JPH06170473A - Method and device for producing double wall pipe member - Google Patents

Abstract

PURPOSE: To shorten the time for production of a tubular member by forced feeding fluid between both tubes after bending a workpiece, then expanding the tube on an outer side in at least a portion in a longitudinal direction. CONSTITUTION: The double walled tubular member having a stable shape which is at least partly bent and is provided with an intermediate space in one portion in a longitudinal direction is produced. The tube 3 for forming the wall on the inner side is inserted into the tube 5 for forming the wall on the outer side and the workpiece 1 produced at this time is at least partially bent. After the workpiece 1 is, thereupon, bent, the fluid 79 is force bed between both tubes 3 and 5, and the tube 5 on the outer side is expanded at least in one portion in the longitudinal direction. A fluid source 75 for force feeding the fluid 79 between both tubes is disposed. As a result, the mass production of the tubular member may be implemented automatically, i.e., without requiring manual work, by using simple appliances.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing a shape-stable double-walled tube member which is at least partially folded and has an intermediate space between the walls in at least part of its length. It relates to the device. That is, the tube member forms a double wall bent tube.

[0002]

2. Description of the Related Art A double-walled pipe member of this kind has a wall made of steel, for example, and is used particularly as a component of an exhaust gas device or, in short, an exhaust gas pipe of an internal combustion engine.

In the case of a double-walled tubular member of an exhaust system with a circular cross section, the radial distance between the outer surface of the inner wall and the inner surface of the outer wall is usually approximately 2 mm to 5 mm. In the known method for producing this type of tube member, first two straight tubes are fitted together. In this case, both tubes have a given diameter of the inner wall or the outer wall of the tube member to be manufactured. Before bending the tubes, the intermediate space between the tubes and possibly the inner space of the inner tube are also filled with a solid filling material. The solid filling material consists, for example, of sand, ice or an alloy which melts at approximately 70 ° C. In this case, the ice or alloy is filled in a liquid agglomerate and is fixed in the tube by cooling. After bending both tubes which are fitted together, the filling material is separated.

In this known method, it is relatively difficult to hold both pipes in a coaxial position with each other when filling the filling material, and to hold it so as not to interfere with the filling material filling process. Furthermore, when using sand as the filling material, the sand is relatively slow before bending the tubes into the narrow, annular gap-like intermediate space existing between the tubes and the inner space of the inner tube. After sliding the pipe only and bending the pipe, it is more inconvenient and slowly exits the pipe. If ice is used as the filling material, the tube must be cooled to below the freezing point of the water after filling with water and kept at a temperature below the melting point of ice during the bending process to bend the tube. It must be heated again later. When using an alloy that melts at about 70 ° C., the tube and alloy must be heated above the melting temperature of the alloy, both for charging and for discharging. Therefore, in the case of any of the above-mentioned filling materials, charging and discharging of the filling material is troublesome and requires time. Also, if the filling material does not completely fill the intermediate space between the two pipes during the bending process of the pipes, or if it is not discharged completely therefrom, the risk that the two pipes will not be coaxial with each other during bending, And / or there is the risk that the cross-sectional shape of both tubes will be deformed separately. As a result, the distance between the two pipes varies depending on the location, and in some cases, the two pipes come into contact with each other.

In a method for producing a double-walled curved pipe member known from JP 61-172625 A, a straight inner pipe is inserted into a straight outer pipe and a space between the two pipes is provided. Of the intermediate space is filled with a filling material before bending the tube. In this known method, the filling material consists of ethyl silicate and powders of Al ₂ O ₃ and SiO ₂ . When the filling material reaches a hard rubber-like state after charging the filling material between the two tubes, the fitting tubes are bent and then heated. The filling material sinters when heated. This method is similar to the above-mentioned known method in which the filling material is charged between the tubes to be bent, that both tubes must be held in a coaxial position with each other when the filling material is filled. There are drawbacks. Also, during bending, the filling material may be deformed so that the cross-sectional shapes of the tubes that are fitted together change differently and the desired spacing may not be achieved after bending. Furthermore, in the tube member produced by this method, there is no hollow intermediate space between the two tubes, and there is a sintered filling material, so that the weight of the tube member becomes large and the heat insulating property is impaired. .
When the pipe member is used as an exhaust gas pipe, since the pipe member is heated strongly during use, there is a risk that the organic components of the sintered filling material may be burned in whole or in part when the pipe member is used, and components that have not been burned. There is a risk of accumulating at one or more points in the intermediate space between the tubes.

