WO1992009778A1

WO1992009778A1 - A method and an apparatus for manufacturing closed spacer frames of hollow thin-walled profiles

Info

Publication number: WO1992009778A1
Application number: PCT/DK1991/000362
Authority: WO
Inventors: Joergen Skovgaard Madsen
Original assignee: Skovgaard & Co. A/S
Priority date: 1990-11-28
Filing date: 1991-11-28
Publication date: 1992-06-11
Also published as: JPH06511433A; DK282090D0; AU8944491A; CA2097174A1; DK282090A

Abstract

A closed spacer frame (19) is manufactured by welding the profile ends for making an endless profile which is bent by a tool (17, 18) for making a desired frame form, the outer end portion (75) of the endless profile overlapping the endless profile (73). The profile ends are then separated by means of a saw (16) situated between two jaws (15) in a combined saw apparatus and welder and which cut the endless profile which is led bent away from the outline of the frame after the one jaw (15) is opened while the other jaw (15) maintains the bended frame. The two end portions of the frame (19) are then placed end-to-end in the jaws (15) and are butt welded (at 21) for making the closed frame (19). During the conveying and bending the acceleration, velocity and deacceleration of the profile are controlled by a computer which calculates the allowable maximum values for frame forms and sizes where no permanent deformation in the formed frame occurs.

Description

A METHOD AND AN APPARATUS FOR MANUFACTURING CLOSED SPACER FRAMES OF

HOLLOW THIN-WALLED PROFILES.

Background of the Invention.

The present invention relates to a method of manufacturing closed spacer frames of hollow thin-walled profiles comprising welding the profile bars end-to-end for making a substantially endless profile, the endless profile being bent in predetermined angles a number of times for making the desired frame form and in a way causing the outer free end portion to overlap the endless profile as the overlapping portions extend parallelly and immediately adjacent each other, positioning the endless profile in relation to the cutting means, maintaining the endless profile during the cutting which separates the frame from the endless profile in a point located at the end of the adjacent outer free end portion.

Such method is known from i.a. US Patent No. 4,597,279 and from EP No. 121,873. The methods disclosed therein are used for bending rectangular spacer frames by using profile bars having a length corresponding to the circumference of the frame made. The method is disadvantageous in that a great wastage occurs as the cutting of the desired length for forming a spacer frame often means that the remaining part of a standard profile bar has to be discarded as it is too short to be used for manufacturing another frame. A solution to this is described in DE No. 3,221,986 and consists in assembling the profile bars by means of loosely mounted junctions for forming an endless profile. This is uneconomical in so far as the price of the junctions and wage costs for mounting exceed the price of the remaining part of a profile bar. A further improvement is described in EP No. 192,921 in which a welding of the profile bars is proposed and a subsequent bending and cutting as described above.

The prior art methods require the use of a plant which is dimensioned on the basis of the largest frames to be manufactured. Accordingly, the manufacturing will be slow due to the long transport routes for the profiles. Moreover, such a plant requires much space and it is difficult for an operator to monitor the entire process. If any defects are to be remedied the operator has to walk relatively long distances to be able to intervene in all the part processes of the method. The known methods are slow as acceleration, velocity and deacceleration are fixed at one or several levels which is based on the weakest frame to be manufactured. Thus the most advanced known solution uses only four levels.

It is the object of the present invention to provide a method of the type mentioned above which remedies the above-mentioned drawbacks which method moreover makes it possible to reduce the time used on manufacturing a frame at the same time as the frame is manufactured in any desired form and size.

According to the invention this is obtained with a method which is characterized in comprising the said cutting between two jaws, the profile being maintained during the cutting, bending backwards the endless profile while the bended frame is maintained at the one end portion by the one jaw so that said profile does not overlap any part of the frame, reclosing and maintaining the other jaw round the other end portion of the bended frame, placing through a mutual displacement of the two jaws the two end portions of the separated and bended profile end-to-end and welding them together for forming the closed frame, and controlling the acceleration, velocity and deacceleration for the conveying and bending of the profile with a computer which calculates the weakest point of the profile and the allowable maximum values in each stage of the manufacturing process which can be used without making permanent deformation in the frame produced.

