Patent Publication Number: US-11376753-B2

Title: Disposable utility knife with safety lock

Description:
RELATED APPLICATIONS 
     This application claims priority the benefit of U.S. Provisional Patent Application, No. 62/699,741, filed Jul. 18, 2018, entitled: “Low-Cost Disposable Utility Knife with Safety Lock,” the contents of which are incorporated herein in their entirety. 
    
    
     FIELD OF THE INVENTION 
     The present invention relates to knives of the type commonly used to open and cutup corrugated boxes, cut sheetrock and other materials, and more particularly, to such knives that are disposable (i.e., of the type which provides no access to replace blades). 
     BACKGROUND OF THE INVENTION 
     So-called utility knives have been around for several decades. There have been numerous designs over the years, but regardless, all utility knives are generally simple in construction, providing a handle, a blade holder, and a selectively retractable razor blade. 
     The blade used in most utility knives has been standardized. It is generally made from sheet steel and is trapezoidal in planar shape. The long edge of the trapezoid-shaped blade is sharpened and defines the cutting edge of the blade. The short edge, opposite the cutting edge, (or top edge) of the blade includes two symmetrical U-shaped notches, directed towards the cutting edge. The two sides are symmetrically angled to connect the short edge with the long cutting edge, as is well known by those of ordinary skill in the art. 
     The blade fits snugly within the blade holder and the blade holder fits slidably within the handle. A conventional utility knife handle is usually made up of two hollow halves that may be selectively locked to each other to form a study handle and define a combined hollow cavity in which the blade holder and blade may reside and operate (as well as provide storage for additional blades). The combined handle assembly further includes a slot through which a portion of the blade holder may pass, in the form of a tab (finger purchase). The tab provides operational access to the user so that the user may selectively slide the blade holder, and therefore the blade as desired within a restricted range of displacement, while holding the handle. The blade holder (and blade) may be selectively displaced between a fully retracted position and an extended position. The blade in the fully retracted position is safely positioned within the housing. In contrast, the blade in the extended position exposes a portion of its cutting edge beyond one end of the handle so that useful cutting work may be performed by the user. 
     The blades of many such conventional utility knives can be replaced when they become dull, either by separating the two handle-halves or by feeding a new blade directly into the blade holder from the front of the knife. Although providing a feature of allowing replacement of a dull blade is generally beneficial, there has been a growing demand to provide a simple, safe and easy to use disposable utility knife that can be used and then just thrown away when the blade becomes dull. In response to this demand, several disposable utility knives are commercially available today. Some of these disposable utility knives include automatically activated safety covers or shields which move to cover and protect the otherwise exposed sharpened edge when the blade is not being used to cut, yet remains on “standby” with the blade protruding from the handle. 
     A problem with conventional disposable type utility knives is that they are still relatively expensive, considering that they only provide a single blade and when that blade dulls, the knife must be disposed. These knives also typically only offer a short cutting edge, between ¼″ and ⅜″. There have been complaints that the short cutting edge is not sufficient to fully cut thick corrugated shipping boxes and the shorter blade often dulls more quickly since a concentrated section of the blade is relied upon to perform all the cutting. 
     Accordingly, there remains room for improvement and variation within the art. 
     SUMMARY OF THE INVENTION 
     It is one aspect of at least one of the present embodiments to provide a useful, low cost disposable utility knife that is made up of few parts. 
     It is another aspect of at least one of the present embodiments to provide a disposable utility knife that is easy to manufacture and assemble. 
     It is another aspect of at least one of the present embodiments to provide a useful, low cost disposable utility knife that provides extended use for cutting. 
     It is yet another aspect of at least one of the present embodiments to provide a utility knife that is easy to use and that uses both sides of the conventional utility blade without opening the handle assembly. 
     It is yet another aspect of at least one of the present embodiments to provide a utility knife that is easy to use and that uses both sides of the conventional utility blade without opening the handle assembly, and provides an intuitive safety lock. 
