WALL-IRONING DEVICE

Abstract: The invention relates to a device for wall-ironing sleeves (10), e.g. can bodies, containers etcetera having a wall portion near the open end with a thickness en­ larged with respect to the wall thickness of the sleeve body, said device comprising at least two wall-ironing rings (2, 3, 4) and a wall-ironing mandril (8) movable through said rings (2, 3, 4) and having a relatively broad cylindrical front part (1) and a relatively narrow, cylin­ drical rear part. The invention provides a device of the kind set forth above in which the front part of the wall-ironing mandril, at the end facing the rear part, exhibits an annular recess (9) of a predetermined depht, the position of said recess (9) being such that after having passed through the wall-ironing ring last but one the sleeve wall has at least partly reached the recess, and that the material being located at the area of the recess after having passed through the wall-ironing ring last but one is located at least partly at the rear part after having passed through the last wall-ironing ring.

Description: Short title: Wall-ironing device The invention relates to a device for wallironing sleeves, e.g. can bodies, containers etcetera having a wall portion near the open end with a thickness enlarged with respect to the wall thickness of the sleeve body, said device comprising at least two wallironing rings and a wall-ironing mandril movable through said rings and having a relatively broad cylindrical front part and a relatively narrow, cylindrical rear part. Such a device is known. A larger wall thickness of the aforesaid wall portion is necessary to be able to successfully carry out the following process steps, for example necking, flanging and folding. For this purpose the wall-ironing mandril according to the prior art exhibits said rela tively broad, cylindrical front part and the relatively narrow, cylindrical rear part. It is common practice to use three wallironing rings. With the conventional wall thicknesses and reduction ratios the sleeve wall will pass through the diameter transition between the front and rear parts of the wall-ironing mandril not earlier than in the third ring. This means that in the known technique the thickness of said wall portion can never exceed the wall thickness after the second ring. It may occur that a greater difference of wall thickness between said wall portion of enlarged wall thickness and the sleeve body is desirable. In this respect a greater thickness of the wall portion with a sleeve body thickness remaining the same as well as a constant thickness of the wall portion and a smaller thickness of the sleeve body may be concerned. In both cases the wall thickness re diction in the third ring has to be considerably greater than the conventional reduction. The invention has for its object to provide a device by which the said wall thickness difference can be enlarged without the need for increasing the relative wall thickness reduction in the third ring, whilst it is avoided that the maximum permissible, relative wall thickness reduction is too closely approached or even exceeded. For this purpose the invention provides a device of the kind set forth in the preamble in which the front part of the wall-ironing mandril, at the end facing the rear part, exhibits an annular recess of a predetermined depth, the position of said recess being such that after having passed through the wall-ironing ring last but one the sleeve wall has at least partly reached the recess, and that the material being located at the area of the recess after having passed through the wall-ironing ring last but one is located at least partly at the rear part after having passed through the last wall-ironing ring. The depth of the recess is preferably determined in connection with the desired enlargement of the difference in thickness between said wall portion of enlarged wall thickness and the sleeve body. The invention furthermore provides a wall-ironing mandril having a relatively broad, cylindrical front part and a relatively narrow, cylindrical rear part for use in a device of the kind set forth, said wall-ironing mandril embodying the invention being characterized in that at its end facing the rear part the front part has an annular recess of predetermined depth. The invention will now be described more fully with reference to the accompanying drawing. It shows in Fig.1 a cross-sectional view of a known wall ironing device in the first stage of the walfironing process, Fig.2 a view like Fig.1 in a second stage, Fig.3 a view like Figs.1 and 2 in a third stage, Fig.4 a view like Figs.1,2 and 3 in the end stage of the known wall-ironing process, Fig.5 a detail indicated in fig.4 by V, Fig.6 a sectional view of a device embodying the invention in the same process stage as in Fig.3, Fig.7 a detail indicated in Fig.6 by VII, Fig.8 a view like Fig*6 of the device embodying the invention in the same process stage as in Fig.4, Fig.9 a detail indicated in Fig.8 by IX, Fig.10 a sectional view of a wall-ironing mandril having a recess in the form of a groove in detail and Fig.ll a detailed sectional view of a wall ironing mandril having a recess in the form of a step. The wall-ironing device according to the prior art schematically shown in Fig.1 comprises a wall-ironing mandril 1, a first wall-ironing ring 2, a second wall ironing ring 3, a third wall-ironing ring 4, said wall ironing rings being relatively coupLed by means of a frame 5. Known means for advancing the wall-ironing mandril 1 in an axial direction relative to the unit 2,3,4,5 indicated by an arrow are not shown. In the process phase illustrated in Fig.1 a wall-ironed sleeve 6 is in the situation in which it is wallironed by the cooperation of the wall-ironing mandril 1 with the first wall-ironing ring 2. Fig.2 illustrates the next-following stage in which the sleeve 6 then wall-ironed is further wall-ironed by means of the second wall-ironing ring 3. Fig.3- illustrates the state in which during the third processing stave the wall-ironing sleeve is again subjected to a wall-ironing process by means of the third wall-ironing ring 4. It is noted here that the wall-ironina mandril exhibits a reduction in in-meter from the firs; part to the rear. This step is desgg-=ted in Figs. 2,3,4,5,6,7,8and by reference numeral 7. Fig.4 shots the end stage of the process. It is apparent from the drawing that by the cooperation of the wall-ironing mandril 1 with the third wall- ironing ring 4 the sleeve 6 is subjected to a last reduction in thickness. Owing to the presence of the step 7 the reduction is limited in the last case so that a thickened wall part is formed at the open end of the sleeve. It will be apparent that the diameters of the wall-ironing rings 2,3 and 4 are chosen so that the wall of the sleeve is slightly rolled to greater thinness at each ring. Usual wall thicknesses in the various stages are: initial thickness of sleeve wall 0.30 mm after the first ring 2:0.22 mutwall thickness reduction 27e) after the second ring 3:0.16mm(wall thickness reduction 278) after the third ring 4:0.lOmm (wall thickness reduction 38%). In the detail of Fig.5 reference symbols a and b designate the wall thickness of the sleeve body and Lhe thickened wall part at the open end of the sleeve 6, respectively. The dimension a is 0.10mm and b 0.16mm in accord ance with the foregoing. Figs.6 to 9 schematically illustrate an embodi ment of a device in accordance with the invention. The processing stage of Fig.6 corresponds with that of Fig.3. The processing stage of Fig.8 corresponds with that of Fig. 4. The wall-ironing mandril 8 embodying the in vention shown in Figs.6 to 9 has an annular recess 9. Re ferrying to the description of the prior art and to Figs. 1 to 5 it will be obvious without further explanation how a wall-ironed sleeve 10 is deformed in the cold state by means of the device embodying the invention. The proportioning of the device, that is to say, the diameters of the wall-ironing. rings 2,3,4, the various diameters of the wall-ironing mandril 8, also with regard to the initial thickness of the sleeve 10, is chosen so that after having passedthrough the second wall-ironing ring 3 the sleeve-wall has at least partly reached the recess 9 and that, moreover, tkle material located at the area of the recess 9 after tte passage through the ring 3 is located at least partly in the area of the hindmost part of the wall-ironing mandil 8 after having passed through the ring 4, that is to say, the material forming the part of the relatively small diameter. The latter will be apparent by considering the transition between the situation illustrated in Fig.6 and that of Fig.8. Figs.7 and 9 show more in detail the deformation stages of the relevant part of the sleeve wall. In figs.7 and 9 some thicknesses are indicated by arrows. Reference line c corresponds to a thickness of 0..16 mm, d to 0,18mum, e to 0.10 mm, f to 0.12 mm and g to 0.18 mm. After the preceding explanation with respect to the invention there is no need for emphasizing that the basic idea of the invention resides in the change of thickness between e and g. According to the prior art a maximum reduction for a given material of 0.10 and 0.16 could be obtained. The invention provides in the present embodiment a thickness change of 0.10 and 0.18 mm for the same material. It will be obvious that the invention is not limited to the embodiment described above. Many modifications, particularly of the diameter ratios given, can be applied without departing from the scope of the invention. An example of a variant of the embodiment described in the foregoing is illustrated in Fig.11. Fig. 10 is a detailed view of a wall-ironing mandril 10 having a recess 11 in the form of an uninterrupted groove The structure of this mandril 10 corresponds with that of the mandril 8 of Figs.6 to 9. Fig.ll shows a variant in which a wall-ironing mandril 12 has a recess 13 in the form of an additional step.

