Abstract:
A safety knife for ophthalmic surgical procedures has handle to which a blade holder is attached at one end, holding a pre-installed surgical blade. A blade guard is extended and retracted responsive to the movement of an actuator button on the handle. The blade assumes a curved shape as it is extended, to shape itself about and protect the blade. When the guard is retracted it straightens to allow it to slide into the handle, exposing the blade for use.

Description:
This application claims priority from U.S. patent application Ser. No. 61/252,948, filed Oct. 19, 2009 and entitled “Safety Knife With Curved Guard” which is incorporated herein in its entirety by reference for all purposes as if fully set forth herein. 
    
    
     The present invention relates to knives used for surgery and, in particular, a safety surgical knife having a retractable blade guard that can be extended to protect the blade and retracted to expose the blade for use. The retracting mechanism is placed and designed to allow a user to manipulate the guard without changing the user&#39;s hand position. 
     BACKGROUND OF THE INVENTION 
     Knives and scalpels used in ophthalmic surgery have small and extremely sharp blades. During eye surgery it is desirable to make the incisions as small as possible to allow for faster healing and to obviate the need for stitching the incision closed after surgery has been completed. 
     Surgical instruments are typically arranged by a surgical assistant and passed to the surgeon as needed. When the surgeon is finished using a particular instrument, it is customary for the surgeon to pass the instrument back to the assistant who then retains it for further use or, if use is completed, disposes of the instrument. 
     Operating in as confined a surgical field as the eye requires dexterity, concentration and, often, the use of microscopes or other magnifying devices to allow the surgeon to more clearly visualize the eye tissue. A constant concern during surgical procedures is the accidental cutting of either the surgeon or the assistant by an exposed cutting blade. Accidental cutting may cause serious injury and will also require that the person cut be regloved before surgery can continue. 
     It is known to provide scalpels and knives with blade covers or blade guards to protect the blade itself prior to surgery and to protect the blade users during surgery. Examples of such blade guards are found in the prior art. 
     U.S. Pat. No. 7,022,128 (Morawsky) teaches and describes a surgical knife safety handle having a blade guard that can be extended from and retracted into the handle. 
     U.S. Pat. D496,730 (Morawsky et al) teaches and describes an ornamental design for surgical knife safety handle corresponding to the knife described and claimed in the &#39;128 patent. 
     U.S. Pat. No. 6,626,925 (Newman et al) teaches and describes a shielded surgical scalpel having an extendable and retractable blade guard. 
     A common drawback to the designs shown in the aforementioned references is the necessity for the surgeon to maintain either an uncomfortable hand position during retraction and extension of the guard, or the need for the surgeon to grip the knife in a first position to operate the blade guard, then change grips to use the knife to make incisions. Repositioning the surgeon&#39;s hand after retracting the guard often means that the surgeon&#39;s attention and concentration is drawn away from the operating field and to the knife itself. 
     It is good surgical procedure to have the guard in place when the knife is passed back and forth between the assistant and the surgeon. Prior knife designs tend to require the surgeon&#39;s hand to be repositioned when the surgeon&#39;s use of the knife is completed to extend the guard before passing it back to the surgical assistant. 
     Commonly, the assistant already has the next instrument to be used in one hand ready to pass to the surgeon, while receiving the used instrument in the other hand. It would be awkward and dangerous for the surgical assistant to take a knife with the guard retracted and use a single hand to extend the guard before disposing of the knife. 
     Prior art safety handle designs thus make the extension and retraction of the guard awkward and uncomfortable without repositioning the user&#39;s hand. 
     The present invention provides a safety knife with a retractable and extendable guard and a mechanism designed to allow the movement of the guard without repositioning the user&#39;s hand from a comfortable cutting position. 
     The present invention also provides a guard having a simple, uncomplicated design, the guard being moveable to a fully retracted position where no part of the guard extends past the handle end, leaving the surgeon with a clear and complete view of the blade during surgery. 
     The present design also provides a guard which allows the blade to be viewed directly even when the guard is in its fully extended and protective position. 
     While the following describes a preferred embodiment or embodiments of the present invention, it is to be understood that this description is made by way of example only and is not intended to limit the scope of the present invention. It is expected that alterations and further modifications, as well as other and further applications of the principles of the present invention will occur to others skilled in the art to which the invention relates and, while differing from the foregoing, remain within the spirit and scope of the invention as herein described and claimed. Where means-plus-function clauses are used in the claims such language is intended to cover the structures described herein as performing the recited functions and not only structural equivalents but equivalent structures as well. For the purposes of the present disclosure, two structures that perform the same function within an environment described above may be equivalent structures. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and further aspects of the present invention will best be appreciated upon considering the accompanying drawing wherein: 
         FIG. 1  is a perspective view of a surgical knife embodying certain principles of the present invention with the blade guard extended; 
         FIG. 2  is an enlarged detail view of a portion of the knife of  FIG. 1 ; 
         FIG. 3  is a partial sectional view of a portion of the knife of  FIG. 1 ; 
         FIG. 4  is a perspective view of the knife of  FIG. 1  with the blade guard fully retracted; 
         FIG. 5  is a lateral plan view of the detail of  FIG. 4  illustrating the use of blades at different angles; 
         FIG. 6  is a view along  6 - 6  of  FIG. 1 ; 
         FIG. 7  is a partial lateral plan view of the detail of  FIG. 2 ; 
         FIG. 8  is a perspective view of the curved guard; and 
         FIG. 9  is a perspective view of a portion of the handle. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Referring now to  FIG. 1 , the numeral  10  identifies a surgical safety knife having a handle  12  with a proximal end  14  and a distal end  16 . A blade assembly  18  extends from distal end  16  and a blade guard  20  also extends from distal end  16  to partially surround blade assembly  18 . 
