Abstract:
A screw driver for a screw having a drive socket having an axially extending shaft with a bifurcated tip, the tip having a cross-sectional profile for insertion into a cross-sectional profile of the screw socket. The shaft has a tapered section adjacent the bifurcated tip. A bushing is mounted on an outer surface of the shaft for axial movement therealong. The bushing has inwardly extending protrusions for engaging the tapered section on the shaft upon movement in the axial direction along the shaft in a direction away from the tip. This allows the selective capture or release of the screw by the shaft tip by axial movement of the bushing away from and towards the shaft distal tip.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     The present application is a continuation of U.S. Pat. No. 8,347,768, filed on Mar. 18, 2009, which application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/DE2006/001185 filed Jul. 8, 2006, which claims priority from German Patent Application No. 202005011010.8 filed Jul. 13, 2005 and German Patent Application No. 202005019646.0 filed Dec. 16, 2005, all of which are incorporated herein by reference. 
    
    
     BACKGROUND OF THE INVENTION 
     The invention concerns a screwdriver for an inner profile screw with a shaft and an outer profile head designed to correspond to the inner profile recess of the inner profile screw, in particular for use in connection with the surgical implantation of an implant into the body of a human being. 
     For example, during the implantation of a splint to be screwed to a bone, profile screws are normally used in conjunction with a screwdriver whose head is provided with an outer profile head which engages with the screw inner profile recess. Before screwing, it is important that the inner profile screw is held in such a way to the head of the screwdriver that it can not slip out. 
     From DE 1 866 996 such a screwdriver is known, which works in conjunction with a hollow head screw, and whose shaft is split into two half-sections by a longitudinal gap, which splay themselves apart due to their spring action, and so jam themselves into the screw head. From U.S. Pat. No. 4,779,494 a similarly developed screwdriver is known, with which the non-forcedly separated sections of the shaft are aligned by pushing a bushing forward. 
     In the case of prior art screwdrivers, they produce a clamping force, with which the section of the shaft is pressed against the inner profile recess in the inner profile screw, from the elasticity of the material of the shaft pushed back into the splayed position. The clamping force is therefore not precisely defined, but is dependent on tolerances (also in respect of the inner profile recess of the screw). 
     SUMMARY OF THE INVENTION 
     The invention is based on the task to create a screwdriver, which is simply developed and manufactured, in particular a screwdriver, which applies a reproducible clamping force, independent of the tolerance of the inner profile recess of the screw. 
     According to an exemplary embodiment, a screwdriver for an inner profile screw is developed, which comprises a shaft and an outer tip or head profile designed in a manner which corresponds to the inner profile recess of the inner profile screw, whereby the distal region of the shaft with the outer head profile is formed in a split manner, and a bushing receives the shaft and can be moved in relation to it, whereby at least the one of the sections of the shaft arising from the split is provided with an oblique contact member and the bushing is provided with a contact ring which acts upon the oblique contact member(s), whereby through a movement of the bushing relative to the shaft, the section of the shaft provided with the oblique contact member is split off from the other part, by clamping the inner profile recess with the outer profile head. 
     According to a further exemplary embodiment, a screwdriver for an inner profile screw is developed, which comprises a shaft and an outer head profile designed in a manner which corresponds to the inner profile recess of the inner profile screw, whereby the screwdriver is designed with a screwable bushing that receives the shaft made from an elastic material, the distal region of the shaft with the outer head profile is formed in a split manner, at least one of the sections of the shaft arising from the split is provided with an oblique contact member and the bushing is provided with a contact ring which acts upon the oblique contact member(s), whereby through a rotation of the bushing relative to the shaft, the section of the shaft provided with the oblique contact member is split off from the other part, by clamping the inner profile recess with the outer profile head of the shaft. In particular the screwdriver can be arranged in such a way, that by turning the bushing relative to the shaft, the section of the shaft provided with the oblique contact member is pulled away from the other part, by clamping the inner profile recess with the outer profile head. 
     According to a further exemplary embodiment, a screwdriver for a multi-sided hollow screw head is developed, which comprises a shaft and an outer multi-sided head, designed in a manner which corresponds to the inner multi-sided recess of the inner multi-sided screw, whereby the screwdriver is designed with a screwable bushing that receives the shaft, whereby the distal region of the shaft is formed in a split manner in a symmetry plane with the outer multi-sided head, whereby the two split halves of the shaft are provided with oblique contact members arranged to lie opposite each other, whereby the bushing is provided with a contact ring which acts upon the oblique contact member. By turning the bushing relative to the shaft, the separated halves of the shaft are pulled away from each other by clamping the inner multi-sided recess with the multi-sided head. In particular the screwdriver can be arranged in such a way, that by turning the bushing relative to the shaft, the section of the shaft provided with the oblique contact member is pulled away from the other part, by clamping the inner profile recess with the outer profile head. 
