Note: Descriptions are shown in the official language in which they were submitted.
CA 02241104 1998-06-18
Be it known that I, DALE A. GILBERT, a citizen of the United
States of America and a resident of the city of Wallace in
Shoshone County in the State of Idaho, whose Post Office address
is 203 Woodland Drive, Wallace, Idaho 83873-2427 have made the
invention entitled
TOOL FOR CUTTING RECTILINEAR OPENINGS FOR
ELECTRICAL OUTLET BOXES IN SHEET MATERIAL
of which the following disclosure contains a correct and full
description of the invention and the best mode known to the
inventor of taking advantage of the same.
CA 02241104 1998-06-18
My invention relates to tools for locating and cutting
rectilinear holes in wall sheeting material for pre-established
electrical junction boxes therebeneath.
In modern construction practice commonly wall frames are
established, electrical junction boxes installed therein and
sheeting material such as traditional dry wall thereafter
established on the wall frames to form structural surfaces. At
some point in this construction process, orifices must be
established in the sheeting material to allow access to the
underlying electrical junction boxes for installation of electric
fixtures therewith. In the early history concerning the use of
larger panels of sheeting material for wall surfaces, junction box
orifices were commonly created before installation of the sheeting
material by measurement, plotting and subsequent orifice cutting
with a hand tool such as a knife or a keyhole saw. This process
was time consuming, required substantial expertise and often
produced orifices with rough, irregular and ragged edges that were
not within the limits of accuracy required by pre-manufactured
covers, electrical fixtures and other ancillary structures
associated with the junction box orifices.
These problems have been recognized and responsively various
solutions have become known, both to locate the positions of
orifices and to cut sheeting material to create the orifices.
Most locating methods have provided some type of indexing pins
that have been carried by a junction box to project therefrom and
through sheeting material established thereover. Commonly some
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type of template has been provided for positional association with
the outwardly projecting portions of the locating pins to
determine the position and in some instances the configuration of
a hole to be created.
Normally if saws that cut by reciprocating perpendicularly to
a wall panel are used to create holes, the cutting must be
accomplished before the wall panel is installed to allow operation
of the saw. With the development of hand manipulated routing
tools, this type of rotary cutting tool has become popular for
cutting function box holes and, with an appropriately
sophisticated cutter, this cutting may be accomplished after a
wall panel is installed over a junction box, but such cutting
requires substantial sKill and experience.
Various specialized tools have heretofore been created for
creating junction box holes in sheeting panels especially such as
dry wall. Most such tools have provided two cutting vies, one of
which is associated with the junction box structure beneath a
panel, and has some alignment means projecting through sheeting
material thereover to position the second die on the outer side of
the sheeting material so that after positioning the two dies may
be moved toward each other to create an orifice by severing the
sheeting material between their peripheral edges. Various
mechanical means have been developed to move such dies toward each
other with appropriate force to cause a cutting or severing
action, but most commonly lever linKages or impact means have been
used for the purpose. These cutters require substantial force for
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CA 02241104 1998-06-18
their operation and by reason of this they often are time
consuming, difficult and tiring to operate. Commonly such tools
provide knife-like serrated portions to aid their cutting action
and this again increases the amount of force required for cutting
and tends to cut an irregular and jagged edge, especially in
material such as dry wall where the medial portion of the material
is softer and not particularly cohesive, but the outer surfaces
are tough and substantially more cohesive. Several such tools
have become known both in the patent literature and in the
marketplace, but none appear to have gained any particular
acceptance in the construction industry or any economic viability
in the marketplace.
The instant tool is distinguished from such prior cutters in
that it cuts with reciprocating toothed saw blades that oscillate
parallel to the plane of the sheet material being cut. The power
required by the instant tool is substantially less than that
required by punch and die type cutters and the orifice cut has
smoother, more cleanly defined edges that are perpendicular to the
plane of the material. Both the elongate arcuate configuration
and cutting action of the blades distinguish the instant tool from
single bladed saws of the saber or keyhole type that reciprocate
in a Mane perpendicular to that of the material.beinQ cut to
create an essentially different cutting action.
