Abstract:
A utility knife has a body comprising a blade-receiving cavity defined by first and second generally opposing walls; a retention element laterally moveable with respect to the cavity via a hole in one of the walls; an actuator moveable longitudinally relative to the cavity between a retention position and a release position; the actuator having a recess opening towards the cavity and a cam surface; wherein the hole and the recess are aligned when the actuator is in the release position and offset when the actuator is in the retention position; the actuator in the retention position causes the cam surface to engage the retention element to force the retention element to a protruding position in the cavity; the actuator in the release position allows the retention element to be withdrawn, allowing the blade to be removed. Also, a related method of assembly.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     The present invention is directed generally to utility knives having a releasable blade retention mechanism.  
         [0002]     Utility knives are used for a variety of tasks, such as box cutting, carpet cutting, and the like. Such utility knives employ cutting blades typically having a trapezoid shape with a razor sharp cutting edge along the long lower side and two small U-shaped notches along an opposing shorter upper side for mating the blade to the main body of the utility knife. Over time, the cutting edge of the blade may become dulled, the blade may break, or the blade may otherwise need to be replaced. As such, it is common for utility knives to allow the blade to be replaced. In very simple utility knives, the housing may be formed of two halves that are joined together by a central screw. Replacement of the blade in such devices requires the screw to be removed, the housing halves separated, removal and replacement of the blade, and finally reassembly of the housing. Such an arrangement is shown, for example, in U.S. Pat. Nos. 5,099,578 and 3,192,624. Other utility knives use modified versions of this concept, with housing halves that pivot with respect to one another, or other means to hold the housing halves together. Nevertheless, the manipulation of the housing required to change the cutting blades is less than ideal with such designs. Accordingly, some designs have been proposed that use a “quick release” mechanism that allows the cutting blade to be replaced via the front slit in the housing. Examples of such designs are shown in U.S. Pat. Nos. 6,829,827 and 6,553,674, and U.S. patent application Ser. No. 11/108,322, the later of which is incorporated herein by reference. However, even these quick-release mechanisms may be less than ideal for some circumstances, and there remains a need for alternative utility knife designs that allow for easy cutting blade replacement.  
       SUMMARY OF THE INVENTION  
       [0003]     In one illustrative embodiment, the present invention provides a utility knife having a novel releasable blade locking mechanism that allows the cutting blade to be replaced easily and/or a method of assembling the same.  
         [0004]     In one embodiment, the present invention provides a utility knife comprising: a body comprising a blade-receiving cavity extending to a blade slot opening; the cavity defined by first and second generally opposing walls; the second wall having at least a first hole therethrough; a first retention element moveably coupled to the body so as to be laterally moveable with respect to the cavity via the first hole; an actuator coupled to the body and moveable longitudinally relative to the cavity between a retention position and a release position; the actuator having a first recess opening towards a longitudinal centerline of the cavity and a first cam surface proximate the first recess; wherein the first hole and the first recess are aligned when the actuator is in the release position and offset when the actuator is in the retention position; wherein movement of the actuator to the retention position causes the first cam surface to engage the first retention element to force the first retention element inward to a first position extending at least partially into the cavity; wherein movement of the actuator to the release position allows the first retention element to move away from the cavity centerline to a second position closer to the actuator than the first position. The first retention element may comprise a curved body, such as a sphere. The body may comprise a handle and a head moveably coupled to the handle, wherein the head includes the blade-receiving cavity, the slot, the actuator, and the first retention element. A blade may be disposed partially in the cavity; the blade having at least one retention notch; wherein movement of the actuator to the retention position causes the first retention element to extend into the retention notch so as to couple the blade to the body. The first cam surface may help define the first recess. The actuator may slide longitudinally relative to the body and/or may be biased toward the retention position, such as by a spring disposed longitudinally adjacent the actuator. The utility knife may employ one retention element, or a plurality of retention elements to engage one or more notches on the cutting blade. A corresponding method is described.  
