METHOD FOR FORMING A SHEET OF METAL, TOOL FOR CARRYING OUT THE METHOD AND HOUSING FIXTURE MADE OF THE SHEET OF METAL

Abstract: The tool comprises an upper part with a bending bar (2) and guide bars (3) secured thereto by springs (4), and an under part with a slidable bending base (7) in a machine frame (6), and bending bars (11) movably arranged in recesses (10) in the machine frame. The base part (7) is supported by support bars (9) which are displaceable in such a manner that the base part can slide down between the bars. With this tool it is possible in two working strokes to shape a longitudinally extending projection of dovetailed profile in a sheet of metal (1). The formed sheet of metal (1) with groove (13) is preferably to be used for elongate housing fixtures (17) for fluorescent tubes. The projection (13) is used for retaining components (14), and in the lateral faces of the groove (13) there may be made ventilating holes (16).

Description: METHOD FOR FORMING A SHEET OF METAL, TOOL FOR CARRYING OUT THE METHOD AND HOUSING FIXTURE MADE OF THE SHEET OF METAL. The invention relates to a method for forming a sheet of metal whereby there is formed a longitu¬ dinally extending projection of dovetailed cross— section in the sheet, and a tool for use thereby and a preferred use of the invention for manufactur- ing housing fixtures. For making a longitudinally extending projection of dovetailed cross-section in a sheet of metal it is generally necessary to bend the sheet in a common sheet bending machine provided with bending bars and bending guides. It is necessary to make at least four bendings for obtaining the desired cross-section of the projection. Furthermore, a great deal of space is required around the bending machine since there must be room for the sheet sections and the swings thereof during the bending operation. Such bendings require a fairly time-con¬ suming operation because the sheet must be correctly positioned by each bending operation and in case the opening in the bend is to be fairly small, it is usually necessary to withdraw bending bars in longitudinal direction from the interior of the bent profile which is also time-consuming and complicated. The object of the invention is to provide a method and a tool whereby it is possible to reduce working time and costs in connection with the forming of a longitudinally extending projection of dove- tailed cross-section. This is achieved by proceeding as disclosed in the characterising part of claim 1, for example by using an apparatus as disclosed in the character¬ ising part of claim 4. It is thus possible in one working operation and by the use of a fairly simple tool to carry out the desired forming of a sheet. The tool makes two strokes, the tool being reset after the 1st stroke, and the complete forming is finished in a few seconds. The basic material - the sheet of metal - is firmly retained in the tool during the operation so it is not necessary to swing large bulky sheet sections nor is it .necessary to cut up large sheets in smaller sheet sections before the forming. The cutting up may perfectly well take place after the forming. The tool is moreover very easy to reset in that it is possible to replace the bending bars by other bars which are either of a different size or have another edge design whereby it is possible according to requirements to modify the cross-section of the resulting projection. It is advantageous to proceed as disclosed in the characterising part of claim 2 but it is also possible to separate the two steps so that after the 1st step there will be produced a semi-manufac- ture which, if so desired, may be subjected to another form of working before the 2nd step of the method is taken. If the finished product is to be provided with holes in the projecting sheet section, for example ventilating holes for the fixture mentioned below, the procedure disclosed in the characterising part of claim 3 is preferably followed. If the tool according to the invention is designed as disclosed in the characterising part of claim 5, there is obtained a very simple guiding of the under part of the tool and all the energy required for forming the sheet in the desired shape is supplied through the upper part of the tool. The tool according to the invention will become particularly simple when it is designed as disclosed in the characterising part of claim 6. If suitably dimensioned spring elements are used, for example mechanical, hydraulic or pneumatic springs, the tool will not leave marks in the surface of the work sheet so that for that reason there will be no need for a finishing treatment. The manufactured work sheet with a groove of dove¬ tailed cross-section is particularly suitable for