U.S. patent application number 12/322072 was filed with the patent office on 2009-08-20 for vacuum cleaner.
This patent application is currently assigned to Alfred Kaercher GmbH & Co. KG. Invention is credited to Gottfried Benzler, Daniel Eckstein, Thorsten Langen, Christian Stewen.
Application Number | 20090205159 12/322072 |
Document ID | / |
Family ID | 37847089 |
Filed Date | 2009-08-20 |
United States Patent
Application |
20090205159 |
Kind Code |
A1 |
Stewen; Christian ; et
al. |
August 20, 2009 |
Vacuum cleaner
Abstract
The invention relates to a vacuum cleaner with a dirt collection
tank which has a suction inlet and is in flow connection with at
least one suction unit via at least one filter and at least one
extraction line, and with at least one external air inlet which
opens into the extraction line downstream of the at least one
filter and can be closed by means of at least one closing valve,
wherein the at least one closing valve has a valve member which can
be moved back and forth between a closing position and an open
position, wherein it is acted upon permanently by a closing spring
with a closing force and in the closing position, in addition, by a
magnetic holding device with a magnetic holding force. In order to
develop the vacuum cleaner further in such a manner that it makes a
particularly effective cleaning of the at least one filter
possible, it is suggested in accordance with the invention that the
magnetic holding device comprise an electromagnet with a magnetic
core and a coil which can be acted upon with current for the
purpose of closing the closing valve, wherein at least one
electrical component, which takes up at least some of the energy
stored in the coil when the current acting on the coil ceases, is
connected in parallel to the coil.
Inventors: |
Stewen; Christian; (Marbach,
DE) ; Eckstein; Daniel; (Winnenden-Baach, DE)
; Langen; Thorsten; (Stuttgart, DE) ; Benzler;
Gottfried; (Kirchberg a.d. Murr, DE) |
Correspondence
Address: |
Lipsitz & McAllister, LLC
755 MAIN STREET
MONROE
CT
06468
US
|
Assignee: |
Alfred Kaercher GmbH & Co.
KG
Winnenden
DE
|
Family ID: |
37847089 |
Appl. No.: |
12/322072 |
Filed: |
January 27, 2009 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
PCT/EP2006/007541 |
Jul 29, 2006 |
|
|
|
12322072 |
|
|
|
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Current U.S.
Class: |
15/347 |
Current CPC
Class: |
B01D 46/521 20130101;
F16K 31/404 20130101; A47L 9/20 20130101; B01D 2273/28
20130101 |
Class at
Publication: |
15/347 |
International
Class: |
A47L 9/00 20060101
A47L009/00 |
Claims
1. Vacuum cleaner with a dirt collection tank having a suction
inlet and being in flow connection with at least one suction unit
via at least one filter and at least one extraction line, and with
at least one external air inlet opening into the extraction line
downstream of the at least one filter, said external air inlet
being closable by means of at least one closing valve, wherein the
at least one closing valve has a valve member movable back and
forth between a closing position, said valve member abutting on a
valve seat in said closing position, and an open position, said
valve member being spaced from the valve seat in said open
position, wherein said valve member is acted upon permanently by a
closing spring with a closing force and in the closing position, in
addition, by a magnetic holding device with a magnetic holding
force, wherein the magnetic holding device comprises an
electromagnet with a magnetic core and a coil adapted to be acted
upon with current for the purpose of closing the closing valve,
wherein at least one electrical component is connected in parallel
to the coil, said component taking up at least some of the energy
stored in the coil when the current acting on the coil ceases.
2. Vacuum cleaner as defined in claim 1, wherein a freewheeling
diode and at least one electrical component taking up energy and
being connected in series thereto are connected in parallel to the
coil.
3. Vacuum cleaner as defined in claim 1, wherein a freewheeling
diode and a Zener diode connected in-series thereto are connected
in parallel to the coil, said Zener diode being polarized in an
opposite direction to the freewheeling diode.
4. Vacuum cleaner as defined in claim 3, wherein the Zener diode
has a breakdown voltage of approximately 50 V.
5. Vacuum cleaner as defined in claim 1, wherein the coil and the
at least one component connected in parallel to the coil are
adapted to be connected to a source of AC voltage via an electrical
switching unit and a rectifier unit.
6. Vacuum cleaner as defined in claim 1, wherein the magnetic core
is connected via a potential equalization line to a reference
potential predetermined externally.
7. Vacuum cleaner as defined in claim 6, wherein the potential
equalization line connects the magnetic core to a mains voltage
supply connection, wherein at least one ohmic resistor is connected
into the potential equalization line.
8. Vacuum cleaner as defined in claim 7, wherein two ohmic
resistors with different resistance values are connected into the
potential equalization line in series to one another.
9. Vacuum cleaner as defined in claim 1, wherein the electromagnet
is arranged on a valve holding device forming the valve seat and
wherein the valve member has a magnetizable element associated with
the electromagnet, said element forming a magnetic circuit with the
electromagnet in the closing position of the valve member.
