GB2445546A

GB2445546A - Screw and driver bit

Info

Publication number: GB2445546A
Application number: GB0700304A
Authority: GB
Inventors: Paul John Owen
Original assignee: Individual
Current assignee: Individual
Priority date: 2007-01-09
Filing date: 2007-01-09
Publication date: 2008-07-16
Also published as: GB0700304D0

Abstract

A screw and driver bit combination is described. The combination comprises: a screw 2 with a screw head 4, a threaded shank 6, and a turning axis (Figure 8, 30). The screw head 4 has a top surface 8 and a base 10, which is connected to the shank 6, the screw head 4 also includes at least three socket portions (Figure 4, 12) spaced substantially equally about the turning axis; each socket portion (Figure 4, 12) including a face (Figure 4, 14) which undercuts the top surface 8. The driver bit (Figure 5, 18) comprises: a blade 22 for each socket portion (Figure 4, 12), where each blade has a driving face 26, which is a complementary fit for the undercut face (Figure 4, 14) of the socket portion (Figure 4, 12). The arrangement is such that the bit (Figure 5, 18) may be inserted into the screw head (4) with each blade 22 located in a corresponding socket portion (Figure 4, 12), in an insertion position, with the driving face 26 disengaged from the undercut face (Figure 4, 14). The bit may then be turned about the turning axis (Figure 8, 30) to an engagement position in which each driving face 26 is engaged with the corresponding undercut face (Figure 4, 14); where further turning of the bit (Figure 5, 18) when in the engagement position, causes the turning of the screw 2, so that the engagement between each driving face and each undercut face substantially prevents relative movement between the bit (Figure 5, 18) and the screw head 4 along the turning axis (Figure 8, 30) when the bit (Figure 5, 18) and screw head 4 are in the engagement position.

Description

SCREW AND DRIVER BIT

BACKGROUND

a. Field of the Invention

The invention relates to a screw having a novel design of screw head, and to a driver bit for use with the screw. The term screw' is used herein to refer to a threaded fastener having a screw head and a shank having a screw thread on at least a part of its length. The term includes screws and bolts.

b. Related Art Conventional screws suffer from problems of sliooaae or disengagement of the drive bit from the screw head. This slippage can cause damage to the work being fixed or even personal injury. Many designs have been suggested to try to overcome such problems, including US 6,526,851, US 7,013,767, US 2005/249573, US 2003/2301 76, JP 2000230526 and JP 2006153251, but none is entirely satisfactory.

SUMMARY OF THE INVENTION

According to an aspect of the present invention there is provided a screw and driver bit combination comprising: (a) a screw comprising a screw head and a threaded shank having a turning axis, the screw head having a top surface and a base which is connected to the shank, the screw head including at least three socket portions spaced substantially equally about the turning axis, each socket portion including a face which undercuts the top surface; and (b) a driver bit having a blade for each socket portion, each blade having a driving face which is a complementary fit for the undercut face of the socket portion; the arrangement being such that the bit may be inserted into the screw head with each blade located in a corresponding socket portion in an insertion position with the driving face disengaged from the undercut face, and then turned about the turning axis to an engagement position in which each driving face is engaged with the corresponding undercut face, further turning of the bit when in the engagement position causing turning of the screw, and the engagement between each driving face and each undercut face substantially preventing relative movement between the bit and the screw head along the turning axis when the bit and screw head are in the engagement position.

The invention provides a screw and bit combination in which separation of the bit from the screw head is not possible when the bit has been turned to the engagement position. Turning the bit to the engagement position is akin to turning a key n a lock, and enab'es the screw to be fully driven without risk of unintended separation of the bit from the screw head. The invention also eliminates or reduces the need for the operator to exert force in the direction of drive.

In a preferred embodiment the bit has three blades and the screw head has three corresponding socket portions. The invention will for convenience be described with reference to this embodiment; however it will be understood that the invention is not limited to this embodiment, but could instead be implemented for bits with more blades, for example four or five blades, and screws with corresponding numbers of socket portions.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be further described, by way of example only, with reference to the following drawings, in which: Figure 1 is a perspective view of a screw in accordance with an aspect of the present invention; Figure 2 is perspective view from above and to one side, of the screw head of the screw of Figure 1; Figure 3 is a top plan view of the screw head of Figure 2; Pigure 4 is a skeletal view of the screw head of Figure 3, showing the internal shape and configuration of the socket portions; Figure 5 is a perspective view of a driver in accordance with another aspect of the invention, for use with the screw of Figure 1; Figure 6 is a plan view of the tip of the driver, taken along section Si of Figure 5; Figure 7 is a perspective view of the tip shown in Figure 6; Figure 8 is a perspective view showing a screw and bit in accordance with an embodiment of the invention; and Figure 9 is an action sequence for the bit and screw of Figure 8, illustrating clockwise turning of the bit in the screw head,

DETAILED DESCRIPTION

The screw 2 shown in Figure 1 comprises a screw head 4 which is joined at its base 10 to a screw-threaded shank 6. The shank 6 is of a type known per se and may be of any design or shape; in this example the shank 6 is cylindrical but it could alternatively be conical or tapered. The screw head 4 and shank 6 may be integrally formed.

The screw head 4 is of the counter sunk type has a top surface 8 in which is formed three socket portions 12 which are substantially equally spaced about the central turning axis of the screw 2. in this example, the socket portions 12 are each part of a single opening in the top surface 8; however it would also be possible to form each socket portion 12 as a separate socket, discrete from the oLiels. The socket porons 12 re ent!re!y surroundeci by the top surface 8 of the screw head 4, which can be screwed into a work piece so that the top surface 8 is flush with its surround.

