Note: Descriptions are shown in the official language in which they were submitted.
CA 02189026 2000'U8'15
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EXIT LOCATING COLLATED SCREW
STRIPS AND SCREWDRIVERS THEREFORE
Scope of the Invention
This invention relates generally to a screwdriver
for driving collated screws which are joined together in a
strip, and a novel collated screw strip adapted to
facilitate alignment of screws in the screwdriver.
Background of the Invention
Collated screws are known in which the screws are
connected to each other by a retaining strip of plastic
material. Such strips are taught, for example, by U.S.
Patent 4,167,229 issued September 11, 1979 and related
Canadian Patents 1,040,600 and 1,054,982. Screws carried
by such strips are adapted to be successively incrementally
advanced to a position in alignment with and to be engaged
by a bit of a reciprocating, rotating power screwdriver and
screwed into a workpiece. In the course of the bit engaging
the screw and driving it into a workpiece, the screw becomes
detached from the plastic strip leaving the strip as a
continuous length.
In the use of such collated strips in ,
screwdrivers, the strip serves a function of assisting in
guiding the screw into a workpiece and, to accomplish this,
the strip is retained against movement towards the
workpiece. In the strip, each screw to be driven has its
r , a CA 02189026 2000-08-15
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threaded shaft threadably engaged in a threaded sleeve of
the strip such that on the screwdriver engaging and rotating
each successive screw, the screw turns within the sleeve
which acts to guide the screw as it moves forwardly into
threaded engagement into the workpiece. Preferably, only
after the tip of the screw becomes engaged in the workpiece,
does the head of the screw come into contact with the
sleeves. Further forward movement of the screw into the
workpiece then draws the head downwardly to engage the
sleeve and to rupture the sleeve by reason of the forward
movement of the head with the strip retained against
movement towards the workpiece. The sleeve preferably is
configured to have fragible straps which break on the head
passing through the sleeve such that the strip remains
intact as a continuous length. Since the strip is a
continuous length, on advancing the strip with each
successive screw to be driven, it necessarily results that
portions of the strip from which each screw has been driven
are also advanced to exit from the power screwdriver.
Known power screwdrivers for driving such collated
strips include U.S. Patent 4,146,871 to Mueller et al,
issued March 27, 1976, and U.S. Patent 5,186,085 to
Monacelli, issued February 16, 1993. Such known
power screwdrivers include a rotatable and reciprocally
moving screwdriver shaft which is turned in rotation by an
electric motor. A screwdriving bit forms a forwardmost
portion of the shaft for engaging the head of each
successive screw as each screw is moved into a driving
position, axially aligned under the screwdriver shaft.
An important aspect of such power screwdriver is
the manner and accuracy with which each successively
advanced screw is positioned so as to be properly aligned
axially under the screwdriver shaft for successful initial
and continued engagement between the bit and the screwdriver
head in driving a screw fully down into a workpiece. In the
devices of Mueller et al and Monacelli, the strip is
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effectively held in position, notably, by reason of the
device grabbing and fixing the position of the screw beside
~ the screw to be driven. These devices also teach location
of a screw to be driven in part by the head of the screw to
be driven engaging the surface in a guide channel in which
the screwdriver bit is reciprocal. In each of Mueller et al
and Monacelli, a specific footplate is provided to grasp and
fix the position of the screw beside the screw to be
driven. The footplate engages a workpiece and is spring
biased towards the workpiece. On the device being brought
into engagement with the workpiece, the footplate retracts
towards the device. The footplate has a conical recess
which engages the tip of the screw next to the screw to be
driven and applies a force to that screw pushing it
rearwardly so that its head bears on a locating plate in the
screw feed mechanism. By reason of this next screw being
firmly clamped between the footplate and locating plate, the
strip is effectively locked into position and thereby
positions the screw which is to be driven. Such footplates,
however, have the disadvantage of being separate movable
parts which must move forwardly to permit successive screws
to be advanced and then rearwardly to clamp the next screw.
Another disadvantage of prior art devices in which
the device grabs the screw beside the screw to be driven is
that such systems do not permit the very last screw in any
strip to be driven without possible difficulties. The last
screw therefore frequently has to be discarded and/or may
result in jamming. This is a particular disadvantage where
screws are collated into strips which do not have a large
number of screws. For example, in a simple strip of twenty-
four screws, to discard every twenty-fourth screw is a
substantial disadvantage.
Another disadvantage of prior art devices
appreciated by the applicant is that screw advance
mechanisms such as those used in U.S. Patent 4,146,871
utilize pawls which on withdrawal of the pawl so as to be in
a position to advance the next successive screw of the screw
WO 95129794 PCT1CA95/00253
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strip tend to frictionally engage and to some extent
withdraw the entire screw strip when this is not required.
Such "feed pawl drawback" is disadvantageous insofar as it
can withdraw a screw to be driven from axial alignment with
the driver shaft. '
Summary of the Invention
Accordingly, to at least partially overcome the
disadvantages of previously known systems, the present
invention provides an improved screwdriver assembly which
supports the strip adjacent the screw to be driven on the
exit side of the screw.
An object of the present invention is to provide a
screwdriver assembly for driving collated screws which has
fewer parts and/or is inexpensive to manufacture.
Another object is to provide an improved collated
strip containing screws which includes locating devices on
the strip to assist in locating screws to be driven.
Another object is to provide a collated screw
strip and screwdriver therefore which avoids difficulties
with "feed pawl drawback".
The present invention provides in the context of
collated screws or other fasteners collated together by a
continuous strip which remains intact after a screw has been
driven from the strip, a screwdriver assembly which at least
in part locates a screw to be driven by providing a
rearwardly directed strip supporting surface forward of the
strip to engage an exiting portion of the strip from which a
screw has been driven. The strip supporting surface may be
complementarily shaped to the surface of the strip to be
engaged. In a preferred embodiment, the strip supporting
surface may have a projection or a notch to engage with a
respective complementary notch or projection in a
forwardmost surface of the strip to more positively locate
the strip.
