Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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WO94/21384 21 S 8 9 5 3~ t. PCT~L94/00064
... .
Foam-forming unit, spray head suitable therefor, and an
aerosol comprising such a unit
.
The present invention relates to a foam-forming
unit, in particular intended for an aerosol.
Foam-forming units are generally known and are used
in aerosols for dispensing in foam form a large variety of
products such as shaving foam, hair setting agents,
cleaning agents, insulation foam etc.
The aerosol contains a liquid to be dispensed in
foam form, and a propellant. Both constituents are mixed
with each other, and a foam is formed by passing the
mixture through one or more foam-forming parts.
The outflow aperture of the abovementioned foam-
forming units is generally in the form of a spray nozzle
forming part of a spray head which forms the end of the
outlet channel. An aerosol with a foam-forming unit is
generally operated by pressing with one finger on said
spray head.
Foam-forming aerosols working with air as the
propellant must be placed under air pressure before use.
For this purpose, the foam-forming unit often comprises a
non-return valve, through which air can be forced into the
liquid container of the aerosol.
In this connection, reference is made to Dutch
Patent Application NL-A-77 05241, which discloses a common
aerosol with atomizer unit and liquid container which
operates with air as a propellant. An annular space present
around the atomizer unit and a hollow piston make it
possible for the container to be placed under air pressure
by pumping. During this pressure operation, the annular
space serves as a guide and as a pressure chamber which is
in communication with the pressure chamber in the hollow
piston. The pressure produced in the pressure chambers
during pumping opens a non-return valve present in the
atomizer unit, and air is forced into the container. During
the pumping operation the outflow aperture is located in
WO9Jn~384 21 5~g5 3 - 2 - PCT~L94/00064
the pressure chamber.
If foam-forming parts were to be fitted in the path
of the liquid/gas mixture in such an atomizer unit, the
latter could serve as a foam-forming unit, and the aerosol
could thus dispense foam.
When such an aerosol has to be placed under
pressure again after a quantity of foam has been dispensed,
the outflow aperture is located in the pressure chamber,
and therefore during pumping the pressure is also raised in
the outlet channel which is in communication with the
outflow aperture. Since residues of foam often remain in
said outlet channel after foam has been dispensed, said
residues will also be placed under pressure. Due to the
pressure increase, the foam residues are compressed first
of all, with the result that expansion occurs on a subse-
quent lowering of pressure during the movement of the
piston in the opposite direction, and the foam residues are
foamed again under the influence of the foam-forming parts
present, and thus acquire a greater volume. This means that
during pumping foam often passes out of the outlet channel
via the outflow aperture in the pressure chamber. The foam-
forming unit and the hollow piston may become soiled as a
result. The foams formed generally form a sticky layer when
they dry and can make pumping with the piston difficult,
and blockage of the outflow aperture or the foam-forming
parts may also occur. Since aerosol cans are operated with
one finger by pressing on the spray head in which the
outflow aperture is located, soiling of the outflow
aperture, and thus of the spray head, is also undesirable.
The object of the present invention is to provide a
foam-forming unit which does not have the abovementioned
disadvantages.
In a first aspect of the invention therefore a
foam-forming unit is provided, in particular intended for
an aerosol, at least comprising a mixing chamber, with a
propellant inlet and an inlet for a liquid to be dispensed
in foam form, which mixing chamber by means of a control
valve provided with return means, can be placed in
communication with an outlet channel opening out into an
7~q~3
- 3 -
outflow aperture, one or more foam-forming parts being present in the path between
the inlets and the outflow aperture, while the unit also comprises a non-return valve
through which an aerosol can be placed under pressure using pressure means, during
which operation the outflow aperture is in communication with the pressure means,
the foam-forming unit further comprising valve means which interrupts the
communication between the foam-forming parts and the environment at least in onedirection while using the pressure means, which valve means can be opened when the
aerosol is to be used for the dispensing of foam.
The presence of said valve means ensures that during the pressure operation
to place an aerosol under pressure, the pressure is prevented from being raised and
lowered alternately at the position of the foam-forming parts. In this way it is ensured
that the outflow aperture - and thus the spray head - always remains essentially free
from foam residues. An additional advantage which can be mentioned is that in case
the valve means are opened and only during the dispensing of a foam, foam residues
are also prevented from drying in the outflow aperture, the outlet channel and the
foam-forming parts.