Japanese Unexamined Patent Publication (Kokai) No. 53-122666 discloses a method and an apparatus for manufacturing radish. This device
It has a tightening ring that comes into contact with the outer surface of the tubular mold that is molded, a ring-shaped support member that is arranged at a distance from each other, and an inner sleeve that is arranged inside the mold. During the manufacturing process, a liquid, for example water, is introduced into the ring-shaped intermediate space which exists between the inner cylindrical sleeve and the inner sleeve. The worm and inner sleeve are then hydraulically crushed axially so that the worm bends outwardly between the clamping rings and the inner sleeve curves inward between the support members to form a corrugation. After transforming the originally cylindrical shape into one completed piece,
The similarly deformed inner sleeve is cut off from the assortment as waste material. Thus, this known method is not used for the production of double-walled bent pipes, but for the production of straight axes.

German Patent Publication 068206 discloses a method for manufacturing a curved tubular member. In this method, first, an originally tubular seamless pipe member is bent, then this pipe member is inserted into a hollow space defined by two forming tool parts, and a pressure force is applied inside the hollow space. Partially expanded by fluid. That is, the tubular member produced by this method is not double-walled.

[0008]

SUMMARY OF THE INVENTION It is an object of the present invention, in a method and apparatus for manufacturing double-walled tube members, to overcome the drawbacks of the prior art and to bend tubes that fit together. It is an object of the present invention to provide such a method and apparatus which eliminates the need to insert a filling material between the tubes which must be separated after bending the tubes.

[0009]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a method in which a work piece is bent and a fluid is press-fitted between the two pipes so that the outer pipe is moved in the longitudinal direction. At least partially expanding, the apparatus comprising a fluid source for pressurizing a fluid between the tubes to expand the outer tube at least in at least a portion of said length. It is characterized by.

The tubes used to form the tube members are advantageously made of metallic material, in particular steel. At least this metallic material improves the appearance of the surface,
The outer surface of the tube forming the outer wall can be provided with a thin aluminum coating. The tube has an uninterrupted closed surface in cross section, the surface having continuous smooth outer and inner surfaces along its circumference. Each tube can have, for example, a rounded welded surface along the weld seam. In this case, the weld seam is smoothed, for example by post-processing. Both tubes may consist of non-metallic materials depending on the intended use. However, in this case both tubes need to be deflected by the plastic deformation and the outer tube must be stretchable by this plastic deformation.

The two tubes used to make one tube member have very little clearance, preferably little clearance, and can be easily fitted together for a good fit. It is advantageous to do so. The size of both tubes depends here on the accuracy of the tubes used, the desired accuracy of the tube elements to be manufactured, and above all the size of the cross section of commercially available tubes.

The cross section of the tube used is circular,
To be more precise, it is advantageous to have a torus shape. When the two pipes are fitted coaxially with each other, the radial distance between the outer surface of the inner pipe and the inner surface of the outer pipe is such that before expansion of the outer pipe, the outer radius of the inner pipe is Of at least 0.01%, for example at least 0.03% and at most 3%. When the pipe member is used in an automobile exhaust gas system, the outer radius of the inner pipe is, for example, at least 10 m.
m, at most about 100 mm, and in some cases even larger, but usually 15 mm to 60 mm. The above radial spacing in this case is
It is at least approximately 0.01 mm and at most approximately 1 mm, but preferably at most 0.3 mm. The radial spacing in expanding the outer tube after bending the tube is increased by at least 1 mm, for example 2 mm to 5 mm.

In special cases, the cross section of the tube may be chosen to be oval or elliptical or polygonal. When selecting a polygon, it is advantageous to make the corners of the polygon and / or the faces of the polygon into arcuate transitions, whereby the cross-section of the pipe is partly straight. A part becomes an arc.
In this case, the above-mentioned conditions regarding the distance and the radius measured in the radial direction correspond to the distance measured perpendicular to the surface of the pipe and correspond to the outer radius of the inner pipe, and the inner pipe measured at the opposite circumferential position. It is applied to half the outer diameter of.

Both pipes before bending are obtained, for example, by cutting a long pipe having a required length, and fitted with each other. The work piece formed from a pair of mating tubes is then bent into the desired shape using, for example, a tube bending apparatus having a mandrel insertable into the inner tube. If the tubes fitted together for bending are fitted with a small clearance as described above and at least almost abutted, the tubes will bend by themselves, i.e. without any special treatment, at least almost in practice. Holds perfectly coaxial position.
If, when bending the tubes, the shape of the cross-sections of the tubes changes, at least in part, depending on the type of bending method used, this change in both tubes is the same, i.e. the contour lines of both tubes are cross-sectional. Are parallel to each other. Therefore, before the pipe is bent, the filling material is charged between both pipes and inside the inner pipe, and after the pipe is bent, the filling material is discharged again from the pipe. You can bend the existing pipe.

The fluid used to expand the outer tube is advantageously a liquid, for example water, optionally a free-flowing or viscous oil. However, gas may be used instead of liquid.