10. Vacuum cleaner as defined in claim 9, wherein in the closing
position of the valve member the magnetizable element abuts on the
end side of the electromagnet, thereby forming a gap of air.
11. Vacuum cleaner as defined in claim 10, wherein the gap of air
is narrower than 1 mm.
12. Vacuum cleaner as defined in claim 1, wherein the supply of
current to the coil is adapted to be interrupted several times one
after the other for a period of time of at the most 0.2 seconds at
time intervals of less than one second.
13. Vacuum cleaner as defined in claim 1, wherein the supply of
current to the coil is adapted to be interrupted several times one
after the other for less than 0.2 seconds at time intervals of 10
to 30 seconds.
14. Vacuum cleaner as defined in claim 1, wherein a flexible stop
element is associated with the valve member, said stop element
acting on the valve member with a repulsion force in a position
spaced from the valve seat.
15. Vacuum cleaner as defined in claim 14, wherein the flexible
stop element is designed as a stop spring.
16. Vacuum cleaner as defined in claim 15, wherein the spring
constant of the stop spring is greater than the spring constant of
the closing spring.
17. Vacuum cleaner as defined in claim 15, wherein the closing
spring and the stop spring are designed as helical springs with
different diameters, wherein one of the two helical springs
surrounds the other helical spring in circumferential
direction.
18. Vacuum cleaner as defined in claim 1, wherein the vacuum
cleaner has a single filter.
19. Vacuum cleaner as defined in claim 18, wherein the filter is
adapted to be acted upon with external air over its entire surface
area as a result of the closing valve being opened.
20. Vacuum cleaner as defined in claim 1, wherein the valve member
is movable continuously back into its closing position via its open
position, proceeding from its closing position.
21. Vacuum cleaner as defined in claim 1, wherein the at least one
filter is adapted to be acted upon with external air by means of
the at least one closing valve whilst a vacuum is maintained in the
opening area of a suction hose opening into the suction inlet.
Description
[0001] This application is a continuation of International
application No. PCT/EP2006/007541 filed on Jul. 29, 2006.
[0002] The present disclosure relates to the subject matter
disclosed in International application No. PCT/EP2006/007541 of
Jul. 29, 2006, which is incorporated herein by reference in its
entirety and for all purposes.
BACKGROUND OF THE INVENTION
[0003] The invention relates to a vacuum cleaner with a dirt
collection tank which has a suction inlet and is in flow connection
with at least one suction unit via at least one filter and at least
one extraction line, and with at least one external air inlet which
opens into the extraction line downstream of the at least one
filter and can be closed by means of at least one closing valve,
wherein the at least one closing valve has a valve member which can
be moved back and forth between a closing position, in which it
abuts on a valve seat, and an open position, in which it is spaced
from the valve seat, wherein it is acted upon permanently by a
closing spring with a closing force and in the closing position, in
addition, by a magnetic holding device with a magnetic holding
force.
[0004] Dirt and, preferably, also liquid can be sucked up from a
surface by means of such vacuum cleaners in that the dirt
collection tank is acted upon with a vacuum with the aid of at
least one suction unit so that a suction flow is formed and dirt
and liquid can be sucked into the dirt collection tank. The vacuum
cleaners have one or more filters which are arranged in the flow
path between the dirt collection tank and the at least one suction
unit and serve to separate solids from the suction flow. During
suction operation, dirt particles are increasingly deposited on the
side of the at least one filter facing the dirt collection tank and
so the filter or filters need to be cleaned after a certain length
of time. For the purpose of cleaning, the side of the filter facing
away from the dirt collection tank can be acted upon with external
air in that at least one closing valve is opened so that external
air can flow into the at least one extraction line from the
external air inlet and act upon the side of the at least one filter
facing away from the dirt collection tank.
[0005] In the German Utility Model DE 298 411 U1, it is suggested
for the purpose of cleaning a filter that a suction hose, which is
connected to the suction inlet of the dirt collection tank, be
closed for a short time so that a strong vacuum is formed in the
dirt collection tank on account of the action of the suction unit
and, subsequently, a closing valve is intended to be opened for a
short time. The filter then has external air flowing through it in
a counterflow direction, i.e., contrary to the direction of the
suction flow prevailing during normal suction operation and so dirt
particles adhering to the filter become detached.
[0006] The use of two filters, which are cleaned alternatingly, is
suggested in DE 199 49 095 A1, wherein, during the cleaning of one
filter, suction operation can be maintained via the other filter to
a limited extent.
[0007] The object of the present invention is to develop a vacuum
cleaner of the generic type further in such a manner that it makes
a particularly effective cleaning of the at least one filter
possible.
