Abstract:
A round knife including a handle which is provided in a head end thereof with a slot for receiving pivotally a round knife blade and a support frame. The slot is provided with a protective groove for retaining and locating the support frame. When the support frame is securely engaged with the protective groove, the round knife blade is concealed securely by a protective shield of the support frame. The support frame can be actuated by an actuation piece to rotate so as to expose the round knife blade to execute the cutting operation.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a protective shield of a round knife, and more particularly to a means for rotating and locating the protective shield of the round knife. 
     BACKGROUND ART 
     As shown in FIGS. 1 and 2, a round knife  10  of the prior art comprises a handle  11  which is provided at the front end thereof with a rotatable protective shield  12  covering a round blade  13 . The protective shield  12  is rotated to expose the round blade  13  or to shield the round blade  13 . 
     The round knife  10  of the prior art described above is defective in design because the protective shield  12  can not be easily turned with a finger in spite of the protective shield  12  being provided in the outer side thereof with two protrusions  121  and  122  which are too small in size to stop the finger. In addition, the round blade  13  can be accidentally exposed at such time when the protective shield  12  is exerted on by an external force. In other words, the protective shield  12  of the prior art round knife  10  is a safety hazard. 
     SUMMARY OF THE INVENTION 
     The primary objective of the present invention is to provide a protective shield of a round knife, which is free from the drawbacks or the protective shield of the prior art round knife described above. 
     In keeping with the principle of the present invention, the foregoing objective of the present invention is attained by a round knife comprising a handle with a head portion which is provided with a slot for receiving a round knife blade and a support frame. The support frame is provided with an arcuate protective shield. The round knife blade and the support frame are pivoted in the slot such that the rotating and the locating of the round knife blade are controlled by the support frame. 
     The foregoing objective and features of the present invention will be more readily understood upon a thoughtful deliberation of the following detailed description of a preferred embodiment of the present invention with reference to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a plan view of a round knife or the prior art. 
     FIG. 2 shows another plan view of the round knife of the prior art. 
     FIG. 3 shows a perspective view of a round knife of the preferred embodiment of the present invention. 
     FIG. 4 shows an exploded view of the round knife of the preferred embodiment of the present invention. 
     FIG. 5 shows a schematic plan view of the round knife of the preferred embodiment of the present invention. 
     FIG. 6 shows a sectional view of a portion taken along the direction indicated by a line A—A as shown in FIG.  4 . 
     FIG. 7 shows a sectional view of a portion taken along the direction indicated by a line B—B as shown in FIG.  4 . 
     FIG. 8 is a schematic plan view of the preferred embodiment of the present invention showing that the round knife blade is exposed. 
     FIG. 9 shows a sectional view of a portion taken along the direction indicated by a line C—C as shown in FIG.  7 . 
     FIG. 10 is a schematic view of the preferred embodiment of the present invention showing that the round knife blade is concealed. 
     FIG. 11 shows a schematic view showing that the support frame of the present invention is rotated by the actuation piece. 
     FIG. 12 shows a schematic view of the round knife blade of the present invention being exposed. 
     FIG. 13 shows a schematic view of the present invention in operation. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     As shown in FIGS. 3-6, a round knife  20  embodied in the present invention comprises a handle  21 , a round knife blade  30 , a support frame  40 , an actuation piece  50 , and a bolt  60 . 
     The handle  21  has a head portion  22  which is located at one end thereof and is provided with a slotted area  23  having a seat plate  24 . The slot  23  is provided in the inner side thereof with a semicircular protective groove  25 , and in the opposite ends of the inner side  26  thereof with a retaining tooth  27 . The inner side  26  is further provided in one side thereof with a upturned side  28  opposite in location to the seat plate  24 . The upturned side  28  is provided at two ends thereof with an enlarged portion  281 , an arresting shoulder  282 , and two retaining slots  283  and  284 . The seat plate  24  is provided in the center of the inner side  26  thereof with a protruded ring  241  which is located in the slotted area  23  and is provided with a bolt hole  242 . 
     The round knife blade  30  is disposed in the slotted area of the handle  21  such that the round knife blade  30  is attached to the protruded ring  241 , and that the round knife blade  30  is spaced from and parallel to the seat plate  24 . The round knife blade  30  is provided in the center thereof with a pivoting hole  301  in axial alignment with the bolt hole  242  of the seat plate  24 . 
