METHOD AND BENDING DEVICE FOR BENDING A SHEET METAL PART

Abstract

In a method for bending a sheet-metal part (50) on a profile body (24) having a bending profile (52), the sheet-metal part (26, 28) is pressed against the profile body (24) at an initial contact point (54), wherein bending rollers (26, 28), starting from the initial contact point (54), press the sheet-metal part (50) along the bending profile (52) against the profile body (24) and adapt it plastically to the shape of the profile body (24). Furthermore, a bending device (22) for carrying out the method is specified.

Description

The invention relates to a method for bending a sheet metal part on a profile body comprising a bending profile and a bending device for carrying out the method.

For forming a sheet metal part it has been hitherto usual to give a desired shape to the sheet metal part by stamping or pressing together profile bodies. For example, the sheet metal part according to DE 39 40 984 A1 is positioned between two identical profile bodies comprising bending profiles, which may be moved together in a fitting manner on the bending profiles in the manner of two articulated pieces. The sheet metal part located between the profile bodies is formed by pressing together the profile bodies according to the shape of the bending profiles. The forming process consists in that the sheet metal part is fitted, piece by piece, to the shape of the bending profiles of the profile bodies.

A comparable forming method is known from the publication EP 0 530 956 A1. By pressing together the profile bodies, compressive stresses are produced between the profile bodies and the sheet metal part at pressure points where the profile bodies are applied to the sheet metal part. As the sheet metal part is only applied at comparatively few pressure points by pressing together the profile bodies for forming, but is not guided over an entire bending region of the sheet metal part by the bending profiles of the profile bodies, it leads to uneven distribution of the compressive stresses and thus to uneven forming of the sheet metal part, including deviations of shape such as, for example, undesired buckling of the sheet metal part.

Thus, such a forming method for forming, for example, a bearing configured from a sheet metal part is also unsuitable as a seat plate for a piston roller of a radial piston engine according to the publication DE 198 10 372 A1. A cross section through a cylinder block 2 of the radial piston engine is shown in FIG. 5 and a cross section through a cylinder 4 according to FIG. 5 is shown in FIG. 6. In the radial piston engine, pistons 6 are radially arranged perpendicular to a drive shaft 8, the stroke of the pistons 6 being carried out in the radial direction 10 (only indicated by reference numerals in FIG. 6) relative to the drive shaft 8 by an external stroke ring 12. The bearing 14 is positioned between the piston 6 and a piston roller 16 coupled thereto and serves as a seat plate on the piston side for the piston roller 16 which may be rotated in a rotational axis 18 oriented parallel to the drive shaft 8, illustrated in dotted lines in FIGS. 5 and 6 which, when rotating the drive shaft 8, rolls along an inner face 20 of the stroke ring 12. Deviations in shape on the seat plate lead, during the operation of the radial piston engine, to material wear on the piston roller 16 and also on the seat plate itself, denoted as a bearing 14, as well as possibly to resultant wear to the stroke ring 10.

The object of the invention is to provide a method for bending a sheet metal part on a profile body comprising a bending profile, and a bending device for carrying out the method, by means of which the shape of the sheet metal part may be adapted particularly accurately to the shape of the profile body, relative to the bending profile of the profile body, as a result of bending stresses exerted particularly uniformly on the sheet metal part and as a result of particularly material-protecting forming.

Relative to the method, the aforementioned object according to the invention is achieved by the features of claim 1. Advantageous developments form the subject of the sub-claims referring back thereto.

Relative to the device, the aforementioned object is achieved according to the invention by the features of claim 6. Advantageous developments form the subject of the sub-claims referring back thereto.

Thus, the bending device for bending a sheet metal part, in order to adapt said sheet metal part to a bending profile of a profile body provided therefor, comprises bending rollers, whereby the sheet metal part may be pressed against the profile body at an initial contact point provided on the profile body and may be formed along the bending profile of the profile body. The bending rollers are, in turn, mounted on a carriage which is configured to be able to be lifted at an adjustable distance from the profile body. The bending rollers are connected to one another in the manner of a tension spring.

The method for bending the sheet metal part initially comprises pressing the sheet metal part by means of the bending rollers at the initial contact point of the profile body and subsequently thereto an adaptation of the sheet metal part to the bending profile of the profile body by plastic forming of the sheet metal part, for which the bending rollers press the sheet metal part along the bending profile proceeding from the initial contact point.

The initial contact point, in this case, is understood to be the pointed, linear or planar portion of the profile body against which the sheet metal part is pressed before the start of the bending process on the profile body.