SUMMARY OF THE INVENTION
[0008] This object is accomplished in accordance with the
invention, in a vacuum cleaner of the type specified at the outset,
in that the magnetic holding device comprises an electromagnet with
a magnetic core and a coil which can be acted upon with current for
the purpose of closing the closing valve, wherein at least one
electrical component, which takes up at least some of the energy
stored in the coil when the current acting on the coil ceases, is
connected in parallel to the coil.
[0009] In the case of the vacuum cleaner according to the
invention, at least one closing valve is used, the valve member of
which can be moved back and forth between a closing position and an
open position. Irrespective of its position, the valve member is
acted upon by a closing spring with a closing force in the
direction of its closing position. In the closing position, the
closing member is acted upon, in addition, by a magnetic holding
force, with the aid of which it is ensured that the closed closing
valve reliably closes the flow connection between the inlet for
external air and the side of the filter facing away from the dirt
collection tank. In this position, the normal suction operation of
the vacuum cleaner takes place. If the at least one filter is
intended to be cleaned, at least one closing valve is opened. In
accordance with the invention, the closing valve has an
electromagnet which can be acted upon with current for the purpose
of closing the closing valve. For the purpose of opening the
closing valve, the supply of current to the electromagnet is
interrupted for a short time so that the holding force acting on
the valve member ceases abruptly. During normal suction operation,
the valve member is subject to a difference in pressure since the
pressure of the external air, i.e., normally atmospheric pressure
prevails on its side facing away from the filter whereas the vacuum
of the extraction line is present at its side facing the filter.
When the magnetic holding force ceases, this difference in pressure
results in the valve member transferring into its open position
contrary to the spring force of the closing valve. With increasing
distance from the valve seat, which is associated with the valve
member, the restoring force of the closing spring increases and so
the valve member is returned to its closing position again by the
closing spring. The opening of the closing valve results in the
side of the filter, which faces away from the dirt collection tank,
being acted upon with external air for a short time. This leads, on
the one hand, to a pressure surge which mechanically jars the at
least one filter; on the other hand, the at least one filter has
external air flowing through it in a counterflow direction.
[0010] In order to bring about as abrupt an action on the filter
with external air as possible, it is provided in accordance with
the invention for the magnetic holding force to cease after as
short a time as possible. For this reason, at least one electrical
component, which takes up at least some of the energy stored in the
coil when the current acting on the coil ceases, is connected in
parallel to the coil. The coil forms a large inductivity for the
electrical control circuit of the coil. When the supply of current
is interrupted, the inductivity results in a high countervoltage on
account of self-inductance. This countervoltage is short-circuited
via the at least one electrical component connected in parallel to
the coil, wherein this component takes up at least some of the
energy stored in the coil. This makes it possible to return the
magnetic field of the electromagnet, which prevails during normal
suction operation, practically to zero within a very short period
of time, preferably within less than 20 milliseconds, in
particular, within a period of time of less than 10 milliseconds.
The energy of the magnetic field will be taken up by the at least
one electrical component connected in parallel to the coil when the
supply of current to the coil is interrupted.
[0011] The use according to the invention of at least one
electrical component which is connected in parallel to the coil and
takes up at least some of the energy stored in the coil makes it
possible for the magnetic holding force to drop practically to zero
within a very short period of time. Subsequently, the electromagnet
can again be acted upon with current so that the valve member,
which has been returned to its closing position again by the
closing spring, can be held sealingly on the valve seat by means of
the renewed magnetic holding force.
[0012] The use according to the invention of at least one
electrical component which is connected in parallel to the coil and
takes up at least some of the energy stored in the coil when the
supply of current to the coil is switched off therefore makes a
very short opening of the closing valve possible. External air can,
therefore, be supplied in an impact-like manner to the filter to be
cleaned and can then also be discharged again immediately by the
suction unit which is constantly in flow connection with the
filter. The filter cleaning process is, therefore, carried out in
fractions of a second. This has the advantage that there is no
complete equalization of pressure between the vacuum prevailing in
the dirt collection tank and the atmospheric pressure during the
cleaning of the filter. On the contrary, a vacuum can also be
maintained in the opening area of a suction hose connected to the
suction inlet during the cleaning of the filter and so a more or
less continuous suction operation results for the user despite the
cleaning of the filter.
[0013] It is favorable when a freewheeling diode and at least one
electrical component, which takes up energy and is connected in
series thereto, are connected in parallel to the coil. The
freewheeling diode ensures that an induced countervoltage at the
coil is short-circuited. The freewheeling diode does, however,
absorb only very little of the energy originally stored in the
magnetic field of the electromagnet when the coil is
short-circuited. Therefore, at least one electrical component which
takes up energy is connected in series to the freewheeling diode.
In this respect, an ohmic resistor may be used, for example, or
also a transzorb diode. At least some of the induced countervoltage
is passed to the electrical component taking up energy when the
current acting on the coil ceases. Therefore, the magnetic field of
the electromagnet which prevails during normal suction operation
can be broken down within a very short period of time.
