Toeing nosepiece for screwdrivers

Information

  • Patent Grant
  • 6425306
  • Patent Number
    6,425,306
  • Date Filed
    Tuesday, October 24, 2000
    24 years ago
  • Date Issued
    Tuesday, July 30, 2002
    22 years ago
Abstract
A nosepiece for fastener driving tools with a contact surface for engagement with the workpiece with a rounded profile to facilitate driving fasteners at an angle into the workpiece. Preferably, the contact surface has a first radially innermost portion of the contact surface for engagement of the workpiece when a screw is being driven substantially normal to the surface of the workpiece and a second outer portion of the contact surface radially outwardly from the innermost portion which outer portion is adopted to engage the work surface when a screw is being driven at an angle other than substantially normal to the work surface, the characteristics of the innermost portion of the contact surface and outermost portion of the contact surface varying such that the outer portion provides resistance to slippage of the nosepiece on the work surface when a screw is being driven at an angle to the normal.
Description




SCOPE OF THE INVENTION




This invention relates to screwdrivers having a nosepiece to engage a work surface and through which nosepiece a guideway extends via which a screw is driven into the workpiece and, more particularly, to a nosepiece which is adapted for driving screws at an angle into the workpiece and, preferably, countersinking the screws.




BACKGROUND OF THE INVENTION




Autofeed screwdrivers are known such as those taught in the present inventor's U.S. Pat. No. 5,934,162 in which a nosepiece is adapted to engage a surface of a workpiece and a driver shaft is adapted to drive a screw past the nosepiece and into the workpiece. Many prior art autofeed screwdriving apparatus are particularly adapted to drive screws into a workpiece with the screw disposed normal to the surface of the workpiece. The present inventor has appreciated that disadvantages arise when many known screwdrivers and drivers of other fasteners such as nails and the like are utilized to drive screws at an angle into a workpiece other than normal. Disadvantages which arise include an inability to properly countersink a fastener driven at an angle into a workpiece, difficulties with the nosepiece slipping on the work surface when attempting to drive a fastener at an angle into the workpiece and difficulties with marking or marring the surfaces of finished workpieces by the engagement of the nosepieces. The present inventor has also appreciated that the nosepieces of many autofeed screwdriving mechanisms when used to drive screws at an angle to the normal to the surface of the workpiece have the disadvantage of significantly increasing the depth a screw must be driven to provide for proper countersinking.




The present inventor has also appreciated the disadvantage that the surface contacting portions of nosepieces of many autofeed fastener driving devices are of larger size and diameter than advantageous for driving of screws into the workpiece at an angle which varies from a normal to the surface of the workpiece.




SUMMARY OF THE INVENTION




To at least partially overcome these disadvantages of the previously known devices, the present invention provides a nosepiece for fastener driving tools with a contact surface for engagement with the workpiece with a rounded profile to facilitate driving fasteners at an angle into the workpiece. Preferably, the contact surface has a first radially innermost portion of the contact surface for engagement of the workpiece when a screw is being driven substantially normal to the surface of the workpiece and a second outer portion of the contact surface radially outwardly from the innermost portion which outer portion is adopted to engage the work surface when a screw is being driven at an angle other than substantially normal to the work surface, the characteristics of the innermost portion of the contact surface and outermost portion of the contact surface varying such that the outer portion provides resistance to slippage of the nosepiece on the work surface when a screw is being driven at an angle to the normal.




It is an object of the present invention to provide a nosepiece with a contact surface to contact a workpiece in normal operation sized so that on tilting of the nosepiece to drive a screw at an angle to the vertical into a workpiece, the distance a screw must be driven to be properly countersunk into a workpiece is minimized.




It is an object of the present invention to provide a nose for fastener driving devices which is adapted for driving fasteners into a workpiece at an angle to the normal.




It is an object to provide a nose for a screwdriver which facilitates driving screws into a workpiece at an angle between about 85° and 70° to a normal to the workpiece.




It is an object of the present invention to provide a nosepiece for fastener driving devices which reduces slippage of the nosepiece when used in driving screws at an angle to a normal to the work surface.




