Background of the Invention.

The present invention relates to a method for bending a thin-walled hollow spacer profile for double-glazed windows, which profile has a top side, a bottom side, and two side walls, wherein the profile is positioned in relation to a bending apparatus.

Such method is known from among others EP-B-1,121,873 and WO-89/07495. However, the known methods are connected with drawbacks as it has not been possible to bend hollow profiles of steel with little wall thick¬ ness without strong deformations, which cause forming of external cracks in the corners formed and/or overturned side walls. This makes the profile useless as spacer frames. In the known methods it has been necessary to have a relatively considerable wall thickness at least in the sides so that the profile does not crack or form folds at the bending. Even though attempts have been made to remedy these draw¬ backs, this has not been possible so far, even with use of relatively complicated bending apparatuses.

Thus, it is the object of the present invention to provide a method with which the above-mentioned drawbacks are remedied, and which also is intended for bending of thin-walled hollow spacer profiles for forming of corners, in which the inside angle is acute, for exam- pie down to approximately _. 10°.

According to the present invention this is obtained by a method, characterized in that before the bending, the profile is pre-deformed in the area of the subsequent bending as the side walls of the profile are wedged between two plane lateral guide plates, and as the top side is brought into contact with a first tool part, and as the bottom side is brought into contact with a first dolly on a second tool part, and at least a portion of one of the tool parts may be displaced towards the other, whereby the pre-deforming is carried out.

As the profile is wedged between the two lateral guide plates and as the profile, between the top side and the bottom side, at the same time is wedged between the first tool part and the second tool part, a control will occur in such a way that the side edges during the pre-

deforming will extend in two parallel planes, which are defined by the lateral guide plates. As the two tool parts are displaced towards each other, it will be possible to carry out a pre-deforming in the area of the bending. Hereby, it will be possible to establish a displacing/- floating of the material between and in the side walls of the profile, and the top side and bottom side in a way which may easily be con¬ trolled. Furthermore, the pre-deforming will make it possible to carry out the subsequent bending without risk of formation of folds and cracks in the profile. Thus, among others the material at the top side and bottom side of the profile is displaced to a position in the vici¬ nity of a neutral axis for the bending. Hereby, less forces occur, and therefore, less risk of formation of cracks and folds at the subse¬ quent bending. As the first and the second tool part during the bend¬ ing secures the profile with a well-defined position of the tool parts, and with a well-defined securing pressure, it is possible to control the bending process very precisely so that an upsetting occurs in the material within the neutral axis of the bending. By using the method the floating of the material may easily be controlled by adapt¬ ing the bending die to the profile, by varying the pressure of the die, by positioning the bending die in relation to the axis of rota¬ tion for bending, and by adapting the form of the bending mandril to the profile. Hereby, it will be possible to bend the hollow profiles with a very little wall thickness without risk of formation of cracks and folds in the profile.

Furthermore, the use of a pivotal dolly, which effects the profile outside the area, in which the bending occurs, will cause the material to be formed as a free bending in the actual outer side of the corners formed. Even though a free bending occurs, the profile is wedged be- tween the lateral guide plates and the two tool parts in such a way that the side walls and the inner side of the corner abut and are formed by the lateral guide plates and the bending mandril. This makes it possible to make use of the method on an apparatus, which does not require complicated rollers, dollies or other things, including equip- ment for dry matter filling of the profile for forming of the outer side of the corner during the bending.

The actual bending to an angle of approximately 90° for the inside corner is preferably carried out by a method as described in claim 2.

If it is desired to carry out a bending of the inside corner to an acute angle, which is less than 90°, one may advantageously use the method, which is defined in claims 3 or 4. After the first bending to an angle of approximately 90° is carried out, a subsequent bending for forming of an acute angle in the inside corner may be effected by dis¬ placing the first tool part from the inside corner. This may be effec¬ ted without risk of the side walls slanting in the corner area as there will still be a controlling of the side walls of the profile because of the wedging between the two lateral guide plates.

