Prior Art
[0001] EP 2 223 778 A2 describes a switching device for garden tools, in particular for electrically driveable
garden tools, which comprises an operating unit to control a motor and a conversion
unit to convert a mechanical movement into a proportional electrical signal. The operating
unit comprises at least one switch operating element to actuate at least one electrical
switch to open and/or close an electrical circuit, and comprises a speed operating
element for adjusting a rotation speed of the motor. The conversion unit comprises
a conversion element which is arranged at a distance to the speed operating element.
[0002] To convert a mechanical movement of the speed operating element into an electrical
signal to adjust a rotation speed of the motor, the speed operating element has to
be brought into contact with the conversion element via a movement of the speed operating
element relative to the conversion element for converting a mechanical movement into
a proportional electrical signal.
Summary of the Invention
[0003] The invention relates to a switching device for garden tools, in particular for electrically
driveable garden tools, which comprises at least one operating unit to control at
least one motor, and at least one conversion unit to convert a mechanical movement
into a proportional electrical signal, wherein the operating unit comprises at least
one switch operating element to actuate at least one electrical switch to open and/or
close an electrical circuit, and comprises at least one speed operating element for
adjusting a rotation speed of the motor.
[0004] The conversion unit according to the invention comprises at least one conversion
element, which is mechanically coupled to the speed operating element for converting
a mechanical movement of the speed operating element into an electrical signal to
adjust a rotation speed of the motor. Hence, a movement of the speed operating element
is directly transferred to the conversion element. Preferably, the speed operating
element is mechanically coupled to the conversion element in such a manner that every
movement of the speed operating element is directly transmitted to the conversion
element. The term "operating unit" shall define a unit comprising at least one element,
in particular an operating element, which can be directly actuated by an operator
and which is provided to change and/or to influence a process and/or a state by an
actuation and/or by an input of at least one parameter. An "operating element" shall
define an element provided to receive an input from the operator in an operation process,
wherein the element is directly contacted by the operator and a force exerted on the
operating element can be sensed and/or mechanically transferred to actuate a device.
The speed operating element is provided to be actuated directly by the operator, in
particular by fingers of the operator's hand, so as to control a rotation speed of
the motor. Preferably, the speed operating element is moveably supported, in particular
pivotally moveably supported. However, it is also possible that the speed operating
element is translationally moveably supported. An operating force to move the speed
operating element is preferably less than 25 N. Preferably, the operating force to
move the speed operating element is in a range between 20 N and 5 N.
[0005] The term "mechanically coupled" shall define a connection between at least two elements,
wherein the two elements directly abut on each other in every position of the two
elements or wherein the two elements are directly fixed to each other or connected
to each other via at least one further element directly connected to the two elements
so as to transfer a movement of the one element to the other element. Preferably,
the speed operating element rotates the conversion element to convert a mechanical
movement of the speed operating element into a proportional electrical signal. The
switching device according to the invention can advantageously achieve a highly fail-safe
electronics to control a motor. If an error occurs within the mechanical connection
between the speed operating element and the conversion element, a starting of the
motor can advantageously be stopped to prevent a possible injury of the operator by
a driven insert tool driveable by the motor.
[0006] Moreover, the conversion unit comprises at least one tapping element mechanically
coupled to the speed operating element and to the conversion element. The tapping
element is provided to transfer a movement of the speed operating element to the conversion
element. Preferably, the tapping element is fixed to the speed operating element and/or
to the conversion element by a positive and/or a non-positive connection. It is also
possible that the tapping element is fixed to the speed operating element and/or to
the conversion element by a different connection which is considered expedient by
a person skilled in the art. The speed operating element can advantageously be located
at a distance to the conversion element without losing an opportunity of directly
transmitting a movement of the speed operating element to the conversion element,
because of the connection via the tapping element. Moreover, it is advantageously
possible to protect the conversion unit against wet conditions, in a manner independent
of a protection against wet conditions of the operating unit.
