by this method, creases likely occur in the neck portion, and as the result, coatings on the inner and outer surfaces of the neck portion are damaged, resulting in occurrence of peeling of the coatings, and of poor sealing, as well as poor seaming.

This method has not been therefore satisfactory.

It is an object of the present invention to provide a method of producing a neck-in can, which can provide good seaming without occurrence of creases in the neck portion and without adversely affecting the coatings even if the necking is carried out simultaneously with seaming The present inventor has made various experiments on the causes of the occurrence of creases in the can neck portion and of the occurrence of inferior seaming involved in the methods of producing a neck-in can heretofore proposed, and as the result the inventor has found that these problems were caused by (i) the rate of reduction in diameter and amount of reduction in diameter of the neck portion of the can body, (ii) the difference between the curl opening diameter of the cover and tte outside diameter of the flange of the can body, (iii) the configuration of the flange, (iv) the configuration of the seaming roll, and the like. Then the inventor has learned that good neckin cans may be obtained by improvement of the aforementioned points and even by carrying out the necking simultaneously with rolling.

More specifically, with respect to the abovedescribed point (i), it has been confirmed that in the thickness in the range of 0.14 to 0.24 mm which is the wall thickness of a can body of a normal metal can though there is a slight variation according to the wall thickness of the can body and the diameter of the can body, in the case where seaming is made in tha condition that the rate of reduction in diameter of the outside diameter B of the neck portion with respect to the outside diameter A of the can body shown in FIG. 1 isa thin 5%, no creases occurred and good seaming was accompli;hed. When the rate of reduction in diameter exceeds 5%, creases and peeling of coatings occurred.When the rate of reduction in diameter exceeds 3.5 mm, in the width of the flange F Q L from 1.5 to 2.2 mm with which good moldability is obtained during necking molding at the time of rolling, the can- cover is difficult to fit in the flange portion of the can body, and molding is actually impossible to make.

With respect to the above-described point (ii), FIG. 2 shows the relationship between the curl opening diameter COD of the can cover and the outside diameter FQD of the flange of the can body under the condition that the can cover 1 prior to seaming has been fitted in the flange 3 of the can body 2, and if the difference therebetween is less than 0,2 mm, the accuracy of centering between the cover 1 and the can body 2 by a seamer becomes severe, and variation in dimensions of the cover 1 and can body 2 is directly concerned, because of which the cover 1 cannot be fitted in the flange 3 of the can body 2, thus producing inferior seaming.On the other hand, when the aforesaid difference is excessively great, that is when the COD is excessively great, since a dimension of an end flange portion l' required for seaming is substantially constant, the difference between a chuck wall portion 1" of the cover 1 and the inside diameter of the can body becomes small, and the seamed portion after seaming and necking is bulged from the can body. Accordingly, to obtain good necking at the time of seaming , (COD - FQD) need be 0.2 mm or more, preferably 0.5 mm or more, the upper limit being preferably 3.2 mm or less.

With respect to the above-described point (iii), which is concerned with the configuration of the flange, if the flange width FQL (see FIG. 3) of the can body is short, it is hard to be laid along the flanging die when the flange is molded, and therefore the dimension and shape are apt to be varied and variation of a body hook after seaming increases. On the other hand, if the flange width is too long, the cover will not be fitted in the flange.

Also, the seamed shape is affected even by the radius of curvature R of a flange curved portion. That is, if the R is small, the shape of the flange is easily determined even if the F QL is short, and the variation is small.

Furthermore, since the flange height beomes small, seaming becomes stabilized. From this standpoint, it has been confirmed that good seaming can be done when FQL is above 1.2 mm but less than 2.6 mm, preferably in the range from 1.5 mm to 2.2 mm as described above, and R is in the range of R=1.6 mm or less.

With respect to the above-described point (iv), which is concerned with the shape of a seaming roll, the necking molding is carried out by a lower jaw of a first seaming roll to the approximately desired rate of reduction in diameter, and subsequently finishing is carried out by a second seaming roll. Accordingly, if positions of the lower jaws of the first and second seaming rolls are different, two molded traces result. This phenomenon was possible to be overcome by increasing the R of a contact portion of the lower jaw more than 0.8 mm, making the same positions of contact portions 7 and 8 of the first seaming roll 5 and the second seaming roll 6, and changing the shape of the contact portion of the second seaming roll.

(see FIG. 4) It is desired that the detailed points (i) to (iv) all exist concurrently. But, the aforementioned object can be achieved even if all of these points do not always exist.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a sectional view of an essential part of a neck-in can produced by a method according to the present invention; FIG. 2 is a sectional view of an essential part of a can prior to seaming according to the present invention; FIG. 3 is a sectional view of an essential part of a flange portion of a can body; FIGS. 4 (a) and (b) are respectively schematic sections of a seaming roll according to the present invention; and FIGS. 5 (a) through (c) are respectivley sectional views of essential parts showing the steps of necking according to the present invention.