The valve means are present, to interrupt the communication between the foam
forming parts and the environment at least in one direction, as it will be clear from the
subsequent description of the invention, that only a pressure increase or a pressure
decrease at the position of the foam forming parts does not give rise to the problems
described earlier.
In this respect further reference is made to FR-A-2 206 743 which discloses a
foam-forming unit comprising a mixing chamber, with a propellant inlet and an inlet for
a liquid to be dispensed in foam form, said mixing chamber being designed to be placed
in communication with an outlet channel opening out into an outflow aperture, bymeans of a control valve. Further one or more foam-forming parts are present in the
path between the inlet and the outflow aperture. The pressure means are designedhowever as a separate unit also comprising the non-return valve. Said non-return valve
therefore does not form a part of the foam-forming unit but of the pressure means.
The foam-forming unit according to the present invention
21~ q'~3
- 3a -
is one assembly which can be mounted onto an aerosol container. The problems
which are overcome by the foam-forming unit according to the present inventions are
not encountered with the aerosol according to FR-A 2 206 743.
The present invention is not restricted to placing under pressure in the manner
described in NL-A-77 05241, but also extends to foam-forming units for aerosols
which can be placed under pressure by means of, for example, a cap over the foam-
forming unit, which cap is in communication with pressure means.
In the present description the liquid to be dispensed in the foam form is not
limited to liquids with a low viscosity, but the meaning thereof also extends to more
viscous products, or even paste-like products and powder containing products, which
are to be dispensed in foam form.
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WO94/21384 215~9~ 4 - PCT~L94/00064
The valve means for interrupting the communication
between the foam-forming parts and the environment are
preferably formed by the control valve being a non-return
control valve.
Also preferably the non-return valve for placing an
aerosol under pressure is formed by the control valve.
In this way the control valve has multiple
functions, and the number of components for the foam
forming unit according to the invention is reduced. It is
possible, as will be described lateron with reference to
the enclosed drawings, to design the control valve as a
non-return control valve, which means that when external
pressure is applied to the foam forming unit, the control
valve can be opened and a propellant, e.g. air, can be
pressed into the unit and aerosol, on which it is mounted.
Hereby it is prevented that during a subsequent pump
stroke, in which the pressure is lowered frequently even to
a negative gauge pressure, the control valve will prevent
the pressure at the position of the foam forming parts to
be decreased also.
For pressurizing the aerosol, a separate non-return
valve can be present, through which the propellant e.g. air
is forced into the aerosol, however to reduce the number of
components it is advantageous to use the control valve as
the non-return valve through which the aerosol is
pressurized.
Preferably, the control valve is a tilting valve,
which advantageously can interact with a flexible cap,
which forms the outlet channel and is provided with an
outflow aperture.
This embodiment will be explained in greater detail
with reference to the appended drawing.
The unit according to the invention has the
advantage that during the pressure operation any foam
residues which are present in the outlet channel past the
control valve are blown back into the aerosol, while
compression and expansion of foam residues are prevented
from occurring at the foam-forming parts.
It is particularly advantageous if the tilting
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WO94/21384 215 8 9 5 3 ` ~ PCT/NL94/00064
-- 5
valve comprises a disc-shaped valve body and a stem part,
and that the disc-shaped valve body can interact with a
sealing ring. Preferably said sealing ring also forms the
seal of the non-return valve.
In the latter case the seal fulfills two functions
simultaneously, which means that only one seal needs to be
manufactured and fitted. Depending on the specific design
characteristics it can be advantageous either to have only
a control valve, which also functions as a non-return valve
through which the aerosol can be pressurized, or that a
separate return valve is present, through which the aerosol
is pressurized.
Especially in the case in which placing under
pressure of the aerosol takes place through the control
valve, it is advantageous that the unit comprises a second
non-return valve upstream of the control valve, seen in the
intended direction of flow of foam, which has the function
of connecting the outlet channel, during placing under
pressure of an aerosol, directly with the interior of the
aerosol, bypassing the propellant inlet and liquid intlet.
If an aerosol is placed under pressure through the
control valve, the propellant must be forced through the
propellant inlet and liquid inlet, which usually are
relatively narrow and therefore the force required to press
the propellant through said channels is relatively high.
The presence of a second non-return valve obviates said
increased force, as this will be opened at a certain
pressure, which is relatively low.
