Abstract:
A system for electrostatically cleaning surfaces includes an electrostatically chargeable brush, having conductive polymer bristles, moveably disposed adjacent to a solid surface to be cleaned. The system also includes an actuator, configured to linearly move a solid element toward and through sliding contact along the solid surface, the brush being positioned to contact at least one of the solid surface and the solid element prior to the sliding contact, to electrostatically remove dust and the like therefrom.

Description:
FIELD OF THE DISCLOSURE 
     The present disclosure relates generally to devices for electrostatically cleaning surfaces. More particularly, the present disclosure relates to a device and method for electrostatically cleaning surfaces, such as those of a releasable pin lock actuation mechanism. 
     BACKGROUND 
     There are a variety of industries and activities in which the careful and controlled mitigation or removal of dust can be very desirable. For example, in the operation of machines or in manufacturing, such as automotive or aircraft manufacturing, the regular or controlled removal of dust from surfaces can be important for the proper fabrication or operation of a part or a machine. As another example, industries that handle or process powders or powdered materials, such as food, minerals or chemicals, often have a need to remove dust from surfaces. Careful, and thorough dust removal and control can be especially important where dust or powdered materials may be hazardous or detrimental to the lifetime of machinery. 
     Existing devices and methods for dust removal from surfaces present a variety of challenges. For example, chemical or water wipes are often used for dust removal, but these are typically disposable, one-time use items that generate waste, and can have other negative aspects. Brushes are often used for dust removal, but present the potential for redeposition of electrostatically charged dust particles onto the surface, or the charging of uncharged particles by the brush through tribologic charging rendering the brush ineffective. Additionally, dust removal brushes that are known generally cannot change the electrostatic state of the particles that are being brushed. 
     The present application relates to one or more of the above issues. 
     SUMMARY 
     It has been recognized that it would be desirable to have a device and method for electrostatically cleaning surfaces that does not produce significant waste or leave chemical residues. 
     It has also been recognized that it would be desirable to have a device and method for electrostatically cleaning surfaces that is resistant to redeposition of electrostatically charged dust particles onto a surface, or the charging of uncharged particles by a brush through tribologic charging. 
     It has also been recognized that it would be desirable to have a device and method for electrostatically cleaning surfaces, the device being self-cleaning. 
     In accordance with one embodiment thereof, the present application discloses a system for electrostatically cleaning surfaces. The system includes an electrostatically chargeable brush, having conductive polymer bristles, moveably disposed adjacent to a solid surface to be cleaned. The system also includes an actuator, configured to linearly move a solid element toward and through sliding contact along the solid surface, the brush being positioned to contact at least one of the solid surface and the solid element prior to the sliding contact, to electrostatically remove dust and the like therefrom. 
     In accordance with another embodiment thereof, the present application provides a releasable pin lock mechanism, including at least two adjacent receiving lugs, associated with independently moveable structures, each receiving lug having a receiving lug hole of a common size, the receiving lug holes being aligned along an axis, and a moveable locking pin, aligned along the axis, and having a size substantially equal to the size of the receiving lug holes. The mechanism also includes a pin actuator, configured to selectively axially insert the locking pin into the receiving lug holes and remove the pin therefrom, and an electrostatically chargeable brush, associated with at least one of the locking pin and the receiving lug hole, configured to electrostatically attract dust and the like from at least one of the locking pin and the receiving lug holes. 
     In accordance with yet another embodiment thereof, the present application provides an aircraft having a folding wing, including an inboard fixed wing portion, and a folding outboard wing tip portion, hingedly connected to the inboard fixed wing portion and moveable between a lowered, locked position, and a raised, unlocked position. The aircraft further includes a releasable pin lock mechanism, configured to fix the outboard wing tip portion in the locked position, including a moveable locking pin and a receiving lug hole, and an electrostatically chargeable brush, associated with the pin lock mechanism. The electrostatically chargeable brush is configured to electrostatically attract dust and the like from at least one of the locking pin and the receiving lug hole. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a commercial aircraft having folding wing tips. 
         FIG. 2  is an upper perspective view of internal wing structure associated with an embodiment of an internal wing tip locking mechanism for a folding wing tip, showing the wing tip pivoting axis and the pin locking axis. 
         FIG. 3  is a close-up perspective view of a portion of  FIG. 2 , showing the pin locks and pin actuators of the wing tip locking mechanism. 
         FIG. 4  is a free body diagram of a folding wing tip locking mechanism like that of  FIGS. 2 and 3 , showing the relationship of the wing pivoting axis and the pin locking lug holes. 
