WO2017106913A1

WO2017106913A1 - Driver with mechanism for releasably securing the driver to a screw

Info

Publication number: WO2017106913A1
Application number: PCT/AU2016/051264
Authority: WO
Inventors: Tegan CHENG; Justin BOBYN; David Little
Original assignee: The Sydney Children's Hospitals Network (Randwick And Westmead)
Priority date: 2015-12-23
Filing date: 2016-12-21
Publication date: 2017-06-29

Abstract

A driver is disclosed for driving a screw, the driver including a driver shaft and an engagement portion at a distal end of the shaft, the engagement portion configured to locate in a receiving cavity of a head of a screw, the direction of elongation of the driver shaft defining a driver axis. The engagement portion of the driver comprises a first engagement part and a second engagement part, the first and second engagement parts being relatively rotatable about the driver axis such as to move between: a first rotational position in which the engagement portion is locatable in the receiving cavity; and a second rotational position which, when the engagement portion is located in the receiving cavity, secures the driver to the screw. A screw for use with the driver is also disclosed, which screw can have a receiving cavity with one or more undercut regions.

Description

"Driver with mechanism for releasably securing the driver to a screw" Technical Field

[0001] The present disclosure relates to screws and drivers for driving screws and particularly wherein the driver is configured to be releasably secured to the screw.

Background

[0002] Screw and drivers are employed in a wide range of technical fields and working environments. When initially driving a screw into material, a person will commonly hold the screw in engagement with the driver, ensuring that the screw does not disengage the driver prior to the screw being held in the material. This reduces the likelihood that the screw will fall to the ground or get lost.

[0003] In some instances it is not practical for a user to hold the screw and the driver at the same time. Moreover, the working environment may be such that undesirable release of the screw driver is more commonplace and/or has more significant consequences. For example, screws and their drivers are used in orthopaedic surgery and loss or dropping of the screw during orthopaedic surgery can significantly increase risks of contamination and interference with surgery and the patient's wellbeing. As another example, screws and their drivers are used in the electronics industry and loss or dropping of the screw can damage electronic componentry. In some instances, a dropped screw may not be easily accessible or recoverable thereafter.

[0004] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present disclosure as it existed before the priority date of each claim of this application. Summary

[0005] The present disclosure may generally provide a driver for driving a screw, and optionally a screw designed specifically for use with the driver, wherein the screw is releasably secured to the driver as a result of relative rotating parts of the driver, e.g., about a driver axis.

[0006] According to one aspect, the present disclosure provides a driver for driving a screw, the driver comprising:

a driver shaft and an engagement portion at a distal end of the shaft, the engagement portion configured to locate in a receiving cavity of a head of a screw, the direction of elongation of the driver shaft defining a driver axis;

wherein the engagement portion of the driver comprises a first engagement part and a second engagement part, the first and second engagement parts being relatively rotatable about the driver axis such as to move between:

a first rotational position in which the engagement portion is locatable in the receiving cavity; and

a second rotational position which, when the engagement portion is located in the receiving cavity, secures the driver to the screw.

[0007] The first and second engagement parts may be moved to or from the second rotational position when located in the receiving cavity. When moved to the second rotational position, the second engagement part may be moved into a strong frictional engagement with a surface defining the receiving cavity. Additionally or alternatively, when moved to the second rotational position, the second engagement part may be moved into a captive locking engagement within an inner region of the receiving cavity. Meanwhile, forces to drive the screw may be transferred from the driver to the screw at least via the first engagement part.

[0008] The second engagement part may be located distally of the first engagement part along the driver axis. Alternatively, the second engagement part may be located proximally of the second engagement part along the driver axis. One of the first and second engagement parts may be an extension of the driver shaft, e.g., it may be integrally formed with the driver shaft.

[0009] When located in the receiving cavity and moved from the first position to the second position, the first engagement part may maintain a substantially fixed position within the receiving cavity, whereas the second engagement part may move within the receiving cavity. The movement may be such that, in one or more predetermined radial directions of the driver and screw, the second engagement part is caused to project further outwardly. The one or more radial directions of the driver extend outwardly from, and perpendicular to, the driver axis.

[0010] According to one aspect, the present disclosure provides a driver for driving a screw, the driver comprising:

wherein the engagement portion of the driver comprises a first engagement part and a second engagement part, the first and second engagement parts being relatively rotatable about the driver axis such as to move between a first rotational position and a second rotational position, wherein, in the second rotational position, the second engagement part projects further outwardly along one or more predetermined radial directions of the driver than in the first rotational position.

[0011] In aspects disclosed herein, the second engagement part may be caused to project further outwardly along one or more predetermined radial directions by rotating one or more protrusive regions of the second engagement part into alignment with the one or more predetermined radial directions. Thus, the second engagement part need not change shape to project further outwardly in the one or more radial directions of the screw.

[0012] The one or more protrusive regions may be provided by corner regions or projecting point regions of the second engagement part. The one or more predetermined radial directions of the driver may be fixed relative to the first engagement part. In some embodiments, the one or more predetermined radial directions may extend through non-protrusive regions (or lesser protruding regions) of the first engagement part such as sides or recesses of the first engagement part. In these embodiments, causing the second engagement part to project further outwardly along one or more predetermined radial directions of the driver may comprise rotating one or more corner or point regions of the second engagement part into alignment with one or more side or recessed regions of the first engagement part.

[0013] By projecting further outwardly along one or more predetermined radial directions of the driver (and of the screw when engaged therewith), protrusive regions of the second engagement part may be brought into the strong frictional contact with surfaces defining the receiving cavity, or brought into the captive engagement, e.g. within undercut regions of the receiving cavity, which undercut regions may be located along the one or more predetermined radial directions of the screw.

[0014] In the first position, the one or more protrusive regions of the second engagement part may project radially outwardly from the driver axis substantially no further than any region of the first engagement part. In one embodiment, the first and second engagement parts have substantially the same non-circular outer shapes.

Therefore, so that no protrusive regions of the second engagement part projects radially outwardly of any region of the first engagement part, the shapes of the first and second engagement parts may be placed into alignment in the first rotational position. Outer surfaces of the first and second engagement parts may therefore be flush with each other. Nevertheless, the first and second engagement parts need not necessarily have the same outer shapes.

[0015] In the first rotational position, the first and second engagement parts can take a relatively streamline configuration where the second engagement part will not obstruct insertion of the engagement portion into the receiving cavity of the screw. [0016] In the second rotational position, the second engagement part may have been moved such that one or more protrusive regions of the second engagement part project radially outwardly from the driver axis, further than regions of the first engagement part, at least along the one or more predetermined radial directions of the driver. As indicated, in one embodiment, the first and second engagement parts have substantially the same non-circular outer shapes. Therefore, so that one or more protrusive regions of the second engagement part project radially outwardly of the first engagement part, the shapes of the first and second engagement parts may be placed into misalignment in the second rotational position. Outer surfaces of the first and second engagement parts may no longer be flush with each other.

[0017] Nevertheless, depending on the configuration of the receiving cavity, the one or more protrusive regions of the second engagement part need not necessarily project further outwardly than the first engagement part, in the second rotational position, to achieve the securing. In general, when located in the receiving cavity, as long as the second part may be caused to project further outwardly in at least one predetermined radial direction of the screw, it may be possible to bring the second engagement part into frictional or captive engagement with the receiving cavity, in that radial direction.

[0018] As discussed above, the driver can rely in some embodiments on a frictional engagement between the second engagement part and one or more inner surfaces of the receiving cavity to secure the driver to the screw. An advantage of this technique is that the driver may be used with a number of different types of standard screws or otherwise.

[0019] Standard screws may comprise a head portion and a threaded screw shaft projecting from the head portion, the direction of elongation of the screw shaft defining a screw axis. The one or more radial directions of the screw extend outwardly from, and perpendicular to, the screw axis. [0020] The head portion comprises the receiving cavity. When the engagement portion of the driver is received in the receiving cavity, rotation of the driver about the driver axis can cause rotation of the screw about the screw axis.

[0021] The receiving cavity is defined by one or more inner surfaces, including side surfaces and a bottom surface. An opening of the receiving cavity is provided generally at an opposite end of the receiving cavity to the bottom surface. The bottom surface may be complete or may include an orifice therein, e.g. if the screw is cannulated. The engagement portion of the driver can be received in the receiving cavity via the opening, whereupon a tip of the engagement portion can move into engagement with, or rest close to, the bottom surface of the receiving cavity. One or more side surfaces that define the cavity may depend from the opening in a direction parallel to the screw axis and provide the cavity with a uniform outer profile along the screw axis. Alternatively, the one or more side surfaces may depend at an angle or non-linearly from the screw axis, e.g., such that they define a sloped or tapered receiving cavity or otherwise.

[0022] The shape of the receiving cavity may be substantially the same as the shape of the engagement portion of the driver when its first and second engagement parts are in the first rotational position. However, to ensure ease of insertion of the engagement portion of the driver into the receiving cavity, and to provide for a degree of size tolerance between different drivers and screws, the cavity may be slightly larger than the engagement portion. While the difference in size is relatively small, the engagement portion may still assume a relatively loose fit when first received into the receiving cavity and prior to rotation of the screw. Although there may be some degree of abutment between the engagement portion and the one or more side surfaces of the receiving cavity, the frictional engagement resulting from the abutment will generally not be sufficient to secure the engagement portion therein.

[0023] However, after insertion, the first and second engagement parts can be rotated relative to each other from the first rotational position to the second rotational position. The arrangement is such that the second engagement part can be rotated into a position in which outer surfaces of protrusive regions thereof are pressed against one or more of the side surfaces defining the receiving cavity. Thus, the second engagement part can realise a relatively strong frictional engagement with inner surfaces of the receiving cavity, releasably securing the driver to the screw.