In an advantageous configuration of the method according to the invention, not only is the fluid charged between the two tubes in order to enlarge the outer tube, but also at the same pressure in the inner space of the inner tube. This facilitates maintaining the shape of the inner tube as it expands. However, if the inner tube can withstand enough pressure to withstand the fluid pressure required to expand the outer tube, then fluid may not be forced into the inner tube. further,
Before expanding the outer tube, when temporarily expanding the outer tube by inserting a mandrel made of members pivotally attached to each other or a mandrel made of a flexible rod into the inner tube. Alternatively, the inner tube may be reinforced without charging the fluid into the inner tube.

When enlarging the outer tube, it is advantageous to fix the contour of this outer tube by means of the forming tool, in short the hollow space of the mould. This forming tool comprises two or possibly more forming tool parts, in short, mold parts, which can be pressed against one another, accessible to one another for abutment and detachable. Is. The forming tool is closed after inserting a work piece composed of two tubes which are fitted and bent together and, after enlarging the outer tube, opened to remove the work piece.
The forming tool is advantageously constructed as follows: in the closed state, at the opposite ends of the outer tube arranged in the forming tool, the short ends of the outer tube. Enclose the end part so that it fits well,
Briefly, it surrounds the outer surface of the outer tube and thus prevents expansion of the end portion of the outer tube. To this end, the remaining portion of the outer tube between the two end portions is enlarged. The length of this part which expands during the production of the tubular member is expediently at least 50%, preferably at least 80%, for example approximately at least 90% of the total length of the outer tube.

If the end portions of the outer tube are not enlarged during the expansion process according to the above embodiment of the invention, the end of the workpiece having the unexpanded end portion of the outer tube. At least one or both of the parts can additionally be cut off from the main part of the central part of the workpiece if required. When cutting off both ends of the workpiece,
The intermediate space between the two tubes extends over the entire length of both tubes in the finished tube member or, if the tubes are not of equal length, over the shorter tube.

However, in some cases, if the shape and weight accuracy of the manufactured pipe member are not particularly strict, the outer pipe may be expanded without performing the expansion process in the hollow forming tool. Good.

[0020]

Embodiments of the present invention will be described below with reference to the accompanying drawings.

At least partially folded,
In order to produce a longitudinal, shape-stable, double-walled tubular member in which at least a hollow space is provided between the walls in the longitudinal direction, first of all, a metallic straight cylindrical shape as shown in FIG. 1 is used. Prepare two tubes 3 and 5. For example, a commercially available relatively long tube is cut to prepare the two tubes 3 and 5. The outer diameter of the tube 3 is slightly smaller than the inner diameter of the tube 5.
The tubes 3, 5 have, for example, an outer diameter of 44.45 mm or 47.45 mm.
It can be formed from a commercially available tube with a wall thickness of 5 mm and a wall thickness of 1.5 mm. In this case, the inner diameter of the tube 5 is about 0.025 mm larger than the outer diameter of the tube 3. On the other hand, the tube 3 with the smaller outer diameter is slightly longer than the tube 6 with the larger outer diameter.

The wall thicknesses of the pipe shown in FIG. 1 and the pipe described below are exaggerated from the actual thickness for easy understanding.

Both tubes 3, 5 consist of a metallic material, ie at least to a large extent of stainless steel. In order to improve the appearance of the outer surface of the finished tube member, the outer surface of one of the tubes 5 and, for example, the inner surface depending on the purpose of manufacturing this tube,
A thin aluminum coating having a thickness of approximately 0.01 mm to 0.03 mm may be provided. The tube 3 with the smaller outer diameter can be made entirely of stainless steel, although it is almost invisible when the tube member is completed, and in some cases at least the outer surface can be provided with an aluminum coating.

The tube 3 is inserted into the tube 5 either manually or mechanically using suitable equipment. In this case, both tubes may be fitted with each other by being lubricated with a lubricant such as oil. Tube 3
1 in FIG. 1 by inserting
The workpiece shown in is obtained. This work piece has two tubes 3 and 5 which are coaxial with respect to an axis 7. Inner tube 3
Protrudes slightly from the outer tube 5 at least at the right end in FIG. 2, for example at least about 0.5 mm or at most about 5 mm.

The apparatus for producing the double-walled tube member comprises:
It has a bending device 11 shown in FIG. The bending device 11 is, for example, a pipe bending device having a normal structure, and has a pedestal 13 which is simply illustrated in the drawing. A guide element 15 is fixed to the pedestal 13 firmly, but in a positionally adjustable manner, and a bending disc 17 composed, for example, of a roller is rotatably supported. The bending disc 17 is provided with clamping jaws 19 for removably fixing the work piece 1. Furthermore, the bending device 11 has a mandrel 21 which is fixed to the pedestal 13 so that its position can be adjusted. The free end of the mandrel 21 is fitted into the tube 3 inside the workpiece 1 with very little radial play. Originally straight, the work piece 1 is at least partially a mandrel 2
1 and is bent by rotating the bending disc 17 and the tightening jaws 19. This is done at standard room temperature, ie by cold forming. Bending device 1
1 is configured to perform a manual operation during a bending process or an electrically and / or hydraulically and / or pneumatically driving means which does not require human power, and in some cases, to perform a fully automatic operation. can do. The workpiece 1 is bent along a plane when the two longitudinal regions are spaced from each other, as shown in FIG. 2, for example, so that after bending the workpiece 1 its axis 7 Lies in one plane and has, for example, the shape of a letter S or Z somewhat stretched.