     It is yet another aspect of at least one of the present embodiments to provide a portable utility knife comprising: a hollow elongated handle sized and shaped to be easily gripped by a user&#39;s hand, the handle including an upper surface and opposing first and second ends, the hollow handle defining a cavity therein; an elongated slot disposed along the upper surface, the slot providing access through the handle to the cavity; a first opening located at the first end and a second opening located at the second end, the first and second openings extending through the handle to the cavity; a blade shuttle positioned within the cavity and selectively slidable between the first end and the second end; a razor blade secured to the shuttle, the razor blade having a cutting edge, the cutting edge defining a first cutting edge section and a second cutting edge section so that when the shuttle is positioned within the cavity and adjacent the first end, the first cutting edge section of the razor blade extends through the first opening of the handle to expose the first cutting edge section to provide useful cutting work, and when the shuttle is positioned adjacent the second end, the second cutting edge section of the razor blade extends through the second opening to expose the second cutting edge section to provide useful cutting work; 
     a tab attached to the blade shuttle, the tab extending through the elongated slot so that a portion of the tab is accessible to a user, the tab may be used to slide the shuttle within the cavity between the first and second ends; and a movable locking component attached to the handle, the locking component being selectively moveable between a first position, wherein the tab is prevented from sliding within the elongated slot, and a second position, wherein the tab is permitted to slid within the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the locking component is U-shaped and is pivotally attached to the handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the U-shaped locking component is pivotally attached to the handle across the elongated slot and is pivotal between a down position, wherein the tab is physically blocked from sliding along the elongated slot, and an up position, wherein the tab is permitted to slide along the elongated slot under the U-shaped locking component. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the elongated slot includes at least one locking notch into which the tab may selectively engage to lock the tab with respect to the handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the tab is spring-biased to automatically engage the at least one locking notch when the tab aligns with the locking notch during sliding displacement along the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the at least one locking notch is positioned at the midpoint of the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the locking component is located at the middle of the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide safety knife for use by a user, the knife comprising: an elongated handle having opposing first and second ends; a blade assembly slidably attached to the handle, the blade assembly being selectively slidable between the first and second ends, the blade assembly including a cutting edge that is exposed for useful work by the user when the blade assembly is located adjacent one of the first and second ends; and 
     an obstructive component moveably attached to the handle, the obstructive component being moveable between an obstructive position, wherein sliding passage of the blade assembly between the first and second ends of the handle is prevented and a non obstructive position, wherein sliding passage of the blade assembly between the first and second ends is permitted. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the elongated handle is hollow and the blade assembly is slidably disposed within the hollow handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the blade assembly further comprises a tab and wherein the hollow handle comprises an elongated slot through which the tab is positioned and along which the tab may slide. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the obstructive component is a U-shaped member that is pivotally attached to the handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the U-shaped obstructive component is pivotally attached to the handle across the elongated slot and is pivotal between a down position, wherein the tab is physically blocked from sliding along the elongated slot, and an up position, wherein the tab is permitted to slide along the elongated slot under the U-shaped locking component. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the elongated slot includes at least one locking notch into which the tab may selectively engage to lock the tab with respect to the handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the tab is spring-biased to automatically engage the at least one locking notch when the tab aligns with the locking notch during sliding displacement along the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the at least one locking notch is positioned at the midpoint of the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the obstructive component is located at the middle of the elongated slot. 
     It is yet another aspect of at least one of the present embodiments to provide a safety knife for use by a user, the knife comprising: an elongated handle having opposing first and second ends; a blade assembly slidably attached to the handle, the blade assembly being selectively slidable between the first and second ends, the blade assembly including a cutting edge that is exposed for useful work by the user when the blade assembly is located adjacent one of the first and second ends; an access tab attached to the blade assembly, the access tab being accessible to the user; and a U-shaped locking component pivotally attached to the handle between a blocking position, wherein the tab is physically blocked from sliding between the first and second ends, and a non-blocking position, wherein the tab is permitted to slide between the first and second ends; an obstructive component moveably attached to the handle, the obstructive component being moveable between an obstructive position, wherein sliding passage of the blade assembly between the first and second ends of the handle is prevented and a non obstructive position, wherein sliding passage of the blade assembly between the first and second ends is permitted. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the handle includes at least one locking notch into which the tab may selectively engage to lock the tab with respect to the handle. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the tab is spring-biased to automatically, engage the at least one locking notch when the tab aligns with the locking notch during sliding movement between the first and second ends. 
     It is yet another aspect of at least one of the present embodiments to provide a knife wherein the at least one locking notch is positioned generally at the midpoint between the first and second ends. 
     As described herein, a low cost disposable utility knife includes a hollow handle having an elongated slot and an opening at each end. A blade shuttle holds a trapezoidal razor blade and is slidably mounted on tracks integrally formed within the hollow handle and slidable between each end of the handle. When the shuttle is located at either end, a cutting edge of the razor extends beyond the opening of the adjacent handle end and is accessible for useful cutting work by a user. The shuttle includes a tab that is positioned within the elongated slot and includes a portion that is accessible to the user. The user may use the accessible tab to slide the shutter and the blade within the handle between the two ends, as desired. A U-Shaped flip lock is pivotally attached to the handle between a down position, wherein the tab is physically blocked from sliding along the elongated slot, and an up position, wherein the tab is permitted to slide along the elongated slot, passing under the U-shaped flip lock. 
