Not Applicable
This application relates generally to off-axis engagement capability of a screw and screw driver.
Some screw and screw driver configurations are known to be capable of driving screws when the screw driver and screw are not in precise co-axial alignment. However, the degree to which such configurations provide for off-axis engagement is limited by a lack of design elements that specifically enhance off-axis engagement range.
A screw engagement system is provided for transmission of torque and rotational motion from a screw driver to a screw. The system includes a screw comprising a screw shaft axially extending from a screw head, and a screw head recess formed axially into the screw head from an end surface of the screw head. The screw head recess includes a plurality of screw head recess grooves arranged circumferentially around and formed radially outwardly into the screw head from an inner circumferential surface of the screw head recess. The system also includes a driver comprising a driver head having the general shape of a spherical frustum and including a plurality of splines that are defined by driver head grooves formed into and arrayed circumferentially around the driver head. The splines are configured to engage the screw head recess grooves and transmit torque and impart rotational motion to the screw therethrough.
Also provided is screw that comprises a screw shaft axially extending from a screw head and a screw head recess formed axially into the screw head from an end surface of the screw head. The screw head recess includes six screw head recess grooves arranged circumferentially around and formed radially outwardly into the screw head from an inner circumferential surface of the screw head recess. The screw head recess is configured to receive a driver comprising a driver head having the general shape of a spherical frustum and including a plurality of driver head splines that are defined by driver head grooves formed into and arrayed circumferentially around the driver head, the screw head recess grooves being configured and positioned to receive and engage the driver head splines and to receive torque transmission and rotational motion therethrough. The screw head recess is also configured to receive a driver comprising a driver head having the general shape of a hexagonal prism and including six driver head corners that are defined by intersections of six facets arrayed circumferentially around the driver head, the screw head recess grooves being configured and positioned to receive and engage the driver head corners and to receive torque transmission and rotational motion therethrough.
A screw engagement system that allows for off-axis transmission of torque and rotational motion from a screw driver to a screw, is generally shown at 10 in the drawings. The system 10 may include a screw 12 that may comprise a screw shaft 14 axially and integrally extending from a screw head 16. A screw head recess 18 may be formed axially into the screw head 16 from an end surface 20 of the screw head 16 opposite the screw shaft 14.
The system 10 may also include a screw driver 22 having a screw driver head 24 configured to engage the screw head recess 18 and to transmit torque and impart rotational motion to the screw 12 therethrough. The screw head recess 18 may be configured to receive the screw driver head 24 and to transmit torque and rotational motion from the screw driver 22 to the screw 12.
The screw driver head 24 may have the general shape of a spherical frustum and may include a plurality of longitudinal ribs or splines 26 defined by parallel longitudinal screw driver head grooves 28 extending into and arrayed equally-spaced circumferentially around the screw driver head 24. As shown in
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In practice, this system 10 can be used to drive the screw 12 into threaded engagement, by first positioning either the screw 12 for threaded insertion into, for example, bone tissue, and engaging the screw driver head 24 with the screw head 16 such that at least some of the splines 26 of the screw driver head 24 are at least partially received in the screw head recess grooves 38. The screw 12 may then be rotated and driven into threaded engagement with the bone tissue by rotating the screw driver 22 and applying sufficient axial pressure to the screw driver 22 to prevent the screw driver head splines 26 from skipping out of engagement with the screw head recess grooves 38.
This system 10 can also be used to remove the screw 12 from threaded engagement from, for example, bone tissue, by engaging the screw driver head 24 with the screw head 16 such that at least some of the splines 26 of the screw driver head 24 are at least partially received in the screw head recess grooves 38. The screw 12 may then be rotated and backed-out from threaded engagement with the bone tissue by rotating the screw driver 22 and applying sufficient axial pressure to the screw driver 22 to prevent the screw driver head splines 26 from skipping out of engagement with the screw head recess grooves 38.
In the embodiment shown in the drawings, the configuration of the screw driver head 24 and screw head recess 18 allow for transmission of approximately 35 Ncm of torque from the screw driver 22 to the screw 12, with the screw driver rotational axis 32 and screw rotational axis 40 being at any included angle in the range of 180 degrees through approximately 165 degrees, and without causing any visual deformation to either the screw head recess 18 or the screw driver head 24. This is sufficient torque transmission to drive the screw 12 into bone tissue, and to remove the screw 12 from bone tissue.
Alternatively, the screw 12 may be driven into threaded engagement with the bone tissue, or removed from such engagement, by first inserting the head of a conventional hex head cap screw driver 42 into the screw head recess 18 with the cap screw driver 42 in approximate axial alignment with the screw 12 as shown in
This description, rather than describing limitations of an invention, only illustrates an embodiment of the invention recited in the claims. The language of this description is therefore exclusively descriptive and is non-limiting.
Obviously, it's possible to modify this invention from what the description teaches. Within the scope of the claims, one may practice the invention other than as described above.
This patent application claims priority from U.S. Provisional Patent Application Ser. No. 62/636,395 filed Feb. 28, 2018 and Patent Cooperation Treaty International Patent Application Serial Number PCT/US2019/017765 filed Feb. 13, 2019, the entire contents of which are incorporated herein.
Filing Document | Filing Date | Country | Kind |
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PCT/US2019/017765 | 2/13/2019 | WO | 00 |
Number | Date | Country | |
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62636395 | Feb 2018 | US |