Note: Descriptions are shown in the official language in which they were submitted.
CA 02324627 2000-10-26
, =
Title
DOUBLE ARM PAWL FOR AUTOFEED SCREWDRIVER
Scope of the Invention
This invention relates to an improved screw advancing pawl for a strip
advance and release mechanism of an apparatus which sequentially advances and
drives
fasteners retained in a holding strip.
Background of the Invention
Autofeed screwdriver tools are known including U.S. Patent 5,570,618 to
Habermehl, issued November 5, 1996 and U.S. Patent 5,974,662 to Habermehl,
issued
August 10, 1997 which have an advance mechanism utilizing a pawl with a single
pawl
arm to engage a screwstrip and advance the screwstrip.
The present inventor has appreciated that under some abnormal
conditions, such as when the tool is not operated in a proper manner,
disadvantages arise
in that the known single pawl may not be moved into a position to engage any
screws
remaining in the strip and the strip may drop out of the tool.
Summary of the Invention
The invention at least partially overcomes the disadvantages of the prior
art by providing a blocking and/or advance pawl mechanism for an autofeed
fastener
driving tool with at least two pawl arms with at least one of the pawl arms
maintained
rearward of a next fastener to be driven from a strip holding fasteners spaced
in a row.
Preferably, the advance pawl mechanism provides for simultaneously manual
deactivation of the at least two pawl arms to permit withdrawal of the
screwstrip.
An object of the present invention is to provide an improved pawl for use
in an autofeed screwdriving tool.
1
CA 02324627 2000-10-26
Another object is to provide a pawl for blocking withdrawal of a
screwstrip from an autofeed fastener driving tool which has two spaced arms
each of
which are adapted to block withdrawal of a screwstrip.
Another object is to provide a pawl for advancing screwstrips in an
autofeed fastening tool which has two spaced arms to engage two spaced screws
in the
screwstrip.
Accordingly, in one aspect, the present invention provides an apparatus for
sequentially driving fasteners from a fastener strip comprising a plurality of
fasteners
secured in a row in a holding strip, the apparatus comprising:
a slide body having a lateral screwstrip receiving channelway and a
guideway bore intersecting the channelway, the channelway configured to
slidably
receive the strip;
an elongate driver shaft having a shaft axis of rotation, said shaft including
a fastener driving bit for engaging and driving fasteners in succession into a
workpiece,
said shaft being journalled and longitudinally slidably housed in said bore
for reciprocal
movement relative the slide body between an engaged position and a withdrawn
position;
an advance mechanism mounted to said slide body for incrementally
forwardly advancing the strip carrying the screws in the strip with the axis
of each screw
to pass in succession along a plane of advance within the channelway into the
bore, said
advance mechanism including a linkage member housed in said slide body and
reciprocally movable between an advanced position and a retracted position as
a function
of cyclical reciprocal relative movement of the slide body and driver shaft,
a pawl pivotally mounted on the linkage member for pivoting between a
first blocking position and a second passage position,
the pawl having a first arm with a first screw engaging surface and a
second arm with a second screw engaging surface,
in the first blocking position, both the first and second engagement
surfaces are positioned in the plane of advance such that the first engagement
surface
blocks any screw in the screwstrip immediately forward of the first engagement
surface
2
CA 02324627 2000-10-26
from movement relative the first engagement surface rearwardly pass the first
engagement surface and the second engagement surface blocks any screw in the
screwstrip immediately forward of the second engagement surface for movement
relative
the second engagement surface rearwardly past the second engagement surface,
in the second passage position, both the first and second engagement
surfaces are positioned out of the plane of advance such that they do not
block screws in
the screwstrip forward of the first or second engagement surfaces from
movement
relative the first and second engagement surfaces rearwardly past the first or
second
engagement surfaces.
Further aspects of the invention will become apparent upon review of the
following detailed description.
Brief Description of the Drawings
Further aspects and advantages of this invention will become apparent
from the following description taken together with the accompanying drawings
in which:
Figure 1 is a pictorial view of a power screwdriver in accordance with a
first preferred embodiment of the present invention;
Figure 2 is a rear view of the components of the driver attachment in
Figure 1;
Figure 3 is an exploded pictorial view of the driver attachment shown in
Figure 1;
Figure 4 is a schematic partially cross-sectional view of the driver
attachment of Figure 1 in a fully extended position as seen in Figure 1
through a plane
passing through the longitudinal axis of the drive shaft and centrally of the
screws in the
screwstrip;
Figure 5 is a view identical to Figure 4 but with the drive attachment in a
partially retracted position in driving a screw into a workpiece;
Figure 6 is a partial pictorial view of the forward end of the slide body
shown in Figure 3;
3
CA 02324627 2007-04-19
Figure 7 is a schematic side view showing a forward end of the slide
body of Figure 6 driving a screw into a workpiece, with the screw normal to
the outer
surface of the workpiece;
Figure 8 is a schematic side view substantially the same as that shown in
Figure 7, however, showing the screw being driven into the workpiece at an
angle to the
vertical;
Figure 9 is a schematic cross-sectional view along line 9-9' in Figure 4
showing merely the screwstrip and the shuttle in a fully advanced position;
Figures 10 and 11 are views the same as Figure 9 but with the shuttle
being withdrawn in an intermediate position in Figure 10 and in a fully
withdrawn
position in Figure 11;
Figure 12 is a view similar to Figure 9 but with a modified pawl;
Figure 13 is a pictorial view of the nosepiece shown in Figure 1
schematically showing a screw received therein;
Figure 14 is a pictorial view of the nosepiece as in Figure 13 with a screw
in a different position;
Figure 15 is a cross-sectional view of the nosepiece of Figure 14 along
section line XV-XV';
Figure 16 is an elevational rear view of the slide body 20 of Figure 3;
Figure 17 is a cross-sectional view similar to that in Figure 15, however,
of another second embodiment of a nosepiece in accordance with the present
invention;
Figure 18 is a pictorial view of a third embodiment of a nosepiece in
accordance with the present invention.
Detailed Description of the Drawings
Toeing Nosepiece
Reference is made first to Figure 1 which shows an autofeed screwdriver
attachment of the type disclosed in U.S. Patent 5,934,162, issued August 10,
1999.
4
CA 02324627 2000-10-26
The operation of the device shown in Figures 1 to 5 is known and,
therefore, its operation will now only be briefly disclosed with reference to
Figures 1 to
5. The major components of the mechanism comprise a housing 18 and a slide
body 20.
The housing 18 is adapted to be secured to a driver housing 30 (only shown in
Figure 4)
of a power driver 11 with a chuck 32 of the power driver engaging a driver
shaft 34 for
rotation of the driver shaft about an axis 52. The slide body 20 is received
within the
housing 18 for relative sliding parallel the axis 52. The slide body 20 has a
nose portion
24 with a guideway 82 extending axially therethrough coaxially about the
driver shaft 34.
A screw feed channel element 76 provides a channelway 88 which extends
radially
relative the longitudinal axis 52 to intersect with the guideway 82 and
provide a
mechanism for screws 16 held in a plastic strip 13 to be successively fed into
the
guideway 82 into axial alignment with the driver shaft for driving forwardly
from the
guideway 82 by the bit 122 carried on the forward end of the driver shaft 34.
An exit
opening 87 is provided in the guide tube 74 to permit spent plastic strip 13
from which
screws 16 have been driven to exit from the guideway 82. An advance mechanism
is
provided to successively advance screws into the guideway 82 with each
subsequent
cycle of retraction of the slide body 20 into the housing 18 so as to drive a
screw, and
extension of the slide body 20 out of the housing 18 to withdraw the driver
shaft 34
rearwardly and advance a new screw into the guideway 82.
In one aspect, the present invention is directed to the configuration of the
forward end of the nose portion 24 for advantageous engagement with a
workpiece.
As may be best seen in Figures 6 and 7, the nose portion of the slide body
20 has a forward contact surface generally indicated 130 adapted to engage the
outer
surface 132 of a workpiece 134. The nose portion is shown in Figure 6 with the
guideway 82 opening forwardly through the contact surface 130 as a fastener
exit
opening 136. The contact surface 130 is shown to extend from the fastener exit
opening
136 radially outwardly relative the axis 52 and rearwardly.
The contact surface 130 is shown as comprising a smooth, part spherical
surface 140 and a plurality of protrusions 142. As best seen in Figure 7, the
part
CA 02324627 2000-10-26
spherical surface 140 is effectively shown as a portion of a sphere of a
radius 143
centered on point 144 on axis 52. The center of the sphere is located relative
to the
fastener exit opening 136 such that from the fastener exit opening 136, the
surface 140
extends radially to the side and rearwardly but not forwardly. The part
spherical surface
140 is shown extending radially from the exit opening 136 to a rearward edge
146
rearward of which the surfaces of the nose portion are shown to extend
rearwardly at
least at an angle of about 75 from the axis 52 as indicated by surface 145 on
the left-
hand side of Figure 7. Preferably, the radius 143 of the sphere is as small as
possible so
that when driving a screw with the axis 52 tilted only a minimal additional
distance is
required for driving the screw into a fully countersink position compared to
that when the
axis 52 is normal the surface of the workpiece. Preferably, the radius 143 of
the sphere is
not greater than three times, more preferably, two times or one times the
diameter of the
guideway 82. Preferably, the radius 143 is about equal to the diameter of the
guideway
82 although the radius 143 may be less than the diameter of the guideway 82.
