Abstract:
An improved utility knife has a blade housing, a handle region, and an end cap. The end cap is removably attached to the handle region. The handle region is cylindrical, with a slight taper and includes an interior storage chamber. The blade housing has a blade channel for permitting retraction and extension of the blade. Clench plates hold the blade securely within the blade channel and are slidable within it. An axis of the blade-holding portion of the knife is tilted relative to the axis of the gripping portion.

Description:
CROSS REFERENCE TO RELATED APPLICATION 
       [0001]    This application is a continuation-in-part of patent application Ser. No. 11/936,402, filed on Nov. 7, 2007, which is herein incorporated by reference in its entirety. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    1. Field of the Invention 
         [0003]    The present invention relates to an improved utility knife designed for a variety of uses. Specifically, the invention provides a utility knife having a handle that is easily held firmly by an operator and directs the force of the operator&#39;s grip in the direction of the knife blade, while also stabilizing the blade, and having a blade that is retractable. 
         [0004]    2. Prior Art 
         [0005]    Typical utility knives of the prior art include a parallelepiped handle and have an approximately rectangular cross section, may be seen in U.S. Pat. Nos. 6,907,668, 7,131,204, 6,865,816 and 6,951,055. They may have either a stationary or retractable blade. It is common for replacement blades to be stored within the handle. The replacement blades are usually accessed by opening the handle, which is usually made of two halves held together by a screw, as shown in U.S. Pat. No. 7,186,067. 
         [0006]    The typical shape of a utility knife handle does not provide the most ergonomically effective design for firmly grasping a knife and stabilizing a knife or transferring force applied by the hand of an operator to the blade of the knife. When a relatively large amount of force must be applied, and operator&#39;s hand may easily tire or slip along the handle. This ergonomic and mechanical inefficiency also provides a utility knife difficult for persons having decreased strength of grip, as commonly comes with increasing age. As life expectancy increases, it becomes more desirable to develop common household hand tools that are easily operated by persons with a relatively weaker grip. 
         [0007]    Attempts have been made to improve the design of utility knife handles, as can be seen in U.S. Pat. No. 6,829,827, which employs a pistol-grip type handle. Such a design is only moderately effective but greatly increases the bulk of the knife, making it less practical for inclusion in a readily portable, compact tool box. 
         [0008]    Because strong force is frequently applied to utility knives, it has been necessary to form them from strong, durable materials such as metals. More recently, it has become more practical to form utility knives from polymer and/or composite materials. These materials typically have smooth surfaces, increasing the difficulty of adequately gripping the handle. Such handles slip within an operator&#39;s grasp. In addition, the cast metal surface of such handles leads to blisters. More comfortable and more easily grasped plastics usually do not provide sufficient strength to the tool to be adequate material for manufacturing utility knives. 
         [0009]    It is known to apply various coatings to the handle of a utility knife to increase gripping, as shown in U.S. Pat. Nos. 7,186,067 and 7,055,407. However, applying additional coatings during manufacture adds significant cost to production of the knives. 
       SUMMARY OF THE INVENTION 
       [0010]    The inventive retractable blade utility knife includes (a) substantially cylindrical handle region radially symmetrical about a first axis, having a back end, a front end, a plurality of circumferentially alternating axially disposed ribs and furrows; (b) a blade housing integral with a front end of the handle region, the region having an elongate blade channel, said channel comprising an upper wall, a lower wall and a clenching plane, said front end defining a second axis having a downward tilt relative to said first axis; (c) a clench plate assembly for securing a blade within the blade housing, said assembly including a tab for the selectable extension or retraction with said channel; and (d) a fastener passing a through a bore in the clench plate assembly and removably attachable to a bore in the blade channel, in which the clench plate assembly is tightened to firmly secure a blade within the blade channel and may be loosened to facilitate replacement of the blade. 
         [0011]    It is an object of the invention to provide an improved utility knife having an easily gripped handle having a retractable blade and a blade housing having relatively few moving parts. 
         [0012]    It is also an object to provide an improved utility knife having an ergonomically effective handle. 
