Metal bellows and method for manufacturing a metal bellows

Abstract

Metal bellows (10), with a bellows wall (16) extending around a longitudinal axis (12) and enclosing a bellows interior space (14), wherein the bellows wall (16) has inner folds (18) and outer folds (20) which are connected to each other via wall flanks (22), wherein the inner folds (18) and the outer folds (20) are shaped such that they each enclose an annular space (24, 25), characterized in that the wall flanks (22), the inner folds (18) and the outer folds (20) are formed integrally together, wherein the bellows wall (16) has a smaller wall thickness at the outer folds (20) than at the inner folds (18).

Description

[0001] The invention relates to a metal bellows having the features of the preamble of claim 1. Furthermore, the invention relates to a method for producing a metal bellows.

[0002] Metal bellows and methods for producing metal bellows are known from the prior art. One design of metal bellows involves subjecting a metal tube to internal pressure and deforming it into a metal bellows (bellows), as described, for example, in DE 20 2011 102 549 U1. This allows metal bellows to be manufactured cost-effectively. In another design, a metal bellows is formed by several corrugated discs, with adjacent discs being alternately welded to one another on their inside and outside (membrane bellows), as described, for example, in DE 20 2013 007 501 U1. This allows for better deformation properties of the bellows, for example, greater possible elongations.

[0003] A disadvantage of a bellows is that its deformation, for example its elongation, and its durability are comparatively limited. A disadvantage of a diaphragm bellows is that its manufacture by welding is structurally complex and therefore comparatively expensive. JP 2012 - 167 748 A and JP 2010 - 281 443 A each show a metal bellows with an annular space located at each of its outer folds. JP S56 - 20 863 A shows a bellows with an annular space at the inner and outer folds according to the preamble of claim 1. FR 1 258 822 A shows a device for producing a bellows by subjecting the interior to an active medium.

[0004] The invention is based on the object of enabling a cost-effective production of a sufficiently durable and deformable metal bellows.

[0005] The invention solves the problem by a metal bellows having the features of claim 1. According to this, the inner folds and the outer folds on the metal bellows are shaped in such a way that they each enclose an annular space, particularly in their radial end regions (fold end region).

[0006] In this way, a metal bellows is created that has advantageous deformation properties, allowing large axial movements to be compensated and high elongation and shortening (compression) to be achieved. This is achieved due to the fact that the design of the inner folds and the outer folds with annular spaces reduces the loads acting on the folds, for example during axial deformation (e.g. shortening). This has advantages when using the metal bellows, as it can improve durability. In addition, the folds with annular spaces enable cost-effective production of the metal bellows through internal high-pressure forming (often referred to as "hydroforming") and upsetting of the metal bellows, as damage to the folds can be avoided. In other words, the proposed metal bellows has the advantages of a diaphragm bellows in its application, but is more cost-effective to manufacture.The inner folds can also be called “inner folds” and the outer folds can also be called “outer folds”.

[0007] The fold enclosing the annular space can have a cross-sectional shape in the form of a loop, eyelet, or the like. The annular space can have a circular, elliptical, or oval cross-section, for example, in some sections. Symmetrical or asymmetrical configurations are possible. The present metal bellows is, in particular, a bellows manufactured by internal high-pressure forming and subsequently deformed, in particular compressed.

[0008] The transition from adjacent wall flanks to a fold formed on these wall flanks, e.g., from two adjacent wall flanks to an outer fold, is particularly designed such that sections of adjacent wall flanks directly abut one another (contact area). This contact area is located on the side of the annular space facing these wall flanks. This direct contact closes the annular space. The adjacent wall flanks can form a linear contact (e.g., a circular line) or a planar contact (e.g., a circular ring) in the contact area.

[0009] These contact areas limit the bending load at the boundaries of the annular spaces of the inner and outer folds, which are radially opposite the wall flanks, by deflecting the bellows axial movements into a rolling of the adjacent wall flanks against each other.

[0010] Specifically, the inner and outer folds are continuously connected to one another via intermediate transition flanks. The distance between two adjacent wall flanks bordering an identical fold can also be referred to as a "pitch." Relative to the longitudinal axis, the inner fold is arranged radially inward and the outer fold is arranged radially outward (radial direction oriented orthogonal to the longitudinal axis). The inner fold forms a "valley." The outer fold forms a "mountain." An outer fold and the wall flanks adjacent to this outer fold form a corrugation. Adjacent corrugations along the longitudinal axis are connected to one another via an inner fold.

[0011] In a preferred embodiment, the inner folds and / or the outer folds can each directly enclose the annular space. This means that the walls of the folds border directly on the annular spaces. This enables a structurally simple design of the folds without additional components (outer fold / inner fold and / or annular space free of additional components). In addition, the inner folds and / or the outer folds each completely enclose the annular space. This also contributes to a structurally simple design.

