Abstract:
A re-useable fastener intended for the temporary assembly of a pair of objects that are made from composite material. The fastener body itself is made of a self-shape restoring elastomer with a tubular shank to be placed in aligned holes in the parts. It has a head at one end of the shank and an axial passage from head end to blind end. A headed, threaded bolt fits in the passage. A metal washer fits against the head, around the passage. An internally threaded insert is fitted in the shank to receive the bolt with its head against the washer. When tightened, the blind end of the shank forms a bulb, and the shank enlarges. When untightened, the body relaxes and the body can be removed. Alternatively, the bolt head can bear against the blind end, and a nut can be threaded onto the bolt shank, bearing against the washer to set the fastener. If desired a tubular rigid body can be placed inside the passage within the depth of the holes to limit the deformation of the shank inside the hole.

Description:
CROSS-REFERENCE TO OTHER APPLICATION  
       [0001]     This is a continuation-in-part of applicant&#39;s U.S. patent application Ser. No. 10/831,968, filed Apr. 26, 2004, titled “FASTENER FOR THE TEMPORARY JOINDER OF PARTS MADE OF COMPOSITE MATERIAL, which will be abandoned after the timely filing of this continuation-in-part application. 
     
    
     FIELD OF THE INVENTION  
       [0002]     The temporary joinder of parts which are made from composite materials, utilizing a blind fastener.  
       BACKGROUND OF THE INVENTION  
       [0003]     When parts of a total assembly are to be joined permanently, it is common practice initially to gather them in place on a fixture or a jig, and then fastener-by-fastener, secure them together to form the final assembly. The initial assembly of parts is held together by temporary fasteners, which are individually removed at the time when a permanent fastener is to be installed in their place. This initial assembly is made from one side only (a “blind” assembly) for convenience of the assembler. Using fasteners tightened from both sides would be unnecessarily time consuming and often not possible, for example when the final fastener is itself a blind fastener.  
         [0004]     This is not, of course, a new concept. Since the earliest days of aircraft assembly it has been a conventional procedure. Temporary fasteners are well known for this purpose. A historical example is the CLECO, which provides hooks on its blind end to engage the back side of a part around the hole. These are hard metallic fasteners that are well enough suited for use with metal structures such as an aluminum alloy stringers. Such parts are ordinarily not notch-sensitive, and small scratches and indentations caused by assembly techniques are acceptable.  
         [0005]     The situation is different with composite materials. These materials are formed from organic plastics reinforced with substances such as fibers and cloths. These are less forgiving of damage done during assembly of a structure. A hole and its boundaries, once formed, must be protected against damage.  
         [0006]     It is an object of this invention to provide a temporary fastener which presents only conformable surfaces to the composite material, which fastener is readily installed, and is readily removed. Meanwhile when installed it provides a suitable and sufficient structural fastener to hold the parts together in proper relationship.  
       BRIEF DESCRIPTION OF THE INVENTION  
       [0007]     The temporary fastener of this invention includes a body having a central axis, an axially extending tubular shank with a laterally-extending head at its headed end and a blind end spaced from the head. This body is formed from a compliant material that can be deformed by sufficient force to form an upset on the blind end that with the head on the head end will hold the parts together without deforming the parts themselves or damaging their confronting surfaces.  
         [0008]     A puller comprises a headed and a threaded shank. A washer surrounds the axial passage at the headed end, providing a rigid engagement surface for the puller.  
         [0009]     In one embodiment of this invention, the head of the puller bears against the washer, and is threaded into an insert that is cast into the blind end of the shank of the body.  
         [0010]     In yet another embodiment, the head of the puller bears against the blind end of the shank of the body, and a nut is threaded onto the puller shank, bearing against the washer, to pull the blind end toward the head and upset the body shank to form a bulge that holds the parts together.  
         [0011]     According to a preferred but optional feature of the invention, the body has incorporated into its tubular shank a rigid reinforcement located between the head and the blind end of the shank, terminating at an axial location along the shank spaced from the blind end so as to leave an un-reinforced portion of the shank available to form a temporary enlargement, called herein a bulge or an upset. This reinforcement can be inside the shank or outside of it, as preferred and may include a head of its own.  
