Patent Publication Number: US-8539680-B2

Title: Utility knife

Description:
The invention relates generally to utility knives and more particularly to a utility knife with an improved housing assembly. 
     BACKGROUND OF THE INVENTION 
     Utility knives typically comprise a knife housing that is typically provided with an aperture that receives a blade such that the blade extends from the housing. A user can grasp the housing and use the blade for cutting or slicing. When the blade becomes worn, dull or breaks the housing may be opened to allow replacement of the blade. 
     SUMMARY OF THE INVENTION 
     The utility knife comprises a first housing portion carrying a strike plate and a second housing portion carrying a sliding nut assembly comprising a rotatable screw and a sliding nut. The sliding nut engages the strike plate upon rotation of the screw to draw the first housing portion toward the second housing portion. 
     The first housing portion may comprise a first perimeter edge that abuts a second coextensive perimeter edge on the second housing portion. A raised lip may extend from the first perimeter edge toward the interior of the first housing portion and be received in a recess formed in the second perimeter edge of the second housing portion. A first supporting surface may be provided on the first housing portion and a second supporting surface may be provided on the second housing portion, where the first and second supporting surfaces comprise generally planar surfaces that face one another and are spaced from one another approximately the thickness of a blade. A magnet may be formed in one of the first supporting surface and the second supporting surface. 
     The front edges of the first housing portion and second housing portion may be formed with overlapping locking mechanisms that engage one another to prevent the first housing portion from separating from the second housing portion. The sliding nut assembly may be located at a generally central location of the first and second housing portions. The strike plate may comprise a flat, generally C-shaped plate member fixed to the first housing portion that includes a recessed area for receiving the sliding nut. The sliding nut assembly may comprise a rotating screw that includes a head that is disposed on the outside of the second housing portion. The screw may include a screw thread that threadably engages the sliding nut. The sliding nut may be prevented from rotating relative to the screw but is allowed to travel along the longitudinal axis of the screw when the screw is rotated. The sliding nut may include a projection that engages a stop to prevent the sliding nut from rotating. When the housing is in the closed position the periphery of the sliding nut may be positioned behind the strike plate such that rotation of the screw pulls the sliding nut toward the strike plate until the sliding nut is in tight engagement with the strike plate. 
     A blade holder may be located in the housing, where the blade holder comprises a wireform clamp having one end secured to the housing and a second free end where the wireform is bent such that the free end acts as a spring clamp to hold the blades. The blade holder further comprises a support that is angled relative to the housing wall such that the blades are supported at an angle in the housing. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a front view of an embodiment of the utility knife of the invention in the closed position. 
         FIG. 2  is a section view taken along line  2 - 2  of  FIG. 1 . 
         FIG. 3  is a front view of the utility knife of  FIG. 1  in an open position. 
         FIG. 4  is a section view taken along line  4 - 4  of  FIG. 3 . 
         FIG. 5  is a front view of the inside of a first housing portion of the utility knife of  FIG. 1 . 
         FIG. 6  is a front view of the inside of a second housing portion of the utility knife of  FIG. 1 . 
         FIG. 7   a  shows an engagement structure between the housing portions in a closed position. 
         FIG. 7   b  shows the engagement structure of  FIG. 7   a  between the housing portions in an open position. 
         FIG. 8   a  shows a second engagement structure between the housing portions in a closed position. 
         FIG. 8   b  shows the second engagement structure of  FIG. 8   a  between the housing portions in an open position. 
         FIGS. 9 and 10  are block diagrams illustrating methods of operating the knife. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS OF THE INVENTION 
     The utility knife is shown generally at  1  in the figures and comprises a first housing portion  2  and a second housing portion  4 . The housing portions are releasably interlocked with one another to form the completed knife housing  6 . The knife housing  6  has a generally elongated profile that may be comfortably grasped by a user&#39;s hand with the front end or nose  6   a  of the knife extending from the user&#39;s hand. Toward the rear end or butt  6   b  of the housing  6  a hand grip  8  is formed that may be comfortably gripped. 
     The first housing portion  2  comprises a perimeter edge  10  that abuts a coextensive perimeter edge  12  on the second housing portion  4  in the assembled housing  6  to define a generally open interior. Near the rear end  6   b  the first housing portion  2  a raised projection  14  is formed that extends from the perimeter edge  10  toward the interior of the first housing portion  2 . Raised projection  14  extends into a recess  16  formed in the perimeter edge  12  of the second housing portion  4  to align the housing portions fix the position of the housing portions together as will hereinafter be described. 
     Formed near the front end  6   a  of the housing  6  is a blade support structure comprising a first blade supporting surface  20  formed on the first housing portion  2  and a second blade supporting surface  22  formed on the second housing portion  4 . The surfaces  20  and  22  comprise generally planar surfaces that face one another when the housing  6  is assembled and are spaced from one another approximately the thickness of a blade  24  such that the blade is supported between the surfaces. The surfaces  22  and  24  are spaced from one another such that a slotted aperture  18  is created at the nose  6   a  of the housing  6  through which the blade  24  extends during use. A magnet  26  may be formed in one of the surfaces, shown on surface  22 , to hold the blade  24  in position during assembly and disassembly of the housing  6 . 