         FIG. 5  is a lower perspective view of internal wing structure associated with just the folding wing tip portion of another embodiment of a wing tip locking mechanism. 
         FIG. 6  is a free body diagram of a folding wing tip locking mechanism like that of  FIG. 5 , showing the relationship of the wing pivoting axis and the pin locking lug holes. 
         FIGS. 7A and 7B  are side and top view free body diagrams, respectively, of a generic pin locking mechanism with the pin locking lug holes aligned. 
         FIG. 8A  is a schematic diagram of an embodiment of an electrostatic cleaning system associated with a pin lock mechanism, the pin having an elongate electrically chargeable brush attached at its distal end. 
         FIG. 8B  is a schematic diagram of an embodiment of an electrostatic cleaning system associated with a pin lock mechanism, with an annular electrically chargeable brush disposed adjacent to the pin hole opening. 
         FIG. 8C  is a schematic diagram of an embodiment of an electrostatic cleaning system associated with a pin lock mechanism, with both an elongate electrically chargeable brush attached to the distal end of the pin and an annular electrically chargeable brush disposed adjacent to the pin hole opening. 
         FIG. 8D  is a schematic diagram of an embodiment of an electrostatic cleaning system associated with a pin lock mechanism, the pin having an electrostatic brush attached at its distal end that is grounded for continuous discharge and can be mechanically cleaned by maintenance personnel. 
         FIG. 8E  is a schematic diagram of an embodiment of an electrostatic cleaning system associated with a pin lock mechanism, with an elongate electrostatic brush attached to the distal end of the pin and an annular electrostatic brush disposed adjacent to the pin hole opening, both of which are grounded for continuous discharge and can be mechanically cleaned by maintenance personnel. 
         FIG. 8F  is a schematic diagram of another embodiment of an electrostatic cleaning system associated with a pin lock mechanism, in which both an elongate electrostatic brush attached to the distal end of the pin and an annular electrostatic brush disposed adjacent to the pin hole opening are grounded for continuous discharge and also include a switch that can electrically connect the brushes to an electrical connection that can be used for electrostatic cleaning of the brushes by maintenance personnel. 
         FIG. 9  is a flow diagram of an aircraft production and service methodology. 
         FIG. 10  is a block diagram of an aircraft. 
     
    
    
     While the disclosure is susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and will be described in detail herein. However, it should be understood that the disclosure is not intended to be limited to the particular forms disclosed. Rather, the intention is to cover all modifications, equivalents and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION 
     Disclosed herein is a system and method for electrostatically cleaning surfaces that overcomes some of the challenges of prior dust removal devices and methods. The system and method disclosed herein is shown and described in the context of cleaning the interior surface of a releasable pin lock mechanism for a folding aircraft wing, but it is not limited to this application. Shown in  FIG. 1  is a perspective view of a wide body aircraft  100 , which includes a fuselage  102 , a main wing  104  attached to the fuselage  102 , and a tail structure  106  that includes a vertical stabilizer  108  and a horizontal stabilizer or elevator  110 . The main wing can include ailerons  112  and wing flaps  114  along its trailing edge  116 , and the leading edge  118  of the wing  104  can include moveable slats  120  for increasing lift during takeoff. The aircraft  100  also includes turbofan jet engines  122 , in this case mounted to the main wings  104 , for providing thrust for flight. 
     Unlike most conventional commercial aircraft, the aircraft  100  includes folding wing tips  124 , which have a lowered position for use during flight, indicated in dashed lines at  126 , and a raised position, shown at  128 . Folding wings are common in naval aircraft that are designed to operate within the constraints of limited hangar and deck space of aircraft carriers, but have not been widely used for commercial aircraft. In recent years, however, there has been a desire to accommodate larger commercial aircraft using airport facilities, such as aircraft terminals, gates, etc., that were originally designed for smaller aircraft. Advantageously, the raised position of the wing tips  124  of the aircraft  100  can be used when the aircraft is on the ground, such as during taxiing and when at an aircraft gate, allowing larger aircraft with a greater wingspan to use facilities that were designed for aircraft with a smaller wingspan. Wider use of large aircraft without modifying aircraft gates, terminals, and other related facilities is believed to be desired by commercial aircraft operators. 
