Method of fitting a top or a bottom to the body of a can and machine for executing this method

In a method of fitting a top or a bottom to the body of a can, the top or bottom is placed inside a die having a rolling surface. The top or bottom has an inwardly rolled edge defining a support surface adapted to be substantially mated with at least part of the rolling surface. An end portion of the can body is inserted between this rolling surface and this support surface. Thrust is then applied to the can body until it causes the end portion to roll around and envelop the support surface. The corresponding machine comprises at least one rolling die incorporating a bush defining a first rolling surface facing radially inwards and a plurality of jaws disposed along a perimeter corresponding to the shape of the can. The jaws are movable towards an inside wall of this bush and are shaped to define at least part of a second rolling surface which faces radially outwards. This second rolling surface is adapted to form an extension of the first rolling surface when the jaws are positioned close to the inside wall of the bush.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
The invention concerns a method for fitting a top or a bottom to the body 
of a can, by internal rolling; it also concerns a machine for executing 
this method. 
2. Description of the Prior Art 
Many cans, at least partly in metal, are made by peripheral crimping 
forming a bead projecting circumferentially at the ends of the can. This 
bead is an area especially sensitive to corrosion (formation of rust when 
the can is left in a moist place, such as a bathroom, for example). Also, 
the esthetic result is poor, which may constitute a disadvantage for some 
articles such as perfumery products sold in aerosol type containers. In 
this specific area where the decoration of the packaging is important to 
promoting the product the presence of the bead interrupts the decoration 
and emphasizes in an unesthetic way the end of the package. Also, because 
the crimping process is applied after the body of the can is decorated by 
painting and varnishing it, known crimping tools damage the coating, which 
is one reason for the vulnerability of this area to corrosion. Finally, 
the presence of the external bead prevents stacking of such metal 
packages, which raises problems for storing and handling them. 
Attempts have been made to produce an internal, non-projecting crimp, as 
evidenced by U.S. Pat. No. 3,452,897, for example. At the time of writing, 
however, there would not seem to have been any industrial exploitation of 
this type of crimp. Furthermore, using it entails soldering before the 
operations which lead to the formation of the internal crimp, which 
substantially increases manufacturing costs. 
The invention makes it possible to remedy these disadvantages by proposing 
a new method of fitting a top or a bottom to the body of a can producing 
an internal crimp with no bead projecting from the periphery of the 
corresponding end of the can. The basic idea of the invention is to use a 
rolled edge preformed on said top or bottom as a support or reaction 
surface during internal rolling of the end portion of the can body. 
SUMMARY OF THE INVENTION 
In one aspect, the invention consists in a method of fitting a top or a 
bottom to the body of a can, wherein there is placed inside a die having a 
rolling surface a top or a bottom having an inwardly rolled edge that 
defines a support surface adapted to be substantially mated with at least 
part of said rolling surface, an end portion of said can body is inserted 
between said rolling surface and said support surface and a thrust is 
applied to said can body until it causes said end portion to become 
rolled, enveloping said support surface. 
In another aspect, the invention consists in a machine for fitting a top or 
a bottom to the body of a can, comprising at least one rolling die 
incorporating a bush defining a first rolling surface facing radially 
inwards and a plurality of jaws disposed along a perimeter corresponding 
to the shape of the can and adapted to be movable towards an inside wall 
of said bush, said jaws being shaped to define at least part of a second 
rolling surface facing radially outwards and adapted to form an extension 
of said first rolling surface when said jaws are positioned close to said 
inside wall of said bush. 
The invention will be better understood and other advantages of it will 
emerge more clearly from the following description given by way of example 
only and with reference to the appended schematic drawings.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Referring to the drawings, there is shown a machine 11 for fitting tops or 
bottoms 12 to respective tubular can bodies 13. This machine primarily 
comprises a drum 14 rotating about its main axis 15 in order to sequence 
the various operations and in this instance carrying four assemblies 16 
each comprising a rolling die 18 and piston 19. These four assemblies are 
regularly disposed at the periphery of the drum and offset angularly 
relative to each other by 90.degree.. Each rolling die 18 comprises a 
generally bell-shaped bush 20 containing jaws 21 movable radially by a 
plunger 22 having a bearing surface the cross-section of which varies 
axially and which is movable along an axis parallel to the arrow A (FIG. 
8). In the example shown, which concerns the fitting of circular bottoms 
to cylindrical can bodies, the bush 20 has a circular bottom opening and 
the jaws 21 are arranged regularly and circumferentially inside said bush, 
the bearing surface of variable cross-section being in this instance a 
frustoconical bearing surface 26. It is to be understood, however, that 
these shapes are conditioned merely by that of the crimping contour. 
Depending on the shape of the can, the shape of the bush, the arrangement 
of the jaws and the shape of the plunger could be substantially different 
without departing from the scope of the invention, the necessary 
structural modifications lying within the competence of those skilled in 
the art. 
According to an important characteristic of the invention, the rolling 
surface is divided within the die 18 between the inside surface of the 
bush 20, in the vicinity of its bottom opening, and surface portions of 
the jaws 21. To be more precise, the bush 20 defines a first rolling 
surface 20a extending radially inwards from the edge of its opening and 
having an appropriate curved radial profile, whereas each jaw 21 has a 
curved profile surface 21a extended in its lower part by a small 
projecting bead 25. The set of surfaces 21a thus forms a second rolling 
surface, discontinuous in the circumferential direction, generally 
oriented outwardly and forming an extension of said first rolling surface 
20a when said jaws are placed near the inside wall of said bush, due to 
the action of the plunger 22. This situation is clearly visible in FIG. 8. 