manufacturing housing fixtures for elongate light sources such as fluorescent tubes, as disclos¬ ed in the characterising part of claim 7. The projection can be used for suspension purposes both of the entire fixture and of the required components inside the fixture. It is particularly advantageous if the housing fixture is designed as disclosed in the characteris¬ ing part of claim 8. There is thus obtained effici- ent ventilation and no light will radiate through the ventilating holes. There is thus obtained a very high degree of freedom with regard to the design of the fixture. It is moreover possible to increase the light efficacy and the life of the fluorescent tube as well as the socket therefor if the reflector is placed in such a manner that the ventilating air is diverted from the end sec¬ tions of the flourescent tube. The invention will be further explained in the following with reference to the drawing showing the method and the tool, and a preferred use of a bent sheet manufactured according to the invention wherein Fig. 1 shows a side view of the tool in its starting position, Fig. 2 shows a side view of the tool making the 1st stroke, Fig. 3 shows a side view where the movable upper part is withdrawn and the tool is ready to make the 2nd stroke. Fig. 4 shows a side view of the 2nd stroke of the tool where the sheet is com¬ pletely bent. Fig. 5 shows on a larger scale an example of use of the bent sheet. Fig. 6 shows a plane section of the housing 6 being centrally provided with a vertically slid- able base part 7 resting on longitudinally extending * _• support bars 9 arranged in a hollow space 8 under the base part. The base part 7 has a surface part which corresponds to the underside of the bending bar and is arranged under same. Symmetrically with the centre there are longitudinally extending recesses 10 wherein in either side there are arrang¬ ed bending bars 11, the facing edges of which have an edge shape corresponding to the desired final profile of the projection in the sheet 1. The bending bar 11 rests on sloping or rounded shoulders on the base part 7. The tool carries out the bending according to the following method: The sheet of metal 1 is placed as shown in Fig. 1 where the tool is its starting position. The sheet 1 is secured for example by support means, plane elements, table elements or similar not shown holding means. When the sheet 1 is correctly placed, the upper part is moved downwards, see arrow in Fig. 1, and the sheet is bent/made to project as shown in Fig. 2. There is thus already in the 1st wording stroke formed .a quadrangular projection 12 with square or rectangular cross-sec¬ tion and the 1st stroke of the tool is completed and the upper part returns to the starting position, see Fig. 3. The under part is then set in that the support bars 9 by means of pneumatic or hydraul¬ ic working cylinders are moved sideways, see arrows in Fig. 3. It is now possible for the base part 7 to pass between the support bars 9, but this fixture in Fig. 7 seen in the direction VI-VI, and Fig. 7 shows a plane section of the housing fixture in Fig. 6 seen in the direction VII-VII. Figs. 1-4 of the drawing show in succession a tool according to the invention ■ performing the two forming steps whereby a sheet of metal 1 is given the desired projection. On the drawing the tool is shown in side view in that the extension of the tool and the sheet of metal 1 perpendicularly to the plane of the drawing is only limited by the size of the work- pieces that are desired to be worked. The tool is in Fig. 1 shown in its starting position in that the upper part is placed over the sheet of metal 1 to be worked and the under part is situated under the sheet of metal. The upper part consists of a longitudinally extending bending bar 2 shaped as a ram. Firmly thereto there is securely anchored one or more cross-beams or bars 5 functioning as supports for spring elements 4 which spring elements carry longitudinally extend¬ ing guide bars 3. The spring elements 4 are adapted in such a manner that their starting position is as shown in Fig. 1, ie. the underside of the guide bars 3 is flush with the underside of the bending bar 2. The under part is built up by a machine frame will only take place when the upper part is again moved downwards in that the upper part in its 2nd stroke presses down the work sheet 1, the base part 7 and the bending bars 11, see arrows in Fig. 3, to reach the final position, see Fig. 4. The projection 12 has then become a projection 13 with dovetailed cross-section. The tool then returns to the starting position as in Fig. 1, and the bent work sheet can be removed. The guide bars 3 are flexibly suspended and hold the plane part of the work