It is an object of the present invention to provide a fastener driving tool which minimizes the increased extent to which a fastener must be driven to properly countersink a fastener into a workpiece when the fastener is driven at an angle which is not normal to the surface of the workpiece.




Accordingly, in one of its aspects, the present invention provides a screwdriver comprising:




a nosepiece having a forward workpiece contact surface,




the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening,




an elongate driver shaft received in the guideway rotatable about an axis,




the driver shaft having a forward end to engage and drive a threaded fastener,




the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out of the nosepiece via the fastener exit opening,




the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly,




the contact surface comprises a radially innermost zone adjacent the fastener exit opening, and an outer zone radially outward and rearward from the innermost zone, the outer zone includes friction enhancing protrusions,




each protrusion extending forwardly to a forward extent rearward of the forward extent of the inner zone wherein when the nosepiece is urged forwardly into a flat surface of a workpiece with the axis at an angle between normal to the flat surface of the workpiece and about five degrees to a normal to the flat surface of the workpiece,




the innermost zone alone engaging a flat surface of a workpiece and the outer zone and its protrusions not engaging the flat surface;




when the nosepiece is urged forwardly into a flat work surface of a workpiece with the axis at an angle of greater than five degrees to a normal to the flat surface the protrusions of the outer zone engaging the flat surface.




In another aspect, the present invention provides a screwdriver comprising:




a nosepiece having a forward workpiece contact surface,




the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening,




an elongate driver shaft received in the guideway rotatable about an axis,




the driver shaft having a forward end to engage and drive a threaded fastener,




the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out of the nosepiece via the fastener exit opening,




the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly,




the guideway defining a generally cylindrical space coaxially about the axis having a diameter marginally greater than a head of a fastener to be driven and adapted to assist in locating a screw within the guideway coaxially aligned with the driver shaft,




wherein while maintaining the contact surface urged forwardly into constant engagement with a flat surface of a workpiece, on tilting the screwdriver from a position with the axis normal the flat surface to a position with the axis at an angle to the flat surface of not less than 70 degrees, the radially innermost points at which contact occurs between the contact surface and the flat surface are located on the contact surface a distance radially from the axis not greater than two times the diameter of the guideway.




Preferably, the contact surface is a segment of a spherical surface of a radius centered on the axis,




the radius of the spherical surface being not greater than about two times the diameter of the guideway.




More preferably, the exit opening lies in a plane normal the axis,




the contact surface lies rearward of the surface of a cone extending rearwardly at an angle of at most 45° and centered on the axis at a point forward of a first point on the axis where the plane intersects the axis by at least one half a diameter of the guideway.











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:





FIG. 1

is a pictorial view of a power screwdriver in accordance with a first preferred embodiment of the present invention;





FIG. 2

is a rear view of the components of the driver attachment in

FIG. 1

;





FIG. 3

is an exploded pictorial view of the driver attachment shown in

FIG. 1

;





FIG. 4

is a schematic partially cross-sectional view of the driver attachment of

FIG. 1

in a fully extended position as seen in

FIG. 1 through a

plane passing through the longitudinal axis of the drive shaft and centrally of the screws in the screwstrip;





FIG. 5

is a view identical to

FIG. 4

but with the drive attachment in a partially retracted position in driving a screw into a workpiece;





FIG. 6

is a partial pictorial view of the forward end of the slide body shown in

FIG. 3

;





FIG. 7

is a schematic side view showing a forward end of the slide body of

FIG. 6

driving a screw into a workpiece, with the screw normal to the outer surface of the workpiece;





FIG. 8

is a schematic side view substantially the same as that shown in

FIG. 7

, however, showing the screw being driven into the workpiece at an angle to the vertical;





FIG. 9

is a schematic cross-sectional view along line


9


-


9


′ in

FIG. 4

showing merely the screwstrip and the shuttle in a fully advanced position;





FIGS. 10 and 11

are views the same as

FIG. 9

but with the shuttle being withdrawn in an intermediate position in FIG.


