SK279558B6 - Method and apparatus for bending a multiple tube - Google Patents

Abstract

In the bending of a multiple tube (6) having a plurality of compartments (7, 8) extending side-by-side in the longitudinal direction of the tube, a bending location is moved progressively along the tube (6) and during bending a mandrel (12, 13) is located inside each said compartment (7, 8) at the bending location. At least one of said mandrels (12, 13) might be free to move, under constraint by a resilient force, in the longitudinal direction of the tube. To improve control of the tube shape, during at least part of the bending the position of at least one of the mandrels (12, 13) relative to the tube at the bending location varies in dependence on at least one parameter of the bending.

Description

Technical field

The invention relates to a method of bending a pipe in a bending plane, wherein the pipe is provided with a plurality of sections arranged side by side in the longitudinal direction of the pipe. During bending, each of the tube sections reaches the bending core. The invention also relates to an apparatus for carrying out this method.

A pipe in this specification and claims means a pipe that comprises a plurality of pipes, in this case called sections, joined into an integral pipe and arranged longitudinally along the pipe. The sections are typically separated from one another by one or more partitions. The partition may be formed by a double wall, in which case each section forms a completely separate tube, or the partition may form a common wall between two compartments. Typically, such a pipe is of metal, for example steel.

BACKGROUND OF THE INVENTION

The known tube is a so-called DD-tube, which comprises two compartments, each with a D-shaped cross section, which are connected by their flat parts which are adjacent to each other. The cross section of the DD-tube may be circular, elliptical or other. The partition between them is formed by a common wall.

DD-pipes are increasingly being used for exhaust pipes in the automotive industry. The attractiveness of DD tubes is that this shape is suitable for internal combustion engines with high specific power, these tubes occupying little space in the vehicle, thus increasing the structural flexibility needed for example to design aerodynamic bodies.

The DD-tube is usually made in the form of a straight tube with two compartments, and is then formed into a desired shape by a bending operation, for example, into the shape of an exhaust tube.

In the current practice, it is known to bend the DD tube in a bending plane transversely against a crossbar between the two D-shaped compartments. In the known method, a bending core is inserted into each of the D-shaped compartments. For this purpose, each bending core has an outer sleeve with practically a constant cross-section, the cross-section corresponding to the cross-section of the D-shaped section. A round bending template is used. The tube is bent around the template. Each core is inserted far enough into the tube such that the front boundary of the outer sleeve of the bending core lies about 2 to 5 mm in front of the radius beyond the contact point of the tube with the bending template. The correct position of each core is determined for each tube size, bend radius, etc. experimentally, and then it is not changed. If the bending core is inserted into the tube farther than the above-mentioned position, then an outbreak occurs in the bend to be formed, which is a fingerprint of the transition area. If the bending core is inserted further into the tube, there is a danger that the bending core will be drawn into the bend during bending, which is an obstacle to the bending operation and may cause damage to the bending core and other parts of the bending device.

In a known manner, a bend of about 90 ° can be formed, which means that the multiple tube is bent by 90 °. In the case of a larger bend, the outer wall of the DD-pipe on the inside of the bend is wrinkled and the compartment is flattened on the outside of the bend. A disadvantage of this is that when such a pipe is used as an exhaust pipe, the gas balance between the internal combustion engine cylinders associated with one D-shaped section and the cylinders associated with the other D-shaped section is disrupted.

A further disadvantage of the known method arises when attempting to bend the DD-tube in two opposing bends in the same bending plane, i. Since the position of the bending core on the inside of the bend may differ from the position of the bending core on the outside of the bend, then when performing an S-shaped bending, the bending cores must be moved from one compartment to one during the bending operation. second. This leads to loss of production time.

US-A-4,009,601 discloses a method and apparatus for bending double tubes, in particular two concentric circular tubes. The metal core, composed of the outer metal core and the inner metal core, is inserted into two concentric circular tubes in the prescribed position and is fixed therein during the bending operation. The inner metal core and the outer metal core are fixedly fixed to each other by means of a metal rod and a connecting flange.

DE-A-27 32 046 describes a method for bending two tubes, one of which is inserted into the other, and an apparatus for carrying out the method. According to this specification, two cores are used, a circular core which is inserted inside the smaller tube and a crescent-shaped core between the smaller and larger tubes. Both cores are connected by means of fixed bars to the handle and are fixed in their positions during bending.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a tube bending method which allows multiple tubes to be bent at least at right angles, wherein the cross-sectional shape of the tube section does not substantially change and no wrinkling occurs on the outer wall.

