Abstract:
The utility knife includes a handle and a replaceable blade having a lock retention notch. A blade lock mechanism includes a blade lock associated with the handle which automatically engages the lock retention notch on insertion of the blade into the handle. The blade lock mechanism further includes a means for manually disengaging the blade lock from the lock retention notch in order to remove the blade from the handle.

Description:
BACKGROUND OF THE INVENTION 
       [0001]    The present disclosure generally relates to a utility knife. More particularly, the invention relates to a utility knife having a blade lock mechanism for automatically retaining a replaceable blade upon insertion of the blade into the utility knife handle. 
         [0002]    Utility knives generally known in the art include replaceable or interchangeable knife or box cutting blades. These knives may include blades that are fixed at one end during assembly and are thereafter continuously exposed. Without a protective guard, the constantly exposed knife blade presents a continuing risk of injury to users and a continual risk of damage to objects that come in contact with the knife blade. This risk exists even when the knife is not in use. These fixed blade knives require disassembly of the knife body to remove or replace a worn out or damaged blade. During disassembly, users risk losing or damaging knife components including the handle, blade, or blade retaining mechanism. In some cases, reassembly is complicated and requires instruction manuals or other special tools and supplies developed by the manufacturer. Such burdens decrease the overall efficient operation, user convenience, and performance of the knife because of the additional time, money, and energy required to replace the utility blade. Disassembly and reassembly are simply an inconvenient burden placed on the end user. 
         [0003]    In another utility knife design, the knife handle utilizes a slideably retractable knife blade. In one example, the knife blade includes a continuous multiblade unit that is capable of extension beyond the end of the knife handle through the use of a button mechanism. This mechanism is incorporated into the knife blade handle and is depressed into a channel for slideably extending and retracting the multiblade unit. The individual blades are separated by scorelines located at intermittent intervals along the length of the continuous multiblade unit. Individual blades that wear out, break, or simply need replacement are separated from the continuous multiblade unit along the scorelines separating the individual blades. A new blade previously concealed within the utility knife handle replaces the old blade, once the old blade is separated. The method of replacing blades by means of breaking off worn out or broken blades certainly presents the danger of inadvertent injury to the user or surrounding objects. 
         [0004]    In a similar design, the multiblade utility knife may be actuated by a thumbscrew. The thumbscrew is manually operated and requires loosening before the knife is capable of being extended or retracted. Once freed, the thumbscrew mechanism slides lengthwise along the handle to extend or retract the utility knife. The thumbscrew then requires retightening once the utility blade is in the desired position. Typically, both the button mechanism and thumbscrew designs require disassembly of at least a two-piece knife handle to remove and replace the continuous multiblade knife unit. 
         [0005]    Other utility blades include designs that enable users to store a rotatable utility blade or box cutting blade in the handle or a portion of the handle thereof. In these designs, the knife blade is mounted to an arm that rotates upon an axis point connected to one end of the utility knife handle. The blade is initially rotated from a stored position concealed within the handle to an extended position wherein the knife is capable of being used as a cutting apparatus. Some designs allow the knife to be locked into place by an engagement mechanism. The locking mechanism prevents inadvertent dislodgement of the knife from the extended position. When not in use, the blade is rotated back to a stored position by unlocking the engagement mechanism, if present, by the use of a button mechanism or the like. The blade then rotates around the pivot point at one end of the blade handle and back into the base of the handle for safe storage. But, for reasons for stability and safety, the utility blade is generally locked into the rotatable arm. Blade replacement therefore requires disassembly of the handle unit or the rotational arm in order to remove and replace the blade. Another disadvantage to this design is that the knife handle and rotatable utility blade arm include a series of mechanical parts. This increases material, manufacturing, and labor costs to develop and assemble the knife unit. Increasing the complexity of the knife blade retention mechanism increases usage difficulties and expense. Again, knife blade replacement may require complicated operation, manufacturer instructions, or special tools. 
         [0006]    In still another utility knife design, the knife blade could be automatically retractable by a spring-biasing mechanism. The knife blade automatically retracts into the handle unit upon release of an operating lever. In the retracted position, a spring biases the utility blade carrier unit rearwardly. The carrier unit is released when a user compresses a protruding release mechanism mechanically coupled to the knife blade carrier. The spring releases the utility blade carrier unit, resulting in the extension of the utility blade. Again, these utility knife blade designs typically require manual separation of multiple handle pieces in order to replace worn out or broken blades. In one particular design, the user must remove an outer cover to expose the interior of the knife unit. Removal of the outer cover requires the use of a screwdriver or other tool to dislodge or unscrew the outer cover. Thus, additional tools, time, and handling are required. Such factors all reduce the ease of replacing the knife blade. 