[0007] In a preferred embodiment of the switching device according to the invention, the
tapping element is flexible. Preferably, the tapping element is flexible concerning
a resistance against a bending load. The tapping element is primarily provided to
transmit tensile and/or compressive forces. The tapping element can advantageously
be adapted in a constructively simple manner to different constructive solutions of
an arrangement of the speed operating element relative to the conversion element.
Furthermore, large distances between the speed operating element and the conversion
unit can advantageously be bridged.
[0008] In addition, the conversion unit comprises at least one spring element to exert a
spring load on the conversion element in at least one direction. Preferably, the spring
element is embodied as a leg spring. It is also possible that the spring element is
embodied in a different shape which is considered expedient by a person skilled in
the art. The conversion element can advantageously be moved into a start position
by the spring element if a mechanical damage, in particular a mechanical damage of
the tapping element, occurs. Therefore, a highly fail-safe switching device can advantageously
be achieved.
[0009] Moreover, the conversion unit comprises at least one adjusting unit to adjust at
least one tapping element of the conversion unit. Preferably, the adjusting unit is
embodied as a mechanical adjusting unit to adjust a position of a supporting element
of the tapping element relative to the speed operating element and/or relative to
a motor housing of the garden tool. It is also possible that the adjusting unit is
embodied as an electronic adjusting unit to adjust an electrical parameter which depends
on a position of the tapping element of the conversion unit relative to the speed
operating element and/or relative to the motor housing. By means of the adjusting
unit according to the invention, a comfortable adjustment of the tapping element can
advantageously be achieved in the case of a geometrical and/or dimension deviation.
Therefore, a precisely working switching device can advantageously be achieved. Furthermore,
a long life expectancy can advantageously be achieved.
[0010] In a preferred embodiment of the switching device according to the invention, the
tapping element is translationally moveably supported. Therefore, a precise transmitting
of a movement of the speed operating element can advantageously be achieved. Furthermore,
a compact and simple embodiment of the tapping element can advantageously be achieved.
[0011] Preferably, the tapping element is embodied as a Bowden cable. In a preferred embodiment
of the switching device according to the invention, the tapping element is embodied
as a push/pull Bowden cable. A safe and weatherproof construction to transmit a movement
of the speed operating element to the conversion element can advantageously be achieved.
[0012] In a preferred embodiment of the switching device according to the invention, the
conversion unit is embodied as a potentiometer. Therefore, a constructively simple
and cost-efficient embodiment of the conversion unit can advantageously be achieved
to convert a mechanical movement into a proportional electrical signal. Moreover,
a garden tool, in particular an electrically driveable garden tool, is proposed, which
comprises at least one switching device according to the invention. The electrically
driveable garden tool can be energized by a portable accumulator or by a cable which
can be connected with an electrical socket e.g. of a local power network. Preferably,
the electrically driveable garden tool is embodied as an electrically driveable brushcutter.
It is also possible that the switching device is used in another garden tool, like
a hedge trimmer, a leaf blower, a chain saw etc. The garden tool according to the
invention has the advantage that a comfortable and safe usage can be realized. Thus
a garden tool with a high ease of use can advantageously be achieved.
[0013] In addition, a method to control an electric motor of an electrically driveable garden
tool with a switching device according to the invention is proposed. A comfortable
switching method with a high security level can advantageously be achieved.
[0014] The switching device according to the invention, the garden tool according to the
invention and/or the method to control a motor of a garden tool with a switching device
according to the invention is/are not to be limited to the utilization and the embodiment
described above. In particular, the switching device according to the invention, the
garden tool according to the invention and/or the method to control a motor of a garden
tool with a switching device according to the invention can have a differing number
of elements, components and units for a satisfying function as specified herein.
Brief Description of the Drawings
[0015] Further objects, features and advantages of the present invention will become apparent
from reading the following detailed description, taking in conjunction the accompanying
drawing wherein a particular embodiment of the invention is disclosed as an illustrative
example.
