EP0014461B1 - Device for bending metal tubes - Google Patents

Abstract

A bending device for metal pipe with and without plastic jacketing has a short cylindrical segment including a circumferential groove which determines the bending radius of the pipe to be bent and a support for holding the pipe to be bent tangentially with respect to the groove. A lever is mounted for concentric pivotable movement about the segment and a pressing block is mounted on the lever for pivotal movement about an axis parallel to the segment axis. The pressing block has a working surface which has an approximately semicircular, concave cross section in a plane disposed parallel to the pivot axis of the pressing block and the segment axis and a concave cross section in a plane disposed perpendicular to those axes.

Description

The invention relates to a bending device for metal pipes with une without plastic sheathing, in particular for installation pipes, consisting of a segment of a flat cylinder, on the circumference of which a groove defining the bending radius R _{1 of} the pipe is arranged and to which an abutment for the tangential mounting of the pipe to the groove and an axis concentric to the cylinder axis for attaching a lever are assigned, which can be pivoted continuously and concentrically about the segment during the bending process by means of the axis and on which a pressure piece with a working surface is arranged on an axis parallel to the segment axis, which in a parallel to the axis-extending plane has an approximately semicircular, concave cross-section with the radius R _o .

From US-A-2820504 a pipe bending device with a toroidal pressure piece is known, which forms a rigid unit with an actuating lever. During the bending process, this pressure piece cannot be pivoted about a concentric axis of the cylinder segment in one pass by sliding on the tube. Rather, the pressure piece is guided on the edge of the cylinder segment on rails, so that by repeatedly levering the pressure piece around imaginary pivot axes that lie on the rails, the tube is pressed in sections into the groove of the cylinder segment. The pressure piece is therefore a type of molding press, the inner shape of which corresponds to the outer shape of the finished bent tube. Absolutely smooth bends cannot be achieved with the known device; rather, impressions of the pressure piece can be seen on the pipe surface at regular intervals.

GB-A-1384575 discloses a bending device for producing additional curvatures on pipes which have already been bent, the principle of which acts as a kind of kinematic reversal of the principle of action of the bending device described at the outset. Here, the pressure piece is arranged stationary, and the cylinder segment with the circumferential groove is - hydraulically driven, pivotable relative to the pressure piece. However, the pressure piece is designed in the manner of a gutter, i.e. H. it runs in a straight line in the pipe direction. This means that no other effects can be achieved than with the object described at the beginning.

A bending device with a cylinder segment and a circumferential groove is likewise known from US Pat. No. 3,410,125, which can be pivoted about the axis of the cylinder segment with respect to a two-part pressure piece. Here, the pressure piece pulls the tube into the circumferential groove. Here, too, the pressure piece is designed to be straight in the longitudinal direction of the tube, since the tube which was initially stretched is pulled out of it. Here too, no other effect can be achieved than with the object described at the beginning.

From US-A-2171 907 a bending device of the type described above is known, in which the pressure piece can be implemented in the circumferential direction and has a plurality of grooves on its circumference for interaction with segments of different diameters or radii of curvature. However, all grooves have straight surface lines.

With the exception of the object of US-A-2 820 504, which is based on another principle of action, all the bending devices described above have thrust pieces whose working surface facing the tube or segment is designed as a half-cylinder surface and is complementary to the tube to be bent. Such a surface is concave, but only with respect to a cross section that lies in a plane that runs parallel to or through the axes of the segment and pressure piece. The surface lines run in a straight line in all cases.

With such a bending device, tubes made of soft copper can be easily bent down to a ratio of bending radius R ₁ to tube diameter D _o of approximately 3: 1. In any case, this applies to crystallization tubes made of soft copper with external diameters of, for example, 15, 18 or 22 mm and a wall thickness of 1.0 to 1.5 mm. In the installation industry, the smallest possible bending radius is aimed for, the bending should be free of folds, but in any case without cracks. Another criterion is the lowest possible flattening, ie a deviation from the original circular cross-section of the pipe. In general, a flattening of about 10% of the original pipe diameter is considered tolerable.