         [0005]     In another embodiment, the present invention provides a utility knife comprising: a body comprising a blade-receiving cavity extending to a blade slot opening; the cavity defined by first and second generally opposing walls; a blade retention means for releasably coupling a blade disposed in the cavity to said body while said blade is in an operative cutting position. The second wall may comprise at least a first hole therethrough; and the blade retention means may comprise: an actuator coupled to the body and moveable longitudinally relative to the cavity between a retention position and a release position; and a first retention element moveably coupled to the body so as to be laterally moveable outward away from a centerline of the cavity when the actuator is in the release position, and disposed at least partially in the cavity when the actuator is in the retention position. The blade retention means may further comprise a second retention element moveably coupled to the body so as to be laterally moveable away from a centerline of the cavity when the actuator is in the release position, and disposed at least partially in the cavity when the actuator is in the retention position, the second retention element distinct from the first retention element and longitudinally spaced therefrom. The body may comprise a handle and a head moveably coupled to the handle, wherein the head includes the blade-receiving cavity, the actuator, and the first retention element. The actuator may be biased toward the retention position. A corresponding method is described.  
         [0006]     In yet another embodiment, the present invention provides a utility knife comprising: a body comprising a blade-receiving cavity extending to a blade slot opening; the cavity defined by first and second spaced walls; a blade disposed partially in the cavity; the blade having at least a first retention notch; an actuator coupled to the body and moveable longitudinally relative to the cavity between a retention position and a release position; a first ball moveably coupled to the body; wherein movement of the actuator to the retention position causes the ball to move laterally so as to extend into the retention notch and thereby lock the blade relative to the cavity; wherein movement of the actuator to the release position allows the ball to move laterally out of the retention notch so as to unlock the blade relative to the cavity and thereby allow the blade to be removed from the cavity. The blade may further comprise a second retention notch, with the knife further comprising a second ball moveably coupled to the body; wherein movement of the actuator to the retention position causes the first and second balls to move laterally so as to extend into the first and second retention notches respectively; wherein movement of the actuator to the release position allows the first and second balls to move laterally out of the first and second retention notches respectively. A corresponding method is described.  
         [0007]     In another embodiment, the present invention provides a method of assembling a utility knife, comprising: providing a utility knife body, the body comprising: a blade-receiving cavity defined by first and second generally opposing walls; the second wall having at least a first hole therethrough; an actuator coupled to the body and moveable longitudinally relative to the cavity between a retention position and a release position; the actuator having a first recess opening towards a longitudinal centerline of the cavity and a first cam surface; a first retention element moveably coupled to the body so as to be laterally moveable with respect to the cavity via the first hole; the method further comprising causing the actuator to assume the retention position such that the first recess is offset from the first hole and forcing the first retention element laterally toward the centerline by engaging the first retention element with the first cam surface; and moving the actuator to the release position and thereby aligning the first recess and the first retention element to allow the first retention element to retract away from the centerline. The method may further comprise inserting a blade into the cavity and moving the actuator from the release position to the retention position. The method may further comprise removing the blade from the cavity with the actuator in the release position. The second wall may comprise a second hole, the utility knife body may further comprise a second retention element moveably coupled to the body so as to be laterally moveable with respect to the cavity via the second hole; and the actuator may further comprise a second recess, spaced from the first recess, opening towards the centerline and a second cam surface; and the method may be such that causing the actuator to assume the retention position comprises offsetting the second recess from the second retention element and moving the actuator to the release position comprises aligning the second recess and the second retention element. The method may further comprise inserting a blade into the cavity and moving the actuator from the release position to the retention position; wherein the blade includes a notch disposed distally from a cutting edge; wherein moving the actuator to the retention position causes the first retention element to be disposed in the notch while the blade is disposed in the cavity. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0008]      FIG. 1  shows a utility knife constructed in accordance with one embodiment of the present invention.  
         [0009]      FIG. 2  shows a partially exploded view of a utility knife constructed in accordance with another embodiment of the present invention.  
         [0010]      FIG. 3  shows a perspective view of a utility knife head of  FIG. 2  with a blade attached.  
         [0011]      FIG. 4  shows a sectional view with the actuator in the locked or retention position along line IV-IV.  
