Abstract:
A surgical ratchet assembly includes a handle, a driver, a ratcheting mechanism and a locking mechanism. The driver is received within the handle in a rotatable relationship with respect thereto. The ratcheting mechanism is interposed between the handle and the driver. Unlocking of the locking mechanism enables ready disassembly of the assembly for cleaning and component sterilization. A superelastic biasing means is used. The cap reverser further prevents rotation beyond the depressions therein.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims priority to U.S. Provisional patent application, Ser. No. 60/678,245, of the same name, filed on May 5, 2005, the content of which is incorporated herein by reference thereto. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     This invention relates to drivers for rotary surgical cutting tools, and, more particularly, to drivers used in maxillo-facial, neuro, dental and orthopedic surgery, including reamer drivers.  
         [0003]     Screwdrivers and other hand-held tools are often utilized to insert, remove and/or adjust fasteners attached to various items. The tool is used to rotate the fasteners into or out of apertures in the items to properly position the fasteners with respect to the items. The rotation is controlled such that there is relatively free rotation in one direction and driven, locked rotation in the opposite direction.  
         [0004]     Ratcheting mechanisms of this type take various forms, such as those disclosed in U.S. Pat. Nos. 5,613,585; 5,619,891; 5,778,743; 5,873,288; and 5,943,755, the contents of which are incorporated herein by reference thereto and relied upon. In each of these mechanisms, a pair of pawls are disposed within a housing for the tool. The pawls are selectively engageable and disengageable from a toothed gear disposed within the tool housing in order to enable the gear to rotate in a specified direction when adjusting, inserting or removing a fastener However, while tools incorporating ratcheting mechanisms of this type are useful in adjusting, inserting and removing fasteners from various items, the mechanisms also have certain drawbacks. For example, due to the large spacing of the teeth on the gear, ratchet tools must often be rotated more than approximately 10 degrees in order to advance the ratcheting mechanism to the next locking position. In situations where precise movements of a fastener are necessary, the tools incorporating mechanisms of the above-referenced type with gears of this size are not suitable as these mechanisms are very “coarse” and do not allow for precise movements of the fastener.  
         [0005]     Further, the prior art ratcheting mechanisms generally include a large number of parts assembled within the housing in order to complete the ratcheting mechanism, the complexity increasing the time and expense necessary for manufacturing tools incorporating these prior art ratcheting mechanisms.  
         [0006]     Therefore, what is needed is a simpler mechanism with fewer parts of simpler form.  
       SUMMARY OF THE INVENTION  
       [0007]     A surgical ratchet assembly includes a handle, a driver, a ratcheting mechanism and a locking mechanism. The driver is received within the handle in a rotatable relationship with respect thereto. The ratcheting mechanism is interposed between the handle and the driver. The ratcheting mechanism includes a pawl which can be selectively locked out of engagement with a toothed hub via a reverser. A pair of pawls is preferred. A locking mechanism releasably holds the handle to the ratchet mechanism. Cantilever springs bias the pawl into engagement with the toothed hub.  
         [0008]     In a feature of the invention, the cantilever springs are made of super-elastic material, thereby providing lasting, reliable activation of the pawls and long life to the ratchet.  
         [0009]     In another feature, the cantilever form and the use of nickel-titanium in the construction of the cantilever springs enables the spring to exert a nearly constant biasing force biasing the pawl into engagement with the hub.  
         [0010]     In another feature, the narrow form of the springs permit the bulk of the ratchet mechanism to be reduced without sacrificing strength or reliability.  
         [0011]     In another feature, the cantilever springs enter the assembly from the side of the housing, thus permitting maintenance and/or replacement without having to disassemble the housing assembly (e.g., removing the reverser is not necessary to access the springs).  
         [0012]     In another feature, the reverser includes a position in which both pawls are in an engaged position, thus locking the ratchet mechanism against free movement in either direction.  
         [0013]     The object of the invention is to provide a ratchet that is easy to operate and does so reliably.  
         [0014]     Another object of the invention is to provide a simpler mechanism with fewer parts as no mounting pin is required for the biasing springs. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]      FIG. 1  is a perspective view of the ratchet handle of the invention.  
