Abstract:
A high speed surgical instrument is designed with a clutch that automatically locks a cutter which is easily assembled and disassembled without moving parts. The clutch includes a pin and U-shaped pin that compliments a configured groove section at the proximal end of a cutter. that fits into a clutch mechanism in the drill or attachment. The cutter includes axially spaced and opposed grooves judiciously located and a flat end portion that allows easy ingress and egress for locking into the clutch mechanism. A square or multi-sided bore configuration of a journal type bearing made from a high temperature resistance polymer material allows the drill to operate at high speeds with a reduction in the diameter of the distal end of the cutter support.

Description:
TECHNICAL FIELD  
         [0001]    This invention relates to high speed surgical instruments and particularly to mechanism for providing a high speed drill having clutching mechanism for holding and locking cutters or tool bits into the surgical drill or attachment used for surgical procedures, with the feature of reducing the diameter of the cutting end to provide visualization to the user and to the combination of clutch mechanism and a unique designed cutter end for coupling the cutters tool bit to the surgical drill and/or attachment in the absence of mechanical moving parts. The surgical instrument includes unique bearings for supporting a cutter driven by a high speed drill, the cutter includes judicious cut out portions at the proximal end that cooperates with the clutch mechanism in the drill or in an attachment which may be bent and driven by the drill motor with the benefit that the diameter of the distal end of the attachment is made smaller than the diameter of the distal end of heretofore known surgical instruments.  
         CROSS REFERENCES  
         [0002]    The following patent applications, contemporaneously filed with this patent application and assigned to the same assignee, relate to the subject matter of this patent application and are incorporated herein by reference. They include the patent application entitled “Bearings for Surgical Instruments” filed by Eddy H. Del Rio, Douglas A. Perry, Jose M. Lamanna, and Thomas D. Anspach (Attorney Docket No. N880) and the patent application entitled “Miniature Cutter Shaft Configuration” filed by Eddy H. Del Rio, Douglas A. Perry, Jose M. Lamanna and Thomas D. Anspach (Attorney Docket No. N879).  
         BACKGROUND OF THE INVENTION  
         [0003]    The surgical drill typically accommodates sundry tool bits such as cutting burrs, saw blades, etc, (cutters) and different sizes thereof and during a surgical procedure different tool bits and sizes may be required for use with the surgical drill. It is therefore necessary for the surgical drill or attachment sometimes referred to as a Micro Dissection Attachment (MDA) to provide means for coupling the tool bit easily and timely with a minimum of time required to remove the incumbent tool bit and replace it with a new one.  
           [0004]    This invention constitutes an improvement on surgical drills and/or attachments by incorporating a unique design within the drill and/or attachment so as to be capable of easily locking the cutter in place. This invention is characterized as simple to assemble and disassemble, requiring minimum amount of time for performing these function, while having the ability to reliably secure or lock the cutter in the clutch mechanism. In accordance with this invention the tool bit is inserted in the surgical drill or attachment to a point beyond where the operator feels a slight force exerted by a latching spring and slightly rotates the tool bit to its locked position. The operator, of course, has no limitations as to when the rotation of the tool bit starts when inserted into the attachment and/or drill, except at the end of the travel. The removal is merely by turning and pulling on the tool bit simultaneously in the direction for removal from the drill or attachment. We have found that the assembly and disassembly, with a minimum of experimental time or leaning time to obtain the requisite skill, the procedure is almost instantaneous. The rotating mechanism of the drill and/or attachment needs to be held stationary during this procedure. Obviously, as is apparent from the above paragraphs, the clutch mechanism does not require movable parts as is typically utilized on drills that lock the tool bit into place.  
           [0005]    U.S. Pat. No. 5,405,348 granted on Apr. 11, 1995 to William E. Anspach, Jr. and Eddy H. Del Rio, the joint inventor of the present application, and entitled “Surgical Cutting Instrument” exemplifies the cutters to which this invention pertains. In this patent It will be appreciated that the proximate end of the cutter fits into jaws of a clutch that is activated mechanically by positioning the jaws radially inward to bear against the outer surface of the cutter shaft to secure it in place during the drilling procedure and the jaws are retracted to release the cutter. Obviously, in the heretofore known mechanism of the type known and that being described herein, this procedure or similar procedure for assembly and disassembly of the cutter is not only cumbersome but is also time consuming. This invention constitutes an improvement of this type of mechanism by incorporating within the drill and/or attachment a unique attachment design for automatically retaining and locking the drill bit or cutter and which clutch mechanism is characterized by avoiding the typical manually operated clutching mechanism.  
