EP0647487A1

EP0647487A1 - Machine for forming a curl

Info

Publication number: EP0647487A1
Application number: EP94307019A
Authority: EP
Inventors: Jean Bernard Desruelle; Pierre Gorgeon
Original assignee: CarnaudMetalbox SA
Current assignee: Crown European Holdings SA
Priority date: 1993-10-11
Filing date: 1994-09-26
Publication date: 1995-04-12
Also published as: FR2711080B1; FR2711080A1

Abstract

A machine comprising a tool-holder head (12) carrying a plurality of rollers (22) each having a curling groove (23), the rollers having their axes approximately coplanar and cutting the axis of rotation (13) of the tool-holder head at the same point. The arrangement of rollers makes it possible to form a curl of small diameter at the end of a cylindrical element such as a can body.

Description

The invention relates to a machine for forming a curl at the end of a metal cylindrical element, for example a can body. In particular the machine enables a curl of small size to be formed on such a cylindrical element, even if the latter is made from thin sheet steel which is typically difficult to work, such as for example "double reduced" steel.
In order to form a curl at the end of a metal can body, it is known to use a tool comprising an annular shaping groove presenting the appropriate curling radii. With this technique, the force necessary to form the groove is considerable and is all the greater the smaller the curl is. This force, which has to be able to be supported axially by the can body does not therefore allow a curl of any desired diameter to be realised on a can body of given thickness.
The invention concerns a new curling technique allowing the force necessary for realising the curl to be reduced very considerably. It thus allows a curl of much smaller diameter to be obtained.
According to the present invention, there is provided a machine for forming a curl at the end of a metal cylindrical element such as, for example, a can body, comprising a base onto which in use the element fits and a tool-holder head for covering the end of the element end, the base and the tool-holder head assuming a common axis and being spaced from one another, and means for bringing about a controlled axial drawing together of the base and the tool-holder head, characterised in that the machine further comprises rotating means for driving the tool-holder head or the base around the common axis and in that the tool-holder head is provided with a plurality of rollers arranged in a circle and concentrically to the common axis, each provided with a curling groove and mounted in free rotation along approximately coplanar axes, perpendicular to and cutting the common axis.
According to another advantageous characteristic of the invention, each roller is mounted so as to be moveable along the direction of its own axis of rotation within a predetermined clearance of the order of a tenth of a millimetre. This clearance allows a self-centering of the rollers when these enter into contact with the edge to be curled.
In a preferred embodiment, the rollers are distributed unevenly in a circle. This particular feature makes it possible to prevent the cylindrical element losing its cylindrical shape (which would result in a shape presenting faintly delineated longitudinal facettes) at the moment when the rollers enter into contact with the edge to be curled.
A preferred embodiment will now be described, by way of example only, with reference to the drawings, in which:

Figure 1 is a half side-section of the machine;
Figure 2 is a plan view of a ring for holding the rolls; and
Figure 3 is a section of the ring of figure 2.

