Patent Abstract:
A self-locking pin having a shaft, a headed end, and detent means biased in a bore in the pin. The portion of the detent or plunger that extends outwardly from the bore is wedge-shaped, while the portion of the plunger disposed inside the bore is cylindrical. A transitional angle is formed at the point where the configuration of the plunger changes from cylindrical to wedge-shaped. The transitional angle defines shoulders on either side of the plunger. The shaft is staked at points along the perimeter of the bore so that the inwardly extending surface created by the staking abuts the shoulders and prevents the plunger from rotating or being removed from the bore. In an alternate embodiment, the plunger may be rotated to a locked depressed position.

Full Description:
RELATED APPLICATION 
   This application is a divisional of U.S. patent application Ser. No. 10/421,336, filed Apr. 23, 2003 now U.S. Pat. No. 6,872,039. 

   BACKGROUND OF THE INVENTION 
   1. Field of Invention 
   The invention relates to fasteners, namely threadless fasteners and more particularly to a threadless fastener for retaining two or more structures through apertures formed in each structure. 
   Detent pins are well known in industry. Many of these pins fall into the category of safety bolts. Safety bolts have a threaded end to which a nut can be attached to as well as a detent mechanism along the length of the bolt. The main fastening mechanism in safety bolts is threading the nut on the end of the bolt. These products are often used in the aircraft industry so an extra safety factor is present in case vibrations cause the nut to loosen or someone forgets to tighten the nut. The detent mechanism is this extra safety factor. However, these dual fasteners make safety bolts more difficult and thus more expensive to manufacture. Additionally there are some applications where such a bolt cannot be used because it is either impractical or impossible to access the threaded end of the bolt after it is inserted through an aperture. Also, screwing the nut on the end of the bolt causes an increase in assembly time. 
   Cotter pins are also well known in industry. A bolt with a cotter way is inserted through an aperture. A cotter pin is then inserted through the cotter way so the bolt cannot be removed from the aperture. It is thus obvious that access to the backside of the workpiece is necessary for a cotter pin to be utilized. Here again, insertion of the cotter pin in the cotter way is an extra step that will take more time during assembly. 
   There is a need in the market for a self-locking pin which is simple to manufacture and can be installed with little effort and in applications where there is no access to the opposing side of the workpiece and thus a nut cannot be applied to the threaded end of a pin. 
   2. Description of Prior Art 
   One type of prior art bolt is disclosed in U.S. Pat. No. 4,759,671 to Duran. Duran discloses a self-retaining bolt assembly in which the detent is a solid spherically shaped ball element with cut out sections and these cut out sections must be configured to saddle protuberances in the hole to prevent rotation. The periphery of the hole is peened in order to retain the detent in the hole. The shaft and detent of this bolt must both be machined carefully to assure a proper fit and retention for the detent. 
   Another prior art bolt is disclosed in U.S. Pat. No. 3,561,516 to Reddy. Reddy discloses a bolt with diametrically opposed detents slidably disposed in one hole. Each detent has a lateral passage with a sloped cam surface. These sloped cam surfaces engage a cam member which retains the detents in the hole. The detents are pulled into the hole when a force is exerted on the cam surface of the cam member by the cam surfaces of the detents. The detents are moved outwardly by the biasing means disposed between the detents. A number of carefully machined parts, which are difficult to install properly, are required. Additionally, the passageway extending along the axis of the bolt weakens the bolt. 
   A prior art bolt is disclosed in U.S. Pat. No. 2,361,491 to Nagin. Nagin disclosed a detent, generally circular in section, with a 45-degree slope at the upper end. A V-shaped groove with plane cam faces is formed in the body of the detent. The detent is slidably disposed in a hole in the shank. A circular passage extends along the bolt axis. A pin is slidably disposed in this passage. The pin is biased with a spring to engage the V-shaped groove and retain the detent in the hole. This bolt also must be carefully machined and installed to operate correctly. Additionally the passage in the shaft weakens the bolt. 
