U.S. patent application number 12/319280 was filed with the patent office on 2009-07-16 for woodworking machines with overmolded arbors.
Invention is credited to David A. Fanning, J. David Futmer, Stephen F. Gass.
Application Number | 20090178524 12/319280 |
Document ID | / |
Family ID | 34198150 |
Filed Date | 2009-07-16 |
United States Patent
Application |
20090178524 |
Kind Code |
A1 |
Gass; Stephen F. ; et
al. |
July 16, 2009 |
Woodworking machines with overmolded arbors
Abstract
Power equipment with various safety systems is disclosed. Table
saws with safety systems and/or blade retraction are disclosed.
Over-molded arbors are disclosed for use in power equipment with
safety systems and/or blade retraction, including arbors with fiber
and/or prepreg over-molding.
Inventors: |
Gass; Stephen F.;
(Wilsonville, OR) ; Futmer; J. David; (West Linn,
OR) ; Fanning; David A.; (Vancouver, WA) |
Correspondence
Address: |
SD3, LLC
9564 S.W. Tualatin Road
Tualatin
OR
97062
US
|
Family ID: |
34198150 |
Appl. No.: |
12/319280 |
Filed: |
January 5, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10923290 |
Aug 20, 2004 |
7472634 |
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12319280 |
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11647676 |
Dec 29, 2006 |
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10923290 |
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60496550 |
Aug 20, 2003 |
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Current U.S.
Class: |
83/62.1 ;
83/58 |
Current CPC
Class: |
B27G 19/02 20130101;
Y10T 83/089 20150401; Y10T 83/7697 20150401; Y10T 83/7726 20150401;
F16P 3/12 20130101; Y10T 83/081 20150401 |
Class at
Publication: |
83/62.1 ;
83/58 |
International
Class: |
B27B 3/18 20060101
B27B003/18; B26D 5/00 20060101 B26D005/00 |
Claims
1. A woodworking machine comprising: a cutter; a conductive arbor
on which the cutter is mounted; overmolding on at least a portion
of the arbor; a detection system adapted to detect a dangerous
condition between a user and the cutter, where the detection system
includes at least one electrode positioned adjacent the arbor and
where the overmolding electrically insulates the electrode from the
arbor; and a reaction system adapted to perform a specified action
to mitigate the dangerous condition upon detection of the dangerous
condition by the detection system.
2. The woodworking machine of claim 1 where the overmolding is bulk
molding compound.
3. The woodworking machine of claim 1 where the arbor includes at
least one section with a diameter larger than another section of
the arbor, and where the overmolding covers at least the section
with the larger diameter.
4. The woodworking machine of claim 1 where the overmolding acts as
a dielectric.
5. The woodworking machine of claim 1 where the electrode is made
from powder metal.
6. The woodworking machine of claim 1 where the electrode includes
at least one screw boss.
7. An arbor for a woodworking machine, the arbor comprising: a
generally elongate, metal shaft having two ends; a first region
adapted to support a blade adjacent one end of the shaft; a flange
adjacent the first region; a nonconductive overmolding on at least
a portion of the arbor other than the first region or the
flange.
8. The arbor of claim 7 where the overmolding is bulk molding
compound.
9. The arbor of claim 7 where a section of the overmolding forms at
least one bearing seat for a bearing.
10. The arbor of claim 7 where the overmolding forms at least two
bearing seats for two bearings.
11. The arbor of claim 10 where the two bearing seats are of
different diameters.
12. A woodworking machine comprising: a cutter; a detection system
adapted to detect a dangerous condition between a user and the
cutter, where the detection system includes at least one electrode
positioned adjacent the arbor; a reaction system adapted to perform
a specified action to mitigate the dangerous condition upon
detection of the dangerous condition by the detection system; and
overmolded arbor means for supporting the cutter and for insulating
the electrode from the arbor.
Description
CROSS-REFERENCE TO RELATED APPLICATION
[0001] This application is a continuation of the following U.S.
patent applications: Ser. No. 11/647,676, filed Dec. 29, 2006, and
Ser. No. 10/923,290, filed Aug. 20, 2004, which in turn claimed the
benefit of and priority from U.S. Provisional Patent Application
Ser. No. 60/496,550, filed Aug. 20, 2003. The disclosures of these
applications are herein incorporated by reference in their
entireties.
FIELD
[0002] The present disclosure relates to woodworking machines and
more particularly to woodworking machines with overmolded arbors.
The disclosure further relates to table saws with safety systems
and blade retraction.
BACKGROUND
[0003] A table saw is a power tool that includes a work surface or
table and a circular blade extending up through the table. A person
uses a table saw by moving a work piece past the spinning blade to
cut the work piece. When spinning, the circular saw blade presents
a risk of injury to a user of the saw. Accordingly, safety features
or systems are incorporated with table saws to minimize the risk of
injury. Probably the most common safety feature is a guard that
physically blocks an operator from making contact with the blade.
In many cases, guards effectively reduce the risk of injury,
however, there are many instances where the nature of the
operations to be performed precludes using a guard that completely
blocks access to the blade.
[0004] Other safety systems try to prevent or minimize injury by
detecting and reacting to an event. For instance, U.S. Pat. Nos.
3,953,770, 4,075,961, 4,470,046, 4,532,501 and 5,212,621, the
disclosures of which are incorporated herein by reference, disclose
radio-frequency safety systems which utilize radio-frequency
signals to detect the presence of a user's hand in a dangerous area
of a machine and thereupon prevent or interrupt operation of the
machine. U.S. Pat. Nos. 3,785,230 and 4,026,177, the disclosures of
which are herein incorporated by reference, disclose a safety
system for use on circular saws to stop the blade when a user's
hand approaches the blade. The system uses the blade as an antenna
in an electromagnetic proximity detector to detect the approach of
a user's hand prior to actual contact with the blade. Upon
detection of a user's hand, the system engages a brake using a
standard solenoid.
[0005] U.S. Pat. No. 4,117,752, which is herein incorporated by
reference, discloses a braking system for use with a band saw,
where the brake is triggered by actual contact between the user's
hand and the blade. However, the system described for detecting
blade contact does not appear to be functional to accurately and
reliably detect contact. Furthermore, the system relies on standard
electromagnetic brakes operating off of line voltage to stop the
blade and pulleys of the band saw. It is believed that such brakes
would take 50 ms-1 s to stop the blade. Therefore, the system is
too slow to stop the blade quickly enough to avoid serious
injury.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a schematic block diagram of a machine with a
fast-acting safety system.
[0007] FIG. 2 is a schematic diagram of an exemplary safety system
in the context of a machine having a circular blade.
[0008] FIG. 3 is a perspective view of a contractor style table
saw.
[0009] FIG. 4 is a right side elevation view of the table saw shown
in FIG. 3 with the stand, cabinet, and several other parts redacted
for clarity.
[0010] FIG. 5 is a left side elevation view of the saw shown in
FIG. 3.
[0011] FIG. 6 is a front elevation view of the saw shown in FIG.
3.
[0012] FIG. 7 is a back elevation view of the saw shown in FIG.
3.
[0013] FIG. 8 is a top elevation view of the saw shown in FIG. 3,
with the tabletop and other components removed for clarity.
[0014] FIG. 9 is a bottom view of the saw shown in FIG. 8.
[0015] FIG. 10 is a left side elevation view showing components
used to adjust the elevation of the blade, and with other
components removed for clarity.
[0016] FIG. 11 is a right side elevation view of the components
shown in FIG. 10.
[0017] FIG. 12 is a side elevation view of a cartridge bracket and
other components used to adjust the elevation of the blade.
[0018] FIG. 13 is a perspective view of the cartridge bracket and
other components shown in FIG. 12.
[0019] FIG. 14 is a front elevation view of the cartridge bracket
and other components shown in FIG. 12.
[0020] FIG. 15 is a back elevation view of the cartridge bracket
and other components shown in FIG. 12.
[0021] FIG. 16 is a side elevation view of a brake cartridge and
cartridge bracket, with a retaining handle raised.
[0022] FIG. 17 is similar to FIG. 16, except the retaining handle
is in a different position.
[0023] FIG. 18 is a perspective view of a possible brake
cartridge.
[0024] FIG. 19 shows geometry for an alternative bracket.
[0025] FIG. 20 shows a possible arbor assembly.
[0026] FIG. 21 shows the arbor assembly of FIG. 20 with an
electrode sheath removed.
[0027] FIG. 22 shows another possible arbor assembly.
[0028] FIG. 23 shows the arbor assembly of FIG. 22 with an
electrode sheath removed.
