U.S. patent application number 13/799177 was filed with the patent office on 2013-08-01 for electromagnetic mode change mechanism for power tool.
This patent application is currently assigned to BLACK & DECKER INC.. The applicant listed for this patent is BLACK & DECKER INC.. Invention is credited to John D. Cox, Robert S. Gehret, Michael T. Haupt, Joseph P. Kelleher, Robert G. Kusmierski, Robert J. Opsitos, JR., Daniel Puzio, Craig A. Schell.
Application Number | 20130192860 13/799177 |
Document ID | / |
Family ID | 48869283 |
Filed Date | 2013-08-01 |
United States Patent
Application |
20130192860 |
Kind Code |
A1 |
Puzio; Daniel ; et
al. |
August 1, 2013 |
ELECTROMAGNETIC MODE CHANGE MECHANISM FOR POWER TOOL
Abstract
A mode change mechanism for a power tool includes an actuator
with a permanent magnet. The actuator is moveable between a first
position for a first mode of operation, and a second position for a
second mode of operation. A first positioning member is adjacent
the first position composed of a ferromagnetic material to attract
the permanent magnet. A second positioning member is adjacent the
second position and composed of a ferromagnetic material to attract
the permanent magnet. An electromagnet may be energized to move the
actuator between the first position and the second position. When
the electromagnet is not energized and the actuator is in the first
position. the actuator is retained in the first position. When the
electromagnet is not energized and the actuator is in the second
position, the actuator is retained in the second position. When the
electromagnet is energized, the actuator moves between the first
and second positions.
Inventors: |
Puzio; Daniel; (Baltimore,
MD) ; Gehret; Robert S.; (Hampstead, MD) ;
Cox; John D.; (Lutherville, MD) ; Opsitos, JR.;
Robert J.; (Felton, PA) ; Kusmierski; Robert G.;
(York, PA) ; Schell; Craig A.; (Street, MD)
; Haupt; Michael T.; (Abingdon, MD) ; Kelleher;
Joseph P.; (Parkville, MD) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
BLACK & DECKER INC.; |
Newark |
DE |
US |
|
|
Assignee: |
BLACK & DECKER INC.
Newark
DE
|
Family ID: |
48869283 |
Appl. No.: |
13/799177 |
Filed: |
March 13, 2013 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13494325 |
Jun 12, 2012 |
|
|
|
13799177 |
|
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|
|
61500872 |
Jun 24, 2011 |
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Current U.S.
Class: |
173/47 ;
335/219 |
Current CPC
Class: |
B25F 5/00 20130101; B25B
23/1475 20130101; B25B 21/00 20130101; B25B 23/147 20130101; B25F
5/001 20130101; B25B 21/02 20130101; H01H 36/0073 20130101; B25B
23/0035 20130101 |
Class at
Publication: |
173/47 ;
335/219 |
International
Class: |
B25F 5/00 20060101
B25F005/00; B25B 21/00 20060101 B25B021/00 |
Claims
1. A power tool comprising: a housing coupleble to a source of
electric power; a motor disposed in the housing; an output shaft
received at least partially in the housing; a transmission in the
housing and coupled to the motor and the output shaft for
transmitting torque from the motor to the output shaft; a mode
change mechanism having an actuator, a positioning member, and an
electromagnet, the actuator including a permanent magnet and being
moveable between a first position for a first mode of operation of
the power tool, and a second position a second, different mode of
operation of the power tool, and the positioning member and the
electromagnet configured to (i) retain the actuator in the first
position when the electromagnet assembly is not energized and the
actuator is in the first position, (ii) retain the actuator in the
second position when the electromagnet assembly is not energized
and the actuator is in the second position, and (iii) move the
actuator from one of the first position and the second position to
the other of the first position and the second position when the
electromagnetic assembly is momentarily energized.
2. The power tool of claim 1, wherein the positioning member
comprises a second permanent magnet adjacent to the first position,
and stationary relative to the actuator, wherein the actuator
permanent magnet and the second permanent magnet are configured to
attract when the actuator is in the first position and repel when
the actuator is in the second position.
3. The power tool of claim 2, wherein the actuator permanent magnet
and the second permanent magnet each include an array of permanent
magnets, with a portion of each array arranged to exert an
attractive force between actuator permanent magnet and the second
permanent magnet, and a remaining portion of each array of the
permanent magnets arranged to exert a repulsive force between
actuator permanent magnet and the second permanent magnet.
4. The power tool of claim 2, wherein the electromagnet can be
momentarily energized by current flowing in a first direction to
move the actuator from the first position to the second position,
and can be momentarily energized by current flowing in a second
opposite direction to move the actuator from the second position to
the first position.
5. The power tool of claim 1, wherein the positioning member
comprises a first positioning member adjacent the first position
and composed of a ferromagnetic material to attract the permanent
magnet when the actuator is in the first position, and a second
positioning member adjacent the second position and composed of a
ferromagnetic material to attract the permanent magnet when the
actuator is in the second position.
6. The power tool of claim 5, wherein the electromagnet comprises a
first electromagnet adjacent to the first position and a second
electromagnet adjacent to the second position, such that when one
of the first electromagnet and the second electromagnet is
energized, the actuator moves from the first position to the second
position, and when the other of the first electromagnet and the
second electromagnet is energized, the actuator moves from the
second position to the first position.
7. The power tool of claim 6, further comprising a control circuit
configured to control energization of the first and second
electromagnets in response to an input condition, the input
condition comprising one of a user selection of a desired power
tool operating condition and a sensed power tool operating
condition.
8. The power tool of claim 1, wherein the actuator, the positioning
member, and the electromagnet comprise a portion of a clutch, the
clutch having an input member coupled to the transmission, an
output member coupled to the output shaft, and a coupling device
movable between a driving position in which torque is transmitted
from the input member to the output member and a clutching position
in which torque transmission from the input member to the output
member is interrupted, and wherein when the actuator is in the
first position, the actuator retains the coupling member in the
driving position, and when then actuator is in the second position,
the actuator allows the coupling member to move to the clutching
position.
9. The power tool of claim 8, wherein the input member comprises an
input sleeve defining a radial bores, the output member comprises
an output cylinder received in the input sleeve defining a groove,
the coupling member comprises a drive ball received in the bore,
and the actuator comprises a actuation sleeve received over the
input sleeve, wherein when the actuation sleeve is in the first
position, the ball is retained in the groove to transmit torque
from the input sleeve to the output cylinder, and when the
actuation sleeve is in the second position, the ball is permitted
to escape the groove to interrupt torque transmission from the
input sleeve to the output cylinder.
10. The power tool of claim 8, wherein the input member comprises a
ring gear of the transmission having a recess, the output member
comprises a portion of the output shaft, the actuator comprises a
sleeve, and the coupling member comprises a leg extending from the
sleeve, wherein when the sleeve is in the first position, the leg
engages the recess to inhibit rotation of the ring gear, which
enables torque transmission to the output member, and when the
sleeve is in the second position, the leg does not engage the
recess to allow rotation of the ring gear, which interrupts torque
transmission to the output member.
11. The power tool of claim 1, wherein the actuator, the
positioning member and the electromagnet comprise a portion of a
tool holder, the tool holder coupled to the output shaft for
releasably retaining a power tool accessory, wherein when the
actuator is in the first position, the accessory is retained by the
tool holder, and when the actuator is in the second position the
accessory is releasable from the tool holder.
12. The power tool of claim 11, wherein the tool holder comprises a
socket drive having a retractable retention pin and a linkage
coupled to the retention pin for selectively retracting the
retention pin, and wherein the actuator comprises a ring configured
to move the linkage and the retention pin between a retention
position and a release position when the actuator is in the first
position and the second position, respectively.
13. The power tool of claim 1, further comprising a stop to prevent
contact between the actuator and the positioning member when the
actuator is in the first position.