[0014] In one preferred configuration, a freewheeling diode and a
Zener diode, which is polarized in the opposite direction to the
freewheeling diode and is connected in series to it, are connected
in parallel to the coil. As already explained, an induced
countervoltage can be short-circuited via the freewheeling diode.
Since this absorbs only a little of the energy originally stored in
the coil, a Zener diode, which is polarized in the opposite
direction, is connected in series to the coil. The Zener diode is,
therefore, connected in a reverse direction with respect to the
countervoltage of the coil generated by way of self-inductance and
so a not inconsiderable voltage drops away at the Zener diode when
the supply of current to the coil is switched off. The magnetic
field of the electromagnet, which prevails during normal suction
operation, can be returned practically to zero in a particularly
short period of time by means of the Zener diode. As a result, the
magnetic holding force, which keeps the valve member in its closing
position when current acts on the coil, breaks down within a very
short period of time and the valve member can lift away from the
associated valve seat.
[0015] The Zener diode preferably has a breakdown voltage of more
than 50 V. This has the advantage that the induction current of the
coil can be returned practically to zero within a very short period
of time by means of the Zener diode. The breakdown voltage of the
Zener diode can, for example, be approximately 56 V.
[0016] The coil and the at least one component connected in
parallel to the coil, i.e., for example, the freewheeling diode and
the Zener diode polarized in the opposite direction to it, can
preferably be connected to a source of AC voltage via an electrical
switching unit and a rectifier unit. The electrical switching unit
makes it possible to carry out the cleaning of the filter as a
function of the drop in pressure at the filter and/or dependent on
time. For example, it may be provided for a pressure sensor to be
arranged both upstream and downstream of the filter and for the
supply of current to the coil to be interrupted for a short time as
a function of the pressures detected by the sensors in order to
carry out cleaning of the filter. Alternatively, cleaning of the
filter may be carried out at preferably uniform time intervals.
[0017] The electromagnet normally has an iron core, onto which the
coil is wound. During normal suction operation, it may be possible
for the iron core to be statically charged on account of dirt
particles flowing past. The static charge can assume values which
represent a hazard, in particular, for the electrical switching
unit connected to the coil. As a result, the control of the
electromagnet may be impaired. In one preferred configuration of
the vacuum cleaner according to the invention, the iron core is,
therefore, connected via a potential equalization line to a
reference potential predetermined externally.
[0018] The reference potential can be earth potential or also an
external DC or AC voltage potential. The potential of the iron core
can be balanced with the external reference potential via the
potential equalization line. As a result, a static charging of the
iron core, which impairs the control of the electromagnet, is
avoided. In particular, a very short-time interruption of the
supply of current to the electromagnet can be impaired by a static
charging of the iron core.
[0019] It is favorable when the potential equalization line
connects the iron core to a mains voltage supply connection,
wherein at least one ohmic resistor is connected into the potential
equalization line. The ohmic resistor preferably has resistance
values of at least 10 M.OMEGA., in particular, resistance values of
approximately 15 to 25 M.OMEGA..
[0020] It is of particular advantage when at least two ohmic
resistors with different resistance values are connected into the
potential equalization line in series to one another. As a result,
a first ohmic resistor can, for example, have a resistance value of
approximately 8 M.OMEGA. and a second ohmic resistor can have a
resistance value of approximately 12 M.OMEGA.. The use of different
ohmic resistors has the advantage that during assembly of the
vacuum cleaner the risk is reduced of two low-impedance resistors
being used by mistake. The electrical safety of the vacuum cleaner
is improved as a result.
[0021] The movable valve member is held reliably in its closing
position with the aid of the electromagnet used in accordance with
the invention. In order to open the closing valve, the supply of
current to the electromagnet is interrupted for a short time. It is
of advantage when the electromagnet is arranged on a valve holding
device which forms the valve seat and when the valve member has a
magnetizable element which is associated with the electromagnet and
forms a magnetic circuit with the electromagnet in the closing
position of the valve member. The magnetizable element, for
example, an iron-bearing plate bundles the field lines of the
electromagnet in the valve member so that it is kept reliably in
its closing position due to the action of the magnetic holding
force. If the valve member is, however, at a relatively slight
distance of, for example, two millimeters from the valve seat, the
magnetic circuit is interrupted since the magnetizable element is
also at a corresponding distance in relation to the electromagnet.
As a result, the holding force exerted by the electromagnet has
only a very short range. During an opening movement, the valve
member thus experiences a magnetic holding force only in the
immediate area of the valve seat; the magnetic force is already so
slight at a distance of approximately 2 mm between the
electromagnet and the magnetizable element that it cannot return
the valve member to its closing position. On the contrary, the
closing spring is used to return the valve member.