           [0006]    The invention is best described as having a combination of features that reduces the diameter of the support for the cutter to improve visibility for the surgeon, permits easy assembly and disassembly of the cutter or tool bit in a efficacious high speed surgical drill.  
         SUMMARY OF THE INVENTION  
         [0007]    An object of this invention is to provide an improved clutch design for surgical drill and/or attachments wherein the proximal end of the cutter is configured to be easily assembled and disassembled in the unique designed automatic clutch mechanism.  
           [0008]    A feature of this invention is that the clutch mechanism includes a hair pin shaped spring extending transversely through the wall of a rotating spindle or shaft of the drill and/or attachment to bear against the proximal end of the shaft of the cutter so as to bias the spindle or drill shaft to lock the cutter against a lock pin that also extends laterally into the bore of the spindle or drill shaft.  
           [0009]    A clutch mechanism for a surgical drill or attachment that is characterized as relatively simple to fabricate, relatively inexpensive, easy to install the cutter into the clutch mechanism and to remove therefrom, is reliable to rotate with the drill motor and is rotatable in a clockwise and/or counterclockwise direction, and requires no mechanically moving jaws that are typically used with locking clutches.  
           [0010]    A feature of this invention is an improved clutching mechanism in combination with a cutter with the cutter having a unique slot and groove configuration that mates with a generally U-shaped hair spring and pin for facilitating the assembly and disassembly of the cutter while locking the same and permitting clockwise and/or counterclockwise rotation.  
           [0011]    Another feature is an improved attachment for a high speed surgical drill including a unique clutch in the attachment mating with a judicious groove arrangement formed on the proximal end of the cutter and for being supported in a reduced diameter tube attached to the attachment which reduction in diameter is a result of a unique bearing. The bearing is made from a polyimide resin/graphite compound that is formed in a journal bearing with a polygon shaped straight through central bore. The square bore configuration in a journal bearing made from a polyamide/graphite (60/40 ratio) resulted in a 3 mm diameter tube at the distal end, providing an efficacious surgical cutter instrument permitting the surgeon a line-on-line vision of the cutter at the cutting cite.  
           [0012]    The foregoing and other features of the present invention will become more apparent from the following description and accompanying drawings. 
       
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0013]    [0013]FIG. 1 is an exploded view in elevation illustrating the attachment for a surgical drill motor and the cutter of this invention;  
         [0014]    [0014]FIG. 2 is an exploded view in perspective of the details of the attachment depicted in FIG. 1;  
         [0015]    [0015]FIG. 3 is a sectional view of the assembled attachment depicted in FIG. 2;  
         [0016]    [0016]FIG. 4 is a perspective view of a bearing forming a portion of an embodiment of this invention;  
         [0017]    [0017]FIG. 5 is a sectional view of the bearing depicted in FIG. 4;  
         [0018]    [0018]FIG. 6 is a front end view of the bearing depicted in FIG. 5;  
         [0019]    [0019]FIG. 7 is an enlarged and exaggerated schematic illustration of the square configuration and the two point contact of the bearing;  
         [0020]    [0020]FIG. 8 is a fragmentary perspective view of the proximate end of the cutter;  
         [0021]    [0021]FIG. 9 is a fragmentary view in elevation of the proximal end of the cutter depicted in FIG. 8;  
         [0022]    [0022]FIG. 10 is a sectional view taken from line  10 - 10  of FIG. 9;  
         [0023]    [0023]FIG. 11 is a sectional view taken from line  11 - 11  of FIG. 9;  
         [0024]    [0024]FIG. 12 is an exploded partial view in perspective showing the details of the clutch mechanism of this invention;  
         [0025]    [0025]FIG. 13 is a perspective view of the spring used in the clutch mechanism of FIG. 12;  
         [0026]    [0026]FIG. 14 is a perspective view taken from the top view of the spring depicted in FIG. 13;  
         [0027]    [0027]FIG. 15 is a fragmentary view in section illustrating the insertion of the cutter into the clutch mechanism of this invention;  