   SUMMARY OF THE INVENTION 
   The present invention, a self-locking pin, provides a pin with a uniquely shaped detent or plunger, which facilitates easy installation of the pin through an aperture in an object. In addition, the novel plunger in combination with a staking process non-rotatably retains the detent in its hole. 
   In one embodiment the self-locking pin has an elongated shaft with a first end and a second headed end. The shaft has a hole bored in it with a plunger slidably disposed in the hole. The plunger has a lower cylindrical portion and an upper wedge-shaped portion. A shoulder is formed on the lateral sides of the plunger where these two portions meet. The plunger is biased in the hole. The shaft of the pin is staked on lateral sides of the plunger with a perpendicular radius punch to retain the plunger in the hole. The location of the staking corresponds to the plunger&#39;s shoulders. 
   In an alternate embodiment, the plunger is formed with shoulders on its leading and trailing sides. In this embodiment, the shaft is then staked on the leading and trailing sides of the plunger. 
   In yet another embodiment, the plunger is formed with a shoulder only on its trailing side. In this embodiment, the shaft is staked on the trailing side of the plunger. 
   In a final embodiment, the hole is bored through the entire shaft. Two plungers are then disposed in the hole and each opening to the hole is staked on lateral sides of the plungers. 
   The plunger can have different shapes depending upon the application. Another alternate embodiment includes a plunger that can be locked in its depressed position allowing the pin to be freely inserted or removed until the plunger is unlocked. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a perspective view of a pin in accordance with the invention. 
       FIG. 2  is an exploded perspective view of the pin in  FIG. 1 . 
       FIG. 2A  is an alternate exploded perspective view of the pin in  FIG. 1 . 
       FIG. 2B  is another alternate exploded perspective view of the pin in  FIG. 1 . 
       FIG. 2C  is yet another alternate exploded perspective view of the pin in  FIG. 1 . 
       FIG. 3  is a top plan view of the pin of  FIG. 1 . 
       FIG. 4  is a side elevation view of the pin of  FIG. 1 . 
       FIG. 5  is an end elevation view of the pin of  FIG. 1 . 
       FIG. 6  is a cross sectional view of the pin of  FIG. 3  taken along line  6 — 6  of  FIG. 3 . 
       FIG. 7  is a top plan view of the wedge-shaped plunger of  FIG. 2 . 
       FIG. 8  is a front elevation view of the wedge-shaped plunger of  FIG. 7 . 
       FIG. 9  is a side elevation view of the wedge-shaped plunger of  FIG. 8 . 
       FIG. 10  is an exploded perspective view of an alternate embodiment of the pin of  FIG. 1  with a spring retaining cavity. 
       FIG. 11  is a perspective view of an alternate embodiment of the wedge-shaped plunger of  FIG. 2 . 
       FIG. 11A  is a perspective view of another alternate embodiment of the wedge-shaped plunger of  FIG. 2 . 
       FIG. 12  is a perspective view of a double-wedged embodiment of the plunger. 
       FIG. 12A  is a perspective view of a conical embodiment of the plunger. 
       FIG. 12B  is a perspective view of a radiused embodiment of the plunger. 
       FIG. 13  is a cross sectional view of an alternative embodiment of the pin with two wedge-shaped plungers taken along line  13 — 13  of  FIG. 16 . 
       FIG. 14  is a perspective view of the pin of  FIG. 1  using the wedge-shaped plunger of  FIG. 11 . 
       FIG. 15  is a perspective view of the pin of  FIG. 1  using the wedge-shaped plunger of  FIG. 11A . 
       FIG. 16  is a perspective view of the pin of  FIG. 13 . 
       FIG. 17  is a side elevation view of the pin of  FIG. 1  installed in an aperture through a panel. 
       FIG. 18  is a perspective view of another alternate embodiment pin, similar to the pin shown in  FIG. 14 . 
       FIG. 19  is a perspective view of the alternate embodiment pin showing the plunger being locked. 
       FIG. 20  is a perspective view of the alternate embodiment pin with the plunger locked. 
