Note: Descriptions are shown in the official language in which they were submitted.
CA 02898480 2015-07-27
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ANTI-SLIP SCREWDRIVER BIT
FIELD OF THE INVENTION
The present invention relates to screwdriver bits for driving respective screw-
heads, and more
particularly, to anti-slip screwdriver bits capable of substantially reducing
the likelihood of
premature disengagement of the screwdriver bit from the screw-head.
BACKGROUND OF THE INVENTION
In present-day manufacturing and construction there are numerous different
screw-head types and
corresponding screwdriver bits in use. For example, in the construction
industry, the two most
commonly used screw-head/screwdriver bit types are the Robertson-type and the
Phillips-type.
Unfortunately, both of these screw-head/screwdriver bit types ¨ as well as
various other screw-
head/screwdriver bit types - have a tendency to "cam-out", i.e. the
screwdriver bit slips up and
out of the screw-head when the applied torque exceeds a threshold. While this
feature can be
employed to prevent application of excessive torque and resulting shearing-off
of the screw-head,
it frequently results in unwanted cam-outs of the screwdriver bits,
particularly when the
screwdriver bit is not exactly aligned with the screw-head. Premature cam-outs
of the
screwdriver bits frequently occur in a violent manner ¨ in particular when
used with power tools
¨ injuring the hand of the user and damaging both the screw-head and the
screwdriver bit. It may
take only one cam-out incident to ruin a new screwdriver bit.
It is desirable to provide an anti-slip screwdriver bit that is capable of
substantially reducing the
likelihood of premature disengagement of the screwdriver bit from the screw-
head.
It is also desirable to provide an anti-slip screwdriver bit that is
implementable with existing
screwdriver bit types.
It is also desirable to provide an anti-slip screwdriver bit that is
employable for driving existing
screw-head types.
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SUMMARY OF THE INVENTION
Accordingly, one object of the present invention is to provide an anti-slip
screwdriver bit that is
capable of substantially reducing the likelihood of premature disengagement of
the screwdriver
bit from the screw-head.
Another object of the present invention is to provide an anti-slip screwdriver
bit that is
implementable with existing screwdriver bit types.
Another object of the present invention is to provide an anti-slip screwdriver
bit that is
employable for driving existing screw-head types.
According to one aspect of the present invention, there is provided an anti-
slip screwdriver bit for
transmitting torque to a screw-head. The anti-slip screwdriver bit comprises a
shaft for receiving
the torque about its longitudinal axis. A screw-head engaging element is
connected to the shaft
for receiving the torque and transmitting the same to the screw-head about the
longitudinal axis.
The screw-head engaging element has a plurality of screw-head engaging
surfaces for being
engaged with respective surfaces of the screw-head. At least two of the screw-
head engaging
surfaces have a recess such that only an outer edge surface area of each of
the at least two screw-
head engaging surfaces is capable of engaging the respective surface of the
screw-head.
According to the aspect of the present invention, there is provided an anti-
slip screwdriver bit
adapted for transmitting torque to a Phillips-type screw-head. The anti-slip
screwdriver bit
comprises a shaft for receiving the torque about its longitudinal axis. A
screw-head engaging
element is connected to the shaft for receiving the torque and transmitting
the same to the screw-
head about the longitudinal axis. The screw-head engaging element has four
pairs of screw-head
engaging surfaces with the screw-head engaging surfaces of each pair facing in
opposite
direction. Each of the screw-head engaging surfaces has a recess such that
only one outer edge
surface area is capable of engaging the respective surface of the screw-head.
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According to the aspect of the present invention, there is provided an anti-
slip screwdriver bit
adapted for transmitting torque to a Robertson-type screw-head. The anti-slip
screwdriver bit
comprises a shaft for receiving the torque about its longitudinal axis. A
screw-head engaging
element is connected to the shaft for receiving the torque and transmitting
the same to the screw-
head about the longitudinal axis. The screw-head engaging element has a square
shaped cross-
section and four screw-head engaging surfaces. Each of the screw-head engaging
surfaces has a
recess such that two outer edge surface areas are capable of engaging the
respective surface of the
screw-head.