The cutting of holes in dry wall panels by hand manipulated
routers has not proven completely satisfactory. The router cutter
in general has had some substantial diameter, considerably greater
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than the thickness of an ordinary saw blade, and it commonly
operates at a relatively high rotary speed. By reason of this
nature and operation, a router cuts a large volume of dry wall
material at relatively high speeds to create a substantial volume
of particulate material of a relatively fine nature that is an
environmental hazard in the workplace and difficult to clean up.
If cutting is accomplished with a wall panel in place, as is often
done, it is difficult to configure a router blade so that it may
be guided by the junction box structure and yet be maintained in a
Position where the cutting portion of the blade does not come into
contact with the junction box, or wiring therein to cause damage
to either the router blade or wiring. It also is difficult to
positionally maintain a hand manipulated router, especially when
inserting a cutter blade through a sheeting panel to create an
initial hole, and often wild cuts are made that extend outside the
area desired to be cut to disfigure and damage a wall panel.
The instant tool in distinguishment provides four
rectangularly arrayed, relatively thin saw blades that cut by
reciprocating action and remove a substantially smaller volume of
material from cuts than is removed by router blades. The
reciprocating action of the multiple saw blades is of a different
cutting nature and the cutting action is at multiple spaced points
to provide substantially more stability and controlability. The
cutting speed of the blades is slower than the rotary speed of a
router blade so as to create larger particles of removed material
that are not so environmentally undesirable as the smaller
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CA 02241104 1998-06-18
particles created by a high speed rotary cutter.
The problem of chatter between a tool and sheet material
being cut is also solved in the instant tool. Firstly, an
alignment blade is positionally maintained by a template during
the cutting process so that the tool may not move materially from
its properly aligned ppsition. Additionally, the cutting edges of
the saw blades used in the instant tool are of a convex arcuate
configuration so that the length of a saw blade that initially
contacts a panel is relatively short and the teeth on the blade
are angled in opposite directions on each side of its middle, so
that a blade cuts on one side of the middle in only one direction
of travel. The square array of four spaced, simultaneously
cutting blades also aids positional stability of the tool. These
features substantially do away with any chatter of the tool during
its use and resolve positional maintenance problems to prevent
accidental wild cuts.
My tool, in distinction from self-powered cutting tools such
as the ordinary router, is releasably attachable to a separate
source such as an ordinary motorized electric drill for powering
thereby. The use of a separate, readily available tool to provide
a powering source substantially reduces the costs and complexity
of my tool, but yet the powering source it uses may be one
commonly available in most construction settings.
In the accompanying drawings which form a part hereof
and wherein like numbers of reference refer to similar parts
throughout:
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Figure 1 is an isometric surface view of my tool and an
associated positioning template, showing various of the tool
parts, their configuration and relationship and the relationship
of the tool to the positioning template.
Figure 2 is an isometric surface view of a positioning
template for use with a multiple cavity junction box.
Figure 3 is a somewhat enlarged isometric surface view of the
body portion of my tool with the casement removed to show internal
structure.
Figure 4 is an elongate medial vertical cross-sectional view
through the tool of Figure 1, taken on the line 4-4 thereon in the
direction indicated by the arrows.
Figure 5 is a traverse medial vertical cross-sectional view
through the tool of Figure 1, taken on the line 5-5 thereon in the
direction indicated by the arrows.
Figure 6 is a horizontal cross-sectional view through the
notch portion of the positioning blade of Figure 4, taken on the
line 6-6 thereon in the direction indicated by the arrows.
Figure 7 is a horizontal cross-sectional view through the
tool of Figure 3, taken on the line 7-7 thereon in the direction
indicated by the arrows to show the end saw blade plate.
