U.S. patent application number 12/401839 was filed with the patent office on 2009-09-17 for undercut saw height adjustment, handle, blade guard improvements.
This patent application is currently assigned to Crain Cutter Company, Inc.. Invention is credited to Lance D. Crain, Tan D. Nguyen.
Application Number | 20090229436 12/401839 |
Document ID | / |
Family ID | 41061539 |
Filed Date | 2009-09-17 |
United States Patent
Application |
20090229436 |
Kind Code |
A1 |
Crain; Lance D. ; et
al. |
September 17, 2009 |
UNDERCUT SAW HEIGHT ADJUSTMENT, HANDLE, BLADE GUARD
IMPROVEMENTS
Abstract
An undercut saw including a motor, a drive shaft rotated by the
motor, a blade mount mechanically linked to the drive shaft, the
blade mount allowing a saw blade to be mounted and a fixed blade
guard circumscribing a portion of the saw blade. The fixed blade
guard includes a top plate and a height adjustment skirt in
telescoping attachment joined by fasteners. A guide washer
including a guide washer slot runner is configured to move up and
down in a slot on the height adjustment skirt.
Inventors: |
Crain; Lance D.; (Fremont,
CA) ; Nguyen; Tan D.; (Milpitas, CA) |
Correspondence
Address: |
SCHNECK & SCHNECK
P.O. BOX 2-E
SAN JOSE
CA
95109-0005
US
|
Assignee: |
Crain Cutter Company, Inc.
Milpitas
CA
|
Family ID: |
41061539 |
Appl. No.: |
12/401839 |
Filed: |
March 11, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61035704 |
Mar 11, 2008 |
|
|
|
Current U.S.
Class: |
83/373 ; 30/390;
30/517 |
Current CPC
Class: |
Y10T 83/546 20150401;
B27B 9/02 20130101; B27B 5/08 20130101 |
Class at
Publication: |
83/373 ; 30/517;
30/390 |
International
Class: |
B26D 5/00 20060101
B26D005/00; B23D 51/01 20060101 B23D051/01; B27B 9/04 20060101
B27B009/04 |
Claims
1. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a rotary power unit having
a motor housing; at least one handle on said motor housing; a motor
housed within said motor housing; a drive shaft rotated by said
motor; a blade mount mechanically linked to said drive shaft such
that when said drive shaft is rotated by said motor, said blade
mount is rotated such that when a blade is mounted on said blade
mount, said blade is rotated; a fixed blade guard assembly joined
to said motor housing, said fixed blade guard assembly
circumscribing a portion of said circular saw blade when said
circular saw blade is mounted on said blade mount, said fixed blade
guard assembly including: a top plate fixedly joined to said motor
housing, said top plate including a fastener hole; a height
adjustment skirt in telescoping attachment to said top plate, said
height adjustment skirt including a fastener slot through to said
fastener hole in said top plate; a guide washer including a
substantially horizontal hole alignable with said slot in said
height adjustment skirt and alignable with said fastener hole in
said top plate; said guide washer including a guide washer slot
runner insertable within a guide washer slot in said height
adjustment skirt; and a guide washer fastener assembly fastenable
into said fastener hole in said top plate, through said slot in
said height adjustment skirt, and through said substantially
horizontal hole in said guide washer; said guide washer fastener
assembly configured such that when in a tightened position it will
hold said top plate against an inner surface of said height
adjustment skirt, and will hold said guide washer against an outer
surface of said height adjustment skirt, such that said top plate
is frictionally held against said height adjustment skirt; and said
guide washer fastener assembly configured such that when it is in a
loosened position said height adjustment skirt will telescope in
relation to said top plate; wherein when said guide washer fastener
assembly is in a loosened configuration, a telescoping motion of
said height adjustment skirt is guided by said guide washer slot
runner moving within an area confined by the guide washer slot in
said height adjustment skirt.
2. The undercut saw of claim 1 wherein said guide washer includes a
radial shaped face in a flush contact with a guide washer channel
of said height adjustment skirt.
3. The undercut saw of claim 1 wherein said guide washer slot
runner contacts a downwardly protruding back edge of said top plate
when said guide washer fastener assembly is in a tightened
position.
4. The undercut saw of claim 1 further including: a lead threaded
member rotatably mounted to the height adjustment skirt; and a
substantially vertical tapped hole in said guide washer engaged by
the lead threaded member, wherein when said undercut saw is placed
with said height adjustment skirt flat on a floor surface, and said
guide washer fastener assembly is in a loosened configuration,
turning said lead threaded member raises and lowers said top
plate.
5. The undercut saw of claim 1 further including a removable blade
cover being on a bottom surface of said height adjustment skirt,
said blade cover covering the blade past a depth of the teeth.
6. The undercut saw of claim 1 further including a removable blade
cover being on a bottom surface of a downwardly protruding back
edge of said top plate, said blade cover covering the blade past a
depth of the teeth.
7. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a rotary power unit having
a motor housing; at least one handle on said motor housing; a motor
housed within said motor housing; a drive shaft rotated by said
motor; a blade mount mechanically linked to said drive shaft such
that when said drive shaft is rotated by said motor, said blade
mount is rotated such that when a blade is mounted on said blade
mount, said blade is rotated; a fixed blade guard assembly joined
to said motor housing, said fixed blade guard assembly
circumscribing a portion of said circular saw blade when said
circular saw blade is mounted on said blade mount, said fixed blade
guard assembly including: a top plate fixedly joined to said motor
housing, said top plate including a fastener hole; a height
adjustment skirt in telescoping attachment to said top plate, said
height adjustment skirt including a fastener slot through to said
fastener hole in said top plate; a lead guide washer including a
substantially horizontal hole alignable with a guide washer slot in
said height adjustment skirt, and said fastener hole in said top
plate, and a substantially vertical tapped hole; a guide washer
fastener assembly fastenable into said fastener hole in said top
plate, through said slot in said height adjustment skirt, and
through said horizontal hole in said lead guide washer; said guide
washer fastener assembly configured such that when in a tightened
position it will hold said top plate against an inner surface of
said height adjustment skirt, and it will hold said lead guide
washer against an outer surface of said height adjustment skirt,
such that said top plate is frictionally held against said height
adjustment skirt; said guide washer fastener assembly configured
such that when in a loosened position said top plate will telescope
in relation to said height adjustment skirt; and a lead threaded
member threadable into said substantially vertical tapped hole in
said lead guide washer, said lead threaded member rotatably
fastened to said height adjustment skirt; wherein when said guide
washer fastener assembly is in a loosened position, said top plate
is raised and lowered by turning said lead threaded member.
8. The undercut saw of claim 7 wherein a radial shaped face of said
lead guide washer rests flush against a guide washer channel of
said height adjustment skirt.
9. The undercut saw of claim 7, wherein said lead guide washer
includes a guide washer slot runner insertable within a slot in
said height adjustment skirt.
10. The undercut saw of claim 9 wherein said guide washer slot
runner contacts a downwardly protruding back edge of said top plate
when said guide washer fastener assembly is in a tightened
position.
11. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a motor configured to
produce rotational movement about a first axis of rotation and a
spindle rotatably powered by said motor for rotation about a second
axis of rotation which is perpendicular to the first axis of
rotation; a motor housing enclosing said motor and said spindle,
said motor housing including a spindle housing having a toothed
surface formed on an outer surface, said spindle housing including
a spindle housing handle mounting hole proximate to said toothed
surface; a handle with a toothed surface on an inner face and a
handle mounting hole proximate to said toothed surface, said
toothed surface of the handle interlockable with said toothed
surface on said spindle housing; and a handle fastening fastener
fastening said handle to said spindle housing at said spindle
housing handle mounting hole; wherein when said handle fastening
fastener fastens said handle on said spindle housing, with said
toothed surface on said handle interlocked with said toothed
surface on said spindle housing, said handle is prevented from
rotating.
12. The undercut saw of claim 11, wherein said spindle housing has
two toothed surfaces on opposite outer side surfaces and two handle
mounting holes proximate to said two toothed surfaces, a handle
including two toothed surfaces on opposite inside surfaces
interlockable with said two toothed surfaces on said spindle
housing, and two handle fastening fasteners, wherein when said two
handle fastening fasteners fasten said handle to said spindle
housing at said two handle mounting holes, with said two toothed
surfaces on said handle interlocked with said two toothed surfaces
on said spindle housing, said handle is prevented from
rotating.
13. The undercut saw of claim 12, further including said handle
having two handle sections joined at a pivot.
14. The undercut saw of claim 11, wherein: said handle further
includes a boss on said inner face of said handle proximate to said
handle mounting hole; and when said handle is oriented at a preset
angle and position in relation to said first axis of rotation, said
boss contacts said spindle housing preventing said toothed surface
on said handle from interlocking with said toothed surface on said
spindle housing.
15. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a motor configured to
produce rotational movement about a first axis of rotation and a
spindle rotatably powered by said motor for rotation about a second
axis of rotation which is perpendicular to the first axis of
rotation; a motor housing enclosing said motor, said motor housing
including a spindle housing enclosing said spindle, said spindle
housing including a spindle housing handle mounting hole; a handle
rotatably fastenable to said spindle housing at said spindle
housing handle mounting hole, said handle having an inner surface
including a boss and a handle hole proximate to said boss; and a
fastener rotatably fastening said handle to said spindle housing at
said spindle housing handle mounting hole; wherein when said handle
is rotated towards said spindle housing, said boss contacts said
spindle housing to stop said handle from rotating past a preset
angle in relation to the motor's first axis of rotation.
16. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a rotary power unit having
a motor housing; at least one handle on said motor housing; a motor
housed within said motor housing; a drive shaft rotated by said
motor; a blade mount mechanically linked to said drive shaft such
that when said drive shaft is rotated by said motor, said blade
mount is rotated such that when a circular saw blade having teeth
is mounted on said blade mount, said circular saw blade is rotated;
a fixed blade guard assembly joined to said motor housing, said
fixed blade guard assembly circumscribing a portion of said
circular saw blade when said circular saw blade is mounted on said
blade mount, said fixed blade guard assembly including: a top plate
fixedly joined to said motor housing; a height adjustment skirt in
telescoping attachment to said top plate; a removable blade cover
on a bottom surface of said height adjustment skirt, said blade
cover covering the circular saw blade past a depth of the
teeth.
17. The undercut saw of claim 16 further including: a guide washer
contacting a guide washer channel on said height adjustment skirt;
said guide washer having a guide washer slot runner slightly
narrower than and fitting in a slot in said height adjustment
skirt; a guide washer fastener assembly engaging a downwardly
protruding back edge of said top plate through a hole in said guide
washer; said guide washer fastener assembly when tightened applying
a frictional holding force to said guide washer, said height
adjustment skirt and said downwardly protruding back edge of the
top plate; said guide washer fastener assembly when loosened
decreasing a frictional holding force so that said height
adjustment skirt telescopes with respect to said top plate.
18. An undercut saw configured to cut a substantially vertical wall
surface while a fixed blade guard assembly moves across a
substantially horizontal floor surface on which said undercut saw
is placed, said undercut saw comprising: a rotary power unit having
a motor housing; at least one handle on said motor housing; a motor
housed within said motor housing; a drive shaft rotated by said
motor; a blade mount mechanically linked to said drive shaft such
that when said drive shaft is rotated by said motor, said blade
mount is rotated such that when a circular saw blade having teeth
is mounted on said blade mount, said circular saw blade is rotated;
a fixed blade guard assembly joined to said motor housing, said
fixed blade guard assembly circumscribing a portion of said
circular saw blade when said circular saw blade is mounted on said
blade mount, said fixed blade guard assembly including: a top plate
fixedly joined to said motor housing; a height adjustment skirt in
telescoping attachment to said top plate; and a removable blade
cover on a bottom surface of a downwardly protruding back edge of
said top plate, said blade cover covering the circular saw blade
past a depth of the teeth.
19. The undercut saw of claim 18 further including: a guide washer
contacting a guide washer channel on said height adjustment skirt;
said guide washer having a guide washer slot runner slightly
narrower than and fitting in a slot in said height adjustment
skirt; a guide washer fastener assembly engaging a downwardly
protruding back edge of said top plate through a hole in said guide
washer; said guide washer fastener assembly when tightened applying
a frictional holding force to said guide washer, said height
adjustment skirt and said downwardly protruding back edge of the
top plate; said guide washer fastener assembly when loosened
decreasing a frictional holding force so that said height
adjustment skirt telescopes with respect to said top plate.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application claims priority from U.S. provisional
application No. 61/035,704, filed Mar. 11, 2008.
TECHNICAL FIELD
[0002] The invention relates to power tools and more specifically
to power tools for installation of flooring.
BACKGROUND ART
[0003] An undercut saw is a specialty circular power saw used by
flooring installers for undercutting walls, moldings, door jams,
and cabinetry so that new floors may be installed underneath. When
the area is undercut using the saw, the new flooring is simply slid
underneath the undercut area, which saves time and presents a
visually appealing finish. Without an undercut saw, the flooring
should be precisely cut to fit around these areas, which is
laborious, costly, and often leaves unsightly gaps.
[0004] Most existing undercut saws have been constructed with a
fixed blade guard assembly which consists of two telescoping parts
that serve both as a blade guard and a height adjustment mechanism
for the saw. As shown in FIG. 1, existing undercut saw 100 has a
fixed blade guard assembly 120 consisting of a first top plate 140
and a second height adjustment skirt 160. Top plate 140 is fixedly
joined to a rotary power unit 180 (commonly circular saw or grinder
based power units). When movable guard 200 is retracted, the front
of the top plate 140 preferably covers less than 180 degrees of the
circular saw blade 220 so the saw 100 can operate in tight areas,
such as inside corners. The back of the top plate 140 has a
downwardly protruding back edge 240 which is typically
semi-circular so that it can be precisely machined to a controlled
outside diameter. The downwardly protruding back edge 240 of the
top plate 140 mates with an inner surface 260 formed in the height
adjustment skirt 160 which is also semi-circular. These two mating
semi-circular parts may telescope up and down creating a height
adjustment mechanism for existing undercut saw 100, while also
providing a fixed blade guard assembly 120 surrounding the back of
the blade 220. Base 450 is an integral part of height adjustment
skirt 160. The bottom surface 451 of the base 450 forms the surface
upon which the saw is placed while in use on a floor surface.
