EP1183114A1

EP1183114A1 - Bending block for a bending device and bending method for tubes

Info

Publication number: EP1183114A1
Application number: EP00943718A
Authority: EP
Inventors: Thomas Flehmig; Uwe Kneiphoff; Klaus Blümel; Klaus GÖHLER
Original assignee: ThyssenKrupp Stahl AG
Current assignee: ThyssenKrupp Steel Europe AG
Priority date: 1999-06-09
Filing date: 2000-05-16
Publication date: 2002-03-06
Anticipated expiration: 2020-05-16
Also published as: ES2189761T3; DE50001106D1; WO2000076683A1; ATE231038T1; DE19926330A1; DE19926330C2; EP1183114B1; US6658912B1

Abstract

The invention relates to a bending mandrel for a bending device and also to a bending method for pipes, more particularly pipes which have a large diameter-to-wall thickness ratio and are to be bent by a small radius, for example, of the order of magnitude of the pipe diameter. To this end use is made of a bending mandrel (5, 6) to whose rigid head (5) assembly (6) of springy sheet metal lamellae (6a, 6b) is attached to improve the bendability of the bending mandrel (5, 6) while maintaining a satisfactory supporting action, the lamellae (6a), with the exception of the outer lamellae (6b), having window-like cutaway portions (6c).

Description

BENDING PIN FOR A BENDING DEVICE AND BENDING METHOD FOR PIPES

The invention relates to a bending mandrel for a bending device for pipes, consisting of a rigid head and a package of superimposed, flexible lamellae attached to it with only one end, which bend is perpendicular to the lamellae plane by sliding the lamellae.

Such mandrels are used in pipe bending devices to support the pipe from the inside during the bending process. This support is intended to counteract a buckling of the tube, a wave formation on the inner bending bend, flattening on the outer bend, an oval deformation of the cross section and a springback of the tube after the bending process. The risk that the aforementioned effects occur when the mandrel is not used is particularly great for pipes which have a large ratio of the outside diameter to the wall thickness and which have a comparatively small radius, e.g. in the order of the pipe diameter to be bent. Typical wall thicknesses of such pipes are e.g. at 1.5 mm with a pipe diameter of 150 mm.

Various types of bending mandrels belong to the prior art, with which not all of the aforementioned disadvantages can be avoided.

In a bending mandrel designed as a link mandrel ₍ DE 197 07 228 AI) there are several on a rigid head massive links arranged in a row and articulated together. The joints are formed by mutually sliding link surfaces, of which the link surface of one link is convex and the link surface of the other link is concave. With such a bending mandrel, the circular cross-section of the tube supported on it is obtained during the bending process because of the massive formation of the links in the area of each link, but not over the entire axial length of the arc. This is because the tube is only supported on axially offset narrow ring zones because of the convex (spherical) shape of the links. In the unsupported areas, the pipe can deform undesirably, be it flattening or be it folds.

This undesired deformation of the tube during bending should be avoided by another known solid inner mandrel (EP 0 856 367 A2). In this case, the mandrel consists of plastic (polyurethane) and is solid. The disadvantages of such a mandrel are, on the one hand, that the bending ability of a solid mandrel is not sufficient to bend tubes with small bending radii, and, on the other hand, that a compromise must be made between the bending ability of the mandrel and the dimensional stability for the support. If a high degree of dimensional stability is to be ensured, large bending forces must be exerted. The larger the pipe diameter, the greater the bending force must be. It goes without saying that the use of such a mandrel for pipes with a large diameter is quickly limited for this reason. _S is inally a bending mandrel of the type mentioned is known (JP 619 8349) in which a package forming stacked flexible fins are arranged between the outer plastic, bears against the pipe inner side plates made of spring steel. Since the individual slats can slide on one another, the bending force to be used for the bending process is smaller in comparison to the other bending mandrel made of solid plastic material. Nevertheless, the bending force to be used is undesirably high, especially when pipes with a large cross section and a small bending radius are to be bent.

Based on this prior art, the invention has for its object to provide a mandrel, the use of which the tube is bent without excessive bending force without flattening or other undesirable deformations.