10


and in a fully withdrawn position in

FIG. 11

;





FIG. 12

is a view similar to

FIG. 9

but with a modified pawl;





FIG. 13

is a pictorial view of the nosepiece shown in

FIG. 1

schematically showing a screw received therein;





FIG. 14

is a pictorial view of the nosepiece as in

FIG. 13

with a screw in a different position;





FIG. 15

is a cross-sectional view of the nosepiece of

FIG. 14

along section line XV-XV′;





FIG. 16

is an elevational rear view of the slide body


20


of

FIG. 3

;





FIG. 17

is a cross-sectional view similar to that in

FIG. 15

, however, of another second embodiment of a nosepiece in accordance with the present invention;





FIG. 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 FIG. 1 which shows an autofeed screwdriver attachment of the type disclosed in U.S. Pat. No. 5,934,162, issued Aug. 10, 1999, the disclosure of which is incorporated herein by reference.




The operation of the device shown in

FIGS. 1

to


5


is known and, therefore, its operation will now only be briefly disclosed with reference to

FIGS. 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

FIG. 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

FIGS. 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

FIG. 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

FIG. 7

, the part 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 FIG.


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.





FIGS. 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

FIGS. 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

FIG. 6

, radially outward of the innermost zone


154


, an outer zone


156


is 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

FIG. 7

, the forward distal ends of the protrusions


142


have a forward extent which is rearward of the innermost zone


154


. In

FIG. 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

FIG. 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

FIG. 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

FIG. 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 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

FIG. 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

FIG. 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

FIG. 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


.





FIG. 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

FIG. 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

FIG. 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 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.

FIG. 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 1⅝ 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

FIG. 8

, are in the range of 60° to 85° and, more preferably, about 65° to 80° and, even more preferably, about 75°.

FIG. 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

FIG. 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 different fasteners including screws and other threaded fasteners and nails, tacks, studs, posts and the like.




The protrusions


142


are shown in

FIG. 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 {fraction (1/10)} or {fraction (1/15)} or {fraction (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


.




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

FIG. 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 FIG.


8


.

FIG. 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

FIG. 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

FIG. 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=


2


X


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.




An autofeed screwdriver as illustrated in

FIGS. 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

FIG. 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

FIG. 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


.

FIGS. 4 and 5

show in cross-section the interaction of these components.




As seen in

FIG. 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

FIG. 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

FIG. 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 FIG.


3


. The cam pin


502


is received in cam slot


506


between the first and second camming surfaces


508


and


510


for engagement of each under different conditions of operation. Spring


69


about axle


50


, as shown in

FIG. 5

, biases the lever


48


in a clockwise direction as seen in FIG.


5


and thus biases the lever to pivot in a direction which moves a shuttle


96


shown in

FIG. 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

FIG. 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


.




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. Pat. No. 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, the guide tube has a forward section which has an access opening


86


, shown in

FIGS. 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

FIG. 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

FIGS. 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

FIGS. 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 behind the plastic retaining strip


13


. The lesser side wall


92


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

FIG. 2

, the major side wall


91


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

FIG. 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 pawl


99


has a first pusher arm


101


at its forward end to engage a first lead screw


16




a


and a second pusher arm


601


to engage a second screw


16




b


. 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

FIG. 11

, is disposed about post


100


between pawl


99


and shuttle


96


and urges the first pusher arm


101


counterclockwise as seen in FIG.


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 FIG.


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

FIG. 9

, the cam faces


107


and/or


607


will engage the screws


16




b


and


16




c


, 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

FIG. 11

, the engagement faces


108


and


608


will engage the screw


16




b


and


16




c


, respectively, and/or strip


13


and advance the screwstrip to the right as seen in

FIG. 11

so as to position a screw


16




b


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

FIG. 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

FIGS. 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

FIG. 11

, a dashed line


611


represents a plane of advance in which the axis of each of the screws


16


lie 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 dashed axis line


612


. To the left of axis line


612


, spent strip


13


is shown with a broken sleeve


220




a


from which a screw has been driven.




As seen in

FIG. 9

, the engagement face


108


of the first pusher arm


101


is engaged behind the first screw


16




a


and the engagement face


608


of the second pusher arm


601


is engaged behind the second screw


16




b


, 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

FIG. 9

, the first screw


16




a


in sleeve


220




a


is axially in line with the axis


52


of the driver shaft ready for driving.