14. A mode change mechanism for a power tool, the mode change
mechanism comprising: an actuator including a permanent magnet and
being moveable between a first position for a first mode of
operation of the power tool, and a second position a second,
different mode of operation of the power tool; a first positioning
member adjacent the first position and composed of a ferromagnetic
material to attract the permanent magnet when the actuator is in
the first position; a second positioning member adjacent the second
position and composed of a ferromagnetic material to attract the
permanent magnet when the actuator is in the second position; and
an electromagnet configured to be energized to move the actuator
between the first position and the second position, wherein (i)
when the electromagnet is not energized and the actuator is in the
first position. the actuator is retained in the first position,
(ii) when the electromagnet is not energized and the actuator is in
the second position, the actuator is retained in the second
position, and (iii) when the electromagnet is energized, the
actuator moves from one of the first and second positions to the
other of the first and second positions.
15. The mode change mechanism of claim 13, wherein the
electromagnet comprises a first electromagnetic coil adjacent the
first position, and a second electromagnetic coil adjacent the
second position.
16. The mode change mechanism of claim 14, wherein energizing the
first electromagnetic coil creates a magnetic force to move the
permanent magnet and the actuator away from the first positioning
member to the second position, and energizing the second
electromagnetic coil creates a magnetic force to move the permanent
magnet and the actuator away from second positioning member ember
and to the first position.
17. The mode change mechanism of claim 13, wherein energizing the
electromagnet by causing current to flow in a first direction
creates a magnetic force to move the permanent magnet and the
actuator away from the first positioning member and to the second
position, and energizing the electromagnet by causing current to
flow in a second opposite direction creates a magnetic force to
move the permanent magnet and the actuator away from the second
positioning member and to the first position.
18. The mode change mechanism of claim 13, further comprising a
first stop to prevent contact between the actuator and the first
positioning member when in the first position, and a second stop to
prevent contact between the actuator and the second positioning
member when in the second position.
19. A method of operating a mode change mechanism of a power tool,
the method comprising: determining whether the power tool should be
operating in a first mode of operation or a second mode of
operation; determining whether an actuator that includes a
permanent magnet is in a first position that causes the power tool
to operate in the first mode of operation or a second position that
causes the power tool to operation in the second mode of operation;
energizing an electromagnet to cause the actuator and the permanent
magnet to move between the first position and the second position
if the actuator is in the first position and the power tool should
be operating in the second mode of operation, or if the actuator is
in the second position and the power tool should be operating in
the first mode of operation; retaining the actuator, without
energizing the electromagnet, in the first position if the actuator
is in the first position and the power tool should be operating in
the first mode of operation, or in the second position if the
actuator is in the second position and the power tool should be
operating in the second mode of operation.
20. The method of claim 17, wherein retaining the actuator
comprises providing a first ferromagnetic positioning member
adjacent the first position to attract the permanent magnet when
the actuator is in the first position, and providing a second
ferromagnetic positioning member adjacent the second position to
attract the permanent magnet when the actuator is in the second
position.
21. The method of claim 17, wherein energizing the electromagnet
comprises energizing a first electromagnetic coil adjacent the
first position to create a magnetic force that moves the permanent
magnet and the actuator away from the first position to the second
position when the actuator is in the first position and should be
in the second position, and energizing a second electromagnetic
coil adjacent the second position to create a magnetic force that
moves the permanent magnet and the actuator away from the second
position to the first position when the actuator is in the second
position and should be in the first position.
22. The method of claim 17, wherein energizing the electromagnet
comprises causing current to flow through the electromagnet in a
first direction to create a magnetic force that moves the permanent
magnet and the actuator away from the first position to the second
position when the actuator is in the first position and should be
in the second position, and causing current to flow through the
electromagnet in a second opposite direction to create a magnetic
force that moves the permanent magnet and the actuator away from
the second position to the first position when the actuator is in
the second position and should be in the first position.
Description
PRIORITY CLAIMS
[0001] This application claims priority under 35 U.S.C. .sctn.120
as a continuation-in-part of U.S. patent application Ser. No.
13/494,325, filed Jun. 12, 2012 (published as U.S. Patent App. Pub.
No. 2012/0325509), which claims priority under 35 U.S.C.
.sctn.119(e) to U.S. Provisional Patent Application No. 61/500,872,
filed Jun. 24, 2011. Each of the aforementioned patent applications
is hereby incorporated by reference.
TECHNICAL FIELD
[0002] This application relates to an electromagnetic mode change
mechanism for changing the mode of operation of a power tool.
BACKGROUND
[0003] This section provides background information related to the
present disclosure which is not necessarily prior art. There are
various examples of power tools that include a mode change
mechanism that is selectively movable to change a mode of operation
of the power tool. Many such power tools include a user actuated
mechanical button or switch positioned on the housing to
selectively move the mode change mechanism. In other of these power
tools, the mode change mechanism may be selectively moveable by
another mechanical device in response to a tool condition, e.g., a
spring that moves an actuator in response to an output torque.
[0004] U.S. Pat. No. 7,452,304, which is incorporated by reference,
discloses a power tool with a multi-speed transmission that
includes a plurality of planetary gear stages. One or more of the
ring gears of the planetary gear transmission are selectively
moveable by actuation of a mechanical switch on the housing to
selectively engage different sets of planet gears and change the
overall speed reduction ratio of the transmission.
[0005] U.S. Pat. No. 7,717,192, which is incorporated by reference,
discloses a power tool with a selectively moveable collar that
changes the mode of operation of the tool between a low speed mode,
a high speed mode, and a hammer mode. Rotation of the collar causes
movement of a shift pin to change the mode of operation.
[0006] U.S. Patent App. Pub. No. 2011/0152029, which is
incorporated by reference, discloses a hybrid impact driver and
drill with a selector that is selectively moveable to change
between an impact mode and a drilling mode, as well as to change a
speed setting of the transmission.
[0007] U.S. Patent App. Pub. No. 2012/0074658, which is
incorporated by reference, discloses a power tool with a tool bit
holder integrated into the power tool housing. The housing includes
a button or rotational switch that is moveable to move a shifter
between a first position that locks a tool bit in the holder, and a
second position that enables release of the tool bit from the
holder.
[0008] U.S. Patent App. Pub. No. 2012/0325509 (to which this
application claims priority), which is incorporated by reference,
discloses an impact wrench with a socket drive for receiving a
socket wrench accessory. The socket drive includes a moveable
retaining pin for selectively retaining and releasing the socket
wrench accessory from the socket drive. The power tool includes a
button or switch for selectively moving the retaining pin to retain
the socket wrench accessory on the socket drive or to release the
socket wrench accessory from the socket drive.
[0009] U.S. Pat. No. 8,347,750, which is incorporated by reference,
discloses a power tool with a transmission that includes a radially
expanding clutch assembly. The clutch assembly includes a shaft
member that can receive an input torque and a gear member that can
provide an output torque. The radially expanding clutch assembly
also includes a clutch spring that selectively contains rolling
members within longitudinal grooves in the shaft member. In the
drive condition the rolling members are held in the grooves by the
spring, and torque is transmitted from the shaft member to the gear
member. In the clutch out condition, the spring expands, allowing
the rolling members to move out of the grooves, which interrupts
torque transmission from the shaft member to the gear member.
[0010] U.S. Pat. No. 7,452,304, which is incorporated by reference,
discloses a power tool with a torque clutch having a clutch member
that presses a spring against a pin that engages ramps on a face of
one of the ring gears. When the output torque overcomes the spring
force, the pin rides over the ramps, enabling the ring gear to
rotate, which interrupts torque transmission from the transmission
to the output shaft.
SUMMARY
[0011] In an aspect, a power tool includes a housing coupleble to a
source of electric power, a motor disposed in the housing, an
output shaft received at least partially in the housing, and a
transmission in the housing and coupled to the motor and the output
shaft for transmitting torque from the motor to the output shaft. A
mode change mechanism has an actuator, a positioning member, and an
electromagnet. The actuator includes a permanent magnet and is
moveable between a first position for a first mode of operation of
the power tool, and a second position a second, different mode of
operation of the power tool. The positioning member and the
electromagnet are configured to (i) retain the actuator in the
first position when the electromagnet assembly is not energized and
the actuator is in the first position, (ii) retain the actuator in
the second position when the electromagnet assembly is not
energized and the actuator is in the second position, and (iii)
move the actuator from one of the first position and the second
position to the other of the first position and the second position
when the electromagnetic assembly is momentarily energized.