In this respect it is noted, that in the foam forming
unit according to the invention preferably a third non-
return valve is also present, which can be designed as a
ball, to interrupt the communication between the outlet
channel and the propellant inlet and liquid inlet during
pressurization, to prevent the propellant to pass through
said inlet. In this way residual liquid present upstream of
the third non-return valve will not be blown back into the
aerosol, which has the advantage that when using the
aerosol again after pressurizing it, the time, which will
lapse between opening the control valve and dispensing foam
WO94/21384 2 ~ 5 8 9 5 3 PCT~L94/00064
-- 6
will be reduced.
The valve means f~ interrupting the communication
between the foam forming parts and the environment at least
in one direction can also be designed in many other ways
and in other preferred embodiments these are present in the
outlet channel downstream of the control valve, seen in the
intended direction of flow of foam.
The valve means then are advantageously in the form
of a rotary or slide valve in the outlet channel, which
valve is connected to the control valve and provided with
return means. These valve means open at the moment at which
the control valve is depressed. The communication between
the outlet channel and the environment is thus always
interrupted when the foam-forming unit is not in use.
The valve means can also be made independent of the
control valve, in which case the valve means are then
preferably in the form of a non-return valve. A particu-
larly practical embodiment of this is a ball biassed by
means of a spring in a direction opposite to the intended
direction of flow of foam. A non-return valve is understood
to mean a valve which is opened at an adjustable pressure.
In other words, such a valve is always closed until the
control valve is depressed and the foam-forming unit is put
into operation, and the pressure of the mixture to be
dispensed is sufficiently high.
The pressure decreases during use particularly in
the case of aerosols operating with air as the propellant.
When the pressure in the aerosol becomes too low and the
non-return valve closes, this is a warning to the user that
the aerosol must be placed under pressure again.
Another embodiment of the unit according to the
invention is one in which the sealing means are in the form
of a rotary valve provided with return means, which valve
comprises a cylindrical part which has a passage which
through rotation can place the outlet channel in communica-
tion with the environment, in such a way that the rotary
valve is opened when the control valve is moved. This and
preceding embodiments will be explained in greater detail
in the description of the drawing given below.
~ I ~ 8q~ ~
The invention also provides a spray head for a foam forming unit, at least
comprising a spray nozzle and a channel in communication therewith, which spray
head is characterized in that it comprises valve means of the type described in one or
more of the claims 9-13 for interrupting the communication between foam-forming
parts and the environment at least in one direction, said foam-forming parts being
present in the spray head and/or in the foam-forming unit.
Finally, the invention provides an aerosol, at least comprising a container place
under pressure or to be placed under pressure, and a foam-forming unit, which aerosol
is characterized in that the abovementioned foam-forming unit is a foam forming unit
according to the invention.
The invention will now be explained in greater detail with reference to the
appended drawing, in which:
Fig. 1 shows a diagrammatic section of an aerosol according to the prior art;
Fig. 2 shows a diagrammatic section of a first embodiment of a foam-forming
unit according to the invention;
Fig. 3a shows a perspective view of an embodiment of a spray head according
to the invention, with rotary valve;
Fig. 3b shows a section of the spray head according to Fig. 3a;
Fig. 4a shows a perspective view of another embodiment of a spray head
according to the invention, with slide valve;
Fig. 4b shows a section of the spray head according to Fig. 4a;
Fig. 5a shows a front view of a spray head according to the invention, with
diaphragm seal;
Fig. 5b shows a cross-section of the embodiment according to Fig. 5a;
Fig. 6 shows a section of a spray head according to the invention, with a ball
valve;
Fig. 7a shows a perspective view of an embodiment of the aerosol according
to the invention, with a swing valve closure;
Fig. 7b shows a section of the embodiment according to Fig. 7a;
WO94/2l384 21589~3 i PCT~L94/00~64
Fig. ~ shows a sec~ion of another embodiment of the
aerosol according to the invention, with a slide valve; and
Fig. 9 shows a diagrammatic section of yet another
embodiment of a foam forming unit according to the
invention.
Fig. 1 shows diagrammatically an atomizer unit 1
according to the prior art, which can be accommodated in an
aerosol 2 by wedging it between a cap 3 and a neck 4 of the
aerosol 2. Such an atomizer unit is described in NL-A-77
05241.