         [0012]     According to another optional feature of the invention, the shank has an outer wall with a tapered shape that has a cross-section increasing in diameter from the blind end to facilitate insertion of the shank into a workpiece.  
         [0013]     In all situations the fastener can be released and withdrawn merely by unthreading the puller or its torque device. The body then shrinks to its previous dimensions so as readily to be removed.  
         [0014]     The above and other features of this invention will be fully understood from the following detailed description and the accompanying drawings, in which: 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a side view of the preferred embodiment of the fastener of the invention;  
         [0016]      FIG. 2  is an axial cross-section taken at line  2 - 2  in  FIG. 1 ;  
         [0017]      FIG. 3  is a top view taken at line  3 - 3  in  FIG. 1 ;  
         [0018]      FIG. 4  is an axial cross-section showing the fastener loosely assembled;  
         [0019]      FIG. 5  is a view similar to  FIG. 4 , but with the fastener inserted into the parts to be joined.  
         [0020]      FIG. 6  shows the fastener fully installed;  
         [0021]      FIG. 7  is an exploded view of the components of the fastener with a modification;  
         [0022]      FIG. 8  is an axial cross-section of another embodiment of the invention;  
         [0023]      FIG. 9  is an axial cross-section of a metal reinforcement preferably formed as part of a washer, and embedded into the body;  
         [0024]      FIG. 10  is an end view of  FIG. 9 ;  
         [0025]      FIG. 11  is an axial cross-section of the preferred embodiment of this fastener loosely inserted in a workpiece;  
         [0026]      FIG. 12  is a view similar to  FIG. 11 , but with the fastener set;  
         [0027]      FIG. 13  is an axial cross-section showing another modification of the invention, unset; and  
         [0028]      FIG. 14  is yet another axial cross-section showing another embodiment of the invention unset. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0029]     Referring to the drawings,  FIG. 1  shows the body  10  of a fastener  11  ( FIG. 4 ) according to the invention. body  10  has a central axis  12  with an axial passage  13  extending from its headed end  14  to its blind end  15 .  
         [0030]     The body includes a tubular shank  16  with an outer cylindrical surface  17 . It further includes a laterally extending head  18  with a shoulder  19 . In the preferred embodiment a recess  20  is formed around the opening of the passage at the headed end.  
         [0031]     An insert  25  is pressed or cast into the blind end of the fastener. It carries an internal thread  26 . The insert is preferably made of metal, often brass.  
         [0032]     As best shown in  FIGS. 4-6 , a metal washer  28  has an upper contact surface  29  and a central hole  30 . It fits neatly into recess  20 .  
         [0033]     A puller  32  comprises a bolt having a shank  33  with an external thread  34 . Thread  34  is engageable with thread  26  in the insert, but clears the wall of the passage and the wall of the hole in the washer. Its function is to engage the insert and put shank  16  into compression.  
         [0034]     The puller further includes a head  35  which bears against contact surface  29 . A screw slot  36  or other tool-engagement means such as a socket is formed in the head to turn the puller. It will be noted that the under surface  37  of the puller head is smooth so as to reduce resistance to turning the puller when the fastener is being installed.  
         [0035]      FIG. 5  shows the loose fastener placed in holes  40 ,  41  in parts  42  respectively. Notice the freedom of fit, with clearances between the walls of the holes and the outer surface of the fastener. The fastener can readily be inserted. This invention provides its best advantages for temporary assembles of parts made of composite materials although it is useful with other materials as well, such as aluminum alloys, and steel alloys.  
         [0036]     As shown in  FIG. 6 , the puller can be rotated. The effect is to pull the insert toward the head of the body. In so doing, it will swell the shank of the body to fit closely in the holes in the parts. This will serve to align them. It will also create a bulge  45  on the blind end which acts as a clamp with the head of the body to press the parts together. The temporary assembly is now completely rigid.  
         [0037]     To release it, the puller is simply unthreaded. The fastener will relax and can readily be removed and re-used. This relaxation is the consequence of the character of the body to restore itself to its relaxed shape.  