[0024] The relative rotation between the first and second engagement parts may be carried out in different directions, e.g. clockwise or anti-clockwise, depending on whether or not the driver is being used to insert or remove the screw. For example, when the screw is to be driven in a clockwise direction, e.g., to insert the screw, the second engagement part may be rotated in an anticlockwise direction to frictionally engage inner surfaces of the receiving cavity. This force, applied in the anticlockwise direction, will assist in maintaining a clockwise-directed abutment of the first engagement part with one or more inner surfaces of the receiving cavity to apply a clockwise driving force to the screw to cause clockwise rotation of the screw.

Similarly, when the screw is to be driven in an anticlockwise direction, the second engagement part may be rotated in a clockwise direction to frictionally engage inner surfaces of the receiving cavity. This force, applied in the clockwise direction, will assist in maintaining an anticlockwise-directed abutment of the first engagement part with one or more inner surfaces of the receiving cavity to apply an anticlockwise driving force to the screw to cause anticlockwise rotation of the screw.

[0025] The frictional securing may be such that the screw cannot easily be separated from the driver, e.g., by hand or under the effects of gravity. In some embodiments, the only practical way to release the screw from the driver may be to reverse the relative rotation of the first and second engagement parts, i.e. to move the first and second engagement parts from the second rotational position back to the first rotational position.

[0026] In another embodiment the driver can rely on a captive engagement of the second engagement part in the receiving cavity to secure the driver to the screw. To enable this, a standard screw may be modified, or a screw may be constructed from scratch, at least to include one or more undercut regions of the receiving cavity. One or more protrusive regions of the second engagement part may locate in the undercut regions following movement of the first and second engagement parts to the second rotational position.

[0027] The receiving cavity, along the screw axis, may have a first cavity portion adjacent the opening and a second cavity portion spaced from the opening. When the engagement portion is inserted into the receiving cavity, the first engagement part can locate in the first cavity portion and the second engagement part can locate in the second cavity portion.

[0028] In accordance with discussions above, in one aspect of the present disclosure there is provided a screw for use with a driver, the screw comprising:

a head portion:

a threaded screw shaft projecting from the head portion, the direction of elongation of the screw shaft defining a screw axis; and

a receiving cavity in the head portion for receiving an engagement portion of a driver to drive the screw, the receiving cavity defined by one or more side surfaces and a bottom surface and having an opening via which the engagement portion of the driver is insertable into the receiving cavity;

wherein, along the screw axis, the receiving cavity comprises a first cavity portion adjacent the opening and a second cavity portion spaced from the opening; and wherein the second cavity portion comprises one or more undercut regions.

[0029] The one or more undercut regions may be defined at least by one of more side surfaces and by one or more top surfaces of the receiving cavity. The side surfaces may extend substantially parallel to the screw axis or at an angle relative to the screw axis. The top surfaces may extend substantially perpendicular to the screw axis and may generally face the bottom surface of the receiving cavity. The top surfaces may provide surfaces against which protrusive regions of the second engagement part abut at least if an attempt is made to remove the engagement portion of the driver from the receiving cavity when the engagement parts are in the second rotational position. [0030] To provide the one or more undercut regions, part of the second cavity portion may extend outwardly of the first cavity portion along one or more predetermined radial directions of the screw. The radial directions of the screw extend outwardly from, and perpendicular to, the screw axis. The top surfaces may therefore be provided at the locations where the second cavity portion extends further outwardly than the first cavity portion.

[0031] Nevertheless, the second cavity portion does not necessarily have to extend outwardly of the first cavity portion, along one or more radial directions of the screw, to define undercuts. For example, if the second cavity portion is not immediately adjacent the first cavity portion, the second cavity portion may have smaller dimensions than the first cavity portion, while still including one or more undercut regions defined by one or more side surfaces and one or more top surfaces. If the second cavity portion is not immediately adjacent the first cavity portion, the first and second cavity portions may be separated by a third cavity portion, for example.

[0032] When the first and second engagement parts are in the first rotational position, the first and second engagement parts can take a relatively streamline configuration such that the first engagement part can locate in the first cavity portion and the second engagement part can move through the first cavity portion to the second cavity portion. However, once located in the second cavity portion, the first and second engagement parts can be moved to the second rotational position wherein one or more protrusive portions of the second engagement part move into the one or more undercut regions of the receiving cavity. Thereafter, any attempt to retract the engagement portion of the driver from the receiving cavity of the screw is prevented by abutment between the protrusive regions of the second engagement part and one or more top surfaces defining the undercut regions, as discussed above.

[0033] Thus, the second engagement part can realise a relatively strong captive engagement with the cavity, releasably securing the driver to the screw. The securing may be such that the screw cannot easily be separated from the driver, e.g., by hand or under the effects of gravity. In some embodiments, the only practical way to release the screw from the driver may be to reverse the relative rotation of the first and second engagement parts, i.e. to move the first and second engagement parts from the second rotational position back to the first rotational position.

[0034] In some embodiments, the second cavity portion may have a depth that is similar or smaller than the depth of the second cavity portion. The second cavity portion may have a sufficient depth to receive a second engagement part of a sufficient size to have suitable strength and rigidity to perform its function. The second cavity portion may have a depth that is at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the depth of the first cavity portion. The second cavity portion may have a depth that is between 20% and 120% of the depth of the first cavity portion, between 30% and 100% of the depth of the first cavity portion, between 40% and 80% of the depth of the first cavity portion, or otherwise.

[0035] In some embodiments, the second cavity portion may extend outwardly of the first cavity portion along one or more predetermined radial directions of the screw, such that the radius of the second cavity portion along those radial directions is at least 10%, at least 15%, at least 20%, at 25%, least 30%, at least 35% or at least 40% greater than the radius of the first cavity portion, or otherwise.

[0036] The term "undercut" is used herein to describe regions, absent of material, which are, for example, spaced from the opening of the receiving cavity and are partially defined by overhanging (top) surfaces of the screw. The term "undercut" should not be construed as requiring any particularly formation technique. While cutting may be used to form undercut regions, other formation techniques such as moulding, grinding, etching or otherwise may be used.

[0037] The receiving cavity of the screw head (or at least the first cavity portion thereof) may take any shape suitable for receiving an engagement portion of a driver such that rotation of the driver about the driver axis causes rotation of the screw about the screw axis. In this regard, the screw may be one of a wide variety of screw head types, including, for example, slotted (e.g. slot or cross-recess), polygonal socket (e.g., triangular socket, square socket, pentagon socket, or hex socket), polylobular socket (e.g. pentalobular socket or hexalobular socket), cruciform socket (e.g. Phillips or Frearson) or star socket (e.g. double-square, triple square or double hex), or otherwise. An example of a screw head with a hexalobular socket is the Torx™ screw head, although it may also be considered a type of star socket in certain instances.

[0038] The driver may take many different configurations for driving screws. For example, the driver may be a manual or powered driver. The driver may be a torque- limiting screwdriver with a mechanism for preventing over- tightening of screws, and/or the driver may be a ratcheting screwdriver. The driver may be independently operable or may require connection to an additional device for operation. In one embodiment, the driver is a manual screwdriver including a handle affixed to a proximal end of the driver shaft, generally at an opposite end to the engagement portion of the driver. In another embodiment, the driver is a screwdriver bit, which is connected or connectable to a powered or mechanically operatable mechanism, such as an electric or mechanical drill, to rotate the screwdriver bit. The driver and screw may be used in a wide variety of applications, including for medical use or otherwise. In one embodiment, the screw is an orthopedic (bone) screw.

[0039] To relatively rotate the first and second engagement parts of the driver between the first and second rotational positions, the driver may comprise a rotation mechanism. The rotation mechanism may comprise an elongate element such as a rod that is fixed to one of the first and second engagement parts, e.g. the second engagement part, at the distal end of the driver, and that extends along the driver axis to a more proximal position of the driver. A rotational force may be applied to a proximal end of the elongate element, rotating the elongate element about its own axis and therefore transferring rotational forces to the engagement part that is fixed to the elongate element. The elongate element may reach through a channel extending through the shaft. When the first or second engagement part, to which the elongate element is fixed, is located distally of the other of the first and second engagement parts, the elongate element may extend through an opening in the other of the first and second engagement parts. The rotation mechanism, or at least parts thereof, may be capable of being disassembled from the rest of the driver, e.g. to allow cleaning. This may be particularly advantageous when the driver is to be used in surgical

environments, for example. Additionally or alternatively, the driver may comprise one or more openings, e.g. in its shaft, to receive cleaning fluid and/or cleaning implements to clean the driver, including the rotation mechanism.

[0040] In one embodiment, the second engagement part is positioned distally of the first engagement part and the elongate element is a rod that is fixed to a proximal end surface of the second engagement part and that extends from the second engagement part, through a channel extending between proximal and distal surfaces of the first engagement part and through a channel in the shaft.

[0041] An actuation element, such as a lever, knob, button or slider, may be connected to a proximal region of the elongate element, which actuation element is engageable by hand or by other means such as a tool, in order to rotate the elongate element. The elongate element may extend up to or through an opening at the proximal end of the driver (e.g. at a proximal end of the handle of the driver) and the actuation element may be positioned at the proximal end of the driver. Alternatively, the elongate element may terminate before the proximal end of the driver and/or the actuation element may be positioned at an intermediate location of the driver. For example, the actuation element may be accessible through a slot at a lateral side of the driver shaft. By terminating before the proximal end of the driver, the rotation mechanism may be arranged so that it does not interfere with other mechanisms that may be present in the driver, such as a ratchet mechanism or otherwise.