Figure 8 is a horizontal cross-sectional view through the
tool of Figure 3, taken on line 8-8 thereon in the direction
indicated by the arrows to show the side saw blade plate.
MY tool provides body 10 mounting driving linkage 11,
cutting structure 12 and centering structure 13 that are
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CA 02241104 1998-06-18
partially covered by casement 14 which mounts external powering
mechanism 16. Positioning template 15 is associated with the
tool for positioning over a junction box.
Referring to Figure 3, it is seen that body 10 is a
rectilinear structure formed with slightly peripherally larger
top 17 interconnecting similar longer sides 18 and similar
shorter ends 19 to define outwardly projecting top peripheral
rim 17a. Top 17 defines medial drive shaft hole 20 and spacedly
adjacent casement bolt holes 21 each threadediy carrying
casement fastening bolts 22.
The upper portion 20a (Figure 5) of the drive shaft hole 20
is somewhat diametrically smaller than the lower portion 20b to
accommodate the fastening of bearing structure for a drive shaft
in the body. The bearing structure provides bearing housing 23
depending from the medial portion of tool body 10 and fastened
thereto by bolts 24 extending therebetween as seen in Figure 4.
The bearing housing 23 defines medial channel 25 and inwardly
extending lower rim 26 to maintain upper bearing 27 and lower
bearing 28 in vertical relationship with collar 29 communicating
between the two bearings 27, 28 to maintain spacing. The size of
medial channel 25 is substantially the same as that of lower
portion 20b of the drive shaft hole 20 so that the bearings 27, 28
are positionally maintained within the body 10 and bearing
casement 23, as illustrated particularly in Figures 4 and 5.
Driving linkage 11 provides vertically oriented drive shaft
carried in its medial portion in bearings 27 and 28 to extend
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CA 02241104 1998-06-18
both spacedly above and below the body I0. The upper portion 30a
of the drive shaft is threaded to carry inner locking nut 31 and
outer driving nut 32 having a hexagonal, vertical surface
extending above the upper portion of body 10 to allow irrotatabie
intercommunication with a powering mechanism I6. bower portion
30b of the drive shaft is diametrically larger than the upper
portion 30a to aid interconnection of eccentric driving shaft 34
depending therefrom. This eccentric driving shaft 34 is a bolt-
like element having larger head 34a and threaded portion 34b
extending into threaded engagement with portion 30b of the lower
drive shaft. The body portion of the eccentric driving shaft
carries bearings 33 maintained in spaced relationship by spacing
collar 97 therebetween and positionally maintained between the
eccentric driving shaft head 34a and enlarged portion 30b of the
primary drive shaft.
As illustrated in Figures 3-4, paired side plate springs 35
both of similar configuration are fastenably carried by each
shorter end 19 of body IO to depend spacedly therebelow. Spaced
bolts 36 extend through holes defined in the upper portion of the
side plate springs 35 and into threaded engagement with the
adjacent portion of body 10 to releasably interconnect the
elements. The medial portion 35a of each side plate spring 35
normally has less width than the end portions to provide a thinner
cross-sectional area of material to regulate the elasticity of the
Plate spring. The lower end portion of each side plate spring 35
interconnects rectiiine~r side saw blade plate 37 extending
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CA 02241104 1998-06-18
therebetween by spaced bolts 38 extending through holes defined in
the side plate springs and into threaded engagement with the
adjacent portions of the side saw blade plate 37.
Side saw blade plate 37, as seen especially in Figure 8,
defines medial slot 39 to slidably receive a bearing 33 carried on
eccentric drive shaft 34. This slot 39 has a width incrementally
greater than the diameter of bearing 33 and a length sufficient to
accommodate the lineal motion of the eccentric shaft 34 in an
elongate direction between the side plate springs 35, so that as
the eccentric shaft 34 rotates, the side saw blade plate 37 will
be moved only forwardiy and rearwardly in an elongate plane. The
medially forward and rearward portions of the side saw blade plate
37 define fastening bolt channels 40 to allow the passage of
fastening bolts communicating between the body and the centering
structure without interference with the oscillatory motion of the
side saw blade plate 37.
