Abstract:
Fastener clearing systems and methods for a fastener delivery system are provided. In one embodiment, a system includes an extractor tool having one or more vacuum generators in fluid communication with a catcher for retaining fasteners during transport. The vacuum generators are selectively activated to draw fasteners into the catcher. A backflow port is formed in the extractor tool and introduces pressurized air into the catcher to dislodge fasteners that adhere to the catcher after the vacuum generators have been deactivated. The backflow port may be formed in a fitting positioned between vacuum generators and securing the vacuum generators to one another. The vacuum generators and fitting may define a common fluid channel opening into a fastener seat adapted to receive a portion of a fastener.

Description:
FIELD OF THE INVENTION 
       [0001]    This invention relates generally to systems and methods for automated delivery of fasteners and, more specifically, to pneumatic fastener delivery systems. 
       BACKGROUND OF THE INVENTION 
       [0002]    Automated fastener delivery systems in aeronautical applications should provide consistent operation. A typical aircraft will include thousands of fasteners, which must be installed quickly and cost-effectively. However, tools used to handle the fasteners may become fouled by contaminants, oils, or coatings that are carried by the fasteners. As a result, fasteners may adhere to tooling rather than releasing predictably. Lodged fasteners prevent consistent delivery of fasteners and cause delay when they must be removed by hand. 
         [0003]    Fastener handling tooling using suction heads to pick up or move fasteners is particularly vulnerable to this problem. A typical suction head creates a vacuum that draws the fastener into the suction head and retains the fastener. The suction head may then be moved to another location where the vacuum is deactivated and the fastener is allowed to fall under the force of gravity. The simplicity of operation and minimal moving parts of suction heads make them very cost effective. However, when the suction head is fouled by oils or other contaminants, a fastener may remain within the grip of the suction head after the vacuum is deactivated. Accordingly, although suction heads are an effective material handling tool, there is room for improvement. 
       SUMMARY 
       [0004]    The present invention is directed to methods and apparatus for automated delivery of fasteners to an installation tool. Embodiments of the invention enable consistent release of fasteners and other components from a suction head of fastener handling tooling in an automated fastener delivery system. 
         [0005]    In one embodiment, an apparatus includes one or more fastener storage devices and an unloading mechanism in communication with the fastener storage device. The unloading mechanism includes a fastener seat having a fluid channel coupled thereto. A pneumatic control system regulates air flow between a pressurized air source and the fluid channel. The control system generates both overpressure and vacuum within the fluid channel. Vacuum may be generated by pneumatic vacuum generators in fluid communication with the fluid channel. Overpressure may be generated by releasing pressurized air into the fluid channel through a backflow port. In one embodiment, the backflow port is formed in a fitting securing first and second vacuum generators to one another. 
         [0006]    In operation, a pneumatic control system generates a vacuum within the fluid channel to draw at least one fastener from the fastener storage device into the fastener seat. The unloading mechanism is then moved to the delivery conduit. The control system then generates overpressure within the fluid channel to expel the fastener into the delivery conduit. In some embodiments, the vacuum is first deactivated and the fastener is allowed to fall into the delivery conduit. If the fastener fails to fall, then overpressure is generated within the fluid channel to expel the fastener. Whether the fastener falls may be determined by a proximity sensor secured on or near the delivery conduit. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0007]    Embodiments of the present invention are described in detail below with reference to the following drawings. 
           [0008]      FIG. 1  is a perspective view of a portable fastener delivery system suitable for use with a fastener clearing system, in accordance with an embodiment of the present invention; 
           [0009]      FIG. 2  is a perspective view of a delivery conduit, in accordance with an embodiment of the present invention; 
           [0010]      FIG. 3  is a perspective view of an extractor mechanism, in accordance with an embodiment of the present invention; 
           [0011]      FIG. 4  is a side view of an extractor catcher, in accordance with an embodiment of the present invention; and 
           [0012]      FIG. 5  is a process flow diagram of a method for using a fastener clearing system, in accordance with an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0013]    The present invention relates to systems and methods for automated delivery of fasteners to a fastener installation tool, and more specifically, to improved fastener clearing systems and methods. The present invention is suitable for use in fastener delivery systems, including the type generally disclosed, for example, in U.S. Pat. No. 6,688,489 issued to Daniel D. Bloch et al., which is incorporated herein by reference. Many specific details of certain embodiments of the invention are set forth in the following description and in  FIGS. 1 through 5  to provide a thorough understanding of such embodiments. One skilled in the art, however, will understand that the present invention may have additional embodiments, or that the present invention may be practiced without one or more of the details described in the following description. 
