Abstract:
An exchangeable blade knife includes a handle and a blade adapted to be removably coupled to the handle. A bias mechanism is coupled to the handle, the bias mechanism applying a bias on the blade in a lateral direction to press the blade against the handle. The blade may be removed from the handle without also removing the bias mechanism from the handle.

Description:
FIELD OF THE INVENTION  
       [0001]     The present invention relates to a handheld knife having an exchangeable blade. In particular, the present invention relates to an exchangeable blade knife having an improved system for coupling the blade to the handle.  
       BACKGROUND OF THE INVENTION  
       [0002]     Fixed blade knives have a sharpened blade that is attached to a handle in any one of a variety of ways known in the art. In order to provide a secure feel and strong design, the blade typically has a tang portion that extends well into the handle, in many designs extending the length of the handle through to the back of the knife. The handle sides are secured to the tang of the blade with screws or other fasteners or with an adhesive. Because the blade and tang are typically made of metal, such as with steel, a one-piece blade and tang extending the length of the overall knife provides a strong design, as compared to designs having a shorter tang that is secured near the front end of the handle.  
         [0003]     Certain knife designs provide the feature of a removable blade. A removable blade may be desirable in order to provide a knife system having a single handle that may be used with various types of blades, such as knife blades, saw blades, and other tools having a common attachment mechanism that may be secured to the handle. In such an exchangeable blade design, a mechanism used to secure the interchangeable blades with the handle is provided, such as a screw, lever, or button-type mechanism.  
         [0004]     One challenge associated with exchangeable blade knife designs relates to securely coupling the blade to the handle. Because such designs are intended to provide the functionality of a fixed blade knife while providing the additional feature of an exchangeable blade, it is desirable to provide the secure feel of a conventional fixed blade knife having a tang that extends the length of the handle while also providing the exchangeability function. Accordingly, the design of the exchangeable blade knife must minimize movement or play in the blade when the blade is attached to the handle. Such play is typically manifested in uninhibited lateral movement of the blade that is permitted by free space between the blade tang and the handle sides when the components are assembled. Such free space is typically the result of manufacturing tolerances resulting in variability in the thickness of the blade tang and the thickness of the receiving slot in the handle.  
         [0005]     One way of reducing play in the blade is to use a screw or screws to attach the exchangeable blade to the handle. Tightening the screw or screws reduces blade movement within the handle. However, a disadvantage of this approach is that the utilization of screws hampers the ease of exchanging the blade by requiring the user to manually remove and re-attach the screw or screws, and may require the use of an additional tool such as a screwdriver. Further, the use of a screw presents the disadvantage of having a loose part, such as the screw or a portion of the handle side, when exchanging the blade, which can increase the chances of dropping and perhaps losing a necessary part of the knife when exchanging blades.  
         [0006]     Another approach to reducing movement of the blade in the handle is to tighten the manufacturing tolerances of the blade and/or the handle. For example, tightening the tolerance of the components will result in a decrease in the amount of play between the blade and the handle when the knife is assembled. A disadvantage of this approach is that tightening tolerances results in an increase in manufacturing costs, both in tooling and in the number of parts that must be reworked or discarded because the manufactured parts do not meet the prescribed tolerances.  
         [0007]     Accordingly, there is a need for an exchangeable blade knife that is designed to reduce the amount of play between the blade and the handle when the knife is assembled while still affording an easy method of removing and attaching the exchangeable blades and without requiring attachment parts that must be removed from the handle when exchanging the blade. Further, there is a need for an exchangeable blade knife that exhibits reduced movement or play in the blade without also requiring higher manufacturing tolerances in the blade or handle components.  
         [0008]     It would be desirable to provide a system and/or method that provides one or more of these or other advantageous features. Other features and advantages will be made apparent from the present specification. The teachings disclosed extend to those embodiments that fall within the scope of the appended claims, regardless of whether they accomplish one or more of the aforementioned needs.  