Similar opposed end plate springs 41 are fastenably carried
by each of the longer sides 18 of body 10 by bolts 42 extending
through holes defined in the upper portion of the springs 41 and
into threaded engagement with the adjacent portion of the body 1~.
The end plate springs 41 define a medial channel 41a to lessen the
overall effective cross-sectional area of the spring 41 to
regulate elastic tension generated thereby when the spring is
flexed perpendicularly to the plane of greatest area therethrough.
The lower end portions of end plate springs 41b fastenably carry
rectilinear end saw blade plate 43 therebetween by bolts 44
CA 02241104 1998-06-18
extending through holes defined in the lower portions of the side
plate springs and into threaded engagement with the adjacent
portions of the sides of the end saw blade plate. Similar forward
and rearward end portions 43a of saw blade plate 43 extend
vertically upwardly further than the medial portion 43b and define
end plate spring slots 45 to allow the passage of the medial
portions 35a of side plate springs 35 therebelow so that the side
saw blade plate 37 may be carried spacedly below the end saw blade
plate 43. The end portions 43a of the end saw blade plate are
spaced sufficiently from each other to allow free rotation of
enlarged lower medial portion 30b of drive shaft 30 therebetween.
End saw blade plate 43 in its medial portion, as seen
especially in Figure 7, defines elongate drive shaft slot 46
extending with its longer dimension in a forward-rearward
direction. This drive shaft slot 46 has a width incrementally
greater than the diameter of bearing 33 to allow slidable motion
of that shaft therein, and has a length in the lateral direction
sufficient to allow motion of the eccentric shaft in this
direction without restraint so that the end saw blade plate 43
will be moved in a laterally reciprocating motion as the eccentric
shaft 34 carrying bearing 33 in that slot 46 is rotated. The end
plate spring slots 45 are of sufficient size and so configured as
to allow passage of fastening bolts interconnecting the body and
centering structure and accommodate the reciprocating motion of
the end saw blade plate 43 without interference from those
fastening bolts.
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As illustrated especially in Figure 3, cutting structure 12
provides pairs of similar flat, planar end saw blades 48 and side
saw blades 50. The end saw blades 48 are structurally fastened to
the forward and rearward surfaces of the end saw blade plate 43 by
spaced bolts 49 extending through holes in the upper portion of
the end saw blades and into threaded engagement with the portion
of the end saw blade plate 43 adjacent thereto. Paired spaced
bolts 51 communicate through holes defined in the upper portion of
side saw blades 50 to fasten these side saw blades to the side
portions of side saw blade plate 3~. The vertical extent of the
end saw blades 48 and side saw blades 50 is such that the
lowermost portions of all blades are substantially coplanar to
allow simultaneous cutting action by portions of ail blades.
Each saw blade 48, 50 has a lower symmetrically configured
arcuate edge that defines a plurality of teeth 53 that are cut to
pitch in opposite directions on opposite sides of the mid point of
the arcuate lower edge of the blade, so that the teeth on one side
of each saw blade cut in the opposite direction to the teeth on
the other side of that blade. The saw teeth 53 are configured
similarly to those of an ordinary carpenter's saw, with a
reasonably fine pitch to make smoother cuts. The longer dimension
of the saw blades must be such that neither set of end or side saw
blades interferes with the other set during their reciprocating
motions, though the blades at the extreme points of their motion
Path should extend substantially to the adjacent saw blade to
properly cut a junction box orifice.
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Centering structure 13 as seen in Figures 4 and 5 provides
saber-like positioning blade 54 having relatively acute, vertical
side edges 55 and truncated pointed outer end 56. The blade
spacediy inwardly of its end 56 optionally may define notch 57 to
aid in removing a positioning template over a junction box through
an orifice after cutting. Such a notch 57 is not essential to my
invention, however, and normally the tool functions well without
the notch.