The invention also relates to an apparatus for use by the method as described above, and consisting of a first tool part for contact with the top side of the profile, a second tool part for contact with the bottom side of the profile, and two plane lateral guide plates for contact with the side walls of the profile, said two tool parts are suspended for displacing against each other for wedging of the top side and bottom side of the profile, and in which at least a portion of the second tool part is suspended pivotally for pivoting in rela¬ tion to the remaining portion of the second tool part around the first tool part for bending the profile around it, and in which the two lateral guide plates are arranged for mutual displacing perpendicular to the displacements of the first and the second tool parts in order to wedge the side walls of the profile, characterized in that the first tool part comprises a bending mandril, which is built together with one of the lateral guide plates, and that the second tool part at one hand comprises a first dolly in form of a bending die, which may be displaced towards the bending mandril to be able to wedge the pro¬ file there between before the bending starts and at least during an initial bending, and at the other hand of a second dolly in form of a pivoting bending arm, which abuts the bottom side of the profile, and which is arranged for a pivoting around the bending mandril.

This apparatus may be made from relatively simple elements. Thus, the two lateral guide plates will simply be made up of plane plates, and the bending mandril and the bending die may be made with an embodi¬ ment, which makes both the pre-deforming and the bending possible. The bending mandril will be able to be displaced away from its position, abutting the inside corner after an initial bending. A possible subse¬ quent bending may be carried out by pivoting the pivotal bending arm

of the second tool part through a further angle. As the profile is pre-deformed, the last sequence of the bending to the angle for the inside corner will be able to occur, only by wedging the profile be¬ tween the lateral guide plates. Thus, the apparatus may be used to form bends with an inside angle as small as approximately 10°.

Furthermore, the apparatus is simplified by the bending mandril and the bending die being made up of interchangeable elements, which are adapted to the actual profiles to be bended. This is advantageous as demands for the displacing/floating of the material and the securing of the profile are individual for each type profile. Thus, by pre- deforming and bending different types of profiles, one may use the same apparatus only by replacing the bending die and the bending man¬ dril.

Brief description of the drawing.

The invention will now be further explained with reference to the ac¬ companying drawing wherein

Fig. 1 illustrates a cross section through an embodiment of a hol¬ low thin-walled spacer frame, which may be bended by a me¬ thod according to the invention,

Fig. 2 illustrates a schematic and partial side view for illustra¬ tion of a pre-deforming, which is carried out by a method according to the. invention,

Fig. 3 illustrates a partial section according to line III-III of Figure 2, for illustration of an embodiment for a bending die used,

Fig. 4 illustrates a view corresponding to Figure 2, and which il- lustrates the use of a second embodiment for the bending die,

Fig. 5 illustrates a section corresponding to Figure 3, and taken according to line V-V in Figure 4,

Fig. 6 illustrates a partial side view for illustration of a cor- ner, which is bended through 90°,

Figs. 7 and 8 illustrate sectional views taken according to lines VII- VII, respectively VIII-VIII in Figure 6 for illustration of the appearance of the profile in the bended corner,

Fig. 9 illustrates a front view of an apparatus for use by a method

according to the invention,

Fig. 10 illustrates a side view of the apparatus illustrated in Fi¬ gure 9,

Fig. 11 illustrates a rear view of the apparatus illustrated in Fi- gure 9,

Fig. 12 illustrates a partial sectional view through the apparatus illustrated in Figures 9-11 for illustration of the punching of a hole,

Fig. 13 illustrates an enlarged fragmentary view of the punching illustrated in Figure 12,

Fig. 14 illustrates a partial sectional view taken according to line XIIII-XIIII in Figure 13,

Fig. 15 illustrates a view corresponding to Figure 12, but for il¬ lustration of the bending of a profile by the method accor- ding to the invention,

Fig. 16 illustrates an enlarged fragmentary view of the bending il¬ lustrated in Figure 15,

Fig. 17 illustrates a partial sectional view taken according to line XVII-XVII in Figure 16, Fig. 18 illustrates a partial view corresponding to Figure 16, but for illustration of the continuing bending for forming of an acute inside corner,

Fig. 19 illustrates a view corresponding to Figure 18, but for il¬ lustration of the forming of a more acute inside corner, Fig. 20 illustrates a front view of the first tool part, which is used by a method according to the invention,

Fig. 21 illustrates a side view of the first tool part illustrated in Figure 20,

Fig. 22 illustrates a rear view of the first tool part illustrated in Figure 20, and

Fig. 23 illustrates a side view corresponding to Figure 21, but shown from the opposite side.

Figure 1 illustrates a cross section through a thin-walled hollow spa- cer profile 1 before it is bended. The profile has a top side 2, a bottom side 3, and two side walls 4,5. It is significant that a top side and a bottom side are mentioned only for the purpose of orienta¬ tion in the accompanying drawing. A rolling 6 is found at the top side of the profile as the profile 1 is formed from a plate-shaped mate-

rial. Furthermore, ventilation holes 7 are found at the top side 2 so that the air in the inside of a formed double-glazed window has con¬ nection with the inside 8 of the hollow spacer profile, which may be filled with drying agents.