         [0007]    Thus, there remains a need for a utility knife incorporating a simple and inexpensive construction that includes a small number of component parts and does not require disassembly of the utility knife to remove or replace the knife blade. Furthermore, the knife blade removal mechanism should be simple and should not require the use of special tools. A quick and easy knife blade engagement and release mechanism is therefore needed for blade replacement or complete blade removal for periods of non-use. The present invention provides such a device. 
       SUMMARY OF THE INVENTION 
       [0008]    The present invention is directed to a utility knife having a handle with a replaceable blade retained therein. The utility knife includes a blade lock mechanism and a blade lock associated with the handle that automatically engages the lock retention notch of a replaceable blade upon insertion of the blade into the handle. The blade lock mechanism further includes a means for manually disengaging the blade lock from the lock retention notch in order to remove the blade from the handle. In one embodiment, the utility knife handle may further include a guide for aligning the blade within the handle. Alternatively, the utility knife may have an angled handle head further exposing a cutting edge of the blade when inserted in the handle. A debris release channel may also be integrated into the handle to prevent debris from clogging the interior of the handle due to replacement of the utility knife blade. 
         [0009]    In an alternative embodiment of the present invention, the blade lock mechanism comprises a spring manually actuable by a lock release mechanism. The lock release mechanism may include a button externally accessible from the handle. Accordingly, the blade is sandwiched between the spring and the lock release mechanism after insertion of the blade into the handle. The blade lock is attached to the handle and automatically engages the lock retention notch of the replaceable blade after insertion. To remove the blade from the handle, the lock release mechanism compresses the spring into a chamber in the handle and depresses the blade within a slot formed in the handle to disengage the lock retention notch from the blade lock. Thereafter, the blade may be removed from the utility knife and replaced. The spring may comprise a cantilever spring, a flat spring or a coil spring. 
         [0010]    In another alternative embodiment of the present invention, the blade lock mechanism is pivotally coupled to the handle and comprises a pivotable arm and a spring coupled to a proximate end of the arm. The blade lock is accordingly located on a distal end of the arm. To remove the blade from the handle, the pivotal arm is rotated, compressing the spring, such that the blade lock disengages the lock retention notch of the replaceable blade. In this position, the replaceable blade is removed from the handle. Again, the spring may comprise a cantilever spring, a flat spring or a coil spring. 
         [0011]    In a particularly preferred embodiment of the present invention, the handle includes a recess therein for providing access to the proximate end of the arm. The recess is used in association with a collar that prevents access to the proximate end of the arm when the blade moves out from a fully extended position. Thereafter, the blade lock cannot be disengaged from the lock retention notch because the collar prevents access to the proximate end of the arm, which requires depression to remove the blade lock from the lock retention notch. Accordingly, this prevents inadvertent dislodgement of the replaceable blade from within the handle during periods of nonuse. 
         [0012]    Other features and advantages of the present invention will become apparent from the following more detailed description, when taken in conjunction with the accompanying drawings, which illustrate, by way of example, the principles of the invention. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0013]    The accompanying drawings illustrate the invention. In such drawings: 
           [0014]      FIG. 1  illustrates a perspective view of a utility knife of the present invention; 
           [0015]      FIG. 2  illustrates an exploded view of a utility knife and the internal knife blade release mechanism of  FIG. 1 ; 
           [0016]      FIG. 3  further illustrates an exploded view of the utility knife shown in  FIG. 1 ; 
           [0017]      FIG. 4  is an inverted exploded view of the utility knife of  FIG. 3 ; 
           [0018]      FIG. 5  illustrates the internal knife blade retention mechanism of a utility knife of  FIG. 1 ; 
           [0019]      FIG. 6  is a cross-sectional view of  FIG. 1  taken along lines  6 - 6 , illustrating the knife blade in the locked position; 
           [0020]      FIG. 7  is a cross-sectional view of  FIG. 1  taken along lines  6 - 6 , wherein the knife blade is unlocked by a release button; 
           [0021]      FIG. 8  is a perspective view of a prior art utility knife incorporating a known side release mechanism; 
           [0022]      FIG. 9  illustrates an exploded view of the utility knife of  FIG. 8 , illustrating the internal knife blade release mechanism; 
           [0023]      FIG. 10  is another exploded view of the utility knife of  FIG. 8 ; 
           [0024]      FIG. 11  is a cross-sectional view of  FIG. 8  taken along lines  11 - 11 , illustrating the knife blade in the locked position; 
           [0025]      FIG. 12  is an alternative view of  FIG. 8  taken along lines  11 - 11 , wherein the knife blade is unlocked by a release button; 
           [0026]      FIG. 13  is a cross-sectional view of  FIG. 8  taken along lines  13 - 13 , illustrating the knife blade in the locked position; 
