U.S. patent application number 09/929238 was filed with the patent office on 2002-02-14 for miter saw with improved safety system.
Invention is credited to D'Ascenzo, David S., Fanning, David A., Gass, Stephen F..
Application Number | 20020017179 09/929238 |
Document ID | / |
Family ID | 27585534 |
Filed Date | 2002-02-14 |
United States Patent
Application |
20020017179 |
Kind Code |
A1 |
Gass, Stephen F. ; et
al. |
February 14, 2002 |
Miter saw with improved safety system
Abstract
A miter saw is disclosed having a base, a blade supported by the
base, a detection system adapted to detect a dangerous condition
between a person and the blade, and a reaction system associated
with the detection system to cause a predetermined action to take
place upon detection of the dangerous condition. The blade is
rotatable, and moves into a cutting zone to cut a workpiece. The
predetermined action may be to stop the blade from rotating, to
create an impulse against movement of the blade into the cutting
zone, or to cause the blade to move away from the cutting zone.
Inventors: |
Gass, Stephen F.;
(Wilsonville, OR) ; D'Ascenzo, David S.;
(Portland, OR) ; Fanning, David A.; (Vancouver,
WA) |
Correspondence
Address: |
SD3, LLC
22409 S.W. NEWLAND ROAD
WILSONVILLE
OR
97070
US
|
Family ID: |
27585534 |
Appl. No.: |
09/929238 |
Filed: |
August 13, 2001 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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60225056 |
Aug 14, 2000 |
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60225057 |
Aug 14, 2000 |
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60225058 |
Aug 14, 2000 |
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60225059 |
Aug 14, 2000 |
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60225089 |
Aug 14, 2000 |
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60225094 |
Aug 14, 2000 |
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60225169 |
Aug 14, 2000 |
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60225170 |
Aug 14, 2000 |
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60225200 |
Aug 14, 2000 |
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60225201 |
Aug 14, 2000 |
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60225206 |
Aug 14, 2000 |
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60225210 |
Aug 14, 2000 |
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60225211 |
Aug 14, 2000 |
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60225212 |
Aug 14, 2000 |
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Current U.S.
Class: |
83/58 ; 83/490;
83/DIG.1 |
Current CPC
Class: |
B23D 47/08 20130101;
Y10T 83/7734 20150401; F16P 3/12 20130101; Y10T 83/081 20150401;
B23D 59/001 20130101; Y10T 83/7726 20150401; B27G 19/02 20130101;
Y10T 83/089 20150401; Y10T 83/8773 20150401; Y10T 83/613 20150401;
B27B 5/38 20130101; Y10T 83/7693 20150401; B27B 13/14 20130101;
Y10T 83/7697 20150401; Y10T 83/7788 20150401; F16P 3/148 20130101;
B27G 19/00 20130101 |
Class at
Publication: |
83/58 ; 83/490;
83/DIG.001 |
International
Class: |
B23D 045/04 |
Claims
1. A miter saw comprising: a support structure having a cutting
zone; a blade supported by the support structure so that the blade
may move into the cuffing zone; a motor adapted to drive the blade;
a detection system to detect contact between a person and the
blade; and a reaction system adapted to create an impulse against
movement of the blade into the cutting zone upon detection by the
detection system of contact between the person and the blade.
2. The miter saw of claim 1, where the reaction system is adapted
to move the blade in a direction away from the cutting zone upon
detection by the detection system of contact between the person and
the blade.
3. The miter saw of claim 1, where the blade is rotatable, and
where the reaction system is further adapted to stop rotation of
the blade upon detection by the detection system of contact between
the person and the blade.
4. The miter saw of claim 3, where the reaction system includes a
brake mechanism adapted to engage and stop the rotation of the
blade, and where the engagement of the brake mechanism with the
blade creates the impulse against movement of the blade into the
cutting zone.
5. The miter saw of claim 4, where the engagement of the brake
mechanism with the blade moves the blade in a direction away from
the cutting zone.
6. The miter saw of claim 4, where the blade has angular momentum
when rotating, and where the engagement of the brake mechanism with
the blade creates the impulse due, at least partially, to the
angular momentum of the blade.
7. The miter saw of claim 3, where the reaction system includes a
brake mechanism adapted to engage and stop the rotation of the
blade, and where the brake mechanism is coupled to the support
structure to maintain an operative position relative to the blade
as the blade moves into the cutting zone.
