Patent Publication Number: US-2009235533-A1

Title: Utility knife with a fixed blade and a self-retracting blade

Description:
BACKGROUND OF THE INVENTION 
     1. Field of Invention 
     The invention relates to utility knives and more particularly to a utility knife having a fixed blade in a first handle at one end and a self-retracting blade in a second handle at the other end. 
     2. Description of Related Art 
     Utility knife is a common tool used in various trades and crafts for a variety of purposes. Conventionally, the blade of a utility knife is retractable and is solely capable of performing a single function (e.g., cutting a paper box). However, it suffers from a couple of disadvantages. For example, it is not uncommon that a person may carry two or more utility knives when doing a job. This is cumbersome. Moreover, the person has to replace the utility knife being used with another utility knife of a different function if such need arises. This can lower working efficient and is inconvenient. Thus, the need for improvement still exists. 
     There have been numerous suggestions in prior patents for utility knife. For example, U.S. Pat. No. 7,316,070 discloses a self-retracting utility knife. 
     SUMMARY OF THE INVENTION 
     It is therefore one object of the invention to provide a utility knife having a fixed blade in a first handle at one end and a self-retracting blade at the other end so that a user may have two blade options when using the utility knife, thereby increasing working efficiency. 
     The above and other objects, features and advantages of the invention will become apparent from the following detailed description taken with the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a preferred embodiment of utility knife according to the invention; 
         FIG. 2  is an exploded view of the utility knife; 
         FIG. 3  is a lengthwise sectional view of the second handle of the utility knife of  FIG. 1 ; 
         FIG. 4  is a view similar to  FIG. 3  where the first handle is being disengaged from the housing of the second handle by pulling prior to replacing the retractable second blade; and 
         FIG. 5  is a view similar to  FIG. 1  where the retractable blade has been extended by pushing the actuator. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring to  FIGS. 1 to 5 , a utility knife in accordance with a preferred embodiment of the invention comprises a first handle  10  and an opposite second handle  20 . Each component is discussed in detail below. 
     The first handle  10  comprises a first portion  11  including a rectangular recess  12  having a threaded hole  121 , a second portion  14  complimentary to the first portion  11 , a rectangular first blade  13  fitted on the recess  12 , the first blade  13  having two cutting edges and three equally spaced holes (not numbered) formed along a lengthwise central line in which the hole adjacent one end of the first blade  13  is aligned with the threaded hole  121 , a screw  15  adapted to drive through a hole (not numbered) of the second portion  14  and the end hole of the first blade  13  into the threaded hole  121  to threadedly secure the second portion  14  and the first portion  11  together to assemble a hook-shaped housing (not numbered), and a notch  16  formed at a bend of the housing in which a portion of the first blade  13  is exposed at the notch  16 . 
     The orientation of the first blade  13  can be changed when a portion of either cutting edge thereof becomes worn or damaged. That is, the first blade  13  can be flipped 180 degrees relative to a widthwise axis of symmetry thereof. Also, one cutting edge of the first blade  13  can be flipped 180 degrees relative to a lengthwise axis of symmetry thereof to expose a portion of the other cutting edge thereof at the notch  16  when one cutting edge thereof becomes worn or damaged. 
     The second handle  20  comprises a bifurcation  21  extending out of the first handle  10  and aligning therewith, the bifurcation  21  including a first section  211  of reduced width integrally formed with the first portion  11  of the first handle  10 , a second section  212  having a width larger than that of the first section  211 , and two opposite slanting projections  213  at a joining portion of the first and second sections  211 ,  212 , two flexible latches  214  each extending from the joining portion of the first and second sections  211 ,  212  toward the first portion  11  of the first handle  10 , two heads  215  having an outwardly convex portion each on an end of the latch  214 , a first spring-engaging portion  216  formed on the bottom of the first section  211  of the bifurcation  21 , and two slides  217  on both sides of the second section  212 . 
     The second handle  20  further comprises a housing  24  having a front blade opening (not numbered), a lengthwise central slot (not numbered), two parallel grooves  241  on both sides of the slot, two depressions  242  at both open ends of the grooves  241 ; an actuator  22  having a knob (not numbered) with a convex manually engageable surface (not numbered) so that a person may move the actuator  22  axially through the slot between retracted and extended positions; a coil spring  26  having one end anchored at a second spring-engaging portion  221  on the bottom of the actuator  22  and the other end anchored at the first spring-engaging portion  216  so that the actuator  22  is always pulled to engage with a transverse member (not numbered) formed across the legs of the bifurcation  21  (i.e., on the rear portion of the second section  212  of the bifurcation  21 ) when the actuator  22  is in an inoperative position (i.e., retracted position); a trapezoidal second blade  23  releasably secured to a blade carrier (not numbered) on the bottom of the actuator  22 ; and a locking member  25  slidably positioned on a portion between the transverse member and the first handle  10  (i.e., sitting on the first section  211 ), the locking member  25  including two flexible legs  251  each disposed between the first section  211  and the latch  214  to slidably fasten on the bottom of the first section  211 , and two opposite ridges  252  each formed on an end of the leg  251  facing the first handle  10 . 
     A first operation (i.e., cutting operation) of the invention will be described in detail below. As shown in  FIG. 3 , the locking member  25  is disposed between the rear portion of the second section  212  of the bifurcation  21  and the first handle  10  and the heads  215  are matingly engaged with the depressions  242  because the ridges  252  are urged against the heads  215 . Hence, the housing  24  of the second handle  20  is secured to the first handle  10 . In this position, a user may use the exposed first blade  13  to cut an object. In this position, a user may alternatively push the knob of the actuator  22  to move the actuator  22  axially through the slot of the housing  24  to extend the second blade  23  out of the blade opening of the housing  24  for cutting (see  FIG. 5 ). It is envisaged that the second blade  23  will automatically retract into its inoperative position due to the releasing of the compression force of the spring  26  after releasing the actuator  22 . 
     A second operation (i.e., the second blade  23  replacement operation) of the invention will be described in detail below. As shown in  FIG. 4 , the user may slide the locking member  25  toward the first handle  10  to disengage the ridges  22  from the heads  215 . Next, the user may slightly push the housing  24  away from the first handle  10  to cause the heads  215  to clear the depressions  242 . Thereafter, the housing  24  can be detached from the bifurcation  21  by further pushing. Thereafter, the user may replace the worn or damaged second blade  23  with a new one. 
     While the invention herein disclosed has been described by means of specific embodiments, numerous modifications and variations could be made thereto by those skilled in the art without departing from the scope and spirit of the invention set forth in the claims.