Abstract:
An improved shackle apparatus and a locking mechanism for the same. The shackle is of a thimble type design and includes a locking mechanism for locking the shackle open and closed. The shackle apparatus allows for secure locking, easier operation, higher strength and less susceptible to problems of wear. The locking mechanism includes a plunger pin connected to a knob that mates with the shackle body to prevent the plunger pin from rotating and/or retracting, and the shackle from opening. This design prevents the plunger from both rotational as well as translational movement during extreme flogging, dragging and impact to prevent accidental opening. The shackle can be operated with one hand for the inside surface of the hook is “proud” above the surface of the clevis. This arrangement transforms any force applied to the latching side of the shackle into a moment which helps the hook close and allows the plunger pin to be snapped closed with the use of one hand. Higher strength is accomplished by implementing a structural protrusion on the shackle body which interlocks with the hook and reduces shear stress on the plunger pin. Less susceptibility to problems of wear is accomplished by thinning the hook and providing a boss around its pivot so as to increase the clearance between any burrs or deformed metal on the clevis and hook.

Description:
FIELD OF THE INVENTION  
         [0001]    The invention relates to shackles used for joining two members under tension and more particularly to a locking shackle apparatus and a locking mechanism for the same.  
         BACKGROUND OF THE INVENTION  
         [0002]    The technique of attaching two members together under tension, such as a rope or cable, can be accomplished with the use of a shackle. In many instances such as in the field of sailing, it is desired to reduce to a minimum the distance between the attachment point of the line and the latching throat of the shackle. Such an instance occurs on a halyard when desiring to hoist the sail to the extreme top of the mast. In other instance, it is desired to reduce to a minimum the overall width and profile of the shackle such as to allow the shackle to pass through a Genoa block or other tight passage. In both cases, the desired arrangement consists of a thimble-like snap shackle onto which the line or cable can be directly spliced around its body.  
           [0003]    Thimble-like rope type snap shackles such as described are commercially available but have many drawbacks. First, they are often subject to violent flogging and impact against a mast or are repeatedly dragged across a deck. Existing snap shackles are extremely prone to accidentally popping open under such circumstances. This accidental opening is so common that the current “state of the art” procedure in the sailing industry has been to wrap masking tape around the shackle. A second drawback with current thimble type shackles is the difficulty in quickly opening or closing the shackle with limited sense of feel or sight. In many instances, sailors are in rough seas or are wearing gloves and it is not always possible to physically look at or feel the shackle when operating it. Existing thimble type shackles require the plunger knob to be precisely aligned before it can be operated, resulting in dangerous or inefficient situations. A third problem with existing thimble type rope shackles and with plunger pin shackles in general is that a high side loading is applied to the plunger pin. Frequently the plunger pin becomes permanently bent and the shackle is inoperative. Finally, a fourth problem with rope shackles and other shackles in general is the binding of the hook against deformed or fretted material along the inside of the clevis. After extended use, the constant pressure and sliding of a fitting latched to the shackle throat tends to deform and erode the material along the inside walls of the clevis slot. Eventually the clearance between the clevis wall and the pivoting hook decreases to a point where the hook begins to bind and no longer hinges correctly.  
           [0004]    The earliest attempt to solve some of these problems was with a J-Lock shackle containing a plunger pin. However, these shackles did not have any method of locking the pin into place. As a result, the plunger pin would often pop open during either severe flogging or when dragged across the deck. These old J-Locks were cast from bronze and were produced at least 40 years ago and by some account, perhaps up to 100 years ago.  
           [0005]    The next attempt to improve the shackle was a new design on the J-Lock that was made about 30 years ago. In this design, the knob on the plunger pin contained a notch, which had to be turned to the correct orientation so as to allow a keyway on the body to line up with the slot in the knob. To open the shackle, the knob would be turned to the correct orientation so as to allow the notch in the knob to pass over the keyway type protrusion on the body. To close the shackle, the notch would again be lined up, the plunger pin snapped shut, and the knob then turned to some random orientation so as to misalign the notch with the keyway protrusion.  
           [0006]    While this J-Lock design was an improvement over the earliest version, there are several drawbacks with this design. First, during flogging, the knob tended to rotate from vibration and eventually work its way to the orientation such that the notch and keyway line up. Then, the shackle would pop open. Second, when pulled over a deck, the knob tended to roll and invariably rotate to the “bad” orientation whereas it eventually pops open. For years, the solution to this rotation and vibration problem has been to wrap tape around the knob and shackle so as to lock it in place. The tape must be ripped off whenever the shackle must be opened, and re-tapped the next time it is shut. This is very inconvenient and can be very dangerous to sailors in rough waters, but has been the only way to prevent opening during flogging or handling. The procedure has been the “state of the art” for as long as most sailors can remember.  
