METHOD AND MEANS FOR ESTABLISHING A DRAWPROOF INSERTION JOINT BETWEEN THIN WALLED PIPES

Abstract: Pipe joints of the insertion socket type are widely used in drainage installations of stainless plate pipes, but not where internal overpressures may occur, because the pipe joints should then be secured against retraction. The pipes may be joined by welding or be provided with welded flanges bolted joints, but such works are expensive to carry out in situ. According to the invention a retraction blocking is established by introducing onto the smooth pipe end (6) a flange element (14) and then working out, by simple tool means, a number of outwardly projecting bulgings (16) on the pipe wall, such that the flange element (14) will then be blocked against retraction from the pipe. An opposed flange part (18, 20) has been mounted for abutting engagement with the rear end of the socked widening (8, 10) on the other pipe, and after insertion of the smooth pipe end (6) into the socket (8) the flange members (14, 20) may then be interconnected, e.g. by means of drawbolts or a bayonet lock. Alternatively, connector muff shells (A, B) may be placed over the joint and held together by a surrounding ring member (E).

Description: Method and means for establishing a draw/proof insertion joint between thin walled pipes. The present invention relates to a pipe joint of the insertion socket type, i.e. where one of the pipes is preshaped with a widened socket portion which can receive a smooth end portion of the other pipe, op¬ tionally a resulting end portion after a shortcutting of this other pipe in situ. It is a reasonably simple prob¬ lem to provide a sealing between such pipe ends, as in the preshaped socket there may be mounted a sealing ring for radial sealing against the inserted smooth pipe end. What is more problematic is that while such an insertion joint may well be tight under ambient pressure condi¬ tions both outside and inside the pipes, an internal overpressure may give rise to axial forces seeking to separate the pipe joint. Thus, when overpressure situations are anticipated, this simple type of pipe joint is not used, but replaced by more expensive joints, either welding joints or joints requiring working of thick walled pipes or join¬ ing elements, e.g. cutting or threading. The invention concentrates specifically on thin walled pipes, primarily pipes made of stainless steel plate material. Pipes of this type are used increasingly in drainage systems, in which it will normally be suf¬ ficient to use pure insertion joints, which should not resist noticeable axial forces. It has been found, how¬ ever, that even in this field there may be installations in which an overpressure has to be anticipated, such that it will be highly desirable that the insertion joints between the applied thin walled pipes are secured against separation by occurring axial separation forces. Apart from quite elementary and expensive possibi¬ lities for fixed joints between the ends of thin plate pipes, viz. a direct welding together and a bolting together of end flanges secured by welding, there is not from practice known any usable technique for a 'blocked insertion joint' made in situ between the ends of thin walled pipes, at least not when it is a condition that one of the pipe ends may have to be a smooth pipe end, cut in situ, that is generally as a simple, smooth pipe end, whether cut in situ or used without being shor¬ tened. Thus, in connection with the invention it has been recognized that there may well be a need of providing a drawproof joint between insertion joined, thin walled pipes, without instead choosing more expensive solutions involving conventional joints. It will also be required that the joined pipes be mutually turnable, as on many drainage elements there are integrated branch pipes that should be mountable with correct orientations. For this reason joints such as bolt joints between welded flange parts will be un¬ suitable, apart from such a solution being far too ex¬ pensive. In DK-B-150,952 and 163,375 there are suggested joints referring to butt joints with the use of flange carrying bushes to be inserted into the pipe ends to be joined, but for the invention it is not desired to use butt joints, particularly not with the use of elements placed inside the pipes, as such a mounting will involve a restriction of the cross sectional flow area. From DE-B-1,037,219 it is known that pipes of glass or ceramics can be shaped with end portions having in¬ creasing outer diameter towards the ends, such that at butt joints it is possible to establish holding connec¬ tions between the rear sides of these preshaped widen- ings on the pipe ends. This, however, is remote from the present invention, where it is presupposed that inser¬ tion joints are used and that in each joint one of the pipes may have a simply cut end 7 without any. possibility of prefabricated widenings. For the invention it is a main consideration that on the mounting site it will be reasonably easy to form local deformations on the smooth, optionally cut pipe end, such that hereby an axial abutment for a surround¬ ing ring body can be provided; this ring may form a projecting flange member that is suited for axial coupl¬ ing with a corresponding ring flange member placed on the other, socket carrying pipe, axially supported by the widening forming the socket. The deformations to be worked out on the smooth pipe end