The apparatus used to manufacture the double-walled tube member is provided with a pressing machine 31, which is illustrated schematically in FIG. The press machine 31 has, for example, a frame 33.
The base 33 holds a lower support 35 and an upper support 37. The lower support 35 is, for example, fixed to the pedestal 33 and thus belongs to the pedestal 33 and forms the pedestal of the pedestal 33. The upper support 37 is guided by a column of the pedestal 33 so as to be movable in the vertical direction, and can be easily adjusted in the vertical direction by a position adjusting device 39 shown in the figure. The position adjusting device 39 has at least one hydraulic cylinder 41 fixed to the pedestal 33, and a piston 43 movable in the hydraulic cylinder 41.
The shaft of the piston 43 is connected to the upper support 37.

The forming tool 51, a part of which is shown in FIGS. 3 and 4 to 6, has two forming tool parts 53 and 55. The lower forming tool portion 53 is fixed to the lower support 35. The other upper forming tool portion 55 is fixed to the upper support 37. The forming tool 51 is closed or opened using a press such that the upper forming tool portion 55 is pressed against the lower forming tool portion 53 or is pulled upward from the lower forming tool portion 53.
The forming tool parts 53 and 55 are provided with a vertically long concave portion 53a or 55a on the other forming tool part side, respectively. Each of the recesses 53a and 55a has a central main portion 53b or 55b.
And the end portion 5 which is narrower and shorter at both ends of this main part
It has 3c or 55c. When the forming tool 51 is closed, i.e. when the two forming tool parts 53, 55 are joined together, the recesses 53a, 55a form an elongated hollow space 57 for receiving the workpiece 1. In this case, both recesses 53
Each of a and 55a at least roughly forms, for example, exactly half of the hollow space 57. The two concave main portions 53b and 55b are hollow space main portions 5 having a circular cross section.
7b is formed. In this case, the radius of the hollow space main portion 57b is at least 1 m greater than the outer diameter of the tube 5 outside the workpiece 1.
m, eg at least 2 mm larger. The end portions 53c, 55c of the recess 53a or 55a are paired to form a short straight cylindrical end portion 55c of the hollow space 55. The diameter of the end portion 55c is the outer pipe 5 of the workpiece 1.
Is almost equal to the outer diameter of. Therefore, both end portions of the outer tube 5 enter the hollow space end portion 57c in the radial direction with at least almost no clearance.

The hollow space 55 is somewhat longer than the workpiece 1, so that at least the end portion 57c at the right end of the hollow space 57 in FIG. 3 has a free area after insertion of the workpiece 1. That is, both hollow space end portions 57c have such free areas after insertion of the workpiece 1.

3 to 6, the difference between the radius of the hollow space main portion 57b and the radius of the hollow space end portion 57c is such that the wall thickness of both pipes is exaggerated compared to the actual diameter of both pipes. As illustrated, the illustration is exaggerated.

The hollow space 57 shown in FIG. 3 and the work 1 arranged in the hollow space 57 are the work 1
The axis 7 and the axis of the hollow space 57 which coincides with the axis 7 may be arranged in the vertical plane. In this case, the recesses 53a, 5 of both forming tool parts 53 or 55
The opposing surfaces defining 5a are flat and horizontal in the vertical cross-section taken perpendicular to the drawing plane of FIG. However, in FIG. 3, the work piece 1 and the hollow space 57 are represented by the axis 7 in the vertical plane for the sake of clarity. If the axis 7 of the work piece 1 lies in one plane, rather, the axes of the work piece 1 and the hollow space 57 are in the horizontal plane, ie perpendicular to the direction of movement of the upper forming tool part. It is practical to construct a forming tool that defines a hollow space for accommodating the workpiece 1, as in the plane. In this case, the surfaces defining the recesses of both forming tool parts on opposite sides of the forming tool parts lie in a plurality of planes, i.e. in a plurality of horizontal planes like the axis of the workpiece. is there. As will be described later, in most cases, the workpiece actually has a plurality of three-dimensionally extending axes.

When the forming tool 51 is closed, the two forming tool portions 53 or 55 face each other and are recessed 53a, 55a.
The surfaces defining the are joined together. Forming tool 51
Is the packing means 6 as shown in FIGS.
1 is provided. The packing means 61 closes the forming tool 51 and inserts the workpiece 1, and thereafter the hollow space end portions 5
Seal the free area of 7c to the surroundings. The packing means 61, for example, in each hollow space end portion 57c,
Two semi-circular packings 63 or 65 which are mounted in the grooves of the forming tool part 53 or 55 and which surround the outer tube 5 and form a ring adjoining this tube 5, and a packing 6
7 and 7. The packing 67 is held by, for example, a groove provided in the molding tool portion 53, is formed into a substantially C shape in the plan view of FIG. 5, and extends from one end of the packing 63 to surround the free region of the hollow space end portion 57c. And extends to the other end of the packing 63. 4 to 6, the packings 63, 65, 67 are shown as an integral member, for example, a rubber-elastic deformed member. However, as is known in the field of high-pressure packing, two parts different in strength and elasticity or You may comprise from more parts.