     There are a variety of wing folding and locking mechanisms that have been used for folding wing aircraft. Shown in  FIG. 2  is an upper perspective view of a portion of the internal wing structure associated with one embodiment of a folding wing tip pivoting and locking mechanism  200  that can be used in a commercial aircraft, showing the wing tip portion  202  in the down and locked position. For reference, the fore, aft and inboard, outboard directions related to this view are shown at  204 . The wing includes a fixed inboard wing portion  206  and a folding outboard wing tip portion  202  attached via a hinge  208  having a pivoting axis  210 . It is to be appreciated that the pivoting axis  210  of the hinge  208  lies at an angle relative to the structure of the wing because of the swept angle of the wing. The pivoting axis  210  at this angle allows the wing tip portion  202  to fold upward along an axis  210  that is generally parallel to the fore-aft axis of the aircraft shown at  204 , and illustrated in  FIG. 1 . 
     The fixed inboard wing portion  206  includes main wing spars  212  that run lengthwise through the wing, and generally transverse ribs  214  that interconnect the spars fore to aft in the wing structure and help provide the airfoil shape of the wing cross-section. The folding outboard wing tip portion  202  also includes wing tip spars  216  that run lengthwise through the folding wing tip portion  202 , with generally transverse ribs  218  that interconnect the wing tip spars  216  fore to aft in the wing tip structure  202 . A group of main spar extension lugs  220  extend in an outboard direction from the main wing spars  212  to the hinge connection  208 . Each main spar extension lug  220  also includes an opposingly paired fixed lug portion  222  that is parallel to the main spar extension lug  220 , but does not extend to the hinge connection  208 . Similarly a group of wing tip spar extension lugs  224  extend in an inboard direction from the wing tip spars  216  through the hinge connection  208  and to a position adjacent to the main spar extension lugs  220  and their opposing fixed lug portions  222 . 
     In the configuration of  FIG. 2  the wing tip spar extension lugs  224  are interleaved between the main spar extension lugs  220  and their opposing fixed lug portions  222 . A close-up perspective view showing these and other features is provided in  FIG. 3 . The wing tip spar extension lugs  224 , the main spar extension lugs  220  and the opposing fixed lug portions  222  are all parallel to each other, and at a location inboard from the pivoting axis  210 . Each of these spar extension lugs  220 / 224  and opposing fixed lug portions  222  include a pin lock lug hole  226 , each of which can include an internal pin bushing  228 . A group of pin lock actuators  230  are each fixedly attached to either a main spar extension lug  220  or an opposing fixed lug portion  222  of the inboard fixed wing portion  206 , each pin lock actuator  230  including a linearly moveable locking pin  232 . When the wing tip  202  is in its lowered position, the pin lock lug holes  226  of each group of the interleaved wing tip spar extension lugs  224 , the main spar extension lugs  220  and the opposing fixed lug portions  222  are all aligned along pin locking axis  234 . In this position, each of the pin lock actuators  230  can extend the locking pin  232  through the aligned pin lock lug holes  226  so that the pin  232  is received in the lug holes  226  with a sliding fit, to securely lock the wing tip  202  in the lowered position. Advantageously, the configuration shown in  FIGS. 2 and 3  contains the wing tip locking mechanism entirely within the envelope of the wing airfoil shape. 
     When the locking pins  232  are retracted, the wing tip  202  can be raised. Shown in  FIG. 4  is a free body diagram of a folding wing tip locking mechanism  200  like that of  FIGS. 2 and 3 , with the wing tip portion  202  in the raised position. This shows the relationship of the wing pivoting axis  210  and the axis  234  of the pin locking lug holes  226 . In this position the pin lock lug holes  226  of the fixed wing portion  206  are not aligned with the pin lock lug holes  226  of the spar extension  224  of the wing tip portion  202 . It is to be appreciated that the present disclosure relates to the pin lock mechanism itself. Consequently, the mechanism for raising and lowering the wing tip portion  202  is not shown. 
     It is to be appreciated that a variety of other configurations of folding wing mechanisms can be used. Shown in  FIG. 5  is a lower perspective view of a portion of the internal structure of another embodiment of a wing tip portion  502  of a folding wing aircraft. This view is looking in an outboard direction at the underside of only the wing tip portion  502  at the hinge connection location, and does not show any of the associated fixed inboard wing portion. The top skin of the wing tip is indicated at  504 . Like the other configuration shown in  FIGS. 2 and 3 , in this embodiment the wing tip portion  502  includes longitudinal wing tip spars  516  and transverse ribs  518 . Extending inboard from the wing tip spars are a group of wing tip spar extensions  524 , which extend inboard to a hinge location  508 , with a group of common hinge pin lug holes  550  extending along a pivoting axis  510 . 
