Note: Descriptions are shown in the official language in which they were submitted.
~~ 'O 94/00046 ~ ~ ~ ~ ~ ~ J PCT/GB93/01325
1
DUAL CYCLONIC VACUUM CLEANER
The invention relates to a vacuum cleaner,
particularly but not exclusively to a dual cyclonic
vacuum cleaner.
A dual cyclonic vacuum cleaner comprises a dirty air
inlet communicating with a clean air outlet by means of
an airflow path, two cyclones being sequentially
arranged in the airflow path. In use, air flowing along
the airflow path from the dirty air inlet to the clean
air outlet passes through a first of the two cyclones
and subsequently through a second of the two cyclones.
The first cyclone is a "low efficiency" cyclone designed
to remove relatively large particles from the airflow,
whilst the second, "high efficiency" cyclone is designed
to remove fine dust particles from the airflow. A
vacuum cleaner having these features expels air which is
dirt- and dust-free to a higher degree than other known
vacuum cleaners. Examples of such vacuum cleaners are
known from published European application No. 0489565
and European patents Nos. 0042723 and 0134654.
Another advantage of the dual cyclonic vacuum
cleaner is that the dirt-collecting chambers are highly
CA 02138985 2003-05-07
WO 94/00046 PCT/GB93/01325
2
unlikely to become blocked because of the size and
rigidity of the chambers. However, it is inevitable
that the dirty air inlet, either in the form of a
cleaner head or a tool attached to a hose or wand, can
become blocked to a greater or lesser extent.
Naturally, this reduces the airflow along the airflow
path. A single cyclonic vacuum cleaner operates in the
same manner but utilises only one cyclone which can
become inefficient if the airflow rate though the
cyclone is reduced.
Vacuum cleaner airflow rates are measured at various
orifice sizes. The flow rates start at an effective
orifice size of SOmm diameter and are reduced to zero at
zero diameter. Any flow rate in any givan machine
therefore has an equivalent "effective orifice" size.
In practice, a vacuum cleaner being used through a hose
or wand typically has an effective orifice size of 32mm
diameter if it is fully open. A vacuum cleaner
operating on a carpet through a cleaner head has an
effective orifice of about l9mm diameter. A crevice
tool being used on the end of a wand handle may have an
effective orifice of about l5mm diameter. Thus it can
be seen that, in its normal range of use, a vacuum
cleaner has to deal with airflows equivalent to those
obtained through orifices of from i5mm to 32mm diameter.
At all of these flow rates achieved in normal use,
the second cyclone of a dual cyclonic vacuum cleaner
'O 94/00046 ~ ~ ~ ~ ~ ~ J PCT/GB93/01325
3
maintains a good level of fine dust separation.
However, it has been found that the separation
efficiency of the second cyclone is reduced if the
airflow rate through the second cyclone is reduced to
below that of an effective orifice size of l3mm. This
can be caused by a number of things; for example, a
blockage occurring at any point along the airflow path,
or by the user putting a hand or other object over the
air inlet. Furthermore, the efficiency of the second
cyclone is reduced if the flow is interrupted in a
pulsing manner or if the suction through the cleaner
head causes the cleaner head to seal itself partially or
completely against the surface to be cleaned. A similar
problem arises when the airflow through the cyclone of a
single cyclonic vacuum cleaner is reduced.
Depending upon the specific design of the cyclonic
vacuum cleaner, the air discharged from a cyclonic
vacuum cleaner may be substantially dust free and may in
fact be cleaner than the air which is emitted from a
vacuum cleaner which utilises a bag or other filter
media. However, under certain operating conditions,
cyclonic vacuum cleaners may emit larger than desired
quantities of fine particulate matter. For example, if
the vacuum cleaner picks up a particularly heavy
concentration of fine particulate matter, part of the
fine particulate matter may pass through the two
cyclones and be exhausted from the second cyclone. This
213898
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may result in the deposition in a room of a layer o.f
fine dust particles. Further, the filtered exhaust air
may be passed by the motor housing to cool the motor.