From the position of

FIG. 9

, in use of the tool, the lead screw


16




a


is driven from sleeve


220




a


and the shuttle


96


is withdrawn to the right passing through the position of

FIG. 10

to assume the position of FIG.


11


. Thus, as seen in

FIG. 10

, arrow


610


represents the withdrawal of the shuttle


96


relative the driver shaft and screwstrip


14


.




From the position of

FIG. 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


16




b


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


16




c


and further pivot the pawl


99


so that the second arm


601


may pass to the left of the screw


16




c


.

FIG. 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


16




c


in sleeve


220




c.






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


16




b


and the second pusher arm


601


moving to the right past screw


16




c


, 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


16




b


and


16




c


and advance them to the left, indicated by arrow


613


, as seen in FIG.


1


.





FIG. 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


16




b


and


16




c


in sleeves


220




b


and


220




c


and with the screw


16




a


, not seen, as it has been driven from the fractured sleeve


220




a


. From the position of

FIG. 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


16




b


in the sleeve


220




b


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

FIG. 9

to the right sufficiently to have the first pusher arm


101


engage to the right of the screw


16




b


in sleeve


220




b


. For example, if a shuttle


96


having only arm


101


and not arm


601


move to the right only as far as shown in

FIG. 10

, then, after the screw


16




a


in sleeve


220




a


is driven from sleeve


220




a


, 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. Pat. No. 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

FIG. 10

, the second pusher arm


601


is to the right of screw


16




b


in sleeve


220




b


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

FIGS. 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

FIG. 10

until rotation of the first arm


101


is stopped by abutment


614


in the 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

FIG. 9

to the position of

FIG. 10

, the engagement faces


108


and


608


are moved substantially transversely relative the length of the screwstrip


14


to become disengaged from the screws


16




a


and


16




b


. 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


16




b


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

FIGS. 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.

FIG. 12

is identical to

FIG. 9

other than in the location of the second pusher arm


601


on the pawl


99


.

FIG. 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

FIG. 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


16




b


of preventing undesired withdrawal of the screwstrip


14


. Provided the engagement surface


608


is to the right of screw


16




b


, it will, if the screwstrip


14


is attempted to be moved to the right, pivot under the bias of the spring to engage screw


16




b


and prevent rearward removal of the screwstrip


14


.




The pawl


99


is shown in

FIGS. 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.




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.




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

FIG. 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 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

FIGS. 13

to


16


which show the nose portion


24


of the slide body


20


shown in

FIGS. 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

FIG. 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

FIG. 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

FIG. 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

FIG. 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 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

FIGS. 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 wall


81


.

FIG. 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

FIG. 13

from the position in

FIG. 13

to the position in FIG.


14


. When the tip


15


reaches the position in

FIG. 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.





FIG. 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


.





FIG. 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


.





FIG. 16

shows an end elevation view of the slide body


18


of

FIG. 4

, however, with the lever


48


and shuttle mechanism removed.

FIG. 16

thus represents a view of the nose portion


24


and rear portion


22


as viewed along line XVII-XVII′ in FIG.


5


. As seen in

FIG. 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

FIG. 15

, radially outwardly directed surface


260


of the hook-shaped first end


240


angles inwardly into the guideway


82


so as to assist in guiding as a cam surface the shank of a screw towards the wall


242


and, hence, into the guideway


82


. While not necessary, it is preferred as shown in

FIG. 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


forward of the access opening


86


such as taught in U.S. Pat. No. 5,699,704, issued Dec. 23, 1997, the disclosure of which is incorporated herein.




Reference is now made to

FIG. 17

which shows a cross-sectional view through another embodiment of a nosepiece similar to that in FIG.


15


. The embodiment of

FIG. 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


.





FIG. 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

FIG. 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

FIG. 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.




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

FIGS. 3 and 5

.




A depth setting cam member


114


is secured to the housing


18


for rotation about a pin


116


, shown in

FIG. 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

FIG. 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

FIGS. 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 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

FIGS. 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

FIGS. 4 and 5

. As seen in

FIG. 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 II 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

FIG. 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.




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 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

FIGS. 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 FIG.


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 pawl


99


, 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




(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 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 (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.




