Abstract:
A molding device for curing of composite components comprising: a molding die, composite material in the molding die, heat application means, sheathing means for the composite material and the molding die and vacuum means for the application of vacuum to the composite material in the molding die. The heat application means comprise at least one heat pipe with a heat exchanger attached to the molding die for thermal conduction to the composite material.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application claims priority to European patent application No. 13 400022.3 filed on Oct. 15, 2013, the disclosure of which is incorporated in its entirety by reference herein. 
       BACKGROUND OF THE INVENTION 
       [0002]    (1) Field of the Invention 
         [0003]    The invention is related to a molding device for composite components with the features of the preamble of claim  1 . 
         [0004]    (2) Description of Related Art 
         [0005]    Molding of composite components in molding dies needs typically 180° C. for curing. When a thermal capacity is large of a molding die that is used for molding, it takes time for the heat to transfer from a heat source to a pressing surface contacting a product to be molded. Oil as heat transfer medium is incompatible with composite components and thus disadvantageous for the molding of composite components. Standard heat pipes provide heat at a temperature range from −20° C. to 230° C. depending from used internal medium. Standard heat pipes provide said heat with a safe isolation of any heat transfer medium from the composite components. 
         [0006]    The document JP H05-91820 discloses a heat pipe embedded in a molding die for thermally molding material, so as to increase a thermal conductivity of the molding die. 
         [0007]    The document U.S. 2013/040012 A provides a compression molding apparatus performing a molding by providing a raw material into a molding die, and applying heat and pressure to the raw material. The apparatus includes a first molding die that forms a molding frame that surrounds a region where the raw material is compression-molded; a second molding die that compresses the raw material provided into the molding frame; and a heat source section that supports and heats the second molding die. The second molding die includes a heat pipe that has one end positioned on a side of the heat source section and the other end positioned on a side of a pressing surface pressing the raw material, and a heat insulating layer that wraps the heat pipe along a longitudinal direction of the heat pipe. The compression molding apparatus of U.S. 2013/040012 A is not suitable for vacuum molding. 
         [0008]    The object of the invention is to provide a molding device suitable for vacuum molding of composite components. 
         [0009]    The solution to the problem is provided with a molding device with the features of claim  1 . 
       BRIEF SUMMARY OF THE INVENTION 
       [0010]    According to the invention a molding device for curing of composite components comprises a molding die for composite material in the molding die and heat application means to the molding die. Sheathing means encompass the composite material and the molding die for sealing off towards at least one vacuum chamber and vacuum means are provided at the molding device for the application of vacuum to the composite material in the molding die. The heat application means comprise at least one heat pipe, preferably with a heat exchanger, attached and/or integrated to the molding die for thermal conduction to the composite material on the molding die. The inventive molding device can be applied to any hot-molding of a composite component to be cured, for example tools which have been milled, casted or produced by electro plating. 
         [0011]    A base plate of the molding device is in a two dimensional contact with a heat exchanger attached to the molding die for increased thermal conduction to the composite material inside vacuum, so that heat is effectively transferred through the vacuum by means of the heat pipe and through the molding die to the composite material to be cured. In the inventive molding device, the heat pipe has one end positioned on a side of a heat source section and the other end positioned on a surface adjacent the composite material to be molded. Thereby, it is possible to provide improved thermal conductivity 
         [0012]    In the heat pipe, a working fluid that is locally heated and evaporated condenses at a part to which the heat is to be supplied. The heat transferred through the heat pipe is instantaneously moved to the surface contacting the composite material to be cured and the heat diffuses into the entire molding die. 
         [0013]    The inventive molding device avoids the leakage risks related to fluidic systems with a concept simple to connect and regulate with standard plant/equipment. The inventive molding device allows application to e.g. an autoclave or oven by economic system adjustment during design of any new tooling or the inventive molding device can be retrofitted to existing molding devices. The changes depend on which embodiment is desired. For e.g. a molding device with integrated heat pipes in the molding die and the existing base plate the following work would be required: Drilling and threat cutting of the base plate for mounting the outer heat exchanger. 