If the exhaust air occasionally includes more than
desired quantities of fine particulate matter, the motor
may experience a build up of fine particulate matter
which could decrease the life expectancy of the motor.
It is therefore an object of the invention to
maintain a high standard of dust separation in the
second cyclone even when the airflow in the vacuum
cleaner falls to a rate below that of an effective
orifice size of l3mm. It is a further object of the
present invention to provide a cyclonic vacuum cleaner
which maintains good separation standards at all airflow
rates through the di rty ai r i n1 et.
The invention provides a vacuum cleaner comprising a
dirty air inlet communicating with a clean air outlet by
means of an airflow path, a cyclone being arranged in
the airflow path such that, in use, air flowing along
the airflow path from the dirty air inlet to the clean
air outlet passes through the cyclone, characterised in
that at least one bleed value is provided, downstream of
the dirty air inlet, for introducing bled air into the
cyclone to maintain the air flow therein, the or each
bleed valve being operable when, in use, either the
pressure of the air flowing along the airflow path falls
to or below a predetermined level or the amount of
particulates in the air at or adjacent the clean air
outlet exceeds'a predetermined level. The bleed valve
operates so as to
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~O 94/00046 PCT/GB93/01325
maintain the airflow rate in the cyclone and thus retain
efficient dust separation therein.
Advantageously, the at least one bleed valve is
arranged in the wall of the air flow path upstream of
the cyclone. Alternatively, the at least one bleed
valve could be arranged in the wall of the cyclone
adj acent the inlet thereto.
Preferably, two cyclones are arranged sequentially
in the airflow path, the bleed valve or valves being
arranged between the two cyclones. This arrangement
means that the efficiency of the second cyclone is
mai ntai ned.
Advantageously, a plurality of bleed valves are
provided; preferably three. This arrangement allows the
bled air to be introduced to the airflow in the vacuum
cleaner in increments so that the airflow from the dirty
air inlet is not substantially reduced in a single
step. Any reduction that occurs is made in increments
with the incremental introduction of bled air.
It is preferred that all the bleed valves are
substantially identical to one another; i.e. they have
the same effective area and are designed to open at the
same pressure conditions. This gives a satisfactory
gradual transfer from the state of no bled air being
introduced to the cyclone to the state of all of the air
introduced to the cyclone being bled. It is important
that this transfer be gradual to allow cleaning to be
WO 94/00046 ~ 1 j g ~ $ j PCT/GB93/01325
6
maintained either through a tool at the end of the wand
or through the cleaning head, even to the point at which
the last valve is actuated, which is a very blocked
condition.
It is preferred that the or each bleed valve is
designed to open when the pressure in the airflow path
is that produced by an airflow equivalent to an
effective orifice of between lOmm and l5mm diameter or
less. More preferably, the or each bleed valve is
designed to open when the pressure in the airflow path
is that produced by an airflow equivalent to an
effective orifice of l3mm diameter or less. This
ensures that an airflow equivalent to an effective
orifice of l3mm diameter is maintained in the cyclone
and thus that the separation efficiency is maintained.
It is advantageous if the or each bleed valve is
spring-loaded and if the effective area, or total
effective area, of the or each bleed valve is between
120mm2 and 150mm2, preferably substantially
132mm2, i.e. the area of an effective orifice of l3mm
diameter.
It should be noted that, by maintaining an airflow
of at least an effective orifice diameter of l3mm
diameter, an airflow sufficient to cool the motor of the
cleaner is ensured. This means that the risk of the
motor overheating is minimised. Furthermore, the
maintenance of tha airflow to achieve satisfactory
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separation means that there is no substantial risk of
damage to the motor.
In an alternative embodiment, the vacuum cleaner may
also include adjustment means for varying the size of a
single bleed valve for controlling the flow of bled air
into the second cyclone, so that an increased flow of
bled air can be admitted when the vacuum claner is used,
for example, to vacuum a large concentration of fine
particulates. The adjustment means may advantageously
comprise a movably mounted door. The door may be
moveable between a first position in which it restricts
the flow of bled air through the bleed valve and a
second position in which the door restricts the flow of
bled air through the bleed valve to a lesser extent than
when the door is in the first position. Means mounting
the door for a decrease in pressure in the cyclone to
move the door from the said first position towards the
second position may also be provided. Furthermore,
means biasing the door into the first position, whereby
the door will move towards the second position as the
pressure in the cyclone decreases thereby admitting an
increased flow of bled air into the cyclone may also be
provided.
