Router device

A router attachment for adapting a conventional screw gun for cutting sheets of drywall material includes a housing that is removably securable to the housing of the screw gun, an input shaft rotatably mounted in the housing for coupling with the screwdriver shaft of the screw gun, an output shaft rotatably mounted in the housing for coupling with a router bit and a step-up gear assembly for associating the input and output shafts so that rotation of the input shaft at a first rate of rotation drives rotation of the output shaft at a second, higher rate of rotation.

BACKGROUND OF THE INVENTION 
A popular form of construction of interior walls and partitions includes a 
metallic or wooden structural framing covered on at least one side by 
sheets of drywall material, i.e. gypsum board. The sheets of drywall 
material are available in standard sizes, e.g. 4'.times.8'.times.1/2", and 
are cut to size in the field and secured to the structural framing using, 
e.g. screws. The cutting-to-size operation involves both trimming the 
edges of the boards and providing cut out areas through the boards to 
provide access to fittings, e.g. electrical boxes, mounted on the 
structural framing. 
The speed, efficiency and quality of drywall installation are factors of 
paramount importance to dry wall contractors. In order to meet these 
demands the state of the art of drywall tools and installation techniques 
have evolved from a manual nailing procedure to installation of screws 
with a screw gun, i.e. a hand held device having a screwdriver tip driven 
by a variable speed electric motor, and from cutting sheets of drywall to 
size with a razor knife or saw to cutting sheets of drywall to size with a 
drywall router, i.e. a hand held device having a router bit driven by an 
electric motor. 
There is a constant effort in this art to further increase the productivity 
of drywall installations and tools which offer even slight advantage with 
regard to time and labor savings are warmly received by the industry. 
SUMMARY OF THE INVENTION 
A router attachment device for a rotary output device is disclosed. The 
router attachment includes a router attachment housing means for removably 
attaching the router attachment to the rotary output device housing, input 
means, rotatably mounted in the router attachment housing, for coupling 
with output means on said rotary device, output means, rotatably mounted 
in the router attachment housing, for coupling the router attachment to 
the router bit and step-up means for operatively associating the input 
means and the output means so that rotation of the input means relative to 
the router attachment housing at a first rate of rotation drives rotation 
of the output means at a second rate of rotation, wherein the second rate 
of rotation is higher than the first rate of rotation. 
In a preferred embodiment, the rotary output device is a screw gun and 
router attachment device is for adapting the screw gun for cutting sheets 
of drywall material. The input means of the attachment device couples with 
the rotary output screw driver tip of the screw gun. 
Use of the router attachment of the present invention allows more efficient 
installation of sheets of wallboard material. A workman can easily carry 
both a screw gun and the lightweight router attachment and quickly attach 
or detach the router attachment to the screw gun as needed, as opposed to 
switching back and forth between the screw gun and separate conventional 
router. The router attachment is more easily carried, e.g. in a pouch or 
holder on the workman's belt, than is the heavier and more cumbersome 
conventional router. Furthermore, use of the router attachment of the 
present invention eliminates the need to maintain electrical connections 
between a power source and two separate motorized tools and the 
elimination of one of the associated electrical cords provides, safer and 
less cluttered workplace. 
In a preferred embodiment, the input means comprises an input shaft 
extending axially from a first end to a second end and means for coupling 
the first end of the input shaft with the screwdriver tip of the screw 
gun. The output means comprises an output shaft extending axially from a 
first end to a second end and means for mounting a router bit on the 
second end of the output shaft for rotation therewith. The step-up means 
comprises an outer gear concentrically mounted on the second end of the 
input shaft and having inner and outer diametral surfaces, wherein a 
plurality of circumferentially spaced apart first gear teeth are defined 
in the inner circumferential surface. The step-up means further comprises 
an inner gear concentrically mounted in the first end of the output shaft 
and having an outer diametral surface wherein a plurality of 
circumferentially spaced apart second gear teeth are defined in the outer 
diametral surface. The inner gear is eccentrically mounted within the 
outer gear so that the first gear teeth engage the second gear teeth.