The blade 54 depends from structural interconnection with
flat mounting plate 58. This mounting plate 58 has a generally
rectilinear peripheral shape, with its edges of somewhat Less
dimension than the distance between the saw blades 48, 50 adjacent
thereto to allow appropriate motion of those saw blades without
interference from the mounting plate. The mounting plate 58 is
supported spacedly outwardly of side saw blade plate 87 by plural
bolts 59 depending from body 10. The bolts 59 have threaded inner
end portions 59a fastenabiy engaged in holes defined in body i0
and threaded outer end portions 59b that pass through holes 60
defined in mounting plate 58 to carry nuts 61 on the outer surface
of the fastening plate 58 for interconnection with the body.
Casement 14 provides a cover for operative mechanism of my
tool and interconnects and positionaliy maintains the tool on a
separate powering mechanism, in the case illustrated in Figure 5
an ordinary electrically powered drill. As seen in Figure I, the
casement i4 provides a rectilinear peripherally defined body
formed by structurally joined top 62, similar sides 63 and similar
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CA 02241104 1998-06-18
ends 64, with the sides and ends depending to a position
approximately coplanar with the top of blade mounting plate 58.
Top 62 defines fastener holes 21 to accept headed fasteners 22
which pass therethrough and into fastenable engagement in threaded
holes defined in the top and adjacent upper portion of body 10 to
reieasably fasten the casement on the tool body.
The medial portion of casement top 62 defines medial orifice
67 to allow passage of drive shaft 30 thereabove. Peripherally
defined cylindrically tubular neck 68 extends from structural
communication with top 62 spacedly upwardly to fastenably
interconnect with the body portion of the powering tool inwardly
of its chuck so as to positionaliy maintain my cutting tool on the
powering tool, while yet not interfering with the rotation of the
chuck of the powering tool, as illustrated particularly in Figures
4-5. The upper portion of this cylindrical neck 68 defines
vertical slot 69, with similar spacedly opposed fastening ears 7~
on both sides of the slot 69 to allow fastenable tightening of the
upper portion of the neck 68 about a powering tool body by
tightening bolt 7I extending through cooperating holes 73 defined
in each ear 70.
As seen in Figure 5, the interconnection between a drill
chuck 72 and driving nut 32 carried by drive shaft 30 is
accomplished by connecting structure 74 defining in its inner
portion female hexagonal channel 75 to irrotatably carry driving
nut 32 and cylindrical drive shaft 76 in ids outer portion to
communicate with an ordinary Jacobs type chuck 72 of a powering
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tool 16. This type of connecting structure may be convenient for
use with my tool, but it is not necessary as if the neck 68 is
shorter than illustrated, a powering tool may be connected
directly with driving nut 32 for powering of the tool.
Positioning template 1~ for a single junction box, as shown
in Figure 1, provides a concave medial truncated pyramidal portion
formed by similar sides 77 interconnecting similar ends 78 and
bottom ~9. Flange 8~ extends spacedly outwardly from the medial
pyramidal portion to define chamfered peripheral edge 8i. The
flange 8~ carries in the medial portion of each end at least one
positioning pin 88 extending spacedly on both sides of the flange
to communicate with fastener holes defined in junction boxes and
extend W sibiy through sheeting material thereover. The medial
portion of bottom 79 defines blade alignment slot 82,
symmetrically between positioning pins 88, that is incrementally
larger than the peripheral cross-sectional dimensions of
positioning bade 54.