     Shown in  FIG. 6  is a free body diagram of a folding wing tip locking mechanism  500  configured for a folding wing tip  502  like that of  FIG. 5 , showing the relationship of the wing pivoting axis  510  and the pin locking lug holes  526  with the wing tip portion  502  in the folded or raised position. Viewing  FIGS. 5 and 6  together, extending downward from the wing tip spar extensions  524  at the hinge location are a group of pin locking extension lugs  525 . These pin-locking extension lugs  525  each include a pin lock lug hole  526 , and are configured for interleaving with main wing pin locking extensions  520  that are attached to the main wing spars (not shown). The pin lock lug holes  526  align along a pin lock axis  534 , so as to allow a group of pin locking mechanisms  530  (like those shown in  FIGS. 2 and 3 ) to be used with the configuration of  FIGS. 5 and 6 . As shown in  FIG. 6 , the pin locking mechanism  530  is disposed below the hinge axis  510  of the folding wing portion  502 , so that the pin locking mechanism  530  (and possibly other structure associated with raising and lowering the wing tip) can be disposed within a pod  552  that extends below the wing. 
     Shown in  FIGS. 7A and 7B  are side and top view free body diagrams, respectively, of a pin locking mechanism  700  with the pin locking lug holes  726  aligned. In these views the inboard fixed wing portion  706  and the outboard folding wing tip portion  702  are shown as generic fixed structures to which the extension lugs  720 / 724  and hinge and pin actuators  730  are attached. The parallel and interleaved relationship of the wing tip lug extensions  724  and the man spar lug extensions  720  is clearly shown in the top view of  FIG. 7B . When the wing tip  702  rotates about the pivoting axis  710  until the lug holes  726  align, the wing tip  702  can be locked into place at each pin lock location via the associated pin locking actuator  730  extending the associated pin (not shown) into the lug holes  726  in a sliding fit. When the locking pins  732  are retracted out of the lug holes  726 , the wing tip  702  can be raised. The raised position of the wing tip  702  and lowered position of wing tip spar extension  724  are shown in dashed lines at  702   a  and  724   a.    
     Referring again to  FIGS. 2 and 3 , the clearance between the locking pins  232  and the pin bushings  228  within the lug holes  226  is tightly controlled, so that the pin within the bushing is very secure. At the same time, the wing tip locking mechanism  200  is designed to be locked and unlocked repeatedly during the life of an aircraft (e.g. before and after every touchdown), and dust accumulation within the pin bushing when the aircraft is on the ground and the wingtips are raised, is a concern. During actuation of the wingtips to the raised position, it is desirable that the pin  232  slide freely in the bushing, and be unimpeded. This freedom of movement can be compromised due to dust accumulation. In one embodiment of this sort of folding wing pin locking mechanism, the pin moves through actuation within about 14 seconds, sliding into the corresponding lug holes  226  with the pin moving at a rate of approximately 1″ per second. Hence, it is desirable that hole  226  be clear of dust and debris for the pin to be inserted with minimum force. It is thus desirable to reduce dust and debris that might accumulate on the pins  232  or within the lug holes  226  in order for the pin locking mechanisms  200  to be actuated and to provide a secure wing tip lock and to operate reliably for a long period of time. As noted previously, some systems and methods for the removal of dust from aircraft surfaces present a variety of potentially undesirable characteristics for airplane operation, such as the generation of waste, application of chemicals, redeposition of electrostatically charged dust particles or the charging of uncharged particles and accessibility of the surface to be cleaned. 
     More generally, electrostatically charged particles will cling to surfaces that have an insufficient electrical conductivity to reduce the electrostatic attraction of the particles. Examples of electrostatic particle/surface interaction can be seen on car dashboards (e.g. a plastic surface) with inorganic and organic particulates. Simple mechanical removal (e.g. brushing/wiping) of particles from the surfaces can be inhibited by the electrical attraction of the particles to the surface. Indeed, brushing may enhance the attraction of the surface to the particles through triboelectric charging, leading to increased surface-to-particle attraction. 
     Advantageously, as described herein, a system and method for electrostatically cleaning surfaces has been developed that overcomes some of the challenges of prior dust removal devices and methods. While the system and method disclosed herein is shown and described in the context of a releasable pin lock mechanism for a folding aircraft wing, it is believed that this system and method can be used in a variety of applications and industries, such as automotive and aircraft manufacturing, the processing and handling of mineral, food or chemical powder materials, and in the handling of radioactive materials, for example. Any product or operation where the careful and controlled removal of dust is desirable, particularly where dust is to be removed repeatedly or periodically, can potentially benefit from this system and method. More specifically, in applications that are similar to those shown herein, it can be used with a variety of pin locking mechanisms, such as for bank vaults, and the cleaning of elongated pipes and barrels. 