DETAILED DESCRIPTION OF THE INVENTION 
Referring to FIGS. 1 and 2, which the router attachment 2 of the present 
invention is shown mounted on a conventional screw gun 4 with router bit 
12 mounted in chuck 14 and secured by set screw 110, and to FIGS. 4 and 5, 
which show end views of the router attachment dismounted from a screw gun, 
the router attachment 2 includes a housing body portion 6 and a housing 
collar portion 7. The screw gun 4 includes a variable speed electric motor 
(not shown) and clutch mechanism (not shown) disposed within a housing 3, 
a tubular housing portion 5 extending axially from the housing portion 3 
and a tubular collar 9 extending axially from the tubular housing portion 
5. A screw driver shaft 53, having a hexagonal cross section, extends from 
the housing portion 3 through the tubular housing portion 5 and collar 9 
to screwdriver tip 52. The screwdriver shaft 53 is operatively connected 
with the clutch mechanism so that the screw gun motor is decoupled from 
the screwdriver shaft unless the screwdriver shaft 53 is axially 
compressed toward the screw gun 4. Axial compression of shaft 53 toward 
screw gun 4, e.g. when the screw gun 4 is pressed against the head of a 
screw to be installed, engages the clutch mechanism and the screw gun 
motor is coupled with the screwdriver shaft 53 to rotate the shaft and 
screwdriver tip 52. 
The tubular housing portion 5, collar 9, screwdriver shaft 53 and tip 52 
are slidably received within collar portion 7 of the router housing 6. 
Screwdriver shaft 53 and tip 52 are received within and engaged with hex 
sprocket 50, as discussed below. The router attachment 2 is installed so 
that input shaft 18 contacts and compresses screwdriver shaft 53 toward 
the screw gun 4 thereby engaging the clutch mechanism and the router 
attachment 2 is then removably secured to the screw gun 4 by tightening 
set screw 10 against collar 9 to allow one-handed operation of the screw 
gun 4 and attached router attachment 2. Alternatively, the operator may 
operate screw gun 4 with one hand and manually secure router attachment 2 
with his other hand by gripping housing 6. 
Alternatively, as shown in FIG. 7, the router attachment 2 may be removably 
secured to the housing by a block 60 slidably mounted in a recess 62 
defined within collar portion 7', and manually displaceable by 
quick-release cam 64, pivotably mounted on collar portion 7'. The collar 
portions 7, 7' are interchangeable and may be selectively secured to 
housing body portion 6 with screws 63. It will be appreciated that 
differently configured collar portions may be provided to adapt the router 
device 2 to fit a variety of different rotary output devices, e.g. screw 
guns with differently configured housings. 
Referring to FIG. 3, an input shaft 18 extending from a first end 20 to a 
second end 22 and is extended by a concentrically mounted stub 23. The 
input shaft 18 and stub 23 are rotatably mounted in housing 6 by bearings 
24, 26. Bearing 26 is held in place by mounting block 27. An output shaft 
28 extending from a first end 30 to a second end 32 is rotatably mounted 
in housing 6 by high-speed bearings 33, 35. Chuck or sleeve 14 is secured 
to the second end 32 of output shaft 28. Chuck 14 (preferably aluminum) 
has a flared base 102 and has a first axial opening 104 extending from 
base 102. Opening 104 is slidably received over output shaft 28 and 
attached thereto for rotation therewith using a threadable screw 16. 
Sleeve 100 is positioned such that a small gap 106 is present between base 
102 and housing 6. A second axial opening 108 of smaller diameter than 
opening 104 is coaxial with opening 104 and sized to receive a router (or 
drill bit) 12 (which is locked in opening 108 by a threaded screw 110). Of 
course, opening 108 may be sized to receive any size router or drill bit. 
Similarly, sleeve 14 may be interchangeable with other sleeves having 
differing sized openings 108. 
Referring to FIGS. 3 and 6, input shaft 18 is operatively associated with 
output shaft 28 by gear assembly 34. Gear assembly 34 includes outer gear 
36 having an outer diametral surface 38, an inner diametral surface 40 and 
a plurality of gear teeth 42 defined on the inner diametral surface 40. 
Input shaft 18 and outer gear 36 are formed in one piece with outer gear 
36 being concentrically formed on the second end 22 of input shaft 18. 
Stub 23 is concentrically mounted in a corresponding bore to effectively 
extend the input shaft through gear 36. Gear assembly 34 further includes 
inner gear 44 having an outer diametral surface 46 and a plurality of gear 
teeth 48 defined on the outer diametral surface 46. Inner gear 44 is 
concentrically mounted on the first end 30 of output shaft 28. Output 
shaft 28 and inner gear 44 are mounted eccentrically, relative to input 
shaft 18 and outer gear 36, so that the gear teeth 42, 48 of the 
respective gears 36, 44 mesh. 