The atomizer unit comprises an annular space 6
which is surrounded by a wall 5 and can serve as a first
pressure chamber. A spray head 7 is also present. Foam-
forming parts can be disposed in the spray head, in order
to make the atomizer unit a foam-forming unit. Examples of
such foam-forming parts are shown here as two small screens
8.
The outflow aperture is indicated by 9. Said
outflow aperture 9 is in communication with an outlet
channel lO which is present in a part 11 of the control
valve and is provided with a spring 12. When the spray head
7 is depressed against the action of the spring 12, the
outlet channel lO is placed in communication with a mixing
chamber 13 which is in turn in communication - by way of
air supply channels 14 and liquid supply channel 15 - with
the interior of the aerosol 2. The liquid supply channel 15
is connected to a riser tube 16, which projects into the
liquid. For a good seal between the part 11 and the wall
17, a sealing ring 18 is present. The fastening of said
sealing ring to the wall 17 is indicated by 18'.
A piston 19, with a transverse flange 20 lying
closely against the inside of the wall 5, is also shown.
Said piston 19 is often made integral with a cap
covering the cover 3.
When the piston 19 is moved downwards, the air
present in the space 6 and in the chamber 21 is forced into
the aerosol through channels 22, which are kept closed by
the seal 18 during the return stroke of the piston and
during use of the aerosol. During the pressure-increasing
..., .. ~ ..
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W094121384 PCT~L94tO0064
g
pumping stroke, said seal can move away slightly from the
wall 17, in order to let air through.
When such an atomizer unit is used for forming
foam, foam is often present in the outlet channel 10
between the screens 8 and extends to before the nozzle 9.
When the piston 19 is moved downwards in the annular space
6, a pressure increase will occur in said space and in the
pressure chamber 21, which pressure increase also occurs in
the outlet channel 10. When an upward movement of the
piston causes the pressure to decrease again, or even
causes a negative gauge pressure to occur, the foam
compressed in the pressure-increasing stroke will again
expand to a greater volume through the screens 8 and emerge
out of the nozzle 9, with the adverse soiling consequences
discussed earlier. A greater volume is intended to mean a
volume of foam greater than originally present before the
compression, i.e. the pressure increase, stroke of the
piston.
Fig. 2 shows a first embodiment of a foam-forming
unit according to the invention, with the same pump
mechanism as the atomizer unit according to Fig. 1. Here
again, an outside wall 23 with an annular space 24 is
present, in which space a piston can be moved up and down
so that an aerosol formed with the unit can be placed under
pressure.
In this embodiment, the foam-forming unit comprises
four parts 25, 26, 27 and 28. The part 25 has on the
underside an aperture 29 in which an immersion tube can be
fixed. This part 25 also lies closely against the inside of
the wall 31 at 30.
The part 27 comprises a number of lobes on the
outside, which lobes rest against the inside of the wall
31, in order to centre this part and to form channels 54.
The part 28 in this case contains four wings 32,
which form a support for a spring 33. The spring 33 forms
the return means of a valve disc 34 of a tilting valve.
The valve disc 34 has a projecting stem part 35, a
dish-shaped part 36 with raised edge, and a number of
positioning lobes 37 which centre the valve disc by resting
WO94/21384 ~15~ r . PCT~L94/00064
1 0 -
against the inside of the part 20. The valve disc 34 lies
with the raised edge of the dish-shaped part against a
sealing ring 38.
The wall 31 is provided at the top side with a
number of apertures 39, 40 and 41. The stem part 35 of the
valve body 34 projects through the aperture 41. The
aperture 40 serves to allow through foam which has formed.
Finally, aperture 39 with sealing ring 39 forms a non-
return valve.
A flexible cap 42 surrounds the foam-forming unit
at the top side. The latter has an outflow aperture 43 and
defines an outlet channel 44.
In the following description of how the unit works
it is assumed that the unit is fixed on an aerosol
container, and that the container contains liquid to be
foamed and air under pressure.
When pressure is applied to the cap at the position
of 45, the valve body 34 is moved to the position indicated
by dashed lines. The control valve is opened at that
moment. Liquid will flow via the riser tube (not shown)
through the aperture 29 and an annular space 46 into a
mixing chamber 47. The annular space is formed between the
outside wall of the part 26 and the inside wall of the part
25. Propellant flows, via passages 48 present in the part
25 and channels 49, 49' formed by grooves in the outer
surface and the end face of the part 25, also into the
mixing chamber 47, where it mixes with the liquid.
