EP0745052A1

EP0745052A1 - Industrial barrel

Info

Publication number: EP0745052A1
Application number: EP95942706A
Authority: EP
Inventors: Reinhard Nolting; Hans U. Weigel; Rolf Klein; Reinhard Poprawe; Rainer Fischer
Original assignee: Sulo Eisenwerk Streuber and Lohmann GmbH
Current assignee: Sulo Umwelttechnik GmbH
Priority date: 1994-12-20
Filing date: 1995-12-20
Publication date: 1996-12-04
Also published as: HUT75010A; CZ244796A3; PL316010A1; WO1996019385A1

Abstract

Industrial barrel made of metal with a shell (10) in whose end portions essentially flat barrelheads (12) are fixed by means of welding, characterized in that the shell (10) and/or the barrelheads (12) beads (18) are provided on and along the welds.

Description

INDUSTRIAL BARREL

The invention relates to an industrial barrel made from metal with a shell, in whose end portions essentially flat barrelheads are fixed by welding, and a process for its production •.

With metal barrels it is per se prior art to join the two barrelheads to the shell by welding However, today's industrial barrels are subject to high and constantly increasing demands, for example with regard to safety, reutihzation, minimization of dead space, economy etc These demands can no longer be sufficiently met with existing manufacturing processes However, in the production of industrial barrels with the aid of new welding techniques, e g with the aid of laser welding, particularly for inserting top and bottom barrelheads, offers good development opportunities

There are a series of test methods with which demands made in practice are simulated and 1 -> industrial barrels are tested with regard to their safety One such test is an excess-pressure test (burst test), where the inside of the barrel being tested is exposed to excess pressure until the barrel bursts Another important test method is the drop test, which simulates a situation in which a barrel is unintentionally dropped during handling, e g during loading or transport from a pre-set height onto a hard surface 2<ι

In the above-mentioned burst test, even barrels in which the barrelheads are welded by means of lase^r welding can only withstand limited internal pressures because high static tensile forces occur which act directly on the welded joint During these tests the metal does not usually rupture within the very homogeneous and strong weld, but in the immediate vicinity thereof 2-^; During fall tests very high tensile forces occur which laser-welded barrels cannot withstand to the required degree either

Their strength could be considerably increased by using higher-grade steels, but the use of expensive steels for a relatively simple mass product such as an industrial barrel is in general vι not acceptable for economic reasons

Further problems can occur during the laser-welding of metal barrels in that during the welding process, the surface pressure and the precise fit between the parts to be welded, i e the shell and the barrelheads, are insufficient A precise fit could be achieved with stricter tolerances, 3^** although these would entail disproportionately high costs in the production of industrial barrels DE 36 00 532 A1 describes a process for manufacturing barrels from thin sheet metal The barrelheads are formed as flat plates and are pushed into the shell from the ends until each one abuts against a bead provided for it The fit that is achievable with this solution between the inner wall of the shell and the edges of the barrelheads can at best only provide the necessary ^•^ precision and the necessary contact pressure for small containers such as e g food cans

The welding of barrels with the aid of laser beams is disclosed in DE 38 13 433 A1 In this process the barrelheads are first punched out as round plates and are then worked into flat pots by deep drawing An externally projecting annular ring is then contrived around the in circumferential edges of these pots The pots are inserted into the ends of the barrel shell until this annular ring rests against the edge of the shell An inwardly projecting, circumferential bead in the shell is supposed to create a higher surface pressure between the inner wall of the shell and the outer wall of the pots

l -- This invention is based on the task of providing an industrial barrel made from metal and a process for manufacturing it of a kind which will considerably increase the mechanical stability of the finished barrel and hence also the safety of this barrel

According to the invention, for an industrial barrel of this type this task is solved by the features " of claim 1 and the features of process claims 8 and 9

In the industrial barrel according to the invention, beads are provided in the shell and/or the barrelheads bordering on and along the welds, which, under severe loads, allow a certain deformation and expansion of the barrel walls and relieve the strain on the weld

2-.

