Note: Descriptions are shown in the official language in which they were submitted.
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IMPACT TOOL
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation-in-part of co-pending U.S.
Patent Application
No. 13/293,462 filed on November 10, 2011, which claims priority to U.S.
Provisional Patent
Application No. 61/414,296 filed on November 16, 2010, the entire contents of
both of which
are incorporated herein by reference.
FIELD OF THE INVENTION
[0002] The present invention relates to tools, and more particularly to
power tools.
BACKGROUND OF THE INVENTION
[0003] Impact tools or wrenches are typically utilized to provide a
striking rotational
force, or intermittent applications of torque, to a tool element and workpiece
(e.g., a fastener) to
either tighten or loosen the fastener. Conventional impact wrenches (i.e.,
either pneumatic or
battery-powered) typically include a pistol grip-style housing having a handle
portion grasped by
the operator of the impact wrench and a motor portion extending from the
handle portion. As a
result of such a configuration, conventional impact wrenches are often
difficult to maneuver
within small work spaces.
SUMMARY OF THE INVENTION
[0004] The invention provides, in one aspect, an impact tool including a
housing, a motor
supported in the housing and defining a first axis, an output shaft rotatably
supported in the
housing about a second axis oriented substantially normal to the first axis,
an impact mechanism
coupled between the motor and the output shaft and operable to impart a
striking force in a
rotational direction to the output shaft, and a battery electrically connected
to the motor and
oriented along a third axis substantially parallel with and offset from the
first axis.
[0005] Other features and aspects of the invention will become apparent
by consideration
of the following detailed description and accompanying drawings.
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BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 is a front perspective view of an impact tool according to
an embodiment
of the invention.
[0007] FIG. 2 is a side view of the impact tool of FIG. 1.
[0008] FIG. 3 is an exploded perspective view of the impact tool of FIG.
1.
[0009] FIG. 4 is a cross-sectional view of the impact tool of FIG. 1
through line 4--4 in
FIG. 1.
[0010] FIG. 5 is a front perspective view of an impact tool according to
a second
embodiment of the invention.
[0011] FIG. 6 is a side view of the impact tool of FIG. 5.
[0012] FIG. 7 is an exploded perspective view of the impact tool of FIG.
5.
[0013] FIG. 8 is a cross-sectional view of the impact tool of FIG. 5
through line 8--8 in
FIG. 5.
[0014] FIG. 9 is an exploded perspective view of a portion of an impact
tool according to
a third embodiment of the invention.
[0015] FIG. 10 is an assembled, cross-sectional view of a portion of the
impact tool of
FIG. 9.
[0016] Before any embodiments of the invention are explained in detail,
it is to be
understood that the invention is not limited in its application to the details
of construction and the
arrangement of components set forth in the following description or
illustrated in the following
drawings. The invention is capable of other embodiments and of being practiced
or of being
carried out in various ways. Also, it is to be understood that the phraseology
and terminology
used herein is for the purpose of description and should not be regarded as
limiting.
DETAILED DESCRIPTION
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100171 FIGS. 1-4 illustrate a first embodiment of an impact tool 10
including a drive end
14 having a non-cylindrical bore 18 (FIG. 4) within which a fastener, a tool
bit, or a driver bit 20
may be received. In the illustrated construction of the tool 10, the non-
cylindrical bore 18
includes a hexagonal cross-sectional shape. However, the non-cylindrical bore
18 may be
shaped in any of a number of different ways to receive any of a number of
different fasteners,
tool bits, and/or driver bits 20. The drive end 14 includes an output shaft 22
(FIG. 3) having a
detent (not shown) utilized to lock or axially secure the fastener, tool bit,
and/or driver bit 20 to
the drive end 14 of the tool 10, a sleeve 30 positioned over the output shaft
22 for actuating the
detent between a locked and an unlocked configuration, and a biasing member
(e.g., a
compression spring 26) for biasing the sleeve 30 toward a position in which
the detent is in the
locked configuration. Alternatively, the detent, the sleeve 30, and the spring
26 may be omitted
from the output shaft 22, such that the fastener, tool bit, and/or driver bit
20 is not lockable to the
drive end 14 of the tool 10.
