Vacuum cleaner with three-wire power-supply and communication connection between functional units to be coupled

A vacuum cleaner is provided which has a motor housing (2) and a hose (8), which can be coupled via two mains-voltage wires (38, 42), one communication wire (48) and contacts (32, 34, 30). The motor housing (2) and the handle (10) of the hose (8) include microprocessors (6, 12) which communicate with one another via the communication wire (48). The first reference signal (26) of the one microprocessor (6) is connected to the one mains voltage terminal (18) and the second reference signal (44) of the other microprocessor (12) is connected to the other mains voltage terminal (40).

FIELD OF THE INVENTION 
The invention relates to a vacuum cleaner comprising: a first functional 
unit, and a second functional unit which can be coupled electrically to 
the first functional unit; which first functional unit comprises a first 
mains voltage terminal and a second mains voltage terminal for receiving 
an alternating mains voltage, and a first data processing unit having a 
first reference terminal and a first communication terminal; which second 
functional unit comprises a first mains voltage terminal and a second 
mains voltage terminal for receiving the alternating mains voltage, and a 
second data processing unit having a second reference terminal and a 
second communication terminal; which first mains voltage terminal of the 
first functional unit can be coupled to the first mains voltage terminal 
of the second functional unit via a first mains voltage wire and a first 
mains voltage contact; which second mains voltage terminal of the first 
functional unit can be coupled to the second mains voltage terminal of the 
second functional unit via a second mains voltage wire and a second mains 
voltage contact; and which first communication terminal can be coupled to 
the second communication terminal via a communication wire and a 
communication contact. 
BACKGROUND OF THE INVENTION 
Such a vacuum cleaner ms known from U.S. Pat. No. 4,654,924. This known 
vacuum cleaner comprises three functional units, i.e. a motor housing, a 
hose with a handle and a suction nozzle. The controls are arranged on the 
handle, which for this purpose includes control buttons for activating 
various functions of the vacuum cleaner. The handle further includes an 
indicator device or display screen to give various indications about the 
operating condition of the vacuum cleaner. For a correct operation of the 
system the motor housing and the handle include data processing units 
which should be capable of communicating with one another. A suction 
nozzle can be attached to the hose, which nozzle comprises a rotating 
brush driven by an electric motor which is powered by the alternating 
mains voltage. The suction nozzle also accommodates a data processing unit 
which communicates with the data processing unit in the handle. In order 
to provide data communication between the handle, the motor housing and 
the suction nozzle and to supply mains voltage to the electric motor of 
the brush the functional units can be coupled by means of three wires. 
Therefore, the hose is provided with three wires, a first and a second 
mains voltage wire for mains voltage supply and a communication wire for 
the data communication, which three wires are connected to the motor 
housing via contacts. The data processing units in the motor housing and 
in the handle receive a direct voltage supply from rectifier circuits, 
which locally convert the alternating mains voltage into a suitable direct 
voltage. A similar three-wire connection is present between the hose and 
the suction nozzle. 
In the known vacuum cleaner one of the two mains voltage wires also 
functions as a return wire for the data signals. This is achieved by 
connecting the signal earth or reference terminal of the first and the 
second data processing unit to the same mains voltage terminal. A problem 
of this arrangement is that current surges in the return wire, produced by 
the electric motor of the brush or by other causes, may disturb the data 
communication. This can be remedied by selecting a comparatively high 
signal level for the data communication. This has the drawback that the 
microprocessors used for data communication cannot withstand or are not 
suitable for such high signal levels, which necessitates the use of 
separate voltage conversion stages with a separate high supply voltage. 
However, the use of the vacuum cleaner causes a substantial soiling of the 
contacts coupling the three wires of the functional units to one another. 
The contacts for the mains voltage are self-cleaning as a result of the 
high alternating mains voltage in the case of an open or soiled contact. 
However, the voltage across an open or soiled contact for the 
communication wire is substantially lower and is approximately 19 V for 
the known vacuum cleaner. Consequently, the cleaning effect of this 
voltage, which is comparatively low in relation to the alternating mains 
voltage, is substantially smaller, so that the risk of the data 
communication being disturbed by an open or soiled communication contact 
is substantially greater. 