Already when bending pipes made of soft copper using the known bending device, considerable effort was required, the size of which could of course be influenced by the length of a hand lever and / or by a transmission gear. However, this expenditure of force already left traces on the bent tube, for example with regard to the flattening mentioned above and with regard to visible impressions at the point where the tube lies against the abutment. The high power requirement can be explained as follows: in the initial position of the bending device and (straight) tube, the axis of the pressure piece, which is also referred to as a sliding block, lies in a plane that is essentially perpendicular to the tube and segment axis. If the pressure piece or the sliding block is now moved relative to the pipe about the segment axis, the pressure piece adjusts itself essentially to the pipe surface closest to the pressure piece axis in such a way that the surface lines of the working surface run tangentially to the pipe surface. Because of the inevitable friction that is reduced by lubricants but not on can be lifted, the pressure piece tends to tilt about its axis, which increases the contact pressure due to the given geometric conditions, although the distance between the axes of the segment and pressure piece remains unchanged. As a result of the considerable transmission ratio, this process takes place on the edge of self-locking, with considerable tensile forces being exerted on the outer fibers of the tube. It can be assumed that both these tensile forces and the increased contact pressure of the pressure piece are the cause of the relatively large flattening of the pipe cross section in soft copper. This flattening is almost unavoidable, although both the circumferential groove in the segment and the working surface in the pressure piece are complementary to the tube.

The prior art also includes a bending device of the type described in the introduction, in which the pressure piece is designed as a roller which represents a negative torus, i. H. the concave surface of revolution of the roller is formed by a half circular arc. It was surprisingly found that this does not significantly improve the conditions either, apparently because the pipe to be bent bears under the influence of the considerable deformation forces on different diameters on the roller surface, so that a noticeable braking effect is also produced thereby.

As soon as the tubes made of soft copper are replaced by tubes made of hard copper, brass or steel, the bending devices with the known pressure pieces with the required small bending radii have proven to be unusable at all. Hard copper tubes, d. H. Such pipes, which come directly from the drawing process of the manufacturing plant, are often used by installers because they have greater strength and are also cheaper.

As soon as a tube made of hard copper is inserted into one of the beige devices that can be used for tubes made of soft copper, there is an extraordinarily high power requirement, which after a slight bend of the tube of about 10 to 15 degrees to a clearly visible flow of the Copper and then an abrupt rupture of the tube on the outside. Similar conditions arise for brass and steel pipes. Ratios R1: Do of 3: 1, even of 5: 1, cannot be achieved in this way. Pipes coated with plastic cannot be processed with the specified bending devices, even with large bending radii, because the slide shoe peels off the plastic skin, so that the bent pipe would have to be discarded.

The invention has for its object to provide a bending device of the type described above, with which both pipes made of soft copper and hard copper as well as brass and steel pipes with the smallest possible ratio R _i : D _o reliable, with the least possible flattening and with low power requirements can be bent.

The object is achieved in the bending device specified in the introduction in that the working surface of the pressure piece is designed as a toroidal surface, the large radius R _{2 of which is} between two to ten times the bending radius R _{1 of} the tube and that the ends of the toroidal surface at the Transition points «A and« B are rounded in the end faces of the pressure piece.

The design of the work surface as a toroidal surface means in principle that the pressure piece is additionally concave in a plane I-I which is perpendicular to the axes. With regard to an unbent pipe, this measure has the consequence that the pressure piece is supported on the pipe only with two substantially semicircular lines, or that the center of the pressure piece, which is in the immediate vicinity of the pressure piece axis, is set back relative to the pipe surface . The rounding of the transition points between the toroidal surface and the end faces of the pressure piece has the consequence that the sliding process is promoted and that lubricants that are either already present on the pipe surface as drawing oils or are subsequently applied in the form of special lubricants are easier to bend between the working surface and the surface during the bending process Pipe surface can get, because of a wedge effect given by the rounding. It has proven to be entirely sufficient to provide a minimum edge radius of 0.5 mm.