[0029] FIG. 24 shows a cross-sectional view of the arbor assembly
shown in FIG. 23.
[0030] FIG. 25 shows an alternative trunnion brace.
[0031] FIG. 26 shows another view of the alternative trunnion brace
of FIG. 25.
[0032] FIG. 27 shows a top view of the alternative trunnion brace
of FIG. 25.
[0033] FIG. 28 is a perspective view of a pivoting coupler that may
be used in a dust collection system.
[0034] FIG. 29 shows a top view of the pivoting coupler shown in
FIG. 28.
[0035] FIG. 30 shows a barrel nut used in the saw shown in FIGS.
4-11.
[0036] FIG. 31 shows a link used in the saw shown in FIGS.
4-11.
[0037] FIG. 32 shows another barrel nut used in the saw shown in
FIGS. 4-11.
[0038] FIG. 33 shows an over-molded arbor.
[0039] FIG. 34 shows one way prepreg can be wrapped on an
arbor.
DETAILED DESCRIPTION
[0040] A table saw that may incorporate a safety system according
to the present invention is shown schematically in FIG. 1 and
indicated generally at 10. Saw 10 may be any of a variety of
different table saws. Saw 10 includes an operative structure 12
having a cutting tool 14 and a motor assembly 16 adapted to drive
the cutting tool. Saw 10 also includes a safety system 18
configured to minimize the potential of a serious injury to a
person using the saw. Safety system 18 is adapted to detect the
occurrence of one or more dangerous conditions during use of the
saw. If such a dangerous condition is detected, safety system 18 is
adapted to engage operative structure 12 to limit any injury to the
user caused by the dangerous condition.
[0041] Saw 10 also includes a suitable power source 20 to provide
power to operative structure 12 and safety system 18. Power source
20 may be an external power source such as line current, or an
internal power source such as a battery. Alternatively, power
source 20 may include a combination of both external and internal
power sources. Furthermore, power source 20 may include two or more
separate power sources, each adapted to power different portions of
machine 10.
[0042] It will be appreciated that operative structure 12 may take
any one of many different forms. For example, operative structure
12 may include a stationary housing configured to support motor
assembly 16 in driving engagement with cutting tool 14.
Alternatively, operative structure 12 may include one or more
transport mechanisms adapted to convey a work piece toward and/or
away from cutting tool 14.
[0043] Motor assembly 16 includes at least one motor adapted to
drive cutting tool 14. The motor may be either directly or
indirectly coupled to the cutting tool, and may also be adapted to
drive work piece transport mechanisms. The particular form of
cutting tool 14 will vary depending upon the various embodiments of
saw 10. For example, cutting tool 14 will typically be a single,
circular rotating blade having a plurality of teeth disposed along
the perimetrical edge of the blade. Alternatively, the cutting tool
may be a plurality of circular blades, such as a dado blade or dado
stack.
[0044] Safety system 18 includes a detection subsystem 22, a
reaction subsystem 24 and a control subsystem 26. Control subsystem
26 may be adapted to receive inputs from a variety of sources
including detection subsystem 22, reaction subsystem 24, operative
structure 12 and motor assembly 16. The control subsystem may also
include one or more sensors adapted to monitor selected parameters
of saw 10. In addition, control subsystem 26 typically includes one
or more instruments operable by a user to control the saw. The
control subsystem is configured to control saw 10 in response to
the inputs it receives.
[0045] Detection subsystem 22 is configured to detect one or more
dangerous or triggering conditions during use of saw 10. For
example, the detection subsystem may be configured to detect that a
portion of the user's body is dangerously close to, or in contact
with, a portion of cutting tool 14. As another example, the
detection subsystem may be configured to detect the rapid movement
of a workpiece due to kickback by the cutting tool, as is described
in U.S. patent application Ser. No. 09/676,190, now U.S. Pat. No.
7,055,417, the disclosure of which is herein incorporated by
reference. In some embodiments, detection subsystem 22 may inform
control subsystem 26 of the dangerous condition, which then
activates reaction subsystem 24. In other embodiments, the
detection subsystem may be adapted to activate the reaction
subsystem directly.
[0046] Once activated in response to a dangerous condition,
reaction subsystem 24 is configured to engage operative structure
12 quickly to prevent serious injury to the user. It will be
appreciated that the particular action to be taken by reaction
subsystem 24 will vary depending on the type of saw 10 and/or the
dangerous condition that is detected. For example, reaction
subsystem 24 may be configured to do one or more of the following:
stop the movement of cutting tool 14, disconnect motor assembly 16
from power source 20, place a barrier between the cutting tool and
the user, or retract the cutting tool from its operating position,
etc. The reaction subsystem may be configured to take a combination
of steps to protect the user from serious injury. Placement of a
barrier between the cutting tool and teeth is described in more
detail in U.S. Patent Application Publication No. 2002/0017183 A1,
entitled "Cutting Tool Safety System," the disclosure of which is
herein incorporated by reference. Retracting the cutting tool is
described in more detail in U.S. Patent Application Publication No.
2002/0017181 A1, entitled "Retraction System for Use in Power
Equipment," and U.S. Patent Application Ser. No. 60/452,159, filed
Mar. 5, 2003, entitled "Retraction System and Motor Position for
Use With Safety Systems for Power Equipment," now U.S. Pat. No.
7,098,800, the disclosures of which are herein incorporated by
reference.
[0047] The configuration of reaction subsystem 24 typically will
vary depending on which action or actions are taken. In the
exemplary embodiment depicted in FIG. 1, reaction subsystem 24 is
configured to stop the movement of cutting tool 14 and includes a
brake mechanism 28, a biasing mechanism 30, a restraining mechanism
32, and a release mechanism 34. Brake mechanism 28 is adapted to
engage operative structure 12 under the urging of biasing mechanism
30. During normal operation of machine 10, restraining mechanism 32
holds the brake mechanism out of engagement with the operative
structure. However, upon receipt of an activation signal by
reaction subsystem 24, the brake mechanism is released from the
restraining mechanism by release mechanism 34, whereupon, the brake
mechanism quickly engages at least a portion of the operative
structure to bring the cutting tool to a stop.
[0048] It will be appreciated by those of skill in the art that the
exemplary embodiment depicted in FIG. 1 and described above may be
implemented in a variety of ways depending on the type and
configuration of operative structure 12. Turning attention to FIG.
2, one example of the many possible implementations of safety
system 18 is shown. System 18 is configured to engage an operative
structure having a circular blade 40 mounted on a rotating shaft or
arbor 42. Blade 40 includes a plurality of cutting teeth (not
shown) disposed around the outer edge of the blade. As described in
more detail below, braking mechanism 28 is adapted to engage the
teeth of blade 40 and stop the rotation of the blade. U.S. Patent
Application Publication No. 2002/0017175 A1, entitled "Translation
Stop For Use In Power Equipment," the disclosure of which is herein
incorporated by reference, describes other systems for stopping the
movement of the cutting tool. U.S. Patent Application Publication
No. 2002/0017184 A1, entitled "Table Saw With Improved Safety
System," U.S. Patent Application Publication No. 2002/0017179 A1,
entitled "Miter Saw With Improved Safety System," U.S. Patent
Application Publication No. 2002/0059855 A1, entitled "Miter Saw
with Improved Safety System," U.S. Patent Application Publication
No. 2002/0056350 A1, entitled "Table Saw With Improved Safety
System," U.S. Patent Application Publication No. 2002/0059854 A1,
entitled "Miter Saw With Improved Safety System," U.S. Patent
Application Publication No. 2002/0056349 A1, entitled "Miter Saw
With Improved Safety System," U.S. Patent Application Publication
No. 2002/0056348 A1, entitled "Miter Saw With Improved Safety
System," and U.S. Patent Application Publication No. 2002/0066346
A1, entitled "Miter Saw With Improved Safety System," U.S. Patent
Application Publication No. 2003/0015253 A1, entitled "Router With
Improved Safety System," U.S. Patent Application Publication No.
2002/0170400 A1, entitled "Band Saw With Improved Safety System,"
U.S. Patent Application Publication No. 2003/0019341 A1, entitled
"Safety Systems for Band Saws," U.S. Patent Application Publication
No. 2003/0056853 A1, entitled "Router With Improved Safety System,"
and U.S. Provisional Patent Application Ser. No. 60/406,138,
entitled "Miter Saw With Improved Safety System," filed Aug. 27,
2002 by SD3, LLC, now U.S. Patent Application Publication No.
2006/0230896 A1, the disclosures of which are herein incorporated
by reference, describe safety system 18 in the context of
particular types of machines.