         [0014]    Referring to  FIG. 1 , a fastener delivery system  10  generally includes an unloading mechanism  12  in communication with a fastener storage device  14 , wherein a control system  16  causes the unloading mechanism  12  to remove a fastener having a specific configuration from the fastener storage device  14  and transport the fastener to a delivery conduit  18 , wherein the fastener is delivered to a work station. As shown, the fastener delivery system  10  may be disposed within a portable platform, such as a mobile cart  20 , so that a variety of fasteners may be delivered to a plurality of work stations located throughout a manufacturing facility. 
         [0015]    The fastener delivery system  10  generally removes and delivers fasteners using a pneumatic source  22 . In one particular embodiment, the pneumatic source  22  is shop air at 90 psi (pounds per square inch). The pneumatic source  22  may be activated by the control system  16  and is in communication with both the unloading mechanism  12  and the delivery conduit  18  through flexible tubing  24 . The fittings that connect the pneumatic source  22  and the flexible tubing  24  are not shown for clarity. The pneumatic source  22  activates one or a plurality of vacuum generators  26  to remove a fastener from the fastener storage device  14  and secure the fastener within the unloading mechanism  12 . The fastener storage device  14  may include a plurality of tubes  28 . The tubes  28  may bear seals  30  for engaging the unloading mechanism  12 . Once the fastener is secured within the unloading mechanism  12 , the control system positions the unloading mechanism  12  adjacent the delivery conduit  18 , wherein the vacuum generators  26  are deactivated and the fastener is transported through the delivery conduit  18  by gravity and by pressurized air from the pneumatic source  22 . 
         [0016]    Referring to  FIG. 2 , the delivery conduit  18  further comprises a drop station  32  in communication with a first fastener delivery tube  34  and a second fastener delivery tube  36 . As shown, the drop station  32  further comprises a plurality of drop plates  38  that define chutes  40 , through which the fasteners are dropped as previously described. In one particular embodiment, the chutes  40  are tapered, although a variety of shapes may be employed to effectuate transport of the fastener through the delivery conduit  18 . The plurality of drop plates  38  are employed to facilitate rapid interchangeability for a variety of fastener configurations. Alternately, a single drop plate may be employed rather than the plurality of drop plates  38 . 
         [0017]    As further shown in  FIG. 2 , the first fastener delivery tube  34  extends from the drop station  32  and is in communication with the second fastener delivery tube  36 . Generally, a fastener is transported through the first fastener delivery tube  34  by gravity until the fastener passes beyond a proximity sensor  42 . When the proximity sensor  42  detects the presence of a fastener, the proximity sensor  42  notifies the control system  16 , and the control system  16  then activates the pneumatic source  22  ( FIG. 1 ). Accordingly, the pneumatic source  22  provides pressurized air through the second fastener delivery tube  36  to deliver the fastener to the work station. The workstation may include an end effector suitable for installing the fastener. 
         [0018]    The first fastener delivery tube  34  may be rigid in order to facilitate efficient transport of the fastener by gravity. Accordingly, in one particular embodiment, the first fastener delivery tube  34  is fabricated from aluminum tube stock or other rigid material commonly known in the art. The second fastener delivery tube  36  may be flexible so that the fastener may be delivered to a plurality of work stations throughout a manufacturing facility. Accordingly, the length of the second fastener delivery tube  36  may be varied to accommodate the required distance from the portable fastener delivery system  10  to the work station. The amount of time that the pneumatic source  22  provides pressurized air through the second fastener delivery tube  36  is a function of the length of the delivery tube and the fastener configuration being delivered, and therefore, the amount of time that pneumatic source  22  is activated must be adjusted according to the length of the second fastener delivery tube  36 . 