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The locating system comprising the strip
supporting surface and complementary strip may be used alone
' or in conjunction with one or more other locating features
such as those in which the head of a screw is engaged within
~ a guideway. The locating system of the strip supporting
surface and complementary strip is advantageous in
permitting the last screw in a strip to be driven.
In one of its aspects, the present invention
provides a screwdriver assembly to drive screws collated
together in a strip spaced in parallel -relation from each
other, the screwdriver comprising:
a cylindrical guideway to receive a screw
coaxially therein,
a screw-and-strip entranceway opening generally
radially into the guideway on a first side thereof,
a strip exitway opening generally radially out of
the guideway on a second side thereof opposite the
entranceway,
the guideway entranceway and exitway juxta-
positioned to permit screws collated in a strip spaced in
parallel relation from each other to be successively
advanced through the entranceway radially into the guideway
to locate each successive screw coaxially within the
guideway with portions of the strip from which screws have
been driven extending from the guideway via the exitway,
elongate, rotatable driver shaft means having at a
forward end bit means, the shaft means reciprocally movable
axially in the guideway to engage the screw with the bit
means and drive the screw axially forwardly from the
guideway into a workpiece,
the exitway having an axially, rearwardly directed
' strip supporting surface axially forward of the strip for
engagement by the strip to support the strip against
movement forwardly on the shaft means driving a screw
axially forwardly.
Preferably, the strip supporting surface includes
a screwdriver assembly as claimed in claim 1 wherein the
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strip supporting surface includes support locating deans to engage
in registry with strip locating means on the strip to locate the
strip in a desired position to assist in maintaining the screw
coaxially disposed within the guideway.
In one of its aspects, the present invention provides a
screwdriver assembly to drive threaded fasteners collated
together in a strip spaced in parallel relation from each other,
the screwdriver comprising:
a cylindrical guideway to receive a fastener coaxially
therein,
a fastener-and-strip entranceway opening generally
radially into the guideway on a first side thereof,
a strip exitway opening generally radially out of the
guideway on a second side thereof opposite the entranceway,
the guideway, the entranceway and the exitway
juxtapositioned to permit fasteners collated in a strip spaced
in parallel relation from each other to be successively advanced
through the entranceway radially into the guideway to locate each
successive fastener coaxially within the guideway with portions
of the strip from which fasteners have been driven extending from
the guideway via the exitway,
an elongate, rotatable driver shaft having at a forward
end a bit, the shaft reciprocally movable axially in the guideway
to engage the fastener with the bit and drive~the fastener
axially forwardly from the guideway into a workpiece,
the exitway having an axially, rearwardly directed strip
supporting surface axially forward of the strip for engagement
by the strip to support the strip against movement forwardly on
the shaft driving a fastener axially forwardly.
In another of its aspects, the invention provides in
combination:
(a) a screw driver assembly to drive screws collated
together in a strip spaced in parallel relation from each other,
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the screwdriver comprising:
a guideway to receive a screw coaxially therein,
a screw-and-strip entranceway opening generally radially
into the guideway on a first side thereof,
a strip exitway opening generally radially out of the
guideway on a second side thereof opposite the entranceway,
the guideway, the entranceway and the exitway
juxtapositioned to permit screws collated in a strip spaced in
parallel relation from each other to be successively advanced
through the entranceway radially into the guideway to locate each
successive screw coaxially within the guideway with portions of
the strip from which screws have been driven extending from the
guideway via the exitway,
elongate, rotatable driver shaft means having at a
forward end bit means, the shaft means reciprocally movable
axially in the guideway to engage the screw with the bit means
and drive the screw axially forwardly from the guideway into a
workpiece,
the exitway having an axially, rearwardly directed strip
supporting surface axially forward of the strip for engagement
by the strip to support the strip against movement forwardly on
the shaft means driving a screw axially forwardly, and
(b) a plastic holding strip holding screws spaced in
parallel side-by-side relation from each other,
the strip having joining lands which extend both between
the screws and axially relative the screws, and
the lands having a forwardly directed surface for
engagement with the strip supporting surface of the exitway.
In another of its aspects, the invention provides in
combination:
(a) an apparatus for driving with a power driver
fasteners such as screws or the like, which are joined together
in a strip comprising:
housing means;
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elongate drive shaft means for operative connection to a
power driver for rotation thereby and defining a longitudinal
axis;
slide body means coupled to the housing means for
displacement parallel to the axis of the drive shaft means
between an extended position and a retracted position;
spring means biasing said body means forwardly relative
to the housing means parallel the axis to the extended position;
guide channel means for said fastener strip extending
through said body means;
the body means including guide tube means coaxially about
the axis of the drive shaft means adapted to receive
correspondingly sized screws when advanced therein via the guide
channel means and to locate the screws axially in alignment with
said drive shaft means for engagement in driving of the screws
from the guide tube means by the drive shaft means;
an axially, rearwardly directed strip supporting surface
carried on the guide tube means axially forward of the strip for
engagement by the strip to support the strip against movement
forwardly on the shaft means driving a screw axially forwardly,
the strip supporting surface immovably mounted on the
guide tube means against movement relative the slide body means
during normal operation of the apparatus to successively advance
and drive screws, and
(b) a plastic holding strip holding screws spaced in
parallel side-by-side relation from each other,
the strip comprising spaced parallel sleeves
interconnected by joining webs with one of the screws received
in each sleeve, the joining webs extending both between adjacent
sleeves and axially relative the screws,
the strip having a forwardly directed surface on the
sleeves and webs for engagement with the strip supporting
surface,
each screw having a head at one rear end, a tip at the
CA 02189026 2000-OS-18
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other forward end and a threaded shank extending from below the
head to the tip,
each screw received in each sleeve spaced a uniform
distance from each adjacent screw with the screw's dead extending
from one rear end of the sleeve and the screw's tip extending
from the other forward end of the sleeve,
the forwardly directed surface being spaced a constant
distance rearwardly from the tips of the screws,
the sleeve threadably engaging the threaded shank, the
sleeve having a reduced strength portion between the lands such
that a screw on being threaded tip first into a workpiece is
automatically separated from its sleeve while simultaneously
maintaining the length of the strip substantially intact and
while guiding the screw by threaded engagement of the screw in
its respective sleeve.