It was surprisingly found that the measure according to the invention, in contrast to the deterioration in the conditions to be expected as a result of Hertzian relationships, leads to a significant improvement: for example, pipes made of hard copper, brass and steel with an outer diameter of 18 mm could be readily used be provided with a bending radius between 45 and 65 mm, whereby a hardness saving of around 30% (under otherwise identical transmission ratios) was observed in hard copper compared to soft copper. The pipe surface was perfect and showed no wrinkles. No impression was observed at the site of the abutment either. The flattening was between 0.8 and 1.2 mm, i.e. H. between about 4.5 and 6.7%. This is significantly less than the limit values of 10% of the pipe diameter specified in the relevant processing guidelines.

Optimal conditions with regard to the bending process are obtained by the features in the characterizing part of claim 2, wherein an optimization of the ratios can be observed for example at R ₂ : R ₁ = 5: 1. In a very particularly expedient manner, the torus surface, when set in relation to the circumference of the segment, extends over an angular range «A» between 40 and 50 degrees, whereby it is advisable to arrange the axis of the pressure piece in its longitudinal direction slightly off-center, so that the ends of the pressure piece interacting with the tube form lever arms of different lengths, the length of which is designated «X and« Y » . Depending on the deformation properties of the tube, the length "Y of the lever arm that is furthest away from the segment in the working position can be selected to be about 20 to 40% shorter or longer than the length" X of the other lever arm. If "Y is shorter than" X, the contact pressure of the edge of the pressure piece closest to the segment is slightly less than at the opposite end of the pressure piece, so that the pressure piece slides even more easily on the tube.

With regard to the bending of plastic-coated metal pipes, in particular steel pipes, it has proven to be particularly expedient to produce the pressure piece from a mechanically highly stressable plastic, such as polyamide. To increase the mechanical strength of this material, it is particularly expedient to provide the plastic with glass fiber inserts or to embed metal inserts, which are preferably oriented in the longitudinal direction of the pressure piece. It is particularly useful to use a plastic that either has good sliding properties by nature or is provided with lubricants.

Further advantageous refinements of the subject matter of the invention and their advantages emerge from the remaining subclaims. This applies in particular to the dimensioning of the length and to the geometric arrangement of the pressure piece in the lever according to the features in the characterizing part of claims 5 and 6. These features will be explained more easily in connection with the figures.

An embodiment of the subject matter of the invention is described below with reference to Figures 1 to 6.

• Figur 1 einen Horizontalschnitt durch eine vollständige Biegevorrichtung mit eingesetztem Rohr in Ausgangsstellung (ausgezogen) sowie in einer Zwischenstellung (strichpunktiert) bei der Herstellung eines Rohrkrümmers von 90 Grad, und zwar entlang der Symmetrieebene I-I in Figur 2,
• Figur 2 eine Draufsicht auf den Gegenstand von Figur 1 in Richtung des Pfeils II, wobei der das Segment und das Druckstück umgreifende, gegabelte Hebel im Bereich der Lagerstellen der Achsen teilweise geschnitten ist,
• Figur 3 eine perspektivische Ansicht des Druckstücks in vergrößertem Maßstab,
• Figur 4 eine Draufsicht auf einen fertigen Rohrkrümmer zur Erläuterung der für die Beurteilung wichtigen kristischen Abmessungen,
• Figur 5 einen Teilausschmitt aus Figur 1 mit einer Zusatzeinrichtung für größere Rohrdurchmesser, und
• Figur 6 eine Seitenansicht der Zusatzeinrichtung nach Figur 5,

Show it :

