Patent Publication Number: US-7905022-B2

Title: Folding knife having a locking mechanism

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is a divisional application of U.S. patent application Ser. No. 11/374,289, filed Sep. 16, 2005, now pending, which application is incorporated herein by reference in its entirety. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates generally to a folding knife, and particularly to a folding knife with a locking mechanism. 
     2. Description of the Related Art 
     Folding knives enjoy wide popularity, particularly among sportsmen, campers, hikers, and many others engaged in outdoor activities. Common elements to folding knives include a handle and a blade pivotally connected to an end of the handle so that the blade pivots with respect to the handle between an open position in which the blade is extended away from the handle, and a closed position in which the blade is at least partially received within the handle. Many folding knives also include a locking mechanism to maintain the blade in the open position and/or the closed position. 
     Examples of folding knives, including folding knives with locking mechanisms, may be found in U.S. Pat. Nos. 1,454,665; 1,743,022; 4,040,081; 4,173,068; 4,404,748; 4,451,982; 4,502,221; 4,612,706; 4,719,700; 4,776,094; 4,805,303; 4,811,486; 4,837,932; 4,893,409; 4,974,323; 4,979,301; 5,044,079; 5,060,379; 5,095,624; 5,111,581; 5,293,690; 5,325,588; 5,331,741; 5,425,175; 5,426,855; 5,502,895; 5,515,610; 5,537,750; 5,546,662; 5,596,808; 5,615,484; 5,685,079; 5,689,885; 5,692,304; 5,737,841; 5,755,035; 5,802,722; 5,815,927; 5,822,866; 5,826,340; 5,887,347; 5,964,036; 6,079,106; 6,154,965; 6,338,431; 6,378,214; 6,427,335; 6,438,848; 6,490,797; 6,594,906; D348,599, and D373,296; and U.S. Patent Application Nos. 2002/0157260; 2003/0070299; and 2004/0031155, the entire disclosures of which are herein incorporated by reference for all purposes. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a side view of a folding knife according to an embodiment of the invention, shown with the blade in a closed position. 
         FIG. 2  is a side view of the knife of  FIG. 1 , shown with the blade in an intermediate position. 
         FIG. 3  is a side view of the knife of  FIG. 1 , shown with the blade in an open position. 
         FIG. 4  is a front plan view of the knife of  FIG. 1 , shown with the blade in the open position. 
         FIG. 5  is a front plan view of the knife of  FIG. 1 , shown with the blade in the closed position. 
         FIG. 6  is an isometric view showing a user&#39;s hand positioned for using the knife of  FIG. 1  with the blade in the open position. 
         FIG. 7  is a side view of the knife according to an embodiment of the invention, shown with a wrench removed from a handle frame. 
         FIGS. 8A and 8B  are cutaway views of a portion of a knife according to another embodiment of the invention, showing a safety lock in an open and a closed position, respectively. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     In the following description and the accompanying figures, certain specific details are set forth in order to provide a thorough understanding of various embodiments of the invention. However, one skilled in the art will understand that the invention may be practiced without these details. 
     Embodiments of the present invention relate generally to folding knives. For the purpose of this disclosure, the portion of a knife handle into which the blade is received while folded, generally including a slot or channel, will be referred to as the top or front, while the portion opposite will be referred to as the back or bottom of the handle or knife. Where practical, depictions of knives will be oriented in the figures accordingly, to avoid confusion. These and other terms that logically follow, such as side and end, are used for convenience and clarity, and do not limit the scope of the invention. Likewise, directional terms, such as force vectors and rotational directions, are to be understood with reference to the structure as shown in the accompanying figures, and are not intended to limit the scope of the invention. 
       FIGS. 1-6  depict an embodiment of a folding knife  20  having a blade  22 , a handle  24 , and a locking mechanism  28 . Blade  22  includes a tang  23  pivotally connected to the handle  24 . The blade  22  pivots with respect to the handle  24  about a pivot axis P between an open position ( FIG. 3 ) and a closed position ( FIG. 1 ). In the open position, the blade  22  extends away from the handle  24 , where it is deployed and ready for use. Rotation of the blade toward the open position may be limited by contact between a portion of the blade and a portion of the handle when the blade is in the fully open position. Alternatively, rotation toward the open position may be limited by some other limiting means such as are known in the art. 
     From the open position, the blade  22  may be folded towards the handle  24 , pivoting about pivot axis P, into the closed position. In the closed position, blade  22  extends along handle  24 . Rotation of the blade toward the closed position may also be limited by any of a variety of methods, one of which is described below. 
