Vacuuming device comprising a vacuum cleaner and a bag filter
FIELD OF THE INVENTION
The invention relates to a vacuum-cleaning apparatus comprising a vacuum
cleaner and a filter bag made of non-woven fabric.
DEFINITIONS
The description of the prior art and the invention is based on the standards,
definitions and measuring methods specified below:
EN 60312: EN 60312 denotes the standard in version EN 60312:1998 + A1:2000
+ A2:2004.
EN 60335: EN 60335 denotes the standard in version EN 603352:2010.
Determination of air data: The air data of a vacuum cleaner are determined
according to EN 60312, chapter 2.8. The measuring device B according to chapter 5.2.8 is
used. If motor-fan units solo are measured, viz. without a vacuum cleaner case, the
measuring device B is applied equally.
The measurement of the reduction of the maximum airflow with a partially filled
dust container according to chapter 2.9 is carried out with orifice 8 (40 mm).
Nominal electric input power of a vacuum cleaner: The input power of a
vacuum cleaner is determined according to EN 60335. According to EN 60335 and EN
60312 the input power is denoted with P . According to EN 60335 the nominal input power is
the arithmetic mean from the maximum input power and the minimum input power. The
maximum input power is measured at the highest airflow (open airflow), and the minimum
input power at an airflow of 0 l/s (sealed suction). Electromotively driven attachments such as
brushes and the like are disregarded in the input power determination.
Airflow: According to EN 60312 the airflow is determined using the version B
measuring chamber. In the prior art this airflow is often also referred to as volume flow or
suction airflow.
Airflow drop, constant airflow: The airflow drop is determined in usability tests of
vacuum cleaners following EN 60312 (chapter 2.9 of this standard) using the version B
measuring chamber. Deviating from the standard the reduction of the airflow is tested by
vacuuming 400 g of DMT8 test dust in 50 g portions, provided the highest usable volume of
the filter bag (see chapter 2.7 of this standard) is above 2 l. The three conditions described in
chapter 2.9.1.3 of the standard as leading to the discontinuation of the test are disregarded.
Chapter 2.9.1.3 is relevant for volumes below 2 l. This method of measuring the airflow drop
thus modified as against the EN 60312 standard will be referred to as “analogous to EN
60312” in the present description and the present patent claims.
A constant airflow q is assumed if the airflow qc is not lower after the vacuuming of
the DMT8 test dust than the airflow qmax with an empty dust container (cyclone vacuum
cleaner), respectively empty filter bag (bag vacuum cleaner). Typically, 400 g of DMT8 test
dust are vacuumed in 50 g portions. The test is performed with orifice 8 (40 mm). With regard
to the definition of the term orifice reference is made to EN 60312, chapter 5.2.8.2. This
orifice corresponds to a relatively open floor nozzle. The airflow drop is calculated according
Airflow drop [%] = ((q - q )/q ) x 100
max c max
q = maximum airflow with empty dust container
q = maximum airflow with partially filled dust container
However, in the present description of the prior art and the invention a substantially
constant airflow does not mean that the airflow remains constant in different working
situations, e.g. the vacuuming of carpeted floors, respectively hard floor surfaces, or the
vacuuming with accessory nozzles. The different orifice areas of these nozzles and the
differently strong reduction of this orifice area on different floor coverings result in different
airflows, depending on the working situation. With respect to EN 60312 this would
correspond to a test with different orifices, with orifice 0 corresponding to a state with a
clogged nozzle. Orifice 9 (50 mm) corresponds to a nearly unobstructed inflow. Current floor
nozzles typically have an operating point in the range of orifice 7 (30 mm) to 8 (40 mm).
Power increase of the fan motor: The power increase of a fan motor implies an
increase of the input power [W]. In a universal motor the power is adjusted by a phase-angle
control. In the SR motor (see below) the control voltage of the motor is controlled.
SR motor: An SR motor is a switched reluctance motor which is characterized by
a simple and robust construction and high possible speeds (> 100,000 rpm). The torque is
generated by the reluctance force.
Flat bags: Flat bags as used in the present invention are filter bags whose filter
bag wall comprised of two individual layers of a filter material with identical surface areas is
formed such that the two individual layers are connected to each other only at their
circumferential edges (the term identical surface area does not preclude, of course, that the
two individual layers differ from each other by the fact that one of the layers includes an inlet
opening).