As the profile is conveyed for bending in the form of the welded endless length substantially any waste is avoided and the welding can be carried out automatically without the use of expensive junctions. However, in certain cases it may be necessary to cut a piece of the free end part of the profile to avoid that the profile is bent in a welding. To make sure that the manufactured frame is flawless it is desirable to avoid a bending in the welding. This is quite simply effected by the computer calculating where the bendings are to be made and then the positioning means, e.g. in form of the feed rollers which can be guided for reciprocating rotation, make a correct positioning of the profile and said piece of the free end portion is optionally cut off. This is preferably necessary for manufacturing frames having one or several very short side/s but it may occur in all frame sizes and forms.

As the cutting is made with a cut after the bending of the spacer frame, said cut being situated between two jaws maintaining the profil and vis-a-vis the end of the free end portion, the frame will have very exact side length. By welding which is made with the two end portions of the frame maintained in the two jaws no distortion in the frame thus occurs. Moreover, the method will be fast as the two jaws preferably consist of welding jaws in a butt welder.

The frame can be manufactured with any polygonal form, a triangular form, a quadrangular form, a pentagonal form, etc. as each corner can be bent in an individual angle which is controlled by the computer. It only has to be ensured that after the last bending the outer free end portion of the profile is placed parallelly and adjacent the endless profile. As each sequence during the conveying and bending is optimized by the computer it is possible to reduce the manufacturing time in relation to conventional manufacturing of frames where acceleration, velocity and deacceleration are dimensioned for the worst imaginable situation, which means that certain frame sizes are manufactured at an acceleration, velocity and deacceleration which could be increased.

Be defining acceleration, velocity and deacceleration for conveying and bending on the basis of the formulae stated in claim 5, it becomes possible to make a continuous optimizing by means of the computer. By doing so, the least possible manufacturing time is obtained for frames of any form and size.

Moreover, the invention relates to an apparatus for manufacturing closed spacer frames of hollow thin-walled profiles which are bent in predetermined angles a number of times for forming the desired closed form, which apparatus comprises a magazine for the profile bars, a supporting table for supporting the profile during its bending, a welder for welding the profile bars, a feed unit, a cutting apparatus, and a bending tool, and which apparatus is characterized in that it comprises two independent units partly consisting of the magazine of the profile bar and the supporting table and partly of a working unit which in order comprises the welder, the feed unit, a combined cutting apparatus and welder, and the bending tool which has a movable land for bending the profile, and a computer for monitoring and controlling the operation of the working unit.

According to the invention the method can be performed in a safe way with this apparatus. Moreover, the apparatus is advantageous in that it is easy and quick to service. When service and maintenance are to be made the manufacturer only needs to stop his work for a short time as the working unit can be replaced with a similar working unit within a few minutes. This is not possible with the prior art apparatuses in which the supporting table is built together with and constitutes an integrated part of a space-requiring apparatus having several separate apparatus portions for conveying, sawing, bending, welding, etc. Thus, in prior art apparatuses defects have to be repaired in situ by experts, either travelling fitters or local engineers. If there is a need for spare parts after the fault is detected, this will usually involve forwarding time as it is too expensive for a user to have an extensive stock of spare parts. As all working parts in an apparatus according to the invention are contained in one compact working unit this part can just be replaced by unskilled labour, and the damaged working unit can subsequently be forwarded to the factory for service. Thus a fitter or a local engineer need not to be equipped with fault-detecting equipment or a large spare parts assortment. Moreover, it is possible to reduce the area requirements substantially in relation to area requirements for the prior art apparatuses. This is possible due to the fact that all working parts are combined in the right order and in one unit.

Brief description of the drawing.