[0049] In the exemplary implementation, detection subsystem 22 is
adapted to detect the dangerous condition of the user coming into
contact with blade 40. The detection subsystem includes a sensor
assembly, such as contact detection plates 44 and 46, capacitively
coupled to blade 40 to detect any contact between the user's body
and the blade. Typically, the blade, or some larger portion of
cutting tool 14 is electrically isolated from the remainder of saw
10. Alternatively, detection subsystem 22 may include a different
sensor assembly configured to detect contact in other ways, such as
optically, resistively, etc. In any event, the detection subsystem
is adapted to transmit a signal to control subsystem 26 when
contact between the user and the blade is detected. Various
exemplary embodiments and implementations of detection subsystem 22
are described in more detail in U.S. Patent Application Publication
No. 2002/0017176 A1, entitled "Detection System For Power
Equipment," U.S. Patent Application Publication No. 2002/0017336
A1, entitled "Apparatus And Method For Detecting Dangerous
Conditions In Power Equipment," U.S. Patent Application Publication
No. 2002/0069734 A1, entitled "Contact Detection System for Power
Equipment," U.S. Patent Application Publication No. 2002/0190581
A1, entitled "Apparatus and Method for Detecting Dangerous
Conditions in Power Equipment," U.S. Patent Application Publication
No. 2003/0002942 A1, entitled "Discrete Proximity Detection
System," and U.S. Patent Application Publication No. 2003/0090224
A1, entitled "Detection System for Power Equipment," the
disclosures of which are herein incorporated by reference.
[0050] Control subsystem 26 includes one or more instruments 48
that are operable by a user to control the motion of blade 40.
Instruments 48 may include start/stop switches, speed controls,
direction controls, light-emitting diodes, etc. Control subsystem
26 also includes a logic controller 50 connected to receive the
user's inputs via instruments 48. Logic controller 50 is also
connected to receive a contact detection signal from detection
subsystem 22. Further, the logic controller may be configured to
receive inputs from other sources (not shown) such as blade motion
sensors, work piece sensors, etc. In any event, the logic
controller is configured to control operative structure 12 in
response to the user's inputs through instruments 48. However, upon
receipt of a contact detection signal from detection subsystem 22,
the logic controller overrides the control inputs from the user and
activates reaction subsystem 24 to stop the motion of the blade.
Various exemplary embodiments and implementations of control
subsystem 26 are described in more detail in U.S. Patent
Application Publication No. 2002/0020262 A1, entitled "Logic
Control For Fast Acting Safety System," U.S. Patent Application
Publication No. 2002/0017178 A1, entitled "Motion Detecting System
For Use In Safety System For Power Equipment," and U.S. Patent
Application Publication No. 2003/0058121 A1, entitled "Logic
Control With Test Mode for Fast-Acting Safety System," the
disclosures of which are herein incorporated by reference.
[0051] In the exemplary implementation, brake mechanism 28 includes
a pawl 60 mounted adjacent the edge of blade 40 and selectively
moveable to engage and grip the teeth of the blade. Pawl 60 may be
constructed of any suitable material adapted to engage and stop the
blade. As one example, the pawl may be constructed of a relatively
high strength thermoplastic material such as polycarbonate,
ultrahigh molecular weight polyethylene (UHMW) or Acrylonitrile
Butadiene Styrene (ABS), etc., or a metal such as aluminum, etc. It
will be appreciated that the construction of pawl 60 may vary
depending on the configuration of blade 40. In any event, the pawl
is urged into the blade by a biasing mechanism in the form of a
spring 66. In the illustrative embodiment shown in FIG. 2, pawl 60
is pivoted into the teeth of blade 40. It should be understood that
sliding or rotary movement of pawl 60 might also be used. The
spring is adapted to urge pawl 60 into the teeth of the blade with
sufficient force to grip the blade and quickly bring it to a
stop.
[0052] The pawl is held away from the edge of the blade by a
restraining mechanism in the form of a fusible member 70. The
fusible member is constructed of a suitable material adapted to
restrain the pawl against the bias of spring 66, and also adapted
to melt under a determined electrical current density. Examples of
suitable materials for fusible member 70 include NiChrome wire,
stainless steel wire, etc. The fusible member is connected between
the pawl and a contact mount 72. Preferably, fusible member 70
holds the pawl relatively close to the edge of the blade to reduce
the distance the pawl must travel to engage the blade. Positioning
the pawl relatively close to the edge of the blade reduces the time
required for the pawl to engage and stop the blade. Typically, the
pawl is held approximately 1/32-inch to 1/4-inch from the edge of
the blade by fusible member 70, however other pawl-to-blade
spacings may also be used within the scope of the invention.
[0053] Pawl 60 is released from its unactuated, or cocked, position
to engage blade 40 by a release mechanism in the form of a firing
subsystem 76. The firing subsystem is coupled to contact mount 72,
and is configured to melt fusible member 70 by passing a surge of
electrical current through the fusible member. Firing subsystem 76
is coupled to logic controller 50 and activated by a signal from
the logic controller. When the logic controller receives a contact
detection signal from detection subsystem 22, the logic controller
sends an activation signal to firing subsystem 76, which melts
fusible member 70, thereby releasing the pawl to stop the blade.
Various exemplary embodiments and implementations of reaction
subsystem 24 are described in more detail in U.S. Patent
Application Publication No. 2002/0020263 A1, entitled "Firing
Subsystem For Use In A Fast-Acting Safety System," U.S. Patent
Application Publication No. 2002/0020271 A1, entitled
"Spring-Biased Brake Mechanism for Power Equipment," U.S. Patent
Application Publication No. 2002/0017180 A1, entitled "Brake
Mechanism For Power Equipment," U.S. Patent Application Publication
No. 2002/0059853 A1, entitled "Power Saw With Improved Safety
System," U.S. Patent Application Publication No. 2002/0020265 A1,
entitled "Translation Stop For Use In Power Equipment," U.S. Patent
Application Publication No. 2003/0005588 A1, entitled "Actuators
For Use in Fast-Acting Safety Systems," and U.S. Patent Application
Publication No. 2003/0020336 A1, entitled "Actuators For Use In
Fast-Acting Safety Systems," the disclosures of which are herein
incorporated by reference.
[0054] It will be appreciated that activation of the brake
mechanism will require the replacement of one or more portions of
safety system 18. For example, pawl 60 and fusible member 70
typically must be replaced before the safety system is ready to be
used again. Thus, it may be desirable to construct one or more
portions of safety system 18 in a cartridge that can be easily
replaced. For example, in the exemplary implementation depicted in
FIG. 2, safety system 18 includes a replaceable cartridge 80 having
a housing 82. Pawl 60, spring 66, fusible member 70 and contact
mount 72 are all mounted within housing 82. Alternatively, other
portions of safety system 18 may be mounted within the housing. In
any event, after the reaction system has been activated, the safety
system can be reset by replacing cartridge 80. The portions of
safety system 18 not mounted within the cartridge may be replaced
separately or reused as appropriate. Various exemplary embodiments
and implementations of a safety system using a replaceable
cartridge, and various brake pawls, are described in more detail in
U.S. Patent Application Publication No. 2002/0020261 A1, entitled
"Replaceable Brake Mechanism For Power Equipment," U.S. Patent
Application Publication No. 2002/0017182 A1, entitled "Brake
Positioning System," U.S. Patent Application Publication No.
2003/0140749 A1, entitled "Brake Pawls for Power Equipment," and
U.S. Provisional Patent Application Ser. No. 60/496,568, entitled
"Motion Detecting System for use in a Safety System for Power
Equipment," filed Aug. 20, 2003 by SD3, LLC, now U.S. Patent
Application Publication No. 2005/0041359 A1 the disclosures of
which are herein incorporated by reference.
[0055] While one particular implementation of safety system 18 has
been described, it will be appreciated that many variations and
modifications are possible within the scope of the invention. Many
such variations and modifications are described in U.S. Patent
Application Publication No. 2002/0170399 A1, entitled "Safety
Systems for Power Equipment," U.S. Patent Application Publication
No. 2003/0037651, entitled "Safety Systems for Power Equipment,"
and U.S. Patent Application Publication No. 2003/0131703 A1,
entitled "Apparatus and Method for Detecting Dangerous Conditions
in Power Equipment," the disclosures of which are herein
incorporated by reference.
[0056] FIG. 3 shows a table saw 100 often called a contractor saw.
