EP0332870B1 - Apparatus for bending panels, in particular panels for coating hulls of aeroplanes, rockets or the like - Google Patents

Description

The invention relates to a device for the bending deformation of panels, in particular panels for the planking or the constructive formation of the cell of aircraft, rockets or the like, with stiffening ribs arranged on one side on a molting layer, crossing stiffening ribs with the formation of node points, the device for achieving a Component curvature has force-actuated, mutually adjustable forming members, provided for a form-fitting attack in each case at adjacent nodes and change in length of the stiffening ribs running in the component curvature direction.

Such panels are made from materials with elastic and plastic forming behavior, such as aluminum.
In the case of parts for the specified use, it is of particular importance, for reasons of reducing the air resistance, to make the panel exterior exposed to the air flow smooth and with a constant curvature. In addition, such components for aircraft, including general aviation, must be able to be produced with work equipment, that allow inexpensive production.
Such panels can either be of integral construction, consisting of planking with integrated, crossing reinforcing ribs (rib belts, stringers) or of differential construction, that is to say with reinforcing ribs riveted onto the skin.

EP-A-0 078 891 B1 (& US-A-4 498 325), which is considered to be the closest state of the art, has already disclosed a method and a device for bending the panels, in particular for cladding the cell of aircraft, have been proposed, according to which the deformation is brought about by a plastic, linear change in length of the stiffening ribs extending in the direction of the curvature, and the introduction of the deformation forces on the stiffening ribs takes place at such a distance from the molting that the panel has a stress curve with inside the molting is subject to lying neutral fiber.

From US-A-2 958 242, a device for forming sheet metal profile strips of relatively small thickness is known, which carries pivoting members pivotable about bearing axes on a fixed support member. The forming members are inevitably controlled in the forming process as a function of a pivoting movement as a function of a cam having an cam, the forming members being attacked on the workpiece by means of frictional engagement.
Forming devices designed in this way do not allow the direction of action of the forming forces to be adapted to the changing curvature during the forming process due to the unchangeable bearing distances of the forming members.
Furthermore, to form components with larger wall thicknesses is a frictional Attack of the forming members does not transmit the forming forces sufficiently.
In addition, due to the unchangeable mounting of the forming members, a free adjustment of the device to the dimensions of the workpiece to be formed is only possible to a limited extent.
The invention is based on devices designed according to EP-A-0 078 891 B1 and aims to improve the known device designs, in such a way that between adjacent nodes of the stiffening ribs, components subjected to bending deformation, the components running in the direction of curvature , the rib belt subjected to the shaping after completion of the shaping process has a constant distribution of strain and thus internal stress distribution over its entire extent.

The object is achieved compared to the prior art by means of a device according to the features of claim 1 and in a further advantageous embodiment according to the features of the claims following claim 1.

A forming device designed according to the invention allows the Introduction of the forming forces on the workpiece, in relation to the direction of force application, on the sections of the rib belts to be subjected to a change in length, and thus to bring about a force introduction from which a residual stress distribution in the rib belts results, which extends over the entire extension of the rib belts between each has two adjacent nodes uniform course.
The introduction of force can thus take place perpendicular to the stringers running transversely to the direction of curvature, that is to say at right angles to the line between the pivot axes of the pivotable shaping members and the force application points of the members on the workpiece.

Due to the pivotability of the pairs of clamping jaws on the shaping members, an adaptation, according to the respective degree of shaping during a shaping process, can be freely adjusted about its pivot axis. This enables force to be applied to the workpiece, which is able to compensate both compensatory movements of the tool, or the device and also the workpiece itself, and an adaptation of the clamping jaws to the direction or position of the stringer, which changes during the forming process.

The invention is explained in more detail below with reference to an embodiment shown in the drawing.

Figur 1

schematisiert in Perspektive einen Ausschnitt aus einem Paneel in umgeformtem Zustand,

Figur 2

in schematisierter Darstellung eine Umformeinrichtung nach dem Stand der Technik in einer Umformstellung und Angabe der Richtung des Angriffs der Umformkraft am Werkstück,

Figur 3

in einem Kräftediagramm die Einleitung der Umformkräfte in das Werkstück, in schematischer Darstellung und in Gegenüberstellung bekannter Ausführungen einer Umformeinrichtung gegenüber der erfindungsgemässen Ausbildung,

Figur 4

in schematisierter Darstellung den Aufbau der erfindungsgemässen Umformeinrichtung in Verbindung mit der Krafteinleitung am Werkstück,

Figur 4a

schematisiert in einer ausschnittweisen Darstellung eine Draufsicht auf das Paneel mit dem Angriff der Umformglieder,

Figur 5

eine Ausführungsform der erfindungsgemässen Einrichtung nach Figur 4 in einer Seitenansicht und

Figur 6

eine Ansicht der Umformeinrichtung gesehen in Richtung des Pfeiles X der Figur 5.

