The present invention relates to a folded-seam connection according to the preamble of Claim 1 and to a method of producing it as well as to a device for performing the method.

Folded-seam connections according to the preamble of Claim 1 are well known in ventilation and air-conditioning tech- nology. These connections have the inherent drawback that they are not tight, since after it has been produced any folded-seam connection will tend to spring back, i. e. to open. The resulting leakage losses of connections of this type, however, are frequently unacceptable on the grounds of hygiene, health and/or energy, so additional action is necessary for sealing, for example for inserting a strip of rubber and/or for securing the folded-seam connection by adhesion; cf. inter alia WO 00/27557, Figs. 10 to 13, in which various ways in which to clamp seals are illustrated.

This leads to further drawbacks: As well as the resulting high outlay in materials and time for introducing addi- tional sealing material into the folded-seam connection its effectiveness is substantially dependent upon the careful- ness of the user (worker). In addition, even synthetic sealing materials tend to become brittle and withstand only slight differences in pressure, in particular if relatively large gaps and/or shearing forces are involved.

The object of the present invention is therefore to provide a metallic sealing folded-seam connection which can ade- quately meet the high sealing demands in practice today.

In particular, the folded-seam connection should also be suitable for ventilation units of Sealing Class C, without additional sealing means and/or subsequent processing being required. This Class C, applied to folded-seam connections of high sealing tightness, has been defined by the Commit- tee of Producers of"Ventilation and Drying Plants (EUROVENT)"and corresponds to a maximum leakage of for ex- ample 0, 01 m3 of air per s, with a test area of 200 m2 un- der a test pressure of 1000 Pa.

A method should likewise be disclosed which will allow folded-seam connections of this type to be produced eco- nomically. In addition, a suitable device should be pro- vided which will ensure the quality of the folded-seam con- nection in an economic manner and which can be applied as universally as possible, i. e. is suitable for pipes, pipe segments and pipe bends.

It should be possible to produce with conventional techno- logy the folded-seam connection to be provided, which should not require any special training on the part of the processing personnel and which should at least correspond in its appearance and stability to the customary one.

This object is attained by the features of Claims 1,4 and 5.

The folded-seam connection provided according to Claim 1 produces in the interior of the fold a form fitting seal, in particular on the external diameter of the flange-like double fold as a result of the relatively large bending ra- dius of the surrounding second outer double fold. As a re- sult, the springing back of the connection is minimized ;

the metallic seal is durable and susceptible to vibration to only a negligible degree.-The radius of embracing in the region of the greatest external diameter on the exter- nal double fold is greater than an enclosed flange turned over in a single manner (also called a single edge). This prevents over-extension of the bending point, which is im- permissible in terms of materials, and thus massive mate- rial displacement, hairline cracks and subsequent corrosion on the fold, as frequently observed on existing ventilation units.

The term"all around continuous"used in the Claim accord- ingly means that a form fitting sealing face is provided which rests against the matching member and which extends in a linear and coaxial manner and without interruptions over the entire periphery of the folds.

If a folded-seam connection according to the invention is cut open, in contrast to a connection with a flange turned over in a single manner it displays an almost ideal metal- lic sealing contact face which embraces the entire inner double flange in a precise manner with respect to its shape.

What is crucial for the proper sealing behaviour of the connection is the above-mentioned all around continuous de- sign of the sealing faces, since, in addition to the actual closure, these form one or more high-quality labyrinth seals with minimal leakage losses.

In contrast, it has been found to be advantageous if the flange-like double fold has an air gap situated on the in- side, so that there is a deliberate springing action of the

inner fold against the interior of the second double fold.

This ensures a durable metallic seal even when operating with varying pressure ratios.