[0042] The rotation mechanism may comprise one or more stops to limit a degree of relative rotation of the first and second engagement parts. The one or more stops may be configured to act directly against the elongate element, actuation element, or a further element such as a pin projecting therefrom. The stops may ensure that a user can arrive at the first and second rotational positions by simply rotating the rotation mechanism until it hits a respective stop. The spacing of the stops may be such that, in the first rotational position, a most streamlined, in-phase arrangement of the first and second engagement parts is achieved (e.g. by having the first and second engagement parts aligned) and, in the second rotation position, a most non-streamlined, out-of- phase arrangement of the first and second parts is achieved.

[0043] The rotation mechanism may be biased, e.g. by a spring or other resiliently flexible element. The biasing may be configured to cause the first and second engagement parts to be biased into one of the first and second rotational positions. For example, in one embodiment the first and second engagement parts can be biased to the second rotational position so that their default position is for securing to the screw. This arrangement may be advantageous as it can ensure that, during any mishandling of the driver, which might cause a user to disengage the rotation mechanism, the screw can remain attached to the driver. Moreover, if a user is to transfer the driver to another user, the screw can remain secured to the driver during the transfer. Such a transfer may occur in a number of circumstances, such as during a medical operation, where a nurse may secure a screw to the driver and then pass the driver, with the screw secured thereto, to a surgeon.

[0044] As indicated, in some embodiments, the first and second engagement parts may have substantially identical (usually non-circular) shapes. The shapes may be rotatable about a common central axis. As examples, the shapes maybe polygonal, polylobular or star-shapes. When the first and second engagement parts are in the first rotational position, the shapes can be aligned and "in phase". When the first and second engagement parts are in the second rotational position, the shapes can be misaligned and "out of phase". The degree of misalignment in the second rotational position may be such that the shapes are maximally out of phase and thus protrusive regions of the second engagement parts project to a maximum degree beyond sides, or recessed areas, of the first engagement part.

[0045] For example, where the shapes of the two engagement parts are squares, the squares may be moved from being in phase to 45 degrees out of phase, whereupon each corner of one of the squares aligns with and projects beyond the centre of a respective side of the other of the squares. In this example, stops of the rotation mechanism may set the range of rotation to 45 degrees, although a similar result can also be achieved by setting the range of rotation to 45 + (n * 90) degrees, where n is 1, 2 or 3.

[0046] As another example, where the shapes of the two engagement parts are hexagons, the hexagons may be moved from being in phase to 30 degrees out of phase, whereupon each corner of one of the hexagons aligns with and projects beyond the centre of a respective side of the other of the hexagons. In this example, stops of the rotation mechanism may set the range of rotation to 30 degrees, although a similar result can also be achieved by limiting the range of rotation to 30 + (n * 60) degrees, where n is 1, 2, 3, 4 or 5.

[0047] As another example, where the shapes of the two engagement parts are hexalobular, the hexalobular shapes may be moved from being in phase to 30 degrees out of phase, whereupon each peak (or blunted point) of the hexalobular shape aligns with and projects beyond the centre of a respective trough (or blunted recess) of the other of the hexalobular shapes. In this example, stops of the rotation mechanism may set the range of rotation to 30 degrees, although a similar result can also be achieved by setting the range of rotation to 30 + (n * 60) degrees, where n is 1, 2, 3, 4 or 5.

[0048] As another example, where the shapes of the two engagement parts are 8- pointed stars (e.g. double-square shaped), the shapes may be moved from being in phase to 22.5 degrees out of phase, whereupon each point of the star shapes aligns with and projects beyond the centre of a respective valley of the other of the star shapes. In this example, stops of the rotation mechanism may set the range of rotation to 22.5 degrees, although a similar result can also be achieved by setting the range of rotation to 22.5 + (n * 45) degrees, where n is 1, 2, 3, 4, 5, 6 or 7.

[0049] In each of the above examples or otherwise, where the first and second engagement parts have substantially identical polygonal, polylobular or star-shapes and are rotatable about a common central axis, the range of relative rotation (x) of the two shapes can be set by the following formula, where y is the number of corners, blunted points or points, respectively, of the polygonal, polylobular or star-shapes: x = (180/y) + (n*(360/y))

where n is an integer >0 and <y

[0050] The rotation mechanism may comprise a cam or lock feature for releasably maintaining the rotation mechanism of the driver, or more particularly the first and second engagement parts, in their first rotational position and/or second rotational position. The cam or lock feature may reduce the risk that the first and second engagement parts are released undesirably from the first rotational position and/or second rotational position. The lock feature may comprise a switch mechanism, which may need to be activated to return the first and second engagement parts to, e.g., the first rotational position, ensuring that the securing between the driver and the screw is less likely to be released unintentionally.

[0051] In discussions above, features for securing a driver to a fastener, and particularly a screw, are disclosed. However, these features can be applied in relation to other types of fasteners that are rotated by a driver to provide fastening, which fasteners can include a receiving cavity in a head thereof to receive an engagement portion of a driver. As an example, drivers disclosed herein may be secured to bolts or studs.

[0052] According to one aspect, the present disclosure provides a driver for driving a fastener, the driver comprising:

a driver shaft and an engagement portion at a distal end of the shaft, the engagement portion configured to locate in a receiving cavity of a head of the fastener, the direction of elongation of the driver shaft defining a driver axis;

a second rotational position which, when the engagement portion is located in the receiving cavity, secures the driver to the fastener. [0053] According to one aspect, the present disclosure provides a driver for driving a fastener, the driver comprising:

a driver shaft and an engagement portion at a distal end of the shaft, the engagement portion configured to locate in a receiving cavity of a head of a fastener, the direction of elongation of the driver shaft defining a driver axis;

[0054] In another aspect of the present disclosure there is provided a fastener for use with a driver, the fastener comprising:

a head portion:

a threaded shaft projecting from the head portion, the direction of elongation of the shaft defining a fastener axis; and

a receiving cavity in the head portion for receiving an engagement portion of a driver to drive the fastener, the receiving cavity defined by one or more side surfaces and a bottom surface and having an opening via which the engagement portion of the driver is insertable into the receiving cavity;

wherein, along the fastener axis, the receiving cavity comprises a first cavity portion adjacent the opening and a second cavity portion spaced from the opening; and wherein the second cavity portion comprises one or more undercut regions.

[0055] Any one of more features of screws described herein can be applied, mutatis mutandis, to other types of fasteners including bolts or studs, for example.

[0056] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps. Brief Description of Drawings

[0057] By way of example only, embodiments are now described with reference to the accompanying drawings, in which:

[0058] Fig. la shows a side view of a driver according to an embodiment of the present disclosure, and Fig. lb shows a cross-sectional side view of the driver of Fig. la;

[0059] Figs. 2a, 2b and 2c show side, oblique and distal end views, respectively, of a distal region of the driver of Fig. la, with first and second engagement parts of an engagement portion of the driver in a first rotational position;

[0060] Figs. 3a, 3b and 3c show side, oblique and distal end views, respectively, of a distal region of the driver of Fig. la, with first and second engagement parts of the engagement portion of the driver in a second rotational position;

[0061] Figs. 4a, 4b, 4c and 4d show oblique, side, oblique transparent and top views, respectively, of a screw according to an embodiment of the present disclosure;

[0062] Figs 5a and 5b show cross-sectional side views of the distal region of the driver of Fig. la, and the screw of Fig 4a, when the engagement portion of the driver is located in a receiving cavity of the screw and the first and second engagement parts of the engagement portion are in a first rotational position (Fig. 5a) and in a second rotational position (Fig. 5b);

[0063] Figs. 6a and 6b show top views of the distal region of the driver of Fig. la, and the screw of Fig 4a, when the engagement portion of the driver is located in the receiving cavity of the screw and the first and second engagement parts of the engagement portion are in the first rotational position (Fig. 6a) and in the second rotational position (Fig. 6b); [0064] Figs 7a and 7b show cross-sectional side views of the distal region of the driver of Fig. la, and a different screw, when the engagement portion of the driver is located in a receiving cavity of the different screw and the first and second engagement parts of the engagement portion are in a first rotational position (Fig. 7a) and in a second rotational position (Fig. 7b);

[0065] Figs. 8a and 8b show top views of the distal region of the driver of Fig. la, and the different screw of Fig 7a, when the engagement portion of the driver is located in the receiving cavity of the screw and the first and second engagement parts of the engagement portion are in the first rotational position (Fig. 8 a) and in the second rotational position (Fig. 8b);

[0066] Fig. 9 shows an oblique view of a distal region of a driver according to another embodiment of the present disclosure;

[0067] Figs. 10a and 10b show cross-sectional side views of the distal region of the driver of Fig. 9, and a screw according to another embodiment of the present disclosure, when an engagement portion of the driver is located in a receiving cavity of the screw and first and second engagement parts of the engagement portion are in a first rotational position (Fig. 10a) and in a second rotational position (Fig. 10b);

[0068] Figs. 11a and 1 lb show cross-sectional side views of a distal region of a driver according to another embodiment of the present disclosure, and a screw according to another embodiment of the present disclosure, when an engagement portion of the driver is located in a receiving cavity of the screw and first and second engagement parts of the engagement portion are in a first rotational position (Fig. 11a) and in a second rotational position (Fig. l ib);

[0069] Figs. 12a and 12b show distal end views of a driver according to an embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 12a) and in a second rotational position (Fig. 12b), and Fig. 12c shows a top view of a screw according to an embodiment of the present disclosure suitable for use with the driver of Figs. 12a and 12b;

[0070] Figs. 13a and 13b show distal end views of a driver according to another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 13a) and in a second rotational position (Fig. 13b), and Fig. 13c shows a top view of a screw according to another embodiment of the present disclosure suitable for use with the driver of Figs. 13a and 13b;

[0071] Figs. 14a and 14b show distal end views of a driver according to yet another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 14a) and in a second rotational position (Fig. 14b), and Fig. 14c shows a top view of a screw according to yet another embodiment of the present disclosure suitable for use with the driver of Figs. 14a and 14b;