The connection of the individual layers may be realized by a welding seam or
adhesive seam along the total circumference of the two individual layers. However, it may
also be realized such that one individual layer made of a filter material is folded about one of
its axes of symmetry while the other, open circumferential edges of the so created two sub-
layers are welded or bonded to each other (so-called tubular bag). Thus, this type of
manufacture requires three welding or bonding seams. Two of those seams then form the
filter bag edge. The third seam may equally form a filter bag edge or lie on the filter bag
surface.
Flat bags as used in the present invention may also comprise so-called gussets.
These gussets may be fully unfoldable. A flat bag having such gussets is shown, for
instance, in DE 20 2005 000 917 U1 (see Fig. 1 with folded gussets, and Fig. 3 with unfolded
gussets). Alternatively, the gussets may be welded to sections of the circumferential edge.
Such a flat bag is shown in DE 10 2008 006 769 A1 (see Fig. 1 thereof).
Surface folds: A filter bag whose filter bag wall comprises surface folds is known
per se from the prior art, e.g. from the European patent application 10163463.2 (see in
particular Fig. 10a and Fig. 10b, respectively Fig. 11a and Fig. 11b thereof). If the filter bag
wall comprises a plurality of surface folds this material is also called a pleated filter material.
Such pleated filter bag walls are shown in the European patent application 10002964.4.
Fig. 1 and Fig. 2 show a cross-section of a filter bag comprising a wall with two
surface folds. Such surface folds enlarge the filter surface of the filter bag so that a higher
dust absorption capacity of the filter bag, along with a high collection efficiency and longer
service life, is obtained (as compared with a filter bag having same outer dimensions and
without surface folds).
Fig. 1 shows a filter bag 1 comprising a filter bag wall 10 with two surface folds 11
in the form of so-called dovetail folds. The figure shows a cross-section of the filter bag
through the filter bag center. The longitudinal axes of the surface folds accordingly extend in
one plane which, again, extends perpendicular to the plane of projection, and the surface
folds extend at their longitudinal ends into the welding seams of the filter bag which extend in
parallel to the plane of projection and are positioned in front of and behind the plane of
projection. Thus, the strongest unfolding of the surface folds is in the middle thereof. The
filter bag is here shown in a state in which the surface folds are already unfolded to some
extent.
Fig. 2 shows a filter bag 2 comprising a filter bag wall 20 with two surface folds 21
in the form of so-called triangular folds. The figure shows a cross-section of the filter bag
through the filter bag center. The longitudinal axes of the surface folds accordingly extend in
one plane which, again, extends perpendicular to the plane of projection, and the surface
folds extend at their longitudinal ends into the welding seams of the filter bag which extend in
parallel to the plane of projection and are positioned in front of and behind the plane of
projection. Thus, the strongest unfolding of the surface folds is in the middle thereof. The
filter bag is here shown in a state in which the surface folds are already unfolded to some
extent.
Apart from the surface folds illustrated in Fig. 1 and Fig. 2 surface folds having
different shapes are feasible, too. It should not be regarded as a limitation that the surface
folds in the embodiments of Fig. 1 and Fig. 2 extend perpendicular to a bag edge. Of course,
the surface folds may also extend at an angle to the bag edges.
Suction power: The suction power is the product of negative pressure [kPa] and
airflow [l/s]. According to EN 60312 the suction power is denoted with P2.
Efficiency: The efficiency of a vacuum cleaner or a motor-fan unit is determined in
accordance with EN 60312, chapter 2.8.3.
PRIOR ART
Any discussion of the prior art throughout the specification should in no way be
considered as an admission that such prior art is widely known or forms part of common
general knowledge in the field.
The requirements made on vacuum-cleaning apparatus have been subject to
considerable change in recent years.
One essential point expected by the users of vacuum-cleaning apparatus is that
the vacuum-cleaning apparatus produces a constant airflow even as the dust load increases
or, in other words, that the vacuum-cleaning apparatus does not experience an airflow drop
as the dust load increases.
The study by “AEA Energy & Environment Group” on behalf of the “European
Commission Energy” for the definition of the requirements on an eco design for vacuum
cleaners demonstrates that it would be desirable to limit the input power to below 1100 W in
the future for energy policy aspects. The users of vacuum cleaners do expect, however, that
the cleaning performance will not significantly deteriorate as compared to vacuum-cleaning
devices with a substantially higher input power as are available nowadays.
