Abstract:
Knife structure employing a push button and a slide block drivingly connected with the push button. An engaging plate is disposed in the knife grip and controlled by the push button. The knife blade is formed with multiple locating notches for the engaging plate to engage therein and permit unfolding the knife blade in a stage by stage manner to provide convenience and safety in use.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to a foldable knife structure in which the knife blade may be automatically controllably unfolded in a stage by stage manner for convenience and safety in use. 
     There are various kinds of knives with different dimensions and patterns for different uses. For example, a chopper knife is used to cut meat or vegetable, a paper knife is used to cut paper or pare a pencil, a spring knife is used in mountaineering, a hatchet knife is used outdoors, a clasp knife is portable, etc. With respect to a spring knife, a blade is quickly unfolded for use by means of a resilient member. The conventional spring knife is generally designed so that one side of the grip of the knife is pressed to unfold the blade from the other side of the grip into an extended state. Alternatively, the back of the knife may be depressed to unfold the blade. 
     As shown in FIG. 1, each of the above described conventional knives has a knife grip  2  for receiving the blade  1 . When not used, the blade section  10  of the knife blade is hidden in the grip  2  for easy carrying. However, in actual use of the knife, some shortcomings exist in conventional knives as follows: 
     1. When folding the knife blade into the grip, only a small part of the knife back is exposed to the exterior. Therefore, it is not easy to extend the knives blade. In some knife, the face of the blade near the back thereof is formed with a shallow groove for conveniently drawing out the blade. However, since the blade is made of metal and has a polished face, the shallow groove rends it difficult for a user to easily unfold and extend the blade. 
     2. The convent ional knife structures lack safety designs for protecting the user, especially the user&#39;s hand, from being injured. Especially, with respect to a spring knife, the blade is quickly unfolded by a resilient member. This often leads to accidental cutting or stabbing of the user. Moreover, the resilient member of the spring knife is often designed with a poor position and structure so that after being extended, the blade cannot be quickly and safely folded. 
     SUMMARY OF THE INVENTION 
     It is therefore a primary object of the present invention to provide a knife structure employing a push button and a slide block operatively connected with the push button. An engaging plate i s disposed in the knife grip and controlled by the push button. The knife blade is formed with multiple locating notches for engagement by the engaging plate to unfold and extend the knife blade in a stage by stage manner and provide convenience and ensure safety in use. 
     The present invention can be best understood through the following description and accompanying drawings wherein: 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a conventional knife; 
     FIG. 2 is a perspective exploded view of the knife structure of the present invention; 
     FIG. 3 is a perspective assembled view of the knife structure of the present invention; 
     FIGS. 4A,  4 B and  4 C are plane views respectively showing the operation of the push button and slide block of the knife structure of the present invention in different stages; 
     FIG. 5 is a side view showing the unfolding operation of the knife structure of the present invention; 
     FIG. 6 is a view showing the movement of the slide block inside the knife grip of the knife structure of the present invention; 
     FIG. 7 is a perspective exploded view of another embodiment of the knife structure of the present invention; 
     FIGS. 8A and 8B respectively show the operation of the resilient member of the embodiment of FIG. 7 of the present invention in different stages; and 
     FIG. 9 is a perspective exploded view of still another embodiment of the knife structure of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Please refer to FIGS. 2 and 3. The knife structure of the present invention includes a knife blade  1  and a knife grip  2 . As shown in FIG. 2, the knife blade  1  basically includes a blade section  10  for cutting and a semicircular connecting section  11  at one end. The connecting section  11  is formed with a through hole  12 . An edge of the connecting section  11  is formed with a first engaging notch  13 , a second engaging notch  14  and a third engaging notch  15 . The first engaging notch  13  provides a securing effect when the blade  1  is totally folded into the grip  2 . The second engaging notch  14  provides a safety effect for the blade  1  to slowly unfold out. The third engaging notch  15  provides a firm locking effect when the blade  1  and the grip  2  are totally unfolded for cutting an article. In addition, an engaging block  16  is defined between the first and second engaging notches  13 ,  14 . The thickness of the engaging block  16  is less than one half the thickness of the connecting section  11 , whereby the blade  1  can be quickly and easily unfolded for use. 