[0072] Figs. 15a and 15b show distal end views of a driver according to another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 15a) and in a second rotational position (Fig. 15b), and Fig. 15c shows a top view of a screw according to another embodiment of the present disclosure suitable for use with the driver of Figs. 15a and 15b;

[0073] Figs. 16a and 16b show distal end views of a driver according to yet another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 16a) and in a second rotational position (Fig. 16b), and Fig. 16c shows a top view of a screw according to yet another embodiment of the present disclosure suitable for use with the driver of Figs. 16a and 16b; [0074] Figs. 17a and 17b show distal end views of a driver according to another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 17a) and in a second rotational position (Fig. 17b), and Fig. 17c shows a top view of a screw according to another embodiment of the present disclosure suitable for use with the driver of Figs. 17a and 17b;

[0075] Figs. 18a and 18b show distal end views of a driver according to yet another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 18a) and in a second rotational position (Fig. 18b), and Fig. 18c shows a top view of a screw according to yet another embodiment of the present disclosure suitable for use with the driver of Figs. 18a and 18b;

[0076] Figs. 19a and 19b show distal end views of a driver according to another embodiment of the present disclosure when first and second engagement parts of an engagement portion of the driver are in a first rotational position (Fig. 19a) and in a second rotational position (Fig. 19b), and Fig. 19c shows a top view of a screw according to another embodiment of the present disclosure suitable for use with the driver of Figs. 19a and 19b;

[0077] Figs. 20a and 20b shows cross-sectional side views of screws according to further embodiments of the present disclosure;

[0078] Fig. 21 shows a side view of a driver according to another embodiment of the present disclosure;

[0079] Figs. 22a and 22b show side views of female and male sections, respectively, that are assembled to form the driver of Fig. 21 ; [0080] Fig. 23a and 23b illustrate side views of a proximal end region of the driver of Fig. 20 when first and second engagement parts of the driver are in a first rotational position (Fig. 23a) and a second rotational position (Fig. 23b);

[0081] Fig. 24 shows a side view of a driver according to yet another embodiment of the present disclosure;

[0082] Fig. 25 shows a side view of a driver according to another embodiment of the present disclosure; and

[0083] Figs. 26a and 26b show side views of female and male sections, respectively, that are assembled to form the driver of Fig. 25;

[0084] Fig. 27 shows an oblique view of a driver according to another embodiment of the present disclosure;

[0085] Figs. 28a and 28b show exploded front and rear oblique views, respectively, of the driver of Fig. 27;

[0086] Fig. 29 shows an oblique view of a driver according to yet another embodiment of the present disclosure;

[0087] Figs. 30a and 30b show exploded front and rear oblique views, respectively, of the driver of Fig. 29.

Description of Embodiments

[0088] A driver 10 for driving a screw into material, according to an embodiment of the present disclosure, is illustrated in Figs, la and lb. The driver 10 is a manual screwdriver and includes a mechanism to releasably hold the screw, reducing the likelihood that the screw will disengage the driver prior to the screw being secured in the material. Accordingly, the possibility of the screw falling to the ground and/or getting lost may be reduced. [0089] The driver 10 includes a driver shaft 11 and an engagement portion 12 at a distal end of the shaft 11. The engagement portion 12 is configured to locate in a receiving cavity 23 of a head of a screw 20 in order to engage and drive the screw 20 (see e.g. Figs. 4a to 6b, discussed in more detail below). The direction of elongation of the driver shaft 11 defines a driver axis D. Along the driver axis D, at an opposite end of the shaft 11 from the engagement portion 12, a handle 13 is provided for a user to grip and cause rotation of the entire driver 10 in order to rotate and drive the screw 20.

[0090] The engagement portion 12 of the driver includes a first engagement part 121 and a second engagement part 122. In this embodiment, the second engagement part 122 is located distally of the first engagement part 121 and provides the distal end or tip of the driver 10. The first engagement part 121 is fixed to the driver shaft 11, and the second engagement part 122 is rotatable relative to the first engagement part 121 about the driver axis D. The first and second engagement parts 121, 122 are relatively rotatable such as to move between a first rotational position in which the engagement portion is locatable in and releasable from the receiving cavity 23 of the screw 20, and a second rotational position in which the engagement portion 12 is secured in the receiving cavity of the screw 20.

[0091] The driver 10 includes a rotation mechanism operable by the user to relatively rotate the first and second engagement parts 121, 122 between the first and second rotational positions. Referring to Fig. lb, the rotation mechanism includes a rod 14, which rod 14 is fixed to the second engagement part 122 and extends from the second engagement part 122 through a channel 15 to the proximal end of the driver 10. The channel 15 extends centrally through the first engagement part 121, the driver shaft 11 and the handle 13, along the driver axis D. At the proximal end of the driver 10, the rod 14 is fixed to an actuation element and specifically a rotatable knob 16 in this embodiment. Upon rotation of the knob 16, the rod 14, and thus the second engagement part 122 connected to the rod 121, are caused to rotate about the driver axis D. Rotation of the knob therefore causes relative rotation of the first and second engagement parts 121, 122. [0092] Figs. 2a to 2c and 3a to 3c illustrate in isolation a distal end region of the driver 10, including the engagement portion 12 . As can be seen, the first and second engagement parts 121, 122 have substantially the same non-circular outer shapes. In this embodiment, the outer shapes, each defined in a plane perpendicular to the driver axis D, are hexagonal shapes.

[0093] Figs. 2a to 2c show the first and second engagement parts 121, 122 in the first rotational position. When in the first rotational position, the outer shapes of the first and second engagement parts 121, 122 are substantially aligned or "in phase".

Accordingly, no regions of the second engagement part 122 project radially outwardly of any region of the first engagement part 121. The outer surfaces of the first and second engagement parts 121, 122 are therefore substantially flush with each other.

[0094] Figs. 3a to 3c show the first and second engagement parts 121, 122 of the engagement portion 12 in the second rotational position. When in the second rotational position, the outer shapes of the first and second engagement parts 121, 122 are substantially misaligned or "out of phase". Accordingly, protrusive regions 1221 of the second engagement part 122, which are provided by corner regions 1211 of the hexagonal shapes in this embodiment, are caused to project radially outwardly of the first engagement part 121 along predetermined radial directions P, for example. The outer surfaces of the first and second engagement parts 121, 122 are therefore no longer flush with each other. Radial directions P of the driver extend outwardly from, and perpendicular to, the driver axis D.

[0095] In this embodiment, when the first and second engagement parts are in the second rotational position, the degree of misalignment between the outer shapes of the first and second engagement parts 121, 122 is such that the shapes are maximally out of phase and thus protrusive regions 1221 of the second engagement part 122 project to a maximum degree beyond sides 1211 of the first engagement part 121 along the predetermined radial directions P. Since the outer shapes of the two engagement parts 121, 122 are hexagonal, the shapes are moved from being in phase in the first rotational position to 30 degrees out of phase in the second rotational position. When in the second rotational position, the protrusive regions (corners) 1221 of the hexagon shape of the second engagement part therefore align with and project beyond the centre of respective sides 1211 of the hexagon shape of the first engagement part 121. A similar result can also be achieved by rotating the parts from 0 to 30 + (n * 60) degrees, where n is 1, 2, 3, 4 or 5.

[0096] A screw 20 configured for use with the driver of Figs, la to 3c is illustrated in Figs. 4a to 4d. The screw 20 comprises a head portion 21 and a screw shaft 22 extending from a bottom side of the head portion 21. The direction of elongation of the screw shaft 22 defines a screw axis S. The screw shaft 22 is threaded and may have a pointed end, although, for simplicity, these features are not illustrated in Figs. 4a to 4d. Radial directions R of the screw extend outwardly from, and perpendicular to, the screw axis S.

[0097] The head portion 21 comprises a receiving cavity 23 for receiving the engagement portion 12 of the driver 10, as illustrated in Figs. 5a and 5b. When the engagement portion 12 of the driver is received in the receiving cavity 23, rotation of the driver 10 about the driver axis D can generally cause rotation of the screw 20 about the screw axis S to drive the screw 20.

[0098] Referring to Fig. 5a, the receiving cavity 23 is defined by inner surfaces, including side surfaces 231 and a bottom surface 232. An opening 233 of the receiving cavity 23 is provided generally at an opposite end of the receiving cavity 23 from the bottom surface 232. The side surfaces 231 depend from the opening 233 in a direction parallel to the screw axis S. The engagement portion 12 of the driver can be received in the receiving cavity 23 via the opening 233, whereupon the distal end of the engagement portion 12 moves into engagement with, or rests close to, the bottom surface 232 of the receiving cavity 23.

[0099] In this embodiment, the receiving cavity 23 is divided into two parts, a first cavity portion 23a partially defined by first side surfaces 231a, and a second cavity portion 23b partially defined by second side surfaces 231b (see Figs. 4b and 5a). The first cavity portion 23a is located adjacent the opening 233 and the second cavity portion 23b is spaced from the opening, towards the bottom of the receiving cavity 23.

[0100] Along the driver axis D, the second cavity portion 23b can have a depth that is similar or smaller than the depth of the first cavity portion 23a, for example. In this embodiment, as identified in Fig. 5a, the depth D2 of the second cavity portion 23b is about 30% of the depth Dl of the first cavity portion 23b. In general, in some embodiments of the present disclosure the second cavity portion may have a depth that is similar or smaller than the depth of the first cavity portion, but that is capable of receiving a second engagement part that is of a sufficient size to have suitable strength and rigidity to perform its function. The second cavity portion may have a depth that is at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the depth of the first cavity portion or otherwise. The second cavity portion may have a depth that is between 20% and 120% of the depth of the first cavity portion, between 30% and 100% of the depth of the first cavity portion, between 40% and 80% of the depth of the first cavity portion, or otherwise.