In particular, in the case of non-plated pipes an insulat- ing layer of a polymer applied in the liquid state may be advantageous, since no contact corrosion occurs at the con- nection point in the fold; the thin layer remaining after hardening will then additionally take on a compensating and sealing function. Functionally an insulating layer does not alter the basic principle of positive locking effective during the closing procedure and produced by external forces, even if the metallic contact faces are supplemented by thin intermediate layers or if a metallic plating of the metal sheet is replaced and/or supplemented by an insulat- ing layer.

Advantageous embodiments of the subject of the invention are characterized in the dependent claims.

An air gap subjected to a powerful external clamping action between the flange parts, which results in the strong springing action thereof, is particularly advantageous.

This improves the sealing as a result of the high pressing between the contact faces on the one hand and can compen- sate thermal expansion and vibration, without increased leakage, on the other hand.

The sealing behaviour can be additionally improved by the inclusion of an additional insulating layer between the outer and the inner fold.

The folded-seam connection can be produced on a bordering and folding/closing machine of the type GORELOCKER BETA 3 of the firm Spiro International S. A., CH-3178 Boesingen (cf.

Brochure 05.1998), by means of suitable rollers.

This takes place in that in a first method step a flange- like double fold is produced at a first pipe end, in a sec- ond method step a folding tab with an internal diameter larger than the flange-like double fold is formed on the other pipe end to be joined, in a third method step the folding tab is pushed over the double fold and after that the projecting part of the folding tab is pressed and clamped against the flange-like double fold in an abutting manner, so that the latter is surrounded in a sealed man- ner.

In a device according to the invention which is preferably used, the production of the flange-like double fold at the first pipe end takes place in that in a first method step the first pipe end is put onto a rotating first shaping roller fixed in the axial position on the machine bench, with peripheral contact on the inside of the pipe and said roller, in a second step a second shaping roller likewise rotating is pushed in the tangential plane thereof until it touches the pipe end on the outside so that the latter jointly rotates in synchronism, in a third step the second shaping roller is pushed stepwise in the tangential plane by the width of the double fold against the first shaping roller so that a continuous folding tab is impressed at the pipe end, in a fourth step a lower delivery roller is pushed further in the direction towards the shaping roller in a second plane situated at a lower level than the tan- gential plane by at least twice the thickness of the pipe

material, wherein a lower roller is drawn back under the second shaping roller in synchronism in the opposite direc- tion, so that the folding tab is closed and a flange-like double fold is formed.

A device which is particularly suitable for producing a flange-like double fold is characterized in that a dis- placeable lower roller is constructed in the form of a hol- low shaft, a drive shaft carrying a shaping roller fixed in the axial position thereof is provided in the interior of the hollow shaft, the delivery roller is constructed in the form of a hollow shaft, a drive shaft carrying an upper displaceable shaping roller is provided in the interior of this hollow shaft, the delivery roller and the shaping roller are arranged in slides so as to be displaceable in synchronism, and in addition the two rollers are arranged in a slide likewise displaceable against the axially fixed shaping roller and the displaceable shaping roller.-This allows a particularly economic mode of operation.

The shaping roller arranged displaceably and the lower de- livery roller situated thereunder are guided in a particu- larly precise and stable manner if they are mounted in a slide provided with linear ball bearings.

A very simple possibility of displacement for the further slides, which carry the lower delivery roller likewise dis- placeable in turn and a lower shaping roller, is achieved by lateral guide plates.

The desired linear displacements of the slides are perform- ed by hydraulic cylinders, which makes a highly compact and advantageous design of the device.

A further advantage consists in the embodiment of a desired synchronous running of the slide, which is made possible by hydraulic components which are likewise available commer- cially.

The drive shafts of the driven rollers are driven in a highly space-saving manner by way of universal-joint shafts and hydraulic motors and are supplied by a central hydrau- lic unit and are set and regulated by components known per se to a peripheral synchronism, i. e. to the same peripheral speed of the rollers.