will not need to be continuously annular, as it may be sufficient that they are provided as a limited number of discrete exterior bulgings, which, in connection with thin walled pipes, are easy to produce by means of a suitable hand tool in such a manner that the pipe wall is not perforated. Where only relatively small axial forces should be re¬ sisted the bulgings may be round beads, but for higher forces it is advantageous to provide bulgings of an oblong shape seen in the peripheral direction; by way of example, a peripheral extension of 5-10 mm per bulging may be sufficient, e.g. with a total bulging length of 10-20 percent of the circumference. On the smooth pipe end the added ring flange should be located spaced so far from the free pipe end that the latter may be brought into a safe radial sealing engage¬ ment with the sealing ring in the socket portion of the other pipe, and then the joint may be locked against axial separation solely by the projecting flange por¬ tions at the meeting pipe ends being interconnected in a drawproof manner. This may be done by means of longi¬ tudinal flange bolts between outwardly projecting, axially widely separated flange portions, but in prac¬ tice it will be preferable to use flange portions lo¬ cated relatively close to each other, this being pos- sible with the use of cup shaped flanges. In that case it will even be possible to join the flanges particular¬ ly easily, viz. by a bayonet locking. It is to be emphasized that a bolt or bayonet con¬ nection between the flanges will not prevent a free mutual turning between the joined pipes, as both of the flange members or at least one of them may be held free¬ ly rotatably on the respective pipe. The flanges should only serve to secure the joint against axial separation, and the joining work will be facilitated in that it is not required to establish a holding between the deforma¬ tions on the smooth pipe end and the flange member sup¬ ported thereby. It will not either be required to work out an axial tightening together of the pipe ends, as the radial sealing will be fully sufficient, and for this reason a bayonet coupling can be fully satisfac¬ tory. It is a preferred possibility that the drawproof connection between the pipe ends be established by means of muff shells, which are inserted laterally over the joint from opposite sides in a manner such that inwardly protruding edge flanges at the free muff ends become located behind the respective widenings on the pipe end portions, these shells being held together by means of an exterior tightening strap or an outer, short locking tube. Hereby it is also possible to establish the dis¬ cussed joints at so-called branch pipes, that is short pipes branched off from the side of a main pipe, e.g. a downlet pipe, and terminated in a widened socket por¬ tion; for this type of pipes there is no possibility of mounting a flange member by axial insertion. In the following the invention is described in more detail with reference to the drawing, in which: Fig. 1 is a perspective view of a pair of pipe ends to be joined in accordance with the invention, Fig. 2 is a longitudinal sectional view of the joined pipe ends, Figs. 3-5 are corresponding sectional views of other embodiments of the joint, fig. 6 is a perspective fractional view illustrat¬ ing a preferred embodiment of the invention, Fig. 7 is a longitudinal sectional view thereof, Fig. 8 is a side view, partly in section, of another embodiment of the invention, Fig. 9 is a longitudinal sectional view of still a further embodiment, Fig. 10 is a sectional view of a modified flange mounting on a pipe socket portion, Fig. 11 is a perspective exploded view of an impor¬ tant embodiment of the invention, and Fig. 12 a sectional view thereof, when assembled. Fig. 1 shows two fully conventional thin sheet pipes 2 and 4, of which the pipe 2 has an originally smooth pipe end 6, while the counter end of the pipe 4 is preshaped with a socket widening 8 and with a local widening 10 thereon for holding an interior sealing ring 12, v/hich, by insertion of the pipe end 6 into the socket 8, provides for full sealing between these parts. Hereafter the problem is only to prevent the thus con¬ ventionally insertion joined pipe ends from being se¬ parated axially by an occurring internal overpressure in the pipe system. The smooth pipe end 6 may be provided with a slightly crimped edge worked out either in the factory or in situ, such that the pipe end is particularly easy to insert into the sealing socket 8, but the pipe end 6 may also be unworked after simple cutting; also in that case it will be possible to insert the pipe end into the sealing socket of the pipe 4. Normally there will be nothing on the smooth pipe end 6 that can prevent this pipe from a retraction or repulsion from the socket portion 8 in response to an inner overpressure i the pipe connection, but according to the invention this is remedied by working, in situ, the smooth pipe end such that outwardly projecting por¬ tions are provided which can support a surrounding flange element 14 in the direction of retraction. Such projecting portions are shown as local deformations 16, which may be produced in situ by means of a suitable hand tool subsequent to the flange element 14 being introduced over the smooth pipe end, optionally upon cutting back the latter. The hand tool may be adapted such that by an introduction at both sides of the pipe wall