     Shown in  FIGS. 8A-8F  are several different embodiments of a pin locking mechanism  800  having an electrostatic cleaning system in accordance with the present disclosure. Identical or similar elements in  FIGS. 8A-8F  are given identical or similar reference numerals, for ease of reference. It is to be understood that size, shape, spacing, etc. of the various components in  FIGS. 8A-8F  are not intended to necessarily represent the actual appearance of this sort of device, but are shown in a manner that helps to clearly illustrate the general parts of the system and their operation. 
     Shown in  FIG. 8A  is a schematic diagram of one embodiment of an electrostatic cleaning system  850   a  associated with a releasable pin lock mechanism  800 . Three lug extensions  820 / 822 ,  824  are shown with aligned lug holes  826 . Pin bushings  828  are disposed within these lug holes  826 . The pin bushings are typically of a material such as hardened steel. Two of these lug extensions  820 / 822  can be considered as being affixed to one structure (e.g. the inboard fixed wing portion of an aircraft), while the third lug extension  824  can be considered as being attached to a moveable structure (e.g. a folding wing tip). 
     A locking pin  832  is shown attached to a pin actuator  830 , which is configured to extend the pin along a pin lock axis  834  into the aligned lug holes  826  or retract it from them. The pin  832  is typically of high strength steel, such as 17-4 or 15-5. In the embodiment of  FIG. 8A , the pin  832  includes an elongate electrically chargeable brush  852  attached at the distal end  854  of the pin  832 . This brush  852  has a form that is similar in configuration to a bottle brush, with a cylindrical array of electrostatically conductive bristles  856  with an outer diameter that is slightly larger than the inner diameter of the lug holes  826 . The brush  852  is flexible and fatigue resistant, with bristles  856  that can flex in both directions and be connected to the ‘charged’ surface during movement of the brush. The bristles have a conductivity that does not cause the voltage source to be directly applied to the structure that is being cleaned. 
     Those of skill in the art will appreciate that the use of standard metal or polymeric brushes for dust removal can lead to redeposition of the charged particles or the charging of uncharged particles by the brush (tribologic charging). Typical brushes also cannot change the electrostatic state of the particles that are being brushed. In the system disclosed herein, these issues are addressed. Advantageously, the bristles  856  of the elongate brush  852  are of a material that can conduct limited amounts of electricity and transmit an accumulated electrical charge, i.e. a leaky capacitive circuit is established. It is desirable that the electrical conductivity of the brush  852  and bristles  856  be sufficient to allow for charge decay (to a neutral state of charge) in less than about 1 second. It is also desirable that the brush  852  not induce a secondary state of charge (tribologic) on the brushed surface, and that the bristles  856  will not accumulate excessive particles (leading to capacitive insulation) due to attraction from charging of particles or of the brush  852 . Examples of suitable materials for the bristles  856  include polymeric filaments of having a conductivity in the range of 10×10 5  to 10×10 7  ohm-m are considered suitable. Specific examples of materials that fall into this category include PEEK, Nylon 6-10 and Nylon 6-12. The bristle filaments can have up to 30% carbon black content as a conductive filler. The electrical conductivity of the bristles  856  enables the brush  852  to attract electrostatically charged particles from the pin bushings  828  as the pin  832  is extended into or retracted from the lug holes  826 . 
     The locking pin  832  and the shaft  858  of the brush  852  are electrically conductive (e.g. of metal) and are electrically attached to one pole of a first reversible voltage source  860   a . The other pole of the voltage source is grounded. For an aircraft folding wing tip locking mechanism, this voltage source can be associated with the aircraft electrical system, or it can be a separate system, if desired. With the polarity of the first voltage source  860   a  in one configuration, dust particles will adhere to the bristles  856  of the brush  852  as it moves through the pin bushings  828  in the lug holes  826 . After passage of the brush  852  through the pin bushings  828 , the first voltage source  860   a  can be reversed in polarity, and thus the brush  852  can be charged or discharged with application of electricity. The change in polarity can lead to the electrostatic attraction or repulsion of charged particles at will. Thus, repulsion of the attracted particles (those that stick to the bristles  856 ) can be facilitated by changing the polarity of the bristles  856  leading to selective repulsion of dust particles  862  onto a collection device  864 , or generally discharged to the environment outside of the bushing. Multiple collection devices  864  can be provided, such that the brush  852  can be cleaned after each extension and retraction of the pin  832  and the brush  852  through the lug holes  826 . To accomplish this, the polarity of the first voltage source  860   a  is reversed, such as via an automatic controller  866 , so that the brush  852  then repels the accumulated dust particles  862  away from the lug or onto a collection device. In this way, the electrostatic brush  852  can be self-cleaning. 