The forming tool portion 53 has a hole 53d formed by a stepped perforation portion. This hole 53d allows the free region of one hollow space end portion 57c to be formed in the forming tool portion 53c.
Is fastened, for example welded, to a connecting member 69, shown here as a sleeve.

At least one hydraulic cylinder 41 of the position adjusting device 39 is connected to a fluid source (not shown) for supplying and discharging hydraulic fluid via at least one fluid guide tube. The position adjusting device 39 and / or the fluid source may selectively move the upper support 37 and the upper forming tool portion 55 fixed thereto to a long distance with a relatively small force or a large force to a slow speed. It may be configured to move by.

The connecting member 69 is connected to the fluid source 75 via the fluid guide tube 73. The fluid guide tube 73 is advantageously as short as possible, in which case the fluid guide tube 75 is fixed directly to the forming tool part 53. Fluid source 7
5 is configured as follows, that is, when the molding tool 51 is closed, the fluid 79 is filled with the hollow space 5 in a manner described below.
It is configured to press into the hollow space 7 again to release the hollow space 57 from the fluid pressure again, for example at least part of the fluid in the hollow space 57 being discharged from the hollow space 57. Advantageously, the fluid is one liquid, for example water. The fluid source 75 is, for example, a tank 77 for storing a fluid 79 and two pump devices 81, 83.
And have. Pump device 8 of the two pump devices
1 is a pump device for sucking a large amount of fluid per unit time, but a pump device for producing a relatively low pressure. On the other hand, the pump device 83 is for generating a high pressure, but is a pump device that only needs to supply a small amount of fluid per unit time. Pump device 8
3 can have, for example, multi-stage pumps, or separate pumps arranged in series, or at least one pump and a booster connected to its output.
The pump device 81 has an input connected to the fluid tank 77 and an output connected to the connection member 69 via the check valve 85. The pump device 83 has an input connected to the fluid tank 77 and an output directly connected to the connection member 69. Furthermore, a valve 87 is provided. The valve 87 connects the connecting member 69 to the fluid tank 77 in the valve open state in order to reduce the pressure.

Workpiece 1 bent by bending device 11
Can be further bent using the press 31, the forming tool 51 and the fluid source 75. For this reason, the workpiece 1 is formed in the recess 5 of the lower forming tool portion 53 with the forming tool 51 opened.
Insert into 3a. Next, the forming tool 51 is closed using the position adjusting device 39. Next, as shown by the arrow in FIG. 6, a fluid 79 made of water is supplied from the fluid source 79 to the connecting member 69. The fluid, ie water, first reaches the hollow space end portion 57c directly connected to the connecting member 69, then the inner space of the inner pipe 3, and then passes through this inner pipe 3. 3 reaches the free area of the end portion 57c of the hollow space 57 at the left end of the workpiece 1 in FIG. Furthermore, at both ends of the work piece 1, fluid, ie water, penetrates between the outer surface of the inner tube 3 and the inner surface of the outer tube 5. In order to facilitate and facilitate a fluid of water at least between the tubes 3 and 5 which are fitted into each other with almost no clearance, the inner tube 3 is provided at both ends of the workpiece 1 with an outer tube. It projects from the tube 5. The air present in the free area of the hollow space end portion 57c and the workpiece 1 before the water is supplied is at least 1 by the supplied water.
It is compressed into individual bubbles and in some cases partially dissolved in water.

Water which only requires a relatively low pressure to supply water to the work piece 1 in the hollow space 57 and to compress the air in the hollow space end portion 57c and the work piece 1. In the initial stage of the supply process, water is supplied by the pump device 81 having a relatively large pump efficiency. If the free hollow space end portion 57c and the inner space of the inner tube 3 are at least substantially filled with water, and the pressure generated by the pump device 81 is not sufficient to supply additional water, the pump device 81 Are turned off, which in turn actuates the pump device 83, which has a smaller pumping efficiency and is capable of producing a greater pressure.

