SECURING END COVERS TO ROTATIONALLY SYMMETRIC BODIES

Abstract: A method of securing an end cover (10) to a tubular body (18) involves forming the cover (10) with a flange (12) whose outer peripheral margin (14) is curled back on itself and forming the body (18) with a frusto-conical flange (20) whose larger end is smaller in diameter than the inner extremity of the curl (14). The cover (10) is seated on the flange (20) and pressure is applied via the cover to deflect the flange (20) downwardly thereby bringing its outer peripheral margin into registry with a groove (16) afforded by the curl (14) and also rendering the flanges (12, 20) generally parallel. There­ after the flanges (12, 20) are rolled together to form a triple seam.

Description: DESCRIPTION SECURING END COVERS TO ROTATIONALLY SYMMETRIC BODIES This invention relates to a method for securing an end cover to a rotationally symmetrical body (e.g. a cylindrical body) by seam rolling together flanges on said cover and body. One form of seamed joint which is coming into widespread use is the so-called triple seam which involves seam rolling the flanges together so that the resulting joint between the cover and the body comprises seven thicknesses of material. One method of forming a triple seam joint which has been used in the past is disclosed in British Patent No. 1153872. This form of a seam joint suffers from the drawback that the seaming operation has to be carried out in two stages using separate seaming rollers having grooves of differing cross section. Also, the first stage in which the cover flange is folded over the body flange involves bending the marginal edge of the cover flange through a small radius of curvature and this inevitably results in relatively rapid wear of that seaming roller. In general, the seam jointing equipment forms a part only of a continuous production line for the manufacture of for example drums for storage of chemicals which means that frequent replacement of the small radius seaming roller interrupts continuity of production. The above mentioned drawback resulting from use of a small radius seaming roller can be avoided by folding back the marginal edge of the cover flange through 1800 before assembling the cover to the body, as disclosed in British Patent No. 1325706. According to this patent, a special form of body flange is employed which curves continuously over substantially its full width with a large radius of curvature. To enable the cover flange to be assembled to the body flange, the outer diameter of the latter must be less than the inner diameter of the folded back edge on the cover flange. Seam rolling of the two flanges is carried out by means of a single seaming roller whilst applying carefully controlled pressure to the cover and body in an axial direction. With this method, the folding back operation does not form part of the continuous production line and consequently whilst such folding back may involve the use of a small radius seaming roller, replacement through wear does not interrupt continuity. However this latter method suffers from the drawback that in practice during seam rolling the cover and body flanges together, the edge of the body flange may fail to register within the previously folded back edge of the cover flange as rolling proceeds leading to rejection of the joint and consequent scrapping of the body and cover. Such misregistry may occur for instance if the cover flange is not truly perpendicular to the axis of the body. Also, rolling of the flanges together requires close control over the seaming roller and the applied axial pressure because the body and cover flanges are not in face-to-face contact as in for example the method disclosed in Patent No. 1153872. The object of the present invention is to provide an improved method and apparatus for use in the production of triple seam joints wherein seam rolling can be performed in a single step without the risk of the body flange failing to register with a preformed folded back edge on the cover flange. According to the present invention we provide a method of securing a cover to an open end of a rotationally symmetric tubular body comprising: (a) providing the cover with a peripheral flange whose outer peripheral margin is folded back on itself; (b) providing the body with a peripheral frusto-conical flange whose larger end is smaller than the diameter of the inwardly directed edge of said folded back margin; (c) locating said cover with its flange seated on the larger diameter end of said frusto-conical flange; (d) applying pressure to displace the cover and body relative to one another so as to deflect the frusto-conical flange abouts its smaller diameter end causing its marginal edge to enter the folded back margin of the cover flange and bring the body flange into generally parallel relation with the cover flange; and (e) rolling the flanges together to form a triple seam. Thus, with the method of the present invention, the body flange is brought into registry with the folded back margin of the cover flange in a manner which practically precludes any