Dual interface screw element and system

Abstract

To provide a screw element having a separate interface for inserting and extracting a screw, and a corresponding system.SOLUTION: The dual interface screw element comprises a screw body (10) having an outer thread (12) and two separate engagement interfaces (13, 15), one for inserting the screw and the other for removing the screw. The removal engagement interface (15) comprises a reverse thread (16) located in an axial recess (36) such that a complementary reverse thread tool applying a torque for extracting the screw body can be tightened against the second engagement interface. The screw is part of a system comprising a removal tool and an insertion tool. Applications include medical applications such as dental implants and bone screws, household applications such as headless wall mounting anchors, and a wide range of other industrial and aerospace applications.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to screws, and more particularly to screw elements and corresponding systems with separate interfaces for inserting and extracting the screw. [Background technology]

[0002] Screws are one of the most ubiquitous machine elements, employed in an endless range of applications ranging from medical devices to heavy machinery, and from household appliances to aerospace applications.

[0003] There are many types of screw heads designed to interface with different screwdrivers or driving tools. Common examples include Phillips, countersunk, Robertson (square), and Torx. Different head designs have different advantages and disadvantages, and each has a limit to the maximum torque that can be applied.

[0004] A common problem with all screw interfaces is that the screw can slip out of the driver or fall out while attempting to position it for insertion. This can sometimes be improved by employing a magnetic bit, but there is still some misalignment between the driver and the screw that can prevent insertion and does not offer a solution for non-magnetic materials.

[0005] A further problem relates to loosening and removing the screw, which creates an inherent conflict between the strong forward axial force required to securely maintain engagement between the driver and the screw head and the desired direction of screw motion, reinforced by a rearward pull-out force. Furthermore, depending on the screw material and surrounding materials, and the time elapsed since the screw was placed in place, the torque required for pull-out can be greater than the insertion torque and may exceed the torque that can be transmitted through the screw interface. Summary of the Invention

[0006] The present invention is a screw element and corresponding system with separate interfaces for inserting and extracting the screw.

[0007] In accordance with the teachings of one embodiment of the present invention, a dual-interface screw element is provided that includes: (a) a screw body having a central axis, a proximal end, a distal end, and a length, the screw body having external threads along at least a portion of its length; (b) a first engagement interface accessible from the proximal end of the screw body that is engaged to apply torque in an insertion direction of the external threads; and (c) a second engagement interface accessible from the proximal end of the screw body and located in an axial recess, the second engagement interface having reverse threads such that a complementary reverse thread tool that applies torque to extract the screw body is tightened against the second engagement interface.

[0008] According to a further feature of an embodiment of the invention, the external thread is a right-hand thread and the reverse thread is a left-hand thread.

[0009] According to a further feature of an embodiment of the invention, the first engagement interface comprises a thread located within the axial recess.

[0010] According to a further feature of an embodiment of the present invention, the threads of the first engagement interface are closer to the proximal end than the counter-threads of the second engagement interface.

[0011] According to a further feature of an embodiment of the invention, the threads of the first mating interface are further proximally than the counter-threads of the second mating interface.

[0012] Also, in accordance with the teachings of one embodiment of the present invention, there is provided a screw system comprising: (a) the above-described screw element; and (b) an extraction tool having a reverse thread portion configured to be inserted into the axial recess and engage with the second engagement interface.

[0013] Also, in accordance with the teachings of one embodiment of the present invention, there is provided a screw system including: (a) the above-mentioned screw element; (b) an insertion tool having a threaded portion configured to be inserted into the axial recess and engage with the first engagement interface; and (c) an extraction tool having a reverse threaded portion configured to be inserted into the axial recess and engage with the second engagement interface.

[0014] According to a further feature of an embodiment of the present invention, the screw body is a dental implant.

[0015] According to a further feature of an embodiment of the present invention, the screw body is a bone screw.

[0016] According to a further feature of an embodiment of the invention, the screw body is a bolt forming part of a joint between two structural elements.

[0017] Also in accordance with the teachings of one embodiment of the present invention, there is provided a dual interface screw element comprising: (a) a screw body having a central axis, a proximal end, a distal end, and a length, the screw body having external threads along at least a portion of its length; (b) a first engagement interface accessible from the proximal end of the screw body that is engaged to apply torque in an insertion direction of the external threads; and (c) a second engagement interface accessible from the proximal end of the screw body and located in an axial recess, the second engagement interface comprising a reverse helical engagement structure such that a complementary reverse helical engagement tool that applies torque to extract the screw body is tightened against the second engagement interface.

