Abstract:
A slotless locking pull pin having a handle, a pin, a housing, an internal spring and a locking mechanism. The pull pin has an internal spring which biases the pin in its normal extended position. The pull pin has a locking mechanism which locks the pin in its retracted position. The locking mechanism may include locking structure located on the pin and a locking plate located in the housing. The locking structure engages the locking plate and holds the pin in its retracted position.

Description:
RELATED APPLICATIONS  
       [0001]     This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 60/777,281, filed 27 Feb. 2006. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     Pull pins are a commonly used method of adjustably attaching two pieces of material. Pull pins are generally used in situations where two pieces slide close to each other and quick adjustment is desired. For example, on the legs of a table or a tripod. The pull pin is threaded into a hole in the first piece and the pin extends through a hole in the second piece. Commonly, the second piece is provided with a number of holes, and a handle of the pin is pulled to retract the pin and allow for adjustments. Pull pins are generally spring loaded such that when the handle is released, the pin returns to its normal extended position.  
         [0003]     Locking pull pins are also common. Locking pull pins are pulls pins which are configured such that they can be locked in the retracted position. Locking pull pins which are currently on the market have a slot located at the end of the pin near the handle. This slot is adapted such that the handle can slide in the slot. When the pin is in its extended position, the handle is slid at least partially into the slot. To lock the pin in the retracted position, the pin is pulled back to the retracted position and the pin is rotated such that the handle rests on the end of the housing. While this type of locking pull pin is commonly used, there are problems associated with it. Most importantly, a slot has to be machined on each pull pin. This machining adds to the labor time associated with making a locking pull pin and therefore increase the cost of such a part. It is desirable to design a pull pin which does not require a slot to be machined on the housing of the pull pin.  
       SUMMARY OF THE INVENTION  
       [0004]     The present invention provides a slotless locking pull pin. The pull pin includes a handle, a pin, a housing, an internal spring, and a locking mechanism.  
         [0005]     In one embodiment the locking mechanism includes a plunger on the pin and a locking plate in the housing. In this embodiment the plunger may be engaged by either a tool or by hand.  
         [0006]     In a second embodiment the locking mechanism includes a protrusion on the pin and a keyhole shaped aperture in the locking plate. In this embodiment the pin is held in locking position by pulling the protrusion through the keyhole and rotating the pin so the protrusion engages the locking plate. To release the pin, the pin is rotated to align the protrusion with the keyhole and the pin is returned and to its extended position.  
         [0007]     In a third embodiment the locking mechanism includes a plunger disposed in the pin and a keyhole shaped aperture in the locking plate. In this embodiment the pin is held in locking position by pulling the pin into the retracted position such that the plunger engages the locking plate. The plunger may have a ramped surface which engages the interior of the aperture in the locking plate to depress the plunger. To release the pin, the pin is rotated to align the plunger with the keyhole and the pin is returned to its extended position.  
         [0008]     In a fourth embodiment the locking mechanism includes a plunger disposed in the pin, a collar, and a locking plate. In this embodiment the pin is held in locking position by pulling the pin into the retracted position such that the plunger engages the locking plate. The plunger has a ramped surface which engages the interior of the aperture in the locking plate to depress the plunger. To release the pin, the collar is pushed toward the housing. The surface of the collar engages the ramped surface on the plunger and depresses the plunger so the pin can be returned to its extended position.  
         [0009]     In a fifth embodiment, the locking mechanism includes a plunger disposed in the pin, a collar, and a locking plate. In this embodiment the plunger does not have a ramped surface, but both the collar and the locking plate have ramped surfaces. In this embodiment the pin is held in locking position by pulling the pin into the retracted position such that the plunger engages the locking plate. The ramped surface of the locking plate engages the plunger and depresses the plunger. To release the pin, the collar is pushed toward the housing. The ramped surface of the collar engages the surface on plunger and depresses the plunger so the pin can be returned to its extended position. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1A  is a partially cut away perspective view of a preferred embodiment of the present invention in the retracted position.  
         [0011]      FIG. 1B  is a perspective view of a preferred embodiment of the present invention in the extended position.  