     The elongated slot may further include at least one locking notch into which a portion of the tab may selectively engage. The tab may be spring-biased to automatically engage the at least one locking notch when the tab resides adjacent thereto. 
     The features of this invention, and the manner of attaining them, will become more apparent and the invention itself will be better understood by reference to the following description of the disclosed embodiments taken in conjunction with the accompanying drawings. Such features, aspects, and advantages of the present invention will become better understood with reference to the following description and appended claims. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A fully enabling disclosure of the present invention, including the best mode thereof to one of ordinary skill in the art, is set forth more particularly in the remainder of the specification, including reference to the accompanying drawings. 
         FIG. 1  is a side elevation view of a utility knife, according to the present invention, including a handle, a blade, a blade shuttle having an integral finger tab and a flip lock shown in a first down and locked position, the blade being shown in an extended position at a first end of the handle labeled “TWO”. 
         FIG. 2  is a perspective view of the knife of  FIG. 1 , according to the present invention. 
         FIG. 3  is a perspective view of the knife of  FIG. 1 , showing the blade shuttle repositioned to a midpoint of the handle, and showing the flip lock being moved to a vertical unlocked position so that finger tab may pass from a first end of the handle, labeled “TWO,” to an opposite end of the handle, labeled “ONE,” according to the present invention. 
         FIG. 4  is a perspective view of the knife of  FIG. 3 , showing the blade shuttle still at the midpoint of the handle, but showing the flip lock being moved to a second down and locked position, thereby preventing the blade shuttle from accidentally returning to the first end of the handle, labeled “TWO,” allowing the finger tab, and the blade shuttle located within the handle, to only advance to the second end of the handle, labeled “ONE,” indicated by the arrow, according to the present invention. 
         FIG. 5  is a perspective view of the knife of  FIG. 4 , showing the flip lock still in the second down and locked position, and showing the finger tab, and therefore the blade shuttle located at the second end of the handle, labeled “ONE,” with the blade in an extended position, according to the present invention. 
         FIG. 6  is a perspective view of one handle half of the knife of  FIG. 1 , showing details of the blade shuttle, the finger tab, and a blade, according to the present invention. 
         FIG. 7  is a plan side view of one handle half of the knife of  FIG. 1 , showing representative blade shuttles and blades and flip locks to illustrate the range of movement of the blade shuttle and blade, from one end of the handle to the other, and the range of movement of the flip lock, from a first locked position, to a unlocked vertical position, and back to a second locked position, according to the present invention. 
         FIG. 8  is a sectional view of the knife of  FIG. 4 , taken along the line  8 - 8  of  FIG. 4 , showing details of the blade shuttle, guide rails, blade support rail, the flip lock, and the finger tab, according to the present invention; 
         FIG. 9  is an exploded perspective view of the knife of  FIG. 1 , showing assembly details, according to the present invention. 
         FIG. 10  is an assembly view of the knife of  FIG. 1 , showing the handle halves in a separated orientation to reveal internal structural details, according to the invention; 
         FIG. 11  is an assembly view of the shuttle and blade, according to the invention. 
         FIG. 12  is an enlarged partial side view of the shuttle, blade and handle halve, showing details of a blade-anti-rotation structure, according to the invention. 
         FIG. 13  is a side view of the shuttle and blade, according to another embodiment of the present invention. 
         FIG. 14 a    is a plan view of a safety label having an exemplary shape, according to another embodiment of the invention. 
         FIG. 14 b    is a perspective view of the knife of the present invention showing the safety label of  FIG. 14 a    secured thereto, and providing the knife with security, according to this embodiment of the invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Reference will now be made in detail to the embodiments of the invention, one or more examples of which are set forth below. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used on another embodiment to yield a still further embodiment. Thus, it is intended that the present invention cover such modifications and variations as come within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present invention are disclosed in the following detailed description. It is to be understood by one of ordinary skill in the art that the present discussion is a description of exemplary embodiments only and is not intended as limiting the broader aspects of the present invention, which broader aspects are embodied in the exemplary constructions. 
     It is to be understood that the ranges mentioned herein include all ranges located within the prescribed range. As such, all ranges mentioned herein include all sub-ranges included in the mentioned ranges. For instance, a range from 100-200 also includes ranges from 110-150, 170-190, and 153-162. Further, all limits mentioned herein include all other limits included in the mentioned limits. For instance, a limit of up to 7 also includes a limit of up to 5, up to 3, and up to 4.5. 
