Abstract:
A retractable knife includes two shells that are secured together by a hook and anchor, and by a cam lever that can be pivoted to separate the two shell and enable quick and easy exchange of blades.

Description:
FIELD OF THE INVENTION 
     The present application relates to a retractable knife, and more particularly to a retractable knife having an improved structure that enables the retractable knife to extend and retract the blade easily and readily. 
     BACKGROUND OF THE INVENTION 
     The body of a conventional retractable knife 50, as shown in FIGS. 6 and 7, includes a main portion assembled from casings 52 and 54. A slot is longitudinally defined in the top face of the main structure and a protruding tip 56 can be pushed back and forth therein. A mount for fixing a blade 60 is integrally formed with the protruding tip 56. The blade 60 is retractable by pulling the protruding tip 56 to the back of the slot. 
     The conventional retractable knife is convenient for users to cut items such as papers, but is inconvenient in that the casings 52, 54 are securely attached by a screw 58, making it difficult to replace the blade. To replace the blade 60, a user has to first unscrew the screw 58, take out the blunt/unsuitable old blade 60, fit the new blade 60 into place and then screw in the screw 58 to secure the two casings 52, 54. The present invention provides a creative and novel means for solving the problems mentioned above. 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an improved structure for a retractable knife. The main characteristic of the present application includes a first shell and a second shell. An aperture is integrally defined within a cam lever and is sized to receive a protuberance. A slot is integrally defined in the first shell and is dimensioned to receive a hook. Therefore, the user can assemble and dissemble the retractable knife safely and swiftly. 
    
    
     The foregoing advantages and objects of the invention will be understood more clearly when taken in light of drawings of the present application. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a retractable knife according to the present invention; 
     FIG. 2 is an exploded perspective view of the retractable knife of FIG. 1; 
     FIG. 3 is a side view in partial section of the retractable knife of FIG. 1 with the second shell removed therefrom; 
     FIG. 4 is a partially cross-sectional view of a retractable knife according to the present application; 
     FIG. 5 is a top plan view in partial section of the retractable knife of FIG. 1; 
     FIG. 6 is a perspective view of a conventional retractable knife; and 
     FIG. 7 is an exploded perspective view of a conventional retractable knife. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Referring to FIGS. 1 and 2, a retractable knife 10 includes a housing comprising a first shell 12 and a second shell 20. A guide rail (not numbered) is formed between corresponding portions of the first and second shells 12, 20. A blade 30 can be extended from or retracted into the retractable knife 10 by being slid along the guide rail. However, operation of the blade 30 is conventional and thus not described in further detail. 
     An anchor is integrally is formed on an inner face of the back bottom end of the lower portion of the first shell 12, such that the first shell 12 is substantially shaped as an &#34;L&#34; when viewed from the top, as shown in FIG. 5. A hook 22 is formed on a rear end face of the second shell 20, and is configured to be received in a indent 142 defined in anchor 14. 
     The first shell 12 defines an opening 16 in a top face thereof near the front and a cam lever 18 is pivotally received therein. The cam lever 18 includes two longitudinal side faces. One of the longitudinal side faces abuts a sidewall partly defining the opening 16 of the first shell 12, and defines an aperture 182 which is substantially semi-circular, and a recess 184 is defined in the aperture 182. 
     The second shell 20 defines a cutout in a top face thereof that is configured to receive a portion of the cam lever 18 therein. 
     A protuberance 26 integrally extends from the top face forming the cutout of the second shell 20. The protuberance is configured to be received in the aperture 182 of the cam lever 18 when the first and the second shells 12, 20 are combined. The cam lever 18 abuts both the top face defining the opening 16 of the first shell 12 and the top face defining the cutout of the second shell 20. The recess 184 of the cam lever 18 engages a stud 262 of the protuberance 26. Thus, with the interlocking between the ridge 22 and the indent 142, contact between the protuberance 26 and the cam lever 18 results in secure yet releasable engagement between the first and second shell 12, 20. To release the engagement between the first and second shell 12, 20, the cam lever 18 is pivoted away therefrom and the stud 262 on the protuberance 26 disengages from the recess 184 of the cam lever 18. Sequentially, the second shell 20 is raised in relation to the first shell 20 such that the engagement between the ridge 22 and the slit 22 is eliminated. 
     Referring to FIG. 2, a user may replace the blade 30 of the retractable knife 10 by pivoting the cam lever 18 away from the first shell 12, whereupon the pin 184 of the cam lever 18 will be pulled away from the stud 262 of the protuberance 26. Meanwhile, the hook 22 of the second shell 20 is pulled away from the indent 142 of the first shell 12 by tilting the second shell 20 outwardly. It will be understood that the user may replace the blades without using screws, so the knife of the invention is much more efficient than the conventional retractable knife. The present invention indeed makes changes the to assemblage and dissemblage of the conventional retractable knife and is novel. 
     It is to be understand that the scope of the invention and of the claims is not limited by the illustrated embodiments, but extends to the equivalent structure as well.