In a further alternative embodiment, the vacuum
cleaner may include sensing means coupled to the outlet
for sensing the amount of particulates in the exhausted
air and for producing an output indicative thereof. The
WO 94/00046 j PCT/GB93/01325
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vacuum cleaner may also have control means coupled
between the sensing means and the door, the control
means being responsive to the output signal for
operating the door to permit an increased flow of bled
air into the cyclone when an increased amount of
particulates is detected in the exhaust.
In accordance with this invention, a method is also
provided of operating a cyclonic vacuum cleaner having
first and second cyclones arranged in series. The
method includes admitting dirty air into the first
cyclone, partially cleaning the dirty air in the first
cyclone to produce partially filtered air and conducting
the partially filtered air from the first cyclone to the
second cyclone. The partially filtered air is further
cleaned in the second cyclone to produce further cleaned
air and is exhausted from the second cyclone. Bled air
is admitted, in addition to the partially filtered air,
into the second cyclone for reducing particulates in the
further cleaned air.
It has been found that the provision of bled air to
the second cyclone reduces the particulate emission in
the exhaust from the second cyclone. Without being
limited by theory, it is believed that the bled air
probably reduces the disturbance to the cyclone action
caused by heavy concentrations of fine particulates, or
by disturbing pulsations which occur when sealed or
partially sealed suction begins and ends, or other
VO 94/00046 PCT/GB93/01325
9
disturbances. Accordingly, even when the vacuum claner
is used to vacuum a large concentration of particulates,
or engages the surface to be cleaned, causing a partial
or fully sealed suction condition, the particulate
emission from the vacuum cleaner may be greatly reduced.
An embodiment of the invention will now be described
with reference to the accompanying drawings, wherein:
Figure Ia is a side view of a first embodiment of a
dual cyclonic vacuum cleaner incorporating the invention
in a first position;
Figure 1b is a side view of the cleaner of Figure la
shown in an alternative position;
Figure 2 is a perspective view of the upper portion
of the cyclone assembly forming part of the cleaner
shown i n Figures la and 1b;
Figure 3 is an enlarged sectional view through a
bleed valve forming part of the invention;
Figure 4 is a perspective view of the housing of a
second embodiment of a dual cyclonic vacuum cleaner
incorporating the invention;
Figure 5 is a cross sectional view through a third
embodi went; and
Figure 6 is a schematic diagram relating to a fourth
embodiment.
A typical dual cyclonic vacuum cleaner is shown in
Figure la in its non-operational position. The vacuum
cleaner comprises a main body 10 incorporating a
WO 94/00046 213 8 9 ~ J P~/GB93/01325
cleaning head 12 and a handle 14 which can be released
for use in the manner of a wand. Various tools and
attachments for the wand may be provided but are not
shown. The means by which the handle 14 is released and
the means by which the airflow is directed from either
the handle 14 or the cleaning head 12 do not form part
of the present invention and are described in other
patents and applications. They will not be described
further here.
The main body 10 incorporates a first cyclone 16 and
a second cyclone 18. The first cyclone is a "low
efficiency" cyclone designed to remove relatively large
particles from the air flowing therethrough. The second
cyclone 18 is designed as a "high efficiency" cyclone
for removing fine dust particles from the airflow. In
use, when the vacuum cleaner is in the position shown in
Fi gure 1 a, the " cyl i nder" mode, the di rty ai r i n1 et i s
formed by the nozzle in the handle 14 which is removed
and used in the manner of a wand. The airflow is
directed from this dirty air inlet to the first, low
efficiency cyclone, subsequently to the second, high
efficiency cyclone and then expelled to atmosphere via
an exit (not shown). Normally, the airflow would be
directed past the motor to give a cooling effect before
being expelled. When the cleaner is to be used in the
" upri ght" mode as s hown i n Fi gure 1 b, the di rty ai r
inlet is formed by the cleaning head 12 and the airflow
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V0 94/00046 PCT/GB93/01325
11
is directed from there to the first cyclone and then to
the clean air exit via the second cyclone.