According to the invention, the surface pressure between the circumferential edge of the barrelheads and the inner wall of the shell is increased by cambering the barrelheads in the shape of a lens to reduce their diameter on insertion, or by widening the diameter of the shell by means of focussed heating If one proceeds in this manner, the barrelheads are positioned in > the barrel ends during the welding process with a flat lens-shaped outwardly directed camber in the elastic range so that the edges of the barrelheads are pressed against the inner surface of the shell with great pressure This results in the high contact pressure needed between the two surfaces to be welded

3*> Where tensile stresses are directed crosswise to the welds, the beads are pulled flat to a certain extent This considerably reduces the tensile effect exerted on the weld and the tensile energy that has to be absorbed by the weld is attenuated by the plastic deformation of the metal within the beads and is gradually broken down Fracture loads in the welds or in their vicinity can be avoided in this way

5 The beads should run at a relatively short distance to the welds, e g for barrels with standard dimensions at a distance of 15 mm to the welds and essentially parallel to them

The beads can be cambered both inwardly and outwardly in both the shell of the barrel and in the barrelheads In cross-section they can have an approximately hemispherical shape with in transition radii to the main surfaces of the shell or barrelheads

The size of the beads in relation to their cross-section depends on the expected stresses and the demands imposed Larger beads result in greater flexibility under stress Moreover, several parallel beads can be used one behind the other to increase the deformation possible under I -^; stress

The process of the invention allows not only the production of a very strong and reliable welded joint between the shell and the barrelheads, out also results in a barrel that is completely free of dead space since the barrelheads are essentially perpendicular to the inner surface of the shell 2<ι and do not form a crack with the latter, as can be seen in the above-mentioned DE 38 13 433 A1 , with an acute cross-section in which barrel content residues can accumulate This complicates the cleaning process needed if the barrel is used repeatedly

Examples of preferred embodiments of the invention will be explained in more detail below with 5 reference to the enclosed drawings, in which

Fig 1 shows a perpendicular part section through the top portion of the shell and, welded to it, the top barrelhead of a laser-welded barrrel,

i Fig 2 is a similar illustration on a smaller scale showing, by way of example, a few of the dimensions that could be used for the beads,

Fig 3 is a diagrammatic illustration of a stopper bead for the barrelheads, Fig 4 shows an axial section of one end of a barrel manufactured according to a first embodiment of the process of the invention with two laser-beam welding variants A and B shown on an enlarged scale,

*^; Fig 5 shows a device for carrying out this process before cambering the barrelhead,

Fig 6 shows this device mounted on the turned-over edge of the shell with the cambered barrelhead,

i n Fig 7 shows another embodiment of the device before the barrelhead is braced and cambered,

Fig 8 shows another embodiment of the device,

1 -^; Fig 9 is a diagrammatic, partially cut view of a shell with two barrelheads and indications of a few of the dev.ce elements needed to implement a second embodiment of a process,

Fig 10 is a diagrammatic top plan view of an induction loop ring for heating the end

2iι portions of a shell

Fig 1 1 is a corresponding illustration of an induction loop ring for non-circular barrels

2*> Fig 1 shows the shell of a barrel 10 and its upper barrelhead 12 A laser fillet weld 14 enters into the material of the shell and the barrelhead from the inside of the angle formed by the shell 10 and the barrelhead 12 At the top end, the shell 10 has a rolled up turned-over edge 16

In both the shell 10 and on the upper barrelhead 12, there are inwardly arch-shaped indented ι beads 18 and 20 at a relatively short distance to the laser fillet weld 14 The bead 20 runs (in a manner not shown) in the barrelhead parallel to the edge thereof and to the laser fillet weld along the entire edge of the barrelhead The bead 18 in the shell 10 runs parallel to the laser fillet weld 14 around the outside of the shell

^ The illustration in Fig 2 essentially coincides with Fig 1 , but is on a somewhat smaller scale Furthermore, here the bead 20 in the barrelhead 12 is upwardly cambered As Fig 2 shows, the two beads should have a radius of 5 cm. The bead 18 in the shell 10 is flatter than the bead 20 in the barrelhead. With radii R5 of 5 mm, the bead 20 in the barrelhead runs over into the bordering material. The radii R15 of the flat bead 18 in the shell are 15 mm.