     The principles of operation of the electrostatic cleaning system shown in  FIG. 8A  can be applied in a variety of configurations. Shown in  FIG. 8B  is a schematic diagram of another embodiment of an electrostatic cleaning system  850   b  associated with a pin lock mechanism  800  in accordance with the present disclosure. As with the embodiment of  FIG. 8A , three lug extensions  820 / 822 ,  824  are shown with aligned lug holes  826 . Pin bushings  828  are disposed within these lug holes  826 . Two of these lug extensions  820 / 822  can be considered as being affixed to one structure (e.g. the inboard fixed wing portion of an aircraft), while the third lug extension  824  can be considered as being attached to a moveable structure (e.g. a folding wing tip). A locking pin  832  is shown attached to a pin actuator  830 , which is configured to extend the pin along the pin lock axis  834  into the aligned lug holes  826  or retract it from them. 
     Unlike the embodiment of  FIG. 8A , in the embodiment of  FIG. 8B  a circular or annular electrically chargeable brush  870  is disposed adjacent to and axially aligned with the lug holes  826 . This brush  870  has a circular or annular shape, with an annular array of electrostatically conductive bristles  872  that extend toward the center  874  of the circle, the inner diameter of the array of bristles  872  being slightly smaller in diameter than the locking pin  832  and the lug holes  826 . 
     The bristles  872  of the annular brush  870  can have the same physical and electrical properties as described with respect to the brush of  FIG. 8A . The flexible bristles will flexibly press against and stay in contact with the outer surface of the pin  832  as it passes through the central opening of the annular brush  870  during extension or retraction of the pin  832 . The bristles  872  are of a material as described above, which can conduct limited amounts of electricity and discharge accumulated electrical charge. The electrical conductivity of the brush  870  enables the brush  870  to attract electrostatically charged particles from the pin  832  as it is extended into or retracted from the lug holes  826 , and will allow for charge decay (to neutral state of charge) in less than about 1 second, without inducing a secondary state of charge (tribologic) on the brushed surface, or accumulating particles due to attraction from charging of particles or of the brush  870 . 
     The annular brush  870  is electrically attached to one pole of a second reversible voltage source  860   b . The other pole is grounded and also attached to one of the extension lugs  820 / 822 . With the polarity of the second voltage source  860   b  in one configuration, dust particles will adhere to the bristles  872  of the annular brush  870  as the pin  832  moves through the annular brush  870  during extension into or retraction from the lug holes  826 . Since the second voltage source  860   b  is reversible in polarity, a change in polarity can lead to the electrostatic attraction or repulsion of charged particles at will. Thus, after passage of the pin  832  through the annular brush  870 , repulsion of the attracted particles can be accomplished by changing the polarity of the annular brush  870 , leading to selective repulsion of the particles  862  into a collection device  864 , in the manner discussed above. After each extension or refraction of the pin  832  through the annular brush  870 , the polarity of the second voltage source  860   b  can be reversed (e.g. via an automatic controller) so that the brush  870  then repels the attracted dust particles  862 . In this way, the annular brush  870  can be self-cleaning. 
     Shown in  FIG. 8C  is a schematic diagram of another embodiment of an electrostatic cleaning system  850   c  associated with a pin lock mechanism  800  that combines all of the features of  FIGS. 8A and 8B . That is, this embodiment includes both an elongate electrically chargeable brush  852  attached to the distal end  854  of the locking pin  832  and an annular electrically chargeable brush  870  disposed adjacent to the lug holes  826 . The locking pin  832  and the annular brush  870  are both electrically connected to switchable voltage sources  860   a, b , as described above, so that the locking pin  832  is electrostatically cleaned of dust as it passes through the annular brush  870 , and the pin bushings  828  are electrostatically cleaned of dust as the elongate brush  852  passes through them during extension or retraction of the locking pin  832 . Following each extension and/or retraction of the pin  832 , the polarity of the voltage applied to each brush  852 ,  870  can be reversed, allowing each brush to release its accumulated particulate load, releasing its retained dust  862  away from the area that was brushed. 