8. The miter saw of claim 3, where the reaction system includes a
first mechanism adapted to stop the rotation of the blade, and a
second mechanism adapted to create an impulse against movement of
the blade into the cutting zone.
9. A miter saw comprising: a support structure having a cutting
zone; a rotatable blade supported by the support structure so that
the blade may move into the cutting zone; a motor adapted to drive
the blade; a detection system adapted to detect contact between the
blade and a person; and a brake mechanism adapted to stop rotation
of the blade upon detection by the detection system of contact
between the blade and the person.
10. The miter saw of claim 9, where the brake mechanism is further
adapted to stop movement of the blade into the cutting zone.
11. The miter saw of claim 9, where the support structure includes
a pivot arm adapted to support the blade and selectively pivotal
toward and away from the cutting zone, and where the brake
mechanism is further adapted to move the pivot arm away from the
cutting zone.
12. The miter saw of claim 9, where the support structure includes
a pivot arm adapted to support the blade and selectively pivotal
toward and away from the cutting zone, where the brake mechanism is
adapted to engage the blade upon detection by the detection system
of contact between the blade and the person, and where engagement
of the brake mechanism with the blade causes the pivot arm to pivot
away from the cutting zone.
13. The miter saw of claim 12, where the blade has angular momentum
when rotating, and where the engagement of the brake mechanism with
the blade causes the pivot arm to pivot away from the cutting zone,
due at least partially, to the angular momentum of the blade.
14. The miter saw of claim 9, where the support structure includes
a pivot arm adapted to support the blade and selectively pivotal
toward and away from the cutting zone, and further comprising a
second brake mechanism adapted to stop the pivot arm from pivoting
toward the cutting zone upon detection by the detection system of
contact between the blade and the person.
15. The miter saw of claim 9, where the support structure includes
a pivot arm adapted to support the blade and selectively pivotal
toward and away from the cutting zone, and further comprising a
second brake mechanism adapted to move the pivot arm away from the
cutting zone upon detection by the detection system of contact
between the blade and the person.
16. The miter saw of claim 9, where the blade has teeth, and where
the brake mechanism includes at least one brake pawl adapted to
pivot into the teeth of the blade.
17. A miter saw comprising: a base having a cutting region; a
blade; a brake system adapted to brake the blade; and a linkage
between the blade and base, where the linkage is configured to
cause the blade to move away from the cutting region when the brake
system brakes the blade.
18. The miter saw of claim 17 where the blade is rotatable, where
the blade has an angular momentum when rotated, and where the
linkage is configured so that the angular momentum of the blade
causes the blade to move away from the cutting region when the
brake system brakes the blade.
19. A miter saw comprising: a base; a housing pivotally connected
to the base; a blade; a mounting system holding the blade in the
housing; and a brake system adapted to brake the blade; where the
mounting system is configured so that the blade pivots into the
housing when the brake system brakes the blade.
20. A miter saw comprising: a base; a swing arm supported by the
base and adapted to move toward a workpiece to be cut; a blade
mounted to move with the swing arm to contact the workpiece when
the swing arm moves toward the workpiece; a detection system
adapted to detect a dangerous condition between a person and the
blade; and a reaction system adapted to interrupt the movement of
the blade and swing arm upon the detection by the detection system
of the dangerous condition between the person and the blade.
21. The miter saw of claim 20, further comprising a piston/cylinder
to limit the speed with which the swing arm can move.
22. The miter saw of claim 20, where the swing arm includes a cam
portion, and further comprising a pawl adapted to engage the cam
portion to stop the movement of the swing arm toward the workpiece
upon the detection of the dangerous condition.
23. A miter saw comprising: a base; a blade supported by the base;
a detection system adapted to detect a dangerous condition between
a person and the blade; and a reaction system associated with the
detection system to cause a predetermined action to take place upon
detection of the dangerous condition.
24. The miter saw of claim 23, where the reaction system includes a
brake system to brake the blade.
25. The miter saw of claim 23, where the reaction system includes a
mechanism to retract the blade.
26. A miter saw comprising: a base; a blade supported by the base;
a detection system adapted to detect a dangerous condition between
a person and the blade; and reaction means associated with the
detection system for causing a predetermined action to take place
upon detection of the dangerous condition.
27. The miter saw of claim 26, where the blade is rotatable, and
where the predetermined action is to stop the blade from
rotating.
28. The miter saw of claim 26, where the base has a cutting zone,
where the blade is adapted to move into the cutting zone to cut a
workpiece, and where the predetermined action is to create an
impulse against movement of the blade into the cutting zone.