[0012] Implementations of this aspect may include one or more of
the following features. The positioning member may include a second
permanent magnet adjacent to the first position, and stationary
relative to the actuator, wherein the actuator permanent magnet and
the second permanent magnet are configured to attract when the
actuator is in the first position and repel when the actuator is in
the second position. The actuator permanent magnet and the second
permanent magnet may each include an array of permanent magnets,
with a portion of each array arranged to exert an attractive force
between actuator permanent magnet and the second permanent magnet,
and a remaining portion of each array of the permanent magnets
arranged to exert a repulsive force between actuator permanent
magnet and the second permanent magnet. The electromagnet may be
momentarily energized by current flowing in a first direction to
move the actuator from the first position to the second position,
and can be momentarily energized by current flowing in a second
opposite direction to move the actuator from the second position to
the first position. A stop may prevent contact between the actuator
and the positioning member when the actuator is in the first
position.
[0013] The positioning member may include a first positioning
member adjacent the first position and composed of a ferromagnetic
material to attract the permanent magnet when the actuator is in
the first position, and a second positioning member adjacent the
second position and composed of a ferromagnetic material to attract
the permanent magnet when the actuator is in the second position.
The electromagnet may include a first electromagnet adjacent to the
first position and a second electromagnet adjacent to the second
position, such that when one of the first electromagnet and the
second electromagnet is energized, the actuator moves from the
first position to the second position, and when the other of the
first electromagnet and the second electromagnet is energized, the
actuator moves from the second position to the first position. A
control circuit may be configured to control energization of the
first and second electromagnets in response to an input condition,
the input condition comprising one of a user selection of a desired
power tool operating condition and a sensed power tool operating
condition.
[0014] The actuator, the positioning member, and the electromagnet
may comprise a portion of a clutch. The clutch may have an input
member coupled to the transmission, an output member coupled to the
output shaft, and a coupling device movable between a driving
position in which torque is transmitted from the input member to
the output member and a clutching position in which torque
transmission from the input member to the output member is
interrupted, and wherein when the actuator is in the first
position. The actuator may retain the coupling member in the
driving position, and when then actuator is in the second position,
the actuator may allow the coupling member to move to the clutching
position. The input member may have an input sleeve defining a
radial bores, the output member may have an output cylinder
received in the input sleeve defining a groove, the coupling member
may have a drive ball received in the bore. The actuator may
include a actuation sleeve received over the input sleeve, wherein
when the actuation sleeve is in the first position, the ball is
retained in the groove to transmit torque from the input sleeve to
the output cylinder, and when the actuation sleeve is in the second
position, the ball is permitted to escape the groove to interrupt
torque transmission from the input sleeve to the output cylinder.
The input member may include a ring gear of the transmission having
a recess, the output member may have a portion of the output shaft,
the actuator may have a sleeve, and the coupling member may have a
leg extending from the sleeve. When the sleeve is in the first
position, the leg may engage the recess to inhibit rotation of the
ring gear, which enables torque transmission to the output member,
and when the sleeve is in the second position, the leg does not
engage the recess to allow rotation of the ring gear, which
interrupts torque transmission to the output member.
[0015] The actuator, the positioning member and the electromagnet
comprise a portion of a tool holder. The tool holder may be coupled
to the output shaft for releasably retaining a power tool
accessory. When the actuator is in the first position, the
accessory is retained by the tool holder. When the actuator is in
the second position the accessory is releasable from the tool
holder. The tool holder may include a socket drive having a
retractable retention pin and a linkage coupled to the retention
pin for selectively retracting the retention pin. The actuator may
include a ring configured to move the linkage and the retention pin
between a retention position and a release position when the
actuator is in the first position and the second position,
respectively.
[0016] In another aspect, a mode change mechanism for a power tool
includes an actuator that includes a permanent magnet and that is
moveable between a first position for a first mode of operation of
the power tool, and a second position a second, different mode of
operation of the power tool. A first positioning member adjacent
the first position is composed of a ferromagnetic material to
attract the permanent magnet when the actuator is in the first
position. A second positioning member adjacent the second position
is composed of a ferromagnetic material to attract the permanent
magnet when the actuator is in the second position. An
electromagnet is configured to be energized to move the actuator
between the first position and the second position, wherein (i)
when the electromagnet is not energized and the actuator is in the
first position. the actuator is retained in the first position,
(ii) when the electromagnet is not energized and the actuator is in
the second position, the actuator is retained in the second
position, and (iii) when the electromagnet is energized, the
actuator moves from one of the first and second positions to the
other of the first and second positions.
[0017] Implementations of this aspect may include one or more of
the following features. The electromagnet may include a first
electromagnetic coil adjacent the first position, and a second
electromagnetic coil adjacent the second position. The first
electromagnetic coil may be energized to create a magnetic force to
move the permanent magnet and the actuator away from the first
positioning member to the second position, and the second
electromagnetic coil may be energized to create a magnetic force to
move the permanent magnet and the actuator away from second
positioning member and to the first position. The electromagnet may
be energized to cause current to flow in a first direction creating
a magnetic force to move the permanent magnet and the actuator away
from the first positioning member and to the second position, and
the electromagnet may be energized to cause current to flow in a
second opposite direction creating a magnetic force to move the
permanent magnet and the actuator away from the second positioning
member and to the first position. A first stop may prevent contact
between the actuator and the first positioning member when in the
first position, and a second stop may prevent contact between the
actuator and the second positioning member when in the second
position.
[0018] In another aspect, a method of operating a mode change
mechanism of a power tool includes the following. It is determined
whether the power tool should be operating in a first mode of
operation or a second mode of operation. It is determined whether
an actuator that includes a permanent magnet is in a first position
that causes the power tool to operate in the first mode of
operation or a second position that causes the power tool to
operation in the second mode of operation. An electromagnet is
energized to cause the actuator and the permanent magnet to move
between the first position and the second position if the actuator
is in the first position and the power tool should be operating in
the second mode of operation, or if the actuator is in the second
position and the power tool should be operating in the first mode
of operation. The actuator is retained, without energizing the
electromagnet, in the first position if the actuator is in the
first position and the power tool should be operating in the first
mode of operation, or in the second position if the actuator is in
the second position and the power tool should be operating in the
second mode of operation.
[0019] Implementations of this aspect may include one or more of
the following features. Retaining the actuator may include
providing a first ferromagnetic positioning member adjacent the
first position to attract the permanent magnet when the actuator is
in the first position, and providing a second ferromagnetic
positioning member adjacent the second position to attract the
permanent magnet when the actuator is in the second position.
Energizing the electromagnet may include energizing a first
electromagnetic coil adjacent the first position to create a
magnetic force that moves the permanent magnet and the actuator
away from the first position to the second position when the
actuator is in the first position and should be in the second
position, and energizing a second electromagnetic coil adjacent the
second position to create a magnetic force that moves the permanent
magnet and the actuator away from the second position to the first
position when the actuator is in the second position and should be
in the first position. Energizing the electromagnet may include
causing current to flow through the electromagnet in a first
direction to create a magnetic force that moves the permanent
magnet and the actuator away from the first position to the second
position when the actuator is in the first position and should be
in the second position, and causing current to flow through the
electromagnet in a second opposite direction to create a magnetic
force that moves the permanent magnet and the actuator away from
the second position to the first position when the actuator is in
the second position and should be in the first position.