The customers' hygiene requirements on a vacuum-cleaning apparatus relate no
longer to a lowest possible dust emission of the apparatus only, but also to the hygienic
disposal of the vacuumed dust.
In terms of the collection concept a difference is made between vacuum cleaners
without filter bags and vacuum cleaners with filter bags. These apparatus each have typical
advantages and disadvantages.
Vacuum cleaners with filter bags are characterized by a high airflow. However, as
the filter bag is more and more loaded the airflow drops more or less strongly. Approximately
up to the year 2000 filter bags made of paper were primarily used. In tests demonstrating the
reduction of the maximum airflow with a partially filled dust container analogous to EN 60312
such paper filter bags show an airflow drop of about 80% (respectively 60% if an internal
tissue is used). After that, filter bags having non-woven fabric inserts slowly began
establishing themselves. Initially, filter bags with non-woven fabric layers of a low dust
storage capacity were used (SMS filter bags). By introducing filter bags of non-woven fabrics
with a capacity layer it was possible to clearly reduce this drop of the airflow (see EP 0 960
645). In tests demonstrating the reduction of the maximum airflow with a partially filled dust
container analogous to EN 60312 such filter bags show an airflow drop of approximately
%. Further enhancements were achieved by an advance filtration by loose fibers in the
bag (DE 10 2007 060 747, DE 20 2007 010 692 and ) or an advance
separation by a bag in the bag (, DE 20 2009 002 970 U1 and DE 20 2006
016 303 U1). Flow deflections and flow distributions in the filter bag are proposed in EP 1
915 938, DE 20 2008 016 300, DE 20 2008 007 717 U1 (dust-storing liner), DE 20 2006 019
108 U1, DE 20 2006 016 304 U1, EP 1 787 560 and EP 1 804 635. In tests demonstrating
the reduction of the maximum airflow with a partially filled dust container analogous to EN
60312 an airflow drop of approximately 15% was achieved with such filter bags. Thus, a
further improvement of the suction power stability is obtained. The European patent
applications 10002964.4, 10163463.2, and 10163462.2 disclose an improved dust storage
capability by pleating the filter material or by providing so-called surface folds. The European
patent application 10009351.7 shows how the suction power stability can be improved by an
optimized positioning of the bag in the vacuum cleaner. Thus, in the tests demonstrating the
reduction of the maximum airflow with a partially filled dust container analogous to EN 60312
filter bags of this type show an airflow drop of about 5%.
With regard to the hygienic disposal of the vacuumed dust, holding plates were
developed by means of which the filter bag, prior to removing it from the vacuum cleaner, is
tightly sealed manually, semi-automatically or automatically (e.g. EP 2 012 640).
Vacuum cleaners without bags – in particular cyclone vacuum cleaners – are
characterized by a substantially constant airflow as the dust collecting container is loaded
with dust. At first sight, the constant airflow of a cyclone vacuum cleaner is an advantage,
compared to vacuum cleaners with filter bags which get clogged more or less strongly as the
load of the filter bag increases so that the airflow is reduced correspondingly. However, this
is bought by a very high nominal electric input power of the cyclone vacuum cleaners. This
high input power is necessary owing to the high losses brought about by the separating
principle, namely the loss for the maintenance of the high rotational speed of the dust-laden
air in the cyclone separator.
By combining a number of cyclone separators to multi-stage cyclones it was
attempted to increase the efficiency and the separating efficiency (EP 0 042 723). With such
vacuum-cleaning apparatus an airflow of 33 l/s can be achieved. However, this is opposed
by a nominal electric input power of far more than 2000 W. Cyclone vacuum cleaners having
an electric input power of approximately 1400 W allow the realization of an airflow of about
l/s.
With conventional vacuum-cleaning apparatus working with filter bags, freshly
inserted and empty, it is nowadays possible to realize an airflow of approximately 40 l/s.
Such vacuum cleaners have a nominal input power of about 1300 W.
However, the airflow strongly decreases with the dust loading, as can be seen in
Fig. 3. Fig. 3 shows the reduction of the airflow in response to the vacuumed amount of
DMT8 dust analogous to EN 60312 in known apparatus with filter bags (e.g. Miele S5210
with a nominal electric input power of 2200 W and different filter bags of a non-woven fabric)
and without filter bags (Dyson DC23 alergy with a nominal electric input power of 1400 W).
In addition to improvements of the filter bags approaches have been made to
realize a constant airflow in vacuum cleaners with filter bags by means of an electronic
control.
