Abstract:
A safety mechanism for a utility knife, including a razor blade mounted in a blade holder slideably mounted in a blade chamber in the housing. A first blade holder includes an arm extending therefrom with an engaging surface thereon. A second blade holder includes a tab extending therefrom. When either blade holder is deployed from the housing, the tab contacts the engaging surface, thereby preventing deployment of the other blade until the original blade is retracted.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application claims the benefit of U.S. Provisional Application No. 60/624,310, filed Nov. 2, 2005, which is incorporated by reference in its entirety. 
     
    
     TECHNICAL FIELD OF THE INVENTION  
       [0002]     The present invention relates generally to the field of cutting tools, and more specifically to a safety mechanism for preventing the accidental deployment of a utility knife blade.  
       BACKGROUND OF THE INVENTION  
       [0003]     Utility knives that incorporate retractable, replaceable razor blades are well known in the art. Utility knives are very versatile, enjoying popularity with the professional construction worker, the domestic handyman, and the amateur hobbyist alike. Utility knives generally include a retractable razor blade mounted within a protective handle or housing. The blade is fastened to a support structure such as a blade carrier or blade pusher, which extends through the surface of the housing. In operation, the blade is extended by sliding the blade holder forward. One deficiency of the prior art designs is that the blade may be inadvertently deployed, becoming a safety hazard. For example, if the blade holder catches on a pocket or a tool belt or is jostled by another tool in a toolbox, the blade may be deployed unbeknownst to the user. An unwary user reaching for a utility knife with the blade deployed can easily receive a severe cut.  
         [0004]     There have been attempts in the prior art to address this problem. For example, U.S. Pat. No. 5,890,294 to Keklak et al. discloses a locking safety utility knife having an operating lever that deploys a blade when squeezed and a ratchet-like locking mechanism releasable by manipulation (depression) of a cam located at the end of the knife. However, the Keklak et al. device still exhibits the problem of accidental disengagement of the safety if the cam is accidentally depressed, allowing the knife to accidentally open and deploy the blade. Moreover, the cam is located on the end of the knife, increasing the likelihood of accidental depression.  
         [0005]     Other known utility knives known in the art have sliding blades that are locked by blade holders that must be depressed as they are slid forward to engage the blade. Again, since the unlocking force and the deploying force may be resolved into a single angular force acting upon the blade holder, accidental release of the blade can readily occur if the blade holder catches on the user&#39;s clothing or on another tool.  
         [0006]     There is therefore a need in the art for a safety mechanism for a utility knife that cannot be accidentally disengaged through the simple depression of a switch or cam. Furthermore, for utility knives with separate controls for deployment of each of two blades, there is a need for a safety mechanism that prevents deployment of both blades at the same time. The present invention satisfies both of these needs.  
       SUMMARY OF THE INVENTION  
       [0007]     The present invention relates to a safety mechanism for a utility knife. The utility knife includes a knife blade mounted in a blade holder that may move between a retracted, blade-stowage position in the housing and a deployed position wherein the blade at least partially protrudes from the housing. The blade holder includes an actuating lever portion protruding from the housing. Two such blade holders are provided such that blades may be deployed from either end of the knife. In one embodiment, a first one of the blade holders includes an arm extending therefrom in the direction of the second blade holder. The second blade holder has a tab that engages the arm of the first blade holder, such that interaction between the arm and the tab prevent one blade holder from being deployed while the other blade holder is deployed.  