it will abut the free edge of the pipe, whereby the deformations 16, in a desirable manner, will be located in the same plane normal to the pipe axis. On the opposite pipe 4 has been introduced, already prior to the mounting of that pipe, a flange member 18 having a foremost, exterior flange 20 and a rearmost, interior flange 22, the latter extending to near the surface of the socket portion 8. Hereby, as shown in Fig. 2, this flange member may be displaced forwardly until the flange 22 abuts the rear side of the widening 10 on the portion 8. When the pipe end 6 is inserted into the socket 8 and the flange element 14 is brought to abut the deformations 16, the two flange parts 14 and 20 may be brought to abut each other. It will be under¬ stood that thereafter these parts may be bolted to¬ gether, when they are provided with the required holes, and thereafter the joint will be locked against separa¬ tion. Instead of such a bolting it may be preferred, however, to use the arrangement shown in Figs. 1 and 2, where the flange 20 is provided with fixed, forwardly projecting locking pins 24 adapted for cooperation with keyhole-like locking holes 26 in the flange element 14, as it is hereby possible to establish a bayonet locking between the flanges by a short mutual rotation of these. For increased stiffness the flange element 14 is shaped with a C-profile, the inner free edge of which will abut the deformations 16 with a good holding ef¬ fect. As shown in Fig. 2 these deformations are shaped such that their flanks facing the flange 14 are rela¬ tively steeply projecting, likewise for securing a good holding engagement. The pipe end 6 will be free to be displaced some¬ what further into the socket 8, and it will also be freely rotatable. Normally, there will be no hard axial engagement between the deformations 16 and the flange element, unless there is an overpressure in the pipe system. In the embodiment shown in Fig. 3 the flange parts are designed with a short axial extension and are bolted together by long connector bolts 28. In Fig. 4 they are coupled together directly, by means of short bolts. It is also shown that the pipe end 6 has been worked by providing an exterior groove 30, in which there is in¬ serted an outwardly projecting locking ring 32 forming an abutment for the outer flange element 14. The working may be effected invertedly, i.e. by rolling up an an¬ nular, outwardly projecting rib, which may then serve the same purpose. By an associated full contact with the inner circumference of the flange element 14 very large axial forces can be resisted. The embodiment shown in Fig. 4 could also be an example of an insertion join between plastic pipes, in which the groove 30 could be formed as a low cutting or by a heat deformation. In the embodiment shown in Fig. 5 the flange parts are made of plastics and in such a manner that in being pushed together they will overlap each other in a snap locking area 34 as shown. Such a joint can be arranged so that it is practically impossible to release, unless it is cut into pieces; however, many pipings are laid in the ground and expected to have a long lifetime without being touched, so the joints should not necessarily be adapted for any easy separation. In the embodiment according to Figs. 6 and 7 there is used, between the flange parts, a particular bayonet locking based on the use of the sheet material itself. One of the flange portions is provided with projecting, slightly outwardly bent tongue members 36 which are introduceable into L-shaped locking tracks 38 in the end area of the other flange part, and also the material portion 40 forming the outer limitation of the L-track is slightly outwardly bent. In this manner a safe rota¬ tion stop is provided between the otherwise parallel sheet parts, which will also hereby be anchored against axial separation. This anchoring effect, however, may be improved e.g. by providing for an outwardly bent end portion on the tongue members 36. It will be a still further possibility that the flange part on the smooth pipe end 6 is secured to the pipe by gluing, such that the pipe end itself will not have to be worked. In Fig. 8 it is shown that the flange element 14 on this pipe end may have a cylindrical, optionally slotted portion 44, which, e.g. by means of a surrounding tightening ring, can be pressed against the surface of the pipe 6 for providing a strong and very durable gluing with the use of modern glue materials. In this embodiment, which may also be actual for plastic pipes, the pipe 6 cannot be rotated relative the flange element 14, but the pipes can still be mutually rotated, because the opposite flange part 20 is rotatable rela¬ tive to the pipe 4. Fig. 9 illustrates the modification that the defor¬ mations 16 on the pipe end 6 are worked out in conjunc¬ tion with quite similar deformations in an inner, cylin¬ drical flange portion 46 of the flange element 14, whereby the latter will be totally locked to the pipe 6, though still by a simple craftsmanlike operation without any use of welding. In Fig. 10 it is shown that the flange 20 on the pipe 4 may be prewelded to the outer end of of the socket portion 8; the flange 20 shown here is adapted for use with the flange 14 according to Fig. 1. For stabilizing the joint as shown in Figs. 11 and 12 there is used two opposed halves A and B of a muff pipe made with a foremost inwardly protruding collar C and a corresponding rear