Abstract:
A blind fastener adapter for a conventional screw-threaded nut and screw comprises a collar and a segmented ring over the collar, the ring and collar having a tapered interface wherein relative axial movement results in a change of diameter of the ring. The adapter further includes a spring adapted to bias the collar and ring into mutual engagement; the collar and ring include means to prevent substantial relative angular movement thereof. The collar is adapted for engagement by a blind side head of the screw in use, and the ring is adapted for blind side engagement of the perimeter of a hole.

Description:
FIELD OF THE DISCLOSURE 
       [0001]    This disclosure relates to a blind fastener and particularly to a blind fastener adapter for a conventional screw-threaded nut and screw. 
       BACKGROUND OF THE DISCLOSURE 
       [0002]    Blind fasteners are well known, and comprise devices insertable from one side through a hole in a member, and having means to anchor the device on the distal side of the hole. A screw-threaded component may be included, to tighten the device to the member. Such fasteners are utilised where access is available from one side only, and may for example clamp members together or be used to provide an anchorage. Typically a blind fastener includes a proximal side screw-threaded component having a screw-threaded distal (or blind) side anchorage arranged for close fitting passage through a hole. Once through the hole, the distal side anchorage changes form so as to resist withdrawal thereof, whereupon the proximal side component is tightened to firmly attach the fastener. The distal side fastener may for example comprise a folding component which is adapted to pass through the hole in folded form, and open out on the distal side to a diameter larger than the hole. 
       BRIEF SUMMARY 
       [0003]    According to the disclosure, there is provided a blind fastener adapter for a conventional screw-threaded nut and screw, the adapter comprising a collar and a segmented ring over the collar, the ring and collar having a tapered interface wherein relative axial movement results in a change of diameter of the ring, the adapter further including a spring adapted to bias the collar and ring into mutual engagement, the collar and ring including means to prevent substantial relative angular movement thereof, the collar bring adapted for engagement by a blind side head of the screw in use, and the ring being adapted for blind side engagement of the perimeter of a hole. 
         [0004]    The blind side head may be a nut or the head of a male fastener, such as a machine screw or bolt. The screw may be a threaded stud, or the shank of a male fastener. 
         [0005]    In an embodiment, the ring and collar are fixed against relative rotation by dogs; such dogs may for example comprise protrusions of one of the ring and collar, and mating recesses of the other of the ring and collar. In one embodiment protruding rails of the collar extend in the direction of the axis of rotation thereof, and engage in close fitting grooves of the ring. 
         [0006]    The ring may have three segments, each segment being restrained by a suitable dog. Each segment may be retained against radial separation by the collar, for example by an enlarged head of a rail engageable in an undercut groove. Each segment may comprise an individually separable component retained solely by a suitable form-locking profile. 
         [0007]    In an embodiment, the spring is a coil compression spring bearing directly on the ring in use, and sized to fit closely around the screw. 
         [0008]    The fastener may include a further coil compression spring outboard the aforesaid coil compression spring and of a diameter insufficient to pass through a hole for which the fastener is intended. Such a further spring provides frictional bias to provide anti-rotational force for the collar, in use. 
         [0009]    The adapter may further include a collared washer at the proximal side of the coil spring, the reduced diameter of the washer being sized to engage closely within the hole for which the fastener is intended, and the washer having an internal recess of sufficient depth to accept the spring when compressed. Such a recess avoids potential coil binding of the spring, which could affect proper tightening of the fastener. 
         [0010]    In another embodiment, the ring has a reduced diameter portion at the proximal side so as to present a shoulder. The reduced diameter portion is also sized for close fitting engagement in the hole for which the fastener is intended, and the shoulder bears on the perimeter of the distal side of the hole in use. 
         [0011]    A further washer may be provided proximally of the segmented ring so as to distribute spring loads applied thereto. Preferably the further washer is a close diameter fit in the hole for which the fastener is intended, and preferably is of a thickness to substantially bridge the clearance between the segmented ring and collared washer in use. Such a close fitting washer provides additional support against lateral forces acting on the fastener in use. 