During the pumping process, the water is at high pressure from the fluid source 75, for example 200M, after turning on the pump device 83.
It is pressed into the inside of the inner pipe 3 and between both pipes 3 and 5 at a pressure of Pa to 300 MPa. In this case, the above-mentioned pressure of water is selected as follows: the main part 5b of the outer tube 5 at the end 57b of the hollow space is cooled by plastic deformation, that is to say for example at normal room temperature. It is selected so as to expand in the radial direction by the inter-deformation and come into contact with the inner surface of the forming tool 51 that defines the hollow space 57. The inner pipe 3 is not deformed because a relatively large fluid pressure prevails on the inner and outer surfaces of the inner pipe 3. The originally existing air, i.e. the air present in the free region of the hollow space main part 57b before the outer tube 5 expands, is compressed during the expansion process and / or is at least largely preformed in both moldings. It is extruded from the hollow space 57 through between the tool parts 53 and 55.

As described above, when the outer pipe 5 expands and comes into contact with the inner surface of the forming tool 51 that defines the hollow space 57 in the region of the main portion 57c of the hollow space 57, the pump device 83 is activated. The water supply is terminated by turning it off. Further, at this time, the valve 87 is temporarily opened to release the hollow space 57 and the workpiece 1 from the fluid pressure. In this case, water can be circulated from the hollow space 57 and the workpiece 1 into the tank 77. After releasing the pressure, the forming tool 51 is opened by the position adjusting device 39, and the workpiece 1 is taken out from the forming tool 51.

The press 31 and the fluid source 75 are the press 3
It may be provided with and / or connected to a control means (not shown) for controlling the position adjusting device 39 and the fluid source 75 to perform the above-mentioned working stroke. In this case, the work steps can be controlled, for example manually, or at least partly manually or automatically.

After the main part 5b of the outer tube 5 in the region of the hollow space main part 57b has been enlarged as described above, there is a free space between the inner tube 3 and the main part 5b of the outer tube 5. An intermediate space 91 is created. This intermediate space 91 extends over most of the length of the workpiece 1. At this time, the workpiece 1 has a shape as shown in FIG.

One end portion of the work piece 1, that is to say one end of the work piece 1 having an unexpanded portion of the outer pipe 5 and an end portion of the inner pipe 3 inside the pipe 5. The partial portion can be divided by, for example, a dividing surface indicated by reference numeral 93 in FIG. 7. This division can be done using, for example, a saw or side milling cutter, or other cutting device.

The inner space of the inner pipe 3 and the intermediate space 91 between the two pipes 3, 5 still contain water even after the outer pipe 5 has expanded and the pressure has been reduced as described above. There is. The water in the inner pipe 3 is usually the forming tool 51.
When the work piece 1 is opened and the work piece 1 is taken out from the forming tool 51, most of the work piece 1 flows out from the inner pipe 3 without any special treatment. The water remaining in the intermediate space 91 after the outer pipe 5 is expanded and the pressure is reduced, part of the water remains in the intermediate space 91 even if the forming tool 51 is opened and the workpiece 1 is taken out. It may remain inside. In any case, the water remaining in the intermediate space 91 can be discharged from the intermediate space 91 by cutting the one end portion of the workpiece 1, so that only air is left in the intermediate space 91. It doesn't exist.

The ends of the two pipes 3, 5 which are located at the left end of the work piece 1 may be firmly and tightly connected to one another and which consist of the flanges shown in FIG. It may be connected or welded with 95. The other ends of the two pipes 3, 5 can be welded firmly and tightly to a connecting element 97, which is likewise constituted by a flange, and thus can be indirectly connected to one another. In this case, a shape-stable guiding member indicated by reference numeral 99 as a whole is produced. This guide member 99 is two walls or outer surfaces which are formed by the remaining parts of the tubes 3, 5 and which are coaxial with at least substantially the common axis 7 and which have a free intermediate space 9 over substantially their entire length.
It has two walls or outer surfaces separated by 1.

The method and device according to the invention can be modified in various respects.

For example, the contour of the work piece that is produced when the work piece is bent can be varied over a wide range. For example, to have only one bend region extending over a portion of the length of the workpiece, or to have multiple bend regions divided by straight regions, or being bent over the entire length of the workpiece. You can bend the workpiece like. In addition, the axis of the work piece is not in one plane, but at least in part forms a markedly three-dimensionally bent line or curve so that the work piece can be used for a wide range of practical uses. The workpiece may be bent such that a part of the curve is bent and a part is a straight line, or the whole is bent. Furthermore, the bending device can comprise heating means for heating the workpiece before and during bending of the workpiece. Instead of the guiding element 15, the bending disc 17 and the clamping jaws 19, the bending device also comprises a control element for determining a curve, a feed slider with a movable support, a support pivotable about a fixed axis. At least two rollers supported by the support, and at least one rotation arm rotatably supported by the support. The rotary arm has a detection roller that rolls on the control element and detects a curve of the control element, and engages with a workpiece.
Bending rollers may be provided that cooperate with the rollers supported by the support to bend the workpiece.