A vacuum-cleaning apparatus is described, for instance, in US 4,021,879, whose
vacuum cleaner comprises a controlling device controlling the vacuum-cleaning apparatus in
such a way that a substantially constant airflow is realized. However, in this apparatus filter
bags made of paper are used. Owing to the great clogging tendency of filter bags made of
paper (about 80% airflow drop with 400 g of DMT8; inner tissues were not used as yet at the
publication date of US 4,021,879) a very broad control range has to be provided for the
nominal electric input power. Although a constant airflow is thus theoretically realizable,
same is very low. For this reason, this concept was not pursued and, therefore, could not be
implemented in a product successful on the market.
DESCRIPTION OF THE INVENTION
It is an object of the present invention to overcome or ameliorate at least one of the
disadvantages of the prior art, or to provide a useful alternative.
It is an object of the invention in at least one preferred form to provide a vacuum-
cleaning apparatus in which a constantly high airflow is realized despite a low nominal
electric input power.
In one aspect, the present invention provides a vacuum-cleaning apparatus
including:
a motor-fan unit having a nominal electrical input power rating of less than 1200W;
a disposable filter bag made of non-woven fabric, wherein the filter bag is of the
type that has an airflow drop of less than 15% with a partially filled dust container when
tested in accordance with EN 60312; and
an electronic controlling device for controlling the electric input power of the motor-
fan unit and maintain the airflow at a substantially constant value of at least 34 l/s when said
filter bag is loaded with DMT8 test dust in accordance with EN 60312,
such that said motor-fan unit has a electric input power during operation of no more
than 1200W during operation.
The present invention is based on the concept that a vacuum-cleaning apparatus
with a filter bag, viz. an empty filter bag, is operated with an input power that is adjusted to be
lower than the maximum power of the motor, so that the input power of the motor can be
increased in correspondence with the increasing load of the filter bag. Surprisingly, it has
shown that only with filter bags having a clogging tendency of less than 15%, preferably less
than 10%, more preferably less than 5% a relatively small increase of the input power of the
motor is necessary to keep the airflow constant on a level required for the efficient vacuum-
cleaning, i.e. at least 34 l/s. Only thus had it been possible to realize a vacuum-cleaning
apparatus that can provide a substantially constant volume flow as the filter bag is
continuously loaded, while, at the same time, the maximum electric input power of the
vacuum cleaner remains below a predetermined value of 1200 W – which is acceptable from
the viewpoint of power consumption.
According to a further development of the above-described invention the vacuum-
cleaning apparatus comprises an electronic controlling device which is adapted to control the
electric input power of the motor-fan unit.
Preferably, the apparatus is then adapted such that the increase of the input power
of the motor-fan unit required to maintain the substantially constant airflow when the filter bag
is loaded with DMT8 dust analogous to EN 60312 is not more than 35%, preferably not more
than 20%, and more preferably not more than 15% in relation to the input power of the
motor-fan unit when the filter bag is empty. According to this embodiment it is possible to
realize vacuum-cleaning apparatus with a constant airflow, with a vacuuming behavior as is
known from today's non-controllable apparatus, whereby the future energy policy standards
can be satisfied without problems.
Particularly suited for such an apparatus is a motor-fan unit comprising a
reluctance motor, preferably a switched reluctance motor. Such motors are characterized in
particular by their robustness and durability.
Alternatively, according to another preferred further development of the invention
an apparatus may be provided wherein the controlling device comprises a throttle valve
which controls the airflow to be substantially constant.
In both alternative further developments of the controlling device the controlled
variables may be the negative pressure downstream of the filter bag, the negative pressure
upstream of the filter bag or the flow rate measured at an optional position in the flow path.
Optional combinations of these three quantities are also feasible.
According to a preferred further development of all inventions described above the
filter bag may be provided in the form of a flat bag. The flat bag shape is the most widely
spread shape for non-woven bags as bags of this shape are very easy to manufacture. As
opposed to the paper filter material used for paper filter bags the non-woven fabric material is
very hard to fold permanently owing to the great resilience, so that the manufacture of more
complex bag shapes, such as block bottom bags or other bag shapes having a bottom, is
very complicated and expensive.
Particularly suited for use in the apparatus according to the invention are vacuum
cleaner bags having a pleated filter material or surface folds. Such vacuum cleaner bags are
characterized by a particularly low airflow drop.