The spacer profile may have other embodiments than the one shown, in which the bottom side 3 is connected with the two side walls 4,5 through a slanting surface 9. Thus, the profile may also be made with a rectangular cross section. The height and the width of the profile may vary within very broad limits. Thus, the profile may vary in heights from 4-8 mm and widths from 5-24 mm. By using the method ac¬ cording to the invention, profiles of steel may be bended with a wall thickness down to approximately 0.2 mm.

Figures 2 and 3 illustrate a side view of respectively an enlarged sectional view through a profile 1, which is pre-deformed. A first tool part 10, which comprises a bending mandril 11 and a lateral guide plate 12. which are built together in an interchangeable unit, abuts the top side 2 of the profile, respectively the one side wall 5 of the profile. The second side wall 4 of the profile abuts a second lateral guide plate 13 in such a way that the profile is wedged between the lateral guide plates. A bending die 14 is pressed upwardly towards the bending mandril 11 at the pre-deformation in such a way that a pre- deforming of the cross section of the profile occurs in the area, in which a subsequent bending has to be carried out. Thus, a displacing/- floating is provided for the material of the profile as well as both the top side 2 and the bottom side 3, which subsequently form the in¬ side corner, respectively the outside corner at the bending. A displa¬ cing of the material in the side walls 4,5 also occurs, which form the lateral flanges in the corner, which subsequently is formed at the bending. Thus, the bending die 11 is made with a central raised part 15, which forms two recesses 16,17, in which a part of the material from the side walls 4,5 and the top side 2, enters at the pre-deform¬ ing and at the bending. Furthermore, the raised, central part 15 has a groove 18, which is parallel to the longitudinal direction of the pro¬ file 1, and which serves for partial receiving of the rolling 6 of the profile 1.

It is noted that both the bending die and the bending mandril have

different embodiments depending on the cross-sectional form of a pro¬ file, which is to be pre-deformed and bended. Thus, Figures 4 and 5 illustrate a side view, respectively a sectional view for illustration of the pre-deforming by using a bending mandril 11 as illustrated in Figures 2 and 3, and a bending die 14', which is different from the one illustrated in Figures 2 and 3. Thus, the bending die 14' illus¬ trated in Figure 4, has a substantially greater extension along the longitudinal axis of the profile, and the bending die 14' also has a V-shaped upper surface of contact, which makes it possible to displace the bottom side 3 of the profile 1 to abut the top side 2 of the pro¬ file on each side of the rolling 6. The bending die 14' which is il¬ lustrated in Figure 5, preferably will be used in connection with pro¬ files having a greater width than the profiles, which will be pre- deformed and bended by using the bending die 14, which is illustrated in Figures 2 and 3.

Even though Figures 2 and 4 illustrate a bending die 14,14' positioned outside a bending centre, which is defined by the substantially cylin¬ drical bending mandril, it will be possible to displace the bending die 14,14' towards the left or the right in Figures 2 and 4, depending on the choice of material, profile form and desired deformation of the corner.

Figures 6-8 illustrate a partial side view through a corner, which is bended through 90", and two sectional views through the profile at two different positions in the bended corner. In Figure 6 a side wall 4 of the profile is illustrated. When the profile is bended, an upsetting of the material is carried out at an inner part 19 at the inside cor¬ ner. Thus, folds do not appear, which in certain situations may be inappropriate regarding strength and the subsequent sealing of a double-glazed window. At an outer part 20 of the side wall 5 a stretching of the material occurs without risk of formation of cracks. As the area where the bending is carried out is pre-deformed, the sub¬ sequent deformation which appears during bending in form of an upset- ting and a stretching will have a smaller extension. Hereby, the risk of rolling at the inner side and cracks forming at the outer side 20 is eliminated.

Furthermore, the top side and the bottom side 2,3 of the profile is

brought nearer a neutral axis for the bending before the bending, which means that the corresponding deformations in form of an upset¬ ting and stretching at the top side and the bottom side 2,3 of the profile are reduced by the subsequent bending. Hereby, the bending may be substantially carried out without risk of folds and cracks at the top side and the bottom side 2,3 of the profile.