         [0016]      FIG. 2   a  is a perspective view of the ratchet mechanism of the invention, showing the workings therein.  
         [0017]      FIG. 2   b  is a perspective view of the cap reverser reverser of the invention.  
         [0018]      FIG. 3  is an exploded view of the ratchet mechanism of the invention  
         [0019]      FIG. 4   a  is a perspective view of an alternate spring of the invention.  
         [0020]      FIG. 4   b  is a perspective view of another alternate spring of the invention.  
         [0021]      FIG. 4   c  is a perspective view of still another alternate spring of the invention.  
         [0022]      FIG. 4   d  is a perspective view of still another alternate spring of the invention.  
         [0023]      FIG. 5   a  is a top view showing the positioning of the biasing means against the pawls of the invention.  
         [0024]      FIG. 5   b  is a perspective view showing the positioning of the biasing means against the pawls of the invention.  
         [0025]      FIG. 6  is a perspective view of a kit of the invention. 
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0026]     This invention has structural similarities to U.S. Pat. No. 6,817,458 to Gauthier, and WO 2004/096069, PCT/IB2004/001244, the contents of both of which are incorporated herein by reference and relied upon  
         [0027]     Referring now to  FIG. 1 , the ratchet handle  10  of the invention is shown, including essentially a handle portion  12 , a coupling end  14 , and a housing assembly  16  in which is disposed a drive spindle  20  having a toothed hub  22 .  
         [0028]     Referring now to  FIGS. 2   a  and  2   b,  a ratchet mechanism  24  is disposed between the toothed hub  22  and the handle  12 , in order to enable a user to selectively torque fasteners (not shown), in a desired direction dependent on the position of a reverser  26 . The reverser  26  is a cap-shaped structure having an internal aperture  30  and position selection holes  32 ,  34  and  36  which pass through a wall  38  of the cap. A crest of a ball detent  40  in the housing  48  enters into such holes  32 ,  34 , or  36  to retain the reverser  26  in the desired position (neutral, locked counterclockwise, free rotating clockwise, and vice-versa). Arcuate cutouts  42  and  44  are located on opposite sides of the aperture  30  and are formed to include corresponding cam surfaces  42   a  and  44   a.  These cam surfaces  42   a  and  44   a  are disposed on an arcuate cam structure  42   b  and  44   b  which passes between a centering shoulder  46  and each pawl  50   a  and  50   b  such that, the adjacent pawl  50   a  or  50   b  may be cammed in or out of engagement with teeth  54  on the toothed hub  22 . The pawls  50   a  and  50   b  are held in functional relationship by their generally circular stem  50   c  and  50   d,  respectively, in arcuate end surfaces  48   a  and  48   b  of slots  48   c  and  48   d  of a housing  48 , into which the pawls are disposed. Elongated, slender wire springs  52   a  and  52   b  (which can have a circular cross-section, oval cross-section, an uncut rectangular cross-section, even polygonal cross section, as typically results from a rolled or extruded manufacturing process and not cut, flat sheet processing), preferably made of Nickel-Titanium alloy (a.k.a., “nitinol”, from the laboratory that developed it, the Nickel/Titanium/Naval Ordinance Laboratory), a super-elastic, shape memory material, are fixed (using, for example, set screws, or by press fitting, or by a staking operation in the housing, and optionally using a mating nickel-titanium alloy component such as a collet device) in holes  49   a  and  49   b,  so as to act as cantilever springs, to urge the pawls  50   a  and  50   b  against the teeth  54  of the hub  22 . Nitinol alloys have the unusual ability to recover a preset shape, even after drastic distortion. Composition is typically 55%-56% Nickel and 44%-45% Titanium, but slight adjustments of this ratio can significantly impact the properties of the material. There are two primary but overlapping categories of Nitinol. “SuperElastic” alloys are characterized by extraordinary kink resistance and flexibility. The Nitinol Wire used in the invention is a super-elastic alloy which can be strained eight to ten times more than ordinary spring steel without permanent deformation. It can be rather severely compressed, bent or otherwise distorted, but returns to its original shape. This impressive “memory” takes advantage of stress-induced martensitic transformation. In other words, a material is super-elastic when, if sufficient stresses are applied, such materials exhibit martensitic activation/transformation (i.e., deform from an austenitic crystal structure to a stress-induced structure postulated to be martensitic in nature), returning thence to the austenitic state when the stress is removed. The alternate crystal structures described give the alloy super-elastic or pseudo-elastic properties. Poisson&#39;s Ratio for nitinol is about 0.3, but this ratio significantly increases up to approximately 0.5 or more when the shape memory alloy is stretched beyond its initial elastic limit. It is at this point that stress-induced martensite is said to occur, i.e., the point beyond which the material is permanently deformed and thus incapable of returning to its initial austenitic shape. Note that although Nickel-Titanim alloys are currently preferred, inexpensive super-elastic steel alloys are now known and of course may be used. The wire used herein has an annealed temper that is straight in shape. A new memory is imparted to the Nitinol wire by restraining the material in exactly the shape required and heating to a temperature above 932° F. (500° C.) for a minimum of five minutes. The shape will be set upon cooling and will exhibit the same flexibility and resistance to deformation as the original wire. And it can be repeatedly retrained to achieve new shapes.  