The invention will now be further explained with reference to the accompanying drawing wherein

Fig. 1 shows a schematic view of an apparatus according to the invention comprising a magazine, a supporting table and a working unit,

Fig. 2 shows a partial view, from above, of a combined saw apparatus and welder which form part of the working unit, Fig. 3 shows a partial end view of the saw apparatus and welder shown in Fig. 2 in direction towards the travelling direction of the profile, Fig. 4 shows a partial side view of the saw apparatus and welder shown in Fig. 2 in a direction perpendicular to the conveying of the profile,

Fig. 5 shows a partial schematic view, from above, for illustrating the mutual placing of a bending tool and the combined saw apparatus and welder holding therein a completed, bended profile,

Fig. 6 shows a partial schematic view for illustrating the profile before it is cut for separating the frame, and

Figs. 7 and 8 outlines for illustrating the indexes used in the optimizing formulae.

Fig. 1 shows an apparatus according to the invention intended for manufacturing closed spacer frames 19 of hollow thin-walled profiles which are bent in predetermined angles a number of times for forming the desired closed frame form. The apparatus comprises two independent units. The two units consist partly of a working unit 1 and partly of a magazine 2 for the profil bars which are to be further processed into complete frames. The magazine 2 is built together with a supporting table 3 which supports a profile during its conveying for subsequent bending, cutting and welding for making a complete frame. The magazine 2 is supported by means of one or several legs 4 which each has a height adjustable base 5 for aligning a guide passage 6 which extends from the magazine 2 to the supporting table 3 and towards the working unit 1. By means of a number of legs 7 the supporting table is connected to length adjustable supporting bases 8. The working unit 1 is provided with height adjustable bases 9 which makes it possible to align the guide passage 6 in the magazine and the supporting table with a guide passage 10 (see Fig. 3) for the transport of the profile in the direction of the arrow 11 (see fig. 2) through the working unit 1. Consecutively, the working unit 1 comprises a welder 12, a feed unit 76, a combined cutting apparatus and welder 13, and a bending tool 14. The working unit contains a computer (which will be explained later) which can be connected to a printing unit 77. The feed unit comprises two feed rollers 76 which bear on an endless profile 73 formed by welding the profile bars in the welder 12, which feed rollers 73 can be rotated backwards and forwards in a controlled way to position the profile 73 in accordance with the calculations made by a computer which forms part of the working unit. In the combined cutting apparatus and welder 13 the cutting apparatus comprises a saw, which will be further explained below.

The welder 12 used for welding the profile bars from the magazine 2 comprises in principle a welder corresponding to the one which is built together with the saw in the combined apparatus 13, and these welders are constituted by butt welders. As the welder 12 is used for welding the profile bars end-to-end in a manner known per se this will not be explained further.

Before a more detailed description is given of the combined saw apparatus and welder, reference is made to the schematic Fig. 5. The saw apparatus and welder 13 comprises two jaws 15 and a saw blade 16 placed between the jaws, said saw blade being arranged to saw off the profile perpendicularly to the longitudinal direction of said profile.