[0018j With reference to FIG. 4, the impact tool 10 includes a housing
34, a motor 38
supported in the housing 34, and a transmission 42 (FIG. 3) operably coupled
to the motor 38 to
receive torque from the motor 38. The output shaft 22 is rotatable about an
axis 46 and operably
coupled to the transmission 42 to receive torque from the transmission 42.
[0019] In the illustrated construction of the tool 10, the housing 34
includes a motor
support portion 48 in which the motor 38 is contained, and a battery support
portion 50 in which
a battery pack 54 is removably received. The battery pack 54 is located
directly below the motor
38 from the frame of reference of FIG. 4, such that the motor 38 and the
battery pack 54 define
respective parallel axes 55, 56. As is discussed below, the motor support
portion 48 is grasped
by the user of the tool 10 during operation. Because of the positioning of the
battery pack 54
relative to the motor 38 within the housing 34, the motor 38 and the battery
pack 54 substantially
fit within the envelope of the user's wrist to facilitate maneuverability of
the tool 10 in small
work spaces. In other words, the impact tool 10 is sufficiently compact to
permit the user to
maneuver the tool 10 throughout the range of motion of the user's wrist
without the housing 34
or the battery pack 54 interfering with the user's arm.
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[0020] The battery pack 54 is electrically connected to the motor 38 via
a variable-speed
trigger switch 60 to provide power to the motor 38. As shown in FIG. 4, the
trigger switch 60 is
located on a side wall 64 of the housing 34 between the respective axes 55, 56
of the motor 38
and battery pack 54 to provide ergonomic access to the trigger switch 60 while
the user is
grasping the motor support portion 48 of the housing 34. The battery pack 54
is a 12-volt power
tool battery pack 54 and includes three lithium-ion battery cells.
Alternatively, the battery pack
54 may include fewer or more battery cells to yield any of a number of
different output voltages
(e.g., 14.4 volts, 18 volts, etc.). Additionally or alternatively, the battery
cells may include
chemistries other than lithium-ion such as, for example, nickel cadmium,
nickel metal-hydride,
or the like. Alternatively, the tool 10 may include an electrical cord for
connecting the motor 38
to a remote electrical source (e.g., a wall outlet).
[0021] The tool 10 also includes a direction switch 68 (FIGS. 1 and 2)
that is toggled
between a first position, in which the motor 38 is activated to rotate the
output shaft 22 in a
forward (i.e., clockwise) direction, and a second position, in which the motor
38 is activated to
rotate the output shaft 22 in a reverse (i.e., counter-clockwise) direction.
[0022] The motor 38 is configured as a direct-current, can-style motor 38
having a motor
output shaft 58 upon which a pinion 62 is fixed for rotation (FIG. 3). In the
illustrated
construction of the tool 10, the pinion 62 is interference or press-fit to the
motor output shaft 58.
Alternatively, the pinion 62 may be coupled for co-rotation with the motor
output shaft 58 in any
of a number of different ways (e.g., using a spline fit, a key and keyway
arrangement, by
welding, brazing, using adhesives, etc.). As a further alternative, the pinion
62 may be integrally
formed as a single piece with the motor output shaft 58.
[0023] With reference to FIGS. 3 and 4, the transmission 42 includes a
single stage
planetary transmission 66 and a transmission output shaft 70 functioning as
the rotational output
=of the transmission 42. The transmission 42 also includes a gear case 74
within which the
planetary transmission 66 is received. The gear case 74 is fixed to the motor
38 (e.g., using
fasteners), and the combination of the gear case 74 and the motor 38 is
clamped between the
opposite halves of the housing 34 (FIG. 3).