[0101] As evident from Figs. 5a to 6b, the first side surfaces 231a define a hexagonal- prism shaped first cavity portion 23 a (hexagonal when viewed along the screw axis S) and the second side surfaces 231b define a cylindrical second cavity portion 23b (circular when viewed along the screw axis S). The hexagon and circle shapes are concentrically positioned along the screw axis S and the perimeter of the circle extends through the corner points of the hexagon. Thus, in some radial directions, the first and second cavity portions 23a, 23b have substantially the same width, whereas in other, predetermined radial directions R the second cavity portion 23b extends radially outwardly of the first cavity portion.

[0102] In the predetermined radial directions R, the second cavity portion therefore has a radius that is greater than the first cavity portion. In this embodiment, as identified in Fig. 5b, the radius R2 of the second cavity portion is about 30% greater than the radius Rl of the first cavity portion. In general, in some embodiments of the present disclosure, the second cavity portion may extend outwardly of the first cavity portion along one or more predetermined radial directions of the screw, such that the radius of the second cavity portion along those radial directions is at least 10%, at least 15%, at least 20%, at 25%, least 30%, at least 35% or at least 40% greater than the radius of the first cavity portion or otherwise.

[0103] Since the second cavity portion 23b extends outwardly of the first cavity portion 23a at least in certain predetermined radial directions R, the second cavity portion 23b provides undercut regions 234 to the receiving cavity 23. The undercut regions 234 are defined by the second side surfaces 231b, which are located radially outwardly of the first side surfaces 231a along radial directions R, and which are further defined by top surfaces 235 of the receiving cavity 23 that connect the second side surfaces 231b to the first side surfaces 231a. The top surfaces 235 extend radially and generally face the bottom surface 232 of the receiving cavity 23.

[0104] The outer shape of the first cavity portion 23a is substantially the same as the outer shape of the first engagement part 121 of the driver 10. In particular, the first cavity portion 23a and the first engagement part 121 of the driver 10 each have substantially the same hexagonal-prism shapes.

[0105] The engagement portion 12 of the driver 10 is inserted into the receiving cavity 23 of the screw 20 with the first and second engagement parts 121, 122 in the first rotational position, as illustrated in Fig. 5a and 6a. In the first rotational position, the first and second engagement parts 121, 122 have a relatively streamlined configuration such that the second engagement part 122 does not obstruct insertion of the engagement portion 12 into the receiving cavity 23 of the screw 20 via the opening 233. When the engagement portion 12 of the driver 10 is inserted into the receiving cavity 23, the first engagement part 121 locates in the first cavity portion 23a and the second engagement part 122 locates in the second cavity portion 23b. At this stage, the undercut regions 234 of the second cavity portion 23b are empty.

[0106] While in the first rotational position, there is nothing to prevent the engagement portion 12 from being released from the receiving cavity 23. In this configuration, there is a substantial risk that the screw 20 can undesirably disengage the driver 10. Accordingly, prior to driving the screw 20, the first and second engagement 121 , 122 parts are moved to the second rotational position as illustrated in Figs. 5b and 6b. While the first engagement part 121 remains in a substantially fixed position relative to the screw 20, movement to the second rotational position causes the second engagement part 122 to rotate relative to the screw 20 such that its protrusive regions 1221 project further outwardly in predetermined radial directions R of the screw 20, and particularly such that the protrusive regions 1221 extend into respective undercut regions 234. Consequently, the top surfaces 235 of the receiving cavity 23 provide surfaces against which the protrusive regions 1221 of the second engagement part 122 will abut, at least if an attempt is made to remove the engagement portion 12 of the driver 10 from the receiving cavity 23 when the engagement parts 121 , 122 are in the second rotational position. Rotation of the first and second engagement parts 121 , 122 from the first rotational position to the second rotational position therefore places the driver 20 into captive engagement with the screw 20.

[0107] Since the outer shape of the first cavity portion 23a is substantially the same as the outer shape of the first engagement part 121 of the driver 10, rotation of the driver 10 about the driver axis D causes the first engagement part to apply a rotational force to the first side surfaces 231a of the screw head 21 and therefore causes rotation of the screw 20 about the screw axis S, thus achieving driving of the screw 20. Driving of the screw 20 can be carried out with the screw 20 in captive engagement with the driver 10. Once driving of the screw 20 has been completed, the first and second engagement parts 121, 122 can be rotated back to the first rotational position, such that the engagement portion 12 can be released from the receiving cavity 23 via the opening 233 and the driver 10 can be disengaged from the screw 20.

[0108] In this embodiment, a screw 20 is disclosed that is modified over standard screws at least in that it includes undercut regions 234 to enable captive engagement with the driver 10 to be achieved. Nonetheless, securing of the driver 10 to a standard screw, or at least to a screw absent of any undercut regions, may also be achieved with the driver 10 according to the present embodiment. [0109] For example, as illustrated in Figs. 7a to 8b, a different screw 30 can also be used with the driver 10. Features of the screw 30 that are in common with the screw 20 described above are provided with the same reference numerals, whereas different parts are provided with new reference numerals. The screw 30 has substantially the same structure as the screw 20 described above, except that its receiving cavity 33 defines no undercut regions. The receiving cavity 33 of the screw 30 is uniform in shape along the screw axis S in this embodiment.

[0110] Generally, in the above embodiments, to ensure ease of insertion of the engagement portion 12 of the driver 10 into the respective receiving cavities 23, 33, and to provide for a degree of size tolerance between different drivers, the receiving cavities 23, 33 are very slightly larger (at least radially) than the engagement portion 12 of the driver 10. Thus, in relation to the screw 30, despite having no undercut regions in the receiving cavity 33, the first and second engagement parts 121, 122 of the driver 10 can still be rotated relative to each other from the first rotational position to the second rotational position axis when located in the receiving cavity 33. Upon rotation to the second rotational position, instead of having protrusive regions 1221 of the second engagement part 122 of the driver 10 extending into undercut regions, the protrusive regions 1221 are pressed against side surfaces 331 that define the receiving cavity 33. If a sufficient torque is applied to the second engagement part 122 during relative rotation, the second engagement part 122 can realise a relatively strong frictional engagement with side surfaces 331 of the receiving cavity 33, again securing the driver 10 to the screw 20. The frictional engagement takes place at regions indicated by item A in Figs. 7b and 8b, for example. The relative rotation between the first and second engagement parts 121, 122 can be carried out in different directions, e.g. clockwise or anti-clockwise, depending on whether or not the driver is being used to insert or remove the screw.

[0111] In general, the securing (locking) of the driver 10 to the screw 20, 30 in embodiments described herein is such that the screw 20, 30 cannot easily be separated from the driver 10, e.g., by hand or under the effects of gravity. The only practical way to release the screw 20, 30 from the driver 10 may be to reverse the relative rotation of the first and second engagement parts 121, 122, i.e. to move the first and second engagement parts 121, 122 from the second rotational position back to the first rotational position.

[0112] In each of the above embodiments, when located in the receiving cavity 23, 33 of the screw 20, 30, and moved from the first rotational position to the second rotational position, the second engagement 122 part moves in the receiving cavity such that, in one or more predetermined radial directions R of the screw, the second engagement part 122 is caused to project further outwardly. It is this effective change in dimension of the second engagement part 122, across the predetermined radial directions R, that enables the second engagement part to move into captive engagement or frictional engagement within the receiving cavity 23, 33.

[0113] Numerous variations of the above-described embodiments are possible, while retaining substantially the same principles for securing a driver and a screw. For example, with reference to Figs. 9, 10a and 10b, in one embodiment a driver 40 is provided with a modified engagement portion 42 in which a second engagement part 422 of the engagement portion 42 is not at the distal end of the driver 40. Rather, in this embodiment the second engagement part 422 is positioned proximally of the distal end of the driver 40, at an intermediate region of a first engagement part 421. A correspondingly modified screw 50 can be provided, in which a second cavity portion 53b of the receiving cavity 53, providing undercuts 531, is not located adjacent a bottom end of the receiving cavity, but is instead located at an intermediate position of a first receiving portion 53a of the receiving cavity 53, along the screw axis S.

Accordingly, captive engagement between the driver 40 and the screw 50 is again achievable. Nonetheless, the driver 40 may also be used to achieve frictional engagement with a screw, e.g. the screw 30 as illustrated in Figs. 7a to 8b.

[0114] As another example, with reference to Figs. 1 la and 1 lb, in one embodiment a driver 60 is provided with an engagement portion 62 that is configured such that a second engagement part 622 of the engagement portion 62 does not extend radially outwardly of a first engagement part 621 of the engagement portion 62, even when the engagement parts 621, 622 are in the second rotational position. A correspondingly modified screw 70 can be provided in which undercut regions of a second cavity portion 73b of a receiving cavity 73 of the screw do not extend radially outwardly of a first cavity portion 73a of the receiving cavity 73. In this embodiment, the second engagement part 622 is spaced from the first engagement part 621 by a shaft section 623 that is narrower than the first and second engagement parts 621, 622. Further, the first and second cavity portions 73a, 73b are separated by a third cavity portion 73c that is narrower than the first and second cavity portions 73a, 73b. Since the second cavity portion 73b extends outwardly of the third cavity portion 73c, undercut regions 731 are nevertheless provided into which the second engagement part 622 of the driver 60 can be captively engaged when in the second rotational position, as illustrated in Fig. 1 lb.

[0115] Further variations of the above-described embodiments are now described with reference to Figs. 13a to 19c. For the purpose of comparison, Figs. 12a to 12b illustrate an engagement portion 81 of a driver, which includes first and second engagement parts 811, 812, and Fig. 12c illustrates a head 82 of a screw, including a receiving cavity with first and second cavity portions 821,822, that are configured generally in accordance with the embodiment of Figs, la to 6b discussed above.