As mentioned in the introduction, it has been found
that, when a blockage occurs in the dirty air inlet
12,14 to such an extent that the airflow through the
second cyclone 18 falls to an effective orifice of l3mm
diameter or less, then the dust separation efficiency of
the second cyclone decreases. Bleed valves 20 are
therefore positioned in the wall of the airflow passage
between the exit from the first cyclone and the entry to
the second cyclone. The location of the bleed valves 20
is shown in Figure 2. The airflow enters the first
cyclone 16 via the entry port 22 and exits the first
cyclone via the mesh screen 24. The air passes upward
to the entry port 26 to the second cyclone 18 and it is
immediately before this entry port 26 that the bleed
valves 20 are located.
Three bleed valves 20 are located in the wall of the
airflow path. Each bleed valve 20 is shown in greatly
enlarged cross-section in Figure 3. Each valve 20
comprises a valve body 30 to which is attached a rubber
washer 32 by means of a fixing disk 34. The fixing disk
34 passes through an aperture in the rubber washer 32
and engages with an aperture 36 in the valve body.
Alternative fixing means can, of course, be used.
Acting between the airflow passage wall 38 and a flange
40 located on the valve body 30, is an air bleed valve
2138985
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spring 42. The spring 42 presses the flange 40 away
from the airflow passage wall 38 so that the rubber-
washer 32 is maintained in sealing contact with the
edges of an aperture in the airflow passage wall 38.
This situation prevails whilst the pressure inside the
airflow passage (i.e to the right of the airflow passage
wall as viewed in Figure 3) combined with the action of
the spring 42 is sufficient to maintain the valve body
in the position shown in Figure 3. However, if the
pressure in the airflow passage falls sufficiently, then
the pressure acting on the valve body outside the
airflow passage becomes sufficient to open the valve 20
by moving the valve body against the action of the
spring 42 towards the right as shown in Figure 3 and
thereby opening the valve 20. Air from outside the
airflow passage (ie. the atmosphere) is thus bled into
the airflow passage
Although the arrangement described above is
preferred, it is equally possible to locate the bleed
valve 20 in the wall of the second cyclone 18 adjacent
the entry port 26. In this event, means must be
provided to ensure that the bled air enters the cyclone
18 in a tangential manner, for e:cample by a baffle plate
(not shown).
It has been found that the provision of three
substantially identical bleed valves 20 in the airflow
passage wall 38 immediately before the second cyclone 18
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13
allows a gradual bleeding of atmospheric air into the
airflow passage. When the pressure in the airflow
passage drops below the threshold pressure, a first
bleed valve 20 opens and the pressure in the airflow
passage is thereby increased, although it will be
appreciated that the increased pressure will still be
less than the ambient pressure due to the suction action
of the motor. I f the ai rf 1 ow from the di rty ai r i n1 et
continues to fall, then a second bleed valve will open
when the combined pressure of the airflow from the dirty
air inlet and the bled air from the first open valve
reaches the threshold pressure of the remaining valves.
Again, the combined pressure is then increased and the
third valve will only be actuated when the combined
pressure of the airflow from the dirty air inlet and the
two open valves falls to the threshold pressure thus
allowing the third valve to open. In this way, an
incremental increase in the bled air is achieved. This
ensures that the cleaning effect at the dirty air inlet
is maintained even though air is bled into the second
cyclone. Furthermore, the airflow is maintained in the
second cyclone and the air passing therethrough will be
efficiently separated from dust particles. The air from
the second cyclone can also be passed across the motor
surface to provide a cooling effect.
It has been found advantageous if each of the three
bleed valves has the same effective area. Ideally, the
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WO 94/00046 PCT/GB93/01325
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combined effective area of the three valves should be
equivalent to the area of the effective orifice of the
airflow at which the bleed valves are to be actuated.