     Located adjacent the top edge of the support surface  20  is a pin  30  that extends from the housing portion  2  toward the housing portion  4  and is dimensioned such that the pin  30  spans the gap between the housing portions. The pin  30  slides into engagement with a groove  32  formed in the top edge of the opposing surface  22  during assembly of the housing  6 . The pin  30  engages one of a plurality of notches  24   a  formed in the blade  24  such that when the blade is positioned in the assembled housing  6  the blade is retained in the housing by pin  30  and cannot be removed without separating the housing portions  2  and  4 . The notch  24   a  engaged by the pin  30  may be selected to adjust the length of the blade extending from the housing  6 . 
     The front edges of the housing portions  2  and  4  are formed with overlapping locking mechanisms. The locking mechanisms engage one another to prevent the housing portions  2  and  4  from separating from one another at the nose  6   a  due to the forces exerted on the housing by the blade during use of the knife. Housing portion  2  includes an engagement element  40  that extends across the plane a-a where the edges  10  and  12  abut. Engagement element  40  defines a bearing surface  40   a  that faces the housing portion  2 . Housing portion  4  includes a mating engagement element  42  that includes a bearing surface  42   a  that faces opposite to bearing surface  40   a . To assemble the housing  6  the housing portion  2  is slid into engagement with the housing portion  4  as shown by arrow b such that bearing surface  40   a  of engagement element  40  is disposed behind bearing surface  42   a  of engagement element  42 . Because of the mechanical interlocking of the engagement elements  40  and  42  the nose  6   a  cannot be pried apart. A similar structure is formed on the bottom front edges of housing portions  2  and  4 . Housing portion  2  includes an engagement element  46  that extends across the plane a-a. Plane a-a is the plane defined by the perimeter edges  10  and  12  in the assembled housing. Engagement element  46  defines a bearing surface  46   a  that faces the housing portion  2 . Housing portion  4  includes a mating engagement element  48  that includes a bearing surface  48   a  that faces opposite to bearing surface  46   a . To assemble the housing  6  the housing portion  2  is slid into engagement with the housing portion  4  such that engagement element  46  is disposed behind engagement element  48 . The engagement of these elements prevents the nose of the knife from being pried open by forces exerted by the blade on the housing during use of the knife. 
     To lock the housing portion  2  to the housing portion  4  a sliding nut assembly is provided on one of the housing portions that engages a fixed strike plate on the other housing portion. In the illustrated embodiment the strike plate  50  is formed on the housing portion  4  at a generally central location. The strike plate  50  comprises a flat, generally C-shaped plate member fixed to the housing portion. The strike plate  50  includes a recessed area  55  for receiving the sliding nut as will be described. The strike plate  50  is secured to the housing portion such that it is spaced from the housing wall  2   d . In the illustrated embodiment the plate  50  is fixed to the housing portion by screws  52  although any mechanism for connecting the plate to the housing may be used. 
     The sliding nut assembly  54  is mounted to the other housing  4  opposite to the strike plate  50 . The sliding nut assembly  54  comprises a rotating screw  56  that extends through a hole  57  formed in the wall  2   c  of the housing portion  2 . Rotating screw  56  has a head  58  that is located on the outside of the housing portion  4  where it may be manipulated by a user to rotate the screw  56 . The head  58  is larger than the hole  57 . The head  58  may include raised areas or other topography to facilitate the user&#39;s grip on the head. The shaft  62  of screw  56  extends through hole  57  and includes a threaded portion  68  with screw threads that threadably engage sliding nut  66  and an unthreaded bearing surface  70  that rotates in hole  57 . A C-clamp  72  is snap fit into an annular groove on the shaft  62  on the back side of the housing portion  4  to retain the screw  56  in the housing portion  4 . 
     The threaded portion  68  of the screw  56  engages a mating threaded  74  hole in the sliding nut  66 . The sliding nut  66  is prevented from rotating relative to the screw  56  but is allowed to travel along the longitudinal axis of the screw as the screw is rotated. In the illustrated embodiment the sliding nut  66  includes a projection  76  that is trapped between a pair of stops  78  such that the sliding nut  66  is prevent from rotating. The screw  56  is dimensioned such that the sliding nut  66  may be positioned behind the strike plate  50 , between the strike plate  50  and the back wall  2   d  of the housing portion  4 , when the screw  56  is in its unloosened position. In the unloosened position the screw  56  is rotated until the sliding nut  66  is positioned at or near the distal end of the screw. The distal end of the screw may be formed with an enlarged flange or a deformed or unthreaded area  69  to prevent the sliding nut from being completely unthreaded from the screw. 