       SUMMARY OF THE INVENTION  
       [0009]     The invention relates to a knife having a handle and a blade adapted to be removably coupled to the handle. A bias mechanism is coupled to the handle, the bias mechanism applying a bias on the blade in a lateral direction to press the blade against the handle. The blade may be removed from the handle without also removing the bias mechanism from the handle.  
         [0010]     The invention further relates to an exchangeable blade knife system having a handle and a blade. The blade has a working position in which the blade is secured to the handle and a removed position in which the blade is not secured to the handle. A bias mechanism is coupled to the handle, the bias mechanism applying a bias on the blade in a lateral direction to press the blade against the handle when the blade is in the working position. The bias mechanism remains coupled to the handle when the blade is moved from the working position to the removed position.  
         [0011]     The invention further relates to a knife having a handle and a blade adapted to be removably coupled to the handle. A means for biasing the blade against the handle applies a bias on the blade in a lateral direction to press the blade against the handle. The blade may be removed from the handle without removing the means for biasing the blade against the handle from the handle.  
         [0012]     The invention is capable of other embodiments and of being practiced or being carried out in various ways. Alternative exemplary embodiments relate to other features and combinations of features as may be generally recited in the claims.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]     The invention will become more fully understood from the following detailed description, taken in conjunction with the accompanying drawings, wherein like reference numerals refer to like elements, in which:  
         [0014]      FIG. 1  is a perspective view of an exchangeable blade knife;  
         [0015]      FIG. 2  is an exploded perspective view of an exchangeable blade knife;  
         [0016]      FIG. 3  is a cut-away elevation view of an exchangeable blade knife;  
         [0017]      FIG. 4  is a cut-away elevation view of an exchangeable blade knife with the exchangeable blade removed from the handle;  
         [0018]      FIG. 5  is a sectional view taken generally along line  5 - 5  of  FIG. 3 ;  
         [0019]      FIG. 6  is a sectional view taken generally along line  6 - 6  of  FIG. 4 ;  
         [0020]      FIG. 7  is a sectional view taken generally along line  7 - 7  of  FIG. 3 ; and  
         [0021]      FIG. 8  is a sectional view taken generally along line  8 - 8  of  FIG. 4 . 
     
    
     DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0022]     Referring to  FIG. 1 , according to an exemplary embodiment of the present invention, a knife, shown as exchangeable blade knife  10 , has a handle  12  and a blade  14 . The handle may include various elements or pieces secured together by fasteners  16 . In the embodiment depicted in  FIG. 1 , knife  10  is an exchangeable blade knife having a removable blade  14  that is removed by depressing release mechanism  18 . In a typical knife construction, blade  14  is made of metal, such as steel or aluminum, and the handle components may be made of a variety of materials including wood, plastic, metal, or various composites. The term “blade” is not intended to be limiting and may include various types of blades and tools, such as knife blades, saws, skinners, and so forth as is known in the art. Further, the term “handle” is intended to be a generic term referring to all of the components in the handle portion of the knife including various liners, handle sides, bolsters, frames, receivers, and so forth as is known in the art.  
         [0023]     Referring to  FIG. 2 , blade  14  includes a working portion  20  and a tang  22 . The working portion  20  may be sharpened to function as a cutting instrument and may be made in various shapes and sizes. In an exemplary embodiment, the handle  12  includes a receiver  24 , a pair of handle halves  26 ,  28 , and a pair of bolsters, mark bolster  30  and pile bolster  32 . The receiver  24  may be made of a material similar to the blade  14 , such as steel. The other handle components may be made of other materials as is desired for comfort, durability, and decorative purposes.  
