Abstract:
A motorized head for applying fiber composite material to an application surface includes a drive roll assembly for applying fiber composite material to an application surface. The drive roll assembly includes a drive roll and a backup roll and a drive roll nip formed between the drive roll and the backup roll. At least one cutter is mounted on the drive roll for cutting fiber composite material, and an ejector mechanism is mounted on the drive roll behind the cutter mechanism. The ejector mechanism positively displaces the leading end of the cut tow material away from the surface of the drive roll to ensure that the cut tow material does not misfeed as it approaches the fiber path chute downstream from the cutter.

Description:
FIELD OF THE DEVICE 
       [0001]    The device relates to a head for applying fiber composite material to an application surface in which the individual lanes of fiber composite material are each driven by a drive roll that includes a cutter for the composite material and an ejector mechanism for displacing the leading end of the cut tow material away from the surface of the drive roll. 
       BACKGROUND 
       [0002]    Composite lay-up machines are well known in the art. Such machines can be divided into two basic types, fiber placement machines that lay bundles of individual fibers onto a surface, and tape laying machines that apply fiber composite material in the form of a wide tape onto a surface. If the surface that receives the fiber composite material is fairly continuous, and does not have a lot of contour, a tape laying machine is normally used. If the surface is highly contoured or discontinuous because of the presence of openings in the surface, a fiber placement machine is normally used. 
       SUMMARY 
       [0003]    A fiber placement head for fiber placement utilizes individual roller sets comprising a drive roll and backup roll for each tow lane in which each drive roll has a tow cutting and restarting zone carried on the roll&#39;s circumference. Each drive roll is geared to and meshes with a back-up roll that captures the tow material in a drive roll nip that is formed therebetween. The drive roll nip receives tow from an upstream fiber path chute and delivers the tow to a downstream fiber path chute. A tow ejector foot is mounted on the drive roll immediately following each of the cutters to prevent the leading end of the cut tow from adhering to the drive roll and misfeeding into the downstream chute. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]      FIG. 1  is perspective view of the fiber delivery mechanism in a fiber placement head. 
           [0005]      FIG. 2  is a detail of a drive roll and a portion of a backup roll. 
           [0006]      FIG. 3  is a detail view showing the drive roll in position prior to cutting the composite material. 
           [0007]      FIG. 4  is a detail view showing the drive roll as the cutter cuts the composite material. 
           [0008]      FIG. 5  is a detail view showing the drive roll after the cutter has cut the composite material prior to actuation of the tow ejector foot. 
           [0009]      FIG. 6  is a detail view showing the drive roll as the tow ejector foot is actuated. 
           [0010]      FIG. 7  is a detail view showing the tow ejector foot returned to the retracted position and the cut end of the composite material in the downstream fiber chute. 
           [0011]      FIGS. 8 and 9  show an alternate embodiment of the invention. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       [0012]      FIG. 1  is a perspective view of the fiber delivery mechanism  10  in a fiber placement head. The mechanism  10  comprises a frame structure  12  which supports an upper array of drive roll assemblies  14  and lower array of drive roll assemblies  16 . Each drive roll assembly comprises a drive roll  18  and a back-up roll  20  that is half the diameter of the drive roll  18 . Each drive roll assembly  14  and  16  feeds fiber composite material along a fiber composite path or lane to the compaction roll  22  located at the front of the frame as well known in the art. The fiber composite materials in the upper and lower lanes are interleaved at the compaction roll  22  to form a continuous layer of side-by-side strips on the application surface. The compaction roll  22  is formed by a series of side by side roller segments  24  so that the outer surface of the compaction roll may adapt to the contour of the surface to which the composite material is being applied. The frame  12  also supports an upper array of restart pinch roll assemblies  26  and a lower array of restart pinch roll assemblies  28  that are positioned between the drive roll assemblies  14  and  16 , respectively, and the compaction roll  22 . The restart pinch roll assemblies  26  and  28  drive the fiber composite material to the compaction roll  22  after the material has been cut by one of the cutters on the drive roll. 