         [0012]      FIG. 2  is a perspective view of an alternate embodiment of a locking mechanism according to the present invention.  
         [0013]      FIG. 3  is a perspective view of a second alternate embodiment of a locking mechanism according to the present invention.  
         [0014]      FIG. 4  is a perspective view of a third alternate embodiment of a locking mechanism according to the present invention.  
         [0015]      FIG. 5A  is a perspective view of the locking mechanism of  FIGS. 1A and 1B .  
         [0016]      FIG. 5B  is a sectional view of the locking mechanism of  FIG. 5A .  
         [0017]      FIG. 6A  is a perspective view of an alternate embodiment of a locking mechanism according to the present invention.  
         [0018]      FIG. 6B  is a sectional view of the locking mechanism of  FIG. 6A . 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     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 structures. While the preferred embodiment has been described, the details may be changed without departing from the invention.  
         [0020]     A preferred embodiment of the invention is shown in photographs attached in the appendix.  
         [0021]      FIGS. 1A and 1B  show a preferred embodiment of the slotless locking pull pin of the present invention. The pull pin includes a handle  10 , a pin  12 , a locking mechanism  22 ,  24 , and a housing  16 . The housing  16  has a threaded portion  18  on at least one end portion thereof. The housing  16  further includes a bore extending through the housing  16 . The pin  12  is disposed within the bore in the housing  16 . The pin  12  is generally cylindrical and has a first end  20  which is normally located outside the threaded portion  18  of the housing  16  and a second end. The handle  10  is attached to the second end of the pin  12 . The handle  10  may be of any type commonly used in the art, including, but not limited to a pull ring or a pull bar.  
         [0022]     The locking mechanism shown in  FIGS. 1A and 1B  includes a locking plate  22  located in the housing  16  and locking portion  24  on the pin  12 . The locking plate  22  has an aperture through which the pin  12  extends. The pin  12  has a locking portion  24  which engages the locking plate  22  to hold the pin  12  in its retracted position. A spring  26  is also disposed within the housing  16  to bias the pin  12  to its normally extended position.  
         [0023]      FIG. 2  shows a first embodiment of a locking mechanism. The locking mechanism includes a plunger  124  disposed in a bore  130  in the pin  112 . The bore  130  extends partway through the pin  112 . The plunger  124  is slidably disposed in the bore  130 . Biasing means  132  are located below the plunger  124 . The biasing means  132  in the preferred embodiment is a coil spring; however other biasing means could be utilized including, but not limited to a leaf spring, compressible material, or elastic material. The biasing means  132  push the plunger  124  to its outwardly extending position where the plunger  124  extends from the surface of the pin  112 . The locking mechanism also includes a locking plate  122 . The locking plate  122  includes a circular hole which is sized just large enough for the pin  112  to fit through.  
         [0024]     In use, the operator either uses a tool to depress the plunger  124 , or depresses the plunger  124  by hand. Once the plunger  124  clears the locking plate  122 , the pin  112  will be returned to its normal extended position by the force of the spring  128  located within the housing  116 .  
         [0025]      FIG. 3  shows a second embodiment of the locking mechanism. In this embodiment, the locking plate  222  includes a keyhole shaped aperture. The pin  212  is provided with a protrusion  224  on its surface. The aperture is sized such that when the protrusion  224  is lined up with the notch  234  of the aperture the pin  212  can be slid through the aperture. In use, the protrusion  224  on the pin  212  is aligned with the notch  234  of the aperture and the pin  212  is pulled to its retracted position. The pin  212  is then rotated so that the aperture engages the locking plate  222 . The pin  212  can then be released and will stay in its locked position. To return the pin  212  to its extended position, the pin  212  is again rotated so that its protrusion  224  is aligned with the notch  234  of the aperture in the locking plate  222 . The pin  212  can then be released and the spring  228  within the housing  216  will return the pin  212  to its normal extended position.  