     Referring to  FIG. 1 , a disposable utility knife  10 , according to the invention is shown having a handle  12 , made up of two halves  12   a  and  12   b , a blade shuttle  14 , supporting a metal razor blade  16 , and a flip lock  18 . The basic structure of knife  10  is that although it is meant to be disposable, it provides the user two separate blades, so this knife will last twice as long as similar knives that offer only a single blade. The basic structure of knife  10  is similar to the one disclosed in U.S. Pat. No. 8,701,293 of Scott Sullivan, entitled “Utility Knife,” in that both designs include a handle and a slidable blade that can be selectively displaced from one end to the other to effectively provide two separate cutting edges. The entire content of U.S. Pat. No. 8,701,293 is hereby incorporated by this reference. 
     Referring to  FIGS. 6, 8, 9 and 10 , each handle half  12   a ,  12   b  is preferably made from an appropriate strong lightweight thermoplastic, such as ABS, and is made so that when the two halves are secured together, a cavity  20  is formed therebetween. 
     Handle half  12   a  includes an arcuate upper surface  22 , defining an upper slot  23 , a first end  24  having a first end recess  26 , a second opposing end  28  having a second end recess  30 . Recesses  26 ,  30  are sized and shaped to accommodate blade  16 , as described in greater detail below. Handle half  12   a  further includes a pair of integrally formed arcuate shuttle guide rails  32   a  and  32   b , and an integrally formed arcuate blade guide rail  34 . Blade guide rail  34 , shuttle guide rails  32   a ,  32   b  and upper surface  22  preferably have common radius of curvature and are therefore effectively parallel to each other. Handle half  12   a  further includes a lower grip-bulge  36 , which provides a gripping point for a user holding the assembled knife  10 . Along upper surface  22  are preferably at least three locking notches  38   a ,  38   b , and  38   c , which help lock blade shuttle  14  at prescribed positions about handle  12 , as described below. Handle half  12   a  further includes upper protrusions  40   a ,  40   b  located adjacent first end  24  and second end  28 , respectively, and lower central protrusion  42 , which are sized and shaped to snugly receive similarly shaped recesses located on the opposing handle half  12   b , as described below. Handle half  12   a  further includes a post  44  which projects outward from the handle half and is centrally located, near upper surface  22 , as shown in  FIG. 8 . 
     Handle half  12   b  has many similar features to that of handle half  12   a , including an arcuate upper surface  50 , defining an upper slot  51 , a first end  52  having a first end recess  54 , a second opposing end  56  having a second end recess  58 . Recesses  54 ,  58  are sized and shaped to accommodate blade  16 , as described in greater detail below. Handle half  12   b  further includes a pair of integrally formed arcuate shuttle guide rails  60   a  and  60   b . Handle half  12   b  does not require a blade guide rail, as does handle  12   a . Shuttle guide rails  60   a ,  60   b  and upper surface  50  preferably have common radius of curvature and are therefore effectively parallel to each other. Handle half  12   b  further includes a lower grip-bulge  66 , which provides a gripping point for a user holding the assembled knife  10 . According to this invention, upper surface  50  does not require any locking notches. Handle half  12   b  further includes upper recesses  70   a ,  70   b , adjacent first end  52  and second end  56 , respectively, and lower central recess  72 , which are sized and shaped to snugly receive similarly shaped protrusions  40   a ,  40   b  and  42  located on the opposing handle half  12   a , introduced above. Handle half  12   b  further includes a post  74  which projects outward from the handle half and is centrally located, near upper surface  50 , as shown in  FIG. 8 . 
     Referring now to  FIGS. 6, 8, 9, 11, and 12 , blade shuttle  14  is meant to securely hold razor blade  16  and move the blade within handle  12 . Blade  16  can be glued to shuttle  14 , but is preferably molded to shuttle  14  during the injection-molding of shuttle  14  using an insert molding process wherein blade  16  is inserted into the mold of shuttle  14  before plastic is injected into the mold. In the injection molding process, the molten plastic forms shuttle  14  around the inserted blade  16 , to create a shuttle and blade assembly, which is shown in  FIGS. 6, 8, 9 and 12 . As shown in  FIG. 11 , blade  16  preferably includes bores  17  which aid in securing blade  16  to shuttle  14  during the molding process, as is well known by those of ordinary skill in the art. 