• 1 shows a horizontal section through a complete bending device with inserted tube in the starting position (extended) and in an intermediate position (dash-dotted) during the production of a pipe bend of 90 degrees, specifically along the plane of symmetry II in FIG. 2,
• FIG. 2 shows a plan view of the object from FIG. 1 in the direction of arrow II, the forked lever encompassing the segment and the pressure piece being partially cut in the region of the bearing points of the axles,
• FIG. 3 shows a perspective view of the pressure piece on an enlarged scale,
• FIG. 4 shows a plan view of a finished elbow to explain the critical dimensions important for the assessment,
• 5 shows a part of Ausschmitt from Figure 1 with an additional device for larger pipe diameters, and
• FIG. 6 shows a side view of the additional device according to FIG. 5,

1 and 2 show a segment 10 in the form of a flat cylinder which is provided with a circumferential groove 11 which has a semicircular cross section which is complementary to the pipe to be bent. When the tube is bent, it lies in the groove 11 so that it determines the bending radius. Two flanges 12 and 13 are formed on both sides of the groove 11, the outer diameter of which corresponds to the bending radius R ₁ . An axis 14 is arranged concentrically to the groove 11 in the segment 10, which is surrounded by two hub parts 15 and 16 which protrude slightly on both sides of the segment 10 beyond its boundary surfaces.

The segment 10 has arisen in that a smaller part has been removed on one side to form a flat stop surface 17. At a peripheral point 18, part of the flanges 12 and 13 was additionally removed along a flat surface, but in such a way that the base of the groove 11 remained unaffected. A base plate 20 is clamped against the stop surface 17 by means of a screw 19, which on its underside protrudes noticeably beyond the segment 10 and the axis 14 and there has a clamping surface 21 of reduced thickness for clamping the device in a vice. The base plate 20 contains a recess 22 which extends over the entire height of the segment 10 and is delimited on one side by an inclined surface 23 which merges approximately tangentially into the base of the groove. On the opposite side, the recess 22 is provided with an abutment 24, which forms a semicircular cutout 25 with a projection 26. The position and shape of the abutment 24 are such that a tube 27 according to FIG. 1 can be inserted into the cutout 25 and into the groove 11 in such a way that it extends tangentially to the groove base and perpendicular to the stop surface 17. The point of contact of the tangent lies in a plane E _l , which runs parallel to the axis 14 and to the stop surface 17.

A forked lever 28 can be pushed onto the axis 14 in the radial direction, namely by means of a slot 29 which is adapted to the axis 14. The lever 28 has two legs 28a and 28b which encompass the segment 10 and the tube 27. Between the legs 28a and 28b there is also a pressure piece 30 which is pivotable on an axis 31 parallel to the axis 14 and has a working surface 32 which is semicircular in cross section, ie in a plane which is parallel to the axes 14 and 31 is trained. As is also apparent from FIG. 1, the pressure piece or the working surface is additionally concave in a plane perpendicular to the axes 14 and 31, which is designated II in FIG. 2, namely the working surface 32 forms a torus area whose large radius R ₂ corresponds to five times the bending radius R ₁ . The small radius R _{o of} the torus surface corresponds to the radius of the tube 27. The center point of the large radius R ₂ lies to a considerable extent outside the left edge of the figure in FIG about an axis that lies in its plane and does not intersect it. It goes without saying that even slight deviations from the mathematically exact definition are permissible.

As can be seen from FIGS. 1 and 2, but in particular from FIG. 3, the working surface 32 is arranged on a long side of the otherwise cuboidal pressure piece 30, the ends of the toroidal surface being well rounded at the transition points A and B into the end faces 33 and 34 . The lines of intersection of the torus surface with the end faces 33 and 34 are semi-circles, neglecting the rounding, which correspond to the cross section of the pressure piece 30 along the axis 31.