[0020] Advantages may include one or more of the following. The
mode change mechanism can be moved by applying a brief impulse of
electrical energy. In this way, the user actuated switch or button
may be replaced with an electronic switch and may be positioned on
the tool housing at virtually any location. Alternatively, the user
actuated switch could be replaced with an automated circuit for
determining when to move the actuator based on one or more input
conditions (e.g., proximity to workpiece, output torque, current
delivered to motor, etc.). Also, heavy mechanical switches can be
eliminated which may reduce the overall size, weight, and
complexity of the power tool. These and other advantages and
features will be apparent from the description, the drawings, and
the claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0021] FIG. 1 is an exploded perspective view of a first embodiment
of a power tool mode change mechanism.
[0022] FIG. 2 is a partial cross-sectional view of the mode change
mechanism of FIG. 1 in a first mode of operation.
[0023] FIG. 3 is a partial cross-sectional view of the mode change
mechanism of FIG. 1 in a second mode of operation.
[0024] FIG. 4 is a graphical representation of the magnetic forces
of components of the mode change mechanism of FIG. 1.
[0025] FIG. 5 is a schematic representation of an electronics
module of the mode change mechanism of FIG. 1.
[0026] FIG. 6 is a flow chart illustrating the operation of the
mode change mechanism of FIG. 1.
[0027] FIG. 7 is a perspective view, partially in section, of a
second embodiment of a power tool mode change mechanism.
[0028] FIG. 8 is a partial cross-sectional view of the mode change
mechanism of FIG. 7 in a first mode of operation.
[0029] FIG. 9 is a partial cross-sectional view of the mode change
mechanism of FIG. 7 in a second mode of operation.
[0030] FIG. 10 is a perspective view of some of the components of a
third embodiment of a mode change mechanism of a power tool.
[0031] FIG. 11 is a perspective view of a power tool having a
fourth embodiment of a mode change mechanism.
[0032] FIG. 12 is an exploded perspective view of the fourth
embodiment of the mode change mechanism for the power tool of FIG.
11.
[0033] FIG. 13 is a partial cross-sectional view of the power tool
and mode change mechanism of FIGS. 12 and 13 in a first mode of
operation.
[0034] FIG. 14 is a partial cross-sectional view of the power tool
and mode change mechanism of FIGS. 12 and 13 in a second mode of
operation.
[0035] FIG. 15 is a schematic representation of an electronics
module of the mode change mechanism of FIGS. 12 and 13.
[0036] FIGS. 16A and 16B are flow charts illustrating the operation
of the mode change mechanism of FIGS. 12 and 13.
[0037] FIG. 17 is a perspective view of another embodiment of a
power tool having a fifth embodiment of a mode change
mechanism.
[0038] FIG. 18A is a cross-sectional view of the mode change
mechanism of the tool of FIG. 17 in a first mode of operation.
[0039] FIG. 18B is a cross-sectional view of the mode change
mechanism of the tool of FIG. 17 in a second mode of operation.
[0040] FIGS. 19 and 20 are partially exploded views of the mode
change mechanism of the tool of FIG. 17.
DETAILED DESCRIPTION
[0041] Example embodiments will now be described more fully with
reference to the accompanying drawings. Example embodiments are
provided so that this disclosure will be thorough, and will fully
convey the scope to those who are skilled in the art. Numerous
specific details are set forth such as examples of specific
components, devices, and methods, to provide a thorough
understanding of embodiments of the present disclosure. It will be
apparent to those skilled in the art that specific details need not
be employed, that example embodiments may be embodied in many
different forms and that neither should be construed to limit the
scope of the disclosure. In some example embodiments, well-known
processes, well-known device structures, and well-known
technologies are not described in detail.
[0042] The terminology used herein is for the purpose of describing
particular example embodiments only and is not intended to be
limiting. As used herein, the singular forms "a," "an," and "the"
may be intended to include the plural forms as well, unless the
context clearly indicates otherwise. The terms "comprises,"
"comprising," "including," and "having," are inclusive and
therefore specify the presence of stated features, integers, steps,
operations, elements, and/or components, but do not preclude the
presence or addition of one or more other features, integers,
steps, operations, elements, components, and/or groups thereof. The
method steps, processes, and operations described herein are not to
be construed as necessarily requiring their performance in the
particular order discussed or illustrated, unless specifically
identified as an order of performance. It is also to be understood
that additional or alternative steps may be employed.
[0043] When an element or layer is referred to as being "on,"
"engaged to," "connected to," or "coupled to" another element or
layer, it may be directly on, engaged, connected or coupled to the
other element or layer, or intervening elements or layers may be
present. In contrast, when an element is referred to as being
"directly on," "directly engaged to," "directly connected to," or
"directly coupled to" another element or layer, there may be no
intervening elements or layers present. Other words used to
describe the relationship between elements should be interpreted in
a like fashion (e.g., "between" versus "directly between,"
"adjacent" versus "directly adjacent," etc.). As used herein, the
term "and/or" includes any and all combinations of one or more of
the associated listed items.
[0044] Although the terms first, second, third, etc. may be used
herein to describe various elements, components, regions, layers
and/or sections, these elements, components, regions, layers and/or
sections should not be limited by these terms. These terms may be
only used to distinguish one element, component, region, layer or
section from another region, layer or section. Terms such as
"first," "second," and other numerical terms when used herein do
not imply a sequence or order unless clearly indicated by the
context. Thus, a first element, component, region, layer or section
discussed below could be termed a second element, component,
region, layer or section without departing from the teachings of
the example embodiments.
[0045] Spatially relative terms, such as "inner," "outer,"
"beneath," "below," "lower," "above," "upper," and the like, may be
used herein for ease of description to describe one element or
feature's relationship to another element(s) or feature(s) as
illustrated in the figures. Spatially relative terms may be
intended to encompass different orientations of the device in use
or operation in addition to the orientation depicted in the
figures. For example, if the device in the figures is turned over,
elements described as "below" or "beneath" other elements or
features would then be oriented "above" the other elements or
features. Thus, the example term "below" can encompass both an
orientation of above and below. The device may be otherwise
oriented (rotated 90 degrees or at other orientations) and the
spatially relative descriptors used herein interpreted
accordingly.
[0046] Referring to FIGS. 1-3, in an embodiment, a mode change
mechanism in the form of an electromagnetic clutch assembly 100 may
replace the radially expanding clutch assembly in the power tool
disclosed in the above-referenced U.S. Pat. No. 8,347,750. The
clutch assembly 100 includes an input shaft 102 and an output shaft
104. The input shaft 102 is fixedly attached to a positioning
member in the form of a hollow input sleeve 106. The output shaft
104 is fixedly attached to an output cylinder 108 that is received
inside the input sleeve 106. The input sleeve includes a plurality
of radial bores 110 that receive a plurality of drive balls 112.
The output cylinder 108 have a plurality of longitudinal grooves
113 that receive the drive balls 114. The input sleeve 106 has a
reduced diameter portion 111 with a rear shoulder 103 and a front
shoulder 105. Received over the reduced diameter portion 111 of the
input shaft 102 and over the input sleeve 106 is an actuator in the
form of an actuation sleeve 114. The actuation sleeve 114 has a
base wall 119 and a cylindrical wall 115 with an internal surface
having a first substantially flat portion 116 and a second ramped
portion 118.
[0047] The actuation sleeve 114 is selectively moveable between a
first position for a first mode of operation (FIG. 2) where the
base wall 119 abuts the front shoulder 105 and the flat portion 116
engages the balls 112 to retain the balls in the grooves 113 of the
output cylinder 108, and a second position for a second mode of
operation (FIG. 3) where the base wall 119 abuts the rear shoulder
103 and the ramped portion 118 engages the balls 112 to allow the
balls to escape the grooves 113 of the output cylinder 108. In the
first mode of operation, when the balls 112 are retained in the
grooves 113, torque is transmitted from the input shaft 102 to the
output shaft 104. In the second mode of operation, when the balls
112 escape the grooves 113, torque transmission from the input
shaft 102 to the output shaft 104 is interrupted.