         [0019]    Additionally, the inner diameter of the second fastener delivery tube  36  should be sized appropriately to prevent tumbling of the fastener along the length thereof, which is generally a function of the overall size of the fastener. Generally, the inner diameter of the second fastener delivery tube  36  may desirably be slightly larger than the diameter of the fastener head yet smaller than the overall length of the fastener to prevent tumbling. Further, the second fastener delivery tube  36  may be fabricated from relatively soft and flexible plastic such as nylon with a relatively smooth inner surface to minimize friction between the fastener and the inner wall of the second fastener delivery tube  36 . 
         [0020]    Referring to  FIG. 3 , the unloading mechanism  12  generally comprises an extractor tool  44  having an extractor catcher  46  attached thereto. As further shown, in this embodiment, the vacuum generators  26  are disposed at an upper end of the extractor tool  44  and the extractor catcher  46  is disposed at a lower end of the extractor tool  44 . 
         [0021]    Although two (2) extractor tools  44 , each having two (2) vacuum generators  26 , are illustrated herein, the portable fastener delivery system  10  according to the present invention may comprise any number of extractor tools  44  and vacuum generators  26  to remove fasteners in accordance with specific operating requirements. Therefore, the illustrated embodiment which uses two (2) extractor tools  44  with two (2) vacuum generators  26  each should not be construed as limiting the scope of the present invention. 
         [0022]    Generally, the unloading mechanism  12  is positioned adjacent the fastener storage device  14  using a linear X-Y positioner  48  that is activated by the control system  16  ( FIG. 1 ). More specifically, the linear X-Y positioner  48  positions an extractor catcher  46  of the unloading mechanism  12  ( FIG. 3 ) adjacent the appropriate fastener storage tube  28  that contains the requested fastener. Accordingly, the X and Y position of each fastener storage tube  28  is stored within the control system  16  as described in greater detail below. Additionally, the extractor tool  44 , along with the extractor catcher  46  attached thereto, may be translated in the vertical direction with a vertical axis positioner  50  as shown. The extractor catcher  46  is translated in the vertical direction in order to engage the extractor catcher  46  with the fastener storage tube  28  for removal of the requested fastener as described in further detail below. Moreover, the vertical axis positioner  50  may be pneumatically controlled and is therefore activated by the pneumatic source  22 . 
         [0023]    In operation, the control system  16  activates the linear X-Y positioner  48  to position the unloading mechanism  12  adjacent the fastener storage device  14 , and more specifically, to position an extractor catcher  46  adjacent the appropriate fastener storage tube  28 . Once the proper extractor catcher  46  is positioned adjacent the appropriate fastener storage tube  28 , the vertical axis positioner  50  moves the extractor tool  44  in the vertical direction until the extractor catcher  46  abuts the seal  30 . 
         [0024]    Referring to  FIGS. 3 and 4 , once the extractor catcher  46  is positioned against the seal  30  of the appropriate fastener storage tube  28 , the pneumatic source  22  (not shown) then activates the vacuum generators  26 , and as a result, one or more of the fasteners  52  within the fastener storage tube  28  move up against the extractor catcher  46 . Once the head of a top fastener  52  abuts the extractor catcher  46  as shown, a seal may be created at the interface between the top fastener  52  and the extractor catcher  46 , thereby causing the remaining fasteners  52  to drop back into the fastener storage tube  28 . As a result, the unloading mechanism  12  removes the top fastener  52  from the fastener storage device  14  without the need for a separate fastener escapement mechanism. 
         [0025]    As shown in  FIG. 4 , the fastener  52  abuts an upper surface  54  of the extractor catcher  46 , and may create a sealed (or at least partially sealed) connection therebetween. In operation, the at least partially sealed connection causes the remaining fasteners to drop back into the fastener storage tube. As further shown, the extractor catcher  46  also comprises a tapered inner surface  56  to further facilitate ease of removal of the fastener  52  from the fastener storage device  14 . The upper surface  54  of the extractor catcher  46  may be modified to accommodate various types of fastener heads. A channel  58  opens into the upper surface  54  of the extractor catcher  46  and is in fluid communication with the vacuum ports of the vacuum generators  26 . 