     As shown in  FIGS. 8, 11 and 12 , shuttle  14  includes a flat trapezoidal-shaped body  80  which extends on both sides of blade  16 , defining a left side  82   a , and a right side  82   b . Body  80  includes a left side guide channel  84   a  and a right side guide channel  84   b . When knife  10  is fully assembled, left side guide channel  84   a  is sized and shaped to snugly and slidably engage guide rails  32   a ,  32   b  of handle half  12   a , as shown in  FIG. 8 . Similarly, right side guide channel  84   b  of body  80  is sized and shaped to snugly and slidably engage guide rails  60   a ,  60   b  of handle half  12   b . Since guide rails  32   a,b ,  60   a,b  follow a slight curve between opposing handle ends, guide channels  84   a ,  84   b  are also formed slightly curved to follow the respective guide rails. As shown in  FIG. 11 , a stem  90  extends from a top surface  122  of shuttle body  80 . As shown in the figures, stem  90  is formed with a slight curve. A finger tab  94  is formed at the upper end of stem  90 . As shown in  FIG. 8 , when knife  10  is assembled, slots  23  and  51  (of the two handle halves  12   a ,  12   b ) combine to form a slot  95  that is sized to fit curved stem  90 . As curved stem  90  slides within slot  95 , eventually stem  90  will align with one of the three locking notches,  38   a ,  38   b , and  38   c . When this happens, the spring-biased stem  90  forces itself into the aligned notch  38 . The natural resiliency of the molded stem  90  provides sufficient spring bias to lock shuttle in place at any of the locations of locking notches  38   a ,  38   b , and  38   c . To release the engaged stem  90  from any notch  38 , finger tab  94  must be pressed (by the user&#39;s finger) laterally against the spring-bias until stem  90  is moved out of engagement of any notch  38   a,b,c . Only then can finger tab  94 , stem  90 , shuttle  14  and blade  16  be displaced along slot  95 . The type of plastic used to make shuttle  14  is preferably strong and resilient, and if possible naturally lubricious. The plastic used to make shuttle  14  can be different from the plastic used to make handle halves  12   a ,  12   b.    
     As shown in  FIGS. 2, 3, and 9 , flip lock  18  is a U-shaped structure with two parallel side bars  96  connected at one end of each to a crossbar  98 . A bearing boss  100  with a central bore  102  is formed at the open end of each side bar  96 . Bore  102  of each bearing boss  100  is sized to snugly fit onto posts  44 ,  74 , so that flip lock  18  becomes pivotally attached to the outside of each handle half  12   a ,  12   b  with crossbar  98  positioned across upper surfaces  22 ,  50  of handle halves  12   a ,  12   b . Flip lock  18  is pivotal between a first locked position (closer to the handle end labeled “ONE”), shown in  FIG. 1 , a vertical unlocked position, shown in  FIG. 3 , and a second locked position (closer to the handle end labeled “TWO”), shown in  FIG. 4 . Each handle half  12   a ,  12   b  may further include a first lock channel  104  and a second lock channel  106 , each of which is sized and shaped to receive a portion of crossbar  98 , as shown in  FIGS. 2, 4 , and  5 . Flip lock  18  is preferably made from a strong resilient plastic, such as ABS or PVC. 
     As shown in the sectional view of  FIG. 8 , shuttle  14  is adapted to snugly slide within handle cavity  20  along shuttle guide rails  32   a  and  32   b  of handle half  12   a  and shuttle guide rails  60   a  and  60   b  of handle  12   b , A shuffle gap  110  is created between shuttle guide rails  32   a ,  32   b  of handle half  12   a  and shuttle guide rails  60   a  and  60   b  of handle  12   b , within which shuffle  14  resides and slides. Shuttle guide mils  32   a,b ,  60   a,b  guide shuttle  14  along the arcuate path defined by the shape of the guide rails as the shuttle moves between first end  24  and second end  28  of handle  12 . As shown in  FIGS. 6, 8 and 10 , handle  12   a  includes blade guide rail  34  which is meant to support blade  16  and prevent shuttle  14  and blade  16  from rotating. When tab  94  is pushed laterally against the natural spring bias of stem  90  to release the stem from one of the locking notches  38   a - c , the lateral push force may cause shuttle  14  to rotate within handle  12  a small degree, thereby forcing blade  16  in the opposite direction, against blade guide rail  34 . Blade guide rail  34  prevents blade  16  from rotating, Since tab  94  will only be pushed in one lateral direction, a blade guide rail  34  is only required on handle half  12   a , as shown in the figures. 