possibility of misregistry thereby avoiding rejection of the joint through this cause. Also, the body flange is brought into substantially parallel relation with the cover flange so that at the commencement of seam rolling both flanges may be in contact over substantially their entire widths. The smaller diameter end of the frusto-conical flange will be constituted by a sharp or small radius junction whose radius of curvature may be less than for example the radius of the junction between the cover and its flange so that deflection of the frusto-conical flange will take place at a well defined position thereby ensuring that the marginal edge of this flange enters into the folded back margin of the cover flange to the desired extent even when the cover flange is not truly perpendicular to the body axis. Preferably the outer peripheral margin of the frusto-conical flange is preformed (i.e. before assembly with the cover) with a slight curl so as to facilitate sliding thereof along the cover flange during deflection of the frusto-conical flange. In its simplest and presently preferred form, the frusto-conical flange is joined directly to the wall of the body (and in this case can be formed by roll flanging or by press flanging) but in a modification it may be joined to the body wall through the intermediary of one or more frusto-conical portions of steeper base angle. In practice, means will be provided for supporting the cover flange against deflection during deflection of the frusto-conical flange. Such means may comprise the combination of the seaming chuck and seaming roller, one or the other or both of which may include or be provided with a supporting portion extending over at least part of the cover flange. In this event, the axial pressure for effecting deflection of the frusto-conical flange may be applied through the agency of the seaming chuck so that once the deflection step has been executed the seam rolling step may be initiated immediately. Alternatively the deflection step may be executed with the aid of a special tool for which the seaming chuck is substituted after the deflection step has been effected. To promote further understanding of the invention reference will now be made to the accompanying drawings in which : Figure 1 is a schemmatic sectional view through the periphery of a cylindrical body and cover showing the disposition of the flanges prior to carrying out the jointing process; Figure 2 is a similar view to Figure 1 but showing the disposition of the flanges after the cover has been displaced axially with respect to the cylindrical body; Figure 3 is a similar view to Figure 1 but showing a modified form of flange on the body; Figure 4 is a similar view to Figure 2 showing the disposition of the modified flange after the cover has been displaced axially with respect to the body; Figure 5 is a similar view to Figure 1 but showing the provision of a tool for providing support for the cover flange during the axial displacement of the cover; ; Figure 6 is a similar view to Figure 5 showing a seaming chuck which has been adapted to provide support for the cover flange during the axial displacement of the cover; Figure 7 is a sectional view through the periphery of the cover and body showing an intermediary stage in the formation of the triple seam; and Figure 8 is a similar view to that of Figure 7 but showing the finished seam between the cover and body. Referring firstly to Figures 1 and 2, the cover 10 is provided with a radial flange 12 which is preformed with a folded back margin 14 so as to provide a radially inwardly directed annular groove 16. At at least one of its open ends, the cylindrical body 18 is formed with a frusto-conical flange 20 which forms an obtuse angle with the cylindrical wall of the body 18 and terminates in a slightly curled edge 22 whose diameter is less than the inner diameter of the folded back margin 14 by an amount A so that the cover 10 may initially be assembled to the body in the manner shown in Figure 1 with the cover flange 12 seating on the larger diameter end of the flange 20. Prior to seam rolling the two flanges 12 and 20 together, the cover is displaced downwardly into the body 18 so as to cause the flange 20 to deflect about its junction 24 with the body wall. To ensure that the deflection takes place at a well defined position, the radius of the junction 24 is relatively sharp and typically it will be less than that of the junction between the cover and its flange 12. The width of the flange 20 and its angle of inclination are such that when the flange 20 is deflected into substantially parallel relation with the flange 12 as shown in Figure 2, the marginal edge of flange 20 enters the groove 16 to such an an extent that the outer diameter of the flange 20 exceeds the inner diameter of the folded back margin 14 by an amount B thereby trapping the cover on the body and ensuring that the flange 20 is properly registered with the groove 16 in preparation for triple seam rolling. Figures 3 and 4 show a similar cover and body assembly except that in this case the frusto-conical