     When the housing is in the closed position, shown in  FIGS. 1 and 2 , the periphery of the sliding nut  66  is positioned behind the strike plate  50 . When the screw  56  is rotated clockwise the sliding nut  66  is pulled toward the strike plate  50  until the sliding nut  66  is in tight engagement with the strike plate  50 . As the screw  56  is tightened engagement of the sliding nut  66  with the strike plate  50  draws the first housing portion  2  toward the second housing portion  4  to clamp the housing portions together. To open the housing  6  the screw  56  is loosened to disengage the sliding nut  66  from the strike plate  50 . The housing portions  2  and  4  are slid relative to one another such that the sliding nut  66  is slid from behind the strike plate  50  and the housing portions  2  and  4  separated from one another. 
     A blade holder  80  is also provided in the housing. The blade holder  80  comprises a wireform clamp  84  having one end  84   a  secured to housing portion  4  such as by screw  82  and a second free end  84   b . The wireform is bent such that the free end  84   b  acts as a spring clamp to hold the blades. The wireform is slightly deformed when a blade or blades are located behind the wireform such that a clamping force is created on the blades to hold the blades in position. A platform may be provided against which that blades may be pressed by the wireform clamp. In the present embodiment the platform comprises a pair of supports  86  spaced such that the blades span the supports. Each support has a first end  86   a  and a second end  86   b  where the second end  86   b  is disposed further away from the wall  2   d  than the first end  86   a  such that the blades are supported at an angle in the housing with the top ends of the blade projecting away from the housing wall  2   d . By angling the support surfaces  86  relative to wall  2   d  a space is provided between the top of the blades and the housing wall  2   d  that allows the user&#39;s fingers to get behind the blades. The blades may be removed by grasping the top edge of the blades and slightly deforming the wireform  84  to release the blades. 
     Operation of the utility knife of the invention will be described with reference to the figures. Assume that the knife is in the assembled condition with the first housing portion  2  and the second housing portion  2  coupled together by the engagement of the sliding nut  66  with the strike plate  50  as shown in  FIGS. 1 and 2 . To open the housing, the screw  56  is rotated in a loosening direction, typically counter-clockwise as viewed in  FIG. 1  (block  901 ). As the screw  56  rotates, the engagement of the screw  56  with the sliding nut  66  moves the sliding nut away from the strike plate  50  (block  902 ). The engagement of extension  76  with stops  78  prevents the sliding nut  66  from rotating with the screw  56 . As a result, the sliding nut  66  is forced to traverse the length of the screw toward the distal end of the screw. 
     As the sliding nut  66  moves away from the strike plate  50  the clamping force is released. Once the sliding nut  66  releases the strike plate  50 , the housing portion  2  is slid relative to the housing portion  2  as shown in  FIGS. 3 and 4  (block  903 ). The housing portion  2  is slid in the axial direction of arrow c toward the rear of the housing  6 . As the housing portion  2  is slid rearward, the sliding nut  66  is moved out from under the strike plate  50  such that the strike plate is not positioned over the sliding nut. Simultaneously, the engagement mechanisms are moved from the engaging positions shown in  FIGS. 7   a  and  8   a  to the non-engaged positions shown in  FIGS. 7   b  and  8   b  (block  904 ). Protrusion  14  slides in groove  16  to guide the housing portion  2  from the position of  FIG. 1  to the position of  FIG. 3 . Once the housing portion is moved to the release position shown in  FIG. 3 , the housing portions can be completely separated from one another by pulling the housing portions  2  and  4  away from one another (block  905 ). The user can access the replacement blades to remove, replace and/or reposition the blade. 
     The housing  6  may be reassembled by reversing the steps described above. The user places the housing portions  2  and  4  together in the offset position shown in  FIGS. 3 and 4  (block  1001 ). In this position the sliding nut  66  is disposed adjacent to, but not behind, the strike plate and the engagement mechanisms are in the disengaged positions shown in  FIGS. 7   b  and  8   b  and the protrusion  14  is in groove  16 . The housing portion  2  is slid to the position shown in  FIGS. 1 and 2  where the edges  10  and  12  of the housing portions  2  and  4  are coextensive (block  1002 ). The engagement mechanisms move to the engaged position of  FIGS. 7   b  and  8   b  and the sliding engagement of protrusion  14  with groove  16  allows the housing portion  2  to the proper position. As the housing portion  2  is slid relative to housing portion  4 , the sliding nut  66  moves to be located under the strike plate  50  (block  1003 ). 
     The screw  56  is rotated in a tightening direction, clockwise as viewed in  FIG. 1 , to move the sliding nut  66  toward the strike plate  50  (block  1004 ). The sliding nut  66  is continued to be rotated to tighten the sliding nut  66  against the strike plate  50  and to draw the housing portions  2  and  4  together (block  1005 ). Once the sliding nut is tightly engaged with the strike plate the assembly of the utility is complete. 
     Specific embodiments of an invention are disclosed herein. One of ordinary skill in the art will recognize that the invention has other applications in other environments. Many embodiments are possible. The following claims are in no way intended to limit the scope of the invention to the specific embodiments described above.