29. The miter saw of claim 26, where the base has a cutting zone,
where the blade is adapted to move into the cutting zone to cut a
workpiece, and where the predetermined action is to cause the blade
to move away from the cutting zone.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims the benefit of and priority from the
following U.S. Provisional Patent Applications: Ser. No.
60/225,056, filed Aug. 14, 2000, Ser. No. 60/225,057, filed Aug.
14, 2000, Ser. No. 60/225,058, filed Aug. 14, 2000, Ser. No.
60/225,059, filed Aug. 14, 2000, Ser. No. 60/225,089, filed Aug.
14, 2000, Ser. No. 60/225,094, filed Aug. 14, 2000, Ser. No.
60/225,169, filed Aug. 14, 2000, Ser. No. 60/225,170, filed Aug.
14, 2000, Ser. No. 60/225,200, filed Aug. 14, 2000, Ser. No.
60/225,201, filed Aug. 14, 2000, Ser. No. 60/225,206, filed Aug.
14, 2000, Ser. No. 60/225,210, filed Aug. 14, 2000, Ser. No.
60/225,211, filed Aug. 14, 2000, and Ser. No. 60/225,212, filed
Aug. 14, 2000.
FIELD
[0002] The present invention relates to miter saws, and more
particularly to a miter saw with a high-speed safety system.
BACKGROUND
[0003] Miter saws are a type of woodworking machinery used to cut
workpieces of wood, plastic and other materials. Miter saws include
a base upon which workpieces are placed, and a circular saw blade
is mounted on a swing arm above the base. A person uses a miter saw
by placing workpiece on the base beneath the blade and then
bringing the blade down via the swing arm to cut the workpiece.
Miter saws present a risk of injury to users because the spinning
blade is often exposed when in use. Furthermore, persons often use
their hands to position and support workpieces beneath the blade,
which increases the chance that an injury will occur.
[0004] The present invention provides a miter saw with an improved
safety system that is adapted to detect the occurrence of one or
more dangerous, or triggering, conditions during use of the miter
saw, such as when a user's body contacts the spinning saw blade.
When such a condition occurs, the safety system is actuated to
limit or even prevent serious injury to the user.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a schematic block diagram of a machine with a
fast-acting safety system according to the present invention.
[0006] FIG. 2 is a schematic diagram of an exemplary safety system
in the context of a machine having a circular blade.
[0007] FIG. 3 is a side elevation view of a miter saw with an
improved safety system according to the present invention.
[0008] FIG. 4 is a cross-sectional top plan view of the miter saw
of FIG. 3.
[0009] FIG. 5 is a side elevation view of another miter saw
according to the present invention.
[0010] FIG. 6 is a side elevation view of another miter saw
according to the present invention.
[0011] FIG. 7 is a side elevation view of another miter saw
according to the present invention.
[0012] FIG. 8 is a side elevation view of another miter saw
according to the present invention.
[0013] FIG. 9 is a fragmentary cross-sectional view of an
electrically isolated blade.
DETAILED DESCRIPTION
[0014] A machine is shown schematically in FIG. 1 and indicated
generally at 10. Machine 10 may be any of a variety of different
machines adapted for cutting workpieces, such as wood, including a
table saw, miter saw (chop saw), radial arm saw, circular saw, band
saw, jointer, planer, etc. Machine 10 includes an operative
structure 12 having a cutting tool 14 and a motor assembly 16
adapted to drive the cutting tool. Machine 10 also includes a
safety system 18 configured to minimize the potential of a serious
injury to a person using machine 10. Safety system 18 is adapted to
detect the occurrence of one or more dangerous, or triggering,
conditions during use of machine 10. 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.
[0015] Machine 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.
[0016] It will be appreciated that operative structure 12 may take
any one of many different forms, depending on the type of machine
10. 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 a movable structure configured to carry cutting tool
14 between multiple operating positions. As a further alternative,
operative structure 12 may include one or more transports
mechanisms adapted to convey a workpiece toward and/or away from
cutting tool 14.