Claims: CLAIMS 1. A device for wall-ironing sleeves having a wall portion near the oten end with a wall thickness enlarged with respect to the wall thickness of the sleeve body, said device comprising at least two wall-ironing rings and a wall-ironing m ndri7 adapted to move through said rings and having a re relatively broad, cylindrical front part and a relatively narrow, cylindrical rear part, characterized in that the front part of the wall-ironing mandril, at the end facing the rear part, exhibits an annular recess of a predetermined depth, the position of said recess being such that after having passed through the wall-ironing ring last but one the sleeve wall has at least partlv reached the recess, and that the material being located at the area of the recess after having passed through the wall-ironing ring last but one, is located at least partly at the rear part after having passed through the last wall-ironing ring. 2. A device as claimed in claim 1, characterized in that the depth of said recess is related with the desired enlargement of the difference in wall thickness between said wall portion of enlarged wall thickness and the sleeve body. 3. A wall-ironing mandril having a relatively broad, cylindrical front part and a relatively narrow, cylindrical rear part for use in a device as claimed in claim 1 or 2, characterized in that at its end facing the rear part the front part of the wall-ironing mandril has an annular recess of predetermined depth. 4. A wall-ironing mandril as claimed in claim 3, characterized in that the width of the recess is of the order of magnitude of 5 to 10 mm.

Inventors: GROOT WASSINK, GERRIT HENDRIK
Applicants: THOMASSEN & DRIJVER-VERBLIFA N.V.
Application year: 1981
Main classification: B21D22
IPC codes: B21D22