Fig. 3 shows in a perpendicular part section similar to Figs. 1 and 2 an upper corner portion of a barrel with a shell 10 and a barrelhead 12 and a turned-over edge 16. Beads 18, 20 are not shown in Fig. 3. However, Fig. 3 shows a circumferential stopper bead 24, which serves as a contact surface for the barrelhead 12. This kind of stopper bead considerably simplifies the positioning of the barrelhead 12 when it is inserted into the shell. In practice, this stopper bead m 24 is provided in addition to at least one of the beads 18, 20 of Figs. 1 and 2, but, whatever the case, is outside the relieving bead 18 of Figs 1 and 2

The process of the invention serves in particular for the production of cylindrical barrels made from steel sheet However, the process of the invention can also be used to manufacture other l ^•; containers using both steel sheet and other metal sheets

The barrel 101 of Fig. 4 has an essentially cylindrical shell 102, in whose two ends a barrelhead 103 is inserted and welded to the shell so that there is no dead space. The shell 102 is made from a cylindrically curved metal whose axially running longitudinal edges are joined to each 2' i other by means of a longitudinal weld 104.

The cylindrical shell 102 can be provided with a turned-over edge 105 before or after the barrelhead is inserted. For high degrees of stress, a reinforcing ring can also be positioned in the turned-over edge. 2-;

For a barrel which holds 55 gallons, i.e. approx. 216 litres, the thickness of the metal sheet is about 1 mm. Barrels of this type have a maximum diameter of 584 mm for a height of approx. 875 mm.

π For a barrel of this type, a steel sheet with a thickness of approx. 1 to 1 .2 mm can be used to manufacture the barrelheads. Each barrelhead 103 consists of an initially flat round which is punched out of flat sheet or cut out with a laser beam. If required, the barrelhead can be provided with reinforcement or expansion beads as explained, but these reinforcement beads must be arranged and shaped in such a manner as to allow the elastic cambering of the

3 barrelhead as described below. To take account of these possibly required reinforcement beads, the rounds will be described in this context as "essentially flat". According to the process of the invention, barrelheads 103 are used whose diameter d1 (cf Figures 5, 6 and 7) is bigger than the inner diameter d of the shell 102 For a barrel of the above-mentioned size, the inner diameter d is 571 mm The diameter d1 of the barrelhead 103

5 should in this case be 1 mm bigger, i e 572 mm The difference in the diameter d1 of the barrelhead and the inner diameter d of the shell 102 has to be selected so that the edge 103c of the barrelhead 103 is pressed firmly against the inside surface 102a of the shell 102, so that as far as possible, there is no crack between the two parts If inaccuracies in the production process of the shell 102 and, possibly, of the barrelhead 103 too result in deviations from the i n circular shape, then these deviations should be compensated for as far as possible through the tensioning process so that any crack between the edge 103c of the barrelhead and the inner surface 102a of the shell 102 amounts to no more than a tenth of the sheet thickness, i e 0 1 mm at most

I *^; With the inner diameter d - 571 mm - of the shell 102 selected in the embodiment the over- dimensioning of diameter d2 of the barrelhead 103 is slightly more than 2 per thousand With smaller container diameters and thinner wall thicknesses it may be necessary to select a slightly larger over-dimensioning in proportion

2<ι To ensure that the round resp the barrelhead 103 can be easily inserted into the end of the shell 102 despite its larger diameter d1 , the invention suggests that before it is inserted into the shell 102, each barrelhead should be cambered to a lens-shaped form by means of force or heat until its diameter d1 is reduced to an insertion diameter d2 (cf Fig 3), which is smaller than the inner diameter d of the shell 102 The elastically cambered barrelhead 103 is then *^; inserted into the shell During this procedure the barrelheads 103 should be inserted into the shell 102 so that they are convexly cambered outwards, as shown in Fig 4 As a result of this convex cambering the barrelheads 103 are slightly concave on the inside, allowing the barrel to be completely drained

π The cambering of the barrelhead 103 in the elastic range can be effected by applying a vacuum to the outer surface 103b of the barrelhead 103, as will be described below with reference to Figures 5 and 6 Alternatively, the barrelhead 103 can be cambered by applying an electromagnetic field in the vicinity of the outer surface 103b, as will be described below with reference to Figure 7 Furthermore, one can bring about the cambering of the barrelhead in the