           [0007]    Thirdly, this J-Lock design is very difficult to quickly line up the notch with the keyway so as to open the shackle in a hurry. When the existing J-Lock is snapped shut and the knob rotated to a random position, it is difficult to find the position that allows the notch to line back up again. One must look or feel for the notch and keyway orientation, usually whilst the user is with gloves and cold fingers. During a sailboat race it is next to impossible to visually observe the orientation of the knob. Thus, the alignment must be done by sense of feel alone and becomes very frustrating.  
           [0008]    A fourth problem with the existing J-Lock design pertains to the alignment of the knob. In many cases, it is desirable to be able to quickly shut the shackle by snapping the hook shut as is done on conventional pull pin shackles. This quick shutting feature is particularly desirable during fast paced sailboat races. With the existing J-Lock, one must first pre-align the knob notch with the protrusion on the body. Assuming no change in orientation occurs, one should then be able to simply snap the hook shut. The hook pushes onto the free end of the pull-pin, forcing the knob to lift up past the body protrusion and then snaps back shut again. This is what would ideally be desired. However, with the existing J-Lock design, even the pre-alignment does not always allow the shackle to operate as desired. The contact of the hook with the free end of the pull-pin sometimes imparts a rotation onto the pull-pin which in turn misaligns the notch on the knob with the protrusion on the body. As a result of this misalignment, the knob jams into the bottom of the body protrusion and will not snap shut. Such a problem is extremely frustrating and causes the loss of valuable time in a sailboat race.  
           [0009]    A fifth problem exists with the current J-Lock shackle. While loading a substantial amount of force onto the pull pin, the pull pin tends to bend and become permanently deformed. It any bending occurs, the pull pin cannot be slid open or closed and the shackle is destroyed.  
           [0010]    And finally, the existing J-Lock hook geometry at the location where the hook pivots through the clevis case fosters fretting and destroys the shackle with continued use. When the hook is shut and the shackle loaded, the loaded member exerting force against the inside surface of the J-Lock is usually a metal ring or other metal fitting. After continued use, fretting and wear on the body clevis and hook surface causes the clevis and hook base material to “roll over” on the edges. Burrs caused from this edge “roll over” eventually reduce the clearance so much that the hook binds inside the clevis and will no longer open or shut smoothly.  
           [0011]    Therefore a need exists in the art for an improved design of a shackle that will not accidentally open when exposed subject to violent flogging and impact against a mast or when repeatedly dragged across a boat deck, that overcomes the difficulty in quickly opening or closing the shackle with limited sense of feel or sight, that does not require high side loading to be applied to the plunger pin, and is not vulnerable to binding of the hook against deformed or fretted material along the inside of the shackle clevis.  
         SUMMARY OF THE INVENTION  
         [0012]    The present invention relates to a shackle with a locking mechanism, the shackle is composed of a shackle body having a hook opening with a shackle pivot hole, a plunger pin opening for a plunger pin with a corresponding plunger pin exit, an anti-rotation plunger means such that the plunger pin opening is located on the anti-rotation plunger means, a hook body having a pivotal end having two sides and a hook pivot hole and a locking end, the pivotal end being pivotally connected within the hook opening of the shackle body by a pivot pin extending through the shackle pivot hole and hook pivot hole, the locking end having a slot corresponding to the plunger pin opening. The plunger pin has a free end and a transition to a smaller end, the smaller end of the plunger pin is axially inserted into the slot of the hook body and extends into the plunger pin opening in the shackle body. The plunger pin has two positions such that the two positions form corresponding settings for the shackle, whereby a closed setting is formed when the free end rests in the slot of the hook body, and an open setting is formed when the free end remains in the shackle body. There is a spring positioned around the smaller end of the plunger pin and located inside the plunger pin opening in the shackle body and constrained by the corresponding plunger pin exit in the shackle body, whereby compression and release of the spring creates the positions of the plunger pin. There is a knob attached to the smaller end of the plunger pin and resting on the anti-rotation plunger means on the shackle body, the knob having an opening that accepts the plunger pin, and a mating means on an axial face which mates with the anti-rotation plunger means such that when the mating means and the anti-rotation plunger means mate the locking mechanism is created whereby the plunger pin is locked into the one of the two positions, lifting the knob compresses the spring and allows the position of the plunger pin to change to the other position.  