     According to a further exemplary embodiment, a screwdriver for an inner profile screw is developed, which comprises a shaft and an outer head profile designed in a manner which corresponds to the inner profile recess of the inner profile screw, whereby the distal region of the shaft with the outer head profile, made from an elastic material, is formed in a split manner, and an outer surface of the section of the outer head profile is thickly formed, and the section next to the insertion in the inner profile recess of the screw elastically converges on the other section as the gap reduces, and gets elastically clamped in the inner profile recess. Preferably, one section can be provided with an oblique contact member, and the other can be provided with a bushing designed with a corresponding oblique contact member, whereby a rotation of the bushing in the direction of the insertion of the outer head profile in the inner profile recess produces alignment of both of the sections of the shaft with each other, and a rotation of the housing in the opposite direction causes the outer head profile to be clamped in the inner profile recess. 
     The split distal region of the shaft can be formed as removable. 
     The plane in which the gap runs can be a symmetry plane, however the gap plane preferably lies eccentrically, i.e. the shaft is asymmetrically split. 
     The profile can be a multi-sided profile but also a Torx or Torx Plus-profile (hexalobular internal driving feature). 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is hereafter explained according to a design example of the invention expressed in drawing which shows: 
         FIG. 1  is an inner profile screw, shown in section view, and the distal end of a shaft of a screwdriver with a tip with an outer head profile; 
         FIG. 2  is a bushing configured to be mounted on to the shaft; 
         FIG. 3  is the inner profile screw and screwdriver of  FIG. 1  rotated by approximately 90°; 
         FIG. 4  is the screwdriver of  FIG. 1  engaged with the bushing of  FIG. 2 ; 
         FIG. 5  is another view of the screwdriver of  FIG. 1  engaged with the bushing of  FIG. 2 ; and 
         FIGS. 6-8  are end views of different embodiments of the screwdriver of  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION 
     As shown in  FIGS. 1-8 , a screwdriver  9  serving to hold and turn an inner profile screw  10  comprises a shaft  12  and a tip outer profile  16  formed at a distal end  11  of the shaft  12 , which corresponds to an inner profile recess  14  of the inner profile screw  10 . In particular, the inner profile screw  10  can be formed as an inner multi-sided recess, which corresponds to an inner multi-sided screw. 
     On the shaft  12 , whose distal end  11  with the tip outer profile  16  is formed in a split manner to include split sections  12   a  and  12   b  separated by a slot  15 , a housing or bushing  18  shown in  FIG. 2  is attached, such that the tip outer profile  16  can extend through a distal portion  19  of the bushing  18 , as shown in  FIGS. 4 and 5 . 
     In particular, the bushing  18  can be formed to screw onto shaft  12 , as shown in  FIG. 1 . 
     Both of the split sections  12   a,    12   b  of the tip outer profile  16  of the shaft  12  are provided with an oblique contact member  20   a,    20   b,  respectively, which are angled with respect to the longitudinal axis  17  of the screwdriver  9 . The bushing  18  is provided with a contact ring  22  along an inner surface of its distal portion  19  which can act upon the oblique contact members  20   a,    20   b.  By moving the bushing  18  relative to the shaft  12  towards the distal end  11  of shaft  12 , the contact ring  22  resets the oblique contact member  20  allowing the split sections  12   a,    12   b  of the tip outer profile  16  of the shaft  12  to be pulled away from each other or otherwise allowing sections  12   a,    12   b  to extend away from each other, as a result of the elasticity of their material, thereby clamping the inner profile recess  14  of the inner profile screw  10 . By axially displacing the bushing  18  towards the proximal end  13  of shaft  12 , the contact ring  22  again resets the oblique contact members  20   a,    20   b,  the split sections  12   a,    12   b  of the tip outer profile  16  are pressed back together, such that the clamping between the inner profile recess  14  of the inner profile screw  10  and the tip outer profile  16  of the screwdriver  9  is reduced. This allows the axial displacement to be carried out by means of a rotation of the bushing  18  opposite to the shaft  12 , in particular when the bushing  18  is formed as screwable with the shaft, i.e. both of the elements comprise a complementary thread. 
