MANUFACTURE OF CAN BODIES

(21) Application Nos. 14152/71 (22) Filed 11 May 1971

(23) Complete Specification filed 25 April 1972 (44) Complete Specification published 12 June 1974

(51) International Classification B21D 21/00 51/32

(52) Index at acceptance

Β3Ε 10Α15 10Κ 1Η2

Β3Α 83A1 83Α9 83Β5 83Β6 B3J 1F2 1F3 1F5 1F6

(72) Inventor JOSEF TADEUSZ FRANEK

(54) IMPROVEMENTS RELATING TO THE MANUFACTURE OF CAN BODIES

(71) We, The Metal Box Company Limited, of 37 Baker Street, London, W1A IAN, a British Company, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement:-

This invention relates to methods of making a metal can body having an end neck and an end flange merging therewith on a cylindrical end portion; to methods of forming such a neck and such a flange; to apparatus for use in the manufacture of such a can body; to can bodies made by such methods or on such apparatus; and to cans including such can bodies.

The process of forming of the said end neck and flange are generally known as “necking” and “flanging” respectively, the former enabling a can end member of smaller diameter to be applied to the end of the can body, i.e. seamed conventionally or otherwise to an outwardly directed end flange on the can body, than would be required if the neck were absent.

The present trend is towards the use of thinner and harder materials for can bodies, especially for beer and other beverage cans and for aerosols. One example of such a material is the recently introduced socalled “double-reduced plate”, in substitution for previously used less brittle and more ductile plate. Because of the small extension possible in the working of these newer materials, it is difficult to flange the bodies Without risk of splitting, by any of the methods at present used.

It is an object of the present invention to provide a method and apparatus which will enable end flanges and neck portions to be produced reliably and economically even on can bodies made of the aforesaid less ductile materials.

According to the invention in one aspect, in a method of making a metal can body, an end neck and an end flange merging therewith are formed simultaneously on a partly-formed can body by relative rolling motion between said can body, rigidly supported and positively gripped internally, and, an external necking tool.

According to the invention in a second aspect, a method of forming an end neck and an end flange merging therewith on a cylindrical end portion of a partly-formed metal can body includes the steps of rigidly supporting and positively gripping at least said end portion of said can body by a rigid mandrel internally over substantially the entire bore of said can body, at least within a portion of said can body other than said end portion thereof, and, while said can body is so supported and gripped, applying relative rolling motion between said end portion and an external necking tool while gradually decreasing the radial distance between the necking tool and the mandrel axis, so that the tool engages the cylindrical end portion of said can body and deforms it against an external surface on the mandrel having a neck portion profiled to correspond substantially with that required for at least the neck and further profiled to provide a guide for deformation of part of said end portion to form a said flange, so forming said neck and flange simultaneously, whereby said flange is formed by plastic deformation induced substantially by the compressive strain of the neck formation.

Such a method may include the further step of subsequently reforming the neck while seaming a can end onto the end flange. Preferably, the said rolling motion is provided between the partly-formed can body and a plurality of said necking tools, spaced apart circumferentially of the mandrel and subjected to relative radial translation between the mandrel and each said tool at the same speed, the initial radial distance between each said necking tool and the mandrel being so set that equal impressions are formed in the can body successively at each point between said tools and the can body.

According to the invention in a third aspect, a method of making a metal can includes positioning a can body having adjacent at least one open end an end portion formed with a neck and flange by a method according to said second aspect of the invention, adjacent seaming tool means for securing to said flange a can end member, placing a said end member on the open end of the can body, and applying relative rotation and generally-radial translation between the can body carrying the end member and the seaming tool means to form a circumferential end seam from a seaming flange of the end member and the end flange of the can body, and simultaneously therewith to reform the end neck of the can body by engagement thereof with a profile of the seaming tool means, whereby to complete the formation of the can body substantially simultaneously with completion of the end seam and of the can.

At this point it is convenient to explain the terminology adopted herein for the can body at various stages in its manufacture. A can body having a neck and flange formed on it is referred to as a can body, even if it is to be subsequently modified by reforming the neck. Thus in all the embodiments envisaged for the invention,, the term “can body” means a can body ready for attachment of a can end member to the end flange adjacent the neck. A can body prior to this stage is referred to as a partly-formed can body”.