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[0024] With continued reference to FIG. 3, the planetary transmission 66
includes an
outer ring gear 94, a carrier 98 rotatable about the motor axis, and planet
gears 102 rotatably
coupled to the carrier 98 about respective axes radially spaced from the motor
axis 55. The outer
ring gear 94 includes radially inwardly-extending teeth 106 that are
engageable by corresponding
teeth 110 on the planet gears 102. The outer ring gear 94 also includes
radially outwardly-
extending protrusions 114, and the gear case 74 includes corresponding slots
(not shown) within
which the protrusions 114 are received to rotationally fix the outer ring gear
94 to the gear case
74, and therefore the housing 34. Alternatively, the outer ring gear 94 may be
fixed to the gear
case 74 in any of a number of different ways (e.g., using snap-fits, an
interference or press-fit,
fasteners, adhesives, by welding, etc.) As a further alternative, the outer
ring gear 94 may be
integrally formed as a single piece with the gear case 74.
[0025] The carrier 98 includes an aperture 134 having a non-circular
cross-sectional
shape (e.g., a "double-D") corresponding to that of a first end 118 of the
transmission output
shaft 70 (FIG. 3). As such, the first end 118 of the transmission output shaft
70 is received
within the aperture 134 and co-rotates with the carrier 98 at all times in
response to activation of
the motor 38. Alternatively, the transmission output shaft 70 may be non-
rotatably coupled to
the carrier 98 in any of a number of different ways.
[0026] With continued reference to FIG. 3, the tool 10 includes an impact
mechanism
138 including an impact mechanism housing 140 clamped between the opposed
halves of the
tool housing 34 and a drive shaft 142 supported for rotation within the
housing 140. In the
illustrated construction of the tool 10, the housing 140 includes an upper
housing portion 126 and
a lower housing portion 130 interconnected to the upper housing portion 126
(e.g., using
fasteners, etc.). The upper housing portion 126 includes a support 143 in
which a needle bearing
145 is received (FIG. 4). A cylindrical first end 148 of the drive shaft 142
is supported by the
needle bearing 145 for rotation relative to the housing 140. An opposite,
second end 152 of the
drive shaft 142 is piloted or supported for rotation relative to the housing
140 by the output shaft
22.
[0027] With reference to FIGS. 3 and 4, the impact tool 10 also includes
a right-angle
bevel gear arrangement 156 coupled between the motor 38 and the drive shaft
142. Particularly,
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the bevel gear arrangement 156 includes a bevel ring gear 160 coupled for co-
rotation with the
drive shaft 142 and a bevel pinion gear 164 engaged with the bevel ring gear
160 and coupled for
co-rotation with a second end 168 of the transmission output shaft 70 (e.g.,
using an interference
fit, a key and keyway arrangement, etc.). As shown in FIG. 4, the bevel pinion
gear 164 is
coaxial with the motor axis 55, and the bevel ring gear 160 is coaxial with
the axis 46 of the
output shaft 22. As such, the respective axes 55, 46 of the motor 38 and the
output shaft 22 are
oriented substantially normal to each other (i.e., at a right or 90-degree
angle).
100281 With reference to FIGS. 3 and 4, the impact mechanism 138 further
includes a
hammer 146 supported on the drive shaft 142 for rotation with the shaft 142,
and an anvil 150
coupled for co-rotation with the output shaft 22. In the illustrated
construction of the tool 10, the
anvil 150 is integrally formed with the output shaft 22 as a single piece and
includes opposed,
radially outwardly extending lugs 172 (FIG. 3).
[00291 The shaft 142 includes two V-shaped cam grooves 158 (only one of
which is
shown in FIG. 3) equally spaced from each other about the outer periphery of
the shaft 142.
Each of the cam grooves 158 includes two segments that are inclined relative
to the axis 46 in
opposite directions. The hammer 146 has opposed lugs 162 and two cam grooves
166 (FIG. 4)
equally spaced from each other about an inner periphery of the hammer 146.