     The support frame  40  is formed of a face plate  41  and a protective shield  42  of a semicircular construction. The face plate  41  is provided in the center thereof with a through hole  411  and two pivot pins  412  and  413 . The protective shield  42  is connected to the support frame  40  and is provided at two ends of the outer wall thereof with racks  421  and  422 . The support frame  40  is disposed in the slotted area  23  of the handle  21  such that the round knife blade  30  is covered by the support frame  40 . As the support frame  40  is rotated, the protective shield  42  is moved into the protective groove  25  such that the two racks  421  and  422  of the protective shield  42  are engaged with the retaining teeth  27  at the opposite ends of the protective groove  25 . The through hole  411  of the support frame  40  is axially aligned with the pivoting hole  301 , of the round knife blade  30  and the bolt hole  242  of the seat plate  24 . 
     The actuation piece  50  is provided with two retaining blocks  51  and  52  with respective two retaining holes  511  and  521 . The actuation piece  50  is engaged with the support frame  40  such that the pivot pins  412  and  413  of the face plate  41  of the support frame  40  are engaged respectively with the retaining holes  511  and  521  of the respective retaining blocks  51  and  52  of the actuation piece  50 , and that the actuation piece  50  can be rotated 180 degrees in relation to the face plate  41  of the support frame  40 . The actuation piece  50  is further provided with two elastic retaining protrusions  53  and  54 , two through holes  55  and  56 , and two angled corners  57  and  58 . 
     The bolt  60  is used to fasten pivotally the round knife blade  30  and the support frame  40  to the handle  21  in conjunction with an elastic washer  61  and a nut  62 . The bolt  60  is received in the through hole  411  or the face plate  41  of the support frame  40 , the pivoting hole  301  of the round knife blade  30 , and the bolt hole  242  of the seat plate  24  of the handle  21 . 
     The head portion  22  of the handle  21  is provided in the outer wall thereof with a skidproof block  29  having thereon a plurality of skidproof fine grooves  291 . 
     As illustrated in FIGS. 7-12, when the round knife blade  30  is concealed by the support frame  40 , the two racks  421  and  422  of the protective shield  42  of the support frame  40  are securely engaged with the two retaining teeth  27  of the protective groove  25 . In the meantime, the actuation piece  50  is securely located on the face plate  41  of the support frame  40  such that the two retaining protrusions  53  and  54  are securely retained in the retaining slots  283  and  284  of the upturned side  28  of the handle  21 , and that the two corners  57  and  58  of the actuation piece  50  are stopped by the two enlarged portions  281  and the arresting side  282 . As a result, the support frame  40  is confined by the actuation piece  50  such that the support frame  40  can not be accidentally rotated to expose the round knife blade  30 . 
     Before the support frame  40  is rotated to expose the round knife blade  30 , the actuation piece  50  must be raised upright at an angle of 90 degrees such that the two retaining protrusions  53  and  54  of the actuation piece  50  are disengaged from the retaining slots  283  and  284  of the upturned side  28  of the handle  21 , and that the two corners  57  and  58  of the actuation piece  50  are moved away from the arresting side  282 . The support frame  40  is thus no longer confined by the actuation piece  50  such that the support frame  40  can be rotated to expose the round knife blade  30 , and that the protective shield  42  is moved into the protective groove  25 . In the meantime, the protective shield  42  is securely located by the two racks  421  and  422  which are engaged with the two retaining teeth  27  of the protective groove  25 . The actuation piece  50  is pressed toward the upturned side  28  at an angle of 90 degrees such that the two retaining protrusions  53  and  54  or the actuation piece  50  are retained respectively in the retaining slots  283  and  284  of the upturned side  28 , and that the two corners  57  and  58  of the actuation piece  50  are arrested by the arresting side  282 . As a result, the support frame  40  is securely located while the round knife blade  30  is in operation. 
     As illustrated in FIG. 13, when the handle  21  is held in one hand of a user of the round knife  20  of the present invention, the thumb is in contact with the skidproof block  29  of the head portion  22  of the handle  21  such that the round knife blade  30  is exerted on by the downward application force “A” of the thumb and the pushing force “B” of the hand. In light of the design of the present invention conforming to the mechanics of the human body, the round knife blade  30  of the present invention can be easily operated to cut a workpiece. 
     The preferred embodiment of the present invention described above is to be regarded in all respects as being merely illustrative and not restrictive. Accordingly, the present invention may be embodied in other specific forms without deviating from the spirit thereof. The present invention is therefore to be limited only by the scope of the following appended claims.