According to the invention in a fourth aspect, there is provided apparatus for use in the manufacture of a metal can body having an end portion comprising an end neck and an end flange merging therewith, including a mandrel constructed to support rigidly a partly-formed can body internally over substantially the entire circumferencc of the mandrel, at least within a portion of said can body other than said end portion thereof, the mandrel having an external' surface including a neck portion so profiled as, when a partly formed can body is so supported thereon, to correspond substantially with the required profile of at least a said neck of the can body end portion, and a necking tool spaced from and external of the mandrel, the mandrel and necking tool being arranged for relative rotation and for relative translation simultaneously with said relative rotation so as to change the distance between them radially of the mandrel, whereby a said neck and flange can be simultaneously produced by rolling action on a said end portion of a partly-formed can body rigidly supported and positively gripped internally by the mandrel, said external surface of the mandrel being further profiled to provide a guide 70 for deformation of part of said end portion to form a said flange.

Preferably, said mandrel has a plurality of jaws movable radially between a rigid extended condition for gripping a can body 75 or a partly-formed can body internally, in which condition outer surfaces of the jaws cooperate to form a substantially continuous circumferential surface of the mandrel, and a retracted condition in which the jaws 80 lie within a circumference smaller than the smallest continuous internal circumference of a said neck.

The mandrel preferably has a plurality of radially movable first jaws which define an 85 arcuate portion of a circle and between them defining a substantial proportion of the circumference of the circle, and between said first jaws an equal plurality of radially movable second jaws which, when the 90 mandrel is expanded, fill in the gaps created by such expansion at the perimeter of the mandrel between said first jaws to form a substantially continuous uniform circular perimeter. 95 Preferably, the outer surfaces of the jaws are profiled to correspond substantially, around the whole circumference, with at least part of the required profile of a said neck. 100 The invention according to further aspects thereof includes a can body made by methods, or on apparatus, according to the invention; and a can including such a can body or made by the method according to 105 said third aspect of the invention.

Various embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, in which:- 110 _ Figures la-c show in elevation, respectively, a body cylinder constituting a first form of partly-formed can body; such a body cylinder necked and flanged at both ends to form a can body; and a second 115 form of can body of the drawn and wall-ironed type having a neck and flange at its open end;

Figure 2 is a fragmentary sectional diagrammatic representation of a first form of 120 apparatus;

Figures 3 and 4 are respectively: a fragmentary sectional elevation of relevant parts of the said first form of apparatus, taken on line Π1-III in Figure 4; and a sec- 125 tional plan on line IV-IV in Figure 3 of an expandable mandrel for use therein, the mandrel being shown in a retracted condition thereof, and necking tools of the apparatus being shown withdrawn from the 130 can body on which the necking and flanging operation has been performed by the apparatus;

Figures 5 and 6 are respectively: a fragmentary sectional elevation on fine V-V in Figure 6 of the said first form of apparatus; and a sectional plan on line VI-VI in Figure 5 of an expandable mandrel for use therein: the mandrel being shown in an expanded condition thereof, and, in Figure 5, the necking tools being shown applied to the can body on which the necking and flanging operation has been performed by the apparatus;

Figure 7 is a fragmentary sectional diagrammatic representation similar to Figure 2, but of a second form of apparatus;

Figure 8 is a diagrammatic sectional elevation showing the top of a can body having an end neck and an end flange merging therewith, and a can end member laid on the top end of the can body ready to be seamed thereto;

Figure 9 is a diagrammatic sectional elevation on line IX-IX in Figure 10, showing a drawn and wall-ironed partly-formed can body in position relative to an expandable mandrel in a modification form, shown with jaws of the mandrel retracted;

Figure 10 is a diagrammatic inverted sectional plan on line X-X in Figure 9;

Figure 11 is a view similar to Figure 9 but showing the jaws in a rigid extended condition gripping the partly-formed can body;

Figure 12 is a diagrammatic inverted sectional plan on line XII-XII in Figure 11;

Figure 13 is a diagram illustrating the process of forming, the end neck of a can body such as is shown in Figures lb, lc or 8, using two necking tools;

Figure 14 is a fragmentary sectional view showing stages in the formation of an end neck and flange on a partly-formed drawn and wall ironed tinplate can body, using a mandrel such as is shown in Figures 9 to 12;

Figure 15 is a view similar to Figure 14 but showing the formation of an end neck and flange on another partly-formed can body, using a slightly modified mandrel;

and

Figures 16 and 17 are fragmentary sectional elevations illustrating respectively first and second operations in the process of seaming the can end member on the same can body.

