Abstract:
A folding knife that uses a four bar linkage mechanism to open and close. The knife can include a means of one hand opening and closing as well as a means to become latched in, and released from, a fixed position. The four bar linkage knife includes a blade, a handle, and the motion of a four bar linkage to open and close the knife. The four bar knife provides inherent safety because the four bar linkage motion can not fold onto the users hand.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    1. Field of the Invention 
         [0002]    This invention relates to a folding knife having a four bar and four pivot mechanical linkage. Particularly to a knife utilizing the motion of the four bar mechanical linkage to rearrange the components of the knife into the open and closed positions. 
         [0003]    2. Description of Prior Art 
         [0004]    An advantage of folding knives is that the sheath protecting the blade is attached to the blade and cannot be lost. A disadvantage of folding knives in general is the possibility of catching a finger between the blade and handle as the blade folds sharp side first into the handle with a scissoring motion as the knife closes. Secondly, all the loads encountered during use of a folding knife bear on the single main pivot and require that the single pivot be of significant strength to prevent the knife from breaking. 
       SUMMARY OF THE INVENTION 
       [0005]    The present invention is a knife with a parallelogram-like mechanical linkage having four bars and four pivots. Extending from one bar of the linkage is a blade and extending from the opposite bar of the parallelogram is the sheath. The two bars of the linkage that connect the blade to the sheath are the forward half and rear half of the handle and rotate in the same direction with each other to sheath and un-sheath the blade. When the knife is open the bars of the parallelogram that are the handle pieces align and become the handle with the sheath being hidden inside the handle. When closing the knife the sheath covers the blade in a non scissoring motion as the handle sections rotate in the same direction until the sheath fully covers the blade. 
         [0006]    The four bar four pivot mechanical linkage is also used as a knife in the anti-parallel format where the bars linking the blade to the handle rotate in opposite directions as they carry the blade in and out of the handle, the bar having the blade being opposite to the bar having the handle. The blade of the anti-parallel knife is pointed in the same direction inside the handle as it is outside the handle when open. Additionally the blade pivots in and out of the handle from a virtual pivot point created by the anti-parallel four bar four pivot linkage. The blade pivots in one direction, then back in the other direction as it enters the handle without the scissoring motion associated with folding knives in general. 
         [0007]    The mechanical structure of the four bar knife, in both parallel and anti-parallel formats, offers safety because the blade cannot fold onto the users hand during closing. Stability of the blade is increased by having two longitudinally oriented pivot points on the tang of the blade thus reducing the structural requirements of the pivot mechanisms. 
         [0008]    An object of this invention is a self sheathing knife that has the safety feature of not allowing the users hand to be caught between the blade and the handle either during use or during closing. 
         [0009]    Another object of this invention is a knife that can be easily mass produced by existing common fabrication methods. 
         [0010]    These and other objects of the present invention will become apparent to those skilled in the art upon reading the accompanying description, drawings, and claims put forth herein. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0011]      FIG. 1  is a side section view of a four bar parallel linkage knife in the open position;  FIG. 1A  shows the knife in the two thirds open position;  FIG. 1B  shows the knife in the one third open position; and  FIG. 1C  shows the knife in the closed position. 
           [0012]      FIG. 2  shows a parallel four bar linkage overlaying the  FIG. 1  knife;  FIG. 2A  shows the four bar linkage overlaying the  FIG. 1A  knife;  FIG. 2B  shows the four bar linkage overlaying the  FIG. 1B  knife; and  FIG. 2C  shows the four bar linkage overlaying the  FIG. 1C  knife. 
           [0013]      FIG. 3  is an exploded view of a parallel four bar linkage knife; and  FIG. 3A  shows the  FIG. 3  knife assembled. 
           [0014]      FIG. 4  shows the parallel four bar linkage knife closed with a section line indicating the location of the  FIG. 4A  detail; and  FIG. 4A  shows the detail of a latch mechanism. 
           [0015]      FIG. 5  shows how the closed knife is held in order to open the knife;  FIG. 5A  shows the knife held one third open;  FIG. 5B  shows the knife held two thirds open; and  FIG. 5C  shows the knife held fully open. 
           [0016]      FIG. 6  shows an anti-parallel four bar linkage overlaying an anti-parallel linkage knife fully open;  FIG. 6A  shows the linkage overlaying the knife three quarters open;  FIG. 6B  shows the linkage overlaying the knife half open;  FIG. 6C  shows the linkage overlaying the knife one quarter open; and  FIG. 6D  shows the linkage overlaying the knife fully closed. 
           [0017]      FIG. 7  is a side section view of an anti-parallel four bar linkage knife open;  FIG. 7A  shows the knife three quarters open;  FIG. 7B  shows the knife half open;  FIG. 7C  shows the knife one quarter open; and  FIG. 7D  shows the knife closed. 