The drawing shows:

Figure 1

schematized in perspective a section of a panel in the deformed state,

Figure 2

in a schematic representation a forming device according to the prior art in a forming position and specifying the direction the attack of the forming force on the workpiece,

Figure 3

the introduction of the forming forces into the workpiece in a force diagram, in a schematic representation and in comparison with known designs of a forming device compared to the design according to the invention,

Figure 4

in a schematic representation the structure of the forming device according to the invention in connection with the introduction of force on the workpiece,

Figure 4a

schematized in a cut-out representation a top view of the panel with the attack of the forming members,

Figure 5

an embodiment of the inventive device according to Figure 4 in a side view

Figure 6

a view of the forming device seen in the direction of arrow X of Figure 5.

In Figure 1, the panel is generally designated 2, its skinning 3, and the crossing stiffening ribs 4 and 5.
For example, the panel 2 is a cladding part for the cell of aircraft, the stiffening ribs 4 to be subjected to a change in length subsequently being referred to as rib belts and the stiffening ribs 5 which intersect with them being referred to as stringers. Furthermore, the panel outer surface lying in the air flow in the installed state of the panel 2 bears the reference number 6 and the node locations formed by the crossing stiffening ribs the reference number 7.
The nodes 7 can also be formed so that instead the stringer 5 are only stubs of the same are combined with the rib belts 4, in order thus to obtain an approach for the form-fitting attack of the forming device.

In Figure 2, a forming device according to the prior art is shown. The forming device 10 contains forming members 11, 11a, at the free end of jaw pairs 12, 12 'are attached to the workpiece 2 for attack. The forming members 11, 11a are arranged on a support axis 15 ', which at the same time forms the piston rod of the working piston 15 of a hydraulically operating servomotor 13. The servo motor 13 receives the piston 15 in a cylinder housing 14 so as to be axially displaceable, forming cylinder chambers, the deforming member 11 being fixedly connected to the cylinder housing 14. The second forming member 11a is in turn firmly connected to the piston rod 15, so that when the servomotor 13, which interacts with a pressure medium control device (not shown here), the two forming members are adjusted parallel and linearly to one another.
Here, the forming forces F in the point of action A are effective at mutually adjacent nodes 7 of the panel 2 in a coaxially directed manner. The direction of attack of the forming forces F acting coaxially opposite one another on the workpiece 2 remains unchanged, regardless of the bending state of the workpiece 2. The linear transfer of the forming forces F to the workpiece 2 results in an uneven distribution of the bending moment at the sections of the ribbed belts 5 which are to be subjected to a change in length and which lie between two adjacent node points. This results in a concentration of the internal stresses in the workpiece in conjunction with an uneven one Curvature course the skinning 3 and thus the outer surface 6 around which the panel 2 is in the installed state.

In the force diagram according to FIG. 3, in addition to forming forces F, which in the shown deforming state of the panel 2 are coaxially directed at an angle to the position of the stringers 5, are denoted by F ′ forming forces which act on the workpiece at the points of attack A and the position of the stringers 5 at right angles to the deformed state and thus to the radius R between the pivot axis of the deforming members and the force application point A.

With A ', the base points of the stringer 5 and the ribs 4 on the skinning 3 are indicated and p represents the bending distance of the attack of the forming forces F and F' in the point of attack A from the base point A '.
H also indicates the difference between the base points A 'and the apex D of the planking 3 in a given state of curvature of the workpiece 2. The difference between the points C, C 'in the line of action of the coaxially directed forming forces F compared to the forming forces F' leaves the difference between the bending stresses effective in the rib belts 4 during the forming process in the forming state shown, caused by the different direction of the attack of the forming forces F. recognize the forces F '.

In the embodiment according to the invention shown in FIG. 4, the shaping members designated 111, 111a are arranged such that they can pivot relative to one another.
In the area of one end of the forming members 111, 111a, as in the known design according to FIG. 2, the pairs of clamping jaws 112, which can be brought into engagement with the workpiece 2, 112 'arranged, which grasp the rib belts 4 to be subjected to a deformation between them and which engage in a form-fitting manner at adjacent nodes 7 of the panel.
In the area of the opposite end of the shaping members, the servo motor designated here 113 acts. Its working piston 115 is supported in an articulated manner on the forming member 111 and the working cylinder 114 on the forming member 111a. The bearing eye of the working piston is designated by 123 here.

Relative to the longitudinal extent of the forming members 111, 111a, an anchor part 130 is arranged between the pairs of jaws 112, 112 'and the servo motor 113, which serves as a support and as a separate pivot bearing for an independent relative pivoting movement of the forming members 111, 111a in the direction of the pivoting plane EE ( Figure 1) is used. Both the cylinder 114 and the working piston 115 of the servo motor 113 engage in an articulated manner on the shaping members 111, 111a by means of a pivot bearing 120, 121.