       FIG. 21  is a cross-section view taken along line  21 — 21  of  FIG. 20  showing the locked plunger. 
   

   DESCRIPTION OF THE PREFERRED EMBODIMENT 
   Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention, which may be embodied in other specific structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims. 
     FIG. 1  illustrates the presently preferred embodiment of the self-locking pin  20  according to the invention. The pin  20  has a generally cylindrical shaft  22  with a first end  24  and a second end  26 . The second end  26  may have an enlarged head  28 . 
   As seen in  FIG. 2 , a re-entrant bore  30  extends partway though the shaft  22  near the first end  24 . The bore  30  extends radially inwardly towards the axis of the shaft. The bore  30  may or may not intersect the central longitudinal axis of the shaft. A plunger  32  is slidably disposed in the bore  30 . The plunger  32  has a cylindrical portion  34  and a wedge-shaped portion  36 . The plunger sits upon a helical coil spring  54 . As shown in  FIG. 2A , a leaf spring  70  may be used as the biasing means. As shown in  FIG. 2B , compressible material  72  may be used as the biasing means. As shown in  FIG. 2C , an elastic material  74  may be utilized as the biasing means. 
     FIGS. 3 ,  4 , and  5 , show views of the pin  20  from the top, side, and end respectively. 
     FIG. 6  shows a cross section of the pin  20 . This illustrates the spring  54  biasing the plunger  32 . While the preferred embodiment uses a helical coil spring, other acceptable biasing means such as, but not limited to, a leaf spring, or a cushion of sufficiently elastic material could be utilized. 
   The plunger  32  can either sit directly on top of the spring  54 , or a cavity  56  can be counter-bored in the bottom surface of the plunger  32  to act as a spring seat and retain the spring  54 . The phantom lines in  FIG. 10  denote this cavity  56 . 
   The preferred embodiment of the plunger is further illustrated in  FIGS. 7 ,  8 , and  9 . The plunger  32  has a transitional angle  38  at the point where the configuration of the plunger  32  changes from cylindrical  34  to wedge-shaped  36 . This transitional angle  38  forms a tapered shoulder  40 . As will be described hereinafter, the shoulder  40  helps retain the plunger  32  in the bore  30 . Referring to  FIG. 9 , the side of the wedge-shaped portion proximate to the first end  24  of the pin  20  is the wedge leading side  42 . The side of the wedge-shaped portion proximate to the second end  26  of the pin  20  is the wedge trailing side  44 . As seen in  FIG. 8 , the wedge also has oppositely disposed lateral sides  46 . In the preferred embodiment, shoulders  40  are formed on each of the lateral sides  46  of the plunger  32 . An abutment  50  is formed on the side opposite leading side  42 . 
   As can be best seen in  FIGS. 1 and 4 , when the plunger  32  is in its normal position in the bore  30 , the cylindrical portion  34  resides below the surface of the shaft  22  and the wedge-shaped portion  36  extends above the surface of the shaft  22 . Referring to  FIGS. 4 and 9 , the wedge leading side  42  of the plunger  32  is proximate the surface of the shaft  22 . The top surface of the plunger  32  extends angularly upwardly away from the surface of the shaft  22  to define a ramped engaging surface  48  and the abutment  50 . The abutment  50  is perpendicular or normal to the axis of the shaft  22  and faces the direction of the second end  26 . 
   The plunger  32  and shaft  22  could be made from any suitable materials such as, but not limited to, alloy steels, carbon steels, stainless steel, or aluminum alloys. 