35 elastic range by locally heating the barrelhead in its central portion, as described below with reference to Figure 8 Figures 5 to 8 show devices which are suitable for implementing the first embodiment of the process according to the invention These devices essentially consist of a fixing device 106 for deforming the barrelhead 103 in the elastic range, for holding the barrelhead and for inserting > the latter into the shell 102

The fixing device 106 is provided with a mating surface 107 which should be provided for at least the portion of the barrelhead that borders on the barrelhead edge 103a However, the mating surface 107 should preferably extend over the entire area of the barrelhead 103 and is in concavely curved according to the desired elastic camber of the barrelhead The fixing device 106 is provided with an essentially cylindrical centering surface 108 that radially limits the mating surface 107 towards the exterior

The diameter d2 of this centering surface is smaller than the inner diameter d of the shell 102

] ^•*. and coincides with the insertion diameter d2 of the barrelhead 103 The fixing device 106 is also provided with an annular step 109 that borders on the centering surface 108 The distance a of the annular step from the mating surface 107 coincides with the axial distance a which the barrelhead 103 should be from the turned-over edge 105 of the shell when inserted into the latter

2< ι

In the embodiment illustrated in Figs 5 and 6, a vacuum can be generated in the vicinity of the mating surface 107 The fixing device 106 is provided with one or several bores 1 10 which open out onto the mating surface 107 and can all be connected to a vacuum source (not shown)

2-.

A sealing ring 1 1 1 is also contrived in the mating surface 107 near the centering surface The fixing device 106 is placed on top of the flat round or the barrelhead 103 as shown in Fig 2 so that the barrelhead edge 103c projects beyond the centering surface 108 equally on all sides This can be achieved by using a centering ring (not shown), whose inner diameter coincides

}n with diameter d1 and which is mounted to the fixing device 106 such that it can be removed in the axial direction

When the fixing device is connected to the vacuum source, a vacuum is generated in the space between the outer surface 103b of the barrelhead 103 and the mating surface 107 This

3*. causes the barrelhead 103 to camber in the shape of a lens, as shown in Figure 6 As a result, its diameter is reduced from the original size d1 to a diameter d2, which is termed the insertion diameter and which is smaller than the inner diameter d of the shell 102 Since the barrelhead 103 is moved against the fixing device 106 by suction, the latter serves simultaneously to hold the barrelhead 103 when it is inserted into the end of the shell 102

*^; To do so, the fixing device with the cambered barrelhead 103 is pushed into the end of the shell 102 until the annular step 109 abuts against the turned-over edge 105 This ensures the correct axial position of the barrelhead 103 in relation to the shell 102 Whilst the barrelhead 103 is being inserted, the fixing device 106 is centered in relation to the shell 102 by means of its centering surface 108 Both the diameter d2 of the centering surface 108 and the insertion m diameter must be selected so that the fixing device 106 and the barrelhead 103 can be inserted without resistance into the shell 102 On the other hand, the diameter d2 should not be too small, so that the fixing device 106 and the barrelhead 103 can centre themselves in relation to the shell 102

l -^; As soon as the fixing device 106 rests on the turned-over edge 105, the vacuum is discontinued Due to its elasticity, the barrelhead tries to return to its original, flat form but cannot do so because its edge 103c fits against the inner surface 102a of the shell 102 Since the original diameter d1 of the barrelhead 103 is bigger than the inner diameter d of the shell 102, the barrelhead 103 is braced or fixed in the shell Therefore, as soon as the vacuum is

2ιι discontinued, the fixing device 106 can immediately be withdrawn from the shell end again and does not hinder subsequent welding in any way

In the device illustrated in Fig 7, a coil 1 2 for generating an electromagnetic field is disposed in the fixing device 106 Instead of one coil 1 12, several individual smaller coils can be 2 provided The structure of the fixing device 106 and the way it is used correspond with the fixing device 106 of the above-described embodiment

When electric current is applied, the electromagnetic field pulls the barrelhead 103 towards the mating surface 107, thereby cambering it elastically At the same time, the electromagnetic 3ι» force generated by the coil 1 12 serves to hold the barrelhead 103 against the fixing device 106 The barrelhead 103 is inserted into the shell 102 in the same way as in the previous embodiment Once the fixing device 106 rests on the turned-over edge 105, the current is switched off and the edge 103c of the barrelhead 103 can abut against the inner surface 102a of the shell 102