         [0024]     Further referring to  FIG. 2 , a release button  40  and a compression spring, shown as release button spring  42 , are used in conjunction with one another to both retain the blade  14  in the handle and to release the blade  14  from the handle. When assembled, a portion of the release button  40  extends through aperture  44  in tang  22  to lock the blade  14  into place. To release the blade  14 , the release button  40  may be depressed against the force of release button spring  42  to disengage the end portion of the release button  40  from the aperture  44 , allowing a narrower portion of release button  40  to slide through a slot  46  in the tang  22  as the blade  14  is released from the handle  12 . The components of the release mechanism are described in more detail below with respect to  FIGS. 5 and 6 . The release button spring  42  normally biases the release button  40  into the locked position. In the exemplary embodiment shown in  FIG. 2 , one end of spring  42  normally resides in a recess  48  in the pile bolster  32 .  
         [0025]     Further referring to  FIG. 2 , a blade bias mechanism, shown as, but not limited to, pin  50  and corresponding pin spring  52 , is used to apply pressure to the tang  22  when blade  14  is assembled with handle  12 . The pressure or bias on tang  22  reduces the movement or play of blade  14  within handle  12 . Because the pin  50  has a head portion that is wider than slot  46 , and an end portion that is narrower than slot  46 , the pin  50  is configured to permit the blade  14  to be inserted and removed from receiver  24  while still providing a bias against the tang  22  when assembled. In the embodiment depicted in  FIG. 2 , the pin spring  52  partly resides in a recess  54  in the pile bolster  32 .  
         [0026]     Further referring to  FIG. 2 , the leading edge of the tang  22  may be beveled such that as blade  14  is inserted into receiver  24 , the tang  22  automatically moves release button  40  and pin  50  to allow passage of the tang  22  past the release button  40  and pin  50 .  
         [0027]     Further referring to  FIG. 2 , a blade bias mechanism, shown as recessed ball and spring mechanism  64 , is located in the pile bolster  32  in an exemplary embodiment. The spring-biased ball provides an additional bias on tang  22  when the blade  14  is assembled with handle  12  to reduce the play of blade  14 . A ball and spring mechanism (not shown) may be provided in the mark bolster  30  instead of, or in addition to, the ball and spring mechanism  64  as to provide a lateral bias on both sides of the tang  22 , and further reduce the potential for movement of blade  14  within handle  12 .  
         [0028]     Referring to  FIGS. 2, 3 , and  5 , tang  22  has a pair of prongs  70 ,  72  that define slot  46  and aperture  44 . The release button  40  has a shaft  76  and an end portion  78 , the end portion  78  having a larger diameter than shaft  76 . The shaft  76  has a diameter that is more narrow than the width of slot  46  between prongs  70 ,  72 . The diameter of end portion  78  is less than the diameter of aperture  44 , but greater than the width of slot  46 . Accordingly, when end portion  78  resides within aperture  44 , the blade  14  is locked in place because the end portion  78  prevents sliding of the blade  14  in the outward direction due to interference with the slot  46 . A flange  74  prevents the release button spring  42  from pushing the release button  40  any further outward from the handle  12  than is shown in  FIG. 5  due to interference with the mark bolster  30 . Referring specifically to  FIG. 3 , receiver  24  includes a tongue  80  that is sized to extend partially into slot  46  to aid in fixing the tang  22  into place within handle  12 . The end portion  78  of the release button  40 , in combination with the receiver tongue  80 , secure, the blade  14  into place and prevent movement of the secured blade  14  in the longitudinal direction and the vertical direction of the blade  14 . However, play may still exist in the lateral direction due to variations in the blade  14  and receiver  24  thicknesses, requiring the blade bias mechanisms described herein to remove the play by applying a bias on the blade  14  in a lateral direction.  
         [0029]     In another exemplary embodiment (not shown), the end portion  78  and the aperture  44  may be configured to mechanically interfere with one another to function as a blade bias mechanism in addition to a release and locking mechanism. For example, the end portion  78  may be tapered such that the distal end of the end portion is wider than the diameter of the aperture so that the end portion  78  wedges into the aperture  44  when the blade  14  and handle  12  are assembled. Because of the interlocking of the end portion  78  and the aperture  44 , the release button spring  42  provides a bias on the tang  22  in a lateral direction against the handle  12  when the blade  14  and handle  12  are assembled in such an embodiment.  
