GB2493528A

GB2493528A - Tool head with enhanced engagement for removing damaged screws

Info

Publication number: GB2493528A
Application number: GB201113680A
Authority: GB
Inventors: Julia Rosamunde Jones; Peter Victor Stamford
Original assignee: Individual
Current assignee: Individual
Priority date: 2011-08-09
Filing date: 2011-08-09
Publication date: 2013-02-13
Anticipated expiration: 2031-08-09
Also published as: GB201113680D0; GB2493528B

Abstract

The tool head 4 includes a drive formation 6 cooperable with a matching drive formation on a head of a screw for driving the screw into and removing the screw from a work-piece. The drive formation may be provided by four radial webs 6 having a first section 12 with an angled outer face 12a that provides a cutting edge 12b on the trailing side in the direction of rotation of the tool bit to drive the screw into the work-piece and which is on the leading side in the direction of rotation of the tool bit to remove the screw from the work-piece. The cutting edge 12b enhances the engagement with the screw head when removing the screw from the work-piece even if the drive formation on the screw head is damaged.

Description

I

TOOL HEADS

This invention concerns improvements in or relating to tool heads for driving screws into and removing screws from a workpiece.

Tool heads for driving screws into and removing screws from a workpiece are known. It often arises however that the drive formations on the screw hcad are damaged especially if the incorrect tool head is used to drive the screw into the workpiece with the result that the screw cannot be easily removed from the workpiece. The present invention seeks to provide an improved tooT head to address this problem.

In particular, it is a desired aim of the present invention to provide a tool head that can be used to remove screws from a workpiecc when the drive formations on the head have been damaged, for example when driving the screw into the workpiece.

According to one aspect of the present invention there is provided a tool head having a drive formation co-operable with a matching drive formation on a head of a screw for driving the screw into a workpiece in response to rotation of the tool head and for removing the screw from the workpiece in response to reversing the direction of rotation of the tool head, wherein the tool head is configured to enhance the engagement with the screw head when removing the screw from the workpiece.

By this invention, the drive formation on the tool head is configured so as to transmit torque from the tool head to the screw to remove the screw even if the drive formation on the screw head was damaged when inserting the screw.

In some forms of the invention, the drive formation on the tooi head has four webs arranged at right angles to each other to take the form of a so-called cross-head drive formation.

In such cross-head drive formation, the webs preferably taper towards a distal or free end of the tool head and the drive formation on the screw head preferably comprises a socket with discrete pockets to receive the webs wherein the pockets taper towards a base or inner end of the socket.

With this arrangement, torque is transmitted from the tool head to the screw head by engagement of the webs in the pockets, more especially between opposed side faces of the webs and the pockets according to the direction of rotation of the tool head.

Preferably, at least one web is provided with an angled or bevelled outer face with respect to a direction of rotation of thc tool hcad about a longitudinal axis of the tool head. As a result, a cutting edge is provided on one side of web so that thc web is urged into the material of the screw head in response to rotation of the tool head to remove the screw. In this way, a level of torque sufficient to remove the screw can be applied even ii the drive formation on the screw head is damaged.

As a result, engagement between the tool head and the screw head may be enhanced and the level of torque that can be transmitted from the tool head to the screw when removing the screw from a workpiecc may be increased whereby removal of the screw can be facilitated even if the drive formation on the screw head is damaged.

Preferably, all the webs of a cross-head drive formation on the tool head are provided with an angled or bevelled outer face.

In preferred forms of the invention, the or each angled or bevelled outer face may be serrated, knurled or otherwise adapted to enhance further engagement with the screw head for transmitting torque from the tool head to the screw when rotating the tool head to remove the screw from a workpieee.

In some forms of the invention, the webs may also be configured to form one or more of a pilot hole for locating a screw, a countersink for locating the screw head flush with the surface of the worlcpiece or a counterbore for recessing the screw head below the surface of the workpiece and/or for inserting a plug to conceal the screw head.

Thus, each web may comprise a first section extending in the axial direction from the distal end of the tool head to at least one further section wherein the drive formation is provided by the first section which may also be employed to form the pilot hole with a second section being employed to form the countersink and a third section being employed to form the counterbore.