         [0012]      FIG. 5  shows the sectional view of  FIG. 4  with the actuator in the release position.  
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0013]     As illustrated in  FIG. 1 , a utility knife, generally designated  10 , is shown constructed according to one embodiment of the present invention. The knife  10  includes a cutting blade  12  and a main body  20 . The blade  12 , as is conventional, has a generally trapezoidal shape, with a lower cutting edge  14  and two notches  16  on its upper edge. It should be noted that while the present description is in the context of a conventional trapezoidal shaped blade, the cutting blade  12  may alternatively take any other configuration known in the art.  
         [0014]     The main body  20  is generally elongate, extending along longitudinal axis  22 . The main body  20  includes a handle section  24  and a head section  30 . The head section  30  may be permanently fixed relative to the handle  24 , including integral therewith, or may be moveable relative thereto. For example, in some embodiments, the head section  30  may be pivotally attached to the handle section  24  so that the utility knife  10  may be open and closed via a folding action about pivot  26 . See  FIG. 2 . For such foldable embodiments, a suitable mechanism, such as a locking detent mechanism (not shown) known in the art, should be employed to prevent unintentional folding during use. The main body  20  should be formed of a suitably strong material, such as steel, aluminum, or hard plastic, but the handle section  24  may include areas of soft elastomeric material on the exterior surfaces as is desired in order to increase comfort and/or to increase grip. In addition, the handle section  24  may advantageously include a suitable belt/pocket clip if desired.  
         [0015]     The head  30  includes a blade-receiving cavity  32 , an actuator  50 , and two retention elements  70 . The cavity  32  is advantageously disposed along the longitudinal axis  22  of the main body  20 , such that the centerline  34  of the cavity  32  is parallel with the longitudinal axis  22 . Two opposing, spaced apart, and generally parallel walls  40 , 42  help define the blade-receiving cavity  32 . The cavity  32  extends forwardly away from the handle  24 , and terminates at a slot-shaped opening  36  between the walls  40 , 42  sized to have the blade  12  extending/inserted therethrough. Wall  40  may be solid, while wall  42  includes two holes  44  that extend laterally therethrough to the blade-receiving cavity  32 . These holes  44  are positioned so as to overlap with the blade&#39;s notches  16  when the blade  12  is properly inserted into the blade-receiving cavity  32 . Wall  42  includes a small cover  38  attached to its outer or outboard face, which may be snap-fitted to wall  42 .  
         [0016]     The actuator  50  is moveably housed in cover  38 , with the outboard portion  54  of the actuator body  52  extending through (or accessible via) a suitable opening in the cover  38  so as to be physically accessible to a user. This outboard portion  54  advantageously includes suitable texturing on its outer surface to increase the user&#39;s grip thereagainst. The inboard portion  56  of the actuator body  52  includes two spaced apart recesses  60  that face inward toward the cavity&#39;s centerline  34 . The inboard portion  56  also includes two cam surfaces  62 , one associated with each of the recesses  60 . The actuator  50  is moveable between a lock or retention position ( FIG. 4 ) and a release position ( FIG. 5 ). Advantageously, the movement of the actuator  50  between these positions is via a sliding motion that is generally parallel to the cavity&#39;s centerline  34 . In the release position, the recesses  60  are aligned with the holes  44  in wall  42 . In the lock position, the recesses  60  are offset from the holes  44 . The actuator  50  may advantageously be biased toward the lock position by suitable means, such as spring  64 .  
         [0017]     The retention elements  70 , which are distinct from the actuator  50 , are moveably disposed in respective holes  44  in wall  42  and move generally laterally toward and away from the actuator  50  so as to selectively protrude into cavity  32  to at least centerline  34 . The retention elements  70  advantageously take the form of spherical balls, but other shapes may be used. For example, the retention elements  70  may take the form of short pins, with angled or curved (e.g., hemispherical) tips disposed toward the centerline  34 . In some embodiments, the retention elements  70  may be biased away from the actuator  50 , such as by springs (not shown), integral with or external to the retention elements  70 ; in other embodiments, the retention elements  70  are not biased.  