- Fig. 1
- shows an electrically driveable garden tool according to the invention comprising
a switching device according to the invention in a schematic representation,
- Fig. 2
- shows a detail view of the switching device according to the invention in a schematic
representation,
- Fig. 3
- shows a detail view of a conversion unit of the switching device according to the
invention in a schematic representation,
- Fig. 4
- shows a detail view of an adjusting unit of the conversion unit in a schematic representation
and
- Fig. 5
- shows an exploded view of the conversion unit and a portion of a motor housing of
the garden tool according to the invention in a schematic representation.
Detailed Description of the Illustrative Embodiment
[0016] Figure 1 shows a garden tool 12 which comprises at least one switching device 10.
The garden tool 12 is embodied as an electrically driveable brushcutter. Therefore,
the garden tool 12 comprises a motor housing 30 to support a motor 16, in particular
an electric motor 16, of the garden tool 12. Moreover, the garden tool 12 comprises
a tool holder 32 which a cutting tool 34 can be mounted to. The cutting tool 34 can
be embodied as a trimmer line cutting tool, as a blade-like cutting tool, as a saw-like
cutting tool etc. The tool holder 32 is rotatably driveable by the motor 16. Hence,
the garden tool 12 comprises a gear 36 which the motor 16 and the tool holder 32 are
connected to. It is also possible that the tool holder 32 is directly driven by the
motor 16. Then, the motor 16 is located in a motor housing 30 to which the tool holder
32 is directly attached. The gear 36 is supported in a gear casing 38 of the garden
tool 12. The tool holder 32 is mounted to the gear casing 38. The gear casing 38 and
the motor housing 30 are connected with each other via a shaft 40 of the garden tool
12. The shaft 40 is embodied as a guidance rod for the garden tool 12. In case the
motor 16 directly drives the tool holder 32, the motor housing 30 (in the alternative
embodiment the gear casing 38 in figure 1 is the motor housing 30) is arranged on
one end of the shaft 40 and a housing for electrical components (in the alternative
embodiment the motor housing 30 in figure 1 is the housing for electrical components)
is arranged at another end of the shaft 40. The garden tool 12 further comprises an
energy supply connection unit 42 to which an energy supply unit 44 can be connected.
The energy supply unit 44 is embodied as an accumulator unit. The energy supply connection
unit 42 is arranged at the motor housing 30. In case the motor 16 directly drives
the tool holder 32, the energy supply connection unit 42 is arranged at the housing
for electrical components which is connected to the motor housing 30/gear casing 38
via the shaft 40. Thus a general construction of the garden tool 12 is well known
to a person skilled in the art.
[0017] The switching device 10 for the garden tool 12 comprises at least one operating unit
14 to control the motor 16 and at least one conversion unit 18 for converting a mechanical
movement into a proportional electrical signal, wherein the operating unit 14 comprises
at least one switch operating element 54 to actuate at least one electrical switch
66 (figure 2) to open and/or close an electrical circuit, and comprises at least one
speed operating element 20 for adjusting a rotation speed of the motor 16, and wherein
the conversion unit 18 comprises at least one conversion element 22 which is mechanically
coupled to the speed operating element 20 for converting a mechanical movement of
the speed operating element 20 into an electrical signal to adjust a rotation speed
of the motor 16. The conversion unit 18 comprises at least one tapping element 24
mechanically coupled to the speed operating element 20 and to the conversion element
22, for mechanically coupling the speed operating element 20 and the conversion element
22 with each other.
[0018] The operating unit 14 further comprises a lock operating element 56 to hold the switch
operating element 54 in an actuated state via a positive and/or a non-positive connection.
Moreover, the switching device 10 comprises a bike handle unit 46. The bike handle
unit 46 is mounted to the shaft 40. Furthermore, the bike handle unit 46 comprises
a handle 48 at which the operating unit 14 is located. The handle 48 can be gripped
by an operator's hand for guiding the garden tool 12 during work with the garden tool
12. Moreover, the bike handle unit 46 comprises a further handle 50 which can be gripped
by the operator. The handle 48 and the further handle 50 are connected with each other
via a handlebar 52 of the bike handle unit 46. The handlebar 52 is u-shaped. Herein,
the handle 48 is arranged at one end of the handlebar 52 which is at a far side of
the handlebar 52 with respect to the end at which the further handle 50 is arranged.