[0017] Motor assembly 16 includes one or more motors adapted to
drive cutting tool 14. The motors may be either directly or
indirectly coupled to the cutting tool, and may also be adapted to
drive workpiece transport mechanisms. Cutting tool 14 typically
includes one or more blades or other suitable cutting implements
that are adapted to cut or remove portions from the workpieces. The
particular form of cutting tool 14 will vary depending upon the
various embodiments of machine 10. For example, in table saws,
miter saws, circular saws and radial arm saws, cutting tool 14 will
typically include one or more circular rotating blades having a
plurality of teeth disposed along the perimetrical edge of the
blade. For a jointer or planer, the cutting tool typically includes
a plurality of radially spaced-apart blades. For a band saw, the
cutting tool includes an elongate, circuitous tooth-edged band.
[0018] 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 machine 10. In addition, control subsystem 26 typically includes
one or more instruments operable by a user to control the machine.
The control subsystem is configured to control machine 10 in
response to the inputs it receives.
[0019] Detection subsystem 22 is configured to detect one or more
dangerous, or triggering, conditions during use of machine 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. Provisional Patent Application Ser. No. 60/182,866, filed
Feb. 16, 2000 entitled "Fast-Acting Safety Stop," 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.
[0020] 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 machine 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. Provisional Patent Application Ser. No. 60/225,206,
filed Aug. 14, 2000, entitled "Cutting Tool Safety System," and
U.S. patent application Ser. No. ______, filed Aug. 13, 2001,
entitled "Cutting Tool Safety System," the disclosures of which are
herein incorporated by reference. Retraction of the cutting tool
from its operating position is described in more detail in U.S.
Provisional Patent Application Ser. No. 60/225,089, filed Aug. 14,
2000, entitled "Retraction System For Use In Power Equipment," and
U.S. patent application Ser. No. ______, filed Aug. 13, 2001,
entitled "Retraction System For Use In Power Equipment," the
disclosures of which are herein incorporated by reference.
[0021] The configuration of reaction subsystem 24 typically will
vary depending on which action(s) 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.
[0022] 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 cutting tool in the form of 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. Provisional Patent Application Ser.
No. 60/225,210, filed Aug. 14, 2000, entitled "Translation Stop For
Use In Power Equipment," and U.S. patent application Ser. No.
______, filed Aug. 13, 2001, entitled "Translation Stop For Use In
Power Equipment," the disclosures of which are herein incorporated
by reference, describe other systems for stopping the movement of
the cutting tool. U.S. Provisional Patent Application Ser. No.
60/225,058, filed Aug. 14, 2000, entitled "Table Saw With Improved
Safety System," and U.S. patent application Ser. No. ______, filed
Aug. 13, 2001, entitled "Table Saw With Improved Safety System,"
the disclosures of which are herein incorporated by reference,
describe safety system 18 in the context of a table saw.
[0023] 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
machine 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.
Provisional Patent Application Ser. No. 60/225,200, filed Aug. 14,
2000, entitled "Contact Detection System For Power Equipment," U.S.
patent application Ser. No. ______, filed Aug. 13, 2001, entitled
"Detection System For Power Equipment," U.S. Provisional Patent
Application Ser. No. 60/225,211, filed Aug. 14, 2000, entitled
"Apparatus And Method For Detecting Dangerous Conditions In Power
Equipment," and U.S. patent application Ser. No. ______, filed Aug.
13, 2001, entitled "Apparatus And Method For Detecting Dangerous
Conditions In Power Equipment," the disclosures of which are herein
incorporated by reference.
[0024] 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, 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, workpiece
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. Provisional Patent Application
Ser. No. 60/225,059, filed Aug. 14, 2000, entitled "Logic Control
For Fast-Acting Safety System," U.S. patent application Ser. No.
______, filed Aug. 13, 2001, entitled "Logic Control For
Fast-Acting Safety System," U.S. Provisional Patent Application
Ser. No. 60/225,094, filed Aug. 14, 2000, entitled "Motion
Detecting System For Use In Safety System For Power Equipment," and
U.S. patent application Ser. No. ______, filed Aug. 13, 2001,
entitled "Motion Detecting System For Use In A Safety System For
Power Equipment," the disclosures of which are herein incorporated
by reference.
[0025] 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 will 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 may 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.
[0026] 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 {fraction (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.
[0027] 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. Provisional
Patent Application Ser. No. 60/225,056, filed Aug. 14, 2000,
entitled "Firing Subsystem For Use In A Fast-Acting Safety System,"
U.S. patent application Ser. No. ______, filed Aug. 13, 2001,
entitled "Firing Subsystem For Use In A Fast-Acting Safety System,"
U.S. Provisional Patent Application Ser. No. 60/225,170, filed Aug.