A method of producing a neck-in can according to the present invention will be described with reference to FIG. 5.

A first seaming is carried out at a groove 9 of a first rolling roll 5 and at the same time a lower jaw 10 thereof gradually presses a head of a can body to effect necking. The necking is given till a flange portion of the can body approximately comes into contact with the outside diameter of a chuck wall portion of a can cover before the first seaming has been terminated (see FIGS.

(a) and (b)). Subsequently, a second seaming is carried out by a second seaming roll 6, and a lower jaw 11 of the second seaming roll 6 further presses a portion being subjected to necking for accomplishment of necking within the rate of reduction in diameter 5% of a neck-in portion and with the amount of reduction in diameter less than 3.5 mm. In the present invention, the necking is carried out within the rate of reduction in diameter 5% and with the amount of reduction in diameter less than 3.5 mm thereby capable of easily attaining the reduction in diameter and obtaining a sufficient width of flange. In addition, even necking can be performed without occurrence of creases in the neck portion and close seaming can be also performed.

Furthermore, since the difference between the diameter of the curl opening of the cover and the outside diameter of the can body flange is set to 0.2 mm or more, good seaming may be done without occurrence of poor seaming even if there is slight unevenness of the dimension and shape when a flange is molded.

In the specific embodiment, a tin-made cover molded to have the outside diameter of a chuck wall smaller in diameter than the inside diameter of a tin-made body and to have a difference of 1.0 mm between the curl opening diameter COD and the can-body flange diameter FD was applied to said tin-made body, which is flanged to have 1.5 mm of the flange width FQL and 1.5 mm of the radius R of a curved portion, by necking using a first seaming roll with a lower jaw to about 4% with respect to the outside diameter of the can body, as well as the first seaming.Subsequently, molding and finishing -by nec)l-ng was carried PUt by a second seaming roll -withfflthe -curved diameter of a contact portion 8 of a lower jaw enlarged and with the position of the contact portion set to the same as the first seaming roll, and finally necking of about 4% as well as the second seaming was carried out. At that time the height of the seaming chuck is that the can height prior to seaming is set to the can height posterior to temporary seaming, which was used as a reference.

If the height of the seaming chuck is set using the can height after seaming as a reference as in prior art, the can body obtained by seaming simultaneously with necking is that since the height of the flange is higher than that of prior art, the amount of cushion of a lifter spring increases, because of which an excessive load is applied to the seamed portion, resulting in occurrence of inferior winding, metal hair, , discontinuous seaming of the cover, etc. This problem can be overcome by an arrangement as shown in the present embodiment in which the can height prior to seaming is set to the can height posterior to temporary seaming, on the basis of which the height of the seaming chuck is set Examination of the thus obtained can shows that no peeling of coatings and poor sealing produced, and no creases in the neck portion occurred.Moreover, no metal hair at the cover panel portion and discontinuous seaming of the cover occured. A good seamed shape was obtained, and a good neck-in can was obtain As a comparative example, necking simultaneously with seaming was carried out with the amount of reduction in diameter 3.6 mm in which the rate of reduction in diameter with respect to the outside diameter of the can body is 5% or more under the above-described conditions. The results showed that creases were conspicuous in the molding by the first seaming roll, and peeling of coatings occurred at the termination of molding by the second seaming roll.

As described above, according to the present invention, even if necking is carried out simultaneously with seaming, good necking and complete seamng may be accomplished without occurrence of creases in the neck portion and without giving the damage to the coatings. It was possible to overcome the problem involved in a method for carrying out necking simultaneously with seaming heretofore proposed.

Claims

1. A method of producing a neck-in can for fitting in a can body a can cover having the outside diameter of a chuck wall smaller than the inside diamtere of said can body, and carrying out necking simultaneously with double seaming by a first seaming roll and a second seaming roll, characterized in that the can cover and the can body are formed so that a difference between a diameter of a curl opening of the can cover and an outside diameter of a flange of the can body is in the range from 0.2 mm to 3.2 mm, said can cover being placed on the end of said can body, and a neck-in portion is formed at lower jaws of the first and second seaming rolls, respectively, so that the rate of reduction in diameter is within 5% with respect to the outside diameter of said can body and the amount of reduction in diameter is less than 3.5 mm.

2. A method of producing a neck-in can according to claim 1, wherein the width of a lange of said can body is formed within the range from 1.2 mm to 2.6 mm.

3. A method of producing a neck-in can according to claim 1, wherein the radius of curvature of the lower jaws of said first seaming roll and said second seaming roll, respectively, is above 0.8 mm, and the lower jaw of said first seaming roll and the lower jaw of said second seaming roll come into contact with the same height-position of said can body.

4. A method of producing a neck-in can substantially as herein described with reference to the accompanying drawings.