The mixture then flows via channels 50, 50' to a
space 51. The channels 50, 50' are formed by grooves in the
part 26. There is additional mixing in the space 51, which
also contains a screen 52 through which the mixture is
foamed. Finally, the foam formed passes via the tilting
valve and the outlet channel 44 through the outflow
aperture 43.
The use of a mixing chamber as described, has the
advantage that the amount of air necessary for producing
foam is reduced when compared with state of the art foam
formers. In this regard reference is made to NL-A-8901877
of applicant, disclosing such a mixing chamber.
WO94/21384 ^ ~ PCT~L94/00064
An aerosol container on which the unit can be
mounted is placed under pressure as follows. Air is forced
into the aerosol via the non-return valve 38, 39, annular
spaces 53 and channels 54 and, finally, apertures 48, by
moving a piston 19 of the type shown in Fig. 1 above the
atomizer unit up and down in the annular space 24. Any foam
residues left behind in the outlet channel 44 are also
forced into the container.
In the case of the foam-forming unit shown in Fig.
2, it is ensured that a pressure rise and a pressure fall
do not occur alternately over the foam-forming unit (screen
52) during the pumping (placing the container under
pressure), with the disadvantages described in the intro-
duction. The outlet channel also has foam residues cleared
from it, so that possible blockages are avoided. When the
pressure becomes so high that the spring tension of the
spring 33 is exceeded, the tilting valve will be opened
slightly, but without adverse consequences, since it is
closed again when the pressure subsequently falls.
The next figures show embodiments of spray heads
according to the invention containing valve means, and
suitable for mounting on conventional atomizer units. Of
course, they can also be integral with the atomizer unit,
or they can be detachable. They are all suitable for the
unit shown in Fig. 1, but also for other units which are
placed under pressure in a similar way, i.e. in which the
outflow aperture is situated in the pressure chamber during
the operation of placing under pressure. An example which
could be given is aerosols with a quick-action coupling
mechanism, in which the spray head and a part of the
aerosol container itself are placed in a space which can be
placed under pressure by way of the non-return valve.
- Similar problems will occur in this case. The latter
pressure operation is also suitable for the foam-forming
unit shown in Fig. 2.
Figs. 3a and 3b show a first embodiment of a spray
head according to the invention, in which a rotary valve 55
with a spring 56 as the return means is used, the rotary
valve 55 comprising an operating lip 57 which interacts
WO94/21384 2 ~ 5 8 9 ~ 3 ; PCT~94/00064
- 12 -
with said spring 56. The rotary valve also comprises a
passage 58 which can place the outlet channel 10 in
communication with the environment when the lip 57 is
depressed. A suitable mode of operation can be obtained
depending on the spring tension of the spring 56 and the
spring tension of the spring 12 of Fig. 1. For example, the
valve 55 can be opened first of all, before the channel 10
is placed in communication with the mixing chamber 13.
Fig. 4a and 4b show another embodiment of a spray
head according to the invention, with a slide valve
comprising a slide part 59 with a tapering recess 60, which
slide part 59 is held in a closed position by a spring 61.
An operating grip 62, comprising a pin 63 which can
interact with the slanting side of the recess 60 of the
slide part 59, is present. The operating grip 62 is also
connected to the spray head 7 by means of a hinge 64. Here
again, the spring tension can be set in a suitable manner
according to the envisaged purpose.
Figs. 5a and 5b show an embodiment of the spray
head according to the invention with a non-return valve
which consists of a diaphragm 66 which contains apertures
67 and is pressed against the spray head 7 by means of an
annular part 65. When the pressure from the outlet channel
10 increases, the diaphragm will move away slightly from
the spray head 7 and clear the apertures 67, with the
result that the foam can be dispensed. However, pressure
from the outside closes the apertures 67.
Fig. 6 shows an embodiment of the spray head with
non-return valve in the form of a ball 69 which is biassed
by means of a spring 68 and shuts off the outlet channel
10. When the pressure in the outlet channel 10 from the
aerosol exceeds the tension of the spring 68, the ball will
be lifted slightly, with the result that foam can be
dispensed.