According to the aspect of the present invention, there is provided an anti-
slip screwdriver bit
adapted for transmitting torque to an Allen-type screw-head. The anti-slip
screwdriver bit
comprises a shaft for receiving the torque about its longitudinal axis. A
screw-head engaging
element is connected to the shaft for receiving the torque and transmitting
the same to the screw-
head about the longitudinal axis. The screw-head engaging element has a
hexagon shaped cross-
section and six screw-head engaging surfaces. Each of the screw-head engaging
surfaces has a
recess such that two outer edge surface areas are capable of engaging the
respective surface of the
screw-head.
The advantage of the present invention is that it provides an anti-slip
screwdriver bit that is
capable of substantially reducing the likelihood of premature disengagement of
the screwdriver
bit from the screw-head.
A further advantage of the present invention is that it provides an anti-slip
screwdriver bit that is
implementable with existing screwdriver bit types.
A further advantage of the present invention is that it provides an anti-slip
screwdriver bit that is
employable for driving existing screw-head types.
BRIEF DESCRIPTION OF THE DRAWINGS
A preferred embodiment of the present invention is described below with
reference to the
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accompanying drawings, in which:
Figures la and lb are simplified block diagrams illustrating in perspective
views a
Robertson-type anti-slip screwdriver bit according to a preferred embodiment
of the
invention implemented for use with a power tool and a manual screwdriver,
respectively;
Figures lc to le are simplified block diagrams illustrating in a front view
and two
detailed front views, respectively, the screw-head engaging element of the
Robertson-type
anti-slip screwdriver bit according to a preferred embodiment of the
invention;
Figures if and lg are simplified block diagrams illustrating in cross-
sectional views a
Robertson-type anti-slip screwdriver bit according to a preferred embodiment
engaged
with a respective Robertson-type screw-head;
Figure 2 is a simplified block diagram illustrating in a front view the screw-
head
engaging element of a Slot-type anti-slip screwdriver bit according to a
preferred
embodiment of the invention;
Figure 3 is a simplified block diagram illustrating in a front view the screw-
head
engaging element of an Allen-type anti-slip screwdriver bit according to a
preferred
embodiment of the invention;
Figures 4a and 4b are simplified block diagrams illustrating in a side view
and two cross-
sectional views, respectively, a Phillips-type anti-slip screwdriver bit
according to a
preferred embodiment of the invention;
Figures 4c and 4d are simplified block diagrams illustrating in cross-
sectional views
contact areas of the Phillips-type anti-slip screwdriver bit according to a
preferred
embodiment when engaged with a respective Phillips-type screw-head; and,
Figures 5a and 5b are simplified block diagrams illustrating in a front view
and a side
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view, respectively, manufacturing steps of the Phillips-type anti-slip
screwdriver bit
according to a preferred embodiment of the invention.
DESCRIPTION OF THE PREFERRED EMBODIMENT
Unless defined otherwise, all technical and scientific terms used herein have
the same meaning as
commonly understood by one of ordinary skill in the art to which the invention
belongs.
Although any methods and materials similar or equivalent to those described
herein can be used
in the practice or testing of the present invention, the preferred methods and
materials are now
described.
While the description of the preferred embodiments hereinbelow is with
reference to Robertson-
type, Slot-type, Allen-type, and Phillips-type screwdriver bits, it will
become evident to those
skilled in the art that the embodiments of the invention are not limited
thereto, but that the anti-
slip screwdriver bit design is also implementable with various other
screwdriver bit types where
desirable and where the screw-head engaging surfaces are of sufficient size
such as, for example,
PoziDriv0-type, and Pentagon-type.