[0116] Figs. 13a to 13c illustrate an embodiment that employs a driver with the same engagement portions 81 as Figs. 12a and 12b, but which is used with a screw 83 having a receiving cavity with a differently shaped second cavity portion 832. Rather than the second cavity portion 832 having a circular shape in a plane perpendicular to the screw axis, the second cavity portion 832 has a petal-shaped arrangement. Undercut regions 833 of the second cavity portion 832 are smaller than undercut regions 823 of the preceding embodiment, yet still enable the second engagement part 812 to relatively rotate to a maximally out-of-phase position relative to the first engagement part 812 when located in the second cavity portion. Surfaces 834 defining the second cavity portion 832 can act as stops to prevent over-rotation of the second engagement part 812 relative to the first engagement part 811, and the reduced size of the undercut regions 833 may ensure greater strength in the construct of the screw 83. [0117] Figs. 14a and 14b illustrate an engagement portion 84 of a driver, which includes first and second engagement parts 841, 842, and Fig. 14c illustrates a head 85 of a screw, including a receiving cavity with first and second cavity portions 851, 852, that are configured in accordance with the embodiment of Figs. 12a to 12c except that the relevant parts 841, 842, 851 are (6-pointed) star-shaped, rather than hexagonal- shaped. In general, the embodiment relies on a star-socket engagement between the engagement portion 84 of the driver and the receiving cavity of the head 85 of the screw.

[0118] Figs. 15a and 15b illustrate an engagement portion 86 of a driver, which includes first and second engagement parts 861, 862, and Fig. 15c illustrates a head 87 of a screw, including a receiving cavity with first and second cavity portions 871, 872, that are configured in accordance with the embodiment of Figs. 12a to 12c except that the relevant parts 861, 862, 871 are hexalobular- shaped, rather than hexagonal-shaped. In general, the embodiment relies on a hexalobular-socket engagement between the engagement portion 86 of the driver and the receiving cavity of the head 87 of the screw.

[0119] Figs. 16a and 16b illustrate an engagement portion 88 of a driver, which includes first and second engagement parts 881, 882, and Fig. 16c illustrates a head 89 of a screw, including a receiving cavity with first and second cavity portions 891, 892, that are configured in accordance with the embodiment of Figs. 12a to 12c except that the relevant parts 881, 882, 891 are cross-shaped, rather than hexagonal-shaped. In general, the embodiment relies on a cross-slot engagement between the engagement portion 88 of the driver and the receiving cavity of the head 89 of the screw.

[0120] In the embodiments illustrated with reference to Figs. 12a to 16c, the engagement portions of the drivers include respective first and second engagement parts of substantially the same outer shape. However, the first and second engagement parts need not have the same outer shape. While the first engagement part has a primary role of driving the screw, and for practical purposes may therefore have a shape that corresponds to common screw driving socket shapes, for example, the second engagement part in particular may be considerably different in shape.

[0121] For example, Figs. 17a and 17b illustrate an engagement portion 90 of a driver, which includes first and second engagement parts 901, 902, and Fig. 17c illustrates a head 91 of a screw, including a receiving cavity with first and second cavity portions 911, 912. The engagement portion 90 and head of the screw 91 are configured in accordance with the embodiment of Figs. 15a to 15c except that the second engagement part 902 has a rectangular shape and the second engagement part 902, and the second cavity portion 912 that receives the second engagement part 902, have a smaller diameter than the diameter of the hexalobular shaped first engagement part 901.

[0122] As another example, Figs. 18a and 18b illustrate an engagement portion 92 of a driver, which includes first and second engagement parts 921, 922, and Fig. 18c illustrates a head 93 of a screw, including a receiving cavity with first and second cavity portions 931, 932, that are configured in accordance with the embodiment of Figs. 15a to 15c except that the second engagement part 922 has a generally ovoid shape and the second engagement part 922 is non-symmetrically positioned about its axis of rotation 923.

[0123] As yet another example, Figs. 19a and 19b illustrate an engagement portion 94 of a driver, which includes first and second engagement parts 941, 942, and Fig. 19c illustrates a head 95 of a screw, including a receiving cavity with first and second cavity portions 951, 952, that are configured in accordance with the embodiment of Figs. 17a to 17c except that the second engagement part 942 has a circular shape and the second engagement part 942 is rotatable relative to the first engagement part 941 about an axis of rotation 943 that is offset from a centre of the engagement part 94.

[0124] While the embodiments of Figs. 13a to 19c depict engagement portions and associated screw heads including second cavity portions with undercut regions to provide for captive engagement, the engagement portions may also be used with screws without undercut regions, relying instead on frictional engagement with the screw head, e.g. in a similar manner to that described above with respect to Figs. 7a to 8b.

[0125] The above embodiments illustrate that the engagement parts can take a number of different configurations while still retaining substantially the same principles for securing a driver and a screw. The receiving cavity of the screw head (or at least the first cavity portion thereof) may take any shape suitable for receiving an engagement portion of a driver such that rotation of the driver about the driver axis causes rotation of the screw about the screw axis. In this regard, the screw may have one of a wide variety of known screw head types, including, for example, slotted (e.g. slot or cross- recess), polygonal socket (e.g., triangular socket, square socket, pentagon socket, or hex socket), polylobular socket (e.g. pentalobular socket or hexalobular socket), cruciform socket (e.g. Phillips or Frearson) or star socket (e.g. double-square, triple square or double hex), or otherwise.

[0126] In the above screw embodiments, including as illustrated in Figs. 5a and 5b, for example, the first and second cavity portions 23a, 23b have side surfaces 231a, 231b that all extend in a direction parallel to the screw axis S. In alternative embodiments, however, at least a portion of the first and/or second side surfaces may extends in a direction having an angle relative to the screw axis. For example, in the embodiment illustrated in Fig. 20a, a screw 96 is provided having a first cavity portion 96a with side surfaces 961a that extend parallel to the screw axis S and a second cavity portion 96b with side surfaces 961b that extend at an angle relative to the screw axis S and, specifically, in this embodiment, at an angle of about 8 degrees,. As another example, in the embodiment illustrated in Fig. 20b, a screw 97 is provided having a first cavity portion 97a with side surfaces 971a that extend parallel to the screw axis S and a second cavity portion 97b with side surfaces 971b that (i) at a position adjacent to the first cavity portion 97a, extend in a direction parallel to the screw axis S and (ii) at a position spaced from the first cavity portion 97a, extend at an angle relative to the screw axis S and, specifically an angle of 15 degrees, in this embodiment. The angling of the side surfaces can ensure that that the thickness or material between the side surface of the receiving cavity and the outer surfaces of the screw head is kept at, or above, a suitable minimum thickness, maintaining the structural integrity of the screw head.

[0127] A driver 1000 for driving a screw into material, according to another embodiment of the present disclosure, is illustrated in Figs. 21 to 23b. The driver 1000 is a manual screwdriver and includes a mechanism to releasably hold the screw, reducing the likelihood that the screw will disengage the driver prior to the screw being secured in the material. Accordingly, the possibility of the screw falling to the ground and/or getting lost may be reduced.

[0128] The driver 1000 is similar to the driver 10 depicted in Figs, la and lb, and includes a includes a driver shaft 1010 and an engagement portion 1020 at a distal end of the shaft 1010. The engagement portion 1020 is again configured to locate in a receiving cavity of a head of a screw in order to engage and drive the screw, and includes first and second engagement parts 1021, 1022 that are relatively rotatable between a first rotational position in which the engagement portion is locatable in the receiving cavity of the screw, and a second rotational position in which the engagement portion is secured in the receiving cavity of the screw. In this embodiment, the first and second engagement parts 1021, 1022 have hexalobular shapes and the driver 1000 is constructed in part by placing a male section 1002 into a female section 1001. The male section 1002 provides a rotation mechanism including a rod 1040 fixed to the second engagement part 1022 and a knob 1060 (removable from the rod 1040 for the purposes of assembly) to turn the rod 1040. The female section 1001 includes a handle 1030 and a channel 1050 that extends through the first engagement part 1021, through the shaft 1010 and through the handle 1030 to the proximal end of the driver 1000.

[0129] An addition to the driver 1000 of the present embodiment, in comparison to the driver 10 of Figs, la and lb, for example, is a groove 1080 located at a proximal end of the handle 1030, which groove 1080 interacts with a pin 1070 projecting from a bottom surface of the knob 1060 of the rotation mechanism. When the knob 1060 is rotated in order to relatively rotate the first and second engagement parts 1021, 1022, the pin 1070 moves along the groove 1080. The groove 1080 follows a circular arc, with opposite first and second end surfaces of the groove 1080 defining first and second stops 1081, 1082 respectively, for limiting movement of the pin 1070, and therefore limiting a degree of relative rotation of the first and second engagement parts 1021, 1022. The stops 1081, 1082 ensure that a user can arrive at the first or second rotational position by rotating the rotation mechanism until the pin 1070 contacts the respective first or second stop 1081, 1082.

[0130] In addition to the groove 1080, a cam mechanism is provided in the handle 1030 for releasably maintaining the first and second engagement parts 1021, 1022 in the first rotational position or the second rotational position. The cam mechanism includes a spring mounted pin 1083 that is spring biased to a location in which a rounded tip of the pin 1083 projects into the groove 1080. The rounded tip of the pin 1083 sits in the path of the pin 1070 and therefore restricts movement of the pin 1070 in the groove 1080, maintaining the pin 1070 in contact with, or close to, either the first or second stop 1081, 1082. Nevertheless, upon application of sufficient rotational force to the knob 1060, the pin 1070 can be forced past the spring mounted pin 1083 with the pin 1070 pushing and pressing the spring mounted pin 1083 away from the groove 1080. Thus, when desired, the first and second engagement parts 1021, 1022 can be moved between the first and second rotational positions. Figs. 23a and 23b provide illustrations of the location of pin 1070 in the groove 1080, at the first and second rotational positions, respectively.