           [0027]      FIG. 14  is a cross-sectional view of  FIG. 8  taken along lines  13 - 13 , wherein the knife blade is unlocked by a release button; 
           [0028]      FIG. 15  illustrates an alternate embodiment of the present invention, wherein the quick release button is formed as a rocker arm; 
           [0029]      FIG. 16  further illustrates the utility knife of  FIG. 15 , wherein the rocker arm is in the unlocked position; 
           [0030]      FIG. 17  illustrates the rocker arm of  FIGS. 15-16  perpendicular to a flat spring, and including a debris release lock; 
           [0031]      FIG. 18  is a side view of the utility knife of  FIG. 15  taken along lines  18 - 18 , illustrating the knife blade in the locked position; 
           [0032]      FIG. 19  is a side view of  FIG. 14  taken along lines  19 - 19 , wherein the knife blade is in the unlocked position; 
           [0033]      FIG. 20  is a perspective view of a utility knife incorporating yet another alternate quick release mechanism incorporating a rocker arm and coil spring; 
           [0034]      FIG. 21  is an exploded perspective view of the utility knife of  FIG. 20 , illustrating the rocker arm and coil spring combination; 
           [0035]      FIG. 22  is an inverted exploded perspective view of  FIG. 21 ; 
           [0036]      FIG. 23  is a side view of  FIG. 20  taken along lines  23 - 23 ; 
           [0037]      FIG. 24  is a cross-sectional view of  FIG. 23  taken along lines  24 - 24 , illustrating the internal alternate rocker arm knife blade release mechanism in the locked position; 
           [0038]      FIG. 25  is another side view of  FIG. 23  taken along lines  24 - 24 , wherein the knife blade is in the unlocked position. 
           [0039]      FIG. 26  is a side view of an alternative utility knife incorporating a rocker arm and coil spring; 
           [0040]      FIG. 27  is a side view of utility knife of  FIG. 26  taken along lines  27 - 27 , illustrating the internal quick release mechanism in the locked position; 
           [0041]      FIG. 28  is a side view of the utility knife of  FIG. 26  taken along lines  27 - 27 , wherein the quick release button is in the unlocked position; 
           [0042]      FIG. 29  illustrates a perspective view of the utility knife of the present invention incorporated into a knife handle; 
           [0043]      FIG. 30  is another perspective view of  FIG. 29 , wherein the knife blade is rotating from a closed position to an open position; and 
           [0044]      FIG. 31  is another perspective view of  FIG. 29 , wherein the knife blade is in the open position. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0045]    As shown in the exemplary drawings for purposes of illustration, the present disclosure for a utility knife is referred to generally by the reference numeral  10 . Turning now to the representative figures in the specification,  FIG. 1  illustrates a utility knife  10  incorporating a knife blade  12 . In this embodiment, the utility knife  10  is constructed of three layers that include a top layer  14 , an intermediate layer  16 , and a bottom layer  18 . It is conceived, however, that two or more layers could be used to form the utility knife  10 . A release button  20  further facilitates the release or engagement of the knife blade  12  within the utility knife  10  via an actuator spring  22 . 
         [0046]    For the button  20  and the actuator spring  22  to properly function as a release or engagement mechanism, the top layer  14 , intermediate layer  16 , and the bottom layer  18  must be secured to one another in the form generally shown in  FIG. 1 . The bottom surface of the top layer  14  is facingly adjacent to the top surface of the intermediate layer  16 . The top surface of the bottom layer  18  is thus facingly adjacent to the bottom surface of the intermediate layer  16 . As shown in  FIG. 1 , the intermediate layer  16  is effectively sandwiched between the top layer  14  and the bottom layer  18 . As further described herein, this sandwiched configuration in combination with the release button  20  and the actuator spring  22  enable the utility knife  10  to effectively accept and retain the knife blade  12 . 
         [0047]    A variety of designs known in the art may be used to retain the top layer  14 , the intermediate layer  16 , and the bottom layer  18  in the sandwiched configuration of  FIG. 1 . In  FIG. 2 , a pair of screws  24  are shown extending vertically through the width of the utility knife  10  and engaging a pair of nuts  26  to secure the top layer  14 , the intermediate layer  16 , and the bottom layer  18  together. As better depicted in  FIG. 3 , the pair of screws  24  extend through a series of holes  28  in the top layer  14 , in the intermediate layer  16 , and in the bottom layer  18 . In this embodiment, the pair of screws  24  may engage the pair of nuts  26  by threaded engagement or any other mechanism known in the art. Additionally, the pair of screws  24  and the pair of nuts  26  may be replaced by other securement devices having a similar function that are known in the art. Such securement devices might include clips, clamps, springs, bolts, rivets or welds. Additionally, it is conceived that chemical adhesives could be used to bind the bottom surface of the top layer  14  to the top surface of the intermediate layer  16  and to bind the top surface of the bottom layer  18  to the bottom surface of the intermediate layer  16 . Thus, eliminating the need of a mechanical device. The important aspect of this sandwiched formation is that the release button  20  and the actuator spring  22  are tensioned against one another. 