14, 2000, entitled "Spring-Biased Brake Mechanism For Power
Equipment," U.S. patent application Ser. No. ______, filed Aug. 13,
2001, entitled "Spring-Biased Brake Mechanism For Power Equipment,"
U.S. Provisional Patent Application Ser. No. 60/225,169, filed Aug.
14, 2000, entitled "Brake Mechanism For Power Equipment," and U.S.
patent application Ser. No. ______, filed Aug. 13, 2001, entitled
"Brake Mechanism For Power Equipment," the disclosures of which are
herein incorporated by reference.
[0028] It will be appreciated that activation of the brake
mechanism will typically 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 are described in more detail
in U.S. Provisional Patent Application Ser. No. 60/225,201, filed
Aug. 14, 2000, entitled "Replaceable Brake Mechanism For Power
Equipment," U.S. patent application Ser. No. ______, filed Aug. 13,
2001, entitled "Replaceable Brake Mechanism For Power Equipment,"
U.S. Provisional Patent Application Ser. No. 60/225,212, filed Aug.
14, 2000, entitled "Brake Positioning System," and U.S. patent
application Ser. No. ______, filed Aug. 13, 2001, entitled "Brake
Positioning System," the disclosures of which are herein
incorporated by reference.
[0029] 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. Provisional
Patent Applications Ser. Nos. 60/182,866, filed Feb. 16, 2000, and
60/157,340, filed Oct. 1, 1999, both entitled "Fast-Acting Safety
Stop," the disclosures of which are herein incorporated by
reference.
[0030] In FIGS. 3 and 4, an exemplary embodiment of machine 10 is
shown in the context of a miter saw 1510, which is also commonly
referred to as a chop saw. It will be understood that miter saw
1510 may be any type of miter saw including a simple miter saw,
compound miter saw, sliding compound miter saw, etc. Typically,
miter saw 1510 includes a base or stand 1512 adapted to hold the
workpiece to be cut. A swing arm 1514 is pivotally coupled to base
1512 to allow the arm to pivot downward toward the base. Attached
to arm 1514 is a housing 1516 adapted to at least partially enclose
a circular blade 40. A motor assembly 16 is coupled to the housing,
and includes a rotating arbor 42 on which the blade is mounted.
Motor assembly 16 includes a handle 1518 with a trigger 1520
operable to run the saw. Blade 40 rotates downward toward base
1512. An optional blade guard (not shown) may extend from the
bottom of housing 1516 to cover any portion of the blade exposed
from the housing. A person uses miter saw 1510 by placing workpiece
on base 1512 beneath the upraised blade and then bringing the blade
down via swing arm 1514 into what may be thought of as a cutting
zone to cut the workpiece. It should be understood that various
embodiments of miter saws with improved safety systems are
disclosed herein and include various elements, sub-elements,
features and variations. Miter saws according to the present
invention may include any one or more of the elements,
sub-elements, features and variations disclosed herein, regardless
of whether the particular elements, sub-elements, features and/or
variations are described together or shown together in the
figures.
[0031] The portion of saw 1510 from which sensors 44 and 46 detect
contact with a user should be electrically isolated from ground and
the remaining portion of saw 1510 to allow an input signal to be
capacitively coupled from one plate to the other. For example,
blade 40 may be electrically isolated from the rest of the saw via
a plastic or other nonconductive bushing, such as shown in FIG. 9
at 1570. Alternatively, the blade and arbor assembly may be
electrically isolated. Also shown in FIG. 9 are insulating washers
1572 and 1574 that isolate blade 40 from arbor flange 1576 and
arbor washer 1578. The insulating washers should be sufficiently
thick that only negligible capacitance is created between the blade
and the grounded arbor flange and washer. A typical thickness is
approximately 1/8-inch, although thicker or thinner washers may be
used. In addition, some or all of the arbor components may be
formed from non-conductive materials, such as ceramics, to reduce
or eliminate the need for bushing 1570.
[0032] An arbor nut 1580 holds the entire blade assembly on arbor
42. Friction established by tightening the arbor nut allows torque
from the arbor to be transmitted to the saw blade. It is
preferable, although not essential, that the blade be able to slip
slightly on the arbor in the event of a sudden stop by the brake to
reduce the mass that must be stopped and decrease the chance of
damage to the blade, arbor, and/or other components in the drive
system of the saw. Alternatively, a threaded arbor bolt may be used
in place of nut 1580. The arbor bolt has a threaded shaft that is
received into arbor 40, and a head that retains the blade assembly
on the arbor.