SUMMARY OF THE INVENTION 
It is an object of the invention to solve the above problems and to provide 
a vacuum cleaner of the type defined in the opening paragraph, which in 
accordance with the invention characterized in that the first reference 
terminal is connected to the first mains voltage terminal of the first 
functional unit and the second reference terminal is connected to the 
second mains voltage terminal of the second functional unit. 
By connecting the reference terminals of the first and the second data 
processing units to the different mains voltage terminals instead of to 
the same mains voltage terminal, a current will flow from the first mains 
voltage terminal to the second mains terminal, or vice versa, via the 
communication contact during data communication. A soiled or open 
communication contact will now also be self-cleaning owing to the high 
alternating mains voltage across the first and the second mains voltage 
terminals. 
The three wires are capacitively coupled to one another. The capacitive 
coupling is considerable especially in the hose as a result of the 
comparatively great length of the three wires. Variations in the voltage 
level of the communication wire with respect to the first or the second 
mains voltage wire therefore occur with a certain time constant, which may 
corrupt the data communication. In order to minimize this corrupted data 
communication a first variant of a vacuum cleaner in accordance with the 
invention is characterized in that the first data processing unit 
comprises a current source for supplying to the first communication 
terminal a signal current whose value varies in response to a data signal 
to be transmitted via the communication wire, and the second data 
processing unit comprises a current-voltage converter for converting the 
signal current into a signal voltage, and a level detector for comparing 
the signal voltage with a reference voltage. 
Data communication is effected with a current source at the transmitting 
side and a current-voltage converter at the receiving side. The 
instantaneous voltage on the communication wire then does not play a part 
in the data transmission because the current source automatically adapts 
itself to the voltage on the communication wire. The data transmission is 
now based on a data signal current instead of a data signal voltage. A 
further advantage thus obtained is that the input impedance at the 
receiving side can be reduced by a suitable construction of the 
current-voltage converter. As a result of this, the communication wire is 
less susceptible to interference and a more robust communication system is 
obtained. Another advantage is that the amplitude of the current supplied 
by the current source can simply be fixed at such a value that 
international interference standards (CISPR standards) are complied with 
for all the prevailing alternating mains voltages. Yet another advantage 
is that the fixed current amplitude allows a current detection at a fixed 
level, so that the receiver does not respond to small interference 
currents. A further advantage is that only the current source should be 
capable of handling the mains voltage; the other parts, specifically the 
current-voltage converter, the level detector and the other circuits in 
the data processing units can be constructed with low-voltage components. 
A second embodiment of a vacuum cleaner is characterised in that the 
current source comprises: a first transistor having a control electrode 
connected to receive the data signal, a first main electrode coupled to 
the first reference terminal via a first resistor, and a second main 
electrode coupled to the first communication terminal. This embodiment is 
simple and cheap and requires a small number of parts, as a result of 
which it is very suitable for use in vacuum cleaners. 
A third embodiment of a vacuum cleaner in accordance with the invention is 
characterised in that the level detector comprises: a second transistor 
having a control electrode coupled to the second reference terminal, a 
first main electrode, and a second main electrode coupled to a supply 
voltage source via a second resistor, and in that the current-voltage 
converter comprises a third resistor connected between the first main 
electrode of the second transistor and the second reference terminal. This 
embodiment is also simple and cheap and requires a small number of parts, 
so that it is also very suitable for use in vacuum cleaners. 
A fourth embodiment of a vacuum cleaner in accordance with the invention is 
characterised in that the first communication terminal is coupled to the 
current source via a first diode and the second communication terminal is 
coupled to the current-voltage converter via a second diode, the forward 
direction of the first diode and the second diode corresponding to the 
direction of the signal current from the current source. The diodes enable 
two-way communication via the communication wire, communication being 
possible from the first to the second data processing unit in one 
half-cycle of the mains voltage and in the reverse direction in the other 
half-cycle. This excludes conflicts as to which of the two data processing 
units is transmitting. 
