Abstract:
Apparatus for cutting plural aligned ply strips includes plural knife blades disposed in a spaced manner such that each knife blade is aligned with and in closely spaced relation to an associated ply strip. The knife blades are pivotally mounted in a common housing and are coupled to a single rotational drive for allowing each knife blade to assume the same predetermined cutting angle relative to its associated ply strip, where the cutting angle may be varied between ±45°. The plural knife blades are coupled to a rotational drive by means of plural circular drive gears and are connected to a linear drive for displacing the knife blades into contact with the ply strips for cutting the strips at the predetermined angle. The severed edges of the aligned ply strips are formed in mutual linear alignment and do not include projecting triangular patterns, or crenelations.

Description:
TECHNICAL FIELD 
     This disclosure relates generally to improvements in the automated manufacture of composite structural assemblies and is more particularly directed to a mechanism and method for the cutting of plural, spaced, aligned ply strips at a predetermined cutting angle for forming a composite ply assembly having a substantially straight edge without tape triangular patterns or crenelations. 
     BACKGROUND 
     Increasingly, in an effort to reduce aircraft weight, designers are turning to the use of composite ply assemblies for the manufacture of structural and skin assemblies. Composite application systems and methods incorporating this fiber placement approach have been developed as described in U.S. Pat. No. 4,699,683. This type of composite line assembly structure and method involves the alignment of plural strips in contiguous edge contact so as to form a single wide band of composite ply strips. The ply strips can vary in width depending on the contour or tracking capability required for the specific structural application. A typical band is formed of 12 individual ¼ inch wide ply, or tape, strips for a total output bandwidth of 3 inches. Thus, a plurality of 3 inch bands would be placed in contiguous edge contact at predetermined orientation until the structure tooling mold is coated. A further embodiment of this type of fiber placement apparatus provides the capability to add, drop off or cut any or all of the contiguous strips allowing tailored flexibility in the configuration and orientation of the individual ply strips in the manufactured ply assembly. 
     Fiber lamentation cutting methods have suffered from a lack of operational capability to alter the orientation of the shear cut angle of each constituent tape from a fixed perpendicular cut as referenced to the centerline direction of the applied ply strip. As a result, ply cuts, or drop offs, occurring during predetermined path applications of +/−45° produce triangular patterns known as crenelations. The resolution of the resulting step triangulation is related both to the composite tape strip width and the applied orientation, or angle. Each constituent ply strip within the total bandwidth of strips incorporates this triangular pattern, or crenelation, with each cut. As a result, at the completion of the tape cutting sequence, the thus-produced edge of the composite ply assembly includes a triangular pattern. 
     Engineered composite assemblies typically include numerous ply laminations each formed by means of an orientation tailored segmented tape cutting process. The very large number of accumulated small tape triangular patterns or crenelations, formed in the built-up laminated ply assembly result in additional structural weight without the benefits of increased structural integrity and mechanical strength. 
     The embodiments of the disclosure are intended to overcome the limitations of the prior art by providing improved apparatus and method for the automated manufacture of composite structural assemblies which include precisely defined, linear edges formed at virtually any angle relative to the longitudinal axes of the connected ply strips and which do not include triangular patterns, or crenelations. 
     SUMMARY 
     Accordingly, embodiments of the disclosure provide an improved apparatus and method for cutting plural aligned, spaced ply strips at virtually any angle relative to their longitudinal axes so as to provide a linear array of aligned, substantially straight cut edges of the ply strips which are free of triangular patterns or crenelations. 
     Embodiments of the disclosure sequentially cut plural flat ply strips disposed in spaced relation in forming a planar array of ply strips where the ply strips are displaced in parallel along their lengths, and where the ply strips may all be cut at virtually any predetermined angle and the severed edges of each of the ply strips form a substantially straight edge with no triangular patterns and all of the severed edges are in linear alignment. 
     Embodiments of the disclosure may also form a composite structural assembly comprised of plural spaced ply strips arranged in a planar array where the ends of the ply strips (1) may be formed at virtually any single angle relative to the strip longitudinal axis, and (2) define plural substantially straight edges with no crenelations extending therefrom and which are linearly aligned. 