The bending of the sheet metal part is always carried out by local plastification at contact points at which the bending rollers apply compressive stress to the sheet metal part. The compressive stress is produced, on the one hand, by lifting the carriage in the direction of the profile body between the respective bending roller and the sheet metal part and, on the other hand, by the connection of the bending rollers in the manner of a tension spring, whereby one bending roller is acted upon by a further bending roller connected thereto in the manner of a tension spring with a tractive force and in the direction thereof, which at the contact point of the bending roller with the sheet metal part acts on the sheet metal part as compressive stress.

The advantages achieved by the invention are, in particular, that by pressing the sheet metal part against the profile body during the bending process, the sheet metal part is fixed and there is no relative movement between the sheet metal part and the profile body, whereby the bending process is carried out relatively inaccurately and an element provided on the bending device or the sheet metal part would be affected in a manner which might damage the material, such that the shape of the sheet metal part might deviate from that of the bending profile of the profile body. Moreover, a local plastification at the contact points between the bending rollers and the sheet metal part is achieved over the entire sheet metal part, including the sheet metal part ends, provided for the forming, by the compressive stress generated by the connection of the bending rollers in the manner of a tension spring, combined with the compressive stress generated by lifting the carriage, acting on the sheet metal part. Moreover, the sheet metal part is guided by bending rollers in continuous contact from an initial contact point along the bending profile on the profile body in the manner of a rolling bending method, as a result of which the shape of the sheet metal part is, furthermore, identical to the bending profile of the profile body. With the continuous guiding of the sheet metal part during the bending process, moreover, buckling of the sheet metal part, which would have a damaging effect on the material, is avoided. Moreover, as a result of the method according to the invention and the bending device according to the invention, the material properties of the sheet metal part are affected to a comparatively small extent.

According to an advantageous embodiment, the compressive stress between the bending rollers and the sheet metal part produced by lifting the carriage and the compressive stress between said bending rollers and the sheet metal part produced by the connection of the bending rollers in the manner of a tension spring, are related to one another such that bending stresses exerted by the bending rollers on the sheet metal part during the bending process for plastic forming of the sheet metal part are approximately uniform over the entire bending profile of the profile body.

According to an advantageous embodiment, the bending rollers are mounted on a carriage such that lifting the carriage moves the bending rollers towards the sheet metal part and presses said metal part against the profile body and fixes said sheet metal part thereto. As a result, an additional fixing device for fixing and securing the sheet metal part during the bending process is not required.

Expediently, the bending rollers on the carriage are rotatably mounted on a single axis such that a further lifting of the carriage, resulting from pressing the sheet metal part against the profile body, causes the bending rollers to roll along the bending profile of the profile body on the sheet metal part, and to press said sheet metal part against the profile body and to form said sheet metal part plastically, such that the sheet metal part adopts the shape of the bending profile of the profile body. By rolling the bending rollers along the sheet metal part by further lifting of the carriage, the contact of the bending rollers with the sheet metal part during the bending process is maintained uninterrupted, whereby a particularly uniform bending process is achieved.

In order to make the shaping of the sheet metal part accurate, it is expedient to lift the carriage in a continuous, uninterrupted bending process, comprising only one step, in the direction of the profile body, both for pressing the sheet metal part against the profile body and for forming the sheet metal part.

In order to design the bending device particularly simply and cost-effectively, the carriage for carrying the bending rollers is of plate-shaped design and provided at a vertical distance parallel to the sheet metal part.

In an expedient development, the carriage is dimensioned with a large surface area such that, by lifting the carriage, the bending rollers which are rotatable on a single axis and displaceably mounted on supports on the carriage, follow a path of the bending profile on the profile body for bending the sheet metal part in a particularly accurate manner.

In order to form the sheet metal part according to the bending profile of the profile body and to avoid a relative movement between the profile body and the sheet metal part, it is expedient to fix the profile body for the bending process.

Moreover, it is expedient to provide on the bending device a counter support which assists the bending process such that the sheet metal part is already fixed to the profile body before the start of the bending process and is secured to the counter support to avoid relative movements between the sheet metal part and the profile body during the bending process, in addition to pressing by the bending rollers.

The counter support is expediently arranged on the carriage and presses the sheet metal part by lifting the carriage at the initial contact point towards the profile body. As a result, for example, at the initial contact point the sheet metal part is prevented from being forced away by compressive stresses exerted by the bending rollers on the sheet metal part.

In an expedient development, the counter support is connected to the carriage in the manner of a compression spring such that, after pressing the sheet metal part against the profile body by means of the counter support, a further lifting of the carriage for forming the sheet metal part by means of the bending rollers carried by the carriage is possible by pressing together the connection which is in the manner of a tension spring.

In order to ensure that the sheet metal part is already fixed rigidly to the profile body before the start of the bending process, it is expedient to provide the counter support at a greater distance from the carriage than the bending rollers, such that when lifting the carriage the counter support firstly comes into contact with the sheet metal part and is pressed against the profile body by means of said counter support, before the bending rollers, which are also connected to the carriage, come into contact with the sheet metal part.