Saw 100 includes a table 102 on which a work piece may be cut. The
table is mounted on a cabinet 104 supported by a stand 106. A blade
guard 108 covers the blade. A motor assembly 110 drives the blade.
Hand wheels 112 and 114 may be turned to adjust the elevation of
the blade (the height the blade extends above the table) and the
tilt of the blade relative to the tabletop, respectively. In
operation, a user makes a cut by pushing a work piece on the table
past the spinning blade.
[0057] FIGS. 4-9 show the internal mechanism of saw 100. A motor
116 is mounted on a bracket 118, which in turn is supported by
motor plate 120 attached to the saw. The motor, bracket and motor
plate are shown in FIGS. 4 and 5.
[0058] A belt 122 extends around a pulley 124 mounted on the drive
shaft of the motor and around a pulley 126 mounted on an arbor 128.
Arbor 128 is mounted in bearings and supported for rotation by an
arbor block 130. A blade 132 is mounted on arbor 128. When motor
116 is running, belt 122 spins arbor 128, thereby spinning blade
132. Blade 132 spins counterclockwise as seen In FIG. 4.
[0059] Arbor block 130 is pivotally mounted on pin 134, and pin 134
is supported by rear trunnion 136. The rear trunnion is
structurally connected to a front trunnion 138 by a large shaft 140
and a small shaft 142. Motor plate 120 is mounted on the ends of
shafts 140 and 142, as shown in FIGS. 4 and 5.
[0060] The front and rear trunnions are supported by front trunnion
block 144 and rear trunnion block 146, respectively. Specifically,
arcuate flanges on the front and rear trunnions extend into
corresponding arcuate grooves on the front and rear trunnion
blocks, as shown in FIG. 8 at 148 and 150. The arcuate flanges and
grooves allow the front and rear trunnions, the arbor block, and
the blade, to tilt relative to the table, as is known in the art. A
rack gear 152 on the front trunnion meshes with a worm gear 154
attached to hand wheel 114, so that a user may adjust the tilt of
the blade by turning hand wheel 114. The front and rear trunnion
blocks, in turn, are bolted to table 102.
[0061] The mechanism to control the elevation of the blade is shown
best in FIGS. 10 and 11. A threaded shaft 160 is supported for
rotation by front trunnion 138 and attached to hand wheel 112 so
that the shaft rotates when the hand wheel is turned. Shaft 160 is
threaded along most of its length, including at the end of the
shaft distal from the hand wheel (the threads are not shown in the
figures). A first barrel nut 162 is threaded on the distal end of
shaft 160. First barrel nut 162 is shown isolated in FIG. 30. The
nut includes two shoulders 164, one extending from each side of the
nut. Each shoulder is held in a notch 166 in a bracket 168, as
shown in FIGS. 10 and 11, one notch on each side of the bracket.
The bracket is a "U" shaped piece that is pivotally mounted on pin
134 and supported by rear trunnion 136. The bracket is shown
separate from the rear trunnion in FIGS. 12 through 15. Apertures
137 in the bracket are shown in those figures, and pin 134 extends
through those apertures to mount the bracket to the rear
trunnion.
[0062] Bracket 168 is connected to arbor block 130 by a link 170, a
second barrel nut 172, and a bolt 174 extending through the arbor
block. These components are also shown in FIGS. 12 through 15, 31
and 32. Link 170 is a "U" shaped piece that is pivotally connected
to the bracket by rivets 176, as shown in FIG. 12. Of course, the
link can be connected to the bracket by other means as well. Barrel
nut 172 has two ends, and each end of the nut extends into and is
captured by apertures in the sides of the link. In that manner, the
barrel nut may pivot around an axis extending between its ends, but
it cannot move toward or away from the bracket. Bolt 174 passes
through an aperture in the arbor block and is held in place by the
head of the bolt on the top of the arbor block, and by a wave
washer and a snap ring or clip that fits into a groove cut into the
bolt under the arbor block. Bolt 174 is then threaded into barrel
nut 172.
[0063] When a user turns hand wheel 112 and shaft 160, first barrel
nut 162 moves along the shaft. In the embodiment shown in FIGS. 4
through 11, when a person standing in front of the saw turns the
hand wheel clockwise, the first barrel nut will travel up the shaft
toward the user. Bracket 168 will then pivot up because the first
barrel nut is held in notches 166 in the bracket. Bracket 168 will
push link 170 and bolt 174 up, thereby causing the arbor block and
blade to rise. Similarly, turning hand wheel 112 counterclockwise
will cause the arbor block and blade to retract. Shaft 160 may flex
as barrel nut 162 moves along the shaft.
[0064] The saw shown in FIGS. 3 through 15 includes a brake
cartridge 200. The brake cartridge is best seen in FIGS. 10 and
16-18. Brake cartridge 200 is a type of reaction mechanism 24, as
discussed above. The brake cartridge includes a shell 202 that
encloses a biasing mechanism 30, restraining mechanism 32, and
release mechanism 34, as discussed above. The brake cartridge also
includes a brake pawl 204 made of fully annealed aluminum. End 206
of the housing extends through an aperture 208 in the brake pawl to
join the housing and pawl, as shown in FIG. 18. Cartridges such as
cartridge 200 are described in more detail in U.S. Provisional
Patent Application No. 60/496,574, entitled "Brake Cartridges for
Power Equipment," filed Aug. 20, 2003 by SD3, LLC, now U.S. Patent
Application Publication No. 2005/0039586 A1, which is hereby
incorporated by reference.
[0065] End 206 of the housing includes an aperture 210, and the
brake cartridge is mounted in the saw by sliding the cartridge onto
pin 134 through aperture 210. Brake cartridge 200 also includes a
flange 212 on the end of the cartridge opposite end 206. Flange 212
is configured to accept a tab 214 on bracket 168, as shown in FIGS.
10, 16 and 17. (Tab 214 is shown best in FIGS. 12-15.) In this
manner, brake cartridge 200 is securely held by bracket 168 so that
the brake cartridge does not pivot relative to bracket 168.
[0066] The brake cartridge is designed so that it automatically
connects with the power source, switches, electrodes, and possibly
other electronics when the cartridge is slid on pin 134 and
positioned by tab 214. A plug 215 is mounted on bracket 168, and a
corresponding plug 216 is part of the brake cartridge. In the
embodiment shown in FIGS. 12 through 15 and 18, plug 215 is a
printed circuit board card edge connector, and plug 216 is a
printed circuit board card edge designed to fit into plug 215. When
a user slides the cartridge on pin 134 and aligns the cartridge
with tab 214, plugs 215 and 216 will be aligned and will connect
when the cartridge is slid all the way on the pin. This facilitates
the installation and replacement of brake cartridges by the user,
and insures that the cartridge is electrically connected to the
rest of the system. The user would not have to make any other
electrical connections to install the cartridge. Of course, many
different types of plugs may be used. For example, a standard,
high-density, 15-pin D-Sub plug may be used instead of a card edge
connector. In that case, the male portion of the D-Sub plug may be
mounted on the cartridge, and the female portion mounted on the saw
so that if a pin on the plug were bent, simply replacing the
cartridge would repair the plug. This configuration, while perhaps
presenting several advantages, is not required; it is simply one of
many arrangements that may be used. A user may install brake
cartridge 168 in a saw by simply reaching through the throat plate
opening in the table while holding the cartridge and then sliding
the cartridge onto pin 134 and tab 214. The throat plate opening in
the table is the opening through which the blade extends.
[0067] A handle 220 is pivotally mounted on a bolt 222 supported by
rear trunnion 136. Handle 220 pivots down to lock brake cartridge
168 onto pin 134, and pivots up so that the brake cartridge may be
removed and replaced. The handle is shown down in FIG. 10, locking
brake cartridge 168 in place. The handle is shown up in FIG. 16,
and is shown at an intermediate position in FIG. 17. A user moves
handle 220 by reaching down through the throat plate opening in the
table and pivoting the handle up or down.
[0068] Handle 220 includes a first surface 230 shaped to correspond
to the outer surface of pin 134. When the handle is fully down,
surface 230 extends around the pin, as shown in FIG. 10. The handle
also includes a second surface 232 shaped to rub against pin 134 as
the handle pivots. The friction that results from the surface 232
rubbing against the pin helps hold the handle in place and provides
a positive feel to the user. Surfaces 230 and 232 are shaped so
that the handle snaps or locks into place around pin 134 when the
handle is pivoted down.