The bending tool 14 is illustrated schematically. It comprises a land 17 which is pivotable to any positions to define the desired bending angle around a bending mandrel 18 which is placed at the inner side of a corner in the closed frame 19. As will appear from Fig. 5 a spacer frame 19 having a very small side length will after the bending has been made be returned to the position where the frame is positioned correctly in relation to the saw 16 (from the position where the last corner is bent in the bending tool 14). By bending frames having large side lengths the frame will however be led further forward to the position where the frame is positioned correctly in relation to the saw 16. It is noted that the bending tool is movable across the level where a frame is situated. As a result it becomes possible to position the bended frame by the reciprocated displacement of the profile and the frame connected thereto. In practice the side length of the frame can be as small as 80 mm or even smaller, and it is thus possible to manufacture quadrangular frames having a minimum side length of appromixately 80 mm. Is is noted that another type bending tool than the one illustrated may be used. The land 17 used intended for abutting the outer side of the closed spacer frame 19 may have any suitable length. Moreover, it is possible to use a replacable land having different lengths dependent on the sizes and forms which the apparatus is arranged to bend. In Fig. 5 an embodiment is illustrated in which the bended spacer frame 19 is separated from an endless profile 73 (not shown in Fig. 5). In the illustrated embodiment the closed frame is positioned with the end portions abutting each other. In the left side of the Figure the jaw 15 is connected with the cam disc 20 of the butt welder and is thus arranged to be directed to the right for making a welding 21 of the two end portions which are situated between the jaws 15. This will be explained further with reference to Figs. 2-4. Figs. 2-4 illustrate the combined saw apparatus and welder 13 seen from different sides. Each of the jaws 15 comprises a clamp 22 for a profile. The clamps 22 are pivotally embedded around a shaft 23 in a bracket 24 which is made in one piece and with a movable land 25. The movable land 25 is through a mounting plate 26 connected with a feed rail 27 which slides in a feed carriage 28 which is connected firmly with the bottom plate 29 of the combined saw apparatus and welder 13. Consequently each movable land 25 can be displaced perpendicularly to a fixed land 30. In the right side, the fixed land 30 is mounted firmly in relation to the bottom frame 29 through a supporting plate 31. In the left side, the supporting plate is mounted movably in relation to the bottom frame 29 through a feed rail 62 and a feed carriage 63, which will be explained later. The supporting plate 31 is connected with fittings 32 which serve as a support for a double-acting cylinder 33. The cylinder 33 is arranged to displace the movable land 25 in relation to the fixed land 30. This is obtained by the piston rod 34 of the double-acting cylinder being connected with the mounting plate 26 for the movable land through fittings 35. On each side of the mounting plate 26 a stiffening plate 36 is mounted to ensure a rigid and solid construction. At its other end (the right side in Fig. 3) the mounting plate 26 for the movable land 25 is connected with fittings 37 which serve as a support for a double-acting cylinder 38 which through a mounting plate 39 and base fittings 40 support an air engine 41 which actuates the saw blade 16. The saw blade 16 is mounted on the engine 41 by means of two flanges 42,43 and the saw blade 16 is mounted in a saw house 44 which is provided with a cover 45. By reciprocation of the double-acting cylinder 38 the saw blade 16 can thus cut the endless profile and the movement of the saw is controlled by way of a feed carriage 46. Moreover, at the right end (according to Fig. 3) two swing fittings 47 are placed which each supports a double-acting cylinder 49 for the clamps 22 of each of the jaws through a pivot 48. Thus, each cylinder 49 has a plunger 50 which is connected with fork fittings 51 which are pivotally connected with the clamp 22 through a pivot 52. By reciprocation of the cylinders 49 the mesh portion 53 of the clamp 22 will pivot in engagement with the profile portions which are situtated in the guide passage 10. On the under side of each mesh portion 53 a rubber facing 54 is mounted for firm but careful engagement with the profile. As shown the mesh portion 53 is formed with two surfaces 53A and 53B for engagement with a profile. Thus, it becomes possible to build up a different pressure simultaneously and in two directions on the profile. This makes it possible to optimize the retaining pressure without the risk of inconvenient remaining deformation in the profile. This is very important in butt welding of thin-walled profiles.