Another method of data signal transfer is used in a fifth embodiment of a 
vacuum cleaner in accordance with the invention, which is characterised in 
that the first data processing unit comprises: a switch connected between 
the first communication terminal and the first reference terminal, to 
supply to the first communication terminal a first signal current whose 
value varies as a result of the switch being turned on and off in response 
to a first data signal to be transmitted via the communication wire, in 
that the second data processing unit comprises: a capacitor connected 
between the second reference terminal and a node, and a first diode which 
is conductive for the first signal current and which is connected between 
the node and the second communication terminal, and in that a 
current-limiting resistor is included in the current path defined by the 
first communication terminal and the second communication terminal. 
In this method the capacitor in the second data processing unit is charged 
via the first diode and the limiting resistor during switching-over of the 
switch in the first data processing unit. Thus, a direct voltage is built 
up across the capacitor simultaneously with the data transfer, which 
direct voltage can be used as a supply voltage for the electronic devices 
in the second data processing unit. This enables a separate power supply 
to be dispensed with, for example in the handle where there is not much 
room for parts. 
According to the invention a sixth embodiment by means of which two-way 
communication and supply-voltage generation are possible is characterised 
in that the switch of the first data processing unit comprises: a first 
transistor of a first conductivity type, having a control electrode 
connected to receive the data signal, a first main electrode coupled to 
the first reference terminal, and a second main electrode coupled to the 
first communication terminal, and in that the second data processing unit 
comprises: a second transistor of a conductivity type opposite to the 
first conductivity type, having a first main electrode connected to the 
second reference terminal, a second main electrode coupled to the bode via 
a first resistor, and a control electrode coupled to the second reference 
terminal via a second resistor and to the second communication terminal 
via a third resistor, and in that the second data processing unit further 
comprises a third transistor of the first conductivity type, having a 
control electrode connected to receive a second data signal a first main 
electrode connected to the node, and a second main electrode connected to 
the second communication terminal to supply a second signal current, and 
in that the first data processing unit comprises a second diode arranged 
in parallel with the first transistor and conducting for the second signal 
current. 
In order to reduce the influence of said capacitive coupling between the 
three wires a seventh embodiment of a vacuum cleaner in accordance with 
the invention is characterized in that the limiting resistor is made up of 
two sub-resistors, one of the sub-resistors being arranged in series with 
the first communication terminal and being shunted by a third diode which 
conducts for the second signal current and the other sub-resistor being 
arranged in series with the second communication terminal and being 
shunted by a fourth diode which conducts for the first signal current. The 
diodes across the sub-resistors short-circuit the resistors at the 
receiving side and create a low impedance as seen from the switch at the 
transmitting side, which switch will behave as a current source owing to 
the sub-resistor at the transmitting side not being short-circuited, 
yielding all the advantages described hereinbefore.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
FIG. 1 shows a vacuum cleaner in accordance with the invention. A first 
functional unit, in the present case a motor housing 2, accommodates a 
suction motor 4 and a first data processing unit 6. The motor housing 2 
can be coupled to a second functional unit, in the present case a hose 8 
provided with a handle 10. The handle 10 accommodates a second data 
processing unit 12. By means of a tube 14 the hose 8 can be coupled to a 
third functional unit, in the present case a suction nozzle 16, which if 
desired may be equipped with a rotary brush driven by a electric motor. 
FIG. 2 shows the block diagram of the electrical connections between the 
motor housing 2 and the handle 10. The motor housing 2 receives 
alternating mains voltage on a first mains voltage terminal 18 and a 
second mains voltage terminal 20, which can be connected to the a.c. mains 
via a mains lead 22 and a mains plug 24. The first data processing unit 6 
has a first reference terminal 26, which is connoted to the first mains 
voltage terminal 18, and a first communication terminal 28, which is 
connected to a communication contact 30. The first mains voltage terminal 
18 is connected to a first mains voltage contact 32 and the second mains 
voltage terminal is connected to a second mains voltage contact 34. The 
handle 10 has a first mains voltage terminal 36, which is connected to the 
first mains voltage terminal 18 in the motor housing 2 via a first mains 
voltage wire 38 and the first mains voltage contact 32. The handle 10 
further has a second mains voltage terminal 40 connected to the second 
mains voltage terminal 20 in the motor housing 2 via a second mains 
voltage wire 42 and the second mains voltage contact 34. The second data 
processing unit 12 has a second reference terminal 44, which is connected 
to the second mains voltage terminal 40, and a second communication 
terminal 46, which is connected to the communication contact 30 via a 
communication wire 48. The first mains voltage wire 38, the second mains 
voltage wire 42 and the communication wire 48 are arranged in the wall of 
the hose 8 and make electrical contact with the motor housing 2 when the 
hose 8 is mechanically coupled to the motor housing 2. For this purpose 
the communication contact 30, the first mains voltage contact 32 and the 
second mains voltage contact 34 are constructed, for example, as a socket 
and pin contact or as a slip ring and wiper. The first mains voltage wire 
38 and the second mains voltage wire 42 can extend from the handle 10 to 
the suction nozzle 16 via the tube 14 to supply voltage to the rotary 
brush. The communication between the handle 10 and the suction nozzle 16 
can proceed in the same way as that between the motor housing 2 and the 
handle 10. To this end the second data processing unit 12 should be 
provided with a further communication terminal 50, which is coupled to a 
data processing unit (not shown) in the suction nozzle 16 via a further 
communication wire 52 in the tube 14. 