Figure la shows a body cylinder, and Figure lb shows this cylinder after it has been necked and flanged in each of its two end portions 70, to form a can body. It will be noted that the provision of the necks 10 and end flanges 11 has caused a reduction in the height of the body as compared with the height of the body cylinder.

The diameter of the flanges 11 is equal in Figure la to that of the cylindrical portion of the body but, as will be seen hereinafter, this need not be the case.

The can body shown in Figure lc is of 70 aluminium or tinplate and is produced by a drawing and wall ironing process, to produce a tube without any longitudinal seam and with an integral base 12. In this type of partly-formed can body, which has only 75 one end capable of being necked and flanged, in the open end portion 70, the diameter of the neck 13 is substantially the same as that of the necks 10 in Figure 2, but the diameter of the flange 14 is is shown as being some- 80 what less than that of the main portion 71 of the body, although it could, if desired, also be made equal to or, as will be seen hereinafter, somewhat larger than that of the main portion 71. 85 In Figure 2, a cylindrical drawn and wall-ironed metal can body 20 is shown supported internally by an expandable mandrel 21 having a plurality of jaws 22 (to be described in more detail with reference to 90 Figures 4 and 6), over substantially its entire bore within the portion of the can body, indicated at 125, immediately below the end portion 70. The end portion has the neck 23 and flange 24, merging therewith, formed 95 in it by a method to be described. The mandrel 21 is mounted for rotation about a first axis 25, conventional driving means (not shown) being provided for the purpose.

A circular tool in the form of a necking 100 roll 26 is mounted to rotate externally of the mandrel 21 and of the partly-formed can body, freely about a second axis 27, disposed in a plane which includes the mandrel axis 25, and in this example parallel to the 105 first axis 25.

The mandrel 21 includes a body member or chuck 28, in axial alignment with the jaws 22 and having an external surface having a profile defined by a first diameter 110 29, which is such that it forms an easy fit with the partly-formed can body (shown dotted at 70¹), and by a second diameter 30 which defines the bore of the neck 23.

The jaws 22 of the mandrel 21 are shown 115 in an expanded condition, their contracted condition being indicated by dotted lines at 22¹¹.

The roll 26 is mounted for translatory movement in the direction of the arrows 31, 120 to give relative radial translation between the roll 26 and mandrel 21, and has a profile which is complementary to that of the neck 23 and flange 24, in association with the diameter 30, an external surface 125 profile 126 of the jaws 22 and the surface 32 of the mandrel body member 28, the latter being solid, in the sense of ηοηexpandable.

The external surface of the mandrel com- 130 prising the surface portions 29, 30 and 126 corresponds substantially with the profile required for the neck 23 and is further profiled, by virtue of the portions 29 and 30, to provide a guide for deformation of part of the end portion 70 to form the flange 24 as will now be described.

In operation, a partly-formed can body, which may for example be a cylinder or a wall ironed tube, is slipped over the diameter 29 of the chuck 28, and the jaws 22 of mandrel 21 are moved to their expanded condition so as internally to support rigidly the partly-formed can body. The mandrel 21 is typically one of a number of identical mandrels mounted on a rotatable turret, which is now rotated to its operating position shown, in which its axis 25 is in the plane containing, the axis 27 of the tool 26 and the direction of radial movement 31 thereof.

Simultaneous powered rotation of the partly-formed can body by the mandrel 21 and translation of the freely rotatable roll 26 towards the partly-formed can body, thus providing relative rotation between the roll 26 and the end portion 70 of the partly-formed can body and also gradually decreasing the radial distance between the tool 26 and mandrel axis 25, causes the end portion 70 to be progressively deformed into the necked and flanged shape shown. In will be seen that in this example the diameter of the flange 24 is less than that of the cylindrical portion of the can body 20. The jaws are then moved to their retracted condition to release the can body. The said relative motion may be obtained by keeping the mandrel stationary and moving the rolls around it.