A plurality of protrusions 142 are shown provided in an array on the
surface 140. Each of the protrusions is shown as a spike-like member which
extends at
least partially forwardly from a base at the surface 140 to a distal end.
Preferably, as
shown, the protrusions extend from the surface 140 parallel to axis 52 about
the base.
Alternatively, the protrusions may extend normal to the surface 140. Each of
the distal
ends of the protrusions are preferably adapted to provide for increased
frictional
engagement with a work surface as is advantageous to prevent slippage.
Figures 5, 6 and 7 show the fastener exit opening 136 lying in a plane
normal the axis 52 such that the surface 140 immediately adjacent the fastener
exit
opening 136 comprises the forwardmost portion of the surface 140.
As shown in Figures 6 and 7, the contact surface 140 includes a radially
innermost zone 154 adjacent the fastener exit opening 136 which innermost zone
154 is
adapted to engage a flat surface of a workpiece when the nose portion 24 is
urged into a
workpiece with the axis 52 substantially normal to the flat surface of the
workpiece. As
seen in Figure 6, radially outward of the innermost zone 154, an outer zone
156 is
6
CA 02324627 2000-10-26
indicated. The protrusions 142 are provided on this outer zone 156 of the
contact surface
radially outwardly from the innermost zone 154 and rearward of the innermost
zone 154.
As shown in Figure 7, the forward distal ends of the protrusions 142 have a
forward
extent which is rearward of the innermost zone 154. In Figure 7, the flat
surface 132 of
the workpiece 134 represents a plane in which the exit opening 136 lies with
the axis 52
normal to the flat surface 132 of the workpiece. As seen in Figure 7, the
forwardmost
extent, i.e. the distal ends, each of the protrusions 142 are spaced
rearwardly from flat
surface 132 by a distance indicated as 158 and, thus, the protrusions 142 are
located such
that they do not engage a flat surface of a workpiece when the axis 52 is
normal the flat
surface of the workpiece. The protrusions 142 are preferably provided with the
forwardmost distal ends of the protrusions 142 terminating at a forwardmost
extent
rearward, relative the axis 52, of the innermost zone 154.
Referring to Figure 7, a dashed line 160 is shown as a line at an angle 162
to the axis 52 and which line 160 represents a plane in which a flat surface
of a workpiece
would need to be disposed so as to engage both the innermost zone 154 and the
distal end
of a radially innermost protrusion 142. It is to be appreciated that any flat
surface
disposed at an angle to the axis 52 in between the line 160 and surface 132
would merely
engage the surface 140 over the innermost zone 154 with the protrusions 142
spaced
rearwardly therefrom. The angle 162 between the line 160 and surface 132 is
preferably
in the range of about 2 to 10 and, more preferably, about 5 . In this
application, an
angle referred to as being "substantially normal the axis" is to be
interpreted as meaning
an angle of not greater than 10 to a normal. The innermost zone 154 is
preferably
defined as being that portion of the surface 140 radially about the fastener
exit opening
136 which engages a flat surface of a workpiece when the axis 52 is
substantially normal
the flat surface, i.e. when the axis 52 is at an angle of less than 10 , more
preferably, less
than 5 from a normal.
Thus, as seen in Figure 7, the protrusions 142 do not engage a flat surface
of a workpiece when the axis 52 is substantially normal the flat surface of
the workpiece
as, for example, when the axis 52 is disposed at an angle of 10 or 5 or less
to a normal
7
CA 02324627 2000-10-26
to the flat surface. The protrusions 142 are adapted to engage a flat surface
of a
workpiece only when the axis 52 is disposed at an angle equal to or greater
than angle
162, preferably, at an angle greater than about 10 or 5 to a normal to the
flat surface.
As seen in Figure 6, the protrusions 142 are shown as arranged in two
concentric rings with radially inner protrusions in the inner ring and
radially outer
protrusions in the outer ring. In Figure 7, a dashed line 164 represents the
surface of a
flat workpiece disposed to engage the distal ends of both a radially inner
protrusion 142
and a radially outer protrusion 142. As seen, line 164 does not engage the
innermost
zone 154. A further line 166 represents the surface of a flat workpiece
disposed to
engage a radially outer protrusion 142 and the rearward edge 146 of the part
spherical
surface 140.
It is to be appreciated that, as seen in Figure 7, a nose portion 24 may be
engaged on a work surface with the axis perpendicular to the work surface and
then
angled to one side to successively adopt configurations in which the relative
position of
the workpiece flat surface 132 is indicated by lines 132, 160, 164 and 166 in
succession.
In accordance with a preferred aspect of the invention, the line 160 is
disposed at an
angle of about 70 to 80 to the axis 52, line 164 is disposed at an angle of
about 50 to
60 to the axis 52 and the line 166 is disposed at an angle of about 20 to 30
to the axis
52.
Figure 7 illustrates the condition in which the nose portion of the slide
body in accordance with the present invention is utilized to drive a screw
into a surface of
a workpiece 134 with the axis 52 normal to the upper surface 132 of the
workpiece. In
the condition shown in Figure 7, the protrusions 142 do not engage the flat
upper surface
132 of the workpiece 134, rather, engagement is accomplished merely over the
innermost
zone 154 of the surface 140.
Referring to Figure 7, line 168 is provided corresponding to line 164,
however, representing a condition where, in effect, the axis 52 is tilted an
equal amount
in an opposite direction. The two lines 168 and 164 intersect at the axis 52
at a point 170.
It is to be appreciated that the contact surface 130 is provided rearwardly
from each of
8
CA 02324627 2000-10-26
these lines 164 and 168, with the lines, when rotated about the axis,
effectively defining a
cone at an angle of angle 172 from the axis and with the point 170 located a
set distance
from the point 171 on the axis lying in the plane of the fastener exit opening
136.
Preferably, the contact surface 130 lies rearward of the surface of the cone
extending
rearwardly at an angle of, at most, 45 from the axis 52 and centered on the
axis 52 at a
point such as 170 forward of the point 171 on the axis where the plane of the
fastener exit
opening intersects the axis by a distance of at least one half the' diameter
of the guideway
82.
A preferred tool in accordance with the present invention is particularly
adapted for driving screws at an angle into a workpiece. Driving screws at an
angle into
a workpiece is referred to as "toeing" a screw into a workpiece. Driving
screws at an
angle is particularly preferred where screws are used to secure plywood floors
to floor
joists. Figure 8 schematically shows two one-half inch thick pieces of wood
flooring
plywood 172 and 174 in abutting relationship overlying a conventional wood
floor
stringer 173 of nominal two-inch thickness which has an actual thickness of
about 1 5/8
inches. As it is preferred that the screw being driven to secure the edge of
each piece of
plywood 174 into the stringer 173 be spaced about a half inch from the edge of
the
plywood, it is preferred, therefore, that the screw be driven at an angle to
the flat upper
surface of the plywood down into the stringer. Preferred angles for driving
screws, such
as shown in Figure 8, are in the range of 60 to 85 and, more preferably,
about 65 to
80 and, even more preferably, about 75 . Figure 8 shows an arrangement with
the axis
52 disposed at an angle of 65 to a normal to the upper surface 132 of the
plywood 174.
Under the conditions shown in Figure 8, the protrusions 142 engage the upper
surface
132 of the plywood and assist in preventing the nose portion 24 from slipping
on the
upper surface 132.
The present invention has been described with reference to a nosepiece for
an autofeed screwdriver. It is to be appreciated that a similar nose could be
provided
with tools of various types to drive fasteners including devices to drive a
wide variety of
9
CA 02324627 2000-10-26
different fasteners including screws and other threaded fasteners and nails,
tacks, studs,
posts and the like.
The protrusions 142 are shown in Figure 6 as comprising an array of
protrusions comprising a first radially inner row of protrusions disposed in a
circular arc
about the axis 52 and a second radially outward row of protrusions disposed in
a second
arc about the axis 52 radially outwardly from the first arc. About seventeen
protrusions
are shown in the inner row and more in the outer row. With the protrusions 142
preferably being of similar length as shown, it follows that the distal ends
of the
protrusions lie on a spherical surface formed by rotating a radius on
centerpoint 144 with
the radius being greater than the radius 143 by the length of the protrusions.
The length
of the protrusions 142 is small relative to the radius 143 of the sphere of
the contact
surface 140, preferably in the range of less than about 1/10 or 1/15 or 1/20
of the radius
143. Protrusions 142 are preferred to be provided of a spike-like
configuration to
frictionally engage the surface of a workpiece, however, various other
friction enhancing
surfaces and surface treatments may be provided in substitution for the
protrusions 142
and their spike-like distal ends.
The preferred embodiment shows the innermost zone 154 of the surface
130 as being smooth as is preferred so as to avoid marking or marring the
surface of a
workpiece when a screw is being driven into a workpiece with the axis 52
substantially
normal the surface of the workpiece. It is appreciated that the innermost zone
154 need
not be smooth but, rather, may merely be provided with any other configuration
which
reduces the likelihood of marking or marring a surface of the workpiece. The
surface of
the innermost zone 154 is to be contrasted with the contact surfaces over the
outer zone
156 which is to provide for frictional engagement as characterized in the
preferred
embodiment by the spike-like distal ends of the protrusions 142.