flange 20 is joined to the main wall of the body 18 through the intermediary of a steeper frusto-conical portion 30 whose width is somewhat less than that of the flange 20. In this embodiment, the arrangement is such that deflection of the flange 20 takes place predominantly about the junction between flange 20 and the portion 30. During the downward displacement of the cover 10 and consequently deflection of the flange 20, it is necessary to support the cover flange 12 to preclude any risk of undesirable deformation. As shown in Figure 5, this may be achieved by means of a special tool 40 which includes a radial projection 42 overlying the flange 12. The tool 40 is employed during the deflection/displacement step and is thereafter substituted by the conventional seaming chuck for subsequent completion of the seam rolling by means of the roller 44. Instead of effecting the deflection/displacement step by means of a separate tool, the necessary axial displacement may be applied through the agency of the seaming chuck in which event the chuck 50 and/or the seaming roller 44 may be suitably adapted to enable the necessary support to be provided for flange 12 during deflection of the flange 20. Thus, for example, as shown in Figure 6, the seaming chuck 50 may be provided with an independently displaceable radially outwardly projecting portion 52 for providing the necessary support for the flange 12. The portion 52 may be movable downwardly with the chuck 50 during the deflection/ displacement step but may be arranged to be withdrawn upwardly to the position shown in broken outline so as afford clearance for movement of the seaming roller 44 radially inwardly to effect the triple seaming operation. Other variations are possible; for example the seaming chuck and/or the seaming roller may be provided with a radial projection or projections which at least partially overly the flange 12, the arrangement being such that the necessary radially inwardmovement of the seaming roller can take place to effect the seaming operation. Figures 7 and 8 show respectively an intermediate stage during seam rolling and the finally formed triple seam which, it will be noted, comprises seven thicknesses of material. Thus, as the seaming roller moves radially inwardly, the rolled seam passes through the disposition shown in Figure 7 and is finally pressed against the side wall of the body 18 by the seaming roller. As is conventional practice in double and triple seam rolling, sealing compound may be introduced at an appropriate stage or stages during the process preferably in such a way that sealing compound is present in the central part of the joint and also between at least some of the layers of the seam as indicated by the reference numeral 60 in Figure 8 so as to afford greater security against leakage and also to strengthen the joint against rupture through impact.

Claims: CLAIMS 1. A method of securing a cover (10) to an open end of a rotationally symmetric tubular body (18) comprising: (a) providing the cover (10) with a peripheral flange (12) whose outer peripheral margin (14) is folded back on itself; (b) providing the body (18) with a peripheral frusto-conical flange (20) whose larger end is smaller than the diameter of the inwardly directed edge of said folded back margin (14); (c) locating said cover (10) with its flange (12) seated on the larger diameter end of said frusto-conical flange (20); (d) applying pressure to displace the cover (10) and body (18) relative to one another so as to deflect the frusto-conical flange (20) about its smaller diameter end (24) causing its marginal edge (22) to enter the folded back margin (14) of the cover flange (12) and bring the body flange (20) into generally parallel relation with the cover flange (12); and (e) rolling the flanges (12,20) together to form a triple seam. 2. A method as claimed in Claim 1 including forming the body (18) and cover (10) in such a way that the junction (24) between the frusto-conical flange (20) and the body (18) has a sharper radius of curvature than the junction between the cover (10) and its flange (12). 3. A method as claimed in Claim 1 or 2 including forming the outer peripheral margin of the frusto-conical flange with a partial curl (22). 4. A method as claimed in any one of Claims 1-3 including supporting the cover flange (12) against deflection during step (d). 5. A method as claimed in any one of Claims 1-4 in which the relative displacement between the cover (10) and body (18) during step (d) is applied through the agency of a seaming chuck (50) used in step (e). 6. A method as claimed in Claim 5 when appendant to Claim 4 in which the seaming chuck (50) and/or seaming roller (44) used in step (e) is/are provided with means (52) which afford support against deflection for the cover flange (12) during step (d). 7. A rotationally symmetric tubular body (18) having a cover (10) secured to an end thereof by the method of any one of Claims 1-6.

Inventors: COLLINGWOOD, ANTHONY ROBERT
Applicants: BUDENBENDER, BERND
Application year: 1982
Main classification: B21D51
IPC codes: B21D51