Thus, if the bleed valves are to be actuated at an
airflow of an effective orifice of l3mm diameter, then
the combined total effective area of the valves should
total 132mm2. If, however, the valves are to be
actuated at an airflow equivalent to an effective
orifice of l4mm, then the bleed valves should have an
effective combined area of 154mm2. This effective
area should be equally divided between the number of
bleed valves present; if three bleed valves are present
then each should have an effective area of 51mm2 but
if four bleed valves are present, then each should have
an effective area of 38mm2. It should be noted that
the effective and actual areas of each bleed valve are
not the same. The actual area of the bleed valve is
restricted by the presence of the valve body near the
valve aperture. Thus the effective area of the bleed
valve can be considerably less than the actual area of
the aperture.
It is within this scope of this invention for any
number of bleed valves to be positioned in the wall of
the airflow path immediately before the inlet to the
second cyclone. Clearly, the greater the number of
bleed valves present, the smaller, the incremental steps
are in which the bled air is introduced into the airflow
' . ~~38~85 ~...: .
..: ....
s
1 5
path. This provides for an ever increasingly gradual
introduction of bled air, but also an ever increasing
cost and maintenance burden. The preferred number of
bleed valves is therefore three. Also, the risk of the
bleed valves themselves becoming blocked by the dirt and
fluff particles introduced into the vacuum cleaner via
the dirty air inlet is very small because the air
passing the bleed valves has already passed through the
first cyclone and all of the larger particles entrained
with the dirty air have been removed.
As will be appreciated, varying amounts of bled air
may be required depending upon the~particular conditions
in which the vacuum cleaner is being operated. For
example, if the vacuum cleaner is being operated in an
area where there is a small concentration of
particulates to be picked up, or on a surface or in an
area where partial or full sealed suction will not
occur, then less bled air, or alternatively no bled air,
may be required. To this end, as shown in Figs. 4, 5
and 6, the vacuum cleaner may also include means for
varying the the size of the bleed valve 76 and,
accordingly, to control the volume of bled air passing
into the second cyclone.
In the embodiment shown in Fig. 4, outer cyclone
casing 70 is provided with a door 78. Door 78 is
provided with a handle 80 at one end thereof. Door 78
is movably mounted on the outer cyclone casing 70 by
WO 94/00046 ~ ~ ~ ~ ~ ~ j PCT/GB93/01325
16
means of a pivot 82 and is moveable between a closed
position and an open position. Door 78 is sized so that
when in the closed position, it completely covers bleed
valve 76 and therefore prevents any bled air from
entering through the bleed valve 76 into the second
cyclone 18.
As shown in Fig. 4, door 78 is in a partially open
position. During vacuuming, the operator may manually
adjust the door 78 from a fully closed position to a
partially opened position or from a partially opened
position to a fully opened position so that an increased
flow of bleed air can be admitted when the vacuum
cleaner is used to vacuum a large concentration of fine
particulates. Alternatively, the operator may elect to
leave door 78 in the fully open position for most
vacuuming purposes.
The bleed valve 76 may also be provided with
automatic means for opening door 78 as the pressure in
second cyclone 18 decreases. Such a decrease in
pressure could occur when a condition of full or
partially sealed suction occurs. An example of such an
automatic means is shown in the alternative preferred
embodiment which is shown in Fig. 5. Once again, bleed
valve 76 is provided with a door 78 which, when in the
closed position, fully covers bleed valve 76 thus
preventing the entry of bled air into the second cyclone
18 during normal vacuuming conditions. Means biasing
~13898~
94/00046 PCT/GB93/01325
17
the door 76 into the closed position are also provided.
Accordingly, the door will move towards the open
position as the pressure in second cyclone 18 decreases
thereby admitting an increased flow of bled air into the
second cyclone as required.
As shown in Fig. 5, member 86 having a first end 88,
a second end 90 and an arm 92 extending between first
end 88 and seond end 90 may be provided. First end 88
is fixedly attached to the inner surface 68 of outer
cyclone casing 70. Second end 90 is fixedly attached to
rear surface 84 of door 78. Arm 92 may be made from any
material which will bias door 78 into the closed
position which is shown in Fig. 5. For example, arm 92
may be made from a resilient material or may incorporate
spring means, such as a leaf spring.
