Method of bending a composite panel

Abstract: A method of bending a composite panel comprises: forming an assembly of two flat face sheets (11,12), and a flat center core (13), the core (13) not joined to a portion of the second face sheet (12); while holding the first face sheet (11) on a support having a stationary portion (30) and a movable portion (40), lifting the non-joined portion of said second face sheet (12) and to bend the non-joined portion to separate it from the core (13); removing a portion of the core (13) to form a V shape at the location of the bend; coating an adhesive on second face sheet or the opposed face of the core and bringing the core into contact with the non-joined portion of the second face sheet to adhere them by rotating the movable portion (40). The bend is formed without cutting the face sheet and without surface defects.

Description: Technical Field The present invention relates to a method of bending a composite panel. Prior Art Composite panels having two face sheets and a center core member between the two face sheets are known. To assemble a bent panel, using a monopoly type die having a pair of a convex type and concave dies and a pressing device, first the two face sheets and the center core member are adhered and fixed. Alternatively, for example, using a monopoly die having a convex die, and covering the two face sheets and the center core member using a non-ventilation sheet, and by evacuating an inner portion of the sheet, the two face sheets and the center core member are adhered and fixed. A method of bending a known composite panel is described in US-A-4078959, and has the features of the first part of claim 1. An outer facing sheet is not affixed to the core at one end in a region where a bend is to be formed. The panel is positioned over a forming tie with this outer facing sheet uppermost. The core and inner facing sheet are formed into the configuration of the tie, after which the unaffixed portion of the outer facing sheet is bent over the core and pressed into place. In another bending processing method of a composite panel, as shown in Japanese Utility Model Publication No. Hei 2-8567, from the outer side of the face sheet which forms the inside of a bend after the bending of the composite panel, a V shape groove is processed and at the apex of this groove the other face sheet, at the outside of the bend, is subjected to bending. In the prior art techniques relating to the bending of the composite panel, the center core member is transformed in a predetermined bending shape. Since the face sheets and the center core member are adhered and fixed, use is made of manual working using a general purpose machine. Further, the face sheet and the center core member which are transformed individually using the monopoly type die having the convex and the concave dies (a monopoly type having an upper portion monopoly die and a lower portion monopoly die) and the pressing device, or for example the concave type monopoly die (the lower monopoly die), the face sheet and the center core member are covered by the non-ventilation characteristic sheet member and the inner portion of the sheet member and the face sheet and the center core member are adhered and fixed. A mutual gap and a partial contact (a local application of pressure) between the center core member, the face sheet and the monopoly die are generated, leading to adhesion failure and a buckling in a thickness direction of the center core member, and reducing strength of the face sheet. Further, in the face sheet in which the partial contact (the local application of pressure) is generated a recess and damage may appear, causing bad outer appearance of the face sheet. Summary of the Invention An object of the present invention is to provide a bending method for a composite panel which avoids the occurrence of the gap or the partial contact (the local application of pressure) between the face sheet and the center core member, achieving a bent composite panel having a high strength. According to the present invention there is provided a method of bending a composite panel as set out in claim 1. The present invention can be applied to a polystyrene foam panel and a honeycomb panel assembled by soldering or brazing or by adhesive. The material of the face sheet can be metal such as aluminum, a FRP (Fiber Reinforced Plastic) or paper, etc. The center core member can be a metal honeycomb, a honeycomb shape paper core, a honeycomb shape FRP (Fiber Reinforced Plastic) core, or foam material such as those based on vinyl chloride, phenylic acid (phenol), acrylic, acrylate or urethane. The joining of the center core member with the face sheet can be by soldering, adhesive or welding etc. Brief Description of the Drawings Fig. 1 is a longitudinal cross-sectional view showing an initial stage of a bending process of a composite panel, in one embodiment according to the present invention; Fig. 2 is a longitudinal cross-sectional view showing a second stage in the process of Fig. 1; Fig. 3 is a longitudinal cross-sectional view showing a third stage following that of Fig. 2 in the bending process; Fig. 4 is the longitudinal cross-sectional view showing a fourth stage following that of Fig. 3 in the bending process; Fig. 5 is a longitudinal cross-sectional view showing