[0048] To facilitate moving the actuation sleeve 114 between the
first position and the second position, the actuation sleeve 114
has a base wall 119 that includes a first plurality of magnets 120
arranged in a first array 126. The input sleeve 106 also has a base
wall 122 with a second plurality of magnets 124 arranged in a
second array 128. Some opposing pairs of magnets from the first
array 126 and the second array 128 are arranged with opposite poles
facing one another (i.e., north facing south or south facing north)
so that they are configured to attract one another. Other opposing
pairs of magnets from the first array 126 and the second array 128
are arranged with the same poles facing one another (i.e., north
facing north or south facing south) so that they are configured to
repel one another. Such magnet arrays enable the magnet arrays to
have varying attractive and repulsive properties depending on the
relative distance and positions of the magnet arrays. Similar
magnet arrays may also be known as coded patterns of magnetic
elements or correlated magnets. Similar magnet arrays are
described, e.g., in U.S. Pat. No. 7,750,778, which is incorporated
by reference, and are sold by Correlated Magnetics Research,
located in New Hope, Ala.
[0049] Referring also to FIG. 4, the first magnet array 126 and the
second magnet array 128 are configured so that the sum of the
attractive force of the magnets arranged to attract one another and
the repulsive force of the magnets arranged to repel one another
varies according to the separation distance between the first array
126 and the second array 128. FIG. 4 illustrates the attractive
force vs. separation distance for the magnets arranged to attract
(curve A), the repulsive force vs. separation distance for the
magnets arranged to repel (curve R), and the net attractive or
repulsive force of all of the magnets vs. distance (curve T). The
net force is strongly positive (attractive) when the separation
distance is less than a predetermined threshold (e.g., 1 mm), and
the net force is weakly negative (repulsive) when the separation
distance is greater than the predetermined threshold.
[0050] The clutch assembly 100 also has an electromagnet 130 in the
form of a coil of wire 132 wrapped around a portion of the input
shaft 102 adjacent to the actuation sleeve 114. When the actuation
sleeve is in the second position (FIG. 3), the electromagnet 130
can be energized by driving current in a first direction, which
generates a magnetic field that repels the first array 126 of
magnets with a force greater than the repulsive force between the
first array 126 and second array 128 of magnets. This tends to push
the actuation sleeve 114 to the first position (FIG. 2). When the
actuation sleeve is in the first position (FIG. 2), the
electromagnet 130 can be energized by driving current in a second
opposite direction, which generates a magnetic field that attracts
the first array of magnets 126 with a force greater than the
attractive force between the first array 126 and the second array
128. This tends to pull the actuation sleeve to the second position
(FIG. 3).
[0051] Referring also to FIG. 5, the electromagnet 130 may be
coupled to an electronics module 138 that includes a driver circuit
140 (e.g., an H-bridge circuit) configured to drive the
electromagnet 130. The driver circuit 140 may be connected to the
output of a control circuit 142 (e.g., a microprocessor or
controller). The control circuit 142 may receive an input from a
torque setting circuit 144 (e.g., from a user input and/or from a
pre-programmed memory device)) that generates a signal
corresponding to a desired torque setting. The control circuit 142
may also receive an input from a torque sensing circuit 146 that
generates a signal that corresponds to the amount of output torque
on the tool. The torque sensing circuit may include one or more of
a current sensor, a position sensor, a torque transducer, a force
sensor, etc. In one possible embodiment, the torque sensing circuit
is similar to the electronic clutch circuit described in commonly
owned U.S. patent application Ser. No. 13/798,210, filed Mar. 13,
2013, which is incorporated by reference. In addition, the control
circuit may receive an input signal from a position sensing circuit
148, which corresponds the current position of the actuation sleeve
118 (e.g., via a Hall effect sensor or a membrane potentiometer).
The controller processes the torque setting input signal, the
torque sensing input signal, and the position sensing input signal
to determine when and in which direction to cause the drive circuit
to energize the electromagnet to change the position of the
actuation sleeve 118.
[0052] Referring also to FIG. 6, in use, first, at step 150, the
control circuit receives an input signal from the torque setting
circuit that corresponds to the desired torque setting. At step
152, the control circuit receives an input signal from the torque
sensing circuit that indicates the output torque. At step 154, the
control circuit receives an input signal from the position sensing
circuit that indicates whether the actuation sleeve 118 is in the
first position or the second position. At step 156, the control
circuit determines whether the sensed torque has exceeded the
desired threshold torque, which indicates that torque transmission
should be interrupted. If YES, then at step 158, the control
circuit determines whether the actuator is already in the second
position (FIG. 3), in which torque transmission is interrupted. If
YES, then control circuit returns to step 150. If NO, then the
control circuit causes the drive circuit to momentarily drive the
electromagnet to attract the actuator from the first position to
the second position to interrupt torque transmission. Once the
actuator is in the second position, current need not be delivered
to the electromagnetic coil to keep the actuator in the second
position, as the repulsive force between the first and second
magnet arrays will keep the actuator in the second position. By
requiring only a momentary burst of current, this saves energy and
drain on a battery (if a cordless tool).
[0053] If at step 156, the control circuit determines that the
sensed torque does not exceed the torque setting, this indicates
that torque transmission should be permitted. Next, at step 158,
the control circuit determines whether the actuator is already in
the first position (FIG. 2), in which torque transmission is
permitted. If YES, then control circuit returns to step 150. If NO,
then the control circuit causes the drive circuit to momentarily
drive the electromagnet to repel the actuator away from the second
position to the first position to allow torque transmission. Once
the actuator is in the first position, current need not be
delivered to the electromagnetic coil to keep the in the second
position, as the attractive force between the first and second
magnet arrays will keep the actuatorin the second position. By
requiring only a momentary burst of current, this saves energy and
drain on a battery (if a cordless tool).
[0054] Referring to FIGS. 7-9, in another embodiment, a mode change
mechanism in the form of an electromagnetic clutch assembly 700 may
replace the torque clutch assembly in the power tool disclosed in
the above-referenced U.S. Pat. No. 7,452,304. The clutch assembly
700 includes a ring gear 702 of the planetary transmission, and a
positioning member in the form of a generally cylindrical
transmission housing 704. The transmission housing 704 receives the
ring gear 702 and other gears of the planetary gear transmission
(not shown), and is fixedly received in a tool housing 706. The
transmission housing 704 includes a plurality of radial bores 710
that receive a plurality of drive balls 712. The ring gear 702 has
a plurality of longitudinal grooves 713 that receive the drive
balls 712. Received at least partially over the ring gear 702 is an
actuator in the form of an actuation sleeve 714. The actuation
sleeve 714 has a base wall 719 and a cylindrical wall 715 with an
internal surface having a first substantially flat portion 716 and
a second ramped portion 718. The tool housing 706 has a rear
internal shoulder 703. The transmission housing 704 has a front
internal shoulder 705.
[0055] The actuation sleeve 714 is selectively moveable between a
first position (FIG. 8) where the base wall 719 abuts the front
shoulder 705 and the flat portion 716 engages the balls 712 to
retain the balls in the grooves 714 of the ring gear 702, and a
second position (FIG. 9) where the base wall 719 abuts the rear
shoulder 703 and the ramped portion 718 engages the balls 712 to
allow the balls to escape the grooves 714 of the ring gear 702. In
the first position (FIG. 8), when the balls 712 are retained in the
grooves 714, the ring gear 702 is not permitted to rotate relative
to the transmission housing 704, which allows torque to be
transmitted from the transmission to an output shaft (not shown),
as will be understood to those of ordinary skill in the art. In the
second position (FIG. 9), when the balls 712 escape the grooves
714, and the ring gear 702 is permitted to rotate freely relative
to the transmission housing 704, which interrupts torque
transmission from the transmission to the output shaft, as will be
understood to those of ordinary skill in the art.
[0056] To facilitate moving the actuation sleeve 714 between the
first position and the second position, the actuation sleeve 714
has a base wall 719 that includes a first array of magnets 726, and
the transmission housing 704 has a second array of magnets 728 that
are arranged similarly to the first array of magnets 126 and the
second array of magnets 128 described above with respect to FIGS.