[0019] The speed operating element 20, the switch operating element 54 and the lock operating
element 56 are each arranged at different sides of the handle 48. The speed operating
element 20 is provided to be actuated by at least one finger of the operator's hand
when the operator grips the handle 48, wherein the at least one finger is different
from a thumb of the operator's hand. In addition, the speed operating element 20 is
pivotally moveably supported at the handle 48. The switch operating element 54 is
provided to be actuated by a thumb of the operator's hand when the operator grips
the handle 48. Moreover, the switch operating element 54 is translationally moveably
supported at the handle 48. The lock operating element 56 is provided to be actuated
by a palm of the operator's hand when the operator grips the handle 48. Furthermore,
the lock operating element 56 is pivotally moveably supported at the handle 48.
[0020] The tapping element 24 is connected to the speed operating element 20 via a positive
and/or a non-positive connection (figure 2). The speed operating element 20 comprises
a connection portion to which the tapping element 24 is connected. In its connection
portion the speed operating element 20 comprises a connection recess in which an end
of the tapping element 24 is located. Furthermore, the tapping element 24 is connected
to the conversion element 22 via a positive and/or a non-positive connection (figure
3). The conversion element 22 comprises a connection portion to which the tapping
element 24 is connected. In its connection portion the conversion element 22 comprises
a connection recess in which an end of the tapping element 24 is located. The conversion
element 22 is arranged in the motor housing 30. Therefore, the tapping element 24
mechanically connects the speed operating element 20 arranged in the handle 48 to
the conversion element 22 arranged in the motor housing 30. The tapping element 24
is flexible. Herein, the tapping element 24 is embodied as a Bowden cable. Therefore,
the tapping element 24 is translationally moveably supported.
[0021] The conversion unit 18 is embodied as a potentiometer. The conversion element 22
is pivotally moveably supported in the motor housing 30. Herein, the conversion element
22 interacts with a resistance element 58 (figure 5) of the conversion unit 18, whereby
an electrical resistance of the resistance element 58 depends on an angle of rotation
of the conversion element 22 relative to the resistance element 58. A rotation speed
of the motor 16 is controllable via a rotational movement of the conversion element
22. This changes the electrical resistance of the resistance element 58 in a well-known
manner. A rotation of the conversion element 22 depends on a movement of the speed
operating element 22 which is mechanically coupled to the conversion element 22 via
the tapping element 24. When the speed operating element 20 is moved, the conversion
element 22 is also moved because of the mechanically coupling via the tapping element
24. The change in the electrical resistance of the resistance element 58 is detected
by a PCBA 62 (printed circuit board assembly) of the switching device 10 to trigger
a speed adjustment of the motor 16.
[0022] Furthermore, the conversion unit 18 comprises at least one spring element 26 to exert
a spring load on the conversion element 22 in at least one direction, in particular
towards a start position of the conversion element 22. In the start position of the
conversion element 22, an electrical energy supply to the motor 16 is disconnected
so that the motor 16, in particular a rotor of the motor 16 does not rotate. The spring
element 26 is embodied as a leg spring. One leg of the spring element 26 is braced
at an inner surface of the handle 48 and another leg of the spring element 26 is braced
at the conversion element 22 (figure 3). When an operating force on the speed operating
element 20 is discontinued, the conversion element 22 is moved into a start position
via a spring load of the spring element 26. The conversion unit 18 further comprises
at least one arrester element 60 provided to limit a maximum angle of movement of
the conversion element 22 relative to the motor housing 30. In its start position
the conversion element 22 abuts on at least one side of the arrester element 60. The
conversion element 22 strikes against another side of the arrester element 60 when
the conversion element 22 is rotated by the maximum angle of movement. It is also
possible that the conversion unit 18 comprises more than one arrester element 60,
which arrester elements 60 are provided to limit a maximum angle of movement of the
conversion element 22.