     Embodiments of the disclosure also provide an improved mechanism and method for forming the cut edges of plural spaced ply strips forming a composite structural assembly in a substantially straight line, where the aligned edges are formed at virtually any angle relative to the longitudinal axes of the ply strips, and where the severed edges may be formed by a cutting action initially directed through the ply strips or initially directed through an underlayment of the ply strips. 
     Embodiments of the disclosure may include apparatus for predetermined angular cutting of a plurality of parallel, spaced ply strips, the apparatus comprising a housing; a plurality of cutting assemblies pivotally disposed in the housing and aligned in a side-by-side, planar array, wherein each cutting assembly is aligned with a respective ply strip; a first displacement arrangement for pivotally displacing the cutting assemblies in said housing so that each cutting assembly is oriented at a common predetermined angle relative to an associated ply strip; and a second displacement arrangement for linearly displacing the cutting assemblies into contact with and severing an associated ply strip with which each cutting element is aligned in forming plural cut end portions in the ply strips, wherein the cut end portions of the ply strips are in linear alignment and do not include triangular patterns or crenelations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The appended claims set forth those features which characterize embodiments of the disclosure. However, the embodiments of the disclosure, as well as further aspects and advantages thereof, will best be understood by reference to the following detailed description of a preferred embodiment taken in conjunction with the accompanying drawings, where like reference characters identified like elements throughout the figures, in which: 
         FIG. 1  is a flow diagram of aircraft production and service method; 
         FIG. 2  is a block diagram of an aircraft; 
         FIG. 3   a  is a planar view, shown partially in section, of a plural knife cutting arrangement with a rotational drive for changing the cutting angle of the knife edges in accordance with one embodiment of the present disclosure; 
         FIG. 3   b  is a perspective view, shown partially in phantom, of another embodiment of an adjustable angle knife edge cutting arrangement in accordance with another embodiment of the present disclosure; 
         FIG. 3   c  is a bottom plan view of the knife edge cutting arrangement with adjustable angular positioning shown in  FIG. 3   a;    
         FIG. 3   d  is a perspective view of a portion of the knife cutting arrangement of  FIG. 3   a  shown in position adjacent a ply strip alignment housing which displaces plural ply strips along their respective lengths for sequential cutting by plural aligned knife edges; 
         FIG. 3   e  is simplified plan view of the plural knife cutting edges shown in  FIG. 3   a  illustrating the angular range of motion of the cutter/shear mechanism of the present disclosure; 
         FIG. 3   f  is a simplified plan view of a typical crenelated pattern formed in the aligned cut patterns encountered in prior art plural ply strip cutting arrangements; 
         FIG. 3   g  is a simplified perspective view of plural aligned severed ply strips having linearly aligned, substantially straight edges cut in accordance with the present disclosure; 
         FIG. 4   a  is a perspective view of another embodiment of a single cutter/shear assembly in accordance with the principles of the present disclosure; 
         FIG. 4   b  is a partial perspective view of the cutting knife used in the single cutter/shear assembly of  FIG. 4   a;    
         FIG. 4   c  is a simplified sectional view of the knife cutting edge shown in  FIG. 4   b  in combination with a fixed reaction knife blade; 
         FIG. 4   d  is a simplified sectional view showing the single cutter/shear assembly of  FIG. 4   a  rotationally mounted in a support housing including plural rotary drive gears; and 
         FIG. 5  is a simplified flow chart showing the series of steps carried out in accordance with one embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION 
     Referring more particularly to the drawings, embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method  100  as shown in  FIG. 1  and an aircraft  102  as shown in  FIG. 2 . During pre-production, exemplary method  100  may include specification and design  104  of the aircraft  102  and material procurement  106 . During production, component and subassembly manufacturing  108  and system integration  110  of the aircraft  102  takes place. Thereafter, the aircraft  102  may go through certification and delivery  112  in order to be placed in service  114 . While in service by a customer, the aircraft  102  is scheduled for routine maintenance and service  116  (which may include modification, reconfiguration, refurbishment, and so on). 