         [0028]    [0028]FIG. 16 is a schematic view illustrating the relationship of the cutter and the clutch mechanism of this invention in the orientation depicted in FIG. 15;  
         [0029]    [0029]FIG. 17 is a fragmentary view similar to the mechanism depicted in FIG.  15  illustrating the cutter when it is in the retained and locked position;  
         [0030]    [0030]FIG. 18 is a schematic view illustrating the relationship of the cutter and the clutch mechanism of this invention in the orientation depicted in FIG. 17;  
         [0031]    [0031]FIG. 19 is a plan exploded view illustrating the position of the grooves and apertures formed in the cutter and clutch mechanism of this invention;  
         [0032]    [0032]FIG. 20 is a fragmentary view partially in section of the spindle housing the clutch mechanism taken along lines  20 - 20  of FIG. 19;  
         [0033]    [0033]FIG. 21 is a sectional view taken along the lines  21 - 21  of FIG. 19; FIG. 22 is a sectional view taken along the lines  22 - 22  of FIG. 19;  
         [0034]    These figures merely serve to further clarify and illustrate the present invention and are not intended to limit the scope thereof. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0035]    To best understand this invention reference is made to FIG. 1 which discloses a MDA generally illustrated by reference numeral  10  which is dimensioned with a minimum diameter of 3 mm at the distal end, being 15 cm long and bent at a 20 degree (°) angle, for example, that rotatably supports a tool bit  12  or cutter having a cutting end  14  at the distal end, an elongated shaft  16  and a clutch portion  17  at the proximal end. The body of the MDA includes the angled housing  18 , the nose cone member  20  extending from the fore end of the angled housing  18 , an elongated tube assembly  22 , that may be stepped toward the distal end  24  and the drive shaft  26  with its clutch shaped end that fits into the drill motor (not shown). The drill motor may be any of the surgical motors manufactured by the assignee of the present invention known in the industry as eMaX™ and microMax™or any other drill motor. (A suitable motor is commercially available from Anspach Companies, Palm Beach Gardens, Fla.). For additional information regarding surgical drills of the type being described herein reference should be made to U.S. Pat. Nos. 5,405,348, 5,494,359 and 5,601,560, which are incorporated herein by reference.  
         [0036]    Next referring to FIGS. 2 and 3 which illustrate the details of the MDA and the bearings of this invention which consists of a spindle  28  that is suitably rotatably supported by commercially available and suitable ball bearings  30  and  32 . As is apparent from FIG. 3 the drive shaft  26  is also suitably rotatably supported in the angled housing  18  by commercially available and suitable ball bearings  34  and  36 . As mentioned in the above paragraphs the drive shaft is suitably coupled to the drill motor (not shown) and driven thereby. The drill motor may use any medium for developing rotational movement and in this instance these motors are electrical. As noted, the spindle  28  is angled relative to the drive shaft  26  requiring beveled gears to change the relative angle. Suitable bevel gears  38  and  40  mounted on drive shaft  26  and spindle  28 , respectively, provide this function. The thrust is absorbed by the thrust bearing  36  and the bearings are pre-loaded by the wave washer  57  and coil spring  16 . The bushing  45  mounted in the aft end of the angle housing  18  is designed to accommodate the fitting connection in the drill motor which includes coupling mechanism that removably affix the MDA thereto. Suitable snap rings  46 ,  48 , anti-rotation pins  51 , spring pins  52  and set screws  54  are utilized to lock the respective components in the housing and together with the thrust washers  56  and wave washer  57  assure that the spindle is snugly fitted into the angled housing  18  and rotates efficaciously and attains long life. A seal  47  may be mounted in the angled housing at the drill attachment end to prevent contaminants from migrating internally and a suitable seal may be a commercially available “O” seal made from an elastomeric material. As mentioned in the above paragraphs, the drive motor and the MDA are merely used herein to describe the preferred embodiment. These bearings that are inserted into the tube assembly  22  which is affixed to the nose cone  20  by the set screw  58  and is held in a non-rotational position and serve to reduce the outer diameter of the distal end of the MDA.  