         [0014]    For the molding die a milling process and a subsequent bonding of the heat pipes into the milled interstices would be required. For the inner heat exchanger a mill on the plant surfaces on the molding die and the base plate may be required. The use of heat-pipes allows on one hand increased heat supply into the inventive molding device by means of heat exchangers, e.g. fins, and allows—on the other hand—a homogenous distribution of energy within the inventive molding device. 
         [0015]    By passive mode of operation, e.g. by putting the inventive molding device into e.g. an autoclave or oven, any overheating can be excluded. The inventive molding device allows a shortening of process time resulting in cost and energy savings. The quality of the composite component to be cured is improved due to time uniform cure by means of the inventive molding device. The inventive molding device with a heat-pipe operates completely independent without any operator intervention as said heat-pipe is wear and maintenance-free. For optimization of molding capacity any autoclave, oven, hot press can be retrofitted to any of the most affected inventive molding devices. Apart from optimization no conversion of autoclave, oven or hot forming means is necessary for the application of the inventive molding device 
         [0016]    According to a preferred embodiment of the invention the heat-pipes are integrated into the molding die for a more homogenous distribution of energy within the inventive molding device. 
         [0017]    According to a further preferred embodiment of the invention the heat exchanger of the heat pipe is inside the molding die. The molding die wraps the heat pipe in the longitudinal direction of the heat pipe. Thereby, the heat of the heat source section is efficiently transferred to the composite material, so that efficient hot-molding becomes possible. 
         [0018]    According to a further preferred embodiment of the invention the heat exchanger of the heat pipe is in contact with the composite material through the molding die. 
         [0019]    According to a further preferred embodiment of the invention a plurality of heat pipes are arranged depending on the situation through the molding die e.g. in parallel or fan type arrangement. 
         [0020]    According to a further preferred embodiment of the invention at least one outer heat pipe is connected for thermal conduction to an inner heat pipe through the molding die. 
         [0021]    According to a further preferred embodiment of the invention a contact force generating element is provided between the heat exchangers, said contact force generating element pressing the die heat exchanger against the molding die and the base heat exchanger against the base plate for better thermal conduction by increased contact forces. 
     
    
     
       BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS 
         [0022]    A preferred embodiment of the invention is presented by means of the description with reference to the attached drawing. 
           [0023]      FIG. 1  shows schematically a structure of a retrofitting molding device according to a first embodiment of the invention; 
           [0024]      FIG. 2  shows schematically a structure of a further molding device according to a second embodiment of the invention; 
           [0025]      FIG. 3   a  shows a perspective view of a another molding device with integrated heat pipes according to the invention; 
           [0026]      FIG. 3   b  shows a cross sectional view of the another molding device with integrated heat pipes according to the invention; 
           [0027]      FIG. 4  shows a perspective view of still another molding device with integrated heat pipes inside the molding die according to the invention; 
           [0028]      FIG. 5  shows a cross sectional view of a heat pipe integrated in the molding die according to the invention; 
           [0029]      FIG. 6  shows a cross sectional view of an alternative molding device with a heat pipe below the molding die according to the invention; 
           [0030]      FIG. 7  shows an alternative molding device according to the invention; 
           [0031]      FIG. 8  shows a lateral view of the retrofitting molding device according to the first embodiment of the invention; and 
           [0032]      FIG. 9  shows a graph of a process with the retrofitting molding device according to the first embodiment of the invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0033]    According to  FIG. 1  a retrofitting molding device  1  comprises a molding die  2  with a base plate  3  and a vacuum chamber  4  within the molding die  2  and the base plate  3 . The composite material  5  to be cured is on the molding die  2 . 