         [0013]      FIG. 2  is a detail view of a drive roll  18  and a portion of a backup roll  20 . The drive roll  18  is mounted by bearings (not shown) on a non-rotating drive roll hub  32  that is secured to the outside frame member  12 . The drive roll  18  may be driven by a drive pinion  34  that engages the internal gear teeth  35  of a ring gear  36  that is attached to the drive roll  18 . Rotation of the drive roll  18  is transferred to the backup roll  20  by a drive transfer arrangement that drivingly couples the drive roll and the backup roll together. In the embodiment shown, external gear teeth  38  on the ring gear  36 , best seen in  FIG. 3 , engage gear teeth  40  on the outside of the backup roll  20 , to positively couple the rotation of the drive roll to the backup roll. The drive roll has two cutter assemblies  48  spaced one hundred and eighty degrees apart, and a drive surface  43  is formed on the outer circumference of the drive roll following each cutter assembly as described more fully below. A tow ejector foot  66  is positioned between the cutter assembly  48  and the drive surface  43  of the drive roll. The backup roll has an anvil  80  mounted on its outer surface, and a backup drive surface  49  is formed on the outer surface of the backup roll following the anvil. 
         [0014]    A drive roll nip  42  is formed between the drive roll  18  and the backup roll  20 . Fiber tow  44  is delivered to the drive roll nip  42  from an upstream fiber path chute  46 , and passes through the drive roll nip  42  into a downstream fiber path chute  47 . Each cutter assembly  48  is followed by a drive zone surface  43  on a first portion of the drive roll  18  that extends counterclockwise around the surface of the drive roll. The drive zone surface  43  is formed by a circumferential portion of the drive roll that has a slightly greater radius than the remaining circumference of the drive roll so that it extends further into the drive roll nip  42 . Likewise, each anvil on the backup roll  20  is followed by the backup drive surface  49  that extends partly around the circumference of the backup roll. When the drive zone surface  43  is opposite the backup drive surface  49 , fiber composite material  44  that is positioned in the drive roll nip  42  is gripped and can be driven by the rotation of the drive roll  18  and the backup roll  20 . The drive zone surface  43  may extend around an angle A that is between ninety and one hundred and thirty five degrees around the circumference of the drive roll, and in one embodiment, the drive zone surface extends for one hundred and thirteen degrees around the drive roll. A free zone surface  45  on a second portion of the drive roll follows the drive zone surface  43 . The free zone surface  45  is positioned relative to the backup roll  20  so that when the free zone surface  45  is opposite the backup roll  20 , fiber composite material  44  can be pulled freely through the drive roll nip  42  without contacting or dragging on the drive roll or the backup roll. This provides clearance for the tow to pull through the head and is sized to reduce the amount of resin from the fiber tow material that is transferred to the surface of the drive roll and the backup roll as the fiber tow is laid onto the application surface. The free zone surface  45  may extend through an angle B that is between forty-five and ninety and degrees around the circumference of the drive roll, and in one embodiment, the free zone surface  45  extends for sixty seven degrees around the drive roll. 
         [0015]    Referring now to  FIG. 3 , the cutter assembly  48  comprises a cutter retainer  50  that is attached to the drive roll  18  by suitable fasteners such as screws  51  for rapid mounting and removal. A cutter blade  52  having a knife edge  54  is mounted between the cutter retainer  50  and a cutter guide insert  56 . The cutter blade  52  has a ramp portion  58  and a spring retaining finger  60  that is formed below the ramp portion  58 . A compression spring  62  is located in a spring pocket  64  formed in the cutter blade retainer  50 , and the end of the spring  62  presses against the underside of the retaining finger  60 . A tow ejector foot  66  is positioned behind the cutter blade retainer  50  and is mounted on a pivot shaft  67 . The tow ejector foot  66  has a ramp surface  68  leading to a lobe  69 , and a return spring seat surface  70 . A compression spring  72  is mounted between the return spring seat surface  70  and another spring retaining surface (not shown) that is part of the drive roll assembly. A cam wheel  74  is mounted on a pivot  76  that is mounted on the non-rotating drive roll hub  32 . The cam wheel  74  is in a position to impact on the ramp surface  58  of the cutter blade and the ramp surface  68  of the tow ejector foot  66  as these elements rotate past the cam wheel. An anvil  80  and an anvil retainer  82  are mounted on the outer circumference of the backup roll  20 . The anvil retainer is held in place by a fastening element such as a screw  81 .  FIG. 3  shows the drive roll in a position just before the cam wheel  74  impacts on the ramp surface  58  of the cutter blade  52 . 
