EP3590618B1 - Method for manufacturing a cladding tube, cladding tube produced by the method, and telescopic tube comprising such a cladding tube - Google Patents

Description

The invention relates to a method for producing a cladding tube from sheet metal. In this case, the cladding tube has a protrusion pointing into the interior of the cladding tube, the protrusion acting as an anti-twist device for an insertion tube, the sheet metal having a first longitudinal edge and a second longitudinal edge, the first and second longitudinal edges being parallel to the longitudinal alignment of the sheet metal, wherein the first longitudinal edge is bent into a first envelope with a first envelope edge and the second longitudinal edge is bent into a second envelope with a second envelope edge, the sheet metal being bent in such a way that the first envelope and the second envelope lie within the cladding tube, the first The envelope edge and the second envelope edge are in direct contact, the first envelope edge and the second envelope edge being welded to one another so that the first envelope and the second envelope together form the projection, the longitudinal edges being bent over by 180 ° so that the envelopes are each at the later inside of the cladding tube attached en, wherein the longitudinal edges are bent in such a way that, after the sheet metal has been formed into the cladding tube and before the two folded edges have been welded, the end face facing the other edge, which extends radially with respect to the axis of the cladding tube and with a first Radius merges into the outer circumference of the cladding tube, and with a second radius merges into the inner circumference of the cladding tube, at least the first radius being smaller than the sheet metal thickness D of the sheet metal. The edge of the envelope forms the folded edge of the envelope. After bending, it forms the new outer edge of the respective edge, so to speak.

Cladding tubes are used in combination with push-in tubes as telescopic tubes. In this case, an insert tube has an outer diameter which corresponds to the inner diameter of the cladding tube, so that the insert tube can be inserted into the cladding tube and is displaceable relative to it. The length of the telescopic tube formed in this way is adjustable and can be expanded by further cladding tubes, the previous cladding tube forming an insertion tube for the surrounding cladding tube.

A method of making a cooling tube is from, among others DE 2 210 006 A1 known. Process of this type used for the production of tubular telescopic rods. However, the flow-forming method used to provide an anti-rotation device for the cladding tube requires an additional manufacturing step and, due to the local material weakening, leads to a lower stability of the cladding tube.

A method according to the preamble of independent claim 1 is from WO2018 / 056886 A1 known.

The object of the present invention is to provide a method for producing a cladding tube with an anti-rotation device from a sheet metal, which is easy to manufacture and has a high level of stability.

The object is achieved by the features of independent claim 1. Accordingly, in a method according to the preamble of independent claim 1, there is an inventive solution to the object when the edges are welded together by means of inductive high-frequency welding, the first radius R1 being smaller than half of the sheet metal thickness D and the second radius R2 is greater than the first radius R1, with a groove being rolled into the sheet metal before or during the bending of the longitudinal edges in the area of the later folded edge, in particular in the area of the first radius R1, and / or the longitudinal edge is thinned to a smaller thickness up to the later folded edge, the smaller thickness of the thinned longitudinal edge being between 50% and 80% of the sheet metal thickness D.

By providing an anti-twist device through the inwardly bent envelopes, an additional production step of flow molding or the use of an additional strip of material for this purpose can be dispensed with, and production can be simplified. In addition, by welding the first folded edge to the second folded edge, a thicker and more stable weld can be provided than through the direct welding of two longitudinal edges.

The sheet is preferably a pure metal sheet without a plastic coating or the like. In any case, the base material of the sheet metal is welded. The sheet metal is more preferably a steel sheet.

Together with the inward bending of the envelopes, the HF welding process can achieve a particularly high surface quality and weld stability.

Advantageous embodiments of the present invention are the subject of the subclaims.

