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(11) | EP 0 131 159 A2 |
| (12) | EUROPEAN PATENT APPLICATION |
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| (54) | Method and device for making grooves in a tin body |
| (57) In the wall of the tin body grooves are introduced between tools radially movable
in opposite senses towards the tin body, one tool being provided with ridges and the
other with grooves registering with the ridges. This method makes it possible, contrary
to the usual rollers, to introduce grooves with fairly small tolerances. Damage of
the lacquer does not occur. Because of the forming of sharper grooves the radial strength
will be improved and the wall thickness of the tin body can be reduced. |
[0002] Radial grooves are provided in tin bodies for stiffening the tin wall to an extent such that a smaller wall thickness can be sufficient. This results in saving of material. The application of radial grooves caused some strength reduction in an axial direction. Moreover a reduction of axial length is caused by radial grooves. In order to optimize the radial strengthening with an acceptable axial strength grooves of accurately defined depth and profile have to be made. Only with an optimum shape and size of the grooves it is possible to minimize the wall thickness.
[0003] Hitherto the grooves have been rolled in the tin body. The disadvantage of this method is that the tolerances are fairly large. This is due inter alia to slip of the forming rollers and the plurality of revolutions of the rollers required to form the grooves. A further drawback of rolling is the phenomenon of the so-called spiralizing occurring in particular in two-partite tins. Moreover damage may be caused of the lacquer applied before the grooves are made. Rolling furthermore only permits of making circular grooves.
[0004] The object of the invention is to obviate these disadvantages by providing a novel method of making grooves in tin bodies. According to the invention grooves are made in a tin body by arranging the wall of the tin body between tools radially displaceable in opposite senses towards the tin body, one tool being provided with ridges and the other tool with grooves registering with the ridges, said tools being subsequently moved towards one another.
[0005] This method eliminates the inconveniences of rolling. In the method according to the invention the tin will only slightly shift along the tools so that damage of the lacquer does not occur. Moreover, the axial reduction in length in making the grooves is limited since in the method embodyig the invention the material will yield less readily. The material will show more elasticity so that sharper grooves are formed, which will improve the radial strength. Owing to these improvements the wall thickness of the tin can be reduced. By this method it is furthermore possible to make other than circular grooves, for example, sloping grooves or rhombic patterns. Both in a radial and an axial direction the strength can thus be improved.
[0006] In a preferred embodiment only the ridged tool is moved to form the grooves so that the second tool serves as a counter-bearing.
[0007] The method can be carried out by a device characterized by circularly arranged, vertically outwardly movable first stamps, first driving means for the radial movement of said first stamps, radially inwardly movable second stamps arranged in a circle around the first stamps, second driving means for moving said second stamps, said stamps being respectively provided with registering ridges and grooves and being movable between a first open position leaving a gap between the stamps and a closed position in which the ridges engage in the grooves and by transport means for moving a tin body axially into and out of said gap respectively.
[0008] By a spring-loaded stop the on-going stroke of the transport means can be limited. After the application of the grooves the resilient stop stretches the tin body. Since only the outer ridged stamps are radially displaced, the second tool serves as a counter-bearing.
[0009] The driving means can be actuated synchronously by means of an axially movable plunger. The driving means may each have a bevelled face co-operating with a bevelled part of the associated stamp.
[0010] The invention will be described more fully with reference to the drawings, which show in
Figs. 1 to 4 different positions of stamps making grooves in a tin body when the method embodying the invention is being carried into effect,
Fig. 5 schematically the supply of tins to the device embodying the invention,
Fig. 6 a sectional view of the device embodying the invention,
Fig. 7 on an enlarged scale part of the device of Fig. 6,
Fig. 8 a sectional view taken on the line VIII-VIII in Fig. 7,
Fig. 9 a sectional view like Fig. 7 in the closed position of the device,
Fig. 10 a sectional view taken on the line X-X in Fig. 9.