     While the blade  22  may be any suitable shape, in the pictured embodiment, the blade  22  includes an aperture  30 . The blade  22  also includes a gate element  32  configured to provide access to the aperture  30 . The gate element  32  is coupled at a first end  33  thereof to the blade  22  and configured to pivot or flex such that a second end  35  is movable between a closed and an open position. The gate element  32  is configured such that it is free to move when the blade  22  is in the closed position. However, when the blade  22  is moved to the open position, the second end  35  of the gate element  32  comes to bear against an engagement surface  25  of the handle  24  such that the gate element  32  is fixed in its closed position. Additionally, in the present embodiment, contact of the gate element  32  with the engagement surface  25  serves to limit travel of the blade  22  toward the open position. Accordingly, the open position of the blade  22  can be defined as the point in rotation of the blade  22  at which the gate element  32  contacts the engagement surface. 
     The aperture  30  and gate element  32  may be used to serve any suitable purpose. For example, the aperture  30  and gate element  32  may provide means for storing the knife by hanging the knife on rings, cords, etc. Additionally, or alternatively, gate element  32  may allow the user to pivot blade  22  to the open position by applying an opening force Fo on the gate element and/or to pivot blade  22  to the closed position by applying a closing force Fc on the gate element  32 . While the blade  22  is in the open position, the gate element  32  provides a stable platform against which a user may place a thumb to apply pressure against the blade during a cutting operation. 
     Although gate element  32  is shown to be in the form of a pivoting closure, any suitable structure configured to provide access to one or more apertures may be used, such as a leaf spring, sliding gate, etc. Additionally, although knife  20  is shown to include one aperture  30  and one gate element  32 , any suitable combination of apertures and gate elements may be used, including no apertures and/or no gate elements. 
     Handle  24  includes a handle element  21  and a locking mechanism  28 . The combined handle element  21  and locking mechanism  28  form a skeletal type handle through which the cutting edge of the blade  22  may be visible, but is nevertheless protected from inadvertent contact by the cooperation of the handle element  21  with the locking mechanism  28 . The handle element  21  forms a back portion of the handle  24  and is provided with a contoured shape to cooperate ergonomically with a user&#39;s hand while in use. The locking mechanism  28  forms a front portion of the handle  24 . Components of the locking mechanism  28  are contoured to comfortably receive a user&#39;s fingers wrapped therearound while in use, as shown in  FIG. 6 . The shapes and contours of the handle  24  may be selected according to desired ergonomic and aesthetic considerations independent of the mechanical operation of the knife  20 , described below. 
     Handle element  21  includes first and second ends  27 ,  29 . Tang  23  of blade  22  is pivotally connected to handle element  21  at the first end  27 . Handle element  21  includes a receiving notch  31 , shaped and configured to receive a part of the locking mechanism  28 , as further described below. 
     The locking mechanism  28  includes short toggles  36  and  37  and long toggles  38  and  39 . It may be seen, with reference to  FIGS. 4 and 5 , which show the knife  20  in plan view, that short and long toggles  36  and  38  are positioned on a first side of the knife  20 , while short and long toggles  37  and  39  are positioned on a second side of the knife  20 . The short and long toggles  36  and  38  and the short and long toggles  37  and  39  define respective sides of a channel into which the blade is received while in the closed position, as shown in  FIGS. 1 and 5 . 
     For the purposes of this description, the structure and operation of the knife  20  will largely be described with reference to  FIGS. 1-3 , which show side elevation views of the knife  20 , looking at the first side thereof. Accordingly, the description will refer primarily to short and long toggles  36 ,  38 , visible in these figures. The structure of the knife  20  is functionally symmetrical, and so it will be understood that the interaction of the short and long toggles  37 ,  39  with other components of the knife  20  is essentially identical to that described with reference to short and long toggles  36 ,  38 , respectively. 
     Referring now to  FIGS. 1-3 , the short toggle  36  is pivotally connected to the second end  29  of handle element  21  at a first pivot point  44 . long toggle  38  includes a first end  40 , which is pivotally connected to the tang  23  of blade  22  at a second pivot point  46 , and a second end  42 , which is pivotally connected to the long toggle  36  at a third pivot point  48 . 
     Rotation points such as pivot points  44 ,  46 , and  48 , as well as pivot axis P, define points at which various components of the knife  20  are rotatably coupled such that the components so coupled are rotatable with respect to each other. The coupling at these points may be effected by the use of rivets, nuts and bolts, pins, bushings, bearings, or any other type of fastener that fulfills the functional requirements. 
