GB2047144A - Can seams - Google Patents

Abstract

A can made of sheet metal in which the edge flange of the body of the can is connected with the flanged edge of the lid by forming a double flanged seam with the hooked sections of the lid and body overlapping in the seam, is characterised by the feature that the quotient from the nominal diameter and the length (L2) of the hooked section (6) of the lid is from 32 to 48 and for the overlap length U of the hooked lid and body section (6, 11) is from 52 to 90. <IMAGE>

Description

SPECIFICATION Can of sheet metal, more especially for beer and other beverages The present invention relates to a tin or can of sheet metal, more especially for beer and other beverages in which the edge flange of the body of the can is adapted to be connected with the flanged edge of the lid to a double flange seam having hooked lid and body sections overlapping in the seam.

Such cans have been known to a considerable extent for decades and have proved to be excellent in use.

It is also known to produce the bodies for such tins having an integral bottom in accordance with the metal drawing method. This applies especially to beer cans or cans for other beverages. Such cans however, are also used for other purposes.

The geometry of the individual sections of body and lid of the can are subject to a fixed standard. This applies especially to the sections which contribute to the forming of the double flange seam. Essential aspects are the production of a double flange seam hermetically sealing even at increased internal pressure and also the requirements of satisfactory deformation of the sections concerned during the forming of the double flange seam, whereby it is to be noted that during these convertion operations, the flanged edges on the body and lid are subjected to a considerable diameter reduction. Not all sheet metal materials and sheet metal thickness can be processed reliably without the risk of crinkling.

It is an object of the invention to alleviate these difficulties and to further develop a can of the kind referred to above so that types of sheet metal or sheet metal thicknesses which have hitherto been unsuitable can be processed into these cans and at the same time obtain a considerable saving of material in these mass produced articles without impairing the formation of the double flange seam on conventional machines or during the production of the double fold or flange seam without crinkling occurring at the hook-shaped flanges ofthe lid.

This object is attained in accordance with the invention in that the quotient from nominal diameter of the can or the lid and the longitudinal dimension of the given said fold or flange section for the length of the hooked lid portions is between from 32 to 48 and for the overlap length of hooked lid and body members the quotient is between from 52 and 90.

A substantial saving of material compared with known cans is obtained herewith. Thus, the comparison figures concerned for the length of the hook edges of the lid are between 20 and 31 and for the overlaps length between from 24 and 52 at hitherto standard dimensions.

Crinkling during the production of the double flange seam occurs when, for example, a cut edge is compelled to assume a smaller peripheral diameter. This constantly occurs during the flanging of circular cans. The crinkles result from the excess peripheral difference. The greater the proportion of this peripheral difference is at the nominal diameter, the greater is also the crinkling formation with comparable sheet metal thicknesses.

On account of the novel development, the proportion of peripheral difference at the nominal diameter is substantially reduced. This substantially reduces the inclination to crinkling or fold formation. Hence sheet metal thicknesses or sheet metal types may be used which hitherto could not be used or could be used only with a considerably greater thickness. This applies especially to so-called DR-sheet metals (DR=double reduced). Since these sheet metals may now be used even with a lesser thickness, a considerable saving of material results therefrom.

The invention is particularly suitable for cans having a nominal diameter in the region of from 50 and 56 mm.

The invention will be described further, by way of example, with reference to the schematic drawing, in which: Figure 1 is a plan view of a lid for a tin or can in accordance with the invention before being connected to the body of the can; Figure 2 is an enlarged fragmentary vertical section through the edge region of the lid of Figure 1; and Figure 3 is an enlarged fragmentary vertical section through the edge region of a can in accordance with the invention.

The invention relates especially to tins or cans having a nominal diameter of from 50 to 65 mm, i.e.

especially to cans for beer or beverages having a diameter of 52, 57, 60 and 63 mm. Thus, in the first plane two-part cans, i.e. tins having bodies produced by the drawing method.

A can of the kind in question is hence comprised of a body 10 and a lid 1. The lid has a lid surface 2 adjoined by a core or chuck wall 5 which merges into the flanged edge 4 having hook-shaped lid portion 6 extending at the outer edge thereof. The hook-shaped portion 6 is obtained by bending or tilting the edge region of the prior drawn lid edge. The length of the hooked portion of the lid before connecting the lid to the body of the can is also designated as tilting height A. The inside width or diameter of the substantially cylindrical wall 5 is denoted by the numeral 3 in Figure 1.