According to the invention, the first radius is smaller than half the sheet thickness D, preferably less than 10% of the sheet thickness D, particularly preferably less than 2% of the sheet thickness, and very particularly preferably the first radius is so small that a sharp one at this point Edge exists. According to the invention, the second radius is larger than the first radius and is preferably more than 30% of the sheet metal thickness D. To achieve such a geometry with a particularly small first radius and to be able to bend the longitudinal edges by 180 ° with the least possible damage, the Before or during the bending of the longitudinal edges, a groove is rolled in the sheet metal in the area of the later folded edge, in particular in the area of the first radius, the groove being made in the side of the sheet metal opposite the later first radius, and / or the longitudinal edge is made up to the later Edge of the cover thinned to a smaller thickness. The smaller thickness of the thinned longitudinal edge is between 50% and 80% of the sheet metal thickness D. Furthermore, the front side preferably runs straight between the first radius and the second radius, so that the front sides of the two folded edges can be at least partially brought into flat contact during welding.

As already mentioned above, this has the advantage that the longitudinal edges can be bent over by 180 ° with as little damage as possible. In addition, it is thereby possible to upset the edges of the envelope with sharp edges before welding on the outer circumference and then to weld the edges of the envelope without breaking.

According to a further particularly preferred embodiment of the present invention, the step of high-frequency welding comprises the use of an impedance core. In particular, a rod made of ferritic material is held in the area of the induction coil in the interior of the cladding tube, it being possible for the heat input to be concentrated further on the edges to be welded.

According to a further embodiment of the present invention, the production of the cladding tube includes an additional step of reworking a weld seam formed by the welding, so that the weld seam has neither an elevated seam nor an arched seam. This ensures a particularly high surface quality in the area of the weld seam. During welding, the folded edges are preferably pressed against one another in such a way that a weld seam protrusion is created on the outer circumference of the cladding tube, which is planed off immediately after welding while it is still hot in order to achieve a high surface quality. The elevation of the weld seam is preferably planed in the line at a distance of 500 mm to 700 mm from the welding point. A particularly economical production is achieved as a result. This embodiment also contributes to rapid production of the cladding tube. By the The above-described upsetting of the edges of the fold before the welding process do not have to be so strongly compressed or upset during welding in order to achieve a clean weld seam on the outer circumference and, after planing off the weld seam, a high surface quality. This also reduces the risk of cracking.

According to an alternative embodiment of the present invention, the width of a weld seam formed by the welding is at least a single thickness of the sheet metal, but is at most three times the thickness of the sheet metal.

According to a further preferred embodiment of the present invention, the first and second folds are bent through 180 °, the first and second folds resting against the inside of the cladding tube. As a result, the rigidity and the geometrical moment of inertia of the cladding tube can be increased further. In particular, through the electrical contact between the envelopes and the cladding tube, the effect of the eddy currents and thus of the heat input on the edges to be welded can be improved by the high-frequency welding step.

More preferably, a first width of the first envelope perpendicular to the longitudinal extent of the cladding tube and a second width of the second envelope perpendicular to the longitudinal extent of the cladding tube are each at least twice the sheet metal thickness D of the sheet metal and preferably at most four times the sheet metal thickness D of the sheet metal. As a result, in particular the region of the carrier profile directly adjoining the weld seam can be reinforced.

According to a further preferred embodiment, a weld seam formed by the welding does not have any excess root relative to the projection. This ensures that an insertion tube can be inserted into the cladding tube without any problems. The absence of a root elevation can in particular be achieved in that the inner second radius of the edge of the fold is greater than the first radius located on the outer circumference,

The present invention also provides a cladding tube which is produced from sheet metal by a method according to one of the preceding claims.

In addition, the present invention provides a telescopic tube with a cladding tube and a push-in tube, the push-in tube being insertable into the cladding tube and in relation to it Cladding tube is displaceable, wherein the insertion tube has at least one longitudinally extending groove along an outer side of the insertion tube, wherein the cladding tube has at least one longitudinally extending projection along an inner side of the cladding tube, wherein the groove and the projection cooperate in the manner of a rotation lock, the cladding tube through a method according to any one of the preceding claims is made from sheet metal.

