CA2893403A1

CA2893403A1 - Fastener driver bit

Info

Publication number: CA2893403A1
Application number: CA2893403A
Authority: CA
Inventors: David Turnbull
Original assignee: Astrotech Services Inc
Current assignee: Astrotech Services Inc
Priority date: 2015-06-01
Filing date: 2015-06-01
Publication date: 2016-12-01

Abstract

A tool set for use in operating recessed head fasteners so that insertion can be carried out without separately supporting the fastener and extraction that allows for axial misalignment between the fastener and the tool. An insertion tool that operates with reduced skipping action so that damage to the tool/fastener interface is minimized and tool life is extended. An extraction tool that operates to transmit torque to the fastener even when the tool axis is not aligned with that of the fastener.
For both tool types. the tip of the tool is shaped to allow axial rotation of the fastener in both clockwise and counter-clockwise directions. For the extraction tooL the tip is also shaped to allow engagement and operation of the bit in situations where the fastener head recess is obscured or obstructed by debris. Both types of bit can be used for insertion and extraction operations as the situation requires. The tools can be used in the form of manually operated screwdrivers or as bits driven by power tools.

Description

FASTENER DRIVER BIT
TECHNICAL FIELD
[0011 The present invention is directed to efficient driving and extraction of fasteners having a square type drive recess or similar drive recesses.
BACKGROUND
10021 This invention provides an improved tool for driving fasteners that require a bit with a square section driving tip. Fasteners such as ROBERTSON screws and the tools required to drive them have been in use for many years and their use is increasing. Such tools and their methods of identification are described in Canadian patent No.

2,318,666.
There are advantages to using fasteners with such enclosed recessed head designs rather than the open slot type, but there has been a continuing need to improve the tools that are used to drive them. The driver tool is commonly produced in the form of a hand operated screwdriver or a power driven bit.
10031 The tools that are presently available for driving these types of fasteners work well if the axis of the tool or driver bit is accurately aligned with the axis of the screw and the axis of the fastener recess in the head of the screw. Sufficient axial force is applied through the driver bit to maintain engagement under the application of torque. However if there is poor alignment and/or insufficient axial force, the driver bit can lose engagement with the recess in the fastener head and slip. During this process the head of the bit is forced partially out of the fastener recess. This "cam out" or "skipping" action usually causes damage to both the fastener and the driver bit. Damage is usually more severe when the bit is power =

driven because many tool rotations typically occur before the drive rotation can be terminated. Also the axial and torsion forces are usually higher when using a power tool compared to a hand-operated screwdriver.
[004] In practice, it is difficult even for an experienced operator to keep a screwdriver or power tool exactly aligned with the screw axis during operation. Misalignment of the screwdriver with the screw axis can occur for a number of reasons, for example where there is restricted or obstructed access or where the screw axis cannot be visually observed. This misalignment can frequently occur during removal of a fastener where the head is countersunk below the surface of the material or where the operator is unable to position and adequately control the tool.
10051 A major feature of the known square driver bits is that the tip can support the fastener during the initial stages of insertion into the desired material.
This characteristic assists the operator during driving of a screw, as only one hand is required to carry out the combined rotation and support functions. . Once the fastener has been inserted sufficiently far to be self-supporting in the material, the axis of rotation of the fastener becomes fixed and any significant misalignment of the screwdriver relative to that axis will cause slippage or skipping of the bit in the screw head recess. The intermittent mechanical disengagement of the bit during rotation can cause significant local damage to the fastener recess and the driver bit.
SUMMARY
10061 The present invention is directed to a new driver bit (insertion tool) as well as a new extraction bit particularly designed for extracting fasteners having a square type recess such _ _ as found in ROBERTSON type fasteners. By appropriately shaping the part of the bit that engages with the fastener recess, the driver bit can continue to provide a rotational torque force to the fastener while the amount of axial force necessary to maintain drive engagement is reduced compared to the force required for existing tools.
[007] For the insertion tool, the bit is shaped to reduce the forces that cause disengagement of the bit while providing the capability of driving fasteners without additional support of the fastener during initial installation. The insertion operation is less prone to the "skipping- effect that is encountered with existing bit designs and the bit of the present invention produces less potential damage to both the fastener and the bit, so the life of the bit is extended if misalignment occurs during operation.
[008] The cxtraction bit is also shaped to provide some clearance from the bottom of the fastener head recess to allow drive engagement and rotation with the presence of debris in the fastener head recess. as may be the case when removing a fastener from an existing location. As the bit is rotated, the grooves in the faces of the bit provide a means for ejection of debris from the fastener head recess. The diameter of the bit at the head of the recess is reduced to allow rotation of the fastener with less skipping, even when the driver axis is misaligned with that of the screw.
DESCRIPTION OF DRAWINGS
[009] Preferred embodiments of the invention are shown in the drawings, wherein:
[0010] Figure 1 is a section through the insertion bit as located in a fastener head recess (partial section across corners) and aligned with the fastener axis;
- .3 -[0011] Figure 2 is a section through insertion bit as inserted into a fastener head recess (partial section across flats) and aligned with the fastener axis;
[0012] Figure 3 is an isometric view of the present invention insertion bit;
[0013] Figure 4 is a view of the insertion bit on the flat side surface of the tip;
[0014] Figure 5 is a view of the insertion bit on the corner edge of the tip;
[0015] Figure 6 is a section of the extraction bit with clearance grooves (on the centreline of the bit);
[0016] Figure 7 is a view of the extraction bit with clearance grooves for debris (looking from the bit drive end);
100171 Figure 8 is a view of the extraction bit with "V" shaped clearance grooves for debris (looking from the bit end);
[0018] Figure 9 is a view of the extraction bit with curved section clearance grooves for debris (looking from the bit end);
[0019] Figure 10 is a sectional view of the tip of the extraction bit when inserted into a fastener recess with its axis inline with the fastener axis;
100201 Figure 11 is an end view of the tip of the extraction bit inserted into a fastener recess with its axis misaligned with the fastener axis; and [0021] Figure 12 is a perspective view of the extraction bit.