[0011] In accordance with the method embodying the invention (see Figs. 1 to 4) a tin body 1 is introduced between two stamps 2 and 3, one stamp 2 having ridges 4 and the other stamp 3 having grooves 5 registering with the ridges. The stamps 2 and 3 are driven by first and second driving means 6 and 7 respectively. The driving means 6 and 7 and the co-operating faces of the stamps 2 and 3 are formed so that during the first part of the axially directed stroke of the driving means 6, 7 (see Fig. 2) the stamps 2 and 3 are radially moved towards one another, whereas during the last part of the stroke (see Fig. 3) solely stamp 2 is radially moved and hence stamp 3 serves as a counter-bearing. The radial movement producing the grooves in the tin body 1 is, therefore, performed solely by stamp 2. After the formation of the grooves the driving means 6, 7 (see Fig. 4) move in opposite axial directions, the stamps 2 and 3 move radially in opposite senses and the tin body is again released.
[0012] Fig. 5 schematically shows the way in which tins 1 are fed to a device as shown in Figs. 6 and 7 in which the assembly of Figs. 1 to 4 is arranged. The tins (Fig. 5) are moved by a worm conveyor 8 in a feeder 9 into a device embodying the invention, which comprises in this embodiment six identical processing stations 10.
[0013] With the aid of the feeder 9 (see Fig. 6) a tin body 1 is moved to a processing station 10. The unit with the stamps is fixed by means of a cap nut 12 to a plunger housing 13 of an upper plunger 14. The plunger 14 is driven by a profiled upper disc 15 and a roller 16. The tin body 1 is moved upwards by means of a lower plunger 17 driven by a lower disc 18 into the unit 11. The tin body 1 is then enclosed in the feed head 19. The upper part can be set in height with the aid of a setting spindle 20. In this way the desired setting for the tin height can be chosen. Since the upper part is adjustable, there is no need for setting a lower part and hence of the feeding part of the tin bodies.
[0014] From Figs. 7 to 10 it will be apparent that the tin body 1 is introduced into the gap between the stamps 2 and 3 up to a resilient stop 22. After the process the spring 23 ensures the ejection of the tin body. The driving means for the stamps 2 and 3, and 6, 7 respectively and the part 24 are fastened to the plunger 14 with the interposition of a spring structure 25. The cylindrical part 21 serves as a guide for the moving parts. During the performance of a stroke of the plunger 14 the driving means 6 and 7 move the stamps 2 and 3 in a manner such that the stamps 3 move radially outwards and engage the tin body. The stroke of the driving means 7 is limited by the stop 26. During the remaining part of the stroke of the plunger 14 the driving means 6 for the stamps 2 are moved axially so that the stamps 2 perform a radially inward movement and make the grooves in the tin body 1, whilst the inner stamps 3 serve as counter-bearings. Subsequently the plunger 14 moves in the opposite axial direction so that again a gap is formed between the stamps 2 and 3. The tin body is then moved to the outside by the head provided with magnets.
1. A method of making grooves in a tin body characterized in that the wall of the
tin body is introduced between tools radially movable in opposite senses towards the
tin body, one tool being provided with ridges and the other with grooves registering
with the ridges and in that subsequently the tools are moved towards one another.
2. A method as claimed in claim 1 characterized in that in order to form the grooves
solely the ridged tool is moved.
3. A device for carrying out the method claimed in claims 1 and 2 characterized by
circularly arranged, radially outwardly movable first stamps, first driving means
for the radial movement of said first stamps, radially inwardly movable second stamps
arranged in a circle below the first stamps, second driving means for moving said
second stamps, said stamps being provided with registering ridges and grooves respectively
and being movable between a first position leaving a gap between the stamps and a
closed position in which the ridges engage in the grooves and by transport means for
moving a tin body axially into and out of said gap respectively.
4. A device as claimed in claim 3 characterized in that the axial inward stroke of
the transport means is limited by a spring-loaded stop.
5. A device as claimed in claims 2 and 3 characterized in that during the movement
forming the grooves solely the outermost stamps is radially displaced.
6. A device as claimed in claims 3 to 5 characterized in that the driving means are
actuated synchronously by an axially movable plunger.
7. A device as claimed in claims 3 to 6 characterized in that the driving means have
each a bevelled face which co-operates with a bevelled part of the associated stamp.