Another object of the invention is also a method by which S-shaped bends can be formed without having to move the bending core from one compartment to another.

According to one aspect of the invention, there is provided a method of bending a multiple tube in a bending plane in which the bending point in relation to the pipe is progressively moved along the tube, wherein during the bending, a core is positioned within each section at the bending point. The method is characterized in that during at least a portion of the bending, the position of the at least one core against the pipe at the bend location varies depending on at least one bending parameter.

It has been ensured that the bending cores should not be held in a fixed position, but should be inserted at a location which depends on at least one bending parameter of the respective section occurring at any time. Tests have indicated that by using the method of the invention, a double-cross DD tube can be bent over a 140 ° bend without wrinkling the outer wall of the DD tube on the inside of the bend, and the cross-section of the individual sub-tubes has greatly changed shape.

The bending cores may be allowed to move relative to each other to assume the best possible position in the tube. Each core may be provided with a resilient stop. Alternatively or additionally, at least one of the bending cores may be pushed to the desired location.

The position of the bending core in each compartment varies during the bending operation, depending, for example, on the bending radius. Thus, the S-shaped bend can be made just by varying the position of the bending core and it is not necessary to pull the bending cores together from the multiple tube and then insert the bending cores together at another location on the tube. Thus, the speed allowed by the method of the invention is higher.

Another embodiment of the method according to the invention is characterized in that one of the bending parameters is the length of the already bent part of the tube.

In the known method, which assumes a DD-tube with a circular cross-section, during the bending, the cross-section becomes flattening, which increases with the length of the already bent part of the tube, i. j. with increasing the angle by which the pipe is bent. In addition, due to its original position, the partition is moved. In the known method, at 90 ° bend, the smallest cross-sectional diameter is approximately 8% smaller than its largest diameter.

In the method of the invention, e.g. found that the smallest cross-section diameter for bending above 140 ° is only about 3% smaller than its largest diameter.

In the method of the invention, wherein the first of the cores is disposed in a first compartment that is bent when bent to a first radius of curvature and the second of the cores is disposed in a second one of the compartments that is bent when bent into a second radius of curvature greater than the first radius of curvature Preferably, during at least the initial bending phase, the first core is positioned opposite the bending site further along the tube than the second core in the opposite direction to the direction of movement of the bending site against the tube. In this initial bending phase, the pipe bend size is preferably less than 20 °. Preferably, after the initial bending phase, at least one of the cores is displaced from the first position to the second position, which is farther along the pipe than the first position in the opposite direction to the direction of movement of the bending site against the pipe.

This arrangement can be explained as follows: during bending, the partition wall located on the outside of the bend is elongated less for bending with a smaller bending radius than for bending with a larger bending radius. During the initial phase, the material flows predominantly to the outside of the bend in the circumferential direction and much less in the longitudinal direction. This can lead to a wall crack if the position of the bending core is not adjusted during the initial phase according to the bending radius and the bending angle.

It has been shown that in practice good results can be obtained if the initial phase corresponds to a bend of 20 ° or less. After bending by 20 °, there is sufficient material supply in the longitudinal direction to avoid cracking. Thus, the bending core is preferably pushed forward by an external compressive force after the initial phase to prevent flattening of the cross-section of the corresponding section. In practice, it has been shown that a forward movement of about 2% of the bending radius is sufficient to maintain the original cross-section at an acceptable degree as indicated. The rate of increase in the compressive force and / or the final value of the compressive force is preferably higher at a higher bending rate of the multiple tube.

This embodiment of the invention has had good results in practice. It is believed that with a higher bending rate, the forces between the bending core and the partition walls will increase due to the increased deformation rate of the material. Larger compressive forces are required to compensate for these larger forces.

At the same time, the invention relates to an apparatus for bending a multiple tube in a bending plane, wherein the tube is formed by a system of sections running simultaneously along the length of the tube, comprising:

a) support on the tube support during bending,

b) bending means for bending the tube around the support at the bend, which in relation to the tube progressively moves along the tube;

c) cores inserted into the respective compartments to support the tube from the inside during bending;

d) positioning means for maintaining the cores at the bend, allowing the at least two cores to be displaced relative to each other in the longitudinal direction of the tube during bending

The device may be provided with compensating means which, during bending, permit the displacement of at least two bending cores longitudinally with respect to each other. That is, at any time during bending, the current position of the bending core in the compartment may be adapted to the bending radius generated at that time and location.