The expandable jaws 22 play an important role because they positively grip the partly-formed can body whilst the roll 26 performs its operation. Without such positive grip the flange width and also the shape of the transition between the neck 23 and the cylindrical portion of the can body 20 could not readily be controlled.

In a practical construction of the apparatus, the mandrel 21 is gear driven, and therefore it is not necessary positively to drive the roll 26.

In Figures 3 and 4 the integers which have already been described with reference to Figure 2 are designated by the same reference numerals.

As is more clearly shown in Figure 4, the jaws 22 of the mandrel 21 consist of a plurality (four in this case) of radially movable first jaws 22¹ and the same number of smaller second jaws 49, also radially movable, between the first jaws 22¹. The outer edge 120 of each jaw 22¹ defines an arcuate portion of a circle, and between them the outer edges 120 define a substantial proportion of the circle when the jaws 22¹, 49 are in their expanded condition (Figure 6).

In addition, Figure 3 shows the mechanism for expanding the jaws 22¹, 49 of the mandrel 21. This comprises an operating sleeve 40, the free end of which is formed 70 with a plurality of surfaces 41, 41¹ generally inclined to the axis 25 and engageable with complementary inclined surfaces or chamfers 42, 42¹ respectively formed at the inner ends of the first and second jaws 22¹, 49 75 respectively. The sleeve 40 is arranged for vertical up and down movement, provided by an operating rod 43 via a pin 44. Downward movement of the sleeve 40 causes it to force the jaws 22¹, 49 radially outwards 80 against the action of compression springs such as 45 which bias the jaws radially inwards against a centre core 46 by abutment against pins such as 47, fixed to a base portion 48 of the mandrel body member 85 28, joined to the upper portion 72 of the mandrel body member 28 by pillars 73, Figure 4, extending between the jaws. The jaws 22¹, 49 are supported on the base portion 48. 90 The second jaws 49 are also biased radially inwardly, for example by compression springs 50, bearing against pins 51 fixed to the base portion 48. The jaws 49 are moved by the mechanism hereinbefore described 95 with reference to Figure 3 in relation to the main jaws 22¹, but the inclination of the surfaces 41¹ and 42¹ is different from that of the surfaces 41 and 42 so that the jaws 49 are moved radially outwards by a greater 100 distance than are the jaws 22¹ by the same axial movement of the operating rod 43.

Thus, as can be seen from Figure 6, the second jaws 49 fill in the gaps created, in the expanded condition of the jaws, at the 105 perimeter of the mandrel between the main jaws 22¹, to form a substantially continuous uniform circular perimeter so that at least the end portion 70 of the can body or partly-formed can body is supported over 110 the entire circumference of the mandrel, being gripped firmly by the portion 121, Figure 5, of the periphery of the jaws below the neck profile thereof.

Figures 5 and 6 show the jaws 22¹, 49 115 of the mandrel 21 in their expanded condition, and it will be seen that the aforesaid circle defined partly by the edges 120 of the jaws 22¹ is completed by the outer edges or filler zones 60 (Figure 6) pro- 120 vided at the free ends of the second jaws 49. All the integers of the mandrel 21 being the same as those shown in Figures 3 and 4 and their relative positions in the expanded state being self-explanatory in 125 Figure 5, no further reference will be made to them. In the retracted condition, as can be seen from a comparison between Figures 4 and 6, the jaws lie within a circumference smaller than that of the continuous circum- 130 ferential surface or perimeter formed by zones 60 and the outer edges 120 of the jaws 22¹ in the expanded condition shown in Figure 6.

As indicated fragmentarily also in Figure 3, two diametrically-spaced necking roll assemblies or heads 61 are provided, one of which is shown in section on a diameter and the other indicated fragmentarily in Figure 5. They are shown laterally displaced towards the mandrel 21 to their full extent, and hence the neck and flange 23 and 24 respectively of the can body 20 are shown fully formed.

The roll 26 is supported by a disc spring 62, which exerts a biasing force adjustable by means of a pressure adjusting screw 63. In Figure 7, which shows diagrammatically a second form of apparatus embodying the invention, integers corresponding to those shown in Figure 2 are denoted by the same reference numerals. This form of apparatus is suitable for the necking and flanging of partly-formed can bodies where the end flange is to be of larger diameter D_t than the diameter Ζ), of the main portion 71 of the can body.