         [0030]     Referring to  FIGS. 4 and 6 , release button  40  is depressed in a lateral direction (see arrow in  FIG. 6 ) to release the blade  14  from handle  12 . When release button  40  is sufficiently depressed, end portion  78  is displaced out of aperture  44  and replaced by shaft  76 , which has a diameter that is more narrow than the slot  46 . Accordingly, the user is able to withdraw blade  14  from handle  12  in order to remove and exchange the blade  14 .  
         [0031]     Referring to  FIGS. 3 and 7 , in an exemplary embodiment, the blade bias mechanism, shown as pin  50 , and pin spring  52 , has a shaft  82  that is more narrow than the width of slot  46  and a pin flange  84  that is of a greater diameter than the width of the slot  46 . Accordingly, when the blade  14  is assembled with the handle  12 , pin flange  84  applies pressure in a lateral direction (see arrow in  FIG. 7 ) against prongs  70 ,  72  to reduce play in the blade  14 .  
         [0032]     Referring to  FIGS. 4 and 8 , when the blade  14  has been removed from the handle  12 , a portion of the pin flange  84  is forced into the plane of the receiver  24 , into a position that would ordinarily interfere with the insertion of tang  22  into handle  12 . However, as discussed above, the prongs  70 ,  72  are beveled to cause the pin flange  84  to be moved aside as blade  14  is inserted into handle  12 .  
         [0033]     In operation, the blade  14  may be released from the handle  12  in order to exchange the blade  14  with another blade or tool by depressing the release button  40  and pulling the blade  14  out of handle  12 . Accordingly, the required mechanical actions necessary to disassemble blade  14  and handle  12  are simplified relative to devices that require the removal of fasteners or the activation of multiple components such as levers and so forth to release the exchangeable blade. Further, the removal operation does not result in loose parts, such as screws, that present the risk of being lost when a blade is being removed and replaced.  
         [0034]     In order to address the issue of excessive movement or play in the blade  14  when assembled with the handle  12 , especially without the utilization of extra fasteners, the blade bias mechanism removes play by applying force in a lateral direction on the tang  22 . The blade bias mechanism may be in the form of the ball and spring mechanism  64  or the pin  50  and spring  52  in two of the embodiments described herein, but may also take other mechanical forms involving mechanisms that apply force on the blade  14  in a lateral direction in order to remove play on the blade  14  when the knife  10  is assembled. Without the utilization of the blade bias mechanism (one such mechanism or multiple mechanisms in combination with one another) the tolerances on the thickness of the blade and handle components would have to be tightened to reduce the amount of play, with a corresponding increase in manufacturing costs and defects. The addition of the blade bias mechanism allows for an increased tolerance, such as permitting a 0.020 inch mismatch in blade-to-handle thickness, both decreasing the cost to manufacture and increasing the quality of the knife relative to alternative approaches of tightening the tolerances on the thickness of all components to within ±0.001-0.002 inches.  
         [0035]     While the detailed drawings and specific examples given herein describe various-exemplary embodiments, they serve the purpose of illustration only. It is to be understood that the invention is not limited in its application to the details of construction and the arrangements of components set forth in the preceding description or illustrated in the drawings. For example, the particular release mechanism and tang configuration is but one way of attaching an exchangeable blade to a handle. Further, the blade bias mechanism is shown in one embodiment as having a shaft and flange configuration to apply a spring bias to the tang but may take other forms that permit the application of a bias to the blade to reduce play in the blade Furthermore, other substitutions, modifications, changes, and omissions may be made in the design, operating conditions, and arrangements of the exemplary embodiments without departing from the scope of the invention as expressed in the appended claims.