     The first and second pivot points  44 ,  46  traverse the knife  20  such that, in the case of the first pivot point  44 , both short toggles  36  and  37  are coupled to the handle by a single fastener, and, in the case of the second pivot point  46 , both long toggles  38  and  39  are coupled to the blade by a single fastener. Third pivot point  48  comprises two separate fasteners, a first fastener coupling the long and short toggles  36  and  38  on the first side of the knife  20 , and a second fastener coupling the long and short toggles  37  and  39  on the second side of the knife, as shown in  FIGS. 4 and 5 . This arrangement allows the blade  22  to pass between the two fasteners of the third pivot point  48  as it moves between the open and closed positions.  FIGS. 4 and 5  also show a clip  54 , provided as an alternate means for securing the knife  20 . 
     Also shown in  FIGS. 4 and 5 , a torsion spring  52  is positioned on the fastener at the first pivot point  44 . The spring  52  is configured to apply a rotational bias to the short toggles  36  and  37  in a counterclockwise direction (as viewed in  FIGS. 1-3 ), relative to the handle element  21 . 
     A first line  47  is defined by the short toggle  36  between the first and third pivot points  44 ,  48 , while a second line  49  is defined by the long toggle  38  between the second and third pivot points  46 ,  48 . A toggle angle T is defined by the angle of the first line  47  with respect to the second line  49 . 
     While the blade  22  is in the closed position, as shown in  FIG. 1 , the first end  40  of the long toggle  38  engages the receiving notch  31  of the handle element  21 . Contact between the first end  40  and the receiving notch  31  limits travel of the blade  22  as it moves toward the closed position. Accordingly, the closed position of the blade  22  may be defined as the point in the rotation of the blade  22  at which the first end  40  of the long toggle  38  contacts the receiving notch  31 . 
     When the blade  22  is moved toward the open position, the pivot point  46  follows an arcuate path around the pivot axis P of the blade  22 . As it does so, the long toggle  38  rotates about second pivot point  46  with respect to the blade  22 , and moves, first, toward the second end  29  of the handle element  21  as the blade  22  approaches a mid-point of travel, and, as the blade passes the mid-point of travel toward the open position, moves away from the second end  29  of the handle element  21 . As a result of the movement of the long toggle  38 , the third pivot point  48  also moves relative to the handle  22 . Because the short toggle  36  is coupled to the handle element  21  at first pivot point  44 , movement of the third pivot point  48  causes the short toggle  36  to rotate with respect to the handle element  21  about the first pivot point  44 , and with respect to the long toggle  38  about third pivot point  48 . 
     While the blade  22  is in the closed position, as shown in  FIG. 1 , the toggle angle T, as defined by the first and second lines  47 ,  49 , has a first value of less than 180°. As the blade  22  moves toward the mid-point of travel between the closed and open positions, as shown in  FIG. 2 , the toggle angle T decreases. As the blade moves beyond the mid-point of travel, the toggle angle T again increases, until, when the blade reaches the open position, the toggle angle T is equal to or greater than 180°, as shown in  FIG. 3 . In the configuration shown in  FIG. 3 , the locking mechanism is in the locked positioned, as explained below. 
     The shape of the second end  42  of the long toggle is selected such that the second end  42  contacts the handle element  21  when the blade  22  is in the open position. Accordingly, the short toggle  36  cannot rotate in a counterclockwise direction beyond the position achieved when the blade  22  is in the open position. Therefore, in order for the blade to be moved back toward the closed position, the short toggle  36  must rotate in a clockwise direction, and the third pivot point must rotate away from the handle  22 . 
     Because the torsion spring  52  applies a counterclockwise rotational bias to the short toggle  36 , the spring resists movement of the blade  22  away from the closed position while the blade is in the closed position. When the blade is rotated beyond the midpoint of travel toward the open position, the bias of the spring  52  urges the blade  22  toward the open position and resists movement of the blade away from the open position while the blade is in that position. 
     It will be recognized that, while the toggle angle T is equal to or greater than 180°, no amount of force on the blade  22  toward the closed position will cause the short toggle  36  to spontaneously rotate in the clockwise direction. Thus, the blade  22  is automatically locked in the open position by the toggle action of the locking mechanism  28  and the bias of the spring  52 . On the other hand, pressure on a heel  50  of the short toggle  36  sufficient to overcome the spring bias will cause the short toggle  36  to rotate away from its locked position and allow the blade  22  to freely rotate to the closed position. 