In Figure 7 a section is illustrated according to line VII-VII in Fi¬ gure 6, which illustrates the form of the profile in the bending but right by the corner. It is shown that the bottom side 3 is drawn in¬ wardly towards the top side 2, and at the same time the top side 2 is pressed slightly outwardly towards the bottom side 3. This corresponds substantially to the cross-sectional form the profile is given before the bending, and which is illustrated in Figure 3. Thus, this illus- trates that further deformations of great importance in this area do not appear.

Figure 8 illustrates a cross-section according to line VIII-VIII in Figure 6, which is a plane taken under 45" in relation to the bended profile 1. Thus, Figure 8 illustrates that the bottom side 3 in two areas 21 at each side of the central part 22 of the top side is fur¬ ther drawn inwardly towards the bottom side 3 of the profile in the actual corner so that a central part 22 is formed having a ridge being slightly outwardly raised in relation to the areas 21 of the bottom side 3. This cross-sectional configuration of the profile in the ac¬ tual corner results from a free forming and illustrates that only a rather unimportant further deformation during the bending occurs, namely the stretching which occurs in the parts 21 of the bottom side 3, which are located in the vicinity of the plane containing line VIII-VIII.

This stretching which occurs in the parts 21 is rather insignificant, and does not give risk of cracks forming as the bottom side 3 is be¬ forehand displaced against the neutral axis of the bending.

It is noted that during the bending the profile be wedged between the two lateral guide plates 12,13, and between the bending mandril 11 and the bending die 14. It is possible to vary the pressure on the bending die 14 depending on what is desired for the bending. In certain cases

a securing of the profile is obtained and in other cases a controlled sliding of the profile is established in relation to the bending die 14. A second dolly 45, which comprises a pivotal bending arm and which constitutes a further portion of a second tool part 25, comprising the bending die 14, is abutted the bottom side 3 of the profile distant from the corner, and is pivotted around the bending mandril 11 in order to bend the corner to a desired, predetermined angle. This is explained more explicitly in the following, in which an embodiment for the apparatus is explained.

Figure 9 illustrates a front view of an apparatus for use by the me¬ thod. The apparatus consists of a fixed supporting duct 23, through which the profile 1 to be bended is guided to the apparatus. The dif¬ ferent elements/parts of the apparatus are supported on a frame 24. The apparatus is arranged as a combined bending and punching appara¬ tus. Hereby, it will be possible to use the same apparatus for pun¬ ching a hole in the frames in case this is desired owing to the sub¬ sequent filling of gas in the double-glazed window. This is the case in approximately 20% of all formed frames. With the apparatus accor- ding to the invention it will thus be possible to quickly and simply carry out both a punching and a bending of a profile 1.

Now the apparatus will be described with reference to Figures 9-11. The apparatus consists of a first tool part 10, which is located at the top side 2 of the profile 1, and a second tool part 25, which is located at bottom side 3 of the profile. The second tool part 25 com¬ prises the bending die 14 and a punching needle (26), which both are located in a casing 27 that may be displaced perpendicular to the plane, wherein the bending occurs in order to adjust a positioning for different widths of profiles. As it appears from Figure 12, this dis¬ placing of the casing 27 occurs, in that the casing is provided with a track 28 extending in a guide 29, which through a console 30 is con¬ nected with the frame 24. A second console 31 is also connected with the frame 24, and contributes to controlling the casing 27.

Thus, as it appears from Figure 10, the lateral guide plate 13 will also be able to be displaced perpendicular to the plane, in which the bending occurs. Via an arm 32 the lateral guide plate 13 is connected with a cylinder 33, which through a side plate 34 and the consoles

30,31 is connected with the frame 24. The bending die 14 and the pun¬ ching needle 26 in the second tool part 25 are activated by means of a cylinder 35, the casing 36 of which is secured to the frame 24. The cylinder 35 optionally activates the bending die 14 or the punching needle 26 through a central block 37 and a plate 38. The plate 38 is mounted on a guide 39 in the casing 36, which also contains the cylin¬ der 35. The plate 38 is activated by the punch 40 of the cylinder 35. The central block 37 may be displaced between a position outside the bending die 14 and the punching needle 26, respectively, by means of a cylinder 41, which through a console 42 is mounted on the plate 38. Both the bending die 14 and the punching needle 26 are surrounded by a return spring 43,44, which ensures that these two elements are re¬ turned to a starting position when the cylinder 35 is inactivated.