           [0013]    The present invention also relates to a locking mechanism for a shackle, the locking mechanism composed of a shackle plunger pin, the plunger pin has a free end and a transition to a smaller end. The locking mechanism is also composed of a spring positioned around the smaller end of the plunger pin, the plunger pin and spring located inside the shackle, the shackle has an anti-rotation plunger means and two positions, the positions are an open and a closed position. Also there is a knob attached to the smaller end of said plunger pin, the knob has an opening that accepts the plunger pin, and a mating means on an axial face which mates with the anti-rotation plunger means such that when the mating means and the anti-rotation plunger means mate the locking mechanism is created whereby the plunger pin is locked into a position. By lifting said knob compresses the spring and allows the position of said shackle to change to the other of the positions of the shackle.  
           [0014]    Therefore, it is an aspect of the invention to provide an improved shackle apparatus which overcomes the deficiencies of the prior art shackle design.  
           [0015]    It is another aspect of the invention to provide an improved shackle apparatus that simplifies the design of prior art shackle designs.  
           [0016]    It is another aspect of the invention to provide an improved shackle apparatus that resists opening during flogging, impact or when dragged over a surface.  
           [0017]    It is another aspect of the invention to provide a means of securing the plunger from motion by the use of a locking arrangement.  
           [0018]    It is another aspect of the invention to provide an improved shackle apparatus that contains a “double locking” plunger pin which is constrained from moving in both rotational and translational directions.  
           [0019]    It is another aspect of the invention to provide an improved shackle apparatus that self-aligns the plunger knob so as to allow easy opening with limited reliance on sight and feel.  
           [0020]    It is another aspect of the invention to provide an improved shackle apparatus that self-aligns the plunger knob so as to allow easy closing with limited reliance on sight and feel.  
           [0021]    It is another aspect of the invention to provide an improved shackle apparatus that contains a plunger knob which can be rotated and placed in a “locked” position which resists both translational and rotational motion.  
           [0022]    It is another aspect of the invention to provide an improved shackle apparatus that contains a knob which contains a mating means that can mate with an anti-rotation plunger means on the shackle body and prevent retraction of the plunger pin by preventing both rotation and lifting of the knob.  
           [0023]    It is another aspect of the invention to provide an improved shackle apparatus that contains a plunger knob which is partially restrained from rotational motion when the shackle is being snapped shut so as to prevent the plunger knob from accidentally rotating into a misaligned position due to rotational force imparted to the free end of the plunger pin by contact from the closing hook.  
           [0024]    It is another aspect of the invention to provide an improved shackle apparatus that contains a structural protrusion between the shackle body and the hook body so as to reduce the amount of stress carried by the plunger pin and increase the overall strength of the shackle.  
           [0025]    It is another aspect of the invention to provide an improved shackle apparatus that consists of a hook opening which contains a contact surface which is “proud” with respect to the surface of the shackle clevis so as to allow any applied force to aid in holding the hook against the shackle body when the plunger pin is snapped closed.  
           [0026]    It is another aspect of the invention to provide an improved shackle apparatus that allows a rope or cable to be directly spliced over the body.  
           [0027]    It is another aspect of the invention to provide an improved shackle apparatus that can be passed through a pulley block or other tight passage.  
           [0028]    It is another aspect of the invention to provide an improved shackle apparatus that contains a minimal distance between the spliced attachment point and the member which the shackle attaches to.  
           [0029]    It is another aspect of the invention to provide an improved shackle apparatus which can be set into in a locked and secured state so as to allow the user to be aware of the engagement of the locked state with a minimal reliance on sight or feel.  
           [0030]    It is another aspect of the invention to provide an improved shackle apparatus which can be easily switched from an unlocked state to a locked state and vise versa.  
           [0031]    It is another aspect of the invention to provide an improved shackle apparatus which resists opening due to accelerations in any translational or rotational direction.  
           [0032]    It is final another aspect of the invention to provide an improved shackle apparatus that attempts to reduce binding of the hook inside the clevis due to wear or fretting.  
           [0033]    These aspects of the invention are not meant to be exclusive and other features, aspects, and advantages of the present invention will be readily apparent to those of ordinary skill in the art when read in conjunction with the following description, appended claims and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0034]    [0034]FIG. 1 is an isometric view of the shackle apparatus in its assemble configuration.  
