Note: Descriptions are shown in the official language in which they were submitted.
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Description
Circuit arrangement and method for controlling a drive for an
adjustable table-top
The invention concerns a circuit arrangement and method for
the control of a drive for an adjustable table-top.
A large number of tables, particularly writing desks with
adjustable tops on which the height of the table-top can be
adjusted by means of a special drive are offered nowadays. A
variety of operating elements are provided to actuate the
height adjustment. The operating elements are connected
through a cable to a drive unit for driving the table-top.
The operating elements may, for instance, be mounted
underneath the table-top at the front edge of the table, or
are glued around the front edge of the table. The intention
is to give the user easy access, whilst at the same time
permitting the cable to be laid underneath the table-top,
since the drive controller is usually located below the
table-top. The user frequently finds this operating position
to be impractical, but due to the cable connection to the
drive controller it cannot be flexibly changed.
Frequently, operating elements are fitted in locations on the
table or the table-top or in a hole or depression in the
table-top. This, however, requires mechanical work on the
table-top, in particular so that the cable can be passed from
the top to the underside of the table-top.
An object of the invention is to provide a circuit
arrangement and method with which a drive for an adjustable
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table-top can be controlled at low cost and without the need
for mechanical work on the table-top.
This object is achieved with the subject-matter of the
independent patent claims. Implementations and further
development of the invention are subject-matter of the
dependent claims.
One embodiment of a circuit arrangement for controlling a
drive for an adjustable table-top comprises an operating unit
and an evaluation unit. The operating unit comprises at least
one activation element by means of which a state of the
operating unit can be changed. The evaluation unit comprises
a sensor unit for wireless detection of the state of the
operating unit. Furthermore, the evaluation unit includes a
control terminal from which a control signal can be output to
a drive controller depending on the state that is detected.
For instance, the at least one operating element can change a
magnetic field that acts on the evaluation unit, while the
sensor unit comprises at least one magnetic field sensor for
detection of the magnetic field.
This makes it possible for the operating unit and the
evaluation unit to be mounted on the table-top independently
of one another. It is possible to control the table-top drive
without mechanical work on the table-top being essential. As
a result of the wireless acquisition of the state of the
operating equipment it is possible, for instance, for the
operating equipment to be attached above the table-top while
the evaluation unit, which can be connected to the drive
controller by cable, can be attached underneath the table-
top.
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In one embodiment of a method for controlling a drive for an
adjustable table-top, a state of an operating unit is
influenced by activating at least one activation element on
the operating unit, as a result of which the activation also
changes a magnetic field acting on the evaluation unit. The
state of the operating unit is detected wirelessly in an
evaluation unit, whereby the detection also detects the
magnetic field. A control signal can be derived from the
state that is detected. This control signal is ultimately
passed on to a drive controller.
This method has the favourable consequence that an activation
element can be activated above the table-top, while the
evaluation of the resulting changed state of the operating
unit can take place through wireless acquisition underneath
the table-top.
The principle upon which this is based also allows a circuit
arrangement, particularly the operating unit, to be flexibly
located in the area of the table-top, for instance at a
convenient position in the working area of the table-top.
The invention is explained below using several embodiments
with reference to the drawings. Elements having the same
function or effects are given the same reference signs.
They show:
Figure 1 a first embodiment of a proposed circuit
arrangement,
Figure 2 a second embodiment of a circuit arrangement,
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Figure 3 a first embodiment of an operating unit,
Figure 4 a third embodiment of a circuit arrangement,
Figure 5 a fourth embodiment of a circuit arrangement,
Figure 6 a second embodiment of an operating unit and
Figure 7 a fifth embodiment of a circuit arrangement.
Figure 1 illustrates an embodiment of a circuit arrangement
for controlling a drive. An operating unit 1 is provided here
with an activation element 11 that is positioned above a
table-top 3. Below the table-top 3, underneath the operating
unit 1, an evaluation unit 2 is positioned, comprising a
sensor unit 21 to which a sensor coupler 29 is attached. A
drive controller 100 is connected through a control terminal
of the evaluation unit 2 to the sensor coupler 29. The
20 operating unit 1 and the evaluation unit 2, which are
substantially parallel to one another, are separated by the
table-top 3.
By activating the activation element 11, a state of the
operating unit 1 is affected or changed. The operating unit 1
may be able to adopt a number of different states. For
instance, activating the activation element 11 may change the
operating unit 1 from a first state into a second state.
The operating unit 1 and the evaluation unit 2 can be coupled
together in a variety of ways. The coupling can, for
instance, be achieved through a magnetic field, in particular
a static magnetic field. Coupling can also be achieved
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through an alternating electromagnetic field. A change in the
state of the operating unit 1 can thus, for instance, be
achieved through a change in the properties of the static
magnetic field. An electromagnetic field can be changed by
changing the inductive and/or capacitive properties of the
operating unit 1.