         [0034]    An outer heat pipe  6  is provided with fins  7  as multi-layered heat exchanger at a free end of the outer heat pipe  6  and with a two-dimensional heat exchanger  8 . The two-dimensional heat exchanger  8  of the outer heat pipe  6  is in planar contact for heat exchange to the base plate  3  of the molding die  2 . The fins  7  of the multi-layered heat exchanger are adapted to supply heat into the outer heat pipe  6  while the two-dimensional heat exchanger  8  is adapted to supply the heat from the fins  7  into the base plate  3 . 
         [0035]    An inner heat pipe  9  is provided with a two-dimensional base heat exchanger  10  and a two-dimensional die heat exchanger  11 . The two-dimensional base heat exchanger  10  is in planar contact for heat exchange with the base plate  3  and the two-dimensional die heat exchanger  11  is in planar contact for heat exchange with the molding die  2  for heat transfer to the composite material  5  to be cured on the molding die  2 . 
         [0036]    Heated air, e.g. from an autoclave, is applied through the fins  7  into the outer heat pipe  6  and said heat is transferred via the two-dimensional heat exchanger  8  to the base plate  3  of the molding die  2 . The two-dimensional base heat exchanger  10  of the inner heat pipe  9  inside the vacuum chamber  4  is heated up through the base plate  3  with the heat from the outer heat pipe  6 . Said heat of the two-dimensional base heat exchanger  10  is transferred via the inner heat pipe  9  to the two-dimensional die heat exchanger  11  for heat exchange with the molding die  2  and for heat transfer into the composite material  5  to be cured on the molding die  2 . 
         [0037]    According to  FIG. 2  corresponding features are referred to with the references of  FIG. 1 . For a further molding device  12  with the fins  7  as multi-layered heat exchanger at a free end of the outer heat pipe  6  integrated in the base plate  3  is in contact with the two-dimensional base heat exchanger  10  of the inner heat pipe  9  at the base plate  3 . The heat of the two-dimensional base heat exchanger  10  is transferred via the inner heat pipe  9  to the two-dimensional die heat exchanger  11  being in planar contact for heat exchange with the molding die  2  for heat transfer to the composite material  5  to be cured on the molding die  2 . 
         [0038]    Heated air is applied to the fins  7  of the outer heat pipe  6  and said heat is transferred via the two-dimensional heat exchanger  8  to the two-dimensional base heat exchanger  10  of the inner heat pipe  9  inside the vacuum chamber  4 . Said heat is transferred to the two-dimensional die heat exchanger  11  for heat exchange with the molding die  2  and heat transfer to the composite material  5  to be cured on the molding die  2 . 
         [0039]    According to  FIG. 3   a ,  3   b  corresponding features are referred to with the references of  FIG. 1 ,  2 . Another molding device  16  comprises a plurality of parallel inner heat pipes  9  integrated into the molding die  2  to provide a good heat distribution in the molding die  2  for a uniform curing of the composite component  5 . The molding die  2  encloses vacuum chambers  4  above the base plate  3 . 
         [0040]    The composite component  5  to be molded comprises a lower carbon fiber composite (CFK) layer  26 , an upper CFK layer  13  and honeycomb  14  between said lower and upper CFK layers  26 ,  13 . The composite component  5  is sealed off by a vacuum foil  15  enclosing as well a lateral part of the molding die  2  and the base plate  3 . 
         [0041]    According to  FIG. 4  corresponding features are referred to with the references of  FIGS. 1-3 . A still another molding device  17  comprises a plurality of fan shaped inner heat pipes  9  integrated for distributing the heat in the molding die  2  for a uniform curing of the composite component  5  which is located on the molding die  2 . 
         [0042]    According to  FIG. 5  corresponding features are referred to with the references of  FIGS. 1-4 . The inner heat pipe  9  with a circular cross section is integrated fitting snugly into an interstice  18  with a rectangular cross section provided in the upper surface of the molding die  2  oriented towards the composite component  5 . 
         [0043]    Fill material  19  with a good heat conductance is provided into the interstice  18  and encloses the inner heat pipe  9 . The upper surface of the molding die  2  oriented towards the composite component  5  and the fill material  19  are finished for adaption to the profile of the molding die  2 . 