         [0038]      FIG. 7  illustrates that the top surface  50  of a body  51  need not be recessed. The washer  52  may instead bear directly on the top surface. As before, the fastener includes an insert  53  and a puller  54 , assembled and installed as above.  
         [0039]     The embodiments of  FIGS. 1-7  require the use of a separate tool, such as a screwdriver or a hex wrench to install it. In contrast the embodiment of  FIG. 8  is self-contained both as to structure and as to installation.  
         [0040]     This embodiment utilizes a body  60 , a washer  61  and an insert  62  as before. The same parts can be used. The difference is the reversed insertion of puller  63 . This puller enters the from the blind end. The head of the puller now bears against the insert. In this embodiment the puller is not threaded to the insert. A clearance is provided, or the insert is not threaded. The head of the puller bears against the insert, or if an insert is not used, then directly on the body shank.  
         [0041]     A torque device  65 , such as a classical wing nut is threaded onto the shank of the puller, and bears against the washer.  
         [0042]     The function is the same for the fastener of  FIG. 1 , but provides the advantage of a self-contained torque device. This will often be a substantial convenience, because no separate torque tool is needed to set the fastener. In every situation the fastener can be removed at its headed end.  
         [0043]     The body may be made from any suitable elastomer which is sufficiently deformable as to be radially enlarged when axially compressed, and tends to be self-shape restoring when deforming forces are released.  
         [0044]      FIGS. 9-12  show the presently-preferred embodiment of this invention. While the embodiments of  FIGS. 1-8  work well, it has been found to be useful to provide a fastener which is more readily inserted into the workpiece, and in which the region where the enlargement occurs is primarily limited to a defined axial length of the fastener, and with a lesser expansive contact of the shank with the walls of the workpiece. I has been observed that the excessive early swelling of the shank can impede the arrays of the workpieces together. Also, it is useful to limit contact of the puller with the elastomer. This can reduce the torque necessary to set the fastener.  
         [0045]      FIG. 11  shows a fastener  70  according to this invention loosely inserted into a pair of holes  71 , 72  in workpieces  73 , 74 , respectively. These holes are aligned and on a common central axis  75 . It is the purpose of this fastener to clamp against upper surface  76  of workpiece  73  and bottom surface  77  of workpiece  74  to hold them together temporarily.  
         [0046]     The workpieces may be of any material, such a composites and metals. The fastener provides best advantage to composites because of it is forgiving of the wall surfaces. It will not crack or depress these walls.  
         [0047]     Fastener  70  includes a body  80  having a lateral extending head  81  with an undersurface  82  which bears against workpiece surface  76 , extending beyond the holes. It has a height  83 , which preferably is tall enough to receive a tool such as pliers to pull the fastener out of the holes when the fastener is to be removed. The body has an annular recess  85  in the upper surface  86  of its head  81 .  
         [0048]     A tubular shank  90  is integral with head  87  and depends from it. The shank has an outer wall  91  which may be cylindrical, but preferably has a small taper (draw) angle of perhaps three degrees included angle. This is enough taper to facilitate pressing the fastener into the holes, but not so large as to result in looseness of fit when the fastener is set.  
         [0049]     The body extends from its headed end  95  to its blind end  96 . A nut  97  is cast into the blind end of the shank.  
         [0050]     Annular recess  85  in the top surface of the head receives annular flange  101  of a rigid reinforcement  102 . The reinforcement has a tubular shank  103  which fits into an internal enlargement  104  in the inside wall  105  of shank  90 . Preferably the reinforcement is molded in place, but it could instead be cemented in or simply pressed in. The reinforcement is made of rigid material such as brass, an aluminum alloy, or a rigid plastic.  
         [0051]     Passage  105  extends from the head end of the fastener to its blind end  96 . It is defined by the inside wall  106  of the reinforcement and by the portion of the shank beyond the reinforcement.  
         [0052]     It will be observed that the reinforcement terminates short of the insert and of the blind end. This leaves the unsupported length  108  of the shank exposed beyond bottom surface  77  of workpiece  74 . By supporting the wall of shank  90  between the shank  103  the reinforcement and the walls of the hole, the workpiece walls are subjected to a reduced lateral force, but enough that the fastener makes a complete fit. Excessive swelling of the shank in the workpiece could make drawing the parts together more difficult. Also the threads of the puller are not in contact with the wall of the body for much of its length, which reduces the torque needed to turn the puller.  