According to a preferred further development of the invention the motor-fan unit is
adapted such that the vacuum cleaner generates, with a filter bag being inserted, with an
orifice 0 a negative pressure between 30 kPa and 6 kPa, preferably a negative pressure
between 20 kPa and 8 kPa, and more preferably a negative pressure between 15 kPa and 8
kPa , and with an orifice 40 an airflow of more than 50 l/s, preferably more than 60 l/s, and
more preferably more than 70 l/s. This special characteristic of the motor-fan unit differs from
the characteristic of motor-fan units used in conventional vacuum-cleaning apparatus in that
the latter generate an essentially higher negative pressure and an essentially lower
maximum airflow. Surprisingly, it has shown that such motor-fan units are particularly energy-
saving in use, yet fulfill the requirements on a constant airflow of sufficient power.
According to a particularly preferred further development of all inventions described
above the vacuum cleaner may have, with an orifice 8 (40 mm), a airflow power of more than
250 W, preferably of more than 300 W, more preferably of more than 350 W. If the invention
is constructed in this way a fully satisfying vacuuming operation is ensured during the
complete filling of the filter bag.
Preferably, the motor-fan unit may have, with an orifice 8 (40mm), an efficiency
according to EN 60335 of at least 20%, preferably of at least 25%, and more preferably of at
least 30%. This further development of the invention results in a particularly energy-saving
vacuum-cleaning apparatus.
According to another further development of all inventions described above the
vacuum cleaner may comprise a filter bag change indicator indicating if, during the vacuum-
cleaning, the airflow drops under the substantially constant value for a predetermined period.
To this end, in particular the sensors can be applied that are provided for measuring the
controlled variables.
According to another preferred further development of the above-described
inventions the filter bag has a volume in a range of 1.5 l to 8 l measured according to EN
60312. Filter bags of this type are primarily used in vacuum cleaners that are constructed as
canister vacuum cleaners, hand-held vacuum cleaners, wet/dry vacuum cleaners or uprights
for domestic use.
BRIEF DESCRIPTION OF THE FIGURES
The figures serve to explain the prior art and the invention, in which
Fig. 1 and Fig. 2 show filter bags according to the prior art with surface folds;
Fig. 3 shows the reduction of the airflow for vacuum-cleaning apparatus comprising
vacuum cleaners and filter bags according to the prior art as well as for a vacuum-cleaning
apparatus without filter bag according to the prior art;
Fig. 4 shows the air characteristics for a motor-fan unit used in vacuum-cleaning
apparatus according to the prior art;
Fig. 5 shows the air characteristics for a motor-fan unit not used in vacuum-
cleaning apparatus according to the prior art, which is particularly suited for implementation
in the present invention; and
Fig. 6 shows the airflow and electric input power of a first and a second
EMBODIMENTS OF THE INVENTION
Fig. 5 shows the characteristic curve of the motor-fan unit according to an
embodiment of the invention. Same is characterized by a comparatively low maximum
negative pressure with an orifice 0, and a high volume flow with orifice 9 (50 mm). Especially
with orifice 0 a negative pressure of 14.3 kPa is obtained. Orifice 9 (50 mm) results in an
airflow of 86.5 dm3/s. Hence, the characteristic curve is very flat. With the maximum airflow
the motor consumes a power of 1240 W. The airflow power (product of negative pressure
and airflow) amounts to a maximum of 498 W with orifice 7 (30 mm).
Fig. 4, however, shows the characteristic data for a motor-fan unit as used
according to the prior art in vacuum-cleaning apparatus. With orifice 0 the motor-fan unit
generates a negative pressure of 35.8 kPa, orifice 9 (50 mm) results in an airflow of 53.5
dm3/s. Hence, the characteristic curve of the fan is very steep. With the maximum airflow the
motor consumes a power of 1900 W. The airflow power is 614 W. In the case of greatly
clogged paper filter bags such a design had been necessary and sensible.
In the particularly preferred embodiment of the present invention filter bags with
surface folds are used as are described in the above chapter DEFINITIONS.
The motor-fan unit shown in Fig. 5, in combination with a filter bag having surface
folds and an installation space adapted to the filter bag, allows with a corresponding
automatic controlling of the airflow the realization of a vacuum cleaner that achieves a high,
constant airflow with an input power of below 1000 W. Fig. 6 shows the results for two
embodiments according to the present invention, both having in common that a very high,
constant airflow is achieved with a low electric input power.