         [0016]    As shown in  FIG. 4 , rotation of the drive roll  18  causes the cam wheel  74  to displace the cutter blade  52  against the force of the compression spring  62 , extending the knife edge  54  into the composite material  44  in the drive roll nip  42 . As the cutter blade  52  extends, the knife edge  54  cuts through the composite material  44  and shears against the edge of the anvil  80  that is mounted on the back-up roll  20 . The synchronized rotation of the drive roll  18  and the backup roll  20  ensures that the anvil  80  is always opposite the cutter  52  when the cam wheel  74  impacts the cutter. 
         [0017]    Although the element  80  is called an anvil, it does not function as an anvil in the sense that the knife edge  54  of the cutter blade does not cut the fiber tow  44  by pressing the fiber tow against the anvil surface. A recess is formed between the anvil  80  and the anvil retainer  82 , and the knife edge  54  of the cutter blade extends into the recess as it shears the fiber tow against the edge of the anvil  80 . 
         [0018]      FIG. 4  shows the spacing between the downstream trailing end  84  of the cut tow and the cutter blade  54  exaggerated for clarity. It will be understood that once the tow  44  has been cut, the drive wheel  18  may stop for a period of time until the next length of tow is required to be fed through the drive roll nip  42 . After the composite material  44  is cut, the application head continues to apply composite material to the application surface until all of the composite material between the compaction roll  22  and the cutter blade  52  has been laid onto the application surface. 
         [0019]      FIG. 5  shows the drive roll in a position just after the cam wheel  74  releases the cutter blade  52  as the cam wheel begins to impact on the ramp surface  68  of the ejector foot  66 . The cutter blade return spring  62  retracts the cutter  52  into the pocket formed between the cutter block retainer  50  and the cutter guide insert  56 . With the drive wheel in this position, the leading end  86  of the upstream tow material may follow the circumference of the drive roll surface and may be adhered to the drive roll surface immediately behind the cutter blade  52 . This can be caused by tow adhesion or curl in the tow material, and may result in the leading end  86  of the tow material not entering the downstream tow chute  47 . 
         [0020]      FIG. 6  shows the drive roll in a position in which the cam wheel  74  rides onto the ramped surface  68  of the tow ejector foot  66  and rocks the tow ejector foot relative to the pivot  67  as shown. The pivoting of the tow ejector foot  66  positively displaces the tow material  44  from the circumferential surface of the drive roll  18  and orients the leading end  86  of the tow material so that it is in alignment with the downstream fiber path chute  47 . 
         [0021]      FIG. 7  shows the drive roll rotated to a position in which the wheel cam  74  is no longer in contact with the ramped surface  68  of the tow ejector foot  66 . The return spring  72  has returned the ejector foot  66  to the retracted position so that it is alignment with the outer circumference of the drive roll  18 , and the rotation of the drive roll  18  and the backup roll  20  has driven the leading end  86  of the tow material into the downstream tow chute  47 . 
         [0022]      FIGS. 8 and 9  show an alternate embodiment of the invention in which the ejector foot is mounted for linear motion. The ejector foot  90  has an elongated mounting slot  91  that is mounted on a post  92  for a linear, plunging motion in a direction that is generally parallel to the motion of the cutter blade  52 . The ejector foot  90  is formed with a lower foot surface  93  and a ramp  94  that comes into contact with the cam wheel  74 . A return spring  95  that is mounted in a pocket  96  formed in the drive roll  18  engages the underside of the ejector foot  90  below the ramp  94  and maintains the ejector foot in a retracted position as shown in  FIG. 8 . 
         [0023]      FIG. 9  shows the ejector foot  90  in an extended position as a result of the ramp  94  coming into contact with the cam wheel  74 . In the extended position, the lower foot surface  93  displaces the tow material  44  from the circumferential surface of the drive roll  18  so that the tow material is in alignment with the downstream fiber path chute  47 . Arrangements other than the elongated mounting slot  91  and the post  92  may be used to mount the ejector foot  90  for linear plunging motion relative to the drive roll  18 . 
         [0024]    Having thus described the invention, various modifications and alterations will be apparent to those skilled in the art, which modifications and alterations will be within the scope of the invention as defined by the appended claims.