         [0012]    A blind fastener adapter according to the disclosure has the advantage of being retro-fittable to a standard machine screw, for example a bolt. This means that special threaded components are not required, and that standard specification threads with known material properties can be used. Standard machine screws are relatively inexpensive compared with special forms. Furthermore, standard fixing tools, such as socket spanners, may be used for both standard and blind fasteners. Moreover, a special supply of blind fasteners is unnecessary provided that a supply of suitable adapters is provided for those instances where a blind fastener is required. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    Other features will be apparent from the following description of an embodiment shown by way of example only in the accompanying drawings, in which: 
           [0014]      FIGS. 1 and 2  illustrate in elevation two variants of a fastener adapter according to the disclosure, in combination with a machine screw and nut; 
           [0015]      FIG. 3  illustrates an exploded fastener adapter according to an embodiment of the disclosure in cross section, in combination with a machine screw and nut; 
           [0016]      FIG. 4  illustrates in axial section the steps of installation of a blind fastener embodying the disclosure; 
           [0017]      FIG. 5  corresponds to  FIG. 4 , and shows the fastener in full side elevation; 
           [0018]      FIG. 6  illustrates a suitable form locking arrangement between collar and ring; 
           [0019]      FIG. 7  illustrates an alternative embodiment having a load spreading washer; 
           [0020]      FIG. 8  shows the embodiment of  FIG. 7  in axial section, and in the assembled condition; 
           [0021]      FIG. 9  is a further alternative having a fitting spring; 
           [0022]      FIGS. 10 to 12  show alternative gripping teeth for segments of the segmented ring; 
           [0023]      FIG. 13  illustrates in elevation an elastomeric fitting ring of the tapered collar; 
           [0024]      FIG. 14  shows a perspective view of a plurality of fastener adapters having differing shouldered washer configurations; 
           [0025]      FIG. 15  shows a cross-sectional view of the fastener adapters of  FIG. 14 ; 
           [0026]      FIG. 16  shows a exploded side view of a fastener adapter according to an embodiment of the disclosure and a machine screw, and 
           [0027]      FIG. 17  shows a cross-sectional view of the fastener adapter and machine screw of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION 
       [0028]    With reference to  FIGS. 1 to 3 , a fastener comprises a conventional hexagonal headed machine screw  11  having a corresponding hexagon nut  12  of the same size. Between the head of the machine screw and the nut the components of an adapter comprise in series, a tapered collar  13 , a segmented ring  14 , a coil compression spring  15  and a shouldered washer  16 . The adapter renders the standard screw and nut suitable for blind (one-sided) installation, and may be filled to the machine screw and nut in either orientation, as illustrated in  FIGS. 1 and 2 , with the proviso that in use the fastener enters a corresponding hole collar first. 
         [0029]    The collar  13  comprises a plain diameter portion  21  for contact with the adjacent hexagon and a tapered portion  22  having three equi-spaced protruding rails  23 . Each rail has an enlarged head  24  ( FIG. 6 ) of constant section. The rails  23  extend in the direction of the axis of the fastener, and the bore  25  of the collar allows free movement along the threads of the fastener. 
         [0030]    The ring comprises three identical and equi-spaced segments  31  each having an undercut recess  32  ( FIG. 6 ) for sliding engagement with the respective enlarged head  24 . The internal surfaces of the segments  31  are arcuate and conical in form, so as to match the conical form of the collar  13 . The proximal side of the segments is shouldered so that in use ring  14  fits closely in the distal side of a hole for which the fastener is intended. 
         [0031]    The spring  15  is a light wire coil compression spring, which in use biases the segments of the ring  14  towards the collar  13  (downwardly as viewed in  FIG. 3 ). 
         [0032]    The shouldered washer  16  has a smaller diameter  41  adapted for close fitting engagement in the proximal side of a hole for which the fastener is intended. The internal diameter  42  is also relieved to accommodate the proximal end of the spring  15 , and is of sufficient depth to accept the spring without coil binding. In other words the spring can be fully compressed and housed within the washer  16 , for reasons which will become apparent. 
         [0033]    In order to convert a standard fastener to blind use, the components of the assembly are assembled in the manner indicated in  FIG. 1  or FIG.  2 —the coil spring  15  lightly biases the ring  14  and collar  13  into engagement, and the ring  14  tends to adopt a position at the base of the taper of the collar  13 , as illustrated in  FIGS. 1 and 2 . In this condition, the outside diameter of the ring is greater than the plain portion  21  of the collar. 