[0131] The driver 1000 described above can be modified by, for example, replacing the groove and pin features, which control a degree of relative movement of the first and second engagement parts, with a clip that is arranged to fix the first and second engagement parts in the second rotational position.

[0132] In more detail, with reference to Fig. 24, a driver 1100 is provided that includes a driver shaft 1110 and an engagement portion 1120 at a distal end of the shaft 1110. The engagement portion 1120 is again configured to locate in a receiving cavity of a head of a screw in order to engage and drive the screw, and includes first and second engagement parts 1121, 1122 that are relatively rotatable between a first rotational position in which the engagement portion is locatable in the receiving cavity of the screw, and a second rotational position in which the engagement portion is secured in the receiving cavity of the screw. In this embodiment, the first and second engagement parts 1121, 1122 have hexalobular shapes and the driver 1100 is constructed in part by placing a male section into a female section. The male section provides a rotation mechanism including a rod 1140 fixed to the second engagement part 1122 and a knob 1160 to turn the rod 1140. The female section includes a handle 1130 and a channel 1150 that extends through the first engagement part 1121, through the shaft 1110 and through the handle 1130 to the proximal end of the driver 1100.

[0133] A hole 1111 is provided in each of the shaft 1110 and the rod 1140. When the first and second engagement parts 1121, 1122 are in the second rotational position (e.g., with their shapes maximally out of phase) the two holes 1111 are arranged to line up. Upon the holes lining up, a pin 1171 of a clip 1170 can be located in the two holes 1111, restricting any further relative rotation of the shaft 1110 and the rod 1140 and thus fixing the first and second engagement parts 1121, 1122 in the second rotational position. The clip 1170 also includes a curved, resiliently flexible element 1172 that snap- fits around the outside of the shaft 1110 when the pin 1171 is located in the holes 1111, releasably maintaining the clip 1170 in position.

[0134] In the preceding embodiments, manual screw drivers are described; however, drivers according to the present disclosure can take any suitable configuration for driving screws. For example, the drivers can also be or provide part of a powered driver. The drivers can be a torque-limited screwdriver with a mechanism for preventing over-tightening of screws, and/or the drivers can be a ratcheting

screwdriver. The driver can be independently operable or may require connection to an additional device for operation.

[0135] In one embodiment, with reference to Figs. 25, 26a and 26b, a driver 1200 is provided in the form of a screwdriver bit, which is connectable at its proximal end 1203 to a powered or mechanically operatable mechanism, such as an electric or mechanical drill, to rotate the screwdriver bit. The driver 1200 includes a driver shaft 1210 and an engagement portion 1220 at a distal end of the shaft 1210. The engagement portion 1220 is again configured to locate in a receiving cavity of a head of a screw in order to engage and drive the screw, and includes first and second engagement parts 1221, 1222 that are relatively rotatable between a first rotational position in which the engagement portion 1220 is locatable in the receiving cavity of the screw, and a second rotational position in which the engagement portion 1220 is secured in the receiving cavity of the screw.

[0136] In this embodiment, the first and second engagement parts 1221, 1222 have hexalobular shapes and the driver 1200 is constructed in part by placing a male section 1202 into a female section 1201. The male section 1202 provides a rotation mechanism including a rod 1240 fixed to the second engagement part 1222 and a knob 1260 to turn the rod 1240. In this embodiment, the knob 1260 projects from a side of the rod 1240. The female section 1201 includes a channel that extends through the first engagement part 1221 and through the shaft 1210 to the proximal end of the driver 1200. In walls of the shaft 1210, a slot 1280 is provided in which the knob 1260 is locatable when the male and female sections 1201, 1202 are assembled. The knob 1260 can be engaged with the rod 1240 via a screw thread engagement, enabling removal of the knob 1260 for insertion of the rod 1240 through the channel of the shaft 1210 during assembly. Alternatively, the knob 1260 can be spring mounted to a recess in the rod 1240, allowing retraction of the knob 1260 into the recess during insertion of the rod 1240 through the channel of the shaft 1210 during assembly. When positioned in the slot 1280, the knob 1260 can be engaged by hand or via a separate tool and rotated in order to relatively rotate the first and second engagement parts 1221, 1222. Opposite first and second ends of the slot 1280 define first and second stops, respectively, for limiting movement of the knob 1260, and therefore limiting a degree of relative rotation of the first and second engagement parts 1221, 1222 between the first and second rotational positions.

[0137] A hole 1211 is provided in each of the shaft 1210 of the driver 1200 and the rod 1240 that extends through the shaft 1210. When the first and second engagement parts 1221, 1222 are in the second rotational position (e.g., with their shapes maximally out of phase) the two holes 1211 are arranged to line up. Upon the holes 1211 lining up, a clip 1170 can be used to fix the first and second engagement parts 1221, 1222 in the second rotational position, in the manner as described above with reference to Fig. 24.

[0138] A driver 1300 for driving a screw, according to yet another embodiment of the present disclosure, is illustrated in Figs. 27 to 28b. The driver 1300 is a manual screwdriver and again includes a mechanism to releasably hold a screw. The driver includes a driver shaft 1310 extending from a handle 1330, and an engagement portion 1320 at a distal end of the shaft 1310. The engagement portion 1320 includes relatively rotatable first and second engagement parts 1321, 1322, configured to locate in, and secure to, a receiving cavity of a head of a screw, in accordance with techniques described above. A difference between the driver 1300 and drivers according to preceding embodiments is the construction of the rotation mechanism for relatively rotating the first and second engagement parts 1321, 1322 of the engagement portion 312.

[0139] In this embodiment, the rotation mechanism includes an actuation element, and specifically a lever 1360, adjacent a distal end of the handle 1330. A central portion of the lever 1360 is connected to a proximal end of a rod 1340, the rod 1340 extending through the shaft 1310 and being fixed at a distal end to the second engagement part 1322, such that rotation of the lever 1360 causes rotation of the second engagement part 1322 relative to the first engagement part 1321. To cause the rotation, a user can engage either end of the lever 1360, e.g. using a thumb or a finger, while gripping the handle 1330.

[0140] The lever 1360 is partially housed in a hub portion 1370 that includes a proximal hub part 1371 and a distal hub part 1372. The proximal hub part 1371 is fixed to the handle 1330 and includes a channel 1373 within which the lever 1360 is rotatable between first and second rotational positions, where side walls of the channel defining respective stops. In the first rotational position the engagement portion 1320 is locatable in and releasable from the receiving cavity of the screw, and, in the second rotational position, the engagement portion is secured in the receiving cavity of the screw, in accordance with embodiments described above. The lever 1360 includes two detents or recesses 1361 that interact with a resiliently biased ball member to releasably hold the lever in the first and second rotation positions, respectively. The proximal and distal hub parts 1371, 1372 are secured together using a worm screw 1374, holding the lever in position.

[0141] A driver 1400 for driving a screw, according to yet another embodiment of the present disclosure, is illustrated in Figs. 29 to 30b. The driver 1400 is a manual screwdriver and again includes a mechanism to releasably hold a screw. The driver 1400 includes a driver shaft 1410 extending from a handle 1430, and an engagement portion 1420 at a distal end of the shaft 1410. The engagement portion 1420 includes relatively rotatable first and second engagement parts 1421, 1422, configured to locate in, and secure to, a receiving cavity of a head of a screw, in accordance with techniques described above. A difference between the driver 1400 and drivers according to preceding embodiments is the construction of the rotation mechanism for relatively rotating the first and second engagement parts 1421, 1422 of the engagement portion 1420.

[0142] In this embodiment, the rotation mechanism includes an actuation element, and specifically a push button 1460, adjacent a distal end of the handle 1430. The push button 1460 is biased by a spring 1461 to an initial position, wherein a distal end 1460a of the button 1460 projects outwardly from an orifice in the outer surface of the handle 1430 as shown in Fig. 29. However, the push button 1460 is movable by a user pressing the button, against the spring bias, to a pressed position in which the distal end 1460a of the button 1460 is closer to the outer surface of the handle 1430 and in which a proximal end 1460b of the button 1460 projects further into a space inside the handle 1430. The user may press the button 1460 using a thumb or a finger, while gripping the handle 1430.

[0143] In the space inside the handle, a rotatable member 1470 is provided that is connected to a proximal end of a rod 1440, the rod 1440 extending through the shaft 1410 and being fixed at a distal end to the second engagement part 1422, such that rotation of the rotatable member 1470 causes rotation of the second engagement part 1421 relative to the first engagement part 1422. The first and second engagement parts 1421, 1422 are rotatable between a first rotational position in which the engagement portion 1420 is locatable in and releasable from the receiving cavity of the screw, and a second rotational position, in which the engagement portion 1420 is secured in the receiving cavity of the screw, in accordance with embodiments described above.

[0144] To cause the rotation, a user can press the push button 1460 to its pressed position, whereupon the proximal end 1460b of the push button 1460 presses against a bearing surface 1471 of the rotatable member 1470, causing the rotatable member 1470 to turn about the driver axis. In this embodiment, the rotatable member 1470 is biased by a spring in the handle (not shown) towards a position in which it places the first and second engagement parts 1421, 1422 in the second rotational position. This arrangement may be advantageous as it can ensure that, during any mishandling of the driver, which might cause a user to disengage the push button 1460, the screw can remain attached to the driver. Moreover, if a user is to transfer the driver to another user, the screw can remain secured to the driver during the transfer. Such a transfer may occur in an operating theatre, for example, where a nurse may secure a screw to the driver and then pass the driver, with the screw secured thereto, to a surgeon.