If the axis of the work piece lies in one plane after bending the work piece, this plane will lie either vertically or horizontally when the outer tube expands (as already mentioned). , I.e. parallel or perpendicular to the direction of movement of the movable forming tool. If, on the other hand, the axis of the workpiece is strongly curved spatially when the workpiece is bent, the axis of the hollow space, which determines the contour of this tube when the outer tube expands, is correspondingly spatial. Needless to say, it bends to. Both forming tools, which are positionally adjustable with respect to each other, should be constructed in the following manner even when the axis of the workpiece is spatially curved, i.e. without considering the recesses of the two forming tool parts: When closed, the axis of the workpiece should extend through or lie in the planes of the two forming tool parts which face and face each other. In this case, both forming tool parts can be constructed, for example, as follows: when the axes of the workpiece and the hollow space are projected on a vertical plane extending along the drawing plane of FIG. 3 and when projected on a horizontal plane. Can also be configured such that the axis is curved at least locally.

If the workpiece is to be manufactured to be relatively strongly spatially curved, three or more forming tools are used to limit the hollow space for accommodating the workpiece during expansion of the outer tube. It is possible to have more forming tool parts that can be separated from one another.

The press and / or the forming tool for accommodating the workpiece during expansion of the outer tube can have locking means. The locking means has at least one adjustable element which mechanically engages each other when the forming tool is closed and thus prevents the forming tool parts from being pulled apart from each other until the locking means is released again. .

Further, the forming tool containing the workpiece during expansion of the outer tube, and / or the fluid source for supplying fluid to the forming tool and the workpiece may include the forming tool and / or the fluid and the workpiece. A heating means may be provided for heating the outer tube before and / or during expansion. Due to such heat deformation, the fluid pressure required to expand the outer pipe can be made smaller than the fluid pressure required for cold deformation if the outer pipe has the same size and the same material. .

The elongated hollow space present in the forming tool when the forming tool is closed has two ends of different height, as in the case of the forming tool shown in FIG. In some cases, instead of arranging a connecting member for supplying and discharging a fluid for enlarging the outer tube at the higher end of the hollow space as in the embodiment of FIG. It may be placed at. In this way, it may be possible for most of the water or other fluid in the hollow space to flow out during pressure reduction before opening the forming tool.
Further, suction means and / or blower means may be provided.
The suction means and / or the blowing means may be arranged in the hollow space of the work piece and the forming tool after the outer tube is expanded and the pressure is reduced, but before the forming tool containing the work piece is opened. Aspirate and / or blow as much of the contained fluid as possible.

In the embodiment shown in FIGS. 7 and 8, the ends of the inner pipe and the outer pipe located at one end of the workpiece are cut, but the non-enlarged portion of the outer pipe and this The end portions of the inner tube surrounded by the non-enlarged portion may be cut at both ends of the work piece or left at both ends of the work piece. In the latter case, the work piece may be heated strongly before welding both pipes to the connecting element, causing the water in the intermediate space between the two pipes to evaporate and be discharged from the intermediate space as vapor. .

Instead of the connecting element consisting of a flange, it may also consist of a sleeve or other suitable member. If the guide member is used for the formation of an exhaust system with a catalyst, both tubes can be welded directly to the catalyst case and / or to other parts of the exhaust system.

Furthermore, the intermediate space between the two tubes may be vulcanized during or before the two tubes are connected to the connecting element.

Next, the advantageous configurations of the present invention will be listed.

(1) The fluid (79) is press-fitted into the inner space of the inner pipe (3) at the same pressure as when the fluid (79) is press-fitted between both pipes (3, 5). A method characterized by.

(2) The inner surface of the outer tube (5) and the outer surface of the inner tube (3) when both tubes (3, 5) are inserted coaxially before the outer tube (5) is enlarged. Is at least 0.01 of half the outer diameter of the cross section of the inner tube (3).
%, No more than 3% of the pipes (3, 5) are used, with the radial spacing given above in relation to the outer radius of the inner pipe (3). Characterized by the use of filling tubes (3, 5) of circular cross section,
The method according to item 1 above.

(3) The inner surface of the outer tube (5) and the outer surface of the inner tube (3) when both tubes (3, 5) are inserted coaxially before the outer tube (5) is enlarged. Of tubes (3, 3) with a spacing of at least 0.01 mm and at most 1 mm.
5), in which case tubes of circular cross section (3,
5) is used, wherein the distance between the inner surface of the outer tube (5) and the outer surface of the inner tube (3) when the outer tube (5) is enlarged is increased by at least 1 mm, The method according to item 1 or 2 above.

(4) After bending the work piece (1) and before enlarging the outer pipe (5), the work piece (1) is separated from the forming tool parts (53, 55) which are separable from each other. Inserting the forming tool (51) into the hollow space (52), and then the outer pipe until the enlarged portion abuts the inner surface of the forming tool (51) defining the hollow space (57). The method described in any one of the above items 1 to 3, wherein (5) is enlarged by a fluid.

(5) After inserting the workpiece (1) into the forming tool (51), the opposite ends of the outer pipe (5) are not enlarged using the forming tool (51). The method according to item 4 above.