These changes in state can be recorded or detected by the
sensor unit 21, and can be converted by the sensor coupler 29
into appropriate control signals for the drive controller
100. The state of the operating unit 1 is detected through
the table-top 3 without wires, i.e. without a cable
connection between the operating unit 1 and the evaluation
unit 2.
Figure 2 illustrates a further embodiment of a circuit
arrangement for controlling a drive. The evaluation unit 2
comprises here at least one magnetic field sensor 22 in the
sensor unit 21. This is used to detect a magnetic field that
is acting on the evaluation unit 2. The magnetic field sensor
22 can, for instance, be implemented using a Hall sensor, or
may comprise a Hall sensor. A Hall sensor supplies a voltage
that depends on a magnetic field that is present at the Hall
sensor. When the magnetic field changes, the voltage at the
Hall sensor therefore also changes. From this change in
voltage, which results from the change in the state of the
operating unit 1, a control signal can be derived for a drive
controller 100.
The magnetic field sensor can also comprise other elements
that are affected magnetically such as, for instance,
magneto-resistive elements or magnetic diodes.
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In this embodiment, the operating unit 1 comprises a magnet
Ml implemented, for instance, in the form of a permanent
magnet. The magnetic field from the magnet M1 can be detected
wirelessly by the magnetic field sensor 22. By means of the
activation element 11, the operating unit 1 can, for
instance, be mechanically moved across the table-top 3, as a
result of which there is a change in the magnetic field
acting at the evaluation unit 2. A movement can, for
instance, be made directly a long a line of movement, or may
also consist of a rotary movement of the operating unit 1 on
the table-top 3.
It is also possible for the magnetic field sensor 22 to be
designed in such a way that it detects a magnetic field that
acts on the evaluation unit 2 at several locations on the
evaluation unit 2, in order, for instance, to be able to
detect several different magnetic states of the operating
unit 1. From a number of different states it is thus possible
to derive a number of different control signals and to pass
them on to the drive controller 100.
Figure 3 illustrates an alternative embodiment of an
operating unit 1, in which a magnetic state of the operating
unit 1 can be changed. In this embodiment, activation of the
activation element 11 can close a switch S1. The switch Sl is
wired into an electrical circuit having a source of voltage
Vl and a coil Ll. The source of voltage V1 represents a
source of electrical power.
Closing the switch Sl creates an electrical current through
the coil Ll. If the source of voltage V1 is a DC source, the
flow of current through the coil L1 will generate a magnetic
field for a certain time, the length of time depending on the
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inductance and the electrical resistance of the coil L1. The
change in state of the operating unit 1 can be determined
from the change in the magnetic field or by the generation of
the magnetic field, by means of a magnetic field sensor 22
not shown here.
If the voltage source V1 is implemented as a source of
alternating voltage, a magnetic field will be generated
continuously by the coil L1 while the switch is closed. This
magnetic field can also be detected by a magnetic field
sensor 22.
The operati_ng unit 1 can also comprise several magnets or
coils for the generation of magnetic fields, and these,
through the activation of a number of activation elements,
can generate and/or affect a magnetic field acting at the
evaluation unit 2.
Figure 4 illustrates a further embodiment of a circuit
arrangement for controlling a drive. In this embodiment, the
sensor unit 21 comprises a resonant circuit 40 comprising a
source of power 4, a capacitor C4 and a coil L4 that acts as
an antenna. The operating unit 1 comprises a first and a
second operating element 11, 12, as well as two resonant
circuits 42, 43, that are constituted respectively by a
capacitive element C2 and a coil L2 and by a capacitive
element C3 and a coil L3. The switches S2, S3, that are
activated by the activation elements 11, 12, can electrically
close the passive resonant circuits 42, 43.
The resonant circuit 40 radiates an alternating
electromagnetic field through the coil L4, which acts as an
antenna. Depending on the state of the operating unit 1, in
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other words on a state of the switches S2, S3, the electrical
properties of the resonant circuit 40 can be affected. When
switches S2, S3 are open, the associated resonant circuits
42, 43 cannot respond; in other words the associated resonant
circuits 42, 43 do not include an effective inductance. By
closing the corresponding switches S2, S3 by means of the
associated activation element 11, 12, an inductance value is
thus changed. Because the state of the operating unit 1
depends on the value of the inductance, the state of the
operating unit 1 also changes.
Closing one of the resonant circuits 42, 43 affects the
electrical properties of the resonant circuit 40. This can be
detected in the evaluation unit 2, and can be used to derive
a control signal to be output at the control terminal 20.
Through suitable tuning of the resonant circuits 42, 43
through an appropriate selection of the values for the coils
L2, L3 and of the capacitive element C2, C3 the electrical
properties of the resonant circuit 40 can be changed in
different ways according to whether resonant circuit 42 or 43
is activated. As a result, different control signals can be
derived.
The operating unit 1 and the evaluation unit 2 can thus be
coupled by means of an electromagnetic field. The coils L2,
L3 function as antennae, and can be switched in or out by
means of the activation element 11, 12. By switching the
antennae in or out, the electromagnetic field can be affected
or changed.