         [0034]    With reference to  FIGS. 4 and 5 , the blind fastener assembly is offered up to a hole, collar first. In the illustrated case a through hole of two plates  51 ,  52  is provided. The dimensions of the adapter and hexagons are selected so that the distal hexagon and collar  13  pass freely through the hole, but the ring  14  does not ( FIG. 4   a ). Further light insertion pressure causes the spring  15  to collapse ( FIG. 4   b ) as the collar and ring separate the segments  31  move radially inwardly in consequence of the form-locking profile of  FIG. 6 . 
         [0035]    The taper is arranged so that the segments are drawn sufficiently inwardly to eventually pass through the hole ( FIG. 4   c ) under pressure from the spring  15 , whereupon the collar and ring become more closely engaged again, which in turn guides the segments to a radially outer condition in which the shouldered portion of the ring engages in the distal side of the hole ( FIG. 4   d ). 
         [0036]    The proximal side hexagon may now be turned to tighten the fastener by hand, a slight proximal pull being sufficient to ensure frictional drag on the distal side hexagon. The drag force may be enhanced by suitable raised formations of the areas in contact, or alternatively the collar may be arranged to lightly grip the adjacent hexagon. 
         [0037]    Final tightening is by spanner or torque wrench, the spring being fully housed within the shouldered washer so as not to impede engagement of the ring  14  and distal side plate  52 . 
         [0038]    The hexagons are selected so as to pass through the hole, though it will be understood that this is not a functional requirement for the distal side hexagon. Furthermore, hexagon heads are not essential, and could be replaced by equivalent means such as screwdriver slots or cap heads incorporating a recessed fastener drive form. Use of the blind fastener is generally intuitive, and accordingly incorrect installation is unlikely. 
         [0039]    In the illustrated embodiment, the fastener is used to clamp two plates together. However the fastener is also suitable for forming a load bearing attachment in any planar surface of which access to the distal side is restricted. In particular, fasteners embodying the disclosure may be used to provide fixings to hollow sections. 
         [0040]      FIG. 7  shows a variation of the embodiment of  FIGS. 1 to 6 , in which the washer  61  is provided on the proximal side of the ring  14 , and against which the light spring  15  acts. The washer  61  is selected to be of smaller diameter than the hole for which the fastener is intended, and is preferably a close fit for reasons which will become apparent. The washer  61  may include a circular recess (not shown) on the proximal side to better locate the spring so as to avoid contact with the screw threads. 
         [0041]    The washer  61  ensures synchronised movement of the segments and, as illustrated in  FIG. 8 , provides additional support against lateral shearing and bearing forces which tend to tip the fastener in the hole, and are illustrated by arrows  62 . The thickness of the additional washer  61  is in practice selected to suit the thickness of the hole for which the fastener is intended, taking into account an allowance for the spigot diameter of the standard shouldered washer  16  and the collar  14 .  FIG. 8  clearly shows how the light spring  15  is housed in a recess of the washer  16  when the components are in the assembled condition. 
         [0042]      FIGS. 7 and 8  also illustrate that it is possible to combine the nut  12  and collar  13  into a single component comprising a threaded cone  63 . External flats  64  or like features may be provided on the cone blank to facilitate holding during thread tapping. 
         [0043]      FIG. 9  illustrates a further modification whereby an additional coil compression spring  65  is provided external to the light spring  15 , and oppositely wound to avoid coil binding. 
         [0044]    During assembly, the additional spring  65  bears on the proximal side of the material in which the hole is formed to ensure sufficient anti-rotational friction force between the distal side and the segmented ring  14 . This feature may avoid the need to give a slight outward pull on the fastener during initial fastening, and can be useful where access is restricted. The additional spring  65  may be used in conjunction with the washer  61 , or not, but is in any event provided with a corresponding recess in the shouldered washer  16  to obviate coil binding where the fastener is fully tightened. 
         [0045]    A somewhat schematic representation of a preferred segment  71  is illustrated in  FIG. 10  and comprises a plain diameter portion  72 , a tapered portion  73  and a dovetail recess  74  which corresponds to a suitable form of the collar  13 . Gripping teeth  75  of suitable form are provided at the shoulders  76  so as to engage the distal side of the hole in use, and contribute to anti-rotation during initial assembly. 
         [0046]    The gripping teeth  75  may extend radially to a partial extent ( FIG. 10 ), radially to a full extent ( FIG. 11 ), axially to a partial or full extent ( FIG. 12 ), or in both radial and axial directions as required by the circumstances of the installation. 
