U.S. patent application number 11/359167 was filed with the patent office on 2006-08-24 for actuation apparatus for power tool.
Invention is credited to Ian S. Bell, Rene Jager, Achim Jung.
Application Number | 20060185865 11/359167 |
Document ID | / |
Family ID | 34401058 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060185865 |
Kind Code |
A1 |
Jung; Achim ; et
al. |
August 24, 2006 |
Actuation apparatus for power tool
Abstract
When the mode change knob of a multi-mode hammer drill is moved
to the hammer only position, an electronic sensor sends a signal to
a control logic circuit. When the user then depresses the trigger
mechanically closing the ON/OFF switch, the control logic circuit
applies a voltage either to a holding relay or to the gate of a
triac which enables the relay or triac to conduct, thus providing a
parallel circuit by-passing the ON/OFF switch. Consequently, when
the user releases the trigger and opens the ON/OFF switch, the
parallel relay or triac maintains current flow to the motor. It can
be seen that in hammer only mode the user can activate the hammer
drill by simply tapping the trigger to depress it and does not need
to hold down trigger during use of the hammer in operation.
Inventors: |
Jung; Achim; (Armsheim,
DE) ; Jager; Rene; (Karben, DE) ; Bell; Ian
S.; (Sunninghill, GB) |
Correspondence
Address: |
Michael P. Leary;Black & Decker Corporation
Mail Stop TW199
701 E. Joppa Rd
Towson
MD
21286
US
|
Family ID: |
34401058 |
Appl. No.: |
11/359167 |
Filed: |
February 22, 2006 |
Current U.S.
Class: |
173/48 |
Current CPC
Class: |
B25D 2216/0038 20130101;
B25D 2250/221 20130101; B25D 2250/261 20130101; B25D 2216/0023
20130101; B25D 16/006 20130101; B25D 2216/0015 20130101; H01H 9/06
20130101 |
Class at
Publication: |
173/048 |
International
Class: |
E02D 7/02 20060101
E02D007/02 |
Foreign Application Data
Date |
Code |
Application Number |
Feb 22, 2005 |
GB |
GB 05 035 58.9 |
Claims
1. An actuation apparatus for a multi-mode power tool having a
housing, a motor with a rotary output shaft disposed in the
housing, drive means for driving a working member of the tool in
response to rotation of said rotary output shaft, and a trigger
disposed on the housing to enable activation of said motor, the
actuation apparatus comprising: a mode control switch adapted for
enabling a user to select between a first mode of operation and a
second mode of operation; a mode selection sensor for providing a
signal indicating which mode of operation of the tool has been
selected; and a control circuit for controlling operation of the
motor in response to the signal, such that when in the first mode
of operation the motor is operated by a first depression of the
trigger and remains activated until deactivated by a second
depression of the trigger, and in the second mode of operation, the
motor is only activated while the trigger is depressed.
2. An actuation apparatus according to claim 1, wherein at least
one said first mode of operation is a hammer mode of the tool.
3. An actuation apparatus according to claim 1, further comprising
an on/off switch for actuating the motor, the on/off switch
mechanically actuated by the trigger.
4. An actuation apparatus according to claim 1, further comprising
a lock-on switch, the lock-on switch actuated by the control
circuit, and Wherein, when the first mode is selected, and in
response to a first depression of the trigger the motor is
energized and when the trigger is released the motor remains
energized.
5. An actuation apparatus according to claim 4, wherein when the
first mode is selected, the control circuit opens the lock-on
switch in response to a second depression of the trigger.
6. An actuation apparatus according to claim 4, wherein the lock-on
switch is connected in parallel with the on/off switch.
7. An actuation apparatus according to claim 4, wherein the lock-on
switch comprises a triac, thyristor, transistor, FET or relay.
8. An actuation apparatus according to claim 1, wherein the control
circuit includes a control logic.