(6) To enlarge the outer tube (5),
The method according to any one of the above items 1 to 5, characterized in that a liquid, for example water, is used as the fluid.

(7) A forming tool (51) is provided, the forming tool (51) joining together when the forming tool (51) is closed and separable from each other to open the forming tool (5). A molding tool part (53, 55), which is formed when the molding tool (51) is closed.
3, 55) forms an elongated hollow space (58) which accommodates the bent work piece (1) and when the outer pipe (5) is expanded. A device configured to determine the contour of (1).

(8) The fluid (79) supplied from the fluid source (75) is supplied to the inner space of the inner pipe (3) and both pipes (3, 3).
Hollow space (5
The end portion (57c) of 7) is connected to a fluid source (75), the forming tool (5) containing the workpiece (1).
Packing means (61) for sealing both ends of the hollow space (57), including each end part of the workpiece (1), to the outer tube (5) and the surroundings when the (1) is closed. The device according to item 7 above, characterized in that:

[0063]

According to the present invention, it is not necessary to charge the filling material between both pipes before bending the pipes fitted together and to separate the filling material after bending the pipes. The work process can be simplified and the manufacturing time of the pipe member can be shortened as compared with the conventional method and apparatus that require charging of materials. There is also the advantage that in the mass production of tube members, it can be carried out almost automatically or completely automatically using relatively simple instruments, i.e. without manual work.

The invention makes it possible to manufacture a tube member in which the walls formed by the two tubes do not come into contact at their ends. On the other hand, if the end portions of both pipes are in contact with each other, the end portions can be cut at one or both ends of the pipe member. In the latter case, the walls of both pipes or pipe members may be connected to each other at their ends by flanges or other connecting elements so that the opposing flanges are spaced from each other over the entire length of the pipe or wall. .

The intermediate space formed between the outer tube and the inner tube by enlarging the outer tube is open upon completion of the tube member, ie it contains only air or is vulcanized. ing. Therefore, such double-walled tube member provides good heat conduction and good sound insulation.

As already mentioned, the inner tube abuts the outer tube during bending of both tubes and is fluid, or possibly otherwise supported, as the outer tube expands. Therefore, it is possible to manufacture without subjecting the surface of the inner tube to a large pressure. Therefore, the inner tube can be constructed to be relatively thin-walled, resulting in light weight and low heat capacity.

By using the pipe member manufactured according to the present invention in, for example, an exhaust gas system, the exhaust gas of a gasoline engine or a diesel engine of a city vehicle can be combined with a catalyst. Since the pipe member manufactured according to the present invention has a good thermal insulation property and the heat capacity of the inner wall is small, in particular, at the time of starting the internal combustion engine and after the start of the internal combustion engine, the catalyst generates a chemical reaction which is carried out in the catalyst. It is heated rapidly to the temperature required to allow Due to the rapid heating of the catalyst to the above temperature, the exhaust gas is separated from harmful substances in the catalyst immediately after the engine is started, and it is necessary to provide an additional auxiliary catalyst for the starting and heating steps of the engine. There is no.

[Brief description of drawings]

FIG. 1 shows a work piece consisting of two straight tubes fitted together.

FIG. 2 is a view showing a bending device when bending a workpiece,
It is the figure which reduced and showed the workpiece compared with FIG.

FIG. 3 is a partial cross-sectional side view of an apparatus for enlarging the outer tube, showing the workpiece in a reduced scale as compared to FIG.

FIG. 4 is an enlarged view of a portion within a circle IV in FIG. 3, which is an enlarged cross-sectional view of the workpiece.

FIG. 5: FIGS. 3 and 4 for fixing the contour of the outer tube
FIG. 5 is a plan view of a lower forming tool of the forming tool illustrated in FIG.

FIG. 6 is a view corresponding to FIG. 4, showing the outer tube in an enlarged state.

7 is a vertical cross-sectional view of the work piece after enlarging the outer pipe, and is a vertical cross-sectional view of the same scale as FIG.

FIG. 8 is a vertical cross-sectional view of the completed tube member.

[Explanation of symbols]

 1 Workpiece 3 Inner Tube 5 Outer Tube 79 Fluid 91 Intermediate Space 99 Tube Member

Claims (2)

[Claims] 1. An intermediate space (9) at least partially folded and between the walls in at least part of its length.
1) The shape-stabilized double-walled pipe member (9)
9) A method for producing a pipe (3) for forming an inner wall, and a pipe (5) for forming an outer wall.
In the above method, in which the workpiece (1) produced at that time is bent at least partially, the fluid (79) is bent between the pipes (3, 5) after the workpiece (1) is bent. Press-fitting to expand the outer tube (5) in at least a portion of said length. 2. A device for carrying out the method according to claim 1, wherein a fluid (79) is press-fit between both tubes (3, 5) and an outer tube (5) is at least said length. A device characterized in that a fluid source (75) is provided for expansion in at least a part of the direction.