     In assembly, shuttle  14  with blade  16  secured therein, is positioned within handle half  12   a  so that curved tab  94  is bent toward locking notches  38   a - c , and so that left side guide channel  84   a  of shuttle body  80  is mounted to shuttle guide rails  32   a  and  32   b . Handle half  12   b  is then positioned against handle half  12   a  so that lower central protrusion  42  of handle half  12   a  enters lower central recess  72  of handle half  12   b , and upper protrusions  40   a ,  40   b  of handle half  12   a  enter upper recesses  70   a ,  70   b  of handle half  12   b , respectfully. The two handle halves  12   a  and  12   b  are then securely bonded to each other, preferably using an ultrasonic welding process so that the two plastic handle halves literally weld to each other at all points of contact. When the handle halves are secured to each other, forming a single handle unit  12 , shuttle  14  and blade  16  can be moved between first end  24  and second end  28 . The final step is to position flip lock  18  over the top of handle  12  so that crossbar  98  resides across upper surfaces  22 ,  50  and so that central bores  102  of each bearing boss  100  resides over each post  44 ,  74  of handle  12 . 
     In operation, a user holds knife  10 , according to the present invention, in one hand. As a starting point in explaining the operation of knife  10 , reference is made to  FIG. 1 , wherein shuttle  14  (not visible in  FIG. 1  because it is located within cavity  20  of handle  12 ) and blade  16  are located at second end  28  of handle  12  so that blade  16  extends past handle  12  exposing a first cutting edge portion  110  for useful work. In this position, stem  90  is engaged with locking notch  38   c  by the stem&#39;s spring-bias. Therefore, when stem  90  of shuttle  14  is engaged in any locking notch  38   a ,  38   b , or  38   c , shuttle  14  and blade  16  are locked in that position. When blade  16  is locked, as described, it will not retract back into handle  12  when the blade is being used to cut material, that is until stem  90  is disengaged from locking notch  38   c  and shuttle  14  pulled back into handle  12  by the user&#39;s thumb. 
     According to the invention, when the user if done cutting for the moment, he or she may disengage stem  90  from locking notch  38   c  by using his or her thumb to move tab  94  against the spring-bias of stem  90  until the stem is disengaged from locking notch  38   c , at which point, the user may use his or her thumb to slide tab  94  within slot  95  to a center position, wherein stem  90  automatically engages with locking notch  38   b , as shown in  FIG. 2 , due to the spring-bias resiliency of stem  90 . 
     A concern with a knife wherein a blade can move from one end of a handle to another end of the handle is that the sharp blade may accidentally move to the opposite end of the handle and cut a user&#39;s hand. To prevent this from happening, according to an important feature of at least one embodiment of the invention, knife  10  includes flip lock  18 . Tab  94  cannot be accidentally moved to the opposite first end  24  of handle  12  because tab  94  is blocked from advancing past flip lock  18 , since crossbar  98  of the flip lock is located between the centrally located locking notch  38   b  and locking notch  38   a , and also crosses over slot  95 . Flip lock  18  effectively retains shuttle  14  and blade  16  safety on one expected side of handle  12 . 
     The user may release shuttle  14  from the central locked position of  FIG. 2  and again advance, the shuttle and blade  16  forward towards second end  28  of handle  12  until stem  90  again engages with locking notch  38   c  and blade  16  again protrudes from handle  12 , as shown in  FIG. 1 . 
     Eventually, first cutting edge portion  110  of blade  16  will dull. At this point, according to the invention, the user may relocate shuttle  14  to the opposite first end  24  of handle  12  to allow usage of a second cutting edge portion  112  of blade  16 . To do this, the user again moves shuttle  14  and blade  16  back to the central locked position, as shown in  FIG. 2 . In this position, flip lock  18  may be pivoted from first locked position (closer to the handle end labeled “ONE”), shown in  FIG. 1 , to a vertical unlocked position, as shown in  FIG. 3  and indicated by arrow  19 , and then finally to a second locked position (located closer to the handle end labeled “TWO”), as shown in  FIG. 4 . In moving flip lock  18  from the first locked position to the second locked position, crossbar  98  will have moved to the other side of tab  94 . This new position now allows the user to advance tab  94  towards the opposite first end  24 , indicated by arrow  114  (towards the handle end labeled “ONE”). When shuttle  14  is moved all the way to first end  24  of handle  12 , as shown in  FIG. 5 , to locked notch  38   a , blade  16  again protrudes from handle  12 , but now revealing second cutting edge portion  112  of blade  16 , which is sharp. The user may now enjoy more cutting time using the newly revealed sharp cutting edge, as shown in  FIG. 5 . 
     According to the invention, the use of flip lock  18  provides an intuitive and readily understandable means to prevent accidental injury to the user of knife  10 . In using flip lock  18 , the user must be aware as he or she flips crossbar  98  over tab  94  and therefore will be aware of the new direction of movement of shuttle  14  and blade  16 . Knife  10  is easy to understand, easy to use, and safe, and it provides twice the cutting life as conventional disposable utility knives. 