The data processing units in the motor housing 2, the handle 10 and, if 
applicable, the suction nozzle 16 permit convenient central control of 
vacuum cleaner functions from the handled 10 by means of control buttons, 
which functions may include power control of the motor 4 and switching 
on/off of the brush motor in the suction nozzle 16. The handle 10 may also 
include a display screen to indicate the operating condition of the vacuum 
cleaner, such as the selected motor power, brush motor on/off, dust bag 
full etc. For a correct operation of the system the motor housing, the 
handle and, if applicable, the suction nozzle include data processing 
units which communicate with one another. It is customary to provide the 
data processing units with programmed microprocessors for a communication 
with one another in accordance with a communication protocol, which 
obviously depends on the tasks and functions of the individual functional 
units. 
FIG. 3 shows a basic circuit diagram corresponding to the block diagram in 
FIG. 2. The first data processing unit 6 functions as a transmitter and 
comprises a first microprocessor 54, which controls a current source 56 to 
convert the voltage pulses of the data signal from the microprocessor 54 
into current pulses. The signal earth of the microprocessor 54 and of the 
current source 56 are both connected to the first reference terminal 26, 
which in its turn is connected to the first mains voltage terminal 18. The 
current source 56 is further coupled to the first communication terminal 
28 to supply the current pulses. The second data processing unit 12 
functions as a receiver and comprises a current-voltage converter 58, a 
level detector 60 and a reference voltage source 62. The current-voltage 
converter 58 couples the second communication terminal 46 to the second 
reference terminal 44 and converts the data signal current, which flows 
from the second communication terminal 46 to the second reference terminal 
44, into a signal voltage whose amplitude is compared with a reference 
voltage Uref from the reference voltage source 62. The level detector 60 
supplies a pulsating output signal, which can be processed further by a 
microprocessor (not shown). Data communication is based on current pulses 
of fixed current amplitude. Between the first mains voltage wire 38, the 
second mains voltage wire 42 and the communication wire 48 parasitic 
capacitances Cp exist. The parasitic capacitances Cp produce a voltage on 
the communication wire 48, which voltage is out of phase relative to the 
voltages on the first mains voltage wire 48 and the second mains voltage 
wire 42. The output of the current source 56 automatically adapts itself 
to the instantaneous value of the voltage difference between the 
communication wire 48 and the first mains voltage wire 38, which precludes 
corruption of the data signal as a result of charging and discharging of 
the parasitic capacitances. The current from the current source 56 has a 
fixed value, which when the current source is designed can simply be 
adjusted to a value which is in compliance with the relevant interference 
standards. The level detector 60 and the reference voltage source 62 
define a current threshold, so that the receiver does not respond to small 
spurious currents. 
FIG. 4 shows the basic circuit diagram of FIG. 3 in more detail. The 
microprocessor 54 of the first data processing unit 6 is powered by a 
first direct voltage supply 64, which converts the alternating mains 
voltage across the first mains voltage terminal 18 and the second mains 
voltage terminal 20 into a suitable direct voltage. The current source 56 
comprises an npn transistor 66 whose first main electrode or emitter is 
connected to the first reference terminal 26 via a resistor 68 and whose 
second main electrode or collector is connected to the first communication 
terminal 28. The control electrode or base is connected to an output 72 of 
the microprocessor 54 by a resistor 70 and to the first reference terminal 
26 by a resistor 74 to receive the data signal from the microprocessor 54. 