         [0029]     Referring to  FIGS. 3   a  to  3   d,  suitable wire springs  52   a  and  52   b  may have a circular cross-section  60 , oval cross-section  62 , and uncut rectangular cross-section  64 , even polygonal cross section  66 , as typically results from a rolled or extruded manufacturing process and not cut flat sheet processing which creates stress risers which limit the functional life of the spring. In addition, the length of the spring  52   a,  and  52   b  may be processed so that the cross-section varies in bending moment of inertia along its length  52 ′, then enabling further control of the biasing forces applied to the pawl  50   a  and  50   b.  With spring material such as super-elastic Nitinol or super-elastic steels, controlled processing of the spring  52   a  or  52   b  in order to vary and control the bending moment of inertia requires that the spring be formed in an annealed state, prior to heat treating to activate super-elastic properties. Further, where the cross-section is varied in form along the length  52   a′  of the spring  52   a  or  52   b  in a non-symmetrical manner, then, a portion of the end  52   c  of the spring may be turned up and then against itself, in order to create a feature by which the spring can be held during processing of the non-symmetrical forming of the spring and to enable fixing of the spring in the desired orientation (the orientation that provides the deflection and force characteristics desired). Orientation can be achieved as well via use of a non-round aperture in the housing  46  into which the end  52   c  is fixed. The spring  52   a  or  52   b  may alternatively be deformed at an end  52   d  to create a feature from which an orientation convention can key off of. Of course, the fixing device (e.g., fastener) must also key off of the non-symmetrical end to orient the spring  52   a  or  52   b  properly in the housing  46 . In any case, after processing, the cross-section should have overall width dimensions that are substantially the same across the centerline of the wire.  
         [0030]     U.S. Pat. No. 5,683,404 to Johnson, entitled “Clamp and Method for its Use”, the content of which is incorporated herein by reference thereto, further discusses shape memory materials that are “pseudo-elastic”, defining these materials to be super-elastic, because of their ability to exhibit super -elastic/pseudo-elastic recovery characteristics at room temperature.  
         [0031]     Thus, a user is able to select which pawl  50   a  or  50   b  is engaged, thereby selecting the direction in which the ratchet handle  10  freely rotates which respect to the spindle  20  and the direction in which the pawls  50   a  or  50   b  lock the teeth  54  as well as the direction in which the pawls are positioned such that the spindle  20  is free to rotation in the opposite direction. The position of the reverser  26  with respect to the housing assembly  16  is determined by a frictional or interference engagement of a ball-detent  40  in one of the holes  32 ,  34 , or  36 .  
         [0032]     Referring now to  FIG. 4 , an exploded view of the ratchet mechanism  24  of the invention includes the housing  48 , the pawls  50   a  and  50   b,  the cantilever springs  52   a  and  52   b,  a stop pin  56  (which engages an elongated slot  58  of the reverser  26 ), the toothed hub  22 , and the reverser  26 . The stop pin  56  is press fit into the housing  48  so as to be fixed therein.  
