Patent Publication Number: US-2012034026-A1

Title: Single-sided fitting

Description:
FIELD OF THE INVENTION 
     The present invention relates to a single-sided fitting. 
     BACKGROUND OF THE INVENTION 
     A bracket or other object can be fixed to a panel by a nut and a bolt, but this requires access to both the front and rear faces of the panel. 
     So-called “blind rivets” are known, which do not require access to the rear side of the panel. However, such blind rivets cannot be removed easily. 
     SUMMARY OF THE INVENTION 
     A first aspect of the invention provides a single-sided fitting comprising a shaft with two or more axially extending legs, each leg having a catch which extends radially outwardly from the leg; a clamping plate with two or more holes each receiving a respective one of the legs; a projection which is carried by the clamping plate and extends axially between the legs towards the catches, the clamping plate and projection being axially movable along the shaft to a locking position where the projection is positioned between the catches thus preventing the catches from moving radially inwardly; and means for preventing the clamping plate and projection from withdrawing back along the shaft away from the catches after they have been moved to the locking position. 
     A further aspect of the invention provides an assembly of parts comprising a structure with a hole passing from a front face of the structure to a rear face of the structure; and a single-sided fitting according to the first aspect of the invention arranged with the shaft passing through the hole, the clamping plate in its locking position applying a compressive force to the front face of the structure, the projection positioned between the catches thus preventing the catches from moving radially inwardly, and the catches applying a compressive force to the rear face of the structure. 
     The structure may comprise a panel, a pair of panels which are fastened together by the fitting, or any other structure. 
     A further aspect of the invention provides a method of attaching a single-sided fitting to a structure, the single-sided fitting comprising a shaft with two or more axially extending legs, each leg having a catch which extends radially outwardly from the leg; a clamping plate with two or more holes each receiving a respective one of the legs, and a projection which is carried by the clamping plate and extends axially between the legs towards the catches, the method comprising:
         passing the shaft and the catches through a hole from a front face of the structure to a rear face of the structure;   moving the catches radially outwardly so they cannot be withdrawn back through the hole;   moving the clamping plate and projection axially along the shaft to a locking position in which the clamping plate engages the front face of the structure and the projection is positioned between the catches, thus preventing the catches from moving radially inwardly;   applying a compressive force to the front face of the structure with the clamping plate;   applying a compressive force to the rear face of the structure with the catches; and   preventing the clamping plate and projection from withdrawing back along the shaft away from the catches after they have been moved to the locking position.       