At the other end of the communication wire 48 a resistor 76 connected 
between the second communication terminal 46 and the second reference 
terminal 44 functions as the current-voltage converter. An optional 
capacitor 78 in parallel with the resistor 76 suppresses high-frequency 
interference voltages across the resistor 76. An npn transistor 80, whose 
base is connected to the second reference terminal 44 via a resistor 82 
and whose emitter is connected to the second communication terminal 46, 
simply combines the functions of level detector and reference voltage 
source. A resistor 84 connects the collector of the npn transistor 80 to a 
second direct voltage supply 86, which converts the alternating mains 
voltage across the first mains voltage terminal 36 and the second mains 
voltage terminal 40 into a direct voltage which is positive relative to 
the second reference terminal 44. The second mains voltage terminal 20 is 
positive relative to the first mains voltage terminal 18 during one 
half-cycle of the mains voltage. If the data signal on the output 72 of 
the microprocessor 54 is logic high a current, whose magnitude is mainly 
determined by the resistor 68, will flow from the second mains voltage 
terminal 40 to the first mains voltage terminal 18 via the resistor 76, 
the communication wire 48 and the communication contact 30. The voltage 
drop across the resistor 76 turns on the npn transistor 80. The signal 
voltage across the resistor 84 is buffered and brought at the desired 
signal level by means of an npn transistor 88, whose emitter is connected 
to the second reference terminal 44, whose base is connected to the 
collector of the npn transistor 80 via a resistor 90, and whose collector 
is connected to the direct voltage of the second direct voltage supply 86 
via a resistor 92. The signal on the collector of the npn transistor 88 
can be processed further by a microprocessor, not shown. The circuit 
arrangement shown enables one-way communication from the first data 
processing unit 6 to the second data processing unit 12 during one 
half-cycle of the mains voltage. 
FIG. 5 shows a circuit arrangement which makes it possible to communicate 
in the opposite direction from the second data processing unit 12 to the 
first data processing unit 6 during the other half-cycle of the mains 
voltage. For this purpose the first data processing unit 6 in addition 
comprises a resistor 94 for current-voltage conversion and a transistor 96 
for level detection, arranged similarly to the corresponding elements in 
the second data processing unit 12 shown in FIG. 4, and the second data 
processing unit 12 in addition comprises a transistor 98 and a 
microprocessor 100, arranged similarly to the corresponding elements in 
the first data processing unit 6. In the first data processing unit 6 a 
diode 102 is arranged between the first communication terminal 28 and the 
collector of the npn transistor 66 and is conductive for the collector 
current of the npn transistor 66, and a diode 104 is arranged between the 
first communication terminal 28 and the resistor 94 and is conductive for 
the collector current of the transistor 98. In the second data processing 
unit a diode 106 is arranged between the second communication terminal 46 
and the collector of the transistor 98 and is conductive for the collector 
current of the transistor 98, and a diode 108 is arranged between the 
second communication terminal 46 and the resistor 76 and is conductive for 
the collector current of the npn transistor 66. The diode 104 and the 
diode 108 prevent the direct flow of current from the first mains voltage 
terminal 18 to the second mains voltage terminal 40 and vice versa. The 
diode 102 and the diode 106 prevent an undesired current flow in the 
collector-base path of the current-source transistor at the receiving 
side. 