           [0018]      FIG. 8  is a side section view of an anti-parallel four bar linkage knife in the open position with an alternate opening tab;  FIG. 8A  shows the knife three quarters open;  FIG. 8B  shows the knife half open;  FIG. 8C  shows the knife one quarter open;  FIG. 8D  shows the knife closed; and  FIG. 8E  shows the knife half open with an additional latch. 
           [0019]      FIG. 9  is an exploded view the knife seen in  FIG. 7D ; and  FIG. 9A  shows the knife assembled. 
           [0020]      FIG. 10  is an exploded view of the knife seen in  FIG. 8 ; and  FIG. 10A  shows the knife assembled. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0021]    In the following description and accompanying drawings the working properties and details of the invention are set forth in order to provide one skilled in the art to utilize the working properties of the invention without these details. The details and materials are used as examples and are not intended to limit the scope of the invention. 
         [0022]      FIG. 1  depicts a side section view of a parallel four bar linkage knife in the open position and with the sheath component  4  hidden behind the handle components  2  and  3 . The sheath  6  component  23  is also contacting bushing  13  whereby said contact provides a stop for the parallelogram motion of the knife when opening. The handle components  2  and  3  are aligned together being the handle of the knife when the knife is open. In  FIG. 1  pin  22  is shown in contact with blade  1  thereby providing an additional stop for the parallelogram motion at the open position.  FIG. 1A  shows said knife in a one third closed position with handle pieces  2  and  3  both rotated counterclockwise and the sheath component  6  partially covering the blade  1 .  FIG. 1B  depicts said knife in a two thirds closed position with handle pieces  2  and  3  both rotated further counterclockwise and the sheath component  6  mostly covering the blade  1 .  FIG. 1C  depicts said knife fully closed with a bushing  20  shown contacting the blade  1  thereby providing a stop for the parallelogram motion when the knife is closed. 
         [0023]      FIG. 2  depicts a parallel four bar linkage overlaying the knife of the present invention whereby each bar can be seen associated with a corresponding component of the knife. The blade  1  is part of bar B 1 . Handle piece  2  is part of bar B 2 . Handle piece  3  is part of bar B 3 , and the blade sheath  6  is incorporated into bar B 6 .  FIG. 2A  depicts the position of the parallelogram bars one third closed.  FIG. 2B  depicts the parallelogram position of the four bar knife two thirds closed.  FIG. 2C  depicts the parallelogram structure of the knife in the closed position. 
         [0024]      FIG. 3  depicts the detailed assembly of the present invention. A blade  1  connecting to handle components  2  and  4  by pin  8 . The blade  1  also connecting to handle components  3  and  5  by pin  9 . Pin  8  and pin  9  moving freely in the blade  1  and attached securely in the handle components  2  and  4 , and  3  and  5  respectively. Bushings  12 ,  13 ,  14 , and  15  provide sufficient clearance between the blade  1  and the handle components  2 ,  3 ,  6 , and  7  for sheath components  6  and  7  to move between without interference. Handle components  2  and  4  are connecting to sheath components  6  and  7  by pin  10 . Pin  10  is attached securely to handle components  2  and  7  but moves freely in sheath components  6  and  7 . Handle components  3  and  5  are connected also to te sheath components  6  and  7  by pin  11 . Pin  11  is securely attached to handle pieces  3  and  5  and moving freely in sheath pieces  6  and  7 . Preventing interference between handle pieces  2  and  3 , and the sheath piece  6  are washers  16  and  17  respectively. Preventing interference between handle pieces  4  and  5 , and the sheath piece  7  are washers  18  and  19  respectively. Bushings  21  and  22  between sheath pieces  6  and  7  are of sufficient thickness allow motion between the blade  1  and the sheath pieces  6  and  7  without interference. The pin  22  is anchored securely in the sheath pieces  6  and  7 .  FIG. 3A  depicts the knife complete. 
         [0025]      FIG. 4  is the same as  FIG. 1C  but with a section line  4 A and section area referring to  FIG. 4A .  FIG. 4A  illustrates a latching mechanism of claim  6  whereby the flexible appendage  25  of sheath  6  is abutting the deflected corner  26  of handle piece  3  and thereby cannot move past feature  26 . Flexible appendage  24 , part of handle piece  3 , is depressed to alternate position  24 A by the users thumb,  FIG. 5 . Appendage  24  in turn pressing appendage  25  bellow the level of the corner  26  and allowing  25  to move past corner  26  to position  25 A and beyond thus unlocking the knife from a closed position. When latching appendage is moving from  25 A to the position shown in solid lines,  25 , the appendage flexes down as it slides past corner  26  then flexing immediately up and abutting the corner  26  thereby locking the knife closed. 