Alternatively, the evaluation unit 2 may also comprise a
number of antennae or coils, two for instance, positioned
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next to one another. In this example, the operating unit
comprises three antennae, of which one is permanently active
and is located in the area of the electromagnetic fields of
the antennae of the evaluation unit, for instance in a
position centrally above the two antennae of the evaluation
unit 2. The second and third antennae of the operating unit
can be positioned in such a way that each of these antennae
is positioned in the primary region of action of the
electromagnetic field of one of the antennae of the
evaluation unit. The second and third antennae of the
operating unit can each be activated by one of the activation
elements 11, 12. In this way the activation of different
activation elements 11, 12 can easily be distinguished.
Figure 5 illustrates a further embodiment of a circuit
arrangement for controlling a drive. The sensor unit 21 in
turn comprises a resonant circuit 40. The operating unit 1
comprises identification circuits ID2, ID3 that can be
activated by the switches S2, S3 operated by the activation
elements 11, 12.
The identification circuits ID2, ID3 can, for instance,
consist of circuits 102, 103 or of chips, such as are
familiar from contact-free identification cards. These are
also known as Radio Frequency Identification (RFID) systems.
An identification circuit ID2, ID3 activated by a closed
switch S2, S3 has an effect on an electromagnetic field
generated by the resonant circuit 40 or on a high-frequency
signal transmitted by the resonant circuit 40. The
identification circuit can modulate the signal or change it
in some other way. The identification circuits ID2, ID3
change the signal, or the electromagnetic field, in different
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ways, so that activation of the different activation elements
11, 12 can be distinguished. If an identification circuit
ID2, ID3 is not activated by closing the corresponding switch
S2, S3, the electromagnetic field or the signal transmitted
by the resonant circuit 40 is not affected.
A change caused by one of the identification circuits ID2,
ID3 is detected in the resonant circuit 40, and a
corresponding control signal is derived from it. In an
alternative embodiment, the evaluation unit 2 can comprise a
reading device for contact-free identification cards.
Figure 6 illustrates an embodiment of an operating unit 1
with an identification circuit ID2. A power supply for the
identification circuit ID2 is provided here by an arrangement
50 for generating a supply voltage, comprising a coil L5,
capacitive elements C5, C6 and a diode D5. A signal
transmitted by the resonant circuit 40 is received by the
coil L5. This signal, which is usually an alternating signal
with a high frequency, is rectified by the diode D5 and used
to charge up the capacitive element C6. The capacitive
element C6 serves to store the charge, and provides a supply
of power for the identification circuit ID2. Alternatively, a
different source of voltage, such as a battery, may also be
used.
Figure 7 illustrates a further embodiment of a circuit
arrangement for controlling a drive. The evaluation unit 2
again comprises a resonant circuit 40, in which a capacitive
element in the resonant circuit 40 consists of capacitor
plates P41, P42 positioned adjacent to one another. An
electrical field between the plates 241, P42 also passes
through the operating unit 1 with the activation element 11.
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When the activation element 11 is activated, for instance by
placing a finger on or close to the activation element 11,
the properties of the electrical field, or the capacitive
properties of the operating unit, are changed or affected.
The state of the operating unit thus, for instance, comprises
the capacitive properties.
As a result of the change in the capacitive properties, the
value of the capacitance, for instance, of the capacitor that
consists of the plates P41, P42 changes, so changing the
oscillation frequency of the resonant circuit 40. This change
can be detected, and a control signal can be derived from it.
The capacitor plates P41, P42 constitute, for instance, a
capacitive proximity switch. The evaluation unit 2 can also
comprise other embodiments of capacitive proximity switches
in order to detect changes in the capacitive properties of
the operating unit 1. The operating unit 1, with the
activation elements 11, can in this embodiment also consist
of a simple adhesive label with no electrical function.
If a circuit arrangement in accordance with one of the
embodiments comprises two activation elements 11, 12, it is
typically possible to achieve two different functions for the
drive controller, for instance that the table is moved to a
higher or to a lower position. The number of possible
activation elements, however, is not in any way limited by
this embodiment. Rather, it is possible for additional
activation elements to be provided that can place the
operating unit 1 into more states that can be evaluated. In
this way, additional actions can be carried out on the
movable table-top, such as changing the inclination of the
table-top.
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Reference key
1 Operating unit
2 Evaluation unit
3 Table-top
11, 12 Activation element
20 Control terminal
21 Sensor unit
22 Magnetic field sensor
29 Sensor coupler
40, 42, 43 Resonant circuit
50 Means for generating a power supply
100 Drive controller
S1, S2, S3 Switches
D5 Diode
L1, L2, L3, L4, L5 Coil, antenna
C4, C5, C6 Capacitive element
V1, V4 Power source
M1 Magnet
ID1, ID2 Identification circuit
P41, P42 Capacitor plate