[0022] As already explained, it can be ensured by means of the at
least one component which is connected in parallel to the coil and
takes up at least some of the energy stored in the coil that the
magnetic holding force ceases within a very short period of time,
for example, within ten milliseconds when the supply of current to
the electromagnet is interrupted. As a result, a short-time opening
movement of the valve member can be achieved which is held in its
closing position preferably with the aid of the magnetizable
element on the electromagnet. It is of advantage when, in the
closing position of the valve member, the magnetizable element
abuts on the end side of the electromagnet, thereby forming a gap
of air. It has been shown that the influence of a residual
magnetization of the magnetizable element on the opening movement
of the valve member can be kept particularly small by making a gap
of air available between the magnetizable element and the
electromagnet. Such a residual magnetization would result in the
valve member still being held, first of all, on the electromagnet
on account of the magnetization of the magnetizable element which
has taken place, despite a drop in the magnetic holding force of
the coil. Such a residual magnetization can be counteracted, for
example, by a special alloy of the magnetizable element. This does,
however, entail not inconsiderable costs. Instead of using such an
alloy, a gap of air between the magnetizable element and the
electromagnet is provided in accordance with the invention. It has
been shown that a very short-time opening movement of the valve
member can be achieved due to such a gap of air being made
available.
[0023] The gap of air is preferably narrower than 1 mm. It can, for
example, be less than 0.7 mm, in particular, approximately 0.5
mm.
[0024] A particularly effective cleaning of the filter is achieved
in one preferred configuration of the vacuum cleaner according to
the invention in that the supply of current to the coil can be
interrupted several times one after the other for a period of time
of at the most 0.2 seconds at time intervals of less than 1 second.
It may, for example, be provided for the supply of current to be
interrupted two, three or even four times one after the other for
approximately 100 milliseconds each at time intervals of
approximately 0.5 seconds. The multiple, short-time interruption in
the current results in the valve member performing a rapid opening
and closing movement several times one after the other so that the
at least one filter to be cleaned is acted upon with a pressure
surge several times at short time intervals and has external air
flowing through it. This results in an alternating mechanical load
on the at least one filter, under the influence of which the filter
or filters are cleaned effectively.
[0025] The supply of current to the coil can preferably be
interrupted several times one after the other for less than 0.2
seconds at time intervals of approximately 10 to approximately 30
seconds. It may be provided, for example, for the supply of current
to the coil to be interrupted for a short time at uniform time
intervals of, for example, 15 seconds. The current can, in
particular, be interrupted three times one after the other for
approximately 0.1 seconds at intervals of 0.5 seconds each.
[0026] In one advantageous configuration, a flexible stop element
is associated with the valve member and this acts on the valve
member with a repulsion force in a position spaced in relation to
the valve seat. A very short opening movement of the valve member
can be achieved in a constructionally simple manner as a result of
the flexible stop element, wherein the valve member is acted upon
first of all only with the closing force of the closing spring,
proceeding from its closing position. Only when the valve member
has a certain distance in relation to the valve seat, will the
flexible stop element become effective and act on the valve member
with a repulsion force. The flexible stop element absorbs the
movement energy of the valve member and accelerates it back in the
direction of the valve seat. With the aid of the flexible stop
element, the closing valve can be closed again within a very short
period of time, in particular, after a period of time of less than
0.2 seconds. The normal suction operation of the vacuum cleaner
can, as it were, be carried on continuously and, nevertheless, an
effective cleaning of the filter can be achieved. External air
enters the dirt collection tank only for a very short period of
time and so the suction flow in the area of the suction inlet of
the dirt collection tank is not noticeably interrupted. The vacuum
cleaner is, consequently, characterized by a constructively simple
construction, wherein all the filters present can have suction air
flowing through them at the same time during suction operation and
wherein the entire side of the at least one filter which faces away
from the dirt collection tank can be acted upon with external air
due to a short-time opening of the at least one closing valve. The
external air is supplied to the filter in an impact-like manner,
wherein the at least one suction unit is permanently in flow
connection with the filter, i.e., also during the time of its
cleaning.
[0027] The flexible stop element can be designed in different
forms. It is preferably designed as a stop spring. This has a
greater spring constant than the closing spring in one preferred
configuration. The stop spring is, therefore, harder than the
closing spring, i.e., a greater force is necessary to compress the
stop spring than is the case for the closing spring. The stop
spring can, like the closing spring, have a linear or also a
non-linear characteristic. For example, it may be provided for the
stop spring and/or the closing spring to become harder with
increasing travel of the spring.
[0028] In one preferred configuration of the vacuum cleaner
according to the invention, the closing spring and the stop spring
are designed as helical springs with different diameters, wherein
one of the two helical springs surrounds the other helical spring
in circumferential direction. This makes a space-saving arrangement
of the closing spring and the stop spring possible and, in
addition, makes a simple assembly possible.
[0029] The closing spring preferably surrounds the stop spring in
circumferential direction. This has the advantage that the valve
member abuts on the closing spring at a relatively large contact
surface and is guided back into the closing position by the closing
spring. The tilting stability of the valve member is improved as a
result.