         [0053]     The exposed length of the body is available to form an upset enlargement or bulge  125 . This arrangement is shown in  FIG. 12 . A puller  120  in the form of a bolt has a head  121  and a threaded shank  122 . The head is provided with a tool engaging shape such as a slot  123  and a bearing surface  124  which bears against the reinforcement.  
         [0054]     The installation of this fastener is straightforward. It is thrust through the holes in the workpiece, blind end first. Then the bolt is turned to draw the nut toward the workpiece ( FIG. 12 ), which bulges the protruding portion of the shank to form bulge  125  shown in  FIG. 12 .  
         [0055]     When the fastener is to be removed, the bolt is turned the other way, backing off the nut. The material of the shank tends to be self-shape restoring, and resumes the condition shown in  FIG. 11 .  
         [0056]     The height  83  of the head of the body provides for a convenient grip by the hand or a tool. Then the fastener can be reused.  
         [0057]     The embodiment of  FIGS. 11 and 12 , utilizing reinforcement  102  reduces the amount of material that needs to be deformed, making the installation easier. The material which contacts the wall of the hole need not expand as much because the clearance is usually quite close. The clamping action is primarily caused by the bulge and the head being brought toward one another by the action of the bolt.  
         [0058]     The dimensions of the fastener are arbitrary, and are designed to fill a hole of selected length and diameter. These details are well within the scope of the skilled artisans.  
         [0059]     The reinforcement may be incorporated in the arrangement of  FIG. 8 .  
         [0060]      FIGS. 13 and 14  show embodiments of the fastener which facilitate and improve the setting of the fastener. The fastener&#39;s principal function is to hold the workpieces together, with the holes aligned. This requires that the parts be pulled together by driving the bulge toward the head. This relative movement of the workpieces is made difficult as the lateral displacement of the shank increases.  
         [0061]     Also it can be minimized by having the contact between the fastener and the wall of the holes made by a hard smooth body which does not swell, and incidentally also reduces the contact between the shank of the fastener body and the thread of the puller, thereby also reducing the torque needed to set the fastener.  
         [0062]     In  FIG. 13 , two workpieces  130 , 131  are shown loosely assembled by a fastener  132 . The fastener includes a body  135  with a head  136  and shank  137 . A metal washer  138  is sunk in a recess  139  in head  136 .  
         [0063]     A central passage  140  extends from the head to the blind end  141  of the body. A metal insert  142  with an internal thread  143  is cast or set in the blind end of the body.  
         [0064]     A reinforcement  145  fits snugly in holes  146  and  147  in the workpieces. It has a tubular shank  148  and peripheral head  149 . Head  149  fits in a recess  150  in the under surface of head  136 . Shank  148  fits in a peripheral recess  151  in shank  137  of the body.  
         [0065]     There is a remaining tubular section  155  of the body which is restrained force outward swelling, but closeness of fit of the reinforcement will generally be sufficient.  
         [0066]     The body length beyond the reinforcement and its free length beyond the workpieces suffices to form a bulge as in  FIG. 12 . This bulge will be formed by turning a puller, threaded into the insert, as before.  
         [0067]      FIG. 14  is similar to  FIG. 13 , except that reinforcement  165  does not include a head. It is a pure cylinder whose length is about the same as shank  104  of reinforecment  102  in  FIG. 12 . It fits against the walls  166 ,  167  of workpieces  168 ,  169  and reduces the wall thickness of shank  170  of fastener body  171 . Apart from this, the embodiments of  FIGS. 13 and 14  are identical.  
         [0068]     This invention thereby provides an inexpensive, convenient and very efficient temporary fastener that respects the structural integrity of the parts in which it is set. It is readily removable and reusable.  
         [0069]     This invention is not to be limited by the embodiments shown in the drawings and described in the description, which are given by way of example and not of limitation, but only in accordance with the scope of the appended claims.