It can be seen that the jaws are pushed radially outwards when the plunger 
is moved axially in the direction of the arrow A, that is to say when its 
frustoconical bearing surface 26 pushes the set of jaws radially outwards, 
bearing against their rear surfaces. An elastic ring 27 of elastomer 
material is placed in a housing defined by groove sections formed on the 
outside of the jaws so as to urge the latter in the direction of radial 
withdrawal when the plunger is moved in the direction opposite that 
indicated by the arrow A. Also, the lower part of the plunger carries 
holding means 29, here in the form of a sucker, adapted to hold a top or 
bottom 12. The security of holding by the sucker is improved by suction 
means (not shown) sequentially connected to a conduit 30 passing axially 
through the plunger 18 and discharging at the center of said sucker 29. 
Each rolling die 18 is disposed above a piston 19, the axis of symmetry of 
which is aligned with the axis of the plunger. This piston is shaped to 
receive a can body 13 vertically, that is to say with an axial end of said 
can body resting on the upper surface of the piston. To this end the 
latter is provided with a slight relief 31 of disc shape the diameter of 
which corresponds to the inside diameter of the can body. The piston is 
movable along the actuation axis of the plunger, that is to say vertically 
in this instance. To be more precise, the drum 14 primarily comprises two 
horizontal plates 33 and 34 spaced from each other and separated by a 
cylindrical part 36 of smaller diameter. The lower plate 34 accommodates 
the pistons 19 in corresponding bores and the lower surfaces of these 
pistons project from the lower surface of the plate so as to be able to 
engage a fixed lifting ramp 40 or some analogous actuator means. The upper 
plate 33 carries the dies 18 aligned with the pistons 19. The cylindrical 
part 36 is provided with semi-cylindrical hollows 37 in the side, the 
shape and size of which are adapted to receive and drive can bodies 13. 
These are inserted between the plates 33 and 34 by conveyor means 39 
provided with a slideway 39a and a coarse threaded screw 39b driving said 
can bodies. The tops or bottoms 12 are also inserted between the plates 33 
and 34, by appropriate further conveyor means 42, in this instance in the 
form of a conveyor belt. The end parts of the conveyor means 39 and 42 are 
arranged substantially tangentially to the drum 14, between the plates 33 
and 34. An auxiliary take-off cylinder 45 provided with semi-cylindrical 
hollows 46 in its side is rotatably mounted in the vicinity of the 
periphery of the cylindrical part 36. It is rotated synchronously with the 
drum 14 and cooperates with a guide 48 to deposit the can bodies fitted 
with their top or bottom onto conveyor means 49 which carry them to a 
crimping station shown in FIG. 7. This is conventional and essentially 
comprises two knurled wheels 52, 54 between which the inside roll 
fastening together the can body 13 and the top or bottom 12 is crushed 
radially to seal the assembly. 
The implementation of the method in accordance with the invention will now 
be described more particularly as illustrated in FIGS. 2 through 6. 
It should be noted that the tops or bottoms 12 which are conveyed towards 
the dies 18 are preformed so that each has an inwardly rolled edge 12a. 
This rolled edge may be obtained in the conventional way by stamping, 
using an appropriately shaped tool, which it has not been considered 
necessary to show, as this operation is in itself banal. The tops or 
bottoms 12 preformed in this way are deposited on the conveyor means 42 so 
that said rolled edges 12a are oriented towards the plate 33 when the tops 
or bottoms reach the end of said conveyor means. The movement of the 
latter is synchronized to the rotation of the drum 14 so that a top or 
bottom 12 arrives below a die 18 in the situation shown in FIG. 2. The 
plunger 22 is then lowered until the holding means 29 comes into contact 
with the center part of the top or bottom 12. This is the situation 
illustrated in FIG. 3. At this stage of the process the jaws 21 are 
retracted relative to the inside surface of the bush 20, since the 
frustoconical bearing surface 26 is not in contact with said jaws. When 
the top or bottom 12 adheres to the sucker the plunger 22 is actuated in 
the direction of the arrow A, the two-fold consequence of which is to 
place the rolled edge 12a opposite said first rolling surface 20a and then 
to bring about radial displacement of the jaws 21 so as to trap the rolled 
edge 12a completely in the annular space defined between the rolling 
surfaces 20a and 21a. It should be noted that from this time the top or 
bottom 12 is trapped by its rolled edge in the die 18 but that it is not 
in practise subjected to any clamping force between the inside surface of 
the bush 20 and the jaws 21. The drum 14 then continues to rotate as far 
as the end of the conveyor means 39 where a can body 13 is positioned on 
the corresponding piston 19. This is the situation shown in FIG. 4. 
Rotation of the drum continues until the piston 19 is actuated upwards as 
it passes over the ramp 40. This is the situation shown in FIGS. 5 and 8 
and its consequence is to insert the upper end portion of the can body 
between the rolling surfaces 20a, 21a and a supporting surface defined by 
the rolled edge 12a of the top or bottom itself. The consequence of this 
movement is to thrust the can body 13 axially until its end portion 
inserted into the die rolls around and envelops the supporting surface 
defined by the rolled edge 12a. From this moment on the top or bottom 12 
and the can body 13 are fastened to each other. The sucker 29 is released 
and the piston 19, passing beyond the ramp 14, redescends into its 
housing. This is the situation of FIG. 6. As rotation continues, the 
assembly reaches the conveyor means 49 which feeds the clamping station 
shown in FIG. 7. The rolled portions of the can body and the top or bottom 
are then clamped radially until said rolled portions are crushed between 
the two knurled wheels 52 and 54. This latter operation produces a 
perfectly sealed crimp, without previous soldering. 
The invention is applicable to fitting a deformable but not necessarily 
metal top or bottom to a metal can body.