[0030] The combined use of an electromagnet, in the freewheeling
circuit of which at least one component taking up energy, for
example, a freewheeling diode and a Zener diode, which is polarized
in the opposite direction thereto, are connected in series to one
another, with a closing spring which acts on the valve member
permanently with a closing force and with a flexible stop element
is of particular advantage since, as a result, the valve member can
be reliably held in a sealing manner on the valve seat in its
closing position and as a result of a very short-time interruption
in the current the valve member can lift away from the valve seat
for a period of time of less than 0.2 seconds on account of the
difference in pressure acting on it and so the closing valve is
opened. At a distance from the valve seat, the valve member meets
the flexible stop element which acts on the valve member with a
repulsion force in the direction towards the valve seat. As a
result of the action of the repulsion force and the closing force
exerted by the closing spring, the valve member again reaches the
valve seat within a very short period of time. The closing spring
has, in this respect, the function of returning the valve member to
the area of the magnetic field of the electromagnet so that the
valve member can be held on the valve seat during normal suction
operation by the electromagnet which is again acted upon with
current.
[0031] The vacuum cleaner can have several filters. It has proven
to be particularly advantageous when the vacuum cleaner comprises a
single filter. It may, in particular, be provided for the filter to
be acted upon with external air over its entire surface area as a
result of simultaneous opening of all the closing valves.
[0032] In a constructionally particularly simple configuration of
the vacuum cleaner according to the invention, this merely has a
single closing valve which is positioned on the side of a filter
holding device with flow passages which faces away from the single
filter. As a result of the closing valve being opened, the single
filter is acted upon with external air over its entire surface
area.
[0033] The configuration of the vacuum cleaner according to the
invention makes it possible for external air to act on the side of
the at least one filter, which faces away from the dirt collection
tank, for a short time during normal suction operation and for this
air to be removed by suction within a short time by means of the
suction unit which is in flow connection with the filter even when
the closing valve is opened. It is favorable when the valve member
carries out a continuous movement back into its closing position
via its open position, proceeding from its closing position, during
the cleaning of the filter. With such a configuration, the valve
member will, first of all, be accelerated powerfully in the
direction away from the valve seat when the closing valve is opened
and, subsequently, braked powerfully with the aid of the closing
spring and, preferably, with the aid of the flexible stop element
and reversed in its direction of movement in order to be
accelerated again in the direction towards the valve seat. The
entire movement of the valve member proceeding from its closing
position via the open position back into the closing position can
take place in fractions of a second, in particular, in a period of
time of less than 200 milliseconds.
[0034] The at least one filter can preferably be acted upon with
external air by means of the at least one closing valve whilst a
vacuum is maintained in the opening area of a suction hose opening
into the suction inlet. If the at least one closing valve is
opened, the pressure on the side of the filter facing away from the
dirt collection tank rises abruptly and is then reduced again. The
abrupt rise in pressure causes an effective cleaning of the filter;
since the rise in pressure does, however, drop again immediately
due to the at least one suction unit, it does not lead to a
complete interruption in the vacuum in the opening area of the
suction hose opening into the suction inlet. On the contrary, a
more or less continuous suction operation can be maintained.
[0035] The following description of one preferred embodiment of the
invention serves to explain the invention in greater detail in
conjunction with the drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0036] FIG. 1: shows a schematic sectional view of a vacuum cleaner
according to the invention;
[0037] FIG. 2: shows an enlarged illustration of detail A from FIG.
1 and
[0038] FIG. 3: shows a block diagram of a supply circuit for an
electromagnet of the vacuum cleaner.
DETAILED DESCRIPTION OF THE INVENTION
[0039] In the drawings, a vacuum cleaner 10 is illustrated
schematically with a lower part which forms a dirt collection tank
12 and with an upper part 14 which is placed on the lower part and
accommodates a suction unit 16. The dirt collection tank 12
comprises a suction inlet 18, to which a suction hose 20 can be
connected. A suction nozzle can be connected to the free end of the
suction hose 20 which is not illustrated in the drawings in order
to achieve a better overview. Alternatively, it may be provided for
the suction hose 20 to be connected to a machining tool, for
example, a drilling unit or a milling unit so that dust which
occurs during operation of the machining tool can be sucked in.
[0040] The upper part 14 forms a suction outlet 22 for the dirt
collection tank 12. A folded filter 24 is held on the suction
outlet 22 and an extraction line in the form of a suction channel
26 is connected to the filter. The folded filter 24 is permanently
in flow connection with the suction unit 16 via the suction channel
26. The dirt collection tank 12 can be acted upon with a vacuum by
the suction unit 16 via the suction channel 26 and the folded
filter 24 and so a suction flow symbolized in FIG. 1 by the arrows
28 is formed, due to the action of which dirt can be sucked into
the dirt collection tank 12. The dirt particles can be separated
from the suction flow 28 by means of the folded filter 24.