In operation, as the pressure inside second cyclone
18 decreases, the vacuum pressure within the air flow
passage 62 will decrease to such a point that the inward
force on the door 78 will become greater than the
outward force on door 78 which is exerted by member 86
thus causing door 78 to deflect inwards away from the
closed position and thus permitting bled air into the
second cyclone. As the pressure inside the second
cyclone increases (whilst remaining below the ambient
pressure), at one point the vacuum pressure will
increase sufficiently such that the outward force from
member 86 will become greater than the vacuum pressure
WO 94/00046 PCT/GB93/01325
213898 18
thus causing door 78 to move to the closed position.
In a further alternative embodiment, door 78 may be
automatically controlled to allow bled air into second
cyclone 18 in response to the amount of particulates
which are exhausted from the air exit port of the second
cyclone. As shown in Fig. 6, a sensor 94 may be
provided on air exit shaft 54. Sensor 94 senses the
amount of particulates in the exhaust from the second
cyclone. To this end, sensor 94 may be provided with a
light source 96 (e.g. a light emitting diode) and a
detector 98 which can be a photodiode. As the amount of
particulates in shaft 54 increases, part of the light
originating from light source 96 is reflected back by
the particulates and picked up by the photodiode 98.
The signal from photodiode 98 is processed and amplified
to produce an output signal 100 which is indicative of
the amount of particulates in the exhaust from the
second cyclone. Output signal 100 is transmitted to
door actuator 102. Door actuator 102 may be any
suitable means which can accept output signal 100 and
move door 78 a predetermined amount in response to the
specific output signal 100 which is received. Door
actuator 102 may be connected to a 100-volt electrical
source or to any other conveniently available power
supply. Shaft 104 is provided so as to connect the door
actuator to door 78. As shown in Fig. 6, shaft 104 is
connected at one end to door actuator 102, and at the
213898 v
19
other end, to the rear surface 84 of door 78.
In operation, as the level of particulate emissions
from the second cyclone increases, the level of
particulates in shaft 54 also increases. This results
in the increased reflection of light from light source
96 which is picked up by detector 98 and results in a
specific output signal 100. Output signal 100 is
indicative of the level of particulates in the exhaust
air. This signal is transmitted to door actuator 102
which, in response to the output signal, causes door 78
to move from a first position in which the door
restricts the flow of bled air through bleed valve 76 to
a second position in which the door restricts the flow
of bled air through bleed valve 76 to a lesser extent
thus permitting an increased flow of bled air into the
second cyclone in response to the increased amount of
particulates detected in the exhaust air.
If a more simplistic system is utilised, then sensor
94 may produce only one output signal. In response to
this output signal, door actuator 102 will cause door 78
to move from the closed postion to a fully opened
position when a level of particulate emission, above a
predetermined limit, is detected in shaft 54.
Alternatively, in a more complex system, sensor 94 may
provide an output signal which varies linearly or in a
-different desired relationship with the level of
_.particulates in shaft 54. As the level of particulates
WO 94/00046 213 8 9 ~ J PCT/GB93/01325
in shaft 54 increases above a predetermined level, a
variable output signal is produced. In response to the
signal, door actuator 102 causes door 78 to move from
the closed position to a partially open position or from
a partially open position to a more fully open position
in response to the level of particulates in shaft 54.
Thus as an increased or decreased amount of particulate
emission is detected in shaft 54, door 78 may be opened
or closed a predetermined amount to adjust the actual
amount of bled air entering the second cyclone.
The invention can be applied to any type of vacuum
cleaner including upright, cylinder, tank, back-pack and
hand-held types. The invention, although described
specifically in relation to a dual cyclonic vacuum
cleaner, is equally applicable to a single cyclonic
vacuum cleaner or to a cyclonic vacuum cleaner having
more than two cyclones as will be apparent to one
skilled in the art. Where more than one cyclone is
used, bleed valves can be used to maintain the airflow
in any one or more of the cyclones as necessary or
des i red.