sheet so that this remains plane and without deformations. The final profile is clearly seen on a larger scale in Fig. 5 which also shows how a mounting 18 or a supporting means or a component part 14 provided with spring elements 15 is suspended in the dovetailed projection 13 of a sheet 1. This will be further described in the following with reference to Figs. 6 and 7 of the drawing. Figs. 6 and 7 of the drawing show an elongate round housing fixture 17 for a fluorescent tube, the electric sockets of which are placed on end plates in the housing fixture. The groove 13 with ventilating holes 16 for cooling air by natural circulation is placed centrally at the top of the fixture so as to obtain good cooling of the components 14. The uneven lines 19 show the natural circulation of the cooling air if in the fixture there is arranged a reflector or screen as shown. The cooling air is thereby diverted from the end sections of the fluorescent tube as shown on the drawing. Cooling of the end sections of the fluorescent tube will increase the luminous efficacy and extend the life of tube as well as sockets. The components 14 may be suspended as shown in Fig. 5 and in the open end of the groove 13 there may be inserted mountings 18 (see Fig. 5) for suspension of the fixture. The mountings may be inserted into the groove from the ends or if the end plates of the fixture block the open ends of the projection, the mountings may be designed for insertion into the longitudinally extending up-turned opening of the projection. The fixture 7 is moreover in the usual manner provided with reflector, antidazzle ribs etc.

Claims: - | _ PATENT CLAIMS 1. Method for forming a sheet of metal whereby there is formed a longitudinally extending projec- 5 tion of dovetailed cross-section in the sheet, c h a r a c t e r i s e d in that the forming is carried out in two successive steps in that a) there is first made a bend in the shape 0 of a longitudinally extending projection in the sheet said projection having square or rectangular cross-section, b) whereupon the side edges of the profile 5 closest to the sheet plane are pressed towards each other while retaining the metal sheet in its plane position. 2. Method according to claim 1, c h a r a c t e r- 0 i s e d in that the sheet remains in the forming tool during the entire forming operation. 3. Method according to claim 1 or 2, c h a r a c ¬ t e r i s e d in that prior to the forming there 5 is made one or more holes in the part of the sheet which after the forming constitutes the lateral walls of the projection. 4. Tool for use in carrying out the method according 0 to claim 1, c h a r a c t e r i s e d in that it consists of an upper part comprising a longitudi¬ nally extending bending bar (2) with longitudinally extending guide bars (3) arranged on either side thereof, and an under part comprising a bending base (7) with a surface area corresponding to the underside of the bar (2) said bending base being vertically slidable in a machine frame (6), and longitudinally extending bending bars (11) which are movably arranged in the machine frame (6) on either side of said bending base (7) and resting thereon, the facing edges of said bars (11) having an edge shape corresponding to the final profile of the projection and where the opposite edges of the bars (11) rest in recesses (10) in the machine frame (6). 5. Tool according to claim 4, c h a r a c t e r ¬ i s e d in that the bending base (7) thereof is supported by two longitudinally extending support bars (9) in the machine frame (6) which bars are manoeuvrable in such a manner that the base part can be moved down between the bars. 6. Tool according to claim 5, c h a r a c t e r ¬ i s e d in that the longitudinally extending guide bars (3) of the upper part are spring coupled to the bending bar (2) in such a manner that the underside of the guide bars and the underside of the bending bar are made to flush in the starting position of the machine. 7. Use of sheet metal according to any one of claims 1-6, c h a r a c t e r i s e d in that the work sheet (1) is bent so as to form a finished housing fixture (17) for elongate light sources (Figs. 6,7) in that the projecting groove (13) extends into the housing fixture and is used for mounting components and similar parts (14) and in that the outwardly extending open part of the groove (13) can be used for mounting suspension fittings. 8. Use according to claim 7, c h a r a c t e r ¬ i s e d in that a range of holes (16) have been made in the lateral faces of the projecting groove (15).

Inventors: KNUDSEN PREBEN, KNUDSEN, PREBEN
Applicants: MYREN AS MASKINFAB, MASKINFABRIKKEN MYREN A/S
Application year: 1986
Main classification: B21D5
IPC codes: B21D13