     Referring now to  FIG. 2 , blade assembly  18  is shown in further detail having cutting edges  22 ,  24  meeting at a blade apex  26 . As seen in  FIG. 2  and as described in more detail hereinbelow, guard  20  is curved when extended and has an accordion-type living hinge  28  formed thereon. 
     Referring now to  FIG. 3 , knife  10  is shown in a partial lateral sectional view. In this view, it can be seen that handle  12  is hollow, having a cylindrical channel  30  terminating at a guide block  32  formed at distal end  16 . In the embodiment shown, blade assembly  18  is embedded in or mounted to guide block  32 . Blade assembly  18  will typically include either a 45 degree blade  34  or a 30 degree blade  36 ; both are shown to demonstrate the positioning of each with respect to guard  20 . 
     As also shown in  FIG. 3 , guard  20  has a first curved portion  38  formed contiguously with a straight portion  40  with hinge  28  formed at the juncture of curved section  38  and straight portion  40 . A guard notch  42  is preferably formed about the outer periphery of guard  20  substantially parallel to and opposite from hinge  28 . 
     Referring now to  FIG. 4 , a detail of knife  10  is shown with guard  20  fully retracted to expose blade assembly  18 . Again, as shown, blade assembly  18  illustrates the placement of either a 45 degree blade  34  or a 30 degree blade  36 . 
     As seen in  FIG. 4 , a button  44  is formed integrally with straight portion  40  of guard  20 . As further seen, handle  12  has a slot  46  formed therethrough from which button  44  protrudes and within which button  44  can be longitudinally moved. As seen in  FIG. 4 , button  44  can be moved proximally to fully retract guard  20  into handle  12 . Conversely, as seen in  FIG. 2 , button  44  can be moved distally to extend guard  20  from handle  12 . 
     As further seen in  FIG. 4 , slot  46  is preferably formed with a slot seat  58  within which button  44  is partially held and which guides button  44  in a straight fore and aft direction when button  44  is moved. 
     Referring now to  FIG. 5 , handle  12  is shown with guard  20  fully retracted and illustrates the relative position of curved portion  38  and straight portion  40 . As seen, hinge  20  and notch  42  provide sufficient play for curved portion  38  to be moved to a substantially straight position in order to allow curved portion  38  to be fully retracted into handle  12 . Preferably, guard  20  is constructed such that curved guard portion  38  takes its curved shape when unstressed. 
     Referring now to  FIG. 6 , curved guard portion  38  is shown fully withdrawn into handle  12 . Preferably, guard  38  is formed with a generally U-shaped cross section terminating at upper edges  48 ,  50 . As seen in  FIG. 6 , guide  32  has a pair of guide channels  52 ,  54 , sized and shaped to receive curved guard portion  38  and to keep guard portion  38  moving in a straight line when extended from or retracted into handle  12 . 
     As seen in  FIG. 6 , curved guard portion  38  is sized and shaped to provide a clearance distance A between curved portion  38  and blade assembly  18 , preferably at least 0.75 mm. 
     Referring now to  FIG. 7 , clearance distance A is also shown to obtain when curved portion  38  is extended from handle  12 . 
     Referring now to  FIG. 8 , guard  20  is shown removed from handle  12 . Preferably, guard  20  and button  44  are made as a single piece with button  44  extending from straight portion  40 .  FIG. 8  shows the curved shape guard portion  38  assumes when unstressed, beginning at hinge  28 . 
     Referring now to  FIG. 9 , handle  12  is shown in a sectional perspective view, with channel  30  visible, extending the length of handle  12 . Also visible is guide block  32  and a portion of slot  46 . 
     Use of the present invention may now be described. Knife  10  is provided with guard  20  fully extended. Blade assembly  18  is substantially surrounded by curved portion  38  of guard  20  with cutting edges  22 ,  24  and apex  26  protected while still allowing the surgeon to visually view and inspect blade assembly  18 . In this position, knife  10  is preferably transferred from the surgical assistant to the surgeon. The surgeon then grips handle  12  of knife  10 . Preferably, slot  46  and button  44  are positioned such that when the surgeon grips handle  12 , he is holding it in the position that he would normally hold it in order to use blade assembly  18  during surgery. 
     The surgeon next uses his thumb to slide button  44  toward the proximal end of handle  12 , thus retracting curved portion  38  of guard  20  into handle  12 . During the retraction process, curved portion  38  is held and guided by guide slots  52 ,  54  formed in guide block  32 . 
     After the surgeon has completed this use of knife  10 , the surgeon then uses his thumb to advance button  44  toward the proximal end  16  of handle  12  thereby extending curved portion  38  of guard portion  20  to surround and protect blade assembly  18 . 
     When guard  20  is retracted, curved portion  38  straightens at hinge  28  allowing curved portion  38  to be drawn longitudinally into handle  12 . Conversely, when button  44  is used to advance guard  20  from handle  12 , curved portion  38  progressively regains its curved orientation until fully extended. 
     In this manner, both surgeon and assistant can conveniently and effectively extend and retract guard  20  using one hand without requiring repositioning of the hand.