U.S. patent application number 13/579713 was filed with the patent office on 2013-01-24 for power tools.
This patent application is currently assigned to GARDENA MANUFACTURING GMBH. The applicant listed for this patent is Martin Bepler, Johan Bjornlinger, Peter Lameli, Ottmar Locher, Par Martinsson, Christoph Schiedt, Johan Svennung, Hans Waigel. Invention is credited to Martin Bepler, Johan Bjornlinger, Peter Lameli, Ottmar Locher, Par Martinsson, Christoph Schiedt, Johan Svennung, Hans Waigel.
Application Number | 20130020102 13/579713 |
Document ID | / |
Family ID | 42634957 |
Filed Date | 2013-01-24 |
United States Patent
Application |
20130020102 |
Kind Code |
A1 |
Bjornlinger; Johan ; et
al. |
January 24, 2013 |
Power Tools
Abstract
A typically battery-operated power tool, such as a chainsaw or
hedge trimmer, comprising a working element (4), a motor (6)
arranged to drive the working element (4) and a controller (9)
arranged to control the speed at which the motor drives the working
element (4), in which there is provided a sensor (12) for at least
one factor indicative of the efficiency with which the power tool
is being operated, the controller (9) being arranged to vary the
speed at which the motor (6) drives the working element (4) should
the factor indicate that the power tool is being operated in a
sub-optimal manner. Typically, the factor is the pressure which the
user is applying the power tool, and the sensor (12) is a sensor
for the current flowing through the motor (6).
Inventors: |
Bjornlinger; Johan;
(Huskvarna, SE) ; Martinsson; Par; (Jonkoping,
SE) ; Svennung; Johan; (Jonkoping, SE) ;
Lameli; Peter; (Nurtingent, DE) ; Locher; Ottmar;
(Ulm, DE) ; Schiedt; Christoph; (Burgrieden,
DE) ; Bepler; Martin; (Ulm, DE) ; Waigel;
Hans; (Schnurpflingen, DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Bjornlinger; Johan
Martinsson; Par
Svennung; Johan
Lameli; Peter
Locher; Ottmar
Schiedt; Christoph
Bepler; Martin
Waigel; Hans |
Huskvarna
Jonkoping
Jonkoping
Nurtingent
Ulm
Burgrieden
Ulm
Schnurpflingen |
|
SE
SE
SE
DE
DE
DE
DE
DE |
|
|
Assignee: |
GARDENA MANUFACTURING GMBH
Ulm
DE
|
Family ID: |
42634957 |
Appl. No.: |
13/579713 |
Filed: |
February 17, 2010 |
PCT Filed: |
February 17, 2010 |
PCT NO: |
PCT/EP10/00973 |
371 Date: |
October 8, 2012 |
Current U.S.
Class: |
173/2 |
Current CPC
Class: |
B25F 5/00 20130101 |
Class at
Publication: |
173/2 |
International
Class: |
E21B 15/04 20060101
E21B015/04 |
Claims
1. A power tool comprising a working element, a motor arranged to
drive the working element and a controller arranged to control the
speed at which the motor drives the working element, in which there
is provided a sensor for at least one factor indicative of the
efficiency with which the power tool is being operated, the
controller being arranged to vary the speed at which the motor
drives the working element, so as to provide feedback through said
speed to the user, should the factor indicate that the power tool
is being operated in a sub-optimal manner.
2. The power tool of claim 1, in which the controller is arranged
to reduce the speed at which the motor drives the working element
in the event of the power tool being used in a sub-optimal
manner.
3. The power tool of claim 1, in which the controller is arranged
to cyclically vary the speed, so as to provide vibrations to the
user, in the event of the power tool being used in a sub-optimal
manner.
4. The power tool of claim 1, in which the at least one factor
comprises the pressure which the user applies the working element
to a subject to be worked.
5. The power tool of claim 1, in which the tool is an electric
power tool and the motor is an electric motor and in which the
sensor comprises a current sensor arranged to measure the current
flowing through the motor.