9. An actuation apparatus according to claim 8 wherein the control
logic includes a microprocessor.
10. An actuation apparatus according to claim 8 and further
comprising a follower relay interlocked to the on/off switch for
providing an electrical signal to the control logic, the electrical
signal indicative of the condition of the on/off switch.
11. An actuation apparatus according to claim 1, wherein the mode
control switch includes a rotatable knob.
12. A hammer drill operable in a first mode of operation and a
second mode of operation, the hammer drill comprising: a housing; a
motor disposed in the housing and supplyable with electric current
via a power circuit; a transmission for driving a working member of
the hammer tool in response to rotation of the motor; an on/off
switch located in the power circuit and selectable to one of an on
position and an off position, and in the on position the on/off
switch conducts electric current to the motor and in the off
position the on/off switch does not conduct electric current to the
motor; a trigger disposed on the housing to enable a user to
position the on/off switch, a mode control switch disposed in the
housing and adapted to enable a user to select one of the first
mode of operation and the second mode of operation; a mode
selection sensor providing a first signal indicating which mode of
operation of the hammer drill has been selected; a lock-on switch
located in the power circuit and in electrically parallel
arrangement to the on/off switch, the lock-on switch selectable to
one of an closed position and an open position, and in the closed
position the lock-on switch conducts electric current to the motor
and in the open position the lock-on switch does not conduct
electric current to the motor; a control circuit for positioning
the lock-on switch, the control circuit receiving the mode selector
sensor first signal, and wherein, when the first mode of operation
is selected, a first depression of the trigger will cause the
control circuit to position the lock-on switch in the closed
position and will maintain the lock-on switch in the closed
position after release of the trigger, and a second depression of
the trigger will cause the control circuit to position the lock-on
switch in the open position.
13. A hammer drill according to claim 12 wherein, when in the
second mode of operation, the motor is supplied with electric
current only while the trigger is depressed.
14. A hammer drill according to claim 13 wherein, the lock-on
switch is in the open position whenever the mode selector switch is
selected to the second mode of operation.
15. A hammer drill according to claim 12 wherein the first mode of
operation is a hammer-only mode.
16. A hammer drill according to claim 12 and further comprising a
follower relay interlocked with the on/off switch, the follower
relay providing a second signal to the control circuit, the second
signal indicating the position of the on-off switch.
17. A hammer drill according to claim 16 wherein, depressing the
trigger will cause the follower relay to send the second signal to
the control circuit.
18. A hammer according to claim 17 wherein, when the first signal
indicates that the mode selector switch is selected to the first
mode, a first sequential receipt of the second signal by the
control circuit will cause the control circuit to place the lock-on
switch in the closed position, and a second sequential receipt of
the second signal by the control circuit will cause the control
circuit to place the lock-on switch in the open position.
19. A hammer drill according to claim 12, wherein the lock-on
switch comprises one of the group consisting of: a triac, a
thyristor, a transistor, an FET, and a relay.
20. An actuation apparatus for a power tool having a housing, a
motor with a rotary output shaft disposed in the housing, drive
means for driving a working member of the tool in response to
rotation of said rotary output shaft, and a trigger disposed on the
housing to enable activation of said motor, the actuation apparatus
comprising: switching means for enabling a user to select between a
hammer mode of said tool, a drilling mode of said tool and/or a
hammer and drilling mode of said tool; detection means for
providing at least one signal indicating which mode of operation of
the tool has been selected; and control means for controlling
operation of the motor in response to at least one said signal,
such that in at least one first predetermined mode of operation
said motor is operated by a first depression of the trigger and
remains activated until deactivated by a second depression of the
trigger, and in at least one second predetermined mode of
operation, said motor is only activated while the trigger is
depressed.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to an actuation apparatus for
a power tool. In particular, the invention relates to a hammer
drill. The invention relates more particularly, but not exclusively
to an actuation apparatus for the trigger of a power tool and to a
power tool incorporating such an apparatus.