[0041] A closing valve 30 is arranged in the upper part 14 above
the folded filter 24 and is illustrated in FIG. 2 on an enlarged
scale. It comprises a valve holding device 32 which is arranged
stationarily in the upper part 14, forms a valve seat and interacts
with a valve member in the form of a circular valve plate 34. The
valve plate 34 is acted upon with a closing force in the direction
towards the valve holding device 32 by means of a closing spring
36. The closing spring 36 has a linear characteristic and is
clamped between the valve plate 34 and a plate-like filter holding
device 38 which has a plurality of flow passages and is arranged
stationarily in the upper part 14. The filter holding device 38 has
an outer annular collar 40, which surrounds the adjacent end area
of the closing spring 36 designed as a helical spring in
circumferential direction, on its upper side facing the closing
valve 30. The valve plate 34 has an annular bead 41, on which the
closing spring 36 abuts on the outer side, on its underside facing
the filter holding device 38.
[0042] In addition to the closing spring 36, the filter holding
device 38 has a flexible stop element in the form of a stop spring
43 which, like the closing spring 36, is designed as a helical
spring and has a linear characteristic. In order to hold the stop
spring 43, the filter holding device 38 comprises on its upper side
facing the closing valve 30 an inner annular collar 44 which is
arranged concentrically to the outer collar 40 and in which the
stop spring 43 engages with an end section. A guiding pin 46 is
integrally formed on the valve plate 34 on the under side, aligned
with the inner annular collar 44, this guiding pin being surrounded
by an end area of the stop spring 43 in the closing position of the
valve plate 34 illustrated in FIG. 2. The stop spring 43 is not
subject to tensioning in the closing position of the valve plate,
in contrast to the closing spring. Only when the valve plate 34 has
lifted away from the valve seat of the valve holding device 32 will
the stop spring 43 come to rest on the underside of the valve plate
34 and will be compressed somewhat during further movement of the
valve plate 34.
[0043] The valve holding device 32 has a plurality of openings
which are not illustrated in the drawings and which open into the
valve seat, on which the valve plate 34 sealingly abuts when it
takes up its closing position. At the level of the valve holding
device 32, the upper part 14 has a lateral opening 48. External air
can flow into the openings in the valve holding device 32 via the
lateral opening 48. If the valve plate 34 takes up a position which
is spaced in relation to the valve holding device 32 and,
therefore, also in relation to the valve seat, the lateral opening
48 is in flow connection with the suction channel 26 via the
openings in the valve holding device 32 and external air can act on
the side of the filter 24 facing away from the dirt collection tank
12. If the valve plate 34 takes up its closing position, the flow
connection between the suction channel 26 and the lateral opening
48 is interrupted.
[0044] In a central area, the valve holding device 32 has a
magnetic holding device in the form of an electromagnet 50 with a
magnetic core 51 which is surrounded by a magnetic coil 52. The end
of the electromagnet 50 on the outer side is formed by a
cylindrical casing 53 which, like the magnetic core 51, is produced
from a magnetizable material. The casing 53 is surrounded in the
circumferential direction by a guiding receptacle in the form of an
annular space 55, in which a guiding sleeve 56 engages which is
integrally formed on the valve plate 34 on the upper side. The
annular space 55 and the guiding sleeve 56 form guiding elements
for the displaceable mounting of the valve plate 34. The guiding
sleeve 56 accommodates a magnetizable element in the form of an
iron plate 58 which abuts on the free end side of the electromagnet
50 in the closing position of the valve plate 34 and forms a closed
magnetic circuit in combination with the magnetic core 51 and the
casing 53. The closed magnetic circuit bundles the magnetic field
lines of the electromagnet 50.
[0045] The supply of current to the electromagnet 50 is illustrated
schematically in FIG. 3. The magnetic coil 52 is in electrical
connection with a rectifier unit 65 via a first current supply line
61 and a second current supply line 62, the rectifier unit being
connected to mains connections 71 and 72 via a first connection
line 67 and a second connection line 68. A source of AC voltage can
be connected in a customary manner to the mains connections.
[0046] An electrically controllable switching unit 74 is connected
into the first current supply line 61; the supply of current to the
magnetic coil 52 can be interrupted with the aid of this switching
unit as a function of a control signal which is made available by a
control unit of the vacuum cleaner 10, which is not illustrated in
the drawings, via a control connection 75 of the switching unit 74.
A freewheeling diode 79 and a Zener diode 80 connected in series to
one another are connected in parallel to the magnetic coil 52 in a
free-running line 77, wherein the Zener diode 80 is polarized in
the opposite direction to the freewheeling diode 79.
[0047] The magnetic core 51 and the casing 53 of the electromagnet
50 form a housing of the electromagnet 50 which is given the
reference numeral 82 in FIG. 3. It is produced from an electrically
conductive material, in particular, from an iron material and is in
electrical connection with the first connection line 67 via a
potential equalization line 84. A first ohmic resistor 86 and a
second ohmic resistor 87 are connected into the potential
equalization line 84 in series to one another. The resistance value
of the first ohmic resistor is, for example, approximately 8
M.OMEGA. whereas the resistance value of the second ohmic resistor
can, for example, be 12 M.OMEGA..