The double-acting cylinder 33 illustrated in Fig. 3 is connected firmly with the mounting plate 26 for the movable land 25 in the right jaw of the combined apparatus (as seen in Figs. 2 and 4). A corresponding double-acting cylinder 33 is connected with the mounting plate 26 of the movable land 25 in the left jaw. However, this cannot be seen from the Figures. Thus, the two jaws can work independently of each other. In the right jaw the movable land 25 is connected with a driver 55. When the cylinder 33 of the right jaw is discharged the driver 55 will also guide the movable land 25 in the left jaw in the direction towards the fixed land 30. This is due to the fact that the cylinder 33 in the left jaw exerts a pressure which is directed opposite and which is lower than the pressure exerted by the cylinder 33 in the right jaw. Both jaws are closed both during sawing and during welding. Thus, the profile is secured during sawing and during welding which is explained later. As the cylinders 33 and 49 in the right and left jaw of the apparatus can work independently of each other, the left mesh portion 53 can be brought into a position where the surface 53B is approximately 1-2 mm from the profile 73. This is due to the fact that the driver 55 acts as a stop and is situated in a position which only allows this displacement of the mesh portion 53 in the left jaw. After the sawing the left jaw can thus only be opened slightly. This is essential for preventing the parallel and adjacent end portion 75 of the frame 19 (see Fig. 6) situated opposite the left jaw from being bent or carried so far away from its parallel position that torsions in the frame occur. Such torsions might cause permanent deformations in the corners of the frame or in the rectilinear portions of the frame. By an activation of the cylinders 33 and 49 in both the right and left jaw the profile is thus maintained during sawing and during welding which is explained more detailed below.

When the frame 19 is bent to the desired form, the endless profile 73 is situated in the feed passage 10 under the mesh portion 53 of the jaws while the outer free end portion of the frame 19 is placed adjacent but outside the jaws 15 by means of movable corner plates (not shown). The endless profile is then sawed off and when the frame is separated from the endless profile, only the left jew is opened as explained above and the endless profile is bent away from the left jaw.

The first free end portion of the frame in the left jaw which is closed around said end portion is placed thereon. During this process the other free end portion of the frame is maintained in the right jaw. The end portions of the profile are now maintained in the jaws 15. The welding is then made by a butt welding known per se. Such butt welding is effected by a step motor 58 activating the cam disc 20 which actuates a step ball bearing 59 which is pivotally embedded around a shaft 60. The shaft 60 is mounted in fittings 61 which are connected firmly with the feed rail 62 which slides in the feed carriage 63 which is connected firmly with the bottom frame 29. A strong compression spring 64 is placed between a bracket 65 which is mounted firmly on the bottom frame 29, and fittings 66 which are connected firmly with the fittings 61. In this way it is ensured that the feed rail 62 and the fittings 61 return in direction towards the cam disc 20. The feed rail 62 is connected with the left jaw 15 and when the step motor 58 traverses different sequences the butt welding 21 is established in a manner known per se. The motor 58 is connected with bearing fittings 68 through fittings 67. The bearing fittings 68 are connected firmly with the bottom frame 29 through struts 69. The cam disc 20 is supported on a shaft 70 which is stabilized by means of two fittings 70 which are connected firmly with the bearing fittings 68. This results in a rigid construction which is necessary for a correct welding. After the butt welding has been carried out, the jaws 15 are opened and the complete closed spacer frame is disengaged and can thus be removed from the apparatus for a subsequent treatment. Usually the saw blade 16 will be detached in the very house 44 but a double-acting cylinder 56 is connected with a movable shield 57 which covers the profile during the welding. Consequently the saw blade is protected against the splash of melted metal which occurs during the welding.