Like the cam
grooves 158 in the shaft 142, each of the cam grooves 166 is inclined relative
to the axis 46. The
respective pairs of cam grooves 158, 166 in the shaft 142 and the hammer 146
are in facing
relationship such that a cam member (e.g., a ball 167, see FIG. 3) is received
within each of the
pairs of cam grooves 158, 166. The balls 167 and the cam grooves 158, 166
effectively provide
a cam arrangement between the shaft 142 and the hammer 146 for transferring
torque between
the shaft 142 and the hammer 146 between consecutive impacts of the lugs 162
upon the
corresponding lugs 172 on the anvil 150. The impact mechanism 138 also
includes a
compression spring 178 positioned between the hammer 146 and the bevel ring
gear 160 to bias
the hammer 146 toward the anvil 150. A thrust bearing 182 is positioned
between the hammer
146 and the spring 178 to permit relative rotation between the spring 178 and
the hammer 146.
100301 As previously discussed, the second end 152 of the drive shaft 142
is piloted or
supported for rotation by the combination of the anvil 150 and the output
shaft 22 (FIG. 4). The
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anvil 150, in turn, is supported for rotation within the impact mechanism
housing 140 by a
bushing 186. Alternatively, a roller bearing may be utilized in place of the
bushing 186.
[0031] In operation of the tool 10, the motor support portion 48 is
grasped by the user of
the tool 10 during operation. Because of the positioning of the battery pack
54 relative to the
motor 38 within the housing 34, the motor 38 and the battery pack 54
substantially fit within the
envelope of the user's wrist to facilitate maneuverability of the tool 10 in
small work spaces.
Furthermore, the tool 10 may access small work spaces that would otherwise be
inaccessible to
conventional impact tools or impact wrenches.
[0032] During operation, the motor 38 rotates the drive shaft 142,
through the
transmission 44 and the bevel gear arrangement 156, in response to actuation
of the trigger
switch 60. The hammer 146 initially co-rotates with the drive shaft 142 and
upon the first impact
between the respective lugs 162, 172 of the hammer 146 and anvil 150, the
anvil 150 and the
output shaft 22 are rotated at least an incremental amount provided the
reaction torque on the
output shaft 22 is less than a predetermined amount that would otherwise cause
the output shaft
22 to seize. However, should the reaction torque on the output shaft 22 exceed
the
predetermined amount, the output shaft 22 and anvil 150 would seize, causing
the hammer 146
to momentarily cease rotation relative to the housing 140 due to the inter-
engagement of the
respective lugs 162, 172 on the hammer 146 and anvil 150. The shaft 142,
however, continues to
be rotated by the motor 38. Continued relative rotation between the hammer 146
and the shaft
142 causes the hammer 146 to displace axially away from the anvil 150 against
the bias of the
spring 178 in accordance with the geometry of the cam grooves 158, 166 within
the respective
drive shaft 142 and the hammer 146.
[0033] As the hammer 146 is axially displaced relative to the shaft 142,
the hammer lugs
162 are also displaced relative to the anvil 150 until the hammer lugs 162 are
clear of the anvil
lugs 172. At this moment, the compressed spring 178 rebounds, thereby axially
displacing the
hammer 146 toward the anvil 150 and rotationally accelerating the hammer 146
relative to the
shaft 142 as the balls 167 move within the pairs of cam grooves 158, 166 back
toward their pre-
impact position. The hammer 146 reaches a peak rotational speed, then the next
impact occurs
between the hammer 146 and the anvil 150. In this manner, the fastener, tool
bit, and/or driver
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bit 20 received in the drive end 14 is rotated relative to a workpiece in
incremental amounts until
the fastener is sufficiently tight or loosened relative to the workpiece.
[0034] FIGS. 5-8 illustrate a second embodiment of an impact tool 10a,
with like
components as the impact tool 10 of FIGS. 1-4 being shown with like reference
numerals with
the letter "a".