In another of its aspects, the invention provides in
combination a holding strip and a plurality of threaded
fasteners,
the strip holding the fasteners spaced from one another
in a row,
the strip comprising spaced parallel sleeves
interconnected by lands with one of the fasteners received in
each sleeve,
each fastener having a head at one rear end, a tip at the
other forward end and a threaded shank extending from below the
head to the tip,
each fastener received in each sleeve spaced a uniform
distance from adjacent fasteners with the fastener's head
extending from one rear end of the sleeve and the fastener's tip
extending from the other forward end of the sleeve,
the sleeve threadably engaging the threaded shank,
the sleeve having a reduced strength portion between the
lands such that a fastener on being threaded tip first into a
workpiece is automatically separated from its sleeve while
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simultaneously maintaining the length of the strip substantially
intact and while guiding the fastener by threaded engagement of
the fastener in its respective sleeve,
the lands having a forwardly directed surface between the
sleeves adapted to support the strip,
the forwardly directed surface being spaced a constant
distance rearwardly from the tips of the fasteners.
Brief Description of the Drawings
Further aspects and advantages of the present invention
will be apparent from the following description taken together
with the drawings in which:
Figure 1 is a pictorial front view of a power driver in
accordance with U.S. Patent 4,146,071 modified to.incorporate a
guide tube in accordance with a first preferred embodiment of the
present invention and having a slide body in an extended
position;
Figure 2 is a cross-sectional top view of the power
driver of Figure 1 along section line II-II';
Figure 3 is a schematic cross-sectional front view of the
power driver of Figure 2 along section line III-III';
Figure 4 is an exploded partially pictorial view of the
front of the slide body of the power screw driver together with
the guide tube as shown in Figures 1, 2 and 3;
Figure 5 is a partial cross-sectional top view along
section line V-V' in Figure 4 with the guide tube inserted in the
slide body;
Figures 6 and 7 are views similar to Figures 4 and 5 but
with the guide tube and slide body modified to have a
configuration in accordance with a second embodiment;
Figures 8 and 9 are views the same as Figures 6 and 7
respectively but with the guide tube modified to have a
configuration in accordance with a third embodiment;
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Figure 10 is a perspective view of a screw strip in
accordance with a fourth embodiment of the present invention
having locating notches or slots;
2189Q26
WO 95119794
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Figure 11 is a view similar to that of Figure 4
showing the guide tube of Figure 4 modified for use with the
notched screw strip of Figure 8;
Figures 12 and 13 show the embodiment of Figure 11
' with the screw strip in different relative positions in a feed
cycle;
Figure 14 is a pictorial view of a guide tube in
accordance with a fifth embodiment of the present invention
adapted-for use with the notched screw strip of Figure 10;
Figure 15 shows a perspective view of a screw strip
in accordance with a fifth embodiment of the present
invention;
Figure 16 is a front elevation view of one screw in
the strip of Figure 15;
Figure 17 is a cross-sectional end elevation view of
the strip in Figure 16 along line 17-17';
Figure 18 is a cross-sectional end elevation view of
the strip of Figure 16 along line 18-18'; and
Figure 19 is a rear view of the strip of Figure 16.
Detailed Description of the Drawings
Reference is made first to Figures 1, 2, and 3 which
show in part an electrically powered screwdriver 10 of the
type disclosed in U.S. Patent No. 4,146,071. The screwdriver
is used in driving screws 12 which have been collated and
secured together in a parallel spaced relationship by a
retaining strip 14 preferably of plastic. Such strips 14 are
taught in U.S. Patent No. 4,167,229.
The screwdriver 10 includes a chuck 18 which is
rotated by an electric motor of a power driver not otherwise
shown. The chuck 18 engages an end of an elongate metal shaft
best seen in Figure 3 consisting of a generally cylindrical
metal mandrel 22 having removably secured to a lowermost end
thereof, an axially aligned metal bit 24. The bit 24 defines
W095129794 ~ ~ g ~ ~ ~ 5 PCT/CA95/00253
_ g
at a- forwardmost end a screwdriving tip 23, adapted for
engaging a complementary shaped recess 13 formed in the head
16 of the screw 12. In a manner described in greater detail
hereafter, while rotating, the mandrel 22 carrying the bit 24
is reciprocated within cylindrical guideway in a guide tube 26
to engage and drive successive screws 12 into a workpiece
28. The guide tube 26 is secured in slide body 52. The
screwdriver 10 of the present invention in essence has
identical elements and operates to drive screws in an
identical manner to that disclosed in U.S. Patent 4,146,871.
In this regard, as best seen in Figures 1, 2 and 3,
the screwdriver has a housing 70 to which a power driver (not
shown) is fixed by the power driver's chuck 18. Slide body 52
is coupled to housing 70 for sliding displacement parallel to
a longitudinal axis through the shaft 20 between an extended
position as shown in Figure 1 and a retracted position shown
in Figure 3. Coil spring 66 biases the slide body 52 relative
to the housing 70 to the extended position. The slide body 52
includes a guide channel for the screw strip 14 carrying the
screw 12. The guide channel is defined under a removable
cover plate 72 shown in Figure 1 and removable by thumb screw
74. The guide channel is best shown in the enlarged view of
the front of the slide body in Figure 4 with the cover plate
72 removed. In Figure 4, a groove 76 receives the head of a
screw 12 with the top of a screw engaging surface 77. A screw
feed advance mechanism is mounted in slide body 52 and
activated by relative movement between the housing 70 and the
slide body 52. In this regard, pawl arm 78 shown in Figures 3
and 4 reciprocates back and forth to advance successive
screws. Pawl arm 78 is moved by a mechanical linkage
including lever 68 moved by wheel 80 engaging ramped surface
82 of the housing 70 shown in Figures 1 and 3 on the slide
body 52 reciprocating between extended and retracted
positions.
Figures 4 and 5 show a guide tube 26 adapted to be
removably secured in a cylindrical bore 54 which extends
through slide body 52, and in this regard, each has a
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complementary shape. To locate the guide tube 26 within the
bore against axial rotation, one side of the guide tube has a
flat external surface 79 to mate with a corresponding flat
surface 81 in the otherwise generally cylindrical bore 54.