Embodiments of the present invention are explained in more detail below with reference to drawings.

Figur 1:

einen Querschnitt eines durch ein erfindungsgemäßes Verfahren hergestellten Hüllrohrs 1.

Figur 2:

einen detaillierten Querschnitt einer Schweißnaht 2 eines durch ein erfindungsgemäßes Verfahren hergestellten Hüllrohrs 1.

Figur 3:

ein erfindungsgemäßes Teleskoprohr 20 mit einem erfindungsgemäßen Hüllrohr1 und einem Einschubrohr 18,

Figur 4:

eine Detailansicht eines der beiden Längsränder im Querschnitt vor dem Umbiegen mit einer eingewalzten Rille,

Figur 5:

die Detailansicht aus Figur 4 mit einem ausgedünnten Randbereich anstatt einer eingewalzten Rille,

Figur 6:

die Detailansicht aus Figur 5 nach dem Umbiegen des Längsrands,

Figur 7:

die Detailansicht aus Figur 6 nach dem Verscheißen der Umschlagkanten, und

Figur 8:

die Detailansicht aus Figur 7 nach dem Abhobeln der Schweißnahtüberhöhung.

Show it:

Figure 1:

a cross section of a cladding tube 1 produced by a method according to the invention.

Figure 2:

a detailed cross section of a weld seam 2 of a cladding tube 1 produced by a method according to the invention.

Figure 3:

a telescopic tube 20 according to the invention with a cladding tube 1 according to the invention and an insertion tube 18,

Figure 4:

a detailed view of one of the two longitudinal edges in cross section before bending with a rolled-in groove,

Figure 5:

the detailed view Figure 4 with a thinned edge area instead of a rolled-in groove,

Figure 6:

the detailed view Figure 5 after bending the long edge,

Figure 7:

the detailed view Figure 6 after the cover edges have been scoured, and

Figure 8:

the detailed view Figure 7 after planing off the weld seam elevation.

This in Figure 1 The cladding tube 1 shown is formed from a sheet metal 10, in particular a sheet metal strip, the sheet metal 10 having a first envelope 3 bent by 180 ° with a first envelope edge 5 and a second envelope 4 bent by 180 ° with a second envelope edge 6. By bending parallel to the longitudinal extension of the sheet metal 10, and thus parallel to the first longitudinal edge 7 and the second longitudinal edge 8, the sheet metal 10 is brought into the shape of the cladding tube 1, the first folded edge 5 and the second folded edge 6 of the formed sheet 10 are against each other. The area of the sheet metal 10 lying between the first folded edge 5 and the second folded edge 6 thus forms a cladding sheet 11 of the cladding tube 1. The envelopes 3 and 4 are bent inward in such a way that the first longitudinal edge 7 and the second longitudinal edge 8 inside the cladding tube 1 lie. The bending and the means for its implementation are already known and are not described in detail here.

The envelopes 3 and 4 are pressed firmly against the cladding sheet 11 of the cladding tube 1 by the 180 ° bending, so that the envelopes 3 and 4 form a double-walled area of the cladding tube 1 with the cladding sheet 11. The first envelope 3 has a first width 13 perpendicular to the longitudinal extension of the cladding tube 1 and the second envelope 4 has a second width 14 perpendicular to the longitudinal extension of the cladding tube 1, the first width 13 and the second width 14 each being at least twice a thickness of the Sheet 10.

In the high-frequency welding step, the cladding tube 1 is continuously passed through at least one induction coil through which alternating current flows, with a gap between the first folded edge 5 and the second folded edge 6 which, after passing through the induction coil, is caused by pressing the first folded edge 5 and the second folded edge 6 together is closed. In this case, the cladding tube 1 is pressed together by profile rollers, so that the material of the folded edges 5 and 6, which is heated to a welding temperature, is welded together to form a weld seam 2.