As mentioned above, the second tool part 25 comprises a second dolly 45 in form of a bending arm for abutting the bottom side 3 of the pro¬ file 1. The bending arm 46 comprises a console 47, which is provided with screws 48, with which the console is bolted to a block 49, which is connected with a toothed wheel 50. The bolts 48 extend through a groove 51, which is formed in a crescent-shaped plate 52, which is secured to the frame 24. Thus, the bending arm 46 is pivotted by acti¬ vating the toothed wheel 50 by means of a step motor (not shown), which may rotate the toothed wheel 50 through a well-defined and pre¬ determined angle, either by use of a toothed belt or by direct contact with the toothed wheel 50.

As mentioned earlier, the first tool part 10 comprises the bending mandril 11 and the lateral guide plate 12, which are built together with it. This combined unit 53 also comprises a punching plate 54 pro- vided with holes for the punching needle. This combined unit, which is located loosely detachable for quick replacement for adapting dif¬ ferent types of profiles, which are to be bended/punched, is illustra¬ ted clearly in Figures 20-23.

The combined unit 53 consists of a stud 55, which is received in a bore 56 (see Figure 14) in a rod 57, which extends through the toothed wheel 50, and which is activated by a cylinder 58 (see Figure 10), which makes it possible to displace the unit 53 according to the double arrow 59. Furthermore, the combined unit 53 comprises a posi-

tioning stud 60, the outer terminal surface 61 of which is intended for abutting a positioning guide 62 (see Figure 17), which is mounted on the console 31. The length of the positioning stud 60 is adapted to the actual profile to be bended, and ensures a correct mutual posi- tioning of the two tool parts 10,25.

The punching plate 54, which is provided with a hole 63, abuts the top side of ft profile, wherein a hole is to be punched as illustrated in Figures 12-14 by rotating the whole unit 53. This occurs by means of a cylinder 64, which is mounted in a console 65. The console 65 has been secured to the frame 24 through a casing 66, whereon the toothed wheel 50 is suspended, and which contains the cylinder 58. The cylinder 64 operates through its piston 67 on an arm 68. The arm via the piston 67, is able to rotate the combined unit 53 between two outer posi- tions. The two outer positions are illustrated in Figure 13 for a pun¬ ching, and in Figure 16 for a bending. The rotation of the unit 53 is limited by the two sides 69,70 of the positioning stud 66, which abuts the punching needle 26 and the bending die 14, respectively.

The hole 63 in the punching plate 54 is connected with a duct 71 in¬ side the unit 53. When the punched pellet is punched from the profile 1, the punching needle 14 will lead this pellet inside the duct 71. The duct 71 leads to a hollow space, which is in connection with an exsuction tube 74, which through a hose 75, is connected with an ex- suction device. Thus, the punched pellet in a safe way is removed from the process and gives no risk of poor functioning. The exsuction through the exsuction connecting piece 74 will also result in exsuc¬ tion and removal of zinc dust and the like, which may be released at the bending. It is significant that the unit 53 at use, is located under an angle of approximately 20-30" in relation to the shown ver¬ tical position. Thus, the duct extends obliquely downwards, which en¬ sures that a punched pellet is always removed because of the gravi¬ tation.

Figure 13 illustrates a partial sectional view, which illustrates how the punching occurs. Thus, it appears that the combined unit 53 is pivotted to a position, in which the punching plate 54 abuts the top side 2 of the profile 1. The lateral guide plates 12,13 are also in contact with the side walls 4,5 of the profile in such a way that this

is secured during the punching. Before the punching, the central block 37 is positioned under the punching needle 26 by means of the cylinder 41. During the actual punching, a smaller deforming occurs of the bot¬ tom side 3 of the profile 1. Before a subsequent bending takes place, a displacing of the profile 1 occurs so that the deforming, which ap¬ pears at the bottom side 3 of the profile, does not appear in the di¬ rect vicinity of a corner. This is automatically controlled by means of a control and a calculating unit (not shown), wherein data concern¬ ing the frame made is stored.

In Figure 14 a further partial section is shown for illustration of the punching. This section illustrates that the punching needle 26 is separated in the middle and that the two parts are connected by means of a connecting stud 76, which makes it possible to easily replace the upper part of the punching needle 26 in approximately 8 minutes when this is necessary, for example because of wear. In a corresponding way, Figure 17 illustrates how the upper part of the bending die is interchangeably located in a recessed wheel 77, which is formed in the lower part of the two part bending die. Thus, both the punching needle and the bending die may be replaced without it being necessary to dis¬ mount the casing 27.