The exterior of the guide tube has a stepped configuration
with a reduced diameter rear section 82 and a larger diameter
main portion 83 with a rearwardly directed shoulder 84
therebetween. The bore 54 is similarly shaped to axially
locate the guide tube as best seen in Figure 5 with a
corresponding forwardly directed shoulder 85 in the bore 54.
As seen in Figure 4, a slot 86 is cut into the guide tube into
which slot the rearmost left hand corner of the cover plate 72
shown in Figure 1 will fit such that the cover plate will
retain the guide tube 26 secured in place.
The slide body 52 carries a foot plate 200 which is
slidably mounted to the slide body 52 for sliding in a
direction parallel the longitudinal axis of the shaft 20
between an extended position shown in Figure 1 and a retracted
position shown in Figure 3. The foot plate 52 is biased to
the extended portion by a spring (not shown) acting between
the foot plate and the slide body. The foot plate 200 has a
touchdown surface 202 to engage a workpiece, an opening 204
through which a screw 12 is to be driven, and a conical
locating recess 206 best seen in Figure 3.
The present invention is focused on features of the
guide tube 26 and its interaction with screw strip 14. A
cylindrical bore or guideway 32 extends axially through the
center of the guide tube 26 with the guideway 32 delineated
and bordered by a radial extending cylindrical sidewall 34,
and open at its forward axial end 36 and its rearward axial
end 38.
Portions of the side wall 34 are removed to provide,
. firstly, an entranceway generally indicated as 48 for the
strip carrying each successive screw 12 to enter the guide
tube 26 on an entry side of the tube and, secondly, an exitway
generally indicated as 50 on the exit side of the guide tube
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26 opposite the entry side for the strip 14~ from which the
screws have been driven to exit guide tube 26.
The entranceway 48 is sized so as to permit the
strip carrying a screw to enter the guideway 32 moving
generally radially While being maintained parallel to the axis
of the guide tube. The exitway 50, is provided of a size to
permit the spent plastic strip 14~ from which screws 12 have
been driven to exit from the guideway 32.
As best seen in Figure 4, the exitway 50 is defined
by forward surface 93, side surface 94 and rear surface 95.
The forward surface 93 is provided as seen in Figure
4 by a portion 96 of the sidewall 34 forward of the exitway 50
being retained between flat surface 79 and a parallel inner
surface 97 extending upwardly from where it is tangent to the
inner sidewall 34.
The forward surface 93 is provided as an axially,
rearwardly directed strip supporting surface which is axially
forward of the strip for engagement of the strip to support
the strip against movement forwardly on the shaft 20 driving a
screw forwardly. As best seen in Figure 5, the forward
surface in effect provides a rearwardly directed shoulder to
engage a forward surface 122 of the strip 14 and prevent its
forward movement. With the forward surface 93 and the forward
surface 122 of the strip 14 having complementary shapes, as
shown with both being flat and planar in Figure 5, their
engagement assists in holding a screw axially in alignment
with the bit 24.
Similar to forward surface 93, the rear surface 95
of the exitway 50 as shown in Figure 5 is provided as an
axially, forwardly directed strip supporting surface which is
axially rearward of the strip 14. The rear surface 95 in
effect provides a forwardly directed shoulder which can engage
a rear surface 123 of the strip 14 to assist in maintaining
the strip 14 guided within the exitway 50.
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The guide tube 26 is indicated as having a rearward
portion 40 adjacent the rearward axial end 38 and a forward
portion 46 adjacent the forward axial end 36. In rearward
portion 40 of the guide tube 26, the sidewall 34 preferably
~ extends 360°. As seen best in Figure 4, the forward portion
46 is shown as having a first engagement section 42 and a
forwardmost section 44.
The forward position 46 has substantially throughout
its length the entranceway 48, shown in the drawings as being
on the right hand side of the guide tube 26. This entranceway
or access opening 48 extends to the forward axial end 36 of
the guide tube 26. The entranceway 48 is sized to permit the
strip 14 carrying a screw 12 to move radially inwardly into
the guideway 32 from the right as seen in the Figures. As the
screw preferably has a screw head diameter marginally smaller
than the diameter of the sidewall 34, it follows that where
the head of the screw is to enter the guideway 32, the
entranceway 48 must have a circumferential extent of at least
about 180°. Where the shank of the screw is to enter the
guideway, the entranceway may have a lesser circumferential
extent.
The first engagement section 42 of the forward
portion 46 is a section into which the head of a screw 12 is
moved when the strip 14 and screw 12 are advanced. In the
first engagement section 42, the wall 34 of the guide tube 26
engages the radially outermost periphery of the head 16 of the
screw 12, to axially locate the screw head 16 coaxially within
the guideway 32 in axial alignment with the bit 24. In this
regard, in the forward engagement section 42, the walls 34
extend about the screws sufficiently to co-axially locate the
screw head. The first engagement section 42 preferably
extends about the screw head at least 120°, more preferably,
at least 150° and, most preferably, about 180°.
When the guide tube 26 is fully inserted and secured
in the bore 54, the forward portion 46 extends beyond a front
surface of the slide body 52 a sufficient distance such that
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the screws 12 are aligned with entranceway 48 and retaining
strip 14 is aligned with exitway 50. ,
The shaft 20 is adapted for sliding insertion into
the guide tube 26 via the rearward axial end 38. The interior ,
sidewall 34 in the rear portion 40 of the guide tube journals
the continuous cylindrical exterior surface of the cylindrical
mandrel 22. Thus, as seen in Figure 3 the guide tube 26
journals the mandrel 22 within the bore 54 with the mandrel
spaced fr-om the walls of the bore rearward of the guide tube.
With the guide tube 26 secured in the slide body 52,
the mandrel 22 and bit 24 are axially aligned with the guide
tube 26 by engagement with the sidewall 34 to maintain the
shaft 20 substantially coaxially aligned in the guide tube
26.