As in Figure 2 As can be seen, the width 15 of the weld seam 2 is approximately twice the thickness of the sheet metal 10, so that the edges 5 and 6 are welded to one another over their entire thickness, but the envelopes 3 and 4 themselves are essentially not welded to the cladding sheet 11 are welded. The means for performing high-frequency welding are already known and will not be described in more detail.

As a result of the welding, the first envelope 3 and the second envelope 4 together form a projection 9 which protrudes into the interior 12 of the cladding tube 1 and acts as an anti-twist device for an insertion tube 20. The root 17 of the weld seam 2 does not protrude beyond the projection 9 formed by the envelopes 3 and 4, so that the weld seam 2 does not have any root elevation. A subsequent step of mechanical post-processing of the weld seam 2 by a step of scraping or planing, the surface quality of the cladding tube is further improved, so that a seam elevation 16 is removed.

As in Figure 3 As shown, the cladding tube 1 forms a telescopic tube 20 together with an insertion tube 18. The projection 9 of the cladding tube 1 engages in a groove 19 located on the outside of the insertion tube 18, so that the projection 9 acts as a rotation lock for the insertion tube 18. The push-in tube 18 can be inserted into the cladding tube 1 and is displaceable with respect to it.

As Figure 4 shows, before or during the bending of the longitudinal edges in the sheet metal preferably a groove 21 is rolled in the area of the later edge of the fold in order to facilitate further deformation and to reduce the risk of cracks. As an alternative or in addition, the longitudinal edge is thinned to a smaller thickness until the later edge of the envelope, as is the case Figure 5 indicates. The smaller thickness is preferably between 50% and 80% of the original sheet metal thickness D of the sheet metal 10. The thinned edge area is then reshaped as shown in FIG Figure 6 is shown. After the sheet metal has been formed into the cladding tube and before the two cladding edges are welded together, the resulting edge 5 has an end face facing the other edge 6, which extends radially in relation to the axis of the cladding tube and with a first radius R1 into the outer circumference of the Cladding tube, and merges with a second radius R2 into the inner circumference of the cladding tube, the first radius R1 being significantly smaller than the sheet metal thickness D of the sheet metal and the second radius R2. In the ideal case, the turning edge is upset during the deformation in such a way that the first radius R1 is particularly small and essentially forms a sharp edge. The end face facing the other folded edge runs essentially straight between the first radius R1 and the second radius R2, so that the two folded edges can be at least partially brought into flat contact during welding, which makes the welding process much easier and a relatively low contact pressure during welding requires. This can reduce the risk of cracks.

As Figure 7 shows, when welding on the outer circumference, a certain weld seam elevation 16 arises, which is also desired, since this weld seam elevation 16, like Figure 8 shows, in a planing step immediately following the welding process, planing can be carried out while still hot in order to achieve a particularly high level of dimensional accuracy and surface quality. A certain elevation 17 also arises on the inner circumference, but due to the relatively large second radius R2 it does not protrude beyond the projection 9 and therefore does not require any further treatment.

Claims (11)