         [0035]    [0035]FIG. 2 is an isometric view of the shackle body.  
         [0036]    [0036]FIG. 3 is a top view of the shackle body.  
         [0037]    [0037]FIG. 4 is a bottom view of the shackle body.  
         [0038]    [0038]FIG. 5 is an isometric view of the hook body.  
         [0039]    [0039]FIG. 6 is a top view of the hook body.  
         [0040]    [0040]FIG. 7 is a side view of the hook body.  
         [0041]    [0041]FIG. 8 is an isometric view of the plunger pin and knob.  
         [0042]    [0042]FIG. 9 is a side view of the plunger pin and knob.  
         [0043]    [0043]FIG. 10 is a top view of the plunger pin and knob.  
         [0044]    [0044]FIG. 11 is a bottom view of the plunger pin and knob.  
         [0045]    [0045]FIG. 12 is a top view of the assembled shackle with the plunger knob in the open position.  
         [0046]    [0046]FIG. 13 is a top view of the shackle apparatus with the knob in the closed position.  
         [0047]    FIGS.  14 - 16  are isometric views of the shackle displaying the method of locking the plunger knob.  
         [0048]    FIGS.  17 - 19  are side views of the shackle apparatus with the hook in the open position.  
         [0049]    FIGS.  20 - 22  are isometric views of the shackle apparatus detailing the shackle body inside wall clevis and pivotal end of hook body.  
         [0050]    [0050]FIG. 23 is a side view of the plunger pin.  
         [0051]    [0051]FIG. 24 is a side view of the pivot pin. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0052]    Referring first to FIG. 1, an isometric view of the locking shackle apparatus  10  is shown. The shackle apparatus  10  is a thimble type shackle apparatus, where the shackle apparatus  10  shape is optimized to meet space requirements. The shackle apparatus  10  is designed to be used on the ends of Genoa sheets and is spliced onto the line around the thimble shape  32  shape section of the shackle body  20  and has a small enough profile that it can actually be fed through the Genoa block. This allows the sheet to be changed from one side of the boat to another without having to feed all the line back through the pulley. As the shackle apparatus  10  fits through the block, the end of the sheet is merely pulled through one block and then fed through the block on the other side of the boat. This drastically speeds up tacking and is very beneficial on racing yachts.  
         [0053]    The shackle apparatus  10  is entirely constructed from high strength stainless steel. In other embodiments, other types of material known by those of ordinary skill in the art that are equally durable are used to manufacture the shackle apparatus  10 . These materials include titanium, aluminum, plastics and nickel-plated steel. The surfaces of the shackle apparatus  10  are highly polished to resist corrosion. In its preferred embodiment, the shackle apparatus has a total width of about 3 inches, a height of about 1½ inches and a depth of about ⅝ inches. In other embodiments the width, height and depth are larger or smaller, but the preferred embodiment ratios are basically consistent.  
         [0054]    Shackle apparatus  10  consists of shackle body  20 , a hook body  40 , where the hook body  40  is attached to the shackle body  20  by a plunger pin  68 . Referring next to FIG. 2, the shackle body  20  has a plunger pin opening  24  for a plunger pin  68 , a shackle body lip  26 , an inside wall clevis  28 , and a structural protrusion  30 . In the preferred embodiment, the shackle body&#39;s dimensions are about 3 inches in width, about 1½ inches in height and about ⅝ inches in depth, but in other embodiments the overall dimension of the shackle body  20  is larger or smaller, but the width to height to depth ratio remains basically the same. The plunger pin opening  24  is dimensioned according to the size of the plunger pin  68  used in constructing the shackle apparatus  10 . The plunger pin opening extends through the shackle body  20  and has a plunger pin exit  23 .  
         [0055]    Referring next to FIGS. 5, 6, and  7 , the hook body  40  consists of a pivotal end  41 , a locking end  43 , a hook body slot  44 , a hook body opening  42 , a proud surface  50 , and an outside hook surface  46 . The hook body opening  42  corresponds to plunger pin exit  23  shown in FIG. 4. The hook body slot  44  corresponds to the structural protrusion  30  shown in FIGS. 2 and 4. The hook body  40  is dimensioned such that it&#39;s length corresponds to the length of the shackle body  20 . The width of the hook body  40  is dimensioned so that the pivotal end  41  fits between the inside walls of clevis  28  in FIG. 2.  