[0018] According to a further feature of an embodiment of the present invention, the reverse helical engagement structure is a reverse thread.

[0019] According to a further feature of an embodiment of the present invention, the reverse helical engagement structure is a helical socket of hexagonal cross section.

[0020] According to a further feature of an embodiment of the present invention, the reverse helical engagement structure is a star-shaped cross-section helical socket. [Brief explanation of the drawings]

[0021] The invention is herein described, by way of example only, with reference to the accompanying drawings. [Figure 1] 1 is a schematic isometric view of a screw element constructed and operative in accordance with an embodiment of the present invention; [Figure 2] FIG. 2 is an axial cross-sectional view of the screw element of FIG. 1 showing the dual engagement interface. [Figure 3] 2 is a schematic isometric view of an insertion tool for engaging the first engagement interface of the screw element of FIG. 1; FIG. [Figure 4] 2 is a schematic isometric view of a removal tool for engaging the second engagement interface of the screw element of FIG. 1; FIG. [Figure 5] 1. FIG. 4 is an axial cross-sectional view of the insertion tool of FIG. 3 engaged with the threaded element of FIG. [Figure 6] 5 is an axial cross-sectional view of the removal tool of FIG. 4 engaged with the threaded element of FIG. 1; [Figure 7] 1 is an axial cross-sectional view of a variant implementation of the invention for use as a dental implant; FIG. [Figure 8] 10 is an axial cross-sectional view of a further alternative implementation of the present invention for use as a bone screw. [Figure 9] FIG. 9 is a view similar to FIG. 8 showing an alternative implementation of the first engagement interface as a hex socket. [Figure 10] 9 is a view similar to FIG. 8 showing an alternative implementation in which the axial positions of the first and second engagement interfaces are swapped. [Figure 11] FIG. 11 is a view similar to FIG. 10 showing an alternative implementation of the first engagement interface as a hex socket. [Figure 12] 2 is an isometric view taken along an axial plane showing an alternative implementation of the screw element of FIG. 1 employing a helical engagement structure having a hexagonal cross section. [Figure 13]FIG. 13 is a partial isometric view of a complementary insertion tool for use with the screw element of FIG. 12. [Figure 14] FIG. 13 is a partial isometric view of a complementary removal tool for use with the screw element of FIG. 12. [Figure 15A] 10 is an isometric view of a further alternative implementation of the screw element of FIG. 1 employing a helical engagement structure having a star-shaped cross section, shown in full view. [Figure 15B] 10 is an isometric view showing a further alternative implementation of the screw element of FIG. 1 employing a helical engagement structure having a star-shaped cross section, shown cut along an axial plane. [Figure 16] FIG. 15B is a partial isometric view of a complementary insertion tool for use with the screw element of FIG. 15A. [Figure 17] FIG. 15B is a partial isometric view of a complementary removal tool for use with the screw element of FIG. 15A. DETAILED DESCRIPTION OF THE INVENTION

[0022] The present invention is a screw element and corresponding system with separate interfaces for inserting and extracting the screw.

[0023] The principles and operation of a screw element and system according to the present invention may be better understood with reference to the drawings and accompanying description.

[0024] Referring now to the drawings, FIGS. 1 and 2 schematically illustrate a dual-interface screw element constructed and operative in accordance with one embodiment of the present invention. Generally, the screw element includes a screw body 10 having a central axis 30, a proximal end 32, a distal end 34, and a length L. The screw body 10 has external threads 12 along at least a portion of its length. The screw element has two separate engagement interfaces, one designed for use in inserting the screw and the other designed for use in removing (loosening) the screw. Accordingly, a first engagement interface 13 accessible from the proximal end of the screw body is configured to engage to apply torque in the insertion direction of the external threads. In the preferred, but non-limiting, case shown here, this first engagement interface 13 includes threads 14 located within an axial recess 36. A second engagement interface 15, located in an axial recess 36 accessible from the proximal end 32 of the screw body 10, includes a reverse thread 16 so that a complementary reverse thread tool (FIG. 4 below) that applies torque to extract the screw body can be tightened against the second engagement interface. In the case of a conventional right-hand external thread 12, the "reverse" thread 16 is a left-hand thread. In any special application requiring a left-hand external thread 12, the "reverse" thread 16 will be a right-hand thread.