The preferred embodiment shows the contact surface 130 which tapers
inwardly and rearwardly almost entirely surrounds about the fastener exit
opening 136. It
is to be appreciated that the nose portion may merely have its contact surface
tapered
inwardly on one or both sides of the fastener exit opening 130.
CA 02324627 2000-10-26
A screw is fully countersunk when no portion of the screw 16 is above the
surface 132. When driving a screw into a workpiece with the axis 52 normal the
flat
surface of the workpiece as seen in Figure 7, full countersinking arises by
driving the
screw so that no portion of the screw is above the flat surface 132 which
coincides with a
plane in which the fastener exit opening 136 lies.
In accordance with an aspect of the present invention, it is advantageous
that on tilting of the nose portion to drive a screw at an angle, that the
radially innermost
point of contact of the contact surface 130 with the workpiece be as close to
the axis 52
as possible. This aspect is illustrated with reference to Figure 8. Figure 8
schematically
shows a screw 16 which has been countersunk into the workpiece when the screw
is
driven into the workpiece with the axis 52 at an angle to the flat surface 132
of the
workpiece. As seen in Figure 8, point 180 is a point about which the contact
surface 130
tilts. This point 180 is shown as the radially innermost point of contact of
the contact
surface 130 with the flat surface 132 of the workpiece. In tilting of the
nosepiece 24
relative the surface 132, point 180 is a fulcrum about which tilting occurs.
In Figure 8,
line 176 represents a plane in which the head of the screw 16 lies when the
screw 16 has
been fully countersunk. Line 178 represents a plane in which the fastener exit
opening
136 lies and, therefore, also represents a plane in which the head of the
screw 16 would
lie if the screw 16 had been driven normal a surface 132 of the workpiece and
fully
countersunk. The distance Y between the two parallel lines 176 and 178
represents the
increased distance the screw had to be driven to fully countersink when the
screw is
driven at an angle to the normal as contrasted with when the screw is driven
normal the
workpiece. The distance from the axis 52 to a point 180 about which the
nosepiece
pivots for tilting is shown as X. The distance Y can be calculated as follows:
Y = 2X tangent (angle A)
where A is the angle of the axis 52 to a line 179 normal to the surface 132.
For any given
angle A, therefore, the location of the tilt or fulcrum point 180 from the
axis 52 increases
the distance Y which the screw must be driven to be fully countersunk.
11
CA 02324627 2000-10-26
An autofeed screwdriver as illustrated in Figures 1 to 5 may be provided
with a depth adjustment mechanism which restricts the depth to which the
driver shaft 34
drives a screw into a workpiece. It is advantageous if the screwdriver may be
provided to
have minimal required adjustment of countersinking. To have the innermost
contact and
fulcrum point 180 at which the contact surface 130 of a nosepiece engages the
workpiece
located as close as possible to the axis 52 is advantageous.
In a situation where the diameter of the guide tube is represented by a
given diameter, which diameter is preferably only marginally greater than the
diameter of
a screw to be driven, the present inventor has appreciated that preferred nose
portions 24
in accordance with the present invention provide for the innermost contact
point 180 of
the contact surface 130 to be within a radius of not greater than three times
or two times
the diameter of the guideway. Preferably, when the axis 52 is tilted at an
angle to a
normal to the surface 132 of up to about 60 , the innermost point of contact
180 is
located a distance from the axis 52 not greater than a distance equal to twice
the radius of
the guideway and, preferably, not greater than a distance equal to 1.5 times
the radius of
the guideway, more preferably, not greater than a distance equal to 1.25 times
the radius
of the guideway.
Driver Attachment
Reference is again made to Figure 1 which shows a complete power
screwdriver assembly 10 in accordance with the present invention. The assembly
10
comprises the power driver 11 to which a driver attachment 12 is secured. The
driver
attachment 12 receives a collated screwstrip 14 comprising a plastic strip 13
and spaced
screws 16 held by the strip 13 to be successively driven.
Reference is made to Figure 3 showing an exploded view of major
components of the driver attachment 12 as housing 18 and a slide body 20
comprising a
rear portion 22 and a nose portion 24. Figures 4 and 5 show in cross-section
the
interaction of these components.
12
CA 02324627 2000-10-26
As seen in Figure 3, the rearmost end 26 of the housing 18 has a
rearwardly directed socket 27 with a longitudinal slot 28 in its side wall to
receive and
securely clamp the housing 18 onto the driver housing 30 of the power driver
11 so as to
secure the housing 18 of the driver attachment to the housing 30 of the power
driver
against relative movement. The power driver 11 has a chuck 32 rotatable in the
driver
housing 30 by an electric motor (not shown). The chuck 32 releasably engages
the driver
shaft 34 in known manner.
As seen in Figure 4, the slide body 20 is slidably received in the housing
18 with the driver shaft 34 received in a bore passing through the slide body
20. A
compression spring 38 disposed between the housing 18 and the slide body 20
coaxially
about the driver shaft 34 biases the slide body away from the housing 18 from
a retracted
position towards an extended position. As shown, the spring 38 is disposed
between the
housing 18 and the slide body 20. Slide stops 25, best shown in Figure 3, are
secured to a
rear portion 22 of the slide body. Two slide stops 25 slide in two
longitudinal slots 40 on
each side of the side wall 42 of the housing 18 to key the slide body to the
housing 18
against relative rotation and to prevent the slide body being moved out of the
housing 18
past a fully extended position.
The rear portion 22 comprises a generally cylindrical element 44 with a
radially extending flange element 46 on one side. A lever 48 is pivotally
mounted to the
flange element 46 by axle 50 for pivoting about an axis of axle 50 normal to
the
longitudinal axis 52 which passes centrally through the drive shaft 34 and
about which
the drive shaft is rotatable. Lever 48 has a forward arm 54 extending
forwardly to its
front end 56 and a rear arm 58 extending rearwardly to its rear end 60.
The rear arm 58 of the lever 48 carries a cam pin 502 near its rear end 60.
The cam pin 502 is a removable cylindrical pin threadably received in threaded
opening
503 in rear arm 58. A cam slot 506 is provided in the side wall 302 of the
housing 18.
The cam slot 506 has a first camming surface 508 and a second camming
surface 510 spaced therefrom and presenting different profiles as best seen in
side view in
Figure 3. The cam pin 502 is received in cam slot 506 between the first and
second
13
CA 02324627 2000-10-26
camming surfaces 508 and 510 for engagement of each under different conditions
of
operation. Spring 69 about axle 50, as shown in Figure 5, biases the lever 48
in a
clockwise direction as seen in Figure 5 and thus biases the lever to pivot in
a direction
which moves a shuttle 96 shown in Figure 2 towards the axis 52 of the guide
tube and
biases the cam pin 502 towards the first camming surface 508.
In operation of the driver attachment, the slide body 20 moves relative the
housing 18 in a cycle of operation in which the slide body moves in a
retracting stroke
from the extended position to the retracted position and then moves in an
extending
stroke from the retracted position to the extended position. Whether in any
position in a
cycle the cam pin 502 will engage either the first camming surface 508 or the
second
camming surface 510 will depend on a number of factors. Most significant of
these
factors involve the resistance to movement of the shuttle 96 in either
direction as
compared to the strength of the spring 69 tending to move the shuttle 96
towards axis 52.
Under conditions in which the bias of the spring 69 is dominant over
resistance to
movement of the shuttle 96, then the bias of the spring will place the cam pin
502 into
engagement with the first camming surface 508 with relative motion of the
lever 48 and
therefore the shuttle 96 relative the position of the slide body 20 in the
housing 18 to be
dictated by the profile of the first camming surface 508. Under conditions
where the
resistance to movement of the shuttle is greater than the force of the spring
96, then the
cam pin 502 will either engage the first camming surface 508 or the second
camming
surface 510 depending on the direction of such resistance and whether the
slide body is in
the retracting stroke or the extending stroke. For example, in an extending
stroke when
the shuttle 96 is engaging and advancing the next screw to be driven and the
resistance
offered to advance by the screwstrip may be greater than the force of the
spring 69, then
the cam pin 502 will engage on the second camming surface 510.
In the preferred embodiment shown, as best seen in Figure 3, the first
camming surface 508 has a first portion 514, a second portion 516 and a third
portion
518. The first portion 514 and the second portion 518 are substantially
parallel the driver
shaft axis 52. Second portion 516 extends at an angle rearwardly and towards
axis 52.
14
CA 02324627 2000-10-26
The second camming surface 510 has a first portion 520 which extends
angling forwardly and away from axis 52 and a second portion 522 which is
substantially
parallel the axis 52.
The third portion 518 of the first camming surface 508 and the second
portion 522 of the second camming surface 510 are parallel and disposed a
distance apart
only marginally greater than the diameter of cam pin 502 so as to locate the
cam pin 506
therein in substantially the same position whether the cam pin 502 rides on
first camming
surface 508 or second camming surface 510.
The cam slot 506 has a front end 512 where the first portion 514 of the
first camming surface 508 merges with the first portion 520 of the second
camming
surface 510. In the front end 512, the width of the cam slot 506 is also only
marginally
greater than the diameter of the cam pin 502 so as to locate the cam pin 506
therein in
substantially the same position whether the cam pin 502 rides on the first
camming
surface 508 or the second camming surface 510.
The first portion 520 of the second camming surface 510 is spaced from
the first camming surface 508 and, in particular, its first portion 514 and
second portion
516 by a distance substantially greater than the diameter of cam pin 502.