[0005] There are practical considerations of this existing height
adjusting mechanism with respect to the fasteners used to hold the
telescoping members at a desired height. The following is a history
of various fastener combinations that have been used. In existing
early model undercut saws, the fasteners used were carriage bolts
socketed into square holes in the downwardly protruding back edge
240 of the top plate 140. The carriage bolts extending from the
back of the top plate passed through slots in the height adjustment
skirt forming threaded ends for mounting additional fasteners.
First mounted on these threaded ends were so-called "guide
washers", which were specialized cast shapes designed to move
within channels formed on a back surface of the height adjustment
skirt. Last mounted on these threaded ends were wing nuts which
were tightened down on the guide washers. The clamping force
generated by the wing nuts pressured the guide washer against an
outer surface of the height adjustment skirt, while the downwardly
protruding back edge of the top plate was drawn against the inner
surface of the height adjustment skirt by the pulling action of the
carriage bolt. This clamping force frictionally held the top plate
at a desired height within the height adjustment skirt.
[0006] In some more recent existing saws, one of which is shown in
FIG. 1, the fasteners consisted of two threaded wing screws 280
which fastened into two tapped holes 300 in the downwardly
protruding back edge 240 of top plate 140. Spring 340 and washer
360 were also mounted on wing screw 280 ahead of guide washer 320.
Spring 340 and washer 360 pressure guide washer 320 against the
curved outer surface 305 of the height adjustment skirt 160 within
an outer guide washer channel 380. Thus, even when a wing screw 280
is loosened, pressure from the spring keeps the guide washer in its
channel, providing at least some stability and guidance for the
assembly during the adjustment process.
[0007] Existing guide washers have typically been generally
trapezoidal cast shapes with a semi-circular inside surface 315
that precisely mates with the curved outer surface 305 within guide
washer channel 380 of the height adjustment skirt 160. Two or three
guide washers along with two or three sets of the aforementioned
fasteners have been used on existing saws.
[0008] Since the rotary power unit 180 and rotatable circular saw
blade 220 are fixedly assembled onto top plate 140, the height at
which top plate 140 is frictionally held by the fasteners
determines the height of cut. The top plate 140 may be frictionally
held at any point in a vertical range of about one inch within the
height adjustment skirt 160. This enables the height of cut for
circular saw blade 220 to be set from floor level (i.e., flush to
the floor or no height of cut) to a height of one inch above floor
level.
[0009] The characteristics of these guide washer and fastener
mechanisms for these existing height adjustment mechanisms are as
follows: First, the guide washers sometimes do not frictionally
hold the assembly together with sufficient force, and the top plate
can shift within the height adjustment skirt as the saw is being
used. Particularly as the user lifts and places the saw at various
locations around a jobsite, the weight of the saw motor can cause
the top plate to slip downward within the height adjustment skirt.
As a result, in some places the undercut is not of sufficient
height, and the user has to re-adjust and re-cut many areas.
[0010] Another characteristic of the existing fastening mechanisms
and guide washers is that they do little to ensure that the top
plate (and thereby the blade) is always parallel with the flat
floor surface on which the saw rests during use. The blade should
be kept parallel to the floor during undercutting so that the blade
will not angle up or down in relation to the floor during a cutting
operation. Keeping the blade parallel with the floor surface
ensures that the height of undercut will be consistent. Otherwise,
angling of the blade may cause the blade to wedge upward or
downward. This can result in inconsistent height of cut. Angling of
the blade can also bog down the motor during a cutting operation,
or even cause the saw to kick back. An improved height adjustment
mechanism that worked to prevent the top plate from being set at
angles that are not parallel to the floor could prevent undesirable
inconsistencies in the height of cut, and would promote safer usage
by reducing the possibility of saw kickback.
[0011] The use of such existing telescoping height adjustment
mechanisms fastened with guide washers and threaded fasteners was
preferred for simplicity and low cost. However, various different
mechanisms for setting and holding the height of cut for an
undercut saw have been designed to address slippage and blade
angling during use. Such designs have largely not been adopted
because they were impractical for jobsite conditions or too
expensive to manufacture. For example, U.S. Pat. No. 5,784,789 to
Vargas discloses an undercut saw with a rack-and-pinion mechanism
for height adjustment. The undercut saw of this disclosure employs
a grinder based power unit. A circular saw blade is mounted onto
its spindle. A cylindrical sleeve is mounted to the grinder motor
to cover the rotating spindle. The sleeve has a rack formed in its
back side. The sleeve is assembled into a base. The base holds the
pinion. Thus, as the pinion is turned, the rack on the sleeve
causes the power unit and blade to move up or down. The rack and
pinion design ensures that blade will move up and down in a precise
manner that keeps the blade parallel with the floor at all times.
Two screws threaded through the base may contact the sleeve to fix
the sleeve at a given height. The rack and pinion mechanism of saw
proved too expensive for mass production, and was prone to binding
from saw dust. As a result, it was not widely adopted.
[0012] U.S. Pat. No. 6,678,960 to Williams discloses an undercut
saw with a housing which rests on a floor surface and itself has a
fixed height. A tapped sleeve is mounted on top of the housing. A
rotary motor with a central axis and a threaded case may be
threaded into the tapped sleeve. The blade when mounted on the
central motor armature axis may be moved up and down within the
housing as the threaded case is turned within the tapped sleeve.
The height is fixed by means of a jam nut also threaded onto the
threaded case. This threaded adjustment mechanism ensures that the
blade will be kept parallel to the floor at all times. The tapped
sleeve and large threads on the motor housing of this design proved
too expensive for mass production. This mechanism was also prone to
binding from saw dust. Furthermore, the requirement that the blade
be mounted on a central armature axis about which the entire
assembly turned required that only motors such as routers having a
single, central armature axis (without any offset spindle gear)
could be employed. Such high RPM low torque motors are not powerful
enough for large amounts of undercut sawing. In particular, a great
deal of power is used by a saw to undercut an inside corner area.
Williams' saw as disclosed could not perform such cuts, due to its
bulky blade housing.
[0013] Other mechanisms for fixing the height of cut are disclosed
within this application, including rack-and-pinion, frictional,
interlocking, and lead screw mechanisms. With regard to Williams'
lead screw mechanism, this is shown in FIG. 9 of Williams. Williams
describes the mechanism as a "jack screw" 160 rotatably fastened
onto an outer sleeve 63 on two bosses 151. When a knob 155 is
turned, a teeter 161 having a lead nut 160 may be raised or
lowered. Teeter 161 has an arm 162 with a thin end 67 which may
pass through a slot through the case and engage a cavity 37 in the
case 30. Spring 166 biases teeter into cavity 37. However, a
separate tightening clamp 76 may close down the diameter of sleeve
63 to frictionally hold the case.