         [0037]    The end of the shaft  16  of the drill bit  12  is configured to fit into a complementary configured retaining bore  58  formed internally of one end of the spindle  28  and together with the latch spring  60  and lock pin  50 , locks the drill bit into place so that it rotates therewith and will be described in detail hereinbelow.  
         [0038]    In this particular embodiment, four (4) similar bearings are utilized with the internal bearings generally indicated by reference numeral  62  and the distal end bearing generally indicated by reference numeral  64 . For the sake of convenience and simplicity, only one of the internal bearings  62  and the distal end bearing  64  will be described.  
         [0039]    All the bearings are made from a synthetic material and preferably polyimide resin and carbon or graphite. The best results have been obtained when the polyimide resin by volume equaled 60 percent (%) of the total volume and the carbon/graphite equaled 40% of the total volume. The material is obtained commercially and is made by Dupont under the trademark of “VESPEL”. “VESPEL” SP-22 and SP-21 have been used and worked satisfactory. The intermediate bearing  62  are formed similar to a journal bearing with the inner straight through bore  66  formed in the cylindrical housing  68  is configured in a square shape in cross section and the corners  70  extending straight through the bore are beveled. The beveled portions are only incorporated to add material to the bearing, and hence, increase its structural integrity. The inlet portion, i.e. the portion facing the distal end  24  of the tube  22 , is beveled in a countersunk manner so as to form a ramp to assist the end of the shaft  16  of the tool bit  12  to enter and pass into and/or through the bearing. The end portion  72  of bearing  64  at the distal end is squared off and hence, not countersunk. The proximal ends of the bearings  62  and  64  may be beveled in order to ease the assembly of the bearings when inserted into the tube  22 . Obviously, the bearing outer diameter is selected to assure a tight fit with the interior surface of the tube  22 .  
         [0040]    The mating end of the cutter  12  is best understood by referring to FIGS. 8, 9,  10  and  11  which show the cutter  12  having a cut-out section at the proximal end  17  which is designed to be coupled to a clutch mechanism carried by the surgical drill motor assembly or in an attachment. The cutter is typically attached to the surgical drill motor to meet certain specifications for performing surgical procedures, as for example, transoral, transphernoidal and similar restricted access approaches. As mentioned in the hereinabove paragraphs, the cutters utilized with these types of bits are well known and the description to follow will focus on the proximate end that is uniquely designed for automatic clutching to be retained in the surgical drill or its attachment.  
         [0041]    The end of the proximal end portion  17  is milled or flattened to form a planar portion  90  extending partly axially inward toward the distal end to define the shoulder  92 . Adjacent to the shoulder  92  and in the planar portion  90  are a pair of diametrically opposed grooves  94  and  96  cut into the shaft  12  and each defining a truncated triangle E with the removed extended apex C (see FIG. 10) forming angle D substantially equal to a 30 degree (°) angle with respect to a plane A extending centrally of the transverse (vertical) axis bisecting the plane B extending centrally of the axial (horizontal) axis and perpendicular therewith. It will be appreciated from FIG. 10 that the apex C lies in coincidence with the top surface of the planar portion  90 . Hence, the groove begins from the flat and has a front wall  95  toward the proximal end  17  of the shaft  12  and a rear wall  97  toward the distal end  14  of shaft  12 .  
         [0042]    Spaced a short axial distance from shoulder  92  and toward the distal end  14  of shaft  12 , are a pair of groove configurations  100  and  102  diametrically opposed to each other and each groove configurations  100  and  102  includes a groove  104  having an extended apex G (see FIG. 11) lying in coincidence with the plane B and a diametrically opposed groove  106  lying in coincidence with plane B and also having an extended apex G each defining a triangle with an angle J being substantially equal to 25°. As will be noted from FIG. 9 the grooves  106  and  108  start just below the outer circumference of the shaft  12 , say at substantially 0.010 inch and the intersection of the base H which is in coincidence with the plane A. As is apparent from the foregoing the groove configurations  100  and  102  are configured identical to each other and when installed in the clutch mechanism of the surgical drill or its attachment, the groove configurations allow the drill bit to be rotated either clockwise or counterclockwise directions. Each of the grooves  106  and  108  have a back wall  110  facing the proximate end  14  of shaft  12  and a forward wall  112  facing the distal end  17  of shaft  12 . The back wall  97  and the back wall  110  are parallel to each other.  