[0069] Handle 220 helps insure that the brake cartridge is
correctly positioned in the saw and plugged into plug 215. If brake
cartridge 200 is not fully slid onto pin 134, then handle 220
cannot pivot down because second surface 230 would contact either
the brake pawl or end 206 of the brake cartridge. Thus, a user
cannot pivot handle 220 down until the brake cartridge is slid all
the way on pin 134. Handle 220 also prevents the brake cartridge
from being removed until the handle is fully up. FIG. 17 shows
handle 220 approximately half way between being fully down and
fully up. In that position, second surface 230 is rubbing against
pin 134 and is in front of end 206 of the brake cartridge, blocking
the brake cartridge from being slid off pin 134. Brake cartridge
200 can only be removed when handle 220 is all the way up, as shown
in FIG. 16. This helps prevent the cartridge from sliding off pin
134 and becoming unplugged. Also, handle 220 is configured so that
it is long enough to extend up through the throat plate opening in
the table so that a user would see the handle and could not install
a throat plate until the handle is pivoted down. This feature helps
to prevent a user from forgetting to pivot the handle down to lock
the brake cartridge into place.
[0070] Brake cartridge 200 is positioned so that it is closely
adjacent the perimeter of blade 132, as shown in FIG. 5. When the
detection subsystem detects a dangerous condition, such as a person
contacting the spinning blade, the control system will trigger the
brake cartridge and the brake cartridge will quickly pivot brake
pawl 204 out, into the teeth of the blade. The teeth will cut into
the brake pawl and bind, thereby stopping the blade from spinning.
The closer the brake pawl is to the perimeter of the blade, the
faster the blade will stop because the brake pawl will have less
distance to travel before it contacts the teeth.
[0071] In the embodiment shown in FIGS. 4 through 15, the elevation
control mechanism, discussed above, is constructed so that the
position of the brake pawl relative to the perimeter of the blade
may be adjusted. This position may be referred to as blade-to-pawl
spacing. As discussed above, the elevation control mechanism
includes link 170, second barrel nut 172 and bolt 174, as shown in
FIGS. 10 through 15 and 30 through 32. Those components help
determine the position of bracket 168 and brake cartridge 200
relative to the blade. When bolt 174 is turned, barrel nut 172 will
travel up or down the length of the bolt. The barrel nut is
captured by link 170, so as the barrel nut moves up and down the
bolt, link 170 also moves. Link 170, in turn, is connected to
bracket 168, as explained. Thus, when bolt 174 is turned, bracket
168 and brake cartridge 200 will pivot toward or away from the
blade. In this manner, a person may infinitely adjust the
blade-to-pawl spacing. The adjustment can be made by extending, for
example, an Allen wrench through the throat plate opening in the
table to engage and turn the head of bolt 174. The ability to
adjust blade-to-pawl spacing is an optional feature. Alternatively,
the position of the brake cartridge relative to the blade may be
fixed for specific blades, or the position may be adjustable
between specific fixed or indexed positions only. Also, different
brake cartridges may be used for different blades, such as dado
blades, and those cartridges may be designed so that the brake pawl
is close to the perimeter of the specific blade for which it was
designed.
[0072] The design of the elevation control mechanism, bracket 168,
brake cartridge 200, and rear trunnion 136 insure that brake
cartridge 200 moves with the blade and is always adjacent the
perimeter of the blade. Because the brake cartridge is mounted on
the bracket, and because the bracket and arbor block are both
pivotally mounted on the same pin, when the arbor block pivots up
or down to change the elevation of the blade relative to the
tabletop, the brake cartridge will also pivot up and down with the
blade and maintain the same blade-to-pawl spacing. Similarly, when
the front and rear trunnions slide relative to the front and rear
trunnion blocks to change the tilt of the blade, the brake
cartridge will move with the blade because the bracket and brake
cartridge are supported by the rear trunnion. Thus, the brake
cartridge maintains its position relative to the blade and is ready
to stop the blade in case of an accident.
[0073] The saw embodiment shown in FIGS. 4 through 11 is also
designed to retract the blade beneath the tabletop when the brake
cartridge stops the blade. Retracting the blade helps minimize the
time the cutting tool is in contact with the user, thereby
minimizing any injury to the user. Moving the cutting tool away
from the point of accidental contact also prevents the cutting tool
from moving toward the user, which could increase any injury to the
user. For example, the spinning blade in a table saw has
substantial angular momentum that could cause the blade to move
upward toward a user when a brake pawl hits the blade, depending on
the position of the brake, the weight of the blade and the amount
of play in the structure supporting the blade. Preventing any such
movement lessens the potential injury to the user. A retraction
system may be used in addition to or instead of other safety
mechanisms.
[0074] Blade 132 spins clockwise when looking at the saw as shown
in FIG. 5, and when it is spinning, the blade will have angular
momentum. When brake cartridge 200 engages and stops the blade, the
angular momentum of the blade will be transferred to the arbor
block, brake cartridge and bracket, and those components will try
to spin in the same direction as the blade due to the conservation
of angular momentum. The arbor block, bracket and brake cartridge
will then all try to move down, or pivot clockwise around pin 134,
because that is the only movement they can make that is in the same
direction as the blade was spinning. The elevation control
mechanism, and particularly bracket 168 and first barrel nut 162,
are designed to use the angular momentum of the blade to retract
the blade in case of an accident.
[0075] As discussed above, and as shown in FIGS. 10 through 15 and
30, first barrel nut 162 includes shoulders 164 that are held in
notches 166 in bracket 168. Notches 166 are part of a slot 250 that
extends through bracket 168 from one side of the bracket to the
other. Shoulders 164 on barrel nut 162 are circular, and notches
166 are shaped to conform to and extend around a bottom portion of
those shoulders, as shown. The top surface of slot 250 contacts the
top of shoulders 164, so that the shoulders are pinched between the
top surface of slot 250 and notches 166. Because slot 250 extends
from one side of the bracket to the other, and because the bracket
is typically constructed of folded or stamped sheet metal, the slot
creates a spring arm 252 in the bracket. Slot 250 is sized so that
shoulders 164 push spring arm 252 down or out when the shoulders
are seated in notches 166. In this manner, spring arm 252 applies a
force against shoulders 164 to help hold barrel nut 162 in
place.
[0076] Bracket 168 also includes a second spring arm 254 having an
upper edge defined by a second slot 256, and having a lower edge
defined by slot 250. Second slot 256, like slot 250, extends from
one side of the bracket to the other. Second spring arm 254
comprises the material extending between slots 250 and 256. Slot
256 is sized and positioned relative to slot 250 so that there is
less material between the ends of the two slots on each side of the
bracket than at other points so that the second spring arm can flex
without deforming.
[0077] As explained above, bracket 168 is "U" shaped, with two
sides and a web or spine connecting the two sides. Slot 256 is
configured so that it creates a socket 258 in the web of the
bracket. A coil spring 260 is held in the socket by tabs that
extend from both the bottom and top of the slot into the coil of
the spring. The spring is sized so that it pushes down on spring
arm 254 to apply pressure to shoulders 166 on barrel nut 162. The
pressure applied by spring 260 and second spring arm 254 further
helps hold barrel nut 162 in place. The bracket shown in 10 through
15 is simply one embodiment of many possible brackets. Brackets may
be designed with varying slots and with or without springs like
spring 260.
[0078] When brake cartridge 200 stops the blade, the angular
momentum creates a significant force tending to urge the blade
down, away from the tabletop, and that force is sufficient to
overcome the force holding barrel nut 162 in notches 166. Thus,
when brake cartridge 200 engages the blade, the angular momentum of
the blade causes bracket 168 to pivot down, and barrel nut 162
snaps out of notches 166. When barrel nut 162 snaps free of notches
166, bracket 168 is then free to pivot down with shoulders 164
sliding in slot 250. Slot 250 is configured so that it extends in
front of notches 166 on each side of bracket 168, and the slot
increases in size so that shoulders 164 can slide freely in the
slot. Slot 250 is also arcuate so that the bracket can pivot down
without binding on the barrel nut. In this manner, the blade and
arbor block become disconnected from the elevation control
mechanism, so the blade retracts beneath the table. The angular
momentum of the blade is so significant that the retraction of the
blade happens very quickly, typically in only a few
milliseconds.
[0079] Using a structure as described above, a force of 5 to 200
pounds or more can be exerted on the barrel nut to hold it in
place. The force can be adjusted by changing the geometry of spring
arms 252 and 254, and/or by changing spring 260, if a spring is
used. The force both eliminates play in the mechanism when the
barrel nut is seated in notches 166, and defines how much force is
required to snap the barrel nut free to retract the blade.