   To assemble the self-locking pin  20 , the spring  54  is first placed in the re-entrant bore  30 . Next, the plunger  32  is placed in the bore  30  in the correct orientation. The pin  20  is held in place, with the plunger  32  in its depressed position, by one tool while another tool punches the shaft  22  using a radius stake punch perpendicular to the pin  20 . The staking  52  causes a change in the shape of the shaft  22  around the entrance to the bore  30 . The smooth round bore  30  is formed to a substantially oval shape with some depth as best shown in  FIGS. 2 and 3 . In the preferred embodiment, the shaft  22  is staked on the lateral sides of the wedge. The staking  52  forms inwardly extending marginal portions. This is best shown in  FIG. 10 . These inwardly extending portions abut the shoulder  40  of the plunger  32  (see  FIGS. 7 through 9 ) as the spring  54  urges the plunger  32  outwardly of the bore  30 . The edge of the staking  52  abuts the flat lateral sides  46  and surface  40  of the plunger  32  and prevents the plunger  32  from rotating or being removed from the bore  30 . Alternately, and as shown in  FIGS. 14 and 15  respectively, a single stake may be placed behind the plunger or a pair of stakes may be placed in front of and behind the plunger. 
     FIGS. 11 and 11A  show first alternate embodiments of the plunger. The plunger  132  embodied in  FIG. 11  has a transitional angle  138  on only the wedge trailing side  144 . This creates only one shoulder  140 , which is located on the wedge trailing side  144 . Using this plunger  132  embodiment, the shaft  22  is preferably staked only on the plunger trailing side as shown in  FIG. 14 . 
   The plunger  232  embodied in  FIG. 11A  has transitional angles  238  on both the wedge trailing side  244  and the wedge leading side  242 . This creates shoulders  240  on both the wedge trailing side  244  and the wedge leading side  242 . Using this plunger  232  embodiment, the shaft is preferably staked on both the wedge trailing side  244  and the wedge leading side  242  as shown in  FIG. 15 . 
     FIGS. 12 ,  12 A and  12 B show other alternate embodiments of the plunger.  FIG. 12  depicts a double-wedge plunger  332  having opposite ramped engaging surfaces  348 ,  350  that meet at an edge  352 .  FIG. 12A  shows a conical plunger  432  terminating at a point  434  and  FIG. 12B  depicts a radiused plunger  532  having a smooth, domed top  534 . It is to be understood that any of the plungers could be staked in any of the pins as described. 
     FIGS. 13 and 16  show an alternate embodiment of the self-locking pin  20  in which two plungers  132  are utilized. As shown in  FIG. 13 , the two plungers  132  are disposed in one bore  30 . The plungers  132  are separated by a spring  54 , biasing each plunger  132  in an outward direction. Each plunger  132  is of the preferred embodiment of the plunger  132 . The shaft  22  is staked on the lateral sides  46  of each plunger  132 . 
     FIG. 17  shows the self-locking pin  20  inserted through an aperture. In regular use, the self-locking pin  20  is inserted through an aperture in at least one object with a restraining surface  60 . The ramped engaging surface  48  of the plunger  32  abuts the inner surface  62  of the aperture. The force of the inner surface  62  of the aperture against the ramped engaging surface  48  of the plunger  32  causes the plunger  32  to be pushed inwardly against the bias of the spring  54  into the bore  30  until the abutment  50  is no longer exposed. The pin  20  can then be installed completely by continuing to push the pin  20  through the aperture. Once the pin  20  is installed and the ramped engaging surface  48  clears the aperture the plunger  32  pops back up against the bias of the spring  54 . As shown in  FIG. 17 , the flat abutment  50  of the plunger  32  abuts the restraining surface  60  of the object, preventing the pin  20  from being withdrawn from the aperture in a similar manner. 
     FIGS. 18 through 21  show an alternate embodiment of the self-locking pin  20  further including a lockable plunger  80 . Plunger  80  includes a recess  82  formed in its ramped engaging surface  48  for receiving a tool T. A single stake  52  is placed behind the plunger  80 . When partially depressed (typically with the use of the tool) the plunger  80  may be rotated, as shown in  FIG. 19 . The rotation allows plunger  80  to be trapped beneath the stake  52  and therefore hold the plunger in a depressed or retracted position (see  FIG. 21 ). Rotating the plunger  80  in either direction allows the plunger to return to its former position where it can be freely depressed and extended. Alternately, the orientation of the plunger may be changed by one hundred eighty degrees (180 degrees). 
   The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

Technology Classification (CPC): 5