         [0013]    It is another object to provide an improved utility knife having a handle that is easily gripped firmly. 
         [0014]    It is a further object to provide a utility knife handle that effectively transfers force from an operator&#39;s hand to the blade of the knife. 
         [0015]    It is a yet further object to provide a utility knife that can withstand the application of strong force, but that is made of a lightweight and inexpensive material. 
         [0016]    It is another object to provide a utility knife having a handle within which extra blades may be stored. 
         [0017]    The above and yet other objects and advantages of the present invention will become apparent from the hereinafter set forth Brief Description of the Drawings, Detailed Description of the Invention, and Claims appended herewith. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         [0018]      FIG. 1  is a side perspective view of the inventive retractable blade utility knife showing the blade extended. 
           [0019]      FIG. 2  is a side view of the knife of  FIG. 1  however showing the blade thereof retracted. 
           [0020]      FIG. 3  is a top view of the invention, as shown in  FIG. 1 . 
           [0021]      FIG. 4  is a bottom view of the invention, as shown in  FIG. 1 . 
           [0022]      FIG. 5  is a side elevational view of the utility knife. 
           [0023]      FIG. 6  is a side elevational view of the opposite side of that shown in  FIG. 5 . 
           [0024]      FIG. 7  is a rear elevational view of the invention. 
           [0025]      FIG. 8  is a front elevational view thereof. 
           [0026]      FIG. 9  is an exploded view showing the rear blade cover cap and the carrier, clench plate and blade assembly retaining means of the utility knife. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0027]    The present invention relates to an improved retractable blade utility knife having a central handle  14  that is generally cylindrical and tapered toward the front toward a knife blade  18 . See  FIG. 1 . The handle is designed for superior effect of gripping and accuracy of directing applied force. It also includes a blade housing  16  that firmly holds blade  18  in place at a slight downward angle relative to an axis  25  of handle  14 . See  FIG. 2 . The invention also preferably comprises an end cap  20  that is geometrically optimized to forwardly direct applied force. The features of the improved utility knife allow it to be made inexpensively and to efficiently direct and leverage applied force through the end cap  20 , handle  14  and to the blade  18 . It is relatively light in weight, has an easily gripped handle, and force-directing features make that make it suitable for use by any user, but also particularly for users having a weakened grip, such as sufferers of arthritis. 
         [0028]      FIG. 1  shows a perspective view of the preferred embodiment of the invention. Utility knife  20  includes a blade housing  16 , a handle region  14  and end cap  20 . End cap  20  is removably attached to handle region  14 . Both end cap  20  and handle region  14  have a diameter of about 29 to 49 millimeters, but preferably 39 mm. Handle region  14  is preferably about 35 to 54 millimeters, but preferably 44 mm in length (See  FIG. 1 ) and is substantially radially symmetric. Region  14  also includes an interior storage chamber  22  (see  FIG. 9 ) accessible by the removal of end cap  20 . Blade housing  16  is designed to employ a standard utility knife blade  18 . It may be made of steel or an inexpensive polymeric material, such as polyolefins, polycarbonates, composite materials or the like. The design of the knife allows less expensive material to be used to manufacture it while still producing a knife capable of withstanding the forces and torques commonly applied to a knife. 
         [0029]    Referring to  FIGS. 2 and 3 , handle  14  extends from the back of the end cap  20  to the front  24  of handle  14 . Handle  14  is cylindrical and slightly tapered such that the diameter at the front of handle is slightly less than the diameter at the end cap  20 . In the view of  FIG. 3 , the longer side of handle  14  is in a range of 45 to 75 mm, but preferably 60 mm. Handle  14  is radially symmetric about an axis  25 . Preferably, handle  14  tapers such that it is slightly frusto-conical in shape. However, it may also be cylindrical, having a constant radius along its length. In one embodiment, the radius gradually declines from about 20 mm at the back of the handle to about 16 mm at the front of handle, and the entire length of the utility knife  20  is about 185 mm, with a possible range of 140 to 230 mm. 