[0023] Moreover, the conversion unit 18 comprises at least one adjusting unit 28 to adjust
the tapping element 24 of the conversion unit 18 (figures 3 and 4). The adjusting
unit 28 is provided to adjust a position of an outer cable housing 72 of the Bowden
cable relative to the speed operating element 20 and/or relative to the motor housing
30. Therefore, the adjusting unit 28 allows a proper assembly in the case of a geometrical
or a dimensional deviation at a fixing portion 70 of the motor housing 30, which one
end of the outer cable housing 72 of the Bowden cable is fixed to. Herein, the adjusting
unit 28 allows an adjustment of a position of the outer cable housing 72 of the Bowden
cable of about 0.5 mm to 5 mm. The adjusting unit 28 is embodied as a bulkhead connection
adjusting unit. Hence, the adjusting unit 28 comprises at least one adjusting element
68 which interacts with the fixing portion 70 of the motor housing 30 for adjusting
a position of the outer cable housing 72 of the Bowden cable (figures 3 and 4).
[0024] A method to control and/or start the motor 16 of the electrically driveable garden
tool 12 with the switching device 10 can comprise the following steps:
The switch operating element 54 is pushed into an actuated position of the switch
operating element 54 by the operator, whereby the electrical switch 66 is actuated.
The electrical switch 66 closes an electrical circuit for energizing the PCBA 62 of
the switching device 10. The PCBA 62 is turned on. It is also possible that the PCBA
62 is only turned on when the speed operating element 20, the switch operating element
54 and the lock operating element 56 are actuated. The electrical switch 66 is embodied
as a micro switch, in particular as a dual micro switch. It is also possible that
the electrical switch 66 is embodied as a different switch which is considered expedient
by a person skilled in the art. In the process of the actuation of the switch operating
element 54, the lock operating element 56 is also moved into an actuated position
of the lock operating element 56. The lock operating element 56 holds the switch operating
element 54 in an actuated position of the switch operating element 54 via a blocking
element 64 (figure 3).
The lock operating element 56 can be depressed without a movement of the switch operating
element 54 but this does not turn on or trigger a signal from the electrical switch
66. A signal from the electrical switch 66 only occurs when the switch operating element
54 is operated. Now that the electrical switch 66 is engaged and the PCBA 62 is in
operation, the motor 16 can be started by a movement of the speed operating element
20. A movement of the speed operating element 20 moves the tapping element 24, which
moves the conversion element 22. Herein, an electrical signal is triggered to start
the motor 16 and to control a rotation speed of the motor 16. Therefore, a rotation
speed of the motor 16 depends on a movement distance of the speed operating element
20 and hence on a movement distance of the tapping element 24 and the conversion element
22.
Preferably, the rotation speed of the motor 16 is adjustable form 0 to 15,000 rpm.
It is also possible that the rotation speed of the motor 16 is adjustable within a
different range which is considered expedient by a person skilled in the art. In case
the operator's hand is removed from the handle 24, the lock operating element 22 releases
the switch operating element 20 and the electrical switch 66 switches off the PCBA
62 and the electrically driveable garden tool 12. The PCBA 62 is located in the motor
housing 30.
[0025] Before the motor 16 is started, the PCBA 62 interrogates a position of the conversion
element 22 relative to the resistance element 58 so as to check a correct angular
position value of the conversion element 22. When the detected angular position value
of the conversion element 22 is outside a predetermined starting range of the conversion
element 22, the PCBA 62 does not allow a start of the motor 16. When the detected
angular position value of the conversion element 22 is within the predetermined starting
range of the conversion element 22, the PCBA 62 utilizes the maximum rotation speed
of the motor 16 and a linear increment of the maximum angle of movement of the conversion
element 22. Based on the start position and the maximum angle of movement of the conversion
element 22, the PCBA 62 calculates a maximum rotation speed threshold value and defines
a linear increment between the maximum rotation speed threshold value and the maximum
angle of movement of the conversion element 22. The maximum rotation speed threshold
value is not set at the position of the maximum angle of movement of the tapping element
24 but rather before this. Once the conversion element 22 has reached the position
which corresponds to the maximum rotation speed of the motor 16, any further rotation
of the conversation element 22 does not alter the rotation speed of the motor 16.