         [0026]    In some applications and conditions, the fastener  52  may tend to adhere to the surface  54 . Adhesion may be caused, for example, by contaminants such as oil or dust within the extractor catcher  46 . Adhesion may also result from coatings applied to a fastener  52 , such as a cetyl alcohol coating applied to prevent galvanic corrosion at interfaces between dissimilar metals. Where adhesion occurs, gravity may be insufficient to dislodge the fastener  52  from the extractor catcher  46 . 
         [0027]    As further shown in  FIG. 3 , the extractor tool  44  may include a backflow port  60  fluidly coupled to the upper surface  54  of the extractor catcher  46 . The blackflow port  60  may be coupled to a source of pressurized gas. For example, in one particular embodiment, one of the flexible tubes  24  may connect the backflow port  60  to the pneumatic source  22 . When a fastener lodges in the extractor catcher  46 , pressurized air may be released through the backflow port  60  to remove the fastener. In some embodiments, pressurized air is automatically and systematically released to ensure release of each fastener  52  each time the vacuum is released to release the fastener  52  from the extractor catcher  46 . Alternately, in other embodiments, pressurized air is released through the backflow port  60  only in instances where the fastener  52  fails to fall from the extractor catcher  46 . In either case, the control system  16  typically regulates the release of air through the backflow port  60 . 
         [0028]    In the illustrated embodiment, the backflow port  60  is formed in a fitting  62  ( FIG. 3 ) which secures the two vacuum generators  26  to one another. Forming the port  60  in the fitting  62  eliminates the need for separate parts for the port  60  and for securing the vacuum generators  26  to one another thereby making the extractor tool  44  more compact. The backflow port  60  may be embodied as an aperture  64  formed in the fitting  62  and a nozzle  66 , or other such fitting, secured thereto for connecting to the pneumatic source  22 . In one embodiment, the aperture  64  slopes downwardly through the fitting  62 , as shown in  FIG. 3 . 
         [0029]    Various arrangements of the vacuum generators  26  and fitting  62  are possible. For example, a single vacuum generator  26  may be used. The fitting  62  having the port  60  formed therein may be disposed above or below the vacuum generator  26  (or generators  26 ). The vacuum generators  26  and fitting  62  may form a continuous channel opening into the upper surface  54  of the extractor catcher  46 . Alternatively, the backflow port  60  may include a separate channel independently connected to the upper surface  54 . 
         [0030]    In some embodiments, each extractor tool  44  includes a backflow port  60 . In others, such as the illustrated embodiment, extractor tools  44  both with and without backflow ports  60  are used. Such embodiments may be practical where multiple types of fasteners are being handled but not all tend to adhere to the extractor catcher  46 . 
         [0031]      FIG. 5  illustrates a method for using a fastener delivery system  10  in accordance with an embodiment of the invention. At block  80 , the control system  16  receives a request for a specific fastener configuration and identifies, through the execution of control software within a computing device (not shown), which fastener storage tube  28  within the fastener storage device  14  contains the proper fastener. At block  82 , the control system activates the linear X-Y positioner  48  to position the unloading mechanism  12  in the proper X-Y position adjacent the fastener storage device  14 , and more specifically, to position the extractor catcher  92  adjacent the appropriate fastener storage tube  28 . 
         [0032]    Once the extractor tool  44  is properly positioned, block  84  includes activating the pneumatic source  22  to cause the vertical axis positioner  50  to force the extractor catcher  46  down against the seal  30  disposed around the fastener delivery tube  28 . When the extractor catcher  46 , or other sealing structure such as the shroud  94  disclosed in U.S. Pat. No. 6,688,489, abuts the seal  30 , block  86  is executed, activating the vacuum generator  26  to cause at least one of the fasteners within the fastener storage tube  28  to move upward against the extractor catcher  46 . When the top fastener abuts the upper surface  54  of the extractor catcher  46 , a seal is at least partially formed therebetween and the remaining fasteners (if any) fall back down into the fastener storage tube  28 . 