       FIG. 6  shows the knife  20  in the hand of a user. It may be seen that the short and long toggles  36 ,  37 ,  38 ,  39  define the front portion of the gripping surface of the handle  24 , and that the simple act of gripping the handle applies pressure to the lock mechanism  28 , insuring that the mechanism remains in the locked position. 
     According to one embodiment, the locking mechanism moves easily into the locked position when the blade  22  is rotated to the open position. According to an alternate embodiment, the blade  22  reaches the open position before the locking mechanism  28  reaches the locked position. That is to say that the blade  22  contacts the handle element  21  or other limiting feature while the toggle angle is just shy of 180°. At this point, the user applies downward pressure at the third pivot point  48 , thereby loading all the rotation points of the knife  20 , and forcing the locking mechanism  28  into the locked position. In this way, constant tension is maintained on the locking mechanism while the blade  22  is in the open position, which eliminates movement and play from the blade, and further discourages spontaneous release of the locking mechanism  28 . 
     According to an embodiment of the invention, the fastener at the first pivot point  44  is provided with an eccentric boss and threaded end. Accordingly, by rotating the fastener relative to the handle element  21 , the precise position of the first pivot point  44  can be adjusted, thereby adjusting the operation of the locking mechanism  28 . To accomplish this, a nut affixed to the threaded end of the fastener is loosened and the fastener is rotated to adjust the position of the first pivot point  44 . The nut is then tightened to lock the fastener in place.  FIG. 7  shows the knife  20  with a wrench  56  sized for this purpose. According to the illustrated embodiment, the nut is stored in an aperture  58  formed in the handle element  21  for this purpose. 
       FIGS. 8A and 8B  show a partial cutaway view of the knife  100  incorporating a safety lock  160  according to an embodiment of the invention. The safety lock  160  is configured to permit a user to lock a blade  122  in the closed position such that it cannot be opened without first releasing the safety lock  160 . 
     The safety lock  160  includes a cam-wheel  162 , and a locking rod  164  coupled at a first end  168  to the handle element  121 . The locking rod  164  has a downward bias and bears against the cam-wheel  162 . A second end  170  of the locking rod extends toward the tang  123  of the blade  122 . The tang  123  includes a locking notch  166  positioned to receive the second end  170  of the locking rod  164  while in the locked position. 
       FIG. 8A  shows the safety lock  160  in the unlocked position. In this position, the cam-wheel  162  is oriented such that the locking rod  164  bears against a flattened face  172  of the cam-wheel  162 , and the second end  170  of the locking rod  164  is disengaged from the locking notch  166 . 
       FIG. 8B  shows the safety lock  160  in the locked position. In this position, the cam-wheel  162  is rotated to an orientation in which the locking rod  164  bears against a larger radius portion of the cam-wheel  162 , causing the second end  170  of the locking rod  164  to move toward the tang  121 . The second end  170  of the locking rod  164  is received in the locking notch  166  of the tang  123 . 
     To lock or unlock the safety lock, a user merely moves the cam-wheel  162  with a thumb or finger. While the cam-wheel  162  is in the unlocked position, as shown in  FIG. 8A  the blade  122  may be rotated toward the open position without interference. However, when the cam-wheel  162  is rotated to the position shown in  FIG. 8B , the locking notch  166  engages the second end  170  of the locking rod  164 , which prevents further rotation of the blade  122 , securely holding the blade in the closed position. 
     Though not shown in the figures, the cam-wheel may be provided with a détente to stop rotation of the cam-wheel at the position shown in  FIG. 8A  when rotated in the counterclockwise direction for example, and to stop rotation of the cam-wheel  162  at the position shown in  FIG. 8B  when rotated in the clockwise direction. In this way, by sliding back with the thumb over the cam-wheel until it stops (i.e., in the clockwise direction), a user may be assured that the safety lock  160  is engaged. Conversely, by pushing forward with the thumb over the cam-wheel until it stops (i.e., in the counterclockwise direction), a user may easily and quickly disengage the safety lock  160 . 
     Although various embodiment of the invention have been described here to illustrate the principles of the invention, those skilled in the art will recognize that various changes in form and detail may be made. Embodiments of the invention may not include all of the features disclosed here with reference to a particular embodiment. Additionally, features disclosed here may be combined with known structures of devices. such combinations also fall within the scope of the invention. 
     All of the above U.S. patents, U.S. patent application publications, U.S. patent applications, foreign patents, foreign patent applications and non-patent publications referred to in this specification and/or listed in the Application Data Sheet, are incorporated herein by reference, in their entirety. 
     From the foregoing it will be appreciated that, although specific embodiments of the invention have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the invention. Accordingly, the invention is not limited except as by the appended claims.