Referring to Figures la to lg, an anti-slip screwdriver bit 100 for
transmitting torque to a screw-
head according to a preferred embodiment of the invention is provided. The
anti-slip screwdriver
bit 100 is implementable for use with a power tool, as illustrated in Figure
la, or as a manual
screwdriver having shaft 10 and handle 12, as illustrated in Figure lb. The
anti-slip screwdriver
bit 100 comprises a shaft 10 for receiving the torque about its longitudinal
axis 11 for driving the
screw-head. A screw-head engaging element 101 ¨ having length Li between a
proximal end
101A and a distal end 101B thereof- is connected to the shaft 10 for receiving
the torque and
transmitting the same to the screw-head about the longitudinal axis 11. The
screw-head engaging
element 101 has a plurality of screw-head engaging surfaces 102 for being
engaged with
respective surfaces of the screw-head. For example, the screw-head engaging
element 101 has a
square cross-section adapted for engaging a Robertson-type screw-head, as
illustrated in Figures
la to 1g. The screw-head engaging surfaces 102 have a recess 106 such that
only outer edge
surface areas 104A, 104B of each of the screw-head engaging surfaces 102 are
capable of
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engaging the respective surface of the screw-head. Each screw-head engaging
surface 102 has
two outer edge surface areas 104A and 104B with the outer edge surface areas
104A and 104B
having a predetermined width WE and, preferably, extending the length Li of
the screw-head
engaging element 101, as illustrated in Figures la and 1 c.
Optionally, the screw-head engaging element 101 has a slightly tapered distal
portion of length
L2 with the outer edge surface areas 104A and 104B extending the complete
length Li of the
screw-head engaging element 101, as illustrated in Figure la.
Alternatively, provision of the recess is omitted on some of the four screw-
head engaging
surfaces 102. For example, only two oppositely placed screw-head engaging
surfaces 102 have a
recess.
Preferably, the recess 106 has a concave curved surface placed between the two
flat outer edge
surface areas 104A and 104B with a maximum depth DR in proximity of the center
of the screw-
head engaging surface 102, as illustrated in Figure ld. Alternatively, the
recess 106 is differently
shaped such as, for example, having a flat center surface at depth DR and
slopes connecting the
same to the two flat outer edge surface areas 104A and 104B, as illustrated in
Figure le. Figures
lf an lg illustrate the screw-head engaging element 101 placed inside a
respective screw-head.
When the torque is applied in clockwise direction ¨ indicated by the block
arrow in Figure if¨
the outer edge surface areas 104A are engaged with the respective screw-head
surfaces 20. When
the torque is applied in counter-clockwise direction ¨ indicated by the block
arrow in Figure lg ¨
the outer edge surface areas 104B are engaged with the respective screw-head
surfaces 20.
Reducing the contact area between the screw-head engaging element 101 and the
screw-head
surfaces 20 to the outer edge surface areas 104A, 104B substantially increases
the contact
pressure at these contact areas when torque is applied, substantially
increasing friction between
the screw-head engaging element 101 and the screw-head. The increased friction
substantially
reduces the likelihood of slip-up and premature disengagement of the screw-
head engaging
element 101 from the screw-head. The best placement for the contact areas is
at the outer edges
of the screw-head engaging surfaces 102, showing a substantial reduction of
the likelihood of
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premature disengagement compared to conventional screwdriver bit designs, even
when the
screwdriver bit is not in good alignment with the screw-head. The anti-slip
screwdriver bit 100
enables the user to exert less force along the longitudinal axis 11 in order
to keep the anti-slip
screwdriver bit 100 engaged with the screw-head and/or to apply higher torque
loads.
Optionally, the outer edge surface areas are provided with means to further
increase friction such
as, for example, grooves, or ridges.
Referring to Figure 2, an anti-slip screwdriver bit 100 for transmitting
torque to a screw-head
according to another preferred embodiment of the invention is provided. Here,
the screw-head
engaging element 101 comprises two substantially parallel screw-head engaging
surfaces 102
facing in opposite directions to form a Slot-type screwdriver bit. Each screw-
head engaging
surface 102 has recess 106 placed between two outer edge surface areas 104A
and 104B with the
outer edge surface areas 104A and 104B having a predetermined width WE and,
preferably,
extending the length Li of the screw-head engaging element 101. When the
torque is applied in
clockwise direction about the longitudinal axis 11, the outer edge surface
areas 104A are engaged
with respective screw-head surfaces. When the torque is applied in counter-
clockwise direction
about the longitudinal axis 11, the outer edge surface areas 104B are engaged
with the respective
screw-head surfaces.
Referring to Figure 3, an anti-slip screwdriver bit 100 for transmitting
torque to a screw-head
according to another preferred embodiment of the invention is provided. Here,
the cross-section
of the screw-head engaging element 101 is a hexagon-shaped comprising six
screw-head
engaging surfaces 102 forming an Allen-type screwdriver bit or an Allen key.