DETAILED DESCRIPTION
[0022] As shown in Figure 1 the screw bit 2 includes a shank 4, a drive shaft 6 and a drive head 8 connected to the drive shank 6 by the reduced neck 10. The drive head 8 is sized to provide additional clearance above the drive head and below the upper surface of the drive recess 44 of the screw 40 to improve the drive characteristics of the screw bit 2. The additional space above the drive head 8 provided by the reduced neck 10, concentrates the drive force in a lower portion of the drive recess 44 and as will be further described with respect to the drawings, allows for more effective driving of the screw. In Figure 1 it can be seen that the cross section through the screw bit 2 has been taken between opposed corners of the drive recess 44.
[0023] In Figure 2, the same screw bit 2 and screw 40 are shown however in this case each of these components have been rotated 45 such that the drive recess and the screw bit are orientated as shown. It is important to note that the effective drive surfaces between the screw bit 2 and the screw 40 are generally at the base or in the lower portion of the drive recess 44 and there is a large portion of the upper section of this drive recess that is not being used. Although the drive force is now transmitted via a reduced area in the lower portion of the drive recess, this arrangement is effective. The beneficial feature may be partially explained in that the drive recess includes a taper and the drive engagement adjacent the bottom of the drive recess is tight. This arrangement does not allow any application of torque forces at the head of the fastener recess but maintains sufficient lateral support of the fastener from the shaft 6 fitting into the upper part of the recess.
[0024] The perspective view of Figure 3 shows the particular relationship of the screw bit 2, the shank 4, the drive shaft 6, drive head 8 and the reduced neck 10. The reduced neck provides additional clearance that assists in providing effective drive force transmission to the scrcw 40 even when the screw bit 2 is not perfectly aligned with the longitudinal axis of the screw fastener.
[0025] Figures 4 and 5 are essentially side elevations of the screw bit 2 with Figure 4 corresponding to the orientation of the screw bit as shown in Figure 2 and Figure 5 corresponding to the screw bit in the orientation of Figure 1.
[0026] As perhaps can be appreciated from a comparison of Figures 4 and 5, the reduced neck 10 provides additional clearance between the drive corners 12 of the drive head 8 as these drive corners extend outwardly from and are spaced further from the reduced neck 10. The additional space above the drive head 8 provides certain clearance advantages during driving of screws as generally shown in Figures 10 and 11.
[0027] As shown in Figure 10, the screw bit 2 has been inserted into the drive recess 44 of the screw head 42 and the bit axis is aligned with the fastener axis. With this arrangement the drive head 8 is in good contact with the lower portion of the drive recess 44 and this relationship is effective for both the driving of the screw as well as the extraction of a screw.
[0028] In Figure 11 the bit axis has been angled and is no longer aligned with the fastener axis 50. The bit axis is shown as 52. With this arrangement the drive head 8 on the left hand side of the drive recess 44 as shown in Figure 11 has been moved slightly deeper into the drive recess. On the opposite side the drive head has been rotated slightly upwardly in the drive recess. The reduced neck 10 allows the drive head 8 to remain deeply inserted in the drive recess 44 and effective drive transmission is maintained. In a conventional screw bit there is no reduced neck 10 and the drive head is generally constant or of upwardly increasing size over a portion of the screw bit generally corresponding to the depth of a drive recess. With a conventional bit, angling of the drive bit as shown in Figure 11 would cause the conventional drive bit to be partially withdrawn from the drive recess and the drive force transmission would be from an upper corner of the drive recess to a generally mid point on the opposite side of the recess. With such an arrangement skipping can occur which is reduced or avoided with the drive bit of the present design.
100291 The extraction bit 100 shown in Figures 6 through 12 includes the drive shank 104, the drive shaft 106, a reduced neck 110 and the drive head 108. The extraction bit is specifically designed to assist in removal of screws where the screws have a recess that generally accepts square drive tools and the angle of the screw is not necessarily known, so misalignment of the bit axis and the screw axis may occur as shown in Figure 11. The corners of the drive head 108 are received in the corners of the drive recess 44 of the screw and a portion of the drive head between these corners has been inwardly recessed either by curved arc 120 as shown in Figure 9, or two angled sections 122 shown in Figure 8, or a particular injection groove 124 shown in Figure 7. In each case, the drive head 108 has the corners thereof project substantially outwardly from the diameter that is defined by the reduced neck 110. In this case the corner edges also project somewhat upwardly from the drive head 108 as shown in Figure 6. This will allow more effective biting of the drive head and the upward extensions thereof in the drive recess 44 of the screw (see Figures 10 and 11). With this arrangement it has been found that providing an area where any material that is accumulated in the screw head can be ejected is of assistance. With respect to the drive head, recesses 120, 122 and 124 allow the corners of the drive head 108 to firmly engage thc drive recess of the screw fastener and the screw fastener can be effectively extracted. The particular reduction between the drive head 108 and the drive shaft 106 accommodates unknown angling of the drive head while still allowing effective extraction of the screws.
[0030] The effective diameter of the extraction bit 100 is reduced at the neck 110 to provide for lateral rotation under conditions of axial misalignment. The degree of diameter reduction at the neck reduces the torsional strength of the bit so this reduction should be minimized and is a trade off with respect to the amount of misalignment that the tool can accoinmodate. In practice, this axial misalignment can be limited to approximately 15 (see Figure 11 and misaligned axis 52 relative to aligned axis 50) for bits that are used for driving wood screws as it is difficult to avoid generating a significant side force component on the screw during rotation at greater angles of misalignment.
10031] The grooves at the tip of the bit can be of any shape but the edges should be sharp to aid in dislodging any obstruction in the fastener recess. The grooves in the faces of the bit can be of any width between the corners of the drive section, but the length must allow for ejection of any debris material past the head of the fastener when the bit is inserted into the fastener recess.
[0032] The material of the working tip of the bits can be forged or machined from hardened steel, however the body can be made from material such as 1020 cold rolled hexagonal steel stock or other suitable material. The driver bit shown in the drawings is depicted with a hexagonal body in Figure 3, this being the current convention that most drive systems utilize, however the body of the bit can be of any desired section or length so long as this does not affect the operation of the tool.