The anchor part 130 pivotally supports the forming members 111, 111a by means of bearings 134, 134a. The armature part 130 also contains adjusting means for changing the distance L of the axes of the bearings 134, 134a, as can be seen from the structural design according to the embodiment of the device according to FIGS. 5 and 6 described below.
FIGS. 5 and 6 show an exemplary embodiment according to the invention, parts corresponding to parts in FIGS. 1 to 4 having the same names and having the same reference numerals.

The shaping members 111, 111a are designed here in the manner of a closed frame, the opening 150 of which serves to receive parts of the servo motor 113 and parts of the armature 130. The pairs of clamping jaws 112, 112 ′ are supported on the frame forming the forming members 111, 111a.

The adjusting device 140 contains a threaded ring 142 which can be screwed onto the thread of the anchor rod 131 of the anchor part 130 and which can be locked. This is supported on the shoulder 144 which supports the bearing bush 143 which carries the pins of the bearings 134, 134a and can be displaced on the anchor rod 131 in such a way that each after setting the threaded ring 142 a corresponding setting of the distance L of the axes of the bearings 134, 134a on the two forming members 111, 111a and thus a change in the direction of the force application of the forming force F 'is effected. As a result, the forming force F 'corresponding to the design of the component 2 during the forming process, or in the final forming position of the links 111, 111a to one another, perpendicular to the extension of the stringers 5 or at right angles to the pivot radius R, about which the forming members 111, 111a can be pivoted are attacking the rib belts 4 in the force application point A.
Instead of the adjustment device 142, 143, 131 shown for changing the distance L, an embodiment is also conceivable with the aid of which it is possible to change the position 134, 134a with the anchor part 130 in the direction of the longitudinal extension of the forming members 111, 111a. Such a change in the distance between the points of application A of the forming force F 'and the axes of the pivot bearings 134, 134a, that is to say a change in the radius R, allows the device to be used on components of different dimensions.

The device also has a stroke limiter 160 which contains a screw 161 which is firmly inserted into the shaping member 111a and an adjusting nut 162 which can be screwed onto the thread and locked.
In addition, a suspension device 170 is provided which is supported on the adjusting nut 162 of the stroke limiter 160. The spring serves to hold the forming members 111, 111a in a predetermined opening position when the actuator 113 is depressurized. This results in an easier placement of the device on the component.
The device can be designed as a mobile tool or as a component of a fixed processing unit.

In the present embodiment of the device, the pairs of clamping jaws 112, 112 'on the forming members 111, 111a are arranged freely pivotable about axes 180 transversely to the direction of the forming force F'. By means of the pairs of jaws 112, 112 'mounted in this way, an automatic adaptation to the position or the degree of deformation of the stringer 5 is ensured during the entire forming process and thus enables a perfect transfer of the forming force F to the component 2. With 178 an adjustment screw is also designated, which is used for the adjustable limitation of the opening path of the device.

Claims (6)

1. Device for bending panels, in particular panels for the covering or constructional formation of the airframe of aircraft or rockets, wherein the covering comprises reinforcing ribs which are disposed on one side and intersect one another to form junction points, the device having power-activated deforming members (111, 111a) which are adjustable relative to one another for the positive-locking engagement at junction points adjacent one another in each case and for altering the length of the reinforcing ribs extending in the direction of curvature of the structural component, characterised in that each of the deforming members (111, 111a) is mounted on an anchor part (130) which is common thereto so as to pivot by means of pivot bearings (134, 134a) relative to and independently of one another in the direction of curvature of the workpiece (2), the distance (L) between the pivot bearings (134, 134a) being adjustable.
2. Device according to claim 1, characterised in that the distance (L) between the pivot bearings (134, 134a) on the anchor part (130) is altered by means of an adjusting device by means of a tracking process during the course of the reshaping process in order to maintain a constantly perpendicular application of the deforming forces (F') on the structural component (2).
3. Device according to claim 1 and/or claim 2, characterised in that means are provided for altering the pivot radius (R) of the deforming members (111, 111a) between the pivot bearings (134, 134a) and the points of application (A) of the deforming forces (F, F') on the structural component (2).
4. Device according to any one of the preceding claims, characterised in that pairs of clamping jaws (112, 112'), which engage at adjacent junction points (7) and retain between themselves in a positive-locking manner a rib web (4) of which the length is to be altered by deforming, are disposed on the deforming members (111, 111a).
5. Device according to any one of the preceding claims, characterised in that the pairs of clamping jaws (112, 112') are mounted on the deforming members (111, 111a) so as to be automatically and freely adjustable by means of pivot pins (180) disposed at right angles to the pivot plane (E-E) as a function of the respective deformation state of the structural component (2).
6. Device according to any one of the preceding claims, characterised in that the components (114, 115, 115', 123) of a servo motor (113) generating the deforming forces (F') engage by means of hinged bearings (120, 121) in the vicinity of the free ends of the deforming members (111, 111a).

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