As in the first form of apparatus, the main feature is the expandable mandrel which grips positively the partly-formed can body and prevents axial movement of the latter during the necking and flanging operation. However, in this second form of apparatus, the upper part 72 of the mandrel body member 28 itself is operated by a cam (not shown) for movement transverse to its axis towards the necking and flanging roll 26.

In a typical case, the maximum movement R of the part 72 as aforesaid is about 0.125",a distance approximately equal to the radial width of the flange 24. Thus the apparatus of Figure 7 would also be suitable for performing a pure flanging operation without necking, without modification. The retracted condition of the mandrel jaws 22 and the retracted position of the part 72 are shown dotted at 22¹¹ and 72¹¹ respectively, and, as in Figure 2, the end portion 70 of the partly-formed can body is likewise shown dotted at 70¹.

It is to be understood that, in the methods above described with reference to Figures 1 to 7, as the neck 23 is formed on the end portion 70 by the relative rolling motion provided between the tool 26 and the profile 30, 32 on the mandrel (said profile being such as to correspond substantially with that required for the neck 23 and flange 24), the flange 24 is produced simultaneously with the neck by such rolling action, the flange being formed by plastic deformation, induced substantially by the compressive strain of the neck formation, from the position shown in dotted lines at 70¹ adjacent the mandrel surface 29 to the final position shown in full lines at 24.

It will also be understood that, although in operation relative rotation and translation is required between the can body end por- 70 tion, i.e. the end portion 70 of the partly-formed can body, (and therefore the mandrel) and the necking tool, either the mandrel or the necking tool or both may be rotatable, and either the mandrel or the necking tool 75 or both may be movable towards the other.

In one alternative arrangement, for example, the necking tool may comprise a fixed bar, suitably profiled, the mandrel being rotatable as described and also movable towards and 80 away from the fixed bar.

Another embodiment of the invention will now be described with reference to Figures 8 to 17.

Figure 8 illustrates the top end portion 85 70 of a drawn and wall-ironed can body the neck and flange of which have been formed in apparatus such as that described with reference to Figure 1, or, preferably, that to be described with reference to 90 Figures 9 to 12. The end flange of the can body, during formation simultaneously with formation of the end neck, undergoes the effect known as flaring, whereby it increases in diameter due to plastic deformation from 95 a cylindrical form to a generally frustoconical or ring-like shape, and may have a final outer edge extending radially beyond the remainder of the can body. In the process now to be described, the neck and 100 flange arc first formed generally as described already, that is to say simultaneously with each other by relative rolling motion between the partly-formed can body, rigidly supported internally, and an external neck- 105 ing tool; but in addition, the neck is reformed by engagement with a profile of seaming tool means during the subsequent operation of seaming a can end member onto the open end of the can body. HO This process of seaming is well known, and comprises positioning a can body having, adjacent at least one open end, an end portion formed with a flange, in a closing machine adjacent to seaming tool means, 115 which may be one or more seaming rolls or a fixed tool; placing the can end member in closing engagement with the open end of the can body (this is done in ordinary production before the can body reaches the 120 seaming tool means); and applying relative rotation between the can body and the seaming tool means to deform the end flange and the adjacent portion of the end member so as to lock the end member sealingly to 125 the can by a double seam. This seam is of conventional form. This seaming process is conventionally carried out in two operations, as it is in the process now to be described.

The can end member is typically of the 130 known form shown at 80 in Figure 8, which also shows the general shape of the end neck 23 and end flange 24, merging therewith in the can body end portion 70, as formed by the neck and flanging process and prior to seaming. This end neck and flange are formed in apparatus generally of the kind described hereinbefore with reference to Figures 2 to 7, but preferably (though not necessarily) modified by substitution of the mandrel 81 indicated in Figures 9 to 12.

The mandrel 81 has a body 82 comprising an upper part 83 joined by pillars 84 to a base 85, first jaws 86 and the same number of second, smaller, jaws 87 being disposed alternately between the pillars 84 and supported on the base 85 between their retracted condition, Figures 9 and 10, and their expanded condition shown in Figures 11 and 12. The jaws 86, 87 are biased towards their retracted condition by springs 122, operating generally in the same manner as the springs 45, 50, Figure 4, but preferably abutting simply upon the body 82 as shown.