[0035] With reference to FIGS. 7 and 8, the impact tool 10a includes an
actuation system
190 for automatically activating and deactivating the motor 38a without
requiring the user to
actuate a separate motor activation trigger. More particularly, the actuation
system 190 activates
the motor 38a in response to physical contact between the driver bit 20a and a
workpiece (e.g., a
fastener), and deactivates the motor 38a in response to removing physical
contact between the
driver bit 20a and the workpiece. In the illustrated embodiment of the impact
tool 10a, the
actuation system 190 includes a force sensor 194 in electrical communication
with the motor 38a
(e.g., via a high-level or master controller) and a linkage 198 extending
between the force sensor
194 and the driver bit 20a for transferring force applied to the driver bit
20a to the force sensor
194.
[0036] As explained in more detail below, the force sensor 194 measures
the magnitude
of the applied force through the linkage 198 and outputs an associated control
signal (e.g., via a
high-level or master controller) to the motor 38a which, in the illustrated
embodiment of the
impact tool 10a, is configured as a variable speed motor 38a. Upon initial
activation of the
motor 38a in response to a force input detected by the sensor 194, the
operating speed and/or
output torque of the motor 38a may thereafter be varied in response to the
measured force input
to the force sensor. For example, as the force applied to the force sensor 194
is progressively
increased, the operating speed and/or output torque of the motor 38a may also
be progressively
increased. Likewise, as the force applied to the force sensor 194 is
progressively decreased, the
operating speed and/or output torque of the motor 38a may also be
progressively decreased.
Such a force sensor is commercially available from Interlink of Camarillo,
California as part
number FSR400. Alternatively, the motor 38a may be configured as a single
speed and/or
constant torque motor such that only an "on/off' signal needs to be supplied
by the force sensor
194 to activate and deactivate the motor 38a, respectively.
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[0037] As a further alternative, the actuation system 190 may include a
potentiometer
rather than the force sensor 194 for activating the motor 38a and varying a
voltage applied to the
motor 38a for either changing the operating speed and/or output torque of the
motor 38a. In such
an embodiment of the impact tool 10a, the linkage 198 may interface with the
wiper of the
potentiometer for rotating the wiper in response to displacement of the
linkage 198.
[0038] With continued reference to FIGS. 7 and 8, the linkage 198
includes a first rod
202 proximate the driver bit 20a, a second rod 206 proximate the force sensor
194, and a biasing
element 210 (e.g., a compression spring) positioned between the rods 202, 206.
As shown in
FIG. 8, the drive shaft 142a includes a stepped cylindrical bore 214 that
progressively decreases
in diameter from a first or upper end 148a of the drive shaft 142a to an
opposite, second or lower
end 152a of the drive shaft 142a. The first rod 202 is located in a first
portion 218 of the stepped
cylindrical bore 214, with a large-diameter end 222 of the first rod 202 being
abutted with an
internal shoulder 226 defining one of the steps in the stepped cylindrical
bore 214, and a small-
diameter end 230 of the first rod 202 protruding from the second end 152a of
the drive shaft
142a. The small-diameter end 230 of the first rod 202 also extends partially
through a stepped
bore 234 within the anvil 150a and the output shaft 22a that is coaxial with
the stepped bore 214
within the drive shaft 142a. In the illustrated embodiment of the impact tool
10a, the linkage 198
also includes a disk-like spacer 238 positioned between the small-diameter end
230 of the first
rod 202 and the driver bit 20a. Like the large-diameter end 222 of the first
rod 202, the spacer
238 is abutted with an internal shoulder 242 defining a step in the bore 234
within the anvil 150a,
thereby limiting displacement of the spacer 238 between the second end 152a of
the drive shaft
142a and the shoulder 242. Therefore, the abutment of the large-diameter end
222 of the first
rod 202 with the shoulder 226, or the abutment of the small-diameter end 230
of the first rod 202
with the spacer 238, limits the extent to which the first rod 202 is
displaceable toward the output
shaft 22a. Alternatively, the spacer 238 may be omitted from the linkage 198,
and the driver bit
20a may directly contact the small-diameter end 230 of the first rod 202 in
response to a reaction
force applied to the driver bit 20a as a result of contact with a workpiece.