         [0030]    A plurality of circumferential ridges  26  surround the exterior of handle  14  perpendicular to axis  25 , thereby corrugating handle  14 . Ribs  26  substantially strengthen utility knife  10 , increasing the amount of force and torque that may be applied to and through it. Ribs  26  and alternating furrows  27  provide an exterior surface of handle  14  that facilitates superior gripping. The corrugated surface created by alternating ribs  26  and furrows  27  prevent an operator&#39;s hand from slipping up or down the handle region along axis  25 . Ribs  26  and furrows  27  are preferably between 2 and 3 millimeters wide. Ribs  26  preferably extend between 2 and 3 millimeters above furrows  27 . Ribs  26  are rigid and preferably made from the same material as the rest of the handle  14 . Ribs  26  work synergistically with an optimized diameter of the handle to allow extremely effective gripping by a user. The strength of grip facilitated by these and other features of the handle are substantial and allow one with a relatively weak grip to effectively hold and manipulate the utility knife  20 . 
         [0031]    Handle  14  also preferably incorporates a plurality of longitudinal channels  28 . In this embodiment, four longitudinal channel  28  extend across handle region  14  parallel to axis  25  and equidistantly spaced approximately 90 degrees apart from another. Longitudinal channels  28  provide additional strength to the utility knife  20  without interfering with the gripping action facilitated by ribs  26  which have a width of about 2 mm. Preferably, about three to eight longitudinal channels  28  are evenly spaced about the circumference of the handle. In the embodiment shown, four channels  28  are spaced 90 degrees apart, extend the entire length of the handle  14  and have substantially the same dimensions as rib furrows  27 . In the preferred embodiment, longitudinal channel  28  (see  FIG. 1 ) is approximately 2 millimeters wide and extends about two millimeters above furrows  27 . The ribs  26  and furrows  27  are therefore both about 2 mm in width. 
         [0032]    Blade housing  16  extends from front  24  of handle  14  to a front end  30  of the entire assembly. Blade housing  16  is centered about forward axis  32 . Blade  18  is parallel to axis  32  which is angled slightly relative to the axis  25  of radial symmetry of the handle  14 . Axis  25  and Axis  32  deviate from one another by a range of about 6 to about 10 degrees, and preferably about 9 degrees. This angle facilitates transfer of force, by a lever effect, through utility knife  20  to the edge  34  of blade  18 . Blade housing  16  (see  FIG. 9 ) is comprised of a blade housing body  36  which includes a blade channel  38 . Blade  18  is inserted into blade carrier  54 . Once blade  18  is properly placed on carrier  54 , clench plate  40  is placed against carrier  54  and both can then slide within channel  38  such that blade  18  lies between the clench plate and blade carrier  54  but in blade housing body  36 . Screw  42  defines an axis  66  centered about a point along axis  32  and is used to secure clench plate  40  tightly into channel  38  to firmly hold the blade in place. In this preferred embodiment, screw  42  also provides an easy method for loosening clench plate  40  and carrier  54 . This method requires few moving parts and the large diameter of screw  42  provides effective contact to be made with its knurled edge. The large diameter of screw head  42  also allows an operator to provide sufficient torque force to tighten the screw even when applying relatively little torque force to its edges. Screw head  42  is preferably about 15 to 25 millimeters wide, and preferably 20 mm wide, and mates with female fastener  44  that is covered by plate  62  during use. See  FIGS. 6 and 9 . 
         [0033]    Blade channel  38 , blade carrier  54 , and clench plate  40  are typically smooth, without a corrugated or other pattern upon their surfaces. See  FIGS. 8 and 9 . 