A more detailed description of the interaction of the cam pin 502 in the
cam slot 508 is found in U.S. Patent 5,934,162 to Habermehl.
The nose portion 24 of the housing 20 has a generally cylindrical screw
guide element or guide tube 75 arranged generally coaxially about longitudinal
axis 52
and a flange-like screw feed channel element 76 extending radially from the
guide tube
75.
The guide tube 75 has a cylindrical bore or guideway 82 extending axially
through the guide tube with the guideway 82 delineated and bordered by a
radially
extending cylindrical side wall 83 and open at its forward axial end and at
its rearward
axial end 85.
The guide tube 75 has a rearward section adjacent its rear end 85 in which
the side wall 83 extends 360 about the guideway 82. Forward of the rearward
section,
-------------
CA 02324627 2000-10-26
the guide tube has a forward section which has an access opening 86, shown in
Figures 4
and 5 as being on the right hand side of the guide tube 75. Screw access
opening 86 is
provided to permit the screwstrip 14 including retaining strip 13 and screws
16 to move
radially inwardly into the guideway 82 from the right as seen in Figure 4 and
5. Each
screw preferably has a head 17 with a diameter marginally smaller than the
diameter of
the side wall 83. It follows that where the head of the screw is to enter the
guideway 82,
the screw access opening must have a circumferential extent of at least 180 .
Where the
shank of the screw is to enter the guideway, the screw access opening may have
a lesser
circumferential extent.
In the forward section, the side wall 83 of the guide tube 75 engages the
radially outermost periphery of the head 17 of the screw 16, to axially locate
the screw
head 17 coaxially within the guideway 82 in axial alignment with the drive
shaft 34. In
this regard, the side wall 83 preferably extends about the screw sufficiently
to coaxially
locate the screw head and, thus, preferably extend about the screw head at
least 120 ,
more preferably, at least 150 and, most preferably, about 180 .
An exit opening 87, shown towards the left-hand side of the guide tube 75
in Figures 4 and 5, is provided of a size to permit the spent plastic strip 13
from which the
screws 16 have been driven to exit from the guideway 82. Forwardly of the exit
opening
87, the side wall 83 of the guide tube 75 is shown as extending about 180
about the
longitudinal axis 52 so as to continue to provide a side wall 83 which can
assist and
positively coaxially guiding the head 17 of a screw 16 being driven.
The screw feed channel element 76 is best seen in Figures 2, 3 and 4 as
providing a channelway 88 which extends radially relative the longitudinal
axis 52 to
intersect with the guideway 82 in the guide tube 75. In this regard, the
channelway 88
opens to the guideway 82 as the screw access opening 86. The channelway 88
provides a
channel of a cross-section similar to that of the screw access opening 86 from
the screw
access opening 86 to a remote entranceway opening 90. The channelway 88 is
defined
between two side walls 91 and 92 joined by a top wall 93. The major side wall
91 is
shown as extending from the heads 17 of the screws 16 forwardly to at least
partially
16
CA 02324627 2000-10-26
behind the plastic retaining strip 13. The lesser side wa1192 is shown as
extending from
the heads 17 of the screws 16 forwardly to above the plastic strip 13.
Stopping the lesser
side wall from extending down over the strip 13 assists in reducing friction
between the
strip 13 and the lesser side wall. The side walls 91 and 92 define the
channelway 88 with
a cross-section conforming closely to that of the screwstrip 14 and its strip
13 and screws
16 with an enlarged width where the heads of the screws are located and an
enlarged
width where the retaining strip 13 is provided about the screws. The side
walls 91 and 92
also have an enlarged funnelling section at the entranceway opening 90 which
tapers
inwardly to assist in guiding the screwstrip to enter the channelway.
Pawl Mechanism
As best seen in Figure 2, the major side wa1191 is provided on its exterior
back surface with a raceway 94 extending parallel the channelway 88 and in
which a
shuttle 96 is captured to be slidable towards and away from the guide tube 75
between an
advanced position near the guide tube and a withdrawn position remote from the
guide
tube. The shuttle 96 has a rear surface in which there is provided a
rearwardly directed
opening 98 adapted to receive the front end 56 of the forward arm 54 of lever
48 so as to
couple the shuttle 96 to the lever 48 for movement therewith.
Shuttle 96 carries a pawl 99 to engage the screwstrip 14 and with
movement of the shuttle 96 to successively advance the strip one screw at a
time. As
seen in Figure 9, the shuttle 96 has a fixed post 100 on which the pawl 99 is
journalled
about an axis parallel the longitudinal axis 52 about which the driver shaft
rotates. The
paw199 has a first pusher arm 101 at its forward end to engage a first lead
screw 16a and
a second pusher arm 601 to engage a second screw 16b. The pusher arms extend
out
from slot 103 in the shuttle 96 and through a slot 105 in the major side wall
91 of the feed
channel element 76 to engage and advance the screwstrip. The pawl 99 has a
manual
release arm 102 which extends out away from the screwstrip through the opening
104
from slot 103 of the shuttle 99. A torsional spring 615, shown only in Figure
11, is
disposed about post 100 between pawl 99 and shuttle 96 and urges the first
pusher arm
17
CA 02324627 2000-10-26
101 counterclockwise as seen in Figure 9. The torsional spring biases the
pusher arms
into the screwstrip 14. The engagement of release arm 102 on the left-hand end
of
opening 104 limits the pivoting of the pawl 99 counterclockwise to the
blocking position
shown in Figure 9.
The first pusher arm 101 has a cam face 107 and the second pusher arm
601 has a cam face 607. On the shuttle moving away from the guide tube 75
towards the
withdrawn position, i.e., to the right from the position in Figure 9, the cam
faces 107
and/or 607 will engage the screws 16b and 16c, respectively, and/or the strip
13 and
permit the pawl 99 to pivot about post 100 against the bias of the torsional
spring to a
passage position so that the shuttle 96 may move to the right relative the
screwstrip 14.
The first pusher arm 101 has an engagement face 108 to engage the screws
16 and the second pusher arm 601 has an engagement face 608 to also engage the
screws
16. On the shuttle moving towards the guide tube 75, that is, towards the
advanced
position and towards the left as seen in Figure 11, the engagement faces 108
and 608 will
engage the screw 16b and 16c, respectively, and/or strip 13 and advance the
screwstrip to
the right as seen in Figure 11 so as to position a screw 16b into the guideway
82 in a
position to be driven and to hold the screwstrip 14 against movement towards
the left.
Preferably, as shown in Figure 4, the engagement face 108 of the first pusher
arm 101
engages the screw 16 between its head 17 and the strip 13 as this has been
found
advantageous, particularly to avoid misfeeding with a nose portion 24 as shown
with
engagement of the screw heads in the channelway 88 and engagement of the spent
strip
13 with the support surface 125.
The operation of the shuttle 96 and pawl 99 in normal operation to
advance the screwstrip are illustrated in Figures 9, 10 and 11, representing
successive
steps in a cycle of reciprocating the shuttle 96 back and forth in the raceway
94.
As seen in Figure 11, a dashed line 611 represents a plane of advance in
which the axis of each of the screws 161ie and along which the screwstrip 14
is advanced
towards the left such that screws may successively be brought into alignment
with the
driver shaft whose axis 52 is to occur at the intersection of advance plane
611 with a
18
CA 02324627 2000-10-26
dashed axis line 612. To the left of axis line 612, spent strip 13 is shown
with a broken
sleeve 220a from which a screw has been driven.
As seen in Figure 9, the engagement face 108 of the first pusher arm 101
is engaged behind the first screw 16a and the engagement face 608 of the
second pusher
arm 601 is engaged behind the second screw 16b, whereby the screwstrip 14 is
held in a
position blocked against movement of the strip to the right relative the
shuttle 96.
In the position in Figure 9, the first screw 16a in sleeve 220a is axially in
line with the axis 52 of the driver shaft ready for driving.
From the position of Figure 9, in use of the tool, the lead screw 16a is
driven from sleeve 220a and the shuttle 96 is withdrawn to the right passing
through the
position of Figure 10 to assume the position of Figure 11. Thus, as seen in
Figure 10,
arrow 610 represents the withdrawal of the shuttle 96 relative the driver
shaft and
screwstrip 14.
From the position of Figure 9 on movement of the shuttle 96 towards the
right relative the screwstrip 14, it is to be appreciated that the camming
surface 107 of the
first arm 101 engages screw 16b and such engagement causes the pawl 99 to
pivot about
axis 100 against the bias of the spring. With further relative movement of the
shuttle to
the right, the camming surface 107 will continue to pivot the pawl 99 until
the camming
surface 607 comes to engage screw 16c and further pivot the pawl 99 so that
the second
arm 601 may pass to the left of the screw 16c. Figure 10 illustrates the
shuttle 96 as
moving to the right as indicated by arrow 610 and with cam face 607 of the
second
pusher arm 601 engaging screw 16c in sleeve 220c.
The engagement of the cam faces with the screws pivots the pawl 99
against the bias of the torsional spring such that the pawl 99 may rotate
clockwise. On
the first pusher arm 101 moving to the right past screw 16b and the second
pusher arm
601 moving to the right past screw 16c, the torsional spring urges the pawl 99
to rotate
about post 100 so that the engagement faces 108 and 608 are positioned ready
to engage
the screws 16b and 16c and advance them to the left, indicated by arrow 613,
as seen in
Figure 11.