     As shown in FIG. 2, the grip  2  is composed of two clamping blocks  20  mated with each other. The grip  2  is formed with a profile conforming to a human hand configuration. The peripheries of the opposite inner faces of the clamping blocks  20  are respectively formed with multiple perforations  21  for screws  22  to pass therethrough and lock the clamping blocks  20 . The inner face of one end of one of the clamping blocks  20  is formed with a recess  23  and locked with a cantilever-like engaging plate  231  which is permitted to bend to a certain extent. The engaging plate  231  is disposed with a projecting tenon  232 . A lateral side of the recess  23  is fixed with an arched resilient member  24 . The other clamping block  20  is formed with a slightly larger depression  25  opposite to the recess  23 . The center of inner face of the depression  25  is formed with a slot  251 . One side of the periphery of the depression  25  is formed with two arched locating notches  252 . A slide block  26  is slidably disposed in the depression  25 . A push button  261  is disposed on the other outer side of the depression  25  and locked with the slide block  26  by screws. One end of the slide block  26  is disposed with an arched hook section  262 . A connecting pin  263  of the push button  261  is passed through the slot  251  to abut against the concave section of the hook section  262 . One side of the slide block  26  is disposed with a resilient plate  264  for snugly fitting into the locating notch  252  so as to restrict the slide block  26  from shifting. In addition, the outer surface of the clamping block  20  is disposed with a resilient clamping plate  27  for hanging and clipping the knife. FIG. 3 shows a complete knife structure. 
     FIGS. 4A,  4 B,  4 C,  5  and  6  show the operation of the present invention. The knife of the present invention can be unfolded in multi-stages with safety. Referring to FIGS. 4A,  4 B,  4 C, in actual use, when depressing the push button  261  (as shown in FIG.  4 A), via the connecting pin  263 , the hook section  262  of the slide block  26  presses the engaging plate  231  downwardly so as to disengage the tenon  232  from the first engaging notch  13  of the blade  1 . By means of the resilience of the resilient member  24 , the tenon  232  is engaged into the second engaging notch  14  to dispose the blade  1  in a slightly opened state (as shown by phantom line of FIG.  5 ). Then, the push button  261  is pushed to drivingly shift the slide block  26  (as shown in FIG. 4B) so as to engage the resilient plate  264  on one side of the slide block  26  into the locating notch  252  (as shown in FIG.  6 ). At this time, the engaging plate  231  is completely pressed by the hook section  262  of the slide block  26  (as shown in FIG. 4C) and the tenon  232  is disengaged from the second engaging notch  14 . When the user totally unfolds the blade  1 , the tenon  232  is engaged into the third engaging notch  15  so as to locate and lock the blade  1  for cutting an article, as shown in FIG.  5 . 
     The periphery of the connecting section  11  at one end of the blade  1  is formed with the first, second and third notches  13 ,  14 ,  15 . By means of the push button  261  and the slide block  26  and the specifically designed tenon  232  of the engaging plate  231 , the blade  1  is unfolded and located in a stage by stage manner. In addition, the resilient member  24  is disposed in the grip  2  so that the blade  1  can be quickly unfolded out so as to more conveniently and safely use the knife. 
     Referring to FIG. 7 which shows another embodiment of the unfolding structure for the blade  1 , wherein a circular rod  28  and a U-shaped resilient member  281  are disposed on one side of the recess  23  of one of the clamping blocks  20 . One end of the resilient member  281  is locked on the clamping block  20 , while the other end thereof is formed with a ring-like section for the circular rod  28  to fit therethrough. Accordingly, when folding the blade  1 , the blade  1  will press against the resilient member  281  and urge the ring-like end thereof to displace horizontally (as shown in FIGS.  8 A and  8 B). When unfolding the blade  1 , the resilience of the resilient member  281  will quickly unfold and extend the blade  1  out for use. 
     FIG. 9 shows still another embodiment of the present invention, in which the push button safety structure on the grip  2  is omitted. However, the first, second and third engaging notches  13 ,  14 ,  15  remain on the periphery of the connecting section  11  at one end of the blade  1 . By means of the engaging block  16  defined between the first and second engaging notches  13 ,  14  and the cooperative resilient member  24  disposed on one side of the recess  23 , the blade  1  still can be unfolded out in a stage by stage manner so as to enhance safety in use. 
     The above embodiments are only used to illustrate the present invention, and are not intended to limit the scope thereof. Many modifications of the above embodiments may be made without departing from the spirit of the present invention.