The length and arrangement of the pressure piece 30 in the lever 28 are made in accordance with FIG. 1 so that in the starting position the one transition point A lies essentially in the plane E ₁ , which runs perpendicular to the tube 27 and radially to the segment axis 14. The other transition point B lies in a plane E2, which likewise runs radially to the segment axis 14, but encloses an angle of 45 degrees with the plane E ₁ . In this starting position, the pressure piece 30, which can also be referred to as a sliding shoe, bears against the (semicircular) transition points A and B on the tube 27 when only a slight force is exerted on the lever 28 in the clockwise direction. To operate the lever 28 by hand, it is provided with a handle bar 35, by means of which the lever 28 is lengthened approximately four to five times (not shown).

As soon as a greater force is exerted on the lever 28 in the clockwise direction, the pressure piece 30 begins to slide on the tube 27 and bend it into the groove 11. After a pivoting angle of the lever 28 of approximately 70 degrees, the position shown in broken lines in FIG. 1 is reached, in relation to which the reference numerals are provided with a ('). It can be seen that the end face 33 'has maintained an essentially radial position with respect to the segment axis 14. The pipe elbow produced by a further 20 degrees after the path of the lever 28 has been completed is shown in detail in FIG. 4, from which the dimensions R ₁ and D _o can also be seen.

From Figure 3 it can still be seen that a bore 36 is arranged for the axis 31 within the pressure piece 30, which is arranged eccentrically between the two end faces 33 and 34, the distances or lever arms X and Y being formed. In a preferred embodiment, the ratio was X: Y = 44:35. In addition to FIG. 3, it should be added that the appearance of the toroidal work surface 32, which is delimited on both sides by flange sectors 37 and 38, is exaggerated to make it clearer improve.

FIG. 5 shows a section from FIG. 1. The upper part of the segment 10 can be seen with the groove 11 and the stop surface 17 to which the base plate 20 is clamped by means of the screw 19. This contains the recess 22 and the abutment 24, which is provided with the semicircular cutout 25. In the cutout 25, the tube 27 is inserted; to this extent there is complete agreement with FIG. 1. In addition, a retaining device 40 is arranged on the side of the base plate 20 or the abutment 24 opposite the segment 10. This consists of a pawl 41, the appearance of which is illustrated by FIG. 6. The pawl 41 is made of a plate and can be pivoted in a plane that runs parallel to the base plate 20 carrying the abutment 24. The clear distance between the base plate 20 and the pawl 41 has the dimension "s". In practice, this dimension can be between half and several pipe diameters. The pawl 41 is pivotable about an axis 42 which is formed by a screw 43 which is screwed to the base plate 20. The distance between the base plate and the pawl 41 is maintained by a spacer sleeve 43, the screw connection being made in such a way that the pawl 41 is freely rotatable on the screw 43. The axis 42 runs parallel to the longitudinal axis of the tube 27.

According to FIG. 6, the pawl 41 has a bore 44 for inserting the screw 43, an actuating lever 45 and a pawl nose 46, the inner surface 47 of which extends essentially concentrically to the central axis of the bore 44 and thus to the pivot axis. A low eccentricity ensures that an increasing lateral force is exerted on the tube 27 when the actuating lever 45 is pressed down in the direction of the arrow 48. Due to this transverse force, the tube 27 is pressed away from the segment 10 into the cutout 25 of the abutment 24.