19
CA 02324627 2000-10-26
Figure 11 shows the shuttle 96 withdrawn rearwardly sufficiently to a
position that the engagement faces 108 and 608 are to the right, rearward of
the screws
16b and 16c in sleeves 220b and 220c and with the screw 16a, not seen, as it
has been
driven from the fractured sleeve 220a. From the position of Figure 11, the
shuttle 96 is
moved to the left relative the axis 52 thereby advancing the screwstrip 14,
moving it to
the left and placing the screw 16b in the sleeve 220b into axial alignment
with the driver
shaft axis 52. In advance of the screwstrip 14, both the first and second
pusher arms 101
and 601 engage their respective screws and urge the screwstrip 14 to advance.
One advantage of the pawl 96 of the present invention having two pusher
arms 101 and 601 which engage two different screws arises in situations where,
in use of
a tool, the shuttle 96 may not move from the position of Figure 9 to the right
sufficiently
to have the first pusher arm 101 engage to the right of the screw 16b in
sleeve 220b. For
example, if a shuttle 96 having only arm 101 and not arm 601 move to the right
only as
far as shown in Figure 10, then, after the screw 16a in sleeve 220a is driven
from sleeve
220a, there is no screw to the left of the only pusher arm 101 which the
pusher arm 101
may engage to stop movement of the screwstrip 14 to the right. In previously
known
devices as taught in U.S. Patent 5,934,162 with merely a single pusher arm
101, where
the single pusher arm does not engage the next screw, the screwstrip 14 can
merely move
rearwardly to the right and fall out of the channelway 88 and, thus, out of
the tool. With
the device of the present invention in the position of Figure 10, the second
pusher arm
601 is to the right of screw 16b in sleeve 220b and will prevent the
screwstrip 14 from
removal or falling out by movement of the screwstrip to the right.
With the pawl 99 in the position shown in Figures 9 and 11, the pawl 99
prevents movement and withdrawal of the screwstrip 14 to the right relative
the shuttle
96. To permit manual withdrawal of the screwstrip 14, the manual release arm
102 may
be pivoted, as by a user's finger, clockwise against the bias of spring so
that the first
pusher arm 101 and second pusher arm 601 are moved away from and clear of the
screwstrip 14. With the release arm 102 manually rotated clockwise from the
position
shown in Figure 10 until rotation of the first arm 101 is stopped by abutment
614 in the
CA 02324627 2000-10-26
shuttle, the screwstrip 14 may be manually withdrawn in a direction toward the
right as
may be useful, for example, to clear jams or change screwstrips.
In manually pivoting the pawl 99 as with a user's thumb from the position
of Figure 9 to the position of Figure 10, the engagement faces 108 and 608 are
moved
substantially transversely relative the length of the screwstrip 14 to become
disengaged
from the screws 16a and 16b. To facilitate this, the axis about which the pawl
99 pivots,
i.e. the axis of post 100, is located to the right relative the longitudinal
of the screwstrip
14 from the rearwardmost screw 16b to be engaged by the second pusher arm 601.
As
well, the engagement faces 108 and 608 are disposed substantially normal to
the plane of
advance 611 of the screwstrip 14 when the pawl release arm 102 is rotated as
far as
possible counterclockwise.
In Figures 9 to 11, the pawl 99 is configured such that the engagement
face 108 of the first pusher arm 101 and the engagement face 608 of the second
pusher
arm 601 are spaced a distance equal to the spacing between screws such that
each face
engages a different screw. Figure 12 is identical to Figure 9 other than in
the location of
the second pusher arm 601 on the pawl 99. Figure 12 shows an alternate
arrangement in
which the engagement faces 108 and 608 are spaced less than the distance
between
screws. The face 608 in Figure 12 serves a purpose as when the shuttle 96 is
not
withdrawn rearwardly to a position with the engagement face 108 to the right
of the
screw 16b of preventing undesired withdrawal of the screwstrip 14. Provided
the
engagement surface 608 is to the right of screw 16b, it will, if the
screwstrip 14 is
attempted to be moved to the right, pivot under the bias of the spring to
engage screw 16b
and prevent rearward removal of the screwstrip 14.
The pawl 99 is shown in Figures 9 to 11 as having a length to engage two
adjacent screws. It is to be appreciated that the pawl could be modified to
have an
increased length to span more than two screws. As well, while the pawl 99 has
two
engagement faces, it could have three or more engagement faces to engage, for
example,
three or more of the screws.
21
CA 02324627 2000-10-26
The figures show pawl 99 carried on a slidable shuttle. However, it is
within the scope of the present invention that the pawl be mounted, for
example, for
pivoting directly on the end of a lever arm as, for example, on the front end
56 of the
forward arm 54 of the lever 48 without any shuttle being provided.
An advantage of the present invention is that while two engagement faces
108 and 608 provide two members to stop removal of the strip by engaging the
screws
that only one release arm 102 needs to be activated by a user to release both
engagement
faces 108 and 608. This provides for a simplified, preferred structure with
only a single
pivot axis required. A single release arm 102 is provided for two engagement
faces.
Such a structure is preferred over two pawls each pivoted about their own axis
and
having two separate release arms or a coupling mechanism coupling the pawls
together
for release of both by moving one of the pawls.
The release arm 102 permits manual withdrawal of the screwstrip 14. A
user may with his finger or thumb manually pivot the release arm 102 against
the bias of
spring so that both the first pusher arm 101 and its engagement face 108 and
the second
pusher arm 601 and its engagement face 608 are moved away from and clear of
the
screwstrip 14 whereby the screwstrip may manually be withdrawn as may be
useful to
clear jams or change screwstrips.
A fixed post 432 is provided on shuttle 96 opposed to the manual release
arm 102 to permit pivoting of the release arm 102 by drawing the release arm
102
towards the fixed post 432 as by pinching them between a user's thumb and
index finger.
The lever 48 couples to the shuttle 96 with the forward arm 54 of lever 48
received in the opening 98 of the shuttle 96. Sliding of the slide body 20 and
the housing
18 in a cycle from an extended position to a retracted position and then back
to an
extended position results in reciprocal pivoting of the lever 48 about axle 50
which slides
the shuttle 96 between the advanced and withdrawn position in its raceway 94
and, hence,
results in the pawl 99 first retracting from engagement with a first screw to
be driven to
behind the next screw 16 and then advancing this next screw into a position to
be driven.
22
CA 02324627 2000-10-26
The nose portion 24 carries the guide tube 75 with its screw locating
guideway 82, the screw feed channel element 76 with its channelway 88, and
screw feed
advance mechanism with the reciprocating shuttle 96 and pawl 99 to advance the
screwstrip 14 via the channelway 88 into the guideway 82. Each of the guideway
82,
channelway 88 and shuttle 96 are preferably customized for screwstrips and
screws or
other fasteners of a corresponding size. In this context, size includes shape,
head
diameter, shaft diameter, retaining strip configuration, length, spacing of
screws along the
retaining strip and the presence or absence of washes amongst other things.
Different
nose portions 24 are to be configured for different screwstrips and screws.
Different
modified slide bodies 20 can be exchanged so as to permit the driver
attachment to be
readily adapted to drive different screwstrips and screws.
Many changes can be made to the physical arrangement of the nose
portion 24 to accommodate different screws and fasteners. For example, the
cross-
sectional shape of the channelway 88 can be changed as can the diameter of the
guideway
82. The length of the side walls 91 and 92 about the channelway 88 can be
varied to
accommodate different size screws which may require greater or lesser
engagement.
The construction of the housing 18 and slide body 20 provide for a
compact driver attachment.
The housing 18 includes side wall 301. The slide body 20 as best seen in
Figure 3 has a part cylindrical portion of a uniform radius sized to be
marginally smaller
than a part cylindrical inner surface of the side wall 301 of the housing 18.
The side wall
301 extends circumferentially about the part cylindrical portion of the slide
body 20 to
retain the slide body 20 therein.
The housing has a flange portion 302 which extends radially from one side
of the part cylindrical portion and is adapted to house the radially extending
flange 46 of
the rear portion 22 and the screw feed activation mechanism comprising the
lever 48 and
cam follower 62. The flange portion 302 is open at its front end and side to
permit the
screw feed channel element 76 to slide into and out of the housing 18.
Concentrically
23
CA 02324627 2000-10-26
located about the drive shaft 34 is the spring 38, the part cylindrical
portions of the slide
body 20, and the interior part cylindrical portions of the housing 18.
Hooked Nosepiece
Reference is made to Figures 13 to 16 which show the nose portion 24 of
the slide body 20 shown in Figures 1 to 8. The nose portion 24 has guideway 82
therethrough defined within wall 81 which extends circumferentially from a
first end 240
of the wall to a second end 242 of the wall. As seen in Figure 15, the wall 81
has a
generally C-shape in cross-section normal the axis 52 of the guideway 82. The
guideway
82 is shown in Figure 15 as represented by the area within a circle about axis
52. The
outer periphery of the guideway 82 is a cylindrical surface delineated in part
by part-
cylindrical portions 244 and 246 of the inwardly directed inner surface 83 of
the wall 81
with the remainder of the outer periphery of the guideway shown as delineated
by two
segments 248 and 249 of a dashed circle line. The access opening 86 is seen in
Figure 15
as providing, in effect, a slotway which is radially outwardly of the guideway
82 and
effectively extends radially outwardly from the guideway 82 as an axially
extending
slotway between the ends 240 and 242 of the wall 81 through the wall 81 to
permit a
screw to enter the guideway 82 radially with the screw maintained
substantially parallel
the axis 52 of the guideway 82. The first end 240 of the wall 81 forms a hook-
shaped
member having a radially inwardly directed bight 250 which extends axially
along the
cylindrical guideway 82 and opens radially inwardly into the guideway 82. The
bight
250 forms a groove-like, channelway or catch trough adapted to assist in
retaining a tip of
a screw which becomes received therein in the bight 250 against removal. The
hook
member about the bight 250 has an inner bight surface shown as comprising
surface 252
on a side closest to the access opening 86 and surface 254 on the side remote
from the
access opening 86.