Embodiments of the invention are explained below with ref- erence to drawings, in which Fig. 1 shows a typical connection in ventilation tech- nology ; two spiral pipes arranged at a right an- gle to each other being connected to each other by means of segment curves and folded-seam con- nections, Fig. 2 shows a folded-seam connection according to Fig.

1 in an enlarged sectional illustration, Figs. 3 to 6 show the individual method steps for pro- ducing an internal flange-like double fold ac- cording to Fig. 2, Fig. 7 shows the joining of a folded-seam connection, Fig. 8 shows the form fitting connection of the folded- seam connection of Fig. 7 by folding over the folding tab,

Fig. 9 shows a preferred device for producing a flange- like double fold, in a partial sectional illus- tration, Fig. 10 is a sectional illustration through the drive shaft on the left-hand side, as viewed in a di- rection at a right angle, and Fig. 11 is a plan view of the device according to Fig. 9 from above.

Fig. 1 shows coiled pipes of plated metal sheet S1 and S2 which are generally known as"spiral pipes"and which are connected to each other by way of segment bends s2 to s5.

The segment bends s2 to s5 are connected to the pipes S1 and S2 by way of conventional detachable connections V. The connection bends s2 to s5 have beads W which are used as for reinforcement and also as limit stop. The actual folded-seam connections according to the invention are des- ignated A; the median line of the pipe connection is desig- nated m and corresponds to the neutral thread.

The folded-seam connection A is shown in an enlarged sec- tional illustration in Fig. 2. The middle segment bends s3 and s4 with the first pipe end X and the second pipe end Y are shown here. Offsets 5 in the form of constrictions are provided here. The pipe end X terminates at a flange-like double fold 1, with its flange parts la and 1b which to- gether form a flange collar. An air gap 3, which acts inter alia as an expansion joint for the segment s3 and at the same time exerts a springing action upon the outer sur- rounding double fold 2, is formed between the flange parts la and lb.

The surrounding double fold 2 adjoins the outer region of the flange parts la and 1b and the bend Ic on the outside with positive locking. Even if the metal sheet of the dou- ble folds displays irregularities, the springing connection illustrated results in contact points which extend more or less concentrically over parts la to lc and at least act as a labyrinth seal.

The connection of the inner flange, i. e. the double fold 1, to the surrounding double fold 2 is made in a manner known per se on a folding/closing machine, for example of the type GORELOCKER BETA 3.

Figs. 3 to 6 show the production of the flange-like double- fold 1. The moulded part or pipe segment to be processed is designated 6 and rests on a support face 29.

In accordance with the method, as shown in Fig. 3, in a first step the pipe end of the segment 6 is turned inside out over a rotating shaping roller 20 and a lower roller 21 which is situated thereunder and which is in the form of a hollow shaft and has a corresponding central lower cavity H which is considerably larger than is necessary for driving the roller 21 without contact.-An adjacent shaping roller 10 and a lower delivery roller 11 are in the rest position.

It is clear from Fig. 4 that the two rollers 10 and 11 have been pushed into the moulded part 6 by a path ao until it is touched by the shaping roller 10 which in the meantime has likewise been set in rotation. As a result of the fric- tion of the external periphery of the roller 10 on the moulded part 6 the latter likewise starts to rotate.-Mutu- ally parallel tangential planes E1 and E2, which character-

ize the possible displacement paths of the rollers 10 and 11, are indicated.

As a result of a stepwise further movement of the rotating shaping roller 11 as far as the end of the path ai, a fold- ing tab 4, which extends over the entire periphery of the underside of the moulded part 6, is formed on the moulded part 6. See Fig. 5.

Whilst the moulded part 6 continues to rotate, as shown in Fig. 6, the lower delivery roller 11 is likewise advanced by the path a2, but in the plane E2, so that the double fold 1 indicated is formed on the moulded part 6. This dis- placement path is possible since the rollers 11 and 21 have cavities H. The synchronization of the movement of the two rollers 11 and 21 results in the formation of a fold accu- rate to shape, without the flange parts being flattened or upset on the rollers.