         [0033]    In block  88 , the control system  16  positions the unloading mechanism  12  over the delivery conduit  18 . Block  88  may therefore include activating the vertical axis positioner  50  to move the extractor tool  44  up and away from the fastener storage device  14  and activating the linear X-Y positioner  48  to position the unloading mechanism  12  in the appropriate X-Y position adjacent the delivery conduit  18 . More specifically, the linear X-Y positioner  48  positions the extractor catcher  46  adjacent the appropriate chute  40  of the drop plate  38 . Block  90  may include causing the pneumatic source  22  to activate the vertical axis positioner  50  to force the extractor catcher  46  down against the drop plate  38 . The extractor catcher  46  and drop plate  38  may form an air tight seal at their contacting surfaces. Alternatively, Block  90  may be omitted and the fastener dropped upon deactivation of the vacuum generator  26  at block  92 . 
         [0034]    At block  92 , the vacuum generator  26  is deactivated and the fastener is allowed to drop into the first fastener delivery tube  34 . Accordingly, the fastener is transported through the first fastener delivery tube  34  by gravity. At block  94 , the control system  16  evaluates whether the fastener has fallen from the extractor catcher  45 . In one embodiment, this occurs as the fastener is transported through the first fastener delivery tube  34  by gravity and past the proximity sensor  42  into the second fastener delivery tube  36 . If the fastener is sensed, then the method proceeds to block  96 . In other embodiments, block  94  may include evaluating the output of a sensor capable of sensing the fastener positioned on the drop plate  38 , within the extractor catcher  46 , or at another point along the path of the fastener. At block  96 , the control system  16  activates the pneumatic source  22  to provide pressurized air through the second fastener delivery tube  36  to deliver the fastener to a work station. 
         [0035]    If the fastener is not sensed, then block  98  is executed. At block  98  the back flow port  60  is activated, permitting air to flow through the backflow port  60  for one or more short bursts (or continuously). Bursts approximately one second in length have been shown to be effective to dislodge some fasteners. The air flowing through the backflow port may have any pressure effective to dislodge the fastener. Shop air at 90 psi or reduced to pressures from 60 to 80 psi has been shown to be effective. After releasing a burst of air (or continuous flow of air) through the backflow port  60 , block  94  may be reexecuted to evaluate whether the fastener has dislodged from the extractor catcher  46 . Blocks  94  and  98  may be executed repeatedly until release of the fastener has been sensed at block  94  or a specific number of iterations have occurred. After the fastener is sensed at block  94 , the delivery conduit may be pressurized at block  96  to deliver the fastener to the work station. The method may then return to block  80  and be repeated, or the method may terminate. 
         [0036]    In some embodiments, a block  100  may be executed before block  94 . Block  100  may include waiting for a period of time before evaluating whether the fastener has been released from the extractor catcher  46 . The amount of time may approximate the expected amount of time for a fastener to fall through the first fastener delivery tube  34  from the extractor catcher  46  to a point near the proximity sensor  50 . 
         [0037]    Various alternative embodiments of the method of  FIG. 5  are possible. In some embodiments, for example, the step of releasing air through the backflow port  60  at block  98  may be executed for each iteration of the method, rather than only in instances where a fastener fails to fall due to gravitational forces. In other embodiments, blocks  96  and  98  may be combined. In such embodiments, pressurized air released from the backflow port  60  may serve both to dislodge fasteners from the upper surface  52  and to force the fastener along the first fastener delivery tube  34 , the second fastener delivery tube  36 , or both. 
         [0038]    Embodiments of the present invention may provide significant advantages over the prior art. For example, by sensing the passing of a fastener into the second fastener delivery tube, embodiments of the invention ensure that those fasteners which adhere within the extractor catcher are promptly detected so that appropriate action may be taken. Further, embodiments of the invention provide a backflow port which allow a fast, efficient, and cost effective means of dislodging fasteners which adhere within the extractor catcher. Thus, embodiments of the invention advantageously enable consistent release of fasteners and other components from a suction head of an automated fastener delivery system, thereby improving the efficiency and reducing costs of the manufacturing operation. 
         [0039]    While preferred and alternate embodiments of the invention have been illustrated and described, as noted above, many changes can be made without departing from the spirit and scope of the invention. Accordingly, the scope of the invention is not limited by the disclosure of these preferred and alternate embodiments. Instead, the invention should be determined entirely by reference to the claims that follow.