[0039] With continued reference to FIG. 8, the second rod 206 is located
in a second
portion 246 of the stepped cylindrical bore 214, with a large-diameter end 250
of the second rod
206 being abutted with another internal shoulder 254 defining one of the steps
in the bore 214,
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and a small-diameter end 258 of the second rod 206 protruding from the first
end 148a of the
drive shaft 142a and proximate the force sensor 194. The drive shaft 142a
includes an annular
retainer 262 that is interference fit within the bore 214 adjacent the second
end 152a of the drive
shaft 142a for maintaining the second rod 206 coaxial with the bore 214. The
actuation system
190 further includes another biasing element 266 (e.g., a compression spring)
positioned between
the retainer 262 and the large-diameter 250 end of the second rod 206 for
biasing the small-
diameter end 258 of the second rod 206 away from the force sensor 194.
100401 In an alternative embodiment of the impact tool 10a, the multi-
piece linkage 198
may be replaced with a single piece linkage configured as a contiguous rod
having a first end
engageable with the driver bit 20a and a second end proximate the force sensor
194.
100411 With reference to FIGS. 7 and 8, the impact tool 10a also includes
an illumination
assembly 270 configured to illuminate the workpiece during operation of the
impact tool 10a. In
the illustrated embodiment of the impact tool 10a, the illumination assembly
270 includes a light
274 (e.g., an LED) positioned within a translucent cover 278 proximate the
output shaft 22a for
illuminating the workpiece. With reference to FIG. 7, the illumination
assembly 270 also
includes a switch 282 for selectively electrically connecting the light 274 to
the battery 54a. The
switch 282 includes an actuator portion or a button 286 that is located on the
sidewall 64a of the
housing 34a at least partially between the motor axis 55a and the battery axis
56a, as shown in
FIG. 6, to facilitate actuation of the switch 282 by the user's thumb while
the motor support
portion 48a is grasped by the user's palm. Alternatively, the button 286 may
be located
elsewhere on the housing 34a, or the switch 282 may be omitted in lieu of
simultaneous
activation and deactivation of the light 274 with the motor 38a by the
actuation assembly 190.
100421 The impact tool 10a further includes a direction switch 68a (FIGS.
5 and 6) that is
manually toggled between a first position, in which the motor 38a is activated
to rotate the output
shaft 22a in a forward (i.e., clockwise) direction, and a second position, in
which the motor 38a
is activated to rotate the output shaft 22a in a reverse (i.e., counter-
clockwise) direction.
100431 In operation of the impact tool 10a, the actuation system 190 is
operable to
automatically activate the motor 38a in response to depressing the driver bit
20a against a
workpiece, thereby obviating the need for a separate, manually actuated motor
activation switch.
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Specifically, in response to a reaction force applied to the driver bit 20a,
the driver bit 20a is
displaced upward from the frame of reference of FIG. 8 to contact the spacer
238. Upon
contacting the spacer 238, both the spacer 238 and the first rod 202 are
displaced upward,
thereby unseating the large-diameter end 222 of the first rod 202 from the
shoulder 226 and
compressing the spring 210. Once the magnitude of the reaction force exceeds
the force exerted
by the spring 266, the large-diameter end 250 of the second rod 206 is
unseated from the
shoulder 254 and the small-diameter end 258 of the second rod 206 is displaced
toward the force
sensor 194. Thereafter, the small-diameter end 258 of the second rod 206
either directly or
indirectly applies a force to the force sensor 194 which, in turn, generates a
control signal (via a
high-level or master controller, as previously described) for activating the
motor 38a.