         [0056]    Referring now to FIG. 23, the plunger pin  68  has a free end  70  dimensioned such that it corresponds to hook body opening  42 . The plunger pin has a transition section  72 , and a smaller end  74 . The smaller end  74  is dimensioned such that it corresponds to the plunger pin slot  24  in the shackle body  20 . In its preferred embodiment, the plunger pin is cylindrical, but in other embodiments, the plunger pin may be of another appropriate shape. In the preferred embodiment, the plunger pin free end  70  has a diameter of approximately {fraction (5/16)} inches and a length of approximately {fraction (9/16)} inches, the transition section  72  a diameter of approximately {fraction (7/32)} inches and a length of approximately {fraction (25/32)} inches, and a smaller end  74  diameter of approximately {fraction (5/32)} inches with a length of approximately {fraction (5/32)} inches. The total length of the plunger pin  68  corresponds to the size of the shackle apparatus  10 .  
         [0057]    Referring next to FIGS. 10 and 11, the knob  62  is shown. In its preferred embodiment, the knob  62  is concentric and has an opening  80  in its center. The opening  80  is designed and dimensioned such that it corresponds with the smaller end  74  of the plunger pin  68  as shown in FIG. 23. In its preferred embodiment, the opening  80  is round, but in other embodiments, the opening  80  is the same shape as the smaller end  74  of the plunger pin  68 , thus corresponding to the other embodiments of the smaller end  74  of the plunger  68 . In its preferred embodiment, the knob  62  has a notch  64  on a radial side. Referring to FIG. 11, the bottom view of the knob, mating means  66  are shown.  
         [0058]    Referring now to FIG. 24, the pivot pin  78  has two sides  86  and a connecting pin  88 . In the preferred embodiment, the two sides are round and dimensioned such that they are slightly larger than the shackle pivot hole  25 . The preferred embodiment of the pivot pin  78  is about {fraction (5/16)} inches in diameter and about ¾ inches long. In other embodiments, the sides  86  are square, triangular, or any other geometric shape that is used by those in the art. The connecting pin is cylindrical and in its preferred embodiment has dimensions of about {fraction (5/16)} inches in diameter by about ¾ inches in length. In other embodiments, the dimensions increase or decrease depending on the size of the shackle apparatus  10  and the size of the shackle pivot hole  25  and hook pivot hole  45 .  
         [0059]    Referring next to FIG. 8, the assembled knob  62  and plunger pin  68  are shown, with the spring  71  around the plunger pin  68  to form the plunger assembly  60 . The spring  71  is shown around the transitional section  72  of the plunger pin  68 . In the preferred embodiment, the spring  71  has a pitch of X and a spring constant k between 6 and 7 lb. per inch. The outer diameter of the spring  71  is about 0.30 inches, and the inner diameter of the spring  71  is about 0.24 inches and the spring  71  wire diameter is approximately 0.03 inches. Thus, the spring  71  exerts a force of 6.7 lb. per inch. In other embodiments, the force of the spring  71  remains the same, but the dimensions of the spring vary to correspond with the alternative embodiments of the plunger pin  68 . But, in all embodiments, the spring  71  is dimensioned such that it fits around the transitional section  72  of the plunger pin  68  so as to allow the plunger pin  68  to move freely. In its preferred embodiment, the spring assembly is accomplished by inserting the smaller end  74  of plunger pin  68  through the spring  71  and into the opening  80  of the knob  62 .  
         [0060]    Referring next to FIG. 4, the spring  71  is located inside the plunger pin opening  24  of the shackle body  20 . The spring  71  will accept the plunger pin  68  smaller end  74  and then the plunger pin  68  transition section  72 . The spring  71  is designed to properly accept and remain around the transition section  72  of the plunger pin  68  and stay inside the plunger pin opening  24  in the shackle body  20 .  
         [0061]    The shackle apparatus  10  is easily assembled through a process of simple steps. Referring first to FIG. 20, the pivotal end  41  of the hook body  40  is placed into the inside wall clevis  28  of shackle body  20 . The pivot pin  78  is then inserted through the shackle pivot hole  25 , into the hook pivot hole  45 , and finally through the other shackle pivot hole  25 . In its preferred embodiment, the shackle pivot hole  25  is round with a diameter of about {fraction (5/16)} inches. The hook pivot hole  45  has identical dimensions to the shackle pivot hole. In other embodiments, the pivot hole is larger or smaller than the preferred embodiment.  