         [0033]     Referring now to  FIGS. 5   a  and  5   b  the cantilever springs  52   a  and  52   b  bias the pawls  50   a  and  50   b  against the teeth  54  of the hub  22  wherein the extremeties  52   e  of such springs are disposed in recesses  50   a′  and  50   b′  of the pawls. The form of the spring  52   a  and  52   b  may be curved in a section  52   e′,  in order to minimize wear on the pawls  50   a  and  50   b.    
         [0034]     The springs  52   a  and  52   b  are secured to the housing  48  at the first end and free to deflect at the second end. Thus, unlike U.S. Pat. No. 6,817,458 to Gauthier, the biasing members are the cantilevered springs  52   a  and  52   b  and not torsional springs. Further, as already mentioned, the cantilever bar of the invention is optionally made of Nitinol, a super-elastic titanium alloy allowing high flexibility and providing a more constant spring force biasing the pawls  50   a  and  50   b  against the teeth  54  of the hub  22 . A constant biasing force provides smoother ratcheting by avoiding drastic variation in biasing force against the teeth  54 , which, if not substantially constant, would cause intermittent dragging of the pawl as it passes from one tooth position to another.  
         [0035]     In addition, to further prevent the reverser  26  from rotating past the depressions therein (ref. column 6, line 6, Gauthier &#39;458), the stop pin  56 , which is separate from the biasing members  52   a  and  52   b,  engages a slot in the cap reverser, similar to Tiede, U.S. Pat. No. 5,613,585 (see column 3, line 25 thereof), the content of which is incorporated herein by reference and relied upon.  
         [0036]     Referring now to  FIG. 6  , the kit  150  is shown, including the ratchet  10 , tools  130 ,  132 ,  134 ,  136 , a T-bar  138  and a guide pin  139 . The components of the kit  150  are organized in a case  160  having recesses into which the ratchet and the tools may be conveniently stored until use. A selection of surgical fasteners and, optionally, bone plates and other hardware, as well as ancillary tools may be conveniently stored until needed in a particular surgical protocol.  
         [0037]     In an advantage of the invention, the cantilever form of the springs  52   a  and  52   b,  together with the fact that the springs are made of super-elastic material provide a lasting, reliable activation of the pawls  50   a  and  50   b  and long life to the ratchet.  
         [0038]     In another advantage, the cantilever form of the springs  52   a  and  52   b  and the use of nickel-titanium in the construction of the cantilever springs enables the springs to exert a nearly constant biasing force biasing the pawls so as to engage them with the hub  22 .  
         [0039]     In another advantage, the narrow form of the springs  52   a  and  52   b  permit the bulk of the ratchet mechanism to be reduced without sacrificing strength or reliability.  
         [0040]     In another advantage, the cantilever springs  52   a  and  52   b  enter the housing  48  from the side of the housing, thus permitting maintenance and/or replacement of such springs without having to disassemble the housing assembly  16  (e.g., removing the reverser is not necessary to access the springs).  
         [0041]     In another advantage, the reverser  26  includes a position in which both pawls  50   a  and  50   b  are in an engaged position, thus locking the ratchet mechanism against free movement in either direction.  
         [0042]     The object of the invention is to provide a ratchet  10  that is easy to operate and does so reliably.  
         [0043]     Another object of the invention is to provide a simpler mechanism with fewer parts as no mounting pin is required for the biasing springs  52   a  or  52   b.    
         [0044]     Although the term “driver” may be used herein, this term is meant to encompass taps, guide pins, screwdrivers, reamer drivers and any tool which needs to be fastened and held, even rotated, in a controlled manner.  
         [0045]     Multiple variations and modifications are possible in the embodiments of the invention described here. Although certain illustrative embodiments of the invention have been shown and described here, a wide range of modifications, changes, and substitutions is contemplated in the foregoing disclosure. In some instances, some features of the present invention may be employed without a corresponding use of the other features. Accordingly, it is appropriate that the foregoing description be construed broadly and understood as being given by way of illustration and example only, the spirit and scope of the invention being limited only by the appended claims.