Optionally, as the force applied to the force sensor 194 is progressively
increased (i.e., in
response to a progressively increasing reaction force applied to the driver
bit 20a), the control
signal may cause the operating speed and/or output torque of the motor 38a to
also be
progressively increased for performing work on the workpiece at an increased
rate or delivering
an increased amount of torque to the workpiece. Once the motor 38a is
activated, the operation
of the impact tool 10a is otherwise identical to that described above in
connection with the
impact tool 10 of FIGS. 1-4.
[00441 Likewise, decreasing the applied force on the force sensor 194
causes the force
sensor 194 to generate a control signal to reduce the operating speed and/or
output torque of the
motor 38a. Further, removing the applied force from the force sensor 194
causes the force
sensor 194 to generate a control signal to deactivate the motor 38a.
100451 Although the actuation system 190 is described and illustrated in
connection with
the impact tool 10a, it may also be incorporated in a non-impact rotary power
tool (e.g., a driver
drill).
[0046] FIGS. 9 and 10 illustrate a third embodiment of an impact tool
10b, with like
components as the impact tool 10a of FIGS. 5-8 being shown with like reference
numerals with
the letter "b".
100471 With reference to FIGS. 9 and 10, the impact tool 10b includes an
actuation
system 290 for automatically activating and deactivating the motor 38b,
without requiring the
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user to actuate a separate motor activation trigger, in response to the
presence or absence of
physical contact between the driver bit 20b and a workpiece (e.g., a
fastener), respectively. The
actuation system 290 includes a microswitch 302, a linkage 294, and a magnet
assembly 296
positioned between the microswitch 302 and the linkage 294 (FIG. 9). The
magnet assembly
296 includes a housing 298 attached to the linkage 294 for displacement
therewith and a torsion
spring 306 mounted to the housing 298. The torsion spring 306 includes an arm
308 that is
engageable with the microswitch 302 for actuating the microswitch 302 which,
in the illustrated
embodiment of the actuation system 290, is normally open. With continued
reference to FIG. 9,
the actuation system 290 also includes a Hall-effect sensor 310 in electrical
communication with
the motor 38b (e.g., via a high-level or master controller). The Hall-effect
sensor interfaces with
a magnet 314 mounted in the housing 298 of the magnet assembly 296, of which
the magnet 314
is also a component. As explained in more detail below, the linkage 294 is
capable of displacing
the magnet assembly 296 toward the Hall-effect sensor 310, therefore causing
the arm 308 of the
torsion spring 306 to engage and actuate the microswitch 302. Following
actuation of the
microswitch 302, a continued application of force applied to the driver bit
20a reduces the gap
between the Hall-effect sensor 310 and the magnet 314.
[0048] The Hall-effect sensor 310 measures a proximity of the magnet 314
and outputs
an associated control signal (e.g., via a high-level or master controller) to
the motor 38b which,
in the illustrated embodiment of the impact tool 10b, is configured as a
variable speed motor 38b.
Upon initial activation of the motor 38b in response to the microswitch 302
being actuated, the
operating speed and/or output torque of the motor 38a may thereafter be varied
in response to the
proximity of the magnet 314 to the Hall-effect sensor 310. For example, as the
linkage 294
displaces the magnet 314 progressively closer to the Hall-effect sensor 310,
therefore decreasing
a distance between the magnet 314 and the Hall-effect sensor 310, the
operating speed and/or
output torque of the motor 38b may be progressively increased. Likewise, as
the distance
between the magnet 314 and the Hall-effect sensor 310 is progressively
increased, the operating
speed and/or output torque of the motor 38a may be progressively decreased.