3* In the embodiment illustrated in Fig 8, a heat-generator 1 13 is disposed in the centre of the fixing device 106 This heat-generator 113 can heat the centre of the barrelhead 103 by induction, broad-band infrared radiation or laser radiation The higher temperature in the centre portion of the barrelhead 103 with respect to the colder temperature of the edge portion of the

^•; latter results in a cambering of the barrelhead in the elastic range With this design of the fixing device, smaller magnetic coils 1 14 can be disposed in the fixing device 106, which need only be strong enough to hold the round or the barrelhead 103, cambered by the supply of heat, against the fixing device 106 until it is inserted with the help of the fixing device 106 into the end of the shell 102 in the above-described manner The heat supply is then discontinued by in switching off the heater 1 13 Due to the good thermal conductivity of steel, the heat is dissipated from the centre of the barrelhead to the edge portion, so that the diameter of the barrelhead expands again and abuts with its edge against the inner wall 102a of the shell

After the barrelhead 103 is securely braced in the shell 102 in the above-described manner, the 1 ^•; two parts are welded by means of energy radiation welding Although it is preferable to use a laser beam for this, an electron beam or an ion beam could also be considered

It is preferable to effect welding using a laser beam on the outer surface of the barrelhead, as shown in Fig 4, variant A The focussed laser beam, which is indicated by the black arrow L, is

2ιι directed at an angle to the barrelhead 103 and at an angle to the wall of the shell 102 onto the connection point of the barrelhead 103 and the shell 102 The precisely dosable laser output can deliver so much heat energy that the material of the shell and the barrelhead melt and losses due to heat conduction to the surrounding material are compensated for The laser output must be set so that the connection point is completely welded through and the root 1 15a

2^ of the weld 115 extends through to the inside of the container Correct setting of the welding conditions should also ensure that the weld root 115a is as smooth as possible In this way, a smooth, crack-free transition from the inner surface 103a of the barrelhead 103 to the inner surface 102a of the shell 102 is created Due to the narrow weld width and the brief period of application of the laser beam the edge portions of the weld 1 15 are only slightly thermally

3d stressed The heat-affected zone of the base material is much smaller than with conventional welding methods To prevent material deformations due to the application of heat during laser beam welding, the outer surface 102b of the area furthest from the laser beam L can be cooled by applying a stream of gas with a high flow rate as indicated by arrow G

* According to variant B of Fig 4, the focussed laser beam L can also be applied radially to the shell 102, whereby the laser output also has to be set so that the material is completely welded through and the root 1 15a of the weld 1 15 extends through to the inside of the container so that in this case too, a crack-free transition of the inner surfaces 103a and 102a of the barrelhead 103 and the shell 102 is guaranteed Cooling takes place in this case by means of a stream of gas G directed onto the outer surface 103b of the barrelhead 103 or onto the inner surface 102a ^ of the shell 102 that lies outside the barrelhead

Fig 9 shows a cylindrical shell 210 of a barrel made from metal, which in the example illustrated has - although it must not necessarily have - the shape of a circular cylinder open at both ends The shell is produced from a metal strip which is rolled up into a cylinder and in welded along the line where the two ends meet up (not shown) The shell 210 has, in the usual manner, two circumferential ribs 212 and 214 which can be formed by beads or by mounted elements which are welded onto the shell of the barrel Outwardly contrived Hangings 216, 218 (indicated only) are provided on the longitudinal ends of the shell

] -; The two longitudinal end portions (not shown) of the shell 210 are encircled by ring-shaped heating devices 220 and 222, which can, for example, be formed by induction loops, as will be explained in more detail below These heating devices 220, 222 are placed around the end portions of the barrel whilst the process is being carried out and are removed again after heating for a pre-set time Inductive heating of the end portions of the barrel expands these end

2n portions in the radial direction so that the inner diameter increases and the two barrelheads 224, 226 can be inserted In Fig 9, the two barrelheads 224, 226 are brought into place by fixing devices 228, 230 The fixing devices are shown diagrammatically with two suction caps 232, 234 and 236, 238 and some distancing pins 240, 242 Electromagnets (not shown) can be used as alternatives to the suction caps The type of handling device for inserting the two