Reference is made to Fig. 6. As mentioned, the above described apparatus comprises a computer which monitors and controls the operation of the working unit 1, i.e. the operation of the welder 12, the conveying 76, the combined saw apparatus and welder 13, and the bending tool 14. The operation takes place by means of air valves not shown which are placed in the working unit. The computer which may be of any type is pre-programmed to control all processes and operations and is also pre-programmed with data for different profiles and frame forms, but can also be provided with specific data contained on discs which are fed to the computer in a manner known per se. Moreover, data can be typed on a keyboard (not shown) which is placed in the working unit. The computer is coded with data for size and form for each frame and records the placing of the welding 72 of the profile bars. On the basis of these data the profile 73 is displaced or it is ensured that an end portions is cut in such a way that a welding 72 is never placed at a corner 74 in the spacer frame 19. By means of deflection plates (not shown) it is ensured that .the outer free end portion 75 is caused to overlap the endless profile 73 so that the overlapping portions run parallelly and immediately adjacent each other. Moreover, it is ensured that the profile 73 and the frame 19 are positioned with the end of the outer free end portion 75 placed via-a-vis the saw 16. In this position the endless profile is maintained in the jaws 15 of the apparatus and subsequently the frame 19 is separated from the endless profile 73. The left jaw 15 is opened. This is effected by discharging the cylinder 33 in such a way that the movable land 25 is displaced outwards a few millimetres. As explained above, the outward movement is limited by the driver 55 which acts as a stop. The cylinder 49 is then activated and the mesh portion 53 is swung upwards so as to allow the end part 75 situated outside to be easily displaced into the left jaw. By means of the feed rollers 76 the endless profile 73 is displaced backwards free of the outline of the frame 19. The free end portion 75 is then manually inserted into the left jaw by the operator simply introducing said end portion under the open mesh portion 53, and subsequently the left jaw is reclosed around the profile. The two end portions in the separated profile of the frame 19 are placed end-to-end and subsequently a butt welding is carried out as described above. During the entire process the frame 19 remains fastened in the right jaw. Thus, there is no risk of dislocating the frame as would be the case if it had to be transported between different working stations.

The computer also controls acceleration, velocity and deacceleration for conveying and bending the profile. This conveying takes place in such a way that the acceleration, the velocity and the deacceleration are optimized without the risk of forming permanent deformations in the profile. The optimizing can advantageously be made on the basis of the formulae stated in claim 5. Thus, it is possible to manufacture any frame size and form at a minimum of time. This is advantageous compared to known conveyings where the acceleration, velocity and deacceleration of the apparatus are pre-adjusted at one or a few predetermined levels which merely ensure that no permanent deformation occurs during the worst imaginable conditions which are fixed for the individual level.

Figs. 7 and 8 are outlines for illustrating the indexes which are used in said formulae and reference numeral 76 designates in Fig. 8 the feed rollers which are used for conveying the endless profile 73 and which are driven by a step motor (not shown) which is controlled by the computer. Fig. 8 illustrates a schematical bending tool 17,18 which at least comprises a mandrel and a movable land 17. The bending tool comprises other elements, but these will not be explained further as they may have any form known in the art. The point A designates the outer portion of the movable land 17. It is noted that the bending angle does not need to be rectangular. Thus, the bending angle inside the frame may vary from approximately 10° to approximately 179°. Thus, it is possible to manufacture any polygonal frame form and simultaneously optimize the manufacturing rate on the basis of the formulae set up.

Claims

C l a i m s :

1. A method of manufacturing closed spacer frames of hollow thin-walled profiles comprising welding the profile bars end-to-end for making a substantially endless profile, the endless profile being bent in predetermined angles a number of times for making the desired frame form and in a way causing the outer free end portion to overlap the endless profile as the overlapping portions extend parallelly and immediately adjacent each other, positioning the endless profile in relation to the cutting means, maintaining the endless profile during the cutting which separates the frame from the endless profile in a point located at the end of the adjacent outer free end portion, c h a r a c t e r i z e d in comprising the said cutting between two jaws, the profile being maintained during the cutting, bending backwards the endless profile while the bended frame is maintained at the one end portion by the one jaw so that said profile does not overlap any part of the frame, reclosing and maintaining the other jaw round the other end portion of the bended frame, placing through a mutual displacement of the two jaws the two end portions of the separated and bended profile end-to-end and welding them together for forming the closed frame, and controlling the acceleration, velocity and deacceleration for the conveying and bending of the profil with a computer which calculates the weakest point of the profile and the allowable maximum values in each stage of the manufacturing process which can be used without making permanent deformation in the frame produced.

2. A method according to claim 1, c h a r a c t e r i z e d in that the welding of the profile bars and of the two end portions of the profile is carried out as a butt welding.