As best shown in Figures 2-4, each socket portion 12 includes a face 14 which undercuts the top surface 8, and a side wall 15. In this example, the undercut face 14 slopes evenly and inwardly from the top surface 8 towards the base 10. The side wall 15 in this example is substantially planar.

Turning now to Figure 5, a driver 16 for use with the screw head 4 is shown. The driver 16 comprises a bit 18 and a driver shank 20. The shank 20 may be of any shank design known per se in the art. In this example, the shank 20 has a hexagonal section for securing in the chuck of an electric screwdriver motor or electric drill. Alternatively the shank 20 could be shaped and sized for manual use as a hand-held screwdriver. The shank 20 and bit 18 may be integrally formed.

The driver bit 18 has three blades 22 which are substantially equally spaced about the turning axis of the bit and which are shaped to fit in the socket portions 12 of the screw head 4. The bit 18 in this example terminates in a flat tip 24 which is a fit for the base 10 of the screw head 4. The shape of the driving portion of the bit 18 is best shown in Figures 6 and 7. Each blade 22 has a driving surface 26 which slopes inwardly towards the tip 24 and which is a complementary fit for the undercut face 14 of the socket portion 12 of the screw head 4. Each blade 22 also has a side surface 28 which is a complementary fit for the side wall 15 of the socket portion 12 of the screw head 4.

In operation, the bit 18 of the driver 16 is inserted (Figure 8) into the screw head 4 of the screw 2 along the turning axis 30. In the initial insertion position shown in Figure 9a, the side surface 28 of each blade 22 is adjacent to the side wall 15 of each socket portion 12. Turning of the bit clockwise from this initial insertion position brings the side surface 28 away from the side wall 15 (Figure 9b) but does not initially turn the screw 2. When the bit has turned through an angle a to the engagement position shown in Figure 9 drMng face 26 of each blade 22 is brought into engagement with the undercut face 14 of each socket portion 12 The angle a is preferably in the range 20-36 ; in this example, the angle a is about 28 (about half a radian). In the engagement position, torque can be efficiently transferred through the mating engagement of the driving faces 26 and undercut faces 14. Also, the bit 18 is securely locked in the screw head 4 so that relative translational motion between the bit 18 and screw head 4 along the turning axis 30 is substantially prevented and the bit cannot be removed. The significant angular separation between the initial insertion position and the engagement position helps prevent inadvertent release of the bit 18 from the screw head 4 during any momentary rest from driving the screw 2 into a work piece.

Once the engagement position shown in Figure 9c has been reached, further turning of the bit 18 causes corresponding turning of the screw 2 (Figure lOd), while the bit 18 remains locked in the screw head 4. Because the bit and screw head are locked together it is not necessary for the operator to exert force into the direction of drive to maintain engagement, as is typically needed when using prior art screws and bits.

Undoing the screw fixing is achieved by turning the bit 18 in the opposite direction, reversing the sequence of motions illustrated in Figure 9. With the side surface 28 of the blade 22 in mating engagement with the side wall 15 of the socket portion, anti-clockwise turning of the screw 2 is possible. With this movement, the locking feature is not operational so the arrangement works in the manner of prior art screws and bits.

In this example, screw fastening was achieved by turning the screw clockwise. It will be understood that the invention is equally applicable to screws having a threaded shank of opposite handedness, by using a screw head and bit which are a mirror image of the exemplified design.

Claims

1. A screw and driver bit combination comprising: (a) a screw comprising a screw head and a threaded shank having a turning axis, the screw head having a top surface and a base which is connected to the shank, the screw head including at least three socket portions spaced substantially equally about the turning axis, each socket portion including a face which undercuts the top surface; and (b) a driver bit having a blade for each socket portion, each blade having a driving face which is a complementary fit for the undercut face of the socket portion; the arrangement being such that the bit may be inserted into the screw head with each blade located in a corresponding socket portion in an insertion pusdui with the driving face dengaged from the undercut face, and then turned about the turning axis to an engagement position in which each driving face is engaged with the corresponding undercut face, further turning of the bit when in the engagement position causing turning of the screw, and the engagement between each driving face and each undercut face substantially preventing relative movement between the bit and the screw head along the turning axis when the bit and screw head are in the engagement position.

2. A combination according to claim 1, wherein each socket portion has a side wall and each blade has a side surface which is a complementary shape to mate with the side wall.

3. A combination according to claim 2, wherein each side wall is adjacent to a side surface when the bit is in the screw head in the insertion position.

4. A combination according to claim 2 or claim 3, wherein each side surface and each side wall are substantially planar.

5. A combination according to any preceding claim, wherein the bit will turn through an angle in the range 20-36 between the insertion position and the engagement position.

6. A combination according to claim 5, wherein the bit will turn through an angle of about 28 between the inserUon position and the engagement position.

7. A combination according to any preceding claim, wherein the undercut face slopes evenly and inwardly from the top surface to the base of the screw head.

8. A combination according to any preceding claim, wherein the socket portions are part of a single opening in the top surface.

9. A combination according to any preceding claim, wherein the bit has three blades.

10. A screw and driver bit combination substantially as herein described with reference to or as shown in the drawings.

11. A screw having a screw head substantially as herein described with reference to or as shown in any of Figures 1-4 of the drawings.

12. A driver bit substantially as herein described with reference to or as shown in any of Figures 5-7 of the drawings.