         [0026]      FIG. 4  shows a third embodiment of the locking mechanism. The embodiment of  FIG. 4  is similar to the embodiment of  FIG. 3 ; however, the embodiment shown in  FIG. 4  includes a plunger  324  disposed in a bore  330  in the pin  312 . The plunger  324  may have a ramped engaging surface which is used as a cam. The ramped engaging surface is proximate the surface of the pin on the side nearest the handle. The ramped engaging surface then extends upward, away from the surface of the pin  312 . This configuration allows the locking plate  322  to engage the ramping surface and depress the plunger  324  into the bore  330 . In this manner the pin  312  may be pulled to its retracted position without aligning the plunger  324  with the notch  334  of the aperture. The pin  312  may be retained in its retracted position by the plunger  324  engaging the locking plate  322 . The pin  312  may be returned to its extended position by rotating the pin  312  so the plunger  324  is aligned with the notch  334  of the aperture in the locking plate  322 . The pin  312  can then be released and the spring  328  within the housing  316  will return the pin  312  to its normal extended position.  
         [0027]      FIGS. 5A and 5B  show a fourth embodiment of a locking mechanism. This embodiment is also shown in  FIGS. 1A and 1B . This embodiment includes a plunger  424  disposed in a bore  430  in the pin  412 . The plunger  424  has a ramped engaging surface  436  which is used as a cam. The ramped engaging surface  436  is proximate the surface of the pin  412  on the side nearest the handle. The ramped engaging surface  436  then extends upward, away from the surface of the pin  412 . The locking plate  422  has a generally circular aperture which is sized such that the pin  412  fits through the aperture. This embodiment also includes a collar  428  which is slidably located on the pin  412  and is located between the handle and the housing  416 .  
         [0028]     In use, the pin  412  is pulled to its locked position. As the pin  412  is pulled, the ramped engaging surface  436  of the plunger  424  engages the inner surface of the aperture in the locking plate  422 . The force of the locking plate  422  causes the plunger  424  to be pushed inwardly into the bore  430 . Once the ramped engaging surface  436  clears the locking plate  422 , the plunger  424  pops back to its normal outwardly biased position. The engagement of the plunger  424  with the locking plate  422  locks the pin  412  and prevents the pin  412  from returning to its extended position.  
         [0029]     To return the pin  412  to its extended position, the collar  428  is pushed toward the housing  416 . As the collar  428  engages the ramped engaging surface  436  of the plunger  424 , the plunger  424  is pushed into the bore  430 . Once the plunger  424  is pushed below the surface of the pin  412 , the pin  412  will be returned to its normally extended position by the force of the spring  426  located in the housing  416 . Although the spring is not shown in this embodiment, the configuration of the spring is the same as the previous embodiments. After the plunger  424  clears the locking plate  422  the plunger  424  will pop back to its normal outwardly biased position.  
         [0030]      FIGS. 6A and 6B  show a fifth embodiment of a locking mechanism. This embodiment includes a plunger  524  disposed in a bore  530  in the pin  512 . The locking plate  522  has a generally circular aperture which is sized such that the pin  512  fits through the aperture. As shown in  FIG. 6B , the aperture in the locking plate  522  is conically shaped and includes a conical aperture surface  540 . This embodiment also includes a collar  528  which is slidably located on the pin  512  and is located between the handle and the housing  516 . As is seen in  FIG. 6B , the interior of the collar  528  has a conical shape similar to that of the locking plate  522 , and includes a collar conical surface  538 . The collar conical surface  538  and the conical aperture surfaces  540  act as cams.  
         [0031]     In use, the pin  512  is pulled to its locked position. As the pin  512  is pulled, the conical aperture surface  540  engages the leading edge of the plunger  524 . As the pin  512  is pulled, the plunger  524  is pushed into the bore  530 . Once the plunger  524  clears the locking plate  522 , the plunger  524  pops back to its normal outwardly biased position.  
         [0032]     To return the plunger  524  to its extended position, the collar  528  is pushed toward the housing  516 . As the collar conical surface  538  engages the plunger  524 , the plunger  524  is pushed into the bore  530 . Once the plunger  524  is pushed below the surface of the pin  512 , the pin  512  will be returned to its normally extended position by the force of the spring  526  located in the housing  516 . After the plunger  524  clears the locking plate  522  the plunger  524  will pop back to its normal outwardly biased position.  
         [0033]     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.