         [0062]    Referring next to FIG. 5, the smaller end  74  of the plunger pin  68  is placed through hook body opening  42  on hook body  40 . Referring now to FIG. 2, the smaller end  74  of the plunger pin  68  is then placed through the plunger pin exit  23  on the shackle body  20 . The smaller end  74  then emerges through plunger pin opening  24 , shown in FIG. 3. The knob  62  is placed over the smaller end  74  and the smaller end  74  is inserted into the knob opening  80 .  
         [0063]    Referring now to FIG. 1, the shackle apparatus  10  is shown in its assembled and closed setting. The structural protrusion  30  rests in the hook body slot  44 , and the free end  70  of the plunger pin  68  rests in the hook body opening  42 . The structural protrusion  30  in the preferred embodiment has dimensions of approximately {fraction (9/32)} inches tall, about {fraction (3/16)} inches wide and about {fraction (7/16)} inches deep. The structural protrusion  30  is just slightly smaller than the hook body slot  44 . The structural protrusion  30  acts to isolate forces applied to the shackle apparatus  10  and prevent bending of the plunger pin  68 . The hook body slot  44  is located just in front of the hook body opening  42 , which houses the plunger pin  68  in the shackle apparatus  10  closed setting. When the shackle apparatus  10  is loaded, the resulting strain causes the hook body  40  to yield until the hook body slot  44  contacts the structural protrusion  30 . At this point, the majority of any additional loading is taken up by the structural protrusion  30  and not by the plunger pin  68 . This arrangement allows the shackle apparatus  10  to handle a higher load without the plunger pin  68  becoming permanently damaged. Additionally, during a catastrophic loading, the structural protrusion  30  increases the overall breaking strength of the shackle apparatus  10  considerably.  
         [0064]    Referring again to FIG. 7, the hook body  40  has an outside surface  48 . This outside surface  48  serves to reduce the effect of plastic deformation and metal “roll over” on the inside wall clevis  28  on the shackle body  20 . Referring now to FIG. 21, the assembled shackle apparatus  10  is shown in an isometric view of the hook body  40  on the inside wall clevis  28  of the shackle body  20 . The outside surface  48  provides adequate clearance between the inside wall clevis  28  because of the implementation of hook boss  21  located on either side of pivot hole  45 . This adequate clearance avoids jamming of the shackle apparatus  10  caused by burrs formed from “roll over”.  
         [0065]    The shackle apparatus  10  has a locking mechanism. Referring now to FIG. 3, the shackle body  20  has an anti-rotation plunger means  22 . This anti-rotation plunger means  22  works in consortium with the mating means  66  on the underside of the knob  62  pictured in FIG. 11. Referring now to FIG. 12, working together, the anti-rotation plunger means  22  and the mating means  66  work to prevent the rotation of the plunger pin  68  so that notch  64  does not line up with lip  26 . Lip  26  prevents the retraction of plunger pin  68  so long as notch  64  is not rotated under lip  26 . This consortium formed between the anti-rotation plunger means  22  and the mating means  66  form the locking mechanism of the shackle apparatus  10 .  
         [0066]    Referring again to FIG. 3, in the preferred embodiment, the anti-rotation mating means  22  is a positive key-type protrusion on either side of the plunger pin opening  24 . Now, referring to FIG. 11, the mating means  66  are keyway slots on the underside of the knob  62 . These mating means  66  can straddle the positive key-type protrusions that are the anti-rotation plunger means  22  and form a locking mechanism. In all other embodiments, the anti-rotation plunger means and the mating means are any design that prevent the knob  62  from rotating, and therefore allow lip  26  to prevent the plunger pin  68  from retracting. It is not necessary in alternate embodiments that the knob rotate 180 degrees to lock or unlock, but rather, just that there be varying positions alternating from lock to unlock reached by rotating the knob around its axis. In all embodiments, the anti-rotation plunger means  22  and the mating means  66  mate, and therefore possess corresponding mating structural patterns. Other embodiments include serrations or a multiple set of grooves under the knob  62  acting as mating means  66 , corresponding to serrations or multiple sets of grooves as the anti-rotation plunger means  22  surface. Other embodiments include a square or other geometric shaped protrusions with 90 degree angles protruding up from and forming the anti-rotation plunger means  22 , and corresponding holes acting as the mating means  66  on the underside of the knob  62 , as well as any kinematic inversion of the mechanism, i.e. instead of a notch in the knob to fit into a keyway on the shackle body, placing the notch on the shackle body to fit into a keyway in the knob. Many other embodiments are possible, and will be readily apparent to those skilled in the art, but in any embodiment, the anti-rotation plunger means  22  and the mating means  66  act in consortium to prevent non-voluntary rotation of the knob  62 .  