[0033] The recess in the head of a ROBERTSON type fastener has slight taper (Fig. 2b) that allows the matching driver tip to provide a tight fit in the head recess and support the fastener while it is being positioned for operation in any orientation from horizontal to vertical and pendant. Ideally, the maximum dimension across the flats of the bit (Fig 1-a) is sized to contact the tapered walls of the fastener recess at a point such that there is a small clearance between the end of the bit and the base of the fastener recess (Figl -b) to prevent the bit bottoming in the recess. In operation, the bit is located in the fastener recess and can be pressed into place by hand. The retention of the fastener with respect to both of the present bit designs may be augmented by magnetic force as used in many currently available adapter devices. The driver, bit and fastener assembly may then be positioned for operation at any orientation.
[0034] Where the fastener is of a machine screw type, it is preferable to manually engage the fastener with the intended recess in the threaded component prior to operation with a powered driver bit.
[0035] These screw bits can be designed for use in association with power drills or can be designed as part of a dedicated hand tool or can be part of a screwdriver that can receive different bits. This design may also be effective with other open cavity drive recesses such as hexagonal or octagonal drive recesses.
[0036] All the prior art designs assume that the fastener head recess has parallel sides, is in ideal condition with no obstruction present and with unrestricted access.
However it is often the case that when screws have to be removed from existing material, the head recess can contain debris such as paint, rust or other granular materials that even in small quantities can prevent the full engagement of an existing driver bit in the fastener head recess. This can cause the driver bit to slip and damage the screw recess. To avoid this. the recess must be completely cleared manually before the bit can achieve proper engagement and this can take an inordinate amount of time particularly when a significant number of fasteners are involved.
[0037] It can also occur that the head of a previously installed fastener is not visible when it is deeply countersunk into material and it is not possible to see its face to engage a driver bit at a suitable angle when extraction is required. The extraction bit design accommodates this situation as it allows for such misalignment in turning of the fastener.
[0038] For the insertion tool, the bit normally contacts the fastener at the base of the recess and at the four upper edges of the recess as shown in figure 2a and 2b. These two levels of contact act to support the fastener during the initial stage of insertion. The tip of the bit contacts the fastener near the base of the recess at the four comer surfaces to transmit drive torque (ref. Figure I a). Figure 2 shows a section of the bit/fastener with rounded part of the bit in contact with the flat sides at the upper edge of the recess. The view in Figure 1 shows the clearance of the bit across the comers of the recess as a result of rounding the part of the bit in that area. The effective diameter of the bit between the two contact levels is reduced so that if the bit is forced out of engagement with the fastener recess due to axial misalignment, the resulting clearance between the bit and the upper edge of the fastener reduces the potential "skipping- effect. Reference the views in Figures 3, 4 and 5.
[0039] In this invention, the tip of the extraction screwdriver or driver bit 100 is shaped so as to allow for misalignment of the driver axis relative to the screw axis and for operation when the screw recess is partially obstructed. The details of the tip shape allow axial rotation of the driver and torque transfer to the screw when a degree of screw/driver axial misalignment occurs. Figure 6 is a section that shows the general shape of the bit that provides drive operation with a fastener axis misaligned from that of the driver bit.
[0040] A perspective view of a preferred structure of the extraction bit 100 is shown in Figure 12.
[0041] Although various preferred embodiments of the present invention have been described herein in detail, it will be appreciated by those skilled in the art, that variations may be made thereto without departing from the scope of the appended claims.