2> barrelheads into the barrel shell 210 is not critical in this context In Fig 9, the fixing devices 228, 230 are shown as plate-shaped with, at their edges, stopper surfaces 244 and 246, which come to rest against the corresponding flangings 216, 218 of the shell 210 when the barrelheads 224, 226 are inserted, thereby fixing the barrelheads 224, 226 in a pre-defined position inside the cylindrical shell until the end portions of the shell of the barrel have I sufficiently cooled off and hence shrunk so that the barrelheads 224, 226 are held braced in position It is also possible to use other elements (not shown) to ensure that the barrelheads camber inwardly or outwardly according to their over-dimension in relation to the inner surface of the barrel

35 Fig 10 shows a circular heating device 220, which is made up of three segments 248, 250, 252, each with an angle at circumference of 120°. As Fig 9 shows, closed induction loops are disposed inside the individual segments. In conjunction with a suitable fixing device (not shown), the segments 248, 250, 252 can be opened and then closed during the procedure of being fitted around the barrel.

Fig. 11 shows a corresponding heating device 254, whose profile essentially corresponds to a square with very rounded corners. According to Fig. 1 1 the heating device 254 consists of two segments 256, 258.

Claims

PATENT CLAIMS

1 Industrial barrel made of metal with a shell (10, 102) in whose end portions essentially flat barrelheads (12, 103) are fixed by means of welding, characterized in that in the shell (10,

-÷ 102) and/or the barrelheads (12, 103) beads (18, 20) are provided bordering on and along the welds (14, 1 15)

2 Industrial barrel according to claim 1 characterized in that the distance of the beads (18, 20) to the weld (14, 1 15) is approximately 15 mm i n

3 Industrial barrel according to claims 1 or 2, characterized in that the beads (18, 20) have an arching camber with transition radii to the adjoining material

4 Industrial barrel according to one of claims 1 to 3, characterized in that in the shell of l -• the barrel an inwardly projecting stopper bead (24) is provided in a pre-set position defined for the positioning of the barrelheads (12, 103)

5 Industrial barrel according to claim 4, characterized in that the stopper bead (24) projects inwardly by at least 0 1 mm d

6 Industrial barrel according to one of claims 4 or 5 characterized in that the stopper bead (24) runs around the entire circumference of the shell (10)

7 Industrial barrel according to one of claims 4 or 5, characterized in that the stopper 2_^ bead (24) is sub-divided into separate sections distributed over the circumference

8 Process for manufacturing an industrial barrel according to claim 1 , wherein barrelheads are attached to both ends of a cylindrical shell of a barrel by means of welding, characterized in that the shell (10) and/or the barrelheads (12) are beaded bordering on and

.<> along the welds (1 )

9 Process according to claim 8, characterized in that in the shell of the barrel, an inwardly projecting stopper bead is contrived in the position defined for positioning the barrelheads (12)

3^*> 10 Process according to claim 8 or 9, characterized in that the barrelheads (12) are manufactured with a diameter which is slightly larger than the inner diameter of the shell, since the barrelhead is cambered in the elastic range in the shape of a lens by force and/or heat before being inserted into the shell, in that the barrelheads are then inserted into each end of

5 the shell and in that the source of force or heat is then discontinued

1 1 Process according to claim 10, characterized in that the cambering of the barrelhead is effected by applying a vacuum to the outer surface of the barrelhead

in 12 Process according to claim 10, characterized in that the cambering of the barrelhead is effected by applying an electromagnetic field in the vicinity of the outer surface of the barrelhead

13 Process according to claim 10, characterized in that the cambering of the barrelhead l ^*; is effected by locally heating the barrelhead in its central portion

14 Process according to claims 8 or 9, characterized in that when the barrelheads are inserted, the shell is heated to a given expansion by a heating device (20, 22) placed around the shell, in that the barrelhead is then inserted into a pre-defined position in the heat-expanded

2d end portion of the shell and in that heating is then discontinued and the barrelhead is welded to the shell

15 Process according to claim 1 , characterized in that the shell (10) is calibrated to a pre-defined inner diameter before heating

2*.

16 Process according to claim 15, characterized in that the shell (10) is manufactured with an under-dimensioned inner diameter which is subsequently expanded to the target dimensions at the two end portions

3d 17 Process according to one of claims 14 to 16, characterized in that the heating devices (20, 22, 54) are induction heaters