         [0067]    Referring now to FIG. 12, the knob  62  and the mating means  66  fit over anti-rotation plunger means  22  on the shackle body  20 . When the knob  62  is twisted such that the mating means  66  and the anti-rotation plunger means  22  mate, the spring  71  in the plunger pin opening  24  pulls the knob  62  down onto the anti-rotation plunger means  22  and locks the knob  62  from further rotating. The knob  62  can seat onto the anti-rotation plunger means  22  in two orientations, zero degrees and 180 degrees. Zero degrees will be assumed to be the orientation where the notch  64  lines up with the shackle body lip  26  and 180 degrees will be assumed to be where the notch  64  is opposite the shackle body lip  26 . Once the anti-rotation plunger means  22  and the mating means  66  are mating, the knob  62  will become locked in place. Thus, the plunger pin  68  will be locked in place as well, locking the shackle apparatus  10  either in the open setting or the closed setting. The anti-rotation plunger means  22  and the mating means  66  working together serve beneficial purposes. First, when the knob  62  is turned to zero degrees the anti-rotation plunger means  22  forces the notch  64  to automatically line up with the shackle body lip  26 . In this orientation, it is very easy to pull the plunger pin  68  to open the shackle apparatus  10  as everything is perfectly lined up. No guesswork or feeling around is required. Thus, the shackle can be snapped shut without the user having to fiddle with the knob  62  orientation. Second, when the knob  62  is lifted slightly and then turned 180 degrees, it seats back down onto the anti-rotation plunger means  22  and locks in place from any rotation. In this orientation, the plunger pin  68  can not accidentally rotate into a position to pop open. During extreme flogging, even if the knob  62  ever does manage to pop off the bottom anti-rotation plunger means  22  temporarily, it then tends to settle back and pop onto the anti-rotation plunger means  22  again to lock into place. One reason the knob  62  does not twist and work its way around to unlock position when the knob  62  is turned such that it is not engaged in the anti-rotation plunger means  22  is that the travel that it can move in the axial direction is very small. Because of this small travel in the engaged position, the knob  62 /plunger pin  68  assembly does not gather enough inertia during flogging to work its way around or off the anti-rotation plunger means  22 .  
         [0068]    Referring to FIG. 12, in the preferred embodiment, the locking mechanism works in consortium with the notch  64  and the shackle body lip  26 , providing an increases security system which ensures that the shackle apparatus  10  remains in the desired setting regardless of accidental knocking and bumping. In the unlocked position, the anti-rotation plunger means  22  and the mating means  66  are mating. The notch  64  is lined up under the shackle body lip  26 . The knob  62  is therefore free to be lifted upwards, causing the spring  71  to compress. The unlocked position allows for the changing of shackle apparatus  10  settings from closed to open or from open to closed. Thus, in this position, notch  64  can pass past the shackle body lip  26 . Mating means  66  seat on top of the anti-rotation plunger means  22  to hold knob  62  in its particular aligned orientation.  
         [0069]    FIGS.  14 - 16  illustrates the process of changing the knob  62  from the unlocked to locked position. Referring to FIG. 14, the shackle apparatus  10  is in the closed setting, and the knob  62  is in the unlocked orientation, for the notch  64  and the shackle body lip  26  are aligned. The anti-rotation plunger means  22  and the mating means  66  are mating, and the notch  64  is lined up under the structural protrusion  26 . Referring next to FIG. 15, the knob  62  has been lifted upward enough by resisting pretension from spring  71  such that the mating means  66  are raised up above the anti-rotation plunger means  22 . The arrow illustrates the movement of the knob  62  to complete the rotation. Knob  62  is dimensioned such that the thickness provides that when the mating means  66  are raised above the anti-rotation plunger means  22 , the top surface of the knob  62  still has a slight clearance between the shackle body lip  26 . Knob  62  is then rotated 180 degrees such that mating means  66  again mate with anti-rotation plunger means  22 . Referring now to FIG. 16, the knob  62  has been released and the spring  71  makes it possible for the knob  62  to snap back down to meet the anti-rotation plunger means  22 , as illustrated by the arrow. In this orientation, the notch  64  is not lined up under the shackle body lip  26 , and can no longer pass past the shackle body lip  26 . Knob  62  is constrained from translation by shackle body lip  26  and from rotation by the interference between mating means  66  and the anti-rotation plunger means  22 . Spring  71  provides a pretension to secure knob  62  against the anti-rotation plunger means  22 . Therefore, the knob is unable to be lifted accidentally, and the shackle apparatus  10  will remain in the current setting until such time that a user chooses to unlock the shackle apparatus  10  and change the setting.  
