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A new drill-type cranial perforator is disclosed of the type which comprises a front drill head assembly made up of a leading inner drill and a trailing outer drill, and a rear support and drive assembly adapted to enable both drills so long as the leading inner drill is encountering a resistive sur

A new drill-type cranial perforator is disclosed of the type which comprises a front drill head assembly made up of a leading inner drill and a trailing outer drill, and a rear support and drive assembly adapted to enable both drills so long as the leading inner drill is encountering a resistive surface and to disable both drills when the leading inner drill stops encountering the resistive surface. The inner drill is coupled to the outer drill and to the rear support and drive assembly by a plurality of lugs, each of the lugs having a cam surface, and the outer drill includes a plurality of drive surfaces which coact with the cam surfaces. The new perforator is characterized by cam surfaces which are beveled outwardly toward an outer surface of the inner drill member in a helical twist, with the degree of bevel increasing progressively along the length of the cam surface.

대표청구항 ▼

An improved drilling implement for drilling holes in bone structures comprising a drill head assembly and a drill head drive assembly; said drill head assembly comprising a hollow outer drill member and an inner drill member coaxially disposed within said outer drill member; said outer drill member

An improved drilling implement for drilling holes in bone structures comprising a drill head assembly and a drill head drive assembly; said drill head assembly comprising a hollow outer drill member and an inner drill member coaxially disposed within said outer drill member; said outer drill member comprising an outer end having a plurality of cutting flutes and an inner end having three circumferentially-spaced lips that extend in a plane at right angles to the longitudinal axis of said outer drill member, each of said lips having a drive surface extending in a plane that intersects the plane of said lip; said inner drill member comprising an outer end having a plurality of cutting flutes and an inner end having (1) an end surface, (2) three circumferentially-extending, mutually-spaced lugs projecting from said end surface parallel to the center axis of said inner drill member, each of said lugs having a cam surface extending circumferentially and at an angle to the longitudinal axis of said inner drill member and disposed to engage one of said drive surfaces and thereby drive said outer drill member when said inner drill member is rotated in a first direction, and (3) a threaded center hole; said drill head drive assembly comprising a drive member, a drill head/drill drive coupling member, a drive adaptor, and biasing means; said drive member comprising an end surface extending transversely of its axis and interrupted by three recesses for receiving said three lugs, each of said recesses being defined in part by side surfaces extending in planes extending parallel to the center axis of said drive member; said coupling member being screwed into said threaded center hole so that it and said inner drill member will rotate as a unit when said inner drill member is rotated in said first direction; said drive adaptor being connected to said drive member so that said drive adaptor and said drive member will rotate as a unit when said drive adaptor is rotated in said first direction; said biasing means being disposed so as to bias said coupling member and said inner drill member axially away from said drive adaptor; said drill head assembly and said drill head drive assembly being arranged so that when said drive adaptor is rotated in said first direction, (a) so long as said inner drill member encounters a predetermined resistance to penetration, said lugs will remain engaged with said side surfaces and said inner drill member will cause said outer drill member to rotate with it as a unit with said drive adaptor, and (b) when said inner drill member no longer encounters said predetermined resistance to penetration, said cam surfaces will coact with said drive surfaces to force said inner drill member forward relative to said outer drill member and said drill head drive assembly sufficiently for said lugs and said side surfaces to be disengaged, whereby said inner and outer drill members will slip relative to said drive member as said drive adaptor is rotated in said first direction, the improvement wherein: said cam surfaces are beveled outwardly toward an outer surface of said inner drill member in a helical twist, and further wherein the degree of bevel increases progressively along the length of each of said cam surfaces.