         [0026]      FIG. 5  depicts a method of opening the invented knife by holding the invention by the back handle piece between the thumb and fore finger. Then squeezing appendage  24  thereby releasing the latch and allowing the knife to swing through positions  FIG. 5A  and  FIG. 5B  and into the open position  FIG. 5C . Swinging the knife back through position  FIG. 5B  to  FIG. 5A  then to position  FIG. 5  closes the knife engaging the latch of  FIG. 4A  locking the knife closed. 
         [0027]      FIG. 6  depicts a four bar anti-parallel linkage numbered with the prefix b and overlaying an outline of the knife handle  34  and blade  30 . Bars b 2  and b 4  are the links that connect the bar b 1 , which carries the blade, to bar b 3  which is the handle. The  FIG. 6  series of figures shows a motion of a four bar anti-parallel linkage that moves a blade  30  in and out of a handle/sheath  33 .  FIG. 6A  shows a one quarter closed position.  FIG. 6B  the knife is half closed and the bar b 1 , that carries the blade  30 , and the bar b 3 , that carries the handle, are in the anti-parallel position.  FIG. 6C  shows the knife three quarters closed.  FIG. 6D  the knife is closed with the blade  30  fully within the handle  33 . 
         [0028]      FIG. 7  is a transparent side view of an anti-parallel four bar knife in a five position sequence from open to closed. The sequence depicts the positions of the blade  30 , relative to the handle  33  as carried by the two links  31  and  32 . A post  39  is shown at the end of opening  40  whereby the ends of opening  40  limit the travel of post  39 . Post  39  is attached to the blade  30  and is used to push the knife open and closed.  FIG. 7A  shows the knife beginning to close,  FIG. 7B  the knife is half closed, and  FIG. 7  three quarters closed, and  FIG. 7D  fully closed. 
         [0029]      FIG. 8  is view of an anti-parallel four bar knife and differs from the knife of  FIG. 7  in the method of operation wherein the lever  51 , used to open and close the  FIG. 8  knife, is an appendage of linking bar  43 . The lever  51  protrudes through the opening  50  in handle piece  45 . Lever  51  is at the end of the opening  50  wherein the length of opening  50  limits the range of motion of link  43  thereby stopping the four bar linkage in open and closed positions.  FIG. 8A  the knife is one quarter closed.  FIG. 8B  the knife is half closed.  FIG. 8C  the knife is three quarters closed, and  FIG. 8D  the knife is fully closed.  FIG. 8E  depicts the knife half open but with link  42 ,  FIG. 8 , replaced with link  43  thereby functioning as an additional latch for the open position and functioning in the same method of the latch depicted in  FIG. 9A  but for the open position. 
         [0030]      FIG. 9  is the exploded view of the knife of  FIG. 7D . Pin  36  passes through link  32  whereby link  32  pivots freely on pin  36  and pin  36  is connected to handle pieces  33  and  34 . Pin  35  passes through link  31  whereby link  31  pivots freely on pin  35  which is connected to handle pieces  33  and  34 . The blade  30  is attached to link  31  by pin  37 . Pin  37  is attached to link  31  and pivots freely in the blade  30 . The blade is also attached to link  32  by pin  38  whereby pin  38  is attached securely in link  38  and pivots freely in the blade  30 . Post  39  is attached securely in the blade  30  and protrudes through opening  40  and is a means by which the knife can be opened and closed. Flexible appendage  32 A is a means by which the knife can be latched.  FIG. 9A  depicts the complete knife in the closed position with appendage  32 A contacting the corner of handle piece  33 . Pressing appendage  32 A down past the corner of handle  33  releases the latch and allows the knife to open. 
         [0031]      FIG. 10  is an exploded view of the knife in  FIG. 8 . The significant difference shown between the knife of  FIG. 9  and the knife of  FIG. 10  is the method operation. The knife of  FIG. 9  is opened and closed by post  39 ,  FIG. 9 , which is attached to the bar of the four bar anti-parallel linkage that has the blade, whereas the knife of  FIG. 10  is opened and closed by appendage  51  protruding through opening  50  from link  43 . Link  43  being a linking bar of a four bar anti-parallel linkage. The construction is the same as that of  FIG. 9 . Pins  46  and  47  attached securely in handle pieces  44  and  45 , and pivoting freely in links  42  and  43 . Pins  48  and  49  pivoting freely in the blade  41  and attached securely in links  42  and  43  respectively. 
         [0032]    Thus it will be appreciated by those skilled in the art that the present invention is not restricted to the preferred embodiments described with reference to the drawings, and that variations may be made therein without departing from the scope of the present invention as defined by the appended claims and equivalents thereof.