6. The power tool of claim 5, in which the controller is arranged
to reduce the speed at which the motor drives the working element
when the current measured by the current sensor exceeds a
limit.
7. The power tool of claim 1, being an electric power tool where
the motor is an electric motor, in which the controller comprises a
variable power control element having an input and an output, in
which the controller is arranged so that, if the factor as measured
by the sensor is indicative of a sub-optimal operation of the power
tool, the power control element reduces the power that is
transmitted from the input to the output.
8. The power tool of claim 7, in which the power tool comprises a
source of electric power, a speed selector operable by a user of
the power tool and operative to take electric power from the source
and output an electric signal indicative of a speed at which the
user desires to operate the power tool, the output of the speed
selector being coupled to the input of the power control
element.
9. A method of operating a power tool comprising a working element,
a motor arranged to drive the working element and a control element
via which a user indicates a desired speed, the method comprising
sensing at least one factor indicative of the efficiency with which
the power tool is being operated, the power tool varying the speed
at which the motor drives the working element from the desired
speed should the factor indicate that the power tool is being
operated in a sub-optimal manner, thereby providing feedback to the
user through the speed at which the working element is being
driven.
10. The method of claim 9, in which the step of varying the speed
comprises reducing the speed at which the motor drives the working
element.
11. The method of claim 9, in which the at least one factor
comprises the pressure which the user applies the working element
to a subject to be worked, the load on the working element as it
works the subject to be worked or the speed at which the motor or
the working element is working; the temperature of a battery of the
tool; the temperature of the motor; the current drawn by the motor,
the integral of the current drawn by the motor, or the power
consumed by the motor.
Description
[0001] This invention relates to power tools, particularly electric
power tools such as, but not limited to, battery operated power
tools including chain saws or hedge trimmers.
[0002] Power tools, and in particular battery-operated electric
power tools such as hedge trimmers and chainsaws are well known in
the prior art. They will typically comprise a battery arranged to
power a motor, the motor being coupled to a working element in
order to drive that working element. A control element is provided
in order to control the level of power supplied to the motor; this
may be a simple on/off control or may provide discrete control over
the voltage or current supplied to the motor. For a chainsaw, the
working element is an endless chain carrying a plurality of bladed
teeth, whereas for a hedge trimmer the working element is generally
a pair of reciprocating blades.
[0003] Particularly for battery-operated products, it is useful to
be able to provide feedback to a user on how efficiently they are
using the power tool. Batteries hold a limited amount of charge,
and efficient use increases the time between charges. Also,
efficient use of the power tool will reduce the heat dissipated in
the battery and the rest of the tool, thus improving the life of
the battery and potentially the other systems.
[0004] According to a first aspect of the invention, there is
provided a power tool comprising a working element, a motor
arranged to drive the working element and a controller arranged to
control the speed at which the motor drives the working element, in
which there is provided a sensor for at least one factor indicative
of the efficiency with which the power tool is being operated, the
controller being arranged to vary the speed at which the motor
drives the working element should the factor indicate that the
power tool is being operated in a sub-optimal manner.
[0005] As such, this provides feedback to a user through the speed
at which the working element is driven. By controlling the motor to
run at a modified speed, the user is encouraged to operate the tool
in a more efficient manner.
[0006] The controller will preferably be arranged to reduce the
speed at which the motor drives the working element in the event of
the power tool being used in a sub-optimal manner. Alternatively,
the controller can be arranged to cyclically vary the speed, so as
to provide vibrations to the user, or could even increase the
speed.
[0007] In the preferred embodiment, the at least one factor
comprises the pressure which the user applies the working element
to a subject to be worked. As such, the power tool may therefore
guide the user as to the efficient pressure to be applied.
[0008] Inexperienced users are particularly liable to use their
power tools in an inefficient manner. Most tools will have a speed
at which they are most efficient. Inexperienced users, particularly
with chain saws, are liable to put too much pressure on the working
element; since the cutting chain in a chain saw is more or less
self-feeding, increased pressure will generally lead to a loss of
efficiency.