As seen in Figure 15, the catch trough or bight 250 is delineated between
the bight surfaces 252 and 254 and circle line segment 248. The bight surface
254 on the
side of the bight remote from the access opening 86 is seen to merge
tangentially into the
24
CA 02324627 2000-10-26
part-cylindrical portion 244 of the inner surfaces about the guideway 82. The
inner
surface 252 on the side of the bight closest the access opening 86 is directed
circumferentially away from the access opening 86.
Reference is made to Figures 13 and 14 which schematically illustrate a
"renegade" screw 16 which has its screw head 17 coaxially within the guideway
82 as
with a bit 122 of the driver shaft 34 engaging the head. The axis of the screw
is out of
axial alignment with the axis of the guideway 82 such that the shank and/or
tip 15 of the
screw is engaged with the inner surfaces of the wa1181. Figure 13 shows the
tip 15 of the
screw 16 engaging the part-cylindrical portion 244 of the inner surface of the
wall 81. In
rotation and driving of the screw 16 by the driver shaft 34, there is a
probability and/or
tendency for the tip 15 of the screw to move along the inner surface of the
wall
circumferentially clockwise as seen in Figure 13 from the position in Figure
13 to the
position in Figure 14. When the tip 15 reaches the position in Figure 14, the
shank and/or
tip of the screw 16 enters the bight 250 as guided therein by engagement with
firstly, the
portion 224 of the inner surface and then, subsequently, with inner bight
surface 254 and
inner bight surface 252. While engagement with the portion 224 and inner bight
surface
254 directs the tip to continue to slide circumferentially toward the access
opening 86,
engagement with inner bight surface 252 tends to catch the tip in the bight
250 and resist
further circumferential movement towards the access opening 86. Preventing
such a
renegade screw 16 from having its tip extend out through the access opening 86
is
advantageous to prevent malfunction of the apparatus and/or jamming.
To assist in retaining the tip 15 of a screw 16 in the bight 250, at least
against circumferential movement towards the access opening 86, the inner
bight surface
252 is directed circumferentially away from the access opening 86. Once a tip
15 of a
screw may be engaged within the bight 250, typically on driving the screw 16
forwardly
by the driver shaft 34, the tip 15 will slide axially forwardly within the
bight 250 until it
leaves the forward end of nose portion 24 and become engaged within a
workpiece for
subsequent driving in an acceptable manner.
CA 02324627 2000-10-26
Figure 15 shows the second end 242 of the wall 81 having a portion 243 of
the inner surface of the wall which extends as a substantially tangential
extension of the
part-cylindrical portion 244.
Figure 15 also shows the distal end of the hook-shaped member as
forming the part-cylindrical portion 246 which assists in defining the
periphery of the
guideway 82. The part-cylindrical portion 246 may be no more than an axially
extending
surface of negligable circumferential extent, however, located the same
distance from
axis 52 as portion 244.
The part-cylindrical portions of the inner surface of the wall 81 effectively
extend circumferentially about the guideway 82 other than over the sector
represented by
the segments 248 and 249 of the dashed circle line. Preferably, this segment
249 has a
circumferential extent as small as practically possible to assist in retaining
the head 17 of
a screw within the guideway 82. It is preferred that the part-cylindrical
portions of the
inner surface of the wall extend about the axis 52 greater than 180 so as to
retain a head
of a screw in the guideway against lateral removal. Conversely, the segment
249
preferably has a circumferential extent of less than 180 and, more
preferably, less than
about 120 at least forward of where the head of the screw must pass radially
into the
guideway 82.
Figure 16 shows an end elevation view of the slide body 18 of Figure 4,
however, with the lever 48 and shuttle mechanism removed. Figure 16 thus
represents a
view of the nose portion 24 and rear portion 22 as viewed along line XVII-
XVII' in
Figure 5. As seen in Figure 16, the channelway 88 with its side walls 91 and
92 and top
wall 93 extends radially into the guideway 82 maintaining throughout the
extent of the
channelway 88 a width between the side walls 91 and 92 sufficiently large to
receive the
head of the screw and permit the head of the screw to pass radially into the
guideway 82.
Forwardly from where the channelway 88 is of enlarged width to receive the
head of the
screw, the channelway is of reduced width, being a width which is merely
sufficient to
permit the shank of the screw to pass therethrough. As best shown in Figure
15, radially
outwardly directed surface 260 of the hook-shaped first end 240 angles
inwardly into the
26
CA 02324627 2000-10-26
guideway 82 so as to assist in guiding as a cam surface the shank of a screw
towards the
wal1242 and, hence, into the guideway 82. While not necessary, it is preferred
as shown
in Figure 16 that the hook-shaped member and its bight 250 extend the entire
length from
where the channelway 88 opens to pass the head of a screw forwardly to the
forward end
of the nose portion.
The hook-shaped member preferably serves at least two functions, firstly,
in assisting and retaining a head of a screw in the guideway and, secondly, in
catching the
tip of any renegade screw. It follows, therefore, that the bight 250 need only
be provided
in forward portions of the guideway 82 where the tip of the screw may be
located.
The hook-shaped member has been shown as having a bight 250 of
constant cross-section along the length of the guideway 82. It is to be
appreciated,
however, that the bight 250 could have a varying cross-section, profile or
configuration
along its axial length. The bight 250 preferably extends axially along the
guideway 82
parallel the axis 52, however, the bight 250 could extend at an angle to the
axis 52 as, for
example, as a part helix.
The nose portion 24, in effect, comprises an open-sided tubular member
having wall 81 circumferentially about a central passageway extending
therethrough and
open at both ends. The central passageway includes the cylindrical guideway 82
and the
screw catch groove or bight 250. The catch groove 250 extends axially along
the
guideway 82 cut into the wall 81 radially outwardly from the guideway 82. The
catch
groove 250 opens radially inwardly into the guideway 82 to define the inner
bight surface
252 which provide a catch surface of the wall 81 located circumferentially
proximate the
slotway-like access opening 86 and directed away from the access opening 86.
The
access opening 86 extends as a slotway extending axially along the guideway 82
and
radially outwardly from the guideway 82 entirely through the wall 81.
In the preferred nose portions 24 shown, the screw access opening 86 is
shown to extend forwardly to the forward end of the nose portion 24. It is to
be
appreciated that the screw access opening 86 need only have an axial length as
long as
any screw to pass therethrough and the wall 81 may extend 360 about the
guideway 82
27
CA 02324627 2007-04-19
forward of the access opening 86 such as taught in U.S. Patent 5,699,704,
issued
December 23, 1997.
Reference is now made to Figure 17 which shows a cross-sectional view
through another embodiment of a nosepiece similar to that in Figure 15. The
embodiment of Figure 17 is shown, however, as having not only a hook-shaped
member
formed on the first end 240 of the wall 83 but also a second similar hook-
shaped
member formed as the second end 242 of the wall 83. The second hook-shaped
member
may function in a similar manner to the first hook-shaped member and both
provide
bights 250 each having surfaces 252 on the side closest to the access opening
86 which
is disposed so as to be directed circumferentially away from the access
opening 86 and
assist in preventing a tip of a screw which becomes received in the bight 250
from
moving from the bight 250 circumferentially towards the access opening 86.
Figure 17 shows the surface 252 of the bight on the second end 242 as
lying along a radial line generally indicated 264 extending from the axis 52
radially
outwardly to a point where the surface 252 engages the outer cylindrical
periphery of the
guideway 82.
Reference is made to Figure 18 which shows a modified version of a
nosepiece in accordance with the present invention which has features similar
to the
other nosepieces. The embodiment illustrated in Figure 18 shows a nosepiece 24
preferably made out of synthetic material as by injection molding from plastic
and to
which a metallic insert 266 has been applied secured to the synthetic
material. The insert
266 is preferably made of wear-resistant metal and is formed from a relatively
thin sheet
of metal. The insert 266 is secured inside the nosepiece so as to provide in a
forward
portion of the nosepiece the inner surfaces about the guideway 82 and to
provide a hook-
shaped member 252 at one side by the metal insert 266 being folded back on
itself to
form a distal end with the bight 250 therein.
28
CA 02324627 2000-10-26
Depth Stop Mechanism
The driver attachment is provided with an adjustable depth stop
mechanism which can be used to adjust the fully retracted position, that is,
the extent to
which the slide body 20 may slide into the housing 18. The adjustable depth
stop
mechanism is best seen in Figures 3 and 5.