Figures 15-19 illustrate different steps of the bending of a profile 1. The central block 37 is positioned under the bending die 14. The combined unit 53 is pi ott _. ed to the outer position, in which the sur¬ face 69 of the positioning stud 60 abuts the punching needle 26. As mentioned earlier, the profile 1 is wedged between the lateral guide plates 12,13. By activating the cylinder 35 the bending die is pressed towards the bottom side 3 of the profile so that the top side 2 of the profile abuts the bending mandril 11. Hereby, a pre-deforming of the profile is carried out as explained above. After the profile 1 is pre-deformed, a bending of the profile occurs. Before the bending is started, the pressure of the bending die 14 may optionally vary either to ensure a securing of the profile or to allow a controlled sliding of the profile in relation to the bending die during the subsequent bending. The bending occurs by rotating the toothed wheel 50, and thereby pivoting the bending arm 46 through a predetermined angle. In Figure 15 the bending arm 46 is pivotted through an angle of appro¬ ximately 80°. The bending arm 46 abuts the bottom side 3 of the pro-

file 1 at a distance from the bending centre. It is significant that as an alternative to a bending arm 46, a punctiform dolly may be used to carry out the bending. The use of an elongated bending arm in¬ volves, however, several advantages as one may obtain a greater sup- porting surface, and it is also possible to bend ends of profiles lon¬ ger because of support further out on the bended end of the profile.

When the bending occurs through the first 90°, the lateral guide plates and the bending die are automatically returned. If the profile is to be bended 90° only, the bending is now finished. A possible sub¬ sequent pre-deforming and bending may occur hereafter, by displacing the profile 1 once again for positioning the profile for a subsequent bending. If the profile is to be bended through a further angle for forming an acute, inside corner, the profile 1 is displaced slightly forward to the position, which is illustrated in Figure 18. Hereby, the inside corner is free of the bending mandril 11. Hereafter, the lateral guide plates 12,13 are again pressed to abut the side walls 4,5 of the profile 1. Furthermore, the combined unit 53 is pivotted in such a way that the punching plate 54 abuts the top side of the pro- file 1. Hereby, the profile will be further secured to its bottom side 3 abutting the supporting duct 23. Hereafter, the bending arm 46 is pivotted through a further angle till the inside corner has an angle of approximately 30". In this position a further bending of the pro¬ file 1 will be made impossible because of the positioning of the com- bined unit 53 inside the bended corner. Because of the pre-deforming and the started bending which occurs, it is not necessary for the bending die and/or the bending mandril to be engaged with the profile in order to control the bending for forming of an inner, acute corner. As the material is beforehand displaced in a desired way, it is suffi- cient that the lateral guide plates 12,13 ensure that the side walls 4,5 cannot be pressed outwardly.

If the corner is to be bended to a more acute angle, the profile 1 is displaced to the position illustrated in Figure 19. This occurs by the profile 1 being released from the wedging between the lateral guide plates 12,13. Subsequently, the cylinder 58 is activated to pull the combined unit 53 inside a guide channel 78 outside the plane, wherein the profile 1 is bended. The profile 1 is subsequently pulled back¬ wards to the position illustrated in Figure 19 till the actual corner

is outside a ring-shaped surface 79, which earlier was directly in continuation of the surface 80 (see Figure 23), which made up the con¬ tact surface of the lateral guide plate 12. Hereafter, the two lateral guide plates are wedged against the profile, which now are made up of the lateral guide plate 13 and the ring-shaped surface 79. Hereafter, the bending arm 46 is pivotted through a further angle. Hereby, it will be possible to form inside corners with angles as small as appro¬ ximately 10°. By this final bending for forming of an acute angle of between approximately 30° and approximately 10°, it is sufficient to secure the profile alone by the wedging between the lateral guide plates as there is no risk of the profile being displaced in its lon¬ gitudinal direction by this last part of the bending.

It is noted that the cylinders which form part of the apparatus are pneumatic cylinders, even if they alternatively may be made of hydrau¬ lic cylinders. The pneumatic cylinders are connected with a control and calculating unit (not shown), which ensure that the necessary steps are activated successively depending on the size for the angle, under which a corner is to be bended. These steps also consist of dis- placing of the profile by means of a driving mechanism (not shown), which is also connected with the control and calculating unit. Thus, no manual operations are required even at bending of the inside corner to an angle as small as 10°.