Each screw-head
engaging surface 102 has recess 106 with depth DR placed between two outer
edge surface areas
104A and 104B with the outer edge surface areas 104A and 104B having a
predetermined width
WE and, preferably, extending the length L 1 of the screw-head engaging
element 101. When the
torque is applied in clockwise direction about the longitudinal axis 11, the
outer edge surface
areas 104A are engaged with respective screw-head surfaces. When the torque is
applied in
counter-clockwise direction about the longitudinal axis 11, the outer edge
surface areas 104B are
engaged with the respective screw-head surfaces.
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It is noted that the invention may be implemented with cross-sections of the
screw-head engaging
element 101 forming other types of convex polygons such as, for example, a
pentagon.
Referring to Figures 4a to 4d, an anti-slip screwdriver bit 100 for
transmitting torque to a screw-
head according to another preferred embodiment of the invention is provided.
Here, the screw-
head engaging element 101 comprises four pairs of screw-head engaging surfaces
102A and
102B, with the screw-head engaging surfaces 102A and 102B being adapted for
engaging a
Phillips-type screw-head. Each pair of screw-head engaging surfaces 102A and
102B forms a
blade 105 of the screw-head engaging element 101 with the screw-head engaging
surfaces 102A
and 102B facing in opposite direction. Each of the plurality of screw-head
engaging surfaces
102A, 102B has one outer edge surface area 104A, 104B capable of engaging the
respective
surface of the screw-head and is recessed towards connecting area 103 with a
neighboring screw-
head engaging surface. When the torque is applied in clockwise direction ¨
indicated by the
block arrow in Figure 4c ¨ the outer edge surface areas 104A of screw-head
engaging surfaces
102A are engaged with respective screw-head surfaces. When the torque is
applied in counter-
clockwise direction ¨ indicated by the block arrow in Figure 4d ¨ the outer
edge surface areas
104B of screw-head engaging surfaces 102B are engaged with respective screw-
head surfaces.
The anti-slip screwdriver bit 100 is, preferably, made of hardened steel such
as, for example,
induction-hardened or surface heat treated steel using conventional forging
and machining
techniques. For example, in a first step, the anti-slip screwdriver bit 100 is
produced employing a
conventional grinding process providing a conventionally shaped screwdriver
bit. In a following
second step, using a different shaped cutting tool, the recess 106 is cut
while leaving the outer
edge surface area 104. Therefore, the anti-slip screwdriver bit 100 is
produced by just adding one
additional grinding step to the same conventional manufacturing process, as
illustrated in Figures
5a and 5b for the manufacturing of a Phillips-type anti-slip screwdriver bit
100. In the first step,
a conventional cutting blade ¨ item 1 in Figure 5a ¨ spins around axis Cl
cutting at arc radius R1
at a depth Dl. In the second step, a modified cutting blade ¨ item 2 in Figure
5a ¨ having a
curved cutting face is employed spinning around axis C2 cutting at a smaller
arc radius R2 and a
slightly deeper depth D2. The second step results in material being cut away
only in the desired
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recess area as the cutting blade leaves the screwdriver bit at locations X,
leaving the outer edge
surface area 104 untouched.
The width WE of the outer edge surface area 104 is determined such that it is
small enough to
provide substantially increased friction while being large enough to prevent
the anti-slip
screwdriver bit 100 from wearing out prematurely. The depth DR and shape of
the recess 106 are
determined to be sufficient to limit contact with the screw-head to the outer
edge surface area
104 while being sufficiently shallow to minimize weakening of the screw-head
engaging element
101. The outer edge surface area 104 and the recess 106 are determined using
standard
engineering and material science technology in dependence upon: the size and
type of the anti-
slip screwdriver bit 100; the maximum torque to be applied; the material of
the anti-slip
screwdriver bit 100; and, the process employed for manufacturing the anti-slip
screwdriver bit
100.
The present invention has been described herein with regard to preferred
embodiments. However,
it will be obvious to persons skilled in the art that a number of variations
and modifications can
be made without departing from the scope of the invention as described herein.
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