[0049] With reference to FIGS. 9 and 10, the linkage 294 includes a rod
318 having a
first end 322 proximate the driver bit 20b and a second end 326 attached to
the magnet assembly
296. As shown in FIG. 10, the rod 318 is located within the stepped
cylindrical bore 214b, and
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includes a shoulder or flange 330 between the first end 322 and second end
326. The flange 330
of the rod 318 abuts the internal shoulder 226b that defines one of the steps
in the stepped
cylindrical bore 214b. The first end 322 of the rod 318 protrudes from the
second end 152b of
the drive shaft 142b and extends partially through the stepped bore 234b of
the anvil 150b. The
linkage 294 also includes the disk-like spacer 238b positioned between the
first end 322 of the
rod 318 and the driver bit 20b. Like the flange 330 of the rod 318, the spacer
238b is abutted
with an internal shoulder 242b defining a step in the bore 234b within the
anvil 150b, thereby
limiting displacement of the spacer 238 between the second end 152b of the
drive shaft 142b and
the shoulder 242b. Therefore, the abutment of the flange 330 of the rod 318
with the shoulder
226b, or the abutment of the first end 322 of the rod 318 with the spacer
238b, limits the extent
to which the rod 318 is displaceable toward the output shaft 22b.
Alternatively, the spacer 238b
may be omitted from the linkage 294, and the driver bit 20b may directly
contact the first end
322 of the rod 318 in response to a reaction force applied to the driver bit
20b as a result of
contact with a workpiece.
[0050] With continued reference to FIG. 10, the second end 326 of the rod
318 protrudes
from the first end 148b of the drive shaft 142a and is attached to the magnet
assembly 296. The
rod 318 is maintained coaxial within the bore 214b by the annular retainer
262b that is adjacent
the first end 148b of the drive shaft 142a. The actuation system 290 further
includes a biasing
element 334 (e.g., a compression spring) positioned between the retainer 262b
and the flange 330
of the rod 318 for biasing the second end 326 of the rod 318 and the magnet
314 away from the
Hall-effect sensor 310.
[0051] In operation of the impact tool 10b, the actuation system 290 is
operable to
automatically activate the motor 38b in response to depressing the driver bit
20b against a
workpiece. Specifically, in response to a reaction force applied to the driver
bit 20b, the driver
bit 20b is displaced upward from the frame of reference of FIG. 10 to contact
the spacer 238b.
Upon contacting the spacer 238b, both the spacer 238b and the rod 318 are
displaced upward,
thereby unseating the flange 330 from the shoulder 242b and compressing the
spring 334. The
magnet assembly 296 is also displaced upward with the rod 318, causing the arm
308 of the
torsion spring 306 to contact and actuate the microswitch 302, which closes
the microswitch 302.
Closing the microswitch 302 completes a circuit in the high-level or master
controller, which
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CA 02907328 2015-10-05
then generates a control signal to initially activate the motor 38b. After the
motor 38b is
activated and the reaction force applied to the driver bit 20b is
progressively increased, the
magnet 314 (which is attached to the second end 326 of the rod 318 through the
housing 298) is
displaced closer to the Hall-effect sensor 310. As the gap between the Hall-
effect sensor 310 and
the magnet 314 is decreased, the control signal output by the high-level or
master controller is
varied to cause the operating speed and/or output torque of the motor 38b to
be progressively
increased. Following actuation of the microswitch 302, continued displacement
of the magnet
314 toward the Hall-effect sensor 310 also causes the torsion spring arm 308
to deflect relative to
the housing 298, thereby providing a biasing force against the linkage 294 in
addition to the
biasing force provided by the spring 334.
[0052] Likewise, decreasing the reaction force applied to the driver bit
20b displaces the
second end 326 of the rod 318 and the magnet 314 away from the Hall-effect
sensor 310 as the
spring 334 biases the rod 318 downward, causing the high-level or master
controller to output a
control signal for reducing the operating speed and/or output torque of the
motor 38b. Further,
removing the driver bit 20b from the workpiece causes the magnet assembly 296,
and therefore
the torsion spring 306, to be biased away from microswitch 302. Upon being
disengaged by the
torsion spring 306, the microswitch 302 resumes an open state, thereby opening
a circuit in the
high-level or master controller to deactivate the motor 38b.
[0053] Although the actuation system 290 is described and illustrated in
connection with
the impact tool 10b, it may also be incorporated in a non-impact rotary power
tool (e.g., a driver
drill).
[0054] Various features of the invention are set forth in the following
claims.
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