         [0008]     In one form of the invention, a safety mechanism for a utility knife is disclosed, comprising: an elongated housing having an apertured anterior end and an apertured posterior end; an anterior blade chamber formed within the anterior end of the housing and aligned with the anterior aperture; a posterior blade chamber formed within the posterior end of the housing and aligned with the posterior aperture; an anterior blade holder slideably mounted in the housing and having an anterior blade-engaging portion positioned in the anterior blade chamber, and an arm operationally coupled to the anterior blade-engaging portion and extending substantially toward the posterior blade chamber, the arm having a contacting surface; a posterior blade holder slideably mounted in the housing and having a posterior blade-engaging portion positioned in the posterior blade chamber, an extension operationally coupled to the posterior blade-engaging portion, and a tab coupled to the extension and adapted to selectively engage the contacting surface; an anterior blade mounted in the anterior blade holder; a posterior blade mounted in the posterior blade holder; wherein the posterior blade holder is adapted to move between a recessed position wherein the posterior blade is completely within the housing and a deployed position wherein the posterior blade extends partially outside of the housing; wherein the anterior blade holder is adapted to move between a recessed position wherein the anterior blade is completely within the housing and a deployed position wherein the anterior blade extends partially outside of the housing; wherein the tab engages the contacting surface when one of the respective anterior and posterior blade holders are in the respective deployed position; whereby if the anterior blade holder is in the deployed position, then the posterior blade holder cannot be moved from the recessed position; and whereby if the posterior blade holder is in the deployed position, then the anterior blade holder cannot be moved from the recessed position.  
         [0009]     One object of the present invention is to provide an improved utility knife. Related objects and advantages of the present invention will be apparent from the following description.  
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0010]      FIG. 1  is a perspective view of the preferred embodiment of the present invention.  
         [0011]      FIG. 2  is an exploded side perspective view of the embodiment of  FIG. 1 .  
         [0012]      FIG. 3  is a side elevational view of the blade holder of the embodiment of  FIG. 1 .  
         [0013]      FIG. 4   a  is a side sectional view of the embodiment of  FIG. 1  with the blade recessed and locked.  
         [0014]      FIG. 4   b  is a side sectional view of the embodiment of  FIG. 1  with the blade recessed and unlocked.  
         [0015]      FIG. 4   c  is a side sectional view of the embodiment of  FIG. 1  with the blade deployed.  
         [0016]      FIG. 5  is a side elevational view of a first type of second embodiment blade holder of the present invention.  
         [0017]      FIG. 6  is a side elevational view of a second type of second embodiment blade holder of the present invention.  
         [0018]      FIG. 7  is an exploded perspective view of a second embodiment housing of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0019]     For the purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.  
         [0020]     Referring now to  FIG. 1 , there is illustrated a first embodiment of the present invention, indicated generally at  20 . With reference to  FIG. 2 , the utility knife  20  includes a housing having an anterior end  24  and a posterior end  26 . Preferably, the housing  20  has 180-degree rotational symmetry about a midpoint  25 . In other words, the preferred embodiment is a double-acting utility knife  20  adapted to deploy a razor blade from either end  24 ,  26 , embodiments having different numbers of blades are likewise contemplated.  
         [0021]     Referring now to  FIG. 2 , the anterior and posterior ends  24 ,  26  of the preferred embodiment have apertures  28   a - b  formed therein. The apertures  28   a - b  are preferably slots, although they may have any convenient configuration. Chambers  30   a - b  are formed in the housing, each adapted to receive a blade holder  32  (see  FIGS. 3 and 4   a - c ). Safety channels  34   a - b  are also formed in the housing adjacent the blade chambers  30   a - b . Safety channels  34   a - b  are formed extending respectively from end walls  35   a - b  and open respectively into blade chambers  30   a - b . A razor blade (illustrated in phantom at  36  in  FIGS. 3 and 4   a - c ) may be removably coupled to each blade holder  32 .  
         [0022]      FIG. 3  illustrates blade holder  32 . Blade holder  32  is adapted to hold a razor blade  36  in the blade-engaging portion  40 , while actuating lever portion  42  extends out above the blade-engaging portion  40 . Blade holder  32  also includes a tab or safety-channel engaging portion  44 , which preferably extends at a substantially 90-degree angle from actuating lever portion  42 . Safety channel engaging portion  44  is adapted to slidingly engage one of the safety channels  34   a - b  when blade holder  32  is operationally positioned in housing  22 .  