     Each of the processes of method  100  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer), as indicated by the “X” in the grid to the right of the flow diagram of  FIG. 1 . For purposes of this description, a system integrator may include without limitation any number of aircraft manufacturers and major-system subcontractors; a third party may include without limitation any number of venders, subcontractors, and suppliers; and an operator may be an airline, leasing company, military entity, service organization, and so on. 
     As shown in  FIG. 2 , the aircraft  102  produced by exemplary method  100  may include an airframe  118  with a plurality of systems  120  and an interior  122 . Examples of high-level systems  120  include one or more of a propulsion system  124 , an electrical system  126 , a hydraulic system  126 , and an environmental system  130 . 
     Apparatus and methods embodied herein may be employed during any one or more of the stages of the production and service method  100 . For example, components or subassemblies corresponding to production process  108  may be fabricated or manufactured in a manner similar to components or subassemblies produced while the aircraft  102  is in service. Also, one or more apparatus embodiments, method embodiments, or a combination thereof may be utilized during the production stages  108  and  110 , for example, by substantially expediting assembly of or reducing the cost of an aircraft  102 . Similarly, one or more of apparatus embodiments, method embodiments, or a combination thereof may be utilized while the aircraft  102  is in service, for example and without limitation, to maintenance and service  116 . 
     Referring to  FIG. 3   a , there is shown a simplified plan view, shown partially in section, of a variable angle cutting element  17  in accordance with one embodiment of the present disclosure.  FIG. 3   c  is a bottom plan view of a portion of the variable angle cutting element  17  shown in  FIG. 3   a  illustrating details of a preferred rotation pivot drive arrangement including a pair of reversing idler gears  14  used to maintain knife cutting edge orientation.  FIG. 3   e  is a plan view of the three shear knife blade assemblies  5  showing their range of rotational motion for severing plural ply strips at a predetermined angle. 
     Variable angle cutting element  17  includes plural cutter assemblies  4 , one for each of three shear knife blade assemblies  5 . Variable angle cutting element  17  provides close non-rotational linear alignment of each knife blade  5  with an associated fixed reaction knife blade  6 . Each cutter mechanism housing  4  is typically press fit, concentric within the inner bore diameter of a circular bearing  21 . The outer diameter of bearing  21  is, in turn, press-fit mounted within a fixed cutter alignment structure  22 . A spindle drive gear  7  is concentrically pressed onto a suitable machined step of the variable angle cutting element  17 . Angular positioning of each of the cutter assemblies  4  is achieved by predetermined, or selected, rotation of a micro servo drive motor  8  transmitted through spindle drive gears  1 ,  2  and  3 , as well as the pair of orientation idler gears  14  as shown in  FIG. 3   c . Drive motor  8  is coupled to spindle drive gear  3  by means of drive gear  7 . Drive motor  8  provides sufficient torque capacity and rotational positioning accuracy for rotationally displacing and positioning the three shear knife blade assemblies  5 . In addition, idler gears  14  may be in the form of a commercial gear which is split along its centerline with an internal spring system which loads each side of the contact gear teeth for eliminating gear system backlash. Ply strip cutting occurs when three knife blade plungers, or actuators,  19  each connected to an associated cutter assembly  4 , displace the three shear knife blade assemblies  5  downward as viewed in  FIG. 3   a . Downward displacement of the knife blade assemblies  5  causes each knife blade assembly to engage a respective ply strip. When a knife blade assembly  5  passes beyond an associated fixed reaction knife blade  6 , as shown for the center shear knife blade assembly in  FIG. 3   a , the ply strip is severed. 