[0012] Advantageously, the wall flanks can be corrugated in the same or opposite directions. This increases the stability of the wall flanks. Another advantage is that, when the metal bellows is compressed, adjacent wall flanks can be in contact with each other, possibly over a large area. The wall flanks can be S-shaped or serpentine (meandering or back-and-forth) in cross-section.

[0013] Conveniently, the wall flanks can merge continuously into the inner folds and / or the outer folds. In other words, the wall flanks and the outer folds and the inner folds are formed integrally. This prevents weakening of the wall flanks and / or the folds in the form of predetermined breaking points. In particular, the wall flanks and / or the folds are free of radial weld seams (a weld seam along the longitudinal axis of the metal bellows may be present).

[0014] Specifically, the bellows wall thickness is thinner at the outer folds than at the inner folds. This makes the bellows wall more elastic at the outer folds than at the inner folds, particularly due to the internal high-pressure forming process. The design of the outer folds with annular spaces protects the outer folds from overloading.

[0015] In a preferred embodiment, the annular space can have a height in the radial direction (height of the annular space orthogonal to the longitudinal axis) that is less than 50 percent, preferably less than 30 percent, more preferably less than 20 percent, of the height between the outer fold and the inner fold. This allows sufficient relief of the folds without excessively restricting the production or deformation of the metal bellows during operation.

[0016] The aforementioned problem is also solved by a method for producing a metal bellows as described above. The metal bellows is characterized by the following steps: - Inserting a metal tube (semi-finished product) into a forming tool, - deforming the metal tube into a metal bellows by applying a pressurised active medium to the interior of the metal tube, whereby internal folds, external folds and wall flanks of the metal bellows are formed by interaction with the forming elements of the forming tool, and - Compressing the metal bellows along its longitudinal axis, whereby the inner folds and the outer folds are deformed in such a way that they each enclose or form a closed annular space.

[0017] With regard to the advantages that can be achieved with the process, reference is made to the above statements on the metal bellows.

[0018] In a preferred embodiment, during the forming of the metal tube into a metal bellows, the wall flanks can be deformed such that they are corrugated in the same or opposite directions. This allows the corrugated structure to be applied to the wall flanks in a particularly advantageous manner, with this application taking place in just one work step. The corrugated structure increases the rigidity of the wall flanks.

[0019] Advantageously, the metal bellows can be compressed by moving the forming elements of the forming tool along the longitudinal axis of the metal bellows, in particular until the wall flanks and / or the forming elements are in contact with one another. This enables features to be reliably applied to the metal bellows in a single work step, with the “contacting” reliably signaling the end of the deformation. In other words, the forming elements of the forming tool are moved towards one another along the longitudinal axis of the metal bellows until the wall flanks and / or the forming elements are in contact with one another and further compression of the metal bellows is not possible. In this case, a forming tool lies between two wall flanks that are connected to one another via an inner fold or an outer fold.

[0020] In a preferred embodiment, the deformation of the metal tube into a metal bellows and the compression of the metal bellows can be performed using the same forming tool. This further facilitates the cost-effective production of the metal bellows, as only one forming tool is required, eliminating the need to handle the metal bellows for transfer to another tool. Throughput times, equipment required for transfer, and floor space in a production facility can be saved.

[0021] The measures described in connection with the metal bellows can be used to further develop the process for producing a metal bellows.

[0022] The invention is explained in more detail below with reference to the figures, in which identical or functionally identical elements are sometimes provided with only one reference numeral. They show: Fig. 1 an embodiment of the metal bellows in a schematic sectional view (partial section).

[0023] Fig. Figure 1 shows a metal bellows, designated overall by reference numeral 10. The metal bellows 10 has a bellows wall 16 extending around a longitudinal axis 12 and enclosing a bellows interior 14. The bellows wall 16 has inner folds 18 and outer folds 20, which are connected to one another via wall flanks 22.

[0024] The inner folds 18 and the outer folds 20 are shaped such that an annular space 24, 25 is enclosed by the inner folds 18 and the outer folds 20, respectively. The inner distance 26 between two adjacent wall flanks 22, oriented along the longitudinal axis 12, initially decreases towards the outer fold 20, i.e., starting from the inner fold 18 radially outward, until sections of the wall flanks 22 directly abut one another in a contact area 28, forming a flat contact. In the annular space 24, the distance 26 increases again. In other words, an area in which adjacent wall flanks 22 are spaced apart from one another (spaced area 27) is followed outward by the contact area 28 and then the annular space 24.

[0025] The same applies to the outer distance 29 between two adjacent wall flanks 22, oriented along the longitudinal axis 12. The outer distance 29 initially decreases radially inward until sections of the wall flanks 22 directly abut one another in a contact area 28', forming a flat contact. In the annular space 25, the distance 29 increases again. In other words, an area in which adjacent wall flanks 22 are spaced apart from one another (spaced area 27) is followed inward by the contact area 28' and then the annular space 25.

[0026] In cross-section, the inner fold 18 and outer fold 20 each form an eyelet, loop, or loop. An inner fold 18 forms a valley 30. An outer fold 20 forms a peak 32. An outer fold 20 and the wall flanks 22 adjacent to this outer fold 20 form a corrugation 34. The outer folds 20 each directly and completely enclose the annular space 24. The inner folds 18 directly and completely enclose the annular space 25.

[0027] The wall flanks 22 are corrugated in the same direction. This means that the wall flanks 22 are corrugated in such a way that adjacent wall flanks 22 largely abut one another upon compression of the metal bellows 10. The wall flanks 22 have a serpentine profile in cross-section.

[0028] The wall flanks 22, the inner folds 18, and the outer folds 20 merge seamlessly into one another, thus forming a single piece. The wall flanks 22, the inner folds 18, and / or the outer folds 20 are thus free of radial weld seams. The bellows wall 16 has a thinner wall thickness at the outer folds 20 than at the inner folds 18.

[0029] The annular space 24, 25 each has a height 36 in the radial direction, which in the present embodiment is less than 20 percent of the height between an outer fold 20 and the inner fold 18.

[0030] The method for manufacturing a metal bellows 10 works as follows: First, a metal tube, which is welded in particular with a longitudinal seam and which represents a semi-finished product for a metal bellows 10 yet to be manufactured, is inserted into a forming tool (not shown) (manual or mechanical insertion).

[0031] The metal tube is then deformed into a metal bellows 10 by subjecting the interior of the metal tube to a pressurized active medium, for example, a water-oil mixture. Through interaction with forming elements of the forming tool (not shown), inner folds 18, outer folds 20, and wall flanks 22 of the metal bellows 10 are formed.

[0032] The metal bellows 10 is then compressed along its longitudinal axis 12, whereby the inner folds 18 and the outer folds 20 are deformed such that they each enclose the inner annular space 24, 25. The inner folds 18, the outer folds 20 and / or the annular space 24, 25 can have the properties already described above.

[0033] During the deformation of the metal tube into a metal bellows 10, the wall flanks 22 are deformed such that they are corrugated in the same or opposite directions (not shown). After deformation, the wall flanks 22 have a serpentine cross-section.

[0034] The compression of the metal bellows 10 is effected by the forming elements of the forming tool (not shown) being moved along the longitudinal axis 12 of the metal bellows 10 and towards one another until the wall flanks 22 and / or the forming elements are in contact with one another.

[0035] The deformation of the metal tube into a metal bellows 10 and the compression of the metal bellows 10 are carried out by the same forming tool (not shown).

Claims

[1] Metal bellows (10), with a bellows wall (16) extending around a longitudinal axis (12) and enclosing a bellows interior (14), wherein the bellows wall (16) has inner folds (18) and outer folds (20) which are connected to one another via wall flanks (22), wherein the inner folds (18) and the outer folds (20) are shaped such that they each enclose an annular space (24, 25), characterized by that the wall flanks (22), the inner folds (18) and the outer folds (20) are formed integrally with one another, wherein the bellows wall (16) has a smaller wall thickness at the outer folds (20) than at the inner folds (18). [2] Metal bellows (10) according to claim 1, characterized by that the inner folds (18) and / or the outer folds (20) each directly enclose the annular space (24, 25). [3] Metal bellows (10) according to claim 1 or 2, characterized by that the wall flanks (22) are corrugated in the same or opposite directions. [4] Metal bellows (10) according to one of the preceding claims, characterized by that the annular space (24, 25) has a height (36) in the radial direction which is less than 50 percent, preferably less than 30 percent, more preferably less than 20 percent, of the height between the outer fold (20) and the inner fold (18). [5] A method for producing a metal bellows (10) according to any one of the preceding claims, the method being characterized by the following steps: - Inserting a metal tube into a forming tool, - deforming the metal tube into a metal bellows (10) by applying a pressurised active medium to the interior of the metal tube, whereby inner folds (18), outer folds (20) and wall flanks (22) of the metal bellows (10) are formed by interaction with shaping elements of the shaping tool, and - compressing the metal bellows (10) along its longitudinal axis (12), wherein the inner folds (18) and the outer folds (20) are deformed such that they each enclose an annular space (24, 25). [6] Method according to claim 5, characterized by that during the deformation of the metal tube into a metal bellows (10) the wall flanks (22) are deformed in such a way that they are corrugated in the same or opposite directions. [7] Method according to claim 5 or 6, characterized by that the compression of the metal bellows (10) is carried out by moving the forming elements of the forming tool along the longitudinal axis (12) of the metal bellows (10), in particular until the wall flanks (22) and / or the forming elements are in contact with one another. [8] Method according to one of claims 5 to 7, characterized by that the deformation of the metal tube into a metal bellows (10) and the compression of the metal bellows (10) are carried out by the same forming tool.

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