BACKGROUND OF THE INVENTION
[0002] Hammer drills are power tools that generally have three
modes of operation, i.e. a hammer only mode, a drill only mode and
a combined hammer and drilling mode. In general, the motor of a
hammer drill is operated by the user depressing a spring-loaded
trigger, and deactivated by the user releasing the trigger such
that it is necessary to hold the trigger down during operation of
the tool.
[0003] UK patent no. 2314288 describes an electric combination
hammer having a drilling mode and a chiselling mode. The hammer
comprises a housing with a handle and a trigger disposed on the
handle for operating an electric on/off switch. The combination
hammer has an operating knob for switching manually between the
drilling mode and the chiselling mode, and the trigger has an
associated detent which, when the operating knob is in the position
corresponding to the chiselling mode, allows the on/off switch to
be latched in a closed position such that even when the user
releases their grip on the trigger the combination hammer remains
in operation.
[0004] The electric combination hammer of GB2314288 suffers from
the drawback that the components for the detent system are
mechanical in nature, comprising cam surfaces and resilient
springs, such that they are susceptible to wear and tear with
repeated use. Also, the use of such mechanical components makes the
hammer expensive to manufacture.
[0005] Preferred embodiments of the present invention seek to
overcome the above disadvantage of the prior art.
BRIEF SUMMARY OF THE INVENTION
[0006] According to an aspect of the present invention, there is
provided an actuation apparatus for a power tool having a housing,
a motor with a rotary output shaft disposed in the housing, drive
means for driving a working member of the tool in response to
rotation of said rotary output shaft, and a trigger disposed on the
housing to enable activation of said motor, the actuation apparatus
comprising:
[0007] switching means for enabling a user to select between a
hammer mode of said tool, a drilling mode of said tool and/or
hammer and drilling mode of said tool;
[0008] detection means for providing at least one signal indicating
which mode of operation of the tool has been selected; and
[0009] control means for controlling operation of the motor in
response to at least one said signal, such that in at least one
first predetermined mode of operation of said tool, said motor is
operated by a first depression of the trigger and remains activated
until deactivated by a second depression of the trigger, and in at
least one second predetermined mode of operation of said tool, said
motor is only activated while the trigger is depressed.
[0010] By providing control means for controlling operation of the
motor in response to at least one said signal, such that in at
least one first predetermined mode of operation of said tool, said
motor is operated by a first depression of the trigger and remains
activated until deactivated by a second depression of the trigger,
and in at least one second predetermined mode of operation of said
tool, said motor is only activated while the trigger is depressed,
this provides the advantage that the need for a mechanical detent
system to latch on the trigger mechanism when a predetermined mode
of operation is selected is eliminated. This is advantageous
because an electronic system is not subject to mechanical wear and
tear to the same extent as a mechanical system and can also be made
much more compact, thus reducing the dimensions of the tool. Also,
the apparatus can be manufactured more cost-effectively than
apparatus incorporating a purely mechanical actuator system.
[0011] In a preferred embodiment, at least one said first
predetermined mode is a hammer mode of the tool.
[0012] This provides the advantage that the operator does not have
to continuously grip the trigger during the hammer mode operation
of the tool, and therefore can move their hands around the body of
the tool whilst it is in operation to provide a better grip.
[0013] The apparatus may further comprise on/off switch means for
actuating the motor and adapted to be actuated by the trigger of
the tool.
[0014] The apparatus may further comprise override switch means
adapted to be closed by said control means, in response to said
first depression of the trigger of the tool, when at least one
predetermined said first mode is selected, such that even when the
trigger is released, the motor remains in operation.
[0015] In a preferred embodiment, when at least one said first
predetermined mode is selected, said control means opens said
override switch means in response to a second depression of said
trigger.
[0016] Said override switch means may be connected in parallel with
said on/off switch means.
[0017] Said override switch means may comprise at least one triac,
thyristor, FET, transistor or relay.