     Although tab  94  and stem  90  is used in combination with locking notches  38   a - 38   c , as described above, in accordance with the present invention, locking notches are not required to carry out the present invention, just preferred. In such instance, stem  90  can be formed straight and can easily, slide along slot  95  without locking. Flip lock  18  would still prevent shuttle  14  and blade  16  from traversing to the opposite end of handle  12 . In use, with this arrangement, the user will have to retain a thumb (or finger) on tab  94  to continually force blade  16  in an extended condition during a cutting operation. 
     It is also contemplated that other types of locking techniques may be used in place of the laterally spring-biased stem  90  and locking notches  38   a - 38   c . This includes a well known push to release type locking action wherein a tab is spring-biased up and will automatically lock into looking notches, similar to the locking notches  38   a - 38   c . With this arrangement, the tab is depressed downward to release the shuttle from any of the locking notches. Other locking mechanisms can be used as well. 
     Applicant has recognized that when shuttle  14  of the present invention is positioned at either end  24 ,  28  of handle  12  and a user pulls tab  94  back using his or her thumb to retract blade  16  into handle  12 , shuttle  14  may torque a bit owing to the moment arm provided by the tab and stem length. This torque may cause shuttle  14  to rotate a bit and therefore bind between guide channels  84   a ,  84   b  and respective guide rails  32 ,  60 . The result is that the shuttle will not move smoothly along guide rails  32 ,  60  until shuttle moves away from the handle end. To overcome this potential issue, the present invention provides specific handle structure to support shuttle  14  at the end locations  24 ,  28  so that it does not rotate when tab  94  is pulled by the user&#39;s thumb. The support structure is shown in  FIG. 12 , wherein a support wall  120  is positioned to snugly contact a portion of upper surface  122  of shuttle  14  when shuttle  14  is advanced fully to either end  24 ,  28  of handle  12 . When a user pulls back on tab  94 , shuttle cannot rotate because the rotational force generated by the user&#39;s pulling force is cancelled by an equal and opposite force generated by upper surface  122  of shuttle  14  contacting support wall  120 . The end result is that shuttle  14  remains aligned with guide rails  32 ,  60  and shuttle moves smoothly along the entire length of the guide rails. 
     According to another feature the invention, shown in  FIG. 13 , a blade  130  is formed to include two different shaped cutting edges, a first cutting edge  132  which is shown straight, and an opposing second cutting edge  134  is shown curved. This manner, knife  10  can offer two different types of cutting, instead of just providing the user with another sharp cutting edge. Also, one side of blade  130  can be formed with a shorter cutting edge than the other so that when one side of the blade is used, it will cut less deep into the material. This may be useful for cutting boxes. If a deeper cut is required, the user may simple slide the shuttle and blade to the opposite side of the knife handle, as described above. 
     Safety Label 
     The present utility knife  10  is inexpensive to manufacture and is meant to provide a user a low cost disposable utility knife. To help keep the costs low, yet provide safety measures at the point of purchase (e.g., in a store), the knife packaging can include features that provide safety to the customer, while allowing the customer a controlled amount of operational access to the knife, without removing the knife from any packaging. 
     Referring now to  FIGS. 9, 14   a , and  14   b , a safety label  130  is shown, according to another aspect of the present invention. As shown in  FIG. 14 a   , a plan view of a label  130  is shown having an exemplary shape to help explain its inventive features, according to the present invention. Label  130  is sized and shaped to be secured to handle  12  of knife  10 , as shown in the  FIG. 14 b   . In this example, label  130  is meant to be centered on top surface  50  of knife  10  and folded down against each outside surface of handle halve  12   a ,  12   b , symmetrically. As shown in  FIG. 14 a   , label  130  is, in this example, generally circular in shape, includes a central opening  132  and defines an upper printable surface  134  and an opposing adhesive surface (not shown). Label  130  is preferably applied to handle  12 , once assembled at a point of manufacture. Label  130  bonds to handle  12  by the adhesive, which is selected depending on the material chosen for handle  12  the material chosen for the label  130  and whether or not the label is to be removed by peeling (see below). An important feature of label  130  is that it is made from a strong tear-resistant material, such as a fiber-reinforced material. One such suitable material is called Tyvek®, made by DuPont™ of Wilmington, Del. Tyvek® is a unique nonwoven material made of 100% high density polyethylene fibers randomly laid and compressed to form a tough, tear-resistant and printable substrate. Tyvek® can be provided with an application-based adhesive on one surface and be printed with product marketing and use information on printable surface  134 . 