Junction boxes of the type commonly used in modern
construction are substantially standardized in both dimension and
configuration. Such a box for a single fixture, as partially seen
in broken outline in Figure 1, has an outwardly opening
rectilinear orifice 83 defined by similar sides 84 and
interconnecting ends 85 with fastening tabs 86 projecting inwardly
from a medial portion of the upper edge of each end. Fach
fastening tab 86 defines medial fastener hole 87 to maintain
electric fixtures (not shown) in or about such boxes. The
CA 02241104 1998-06-18
positioning template 15 is so dimensioned and configured that the
inwardly projecting portions of positioning pins 88, that are the
depending portions in Figure ~, extend into fastening holes 87 of
the junction boxes and the inwardly extending medial truncated
pyramidal portion fits within the orifice and chamber defined by a
junction box with the peripheral flange 80 extending over the
junction box orifice so that the template is positioned relative
to the junction box with blade alignment slot 82 in a unique
orientation. The positioning pins 88 in their outward extension
are incrementally longer than the thickness of sheeting material
thereover that is to be cut, so that when the sheeting material is
placed over a junction box carrying a positioning template 15, the
outward portions of the positioning pins 88 project discernabiy
through the sheeting material to indicate the location of blade
alignment slot 82 therebetween.
A template for a multiple element junction box is illustrated
in Figure 2. This template has the same essential structure as a
single junction box template, with medial pyramidal portion formed
by interconnected similar sides 89, similar ends gU, and bottom g1
with outer flange ~2 having chamfered peripheral edge g3 extending
about the orifice defined by the template. Each end portion of
flange yz carries two or more positioning pins g4 to fit in the
fastening ears knot shown) provided for each individual electrical
fixture to be included in the multiple box. The bottom g1 defines
multiple elongate blade slots 95 to receive the blade of my tool
to position it for cutting an orifice for each individual
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CA 02241104 1998-06-18
electrical fixture. The ends 90 and end portions of flange 92
cooperatively define saw slots 96 to allow passage of the saw
blades of a tool that cut the individual holes, and the blade
slots 95 are so arrayed as to allow the tool to cut one individual
slot portion of a hole for the multiple box when associated with a
particular positioning blade slot. Templates may be formed in
similar fashion for multiple junction boxes for more than two
fixtures as illustrated by extending the principles used to form
the two unit template, and those multiple junction box templates
are within the ambit and scope of my invention.
Having thusly described the structure of my tool and
associated template, their operation may be understood.
A tool is constructed according to the foregoing
specification and positioning templates are formed in sufficient
number and configuration to accommodate the various junction box
orifices to be cut in a panel of sheeting material. An
appropriately configured template is attached within the orifice
of each junction box that is beneath the particular panel by
establishing positioning pins 88 in fastening holes 87 of those
boxes, with the outer portions of the positioning pins projecting
outwardly from the templates. A sheet of wallboard or other
sheeting material that is to be attached to a supporting wall
frame is moved into position spacedly adjacent to the wall frame
where it is to be attached and then moved into adjacency with the
surface of the supporting wall frame by forcing the outwardly
projecting portions of positioning pins 88 into and visibly
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CA 02241104 1998-06-18
through the sheeting material. The sheeting material then is
structurally attached to the underlying supporting frame by known
mechanical fasteners, adhesives or other fastening means so that
it is fastened in final attached position on the wall frame, with
positioning pins 88 projecting visibly therethrough to identify
the location and orientation of each individual junction box
therebeneath.
My cutting tool then is attached to a secondary powering tool
1~, preferably an electrically powered drill as illustrated in
Figures 4 and 5. Upper driving nut 32 is engaged directly in
drill chuck ~~, or as illustrated in connector ~~ with the
connector engaged in the powering tool chuck, and the upper
portion of casement 14 secured about the powering tool body
inwardly of the chuck and its powering shaft to prevent my tool
from rotating relative to the powering tool. The entire
assemblage of cutting tool and powering tool then is manually
positioned outwardly adjacent a junction box hole to be cut as
determined by the visible positioning pins 88.