3. A method according to claims 1 or 2, c h a r a c t e r i z e d in that the first bending is made in such a way that the outer free end portion is located at a rectilinear part of the frame side.

4. A method according to any of the preceding claims, c h a r a c t e r i z e d in that the bending of the profile is controlled in such a way that the welding between subsequent profile bars in the substantially endless profile is always placed on a rectilinear portion of a frame side.

5. A method according to any of the preceding claims, c h a r a c t e r i z e d in that during the conveying of the profile acceleration, velocity and deacceleration are controlled on the basis of the formula

where

M_j is the bending moment for the corner No. j at which this corner is deformed (Nm), j is the index for the corner in the frame which is studied and measured so that the first corner is produced by the first bending of the profile, p is the weight of 1 metre profile (kg/m), g is the acceleration due to gravity (m/s²), μ is the static coefficient of friction between profile and supporting table, and μ = μ_d, dynamic coefficient of friction, when the velocity of the profile is different from zero, β is the angle of the supporting table (rad) in relation to a horizontal plane, l_k is the length of the side k in the frame (m), k is the index for the side in the frame which is viewed and is numbered in such a way that the outer free end portion constitutes the first side in the frame, X_gk and Y_gk are x- og y-co-ordinates to the centre of gravity of the side k (m), as the system of co-ordinates has its zero point in the corner j and x-axis directed towards the travelling direction of the profile, a is the acceleration/deacceleration during positioning (m/s²) , and that the acceleration, velocity and deacceleration during the bending of the profile are controlled on the basis of the formul ae:

and

where

M_def is the bending moment which produces deformation of the profile in the point where the movable land of the bending tool ends (Nm),

M_j is the bending moment which affects the corner j (Nm) during bending, q is the number of the corner which is to be bent, c is the length of the movable land of the bending tool (m), l_q is the length of the side q (m), l_k is the length of the side k (m),

X_gpk and Y_gqk are x- og y-co-ordinates to the centre of gravity of the side k, where the system of co-ordinates has its zero point in the bending centre (m),

X_gpk and Y_gjk are x- og y-co-ordinates to the centre of gravity of the side k, where the system of co-ordinates has its zero point in the corner j (m), ω is the angular velocity for the bending, is the angular acceleration for the bending,

Փ_n is the angle for the corner n (rad), and Փ_j is the angle for the corner j (rad).

6. An apparatus for manufacturing closed spacer frames of hollow thinwalled profiles which are bent in predetermined angles a number of times for forming the desired closed form, which apparatus comprises a magazine for the profile bars, a supporting table for supporting the profile during its bending, a welder for welding the profile bars, a feed unit, a cutting apparatus, and a bending tool, c h a r a c t e r i z e d in that it comprises two independent units partly consisting of the magazine of the profile bar and the supporting table and partly of a working unit which in order comprises the welder, the feed unit, a combined cutting apparatus and welder, and the bending tool which has a movable land for bending the profile, and a computer for monitoring and controlling the operation of the working unit.

7. An apparatus according to claim 6, c h a r a c t e r i z e d in that the combined cutting apparatus and welder is arranged for placing the cutting element consisting of a saw in a position which is located between two jaws which constitute a part of the combined cutting apparatus and welder, that the saw is movable across the travelling direction of the profile, and that the jaws are movable towards each other in direction along the longitudinal axis of the profile.

8. An apparatus according to claims 6 or 7, c h a r a c t e r i z e d in that the jaws have a small extension in the longitudinal direction of the profile.

9. An apparatus according to any of the claims 6-8, c h ar ac t e r i ze d in that the welders used are butt welders.

10. An apparatus according to any of the claims 6-9, c h a r a c te r i z e d in that the elements of the bending tool are loosely placed in the base frame of the bending tool and can be replaced for bending different profile types and sizes, and that the mounting portion of the elements of the bending tool has a polygonal sectional form corresponding to the polygonal sectional forms of recesses in the base frame of the bending tool.