By this additional bracing of the tube 27 against the abutment 24, which takes place in the direction of the reaction force of the bending force, the following is achieved: Under the influence of the bending force, the tube 27 has the tendency to deform slightly elastically outside the actual bending zone, so that in Figure (5) beyond the segment 10 part of the tube 27 moves slightly to the left. This is apparently the reason why the tube 27 slips slightly in the direction of arrow 49 during the bending process. In any case, on the side of the pipe bend facing the segment 10, occasionally and in particular in the case of larger pipe diameters, ie those above 20 mm, do not show the additional device tion according to Figures 5 and 6 slight ripples that adversely affect the appearance of the elbow. The pawl 41 practically completely prevents both the elastic transverse movement of the tube and the slipping, so that the undulation of the tube is avoided in any case. Due to the spacer sleeve 43 or the distance, the pawl 41 generates a bending moment on the tube 27 which is opposite to the elastic deflection and which holds the tube 27 which holds the tube 27 in the predetermined position in the groove 11. In this way, lateral movement of the tube 27 out of the groove 11 is largely eliminated, so that the flattening of the tube to an oval cross section, which otherwise occurs during bending and is not prevented by the flanges 12 or 13 (FIG. 2), is largely prevented. The additional device according to FIGS. 5 and 6 ensures through its interaction with the other parts of the device that the quality of the bent tube is additionally improved.

Claims (12)

1. Bending device for metal tubes (27) with or without plastic coating especially for plumbing, comprising a segment (10) of a plain cylinder, on the periphery of which is arranged a groove (11) corresponding to the bend radius R₁ of the tube (27) and to which is connected an abutment (24) for the tangential locating of the tube (27) in the groove (11) and an axle (14) concentric with the axis of the cylinder for holding a lever (28), which is pivotable during the bending operation by means of the axle (14) continuously and concentrically about the segment (10) and on which is arranged a pressure member (30) on an axle (31) parallel to the segment axis (14) with a working face (32), which has a concave cross-section with a radius R_o, substantially semi-circular in form, in a plane running parallel to the axles (14, 31), characterised in that the working face (32) of the pressure member (30) is formed as a toroidal surface of which the larger radius R₂ lies between two and ten times the bend radius R₁ of the tube (27) and that the ends of the toroidal surface at their edges (« A and « B ») with the end faces (33, 34) of the pressure member are rounded off.

2. Bending device according to claim 1, characterised in that the large radius R₂ of the torus lies between four and six times the bend radius R₁ of the tube.

3. Bending device according to claim 1, characterised in that the edge radius at the edges (« A and « B ») of the toroidal surface and the end faces (33, 34) of the pressure member (30) is at least 0.5 mm.

4. Bending device according to claim 1, characterised in that the working face (32) is arranged on a long side of an otherwise cuboidal pressure member (30).

5. Bending device according to claim 1, characterised in that the length and arrangement of the pressure member (30) in the lever (28) are so chosen that in the initial position (Figure 1) the one edge (« A ») lies substantially in a plane « E1 » which extends peprendicularly to the tube (27) and radially of the segment axis (14), and the other edge (« B ») in a plane « E2 » which likewise extends radially of the segment axis (14), the planes E₁ and E₂ enclosing an angle « a » between 30 and 60 degrees, preferably between 40 and 50 degrees, and in that in this initial position the pressure member (30) lies with both edges « A and « B on the tube (27).

6. Bending device according to claim 5, characterised in that the axle (31) of the pressure member (30) is located in the pressure member space from the ends thereof respectively by distances « X and « Y » and that the ratio X : Y is chosen to be between 1.4 and 0.7.

7. Bending device according to claim 1, characterised in that the pressure member (30) is of plastic.

8. Bending device according to claim 7, characterised in that the pressure member (30) is of glass fibre reinforced plastic.

9. Bending device according to claim 7, characterised in that the plastic is provided with metal inserts.

10. Bending device according to claim 7, characterised in that the pressure member (30) contains a lubricant.

11. Bending device according to claim 1, characterised in that on the side of the abutment (24) opposite the segment (10) is arranged a counter-holding device (40) spaced therefrom by a distance « s » in the lengthwise direction of the tube (27), by which the tube (27) can be braced away from the segment (10) against the abutment (24).

12. Bending device according to claim 11, characterised in that the counter-holding device (40) comprises a latch (41) which is pivotable in a plane which extends parallel to a base plate (20) carrying the abutment (24) and about an axis (42) running parallel to the tube (27).

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