         [0048]    The utility knife  10  as shown in  FIG. 2  illustrates the placement of the release button  20  with respect to the actuator spring  22 . A groove  30  is etched into the top surface of the top layer  14  to provide ample fingertip engagement with the release button  20 . The actuator spring  22  resides in a spring channel  32  (best shown in  FIG. 3 ) and a spring guide  34  (best shown in  FIG. 4 ) and is used to bias the release button  20  in an upward position. The release button  20  extends through a pair of release button holes  36  to protrude out from the top surface of the top layer  14  in the groove  30 . The actuator spring  22  maintains the release button  20  in this protruding position. The combination of the release button  20  and the actuator spring  22  is the mechanism that locks or unlocks the knife blade  12  from the utility knife  10 . 
         [0049]    As shown in  FIG. 4 , the release button  20  has a retaining lip  38  that engages a retaining ledge  40  located beneath the surface of a knife blade channel  42 . A head portion  44  of the release button  20  is preferably flush with the surface of the knife blade channel  42 . Before the knife blade  12  is inserted into the knife blade channel  42 , the head portion  44  of the release button  20  contacts a top surface  46  of the actuator spring  22 . The actuator spring  22  resides in and is retained by the spring channel  32  in the bottom layer  18 . The spring channel  32  prevents movement of the actuator spring  22  during use or transportation of the utility knife  10 . The corresponding spring guide  34  in the intermediate layer  16  allows the actuator spring  22  to extend into a portion of the knife blade channel  42  for proper retainment of the knife blade  12  within the knife blade channel  42 . The spring guide  34 , like the spring channel  32 , helps locate and prevent dislodgment of the actuator spring  22  during use or transportation. The top surface  46  of the actuator spring  22  is facingly adjacent to the head portion  44  of the release button  20 . In this configuration, the release button  20  is pushed up by the actuator spring  22  through the release button holes  36  in the intermediate layer  16  and the top layer  14 . The release button  20  is maintained in this upward position as protruding through the top surface of the top layer  14  and the groove  30  when the utility knife  10  is fully assembled. 
         [0050]    As the knife blade  12  is inserted into the knife blade channel  42 , the head portion  44  of the release button  20  and the top surface  46  of the actuator spring  22  are separated by the knife blade  12 . When fully inserted, the knife blade  12  is wedged between the release button  20  and the actuator spring  22 . In a particularly preferred embodiment, the top surface  46  of the actuator spring  22  is formed by a radiused edge to permit smooth insertion of the knife blade  12 . Furthermore, the head portion  44  of the release button  20  is also preferably rounded to ease the insertion of the knife blade  12 . But, a variety of spring and release button designs could be used pending insertion of the knife blade  12  may be automatically inserted into the utility knife  10 . Once inserted, the knife blade  12  is substantially flush to the bottom surface of the knife blade channel  42 , as best shown in  FIG. 5 . Release of the knife blade  12  is facilitated by depression of the release button  20 . 
         [0051]    Protrusion of the release button  20  through the top surface of the top layer  14  enables external fingertip engagement by a user. The groove  30  formed in the top surface of the top layer  14  enables a user to depress the release button  20  by applying downward pressure thereon and thereafter effectively compressing the actuator spring  22  thereunder. Depression of the release button  20  from an initial position ( FIG. 6 ) to a depressed position ( FIG. 7 ) is the basis of the quick release mechanism that unlocks the knife blade  12  from within the knife blade channel  42  in the embodiments of  FIGS. 1-7 . 
         [0052]    Insertion of the knife blade  12  into the knife blade channel  42  does not require depression of the release button  20 . A user may simply slide the knife blade  12  into an insertion slot  48  ( FIGS. 6 and 7 ) formed on a front end  50  of the utility knife  10  between the intermediate layer  16  and the bottom layer  18 . As best shown in  FIG. 6 , once the knife blade  12  is fully inserted into the knife blade channel  42 , the knife blade  12  is wedged between the top surface  46  of the actuator spring  22  and the head portion  44  of the release button  20 . In this position, the knife blade  12  engages and is retained by a knob  52  ( FIG. 4 ). The knob  52  is configured to engage any one of a pair of engagement slots  54  formed on one side of the knife blade  12 . In the embodiment of  FIG. 4 , the knife blade  12  is configured in a trapezoidal shape such that the engagement slots  54  are located opposite a blade  56 . As shown in  FIG. 6 , one of the engagement slots  54  fits snuggly into and is retained by the knob  52 . It is contemplated in the present disclosure that the knob  52  and the engagement slots  54  could comprise a variety of shapes, sizes, or configurations, including multiple knobs. The important aspect is that there is a mechanism to retain the knife blade  12  in a substantially ridged position when inserted into the utility knife  10  via the release button  20  and the actuator spring  22 . 