[0014] A lead screw mechanism such as Williams' "jack screw"
generally requires a secondary holding mechanism besides the lead
screw to hold the mechanism in position. Otherwise, an accidental
bump on the lead screw knob or even vibration during use can cause
the mechanism to shift unexpectedly. For Williams, the separate
frictional mechanism of clamp 76 provides such a secondary holding
mechanism.
[0015] Williams' jack screw design presents many manufacturing
challenges that make it cost prohibitive. Much as with the threaded
case of the embodiment previously discussed, Williams jack screw
embodiment has a specialized motor housing having a precisely
shaped outer "case" capable of sliding within a sleeve. This is not
preferred as most commonly available power units come in the shape
of a grinder or circular saw, and such power units have no such
precisely shaped case. Furthermore, the tightening clamp used to
frictionally hold the case within the sleeve is a large, tight
tolerance slide fit mechanism which would entail high machining
cost to produce. A lead screw mechanism which did not engage the
case of the power unit would be preferred as just about any power
unit could be employed.
[0016] A lead screw mechanism that worked in conjunction with
existing low cost guide washers and fastener assemblies could
provide additional support for the existing telescoping top plate
and height adjustment skirt at a much lower cost. Such would be
preferred as a low cost mechanism to provide the benefits of
reduced slippage and angling of the blade. Williams teaches that
"peripheral studs" (carriage bolt or wing screw fastener
assemblies) or "wing nuts", are "slow because several fasteners
require adjustment" (Background of the Invention, paragraph 3).
[0017] Some existing undercut saws have been manufactured with a
grinder motor as a power unit. As shown in FIG. 2, grinder motor
370 has a first axis of rotation 375 (long armature axis)
operatively coupled to a perpendicular second axis of rotation 385
(spindle axis). A first handle 380 and switch 400 are typically
located towards the back of the saw. A spindle housing 420 is
typically located at the front of the saw. Spindle housing 420 is
typically made out of aluminum, which is suitable for mounting a
second, forward, movable handle for controlling the front of the
saw.
[0018] Existing grinders typically have a second handle formed in
the shape of a threaded post fastenable into tapped holes on either
side of the aluminum spindle housing. Such threaded posts extend
out quite a distance from either side of the spindle housing, which
is preferred during a grinding operation to provide counter
leverage for the user. However, such a handle assembly is not
suitable for use in undercut saws. The extension of the handle
prevents the saw from entering tight areas, such as inside
corners.
[0019] For this reason, as shown in FIG. 2, existing undercut saws
have been made with a narrow, plastic, U-shaped handle such as
handle 440 for their second, forward, movable handle. U-shaped
handle 440 is bolted into tapped holes 500 on both sides of spindle
housing 420 with bolts 480 and lock washers 460. U-shaped handle
440 is preferably narrower than the width of top plate 140 below so
that it does not prevent the saw from undercutting in tight areas,
such as inside corners.
[0020] The use of bolts 480 and lock washers 460 to bolt a second,
forward, movable handle, such as U-shaped handle 440, to spindle
housing 420 is preferred for simplicity and low cost. The user can
tighten down the bolts 480, and the lock washers 460 tend to hold
the handle in place. The handle 440 can also be rotated backward
(i.e., towards the first, back handle 380) whenever the saw is used
to undercut in a low clearance area, such as underneath the
toe-space of a cabinet.
[0021] However, if the user pushes excessively hard on U-shaped
handle 440, it can rotate forward (towards blade 220). This is not
preferred as this puts the user's hand in closer proximity to blade
220. Forward rotation is also not preferred, because whenever the
handle is oriented at such an angle, the saw is less able to
operate in tight areas, such as inside corners. Some added
mechanism to prevent the forward handle of the saw from rotating
forward from the normally preferred 90 degree angle would be a
usability and safety improvement. A more solid handle and better
mounts on the spindle housing could provide such an improvement.
However, as previously explained, this handle should also be able
to rotate backward for undercutting beneath a toe-space.
[0022] An undercut saw is primarily used to undercut walls, door
jams, and cabinet areas so that new flooring materials may be fit
underneath. Some flooring materials are very thin, such as sheet
vinyl or linoleum. To provide the proper undercut for thin sheet
vinyl, the undercut saw should cut flush to the floor. For this
reason, in most existing saws, as shown in FIG. 3 (a bottom view of
an existing undercut saw), fixed blade guard assembly 120
(comprised of top plate 140, and height adjustment skirt 160) and
movable guard 200 are both open on the bottom. This allows the
blade height to be adjusted as close to the floor as possible.
However, the undercut saw is not always used to undercut flush to
the floor. In many cases, such as for ceramic tile or hardwood
plank flooring, the undercut is made higher, because the flooring
material to be installed is thicker. In such cases, additional
guarding structures may be added to increase safety. Such
structures may be removably mounted onto the components comprising
the fixed blade guard, or the movable blade guard, to cover more of
the blade when the saw is not being used for undercutting to fit
thin materials, such as sheet vinyl.
[0023] It is an object to provide an undercut saw with an improved
mechanism for guiding the telescoping motion of the top plate and
the height adjustment skirt so that during height adjustment the
top plate tends to stay parallel with the base of the saw, thereby
keeping the blade parallel to the floor surface upon which it is
placed during use.
[0024] It is an object to provide an undercut saw with an improved
mechanism for holding a top plate at a fixed elevation within a
height adjustment skirt which is economical enough for mass
production.
[0025] It is an object to provide an undercut saw with an improved
handle fastening mechanism which may be more rigidly fixed to the
spindle housing of a grinder motor, which may be adjusted to
various angles, but stopped from certain angles that are not
preferred.
[0026] It is an object to provide an undercut saw with additional
safety mechanisms which may be removably mounted to the fixed and
movable guards.
SUMMARY
[0027] The device has several embodiments including an undercut saw
with a fixed guard assembly comprising a telescoping top plate and
height adjustment skirt, with some embodiments including improved
guide washers including an added guide washer slot runner. Certain
other embodiments include a lead screw mechanism threaded
vertically through the guide washer to assist in setting and
holding a height of cut. In certain other embodiments having a
right angle grinder motor for their power unit, the saw includes a
handle with a pattern of teeth encircling a hole in the handle for
mounting the handle to the saw's spindle housing. In addition, a
similar pattern of interlocking teeth is formed at a handle mount
location on at least one side of the saw's spindle housing. The
teeth on the handle and the spindle housing may thus interlock to
allow the handle to be fixedly joined at a range of preferred
angles. The handle and the spindle housing may additionally include
certain bosses acting as stops to prevent the handle from being
rotated forward to certain angles which are not preferred. Certain
other embodiments include removable cover plates covering the blade
to increase safety which may be removed to enable the saw to cut
flush to a floor surface.