The outer cylindrical surface of each radially-movable first jaw 86 defines an arcuate portion of a circle, these surfaces between them defining a substantial proportion of the circumference of a circle. The outer cylindrical surface of each radially-movable second jaw 87 also defines an arcuate portion of a circle having the same radius as that mentioned above. When the jaws 86, 87 are in their expanded condition, the said surfaces of the jaws 87 fill in the gaps created by such expansion at the perimeter of the mandrel between the main jaws, to form a substantially continuous uniform perimeter. As described thus far in this paragraph, the jaws 86, 87 are therefore generally similar in function to the jaws 22¹, 49 of the mandrel shown in Figures 4 and 6. However, in the mandrel 81, a peripheral external surface 88 of the mandrel is formed totally on the jaws 86 and 87 as seen in Figures 9 and 14, and has a neck portion or groove 89 profiled to conform with substantially the whole of the required internal surface (90, Figure 14) of the end neck 23 of the can body. The mandrel body 82 is not profiled to conform with the can body neck or flange.

The mandrel outer surface 88 includes a portion 91, Figure 14, beyond the groove 89, the portion 91 being an easy fit within the end portion 70 of the partly-formed can body prior to the necking and flanging operation.

The mandrel body 82 has a pair of fixed coaxial guide rings 92, 93, Figure 11, having upper and lower guide surfaces respectively between which projections 94 of the paws 86, 87 can slide radially. The guide ring 93 has spacers 95 arranged between the jaws and abutting on the guide ring 92. The lower of these two guide rings 92, has a downwardly-facing annular surface 105, Figures 14 and 15 against which the free end 104 of the partly-formed can body 70 initially abuts. In the embodiment shown in Figure 14 the ring 92 has an inner annular control surface which is downwardly divergent (and in this example frusto-conical, though it may be of any suitable shape); 75 the purpose of this will become apparent hereinafter.

The jaw-actuating means for moving the jaws 86, 87 between their retracted and expanded conditions may be of any suitable 80 form, such as that described with reference to Figure 3, or else the jaw-actuating means shown in Figures 9 and 11 comprising an axially-movable expander rod 97 having a head 98 which is formed with inclined 85 operating facets, operating in the manner described with reference to Figure 3, and engaging inclined back faces 99 of the jaws 86, 87, the rod 97 being operated by a suitable cam mechanism (not shown) of known 90 kind, controlling the movement of the rod 97 at all times.

The mandrel 81 may be one of a plurality mounted on a turret or the like which is rotatable between a number of stations of 95 the machine whereof the apparatus described here forms a part, including or consisting of, in succession:

(1) a loading station at which a partly-formed can body is placed on the mandrel 100 with the jaws 86, 87 in their retracted condition;

(2) a necking and flanging “station” (which may be defined by an arc described by the rotating turret carrying the mandrel), 105 at which the neck 23 and flange 24 are formed on the end portion 70 of the partly-formed can body; and

(3) an ejecting station at which the can body is ejected from the mandrel. 110 The jaw-actuating means is then arranged to move the expander rod 97 so as to actuate the jaws to their expanded condition at the loading station or as the turret rotates from the loading station to the neck- 115 ing and flanging station; and to move the rod 97 back to its normal position, so as to retract the jaws, at the ejecting station or as the turret rotates from the necking and flanging station to the ejecting station. 120 Conventional means may be provided for placing the partly-formed can body on the mandrel, or for advancing the mandrel into position into a waiting partly-formed can body, at the loading station. Ejection of 125 the necked and flanged can body from the mandrel may be by gravity, or, if the mandrel axis is so oriented that this is not possible, by suitable means for knocking the can body off the mandrel, or removing the can body 130 by gripping it or by engagement of magnetic means or vacuum sucker means therewith. At this point it should be mentioned that the machine may be arranged so that the (or each) mandrel is arranged vertically as here described and shown in the drawings, or horizontally, or in any other convenient attitude, the other components of the machine, co-operating with the mandrel, being arranged accordingly. If the mandrel is vertical it may be disposed in an inverted attitude, so that the can body supported by the mandrel extends upwards from it instead of downwards as herein described and as shown in the drawings.