[0080] A bumper 262, as shown in FIGS. 4, 10 and 11, is mounted to
the bottom of arbor block 130 above shaft 140. The bumper may be
made from urethane, rubber, or some other cushioning material. Upon
retraction of the blade, the bumper will impact shaft 140 and
thereby limit the downward movement of the blade and arbor block.
Shaft 140 should be sized sufficiently to withstand the force of
the impact from the bumper, and that is why shaft 140 is shown
larger than shaft 142. Alternatively, the bumper may be mounted on
the shaft, in which case the arbor block would pivot down into
contact with the bumper.
[0081] The impact on the arbor block from retracting the blade has
the potential to damage the saw. To help address this concern, the
arbor block may be made from a ductile iron, such as FC25, that is
better able to withstand the impact. Also, the main bearing
supporting the arbor may be bigger than it otherwise would be.
[0082] After the blade and arbor block have retracted, the
elevation control mechanism can be reset simply by reaching through
the throat plate opening in the table and pulling up on the arbor
block until barrel nut 162 snaps into notches 166, or hand wheel
112 may be turned to cause barrel nut 162 to travel back in slot
250 until the barrel nut snaps into place. As shown, slot 250
extends behind and between notches 166, and the slot extending
between the notches is small so that shoulders 164 cannot move back
past notches 166. Once barrel nut 162 snaps into place in notches
166, the elevation control mechanism is again functional and a user
may turn hand wheel 112 to raise and lower the blade.
[0083] When the brake cartridge fires, the blade cuts into the
brake pawl and binds. The spent cartridge will then have to be
replaced with a new one to make the saw functional. To replace the
spent cartridge the blade must first be knocked off the brake pawl.
However, there may still be residual pressure from the spring in
brake cartridge pushing the brake pawl onto the blade. That
residual pressure should be released prior to knocking the pawl off
the blade. Any residual pressure can be released by turning bolt
174 to move the cartridge away from the blade. The brake pawl will
be held on the blade as the cartridge moves away, thereby allowing
the spring to fully expand. The brake cartridge can then be knocked
off the blade and the spent cartridge replaced with a new one.
[0084] An alternative bracket is shown in FIG. 19. Slot 250 in the
bracket shown in FIG. 19 is configured so that first spring arm 252
has sufficient spring force to hold the barrel nut in notches 166
without the use of a coil spring such as spring 160 shown in FIGS.
12-15. In this configuration, slot 250 includes a larger opening on
each side of the bracket at the end of the slot with less material
surrounding the slot. Additionally, notches 166 in the alternative
bracket are configured so that they surround the top portion of the
shoulders of the barrel nut. Encircling the top portion of the
shoulders helps hold the barrel nut in position because as the
elevation of the blade is raised and the bracket pivots up, the
shoulders tend to roll into the notches. In contrast, positioning
notches 166 on the bottom of the shoulders causes the weight of the
arbor block and blade to tend to roll the shoulders out of the
notches when the blade is raised. Notches 166 in FIG. 19 are also
non-circular and are shaped so that they provide point contact with
the shoulders of the barrel nut. The point contact provides a
positive seating of the shoulders in the notches. A drop-off 264 is
also included in slot 250 on each side of the bracket below notches
166. The drop-off is designed to help release the barrel nut as
quickly as possible after a sufficient force is experienced to snap
the barrel nut out of the notches. The drop-off provides almost
immediate clearance for the barrel nut to slide relative to the
slot. FIG. 19 also shows two tabs 266 to which a plug may be
mounted to connect a cartridge to other electric components and
switches in the saw.
[0085] FIGS. 20 and 21 show an arbor assembly 280 that may be used
in detection subsystem 22. The arbor assembly includes an arbor
128, a first insulating bushing 282, and a second insulating
bushing 284. The bushings are made of a hard, nonconductive
material such as a thermoset, a bulk molding compound, or a
thermoplastic. One possible material is 30% glass filled Ultem. The
bushings electrically isolate the arbor and blade from the rest of
the saw. Because the arbor and blade are electrically isolated, it
is possible that a static electric charge may build up on the arbor
as it spins. Any such static electric charge may affect the
detection subsystem in the saw. In that case, the bushings
alternatively may be made of a slightly conductive or static
dissipative material to dissipate any static electricity that may
build up over time.
[0086] Bushings 282 and 284 are mounted directly on arbor 128, and
the bushings provide seats for the bearings to support the arbor in
the arbor block. Each bushing also includes a raised flange to
prevent the side of a bearing from contacting and potentially
grounding the arbor. First and second electrodes 286 and 288,
respectively, are positioned between the bushings and
concentrically around the arbor but not touching the arbor. The
electrodes are made of a conductive material such as bronze, and
they are part of the capacitive coupling that imparts the
electrical signal to the arbor and blade and then monitors that
signal, as discussed above and as discussed in several of the
references incorporated by reference. The electrodes are
electrically connected to the control subsystem of the saw in any
known manner. The electrodes are press fit into and held by an
electrode shell 290, shown in FIG. 20. The electrode shell is not
shown in FIG. 21 so that the electrodes may be seen more clearly.
The electrode shell, in turn, is held in the arbor block around the
arbor. In the arbor assembly shown in FIG. 20, electrode shell 290
includes a flange 292 that is positioned inside the bearing bore in
the arbor block between the bearing and the arbor block. The other
end of the electrode shell is positioned in a bore in the arbor
block adjacent the small arbor bearing. Of course, the electrode
shell may be held in the arbor block in any known way. In this
assembly, the arbor is electrically isolated from the rest of the
saw, and the electrodes provide an effective capacitive coupling to
the blade.
[0087] FIGS. 20 and 21 also show a hole 294 in the arbor and
electrode shell that may be used to detect blade rotation.
Specifically, a light emitting diode and sensor may be positioned
so that as the blade rotates, light shines through hole 294.
Detecting blade rotation may be used to enable the detection
subsystem only when the blade is spinning, as described in U.S.
Patent Application Publication No. 2002/0017178 A1, entitled
"Motion Detecting System for Use in a Safety System for Power
Equipment," which was mentioned above and is hereby incorporated by
reference.
[0088] FIGS. 22 through 24 show an alternative arbor assembly. In
this alternative, arbor 128 is over-molded with a hard,
non-conductive material like BMC (bulk molding compound). The
over-molding is shown at 300. The over-molding takes the place of
insulating bushings 282 and 284 discussed above, and provides
bearing seats for the two bearings that support the arbor. The
over-molding includes a flange 302 to prevent the side of the main
arbor bearing (bearing not shown) from contacting the arbor. A
non-conductive washer 304 is positioned on the end of the arbor
opposite flange 302, adjacent the side of the small arbor bearing
(bearing not shown), and a retaining clip 306 holds washer 304
against the small bearing. Over-molding 300 completely encircles
arbor 128 and extends from flange 302 to bearing 304, and serves to
electrically isolate the arbor and blade from the rest of the
saw.
[0089] Two electrodes 308 and 310 encircle but do not touch the
over-molded arbor. Electrodes 308 and 310 are conductive and may be
made from powder metal. The electrodes are electrically connected
to the control system of the saw at screw bosses 312 and 314,
respectively. The electrodes are held in place by electrode shell
316. Electrode shell 316 is molded from plastic, and it includes
two halves that snap together to encompass and hold the electrodes.
The electrode shell, in turn, is held in the arbor block as
described above for electrode shell 290.
[0090] An advantage of the arbor assembly shown in FIGS. 22 through
24 is that the over-molding insulates the electrodes from the
arbor. That insulation allows the arbor to be closer to the
electrodes than it otherwise could be. Without the over-molding,
the electrodes would have to be spaced a sufficient distance away
from the arbor to prevent the arbor from ever touching an
electrode, and to minimize the chance of a small piece of
conductive material getting between the electrodes and arbor and
conductively coupling them. If the arbor touched or electrically
coupled to an electrode, then the signal on the arbor and blade
would change, and the detection subsystem and control system could
interpret that change as a person touching the blade and then
trigger the brake. The over-molding between the arbor and
electrodes insulates the arbor and eliminates the possibility of
the arbor touching or electrically coupling to an electrode. Thus,
the over-molding on the arbor may be closer to the electrodes than
the arbor alone could be. Having the over-molded arbor closer to
the electrodes results in a better capacitive coupling between the
arbor and electrodes, and improves the ability to impart a signal
to the arbor and blade and to monitor that signal.