[0028] The improved guide washer may incorporate any one of several
added features. The first feature, which will be described herein
as a "guide washer slot runner", is a boss or projection extending
from the inner surface of the guide washer. This projection is
sufficiently long and has a precise width to extend (with a small
degree of play) into its corresponding slot in the height
adjustment skirt. In existing saws, the slots in the height
adjustment skirt served only to allow passage of the bolts
extending through the guide washers to fasten into the downwardly
protruding back edge of the top plate. The added guide washer slot
runner extends into and may contact the edges of the slots in the
height adjustment skirt to guide the telescoping motion of the top
plate and the height adjustment skirt during adjustment. This helps
keep the base of the height adjustment skirt parallel to the top
plate. This helps ensure that the top plate will be adjusted in a
manner that keeps the blade parallel to the floor surface.
[0029] The guide washer may include an additional tapped hole
through a vertical cross section, for receiving an added threaded
member. This threaded member may be rotatably fastened on the base
of the saw's height adjustment skirt using a collar or other nut
type fastener. This threaded member thus forms a lead screw
mechanism capable of lifting or lowering the guide washer (and
thereby the top plate and blade). Such a lead screw mechanism may
be included on one or more guide washers in the assembly, though it
is preferred they be used on all such guide washers. This is so the
height of cut can be adjusted incrementally on all sides through
equal turns of all threaded members. The threaded members provide
added support to hold the desired height of cut and prevent
slippage. The guide washers may still include the existing
fasteners such as wing screws threading into the downwardly
protruding back edge of the top plate to provide a second
frictional mechanism to hold the height of cut.
[0030] In embodiments including a grinder motor for a power unit,
the second, forward, movable handle may be affixed to the spindle
housing with corresponding circular patterns of interlocking teeth
on one or more sides of the handle and the spindle housing. In one
embodiment, a two piece handle assembly is provided, made in two
halves joined by a pivot pin. The pivoting action of the halves
allow the assembly to be closed or opened to enable interlocking or
disengagement of the circular tooth patterns on the handle and the
spindle housing. When these circular tooth patterns are
interlocked, a secure joint is produced between the components
preventing unexpected rotation during use. The handle may be
pivoted open for adjustment backward to a number of angles to
enable the saw to be used in low clearance areas, such as under toe
spaces. Added stops on the handle and the spindle housing prevent
the handle from rotating to forward angles (acute angles less than
90 degrees) in relation to the long armature axis of the saw.
[0031] For improved guarding, removable cover plates may be added
to the bottom of the downwardly protruding back edge of the top
plate, the bottom surface of the height adjustment skirt, or the
movable guard. These cover plates may be removed to enable flush
cutting when installing thin flooring materials, such as sheet
vinyl.
BRIEF DESCRIPTION OF THE DRAWINGS
[0032] FIG. 1 is a side perspective view of an existing undercut
saw showing existing guide washers and guide washer mounting
hardware such as wing screws.
[0033] FIG. 2 is perspective view of an existing undercut saw using
a grinder motor as a power unit and an existing U-shaped handle
mounted to the spindle housing using bolts and lock washers.
[0034] FIG. 3 is a bottom perspective view of an existing undercut
saw showing how the fixed guard assembly and movable guards are
open at bottom to enable flush cutting.
[0035] FIG. 4 is a side view of an undercut saw including an
improved guide washer having an added guide washer slot runner.
[0036] FIG. 5 is a perspective view of an improved, two-part
pivoting handle for an undercut saw with a circular pattern of
teeth which can be interlocked with a corresponding pattern of
teeth on the spindle housing.
[0037] FIG. 6 is a bottom view of an undercut saw showing a
removable cover plate mounted on the base of the height adjustment
skirt, and a removable cover plate on the movable blade guard.
[0038] FIG. 7 shows a removable cover plate mounted on the bottom
of the downwardly protruding back edge of the top plate.
[0039] FIG. 8 is a side perspective view of an undercut saw
including an improved guide washer with guide washer slot runner
and additionally including a threaded member threading through a
vertically tapped hole in the guide washer forming a lead screw
mechanism.
[0040] FIG. 9 is a top view of the undercut saw showing the
preferred locations where the two guide washer assemblies may be
fastened through the height adjustment skirt and into tapped holes
in the downwardly protruding back edge of the top plate.
[0041] FIG. 10 is a perspective view of a guide washer including
the added guide washer slot runner.
[0042] FIG. 11 is a side view of an assembled undercut saw having a
grinder motor for its power unit showing two preferred angles in
the orientation of the forward handle.
[0043] FIG. 12 is a top view of an undercut saw showing preferred
locations of two lead screw mechanisms.
[0044] FIG. 13 is a perspective view of a shoulder pan head
screw.
[0045] FIG. 14 shows a section view of an undercut saw showing how
a shoulder pan head screw may be rotatably mounted to the base
using a hex nut.
DETAILED DESCRIPTION
[0046] As shown in FIG. 4, undercut saw 2000 has a fixed blade
guard assembly 2120 which consists of two parts: a first top plate
2140 and a second height adjustment skirt 2160. A rotary power unit
2180 is fixedly attached to top plate 2140. In the illustrated
embodiment, the power unit is a grinder motor. However, other
embodiments may include other types of power units attached to the
top plate, including circular saw or router type power units. Blade
2220 is mounted on the spindle of rotary power unit 2180 using a
blade mount (not shown) which keeps it parallel to a substantially
flat top face 2130 of top plate 2140.
[0047] Top plate 2140 has a downwardly protruding back edge 2240
which forms a semi-circular vertical edge surface. Height
adjustment skirt 2160 has an inside face 2260 which also forms a
corresponding semi circular vertical edge surface. The downwardly
protruding back edge 2240 of top plate 2140 and inside face 2260 of
height adjustment skirt 2160 together form precisely mating
telescoping surfaces. Base 2450 is an integral part of height
adjustment skirt 2160. Base 2450 has a bottom surface 2451 which is
the surface upon which the saw rests or is moved while in use.
[0048] To fix the height of top plate 2140 in relation to base
2450, top plate 2140 has a tapped hole 2300 which is centered in
the location of a corresponding slot 2310 in height adjustment
skirt 2160. Wing screw 2280 extends through a horizontal hole 2325
in guide washer 2320 and is threaded into tapped hole 2300 in
downwardly protruding back edge 2240 of top plate 2140. Guide
washer 2320 has an added guide washer slot runner 2330. As shown in
greater detail in FIG. 10, guide washer 2320 includes a guide
washer slot runner 2330 having a width 2335 slightly narrower than
slot 2310 (FIG. 4) in height adjustment skirt 2160 (FIG. 4). This
is so it can enter this slot with a slight amount of play. Guide
washer slot runner 2330 has a length 2337 long enough to enter slot
2310 (FIG. 4). In a preferred embodiment, as shown in FIG. 4, guide
washer slot runner 2330 is long enough that, once wing screw 2280
is tightened down on the outer surface of the guide washer, guide
washer slot runner 2330 contacts surface 2347 (on downwardly
protruding back edge 2240 of top plate 2140--exposed within slot
2310). As shown in FIG. 10, guide washer 2320 includes radial
shaped faces 2339, 2341 designed to rest flush against a
corresponding radially-shaped vertical face 2343 (FIG. 4) of guide
washer channel 2345 (FIG. 4). These large corresponding contact
surfaces are used to apply and control frictional holding force
between the components. As shown in FIG. 4, spring 2340 along with
washer 2360 may be mounted on wing screw 2280 ahead of guide washer
2320.