In a known device that uses bending cores, these cores are attached to the frame of the device by fastening means and during bending, the bending cores protrude from the straight portion of the bent tube and extend up to the bending tube bending location.

The positioning means of the core are preferably adapted to apply a resilient force to at least one of the mutually displaceable cores, thereby allowing for proper displacement in the longitudinal direction of the tube. Suitably, the resiliently extending member connects at least one of the sliding cores to a fixed member (e.g., a frame portion). The resiliently expandable member may be a metal tension rod. The resiliently expandable element allows longitudinal displacement of the bending core when the position of each core provided with such a component is determined by the balance between the spring force of the element and the force exerted by the walls of the compartment on the bending core.

A particularly simple embodiment is characterized in that the resiliently expandable element is a tension rod or spring. The rod has the advantage of its simplicity and is not prone to clogging with chips, chips and the like.

By using a DD tube bending device, good results are obtained in a particular embodiment in which at least one core comprises a body having a constant cross-sectional shape in the longitudinal direction of the pipe and a head attached to the body and provided with a first bounding face facing outwards the curvature of the tube when the bending and curvature in the bending plane is substantially coincident with the curvature produced during bending in the wall of the tube, which during bending abuts the first bounding face. Tests with this embodiment have shown that bending thick-walled DD-tubes at larger angles is good without destroying the tube walls or without significantly altering the cross-sectional shape of each D-shaped section.

In particular, to form S-bends, the bending heads and the bending body may be joined together so as to tilt relative to each other about a tilting axis perpendicular to the bending plane. However, in certain applications, the necessary tilt mechanism may be susceptible to contamination, which adversely affects its operation.

A further simplification of the device is achieved by an embodiment characterized in that the bending head has a limiting face which is directed towards the crossbar and extends substantially up to the bend to be made in the crossbar. In this embodiment, the bending head may be rigidly attached

SK 279558 k6 to the bending body, which allows the use of the device also for a pipe in which the material is released from the inside during bending.

A further advantage of the device is that the core head tapers at the tip distant from the bending body to the tip. Since the bending head tapers to the tip, it is also possible to bend across said bending plane without having to change or reposition the two bending cores. In this bending operation, the two bending cores will occupy a longitudinally similar position against the DD-tube.

Since the bending cores move longitudinally along the tube during bending, they may not be pulled out of the tube to move from one bending plane to another bending plane perpendicular thereto, but it is sufficient to rotate the tube 90 ° about the longitudinal axis of the tube. This embodiment makes it possible to fold the pipe in any desired plane with respect to the crossbar.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to the accompanying drawings, in which: FIG. 1 is a cross-sectional view of the DD tube in the plane of the bend, the tube being mounted in the apparatus of the invention; 2 is a view of a bending core for use in the apparatus of the invention, and FIG. 3 is a view of another exemplary embodiment of a bending core for use in an apparatus according to the invention.

DETAILED DESCRIPTION OF THE INVENTION

Fig. 1 shows a radial bending block 1 of a circular circumference which forms a support part in the tube bending device 6. The radial bending block 1 is provided with a tangential part 2 which together with the clamping device 3 serves to fix the tubes 6 to be bent. The radial bending block 1 has at its periphery a semicircular shape recess for receiving the bent tube 6. The radial bending block 1 is rotating together with the clamping device 3 about an axis 4 perpendicular to the image surface. In the illustrated case, the radial bending block 1 and the clamping device 3 are rotated 90 ° clockwise relative to the original position.

The tube 6 is mounted in the apparatus and comprises two separate compartments 7 and 8 which are separated from each other by a common partition 9. The rear end of the tube 6 is fixed by the clamp 20. The clamp 20 is freely movable in the longitudinal direction of the tube 6 during bending. 20 to rotate about the axis, coinciding with the longitudinal direction of the tube 6. In order to avoid deflection of the tube 6 during bending and to control the bending process, the tube is supported by a slide 21. The fixed alignment jaw 22 guides the tube closely along the radial bending block 1.

Bending means, i. j. the radial bending block 1, the clamping device 3 and the slide 21 cooperate in bending the tube at the bending point which extends along the tube simultaneously with the rotation of the radial bending block 1.