a final stage in the bending process of Fig. 1; Fig. 6 is a general perspective view showing the bending apparatus of Fig. 1; Fig. 7 is a front view showing an end portion of a bending table of the bending apparatus of Fig. 6; and Fig. 8 is a longitudinal cross-sectional view of the end portion of a bending table of the apparatus of Fig. 6. Description of the Embodiment A bending process of a composite panel of one embodiment according to the present invention will be explained referring to Fig. 1 to Fig. 5. Firstly, the construction of a composite panel to be subjected to bending will be explained. In Fig. 1, the composite panel to be subjected to bending comprises a face sheet 11 which in use of the panel is an outer face, a face sheet 12 which in use becomes the inner face, and a center core member 13 which is arranged between the two face sheets 11,12. These three members (the face sheet 11, the face sheet 12 and the center core member 13) are united as one body by adhesion. Each of the face sheets 11,12 is a metal sheet such as an aluminum sheet, a steel sheet and the like, or is such a metal sheet having an adhered polyvinyl chloride coating sheet or an adhered melanin resin coating sheet etc. The thickness of the face sheet 11 or the face sheet 12 is about 0.5 mm - 2.0 mm. The center core member 13 is a paper center core member such as a roll core or a paper honeycomb, or further may have a urethane-foam resin which is filled in the cells of such a paper center core member to achieve heat insulation and sound shielding. The thickness of the center core member 13 is about 20 mm - 50 mm. The whole face of the face sheet 11 and the center core member 13 are adhered substantially to each other. The meaning of the whole faces will be made clear by the explanation of the adhesion of the face sheet 12 and the center core member 13. The face sheet 12 and the center core member 13 are adhered only at an adhesion portion 12b but are not adhered at a remaining ion-adhesion portion 12a. The non-adhesion portion 12a can be obtained by avoiding coating an adhesion agent. The non-adhesion portion 12a is a region in which a bending is carried out. The length of the face sheet 12 is shorter than the length of the face sheet 11 by a length 12c. The face sheet 12 is bent to form an inner side of the bend. Accordingly, when the bending of the composite panel is carried out, a peripheral length difference 12c is generated between the face sheet 11 and the face sheet 12. Next, the method of bending this composite panel will be explained. Fig. 1 shows the composite panel set on a bending device. Firstly, the composite panel is laid on a stationary table 30 and a bending table 40 of the bending device with the face sheet 12 above. The upper faces of the stationary table 30 and the bending table 40 are at the same horizontal plane. The non-adhesion portion 12c is laid on the bending table 40. Next, vacuum suction pads 31 and 41 of a vacuum holding device installed on the stationary table 30 and the bending table 40 operate to hold the face sheet 11. A bending table 50 is lowered and is laid on the face sheet 12 of the non-adhesion portion 12a, and a vacuum suction pad 51 of a vacuum holding device installed on the bending table 50 is operated to grip the face sheet 12. A plurality of the pads 31,41,51 are arranged at predetermined positions along the longitudinal direction i.e. the line of bending (see Fig. 6). Next, as shown in Fig. 2, by rotating the bending table 50 upwardly the face sheet 12 at the non-adhesion portion 12a is bent upwardly. In this embodiment of the invention, since the face sheet 12 is bent at a right angle, the contact face of the bending table 50 is brought to the perpendicular. The bending table 50 is at the non-adhesion portion 12a, and its end is positioned at the boundary of the non-adhesion portion 12a and the adhesion portion 12b or at a small distance into the non-adhesion portion 12a from this boundary. The position of the end of the bending table 50 becomes the center of the bending. The side face at this side of the bending table 50 is inclined (as seen in Figs. 1 and 2) so that it does not contact the face sheet 12, when the bending table 50 is rotated. Next, as shown in Fig. 3, the center core member 13 is cut to form a V shape notch by a V cutting device 60, which removes only the center core member 13, leaving the face sheet 11. The position of the V notch is the bending position. The angle of the apex of the V notch is the bending angle and in this embodiment is a right angle. For example, using a knife 61 for carrying out the cutting, two faces are cut at the same time. As shown, the rotating knife 61, such as a router and an end miller, is inclined at a predetermined angle, and is moved along the bending line to remove the center core member 13. If the center core member 13 is a paper member or a member in which a urethane-foam resin is filled in a paper center core, even if the center core member is partially remaining at the left side, it can be crushed during the bending. Next, as shown in Fig. 4, an adhesive is applied from above onto the non-adhesion portion 12a and the V cut portion of the center core member 13, by an adhesive coating device 70. At this time, since the gap between the lifted part of the face sheet 12 and