The first section may extend at a smaller angle relative to a longitudinal axis of the tool head than the second section while the third section may extend parallel to the longitudinal axis of the tool head.

In some forms of the invention, the first section may extend at an angle in the range 10° to 50°, more preferably 20° to 40°, most preferably approximately 30°. The second section may extend at angle in the range 30° to 80°, more preferably 40 ° to 60° and most preferably approximately 45°.

Advantageously, valleys formed between the webs are shaped to guide shavings and/or swarf formed when drilling a hole in a workpiecc away from the distal end and eject the shavings/swarf out of the hole at the rear end of the valleys. For example, the valleys may have a surface that is curved in the direction of rotation to direct the shavings away from the distal end as the tool head rotates. Preferably, the valleys extend into the third section to allow shavings/swan to be ejected when drilling a counterbore in a workpiece.

In some forms of the invention, the tool head forms part of a tool bit for detachable mounting in a chuck of a drill or holder of an adaptable screwdriver. For example the tool bit may have a shank of hexagonal cross-section. In other forms of the invention, the tool head forms an integral part of a drill or screwdriver.

According to another aspect of the present invention there is provided a tool head comprising a drive formation having radial webs co-operable with a drivc formation having slots in which the webs are received on a head of a screw for driving thc screw into a workpiece in response to rotation of the tool head and for removing the screw from the workpiece in response to reversing the direction of rotation of the tool head, whercin at least one web is configured to be urged to engage the material of the screw head to enhance transmission of torque from the tool head to the screw head when removing the screw from the workpiece.

The at least one web may have a bevelled or angled outer face providing a cutting edge on one side of the web that tends to force the web into the material of the screw head when the tool head is rotated in a direction to remove the screw.

The invention will now be described in more detail, by way o example only, with reference to the accompanying drawings, in which: -

D

Figure 1 is a perspective view of a tool bit with a tool head according to the invention; Figure 2 is an enlarged view of the circled area AP in Figure 1; Figure 3 is an end view of the tool bit in the direction of arrow A in Figure 1; Figure 4 is a section on the line AN-AN in Figure 3; Figure 5 is a section on the line AD-AD in Figure 3.

Referring to the drawings there is shown a tool bit having a cylindrical body 2 with a tool head 4 at one end configured for driving a screw (not shown) into and removing a screw from a workpiece (not shown). The body 2 is typically provided with a shank (not shown) which may be of hexagonal cross-section at the other end for insertion in a chuck (not shown) of a drill or tool holder of a screwdriver (not shown).

In this cmbodiment, the tool head 4 has four radial webs 6 uniformly spaced apart to provide a drive formation engageable with a mating drive formation (not shown) in a screw head (not shown) for driving the screw into the workpiece and for removing the screw from the workpiece by reversing the direction of rotation of the tool head 4. It will be understood that we do not intend to be limited to tool heads with four webs and other embodiments may employ more than or less than four webs.

Each radial web 6 tapers towards a distal end of the tool head 4 and preferably terminates in a substantially flat end face 8. The end faces 8 are offset from a central longitudinal axis of the tool head and are preferably uniformly spaced apart to define a cross-shaped recess 10 best shown in Figure 3.

Each web 6 has a first section 12, a second section 14 and a third section 16. The outer faces 12a, 14a of first and second sections 12, 14 extend at an angle to the longitudinal axis of the tool head and the outer face 16a of the third section 16 extends parallel to the longitudinal axis of the tool head 4. A short step 18 is preferably provided between the outer faces 12a, 14a of the first and second sections 12, 14 but this is not essential and the step 18 may be omitted.

As shown, the outer face 12a of the first section 12 extends at a smaller angle to the longitudinal axis than the outer face 14a of the second section 14. For example, the outer face 12a of the first section 12 extends at approximately 27° to the longitudinal axis and the outer face 14a of the second section 14 extends at approximately 45° to the longitudinal axis.

These angles are not intended to be limiting and the sections 12, 14 may extend at other angles with respect to the each other and the longitudinal axis.