In known methods and devices, the slide 21 can slide freely on the guide bar. However, for better control of the material flow in the longitudinal direction, it is preferable to control the slide 21 so as to exert a pressure or pulling force on the tube wall. Good results are obtained with compressive force.

The first core 13 extends into the first section 7; the second core 12 extends into the second compartment 8. The cores 12, 13 are located at the bend location. Each of the bending cores 12 and 13 comprises a bending body 14 and a bending head 15. The bending cores 12 and 13 are articulated by means of steel tension rods 16 and 17 to a rocking arm 18 which is again articulated to the frame 19 of the device, which is not detailed shown. The tension rods 16 and 17 form resilient extensible members that exert elastic pressure on the cores 12 and 13 to provide positioning of each bending core 12, 13 according to the bending parameters in each of the two sections 7, 8.

In the device shown, the walls of the sections 7, 8 tend to pull the cores 12, 13 forward, i.e. during bending. j. On the other hand, the outer wall of the second section 8 arranged on the outside of the bend creates a rearwardly directed force on the second core 12. This force causes, as a result of the elastic extension of the second tensioning rod 16, a slight displacement of the second core 12 rearward. By acting of the second tension rod 16, the swing arm 18 and the first tension rod 17, this displacement of the second bending core 12 rearward causes the first bending core 13 to be moved forward. Correspondingly, the position of the first bending core 13 is influenced by the crossbar 9 and by the action of the tensioning rods 16, 17 and the swing arm 18 influences the position of the second bending core

In this embodiment, the cores can be moved by the pressure of the expandable bars 16, 17 to assume the most suitable relative position during the bending process.

In the initial bending phase, the effect of the forces acting on both cores 12, 13 is such that the first core 13 in the first section

7, which is bent to a smaller radius than the second section

8, is positioned more forward than the second core 12, that is to say further along the tube 6 in the direction of movement of the tube 6, which is opposite to the direction of movement of the bend site. This assists the support effect of the core 12, 13 on the walls of the tube 6 during this phase. After this initial phase, which preferably does not exceed 20 ° bend, the rocker arm 18 is pushed slightly forward, i. j. is printed to the left as shown in FIG. 1. The first core 13 at this point cannot move forward with respect to the contact with the pipe 8. As a result, the second core 12 is pushed forward by the second tensioning rod 16 into a forward position. As mentioned, the magnitude of this position shift may be minimal, e.g. about 2% of the bend radius. The effect is to improve control of the shape of the tube during bending.

As a result of the described force action and the resulting absolute and relative positions of the bending cores 12, 13, the tubes according to the invention can be bent by an angle greater than 90 ° without the cross-sections of the individual tube sections being defined to an inappropriate extent.

To form the S-bends, the clamp 20 and the two bending cores 12, 13 including the tension rods 16, 17 and the rocker arm 18 rotate 180 ° about the longitudinal axis of the tube. After rotation, the second section 8 with the second bending core 12 lies in front of the radial bending block 1 and the first section 7 with the first bending core 13 inside is opposite the skid 21. Then, the bending process can continue to engage again as a result of the forces described. correct location.

Fig. 2 shows a bending core 12, 13 comprising a bending body 14 and a bending head 15 connected thereto. The bending body 14 and the bending head 15 are pivotably connected to each other by a pivot pin or hinge 25. The cross-sections of the bending body 14 and bending head 15 correspond substantially. the cross-section of the respective section of the tube 6 to be bent. The bending body 14 may be connected to the frame of the device by means of a tension spring or by means of a resilient deformable tension bar 16, 17 as described.

Fig. 3 shows an embodiment of a bending core 12, 13 usable in the invention. Two identical bending cores are used. The bending body 14 has a constant cross-section along its entire length, which substantially corresponds to that of the section to be bent.

For the bending core 12, 13 of the tube 6, the limiting face 26 is a flat face that cooperates with the crossbar 9 of the tube 6. The limiting face 27 has a shape corresponding to the shape of the outer wall of the compartment. The bending head 15 has a curvilinear face 28 curved in a plane adjacent to the limiting face 26. During bending, the limiting face 28 cooperates with the crossbar 9 and is shaped to conform to the curvature formed in the crossbar 9. At the same time, the bending head 15 has a rear face 30 which is curved in two mutually perpendicular directions, on one side being curved to conform to the shape of the outer wall of the tube 6 when bent and on the other side curved according to the radius of the intended bend. When bending the tube 6, two such identical bending cores 12, 13 are used and the limiting face 28 of one of the bending cores 12, 13 and the rear face 30 of the second bending core 12, 13 are involved in the bending process. Both cores 12, 13 are thus interchangeable.