1. A method for manufacturing a sheathing tube (1) from a metal sheet (10), the sheathing tube (1) having a projection (9) facing the interior (12) of the sheathing tube (1), wherein the projection (9) acts as an anti-rotation element for an insertion tube (18), the metal sheet (10) has a first longitudinal edge (7) and a second longitudinal edge (8), wherein the first (7) and second (8) longitudinal edges are parallel to the longitudinal orientation of the metal sheet (10), the first longitudinal edge (7) is bent to a first seam (3) with a first seam edge (5) and the second longitudinal edge (8) is bent to a second seam (4) with a second seam edge (6), wherein the metal sheet (10) is bent so that the first seam (3) and the second seam (4) are located inside the sheathing tube (1), the first seam edge (5) and the second seam edge (6) being in direct contact, wherein the first seam edge (5) and the second seam edge (6) are welded together so that the first seam (3) and the second seam (4) cooperate to form the projection (9), the longitudinal edges (7, 8) are bent through 180° so that the seams (3, 4) each abut against the side which is to become the inner side of the sheathing tube (1), the longitudinal edges (7, 8) are bent over so that after the metal sheet (10) has been formed into the sheathing tube and before the two seam edges (5, 6) are welded together, the seam edge (5, 6) has an end face facing the respective other seam edge (5, 6) which runs radially with respect to the axis of the sheathing tube (1) and merges with a first radius R1 into the outer circumference of the sheathing tube, and with a second radius R2 into the inner circumference of the sheathing tube, at least the first radius R1 being smaller than the sheet thickness D of the metal sheet (10), characterized in that the seam edges (5, 6) are welded together by means of inductive high-frequency welding, the first radius R1 being smaller than half the sheet thickness D and the second radius R2 being larger than the first radius R1, and in that a notch (21) is rolled into the metal sheet (10) in the region of the intended seam edge (5, 6), in particular in the region of the first radius R1, before or during the bending of the longitudinal edges (7, 8), and/or the longitudinal edge (7, 8) is thinned to a smaller thickness up to the intended seam edge (5, 6), the smaller thickness of the thinned longitudinal edge being between 50% and 80% of the sheet thickness D.
2. The method according to claim 1, characterized in that the first radius R1 is smaller than 10% of the sheet thickness D.
3. The method according to claim 1, characterized in that the second radius R2 is larger than 30% of the sheet thickness D.
4. The method according to any one of claims 7 to 3, characterized in that the end face extends linearly between the first radius R1 and the second radius R2, so that during welding the end faces of the two seam edges (5, 7) can be brought at least partially into surface contact.
5. The method according to claim 1, characterized in that the step of high frequency welding comprises using an impeder core.
6. The method according to any one of claims 1 to 5, characterized in that the seam edges (5, 6) are pressed together during welding so that a weld reinforcement (16) is produced on the outer circumference of the sheathing tube (1) which is planed off while still warm immediately after welding.
7. The method according to claim 6, characterized in that the planing off the weld reinforcement (16) is carried out following a line at a distance of 500 mm to 700 mm from the welding spot.
8. The method according to claim 1, characterized in that a first width (13) of the first seam (3) perpendicular to the longitudinal extension of the sheathing tube (1) and a second width (14) of the second seam (4) perpendicular to the longitudinal extension of the sheathing tube (1) are each at least twice the sheet thickness D of the metal sheet (10) and preferably at most four times the sheet thickness D of the metal sheet (10).
9. The method according to any one of claims 1 to 4, characterized in that a weld (2) formed by the welding has no root reinforcement (17) relative to the protrusion (9).
10. A sheathing tube (1) manufactured from a metal sheet (10), the sheathing tube (1) having a projection (9), wherein the projection (9) acts as an anti-rotation element for an insertion tube (18), the metal sheet (10) has a first longitudinal edge (7) and a second longitudinal edge (8), the first longitudinal edge (7) is bent to a first seam (3) with a first seam edge (5) and the second longitudinal edge (8) is bent to a second seam (4) with a second seam edge (6), wherein the metal sheet (10) is bent so that the first seam (3) and the second seam (4) are located inside the sheathing tube (1), the first seam edge (5) and the second seam edge (6) being in direct contact, wherein the first seam edge (5) and the second seam edge (6) are welded together so that the first seam (3) and the second seam (4) cooperate to form the projection (9), characterized in that the sheathing tube (1) is manufactured using a method according to any one of claims 1 to 9.
11. A telescopic tube (20) having a sheathing tube (1) and an insertion tube (18), the insertion tube (18) being insertable into the sheathing tube (1) and being displaceable relative to the sheathing tube (1), wherein the insertion tube (18) has at least one groove (19) extending longitudinally along an outer side of the insertion tube (18), the sheathing tube (1) has at least one projection (9) running longitudinally along an inner side of the sheathing tube (1), wherein the groove (19) and the projection (9) interact to form an anti-rotation device, characterized in that the sheathing tube (1) is formed by a sheathing tube according to claim 10.

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