1-4. Therefore, the first magnet array 726 and the second magnet
array 728 are configured so that the net magnetic force is strongly
positive (attractive) when the separation distance is less than a
predetermined threshold (e.g., 1 mm), and the net magnetic force is
weakly negative (repulsive) when the separation distance is greater
than the predetermined threshold.
[0057] The clutch assembly 700 also has an electromagnet 730 in the
form of a coil of wire 732 adjacent to the actuation sleeve 714,
similar to the electromagnet 130 described above with respect to
FIGS. 1-4. Thus, when the actuation sleeve is in the second
position (FIG. 9), the electromagnet 730 can be momentarily
energized by driving current in a first direction, to push the
actuation sleeve 714 to the first position (FIG. 8). When the
actuation sleeve is in the first position (FIG. 8), the
electromagnet 730 can be momentarily energized by driving current
in a second opposite direction, to pull the actuation sleeve 714 to
the second position (FIG. 9). The electromagnet 730 may be coupled
to a similar electronics module as the electronics module 138
illustrated in FIG. 5 and described above. The clutch assembly 700
may be operated according to the method illustrated in FIG. 6 and
described above.
[0058] Alternatively, it is known, e.g. from the aforementioned
U.S. Pat. No. 7,452,304 and related art, that the speed reduction
ratio of a multi-speed planetary transmission may be changed by
selectively preventing rotation of one or more of the ring gears
(which results in a greater speed reduction) or allowing rotation
of one or more of the ring gears (which results in a lesser speed
reduction). Therefore, the clutch assembly 700 could instead be
connected to a controller that receives an input of a speed setting
signal that corresponds to a desired speed setting of the tool.
When the speed setting signal changes, indicating that the desired
speed reduction ratio has changed, the electromagnet 730 can be
driven to move the actuation sleeve 714 to either the first or
second position to change the speed reduction ratio of the
transmission accordingly.
[0059] Referring to FIG. 10, in the above mode change mechanisms
100, 700, or in any other power tool mode change mechanisms, an
actuator 1020 may be moveable between first and second positions
and a positioning member 1022 may remain stationary relative to the
actuation 1020. The actuator 1020 may have a first magnet array
1026 (which is a substitute for the above-described magnet arrays
126, 726) and the positioning member 1022 may have a second magnet
array 1028 (which is a substitute for the above-described magnet
arrays 128, 728). The first magnet array 1026 includes a first
inner ring magnet 1032 and a first outer ring magnet 1030
concentrically mounted on a first non-magnetic backer plate 1034.
Both the first inner and first outer ring magnets 1032, 1030 are
arranged with their north poles facing toward the second magnet
array 1028. The second magnet array 1028 includes a second inner
ring magnet 1038 and a second outer ring magnet 1036 concentrically
mounted on a second non-magnetic backer plate 1040. The second
outer ring magnet 1036 is arranged with its south pole facing the
north pole of the first outer ring magnet 1030 so as to provide an
attractive force. The second inner ring magnet 1038 is arranged
with its north pole facing the north pole of the first inner ring
magnet 1032 so as to provide a repulsive force. The first and
second ring magnet arrays 1026, 1028 together provide a net force
vs. separation distance profile as the profile shown in FIG. 4.
Thus, the actuator 1020 and the positioning member 1022 may be used
in conjunction with an electromagnet (not shown) in the manner
discussed above with respect to FIGS. 1-9 to enable movement of the
actuator between the first and second positions for first and
second modes of operation when the electromagnet is energized, and
allows the actuator to be retained in one of the first and second
positions when the electromagnet is not energized.
[0060] Referring to FIGS. 11-14, in another embodiment, a power
tool such as a drill/driver 1180 includes a mode change mechanism
in the form of an electromagnetic clutch assembly 1100. The power
tool 1180 includes a housing 1182 having a motor housing 1181, a
handle 1182 extending downward from the motor housing 1181, and a
transmission housing 1184 coupled to a front end of the motor
housing 1181. The handle 1182 is coupleable to a removable battery
pack 1186, although it should be understood that the battery could
be integral, or the housing could be coupled to an alternative
source of electrical power such as an AC power source. Disposed in
the motor housing 1181 is a motor 1186 and a control circuit 1188,
which in turn is coupled to the battery pack 1186 and to a trigger
switch 1190 disposed on the housing 1182. The motor 1186 is coupled
to a transmission 1192, which transmits torque from the motor 1186
to a spindle 1194. The spindle 1194 is coupled to a tool bit holder
1196 extending from the housing for removably retaining a tool bit
such as a screwdriver bit. In use, actuation of the trigger switch
1190 causes the controller to deliver electrical power to the motor
1186, which in turn drives the transmission 1192, the spindle 1104,
and the tool bit holder 1196.
[0061] Referring to FIGS. 12-14, the electromagnetic clutch
assembly 1100 includes an output stage ring gear 1102 of the
transmission 1192, the output spindle 1104, and an axially moveable
actuator in the form of an actuator sleeve 1106. The ring gear
meshes with a plurality of planet gears (not shown) which are
carried by an output stage planet carrier 1108. The carrier 1108 is
non-rotationally coupled with the output spindle 1104. The planet
gears also mesh with an input sun gear (not shown) that extends
from the motor or from a previous stage of the transmission. When
the ring gear 1102 is held stationary or grounded relative to the
transmission housing 1184, rotation of the sun gear causes the
planet gears to orbit the sun gear, which causes the planet carrier
1108 to rotate and drive the output spindle 1104 in rotation. When
the ring gear 1102 is not grounded or allowed to rotate relative to
the housing, rotation of the sun gear causes the planet gears to
spin on their axis but not to orbit the sun gear, so that the
carrier 1108, and thus, the spindle 1104 do not rotate. Therefore,
selectively grounding the ring gear 1102 acts as a clutch which
prevents torque transmission when the ring gear 1102 is not
grounded, and allows torque transmission when the ring gear 1102 is
grounded.
[0062] The ring gear 1102 includes a plurality of axial slots 1110
facing the actuator sleeve 1106. The actuator sleeve 1106 has a
ring portion 1112, and a plurality of legs 1114 extending axially
from the actuator sleeve 1106 toward the ring gear 1102. Each leg
1114 terminates in a tooth 1116 configured to engage one of the
slots 1110 in the ring gear 1102. The actuator sleeve is
rotationally fixed relative to the housing, and is moveable axially
between a first position for a first mode of operation (FIG. 13)
and a second position for a second mode of operation (FIG. 14). In
the first mode of operation (FIG. 13), the teeth 1116 of the
actuator 1106 engage the slots 1110 in the ring gear 1102,
preventing rotation of the ring gear, which allows torque to be
transmitted from the transmission to the output spindle 1104. In
the second mode of operation (FIG. 14), the teeth 1116 of the
actuator 1106 do not engage the slots 1110 in the ring gear 1102,
which allows the ring gear 1102 to rotate, thus interrupting torque
transmission to the output spindle 1104.
[0063] To facilitate moving the actuation sleeve 1106 between the
first position and the second position, the actuation sleeve 1106
includes a ring-shaped permanent magnet 1118 coupled to the ring
portion 1112 of the actuation sleeve 1106. In addition, received in
a rear portion 1124 of the transmission housing 1184 is a first
positioning member 1125 having a first ferromagnetic ring 1126 and
a first ring-shaped electromagnet 1128. Received in the front
portion 1120 of the transmission housing 1184 is a second
positioning member 1127 having a second ferromagnetic ring 1120 and
a second ring-shaped electromagnet 1122. When the actuation sleeve
1106 is in the first position (FIG. 13) and neither electromagnet
1122, 1128 is actuated, the actuation sleeve 1106 tends to stay in
the first position due to the attractive force between the ring
magnet 1118 and the first ferromagnetic ring 1126 being greater
than the attractive force between the ring magnet 1118 and the
second ferromagnetic ring 1120 (due to the closer proximity to the
first ferromagnetic ring 1120).