Referring to FIGS. 2, 3, and 4, a hexagonal socket 50 is defined in the 
first end 20 of input shaft 18 for coupling shaft 18 with the hexagonal 
screwdriver shaft 53 of screw gun 4 so that rotation of the screwdriver 
tip shaft 53 drives rotation of input shaft 18. 
The gear assembly 34 steps-up the rate of rotation of the output shaft 28 
relative to the rate of revolution of the input shaft 18. Preferably, the 
gear assembly steps up the rate of revolution of the output shaft 28 
relative to the input shaft 18 by a factor between about 2 and about 10. 
In the embodiment shown in FIGS. 3 and 4 the outer gear 36 has 110 gear 
teeth and the inner gear 44 includes 22 gear teeth, resulting in a step-up 
ratio of 5:1. 
Typically, the variable speed motor of the screw gun allows a rate of 
rotation of the screwdriver tip 52 of up to about 4000 rpm. The preferred 
embodiment of the router attachment 2 of the present invention shown in 
the FIGURES would step-up the 4000 rpm rate of the screwdriver tip 52 to a 
rate of 20,000 rpm at the router bit 12 of the router attachment 2. 
FIG. 8 shows an alternative embodiment which provides a "vacuum cleaning" 
feature to the router attachment of the present invention. Fan 70 is 
mounted on output shaft 28' and a collar 72 extends from housing 6 to 
surround chuck 14. A vented (via filter 82) receptacle 74 is sealingly (by 
gaskets 76) snaplockedly (by recess 78 and hook 80) secured to housing 6. 
During use, e.g. cutting sheet of drywall, the fan 70 rotates to create a 
pressure differential which draws particles and debris generated by the 
cutting, into collar 72 and discharges the particles and debris into 
receptacle 74. Air is allowed to exit receptacle 74 through filter 82, 
while the particles and debris are retained with the receptacle for later 
disposal. 
The housing 6, shafts 18, 28, stub 23, mounting block 27, may be made of 
any suitable material, e.g. metals, polymers, composite materials. In a 
preferred embodiment which offers the beneficial features of lower cost 
and lighter weight, i.e. low density, the housing 6, collar 7, shafts 18, 
28, stub 23, and mounting block 36, 44 are each made of a polymer or of a 
particulate, e.g. glass, carbon, fluorocarbon particles or discontinuous 
fibers, filled polymer matrix composite material. A prototype embodiment 
of the device of the present invention has been machined from an acetal 
thermoplastic (Delrin, E. I. DuPont). Preferably, at least some of the 
elements of the polymer based embodiment of the present invention are made 
by injection molding. 
To use the router attachment of the present invention, a workman removably 
secures the attachment to a screw gun and then operates the combined screw 
gun/router attachment in a manner entirely analogous to the operation of a 
conventional router, except that the screw gun is used as the driving 
force for the router bit. 
Use of the router attachment 2 of the present invention allows more 
efficient installation of sheets of wallboard material. A workman can 
easily carry both a screw gun and the lightweight router attachment and 
quickly attach or detach the router attachment to the screw gun as needed, 
as opposed to switching back and forth between the screw gun and separate 
conventional router. The router attachment is more easily carried, e.g. in 
a pouch or holder on the workman's belt, than is the heavier and more 
cumbersome conventional router. Furthermore, use of the router attachment 
of the present invention eliminates the need to maintain electrical 
connections between a power source and two separate motorized tools and 
the elimination of one of the associated electrical cords provides, safer 
and less cluttered workplace. 
While the present invention has been described by reference to a specific 
preferred embodiment, i.e. a router adapter for adapting a screw gun for 
cutting sheets of drywall material, one skilled in the art will appreciate 
that rotary output devices other than screw guns, e.g. a drill, may be 
adapted to perform cutting operations and that cutting operations other 
than cutting sheets of drywall, e.g. trimming sheets of countertop 
laminate material, may be performed using a router attachment according to 
the present invention by appropriate minor modifications of the embodiment 
shown in FIGS. 1-6. 
While preferred embodiments have been shown and described, various 
modifications and substitutions may be made thereto without departing from 
the spirit and scope of the invention. Accordingly, it is to be understood 
that the present invention has been described by way of illustrations and 
not limitations.