     As shown in  FIG. 3   c , drive gear  7  rotating counterclockwise directly drives spindle drive gear  3  clockwise so as to orient cutter assembly  9  coupled thereto at a predetermined angle of rotation. One of the idler gears  14  engages spindle drive gears  1  and  3  so as to rotate drive gear  1  at the same speed and in the same direction as drive gear  3 . Similarly, the second idler gear  14  engages spindle drive gears  1  and  2 . Both of these spindle gears rotate in the same direction at the same speed as also shown in  FIG. 3   c . This pattern of alternating drive gears and idler gears may be repeated so as to rotationally drive additional cutter assemblies which are not shown in  FIG. 3   c  for simplicity. Therefore, controlled rotational positioning by drive motor  8  of drive gear  7  is repeated through the entire bank of cutter elements so that each cutting blade of each cutter assembly assumes substantially the same angular orientation for engaging a respective ply strip at the same angle of incidence. This is shown in the simplified plan view of  FIG. 3   e , wherein each of the three shear knife blade assemblies  5  is shown having substantially the same angular orientation relative to a 0° reference line drawn through the center of each of the three shear knife blade assemblies.  FIG. 3   e  also shows that the range of rotational motion of each of the shear knife blade assemblies  5  achievable by the mechanism and method of this disclosure is ±45°, where each of the shear knife blade assemblies may be rotationally displaced either clockwise or counterclockwise. 
     The combined predetermined ply strip cutting and controlled rotational orientation of the shear knife blade assemblies  5  relative to the plural ply strips output bandwidth eliminates the scrap crenelated segments  16  shown in  FIG. 3   f  in dotted line form disposed on the ends of three parallel inline ply strips  15  as encountered in the prior art. Each of the ply strips  15  is displaced in the direction of the arrows shown in  FIG. 3   f  by means of a ply alignment housing  18  shown in  FIG. 3   d . Also shown in  FIG. 3   d  is a portion of the variable angle cutting element  17  described above and shown in  FIG. 3   a.  Each of the shear knife blade assemblies  5  is aligned with and closely spaced from an associated ply strip for engaging and severing the ply strip in a timed sequence. More specifically, each ply strip is typically aligned centrally along a respective centerline of its associated shear knife blade assembly  5  and all ply strips are spaced in an equidistant manner from their associated shear knife blade assembly. This timed sequence is under the control of a timer mechanism (not shown for simplicity) connected to, or incorporated in, each of the knife plunger actuators  19  for sequentially displacing each knife blade assembly  5  into contact with a respective ply strip for severing the strip. Each of the actuators  19  displaces an associated shear knife blade assembly  5  toward and into engagement with a respective ply strip  15  for sequentially severing the ply strips so as to form a substantially straight line, or linear array, of smooth cut edges of the ply strips as shown in  FIG. 3   g . The cut edges of the ply strips  15  cut in accordance with the present disclosure shown in  FIG. 3   g  do not incorporate crenelations as in the prior art. 
     The manner in which the ply strips are sequentially cut may be accomplished by any number of well-known ply strip drive mechanisms and timed cutting arrangements. The timed sequence of the cutting of the individual ply strips is a function of the angle at which the individual ply strips are severed as is well known. In addition, the individual knife blades are shown as having a chevron-shaped cutting edge so as not to force the ply strip to one side or the other of the alignment guides shown in the ply alignment housing  18 . The individual knife blades may also be provided with a single shallow raked angle blade. 
     Referring to  FIG. 3   b , there is shown a shear knife blade assembly  28  in accordance with another embodiment of the disclosure. A knife blade  32  is disposed on an end of a cylindrical housing  30 . Also disposed on the cylindrical housing  30  about its outer circumference is a spindle drive gear  31  which allows for the rotational displacement of the housing and knife blade for engaging a ply strip at a predetermined angle. Also shown in  FIG. 3   b  is a reaction knife blade  33  which cooperates with knife blade  32  in forming a sharp edge on a severed ply strip (not shown in the figure for simplicity). 