[0064] To move the actuation sleeve 1106 to the second position
(FIG. 14), the first electromagnet 1128 can be momentarily
energized to create a repulsive force against the ring magnet 1118
and/or the second electromagnet 1120 can be momentarily energized
to generate an attractive force with the ring magnet 1118, with the
sum of these forces being greater than the attractive force between
the ring magnet 1118 and the first ferromagnetic ring 1126. Once
these forces cause the actuator sleeve 1106 to move to the second
position (FIG. 14), the electromagnets 1122, 1128 can be
de-energized, and the actuator sleeve 1106 will remain in the
second position due to the attractive force between the ring magnet
1118 with the second ferromagnetic ring 1120 being greater than the
attractive force between the ring magnet 1118 and the first
ferromagnetic ring (due to closer proximity to the second
ferromagnetic ring 1120).
[0065] To return the actuation sleeve 1106 to the first position
(FIG. 13), the first electromagnet 1128 can be momentarily
energized to create an attractive force with the ring magnet 1118
and/or the second electromagnet 1120 can be momentarily energized
to generate a repulsive force against the ring magnet 1118, with
the sum of these forces being greater than the attractive force
between the ring magnet 1118 and the second ferromagnetic ring
1120. Once these forces cause the actuator sleeve 1106 to move to
the first position (FIG. 13), the electromagnets 1122, 1128 can be
de-energized, and the actuator sleeve 1106 will remain in the first
position, as discussed above. The transmission housing may also
include mechanical stops 1130 and 1132 in front of each of the
ferromagnetic rings 1120, 1126 to prevent complete contact between
the ring magnet 1118 and the ferromagnetic rings 1120, 1126, in
order to require less force to move the actuator sleeve 1106
between the first and second positions.
[0066] Referring also to FIG. 15, the electromagnets 1122, 1128
each may be coupled to an electronics module 1150 that includes a
driver circuit 1152 (e.g., an H-bridge circuit) configured to drive
the electromagnets 1122, 1128. The driver circuit 1158 may be
connected to the output of the control circuit 1188 (e.g., a
microprocessor or controller). The control circuit 1188 may receive
an input from a torque setting circuit 1154 that generates a signal
corresponding to a desired torque setting. The desired torque
setting may be input from a user interface 1148 (e.g., buttons or
electronic controls) coupled to the housing. The control circuit
1188 may also receive an input from a torque sensing circuit 1156
that generates a signal that corresponds to the amount of output
torque on the tool. The torque sensing circuit 1156 may include one
or more of a current sensor, a position sensor, a torque
transducer, a force sensor, etc. In one possible embodiment, the
torque sensing circuit is similar to the electronic clutch circuit
described in the aforementioned commonly owned U.S. patent
application Ser. No. 13/798,210, filed Mar. 13, 2013, which is
incorporated by reference.
[0067] The control circuit 1188 may also receive an input from a
distance setting circuit 1160. The distance setting circuit 1160
that generates a signal corresponding to a desired distance from
the workpiece at which the electromagnetic clutch should interrupt
torque transmission. The desired distance setting may be input from
the user interface 1148. The control circuit 1188 also receives an
input from a distance sensing circuit 1146 that generates a signal
that corresponds to a sensed distance between the tool and the
workpiece. The distance sensing circuit is coupled to a proximity
sensor system 1140 that includes a optical generator (e.g., an LED,
light or laser generator) 1142 and an optical detector 1144. Based
on input from the optical detector 1144 corresponding to the
intensity of light reflected from the workpiece, the distance
sensing circuit 1146 generates a signal that corresponds to the
sensed distance from the workpiece. Other optical and non-contact
devices may be used to sense distance from a workpiece.
[0068] The user interface may also enable the user to select
between a distance sensing mode of operation and a torque sensing
mode of operation. In addition, the control circuit may receive an
input signal from a position sensing circuit 1158, which
corresponds the current position of the actuation sleeve 1106
(e.g., via a Hall effect sensor or a membrane potentiometer). The
controller processes the torque setting input signal, the torque
sensing input signal, the distance setting input signal, the
distance sensing input signal, and the position sensing input
signal to determine when and in which direction to cause the drive
circuit to energize the electromagnets to change the position of
the actuation sleeve 1106.
[0069] Referring to FIG. 16A, in use, at step 1200, the control
circuit first receives a user input of whether to use the distance
sensing mode or the torque sensing mode. If the distance sensing
mode is selected, the control circuit performs the steps
illustrated in FIG. 16B, as described below. If the torque sensing
mode is selected, then at step 1201, the control circuit receives
the input signal from the torque setting circuit that corresponds
to the desired torque setting. At step 1202, the control circuit
receives the input signal from the torque sensing circuit that
indicates the output torque. At step 1204, the control circuit
receives the input signal from the position sensing circuit that
indicates whether the actuator is in the first position or the
second position. At step 1206, the control circuit determines
whether the sensed torque has exceeded the desired threshold
torque, which indicates that torque transmission should be
interrupted. If YES, then at step 1208, the control circuit
determines whether the actuator is already in the second position
(FIG. 14), in which torque transmission is interrupted. If YES,
then control circuit returns to step 1201. If NO, then at step
1210, the control circuit causes the drive circuit to momentarily
drive the electromagnets to move the actuator sleeve from the first
position to the second position to interrupt torque transmission.
Once the actuator sleeve is in the second position, current need
not be delivered to the electromagnets to keep the actuator sleeve
in the second position, as the attractive force between the
permanent magnet ring and the second ferromagnetic ring will do
this. By requiring only a momentary burst of current, this saves
energy and drain on a battery (if a cordless tool).
[0070] If, at step 1206, the control circuit determines that the
sensed torque does not exceed the torque setting, this indicates
that torque transmission should be permitted. Next, at step 1212,
the control circuit determines whether the actuator is already in
the first position (FIG. 13), in which torque transmission is
permitted. If YES, then control circuit returns to step 1201. If
NO, then, at step 1214, the control circuit causes the drive
circuit to momentarily drive the electromagnets to move the
actuator sleeve away from the second position to the first position
to allow torque transmission. Once the actuator sleeve is in the
first position, current need not be delivered to the electromagnets
to keep the sleeve in the first position, as the attractive force
between the permanent ring magnet and the first ferromagnetic ring
will keep the sleeve in the first position. By requiring only a
momentary burst of current, this saves energy and drain on a
battery (if a cordless tool).
[0071] Referring to FIG. 16B, if, at step 1200 in FIG. 16A, the
distance sensing mode is selected, then at step 1301, the control
circuit receives the input signal from the distance setting circuit
that corresponds to the desired distance setting for when to
interrupt torque transmission. At step 1302, the control circuit
receives the input signal from the distance sensing circuit that
indicates the sensed distance of the tool holder from the
workpiece. At step 1304, the control circuit receives the input
signal from the position sensing circuit that indicates whether the
actuator sleeve is in the first position or the second position. At
step 1306, the control circuit determines whether the sensed
distance is less than the desired threshold distance, which
indicates that torque transmission should be interrupted. If YES,
then at step 1308, the control circuit determines whether the
actuator is already in the second position (FIG. 14), in which
torque transmission is interrupted. If YES, then control circuit
returns to step 1301. If NO, then at step 1310, the control circuit
causes the drive circuit to momentarily drive the electromagnets to
move the actuator sleeve from the first position to the second
position to interrupt torque transmission. Once the actuator sleeve
is in the second position, current need not be delivered to the
electromagnets to keep the actuator sleeve in the second position,
as the attractive force permanent magnet ring and the second
ferromagnetic ring will do this. By requiring only a momentary
burst of current, this saves energy and drain on a battery (if a
cordless tool).