[0049] In this embodiment, guide washer slot runner 2330 runs in a
slot 2310 to guide the motion of height adjustment skirt 2160
during height adjustment. Others skilled in the art might imagine
similar combinations of slots through the height adjustment skirt
and bosses (guide washer slot runners) on an inner face of the
guide washer which could run in the slots to perform the same
function. Such may include multiple slots in the outer face of the
height adjustment skirt, for multiple guide washer slot runners on
an inner face of the guide washer. One such slot may be the slot
provided for passage of a fastener used to fasten the top plate
within the height adjustment skirt. Alternatively, the slot may
have no other function than for receiving the boss forming a guide
washer slot runner. The slot itself may be a slot or a groove of
only partial depth in the outer surface of the height adjustment
skirt performing the same function of receiving a slot runner.
However, the embodiment of FIG. 4 is preferred. Multiple slots
weaken height adjustment skirt 2160, making it prone to breakage if
the undercut saw 2000 is dropped. A single, central guide washer
slot runner running within a single slot centers and controls the
assembly on a single vertical axis. Multiple axes would require
tight tolerances on a larger number of surfaces, adding unnecessary
expense.
[0050] In this embodiment, when height adjustment is performed,
normally the saw is turned upside down and rested on the second,
forward, movable handle (as shown as undercut saw 100 of FIG. 3).
Afterwards, wing screw 2280 is loosened, and the height adjustment
skirt 2160 is free to telescope up or down. Guide washer slot
runner 2330 remains in slot 2310 and is pressed up against
downwardly protruding back edge 2240 due to pressure from spring
2340. As height adjustment skirt 2160 is moved up or down, the
outer edges of guide washer slot runner 2330 guide its motion
through contact with the inside edges of slot 2310. This guidance
ensures that the height adjustment skirt will be guided up or down
in a substantially vertical direction. Top plate 2140 thus tends to
stay parallel to base 2450. Thus, the blade will be kept parallel
to the base during adjustment. When the desired height is set, wing
screw 2280 may be tightened down on guide washer 2330, pressing it
against the inner surface of guide washer channel 2345 of height
adjustment skirt 2160, and in turn drawing the downwardly
protruding back edge 2240 of top plate 2140 against inside face
2260 of height adjustment skirt 2160. This clamping pressure on the
components frictionally holds the desired height of cut.
[0051] As used herein, and as shown in FIG. 4, the term "guide
washer fastener assembly" includes at least one threaded fastener
(such as wing screw 2280). The guide washer fastener assembly is
used in conjunction with a guide washer, but the guide washer
itself is considered a separate element. In one embodiment, the
guide washer fastener assembly includes only wing screw 2280. In a
preferred embodiment, the guide washer fastener assembly
additionally includes a washer 2360 installed first on the wing
screw 2280, followed by a spring 2340. In some embodiments, one or
more guide washer fastener assemblies may be included, used in
conjunction with one or more guide washers. However, in one
embodiment, such as shown in FIG. 9, only two such guide washer
fastener assemblies 6000, 6200 are included, (comprising wing screw
2280, washer 2360, and spring 2340). Guide washer fastener
assemblies 6000, 6200 are used in conjunction with two guide
washers 2320, 2321. The use of only two such fastener assemblies
with two guide washers provides ample clamping force on both sides
of fixed blade guard assembly, yet leaves room for other saw
features, such as dust port 6300. Persons skilled in the art may
envision the use of other fastener combinations which may be used
to form a guide washer fastener assembly. For example, another
embodiment of a guide washer fastener assembly may include carriage
bolts and wing nuts used in conjunction with guide washers, as has
been described in existing references.
[0052] As shown in FIG. 4, wing screw 2280 along with tapped hole
2300 work to generate clamping force to frictionally hold the
downwardly protruding back edge 2240 of the top plate 2140 against
the inner surface 2260 of height adjustment skirt 2160. This holds
the height of the top plate 2140 relative to the bottom surface
2451 of base 2450 of height adjustment skirt 2160. Since the rotary
power unit 2180 and rotatable circular saw blade 2220 are fixedly
assembled onto top plate 2140 when the saw is assembled, the height
of the top plate 2140 determines the height of cut. The top plate
2140 may be adjusted and frictionally held in a vertical range of
about one inch within the height adjustment skirt 2160. This
enables the height of cut for circular saw blade 2220 to be set
from floor level (i.e., flush to the floor or no height of cut) to
a height of one inch above floor level. In this embodiment, the
added guide washer slot runner guides the motion of the height
adjustment skirt to help ensure that the blade will be kept
parallel to a floor surface. This prevents angling of the blade.
However, the frictional holding mechanism of this embodiment may
not be sufficient to hold a desired height of cut. Additional
support mechanisms may be added to hold a desired height of
cut.
[0053] As shown in FIG. 8, additional support mechanisms may be
added by including an added vertical tapped hole in the body of the
guide washer, which in conjunction with an added threaded member
may form a lead screw mechanism capable of raising or lowering the
guide washers (and thereby the top plate and blade). Undercut saw
8000 includes a guide washer 8020 including a tapped hole 8040. A
threaded member such as pan head screw 8060 is inserted through a
hole 8080 in the base 8100 of height adjustment skirt 8120. Hole
8080 may be countersunk on its bottom side (not shown) such that
the pan head 8061 of pan head screw 8060 sockets flush within the
countersink. Thus, base 8100 will be a uniform flat surface on its
bottom side 8101, which will not catch on floor surface
irregularities.
[0054] Once inserted in hole 8080, pan head screw 8060 extends
vertically up from base 8100 and may be threaded into tapped hole
8040 in guide washer 8020. Next, collar 8210 is fastened onto pan
head screw 8060 at an elevation forming a slight gap between the
bottom of collar 8210 and a top surface 8260 of base 8100. This gap
enables pan head screw 8060 to rotate within hole 8080. (More
secure, lower cost alternatives exist for pan head screw 8060 and
collar 8210 will be described later.) Finally, for ease of turning,
a knob such as three arm knob 8140 may be fastened on top of pan
head screw 8060.
[0055] The lead screw mechanism formed by a threaded member such as
pan head screw 8060 and tapped hole 8040 may be included in one or
more of the guide washers included in the fixed guard assembly for
the saw. As shown in FIG. 12, in this embodiment, two lead screw
mechanisms 12020, 12040 are used. A single lead screw mechanism
would not evenly lift both sides of the top plate 12060. With two
such mechanisms 12020, 12040, the user may use both hands to turn
the two knobs each by equal amounts of turn, resulting in uniform
level height adjustment. Furthermore, two such mechanisms 12020,
12040 provide adequate support for top plate 12060 during use of
the saw. With three or more such mechanisms, each knob would have
to be turned separately, which is cumbersome.