As best seen in Figure 3, the screws 12 to be driven
are collated to be held parallel and spaced from each other by
a plastic retaining strip 14. In use of the strip 14 in the
screwdriver 10, in order for each successive screw 12a to be
engaged and driven into the workpiece 28, each screw 12a is
first advanced into axial alignment with the mandrel -22 and
bit 24 by the pawl arm 78 of the screw feed mechanism. The
screw feed mechanism engages and advances the plastic strip 14
as the bit 24 and mandrel 22 are moved in the return stroke
away from the workpiece 28 under the force of spring 66. The
screws 12 are moved radially into the guideway 32 through the
entranceway 48. The advanced screw 12a is held in position in
axial alignment with the shaft 20 and bit 24 with its screw
head 16 abutting the sidewall 34 in the first engagement
section 42 of the guideway. As the screw 12a is moved into
the cylindrical guideway 32, the leading portion of the strip
14' from which screws have previously been driven extends
outwardly from the guideway 32 through the exitway 50 in the
forwardmost section 44, permitting substantially unhindered
advance of the screws 12 and strip 14.
The cylindrical guideway 32 has a diameter which is
selected so that the portion of the sidewall 34-about the
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entranceway 48, engages and supports an outermost
circumferential surface of the screw head 16.
In operation, with the guide tube 26 inserted into
slide body 54, a bit 24 having the desired screwdriving tip 23
is secured to the mandrel 22 and the bit 24 and mandrel 22 are
located in the guideway 32 as previously described. A number
of screws 12 collated by plastic retaining strip 14 are
inserted into the screwdriver 10. To drive screw 12a into
workpiece 28, the power driver is activated to rotate the
shaft 20. The mandrel 22 and bit 24, while they are rotated,
are reciprocally movable in the guideway 32 towards and away
from the workpiece 28. In a driving stroke, manual pressure
of the user pushes the housing 70 towards the workpiece 28.
With initial manual pressure the footplate 200 engages the
workpiece 28 and the footplate 200 is slid rearwardly from the
extended portion of Figure 1 to its retracted position of
Figure 3 since the spring biasing the footplate 200 forwardly
is not as strong as the spring 66. In moving rearwardly, the
conical locating recess 206 receives the tip of the screw 12b
next to the screw 12a to be driven. The footplate 200 urges
the screw 12b into surface 77 thereby securely and precisely
locating screw 12b in a relation parallel the axis of the
drive shaft 20. With screw 12b being securely located, the
plastic strip 14 holding the screw 12a assists in locating
screw 12a in alignment with drive shaft 20.
Manual pressure of the user first telescopes the
footplate 200 to the retracted portion where the footplate's
rearward sliding is prevented by screw 12b, thereafter manual
pressure compresses spring 66 so as to move slide body 52
relative the housing 70 into the housing 70 from an extended
position to a retracted position. On release of this manual
pressure, in a return stroke the compressed spring 66 moves
the slide body back to the extended position thereby returning
the mandrel 22 and bit 24 by moving them back from the
workpiece 28.
PCTlCA95/00253
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In a driving stroke as the shaft 20 is axially moved
towards the workpiece 28, the driving tip 23 engages the screw
head 16 to turn the screw 12a in rotation. As is known, the
plastic strip 14 is formed to release the screw 12a as it is
turned in rotation by the bit 24. Preferably, on release of
the screw 12a, the plastic strip 14 deflects away from the
screw 12a outwardly through the exit opening 50 so as not to
interfere with the screw 12a in its movement into the
workpiece 28. After the screw 12a is driven into the
workpiece 28, the mandrel 22 and bit 24 are axially moved away
from the workpiece 28 under the force of the spring 66 and a
successive screw 12 is moved via the screw feed advance
mechanism through the entranceway 48 into axial alignment with
the shaft 20.
Reference is made to Figures 6 and 7 which show as a
second embodiment of the present invention, a modified guide
tube 26 and slide body 52 adapted for driving a screw strip 14
in which hexagonally-headed screws 12 carry washers 208
between the strip 14 and the tips of the screws. Such a screw
strip 14 carrying washer 208 may preferably be of the type
disclosed in U.S. Patent 4,930,630 to Habermehl issued June 5,
1990 which is incorporated herein by reference.
Guide tube 26 in Figures 6 and 7 is identical to
guide tube 26 in Figures 4 and 5 with two exceptions.
Firstly, the guide tube 26 of Figures 6 and 7 is
shown with the first engagement portion 42 as having an
internal sidewall 134 of a diameter greater than the interior
diameter of sidewall 34 in the rear portion 40. The interior
diameter of the forward portion 46 is shown to be larger so as
to permit fasteners to be driven which have a greater head
diameter than the diameter of the mandrel, or which require a
socket 210 as shown in Figure 7 or a bit which is of a greater
diameter than the diameter of the mandrel 22. In Figure 7 the
socket 210 is shown as having a diameter marginally less than
that of the internal sidewall 134 such that engagement between
the sidewall 134 -and the socket 210 assists in coaxially
W0 95129794 PCT/CA95/00253
- 15 -
locating the screws 12 in the guide tube 26 once a screw may
be engaged by the socket 210. Figure 7 shows the mandrel 22
carrying a socket 21o to engage the hexagonal heads of screws
12. The enlarged diameter sidewall 134 extends rearwardly
' beyond the entranceway 48 sufficiently to permit the socket
210 to be withdrawn rearwardly behind each screw to be driven.
Secondly, the guide tube 26 of Figure 6 and 7 is
shown with a second engagement pbrtion 47 having a sidewall
234 with an internal diameter which is greater than the
interior diameter of sidewalls 34 and 134. The diameter of
the sidewall 234 in the second engagement portion 47 is
marginally greater than that of the washers 208 such that
engagement between the sidewall 234 and the washers 208
assists in coaxially locating the screws 12 in guide tube
26. Preferably as shown the sidewall 234 extends about the
washer 208 about 180° to maximize the ability of the sidewall
234 to locate the washer 208. As shown an entranceway 212 is
provided radially into the second engagement portion 47 from
the right between entrance ramp surfaces 214 and 216 which
assist in guiding a washer 208 into the second engagement
portion 47. The sidewall 234 need not extend 180° about the
washer but preferably extends thereabout at least 120°. The
entranceway 212 must have a circumferential extent of at least
about 180° where the washer 208 is to enter.