This solution advantageously provides a possibility to compensate an alteration of
a mechanical parameter of the operating unit 14 and/or the conversion unit 18, for
example a stretching of the tapping element 24, loss of spring stiffness of the spring
element 26, a wear of the support of the speed operating element 20 etc.
[0026] A calculating routine of the PCBA 62 checks after a start of the PCBA 62 the initial
position Y1 of the conversion unit 18. For safety reasons this is only allowed to
be done after PCBA 62 has performed self-tests. This adds a defined "blind" time together
with power supply activation. Once awake the PCBA 62 will then record an initial position
Y1. This recorded position is the zero speed position where all speeds are calculated
from. The motor 16 only starts rotating when the conversion unit 18 reaches a positionY1
+ H1 (with H1 being an additional movement, especially a rotation, of the conversion
unit 18 which is greater than Y1). The speed is regulated between the positions Y1
+X1 and Y1 +X2 (with X1 being higher than Y1 and with X2 being higher than X1). H
1, X1 and X2 are defined as increments of Y1 instead of an absolute value due to the
mechanical constraints of not having an absolute positioning sensor but only a relative
one.
[0027] During operation of the garden tool 12, if the switching device 10 is allowed to
return to zero speed and the conversion unit value read back is smaller than the previous
Y1, then Y1 will be reset to the new recognized value. A self-adjusting function to
consider a bouncing of the spring element 26 can be achieved. In case Y1 is measured
outside the normal/permissible start up range, the full speed of the motor 16 may
not be achievable until the operator releases and reoperates the electrical switch
66 again. This reset allows the switching device 10 including the conversion unit
18 to return to a lower Y1 value within the working parameter range. In short the
auto calibration of the conversion unit value will occur within a value less than
200 Milliseconds, especially within 120 Milliseconds, of the electrical switch 66
being activated, and whenever the motor 16 is stopped.
1. A switching device for garden tools, in particular for electrically driveable garden
tools, comprising:
at least one operating unit (14) to control at least one motor (16);
and at least one conversion unit (18) to convert a mechanical movement into a proportional
electrical signal;
wherein said operating unit (14) comprises at least one switch operating element (54)
to actuate at least one electrical switch (66) to open and/or close an electrical
circuit, and comprises at least one speed operating element (20) for adjusting a rotation
speed of said motor (16), and wherein said conversion unit (18) comprises at least
one conversion element (22) which is mechanically coupled to said speed operating
element (20) for converting a mechanical movement of said speed operating element
(20) into an electrical signal to adjust a rotation speed of said motor (16).
2. The switching device as defined in Claim 1, wherein said conversion unit (18) comprises
at least one tapping element (24) mechanically coupled to said speed operating element
(20) and to said conversion element (22).
3. The switching device as defined in Claim 2, wherein said tapping element (24) is flexible.
4. The switching device as defined in any one of the preceding Claims, wherein said conversion
unit (18) comprises at least one spring element (26) to exert a spring load on said
conversion element (22) in at least one direction.
5. The switching device as defined in any one of the preceding Claims, wherein said conversion
unit (18) comprises at least one adjusting unit (28) to adjust at least one tapping
element (24) of said conversion unit (18).
6. The switching device as defined in any one of Claims 2 to 5, wherein said tapping
element (24) is translationally moveably supported.
7. The switching device as defined in any one of Claims 2 to 6, wherein said tapping
element (24) is embodied as a Bowden cable.
8. The switching device as defined in any one of the preceding Claims, wherein said conversion
unit (18) is embodied as a potentiometer.
9. A garden tool, in particular an electrically driveable brushcutter, comprising:
at least one switching device as defined in any one of the preceding Claims.
10. A method to control a motor (16) of a garden tool with a switching device as defined
in any one of Claims 1 to 8.