[0056] In addition to the added lead screw mechanism supporting the
height of the guide washer, the guide washer may also include
additional frictional mechanisms to further assist in holding the
desired height of cut. As shown in FIG. 8, as previously described,
such a frictional mechanism may include a guide washer fastener
assembly (such as wing screw 8160, washer 8180, and spring 8200
threading into tapped hole 8220 of the downwardly protruding back
edge 8280 of top plate 8240). This guide washer fastener assembly
works in conjunction with guide washer 8020 to frictionally hold a
desired height of cut. The addition of this frictional mechanism is
preferred because the lead screw mechanism alone may slip due to
vibration or accidental bumping of one of the knobs.
[0057] In this embodiment as shown in FIG. 8, the process of height
adjustment is somewhat different. First, the user loosens wing
screw 8160, reducing the frictional hold. However, since pan head
screw 8060 is threaded through tapped hole 8040 in guide washer
8020, top plate 8240 is held at that elevation until three arm knob
8140 is turned. If three arm knob 8140 is turned clockwise, pan
head screw 8060 will be turned clockwise, thereby raising guide
washer 8020 and top plate 8240 to a higher elevation above base
plate 8100. If three arm knob 8140 is turned counter-clockwise,
guide washer 8020 and top plate 8240 will be lowered. When the
desired height is set, wing screw 8160 may again be tightened, and
top plate 8240 and height adjustment skirt 8100 will additionally
become frictionally held at the desired elevation.
[0058] In embodiments including both this type of lead screw
mechanism as well as a guide washer fastener assembly for
frictional holding force (such as wing screw 8160), the guide
washer preferably includes a guide washer slot runner such as guide
washer slot runner 8025. In such an embodiment, guide washer slot
runner 8025 performs a different function in that it prevents guide
washer 8020 from rotating when lifting force is applied by pan head
screw 8060. The reason such rotation is generated and is not
preferred is as follows: Tapped hole 8040 for pan head screw 8060
is offset at least some distance from through hole 8300 for passage
of wing screw 8160 through guide washer 8020. Otherwise, these
components would interfere with each other and not perform their
desired function. With this offset, in the absence of guide washer
slot runner 8025, pan head screw 8060 would lift guide washer 8020
on one side, causing it to rotate on wing screw 8160. An added
feature on guide washer 8020 resists such rotation. An added guide
washer slot runner 8025 can bear against the inner edges of slot
8290 during adjustment, thus preventing such undesirable rotation.
Therefore, in such an embodiment, guide washer slot runner 8025
performs an important, though somewhat different function.
[0059] As previously explained, pan head screw 8060 is rotatably
affixed to base 8100 of height adjustment skirt 8120 by collar
8210. Collar 8210 is affixed to pan head screw 8060 at a slight
elevation above a surface 8260 on a top face of base 8100 forming a
slight gap that permits such rotation. However, when the saw is
lifted off the floor, collar 8210 performs the additional function
of stopping pan head screw from sliding through countersunk hole
8080 through base 8100. Collar 8210 is affixed to pan head screw
8060 by means of a set screw 8211 which may be tightened down on
the threads of pan head screw 8060 at the desired height. However,
collar 8210 is an expensive custom component with a set screw 8211
which may come loose and cause the assembly to fail.
[0060] As shown in FIG. 13, an alternative pan head screw such as
shoulder pan head screw 13000 may be used that includes a shoulder
13020. Shoulder 13020 spaces a standard hex nut such as hex nut
13040 at a desired height allowing shoulder pan head screw 13000 to
rotate within its hole. FIG. 14 shows a partial section A-A of the
area of base 14100 near the countersunk hole for a shoulder pan
head screw 14020. As shown in section A-A, shoulder 14040 of
shoulder pan head screw 14020 supports a common hex nut 14060 at a
height above a top surface 14080 of base 14100. Thus, hex nut 14060
can be tightened down firmly on shoulder 14040 with reduced concern
for coming loose compared with collar 8210 (FIG. 8). Hex nut 14060
is also less expensive than collar 8210 (FIG. 8). Thus, for two
reasons, shoulder pan head screw 14020 and hex nut 14060 are
preferred. However, as shown in FIG. 14, the insertion of either
type of pan head screw within a countersunk hole (such as
countersunk hole 14160) results in a flush surface such as 14140 on
the bottom side of the base of the height adjustment skirt. A flush
surface is preferred so that the bottom side of the base will not
hang up on floor surface irregularities. Hex socket 14180 allows
shoulder pan head screw 14020 to be turned with a hex wrench from
the bottom if desired.
[0061] During height adjustment, as shown in FIG. 14, graduations
14200 may be etched on an outer surface on either side of height
adjustment skirt 14120. These graduations indicate the height of
the circular saw blade 14220 by its relation to a flush bottom edge
14240 of the downwardly protruding back edge 14260 of the top plate
14280. This is because the flush bottom edge 14240 is in the same
flush plane with circular saw blade 14220 (covered in this view by
movable guard 14210). Before performing an undercutting operation,
the user may check on both front sides of the height adjustment
skirt 14120 that the flush bottom edge 14240 of top plate 14280 is
at the same graduation. This ensures that the blade is not angled
in relation to a flat floor surface upon which the saw is to be
placed.
[0062] As defined herein, for the embodiments of FIG. 8 or 14, or
any embodiments including a lead screw mechanism to support a top
plate, the lead screw component (such as pan head screw 8060 of
FIG. 8, or shoulder pan head screw 13000 of FIG. 13, or shoulder
pan head screw 14020 of FIG. 14) will be referred to as a lead
threaded member. Furthermore, the fastener used to fasten the
threaded member to the base of the height adjustment skirt (such as
collar 8210 of FIG. 8, hex nut 13040 of FIG. 13, or hex nut 14060
of FIG. 14) will be defined as a lead threaded member holding
fastener. A guide washer including a threaded hole (such as tapped
hole 8040) in guide washer 8020 of FIG. 8 will be referred to as a
lead guide washer.
[0063] To provide an improved handle for grinder-activated undercut
saws, the second, forward, movable handle may be formed from two
parts joined by a pivot pin. A toothed surface may be formed on at
least one inside surface of a handle which may interlock with a
corresponding toothed surface formed on an outer surface of the
grinder motor spindle housing. As with existing saws of this kind,
and as shown in FIG. 5, undercut saw 3100 is made with a grinder
motor 3180 having a first long horizontal armature axis 3170 and a
second spindle axis 3190. On one end of the long armature axis, a
first rearward handle 3390 with a switch 3400 forms the back end of
the saw. On the other end, an aluminum spindle housing 3420 forms
the front end and houses the spindle. The spindle (not shown) is
operatively coupled to the armature (not shown) at a substantially
right angle. A circular saw blade 3220 is mounted on the spindle on
a blade mount (not shown). Spindle housing 3420 is fixedly joined
to top plate 3140. Top plate 3140 and height adjustment skirt 3160
form a fixed guard assembly 3120 for the undercut saw. A
spring-loaded movable guard 3200 covers circular saw blade 3220 and
is retractable in the counter-clockwise direction to start a
cutting operation.
[0064] The improved handle for the saw is formed from a first, left
half 3460, a second, right half 3480, and an upper pivot pin 3500.