Figures 6 and 7 also show minor modifications of the
footplate 200 so as to avoid interference with the larger
exterior diameter portion of the guide tube 26 which extends
forwardly from the exitway 50, and, to locate locating recess
206 further to the right due to the increased spacing between
centres of the screws shown in Figure 7.
Figures 8 and 9 are views identical to Figures 6 and
7 but showing a third embodiment of the invention in which the
second engagement section 47 includes a forward nose portion
30o in which the sidewall 234 extends 360° about a screw.
Rearward of forward nose portion 300, the entranceway 212 is
provided for access of the washer 208. The forward nose
VJO 95f29794 218 9 0 2 6 PCT/CA95/00253
- 16 -
portion 300 is shown as having its interior surface tapering
inwardly and forwardly to assist in camming the washer 208
into coaxial alignment on downward movement and to prevent a
washer from being caught on the rearward edge of the forward
nose portion 300. The guide tube 26 of Figure 9 may be used
in a driver without footplate 200.
It is to be appreciated that the guide tube 26 for
example as shown in Figures 4 and 5 is adapted to drive the
screws 12 having a shape and size as shown in Figure 5. To
drive screws 12 having a different diameter or length it is
necessary merely to replace the guide tube 24 by a different
guide tube 26. This can be done in the context of Figure 5,
merely by removing the cover plate and possibly the bit. In
some cases, for example to switch from the configuration of
Figure 4 to that of Figure 6, the footplate 200 needs to be
replaced or if provided to be adjustable, adjusted to move the
recess 200 to a correct spacing. Pawl 78 can be configured
via its feed linkage to advance screw strips with different
spacings between screws. Changing of the guide tubes 26 can
be without- substantial disassembly. Guide tube 26 is
preferably made of wear resistant material and as it is
removable this can assist in extending the life of the tool.
While preferred embodiments show tools having
removable guide tubes 26, this is not necessary and a
permanent guide tube 26 could be utilized.
In Figure 7 the exitway 50 is shown to also provide
forward surface 93 to assist in locating the strip 14.
Reference is now made to Figures 10 to 13 which show
a fourth embodiment of the present invention in which the
screw strip 14 is modified to provide a locating system to
permit location of the strip 14 relative the guide tube 26.
Figure 10, shows screws 12 held in a plastic holding
strip 14 substantially in accordance with Canadian Patent
1,054,982, the disclosure of which is incorporated herein by
reference. The strip comprises an elongate thin
pCT/CA95/00153
WO 95/29794
- 17 -
band formed of a plurality of identical sleeves 104
interconnected by lands 106. A screw 12 is received within
° each sleeve 104. Each screw 12 has a head 16, a shank 108
carrying external threads 114 and a tip 116. As shown, the
external threads extend from below the head 16 to the tip
116.
Each screw is substantially symmetrical about a
central longitudinal axis 112. The head 16 has in its top
surface a recess 13 for engagement by the screwdriver bit
24.
Each screw is received with its threaded shank 108
engaged within a sleeve 104. In forming the sleeves about
the screw, as in the manner for example described in
Canadian Patent 1,040,600, the exterior surfaces of the
sleeves come to be formed with complementary threaded
portions which engage the external thread 114 of the screw
12. Each sleeve 104 has a reduced portion between the lands
106 on the first side of the strip and therefore on the
first side of each screw. This reduced strength portion is
shown as a substantially vertically extending longitudinal
slot 118 bridged by two thin strap-like portion or straps
120.
The strip 14 holds the screw 12 in parallel spaced
relation a uniform distance apart. The strip has a forward
surface 122 and a rear surface 123. Locating notches 124
are provided in the strip extending upwardly from the
forward surfaces 122 with the notches 124 spaced from each
other the same distance that the screws are spaced. Notches
124 are preferably formed at the same time that the strip is
formed by an extrusion process which, in effect, captures
the screws between two rotating forming wheels. The forming
wheels may be modified so as to form the plastic strip with
the suitably spaced notches.
The notches 124 are formed with a notch leading
ramp-like engagement surface 142 and a notch trailing ramp-
like engagement surface 144.
CA 02189026 2000-OS-18
-18-
Figure 11 shows an enlarged view of a guide tube 26
similar to the guide tube of Figure 5 but with the exitway 50
having its forward surface 93 provide a tooth-like projection 136
which is shaped to correspond to the notches 124 in the strip.
As seen in Figure 11, the forward surface comprises a
projection leading ramp-like engagement surface 146 and a
projection trailing ramp-like engagement surface 148 which define
the projection 136 therebetween.
A single cycle of driving one screw 12 and.advancing the
strip so as to position the next screw is now described with
reference to Figures 11, 12 and 13.
Figure 11 shows the screwdriver assembly at a point in
time in a cycle when the screwdriver bit 24 has moved forwardly
to engage the recess in the screwdriver head and to initially
urge the screw 12a towards the workpiece. The forward surface 122
of the strip is urged into engagement with the forward surface
of the exitway 50 with the tooth-like projection 136 received in
mating registry in the notch 124 of the screw strip preceding the
screw 12a to be driven. The screw 12a to be driven is thus
positioned by reason of its head 16 engaging the sidewall 34 of
the guideway 32 and the strip having its notch 124 engaged with
the projection 136 of the exitway. Subsequently, the screwdriver
shaft 20 moves forwardly and drives the screw into a workpiece
and, in so doing, the head of the screw passes through the sleeve
104 of the strip rupturing the straps 120.
Figure 12 shows a subsequent position in a cycle in which
after fully driving the screw, the bit 24 has been retracted and
the screw feed mechanism is in the process of advancing the screw
strip towards the left. In the slide pawl 178 moving the next
screw towards the left, disengagement of the projection 136 in the
notch 124 is assisted by interaction between the notch trailing
surface 144 and the projection trailing surface 148 camming the
strip rearwardly away from the projection 136 of the forward
WO 95/29794 ~ ~ ~ ~ ~ ~ ~ PCT~CA95/00253
- 19 -
surface. The screw feed mechanism advances the strip
towards the left until the head 16 of the next screw 12
engages the guideway inner surface 34 as shown in Figure 13
with the notch 124 in rough alignment rearward of projection
136.