The neck 23 and flange 24 are formed simultaneously on the partly-formed can body 20 by relative rolling motion between the partly-formed can body, rigidly supported internally at the necking and flanging “station”, and at least one necking tool or roll 26 constructed, mounted and arranged to operate generally as described hereinbefore with reference to Figure 5, the dimensions of the necking roll assembly being chosen so that in the fully advanced position of the roll (at completion of the necking and flanging operation) the necking roll assembly does not foul the mandrel. In one arrangement, illustrated diagrammatically in Figure 13, there is a plurality of necking rolls, in this case two, 26¹, 26¹¹, spaced apart circumferentially of the mandrel and external thereto, the rolls 26¹ and 26" being of equal diameters. The mandrel 81 is shown in Figure 13 sectioned at the neck 23, the final circumference of which is indicated by the circle in the Figure representing mandrel 23 and indicated by numeral 23. Each roll is part of a necking roll assembly as mentioned above, the two necking roll assemblies being substantially identical and arranged for simultaneous movement of the respective necking rolls towards and away from the mandrel at a radial speed which is the same for each roll 26¹, 26ⁿ. This relative translation movement between the necking rolls and the mandrel is obtained by conventional means such as a cam mechanism.

As can be seen from Figure 13, the point of engagement of each roll 26¹, 26¹¹ with the partly-formed can body 20 has a locus 102, 103 respectively, so that the rolls make successive impressions (i.e. reductions in the radius of the neck 23) having a value d at the point of engagement of the roll with the can body. The initial distance h between each roll 26¹ or 26¹¹ and the mandrel (i.e. at the initial point of contact with the partly-formed can body) is so set that the value of the impression depth d is the same for each of the two rolls. Thus for every revolution of the mandrel the neck 23 is reduced in diameter by twice the depth d.

Preferably, the rolls 26¹, 26¹¹ are arranged diametrically opposite each other.

With reference now particularly to Figure 14, the mandrel 81 is shown therein with the jaws 86 and 87 in their expanded condition, 70 the outer surfaces of the jaws co-operating to form a substantially continuous circumferential external surface of the mandrel whereby the can body is supported rigidly internally over substantially the entire cir- 75 cumference of the mandrel within the portion 71 of the can body immediately below the end portion 70.

In Figure 14, for convenience, the partly-formed can body is shown with its cylin- 80 drical end portion 70 at 70^l in hatched lines, while the end portion 70 of the can body, after necking and flanging, is shown without hatching.

In operation, the partly-formed can body 85 20 is placed over the mandrel with its free end 104 abutting the surface 105, and the jaws 86, 87 are expanded to support the body 20 rigidly. As the rotating necking rolls 26 advance towards the rotating mandrel 90 81, they engage the end portion 70 and deform it against the groove 89, so forming the neck 23. This causes the portion of the end portion 70 encircling the surface 91 to be deformed from its cylindrical shape by 95 flaring outwards and downwards as shown, so that finally the flange 24 is formed.

It will be seen that the deformation of metal to form the flange 24, induced substantially by the compressive strain of the 100 formation of the neck 23, is guided by the upper part 98A of the neck portion or groove 89 of the mandrel and by the shoulder 106 joining the groove 89 to the surface 91. This shoulder tends to act as a fulcrum 105 for the outward flaring of the metal to form the flange.

There is shown in Figure 14 a typical locus 107 which would be described by the outer edge of the free end 104 of the can 110 body end portion 70 during formation of the flange 24, if the ring 92 were not present.

The free end 104 bears upon and slides down the control surface 96, which cooperates with the shoulder 106 in guiding 115 the flange material during flaring, the surface 96 forcing the free end 104 to follow a path different from its free locus 107 and thus increasing the compressive strain of neck and flange formation. 120 In Figure 14 various intermediate stages in the formation of the neck and flange are shown by dotted lines.

Figure 15 shows a mandrel which is modified only in that the lower guide ring 92 125 does not have a control surface such as the surface 96 of Figure 14. Thus the free-end 104 of the partly-formed can body is in this case free to follow its free locus 107, the operation being in all other respects the same 130 as described above with reference to Figure 14.