[0048] The magnetic coil 52 can be acted upon with current via the
rectifier unit 65 and the switching unit 74 for the purpose of
forming a magnetic holding force which keeps the valve plate 34 in
its closing position. The supply of current can be interrupted for
a short period of time by means of the switching unit 74, for
example, for a period of time of approximately 100 milliseconds. As
a result, an induction voltage which is directed opposite to the
original voltage is formed at the magnetic coil 52 as a result of
self-inductance. This induction voltage will be short-circuited via
the freewheeling diode 79 and the Zener diode 80 so that the
associated induction current of the magnetic coil 52 drops away
practically completely within a very short time, for example,
within approximately 10 milliseconds after the supply of current
has been switched off, i.e., within approximately 10 milliseconds
the magnetic field of the electromagnet 50 which prevails during
normal suction operation breaks down completely. The Zener diode 80
is polarized in the opposite direction to the freewheeling diode 79
and is, therefore, operated in a reverse direction so that the
breakdown voltage, which is approximately 56 V in the embodiment
illustrated, drops away at the Zener diode. As a result, a
considerable amount of energy-can be removed from the magnetic coil
52 within a very short period of time and so the induced current
drops away practically completely within the specified period of
time of approximately 10 milliseconds.
[0049] If the user switches the vacuum cleaner 10 on, the suction
unit 16 is started and, at the same time, the magnetic coil 52 is
supplied with current via the switching unit 74 and the rectifier
unit 65 so that the valve plate 34 is acted upon by the
electromagnet 50 with a magnetic holding force which keeps it
reliably in its closing position. The suction unit 16 acts on the
dirt collection tank 12 and the suction channel 26 with a vacuum so
that dirt particles, like drops of liquid, can be sucked into the
dirt collection tank 12. Dirt particles are deposited at the filter
24 and so this gradually becomes clogged during normal suction
operation. The supply of current to the magnetic coil 52 is
therefore interrupted by means of the switching unit 74 several
times for a short period of time at time intervals of, for example,
10 to 30 seconds, in particular, at time intervals of approximately
15 seconds. It may, for example, be provided for the supply of
current to the magnetic coil 52 to be interrupted three times one
after the other for approximately 0.1 seconds at intervals of 0.5
seconds each and for the normal suction operation to then be
restarted for 15 seconds. The interruption in the supply of current
results in the magnetic field of the electromagnet breaking down
within a very short time, for example, within approximately 10
milliseconds on account of the use of the Zener diode 80 and,
therefore, the magnetic holding force for the valve plate 34
ceases. On the other hand, this causes the valve plate 34 to lift
away from the valve seat contrary to the action of the closing
spring 36 on account of the difference in pressure acting on it
which results from the external pressure of the external air
present in the area of the valve holding device 32 and the internal
pressure within the suction channel 26. External air can then flow
into the suction channel 26 abruptly through the opening in the
valve holding device 32. The filter 24 is, therefore, acted upon in
an impact-like manner with external air on its side facing away
from the dirt collection tank 12. This leads to a mechanical
jarring of the filter 24. In addition, the filter 24 has external
air flowing through it in a counterflow direction. This results,
altogether, in an effective cleaning of the filter 24.
[0050] The valve plate 34 lifting away from the valve seat abuts on
the stop spring 43, which acts on the valve plate 34 with a
repulsion force in the direction towards the valve holding device
32, with its underside after a short lifting movement. The stop
spring 43 absorbs the movement energy of the valve plate 34. The
latter is accelerated by the stop spring 43 in the direction
towards the valve seat. If the valve plate 34 approaches the valve
seat, the stop spring 43 releases the valve plate 34. The latter is
returned as far as the valve seat by the closing spring 36 so that
the iron plate 58 again comes to rest on the end side of the
electromagnet 50, wherein a gap of air of approximately 0.5 mm is
formed, however, between the end side of the electromagnet 50 and
the iron plate 58. If the iron plate 58 reaches the end side of the
electromagnet 50, this is again acted upon with current via the
switching unit 74 so that the valve plate 34 is again held
sealingly on the valve seat by the electromagnet 50. The
interruption in the supply of current for the electromagnet 50
takes place merely for a period of time of approximately 100
milliseconds so that the closing valve 40 opens only for a very
short period of time and external air can reach the filter 24.
Subsequently, the electromagnet 50 is again acted upon with current
and the normal suction operation can be continued. On account of
the short opening of the closing valve 30, a vacuum is also
maintained during the cleaning of the filter in the opening area of
the suction hose 20 opening into the suction inlet 18. As a result,
a more or less continuous suction operation is possible for the
user and, nevertheless, a reliable cleaning of the filter is
guaranteed.
* * * * *