     The distal end  11  of the shaft  12  with the tip outer profile  16  and multi-sided head can be formed in a split manner to include split sections  12   a  and  12   b  disposed about a symmetrical plane, which lies parallel to two faces of the multiple sides of the multi-sided head, as shown in  FIG. 8 . Preferably however, the distal end  11  of the shaft  12  is asymmetrically, i.e. eccentrically, split as shown in  FIG. 7 . Such an asymmetric split can in particular lead to one of the two sections of the shaft  12  (e.g., sections  12   a,    12   b ) being smaller than the other section of the shaft  12 , i.e. the two sections exhibit different cross-sectional areas. For example, the smaller of the two sections can exhibit a cross sectional area which comprises one-third to one-eighth of the cross sectional area of the other. Such an asymmetric separation can have the advantage that the force, i.e. from exertion of the torque on the two sections of the shaft by use of the screwdriver  9 , prevents breakage of the shaft or at least delays it, i.e. a fracture only occurs when a larger torque is exercised. 
     Furthermore, the two split sections  12   a,    12   b  of the shaft  12  can be provided with oblique contact members  20   a,    20   b,  respectively, arranged to lie opposite one another and the bushing  18  can be provided with a contact ring  22  acting on one of the oblique contact members  20 . With a rotation of the bushing  18  relative to the shaft  12  toward the distal end  11 , in the case of a screwable bushing  18 , the split sections  12   a,    12   b  of the shaft  12  are separated and pulled or otherwise allowed to extend away from each other, as a result of the elasticity of the material, thereby clamping the inner profile recess  14  of the inner profile screw  10 . By rotating the bushing  18  toward the proximal end  13  of shaft  12  in such a manner that the contact ring  22  again contacts the oblique contact members  20   a,    20   b,  the separated halves, or split sections  12   a,    12   b,  of the tip outer profile  16  are pressed back together. 
     In an alternative embodiment (not shown), the distal region of the shaft  12  with the outer multi-sided head  16  is formed in a split manner in a symmetry plane, in a corresponding manner. One half of the split is cut at a lower angular degree (in the absence of a force) than the other half of the split. The two halves are aligned by bringing in the split outer multi-sided head into the inner multi-sided recess of the screw  10  and clamping themselves as a result of the elasticity of the material of the outer multi-sided head. 
     In a further alternative embodiment, one of the two separated sections  12   a,    12   b  of the shaft  12  is provided with an oblique contact member  20  and the bushing  18  is provided with a contact ring  22  acting on one of the oblique contact members  20 . With a rotation of the bushing  18  relative to the shaft  12  toward the distal end  11 , the split sections  12   a,    12   b  of the shaft  12  are separated and pulled or otherwise allowed to extend away from each other, as a result of the elasticity of the material, thereby clamping the inner profile recess  14  of the inner profile screw  10 . With a rotation of the bushing  18  toward the proximal end  13  of shaft  12  in such a manner that the contact ring  22  again contacts the oblique contact member  20 , the separated sections  12   a,    12   b  of the tip outer profile  16  are pressed back together. 
     In an alternative embodiment (not shown), the distal region of the shaft  12  with the outer head profile  16  is formed in a split manner. One section of the split is cut at a lower angular degree (in the absence of a force) than the other section of the split. The two halves are aligned by bringing in the split outer profile head into the inner recess profile of the screw  10  and clamping themselves as a result of the elasticity of the material of the outer head profile. Thereby, as described in the previous embodiments, a bushing may be provided, by which rotation of the sections with respect to one another enables alignment, and so enables an insertion of the outer multi-sided head into the inner multi-sided recess. By turning back the bushing, the sections again want to engage the cut final position, thereby clamping themselves in the inner profile recess. 
     In a further embodiment, an outward slanting side of one section of the outer multi-sided head is thickly formed, the section itself moves nearer to the other section by insertion into the inner multi-head profile, causing reduction of the gap width, causing a clamping-pressure to be exerted on the corresponding side of the inner multi-sided recess. 
     In each of the above examples, the bushing can thereby—preferably via a torque limiter—be loaded with a defined force, so that the application of a defined clamping force independent of tolerances is assured. Furthermore, in each of the above described examples, the shaft can not only be simply formed in a split manner, but the separation or split can be formed such that one section of the distal end of the shaft is removed, i.e. a groove or a notch in the cross sectional area of the shaft is formed. In other words, the cross-sectional area of the two sections no longer completely reproduce the inner profile of the screw, but provide a total cross section which is smaller than the cross-sectional area of the inner profile of the inner profile screw. Such a recess may, by insertion of the screwdriver, increase the breaking resistance of the shaft of the screwdriver. 
     In particular it should be noted that all of the above, described in connection with characteristics of an embodiment, could also be combined with characteristics of other embodiments.