         [0023]      FIGS. 4   a - c  illustrate blade holder  32  slidingly positioned in housing  22  and in which a blade  36  has been operationally coupled. While  FIGS. 4   a - c  detail a blade holder  32  positioned to deploy a blade  36  from the anterior end  24  of utility knife  20 , it is understood that the illustrated process equally applies through symmetry to a blade deployed from the posterior end  26 .  FIG. 4   a  illustrates blade holder  32  occupying recessed position  46 , with safety channel engaging portion  44  slidingly engaged in safety channel  34   a . Blade holder  32  is prevented from moving towards anterior end  24  (and blade  36  is prevented from exiting slot  28   a ) by the end wall  35   a  of safety channel  34   a  lockingly engaging safety channel engaging portion  44 .  
         [0024]      FIG. 4   b  illustrates blade holder  32  being disengaged from safety channel  34   a . A disengaging force vector acts on blade holder  32  such that channel engaging portion  44  is slid away from end wall  35   a , down safety channel  34   a , and into blade chamber  30   a , thus releasing blade holder  32  and enabling blade holder  32  and held blade (illustrated in phantom at  36 ) for deployment.  
         [0025]     As is shown in  FIG. 4   c , blade  36  is deployed by sliding blade holder  32  towards anterior end  24  of utility knife  20  while maintaining sufficient force on the safety channel engaging portion  44  (by depressing actuating lever portion  42 ) to prevent it from re-engaging safety channel  34   a . Blade (illustrated in phantom at  36 ) in deployed position  50  partially extends through slot  28   a.    
         [0026]     Blade holder  32  is preferably formed from spring steel, but may be made of any material that will exert a biasing force against deformation. The spring steel exerts a biasing force on tab  44 , pushing it into channel  34   a  as soon as it is aligned with channel  34   a . Tab  44  must be pushed against the biasing force to remove tab  44  from channel  34   a  in order for the blade to be deployed.  
         [0027]     A second embodiment of the present invention is illustrated in  FIGS. 5-7 , with continuing reference to  FIGS. 1-4 . Items in the second embodiment that are substantially similar to like items in the first embodiment are given like reference designators. The second embodiment utility knife of the present invention provides a safety feature that prevents accidental (or intentional) deployment of both blades at the same time.  
         [0028]     As shown in  FIG. 5 , in order to provide this feature, a first blade holder  132  in the second embodiment is substantially identical to the blade holder  32 , but includes an arm  60  depending therefrom in the direction of the second blade holder. The arm  60  includes a widened portion  62  at the distal end thereof. Portion  62  includes an engaging surface  62   a.    
         [0029]     A second blade holder  232  of the second embodiment is illustrated in  FIG. 6 . Second blade holder  232  includes an extension  64  with a tab  66  extending substantially perpendicular therefrom. Tab  66  is sized and positioned so as to contact engaging surface  62   a  of the first blade holder  132  if there is an attempt to deploy both blade holders  132 , 232  at the same time. As shown in  FIG. 7 , a channel  70  is formed in the central wall of the utility knife housing in order to allow passage of the arm  60  from the first blade holder  132  to the second blade holder  232 .  
         [0030]     In operation, when first blade holder  132  is retracted, second blade holder  232  may be fully deployed before tab  66  contacts engaging surface  62   a . Once tab  66  is in contact with engaging surface  62   a , first blade holder  132  may not be deployed because the interaction between tab  66  and engaging surface  62   a  prevents such movement. Similarly, if first blade holder  132  is deployed first, engaging portion  62   a  will come into contact with tab  66  once first blade holder  132  is fully deployed. This contact will then prevent deployment of second blade holder  232  until first blade holder  132  is retracted. Consequently, both blades of the utility knife cannot be deployed at the same time.  
         [0031]     While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the invention are desired to be protected.