         [0018]     As illustrated in  FIG. 4 , with the actuator  50  in the lock position ( FIG. 4 ), the recesses  60  are offset from holes  44 , and the cam surfaces  62  engage retention elements  70 . This arrangement forces the retention elements  70  inward toward the cavity&#39;s centerline  34 . Thus, the retention elements  70  are forced to assume positions protruding into the blade-receiving cavity  32 . The retention elements  70  may be forced inward such that they contact the opposing wall  40 , but this is not required in all embodiments. With a blade  12  properly disposed in cavity  32 , at least the tips of the retention elements  70  extend into the blade&#39;s notches  16 . Removal of the blade  12  out slot  36  is prevented by the interference of the retention elements  70  against the boundary of the notches  16 . Thus, the blade  12  is retained against forces that might otherwise pull the blade  12  out of cavity  32 . Advantageously, the retention elements  70  are sized so that they completely fill their respective notches  16  when the actuator  50  is in the retention position, to thereby firmly anchor blade  12  in cavity  32 .  
         [0019]     As illustrated in  FIG. 5 , with the actuator  50  in the release position, the recesses  60  are generally aligned with the retention elements  70 . This allows the retention elements  70  to move outward, away from the centerline  34 , and into recesses  60 . The retention elements  70  can thus withdraw from their protruding positions to corresponding withdrawn positions that are closer to wall  42 . In these withdrawn positions, the retention elements  70  are retracted from the notches  16 , allowing the blade  12  to be removed via front slot  36 . Advantageously, the inward surfaces of the retention elements  70  are configured so that a forward displacement of the blade  12  imparts a lateral component of force on the retention elements  70  to move the retention elements  70  laterally outward. For example, if the retention elements  70  are balls, the interaction of the blade  12  with the curved face of the balls  70  can help urge the balls  70  laterally outward. Of course, this laterally outward movement of the retention elements  70  is prevented by the actuator  50  when the actuator  50  is in the lock position.  
         [0020]     The cam surfaces  62  on the actuator  50  may, if desired, be simple flat surfaces disposed parallel to the cavity&#39;s centerline  34 . However, in order to facilitate movement of the actuator  50  from the release position to the lock position, the cam surfaces  62  may advantageously include angled faces adjacent the recesses  60 . For example, the cam surfaces  62  may be formed, in whole or in part, by chamfers at the front wall of recesses  60 . With this arrangement, the angled interface of the cam surfaces  62  and balls  70  will naturally help force the balls  70  toward the centerline  34  as the actuator  50  is moved toward the lock position.  
         [0021]     As outlined above, the blade retention mechanism (or means) of the actuator  50  with recesses  60  and associated cam surfaces  62 , and the separate retention elements  70 , allow. the blade  12  to be selectively retained in cavity  32  in a position suitable for cutting operations. The retention elements  70  move laterally through holes  44  so as to selectively protrude into cavity  32  so as to engage blade  12  or be retracted toward actuator  50  so as to allow the blade  12  to be removed/replaced.  
         [0022]     The discussion above has assumed that there are two retention elements  70  in the blade retention mechanism, corresponding to the two notches  16  in a conventional utility knife blade  12 . However, there may be only one retention element  70  (and corresponding hole  44  in wall  42 ) in some embodiments. And, it should be understood that the utility knife  10  may include other features known in the art, such as used/replacement blade storage bays, retractable blade safety guards, and the like, without departing from the scope of the present invention.  
         [0023]     The various components of the main body  20  may be made of any suitable material known in the art, such as hardened steel, aluminum, plastics (reinforced and otherwise), ceramics, and the like. The blade  12  may be made from any material known in art of utility blades, such as stainless steel, with or without a hardened surface coating, such as titanium nitride or the like.  
         [0024]     The present invention may, of course, be carried out in other specific ways than those herein set forth without departing from the essential characteristics of the invention. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive, and all changes coming within the meaning and equivalency range of the appended claims are intended to be embraced therein.