Note: Descriptions are shown in the official language in which they were submitted.
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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
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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
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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;
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[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.
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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
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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
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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
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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.
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[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
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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
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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.
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