[0091] As shown in FIG. 24, the arbor directly below the electrodes
has an increased diameter. Increasing the diameter of the arbor
increases the surface area of the arbor under the electrodes making
the capacitive coupling larger. The bulk molding compound in the
gap between the arbor and electrodes also acts as a dielectric to
improve significantly the capacitive coupling. It also may be
advantageous to include a layer of another dielectric or other
material such as Kynar, for example, between the electrodes and
arbor to further enhance the capacitive coupling. With the arbor
assembly shown in FIGS. 22 through 24, there remains an air gap
between the outer surface of the over-molding and the inner surface
of the electrodes of approximately 0.005 to 0.007 inches.
[0092] Other materials that can be used as over-molding include
thermosets, such as the phenolic RX630 from Sumitomo Bakelite Co.
Ltd. (previously from Vyncolit North America Inc.), and
thermoplastics such as the polyetherimide Ultem from General
Electric, including glass-reinforced Ultem 2300 and Ultem 2400.
Still other materials that might be used as over-molding, depending
on the application, include: urethane, fiberglass (plastic and
glass composite), Kepital (acetal copolymer), Kadel (carbon fiber
reinforced polyketone resin), Amodel (glass reinforced, heat
stabilized polyphthalamide), Torlon (polyamide-imide resin), Noryl
GTX (PPE/PA resin), Capron (glass reinforced nylon), Ryton
(polyphenylene sulfide) and epoxy. Material selection depends on
the requirements of the specific application, the cost of the
material, and the mechanical, thermal and electrical properties of
the material, such as the compressive strength, flexural strength,
hardness, melting point, upper service temperature, coefficient of
thermal expansion, dielectric constant and resistivity.
[0093] In applications where the over-molding provides bearing
seats to support an arbor in a power tool and the arbor is expected
to spin over extensive periods of time due to heavy use of the
machine, experimentation and testing have shown that a structurally
reinforced laminate material such as prepreg is particularly
effective. Prepreg is a laminate material made of reinforcing
fibers impregnated with some type of resin. For example, prepreg
can be made from paper, cloth (cotton cloth, for example) or glass
fabric that is impregnated with a polyimide, epoxy, phenolic,
melamine, silicon or other resin. (Prepreg made with a glass fabric
is a type of fiberglass.) Typically the reinforcing fibers are
organized into some pattern or structure, such as being
crisscrossed or woven into cloth or flexible sheets. As used
herein, references to fiber organized into a pattern or structure
include, but is not limited to, fiber crisscrossed or woven into
cloth or flexible sheets as well as fiber spooled or wound around
an arbor. As stated, the reinforcing fibers are impregnated or
coated with resin and typically the resin is partially cured or
reacted during the impregnation process. Sheets and/or strands of
the impregnated material are laid upon and/or against each other
and the resin is cured by application of pressure and high
temperature to form a solid mass. Prepreg is commonly used to make
printed circuit boards and the prepreg for printed circuit boards
is known as G-10 or FR-4 or G-10/FR-4. That type of prepreg is a
glass-epoxy laminate with high strength and dimensional stability
over temperature, and it could be used as an arbor over-molding in
some applications. The label G-10 refers to a standard from the
National Electrical Manufacturers Association (NEMA) and FR-4 is an
abbreviation for Flame Resistant 4. The material G-10 alone lacks
the self extinguishing flammability characteristics of FR-4.
[0094] Testing and use of prepreg as an over-molding material for
bearing seats on arbors in power tools has shown at least some
types of prepreg to be remarkably durable in that application.
[0095] FIG. 33 shows arbor 128 with a prepreg over-molding 402 and
the over-molding includes bearing seats 404 and 406. Before the
prepreg is applied to the arbor, the outer surface of the arbor may
be roughened or abraded in order to increase the friction and/or
adhesion between the arbor and the prepreg. For example, the outer
surface of the arbor under the bearing seats is knurled, as shown
at 407 for bearing seat 404, and the outer surface of the arbor
between the bearing seats is patterned with a double spiral groove,
as shown at 408. The entire outer surface of the arbor under the
prepreg is sandblasted, as shown at 409. Of course, many different
patterns and combinations of knurling, patterning, abrading, etc.,
can be used. The abrading or roughening of the arbor better secures
the prepreg to the arbor because during molding the resin flows
around and into the abraded or roughened areas. This can form a
mechanical interlock against movement of the overmold on the arbor,
as in the case of knurling, or can improve adhesion between the
metal of the arbor and the overmold.
[0096] The prepreg is applied to the arbor by wrapping. The arbor
may be wrapped with only one type of fiber cloth or with several
different fiber cloths to achieve the desired over-molding
characteristics and/or shape. FIG. 34 illustrates how an arbor 128
could be wrapped with a 0.15 mm thick prepreg cloth and a 0.18 mm
thick prepreg cloth. The 0.15 mm thick cloth is wrapped around the
arbor before the 0.18 mm thick cloth and is used to wrap around
sections of the arbor with smaller diameters, as shown at 412.
Alternatively, a thinner cloth, such as a 0.04 mm thick cloth could
be wrapped around the arbor first and the 0.15 mm cloth could be
wrapped over the 0.04 mm cloth. The thinner cloth might better
conform to and/or grip the arbor and it could be used to provide a
cloth and resin surface to contact and help grip or fix subsequent
wrapping by presenting a slightly tacky surface. The 0.18 mm cloth
could be wrapped over the 0.15 mm cloth, as shown at 414 in FIG.
34. Using a thicker cloth minimizes the number of times the cloth
must be wrapped around the arbor to achieve the desired shape and
size, thereby minimizing production cost and time. A 0.04 mm cloth
also could be wrapped over the 0.18 mm cloth to help fix the prior
wrappings in place.
[0097] The over-molding on arbor 128 may include a flange to help
isolate the arbor, such as flange 302 shown in FIG. 33 and
discussed previously. A flange can be made by rolling a portion of
prepreg cloth into a ring and then positioning the ring around the
arbor where desired, as shown at 416 in FIG. 34. The flange is
formed from the ring during pressing and curing of the prepreg.
Different prepreg cloths can be used to make the ring, such as the
0.15 mm thick cloth discussed above, depending on the desired
characteristics. A piece of tape and/or a thin piece of prepreg
cloth (0.04 mm thick, for example) could be used to fix the ring in
place prior to pressing and curing, as shown at 418 (tape 418 might
also serve other functions, as discussed below).
[0098] The arbor also may be wrapped using a string or thread of
prepreg or similar material--like thread on a spool.
[0099] After the arbor is wrapped, it is placed in a mold and
heated and pressed to melt the resin and cause the resin to flow
(at least to some degree) into the desired shape. For example, a
force of 100 kg may be applied to the mold and the mold may be
heated to around 145 degrees Celcius, plus or minus 5 degrees, for
around 30 minutes, depending on the resin used. The mold is
configured to press the prepreg into the desired shape and size,
after which the resin gels and solidifies. If the outer surface of
the arbor was patterned, abraded or roughened, then during molding
the resin would flow at least partially into and around any ridges
and valleys of the patterns or abrasions and solidify to better
secure the over-molding to the arbor, as stated.
[0100] As the arbor is heated and pressed, some of the resin may
escape the mold as flashing. Tape can be applied over surfaces of
the arbor to help protect the surfaces from flashing and to provide
what may be thought of as a seal or gasket between surfaces of the
arbor and the mold, as shown at 418 in FIG. 34. Other material may
also be used to protect exposed surfaces of the arbor. For example,
a small plastic bag or plastic sleeve may be placed over end 410 of
the arbor to protect the arbor and the plastic sleeve may be held
in place with tape.
[0101] After heating and pressing, the resin is allowed to cure. As
an example, curing may take place at room temperature for 10
minutes while the 100 kg force is maintained on the mold, depending
on the resin used. After curing, the over-molding can be ground
and/or machined to a desired shape. Any tape or cloth used to help
seal the mold or minimize flashing, as well as any flashing itself,
can be removed by hand or by grinding or machining.
[0102] One example of a prepreg cloth is "Epoxy Resin Glass Cloth
Prepreg" from Wah Hong Industrial Corp. of Taiwan. This cloth may
be used as the 0.18 mm thick cloth illustrated in FIG. 34. The
cloth is woven from what is referred to as yarn and the yarn is
made of a glass fiber called E-Glass from PFG Fiber Glass
Corporation in Taiwan. E-Glass (1062A) fibers have nominal
diameters of 13.3.+-.0.06 (K).mu.m and they may be treated with a
silane binder to help provide an interfacial bond with resin. The
fibers are woven into a fabric and the fabric is impregnated with a
resin. Wah Hong Industrial Corp. reports the following
specifications for the finished cloth: [0103] Density (per 25 mm):
warp 64, fill 27 [0104] Weight (g/m.sup.2): 212 [0105] R.C. (%):
36.+-.2 [0106] V.C. (%): 0.5-1.5 [0107] Weave: Satin [0108] Width
(mm): 1020.+-.20 [0109] Gel Time: 135.degree. C. 3.0-3.30 min.