[0009] The sensor may comprise a pressure sensor, arranged to
measure the pressure applied using the working element. However, in
the case where the tool is an electric power tool and the motor is
an electric motor, the sensor may comprise a current sensor
arranged to measure the current flowing through the motor. An
increase in current may therefore indicate that too much pressure
is being applied, and so the motor is working in a sub-optimal
state. As such, the controller may be arranged to vary, and
typically reduce, the speed at which the motor drives the working
element when the current measured by the current sensor exceeds a
limit.
[0010] The tool may comprise a power sensor, such as a current
integration unit, which integrates the flow of current over time;
this provides a convenient indication of the power flowing through
the motor; if excessive power is being consumed, then this is an
indication that the motor or any battery may be overheating.
[0011] Additionally or alternatively, the sensor may comprise at
least one of a load sensor, arranged to sense, as a factor, the
load on the working element as it works the subject to be worked; a
speed sensor, arranged to sense as a factor the speed at which the
motor or the working element is working; or a temperature sensor
for sensing the temperature of part of the tool, such as the motor
or a battery of the tool.
[0012] With an electric power tool where the motor is an electric
motor, the controller may comprise a variable power control element
having an input and an output, in which the controller is arranged
so that, if the factor as measured by the sensor is indicative of a
sub-optimal operation of the power tool, the power control element
reduces the power that is transmitted from the input to the output.
For example, the power control element may comprise a controllable
variable resistance, whereby the controller increases the
resistance of the controllable variable resistance should a
sub-optimal operation be determined, for example by the current
through the motor exceeding the limit.
[0013] As such, the power tool may comprise a source of electric
power, a speed selector operable by a user of the power tool and
operative to take electric power from the source and output an
electric signal indicative of a speed at which the user desires to
operate the power tool, the output of the speed selector being
coupled to the input of the power control element. The speed
selector may allow the selection a plurality of discrete different
speeds, such as two different speeds providing simple on/off
control, or may provide a continuous range of speeds, preferably
including zero speed. The controller will then provide feedback
based upon the user's desired speed.
[0014] The power tool may be a trimmer, such as a hedge trimmer,
where the working element comprises at least one, but preferably
two reciprocating blades. In the preferred embodiment, the power
tool is a chain saw, where the working element comprises an endless
chain carrying a plurality of cutting teeth, driven around the
length of the endless chain by the motor.
[0015] Typically, the power tool will be battery-operated electric
power tool, in which the motor is an electric motor, and in which
the source of electricity for the motor is an electric battery.
[0016] According to a second aspect of the invention, there is
provided a method of operating a power tool comprising a working
element, a motor arranged to drive the working element and a
control element by means of which a user indicates a desired speed,
the method comprising sensing at least one factor indicative of the
efficiency with which the power tool is being operated, the power
tool varying the speed at which the motor drives the working
element from the desired speed should the factor indicate that the
power tool is being operated in a sub-optimal manner.
[0017] As such, this provides feedback to a user through the speed
at which the working element is driven. By controlling the motor to
run at a modified speed, the user is encouraged to operate the tool
in a more efficient manner.
[0018] The step of varying the speed will preferably comprise
reducing the speed at which the motor drives the working element.
Alternatively, that step may comprise cyclically varying the speed,
so as to provide vibrations to the user, or could even comprise
increasing the speed.
[0019] In the preferred embodiment, the at least one factor
comprises the pressure which the user applies the working element
to a subject to be worked.
[0020] The pressure may be sensed using a pressure sensor. However,
in the case where the tool is an electric power tool and the motor
is an electric motor, the pressure may be sensed by measuring the
current flowing through the motor. An increase in current may
therefore indicate that too much pressure is being applied, and so
the motor is working in a sub-optimal state. As such, the method
may comprise varying, and typically reducing, the speed at which
the motor drives the working element when the current measured
exceeds a limit.