FIG. 6 shows an alternative circuit arrangement which also provides two-way 
communication. However, a separate direct voltage supply in the second 
data processing unit 12 can now be dispensed with. The circuit 
arrangements shown in FIGS. 3, 4 and 5 operate with switched current 
sources for the data communication. The circuit arrangement in FIG. 6 does 
not use current sources but it employs switches and series resistors. The 
first data processing unit 6 comprises a microprocessor 110 which, via a 
resistor 112, drives the base of a first npn switching transistor 114, 
whose emitter is connected to the first reference terminal 26 and whose 
collector is connected to the first communication terminal 28 via a 
current limiting resistor 116. A diode 118 is arranged in parallel with 
the first switching transistor 114 and has its cathode connected to the 
collector of the first npn switching transistor 114, and another diode 120 
is arranged in parallel with the current limiting resistor 116 and has its 
cathode connected to the first communication terminal 28. The diode 118 
and the diode 120 are cut off when collector current flows from the first 
communication terminal 28 to the first reference terminal 26. The 
collector of the first npn switching transistor 114 is connected to the 
base of a pnp transistor 126 via a diode 122 and a resistor 124. The base 
of the pnp transistor 126 is connected to a positive supply voltage via a 
resistor 128 and a diode 130 in parallel with this resistor, which supply 
voltage is furnished by a direct voltage supply 132, which also provides 
the supply voltage for the microprocessor 110 and the emitter of the pnp 
transistor 126. The collector of the pnp transistor 126 is connected to 
the first reference terminal 26 via a resistor 134 and to a data signal 
input of the microprocessor 110. 
The second data processing unit 12 comprises a microprocessor 136, which 
drives the base of a second npn switching transistor 140 via a resistor 
138, which transistor has its emitter connected to a node 142 and its 
collector to the second communication terminal 46 via a current-limiting 
resistor 144. A diode 146 is arranged in parallel with the second npn 
switching transistor 140 and has its anode connected to the node 142 and 
another diode 148 is arranged in parallel with the first npn switching 
transistor 114 and has its cathode connected to the second communication 
terminal 46. The diode 146 and the diode 148 are cut off when collector 
current flows from the second communication terminal 46 to the node 142. 
The collector of the second npn switching transistor 140 is connected to 
the base of a pnp transistor 154 via a diode 150 and a resistor 152. The 
base of the pnp transistor 154 is connected to the second mains voltage 
terminal 40 via a resistor 156 in parallel with a diode 158, which second 
mains voltage terminal is also connected to the microprocessor 110 and to 
the emitter of the pnp transistor 126. The collector of the pnp transistor 
154 is connected to the node 142 via a resistor 160 and to a data signal 
input of the microprocessor 110. The signal earth of the microprocessor 
136 is connected to the node 142. A capacitor 162, in parallel with a 
voltage-limiting zener diode 164, is connected between the second mains 
voltage terminal 40 and the node 142. 
In the half-cycle of the mains voltage in which the second mains voltage 
terminal 20 is positive relative to the first mains voltage terminal 18 
data communication is possible from the first data processing unit 6 to 
the second data processing unit 12, the first npn switching transistor 114 
being conductive and the second npn switching transistor 140 being cut 
off, and a current flowing from the second mains voltage terminal 40 to 
the first mains voltage terminal 18 via the capacitor 162, the diode 146, 
the diode 148, the communication wire 48, the current-limiting resistor 
116 and the first npn switching transistor 114. This current pulls down 
the voltage on the second communication terminal 46, as a result of which 
the pnp transistor 154 is turned on and a data signal voltage appears 
across the resistor 160. The current also charges the capacitor 162, the 
voltage across the capacitor 162 being limited by the zener diode 164. 
Thus, after an adequate number of data current pulses a supply voltage is 
available between the second reference terminal 44 and the node 142. In 
the other half-cycle of the mains voltage data communication is possible 
in the opposite direction. The diode 130 and the diode 158 protect the 
base-emitter junction of the associated pnp transistors against excessive 
reverse voltages. The diode 122 and the diode 150 isolate the components 
connected to the anode side from excessive reverse voltages. As a result 
of the current-limiting resistor 116 and the current-limiting resistor 144 
the associated first npn switching transistor 114 and second npn switching 
transistor 140 will behave as a current sources, which has the advantage 
already discussed with reference to FIG. 3, that the instantaneous voltage 
on the communication wire 48 resulting from capacitive cross-talk between 
the three wires has no influence or reduces the influence on the data 
signal transfer. If this does not present a problem, it will be adequate 
to use one series resistor without a parallel-connected diode, which 
series resistor may be arranged at an arbitrary end of the communication 
wire 48. 
By way of example the circuit arrangements shown herein use bipolar 
transistors whose control electrode, first main electrode and second main 
electrode correspond to the base, the emitter and the collector, 
respectively. However, the relevant circuit arrangements may also employ 
unipolar transistors, in which case the control electrode, first main 
electrode and second main electrode correspond to the gate, the source and 
the drain, respectively.