         [0047]    A further enhancement is illustrated in  FIG. 13 , in which a composite collar and nut  63  has three equi-spaced male dovetail projections  67  at the base of which are respective groove  66 . Retained by the grooves is a soft elastomeric ring  68 , for example a synthetic rubber O-ring. The axial position of the grooves and the diameter of the O-ring is selected so that in the uninstalled condition, the distal side of the segmented ring  14  is prevented from bottoming on the collar, so that the outside diameter of the segmented ring is just less than the diameter of the hole. In this condition, the fastener will pass freely through to the blind side. 
         [0048]    However, upon tightening, the ring  68  collapses or is displaced to permit the segments to come into functional engagement with the collar, either directly or through compression of the ring, and thus cause the radial movement necessary for engagement of the segmented ring  14  with the distal side of the hole. The ring  68  is essentially a single use fitting component intended to provide smooth passage of the fastener to the distal side of the hole. 
         [0049]    It will be understood that the fitting ring  68  may also be used with a separate nut, the location feature of the ring being provided on the collar. 
         [0050]    It will further be appreciated that the shouldered washer  16  may have different configurations depending upon the application of the blind fastener.  FIGS. 14 and 15  illustrate a plurality of different possible shouldered washer configurations. The examples shown are not intended to be limiting, but merely illustrate a selection of possible configurations. In the examples shown in  FIGS. 14 and 15  the nut  12  of the screw  11  is not shown 
         [0051]    Examples A and B of  FIGS. 14 and 15  show a shouldered washer  16  having a configuration substantially has hereinbefore described. The washer  16  includes a reduced diameter portion  41  adapted for close fitting to the sides of the hole through which fastener extends. 
         [0052]    Example C shows a shouldered washer  16 ′ having a peripheral wall  78  which defines a recess  80 . The hexagonal head of the machine screw  11  is received in the recess with sufficient clearance that an appropriately sized socket or box spanner can fit over the head. The height of the wall  78  is such that uppermost edge  82  of the shouldered washer  16 ′ extends above the head of the machine screw  11 . 
         [0053]    Example D shows a shouldered washer  16 ″ which is similar to that of example C. The washer  16 ″ differs in that the peripheral wall  78  is tapered  84  such that the washer  16 ″ has a semi-domed appearance. 
         [0054]    Example E shows a shouldered washer  16 ′″ which is adapted for use with a countersunk screw  11 . The washer  16 ′″ is provided with a through aperture  86  having a tapered portion  88  which accommodates the corresponding taper of the screw  11  such that the uppermost face  90  of the screw  11  is aligned substantially at the same level as the uppermost edge  82  of the washer  16 ′″. 
         [0055]    Example F shows a further example of a shouldered washer  16 ″″ adapted for use with a countersunk screw  11 . In this example the shouldered washer  16 ″″ is configured such that it is received in a countersunk hole  92 , with the result that both the washer  16 ″″ and head of the countersunk screw  11  are substantially flush with the upper plate  51 . The washer  16 ″″ is provided with tapered outer surface  94  which is dimensioned so as to be received within the countersunk hole  92 . 
         [0056]      FIGS. 16 and 17  show an alternative embodiment of a fastener adapter and machine screw in accordance with the disclosure. Features common to the previously described embodiments are identified with like reference numerals. The hexagon nut  12  is not shown. 
         [0057]    The fastener adapter includes a shear bush  96  which is positioned intermediate the shouldered washer  16  and the spring  15 . The shear bush  96  is substantially tubular and includes a through bore  98 . The through bore  98  may be plain such that the bush  96  is a sliding fit over the thread of the screw  11 . Alternatively, the through bore  98  may be provided with a thread such that the bush  96  may be threaded on to the thread of the screw. In use, the bush  96  is positioned in the hole extending through the two plates  51 ,  52  so as to increase the shear resistance of the blind fastener in the shear plane between the plates  51 ,  52  being fastened. It will be appreciated that the length of the bush  96  is dependent upon the thickness of the plates  51 ,  52 . 
         [0058]    Several modifications and alternatives have been described, and may be used independently or in combination to provide the required technical characteristics for a particular installation. In view of the foregoing description, it is evident that numerous other alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, the disclosure is intended to encompass all such alternatives, modifications and variations which fall within the scope and spirit of the disclosure and the following claims.