     As shown in  FIG. 14 b   , label  130  is securely affixed to handle  12  of knife  10  so that tab  94  and flip lock  18  is positioned within central opening  132 . Central opening  132  is preferably sized and shaped to allow a predetermined and controlled amount of sliding displacement of tab  94  within slot  95  before tab  94  contacts a portion of label  130  and is blocked from further movement by sections  136  of label  130  which cover slot  95 , as shown in  FIG. 14 b   . Also, flip lock  18  may be pivoted between its full range of movement by a customer. Central opening  132  of label  130  is sized and shaped to only allow some sliding movement of tab  94 , and is small enough to stop the sliding movement of tab  94  before blade  16  (not shown in  FIGS. 14 a , 14 b   ) extends beyond either end of handle  12 . In other words, label  130  provides a customer limited “testing” movement of tab  94  and flip lock  18 , when deciding to purchase knife  10 , while preventing the customer from moving tab  94  sufficiently to extend blade  16  beyond either end of handle  12 . Blade  16 , and therefore cutting edges  110 ,  112  remain safely within handle  12  while knife  10  is being “tested” by a customer in a store. Safety label  130 , according to this invention allows a customer to safely handle knife  10  in a store, learn its features without exposing any sharp edges, and while requiring a minimal amount of low-cost packaging (a label). Knife  10 , with the use of safety label  130  is therefore suitable for so-called “dump bin” marketing wherein low-cost minimally packaged products in a store may be provided to a customer in a large bin from which one product may be selectively removed by the customer for purchase. 
     Once a customer purchases knife  10  and prior to use, the customer (user) must cut or peel off label  130  so that tab  94  is allowed free sliding movement along slot  95  of knife  10 . Once tab may slide the full extents, of slot  95 , blade  16  may selectively extend beyond handle  12 , exposing cutting edges  110 ,  112  for useful cutting work by the user. In the case that label  130  is meant to be peeled from handle  12 , the adhesive used to secure label  130  to the handle must be selected to provide such peeling with a predetermined degree of difficulty. If label  130  is meant to be cut (along slot  95 ), the adhesive used may be much stronger since most of the label is meant to remain secured to handle  12 . 
     Although the safety label  130  shown in  FIGS. 14 a , 14 b    is generally circular in perimeter shape with a generally circular central cutout, the shape and size of label  130  may vary according to the specific handle shape and operational details of knife  10 . The specific shape and size of knife  10  and all the components, and label  130  is meant to be exemplary to help explain the present invention. As is understood by those of general skill in the art, other shaped knife components, including handle halves  12   a ,  12   b , blade  16 , shuttle  14 , flip-lock  18 , tab  94 , and label  130  may be used without departing from the spirit and scope of the present invention. 
     An additional aspect of the present invention allows for a process of using a utility knife comprising the steps of providing a portable utility knife comprising: a hollow elongated handle sized and shaped to be easily gripped by a user&#39;s, hand, said handle including an upper surface and opposing first and second ends, said hollow handle defining a cavity therein; an elongated slot disposed along said upper surface, said slot providing access through said handle to said cavity; a first opening located at said first end and a second opening located at said second end, said first and second openings extending through said handle to said cavity; a blade shuttle positioned within said cavity and selectively slidable between said first end and said second end; a razor blade secured to said shuttle, said razor blade having a cutting, edge, said cutting edge defining a first cutting edge section and a second cutting edge section so that when said shuttle is positioned within said cavity and adjacent said first end, said first cutting edge section of said razor blade extends through said first opening of said handle to expose said first cutting edge section to provide useful cutting work, and when said shuttle is positioned adjacent said second end, said second cutting edge section of said razor blade extends through said second opening to expose said second cutting edge section to provide useful cutting work; a tab attached to said blade shuttle, said tab extending through said elongated slot so that a portion of said tab is accessible to a user, said tab may be used to slide said shuttle within said cavity between said first and second ends; and a movable locking component attached to said handle, said locking component being selectively moveable between a first position, wherein said tab is prevented from sliding within said elongated slot, and a second position, wherein said tab is permitted to slid within said elongated slot. 
     Sliding the blade to one of a first end position or a second end position; locking the blade within one of a plurality of locking positions; and, 
     moving a locking lever to allow the blade to retract from one end of the knife and to extend from a second end of the knife. 
     Although preferred embodiments of the invention have been described using specific terms, devices, and methods, such description is for illustrative purposes only. The words used are words of description rather than of limitation. It is to be understood that changes and variations may be made by those of ordinary skill in the art without departing from the spirit or the scope of the present invention which is set forth in the following claims. In addition, it should be understood that aspects of the various embodiments may be interchanged, both in whole, or in part. Therefore, the spirit and scope of the appended claims should not be limited to the description of the preferred versions contained therein.