The use of a control surface such as 96 may be practised in all cases, though it is only necessary in some cases, for example with certain materials or certain dimensions of materials of the can body. It can be seen from the intermediate stages indicated in Figures 14 and 15 that the flange material tends to flare rapidly through a wide angle during a late stage of the necking operation, that is to say when the compressive strain of formation of the neck has reached a certain critical value. Thus for accurate control of flange dimensions the use of a control surface may be desirable especially during this phase of rapid movement of the flange material. The shape of the control surface, if provided, is preferably such as to exert control at least during this phase. It will be noted that only some of the flange material is subjected to a flaring or lever action. This is in contrast to other processes, such as necking and flanging a cylindrical end portion of a partly-formed can body in a die, or forming a flange on a can body cylinder prior to necking, in which processes the whole of the material to form the finished flange is subject to deformation which imposes a turning moment in the region of the root of the flange. The process above described with reference to Figures 14 and 15 uses a shorter “lever arm” and, as a result, the tensile strain at the root of the flange is substantially reduced as compared with the said other processes, and it is possible to provide a generous amount of material for the flange. This enables an end seam having particularly good characteristics, such as maximum overlap between the various element of the seam, to be produced in the seaming operations now to be described with reference to Figures 16 and 17.

After the necking and flanging operation described with reference to Figure 14 or Figure 15, the necking rolls 26 are withdrawn and the mandrel jaws 86, 87 are retracted to release the can body 20, which is then removed. If the other end of the can body is open, a can end member may be seamed thereto, or the said other end may be necked and flanged in the same manner as for the end already described. Eventually, the can body, closed at one end, is filled with a product.

In the case of a can body open at both ends, an end member is attached to one end before filling with a product, and to the other end afterwards. In the case of a can body open at one end only, the end member is attached thereto after filling with the product. The (or each) end member may be applied on a conventional closing machine. However, in the example now to be described, a necked and flanged open end portion of a can body has an end member applied thereto in a closing machine in which the seaming rolls for the first and second seaming, operations have the addition 70 of lower neck reforming profiles as shown at 108 in Figure 16 and 109 in Figure 17, respectively.

With reference now therefore to Figures 16 and 17, the profile of the neck 23 and 75 flange 24 as formed in the necking and flanging apparatus, and shown in unhatched lines in Figure 14 or 15, is shown by dotted lines in Figure 16, as is the initial form of the seaming flange 110 of the can end 80 member 80. The first-operation roll 108 is characterised by the addition of a relieved peripheral profile 111 beneath the seam forming profile 123 of the roll, such that, during the first seaming operation, this pro- 85 file 111 reforms part of the neck 23 of the can body in such a way as to displace metal below the neck diameter inwards while partly forming the end seam 112, so as to create the form of neck shown in full lines at 23¹ 90 in Figure 16 and dotted lines in Figure 17.

The second-operation roll has the addition of another relieved peripheral profile 113 roll. The profile 113 reforms the neck 23 beneath the seam forming profile 124 of the 95 still further to the form shown by full lines at 23¹¹ in Figure 17, in which the neck 23 can be seen to have finally a substantially straight portion 114 extending downwards from the seam. 100 The method of formation of the double end seam 112 by the seaming rolls 108 and 109 from the end flange 24 of the can body and the seaming flange 110, Figure 8, of the end member 80, is conventional; how- 105 ever, it will be seen from Figure 17 that the material of the body flange 24 in the end seam extends over substantially the greatest possible overlap with the adjacent material of the end member, thus giving the seam 110 improved sealing properties over conventional end seams in which it is believed to have not previously been found possible to obtain such a long overlap for a given overall axial length of seam using only two 115 seaming operations. As explained above, the invention enables sufficient material to be available for this to be achieved.

It will be appreciated that although in the foregoing there has been described only the 120 necking and flanging of one end of a can body, both ends of a partly-formed can body open at both ends can be necked and flanged simultaneously by providing like means at both ends, to produce a can body 125 generally as shown in Figure lb.

Moreover, it should be understood that, though of particular use in the production of can bodies made of tin-plate such as the aforesaid “double reduced plate” or like 130 comparatively brittle metal, the invention may also be suitable for the production of can bodies made of more ductile metals such as aluminium where the difficulties arising from brittleness are reduced or absent. It has the important advantage over the methods of the prior art of enabling the two operations of necking and flanging to be performed simultaneously and on a single machine.