     While the embodiments of  FIGS. 8A-8C  are self-cleaning, an electrostatic cleaning system in accordance with the present disclosure can be configured in various other ways. Shown in  FIG. 8D  is a schematic diagram of a pin lock mechanism  800  having an electrostatic cleaning system  850   d  in which the electrostatic brush  852  is grounded for continuous discharge. This embodiment is similar to  FIG. 8A . Three lug extensions  820 / 822 ,  824  have aligned lug holes  826 , with pin bushings  828  disposed within these lug holes  826 . A locking pin  832  is attached to a pin actuator  830 , which is configured to extend the pin along the pin lock axis  834  into the aligned lug holes  826  or retract it from them. 
     The pin  832  includes an elongate bottle brush-type electrostatically chargeable brush  852  attached at its distal end  854 . The elongate brush  852  has a cylindrical array of electrostatically conductive bristles  856  with an outer diameter that is slightly larger than the inner diameter of the lug holes  826 . The bristles  856  of the brush  852  are flexible and fatigue resistant, and can flex in both directions so as to stay in contact with the inner surface of the pin bushing  828  during movement of the brush  852  through the bushing. The bristles  856  have electrical characteristics like those discussed above, which enables the brush  852  to attract electrostatically charged particles from the pin bushings  828  as the pin  832  is extended into or retracted from the lug holes  826 . 
     Unlike the embodiment of  FIG. 8A , in the embodiment of  FIG. 8D  the locking pin  832  (and hence the electrically conductive shaft  858  of the brush  852 ) are not connected to a voltage source, but are electrically grounded, as indicated at  876 . Grounding is achieved by a circuit formed between the pin and aircraft structure. Since the bristles  856  of the brush  852  are of an electrostatically different material than the pin bushings  828  and are electrically grounded, friction between the bristles  856  of the brush  852  and the surface of the pin bushings  828  will generate an electrostatic charge, which will naturally attract dust particles from the pin bushings  828  to the brush  852 . This will lead to the tribologic charging and accumulation of oppositely charged particulates to the brush surface. Dust particles (not shown in  FIG. 8C ) will adhere to the bristles  856  of the brush  852  through this electrostatic attraction as the brush  852  moves through the pin bushings  828  in the lug holes  826 . 
     Since the brush  852  is not attached to a voltage source, removal of dust particles from the brush  852  can be accomplished by a maintenance worker. In the context of a pin locking mechanism  800  for folding aircraft wings, whenever the aircraft is on the ground and the wing tips are raised, a worker can apply an electrically neutral or electrically charged wand  878  or other similar device to the brush  852 . Because of the different polarity between the brush  852  and the wand  878 , rubbing the wand  878  or other device against the brush will cause the accumulated dust particles to be attracted to the wand  878  by electrostatic attraction. In this way, the electrostatic brush  852  can be periodically mechanically cleaned by maintenance personnel. Other cleaning methods, such as mechanical vibration of the brush  852 , can also be used alone or together with an electrostatic device. 
     Shown in  FIG. 8E  is a schematic diagram of a pin lock mechanism having an electrostatic cleaning system that includes both an elongate electrically grounded electrostatic brush  852  attached to the distal end  854  of the locking pin  832  and an annular electrically grounded electrostatic brush  870  disposed adjacent to the lug holes  826 . Three lug extensions  820 / 822 ,  824  have aligned lug holes  826 , with pin bushings  828  disposed within these lug holes  826 . A locking pin  832  is attached to a pin actuator  830 , which is configured to extend the pin along the pin lock axis  834  into the aligned lug holes  826  or retract it from them. This embodiment is similar to that of  FIG. 8C , except that the locking pin  832  and the annular brush  870  are both electrically grounded for continuous discharge, so that the locking pin  832  is electrostatically cleaned of dust as it passes through the annular brush  870 , and the pin bushings  828  are electrostatically cleaned of dust as the elongate brush  852  passes through them. 
     The bristles of the brushes  852 ,  870  can have the same physical and electrical properties as described above. The electrical conductivity of the brushes enables them to attract electrostatically charged particles from the pin  832  and from within the pin bushings  828  as the pin is extended into or retracted from the lug holes  826 , and will allow for rapid charge decay, as discussed above, without inducing a secondary state of charge (tribologic) on the brushed surface, or accumulating particles due to attraction from charging of particles or brush. 
     As with the embodiment of  FIG. 8D , removal of dust particles from the elongate brush  852  and the annular brush  870  can be accomplished by a maintenance worker using a charged wand  878 , mechanical vibration, or other methods, as discussed above. In the context of a pin locking mechanism  800  for folding aircraft wings, this can be done whenever the aircraft is on the ground and the wing tips are raised. Other cleaning methods can also be used alone or together with an electrostatic device, such as mechanical vibration of the brushes. 