A preferred collated screwstrip


14


for use in accordance with the present invention is as illustrated in the drawings and particularly

FIGS. 1 and 4

and are substantially in accordance with Canadian Pat. No. 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 Pat. No. 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

FIG. 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


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. Pat. No. 3,910,324 to Nasiatka; U.S. Pat. No. 5,083,483 to Takaji; U.S. Pat. No. 4,019,631 to Lejdegard et al and U.S. Pat. No. 4,018,254 to DeCaro.




As seen in

FIG. 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

FIGS. 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


.




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

FIG. 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. Pat. No. 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

FIG. 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

FIG. 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

FIGS. 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.




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.



Claims
  • 1. A screwdriver comprising:a nosepiece having a forward contact surface adapted to engage a workpiece, the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening, an elongate driver shaft received in the guideway rotatable about an axis, the driver shaft having a forward end to engage and drive a threaded fastener, the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out of the nosepiece via the fastener exit opening, the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly, the contact surface comprising a radially innermost zone adjacent the fastener exit opening and an outer zone radially outward from the innermost zone and rearward of the innermost zone, the innermost zone engaging a flat surface of a workpiece when the nosepiece is urged forwardly into contact with the flat surface of the workpiece with the axis disposed at first angles substantially normal to the flat surface of the workpiece, an array of relatively small, forwardly extending protrusions adapted for increasing frictional engagement with a workpiece provided on the outer zone, the protrusions extending forwardly and terminating at their forwardmost extent rearward of the innermost zone such that the protrusions do not engage the flat surface of a workpiece engaged by the innermost zone when the axis is disposed at said first angles substantially normal to the flat surface of the workpiece, however, the protrusions do engage a flat surface of a workpiece when the nosepiece is urged forwardly into contact with the flat surface of the workpiece with the axis disposed at an angle of greater than said first angles.
  • 2. A screwdriver as claimed in claim 1 wherein each protrusion comprises a small spike member extending forwardly from the contact surface to a distal end adapted to frictionally engage a work piece against slippage.
  • 3. A screwdriver as claimed in claim 2 wherein each protrusion is connected to the underlying contact surface at a base and extends from the base forwardly generally parallel the axis.
  • 4. A screwdriver as claimed in claim 1 wherein the contact surface from which the protrusions extend comprise a surface selected from a portion of a sphere centered on the axis, a portion of a cone centered on the axis and a surface of revolution which is formed by rotation about the axis of a profile which extends radially outwardly relative the axis and rearwardly about the axis.
  • 5. A screwdriver as claimed in claim 4 wherein the protrusions are arranged in one or more arcs on the contact surface, each arc disposed at constant radius about the axis.
  • 6. A screwdriver as claimed in claim 1 wherein the contact surface extends about the fastener exit opening at least 180 degrees.
  • 7. A screwdriver as claimed in claim 1 wherein when the nosepiece is urged forwardly into contact with a flat surface of a workpiece with the axis disposed at angles between a normal to the flat surface and about 5 degrees to a normal to the flat surface of the workpiece,the innermost zone engages the flat surface but the outer zone and the protrusions do not engage the flat surface.
  • 8. A screwdriver as claimed in claim 1 wherein the contact surface is a segment of a spherical surface of a radius centered on the axis,the guideway defines a generally cylindrical space coaxially about the axis of a given diameter, the radius of the spherical surface being not greater than about two times a diameter of the guideway.
  • 9. A screwdriver as claimed in claim 8 wherein the radius of the spherical surface being not greater than the diameter of the guideway.