         [0034]      FIGS. 3 and 4  show top and bottom views of the embodiment shown in  FIGS. 1-2 . In these figures, it can be seen that axes  35  and  32  both lie in the plane of bilateral symmetry of the blade housing  36 , and therefore do not deviate to either side in the invention. It may also be seen in  FIG. 5  that blade housing  36  tapers downwardly between front  24  of handle  14  and the front  46  of the entire structure. The angle of tapering is substantially greater in blade region  48  (see  FIG. 6 ) than the tapering of handle  14  between end cap  20  and the front  24  of handle  22 . Handle  14  tapers less in order to provide a region that optimally engages an operator&#39;s hand. Blade housing  36  tapers more sharply. The tapering of both handle  14  and blade housing  36  directs a maximum force applied by an operator through handle  14  into blade  18 . This tapering effect maximizes the efficiency with which force applied to handle  14  is transferred to blade  18 . Additionally, the curving of the utility knife  10  resulting from the divergence of axis  25  from axis  32  provides a leverage that further enhances the effective transfer of force from handle  14  to blade  18  due to the physiology of the hand and forearm. This allows an operator with a weaker grip to apply a substantial amount of force to the blade  18  to adequately perform the various functions for which a utility knife is commonly used. Furthermore, the radially symmetric tapering of both the handle and the blade housing provide strength to the utility knife  20  and facilitates a more even distribution of force throughout the knife and into the blade. 
         [0035]    It is noted that end cap  20  is radially symmetrical about axis  25 . See  FIGS. 5-6 . The cap may define any of a variety of shapes, but is preferably hemispherical in shape and preferably has a series of axial strengthening ribs  58  spaced about it. A preferred hemispherical shape provides for even distribution of any force applied to the end cap  20  to the rest of the utility knife. Furthermore, a hemispherical shape of end cap  20  results in any force applied to it that leads to partially providing force in the direction of the front of the utility knife  20  and into blade  18 . 
         [0036]    Handle region  14  is preferably 3 to 5 centimeters in diameter, preferably about 4 centimeters in diameter. This results in a handle that is larger than many of the handles described in the prior art. A cylindrical handle of this size is very well suited to conform with the natural size and radius of curvature of a human hand, enabling it to be more easily grasped. This allows a person with even a weak grip to firmly hold and manipulate the tool. The tapering of the handle region further aids in preventing the knife from slipping through an operator&#39;s grasp in the direction of the front  46  of the knife  20 . Often when using the knife as a cutting instrument, substantial force pulls it in the direction of the front of tool. The tapering of handle region allows an operator to counter such a force effectively by simply maintaining the natural shape of one&#39;s hand about it. 
         [0037]      FIG. 9  is an exploded view showing bore  56  of clench plate  40 , which permits screw  42  to engage thru it and slot  52  and also thru hole  53  of blade carrier  54  so that the screw tightly secures clench plate  40  into clench assembly channel  38  and to nut  44 . This combination assures that carriers  40  and  54  are slidably compressed within channel  38 , such that tab  50  may be effectively used to control the position of the blade. Screw  42  mates with nut  44 , which is held in place by cover  62 . The nut is formed of metal or durable polymer and inserted into a clench plate assembly slot  52  formed in housing body  36 . 
         [0038]      FIGS. 3 ,  4  and  9  also show tab  50  of clench plate  40 . Nut  44  passes thru slot  52  in housing  34 , aperture  53  in blade carrier  54 , and hole  56  in clench plate  40  to firmly hold the clench plate  30  blade channel  38 . Those skilled in the art will appreciate that a variety of screw head designs may also be used that are easily grasped, such as, but not limited to knobs, dials, shoulder type thumbscrews, winged thumbscrews, and cranks.  FIG. 9  also shows housing  36  including outer clench plate  40 , blade carrier plate  54 , rear plate  62  and blade channel  38 , and blade portion  34 . Blade channel  38  is defined by channel housing  36  and engaging shelf  16 . Indentions  64  in blade carrier plate  54  aid in securing knife  18 . Tab  50  of outer clench plate  40  enables the user to advance or retract blade  18  and inner clench plate  54  within channel  38 , as desired, in slot  52 . 
         [0039]    These void spaces of blade channel  38  reduce the amount of material required to manufacture the present invention, however having little effect on the function of the invention. 
         [0040]    While there has been shown and described the preferred embodiment of the instant invention it is to be appreciated that the invention may be embodied otherwise than is herein specifically shown and described and that, within said embodiment, certain changes may be made in the form and arrangement of the parts without departing from the underlying ideas or principles of this invention as set forth in the Claims appended herewith.