FI94601C - Method and tool for bending air-nested nested pipes - Google Patents

Description

- 94601

Method and tool for bending air-nested nested pipes

The invention relates to a method and an apparatus for bending nested pipes, such as exhaust pipes of a vehicle's internal combustion engine, into a desired shape so that the air gap between the pipes remains constant.

The currently used methods of bending double-walled pipes are usually based on the medium between the pipes. The medium can be, for example, frozen water, sand, steel balls or the like. In the actual bending of the double pipe, a standard pipe bending machine can then be used. After bending the tube, the medium is removed.

DE 27 32 046 discloses a method in which a fixed mandrel is used for bending a double pipe between the pipes, which presses against the inner edge of the outer pipe when bending the inner pipe. Because the mandrel is rigid, it cannot be pushed into the bend-20 bend with bending. Another disadvantage of the method is that the inner tube must be loose and it is only centered after bending.

German patent publication DE 40 24 936 discloses a method in which a conventional spherical mandrel is formed inside the inner tube and a flexible mandrel formed of threads of fibers between the nested tubes. The weakness of such a structure is, of course, the lack of rigidity of the mandrel in the direction of the cross-sectional circle. The choice of mandrel materials can also be problematic due to the high forces generated in the shaping 30.

*! EPO publication 0 163 056 discloses a solution in which the mandrel between the nested tubes is a tube to the end of which a piece cut from the tube is articulated, the shapes of which are such that bending can be performed. The weakness of the method according to the invention 35 is e.g. the fact that the mandrel between the tubes 94601 2 cannot be rotated. If the tip piece is in the wrong position during the bending phase, the pull-out force may increase to such an extent that either the tool or the pipe bend will break.

5 Various fixed sleeve mandrels have also been used for bending double pipes. The weakness of the methods has been that they hardly reach angles of more than 20 ° due to the fixed mandrel. If the bending angle is increased in these methods, the inner tube will easily wrinkle, because the fixed sleeve mandrel cannot be pushed with the tube into the bending bend due to the stiffness of the sleeve.

The use of different media when bending double wall pipes causes additional work steps and easily increases costs. The potential offered by modern CNC-15 guided pipe bending machines is also not fully exploited.

A further disadvantage of the known methods and tools has been that no tool has been found which is sufficiently rigid in the radial direction of the circle, but which allows bending in the longitudinal direction.

The method and tool for bending air-spaced nested pipes according to the invention is characterized by what is set forth in the characterizing parts of the following claims.

The advantages of the invention over traditional double-walled pipe bends are the competitiveness of the method and the cost savings. No expensive separate peripherals are needed. Tooling costs are also not unreasonable due to the simple design of the spring mandrel, and. 30 tool changes are easy to perform. The method according to the invention • automatically centers the inner tube, and the method can be used e.g. in blanks in which the inner tube is attached at one end to the outer tube, for example at an expansion or contraction.

From the point of view of manufacturing technology, the main advantage of the method and spring mandrel according to the invention is that the mandrel allows bending in all directions and is sufficiently rigid with respect to the shape of the circle, which facilitates e.g. removal of the mandrel. Rotation of the mandrel is also possible with the structure according to the invention 5, and it is not very sensitive to the point at which the pipes are bent. In other words, the pipe mandrel according to the invention is generally always obtained out of the pipe bend.

In the following, the invention will be explained in detail with reference to the accompanying drawings.

Figure 1 schematically shows a method and tool for bending air-spaced nested pipes according to the invention.

Figure 2 shows the structure of a spring mandrel with a surface section cut from a tube on 15 springs.

Figure 3 shows the structure of a spring mandrel in which the surface parts are made of wire.

Figure 4 shows a cross-section I-I of the mandrel according to Figure 2.

Fig. 5 shows a section II-II across the mandrel according to Fig. 3.

Figure 1 shows a method and tool according to the invention, in which the number 1 refers to a double-walled tube, 2 to an outer tube and the number 3 to an inner tube. The extension 25 of the inner tube is marked with the number 4. The bending bar is the number 5 and its shaft 6. The back bar accompanying the tube is 7. The locking part of the bending bar is 8. The ball mandrel is 9, the ball 10, the joint 11, the arm 12 and the locking piece 13. The spring mandrel is marked number 14 and its arm number 15. Spring mandrel 14. The spring 30 is indicated by the number 16 and the inner and outer surfaces by the numbers 17 and 18. The locking piece of the arm 15 is the number 19. The locking piece of the outer tube 2 is indicated by the number 20. The extension sleeve of the Boos-ter function is the number 21 and the locking piece is the number 22. The various functions are indicated in Figure 1. with arrows. 35 The air gap between pipes 2 and 3 is marked with the number 23.