The outer faces l2a, 14a of the first and second sections 12, 14 are also bevelled or angled with respect to the direction of rotation about the longitudinal axis. The slope of the angled outer face 12a of the first section 12 is in the opposite direction to the slope of the angled outer face 14a of the second section 14. The outer face 12a may be angled from 1 to 10 degrees in the opposite direction to the outer face 14a. Reversing the slope of the angled outer faces 12a, 14a provides cutting edges l2b, 14b on opposite sides of the webs 6 for a purpose described later.

The tool head 4 further comprises valleys 20 between the webs 6 that extend from the distal end to the body 2. As shown, each valley 20 has a curved surface 20a at the rear end that extends from the end of the second section 14 of the web 6 on one side of the valley 20 to the end of the third section 16 of the web 6 on the other side of the valley 20.

In use of the tool bit, the first section 12 of the webs 6 can be used to form a pilot hole in a workpiece for locating a screw, the second section 14 of the webs 6 can be used to form a countersink for locating a screw head flush with the surface of the workpiece and the third section can be used to form a counterbore for recessing the screw head below the surface of the workpicce.

The curvature of the surface 20a relative to the direction of rotation of the tool head 4 is such that shavings/swarf produced when drilling a hole are ejected rearwardly out of the hole as it is formed and do not inhibit drilling of the hole. The valleys 20 extend into the third section 16 so that shavingslswarf can be ejected without removing the tool head from the hole when drilling a counterbore.

When driving a screw into the workpiece, the first section 12 of the webs 6 provides a drive formation that co-operates with a matching drive formation in the head of the screw to drive the screw into the workpiece when the tool bit is rotated in a clockwise direction. More particularly, the screw head has a socket with pockets configured to receive the webs 6 of the tool head 4 such that torque is transmitted from the tool head 4 to the screw head by engagement of opposed side faces of the webs 6 and pockets according to the direction of rotation of the tool head.

When rotating in the clockwise direction, the cutting edges 12b on the first section 12 of the webs 6 are provided along the trailing side of the webs in the direction of rotation of the tool head 4. When it is desired to remove the screw from the workpiece, the direction of rotation of the tool bit is reversed so that the cutting edges 12b on the first section 12 ol the webs 6 are now along the leading side of the webs 6 in the direction of rotation of the tool head 4. As a result, the cutting edges 12b force the webs 6 into the material, usually metal or alloy, of the screw head as the S tool is rotated in a counterclockwise direction that enhances the engagement between the tool head 4 and the screw head so as to loosen and remove the screw.

This is particularly beneficial if the drive formation on the screw head has been damaged when driving the screw into the workpiece, as the webs 6 force a "lift" or "ledge" from the material forming the damaged drive formation on the screw head so as to allow the screw to be loosened and removed.

In contrast, conventional tool bits having webs that do not have outer edges that are angled to enhance the engagement with the screw head when the direction of rotation is reversed to remove the screw, tend to cause further damage to a damaged drive formation on the screw head with the result that removal of the screw is prevented.

In a modification (not shown), the outer face 12a of the first section 12 of the webs 6 may be serrated, knurled or otherwise configured to enhance further the engagement with the screw head when removing the screw from the workpiece.

It will he understood the invention is not limited to the embodiment above-described. For example, although the invention has been described in a tool bit where the tool head is configured to form a pilot hole, countersink and counterbore, it will be appreciated that this is not essential and the invention includes tool bits where the tool head is configured to facilitate removal of the screw by enhanced engagement with the screw head when the direction of rotation is reversed to remove the screw without necessarily being configured to form a pilot hole, countersink and counterbore as provided in the abovedescribed e rn boW ment.

Other modifications that can be made without departing from the invention will be apparent to those skilled in the art. For example, while the invention has been described with reference to a tool bit that can be detachably mounted in a chuck of a drill or in a holder of a screw driver, it will be understood that a screwdriver may be provided in which the tool bit is integral with a shaft of the screwdriver.

A set of detachable tool bits or screwdrivers with integral tool bits may be provided having drive formations of different sizes and/or different shapes for use with a range of screw having matching drive formations mateable with the drive formations of the tool bit for both driving the screw into and removing the screw from a workpieee.