         [0053]    When the knife blade  12  is fully inserted into the knife blade channel  42  and retained by the knob  52 , the user should not experience substantial movement of the knife blade  12 . In such a configuration, the knife blade  12  fits snugly within the housing of the knife blade channel  42 .  FIG. 5  is an exemplary illustration of the knife blade  12  situated in the knife blade channel  42  as retained by the knob  52  in engagement with one of the engagement slots  54 . The knife blade channel  42  further includes a base guide edge  58  and a blade side guide edge  60  configured to fit the shape of the knife blade  12 . When inserting the knife blade  12  within the insertion slot  48 , the base guide edge  58  and the blade side guide edge  60  reside substantially parallel to and adjacent to a base side  62  and the blade  56 , respectively, of the knife blade  12 . Furthermore, an end stop  64  is angled to receive one side of the trapezoidal knife blade  12  to ensure proper location and engagement of at least one of the engagement slots  54  with the knob  52 . 
         [0054]      FIG. 6  illustrates the knife blade  12  as fully inserted into the utility knife  10 . The knife blade  12  fits snuggly between the actuator spring  22  and the release button  20  in the knife blade channel  42 . One of the engagement slots  54  is effectively retained by the knob  52 . In this configuration, the utility knife  10  is in operational use. 
         [0055]    Releasing the knife blade  12  from the utility knife  10  consists of a single disengagement step. Pressure is exerted along the directional arrow in  FIG. 7  such that the release button  20  is depressed against the knife blade  12  and into the body of the knife blade channel  42 . Accordingly, the actuator spring  22  also depresses to facilitate disengagement of the engagement slot  54  from the knob  52 . In this position, the top of the knife blade  12  clears the bottom of the knob  52 . The knife blade  12  is thus freely movable horizontally along the lines located at the front end  50  of the utility knife  10 . In this disengaged configuration, a user may easily remove the knife blade  12  from the utility knife by simply grasping and pulling the knife blade  12  from the insertion slot  48 . Once the knife blade  12  is removed, another new knife blade may be inserted or the utility knife  10  could be safely stowed without a knife blade for future use. 
         [0056]    Additionally, the front end  50  of the utility knife  10  is configured for maximum exposure of the blade  56 . As best shown in  FIG. 1 , the front end  50  contains an angled portion  66  that runs back along the length of the blade  56 . The angled portion  66  provides additional exposure of the blade  56 , thereby increasing cutting surface and efficiency of the utility knife  10  of the present invention. It is also conceived in the present invention that the configuration of the angled portion  66  could include multiple designs or shapes to maximize exposure of the blade  56 . Other alternate embodiments of this concept are further illustrated below. 
         [0057]      FIGS. 8-14  disclose a sample prior art embodiment of the utility knife  10 . In  FIG. 8 , the top layer  14  is connected directly to the bottom layer  18  by the screw  24  and the nut  26  combination ( FIG. 9 ). The top layer  14  and the bottom layer  18  could also be connected by any of the mechanisms or adhesives already described. In this embodiment, the utility knife  10  has a similar, yet shorter, groove  30  of which the release button  20  is accessible for fingertip engagement. Many different designs of the groove  30  are capable of being incorporated into the present invention pending adequate fingertip engagement is provided to actuate the corresponding spring. Additionally  FIG. 8  discloses a radiused edge  68  that provides ample exposure of the blade  56  of the knife blade  12 , similar to the angled portion  66  illustrated in  FIG. 1 . 
         [0058]      FIG. 9  illustrates an exploded view of the utility knife  10  incorporating a prior art blade release mechanism. The blade retaining mechanism shown in  FIG. 9  is a clip  70  that is sandwiched between the top layer  14  and the bottom layer  18 . The clip  70  resides in a clip channel  72  formed into the bottom layer  18 . A spring arm  74  is integrally formed from the clip  70 . The spring arm  74 , as shown in  FIG. 9  has the two knobs  52  formed therein to retain the knife blade  12  via the engagement slots  54 . The two knobs  52  protrude from the clip  70  and are adjacent to an upper rail  76 . As best shown in  FIG. 11 , the top portion of the upper rail  76  biases the head portion  44  of the release button  20  in an upward position. The release button  20  extends through a release aperture  78  formed in the top layer  14  and protrudes from the surface of the groove  30  for fingertip engagement. The release button  20  is effectively held in place by the spring arm  74 .  FIG. 10  better illustrates the placement of the clip  70  within the clip channel  72  of the bottom layer  18  for biasing the release button  20  in this upward position. When the clip  70  is seated within the clip channel  72  untensioned, the spring arm  74  is substantially parallel to the base of the clip channel  72 . 