[0072] If, at step 1306, the control circuit determines that the
sensed distance is not less than the distance setting, this
indicates that torque transmission should be permitted. Next, at
step 1312, the control circuit determines whether the actuator is
already in the first position (FIG. 13), in which torque
transmission is permitted. If YES, then control circuit returns to
step 1301. If NO, then, at step 1314, the control circuit causes
the drive circuit to momentarily drive the electromagnets to move
the actuator sleeve away from the second position to the first
position to allow torque transmission. Once the actuator sleeve is
in the first position, current need not be delivered to the
electromagnets to keep the sleeve in the first position, as the
attractive force between the permanent ring magnet and the first
ferromagnetic ring will keep the sleeve in the first position. By
requiring only a momentary burst of current, this saves energy and
drain on a battery (if a cordless tool).
[0073] Referring to FIGS. 17-20, in another embodiment, a power
tool such as an impact wrench 1710 includes an electromagnetic mode
change mechanism in the form of an electromagnetically actuatable
socket holder 1720. The impact wrench 1710 includes a housing 1712
having a handle 1714, a trigger mechanism 1716 for activating the
impact wrench 1710, and a cover 1760 at a front of the housing
1712. A base 1715 of the handle 1714 is adapted to receive a
battery pack (not shown) for use as a cordless impact wrench. It
should be understood that the present disclosure can also be
applied to pneumatic, hydraulic and corded electrical impact wrench
devices. The impact wrench includes a motor 1711 disposed within
the housing 1712 that drives a transmission and impact mechanism
1713, which in turn drives an anvil 1718 extending from the front
end of the housing 1712, as is generally known in the art, and as
described in the aforementioned U.S. patent application Ser. No.
13/494,325. The anvil 1718 includes a square socket drive 1718a
that is designed to drive a socket wrench (not shown).
[0074] The mode change mechanism in the form of the
electromagnetically actuatable socket holder 1720 is configured to
selectively retain a socket wrench on the square drive 1718a. The
socket holder 1720 includes a radially extending and retractable
retainer pin 1724 configured to engage the socket wrench when it is
coupled to the square socket drive 1718a. The retainer pin 1724 is
received in a radial aperture 1723 in a distal end of the square
socket drive 1718a. A lever pin 1730 is received in an axially
extending bore 1732 provided in the anvil 1718. The lever pin 1730
has a rear end portion with a partially spherical pivot end 1750
received in a concave partially conical bore portion 1732a of the
bore 1732. The lever pin 1730 also has a front end portion that
engages a transverse aperture 1734 provided in the retention pin
1724. In addition, the lever pin 1730 has a mid portion that
engages a transverse aperture in an actuator pin 1748. The actuator
pin 1748 is received in a transverse bore 1727 in a proximal
portion of the anvil 1718. The actuator pin 1748 is biased to a
radially outward direction by a spring 1726 that is received in the
transverse bore 1727.
[0075] Disposed inside of the cover 1760 is an actuator in the form
of an axially moveable cam ring 1740, a first positioning member in
the form of an axially stationary forward ring 1762, and a second
positioning member in the form of an axially stationary rearward
ring 1764. The cam ring 1740 has an inner cam surface 1746 disposed
against an outer cam surface 1744 of the actuator pin 1748. The cam
ring is moveable between a forward position for a first mode of
operation (FIG. 18A) and a rearward position for a second mode of
operation (FIG. 18B). The forward ring 1762 includes a forward
electromagnetic coil 1766 disposed in a first annular ferromagnetic
(e.g., steel) cup 1768. The rearward ring 1764 includes a rearward
electromagnetic coil 1770 disposed in a second annular
ferromagnetic (e.g., steel) cup 1772. The cam ring 1740 is disposed
between the forward and rearward rings 1762, 1764 and includes an
integral permanent magnet ring 1742.
[0076] The forward and rearward electromagnetic coils 1766, 1770
may be selectively energized to move the cam ring 1740 between its
forward or rearward position. To move the cam ring 1740 to its
rearward position (FIG. 18B), the front electromagnet 1766 can be
momentarily energized to create a repulsive force against the ring
magnet 1742 and/or the rear electromagnet 1770 can be momentarily
energized to generate an attractive force with the ring magnet
1742, with the sum of these forces being greater than the
attractive force between the ring magnet 1742 and the first
ferromagnetic cup 1768. Once these forces cause the cam ring 1742
to move to the rearward position (FIG. 18B), the electromagnets
1766, 1770 can be de-energized, and the cam ring 1742 will remain
in the rearward position due to the attractive force between the
ring magnet 1742 with the second ferromagnetic cup 1772 being
greater than the attractive force between the ring magnet 1742 and
the first ferromagnetic cup 1768 (due to closer proximity to the
second ferromagnetic cup 1772).
[0077] To return the cam ring 1740 to the first position (FIG.
18A), the forward electromagnet 1766 can be momentarily energized
to create an attractive force with the ring magnet 1742 and/or the
rearward electromagnet 1770 can be momentarily energized to
generate a repulsive force against the ring magnet 1742, with the
sum of these forces being greater than the attractive force between
the ring magnet 1742 and the rearward ferromagnetic cup 1772. Once
these forces cause the cam ring 1742 to move to the first position
(FIG. 18A), the electromagnets 1766, 1770 can be de-energized, and
the cam ring 1740 will remain in the forward position due to the
attractive force between the ring magnet 1742 and the first
ferromagnetic cup 1768 being greater than the attractive force
between the ring magnet 1742 and the second ferromagnetic cup 1772
(due to the closer proximity to the first ferromagnetic cup
1768).
[0078] Once in the forward or rearward positions the permanent
magnet 1742 is attracted to the first annular cup 1768 if in the
forward position, or the second annular cup 1772 if in the second
position. Thus only a pulse of energy is required to change the
position of the cam ring 1740 and thus the mode of operation.
Continuous power is not required to hold the cam ring in either the
forward or rearward position and this is advantageous for energy
conservation on a cordless tool. Further, it should be understood
that the electromagnetically actuatable socket holder 1720 can be
operated using a single coil and a spring for biasing the cam ring
away from the coil during a non-activated state. The cover 1760 may
also include mechanical stops (not shown) between each of the
ferromagnetic cups 1768, 1772 and the ring magnet 1742 to prevent
complete contact between the ring magnet 1742 and the ferromagnetic
cups 1768, 1768, in order to require less force to move the cam
ring 1740 between the forward and rearward positions.
[0079] When the electromagnets cause the cam ring 1746 to move to
its rearward position in the second mode of operation (FIG. 18B),
the cam surface 1746 of the cam ring 1724 engages the cam surface
1744 of the actuator pin 1748, causing the actuator pin 1748 to
move downward in the bore 1727 in the anvil 1718 against the
biasing force of the spring 1726. As the actuator pin 1748 is moved
downward, the lever pin 1732 pivots in a counter clockwise
direction CCW about pivot end 1750, causing the retainer pin 1724
to be moved radially inward to a retracted or release position.
Once the retainer pin 1724 is in the release position, the socket
wrench can be removed from the square socket drive 1718a. When cam
ring 1724 moves to its forward axial position in the first mode of
operation (FIG. 18A), the spring 1726 causes the actuator pin 1748
to move upward. causing the lever pin 1730 to rotate in a clockwise
direction CW so that the retainer pin 1724 extends in an engaged
position.
[0080] The first and second electromagnetic coils 1766, 1770 can be
electrically connected to the tool battery or an alternative power
source such as an A/C power source by a control circuit, such as
one of the control circuits described above. A user-actuatable
switch for controlling movement of the cam ring 1740 by the
electromagnets can be placed at one or more of multiple different
locations on the power tool 1710, as indicated by the X's in FIG.
17. Thus, the socket release mechanism can be controlled from
virtually any location on the tool. It should be understood that
this type of electromechanical socket release mechanism can be used
with any of the other disclosed embodiments for a socket release
mechanism described in U.S. patent application Ser. No.
13/494,325.
[0081] Numerous other modifications may be made to the exemplary
implementations described above. For example, any of the
above-described combinations of permanent magnet and
electromagnetic assemblies may be exchanged from any of the other
combinations. The above-described electromagnetic assemblies for
moving actuators can be used for any other applications or designs
of power tools that require movement of actuators among two or more
positions. These and other implementations are within the scope of
the following claims.
* * * * *