         [0044]    According to  FIG. 6  corresponding features are referred to with the references of  FIG. 1-5 . An alternative molding device  20  comprises inner heat pipes  9  attached integrally along a lower surface of the molding die  2  oriented away from the composite component  5  for molding. The molding die  2  along the parallel inner heat pipes  9  transfers heat to the composite component  5  on top of the molding die  2 . The molding die  2  encloses vacuum chambers  4  above the base plate  3 . 
         [0045]    The composite component  5  to be molded comprises a lower carbon fiber composite (CFK) layer  26 , an upper CFK layer  13  and honeycomb  14  between said lower and upper CFK layers  26 ,  13 . The composite component  5  is sealed off by a vacuum foil  15  enclosing as well a lateral part of the molding die  2  and the base plate  3 . 
         [0046]    According to  FIG. 7  corresponding features are referred to with the references of  FIG. 1-6 . Eight separate heat pipes  6  each with external fins  7  are arranged in parallel inside the base plate  3  of the molding die  2  for heat transfer to the composite material  5  to be cured on the molding die  2 . 
         [0047]    According to  FIG. 8  corresponding features are referred to with the references of  FIGS. 1-7 . The retrofitting molding device  1  comprises an essentially cubic molding die  2  with the base plate  3  and the vacuum chamber  4  within the molding die  2  and the base plate  3 . The composite material  5  to be cured is on the molding die  2 . 
         [0048]    The outer heat pipes  6  are arranged in L-shape with the fins  7  linked to two separate outer flanges  22  of the outer heat pipes  6 . The two-dimensional heat exchanger  8  comprises two outer flanges  22  enclosing the four outer heat pipes  6 . The two outer flanges  22  of the two-dimensional heat exchanger  8  are shaped for planar contact to the base plate  3 . 
         [0049]    The inner heat pipe  9  is essentially U-shaped with two separate inner brackets  23 . The two-dimensional base heat exchanger  10  and the two-dimensional die heat exchanger  11  comprise respectively inner flanges  24 ,  25  for enclosing the two inner brackets  23  of the inner heat pipes  9 . The two lower inner flanges  24  of the two-dimensional base heat exchanger  10  are shaped for planar contact for heat exchange with the base plate  3  and the two upper inner flanges  25  of the two-dimensional die heat exchanger  11  is in planar contact for heat exchange with the molding die  2  for heat transfer to the composite material  5  to be cured on the molding die  2 . A contact force generating element  27 , e.g. a spiral spring, is arranged between the heat exchangers  10  and  11  in order to press them against the molding die  2  and base plate  3  to reach a better thermal conduction. Alternatively a high contact force can be reached by magnetically designed heat exchangers  10  and  11 . 
         [0050]    According to  FIG. 9  graphs with the temperature at the composite material  5  to be cured on the molding die  2  are plotted in function of the time spent for heating. The graphs to the right show the heat plotted in function of time spent for molding dies of the state of the art, the dashed line to the left shows the desired curve for heat plotted in function of time spent and the graphs to the left adjacent the dashed line show the heat plotted in function of time spent with the molding dies  1 ,  12 ,  16 ,  17 ,  20 . 
       Reference List 
       [0000]    
       
           1  molding device 
           2  molding die 
           3  base plate 
           4  vacuum chamber 
           5  composite component 
           6  outer heat pipe 
           7  fins 
           8  two-dimensional heat exchanger 
           9  inner heat pipe 
           10  two-dimensional base heat exchanger 
           11  two-dimensional die heat exchanger 
           12  further molding device 
           13  upper carbon fiber composite layer 
           14  honeycomb 
           15  vacuum foil 
           16  another molding device 
           17  still another molding device 
           18  interstice 
           19  fill material 
           20  Alternative molding device 
           21  outer bracket 
           22  outer flanges 
           23  inner brackets 
           24  inner lower flanges 
           25  upper inner flanges 
           26  lower carbon fiber composite layer 
           27  contact force generating element