Claims

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. A screw bit engaging a square type drive recess of a screw fastener, said screw bit comprising:
a shank, a drive shaft at an end thereof opposite said shank including a neck of reduced cross section relative to said drive shaft;
a drive head at an end of said neck opposite said drive shaft: and wherein said drive head extends outwardly beyond said neck and includes drive corners positioned to enage drive corners of a square type drive recess of a screw fastener.

2. A screw bit as claimed in claim I wherein said drive head and said neck are of a length greater than a depth of a square type drive recess.

3. A screw bit as claimed in claim 1 or 2 wherein said drive head in a vertical direction is less than 50% of the depth of a square type drive recess of a screw fastener.

4. A screw bit as claimed in claim 1. 2 or 3 wherein said drive head in a direction coaxial with a longitudinal axis of said screw bit has a dimension of 1 mm to 2 mm.

5. A screw bit as claimed in any one of claims 1 to 4 wherein said neck is of a generally circular cross section with a diameter of less than about 3 mm.

6. A screw bit as claimed in claim 5 wherein said neck is inwardly offset from the edges of the drive head to accommodate at least a 15 angulation of the drive bit when received in a square type drive recess without the neck striking the square type drive recess.

7. A screw bit as claimed in claim 1 wherein said screw bit is an extraction screw bit with said drive head between said drive corners being inwardly recessed to define extraction grooves.

8. A screw bit as claimed in any of claims 1 to 7 that allows for operation in a partially obstructed drive recess.