[0145] In this embodiment, cleaning ports 1411 are provided in the shaft 1410 to enable cleaning fluid and/or other tools to be passed through the shaft to clean the driver, e.g. after use. Similar cleaning ports may be included in any of the

embodiments disclosed herein.

[0146] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the above-described embodiments, without departing from the broad general scope of the present disclosure. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims

CLAIMS:

1. A driver for driving a screw, the driver comprising:

2. The driver of claim 1, wherein, when moved to the second rotational position, the second engagement part is configured to move into frictional engagement with a surface defining the receiving cavity to secure the driver to the screw.

3. The driver of claim 1, wherein, when moved to the second rotational position, the second engagement part is configured to move into captive engagement with a region of the receiving cavity to secure the driver to the screw.

4. The driver of claim 3, wherein, when moved to the second rotational position, the second engagement part is configured to move into captive engagement with an undercut region of the receiving cavity to secure the driver to the screw.

5. The driver of any one of the preceding claims, wherein the second engagement part is located distally of the first engagement part along the driver axis.

6. The driver of any one of the preceding claims, wherein the first engagement part is fixed in position relative to the driver shaft.

7. The driver of any one of the preceding claims, wherein, when moved from the first position to the second position, the second engagement part is configured to project further outwardly in one or more predetermined radial directions of the driver and/or screw.

8. The driver of claim 7, wherein, when moved from the first position to the second position, the second engagement part is configured to project further outwardly in one or more predetermined radial directions of the driver and/or screw by one or more protrusive regions of the second engagement part rotating into alignment with the one or more predetermined radial directions.

9. The driver of claim 8, wherein the one or more protrusive regions are provided by corner regions or projecting point regions of the second engagement part.

10. The driver of claim 7, 8 or 9, wherein the one or more predetermined radial directions of the driver extend through one or more non-protrusive regions of the first engagement part.

11. The driver of claim 10, wherein the non-protrusive regions comprise sides or recesses of the first engagement part.

12. The driver of any one of the preceding claims wherein the second engagement part comprises one or more protrusive regions and wherein, in the first rotational position, the one or more protrusive regions project radially outwardly from the driver axis substantially no further than any region of the first engagement part along one or more predetermined radial directions of the screw.

13. The driver of claim 12 wherein the first and second engagement parts have substantially the same non-circular outer shapes and, in the first rotational position, the shapes of the first and second engagement parts are substantially in alignment.

14. The driver of claim 12 or 13 wherein, in the second rotational position, the one or more protrusive regions project radially outwardly from the driver axis further than the first engagement part along the one or more predetermined radial directions of the screw.

15. The driver of claim 14 wherein the first and second engagement parts have substantially the same non-circular outer shapes and, in the second rotational position, the shapes of the first and second engagement parts are in misalignment.

16. The driver of any one of the preceding claims comprising a rotation mechanism to relatively rotate the first and second engagement parts of the driver between the first and second rotational positions

17. The driver of claim 16, wherein the rotation mechanism comprises an elongate element that is fixed to one of the first and second engagement parts and rotatable relative to the other of the first and second engagement parts and that extends along the driver axis.

18. The driver of claim 17, wherein the elongate element extends through a channel in the driver shaft.

19. The driver of claim 17 wherein the second engagement part is positioned distally of the first engagement part and the elongate element is a rod that is fixed to a proximal end surface of the second engagement part and that extends from the second engagement part, and through a channel extending through the first engagement part and through the shaft.

20. The driver of any one of claims 17 to 19, wherein the rotation mechanism comprises an actuation element connected to a proximal region of the elongate element, which actuation element is engageable to rotate the elongate element.

21. The driver of any one of claims 16 to 20 wherein the rotation mechanism comprises one or more stops to limit a degree of relative rotation of first and second engagement parts.

22. The driver of claim 21, wherein the stops are configured such that the first and second engagement parts are placed in the first and second rotational positions by rotating the rotation mechanism until it hits a respective one of the stops.

23. The driver of any one of claims 16 to 22, wherein the rotation mechanism is biased to force the first and second engagement parts towards one of the first and second rotational positions.

24. The driver of claim 23, wherein the first and second engagement parts are biased towards the second rotational position.

25. The driver of any one of the claims 16 to 24, wherein the rotation mechanism comprises a cam or lock feature for releasably maintaining the first and second engagement parts in the first rotational position and/or second rotational position.

26. The driver of any one of the preceding claims wherein the outer shape of each the first and second engagement parts is a polygonal, polylobular or star-shape.

27. A driver for driving a screw, the driver comprising:

28. A screw for use with a driver, the screw comprising:

a head portion:

29. The screw of claim 28, wherein the second cavity portion extends radially outwardly of the first cavity portion in one or more predetermined radial directions perpendicular to the screw axis.

30. The screw of claim 28 or 29, wherein the one or more side surfaces comprise at least one first side surface defining the first cavity portion and at least one second side surface defining the second cavity portion, wherein the second side surface is located radially outwardly of the first side surface, in at least one predetermined radial direction perpendicular to the screw axis, to provide at least one undercut region of the second cavity portion.

31. The screw of claim 30, wherein in all radial directions perpendicular to the screw axis, the second side surface is located radially outwardly of the first side surface.

32. The screw of claim 30, wherein in a first subset of radial directions perpendicular to the screw axis, the second side surface is located radially outwardly of the first side surface and in a second subset of radial directions perpendicular to the screw axis, the second side surface is flush with the first side surface or located radially inwardly of the first side surface.

33. The screw of any one of claims 28 to 32, wherein the radius of the second cavity portion along one or more predetermined radial directions of the screw perpendicular to the screw axis is at least 10%, at least 15%, at least 20%, at 25%, least 30%, at least 35% or at least 40% greater than the radius of the first cavity portion.

34. The screw of any one of claims 28 to 33, wherein the first and second cavities are directly adjacent to each other along the screw axis.

35. The screw of any one of claims 28 to 33, wherein the first and second cavity portions are separated along the screw axis by a third cavity portion.

36. The screw of any one of claims 28 to 35, wherein at least a portion of the first side surface extends, along the screw axis, in a direction parallel to the screw axis.

37. The screw of any one of claims 28 to 36, wherein at least a portion of the second side surface extends, along the screw axis, in a direction parallel to the screw axis.

38. The screw of any one of claims 28 to 36, wherein at least a portion of the second side surface extends, along the screw axis, in a direction having an angle relative to the screw axis.

39. The screw of claim 38, wherein the angle is between 5 degrees and 20 degrees.

40. The screw of claim 38, wherein the angle is about 8 degrees, or about 15 degrees.

41. The screw of any one of claims 28 to 40, wherein the screw is any one of: a polygonal socket screw having a polygonally-shaped first cavity portion; a polylobular socket screw having a polylobularly-shaped first cavity portion; a cruciform socket screw having a cruciform-shaped first cavity portion; and a star socket screw having a star-shaped first cavity portion.

42. The screw of claim 41, wherein the screw is the polygonal socket screw, the first cavity portion having a triangular shape, a square shape, a pentagonal shape, or a hexagonal shape.

43. The screw of claim 41, wherein the screw is the polylobular socket screw, the first cavity portion having a pentalobular shape or a hexalobular shape.

44. The screw of claim 41, wherein the screw is a cruciform socket screw, the first cavity portion having a cross shape.

45. The screw of claim 41, wherein the screw is the star socket screw, the first cavity portion having a double-square shape, a triple-square shape, or a double- hexagonal shape.

46. The screw of any one of claims 41 to 45, wherein second cavity portion of the receiving cavity has a shape that is different from the shape of the first cavity portion.

47. The screw of any one of claims 28 to 46, wherein the second cavity portion has a circular shape.

48. The screw of claim 47, wherein the circular shape of the second cavity portion is concentric with the shape of the first cavity portion.

49. The screw of any one of claims 28 to 48, wherein, along the screw axis, the second cavity portion has a depth that is at least 20%, at least 30%, at least 40%, at least 50%, or at least 60% of the depth of the first cavity portion.

50. The screw of any one of claims 28 to 48, wherein, along the screw axis, second cavity portion has a depth that is between 20% and 120%, between 30% and 100%, or between 40% and 80% of the depth of the first cavity portion.

51. A polygonal socket screw for use with a driver, the screw comprising:

a head portion:

a receiving cavity in the head portion for receiving an engagement portion of a driver to drive the screw, the receiving cavity having, along the screw axis, first side surfaces defining a first cavity portion having a polygonal shape, at least one second side surface defining a second cavity portion, and an opening adjacent the first cavity portion via which the engagement portion of the driver is insertable into the receiving cavity;

wherein at least a portion of the second cavity portion extends radially outwardly of the first cavity portion, in one or more directions perpendicular to the screw axis, to provide one or more undercut regions of the receiving cavity.

52. The screw of claim 51, wherein the polygonal shape defined by the first side surfaces is a triangular shape, a square shape, a pentagon shape, or a hexagon shape.

53. The screw of claim 51 or 52, wherein the second cavity portion defined by the at least one second side surface has a circular shape.

54. A polylobular or star-shaped socket screw for use with a driver, the screw comprising:

a head portion:

a receiving cavity in the head portion for receiving an engagement portion of a driver to drive the screw, the receiving cavity having, along the screw axis, first side surfaces defining a first cavity portion having a polylobular or star shape, at least one second side surface defining a second cavity portion, and an opening adjacent the first cavity portion via which the engagement portion of the driver is insertable into the receiving cavity;

55. The screw of claim 55, wherein the polylobular or star shape defined by the first side surfaces is a pentalobular shape, a hexalobular shape, a double-square shape, a triple-square shape, or a double-hexagonal shape.

56. The screw of claim 54 or 55, wherein the second cavity portion defined by the at least one second side surface has a circular shape.