In an expedient development, on one pressing side facing the profile body, the counter support has a counter profile configured in the manner of a bending profile which is identical to the bending profile of the profile body in the region of the initial contact point, at which the counter support presses the sheet metal part against the profile body. The counter support serves to form the sheet metal part in the region of the initial contact point according to the bending profile of the profile body by pressing together the counter support with the profile body.

In a development of the invention, the profile body is designed as a piston roller, for example for a radial piston engine or a radial piston pump with a roller profile, against which the sheet metal part provided as a seat plate for the piston roller on a piston, may be pressed using the bending rollers. In the profile body designed as a piston roller, it is expedient to press the sheet metal part by means of two bending rollers against the roller profile. The bending rollers press the sheet metal part by lifting the carriage—proceeding from the initial contact point and running in the opposing direction—along the roller profile against the piston roller.

Expediently, the bending rollers are connected to one another via a tension spring which is dimensioned such that pressing the sheet metal part against the piston roller by lifting the carriage over the entire roller profile of the piston roller may be carried out with approximately uniform bending stress.

An embodiment of the invention is described in more detail hereinafter with reference to the drawings, in which:

FIG. 1 shows a diagrammatic construction of the bending device with a sheet metal part provided for forming,

FIG. 2 shows the bending device according to FIG. 1 at the start of the bending process,

FIG. 3 shows the bending device according to FIG. 1 in the middle of the bending process,

FIG. 4 shows the bending device according to FIG. 1 at the end of the bending process,

FIG. 5 shows a cross section through a cylinder block of a radial piston engine and

FIG. 6 shows a cross section through a cylinder according to FIG. 5 with a piston and a bearing for a piston roller coupled thereto.

FIG. 1 shows a bending device 22 with a profile body 24 and bending rollers 26, 28 fixed via a fixing device, not shown, which are mounted on supports 30, 32 on a carriage 34. The bending rollers 26, 28 are arranged via chassis 36, 38 provided on the supports 30, 32 on the carriage 34 and which may be moved counter to an arrow direction identified by an arrow 40 in FIG. 1. The bending rollers 26, 28 are acted upon in the manner of a tension spring via a tension spring 42 provided on the supports 30, 32. On the carriage 34 a counter support 44 is arranged via a compression spring 46, which acts on the counter support 44 in the direction of the arrow indicated by an arrow 48, which is located at right angles to the direction of the arrow 40.

Between the profile body 24 and the bending rollers 26, 28 as well as the counter support 44, a sheet metal part 50 provided for the forming is positioned which is pressed via the counter support 44 at an initial contact point 54 against the profile body 24 and may be pressed via the bending rollers 26, 28 against a bending profile 52 of the profile body 24 designed to be circular in this embodiment. The counter support 44 comprises on one pressing side 56 facing the profile body 24 a counter profile 58, the shape thereof corresponding to the shape of the bending profile 52 of the profile body 24 at the initial contact point 54.

FIG. 1 shows the sheet metal part 50 in a position pressed against the profile body 24, the carriage 34 already having being lifted in the direction of the arrow 48, so that in addition to the counter support 44 the bending rollers 26, 28 which are arranged on opposing sides of the counter support 44 on the carriage 34, are in contact with the sheet metal part 50. By lifting the carriage 34 further in the direction of the arrow 48, the sheet metal part 50 is pressed against the profile body 24. A right-hand portion 60 of the sheet metal part 50 is pressed by means of the bending roller 26 against the profile body 24 and, by lifting the carriage 34 with the bending roller 26, is adapted to the bending profile 52 of the profile body 24 as far as a sheet metal part end 62 on the right-hand portion 60, by plastic forming of the sheet metal part 50. In contrast thereto, the bending roller 28 presses a left-hand portion 64 opposing the right-hand portion 60 of the sheet metal part 50 as far as a sheet metal part end 66 on the left-hand portion 64 against the bending profile 52 of the profile body 24.

FIGS. 2, 3 and 4 show the bending process of the sheet metal part 50 at the start of the bending process (FIG. 2), in the middle of the bending process (FIG. 3) and at the end of the bending process (FIG. 4).

FIG. 2 shows the sheet metal part 50 slightly bent in the direction of the arrow 48, the carriage 34 being lifted such that the outer surfaces 68, 70 of the bending rollers 26, 28 have already been lifted away over the pressing side 56 of the counter support 44 in the direction of the arrow 48. The counter support 44 fixes the sheet metal part 50 to the profile body 24 and at the same time prevents the sheet metal part 50 from buckling at the initial contact point 54, as a result of bending stresses which are exerted by the bending rollers 26, 28, by lifting the carriage 34 onto the sheet metal part 50. The sheet metal part 50 is additionally pressed against the profile body 24 by the counter profile 58 provided on the counter support 44, and at the initial contact point 54, and formed according to the bending profile 52 of the profile body 24.