[0033] Furthermore, it may be desirable to construct the bushing
from a material that is soft enough to deform when the blade is
stopped suddenly. For example, depending on the type of braking
system used, a substantial radial impact load may be transmitted to
the arbor when the brake is actuated. A deformable bushing can be
used to absorb some of this impact and reduce the chance of damage
to the arbor. In addition, proper positioning of the brake in
combination with a deformable bushing may be employed to cause the
blade to move away from the user upon activation of the brake, as
will be discussed in further detail below.
[0034] In an alternative embodiment, the arbor and/or part of its
supporting framework is electrically isolated from ground instead
of isolating the blade from the arbor. One benefit of this
embodiment is that if the blade is electrically connected to the
arbor, then the arbor itself can be used to capacitively couple the
input signal from charge plate 44 to charge plate 46. An example of
such a configuration is disclosed in U.S. Provisional Patent
Application Ser. No. 60/182,866, filed Feb. 16, 2000, which is
incorporated herein by reference.
[0035] Any of the various configurations and arrangements of safety
system 18 described above may be implemented in miter saw 1510. In
the exemplary embodiment depicted in FIGS. 3 and 4, safety system
18 is a cartridge-type system. With the exception of charging
plates 44 and 46, both brake mechanism 28 and detection subsystem
22 are contained within cartridge 80. Examples of suitable
cartridges 80 are disclosed in U.S. Provisional Patent Application
Ser. No. 60/225,201, filed Aug. 14, 2000, entitled "Replaceable
Brake Mechanism For Power Equipment," U.S. patent application Ser.
No. ______, filed Aug. 13, 2001, entitled "Replaceable Brake
Mechanism For Power Equipment," U.S. Provisional Patent Application
Ser. No. 60/225,212, filed Aug. 14, 2000, entitled "Brake
Positioning System," and U.S. patent application Ser. No. ______,
filed Aug. 13, 2001, entitled "Brake Positioning System," the
disclosures of which are incorporated by reference. The cartridge
is configured to be mounted on the front inside surface of housing
1516 by any suitable fastening mechanism 1522, such as by one or
more bolts 1524. The housing may include a movable panel or door
1526 to allow access to the cartridge. Alternatively, cartridge 80
may be inserted into a port or opening in the housing. A pawl 60 is
mounted in the cartridge and is positionable in front of the blade.
Examples of suitable pawls and brake mechanisms incorporating the
same are disclosed in U.S. Provisional Patent Application Ser. No.
60/225,169, filed Aug. 14, 2000, entitled "Brake Mechanism For
Power Equipment," U.S. patent application Ser. No. ______, filed
Aug. 13, 2001, entitled "Brake Mechanism For Power Equipment, U.S.
Provisional Patent Application Ser. No. 60/225,170, filed Aug. 14,
2000, entitled "Spring-Biased Brake Mechanism For Power Equipment,"
and U.S. patent application Ser. No. ______, filed Aug. 13, 2001,
entitled "Spring-Biased Brake Mechanism For Power Equipment," the
disclosures of which are incorporated by reference. It should be
understood that cartridge 80 is not essential to all embodiments of
the miter saw disclosed herein and that miter saw 1510 may be
implemented without requiring a cartridge. Instead, the brake
mechanism of the safety system may be mounted in any suitable
operative position relative to blade 40 without being housed in a
cartridge.
[0036] Charge plates 44 and 46 are attached to the inside wall of
housing 1516 by one or more mounts 1528. The mounts are attached to
the housing by any suitable fastening mechanism 1522, such as by
bolts 1532, and are configured to position the charge plates
parallel to, and closely adjacent, blade 40. As shown in FIG. 4,
the spacing between the charge plates and the blade is preferably
much less than the spacing between the charge plates and the
housing to minimize any parasitic capacitance between the charge
plates and the housing. Alternatively, the housing may be
constructed from an electrically nonconductive material.
[0037] Cables 1534 and 1536 connect the charge plates to safety
system's electronics unit, which may be housed in the cartridge or
elsewhere on the miter saw. Electrical power for safety system 18
is provided by any suitable source, such as a cable extending from
motor assembly 16. In addition to actuating the engagement of the
pawl with the blade, the electronics unit within cartridge 80 is
also configured to interrupt the power to motor assembly 16 when
contact between the user's body and the blade is detected.
[0038] A circular blade spinning at several thousand revolutions
per minute possesses a substantial amount of angular momentum.