the center core member 13 is large, the coating with adhesive can be carried out easily. The adhesive is self-hardening. Next, as shown in Fig. 5, with the apex of the V notch as a center, the bending table 40 is rotated upwardly to the vertical, to bring the face coated with adhesive into contact with the rear face of the face sheet 12. Further, the inclined faces of the V notch of the core member 13 are contacted together. The center core member 13 is maintained in this state until the adhesive has completed its hardening. Next, after the vacuum of the pad 51 of the bending table 50 has been released, the bending table 50 is lifted, and after the vacuum of the pad 41 of the bending table 40 is released, the bending table 40 is reversed to its initial position. The composite panel which has been subjected to the bending process can be removed by means of the bending table 40. In this method of bending the panel bending is achieved without the occurrence of a gap and the partial contact (the local application of pressure) between the face sheets 11,12 and the center core member 13. At the bend, since the face sheet 12 is not separated into two portions after bending, it is not necessary to weld the non-adhesion portion 12a and the adhesion portion 12b, together e.g. using another member. In Fig. 6, the V cutting device 60 and the adhesive coating device 70 are shown mounted on a traveller 80, which moves longitudinally along the bending line of the composite panel, along a rail 81 at a side face of the bending device. The V cutting device 60 and the adhesive coating device 70 are installed on a vertical lift 83. The two ends of the bending table 50 are mounted rotatably on a lifting device 55 by a shaft 53. Reference number 56 shows a drive machine for this rotation. A rotation device of the bending table 40 will be explained by reference to Fig. 7 and Fig. 8. At each end of the bending table 40 a semi-circular flange 43 is arranged, supported by plural rollers 45b and 45c mounted on a circular arc on a frame stand 44. The lower rollers 45b support a lower face of the flange 43. The rollers 45c contact an upper face of a circular arc shape guide rail 43b which is installed on the flange 43. Further, at the lower face of the bending table 40 circular arc shape projection portions are provided at a predetermined spacing and are supported by the frame stand 44. Gear toothing 46 is carried on each flange 43. On the frame stand 44, pinion gears 46b meshing with the toothing 46 are rotatably mounted, driven by a single motor 47. In the illustrated embodiment of the present invention, the bending angle is 90 degrees, but bending at another angle is equally possible, with the appropriate angle of cutting of the V notch. A cutting tool having its cutting faces at the desired angle to each other may be employed. Further, even if the angle of the V cutting is smaller than the bending angle, the center core member 13 may be partially crushed, in the bending of the composite panel. The adhesive can be coated only on the side of the center core member 13 which contacts the face sheet 12, but when the adhesive is coated on the V cut portion as well, a high strength can be obtained. In the present invention, a gap between the face sheet and the center core member and partial contact (the local application of pressure) are avoided, and since neither face sheet is cut at the bend line high strength at the bend can be obtained.

Claims: A method of bending a composite panel comprising the steps: forming an assembly of a flat face sheet (11), a flat second face sheet (12) and a flat center core (13) joined to said face sheets and separating them, with the core (13) not joined to a portion of the second face sheet (12) adjacent an edge thereof; installing said first face sheet on a support having a stationary portion (30), characterized in that said support further has a movable portion (40), and said method further comprises the steps: contacting a lifting member (50) to said non-joined portion of said second face sheet (12) and rotating the lifting member to bend the non-joined portion relative to the core to separate it from the core; removing a portion of the core (13) to form a V shape at the location of the bend; coating an adhesive to at least one of the second face sheet and an opposed face of the core and bringing the core into contact with the non-joined portion of the second face sheet to adhere them, by rotating said movable portion (40) of the support. A method according to claim 1, wherein the first face sheet (11) is held by at least one vacuum suction pad on said support and said non-joined portion of the second face sheet (12) is held by at least one vacuum suction pad of the lifting member (50). A method according to claim 1 or 2, wherein the adhesive is coated on said core member (13). A method according to claim 3, wherein the adhesive is coated on the surfaces of said V shape. A method according to any one of the preceding claims wherein said composite panel assembly is mounted on said support in a substantially horizontal condition.

Inventors: KAWAMURA WATARU, OKADA NORIHISA, KAWAMURA, WATARU, OKADA, NORIHISA
Applicants: HITACHI LTD, HITACHI, LTD.
Application year: 2001
Main classification: B21D11
IPC codes: B29C53, B21D11, B32B3, B21D47, B32B1, B21D5