collar D. By the insertion of these halves over the joint the inner edge of the collar portions C will reach the pipe 2 just in front of the deformations 16 thereon, while the collar portions D will reach the pipe 4 just behind the socket 8 or - as shown in the sectional view - reach the outside of this socket portion just behind the widening 10 for the seal¬ ing ring 12. This mounting of the halves A and B can be made in a fully loose manner and without difficulties of any kind. For a locking together of the two halves A and B a spanner strap can be laid around these parts, but a preferred solution is to introduce a pipe length E over the joined halves. This pipe should be locked against axial sliding off, and that is easily achievable by using a pipe length prepared with a pair of diametrical¬ ly opposite, inwardly protruding beads or bent tongue portions F, which may be introduced into bayonet locking tracks G in the respective muff halves A and B. Another possibility will be to join the muff halves A and B in a mutually overlapping manner and, for example, displace them axially, mutually, for establish¬ ing a locking engagement without any use of outer span¬ ner or joining means. The halves, when mounted, may well be somewhat axially displaceable, since they shall only prevent the two pipe ends from being separated, and this can be ensured even if the length of the muff pipe A,B is somewhat bigger than the distance between the pipe portions 16/8,10, with which the collars C and D co¬ operate for forming a separation stop. Optionally, the pipes may have outwardly projecting parts, secured by gluing, for cooperation with the muff pipe; such parts may also be spring members for snap locking the single muff halves in their mounted posi¬ tions. The muff halves may be hinged together along a common edge, whereby they can be folded together about the pipes, and instead of surrounding locking ring means it is then possible to use coupling parts at the respec¬ tive opposed, free edges of the muff halves. In principle, the muff halves A and B can be re¬ placed by corresponding parts having a similar length profile for forming monolateral holding bridges between the considered pipe portions 16 and 8,10. These holding bridges should not necessarily be coherent in the peri¬ pheral direction, but it will be appreciated that they can hardly be designed to be more simple than when made of a pair of pipe shells.

Claims: C L A I M S : 1. A method of establishing an insertion pipe joint between thin walled pipes, whereby one pipe is preshaped with a widened socket end portion, which can receive a smooth end portion of the other pipe and is provided with an interior sealing ring for sealing radially against the inserted smooth pipe end, by which method the respective pipe end portions are provided with in¬ terlockable flange means, which are coupled together for counteracting an axial separation of the pipe joint, characterized in that, preferably in situ and optionally after shortening of the smooth pipe end, a flange part (14) is mounted on the smooth pipe end in a non-welded manner such that this flange part is blocked against retraction from the smooth pipe end and is connectable with a corresponding flange part on the first pipe, for example prewelded thereto or placed behind an outwardly projecting portion of the socket widening on this pipe, in such a manner that the desired separation stop can be established, the relevant coupling together being ef¬ fected as a final step. 2. A method according to claim 1, characterized in that the flange part (14) on the smooth pipe end is mounted by first introducing it loosely on the pipe and then working out in the pipe wall, somewhat spaced from the end edge, an annular, continuous or preferably dis¬ continuous row of projections by deforming the pipe wall, sufficiently to thereby block the flange part against retraction from the pipe end. 3. A method according to claim 1, characterized in that at least one of the flange parts is left in ro¬ tatable connection with its associated pipe and that the flange parts are joined by a bayonet coupling in being rotated mutually. 4. A method according to claim 1, characterized in that the smooth pipe end is worked for forming projec¬ tions thereon, for example by gluing outwardly project¬ ing parts thereto or by pressing out local bulges or short beads therein, and that for the joining flange means use is made of an axially split muff pipe member, which, at its opposite ends, is rigidly provided with the respective flange parts, shaped as inwardly protrud¬ ing end collars, which are brought to their respective mounting positions by lateral insertion of the muff pipe parts, the joint being stabilized by anchoring together the mounted muff pipe parts. 5. A method according to claim 1, whereby the joint is stabilized by axial introduction of an outer holding sleeve over the mounted muff pipe parts. 6. A pipe joining set for use with a joining method according to claim 1, characterized in comprising the said flange parts and tightening means, respectively the said axially split muff pipe parts having rigid flange portions and means for holding these muff parts together about the pipe joint.

Inventors: SKIBILD JOHANNES BLUECHER, SKIBILD, JOHANNES, BLUECHER
Applicants: BLUECHER JOHANNES SKIBILD, JOHANNES BLUECHER SKIBILD, METAL A/S
Application year: 1992
Main classification: F16L21
IPC codes: F16L21, F16L37