     It is to be understood that the various embodiments shown in  FIGS. 8A-8E  provide alternative arrangements for the brushes. Thus, for example, while the embodiment of  FIG. 8E  includes both an elongate cylindrical brush  852  attached to the locking pin  832  and an annular brush  870  for cleaning the locking pin  832 , the system shown in  FIG. 8E  could be configured with only the annular brush  870 , similar to  FIG. 8B , or both the elongate brush  852  and the annular brush  870  as shown. Indeed, those of skill in the art will recognize that many combinations of the elements of the embodiments shown herein can be used in various configurations and combinations, all of which are intended to be covered by this disclosure. 
     Finally, shown in  FIG. 8F  is a schematic diagram of another embodiment of an electrostatic cleaning system associated with a pin lock mechanism. This figure includes both an elongate electrostatic brush  852  attached to the distal end  854  of the pin  832  and an annular electrostatic brush  870  disposed adjacent to the lug holes  826 , both of the brushes being grounded, as shown at  876  and  880 , for continuous discharge in the manner discussed above. One of the lug extensions  820 / 822  is also electrically connected to the annular brush  870  and electrically grounded at  880 . 
     Additionally, each ground connection  876 ,  880  of the elongate brush  852  and of the annular brush  870  includes a switch  882 ,  886 , which can selectively allow the respective brushes to be electrically connected to an electrical connection socket or plug  884 ,  888 , which can be used for electrostatic cleaning of the brushes by maintenance personnel. That is, with the brushes  852 ,  870  continually grounded, these brushes can be cleaned by maintenance personnel using an electrically conductive wand ( 878  in  FIG. 8E ) or other electrostatic device in the manner discussed above. 
     Alternatively, however, a maintenance worker can temporarily attach an external voltage source (not shown) to one or both of the electrical connection sockets or plugs  884 ,  888 , and actuate the switches  882 ,  886 , allowing a forced change of polarity of the brushes  852 ,  870 , causing them to repel dust and debris that has been attracted, thus cleaning the brushes of accumulated particles. In the context of a pin lock mechanism  800  for an aircraft folding wing, this procedure can be followed when the aircraft is on the ground and the wing tips are raised. For an aircraft, this embodiment has the advantage that it does not involve onboard voltage sources ( 860   a ,  860   b  in  FIGS. 8A-8C ) or onboard dust collection devices ( 864  in  FIGS. 8A-8C ) that can add weight and cost to the aircraft. If desired, the switches  882 ,  886  can be directly coupled to the electrical connection sockets or plugs  884 ,  888 , so that the action of mechanically connecting the external voltage source automatically flips the switches  882 ,  886  to allow the polarity change. 
     The various embodiments of the system and method for electrostatically cleaning surfaces disclosed herein helps to solve the problem of adherent dust removal for devices and systems where this is desirable. It can be used for pin locking mechanisms, like the folding wing pin locking mechanism shown herein. It can also be used in other applications, such as sliding bank vault bolts or locking pins, and other mechanical devices. This system helps reduce some of the undesirable characteristics of some prior approaches. 
     Embodiments of the disclosure may be described in the context of an aircraft manufacturing and service method  900  as shown in  FIG. 9 , for an aircraft  902  as shown in  FIG. 10 . During pre-production, exemplary method  900  may include specification and design  904  of the aircraft  902  and material procurement  906 . During production, component and subassembly manufacturing  908  and system integration  910  of the aircraft  902  takes place. Thereafter, the aircraft  902  may go through certification and delivery  912  in order to be placed in service  914 . While in service by a customer, the aircraft  902  is scheduled for routine maintenance and service  916  (which may also include modification, reconfiguration, refurbishment, and so on). 
     Each of the processes of method  900  may be performed or carried out by a system integrator, a third party, and/or an operator (e.g., a customer). For the 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. 10 , an aerospace vehicle such as an aircraft  902  produced by exemplary method  900  may include an airframe  918  with a plurality of systems  920  and an interior  922 . Examples of high-level systems  920  include one or more of a propulsion system  924 , an electrical system  926 , a hydraulic system  928 , and an environmental system  930 . Any number of other systems may be included. Although an aircraft is given as an example of an aerospace application for the present disclosure, it is to be understood that this is only one example of an aerospace application. Additionally, while an aerospace example is shown, the principles of the disclosure may be applied to other industries, such as the automotive industry, for example. 
     Although various embodiments have been shown and described, the present disclosure is not so limited and will be understood to include all such modifications and variations are would be apparent to one skilled in the art.