4,94601

Figures 2 to 5 show two constructional variants according to the invention, in which the arm 15 of the spring mandrel 14 is referred to by the number 15 and the spring 16. In another solution, the inner and outer surfaces 17 and 18 of the flexible mandrel part 5 are made of tubes 24 and 25 sawn according to longitudinal grooves 26 wherein the surfaces 17 and 18 are formed by longitudinal ribs 27. At the end of the arm 15 there is a relief 28 to which the tubes 24 and 25 are soldered with solders 29. The ends of the ribs 27 have bends 30 which prevent the spring 10 from exiting the space between the tubes 24 and 25 or the like. The tubes 24 and 25 and the ribs 27 can be replaced by a wire 31 forming the surfaces 17 and 18. The wires 31 can be provided with a fold 32 which prevents the spring 16 from escaping.

To enable the use of the spring mandrel 14, the bending machine 15 must be equipped with additional operating devices. The spring mandrel 14 must have its own programmable reciprocating drive movement with respect to speed and in addition a programmable mandrel rotation movement.

The normal ball mandrel 9 of the inner tube 3 must also have its own separate programmable reciprocating movement with respect to speed. In addition, the inner tube needs its own speed-programmable thrust movement, the so-called booster function. Adding additional functions to a modern CNC-controlled put-pipe bending machine also does not incur unreasonable costs due to the programmable basic operating movements already in the machine. It is possible to add the computer programming required by the additional functions to the existing software of the machine.

Before bending the double-walled pipe 1, the pipes 2 30 and 3 must be centered and locked at one end. This can be done, for example, by means of an extension 4, and by welding the pipes 2 and 3 together. The double-walled pipe 1 is placed at its open end in the locking piece 19 of the bending machine. The bending machine pushes the ball mandrel 9 and the spring 35 into the inner part between the tubes 2 and 3 of the mandrel 14 in the right position with respect to the bending last 5.

During bending, it is possible to push and pull the spring mandrel 14 and the ball mandrel 9 separately in the bending bend, and if necessary, the spring mandrel can be rotated.

5 The programmed booster function of the inner tube 3 is required to allow bending of larger bending angles and the use of smaller bending radii. The Boos-ter function gives additional thrust to the inner tube during bending, preventing the inner tube 3 from straightening at the maximum bending angles and keeping the air gap constant at the bending bend at large bending angles.

In the bending of the double-walled pipe 1, it is possible to pull only from the outer pipe 2 with the bending ladder 5. In pipes 1 with several bends, it is possible with the booster function 15 to prevent the inner pipe 3 of the previous bend from straightening by pushing the inner pipe 3 more than the outer pipe 2 during bending.

In order to achieve a good bending result, accurate programming is important to find the correct bending values. Proper lubrication of the mandrels also plays a very important role in the end result of the bending. The method according to the invention is, of course, applicable to different types of programmable bending machines.

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Claims (9)

1. A method and tool for bending air-spaced pipes, by means of which bending or otherwise centered double-wall pipes with air in the tube spacer are bent in the desired shape, characterized in that the bending is carried out by means of a known tube bending machine, which has at least at the bending point arranged resilient mandrels (9 and 14) within the bends (2 and 3), that the mandrel in the space between the tubes (2 and 3) moves back and forth and rotates around its center axis, and that the inner tube (3) is pressed inwardly by the booster action, thereby preventing the straightening of previously made bends. 2. Bending tool for bending air-spaced tubes, a ball mandrel (9) and a spring mandrel (14) used in the air gap (23) between the pipes (2 and 3), comprising a shaft (15) fixed to a shaft (15) flexible part (16, 17, 18), characterized in that the flexible part (16, 17, 18) is assembled by a coil spring (16) or the like, whose outer and inner surfaces (17, 18) are coated with longitudinal ribs (27), trees (31) or similar parts which are connected to the shaft (15) by soldering or a similar jointing method. 3. Device according to claim 2, characterized in that the ends of the ribs (27) have a bend (30) which prevents the spring from coming out through the space between the ribs (27). 4. Device according to claim 2, characterized in that all ribs (27) or some of them are replaced by trees (31) which have a break (32) to prevent the spring (16) from coming. out. Device according to claim 2, characterized in that the ribs (27) are cut off by pipes 35 (24) and (25), and that said grooves (26) do not reach the joint point of the shaft, and the joint. is provided at the entire tubes (24) and (25). 6. Device according to claim 5, characterized in that the ribs (27) are different in width and thickness according to the bending direction of the spring mandrel (14), and that the latch (26) moves in the direction of the longitudinal axis of the spring mandrel (14). or forming an angle with the same. 7. Device according to claim 2, characterized in that the end of the shaft (15) has a relief 10 (28), to which the surfaces (17, 18) are connected by means of a solder joint (29) or a similar joint. 8. Device according to claim 2, characterized in that the spring (16) is slack, the trees of the spring having a gap between them or that the space 15 of the spring (16) between the ribs (27) is so long that the spring (16) can be bent. Device according to claim 2, characterized in that the spring mandrel (14) and the shaft (15) are equally thick over their entire length and slide in the air gap (23). '· • k