Thus, when the pawl engages a circular blade such as is found on
miter saw 1510 and stops the blade within a few milliseconds, the
angular momentum must be transferred to the brake mechanism,
including pawl 60. Because the swing arm of the miter saw is free
to pivot in the direction of blade rotation, the angular momentum
of the blade may be transferred to the swing arm when the blade is
suddenly stopped, causing the swing arm to swing downward. This
sudden and forceful downward movement of the swing arm may cause
injury to the user if a portion of the user's body is beneath the
blade. Therefore, an alternative embodiment of miter saw 1510
includes means for preventing the swing arm from moving downward
when the blade is stopped. In addition, the pawl typically is
mounted at the front of the miter saw to urge the blade to climb
upward away from the user (i.e., deforming the plastic bushing)
when engaged by the pawl.
[0039] It will be appreciated that there are many suitable means
for preventing sudden downward movement of the swing arm. For
example, the pivotal connection between the swing arm and the base
of the miter saw may be electrically lockable, for example using an
electromagnetic leaf brake, to prevent the arm from pivoting. The
signal to lock the connection may be provided by the detection
system. An example of a miter saw with a lockable swing arm is
shown in FIG. 5, in which an electromagnetic leaf brake is
schematically illustrated at 1537. Alternatively, or additionally,
a shock absorber may be connected between the swing arm and the
base to limit the speed with which the swing arm can pivot relative
to the base. This arrangement also serves to limit how far the
blade moves between the time contact between the blade and user is
detected, and the time the blade is stopped by the pawl. An example
of a miter saw with a shock absorber 1539 is shown in FIG. 6
extending between the base and swing arm of the miter saw. While
there are many other ways of connecting the swing arm to the base
to prevent sudden movement of the arm toward the base, most such
arrangements transfer the angular momentum to the swing arm/base
assembly. Depending on the weight and balance of the saw, the
angular momentum may be sufficient to cause the entire saw to
overturn. Therefore, it may be desirable to secure the base to a
stable surface with clamps, bolts, etc.
[0040] Alternatively, the miter saw can be configured to absorb any
angular momentum without allowing the swing arm to move downward.
For example, the exemplary embodiment depicted in FIGS. 3 and 4 is
configured with a pivotal motor assembly to allow the blade to move
upward into the housing upon engagement with the pawl. Motor
assembly 16 is connected to housing 1516 via pivot bolt, or axle,
1540, allowing the motor assembly to pivot about bolt 1540 in the
direction of blade rotation. A spring 1542 is compressed between
the housing and an anchor 1544 to bias the motor assembly against
the direction of blade rotation. The motor assembly may include a
lip 1546, which slides against a flange 1548 on the housing to hold
the end of the motor assembly opposite the pivot bolt against the
housing.
[0041] When the saw is in use, spring 1542 holds the motor assembly
in a normal position rotated fully counter to the direction of
blade rotation. However, once the pawl is released to engage the
blade, the motor assembly and blade to pivot upward against the
bias of the spring. In this embodiment, the pawl is positioned at
the front of the blade so that the pivot bolt 1540 is between the
pawl and the arbor. This arrangement encourages the blade to move
upward into the housing when stopped. The spring is selected to be
sufficiently strong to hold the motor assembly down when cutting
through a workpiece, but sufficiently compressible to allow the
blade and motor assembly to move upward when the blade is
stopped.
[0042] While one exemplary implementation of safety system 18 in
the context of a miter saw has been described, the invention should
not be seen as limited to any particular implementation as the
configuration and arrangement of safety system 18 may vary among
miter saws and applications. For example, the pivoting motor
assembly configuration may also be combined with one or more of the
other systems described above which prevent the swing arm from
pivoting suddenly toward the base. Further, it will be appreciated
that the blade and motor assembly may be configured in any of a
variety of ways to at least partially absorb the angular momentum
of the blade.
[0043] FIG. 7 shows an alternative configuration of miter saw 1510
adapted to absorb the angular momentum of the blade. In this
configuration, the miter saw includes two swing arms 1550 and 1552.
One end 1554 of each swing arm is connected to base 1512, and the
opposite end 1556 of each swing arm is connected to housing 1516,
blade 40, and/or the motor assembly (not shown). The position of
the swing arms relative to each other may vary depending on the
swing arm motion desired. In FIG. 7, swing arm 1550 is connected to
base 1512 somewhat below and forward of swing arm 1552. Typically,
the motor assembly is rigidly attached to end 1556 of swing arm
1550, while housing 1516 is connected to rotate about end 1556 of
swing arm 1550. End 1556 of swing arm 1552 is connected only to the
housing. This arrangement replicates the motion of the motor
assembly and trigger found on many conventional miter saws.