The moulded part 6 with the flange-like double fold at the end thereof can be removed and further processed by return- ing the rollers to the starting position as shown in Fig.

3.

The assembly of the flange connection may be seen in Figs.

7 and 8, which are provided with the reference numerals al- ready used.-It should be noted that as a result of fold- ing over the folding tab 4 the air gap 3 which is rela- tively large in Fig. 7 is reduced in Fig. 8 to an air gap 3'.-This explains the permanent springing effect observed in practice and thus the sealing inside the folded-seam connection.

The method for producing an internal double fold 1, as de- scribed with reference to Figs. 3 to 6, is transformed into a device which is illustrated in Figs. 9 to 11.

As shown in Fig. 9, the displaceable shaping rollers 10 and the delivery roller 11 are mounted in a slide 37 which is likewise displaceable. The roller 10 is fixed on a drive shaft 12 by an axial fastening 22 designed as a screw con- nection with a wedge. The underside of the drive shaft 12 likewise has a wedge 14 which is coupled to an hydraulic motor 26 by way of a universal joint shaft 24. The shaft 12 is fitted in a slide 37 so as to be rotatably mounted by roller bearings 16a and 16b, the slide 37 in turn being displaceable by an hydraulic cylinder 31 with a piston rod 31'. A further, slightly smaller hydraulic cylinder 30 is situated thereon, fastened by bolts 35, and engages with its piston rods 30'on a pin 33 which is inserted in a slide 38 likewise displaceable. Further roller bearings 18a and 18b, which are arranged concentrically to the shaft 12 and which are mounted with their inner rings on the deliv- ery roller 11 designed on the underside as a hollow shaft, are arranged in the slide 38. In addition, a cylindrical cavity 39 is present between the shaft 12 and the bore in the delivery roller 11. The housing of the roller bearings 18a, 18b is designated 18' ; the clearance required for the free rotation of the rollers 10 and 11 is designated L.

The opposite pair of rollers, namely the shaping roller 20 and the lower roller 21 adjacent over the clearance L, are designed in a similar manner. In contrast to the previous one, however, a shaping-roller block 44 is provided which is fixed to the machine, i. e. immovable. The roller 21 is fixed on a drive shaft 13 by an axial fastening 23 designed

as a screw connection with a wedge. The drive shaft 13 likewise has a wedge 14 underneath which is coupled to an hydraulic motor 27 by way of a universal joint shaft 25.

The shaft 13 is fitted in the block 44 so as to be rotata- bly mounted by roller bearings 17a and 17b. An hydraulic cylinder 32 is situated thereon, fastened by bolts 36, and engages with its piston rods 32'on a pin 34 which is in- serted in a displaceable slide 45. Roller bearings 19a and 19b, which are arranged concentrically to the shaft 13 and which are mounted with their inner rings on the displace- able roller 21 designed on the underside as a hollow shaft, are arranged in the slide 45. The housing of the roller bearings 19a, 19b is designated 19' ; the cylindrical air space present is designated 40. The moulded part 6 to be processed rests on a support and sliding face on the ma- chine bench 29.

The hydraulic components are fed through a central hydrau- lic unit 50 which is housed in the machine stand and from which hydraulic lines 49 extend to the control and driving members.

The illustration of the section A-A through the shaft 12 in Fig. 9 is shown in Fig. 10 and shows the components de- scribed above and, in addition, two linear ball bearings 41,42, the bushes 41'and 42'of which are inserted in the slide 37. A fastening frame 46 in the machine stand with its welding seams 47 can be seen at the side.

Threaded bores 28, which are used for fastening lateral plates and guides 38'of the slide 38 screwed thereabove and likewise displaceable, are provided in the displaceable slide 37. The displaceable part 18"is at the same time

the housing of the roller bearings 18a, 18b.-The slide 45 shown in Fig. 9 is designed in a similar manner.