         [0070]    Referring to FIGS.  17 - 19 , the locking procedure of the shackle apparatus  10  is illustrated as well as the change of settings of the shackle apparatus  10  from open to closed. To change the setting of the shackle apparatus  10 , the locking mechanism must be unlocked. The unlocking is done as follows. Referring first to FIG. 17, the shackle apparatus is in the closed setting. To change the setting to open, the user must lift the knob  62  upwards, disengaging the plunger pin  68  from the hook body opening  42 . The spring  71  is compressed. Once the knob  62  is lifted to its highest position, during rotation of the knob  62  so that the notch  64  is not aligned with the shackle body lip  26 , the knob  62  will rest on the shackle body lip  26 , preventing the snapping back of the knob  62 , and thereby allowing for one-handed manipulation of the shackle apparatus  10  and the line, and then a quick one-hand closing of the shackle apparatus  10 . Referring next to FIG. 18, the hook body  40  is pivoted to form the open setting of the shackle apparatus  10 . Referring now to FIG. 19, when the shackle apparatus  10  is to be placed back to the closed setting, the proud surface  50  of the hook body  40  contacts the free end  70  of the plunger pin  68  and compresses the spring  71  to push the plunger pin  68  into the plunger pin opening  24 . As the hook body  40  pushes the plunger pin  68  into the plunger pin opening  24 , the mating means  66  on the knob  62  and the anti-rotation plunger means  22  resist any twisting of the plunger pin  68  due to unsymmetrical or off center forces imparted by contact with hook proud surface  50 . As a result of the guiding created by the mating means  66  against the anti-rotation plunger means  22 , the knob  62  with its corresponding notch  64  retains its proper orientation with respect to the shackle body lip  26 . This characteristic allows the shackle apparatus  10  to be snapped shut by merely rotating the hook body  40  into the plunger pin  68 . Knob  62  does not have to be pre-aligned with respect to the shackle body lip  26  due to the built-in pre-alignment inherent with the configuration. As a result, shackle apparatus  10  can be closed without excess need of physically seeing or feeling the knob orientation. As the hook body  40  is further closed against the shackle body  20 , the free end  70  of the plunger pin  68  pops into the hook body opening  42 , effectively securing the shackle apparatus  10  into the closed setting. At this stage, knob  62  can be lifted, rotated 180 degrees and set back down again mating the anti-rotation plunger means  22  with the mating means  66  so as to place shackle apparatus  10  in a locked state.  
         [0071]    [0071]FIG. 20 and FIG. 19 demonstrate that hook surface  50  is raised or “proud” with respect to the inside wall clevis  28  of the shackle body  20  when the shackle apparatus  10  is in the closed position. This proud arrangement is very subtle, but provides a great benefit. When the shackle apparatus  10  is in use, the sailor is usually unable to use two hands for most operations as one hand is required to hang onto the boat. Assume that the sailor has pulled the plunger pin  68  all the way open so far that the knob  62  is resting above the shackle body lip  26 . In this position, if the knob  62  is turned back so that the notch  64  aligns with the shackle body lip  26 , the plunger pin  68  will snap shut. With the “proud” surface  50  of the hook body  40 , any force created by pulling on the knob  62  helps hold the hook body  40  in a close position. Then, the plunger pin  68  is turned and allowed to snap down, and the shackle apparatus  10  will close. The “proud” surface  50  creates a rotation movement which will hold the hook body  40  firmly against the shackle body  20  at the area where the plunger pin  68  engages the hook body opening  42 , which will allow for snap closing. This becomes even more important for quick closing of the shackle apparatus  10  during sailboat racing or where only one hand of the sailor is available.  
         [0072]    Although the present invention has been described in considerable detail with reference to certain preferred versions thereof, other versions would be readily apparent to those of ordinary skill in the art. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained herein.