At the start of the bending process, a spring force F_Spring which is identified in FIGS. 2, 3 and 4 by an arrow, only has a comparatively small portion of a normal force F_Normal, generating the compressive stress and identified in FIGS. 2, 3 and 4 by an arrow, for the local plastification of the sheet metal part 50. At the start of the bending process, the normal force F_Normal is largely applied by a lifting force F_Stroke generated by lifting the carriage 34.

FIG. 3 shows the bending device 22, in which the sheet metal part 50 is located in the middle of the bending process, and has already been pressed against the profile body 24 as far as just before the sheet metal part ends 62, 66. In contrast to the start of the bending process, the normal force F_Normal is divided in half in the middle of the bending process, as shown in FIG. 3, respectively into the spring force F_Spring produced by the tension spring 42 and the lifting force F_Stroke of the carriage 34.

At the end of the bending process, which is shown in FIG. 4, the carriage 34 is lifted in the direction of the arrow 48 such that the bending rollers 26, 28 have pressed the entire sheet metal part 50 against the profile body 24 and are located at the sheet metal part ends 62, 66 of the sheet metal part 50. In the portion which the bending rollers 26, 28 have covered between the position shown in FIG. 3 and the position shown in FIG. 4 of the bending rollers 26, 28 on the sheet metal part 50, the spring force F_Spring produced by the tension spring 42 predominates over the lifting force F_Stroke of the carriage 34 to produce the compressive stresses between the bending rollers 26, 28 and the sheet metal part 50. The spring force F_Spring corresponds, therefore, approximately to the normal force F_Normal for the local plastification of the sheet metal part 50 and, as a result, compensates for the comparatively low portion of lifting force F_Stroke of the carriage 34.

The combination of the lifting force F_Stroke produced by lifting the carriage 34 and the spring force F_Spring produced by the tension spring 42 placing the bending rollers 26, 28 under tensile load relative to one another allows a particularly accurate forming of the sheet metal part from the initial contact point as far as the sheet metal part ends, along the entire bending profile of the profile body and with uniform bending stress exerted on the sheet metal part.

The invention is not limited to the embodiment shown in the drawings, in particular not limited to a profile body which is configured as a piston roller with a cylinder shell profile. All the features described above and shown in the drawings may be combined with one another in any manner.

Claims

1. Method for bending a sheet metal part on a profile body comprising a bending profile, the sheet metal part being pressed against the profile body at an initial contact point, and bending rollers pressing the sheet metal part along the bending profile against the profile body and plastically adapting to the shape of the profile body.

2. Method according to claim 1, wherein the bending rollers mounted on a carriage are pressed against the sheet metal part by lifting the carriage.

3. Method according to claim 2, wherein the bending rollers, rotatably mounted on a single axis, are guided by further lifting of the carriage on the profile body along the bending profile.

4. Method according to claim 2, wherein by lifting the carriage carrying the bending rollers in a single step for pressing the sheet metal part against the profile body and for adapting the sheet metal part to the shape of the profile body.

5. Method according to claim 2, wherein the sheet metal part before the start of the bending process at the initial contact point is pressed against the profile body by a counter support mounted on the carriage and is held during the bending process at the initial contact point.

6. Bending device for bending a sheet metal part on a profile body comprising a bending profile, with a carriage arranged at a variable distance therefrom, on which bending rollers connected to one another in the manner of a tension spring are mounted for pressing the sheet metal part at an initial contact point and along the bending profile of the profile body.

7. Bending device according to claim 6, wherein bending stresses exerted by the bending rollers on the sheet metal part are approximately uniform during a complete bending process.

8. Bending device according to claim 6 wherein the carriage is configured to be able to be lifted vertically relative to the sheet metal part.

9. Bending device according to claim 6, further comprising supports which are movably arranged on the carriage for guiding the bending rollers mounted on a single axis thereon along the bending profile.

10. Bending device according to claim 6, wherein the profile body is fixed.

11. Bending device according to claim 6, further comprising a counter support for pressing the sheet metal part against the initial contact point of the profile body.

12. Bending device according to claim 11, wherein the counter support is connected to the carriage in the manner of a compression spring.

13. Bending device according to claim 12, wherein the counter support is provided with a pressing side facing the sheet metal part and, in the unloaded state of the compression spring, is at a greater distance from the carriage than the bending rollers which are mounted on the carriage via the supports.

14. Bending device according to claim 13, wherein the counter support on the pressing side comprises a counter profile which is identical to the bending profile of the profile body in the region of the initial contact point.

15. Bending device according to claim 6, wherein the profile body is designed as a piston roller in the manner of a cylinder, which is provided for a radial piston machine.

16. Bending device according to claim 11, further comprising two bending rollers coupled to one another by a tension spring.