[0025] The screw of FIG. 1 is preferably provided as part of a screw system including an extraction tool 24 ( FIG. 4 ) having a reverse threaded portion 28 configured to be inserted into the axial recess 36 and engage the threads 16 of the second engagement interface 15. The screw system also preferably includes an insertion tool 18 ( FIG. 3 ) having a threaded portion 22 configured to be inserted into the axial recess 36 and engage the threads 14 of the first engagement interface 13. The insertion tool 18 and extraction tool 24 each have a shaft 20 and a shaft 26 for transmitting torque to the screw during insertion or extraction. In the preferred, but non-limiting, case shown here, these shafts are hex shafts suitable for attachment to a conventional power drill driver or power impact driver. The ends of both tools (threaded portion 22 and threaded portion 28) may optionally be incorporated into opposite ends of a single straight hex shaft to form a reversible tool (not shown), or into opposite ends of an L-shaped shaft to form a hand-operated tool for insertion and extraction that operates similarly to a hex wrench. As an alternative implementation, a manually operated handle on the shaft may be employed.

[0026] FIG. 5 schematically illustrates the use of an insertion tool 18 to insert the screw body 10 into a base material (not shown). The threads 22 engage the threads 14 within the base of the axial recess 36 by clockwise rotation until fully inserted, which may be defined by the distal end of the shaft 20 abutting the proximal end 32 of the screw body, or by the threads 22 abutting an internal shoulder of the recess 36, as shown in FIG. 5. In this state, the screw body is gripped and aligned with the insertion tool, preventing accidental dropping or misalignment of the screw. Further clockwise rotation of the insertion tool 18 transfers torque to the screw body 10, inserting the screw body into the base material in a conventional manner.

[0027] FIG. 6 schematically illustrates the use of an extraction tool 24 to extract (loosen) a threaded body 10 from a parent material (not shown). The threaded portion 28, which is designed to be undersized so as not to interact with the threads 14, is inserted through the base of the axial recess 36 and then engaged with the internal threads 16 by counterclockwise rotation until fully engaged. The fully engaged condition can be defined by an appropriately positioned and sized shoulder formed on the shaft 26 to engage an internal shoulder in the recess 36 at the transition between the two engagement structures, by a larger shoulder configured to abut the proximal end 32 of the threaded body, or by the threaded portion 28 reaching the end of the threaded recess, as shown in FIG. 6. In this condition, the threaded body is gripped by the extraction tool, so that further counterclockwise rotation of the extraction tool 24 transmits torque to the threaded body 10, thereby loosening it from the parent material. The reverse thread engagement ensures that torque applied to loosen the threaded body only strengthens the engagement with the extraction tool 24, and this engagement also facilitates the application of axial force to assist in extracting the threaded body from its parent material.

[0028] Optionally, a cylindrical spacer element may be introduced to support the portion of shaft 26 (or shaft 20, if the interfaces are reversed, as described below) within the larger diameter recess portion when engaging the smaller diameter engagement interface 15 located away from the proximal end of the screw body. In this case, the spacer element is preferably sized to contact the crests of the threads in the larger diameter recess portion without engaging those threads.

[0029] The threaded element in FIG. 1 is shown only diagrammatically as a cylindrical threaded element with an external thread. The present invention may be advantageously used in all fields of application and in any type of screw or bolt construction, particularly where large tightening torques are required and where subsequent withdrawal of the screw would otherwise be difficult. Non-limiting exemplary uses include implementation as a dental implant 50 ( FIG. 7 ) or bone screw 60 ( FIG. 8 ). Other uses include, for example, household and other applications such as headless wall anchors (where an object may be supported by engaging threads 14 in axial recess 36), as well as all types of screws and bolts that form part of a joint between two structural elements, in household, industrial, and aerospace applications.

[0030] It should be noted that while it is believed highly advantageous to implement both first engagement interface 13 and second engagement interface 15 as a threaded interface (or, more generally, as described further below, a "helical engagement structure"), screws and thread systems in which the first engagement interface is another conventional engagement interface are also within the scope of the present invention. Thus, for example, the first engagement interface may be implemented within the recess 36 of the screw and / or on the surface of the proximal end 32 as a straight slot, a Phillips crosshead, a Torx-star socket, a hex socket, or any other conventional or non-standard thread interface. As one non-limiting example, an exemplary embodiment in which the first engagement interface 13 is implemented as a hex socket is shown in FIG. 9.