This object is achieved with a bending mandrel of the type mentioned in that the slats made of sheet metal, apart from the slats lying in the package, each have a central, window-like cut-out extending in the longitudinal direction of the package, such that the slats are formed of a hollow body partially overlap with their narrow edge areas.

Although the bending mandrel according to the invention consists of lamellae, it is dimensionally stable due to the material “sheet metal” chosen for it and can be bent relatively easily because the central lamellae do not extend over the entire cross section. A wear-resistant material with a high modulus of elasticity, high strength and a low coefficient of friction compared to the tube material is preferably selected for the sheet of the fins. Bronze is suitable for this, but above all steel, especially spring steel.

The bending mandrel can be designed in various ways.

According to a first embodiment, the cutouts in the cut-out slats are open at their unattached ends. According to an alternative embodiment, they are closed at the unattached ends. The closed end can be advantageous for supporting the end which may be particularly heavily loaded in practice.

The bending force required for bending can be further reduced in that at least some lamellae have notches running transversely to their longitudinal direction on their side facing the inner bending arc. The bending force can also be reduced in that a lubricant is provided between the individual slats sliding on one another.

To make it easier to insert the mandrel into a tube, the free end of the package can be rounded off in a spherical shape, cut diagonally or tapering to a point.

Since the mandrel must be inserted into the tube with its head, it must be adapted to the cross section of the tube. In order to be able to attach the slats to the head as easily as possible, he can attach it to the package facing side be fork-shaped or comb-like, wherein part of the slats is fixed between the fork branches or the comb teeth and the remaining slats are attached to the fixed slats.

Since the lamellae move against each other during the bending process with the result that the lamella located on the outer bend remains behind the lamella lying on the inner bend in relation to the plane perpendicular to the pipe axis, the support in this area would be lost, if not according to a further embodiment of the invention it would be provided that the lamellae have a different length, such that the lamellae on the side with the large bending arc have the greatest length and the lamellae on the side with the small bending arc have the smallest length.

In order to avoid spreading the resilient slats, it is provided according to a further embodiment of the invention that the slats are held together at their free ends by a spring struck on the outer slats.

Pipe bending is usually carried out in a bending device with a bending mandrel in such a way that the bending is carried out in sections, the bending mandrel then then having to be repositioned axially accordingly. The invention, however, allows bending in one go, ie without repositioning the mandrel. Accordingly, the invention further relates to a method for bending a tube using a bending mandrel according to the invention in a bending device with a fixed receptacle for the tube with inserted mandrel, one on the side of the small bending arc stationary support body and a pivotable guide piece for the tube around the center of the bending arc. According to the invention, such a method is characterized in that the tube and the bending mandrel used, which extends over the entire length of the bending arc, are axially fixed during the entire bending process. The method according to the invention has become possible because, due to the special configuration of the bending mandrel, the required bending forces are relatively small, so that the bending forces to be applied do not become uncontrollably large, despite the greater axial length over which the lamellae slide on one another during the bending process.

If, as in this method, the tube is held axially fixed during the bending process, the bending-effective area moves around the center of the bending curve during the bending process. The flexible mandrel must therefore be designed accordingly long. An alternative method of the invention manages with a shorter mandrel. In this method, a bending device with a fixed receptacle for the tube with an inserted bending mandrel, a support body arranged on the side of the small bending sheet, in particular rotatable about the center of the bending sheet, and a guide piece for the tube pivotable about the same center of the bending sheet are used. Such a method is characterized in accordance with the invention in that the tube and the bending mandrel used, which extends with its flexible part at least over the bending area of the bending arc, are guided so that they can move axially freely or in a controlled manner during the entire bending process in such a way that the flexible part of the bending mandrel remains in the bending area of the bending sheet. In this method, the tube can be controlled or freely movable in accordance with its different path speeds on the inner bend and on the outer bend, the path speeds of the device part acting on the tube can be adapted in the sense of the smallest possible relative movement. Due to the axial movement of the tube, the area which is effective in bending can be fixed spatially, so that a flexible bending mandrel which only extends over a small length of the bending arc can be used.

The invention is explained in more detail below with reference to a drawing which represents an exemplary embodiment. In detail show:

1 is a bending device with a tube inserted for bending and a mandrel inserted immediately before the bending process in half section and isometric view,

Fig. 2 shows the bending device according to FIG. 1 at the end of

Bending process in side view and in half section,

3 is a bending mandrel in an isometric view and in axial half section in the bending plane,

4 shows the upper half of a plate pack of the bending mandrel according to FIG. 3 in an isometric illustration,

5 shows the lower half of the plate pack of the bending mandrel according to FIG. 3 in an isometric illustration, 6 shows a lamella of the bending mandrel according to FIG. 3 in detail and in side view,

Fig. 7 shows a bending device with a tube inserted for bending and inserted bending mandrel immediately before the bending process in half section and isometric view in an alternative to Fig. 1 embodiment

and

Fig. 8, the bending device of FIG. 7 at the end of

Bending process in side view and in half section.

1 and 2 consists of a fixed receptacle 1, a support body 2 arranged fixedly on the side of the small bending curve and a guide piece 3 which can be pivoted about the center A of the support body 2. In the starting position shown in FIG. 1 for the bending process there is a pipe 4 to be bent in the receptacle 1 and extends beyond the guide piece 3. A bending mandrel is inserted in the tube 4.

3 to 6 show, the bending mandrel consists of a rigid head 5 and an attached package 6 of laminations 6a, 6b stacked on top of each other. To attach the package 6 to the head 5, the head 5 has two fork loads 7, 8. Between these fork loads 7, 8, the fins 6a, with the exception of the outer, somewhat shortened fins 6b, are fastened with bolts. The outer slats 6b are fastened to the other slats 6a by means of screw bolts. The slats 6a with the exception of the outer slats 6b have window-like recesses 6c which are open towards the free end of the pact 6. For the sake of simplicity, this is only shown in FIGS. 3 and 5. The outer slats 6b are formed over the entire surface, so that the slats 6a, 6b stacked on top of one another form a hollow body in which the individual slats 6a, 6b overlap and are supported on one another. In the area of the cutouts 6c, the lamellae 6a, 6b can have grooves 6d running transversely to the bending plane. The recesses 6c and the grooves 6d promote the flexibility of the package 6. It can also be seen from FIG. 3 that the lamellae 6a, 6b are held together at their free end by a tension spring 9. It can also be seen from this figure that the slats 6a, 6b have a different length. The slats shown in the drawing below, which are on the side of the small bending sheet, have the shortest length, while the slats, which are on the opposite side, i.e. on the side of the large bending sheet, have a longer length. With this different length it is achieved that in the bent state the ends lie essentially in a radial plane of the pivot axis. This is advantageous for the support effect, because if the slats are of equal length, the ends are axially offset from one another and the support is therefore partially lost, as shown in FIG. 2.

The embodiment of FIGS. 7 and 8 differs from that of FIGS. 1 and 2 in that the support body 2 ^' is rotatable about the center A of the bending arc, the tube 4 ^{' is} not axially fixed, but is pushed and the flexible part 6 'of the mandrel 5', 6 'has a comparatively short length. For a first bending process according to the invention, the tube 4 is held axially fixed. The support body 2 is non-rotatable. The bending mandrel 5,6 is also axially fixed and its flexible package 6 has a length which extends over the entire length of the bend of the tube 4 to be bent, as shown in FIGS. 1 and 2. Such a configuration makes it possible for the bending mandrel 5, 6 not to have to be adjusted in accordance with the progress of the bending during the bending process. Therefore, the method can be carried out easily and quickly and does not lead to internal damage to the tube 4, which can happen in methods that require the mandrel to be moved.

In a second bending method according to the invention with a device according to FIGS. 7 and 8, on the other hand, the bending mandrel 5, 6 has to be moved relative to the tube 4 in accordance with the bending progress. For this purpose, it is held with its flexible package 6 'in the area of the device which is effective in bending, that is to say in the initial section of the bending sheet. The tube 4 'must therefore be pushed according to the bending progress. This pushing is facilitated by the accompanying support body 2 '. The advantage of this method is above all that because of the short length of the flexible package 6 'of the mandrel 5 ^', the bending force to be applied is small and the undesired relative movement between the inner wall of the tube and the mandrel is limited to the short effective area.

Claims

claims

1. Bending mandrel for a bending device for pipes, consisting of a rigid head (5,5 ') and attached to it with only one end package (6,6') of stacked, flexible lamellae (6a, 6b) which is perpendicular to Slat plane under sliding of the slats (6a, 6b) is flexible to each other, since you rchgek characterized in that the sheet metal (6a, 6b) made of sheet metal, except for the slats (6b) located on the outside in the package (6), each have a central lengthwise direction of the package (6, 6 ') extending, window-like cutout (6c), such that the slats (6a, 6b) partially overlap with their narrow edge areas to form a hollow body.

2. Bending mandrel according to claim 1, so that the sheet of the fins (6a, 6b) consists of a wear-resistant material with a high modulus of elasticity, high strength and a low coefficient of friction compared to the tube material such as steel, in particular spring steel, or bronze.

3. Bending mandrel according to claim 1 or 2, characterized in that the cutouts (6c) in the cut-out lamellae (6b) are open at their unattached ends.

4. bending mandrel according to one of claims 1 to 3, _d adurchgekennzeichnet that the cutouts (6c) are closed in the cut lamellae (6b) at its unattached ends.

5. bending mandrel according to one of claims 1 to 4, d a d u r c h g e k e n n z e i c h n e t that at least some lamellae (6a, 6b) have on their side facing the inner bending arc transverse to their longitudinal direction notches (6d).

6. Bending mandrel according to one of claims 1 to 5, d a d u r c h g e k e n n z e i c h n e t that a lubricant is provided between the individual slats (6a, 6b) sliding on each other.

7. bending mandrel according to one of claims 1 to 6, d a d u r c h g e k e n n z e i c h n e t that the free end of the package (6) is rounded like a ball, cut obliquely or tapering.

8. Bending mandrel according to one of claims 1 to 7, characterized in that the head (5) on its side facing the package (6) is fork-shaped or comb-like and that part of the lamellae (6a) between the fork branches (7,8) or the comb teeth is fastened and the remaining slats (6b) are fastened to the fastened slats (6a).

9. Bending mandrel according to one of claims 1 to 8, characterized in that the lamellae (6a, 6b) have a stepped different length, such that the lamella (6b) on the side with the large bending arc has the greatest length and Slat on the side with the small bending curve has the smallest length.

10. Bending mandrel according to one of claims 1 to 9, d a d u r c h g e k e n n z e i c h n e t that the fins (6a, 6b) are held together at their free ends by a spring (9) struck on the outer fins (6b).

11. A method for bending a tube using a mandrel according to one of claims 1 to 10 in a bending device with a fixed receptacle (1) for the tube (4) with inserted mandrel

(5,6), a support body (2) fixed on the side of the small bending sheet and one around the

Center (A) of the bending arc pivotable guide piece (3) for the tube (4), characterized in that the tube (4) and the bending mandrel (5,6) used, which extends over the entire length of the bending arc, during the entire bending process are axially fixed.

12. A method for bending a tube (4 ') using a bending mandrel (5', 6 ') according to any one of claims 1 to 10 in a bending device with a fixed receptacle (1') for the tube (4 ') with inserted mandrel (5 ', 6'), a support body (2 ') arranged on the side of the small bending arc and rotatable about the center (A) of the bending arc and a guide piece (3') pivotable about the same center (A) for the tube (4 '), characterized in that the tube (4 ^' ) and the bending mandrel used (5 ', 6'), with its flexible package (6 ') at least over the Bending effective area of the bending arc extends during the entire bending process such that it can move axially freely or in a controlled manner in such a way that the flexible package (6 ') of the bending mandrel (5', 6 ') remains in the bending effective area.