         [0059]    In operation, the release button  20  is depressed (shown best between  FIGS. 11 and 12  and between  FIGS. 13 and 14 ) such that the head portion  44  of the release button  20 , as continually mated to the top surface of the upper rail  76 , depresses the spring arm  74  into a spring arm channel  80  ( FIG. 9 ). The groove  30  is configured to provide sufficient fingertip engagement to enable adequate depression of the release button  20  and the corresponding spring arm  74 . Adequate depression requires that the spring arm  74  is depressed far enough into the spring arm channel  80  to disengage the knobs  52  from the engagement slots  54  of the utility blade  12 .  FIGS. 12 and 14  represent the knife blade  12  in the unlocked position such that the knife blade  12  can either be slidingly inserted or slidingly released from the clip  70 . 
         [0060]    In  FIGS. 13-14 , the knife blade  12  is inserted through the insertion slot  48  formed between the top layer  14  and the bottom layer  18 . To insert the knife blade  12 , the release button  20  and the spring arm  74  must be depressed into the spring arm channel  80  such that the knobs  52  are deflected below the surface level of the slide clip channel  72 . This extra step prevents users from automatically inserting a replacement blade into the utility knife  10 , unlike the embodiments of the present invention illustrated in  FIGS. 1-7  and  15 - 31 . Inadequate depression of the release button  20  and spring arm  74  will prevent insertion of the knife blade  12 . Thus, the knife blade  12  can not be automatically inserted into the insertion slot  48  without interference with the knobs  52 . Only after depression of the release button  20  and the spring arm  74  can insertion be accomplished. Upon insertion, the knife blade  12  is guided into the clip  70  by the base guide edge  58  and blade side guide edge  60  show best in  FIGS. 9-10 . The end stop  64  laterally aligns the utility blade  12  such that the pair of knobs  52  engage the engagement slots  54  when the release button  20  is no longer depressed and the spring arm  74  returns to an untensioned position. 
         [0061]      FIGS. 15-19  illustrate an alternative embodiment of a blade retention mechanism of the present invention.  FIGS. 15-17  illustrate the motion of a rocker arm  82  disposed within a slot  84  formed from the assembly of a first body half  86  and a second body half  88 . A pivot pin  90  is concentrically located within an aperture formed in the first body half  86  (not shown), an aperture formed in the second body half  88  (not shown) and an aperture formed in the rocker arm  82  (also not shown). The rocker arm  82  rotates within the slot  84  around the pivot pin  90 . To move the rocker arm  82  from a locked position ( FIGS. 15 and 18 ) to an unlocked position ( FIGS. 16-17  and  19 ), an engagement slot  92  is utilized for fingernail engagement to rotate the rocker arm  82  upwardly along the arrows in  FIG. 16 . A recess  94  formed in the second body half  88  provides adequate fingernail engagement with the engagement slot  92 . 
         [0062]    The blade retention mechanism of  FIGS. 15-19  enable a user to insert the knife blade  12  by either first moving the rocker arm  82  to an unlocked position or by simply automatically inserting the knife blade  12  into the insertion slot  48 . Without first unlocking the rocker arm  82 , users may insert the knife blade  12  into the insertion slot  48  by angling a portion of the knife blade  12  within the insertion slot  48 . The rocker arm  82  is pushed upward slightly by the base side  62  of the knife blade  12  to enable the engagement slots  54  to automatically slide into place without the obstruction of a retainment finger  96  located at the end of the rocker arm  82 . 
         [0063]    Once the knife blade  12  is inserted into the insertion slot  48  and effectively retained by the retainment finger  96  of the rocker arm  82 , the knife blade  12  cannot be removed without manually rotating the rocker arm  82  to the unlocked position via fingernail engagement through the engagement slot  92 . Manual rotation of the rocker arm  82  is required because the retainment finger  96  is held in tension by a flat spring  98 . When the rocker arm  82  is in the locked position, the flat spring  98  resides substantially untensioned in a slot formed as part of the first body half  86  and the second body half  88 . As the rocker arm  82  is rotated to an unlocked position, an edge  100  of the rocker arm  82  rotates and deflects a portion of the flat spring  98  downwardly. In the configuration shown in  FIG. 19 , the flat spring  98  is tensioned and applies a force to the rocker arm  82  at the contact point with the edge  100 . This force creates counter-clockwise rotational moment on the rocker arm  82 . The rotational moment will rotate the rocker arm  82  back into the locked position of  FIG. 18  with any displacement of the flat spring  98 . Hence, the rocker arm  82  is retained in the locked position absent reactant forces to maintain the rocker arm  82  in the unlocked position. Yet, the knife blade  12  may be automatically inserted into the utility knife  10  without manually rotating the rocker arm  82  to the unlocked position. 