         [0043]    The next portion of this description will describe the clutch which may be formed in either the MDA or surgical drill and for description purposes only, the clutch will be described in connection with the MDA and as one skilled in this art will appreciate, the clutch can be mounted in the drill itself. As noted in FIG. 2, the clutch is mounted in the spindle  28  which is best shown in FIGS. 2 and 12- 22  comprising the U-shaped spring  60  and the pin  50  where the pin  50  which traverses through the bore  58  formed in spindle  28  and is judiciously located. As noted from FIGS. 15 and 17 the pin  50  fits into drilled hole  157  (see FIG. 12) that laterally extends through the spindle  28  and intersecting bore  58  similarly to the spring  60  and suitably secured to spindle  28  by any well known means. In this instance the pin  50  is retained in spindle  28  by the race of bearing  32 . The spring  60  is slightly distorted so that the legs  122  and  124  are out of plane with each other. The spring  60  is mounted in the laterally spaced holes  126  and  128  that extend therethrough and bisect the bore  58  and are judiciously located so that when the proximate end of the cutter  12  is inserted it will extend pass the legs  122  and  124  and will be sandwiched there between. The ends  130  and  132  of legs  122  and  124  are bent to say 90° to hold the spring into place and the legs bear against the walls of the holes  126  and  128  to bias the spindle  26  so that it will rotate slightly to align the pin  50  with respect to the shoulder  92  of groove  90  which is best depicted in FIGS.  16 - 18 . As can be seen in FIG. 15, when the cutter  12  is inserted so that the end portion  17  and the flat portion  90  pass the spring  60  the shoulder  92  will bear up against the pin  50 . As mentioned earlier, the combined effect of the user rotating the cutter as it is inserted and the biasing effect of spring  60  on spindle  28  causes the cutter  12  to rotate and spindle  28  will be rotated so that the shoulder  95  bears against the pin  50  and prevents the cutter from dislodging from its position. It will also be appreciated from FIGS. 16 and 18 the configuration M, N, O, P, S, T. of the shoulders and grooves  94 ,  96  and  100 ,  102  are selected to define a locking support that prevents the cutter not only from being dislodged but also prevents any backlash so that the surgeon will have the confidence that the cutter will follow his motions. Obviously, removing the cutter from the clutch, merely requires the operator holding the shaft from rotating which can easily be done by holding the end of spindle  26 , and retracting the cutter as it is being rotated slightly and the groove  100  will be slightly rotated and expose the pin  50  to the space provided by the flat portion  90  and the wall surface of the bore  58  in spindle  28  permitting the cutter to pass the pin and sliding out of the MDA.  
         [0044]    FIGS.  19 - 22  are included herein to illustrate the relationship of the spring  60  and pin  50  and the apertures formed in spindle  28 . As is apparent from these Figs. The drilled holes  126  and  128  are diametrically opposed to each other and are dimensioned to allow the spring  60  to pass therebetween when assembled. Obviously, each hole  126  and  128  bisect the bore  58  so that each leg of spring  60  contacts the cutter outer surface. The drilled hole  127  that extends laterally through the spindle  24 , likewise bisects the bore  58  so that the proximal end of the cutter will pass the pin  50 . Obviously, the flat portion  90  will provide the widest gap with the wall of bore  58  when the cutter is allowed to pass by the pin  50 . Rotation of the cutter and/or spindle  28  will re-position the flat portion  90  and the cutter is now in the trapped position in either groove  94  or  96  depending on the rotation of the drill, i.e. either clockwise or counter clockwise.  
         [0045]    Although this invention has been shown and described with respect to detailed embodiments thereof, it will be appreciated and understood by those skilled in the art that various changes in form and detail thereof may be made without departing from the spirit and scope of the claimed invention. We claim: