Abstract:
A utility knife has a counter-reciprocating blade and blade guard. Preferred utility knifes have an internal mechanism comprising several components that are advantageously coupled via one or more pivot points. Though an appropriate arrangement of pivot points, both stationary pivot points and translating pivot points, the blade and guard counter-reciprocate such that forced retraction of the guard results in forced extension of the blade. While the internal mechanism is in a locked position, the guard locked. Actuation of a trigger can unlock the internal mechanism, which releases the blade guard. Preferably a single actuation of the trigger provides for a single use of the knife.

Description:
This application is a continuation-in-part of U.S. patent application having Ser. No. 11/621,208 filed on Jan. 9, 2007now abandoned. This and all other extrinsic materials discussed herein are incorporated by reference in their entirety. Where a definition or use of a term in an incorporated reference is inconsistent or contrary to the definition of that term provided herein, the definition of that term provided herein applies and the definition of that term in the reference does not apply. 
    
    
     FIELD OF THE INVENTION 
     The field of the invention is utility knives. 
     BACKGROUND 
     Traditionally, utility knives have a blade that either (a) is in a fixed, extended position relative to a knife handle but is externally covered by a blade cover or (b) is stored internally in a cover until the blade is manually extended by sliding the blade out of the knife&#39;s handle. Some progress has been made to protect users from unprotected blades. For example, more recent utility knifes include blades that retract into a handle or a housing when not in use, or that can be covered by a blade cover or guard. However, such knifes still expose a blade in an unprotected position that can cause accident injury to a user. 
     The problem of accidental injury has been long recognized, with numerous solutions put forward at various times. U.S. Pat. No. 4,980,977 to Matin et al. titled “Safety Core Cutting Knife” (January 1991), for example, describes a knife having a safety guard that guards a blade when not in use, and automatically retracts as the blade is removed from a work piece. The guard has a manually triggered self-locking release assembly that automatically relocks the guard when retracted. Unfortunately, Matin&#39;s locking mechanism is external to the housing. Such a configured can be dangerous because the mechanism can readily jam due to debris. The debris could easily interfere with the assembly&#39;s locking or unlocking functions. In addition, Matin&#39;s safety guard pivots externally from the housing and off of the blade, rather than being retracted into the housing. Allowing the blade guard to pivot or otherwise move in an exposed manner increases a risk of the guard interfering with the knife&#39;s operation, with a target work piece, or with the user. 
     U.S. Pat. No. 5,878,501 to Owens et al. titled “Utility Knife with Retractable Blade Guard” (March 1999) describes a utility knife having a blade guard where the blade guard can be withdrawn to expose a cutting edge of a blade. Unfortunately, the Owens configuration allows the cutting edge of the blade to remain exposed across multiple cuts or uses. 
     Still other utility knife designs exist that afford some level of protection. For example, a blade can be coupled to a sliding mechanism disposed within a knife handle. A user can push the sliding mechanism to move the cutting edge of the blade from the handle into an exposed cutting position. The sliding mechanism can also be spring-loaded in a manner that automatically retracts the blade into the handle once a pushing force is removed from the sliding mechanism. Preferred knives should also offer a locking mechanism coupled to the blade or blade guard that prevents accidental extension of the blade. 
     More recently the present inventor pioneered utility knives having a mechanism that automatically re-locks a protective blade guard. For example, U.S. Pat. No. 7,509,742 to Votolato titled “Safety Cutting Apparatus” (March 2009) discloses a utility knife where a blade guard automatically re-locks into a closed position covering a cutting edge of a blade after a single cut. Another example includes U.S. Pat. No. 7,356,928 to Votolato titled “Utility Knife with Safety Guard Having Reduced Play” (April 2008) where a blade guard retracts into a knife handle and can re-lock into a safety position after use. 
     Ideally, a utility knife should protect users from a cutting edge of a blade by both a blade guard and a handle of the knife. In such an approach, the blade can be retracted into the knife handle when not in use, and can be extended for a cutting operation. Additionally, a blade guard can protect the user from the extended cutting edge, and can move out of position when the knife is applied to a surface to be cut. It has yet to be appreciated such a utility knife can be manufactured where the knife blade and blade guard pivot relative to each other in a counter reciprocating fashion within a handle of the knife. 
     Thus, there is still a need for a utility knifes with lockable blade guards. 
     Unless the context dictates the contrary, all ranges set forth herein should be interpreted as being inclusive of their endpoints and open-ended ranges should be interpreted to include only commercially practical values. Similarly, all lists of values should be considered as inclusive of intermediate values unless the context indicates the contrary. 
     SUMMARY OF THE INVENTION 
     The inventive subject matter provides apparatus, systems and methods in which a utility knife comprises a counter-reciprocating knife blade and blade guard. In one aspect of the inventive subject matter, a utility knife comprises a knife handle that forms a housing, in which is disposed the blade and the blade guard. In a preferred embodiment, both the knife blade and the blade guard are at least partially disposed within the housing. In some embodiment, the blade can be fully retracted within the housing when the blade is not in use. The blade and blade guard can be pivotally coupled to interior surfaces of the housing. In a preferred embodiment, when the blade guard retracts into the housing via a pivoting motion relative to the housing, the blade guard&#39;s pivoting motion causes the blade to extend out of the housing in via a second pivoting motion that is counter to that of the blade guard. 
     The counter-reciprocation motion of the blade and the blade guard can be achieved via a coupling mechanism. In a preferred embodiment, the coupling mechanism comprises at least three pivot points. A first stationary pivot point is used to couple a blade holder to the housing of the utility knife where the first pivot point remains stationary to the handle while allowing the blade holder to pivot relative to the housing. A second stationary pivot point can be used to couple a blade guard to the housing of the knife and where the second pivot point also remains stationary with respect to the handle while allowing the guard to pivot relative to the housing. Another translating pivot point can be used to couple the blade holder to the blade guard. The translating pivot can move relative to the knife housing as the blade and the blade guard counter-reciprocate with respect to each other. 
     Preferred utility knifes also comprise a locking mechanism configured to lock a blade guard in an extended closed safety position when not in use. In some embodiments, the locking mechanism can include a pawl and spring where the spring biases the blade guard into a closed position. The pawl can prevent the blade guard from retracting when the knife is in a locked state. The locking mechanism can also include a trigger where actuation of the trigger unlocks the blade guard and allows the blade guard to retract. Preferred locking mechanisms allow a single use of the knife. Once the blade guard is restored to a safety position, the trigger can be actuated again to release the guard. 
     Various objects, features, aspects and advantages of the inventive subject matter will become more apparent from the following detailed description of preferred embodiments, along with the accompanying drawing figures in which like numerals represent like components. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWING 
         FIG. 1  is a cut away side view of an example utility knife. 
         FIG. 2  is an exploded view of the example utility knife. 
         FIG. 3  is a cut away side view showing a close up of a locking mechanism and where the trigger has not been actuated 
         FIG. 4  is the knife of  FIG. 3  where the trigger has been actuated allowing a blade guard and blade to counter-reciprocate. 
         FIG. 5  is the knife of  FIG. 4  where the trigger remains actuated and the blade and blade guard counter-reciprocate. 
         FIG. 6  is the knife of  FIG. 5  where the blade is fully exposed and the locking mechanism can be reset. 
     
    
    
     DETAILED DESCRIPTION 
     In  FIG. 1 , a utility knife  1  generally comprises a housing  10  (only the front portion of which is shown), a blade  20 , a blade guard  30 , a pawl  40 , and a trigger  60 .  FIG. 2  presents an exploded view of utility knife  1 . 
     The following discussion uses various terms to describe relative motion of the components of knife  1 . One should appreciate that the various motions are discussed relative the illustrations, and should not be considered as limiting the inventive subject matter. For example, “upward” means a motion approximately toward the top or superior side of knife  1  and loosely to the top of the page. “Downward” means a motion toward the bottom or inferior side of knife  1  and loosely to the bottom of the page. In a similar fashion, “forward” means moving toward the working end of the knife  1 ; loosely toward the left side of the page, and “rearward” means moving toward the distal, non working-end of the knife  1 ; loosely toward the right side of the page. 
     Housing  10  is preferably sized and dimensioned to fit comfortably in a hand of a user. Housing  10  can be made of any suitable material, including metals, alloys, ceramics, or plastics. In some embodiments, housing  10  can include a cavity (not shown) that can be used for storing additional spare blades or other tool bits. Housing  10  is configured in a ambidextrous fashion where knife  1  can be used by either a right or a left hand. Alternatively, knife  1  could comprise contours on external surfaces of housing  10 . In some embodiments, the contours can provide a better fit specifically for a right or a left hand. Housing  10  can also including one or more of depressions  80  to provide a better grip or provide additional comfort to the user. Depressions  80  can extend partially into housing  10 , or can completely pass through housing  10 . In some embodiments, depressions  80  can be formed from one or more ribs  50  molded into housing  10 , possibly molding into housing pieces  12  or  13 . 
     Housing  10  preferably provides one or more internal pivot points by which internally disposed assemblies can pivot relative housing  10 . For example, housing  10  can include a pivot point represented as a circular slot  32  into which pivot pin  34  of blade holder  24  can be inserted. Another example includes a pivot point comprising pin  34  located on an internal surface of housing  10 , slot  44  on trigger  60 , and slot  42  in blade guard  30 . The various pivot points are described more fully below. 
     One should appreciate that a pivot point can be formed by using a pin as a pivot axis where the pin inserts into a groove or slot. In some embodiments, a pin of a pivot can be located on housing  10 , possibly formed during an injection molding process, were the pin inserts into a slot on blade holder  24  or guard  30 . In other embodiments, the pin of the pivot point could be positioned on blade holder  24  or guard  30  where the pin inserts into a slot molded into housing  10 . As used herein, the term “pivot point” euphemistically represents pin-slot assembly regardless of the number of pins or slots used to form the pivot point. 
     Blade  20  is preferably triangular shaped at one or both ends. In a preferred embodiment, blade  20  has at least one cutting edge  22 , preferably a straight cutting edge. Blade  20  is preferably made of non-rusting alloy. Other blade materials are also contemplated including plastics, wood, ceramics, or other materials capable of carrying a cutting edge  22 . 
     Although a blade  20  preferably comprises one or more straight cutting edges, it is also contemplated that blade  20  could comprise other shapes. For example, blade  20  could comprise a circular blade with a circular cutting edge as described in U.S. Pat. No. 5,765,289 to Schulz et al. titled “Rotary Cutter” (June 1998). 
     In a preferred embodiment, blade  20  is held within blade holder  24 . Blade holder  24  can couple to housing  10  via at least a pivot point comprising pin  34  and slot  32  (e.g., a slot in housing  10 ). 
     Blade guard  30  generally guards the blade  20  when guard  30  is in a fully deployed safety closed position (see  FIG. 3 ). When blade  20  is in use, blade guard  30  can retract into housing  10  in a retracted position (see  FIG. 5 ) which cause blade  20  to rock forward into an exposed position. In a preferred embodiment, blade guard  30  couples to housing  10  via at least a pivot point comprising pin  46 , and slots  44  and  42 . Blade guard  30  also preferably comprises opening  31 , through which at least cutting edge  22  can extend. Blade guard  30  preferably is formed from a translucent material (e.g., a plastic) to allow a user to view a position of blade  20 . Alternatively, blade guard  30  can be made of other materials including metal, wood, opaque plastics, ceramic, or other durable materials. 
     Blade holder  24  and blade guard  30  are preferably coupled together and coupled to housing  10  via a multi-pivot coupling mechanism. In a preferred embodiment, the coupling mechanism comprises at least three pivot points, and more preferably at least four pivot points as shown in  FIG. 1 . It is contemplated that any number of pivot points beyond four could also be used to ensure proper counter-reciprocation of blade guard  30  and blade  20 . In the example shown, blade holder  24  couples to blade guard  30  via a pivot point comprising pin  34  located on holder  24  that inserts into slot  38  of guard  30 . In addition the example coupling mechanism includes pivot points defined by pin  34  that pivotally couples to housing  10  and defined by pin  46  of housing  10  that inserts into slots  44  and  42 . 
     In some embodiments, blade guard  30  can also include a pivot point defined by pin  52  located on pawl  40  that inserts into slot  54  of guard  30 . 
     One should note the differences among the various pivot points. Both pivot points defined by pins  34  and  46  are stationary pivot points due to coupling to housing  10 , and where the pivot points rotate relative to housing  10 , but do not move or translate relative to housing  10 . The pivot point defined by pin  36 , on the other hand, is a translating pivot point where it can move relative to housing  10  as well as allows holder  24  and guard  30  to rotate relative to each other and to rotate relative to housing  10 . For example, as guard  30  retracts or rocks back into housing  10  via pivoting on pin  46 , slot  38  moves upward (i.e., upward relative to the illustration of knife  1 ). As slot  38  moves upward, it carries pin  36  along in an upward direction. The pivot point defined by pin  52  is also a translating pivot point because it can move forward or rearward relative to housing  10 . 
     Pawl  40  operates as part of a locking mechanism to secure blade guard  30  into a locked, safety closed position, and also operates to control the pivoting motion of guard  30 . In a preferred embodiment, pawl  40  pivotally couples to guard  30  via a pivot point defined by pin  52 . As guard  30  rotates around the pivot point defined by pin  46 , pawl  40  slides within housing  10  preferably guided by one or more ribs  50 . In the example shown, pawl  40  prevents guard  30  from pivoting by engaging with stop  56 . In a preferred embodiment, pawl  40  remains in a locked position against stop  56  via a force provided by spring  33  as discussed below. When pawl  40  is released from stop  56 , pawl  40  can move rearward along a rib  50  until stopped by stop  88 . Spring  33  preferably provides a returning force that causes pawl  40  to slide forward back into a locked position at stop  56 . Horizontal movement of pawl  40  between stop  88  and stop  56  at least in part controls how far blade guard  30  can pivot about pin  46 . 
     Pawl  40  is biased forward in a locked position via a force provided by spring  33 . As shown in  FIG. 1  and  FIG. 3 , preferably spring  33  couples to blade holder  24  and to a hook on pawl  40 . Spring  33  is preferably is under tension when knife  1  is a safety position where blade  20  is pulled into a safety retracted positing within housing  10 . Spring  33  also pulls pawl  40  forward toward holder  24 . Because holder  24  is pulled into a retracted position, holder  24  pivots about pin  34  causing pin  36  to move or translate in a downward direction. As pin  36  moves in a downward direction, it carries slot  38  downward as well, which in turn causes blade guard  30  to rock forward by pivoting about pin  46 . Thus spring  33  can bias blade  20  into a retracted safety position, bias blade guard  30  into a close safety position, and can also bias pawl  40  into a locked position so that it is adjacent to stop  56 . 
     Pawl  40  is preferably constructed of a single, continuous piece of material. In a preferred embodiment, pawl  40  is molded from a plastic. Alternative materials include wood, metal, ceramic, or other durable, stiff materials. Pawl  40  also preferably includes catch  47  on a lateral side of pawl  40 . Catch  47  engages with arm  65  of trigger  60  to release pawl  40  from a locked position as discussed below. Pawl  40  also preferably includes a hook, to which spring  33  couples. 
     Trigger  60  preferably comprises a single, unitary piece of material having connector  62 , lifting arm  65 , return lever  70 , and slot  44 . Acceptable materials include plastic, metal, wood, ceramic, or other durable materials. It should be appreciated that trigger  60  could also comprise discrete components coupled together. Lever  70  can engage with a rib  50 , possibly the under side of stop  56  as shown, to supply a return force that causes trigger  60  to remain in an un-actuated state. As trigger  60  is depressed, lever  70  will flex, supplying some resistance to actuation of trigger  60 , and supplying a return force in a manner where trigger  60  will automatically return to the un-actuated state upon release of trigger  60 . 
     Connector  62  extends upward from a main body of trigger  60  and connects to lifting arm  65 . Lifting arm  65  extends from connector  62 , and is sized and dimensioned to engage catch  47  of pawl  40  when trigger  60  is actuated, and while the internal locking mechanism is in a locked state. 
     Trigger  60  preferably couples to housing  10  in a pivotal fashion via pin  46  and slot  44 , which combine to form a stationary pivot point. The configuration shown allows trigger  60  to pivot in an upward direction (e.g., counter-clockwise with respect to the page) for actuation, or downward (e.g., clockwise with respect to the page) when released. One should note that the pivot point defined by pin  46  can be considered a nested pivot point around which multiple components pivot. Furthermore, it should be noted that as trigger  60  is actuated, it pivots in a first direction (e.g., counter-clockwise as shown in the illustration of  FIG. 1 ), while blade guard  30  can pivot in a second direction (e.g., clockwise as shown in the illustration of  FIG. 1 ). 
     Trigger  60  is shown on the underside of housing  10 , and is positioned relatively forward so that trigger  60  is easily operated by the user&#39;s fingers. All other suitable positions are contemplated, including positions on the top or side of the housing  10 . It is also contemplated that trigger  60  could include two, three, or more exposed protrusions that can be accessed from various positions about housing  10 . Although trigger  60  is actuated by depressing trigger  60  into housing  10 , it should be appreciated that trigger  60  could also be actuated by other applied forces including sliding, pressing, pulling, rotating, or other actuations. Those skilled in the art will also appreciate that trigger  60  is merely emblematic of a more general actuator, which could take the form of a button, a push button, a knob, a slider, or even multiple actuator mechanisms and so forth. 
     In  FIG. 3 , utility knife  1  is shown with the blade guard  30  in a deployed safety position, and blade  20  is in retraced safety position inside blade guard  30 . In a preferred embodiment, blade  20  is completely covered by guard  20  when both are in their safety positions. In other embodiments, blade  20  is completely disposed within housing  10  when in its safety position in a manner where cutting edge  22  is completely covered. Preferably, blade  20  is completely locked inside housing  10  when not in use and when blade  20  is in its safety position. Blade  20  can be locked into its safety position via a locking mechanism comprising at least spring  33 , holder  24 , guard  30 , and pawl  40 . Pawl  40  preferably prevents movement of the assembly by resting against stop  56 . 
     When locked, blade guard  30  could have some play (e.g., small pivoting motion) as determined by the surrounding components of the locking mechanism. In a locked position, the play of guard  30  can be limited by housing  10  which prevents counter-clockwise pivoting, and can be limited by pawl  40  which prevents clockwise pivoting of guard  30 . Preferably pawl  40  has a play of less than 5 millimeters, more preferably less than 3 millimeters, even more preferably less than 2 millimeters, and most preferably less than 1 millimeter. Preferably the play is measured between the end of pawl  40  and stop  56 . 
     In  FIG. 4 , trigger  60  has been depressed (e.g., squeezed) toward housing  10  in the direction of arrow  11 , blade  20  is still in a safety position at least partially disposed within housing  10 . Note that although trigger  60  has been actuated, blade holder  24 , blade  20 , and blade guard  30  have not moved or pivoted. One should also note that lever  70  is now in a flexed position and provides a restoring force to trigger  60 . Once a user releases trigger  60 , preferably trigger  60  automatically returns to an un-actuated stated due to the restoring force supplied by lever  70 . The restoring force can also be supplied by alternative means beyond lever  70  including an elastic band, a spring, multiple levers, or by other spring-like materials. 
     As trigger  60  is actuated, connector  62  moves upward and lifts lifting arm  65 . Lifting arm  65  engages with catch  47 , assuming knife  1  is in a locked state. As lifting arm  65  moves upward, it also lifts pawl  40  in a manner where pawl  40  is freed from stop  56 . Pawl  40  is now in an unlocked state, as is blade guard  30 . One should note that pawl  40  does not necessarily move rearward automatically. In fact, in a preferred embodiment, pawl  40  remains in a forward position until pressure is applied to blade guard  30 . As pressure is applied to blade guard  30 , preferably from a surface to be cut, blade guard  30  is free to pivot about pin  46  and retract back into housing  10 , which in turn causes pawl  40  to move rearward toward stop  88 . 
     In  FIG. 5 , a force is applied to blade guard  30  in approximately the direction of arrow  90 . Preferably the force is due to a surface that is being cut. As blade guard  30  reciprocates back into housing  10  by pivoting about pin  46 , guard  30  pushes pawl  40  rearward via their translating pivot point (e.g., pin  52  and slot  54 ). In a preferred embodiment, pawl  40  can be guided rearward along a rib  50  toward stop  88 . Additionally, reciprocation of guard  30  also causes the translating pivot point defined by pin  36  to move upward carrying slot  38  upward as well, which in turn causes blade holder  24  to counter-reciprocate relative to blade guard  30  by pivoting about pin  34 . The counter-reciprocation causes blade holder  24  to rotate forward, thus exposing blade  20  for use via opening  31 . 
     One should note the pin  36  and slot  38  do not necessarily have a precise fit. In some embodiments, as shown, slot  38  provides a groove in which pin  36  moves as necessary. In a preferred embodiment, slot  38  is sized, dimensions, and shaped to allow pin  36  to move according to a desired path. As a result, slot  38  lacks circularity, but could be formed as an oval, an elongated track, or other type of groove. 
     Note that spring  33  has been extended and is under further tension than when knife  1  is in a locked state. The force supplied by spring  33  biases the internal locking mechanism and pivoting coupling mechanism to return to a closed safety position, and preferably to return automatically to a locked state. 
     In  FIG. 6 , knife  1  has blade  20  in fully deployed position. Blade guard  30  has substantially reciprocated back into housing  10  to a retracted position. Blade holder  24 , and blade  20 , has counter-reciprocated out of housing  10  into a fully deployed cutting position. One should note that knife  1  remains in a deployed position via a force applied to blade guard  30 , preferably from a cutting surface, as opposed to a force originating from trigger  60 . 
     When the force on blade guard  30  is removed, the internal assembly automatically returns to a safety position, preferably also resetting the locking mechanism. For example, guard  30  pivots forward out of housing  10  while blade holder  24  pivots back into housing  10  by pivoting in an opposite direction to that of guard  30 . Additionally, pawl  40  slides forward. Note that catch  47  preferably does not re-engage lifting arm  65  until trigger  60  is released and re-actuated again. If blade guard  30  is allowed to return toward its safety position, pawl  40  drops and resets the locking mechanism by engaging with stop  56 . One should note that while blade  20  is deployed, actuation of trigger  60  has no effect. 
     Although knife  1  is shown has a single unitary device, it is also contemplated that the internal mechanism comprising at least the blade and blade guard can be part of a removable cartridge. In some embodiment the cartridge can comprise the blade  20 , blade holder  24 , blade guard  30 , and pawl  40 . A suitable cartridge system that can easily incorporate the disclosed subject matter is co-pending patent application having Ser. No. 12/391,729 to Votolato titled “Utility Tool Having Interchangeable Tool Cartridges” filed on Feb. 24, 2009. 
     The disclosed knife and internal mechanisms afford many benefits and advantages. For example, the cutting edge of the knife always remains covered until the knife is applied to a surface to be cut. Another benefit is that a single actuation of a trigger allows for a single cutting operation. Yet still, another benefit includes that pressure applied by a user to a surface aids in forcing the cutting edge into the surface via leverage created by the internal coupling mechanism of the blade holder, the housing, and the blade guard. Additionally, if a user tampers with the blade guard causing the blade guard to break off, the blade will extend out of the knife handle. The blade will remain disposed within the handle and thus cannot cause accident injuries or damage. Since the blade is always behind the blade guard or in the housing, this provides significant safety and double protection against a user from being cut. 
     It should be apparent to those skilled in the art that many more modifications besides those already described are possible without departing from the inventive concepts herein. The inventive subject matter, therefore, is not to be restricted except in the spirit of the appended claims. Moreover, in interpreting both the specification and the claims, all terms should be interpreted in the broadest possible manner consistent with the context. In particular, the terms “comprises” and “comprising” should be interpreted as referring to elements, components, or steps in a non-exclusive manner, indicating that the referenced elements, components, or steps may be present, or utilized, or combined with other elements, components, or steps that are not expressly referenced. Where the specification claims refers to at least one of something selected from the group consisting of A, B, C . . . and N, the text should be interpreted as requiring only one element from the group, not A plus N, or B plus N, etc.