[0031] All of the exemplary implementations of the present invention shown thus far have the first engagement interface 13 closer to the proximal end 32 than the second engagement interface 15. Depending on various design considerations, particularly the torque levels the thread system is designed for during insertion and withdrawal, the interfaces may be reversed so that the threads 14 of the first engagement interface 13 are located further from the proximal end 32 than the reverse threads 16 of the second engagement interface 15. This option is shown in Figure 10. A further alternative implementation is shown in Figure 11, generally similar to Figure 10, but in which the first engagement interface 13 is implemented as a hex socket.

[0032] The threaded engagement of the first and second engagement interfaces shown thus far is an example of a "helical engagement structure," i.e., any complementary male-female engagement structure in which engagement is achieved by a combination of simultaneous movement along an axis and rotation about that axis. Depending on the specifics of the intended application, material properties, and manufacturing capabilities, other forms of helical engagement structure may be preferred for one or both of the first and second engagement interfaces 13, 15, and the complementary insertion and extraction tools. By way of non-limiting example, FIGS. 12-14 show embodiments of the screw element 110, insertion tool 118, and extraction tool 124, respectively, in which each engagement interface is implemented as a helical engagement element having a hexagonal cross-section perpendicular to its central axis at each location, and FIGS. 15A-17 show embodiments of the screw element 210, insertion tool 218, and extraction tool 224, respectively, in which each engagement interface is implemented as a helical engagement element having a star-shaped cross-section perpendicular to its central axis at each location. Again, the various engagement interfaces may be of different types, the inner and outer structures may be axially interchanged, and the first engagement interface may be replaced with other conventional interfaces.

[0033] It will be appreciated that the above description is by way of example only and that many other embodiments are possible within the scope of the invention as defined in the appended claims.

Claims

1. (a) a screw body having a central axis, a proximal end, a distal end, and a length, the screw body having external threads along at least a portion of the length; (b) a first engagement interface accessible from the proximal end of the screw body that is engaged to apply torque in an insertion direction of the external thread; (c) a second engagement interface located in an axial recess accessible from the proximal end of the screw body, the second engagement interface having a reverse thread such that a complementary reverse thread tool that applies torque to extract the screw body is tightened against the second engagement interface; A dual interface screw element comprising:

2. The dual interface screw element of claim 1 , wherein the external threads are right-hand threads and the reverse threads are left-hand threads.

3. The dual interface screw element of claim 1 , wherein the first engagement interface comprises a thread located within the axial recess.

4. The dual interface screw element of claim 3 , wherein the threads of the first engagement interface are closer to the proximal end than the reverse threads of the second engagement interface.

5. The dual interface screw element of claim 3 , wherein the threads of the first engagement interface are further from the proximal end than the counter-threads of the second engagement interface.

6. (a) the dual interface screw element of claim 1; (b) an extraction tool having a reverse thread configured to be inserted into the axial recess and engage the second engagement interface; A screw system comprising:

7. (a) the dual interface screw element of claim 3; (b) an insertion tool having a threaded portion configured to be inserted into the axial recess and engage the first engagement interface; (c) an extraction tool having a reverse thread configured to be inserted into the axial recess and engage the second engagement interface; A screw system comprising:

8. The dual interface screw element of claim 1 , wherein the screw body is a dental implant.

9. The dual interface screw element of claim 1 , wherein the screw body is a bone screw.

10. The dual interface threaded element of claim 1 , wherein the threaded body is a bolt that forms part of a joint between two structural elements.

11. (a) a screw body having a central axis, a proximal end, a distal end, and a length, the screw body having external threads along at least a portion of the length; (b) a first engagement interface accessible from the proximal end of the screw body that is engaged to apply torque in an insertion direction of the external thread; (c) a second engagement interface located in an axial recess accessible from the proximal end of the screw body, the second engagement interface comprising a reverse helical engagement structure such that a complementary reverse helical engagement tool that applies torque to extract the screw body is clamped against the second engagement interface; A dual interface screw element comprising:

12. The dual interface screw element of claim 11 , wherein the reverse helical engagement structure is a reverse thread.

13. The dual interface screw element of claim 11 , wherein the reverse helical engagement structure is a helical socket of hexagonal cross section.

14. The dual interface screw element of claim 11 , wherein the reverse helical engagement structure is a star-shaped cross-section helical socket.

Images