[0110] Yarn type: E-Glass [0111] Tensile Strength: 250 kgf/mm.sup.2
[0112] Tensile Modulus: 7700 kgf/mm.sup.2
[0113] An example of a 0.15 mm thick prepreg fabric is from
Forthtrack Co., Ltd. of Taiwan and is identified by the designation
E-glass fiber ud-prepreg.(hot-melt) FT-150G/37%. Forthtrack
provides the following specifications for that fabric: [0114]
Weave: Plain [0115] Thickness (mm): 0.04 [0116] Width (mm): 1030
[0117] Weight (g/m): 26 [0118] Thread Count (/inch): Warp 60, Fill
51 [0119] RC (%): 50 [0120] VC: 1.5 [0121] Roll Length (prepreg/m):
150
[0122] An example of a 0.04 mm thick prepreg fabric is from Wah Lee
Industrial Corp. of Taiwan and is identified by the designation
KN303. Wah Lee Industrial provides the following specifications for
that fabric: [0123] Weight (g/m.sup.2): 150 [0124] R.C. (%): 37
[0125] Width (m): 1 [0126] Epoxy: 88 g/m.sup.2 [0127] Gel Time:
135.degree. C. 3.0-3.30 min. [0128] Yarn Type: E-Glass (1062A)
[0129] Another example of a glass fabric is from Porcher Industries
and is identified by the designation Standard E-Glass Fabric Style
106. Porcher Industries provides the following specifications for
that fabric: [0130] Width: 1120 [0131] Weave: Plain [0132] Fibre
Count (Warp/Weft): 22.2.times.22.2 [0133] Warp: EC5 5.5 [0134]
Weft: EC5 5.5 [0135] Weight Ratio Warp/Weft: 50/50 [0136] Weight
(g/m.sup.2): 25 [0137] Finish: 731
[0138] Another prepreg epoxy resin glass cloth is TGFW-800 from Wah
Lee Industrial Corp. in Taiwan. Wah Lee Industrial reports the
following specifications for that cloth: [0139] Basic Weight
(g/m.sup.2): 720 min., 800 nom., 880 max. [0140] Width (mm)<30
cm: .+-.6 [0141] Width (mm)>30 cm: .+-.9.5 [0142] Tail Width
(mm): 13-25 [0143] L.O.I. (%): 0.35-0.61 [0144] Construction, Ends
per Inch: 5 [0145] Construction, Picks per Inch: 4
[0146] The TGFW-800 cloth has a coarser weave than the other cloths
discussed above and is approximately 0.56 mm thick. In some
applications thicker fabric can be used to minimize the number of
times the fabric must be wrapped around the arbor, as stated
previously. However, in some applications the smaller number of
wrappings and/or the coarser weave may affect the final strength
and/or durability of the over-molding. For example, in tests where
a bearing was seated loosely on the over-molding (i.e., the
over-molding and bearing were sized so there was some play or
clearance between them) and the arbor was spun at around 4000 rpm
to test the durability of the over-molding, the outer surface of
the over-molding made from the 0.56 mm thick cloth was turned to
powder or was slightly pulverized within a relatively short period
of time and the play between the over-molding and bearing
increased, while over-molding made from the 0.18 mm thick cloth
discussed above did not.
[0147] A resin that may be used in at least some of the prepreg
cloth described above is called Eporite EHM from Epolab Chemical
Ind. Inc. of Taiwan. That resin is made from modified epoxy resin
(85-95%) combined with dicyandiamine (5-15%). Epolab Chemical
reports the following properties of that resin when cured: [0148]
Flexure Strength (150L/WT.sup.2): 55-60 [0149] Heat distortion temp
(.degree. C.): 120-140 [0150] Short beam shear strength (0.75
L/WT): 3.5-4.0 [0151] Impact strength (5271.42(cos 150.degree.-cos
.theta.)/(W-2.5)T): 85-95
[0152] As an alternative to over-molding an arbor, one or more
bearings supporting the arbor may be over-molded or coated. The
over-molding or coating would electrically insulate the bearing
from the arbor. The over-molding or coating could comprise a
non-conductive material reinforced by fiber organized into a
pattern, such as prepreg.
[0153] The arbor assemblies shown in FIGS. 20 through 24, 33 and 34
are mounted to spin in the arbor block. The blade is mounted on the
end of the arbor adjacent flange 320, and secured with a washer and
nut, as is known in the art. FIGS. 20 and 21 also show pulley 126
around which belt 122 extends to transfer power from the motor to
spin the arbor.
[0154] FIGS. 25 through 27 show a trunnion brace 330 that may be
used as an alternative to shafts 140 and 142 (as shown in FIGS. 4
through 9) to connect front trunnion 138 and rear trunnion 136. End
332 bolts to the front trunnion, and end 334 bolts to the rear
trunnion. Trunnion brace 330 is configured to shroud the portion of
the blade under the table to help prevent a person from
accidentally contacting the blade under the table. This is
especially applicable if the blade is designed to retract. If a
person accidentally touches a spinning blade under the table and
the blade retracts, the person may be more severely injured because
the retraction would move the blade down. Shrouding the blade
minimizes that risk.
[0155] Trunnion brace 330 may be made of cast iron and should be
strong enough to rigidly connect the front and rear trunnions.
Trunnion brace 330 also includes a surface 338 against which a
retracting arbor block may impact. Surface 338 must be sufficiently
strong to withstand the impact of the retracting arbor block, and
that is why the surface is larger and wider than the corresponding
surface on the opposite side of the trunnion brace. Of course, the
bumper discussed above that helps cushion the impact of the
retracting arbor block may be mounted on surface 338.
[0156] Trunnion brace 330 also acts to help collect sawdust. As the
blade cuts, much of the resulting dust will be caught by the
trunnion brace. The trunnion brace is provided with an opening 336
in the bottom to which a vacuum or other dust collection system may
be attached to evacuate the dust.
[0157] Opening 336 in trunnion brace 330 is shaped to accept
pivoting coupler 340 shown in FIGS. 28 and 29. When a user adjusts
the tilt of the blade, the trunnion brace will tilt from side to
side. A pivoting coupler allows a vacuum hose to remain connected
to the trunnion brace as the trunnion brace tilts. Coupler 340
includes two bumps 344 and 346 that mount into holes like hole 342
on the trunnion brace. The bumps are positioned on tabs 348 and
350, and the coupler is molded from plastic, so tabs 348 and 350
allow the bumps to be depressed to mount the coupler on the
trunnion brace. The tabs also provide some spring force to hold the
bumps in their respective holes. Coupler 340 will then pivot on
bumps 344 and 346. Upper section 352 of the coupler is shaped so
that it extends into opening 336 as the coupler pivots. Bottom
section 354 of the coupler is annular so that a vacuum hose or
other conduit can be easily attached.
[0158] The structure disclosed above for a right-tilt saw may be
mirrored for implementation in a left-tilt saw.
INDUSTRIAL APPLICABILITY
[0159] The systems and components disclosed herein are applicable
to power equipment, and specifically to woodworking equipment such
as table saws.
[0160] It is believed that the disclosure set forth above
encompasses multiple distinct inventions with independent utility.
While each of these inventions has been disclosed in its preferred
form, the specific embodiments thereof as disclosed and illustrated
herein are not to be considered in a limiting sense as numerous
variations are possible. The subject matter of the inventions
includes all novel and non-obvious combinations and
sub-combinations of the various elements, features, functions
and/or properties disclosed herein. No single feature, function,
element or property of the disclosed embodiments is essential to
all of the disclosed inventions. Similarly, where the claims recite
"a" or "a first" element or the equivalent thereof, such claims
should be understood to include incorporation of one or more such
elements, neither requiring nor excluding two or more such
elements.
[0161] It is believed that the following claims particularly point
out certain combinations and sub-combinations that are directed to
one of the disclosed inventions and are novel and non-obvious.
Inventions embodied in other combinations and sub-combinations of
features, functions, elements and/or properties may be claimed
through amendment of the present claims or presentation of new
claims in this or a related application. Such amended or new
claims, whether they are directed to a different invention or
directed to the same invention, whether different, broader,
narrower or equal in scope to the original claims, are also
regarded as included within the subject matter of the inventions of
the present disclosure.
* * * * *