From the position in Figure 13, the cycle then
returns to the position shown in Figure 11 with the bit 24
moving forwardly to engage the screw head and urge both the
screw and its strip forwardly. In the strip being moved
forwardly from the position of Figure 13 to the position of
Figure 11, the surfaces of the projection and notch interact
to assist in engagement of the projection and notch.
Engagement between trailing and/or leading surfaces of the
projection and trailing and/or leading surfaces of the notch
will cam the strip to move it to the left or the right to
locate the notch precisely on the projection. Thus, the
interaction between the surfaces of the projection and tooth
will move the strip transverse to the axis of the guide tube
26, that is, along the longitudinal direction of the strip
14.
In the context of a power screwdriver as shown in
Figures 1 to 3, the feed pawl 78 in each cycle on being
moved to the right so as to be able to advance the next
screw to the right of the pawl 78, to some extent
frictionally engages the strip 14 and its screws 12 and can
draw the strip 14 back to the right. Such "feed pawl
drawback" can be disadvantageous. However with a notched
screw strip of Figure 10, the engagement of the notch 124
and the projection 136 can advantageously avoid the
disadvantage of the strip being drawn back by feed pawl
drawback beyond a desired position with the screw in
alignment with the bit 24. To avoid feed pawl drawback the
projection leading surface 146 and the notch leading surface
142 may preferably be perpendicular to the longitudinal
along the strip and thus parallel the drive shaft axis.
Feed pawl drawback may be intentionally designed to occur
W O 95129794 PCTICA95/00253
- 20 -
and be utilized as a vehicle for ensuring positive location
of the notch 124 on the projection 136.
In the preferred embodiments shown, the forward
surface 93 of the exitway 50 is provided with projection 136
to engage notch 124 in the strip. The provision of
projection 136 and uniformly spaced notches 124 are
advantageous to form a system for locating the strip. The
projection 136 and notches 124 may have different
configurations. For illustration the projection and notch
have been shown to extend about 1/3 of the width of the
strip. It is to be appreciated that smaller notches could
readily be used. The notches and projections may have many
other shapes than that shown.
The preferred embodiment shows forward surface 93
having a projection 136 which is generally uniform in a
direction transverse to the longitudinal of the strip.
Surface 93 and/or its projection 136 could be provided to
vary in a direction transverse to the longitudinal to assist
in locating the strip in a desired position in this
direction. However, in the use of a screw strip, it is to be
appreciated that latitude needs to be given for the strip to
deflect transversely to the longitudinal of the strip in the
head of the screw forcing itself through the sleeve and past
the strip.
The extent to which notches and projections may be
desired in any screwdriver assembly will vary to some
measure with factors which will influence the accuracy with
which a screw comes to otherwise be positioned in the
guideway. The length of the screw; the nature of the screw
head such as whether it has a square recess or Phillips
recess and whether a screw head may be shaped for engagement
by a socket; the extent to which the screw head is closely
sized to the diameter of the guideway; the relative position
of the strip on the screws compared to the location of the
head; and where, how and if the advancing pawl engages the
R' O 95729794 2 i 8 9 0 2 6 PCT/CA95/00253
- 21 -
screw and/or its strip; are all features which have a
bearing on whether projections and notches may be desired.
In addition to the forward surface 93 of the
exitway, specific location of the side surface 94 and rear
surface 95 of the exitway may also be advantageous. The
side surface 94 may, to some measure, engage surfaces of the
strip to assist in locating the strip within the exitway.
The rear surface 95 must, in the embodiment of Figures 10 to
13 shown in which the strip must move rearwardly for the
notches 124 to disengage the projection 136, be provided
sufficiently rearwardly from the forward surface 93 that the
strip can move rearwardly and clear the projection 136. In
other configurations such as in Figures 1 to 9 in which the
forward surface 93 does not incorporate a projection but
merely extends radially, the rear surface 95 may be provided
spaced from the forward surface 93 a distance only
marginally larger than the height of the strip so as to
assist in accurately guiding the strip therethrough.
In the context of screw strips utilizing notches
to engage a projection, the screw feed mechanism could
incorporate feed pawls which activate so as to assist in
directing the screw strip rearwardly for disengagement of
the pawl and for subsequent movement forwardly once the next
subsequent notch comes to be aligned above the projection.
While the embodiment of Figure 10 shows notches
124 in the strip 14 and a mating projection 136 of the guide
tube 26, it is to be appreciated that projections could be
provided on the strip and notches about exitway 50 of the
guide tube. Similarly in replacement of any notches or
projections, shoulders, steps and the like could be
substituted.
The invention has been described with reference to
the particular construction of U.S. Patent 4,146,871 for a
power screwdriver incorporating the guideway received in a
slide body. It is to be appreciated that the invention may
readily be adapted to other known fastener installation tool
W O 95129794 218 9 0 2 b PCT/CA95100253
22
configurations including nut drivers and the like and both
power and manual tools. .
The invention has been described with reference to
a preferred screwdriver assembly which incorporates an
automatic screw feed assembly. The invention is, however,
readily adapted for use with other screw feed assemblies
and, as well, for unautomated, manual screw feed systems.
For 'example, in the context of Figures 1 to 6 the feed
mechanism elements, namely lever arm 68 and/or pawl 78,
could be eliminated. The screw strip could be advanced
merely by a user manually grasping the strip where it exits
the exitway 50 and drawing the strip to the left after each
screw has been driven. A simple tool would result having
increased simplicity particularly suitable for manufacture
at low price and sale to the household.
Figure 14 shows a pictorial viewof the guide tube
26 shown in cross-section in Figure 10 and illustrating
features in accordance with a fifth embodiment.
As seen in Figure 14 the guide tube 26 has many
similarities to the guide tubes 26 in the other embodiments
and is adapted to form a guide tube for use, for example in
substitution for the guide tube of Figures 5 and 6. The
entranceway 48 is shown closely sized to the shape of the
screws 12 and with an enlarged head entrance portion 414 and
a reduced shank entranceway 416. This has the advantage
that in a screw being driven once the head advances
forwardly past enlarged head portion 414 the sidewall 34
extends about the head more than 180° so as to positively
locate the head coaxially in the guideway. The guide body
has at its forward end a touchdown ring 416 which extends
360° about a screw being driven.