The faces 30 and 28 converge into a common tip 31. This is made possible by rotating the clamp 20 through an angle of 90 ° against the position shown in FIG. 1, bend the pipe in a bending plane parallel to the crossbar 9. The edges 32 and 33 then participate in the bending process. It is also possible to bend at the rotation angles of the clamp 20 other than 90 °.

As with the bending core of FIG. 2 may have a resiliently expandable element at the bending core of FIG. 3 shows the shape of a tension spring or tension rod.

Claims (15)

PATENT CLAIMS A method of bending a multiple tube (6), which is provided with multiple sections (7, 8) arranged side by side in the longitudinal direction of the tube, in a bending plane, wherein the bending point is progressively displaced along the tube (6) and An intermediate core (12, 13) at each bending section (7, 8), characterized in that during at least a portion of the bending, the position of at least one of the cores (12, 13) varies at the bending point against the tube (6) depending on at least from one bending parameter. Method according to claim 1, characterized in that the at least one bending parameter is the length of the part of the tube (6) that has already been bent during bending. Method according to claim 1 or 2, characterized in that at least one of the cores (12, 13) can move freely during bending under the force of elastic forces in the longitudinal direction of the tube (6). Method according to any one of claims 1 to 3, characterized in that the first core (13) is disposed in a first compartment (7) which is bent during bending into a first radius of curvature and the second core (12) is disposed in a second a section (8) which is bent during bending into a second radius of curvature greater than the first radius of curvature, wherein during at least the initial bending phase the first core (13) is positioned further along the pipe (6) than the second core (6) 12) in the direction against the movement of the bent spot against the pipe (6). Method according to claim 4, characterized in that in the initial bending phase the bending amount of the tube (6) is at most 20 °. Method according to any one of claims 1 to 5, characterized in that after the initial bending phase at least one of the cores (12, 13) is moved relative to the bending position from the first position to the second position which is further along the tube (6). than the first position in a direction opposite to the direction of movement of the bent spot relative to the pipe (6). Method according to claim 6, characterized in that an external compressive force is used for the displacement at the end of the initial phase with at least one displaced core (12). An apparatus for bending a multiple tube (6) having multiple sections (7, 8) arranged side by side in the longitudinal direction of the tube (6), in a bending plane equipped with a bending block (1) to support the tube (6) during bending, by bending means (2, 3, 21), for bending the tube (6) around the bending block (1) at a bend that moves against the tube progressively along the tube (6) by a plurality of cores (12, 13) inserted into the respective compartments ( 7, 8) for reinforcing the tube (6) during bending inside and with locating means (16, 17, 18) for holding the cores (12, 13) at the bending point, characterized in that the locating means (16, 17, 18) ) are suitable for moving at least two cores (12, 13) against each other in the longitudinal direction of the tube (6) during bending. Device according to claim 8, characterized in that the positioning means (16, 17, 18) comprise a resilient element suitable for exerting a resilient force on at least one of the mutually displaceable cores (12, 13) to allow it to be displaced in the longitudinal direction. tubes (6). Device according to claim 9, characterized in that the positioning means (16, 17) comprise a resiliently expandable element connecting at least one of the displaceable cores (12, 13) by the fixed element (18). Device according to claim 10, characterized in that the elastically expandable element is a metal tension rod. Device according to claim 8, characterized in that the positioning means (16, 17, 18) comprise means suitable for applying a compressive force to the at least one core (13) to change its position against the bending point in the longitudinal direction of the tube (6). Device according to claim 8, characterized in that the at least one core (12, 13) comprises a body (14) having a constant cross-sectional shape in the longitudinal direction of the tube (6) and a head (15) connected to the body (14). ) and provided with a first limiting face (28) curved in a plane of bending substantially coincident with the curvature formed during bending in the wall of the tube (6), which during bending adjoins the first limiting face (28). Device according to claim 13, characterized in that the core head (15) is provided with a second restraining face (30) facing in the opposite direction to the first restraining face (28) and which is curved in a bending plane substantially coincident with the curvature formed during bending in the wall of the tube (6) to which the second limiting face (30) adjoins during bending, thereby rendering the core reversible. Device according to claim 13 or 14, characterized in that the core head (15) tapers at its end remote from the body (14) into a tip (31).