Fig. 7a and 7b show a very simple embodiment of a
spray head according to the invention, comprising a swing
valve 70 with a lip 71, which valve can shut off the
outflow aperture 9 by interacting with projections on the
spray head 7. The arrow A indicates how said valve opens,
2 158 9~3
WO94121384 ^ ~ 3~ PCT/NL94100064
- 13 -
and the open position is indicated by dashed lines. The
dimensions of the lip 71 are preferably selected in such a
way that in the open position the piston 21 cannot be
pushed over the spray head. This is to ensure that the
aerosol is not placed under pressure while the swing valve
70 is still in the open position.
Fig. 8 shows another embodiment of the spray head
with a slide valve, in which the sliding head 7 can in fact
be moved over the outlet channel lO against the action of a
spring 72 in order to place the outlet aperture 9 in
communication therewith. In order to ensure a good seal, a
sealing ring 73 is present around the end of the outlet
channel lO. Here again, the tension of the spring 72 can be
selected in such a way relative to the tension of the
spring 12 that during use one of the two valves is opened
earlier, preferably the slide valve first of all.
Finally fig. 9 shows a preferred embodiment, which
is a modified version of the embodiment according to fig.
2. Therefore similar components have been designated with
similar reference numerals. The foam forming unit comprises
again four parts, 25, 74, 75 and 76. The part 76 again
contains a number of wings 32, by which the spring 33 is
supported, forming the return means of the valve body,
comprising a disc-shaped part 36 and a stem part 35. The
disc-shaped part again has a raised edge, which lies
against a sealing ring 77.
Further the wall 3l on the top side has a number of
apertures 40 through which foam, which has been formed, can
pass into the outlet channel 44 and out of the outflow
aperture 43.
The supply of propellant and fluid is altered in
this embodiment, compared with the embodiment of fig. 2 in
- that the part 26 is not present. The liquid can flow
through the riser tube 15 into the part 25 and in the upper
part thereof it is mixed with propellant, which is supplied
via passages 48 and channels 49, 49'. Further said mixture
will flow through the aperture 78 in the part 74 and
through the screen 52.
In this embodiment, a second non-return valve is
W094/21384 215 8 9 5 3 ` PCT~L94100064
. - 14 -
present, which comprises an aperture 79 and a sealing ring
80.
Also a third non-return valve is present, in the
form of the ball 81.
If an aerosol onto which the foam forming unit
according to fig. 9 is mounted has to be brought under air
pressure, the piston 19 can be moved up and down, and
during the downward stroke air will be pressed into the
unit via the outlet aperture 43, enters the apertures 40
and the raised edge of the disk-shaped part of the tilting
valve will be lifted from the sealing ring 77. Further the
ball 81, which is however not absolutely necessary, will be
pressed into the channel 82 and will therefore close off
the connection between the liquid and propellant inlet and
the outlet. The air will then pass through the aperture 79
and will lift the ring 80 from the seat 83 and will enter
the aerosol container via channels 48. It will be clear
that as a result of the presence of the ball 81 the space
in channel 82 and component 25 will not be emptied, i.e. a
mixture of liquid and air will remain therein. The time,
which will lapse as from the moment the tilting valve is
actuated until the moment on which foam is dispensed, is
reduced, compared with other embodiments, in which all of
the unit is cleaned by the air pressed through the unit.
Preferably the channel 49' and passages 78 are not
aligned, so that air supplied via the passages 49' is not
~irectly blown into the apertures 78. Usually 2 to 10 of
these channels and passages are present most preferably
four channels, two passages.
In using the tilting valve is actuated by pressing
on the part 42, and foam is formed in the usual way as
described with reference to fig. 2.
The sealing ring 80 is biassed against the annular
shoulder 83 and will also be pressed against said shoulder
by the internal pressure of the aerosol.
In a preferred embodiment the part 45 of the cap 42 is
designed as a convex part instead of concave as shown in
fig. 2 and 9. If a convex shape is used, this part will be
compressed when dispensing foam, reducing the volume of the
~ WO94/21384 ~215 8 9 S 3 1 ~ ; PCT/NL94/00064
15 --
outlet channel 44. When dispensing is interrupted the
control valve is closed and the part 45 will return to its
original convex shape with a resulting volume increase of
the channel 44. This volume increase sucks foam from the
outlet aperture 43 into the channel 45, whereby the
aperture 43 is cleaned and foam residues near the aperture
43 are removed.
~iJJI~l,~i~i~,~..