         [0064]    Although, as shown in  FIG. 17 , if the rocker arm  82  is rotated to a position substantially perpendicular to the flat spring  98 , the edge  100  loses contact with the flat spring  98 . In  FIG. 17 , the flat spring  98  no longer exerts a rotational force on the rocker arm  82 . Thus, the rocker arm  82  may reside in the substantially perpendicular position of  FIG. 17  without rotating back to the locked position as previously described. In fact, the flat spring  98  now assumes the opposite role. The flat spring  98  will exert a force at the contact point of the edge  100  that creates a clockwise moment on the rocker arm  82 . This opposite rotational moment will attempt to retain the rocker arm  82  in the perpendicular, unlocked position. But, once the rocker arm  82  is rotated beyond a threshold point, the flat spring  98  will again exert the counter-clockwise rotational force on the rocker arm  82  wherein the rocker arm  82  snaps back into the locked position. 
         [0065]    Location of the knife blade  12  within the insertion slot  48  of the utility knife  10  is accomplished in a similar manner as the previous embodiments. As illustrated in  FIG. 18 , the base guide edge  58  and the corresponding blade side guide edge  60  vertically locate the knife blade  12  within the insertion slot  48 . Additionally, the end stop  64  locates the knife blade  12  horizontally within the insertion slot  48 . Once aligned, the retainment finger  94  is easily engageable with the engagement slot  54 . 
         [0066]    As an additional feature,  FIGS. 17-19  illustrate a debris release slot  102  located behind the end stop  64 . During the use of the utility knife  10 , debris can get caught in the insertion slot  48 , especially when the knife blade  12  is inserted or removed. If the end stop  64  did not contain a series of gaps  104 , debris would get pushed back within the body of the utility knife  10 . When a new knife blade  12  is inserted, the debris is trapped and even compacted against the end stop  64 . Removal of the compacted debris necessarily requires the step of disassembling the utility knife  10 . The series of gaps  104  as illustrated in  FIGS. 17-19  provide access to the debris release slot  102  located behind the end stop  64 . As the knife blade  12  is inserted into the insertion slot  48 , any debris residing within the insertion slot  48  is pushed toward the end stop  64  and through the series of gaps  104  and into the debris release slot  102 . Debris that would normally become trapped now resides in the debris release slot  102 . Here, the debris will not restrict easy and full insertion of the knife blade  12  within the insertion slot  48 . The debris exits through a series of exit points  106  formed on a bottom portion  108  between the first body half  86  and the second body half  88 . Debris that would otherwise jam in the insertion slot  48  and prevent insertion of the knife blade  12  therein is effectively flushed out through the debris release slot  102  without disassembly the first body half  86  from the second body half  88 . 
         [0067]      FIGS. 20-25  disclose another alternative embodiment of the present invention embodying a blade retention mechanism. It should be noted that the embodiments of  FIGS. 20-25  disclose only a knife blade retainment head  112  of the utility knife  10 . In  FIG. 20 , the rocker arm  82  resides within a slot (not shown) formed between the first body half  86  and the second body half  88 . The first body half  86  and the second body half  88  are held together by any of the mechanical mechanisms or chemical adhesives as previously disclosed, including the combination of the screw  24  and the nut  26  shown in  FIGS. 21-22 . The rocker arm  82  includes a pivot aperture  110  which pivot pin  90  is concentrically located. A pair of knife body mounting apertures  114  formed in the first body half  86  and the second body half  88  are used in combination with a knife body screw  116  ( FIGS. 29-31 ) to mount the knife blade retainment head  112  to the utility knife  10 . 
         [0068]    The rocker arm  82  has a first end  118  including the retainment finger  96  and a second end  120  including a button protrusion  122 . The retainment finger  96  resides within a retainment finger slot  124  formed in the first body half  86  and formed in the second body half  88 . When the knife blade retainment head  112  is fully assembled, as in  FIG. 23 , a coil spring  126  exerts a vertical force on the second end  120  of the rocker arm  82 . This vertical force creates a counter-clockwise rotational moment on the rocker arm  82  around the pivot pin  90 . In accordance with this counter-clockwise rotational moment, the first end  118  of the rocker arm  82  is forced within the retainment finger slot  124 . A horizontal base  128  is preferably adjacent and flush with a bottom area  130  of the retainment finger  96 . It is the horizontal base  128  that maintains the rocker arm  82  in a substantially horizontal position. 