[0018] In a preferred embodiment, said control means includes
control logic which may include a microprocessor.
[0019] In a preferred embodiment, there I further provided a sensor
for providing an electrical signal to the control logic or
microprocessor indicative of the condition of said on/off switching
means.
[0020] Said switching means may include a rotatable knob.
[0021] According to a further aspect of the present invention,
there is provided a power tool comprising a control apparatus as
defined above.
[0022] In a preferred embodiment, said power tool is a hammer
drill.
BRIEF DESCRIPTION OF THE DRAWINGS
[0023] A preferred embodiment of the present invention will now be
described, by way of example only and not in any limitative sense,
with reference to the accompanying drawings in which:
[0024] FIG. 1 is a side view of a hammer drill;
[0025] FIG. 2 is a circuit diagram of the control apparatus of the
first embodiment of the present invention; and
[0026] FIG. 3 is a circuit diagram of the control apparatus of the
second embodiment of the present invention.
DETAILED DESCRIPTION OF THE INVENTION
[0027] The first embodiment of the present invention will now be
described with reference to FIGS. 1 and 2.
[0028] Referring to FIG. 1, a hammer drill shown generally by 2
comprises a housing 4 having a handle portion 6 for the user to
grip. A motor 100 is disposed in the housing 4 which drives a drive
mechanism 102 via a rotary output shaft 104, also disposed in the
housing 4 and which is capable of driving a bit 8 in a drill mode,
in which the bit is rotated, a hammer mode in which impacts are
imparted to the bit 8, or a hammer and drill mode, in which both
actions are combined. Bit 8 is held in a chuck 10 which is
driveably connected to the drive mechanism 104. The operation of
the drive mechanism will be familiar to persons skilled in the art
and is not relevant to the understanding of the present invention,
and will therefore not be described in greater detail herein.
[0029] A trigger 12 is disposed on the handle portion 6 to enable
the user to activate the hammer drill 2. A mode change knob 14 is
rotatably disposed on the housing 6. The mode change knob has three
positions, one for hammer only mode, one for drill only mode and
one for selecting combined hammer and drilling mode. When the mode
change knob is rotated, it resiliently locks into one of the three
positions indicating the selected mode. An electric cable 16 is
attached to the housing 6 for providing electrical power to the
motor. The electrical power is in the form of 230v A.C. electrical
mains power supply. However, it will be obvious to a person skilled
in the art that hammer drills powered by a 120v A.C. power supply
or a D.C. power supply, such as a battery, could utilise the
present invention in their construction.
[0030] Referring to FIG. 2, the cable 16 provides a 230v A.C.
voltage across contacts 18 and 20. The electric motor 22 is
controlled by an on/off switch 24 which is directly coupled to the
trigger 12 such that when trigger 12 is depressed the switch 24
closes. When the trigger 12 is released, the switch 24 opens. An
electronic sensor 30 detects the position of the mode change knob
14 and hence is able to determine what mode of operation the mode
change knob 14 is set to. When the mode change knob 14 is in the
hammer only mode position, the electronic sensor 30 sends a signal
to the control logic 26 indicative that the knob 14 is set to
hammer only mode. The control logic 26 is utilised to control the
operation of the hammer drill, including the control of the motor
22. The control logic 26 may include a microprocessor, depending on
the complexity of the control required. The control logic 26 is
connected to a first electrical switch 28, for example, an
electrical relay, in order to control the electrical switch 28,
which electrical switch 28 is electrically connected in parallel to
the switch 24.
[0031] A second switch 34 is mechanically connected to the on/off
switch 24 such that when the on/off switch 24 is closed, the second
switch 34 closes, and when the on/off switch 24 is opened, the
second switch opens. The second switch 34 is electrically connected
to the control logic 26.
[0032] The operation of the control apparatus will now be described
with reference to FIGS. 1 and 2.