     Cylindrical housing  30  is hollow and has disposed therein a connected cylindrical-shaped knife plunger actuator  38  for linearly displacing the cylindrical housing  30  and the knife blade  32  attached thereto as previously described in terms of the embodiment shown in  FIG. 3   a . Disposed on opposed outer lateral portions of knife plunger actuator  38  are first and second pins  34   a  and  34   b . Disposed within cylindrical housing  30  are three pairs of slots  35   a  and  35   b ,  36   a  and  36   b , and  37   a  and  37   b  for establishing the angle at which the knife blade  32  engages a ply strip. Each of the slots extends downward from the upper edge of the cylindrical housing  30 , and each pair of slots is adapted to receive one of the first and second pins  34   a  and  34   b . Thus, a first pair of linear slots  35   a  and  35   b  are disposed on opposed portions of the cylindrical housing  30 . With the first and second pins  34   a  and  34   b  respectively disposed in linear slots  35   a  and  35   b , the knife blade  32  may engage a ply strip at an angle of 90° relative to the longitudinal axis of the ply strip. A first pair of curvilinear slots  36   a  and  36   b  extend downwardly in a first direction about the cylindrical housing  30 . With first and second pins  34   a  and  34   b  respectively disposed in curvilinear slots  36   a  and  36   b , knife blade  32  will engage a ply strip at a +45° angle relative to the longitudinal axis of the ply strip. A second set of curvilinear slots  37   a  and  37   b  is also disposed within the cylindrical housing  30  and extend downwardly from the top of the cylindrical housing in a second, opposed direction about the cylindrical housing. Thus, the second set of curvilinear slots  37   a ,  37   b  extend in a direction about the cylindrical housing  30  opposite to the direction of the first set of curvilinear slots  36   a ,  36   b . With the first and second pins  34   a ,  34   b  respectively disposed in curvilinear slots  37   a ,  37   b , knife blade  32  engages a ply strip at an angle of −45° relative to the longitudinal axis of the ply strip. When the knife plunger actuator  38  is linearly displaced downwardly as viewed in  FIG. 3   b , the first and second pins  34   a ,  34   b  each trace a helical path within an associated pair of curvilinear slots ( 36   a  and  36   b  or  37   a  and  37   b ) resulting in rotational displacement of the cylindrical housing  30  and knife blade  32  attached thereto for cutting a ply strip at an angle of either +45° or −45°. 
     Referring to  FIG. 4   a , there is shown a perspective view of a single cutter mechanism  40  in accordance with yet another embodiment of the disclosure. The single cutter mechanism  40  includes a cylindrical spindle housing  44  having an orientation gear  41  concentrically disposed about its outer circumference. Spindle housing  44  further includes a cutter feed-through slot  50  to provide clearance for a ply strip (not shown for simplicity) as needed for a shear knife  45  disposed in the spindle housing  44  which cooperates with a fixed reaction knife blade  47  in severing a ply strip inserted through the cutter feed-through slot  50 . As in the previously described embodiments, cutter mechanism  40  is maintained in position by means of a circular bearing  42  so as to be freely rotatable in a variable angle cutting element by means of an outer gear  43  engaging orientation gear  41 . 
     A further embodiment of the shear knife  45  is shown in  FIG. 4   b . In this embodiment, the knife blade  45  does not undergo a rapid downward motion in severing a ply strip, but rather is quickly moved upward in severing the ply strip to reduce, or minimize, epoxy resin induced tack sticking of the tape to either the guide shoot walls or cutting device edge as shown in  FIG. 3   d . In  FIG. 4   c , a fixed reaction knife blade  67  is shown in cooperation with the shear knife  45  for severing a ply strip. In this embodiment, the shear knife  45  is positioned such that the cutter feed through slot  50  is centered within a suitably sized aperture within the ply alignment housing  18  shown in  FIG. 3   d.    
       FIG. 5  is a flow chart illustrating the sequential series of steps  72 ,  74 ,  76  and  78  carried out in accordance with one embodiment of the method for predetermined angular cutting of a plurality of ply strips of the present disclosure. A brief description of the operation carried out in each step is provided in each block of the flow chart. 
     While particular embodiments of the disclosure have been shown and described, it will be obvious to those skilled in the relevant arts that changes and modifications may be made without departing from the embodiment in its broader aspects. Thus, any such variations are within the scope and spirit of the broad concept and implementation of the embodiments of the disclosure described herein. Therefore, the aim in the appended claims is to cover all such changes and modifications as fall within the true spirit and scope of the disclosure. The matter set forth in the foregoing description and accompanying drawings is offered by way of illustration only and not as a limitation. The actual scope of the embodiments is intended to be defined in the following claims when viewed in their proper perspective based on the prior art.