[0021] The factors may comprise, additionally or alternatively, at
least one of: the load on the working element as it works the
subject to be worked, the speed at which the motor or the working
element is working, the temperature of a battery of the tool, the
temperature of the motor (so that it can be established that the
tool is not overheating), the current drawn by the motor, the
integral of the current drawn by the motor, or the power consumed
by the motor (the latter two factors being indicative of the energy
consumption of the motor, and so potentially can indicate that the
tool may be overheating).
[0022] The power tool may be a trimmer, such as a hedge trimmer,
where the working element comprises at least one, but preferably
two reciprocating blades. In the preferred embodiment, the power
tool is a chain saw, where the working element comprises an endless
chain carrying a plurality of cutting teeth, driven around the
length of the endless chain by the motor.
[0023] Typically, the power tool will be a battery-operated
electric power tool, in which the motor is an electric motor, and
in which the source of electricity for the motor is an electric
battery.
[0024] There now follows, by way of example only, an embodiment of
the present invention, described with reference to the accompanying
drawings, in which:
[0025] FIG. 1 shows a side elevation of a chainsaw according to a
first embodiment of the invention; and
[0026] FIG. 2 shows a circuit diagram of the electric circuit
controlling the chainsaw of FIG. 1.
[0027] A chainsaw according to an embodiment of the invention is
shown in the accompanying drawings. It comprises a housing 1
supporting a cutting element 2. The cutting element comprises an
elongate support 3 over which an endless loop of cutting chain 4
runs. The cutting chain has cutting elements on each link.
[0028] In order to drive the cutting chain 4, a battery 5 and a
motor 6 (both shown in FIG. 2) are provided in the housing 1. The
motor 6 acts to rotate a drive wheel 7 and so drive the chain 4
around the support 3 when current is supplied to it by the battery
5.
[0029] The main control a user has over the operation of the
chainsaw is by the use of the control element main switch 8, which
forms a control element. The user must squeeze both parts 8a, 8b of
the main switch in order to allow current to flow from the battery
5 to the motor 6 and so drive the cutting chain 3 to cut.
[0030] However, in order to provide' feedback to a user of the
chainsaw 1, a feedback controller 9 is provided. This comprises a
control circuit 10 and a variable resistance 11 controlled by the
control circuit 10. The control circuit 10 takes as an input the
output of a current sensor 12, provided in series with the motor;
the output indicates the current flowing through the motor 6.
[0031] As long as the current stays within predetermined normal
limits, then the control circuit 10 will set the variable
resistance 11 to its minimum value, which will not noticeably
affect the flow of power from the battery to the motor; the chain 4
will therefore be driven at full speed.
[0032] However, should the user whilst using the chainsaw press too
hard with the chainsaw on the object to be cut, the load on the
motor 6 will greatly increase, thus increasing the current flowing
through motor and so the current sensor 12. Once the current
reaches a predetermined limit, the control circuit 10 will command
the variable resistance 11 to a higher setting, which will restrict
the power flowing to the motor 6, thus reducing the speed at which
the chain 4 is driven. This can be easily perceived by a user, who
should take it as a signal to press less hard. Once the current
reduces to an appropriate level, the variable resistance will be
reduced back to the minimum level, allowing the user to proceed as
normal.
[0033] Multiple increasing levels of resistance can be provided,
successively slowing the chain down further as the current
increases. Alternatively, the variable resistance can either be off
(resistance substantially zero if current in normal range) or on
(resistance fully applied if current over limit).
[0034] The current sensor may comprise an integration unit, whereby
the integral of the current flowing through the motor 6, typically
over a window in time, can be measured. This gives a measure of the
energy or power consumed by the motor 6, and so can be used to
indicate if excessive power consumption leading to a potential
overheating situation could occur. If such a situation occurs, then
the variable resistance 11 can be used to reduce the current flow
to the motor, and hence reduce the speed of the motor 6 to allow it
to cool down.
[0035] Accordingly, this embodiment of the invention will teach a
user to operate their chainsaw more efficiently, leading in an
improvement in work done per watt-hour consumed.
* * * * *