A depth setting cam member 114 is secured to the housing 18 for rotation
about a pin 116, shown in Figure 5, parallel the longitudinal axis 52. The cam
member
114 has a cam surface 115 which varies in depth, parallel the longitudinal
axis 52,
circumferentially about the cam member 114. A portion of the cam surface 115
is always
axially in line with the rear end 117 of the slide body 20. By rotation of the
cam member
114, the extent to which the slide body 20 may slide rearwardly is adjusted.
The extent the slide body 20 may slide into the housing 18 is determined
by the depth of the cam member 114 axially in line with the rear end 117 of
the slide
body 20. The cam member 114 is preferably provided with a ratchet-like
arrangement to
have the cam member 114 remain at any selected position biased against
movement from
the selected position and with circular indents or depressions in the cam
surface 115 to
assist in positive engagement by the rear end 117 of the slide body 20. A set
screw 119,
as seen in Figure 3, is provided to lock the cam member 114 at a desired
position and/or
to increase resistance to rotation. The cam member 114 is accessible by a user
yet is
provided to be out the way and not interfere with use of the driver
attachment. The depth
stop mechanism controls the extent to which screws are driven into a workpiece
and thus
controls the extent of countersinking.
The slide body 20 may be customized for use in respect of different size
screws by having the location of the stop surface 117 suitably provided
axially on the
slide body 20 as may be advantageous for use of different size screws.
The driver shaft 34 is shown in Figures 4 and 5 as carrying a split washer
120 engaged in an annular groove near its rear end 121 to assist in retaining
the rear end
of the driver shaft in the socket 27 of the housing 18. The driver shaft 34 is
provided
with a removable bit 122 at its forward end which bit can readily be removed
for
29
CA 02324627 2000-10-26
replacement by another bit as for different size screws. Such bits include
sockets and the
like and will preferably be of an outside diameter complementary to the inside
diameter
of the guideway 82.
The slide body 20 is shown in Figures 4 and 5 as having a radially
inwardly extending annular flange 19 which provides the end of a rearwardly
opening
bore 79 within which the spring 38 is received. The annular flange 19 has an
opening
therethrough of a diameter preferably equal to the diameter of the guideway 88
and, in
any event, at least slightly larger than the diameter of the driver shaft 34
so as to assist in
journalling the driver shaft therein.
Insofar as the driver shaft 34 has a removable bit 122, when the driver
attachment 12 is in the retracted position, the bit 122 may be readily
accessible for
removal and replacement.
Operation
Operation of the driver attachment is now explained with particular
reference to Figures 4 and 5. As seen in Figure 4, the screws 16 to be driven
are collated
to be held parallel and spaced from each other by the plastic retaining strip
13.
In operation, a screwstrip 14 containing a number of screws 16 collated in
the plastic retaining strip 13 is inserted into the channelway 88 with the
first screw to be
driven received within the guideway 82. To drive the first screw into the
workpiece 134,
the power driver 11 is activated to rotate the driver shaft 34. The driver
shaft 34 and its
bit 122, while they are rotated, are reciprocally movable in the guideway 82
towards and
away from the workpiece 134. In a driving stroke, manual pressure of the user
pushes the
housing 18 towards the workpiece 134. With initial manual pressure, the
forward end of
the nose portion engages the workpiece 134 to compress spring 38 so as to move
slide
body 20 relative the housing 18 into the housing 18 from an extended position
shown in
Figure 4 to a retracted position. On release of this manual pressure, in a
return stroke, the
compressed spring 38 moves the slide body 20 back to the extended position
thereby
moving the housing 18 and the driver shaft 34 away from the workpiece.
CA 02324627 2000-10-26
In a driving stroke, as the driver shaft 34 is axially moved towards the
workpiece, the bit 122 engages the screw head 17 to rotate the first screw to
be driven.
As is known, the plastic strip 13 is formed to release the screw 16 as the
screw 16
advances forwardly rotated by the driver shaft 34. Preferably, the screw tip
will engage
in a workpiece before the head of the screw engages the strip such that
engagement of the
screw in the workpiece will assist in drawing the screw head through the strip
to break
the fragible straps, however, this is not necessary and a screw may merely, by
pressure
from the drive shaft, be released before the screw engages the workpiece.
Preferably, on
release of the screw 16, the plastic strip 13 deflects away from the screw 16
outwardly so
as to not interfere with the screw 16 in its movement into the workplace.
After the screw
16 is driven into the workpiece 134, the driver shaft 34 axially moves away
from the
workpiece under the force of the spring 38 and a successive screw 16 is moved
via the
screw feed advance mechanism from the channelway 88 through the access opening
86
into the guideway 82 and into the axial alignment in the guideway with the
driver shaft
34.
The screw 16 to be driven is held in position in axial alignment with the
driver shaft 34 with its screw head 17 abutting the side wall 83 in the
guideway 82. As a
screw 16 to be driven is moved into the cylindrical guideway 82, a leading
portion of the
strip 13 from which screws have previously been driven extends outwardly from
the
guideway 82 through the exit opening 87 permitting substantially unhindered
advance of
the screwstrip 14.
To assist in location of a screw to be driven within the guide tube 75, in
the preferred embodiment the exit opening 87 is provided with a rearwardly
facing
locating surface 125 adapted to engage and support a forward surface 222 of
the strip 13.
Thus, on the bit 122 engaging the head of the screw and urging the screw
forwardly, the
screw may be axially located within the guide tube 75 by reason not only of
the head of
the screw engaging the side wall 83 of the guideway but also with the forward
surface
222 of the strip 13 engaging the locating surface 125 of the exit opening 87.
In this
regard, it is advantageous that the forward surface 222 of the retaining strip
13 be
31
CA 02324627 2000-10-26
accurately formed having regard to the relative location of the screws 16 and
particularly
the location of the their heads 17. The forward surface 222 of the strip 13
may be
complementary formed to the locating surface 125.
In the embodiment of the nose portion 24 shown in Figures 1 to 6, on the
bit 122 engaging the head 17 of the screw 16 and urging it forwardly in the
guideway 82,
the strip 13 is preferably held against movement forwardly firstly by the
forward surface
222 of the strip engaging locating surface 125 and, secondly, by the under
surfaces of the
heads 17 of screws in the channelway 88 engaging on the rearwardly directed
shoulders
provided on each of the side walls 91 and 92 where the enlarged width cross-
section of
the channelway 88 accommodating the head of the screws reduces in width as
seen in
Figure 2. Together with the location of the head 17 of a screw 16 coaxially in
the
guideway, the screw 16 to be driven is located axially aligned with the driver
shaft
without any moving parts other than the advance shuttle 96.
The driver attachment 12 disclosed may be provided for different
applications. In a preferred application, the driver may be used for high
volume heavy
load demands as, for example, as in building houses to apply sub-flooring and
drywall.
For such a configuration, it is preferred that with the power driver 11
comprising a typical
screw gun which inherently incorporates a friction clutch and thus to the
extent that a
screw is fully driven into a workpiece, the clutch will, on the forces
required to drive the
screw becoming excessive, slip such that the bit will not be forced to rotate
an
engagement with the screw head and thus increase the life of the bit.
With the preferred embodiments of this invention using but one paw199, a
preferred configuration of the relative timing of pivoting of the lever 48
compared to the
relative location of the slide body in the housing 18 is one in which the
following aspects
(a) and (b) are met, namely:
(a) firstly, the pawl 99 engages the screw to be driven to maintain the
screw in axial alignment with the bit 122 until the bit 122 has
engaged in the recess in the screw head for rotational coupling
therewith; and
32
CA 02324627 2000-10-26
(b) secondly, the pawl 99 sufficiently withdraws itself such that,
before the screw being driven detaches itself from the strip 13, the
pawl 99 is located engaged on the withdrawal side of the next
screw to be advanced.
Aspect (b) is advantageous to ensure that the screwstrip may not be
inadvertently withdrawn or dislodged before the pawl 99 becomes engaged behind
the
next screw to be advanced. While the screw being driven is attached to
screwstrip, the
screwstrip is held by the bit against removal by rearward movement. If,
however, the
screwstrip becomes detached from the screwstrip before the pawl 99 is behind
the next
screw to be driven, then at this time, the screwstrip can move in a direction
opposite the
direction of advance, for example, either to become removed from the feed
channel
element 76 or to be displaced an extent that the pawl cannot engage the next
screw to be
driven.
To have aspects (a) and (b) permits preferred advantageous operation with
merely a single pawl 99 utilized to advance each screw, to hold it in place
until the bit
engages in the screw and then while the screw is held by the bit, to
withdrawal to engage
behind the next screw to be driven such that the pawl is engaged behind the
next screw
when the screw being driven becomes disengaged from the strip. For example,
where
aspect (b) is not satisfied, the difficulty can arise, for example, that in
the movement of
the pawl 99 towards the withdrawal position, the pawl 99 may engage the strip
and itself
move the strip in a direction opposite the advance direction. Having a
relatively weak
spring which urges the pusher arm 101 of the pawl into the screwstrip can
reduce the
likelihood that the pawl 99 may move the strip in a direction opposite the
advance
direction. Movement of the strip in a direction opposite the advance direction
can be
avoided by the screwstrip and screws being engaged in the screwdriver in
frictional
engagement to resist withdrawal. To some measure, such frictional engagement
arises by
reason of the spent screwstrip extending out of the exit opening 87 and the
screw heads,
shanks and/or strip frictionally engaging the screw feed channel element 76
and/or the
guide tube 24. However, any such friction is contrary to a preferred
configuration in
33
CA 02324627 2000-10-26
which the frictional forces to be overcome by advance of the screwstrip are
minimized.