[0033] The mode change knob 14 allows the user to select one of the
three modes in which the hammer drill can operate. When the drill
only or combined hammer and drilling mode is selected, the trigger
12 is used to open and close switch 24 such that when the trigger
is pressed the motor activates and drives the bit either in a
rotary drilling action (drill mode) or a rotating action in which
impacts are imparted to the bit 8 (hammer and drill mode). When the
trigger 12 is released, the switch 24 is opened which interrupts
the connection between contacts 18 and 20 and deactivates the
motor.
[0034] When the mode change knob 14 is moved to the hammer only
position, the electronic sensor 30 sends a signal to the control
logic 26. The control logic 26 then waits for the user to depress
trigger 12 closing switch 24. The control logic 26 knows the status
of the on/off switch 24 due to the status of the second switch 34.
When this happens, the control logic 26 applies a voltage to the
second electrical switch 28 which switches the electrical switch 28
on and enables the electrical switch 28 to conduct, thus providing
a parallel electrical connection bypassing the on/off switch 24.
Consequently, when the user releases trigger 12 to open the switch
24, as the electrical switch 28 is in parallel with the on/off
switch 24, a current continues to flow through the motor 22. It can
be seen that in hammer only mode the user can activate the hammer
drill by simply tapping the trigger 12 to depress it but then does
not need to hold down trigger 12 to maintain operation of the motor
22 during use of the hammer in operation.
[0035] When the user depresses trigger 12 for the second time,
causing the on/off switch 24 to be closed again, which in turn
causes the second switch 34 to close again, which is then detected
by the control logic 26, the electrical switch 28 is switched off
by the control logic 26, so that no current is able to flow through
the electrical switch 28, such that, when the trigger 12 is
released, opening the on/off switch 24, the electrical connection
between contacts 18 and 20 is interrupted and the motor 22
stops.
[0036] A second electrical switch 36 is shown in FIG. 2 in the
electrical circuit between the contact 18 and the motor 22. During
all modes of operation, the electrical switch 36 is normally
switched on at all times by the control logic 26 to allow current
to freely flow through it. However, in certain circumstances, due
to safety or other operational reasons, the control logic 26
switches the second electrical switch 36 off, preventing the motor
22 from being activated by the trigger 12 when depressed.
[0037] It will be appreciated by persons skilled in the art that
the above embodiment has been described by way of example only and
not in any limitative sense, and that various alterations and
modifications are possible without departure from the scope of the
invention as defined by the appended claims.
[0038] In particular, the one press activation of the power drill
has been described in connection with the hammer only mode. The
power tool could be easily adapted such that this mode of operation
is applied to any of the other modes of operation of the tool or
any combination of the modes of operation.
[0039] In the embodiment described, the signals between electronic
sensor 30, the electrical switch 24 and the control logic 26 are
transmitted using electric cables or wires. However, a person
skilled in the art will appreciate that the connections could be
wireless e.g. the signals are transmitted using of a radio
transmitter, or in the form of an optical cable or fibre.
[0040] A second embodiment of the present invention will now be
described with reference to FIG. 3. The design of the second
embodiment is substantially the same as that of the first
embodiment. Where the same features are present in the second
embodiment that are present in the first embodiment, the same
reference numbers have been utilised in the drawings.
[0041] The difference between the first and second embodiments is
that the electrical switches 28, 36 have been replaced by triacs
28', 36'. This provides for a simpler design. Furthermore, the use
of a triac 36' to control the motor 22 not only enables it to be
switched on or off, but also enables its speed to be controlled.
Thus, during the operation of the hammer drill, by controlling the
operation of the triac using the control logic 26, the speed of the
motor is controlled.
[0042] In further embodiments of the present invention, other types
of electrical or mechanical switching devices to those of relays or
triacs can be used, such as transistors, thyristors and FETs in
order to suite the type of power supply, the motor and control
logic etc.
* * * * *