The individual parts may be seen once again in the plan view according to Fig. 11, and likewise the guide plates 45', previously not designated, and in addition adjustment screws 48 which are used for bounding the path and setting the displacement path of the slides 38 and 45.

The mode of operation of the device for the economic pro- duction of high-quality and reproducible flange-like double folds is easy to reconstruct with the aid of Figs. 3 to 6 and the accompanying description. Further details for de- signs of the device correspond to the machine design ac- cording to EP-A1-0 998 997.

Adaptation of the distances between the rollers 10,11 and 20,21 takes place in the simplest manner by intermediate rings (not shown) and affects the clearance L accordingly.

In this way, the ductility and the springing behaviour of the flange-like double fold can be affected and optimized in a simple manner, which also jointly determines the serv- ice life of the rollers and the wear on the moulded part 6.

In a practical test on folded-seam connections according to the invention, leakage losses have been measured which were at least 20% better than the provisions according to EUROVENT, Class C. The double folds produced and tested had typical fold widths of from 4, 0 to 12,0 mm, measured on the internal double fold.

A pre-condition for this, however, is a trouble-free pro- duction of the folds, which is possible in a reproducible

manner by the device according to the subject of the inven- tion.

These high-quality folded-seam connections are particularly important in processing and clean-room technology etc., in which non-defined leakages can lead to hazards of all types. In this case too, the subject of the invention al- lows the use of inexpensive pipe segments in connection with well known coiled pipes (spiral pipes) instead of, as generally used, expensive welded pipes with corresponding connections and/or connections sealed off by resilient in- lays.-In addition, the maintenance required for units of this type is reduced, since metal seals are not subject to wear as a rule.

With respect to further development the device can be auto- mated, in that for example folded-seam connections produced are stored in all their machine settings and control pa- rameters and are then utilized for mass production.-For this purpose,"teaching programmes"which are already known in principle can be used in conjunction with measurement pick-ups (sensors etc.).

L i s t o f R e f e r e n c e s 1 flange-like double fold la, 1b flange parts/flange collars lc curve (radius) between la and 1b 2 surrounding double fold 3,3'air gap 4 folding tab (preliminary stage to 2) 5 offset/constriction 6 moulded part/pipe segment (sheet metal) 10 upper displaceable shaping roller 11 delivery roller (below); hollow shaft 12 to 13 drive shafts 14 to 15 splines (driving means) 16a to 17b lower roller bearings for 12 and 13 18a, 18b roller bearings for 10 18'housings of 18a, 18b 19a, 19b roller bearings for 21 19'housings of 19a, 19b 18'', 19''sliding shoes 20 axially fixed shaping roller 21 displaceable lower roller; hollow shaft) 22,23 axial fastenings (screw connection; wedge) 24,25 universal-joint shafts

26,27 hydraulic motors 28 threaded bores in 37 29 support face/machine bench 30 to 32 hydraulic cylinders 30'to 32'piston rods of 30 to 32 33,34 pins (power transmission) 35,36 coupling bolts 35', 36'threaded bores for 35 and 36 37 displaceable slide for 10 and 11 38 displaceable slide for 11/lateral plate 38'guide plate (above); bearing shield 39,40 cylindrical cavities (air) 41,42 linear ball bearings/ball-bearing guides (shafts) 42', 43'ball-bearing ring/ball-bearing cage 44 shaping-roller block (fixed) 45 displaceable slide for 21/lateral plate 45'guide plate (above) 46 fastening frame 47 welding seams (fillet welds) 48 adjustment screws/end stops 49 hydraulic lines 50 hydraulic unit A folded-seam connection ao to a2 displacement paths

E1, E2 tangential planes H cavities L air gap/clearance m median line/neutral thread Sl, S2 straight pipe sections (spiral pipe) s2 to s5 segment pipe X first pipe end Y second pipe end V pipe connection (conventional) W bead