Alternatively, the motor assembly may be connected to rotate about
end 1556 of swing arm 1550 along with the housing.
[0044] The configuration shown in FIG. 7 causes the housing and/or
motor assembly to rotate as the swing arms pivot. Significantly,
when the swing arms move upward, the housing and/or motor assembly
rotate in the same direction in which the blade rotates during
cutting. As a result, when the pawl engages the blade and transfers
the angular momentum of the blade to the housing and/or motor
assembly, the housing and/or motor assembly tend to rotate in the
same direction as the blade. This causes the swing arms to pivot
upward, drawing the blade away from the workpiece and the user's
body. Thus, as described above, the miter saw configuration
illustrated in FIG. 7 is adapted to absorb the angular momentum of
the blade and translate that angular momentum into an upward force
on the swing arm.
[0045] The configuration shown in FIG. 7 and described above
illustrates a further alternative embodiment of a miter saw with
safety system 18. Specifically, the safety system may be configured
to move the blade of the cutting tool rapidly away from the user
when contact with the user's body is detected in addition to, or
instead of, stopping the blade. This alternative embodiment may be
implemented in the context of any of the cutting tools described
herein. For example, a table saw implemented with safety system 18
may include a swing arm adapted to pivot downward to pull the blade
beneath the upper surface of the saw when a dangerous, or
triggering, condition is detected, such as contact between the user
and the blade while the blade is rotating. A spring (not shown) may
be coupled to the swing arm to increase the speed with which it
drops downward. It will be appreciated that similar implementations
may be configured in the context of all the saws described herein.
In the case of the miter saw, a electromagnetic leaf brake can be
used to stop the movement of the arm upon contact with a user. In
addition, the restraining mechanism can be used to release a spring
to push the arm upward upon contact of the blade and user. With
such systems, it may not be necessary to abruptly stop the blade to
avoid injury.
[0046] Another example of a miter saw 1510 constructed according to
the present invention is shown in FIG. 8. As shown, saw 1510
illustrates another suitable mechanism for stopping the sudden
downward movement of swing arm 1514 when safety system 18 is
actuated and pawl 60 engages blade 40. Swing arm 1514 includes a
cam portion 1560 having a cam surface 1562. Cam portion 1560 may be
integral with the swing arm and housing 1516. A stopping pawl 1564
is mounted to vertical support 1566 adjacent cam surface 1562, and
an actuator 1568 is positioned adjacent pawl 1564. The actuator is
operatively coupled to the control and detection subsystems
associated with brake pawl 60 and cartridge 80 so that when pawl
brake pawl 60 is released, actuator 1568 engages stopping pawl
1564. During normal operation, actuator 1568 maintains the pawl
spaced-apart from cam surface 1562. However, once contact between
the blade and the user's body is detected, the detection system
sends an actuation signal to actuator 1568, which may be the same
or a different signal that triggers the release of brake pawl 60.
In any event, upon receipt of the actuation signal, the actuator
drives against stopping pawl 1564, causing it to pivot into cam
surface 1562, preventing further movement of the swing arm.
Stopping pawl 1564 may be constructed or coated with a high
friction material such as rubber, and/or may be configured with
teeth, etc., to increase its braking action. Cam portion 1560 may
be modified so that it extends as far as possible from the point
around which it pivots, in order to provide as great a moment arm
as possible to help stop the downward motion of the swing arm.
[0047] Safety system 22 may also protect the user from injury by
wrapping the blade with a protective surface upon detection of a
dangerous, or triggering, condition. Alternatively, or
additionally, system 22 may protect the user by disabling the teeth
of the blade. Examples of these embodiments of safety system 22 are
disclosed in U.S. Provisional Patent Application Ser. No.
60/225,206, filed Aug. 14, 2000, entitled "Cutting Tool Safety
System," and U.S. patent application Ser. No. ______, filed Aug.
13, 2001, entitled "Cutting Tool Safety System," which are hereby
incorporated by reference.
[0048] 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 subcombinations
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.
[0049] It is believed that the following claims particularly point
out certain combinations and subcombinations that are directed to
one of the disclosed inventions and are novel and non-obvious.
Inventions embodied in other combinations and subcombinations 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.
* * * * *