Referring to figure 1, the curl forming machine comprises a base 11 and a tool-holder head 12 which have a common axis 13, here a vertical axis, and being arranged at a certain axial distance from one another. This distance is obviously a function of the height of the cylindrical element 14 which has to be inserted between the base and the tool-holder head. The base 11 comprises, for this purpose, a cylindrical portion 11a adapted to the inside diameter of the element 14 and a shoulder 15 on which it can rest.
The machine is provided with means for bringing about the controlled axial displacement between the base 11 and the tool-holder head 12. These means are represented here by a controlled jack 16, on which the base 11 is mounted. The machine is also provided with rotating means 18 for driving the tool-holder head 12, represented by an electric motor 19 and a toothed gearing 20. Of course, the rotary driving means could be connected to the base 11 and/or the jack could be coupled to the tool-holder head 12.
According to one essential aspect the invention, the tool-holder head 12 is provided with several rollers 22 arranged in a circle (figure 2) and concentrically to the axis 13. Each roller 22 is provided with a curling groove 23 with a suitable profile. The rollers 22 are mounted in free rotation along approximately coplanar axes, extending radially, that is to say perpendicularly to the axis 13 and cutting this at the same point. All the grooves 23 are therefore approximately tangent to a circle, the centre of which is situated on the axis 13 and the radius of which corresponds to that of the cylindrical element 14 on which one wishes to form the curl.
The rollers 22 are arranged in an annular hollow 25 opening onto a lower face of the tool-carrier head 12 and including an annular needle bearing 26. The rollers are mounted in this hollow in such a way as to be supported against the needle bearing, at least during the stage of forming the curl. More precisely, the rollers 22 are inserted freely into radial notches 28 of a retaining ring 29 mounted in the annular hollow 25 and fixed to the tool-holder head. This ring is reduced in thickness in its outer part (figure 3) in order to define the shoulder 24 allowing the insertion and the holding of the needle bearing 26.
Another ring 30, of greater diameter than that of the ring 29, is fixed to the tool-holder head in the hollow 25 and allows the rollers to be immobilised radially. It has to be noted that the radial distance separating the two rings 29, 30 is determined in order that each roller is mounted with a predetermined clearance along the direction of its own axis of rotation. This clearance is of the order of a tenth of a millimetre for an element 14 having a diameter of the order of about ten centimetres. One thus obtains a self-centering of the rollers relative to the edge of the element 14 at the moment of the formation of the curl.
The tool-holder head 12 comprises an annular guide 32 centred on the common axis 13 and placed in the vicinity of the arrangement of rollers. This guide comprises a flat annular face 33 situated opposite and at a slight distance from the rollers 22, which allows them to be held in the notches 28. The guide 32 in addition comprises a tapered part 34 and a cylindrical part 35 of slightly larger diameter than the outside diameter of the tubular element 14. This cylindrical part 35 is therefore situated in the vicinity of the assembly of grooves 23 and the rollers 22. The annular guide is mounted on the tool-holder head 12, at the lower part of this, via a bearing 38 or similar. The outer edge of this ball bearing is clamped between the ring 29 inserted in the hollow 25 and another ring 39 fixed to the tool-holder head 12.
The rollers 22 are distributed unevenly in a circle. In order to do this, the radial notches 28 are themselves spaced unevenly in a circle at the outer part of the ring 29 as seen in figure 2. In this example shown in figure 2, each notch 28 is offset angularly from one neighbouring notch by an angle of 35° and from the other neighbouring notch by an angle of 25°. In this example, twelve rollers have been provided, thus distributed in a circle. As mentioned previously, this arrangement of rollers makes it possible to avoid the tubular element 14 losing its cylindrical shape at the moment when the rollers enter into contact with the edge to be curled.
The operation is straight forward and clearly follows from the foregoing description. The tubular element 14 is placed on the base 11, preferably by automatic mechanical means not represented. A clamping system, arranged in the base, is applied against the inside wall of the cylindrical element 14 and firmly connects the element to the base 11. The jack 16 and the tool-holder head 12 are moved to engage the edge to be curled in the guide 32 and then in the assembly of grooves 23 of the rollers 22 which are driven into rotation.
In the case of an inner curl, as shown in the drawings, the position of the grooves 23 of the rollers is such that the edge to be curled enters into contact with the wall of each groove in the vicinity of the outer edge of the latter. In the case of an outer curl, the situation is the reverse, the grooves being arranged in such a way that the edge of the tubular element enters into contact with each groove in the vicinity of the inner edge of the latter. In this case, the difference in diameter between the cylindrical part 35 of the guide 32 and the tubular element 14 is a little bigger so as not to hinder the disengagement of the said tubular element after the formation of the curl.
The curl is formed progressively through rotation of the tool-holder head and simultaneous drawing together between the tool-holder head and the base. The curl is achieved in one complete revolution at most.

Claims

Machine for forming a curl at the end of a metal cylindrical element (14) comprising:
a base (11) and a tool-holder head (12), the base and the tool-holder head assuming a common axis (13) and being spaced from one other and
means for bringing about a controlled axial drawing together of the base and the tool-holder head,
characterised in that the machine further comprises:
rotary means (18) for driving the tool-holder head or the base around the common axis
and in that the tool-holder head is provided with a plurality of rollers (22) arranged in a circle and concentrically to the common axis, each roller being provided with a curling groove (23) and mounted in free rotation along substantially coplanar axes, perpendicular to and cutting the common axis.
Machine according to Claim 1, characterised in that the tool-holder head comprises an annular hollow (25) enclosing a bearing (26) and in that the rollers (22) are mounted in this hollow supported against the bearing.
Machine according to Claim 1, characterised in that the tool-holder head comprises an annular guide (32) centred on the common axis and placed opposite the arrangement of rollers, the guide comprising a tapered part (34) and a cylindrical part (35) situated in the vicinity of the curling grooves.
Machine according to Claim 3, characterised in that the annular guide (22) is mounted on the tool-holder head via a bearing (38).
Machine according to any one of the previous Claims, characterised in that each roller (22) is mounted so as to be moveable along the direction of its own axis of rotation within a predetermined clearance.
Machine according to any one of the previous Claims, characterised in that the rollers (22) are distributed unevenly in a circle.