The exitway 50 is enclosed in the sense that it is
bounded on both sides as well as by its forward surface 93
and rear surface 95.
In the embodiment of Figure 14, the rear surface
95 of the exitway 50 may preferably be spaced a distance
WO 95129799 PCTICA95I00253
- 23 -
above the rearward most point of projection 136 equal to or
marginally less than the width of the strip between forward
surface 122 and rear surface 123. By having this. distance
less than the width of the strip, on the strip being moved
to the left, the land 106 will become compressed across its
width and will deflect to permit the strip to be moved to
the left. This deflection will inherently bias the strip 14
towards the projection 136 such that the notch 124 cannot
become disengaged from projection 136 without compressing
the width of the strip. Alternate embodiments to accomplish
this could provide a spring loaded mechanism carried by
guide tube 26 rearwardly of the strip 14 to bias the strip
14' where it exits the slide body 52 downwardly into the
support surface 93. Such mechanisms would appear
advantageous in a manual system in which a user manually
advances the screw strip to ensure that in handling the
power tool between driving screws that the screw strip may
not be dislodged or become improperly positioned. In a
manual system, it may also be preferable to have a one-way
pawl not dissimilar to pawl 78 which permits a screw to
advance to the left as seen in the Figure 14 but does not
permit the screws once advanced to move back to the right.
Such a pawl could act on any of the screws in the screw
advance guideway 206.
With the invention of the present application, an
advantage is that insofar as the strip is supported by
portions of strip preceding a screw to be driven, the system
of the present invention permits the last screw in any strip
to be driven and is particularly advantageous for use with
shorter length strips such as six to fifty screws in
length. This advantage arises whether or not a footplate
200 as illustrated in Figures 1 to 6 is utilized in that
even with a footplate 200 to pinch the next screw 12b to be
driven, when a last screw 12a is being driven and there is
no screw 12b, support of the last 12a is more particularly
desired.
CA 02189026 2000-OS-18
-24-
The present invention provides a number of different
mechanisms for locating a screw 12a to be driven in alignment with
the drive shaft 20. These include the engagement of a head 16 of
a screw with the sidewall 34 in first engagement portion 42 in the
guide tube, the engagement of a washer 208 with the sidewall 234
in the second engagement portion 47 in the guide tube, the
engagement of the forward surface 122 of a strip on the forward
surface 93 of the exitway, the engagement of indexing notches 124
on the strip with complementary projections 136 in the forward
surface 93 of the exitway, the engagement of the forward surface
123 of a strip on the rear surface 95 of the exitway, and the
holding of a next screw 12b to be driven by the foot plate 200. The
use of anyone or more of these mechanisms may be sufficient to
locate a strip without use of other of the mechanisms. For example
in the context of all the embodiments shown the footplate 200 is
not required and the screw 12 can adequately be located for
practical use merely by eliminating the footplate or eliminating
the portion of the footplate 200 carrying the recess 208 with or
without affixing the remainder of the foot body to the slide body
against relative sliding motion. The embodiment of Figure 9 is
particularly adapted for use with the engagement between the notch
124 and projection 136 and the engagement between the screw head
16 and the sidewall 34 to locate the screw. In~the context of
Figures 6 and 7, the footplate is not required due to second
engagement portion 234. Of course the embodiment of Figures 1 to
7 could be provided with strips having notches 124 to be engaged
by projection 136.
Reference is now made to Figures 15 to 19 which show as a
fifth embodiment of the present invention, another plastic holding
strip 14 of the type taught by Canadian Patent 1,054,982. The
same reference numbers as used to describe Figures 10 to 13 are
used in Figures 15 to 19.
As is the case with the strip of Figures 10 to 13, the
lands 106 in Figures 15 to 19 are shown as extending
218 9 ~ 2 pCT1CA95/00253
WO 95129794
- 25 -
both between adjacent screws 12, that is, horizontally as
seen in the rear view of Figure 19, and axially of the
screws 12, that is, in the direction of the longitudinal
axes 112 of the screws. Thus, the lands comprise webs of
plastic material provided over an area extending between
sleeves 104 and between the forward surface 122 and the rear
surface 123. As best seen in Figure 17, showing a cross-
sectional end view through one land 106, the land 106
effectively is disposed about a plane indicated as 115 in
Figure 17 which is parallel to a plane in which the axes 112
of all the screws lies. Thus, the lands 106 comprise a web
which is disposed substantially vertically compared to the
vertically oriented screws as shown in the figures. The
lands 106 and the sleeves 104, in effect, are disposed as a
continuous, vertically disposed strip along the rear of the
screws 12, that is, as a strip which is substantially
disposed about a plane 115 which is parallel to a plane
containing the axes of all screws.
As shown in dotted lines, the strip 14 of Figures
15 to 19 could be provided with slots 124 in its forward
surface 122, if desired. The strip 14 could also be
provided with a horizontally extending reinforcing flange
125 along its length as illustrated by the dotted lines in
Figure 18. The lands 106 are shown as spaced to one side of
axes 112 of the screws, however, this is not necessary, and
the lands 106 could be provided in alignment with the axes
or otherwise. A preferred feature of the strip is that it
may bend to assume a coil-like configuration due to
flexibility of the lands 106, such that, for example, as
seen in a plan view to Figure 15, the strip could be
disposed with the heads of the screws disposed into a
helical coil, that is, the plane in which all the axes 112
of the screws lie may assume a coiled, helical configuration
to closely pack the screws for use. Having the lands 106
and sleeves as a vertically extending web lying in the plane
parallel that in which the axes 112 permits such coiling.
CA 02189026 2000-OS-18
-26-
As shown in Figures 5, 7, 9, 10, 14, 15 and 19, the
forward surface 122 of the strip is located a constant distance
rearwardly from the tips 116 of the screws.
While the invention has been described with reference to
preferred embodiments, the invention is not so~limited. Many
variations and modifications will now occur to a person skilled
in the art. For definition of the invention, reference is made
to the following claims.