     The single-sided fitting can be removed easily by reversing the procedure described above, that is by withdrawing the clamping plate and projection back along the shaft away from the catches; moving the catches radially inwardly; and withdrawing the shaft and the catches from the hole. 
     Compressing the structure between the clamping plate and the catches makes the fitting secure and unlikely to come loose due to vibration. This makes the single-sided fitting particularly well suited for use in a vehicle such as an aircraft which is prone to vibration. 
     The means for preventing the clamping plate and projection from moving back along the shaft may have a number of forms. For instance it may comprise an internally threaded nut which is carried by the shaft, the clamping plate being positioned between the nut and the catches, wherein the nut can be spun along the shaft to engage the clamping plate in its locking position. Alternatively the shaft may have a series of closely spaced resilient teeth which retract one by one as the clamping plate is moved along the shaft until it engages the structure, at which point the teeth prevent the clamping plate from withdrawing easily. Alternatively the shaft may have a series of closely spaced rigid teeth which are engaged by a resilient catch on the clamping plate, in the manner of a zip-tie. Alternatively, a coil spring or other resilient means may be used to urge the clamping plate towards its locking position in order to prevent it from withdrawing. 
     The single-sided fitting may be used as a fastener for fastening together a pair of panels, as a bracket for mounting a component to a panel or other structure, or for any other suitable purpose. 
     Typically the projection passes through the hole and beyond the rear face of the structure, although it may lie flush with the rear face. 
     The shaft may have two legs only, or it may have three or more legs. 
     The legs may be completely separate parts, but more preferably they are joined together at a head of the shaft remote from the catches. This provides a resilient force which causes the catches to spring radially outwardly after they have passed through the hole. 
     The catches may be at an intermediate position along the length of the legs, but more preferably they are at a distal end of the legs. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the invention will now be described with reference to the accompanying drawings, in which: 
         FIG. 1  is a plan view of a bracket; 
         FIG. 2  is a plan view of the bracket with the washer and nut removed; 
         FIG. 3  is a side view of the bracket with the washer and nut removed; 
         FIG. 4  is a rear view of the bracket with the washer and nut removed, viewed from the left of  FIG. 3 ; 
         FIG. 5  is a section taken along a line A-A in  FIG. 3 ; 
         FIG. 6  is a plan view of a washer; 
         FIG. 7  is a front view of the washer, viewed from the left of  FIG. 6 ; 
         FIG. 8  is a plan view of a nut; 
         FIG. 9  is a rear view of the nut, viewed from the left of  FIG. 8 ; 
         FIG. 10  is a plan view showing the bracket coupled to a panel with the washer in its locking position and the nut in its retracted position; and 
         FIG. 11  is a plan view showing the bracket fixed to the panel with both the nut and washer in their locking positions. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENT(S) 
     A single-sided bracket  1  shown in  FIG. 1  comprises a head  2 , and a shaft comprising two legs  4  which extend axially from the head  2  as shown most clearly in  FIG. 2 . Each leg has a catch  3  with a rear-directed face or lip  5  extending radially outwardly from a distal end  6  of the leg. The legs  4  are each formed with an external thread  7 . The thread  7  extends from the head  2  to a point  8  which is set back from the catches by an unthreaded gap  9 . The unthreaded gap  9  enables the catches to be relatively compact in a radial direction. 
     The shaft carries a washer shown in  FIGS. 6 and 7 . The washer comprises a clamping plate  20  with two holes  21  each receiving a respective one of the legs  4 . A projection or tab  22  is carried by the clamping plate  20  and extends axially between the legs  4  towards their distal ends  6 . The clamping plate  20  and projection  22  can be slid axially along the shaft from the retracted position shown in  FIG. 1  to a locking position shown in  FIG. 10 . 
     An internally threaded nut  30  shown in  FIGS. 8 and 9  is carried by the shaft and can be spun along the thread  7  from the retracted position shown in  FIGS. 1 and 10  to a locking position shown in  FIG. 11 . 
     The bracket is fixed to a panel  40  by the method shown in  FIGS. 10 and 11 . First the legs  4  are compressed together between finger and thumb so the catches  3  can pass through a hole from the front face  41  to the rear face  42  of the panel. When the catches have passed through the hole, the legs are released so that they spring back. As shown in  FIG. 5 , the legs  4  have curved outer faces  10  which lie on a cylinder which is concentric with the axis  11  of the shaft. Thus when the legs spring back, the faces  10  engage the cylindrical wall of the hole in the panel, or are at least concentric with the cylindrical wall of the hole. 
     Next the washer is slid axially along the shaft to a locking position where the rear face of the clamping plate  20  engages the front face  41  of the panel as shown in  FIG. 10 . Next the nut  30  is spun along the thread until it engages the front face of the clamping plate  20  as shown in  FIG. 11 , preventing the clamping plate and projection from withdrawing back along the shaft away from the catches  5 . 
     Finally, the nut  30  is tightened so that the clamping plate  20  applies a compressive force to the front face of the panel and the faces  5  of the catches apply a compressive force to the rear face  42  of the panel. Compressing the panel  40  between the clamping plate  20  and catches  5  makes the bracket secure and unlikely to come loose due to vibration. 
     When the projection  22  is in its locking position between the catches as shown in  FIGS. 10 and 11 , it prevents them from collapsing radially inwardly to release the catches  5  from the rear face  42  of the panel. In its locking position shown in FIG.  10 , the projection  22  passes through the hole and beyond the rear face  42  of the panel. However if the panel  40  is thicker then the projection  22  may lie flush with the rear face  42 . 
     The bracket can be removed by reversing the process described above. 
     Once the bracket is fixed in place as in  FIG. 11 , the head  2  can then be used to hold a cylindrical object such as an aircraft fuel sensor, cable bundle, etc. Although a ring-shaped head  2  is shown in this example, the head may have any required shape. Furthermore, the head  2  may be omitted entirely and the single-sided fitting used as a blind rivet for fastening together a pair of panels. 
     Optionally an anti-rotation feature (not shown) may be provided between the nut and the washer that prevents the nut from spinning backwards due to vibration. 
     Where the bracket is fitted within a fuel tank, then preferably the bracket is sealed to prevent fuel from passing through the hole in the panel. This may be achieved in a number of ways. For example a liquid sealing material may be applied to the unthreaded portion  9  of the shaft and the tab  22  before the bracket is fitted to the panel. After the bracket has been fitted, the liquid sealing material cures to provide a fuel-tight seal with the hole in the panel. The fact that the tab  22  substantially fills the gap between the two legs  4  makes it relatively easy to form a seal in this manner. 
     Although the invention has been described above with reference to one or more preferred embodiments, it will be appreciated that various changes or modifications may be made without departing from the scope of the invention as defined in the appended claims.