The positioning blade 5~ is inserted by manual manipulation
of the tool through the sheet material, with the blade's major
cross-sectional dimension parallel to and at a point medially
between the line joining the centers of the two positioning pins
of the underlying template. The positioning blade 54 is moved
inwardly toward the junction box until it contacts and passes into
blade alignment slot 82 in the positioning template. The tool
then will be positioned over the underlying junction box in a
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CA 02241104 1998-06-18
position to cut a hole for access to the junction box orifice.
The powering tool is then activated to operate my cutting
tool by causing the four saw blades to move lineally in a limited
oscillating fashion. With the tool thusiy operating, it is
manually moved inwardly toward the sheeting material so that the
medial portions of the saw blades contact the surface of the
sheeting material therebeneath and begin cutting that material.
This inward motion of the tool is continued until a hole has been
cut in the sheeting material at which point tool operation is
discontinued. The hole that is cut is incrementally larger than
the template therebeneath so that the template may be removed
through the hole. If desired or necessary, the template removal
may be aided by contacting the portion of the bottom about the
periphery of blade alignment slot 8l with notch 5~, if defined in
the positioning blade 54, and removing the template with aid of
the positioning blade.
This same procedure then is repeated for each junction box
under the particular panel of sheeting material being installed so
that all required junction box holes are created.
The detailed operation of the components of my tool may be
understood with reference to Figures 7 and 8 where the end saw
blade plate 48 and side saw blade plate 8~ respectively are
illustrated. Drive shaft slot 46 defined in end saw blade plate
43 extends in an elongate direction forwardly and rearwardly of
the axis of drive shaft 8~ so that as eccentric shaft 84 is
rotated, it will move the end saw blade plate 43 in a cyclically
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CA 02241104 1998-06-18
reciprocating lateral motion against the bias of its supporting
side plate springs 41. The end saw blade plate will have no
motion in an elongate, forward or rearward direction since there
is no driving force in this direction because of slot 46 and the
plate springs 41 would prevent such motion in any event because of
their inability to flex in this direction. Similarly side saw
blade plate 37 defines drive shaft slot 39 extending in a lateral
direction on both sides of the axis of drive shaft 30 so that as
the drive shaft rotates, eccentric shaft 34 will cause this plate
37 to move in a cyclically reciprocating elongate motion against
the bias of side plate springs 35. The side saw blade plate 37
will have no motion in a lateral direction by reason of the lack
of any driving force in this direction because of slot 39 and the
restraint of motion in this direction by blade springs 35. From
this structure it is seen that the rotary motion of drive shaft
30, as transmitted to the saw blade plates 37 and 43 by the
eccentric drive shaft 34 extending therebetween, will be
translated into its two linear components to cause reciprocating
lineal motion of the two sets of saw blades in a directions
Parallel to the blades to cause cutting action.
From the nature of the saw blades, it is to be noted that no
mote than one-half of any blade, and normally less, will cut
during each half rotation of the drive shaft 30. It is also to be
noted that when a cut is commenced with a particular blade, that
blade will begin cutting only in its medial portion and not over
its entire length by reason of ita arcuately configured cutting
CA 02241104 1998-06-18
edge. These features of my tool tend to relieve the so called
''chatter'' that gives rise to irregular and accidental motion of
the a tool during its operation, as is common with other hand
tools used to cut holes in sheet material.
It is further to be noted that though an electrically powered
drill is specified as the preferred powering source, other
powering tools and even electric motors that provide means for
rotating drive shaft 30 are within the ambit and scope of my
invention. The electrically powered drill is preferred because
the speed of its rotation i.s well adapted to proper functioning of
my tool, whereas if a router were used, its speed would he greater
and my tool may not function as well, may not have as long a life
and may produce more dust. Other common powering tools may
require additional structures or modification of existing
structures to interconnect with my tool and may be clumsy to
manipulate and operate after interconnection.
The foregoing description of my invention is necessarily of a
detailed nature so that the specific embodiment of its best mode
may be set forth as required, hut it is to be understood that
various modifications of detail, rearrangement and multiplication
of parts might he resorted to without departing from its spirit,
essence or scope.
~"1