         [0069]    When the rocker arm  82  is in this horizontal position, as shown in  FIGS. 23-24 , the coil spring  126  remains tensioned. Absent the horizontal base  128 , the coil spring  126  would continue rotating the rocker arm  82  about the pivot pin  90  until the coil spring  126  reached an untensioned state. The coil spring  126  maintains enough tension when the rocker arm  82  is in the horizontal position such that the retainment finger  96  retains the knife blade  12  within the insertion slot  48  via at least one of the engagement slots  54  as shown in  FIG. 24 . In  FIG. 25 , the coil spring  126  is further depressed and tensioned by applying the external force along the illustrated arrow. A pair of button gaps  132  (best shown in  FIGS. 21-22 ) formed in the first body half  86  and formed in the second body half  88  provide adequate fingertip engagement of the second end  120  to adequately depress the button protrusion  122 . Further depression of the coil spring  128  rotates the rocker arm  82  clockwise. The retainment finger  96  is effectively raised out of the knife blade channel  42 . The knife blade  12  is then freely movable laterally within the insertion slot  48 . Absent pressure exerted along the arrow in  FIG. 25 , the rocker arm  82  would return to the substantially horizontal position as shown in  FIG. 24 . The rocker mechanism of  FIGS. 15-31  have the same functionality regardless whether rotation of the rocker arm  82  is clockwise or counter-clockwise. 
         [0070]    As in previous embodiments, the base guide edge  58  and the blade side guide edge  60  locate the knife blade  12  within the insertion slot  48 . In embodiment of  FIG. 24 , a radius edge stop  134  contacts a portion of the blade  56  to locate the knife blade  12  horizontally within the insertion slot  48 . The combination of the base guide edge  58 , the blade side guide edge  60 , and the radius edge stop  134  guide the placement of the engagement slots  54  such that when the knife blade  12  is fully inserted, the retainment finger  96  engages at least one of the engagement slots  54 . The knife blade  12  thereafter resides snugly within the insertion slot  48 . 
         [0071]      FIGS. 26-28  show an alternative embodiment of the knife blade retaining head  112  of  FIGS. 20-25 . Like the embodiments in  FIGS. 20-25 , the knife retainment head  112  of  FIGS. 26-28  is also capable of being incorporated into the utility knife  10  of  FIGS. 29-31  via the knife body mounting aperture  114  and the corresponding knife body screw  116 . As shown in  FIGS. 26-28 , a recess  136  provides fingertip access to a rear portion  138  of the rocker arm  82 . Depression of the rocker arm  82  along the arrow shown in  FIG. 28  rotates the rocker arm  82  counter-clockwise. The coil spring  126  is depressed and the retainment finger  96  is raised from within the retainment finger slot  124 . The knife blade  12  is then freely movable for insertion or removal from the insertion slot  48  ( FIG. 31 ). The retainment finger  96  would no longer engage any one of the engagement slots  54  of the knife blade  12 . Once pressure is released from the rocker arm  82 , along the arrow in  FIG. 28 , the rocker arm  82  rotates back to the position in  FIG. 27  along the pivot pin  90 . 
         [0072]    The incorporation of the recess  136  in combination with a pair of handle recesses  140  formed in a first handle half  142  and a second handle half  144  provide adequate fingertip engagement of the rear portion  138  of the rocker arm  82 . When the knife blade retainment head  112  is integrated into the utility knife  10  in  FIGS. 29-31 , the rear portion  138  is only accessible when the knife blade retainment head  112  is rotated into the fully extended position as shown in  FIG. 31 . When the knife blade retainment head  112  is either in the fully closed posited of  FIG. 29  or in intermediate position as shown in  FIG. 30 , the radius configuration of a handle front  146  prevents fingertip engagement of the rear portion  138  of the rocker arm  82 . The radius configuration of the handle front  146  prevents any inadvertent unlocking of the retainment finger  96  from either of the engagement slots  54  when the knife blade retainment head  112  is not in the fully extended position of  FIG. 31 . The rear portion  138  of the rocker arm  82  is only accessible for releasing the knife blade  12  via the recess  136  in the knife blade retainment head  112  and the handle recesses  140  formed in the first handle half  142  and the second handle half  144 . 
         [0073]    The first handle half  142  and the second handle half  144  may be held together by any of the securement devices or adhesives as previously disclosed, including the knife body screw  116 . 
         [0074]    Although various embodiments have been described in detail for purposes of illustration, various modifications may be made without departing from the scope and spirit of the invention.