The body 10 is provided with a flanged edge projecting radially outwards. In the production of the double fold or flanged seam the fold edge of the body 10 and of the fold edge 4, 6 of the lid 1, such are deformed into the double flanged seam 15 as shown in Figure 3. The fold edge of the body 10 provides a body hook 11 which is caused to overlap with the hook 6 of the lid within the double fold or flange seam. The overlap length is denoted by U, the length of the lid hooks 6 by L2 and the length of the body hooks 11 by L1. The axial height of the double fold seam is designated by H. The axial length of the wall 5 may vary depending upon as to whether a tin is concerned for so-called still beverages or for such beverages filled at excess pressure.The greater depth K1 of the chuck wall in Figure 3 corresponds to that for tins subject to increased internal pressure whilst the depth K2 of the chuck wall in Figure 3 corresponds to that of reduced value in beverages filled at normal pressure. The lid surface 2 or 2a hence assumes correspondingly different positions.

The dimensions of the section essential in forming the double fold or flanged seam depend upon the given nominal diameter of the tin. In the table below the dimensions for the most important parts for hitherto tins and for novel cans are stated and thus for the nominal diameters 52 and 63 mm. The mean values of the actual length and each quotient from the nominal diameter and the length of the individual flange element (FE) concerned are stated individually.

Table for nominal diameters 63 or 52: Actual state New Upper limit Lower limit Fold height 3.2mm Fold height 2.6mm Fold height 2.2mm Fold element 63 52 63 52 63 52 (FE) FE FE FE FE FE FE FE FE FE (mm) (mm) (mm) Lid hook length L2 2.25 28 23 1.70 73 30 1.45 43 35 Overlap U 1.65 38 31 1.15 54 45 1.00 63 52 The essential differences between the prior art and the new can are clearly indicated. Taking into account that the cans expressly concern mass produced articles, the table shows substantial material savings which may be obtained with the new can.

Afurther substantial material saving is also obtained in that now due to the reduced risk of crinkling during the production of the double fold seam, sheet metals which hitherto could be processed without crinkling only in greater sheet thicknesses, can now also be applied in thin sheet thicknesses, e.g. the so-called double reduced (DR) sheet metals. Fold formation or crinkling occurs above all because of the peripheral difference between the periphery of the nominal diameter and the periphery of the larger diameter on which the lid hook is located before the forming of the double fold or flange seam. In the example shown, the value for the peripheral difference lies at more than 40 mm. Since the edge of the lid remains substantially constant regardless of the changes in the nominal diameter, the proportion of this peripheral difference increases when the nominal diameter is reduced. With reference to a nominal diameter of 99 mm, the peripheral difference amounts to 13%. In a can having a nominal diameter of 53 mm, the proportion of peripheral difference amounts to 24%. Thus, in a can of smalier diameter twice as many folds or crinkles have to occur during the making of the double flange seam as in a lid having a larger diameter. A substantial reduction of the lid edge thus has a substantial influence on the crinkling formation, and thus the case with every nominal diameter.

Claims (6)

1. A can made of sheet metal in which the edge flange of the body of the can is adapted to be connected with the flanged edge of the lid and formed into a double flanged seam with the hooked sections of the lid and body overlapping in the seam, characterised by the feature that the quotient from the nominal diameter and longitudinal extension of the said flange section for the length (L2) of the hooked section of the lid is from 32 and 48 and for the overlap length U of the hooked lid and body section from 52 to 90.

2. A can as claimed in claim 1, in which the quotients for the hooked section of the lid is situated from 35 and 43 and for the overlap length from 54 and 75.

3. A can as claimed in claim 1 or 2 in which the flange height (H) is from 2 and 3.

4. A can as claimed in claim 3, in which the flange height is from 2.2 and 2.6 mm.

5. A can as claimed in any of claims 1 to 3 in which the lid is made of double reduced (DR) sheet metal.

6. A can made of sheet metal substantially as herein described with reference to and as illustrated in the accompanying drawings.