  • 10. A screwdriver comprising:a nosepiece having a forward workpiece contact surface, the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening, an elongate driver shaft received in the guideway rotatable about an axis, the driver shaft having a forward end to engage and drive a threaded fastener, the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out of the nosepiece via the fastener exit opening, the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly, the contact surface comprises a radially innermost zone adjacent the fastener exit opening, and an outer zone radially outward and rearward from the innermost zone, the outer zone includes friction enhancing protrusions, each protrusion extending forwardly to a forward extent rearward of the forward extent of the inner zone, wherein when the nosepiece is urged forwardly into a flat surface of a workpiece with the axis at an angle between normal to the flat surface of the workpiece and about five degrees to a normal to the flat surface of the workpiece the innermost zone alone engaging a flat surface of a workpiece and the outer zone and its protrusions not engaging the flat surface; when the nosepiece is urged forwardly into a flat work surface of a workpiece with the axis at an angle of greater than five degrees to a normal to the flat surface the protrusions of the outer zone engaging the flat surface.
  • 11. A screwdriver comprising:a nosepiece having a forward workpiece contact surface, the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening, an elongate driver shaft received in the guideway rotatable about an axis, the driver shaft having a forward end to engage and drive a threaded fastener, the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out to the nosepiece via the fastener exit opening, the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly, the guideway defining a generally cylindrical space coaxially about the axis having a diameter marginally greater than the head of a fastener to be driven and adapted to assist in locating a screw within the guideway coaxially aligned with the driver shaft, wherein while maintaining the contact surface urged forwardly into constant engagement with a flat surface of a workpiece, on tilting the screwdriver from a position with the axis normal the flat surface to a position with the axis at an angle to the flat surface of not less than 70 degrees, the radially innermost points at which contact occurs between the contact surface and the flat surface are located on the contact surface a distance radially from the axis not greater than two times the diameter of the guideway, and an array of protrusions on said contact surface, wherein the contact surface from which the protrusions extend comprise a surface selected from a portion of a sphere centered on the axis and a portion of a cone centered on the axis, and a surface of revolution which is formed by rotation about the axis, of a profile which extends radially outwardly relative the axis and rearwardly about the axis.
  • 12. A screwdriver comprising:a nosepiece having a forward workpiece contact surface, the nosepiece having a guideway extending forwardly therethrough opening forwardly through the contact surface as fastener exit opening, an elongate driver shaft received in the guideway rotatable about an axis, the driver shaft having a forward end to engage and drive a threaded fastener, the driver shaft slidably received in the guideway for relative reciprocal sliding therein along the axis to drive a fastener out to the nosepiece via the fastener exit opening, the contact surface extending from the fastener exit opening radially outwardly relative the axis and rearwardly, the guideway defining a generally cylindrical space coaxially about the axis having a diameter marginally greater than the head of a fastener to be driven and adapted to assist in locating a screw within the guideway coaxially aligned with the driver shaft, wherein while maintaining the contact surface urged forwardly into constant engagement with a flat surface of a workpiece, on tilting the screwdriver from a position with the axis normal the flat surface to a position with the axis at an angle to the flat surface of not less than 70 degrees, the radially innermost points at which contact occurs between the contact surface and the flat surface are located on the contact surface a distance radially from the axis not greater than two times the diameter of the guideway, wherein the contact surface is a segment of a spherical surface of a radius centered on the axis and includes an array of protrusions, the radius of the spherical surface being not greater than about two times the diameter of the guideway, wherein the contact surface comprises a radially innermost zone adjacent the fastener exit opening, the innermost zone engaging a flat surface of a workpiece when the axis is disposed substantially normal to the flat surface of the workpiece, the protrusions provided on an outer zone of the contact surface radially outward from the innermost zone and rearward of the innermost zone, the protrusions extending forwardly and terminating at their forwardmost extent rearward of the innermost zone.
  • 13. A screwdriver as claimed in clam 12 wherein the protrusions do not engage a flat surface of a workpiece engaged by the innermost zone when the axis is disposed at a first angle of less than ten degrees to a normal to the flat surface of the workpiece and the protrusions do engage a flat surface of a workpiece when the axis is disposed at an angle of greater than the first angle.
  • 14. A screwdriver as claimed in claim 13 wherein each protrusion comprises a small spike member extending forwardly from the contact surface to a distal end adapted to frictionally engage a work piece against slippage.
US Referenced Citations (7)
Number Name Date Kind
3353737 Howard et al. Nov 1967 A
3601168 Fernstrom Aug 1971 A
4566619 Kleinholz Jan 1986 A
4581964 Takatsuru Apr 1986 A
5568753 Habermehl et al. Oct 1996 A
6073521 Uno et al. Jun 2000 A
6123244 Huang Sep 2000 A