Left half 3460 is overlapped at relief 3520 with relief 3540 in
right half 3480. Pivot pin 3500 is press fit into upper hole 3580
in right half 3480 and through upper hole 3560 in left half 3460 to
join the two halves. Thus, the two halves may be pivoted closed to
enable interlocking of the circular tooth patterns on the handle
and the spindle housing, or pivoted open to permit disengagement or
disassembly. This assembly of the left half 3460 and right half
3480 with pivot pin 3500 may be referred to as handle assembly
3510.
[0065] Left half 3460 and right half 3480 have circular tooth
patterns 3600 and 3620 (respectively) formed on their inside
surfaces which may engage corresponding circular tooth patterns
3640, 3660 on the left and right hand sides of spindle housing 3420
(respectively). Threaded four arm screws 3680, 3700 may be inserted
through left mounting hole 3720 in left half 3460 and right
mounting hole 3740 in right half 3480 (respectively). Threaded four
arm screws 3680, 3700 may further thread into a tapped left
mounting hole 3760 and tapped right mounting hole 3780 to join
handle assembly 3510 to spindle housing 3420.
[0066] The circular tooth patterns 3600, 3620 of left half 3460 and
right half 3480 are designed to interlock with corresponding
circular tooth patterns 3640, 3660 in the left and right sides of
spindle housing 3420 and will provide a fixed and solid joint when
they are pressed together by threaded four arm screws 3680, 3700.
Because these teeth patterns are circular, handle assembly 3510 may
interlock and become fixedly joined to spindle housing 3420 at a
number of angles. As more clearly illustrated in FIG. 11, for
general undercutting, it is preferred that handle assembly 11000 be
oriented at a right angle A perpendicular to the long armature axis
11020 of grinder motor 11040. This provides comfortable knuckle
clearance and firm grip. However, when undercutting in low
clearance areas, such as underneath toe spaces, it is preferred
that the handle be angled back or at an angle greater than a right
angle in relation to a forward projection of the long armature axis
of the saw, such as angle B. However, it is further preferred that
handle assembly 11000 be restricted from being set or moving
unexpectedly to any angle which is less than a right angle in
relation to a forward projection of the long armature axis 11020 of
the saw. Any such acute angle places the hand unnecessarily close
to blade 11060, and could also cause the handle to extend beyond
the front edge of top plate 11080. Such is not preferred, as that
would prevent the saw from operating in tight areas, such as inside
corners.
[0067] As shown in FIG. 5, others skilled in the art will envision
alternative fasteners to fasten a second, forward, movable handle,
such as handle assembly 3510, to an undercut saw spindle housing,
such as spindle housing 3420. For example, rather than four arm
screws 3680, threaded rods may be threaded into tapped left
mounting hole 3760 and tapped right mounting hole 3780. Threaded
nuts having tapped holes may be threaded onto the ends of the
threaded rods. The use of such threaded rods would make it more
difficult for the user to remove the handle and use the saw without
a handle. Any such fasteners used to fasten a handle or handle
assembly to a spindle housing will be referred to herein as handle
fastening fasteners. Handle fastening fasteners may include a
single fastener or a combination of fasteners combining for this
purpose.
[0068] As shown in FIG. 5, to prevent handle assembly 3510 from
moving or being set at any such acute angle in relation to a
forward projection of the long armature axis of the saw, left half
3460 and right half 3480 include bosses 3800, 3820. When handle
assembly 3510 is joined to spindle housing 3420 at a right angle to
long armature axis 3170, bosses 3800, 3820 come in close proximity
to left and right flats 3840, 3860 of spindle housing 3420. In this
embodiment, if handle assembly 3510 is rotated forward to an acute
angle in relation to the long armature axis 3170, bosses 3800, 3820
will contact left and right flats 3840, 3860. This interference
causes handle assembly 3510 to tip forward, displacing the teeth
and preventing them from interlocking. Hence, the handle cannot be
mounted on the spindle housing at such an angle. In other
embodiments with a freely pivoting handle assembly, bosses 3800,
3820 may contact left and right flats 3840, 3860 to stop the handle
from being rotated forward to any such acute angle.
[0069] Left half 3460 and right half 3480 may be economically
produced as aluminum castings and will easily handle much greater
pushing force than existing U-shaped undercut saw handles fastened
by lock washers and bolts. A flexible rubber coating such as
plastisol may be added to form a softer, slip-resistant gripping
surface on the outer surface of handle assembly 3510.
[0070] To add removable guarding structures to the bottom portion
of the fixed guard of the undercut saw, removable cover plates may
be added to any of the height adjustment skirt, movable guard, or
top plate. Such removable cover plates may be positioned so as to
cover at least a portion of the circumference of the blade past the
depth of the teeth. As shown in FIG. 6, undercut saw 6100 has a
height adjustment skirt 4160 having a base 4450. An additional
flush mounted removable cover plate 4820 may be screwed to base
4450 using screws 4800. Cover plate 4820 covers blade 4810 past the
depth of the teeth. In addition, movable guard 4840 may cover the
blade 4810 past the depth of the teeth with its own removable plate
4860 fastened to movable guard 4840 as by screws 4880.
[0071] As defined herein, in relation to cover plates which may
cover the blade, the phrase "past the depth of the teeth" shall
describe a cover forming a radius as measured from the center of
the circular saw blade which is shorter than a radial distance to
the outermost circumference of the circular saw blade. For example,
cover plate 4820 mounted on base 4450 covers blade 4810 to a radius
alpha (in relation to the center of the circular saw blade 4810).
Radius alpha is a shorter radius than radius delta to the outer
circumference of the circular saw blade 4810. Similarly, cover
plate 4860 mounted on movable guard 4840 covers blade 4810 to a
radius beta (in relation to the center of the circular saw blade
4810). Radius beta is a shorter radius than radius delta.
[0072] In an another embodiment, as shown in FIG. 7, a cover plate
5120 may be removably mounted on a bottom edge of the downwardly
protruding back edge 5240 of the top plate 5140 using screws 5800,
rather than on the base 5450 of height adjustment skirt 5160. Cover
plate 5120 covers blade 5820 past the depth of the teeth. Cover
plate 5120 covers blade 5820 to a radius epsilon. Radius epsilon is
a shorter radius than radius delta (the outer circumference of the
circular saw blade 5820).
[0073] It will be apparent that various alternatives may be
implemented. The Detailed Description discloses a number of
additional features, any one of which may be added alone or in any
combination to an undercut saw to improve saw design. The handle
features and the blade height features may be used separately or
together. Although FIG. 4 illustrates a grinder type saw, the
embodiments and features may easily be adapted to other undercut
saw configurations, including a circular saw type configuration.
The materials, dimensions and positioning are purely exemplary, and
numerous alternatives exist. In FIGS. 1-3, existing saws are shown,
including one having a dust port. The present embodiments and
features may be adapted to such saws, to undercut saws having
stabilizing features. The handle may be adapted to a number of
different tools, some of which are not undercut saws. The
improvements to the telescoping height adjustment skirt could be
implemented on any tool having a telescoping height adjustment
skirts. These are some exemplary alternatives; this is not an
exhaustive list of the alternatives that are possible with the
present invention.
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