Therefore, it is a preferred system with least resistance to advance of the
screwstrip and
with a single pawl that it is most preferred that aspects (a) and (b) being
incorporated in a
tool.
It is also advantageous that in addition to aspects (a) and (b), that after
aspect (a) and before aspect (b), an aspect (c) is met whereby the pawl 99
moves toward
the withdrawal position sufficiently that the pawl 99 is moved out of the path
of the head
of the screw and the driver shaft 34 and its bit 122 as they advance a screw.
This aspect
(c) is advantageous so as to avoid the pawl 99 interfering with the easy
advance of the
screw head, bit and mandrel.
Aspects (a), (b) and (c) can be achieved, for example, by the camming
surfaces moving the lever 48 to hold the shuttle 96 and therefore the pawl 99
at a position
either holding or urging the head of the screw into engagement within the
guide tube in
axial alignment with the bit until the bit engages in the recess in the head,
rotatably
coupling the bit and the screw and preferably driving the screw at least some
distance.
However, before the head of the screw moves forwardly sufficiently to engage
the pawl
99, if the pawl 99 were not moved from the position of aspect (a), the camming
surfaces
causes the lever 48 to pivot moving the shuttle 96 towards the withdrawn
position out of
the way of the axial path of the head of the screw's bit and mandrel. The pawl
99
merely needs to be moved towards the withdrawn position such that it engages
behind the
next screw before the screw being driven disengages from the strip as by the
head of the
screw rupturing the strip. However, it is permissible if the pawl 99 moves
relatively
quickly compared to the advance of the screw being driven to the position
behind the
next screw.
As another fourth aspect to relative timing is the aspect that in the
extension stroke a screw being advanced not interfere with withdrawal of the
driver shaft
and its bit. While embodiments can be configured so all interference is
avoided, this is
not necessary. Advantageously, when aspects (a), (b) and (c) are achieved as
by
minimizing the relative time that the pawl 99 engages the first screw in
satisfying aspect
34
CA 02324627 2000-10-26
(a), and prompt withdrawal to satisfy aspect (c), this can minimize the
relative extent to
which interference can arise between the next screw to be driven and the bit
or mandrel
on the extension stroke.
The driver attachment may be constructed from different materials of
construction having regard to characteristics of wear and the intended use of
the
attachment. Preferably, a number of the parts may be molded from nylon or
other
suitably strong lightweight materials. Parts which are subjected to excessive
wear as by
engagement with the head of the screw may be formed from metal or
alternatively metal
inserts may be provided within an injection molded plastic or nylon parts. The
optional
provision of the nose portion 24 as a separate removable element has the
advantage of
permitting removable nose portions to be provided with surfaces which would
bear the
greatest loading and wear and which nose portions may be easily replaced when
worn.
The screw feed advance mechanism carried on the nose portion has been
illustrated merely as comprising a reciprocally slidable shuttle carrying a
pawl. Various
other screw feed advance mechanisms may be provided such as those which may
use
rotary motion to incrementally advance the screws. Similarly, the screws feed
activation
mechanism comprising the lever 48 and the cam follower have been shown as one
preferred mechanism for activating the screw feed advance mechanism yet
provide for
simple uncoupling as between the shuttle 96 and the lever 48. Other screw feed
activation means may be provided having different configurations of cam
followers with
or without levers or the like.
In the preferred embodiment, the screwstrip 14 is illustrated as having
screws extending normal to the longitudinal extension of the strip 13 and, in
this context,
the channelway 88 is disposed normal to the longitudinal axis 52. It is to be
appreciated
that screws and other fasteners may be collated on a screwstrip in parallel
spaced relation,
however, at an angle to the longitudinal axis of the retaining strip in which
case the
channelway 88 would be suitably angled relative the longitudinal axis so as to
locate and
dispose each successive screw parallel to the longitudinal axis 52 of the
driver shaft.
CA 02324627 2000-10-26
A preferred collated screwstrip 14 for use in accordance with the present
invention is as illustrated in the drawings and particularly Figures 1 and 4
and are
substantially in accordance with Canadian Patent 1,054,982. The screwstrip 14
comprises a retaining strip 13 and a plurality of screws 16. The retaining
strip 13
comprises an elongate thin band formed of a plurality of identical sleeves
interconnected
by lands 106. A screw 16 is received within each sleeve. Each screw 16 has a
head 17, a
shank 208 carrying external threads and a tip 15. As shown, the external
threads extend
from below the head 17 to the tip 15.
Each screw is substantially symmetrical about a central longitudinal axis
212. The head 17 has in its top surface a recess for engagement by the
screwdriver bit.
Each screw is received with its threaded shank 208 engaged within a
sleeve. 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 of the screw
16.
Each sleeve has a reduced portion between the lands 106 on one first side of
the strip 13.
This reduced strength portion is shown where the strip extends about each
screw merely
as a thin strap-like portion or strap.
The strip 13 holds the screws 16 in parallel spaced relation a uniform
distance apart. The strip 13 has a forward surface 222 and a rear surface 223.
The lands
106 extend both between adjacent screws 16, that is, horizontally as seen in
Figure 4, and
axially of the screws 16, that is, in the direction of the longitudinal axes
212 of the
screws. Thus, the lands comprise webs of plastic material provided over an
area
extending between sleeves holding the screws and between the forward surface
222 and
the rear surface 223. A land 106 effectively is disposed about a plane which
is parallel to
a plane in which the axes 212 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, in effect, are disposed
as
continuous, vertically disposed strip 13 along the rear of the screws 16, that
is, as a strip
36
CA 02324627 2000-10-26
13 which is substantially disposed about a plane which is parallel to a plane
containing
the axes of all screws.
A preferred feature of the screwstrip 14 is that it may bend to assume a
coil-like configuration due to flexibility of the lands 106, such that, for
example, the
screwstrip could be disposed with the heads of the screws disposed into a
helical coil, that
is, the plane in which all the axes 212 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
212 permits
such coiling.
The invention is not limited to use of the collated screwstrips illustrated.
Many other forms of screwstrips may be used such as those illustrated in U.S.
Patents
3,910,324 to Nasiatka; 5,083,483 to Takaji; 4,019,631 to Lejdegard et al and
4,018,254
to DeCaro.
As seen in Figure 3, the guide tube 75 has an outboard side which is
partially cut away on its outboard side and has a continuous portion 382 of
its outer wall
which separates the screw access opening 86 from the exit opening 87 on the
outboard
side of the guide tube 75. As used herein, the outboard side is the side to
which the strip
13 is deflected when a screw 16 is separated from the screwstrip 14.
To accommodate deflection of the strip 13 away from a screw 16 towards
the outboard side, the passageway which extends from the screw access opening
or
entranceway 86 to the exit opening or exitway 87 is provided on its outboard
side with a
lateral strip receiving slotway 304 cut to extend to the outboard side from
the cylindrical
guideway 82. The slotway 304, as best seen in Figures 2 and 3, is bounded on
the
outboard side by side surface 306, at its forward end by ramped surface 308
and forward
surface 125, and at its rear end by rear surface 312.
The access opening 86 forms an entranceway for the screwstrip 14
generally radially into the guideway 82 on one side. The exit opening 87 forms
an
exitway for portions of the strip 13 from which screws 16 have been driven,
such portions
being referred to as the spent strip 13.
37
CA 02324627 2000-10-26
The exit opening or exitway 87 is shown as adapted to encircle the spent
strip 13 with the exitway 87 bordered by rearwardly directed forward surface
125,
forwardly directed rear surface 312, inboard side surface 314 and outboard
side surface
316.
As seen in Figure 3, ramped surface 308 is an axially rearwardly directed
surface which angles forwardly from the forward surface 125 towards the
entranceway.
The ramped surface 308 extends forwardly from forward surface 125 with
the ramped surface following the curvature of the side wall 83 as a ledge of
constant
width. The ramped surface 308 is useful to assist in driving the last screw
from a strip as
disclosed in U.S..Patent 5,934,162 to Habermehl.
When the last screw 16 in a strip is located in the guideway, the fact that
the exitway 86 encloses the spent strip 13 prevents the strip from rotating
about the axis
of the guideway to an orientation in which the screw 16 might be able to drop
out of the
guideway or the screw when driven is increasingly likely to jam. The spent
strip 13 may
extend from the exitway 87 at various angles limited only by the location of
the side
surfaces 314 and 316.
The configuration of Figure 3 is advantageous to better ensure that the last
screw 16 in any screwstrip 14 is driven and to generally assist in reducing
the likelihood
of any screw 16 being driven becoming jammed in the guideway with the strip
13.
Preferred strip segments for use with the drive attachment in accordance
with this invention are, as shown in Figure 1, segments of discrete length in
which the
axis of all strips lie in the same flat plane and in which the heads 17 of the
screws are all
located in a straight line.
Reference is made in Figures 1 and 3 to the slide stops 25 which are
secured to the rear portion 22 of the slide body 20 by bolts 402 such that the
slide stops
25 slide in longitudinal slots 40 on each side of housing 18 to key the slide
body and
housing together and to prevent the slide body being moved out of the housing
past a
fully extended position.
38
CA 02324627 2000-10-26
While the invention has been described with reference to preferred
embodiments, many modifications and variations will now occur to persons
skilled in the
art. For a definition of the invention, reference is made to the appended
claims.
39
