Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
-~ 2114945
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~LI. r~lNG VAT,VE FOR A~R~)~OLS
This invention relates to a metering valve for
aerosols .
Valves are known which are affixed to aerosol
cans and are designed to release one measured dose of
product/propellant mixture per actuation. These
valves are typically used with medicinal aerosols,
such as Metered Dose Inhalers for treating asthma and
other conditions, where the product is a powdered drug
suspended in a liquid propellant. There is a present
need for a desiqn of metering valve which does not
employ any sliding sealing faces because some products
or powders can migrate past this type of seal and
cause leakage or incorrect dosage. Examples of
aerosols utilising sliding seal type metering valves
are shown in US-A-3301444.
US-A-2835417 describes a metered dosage valve for
a container of f luid under pressure . The valve has a
tubular measuring chamber having a resilient sealing
gasket at one end with a central opening through which
a hollow valve stem extends into the measuring
chamber. The stem is depressable to close a normally
open discharge passage from the measuring chamber and
then supply fluid to the measuring chamber. When the
valve stem is moved downwardly from its normal
position, the centre portion of the gasket is bent
downwardly so that when the downward force on the stem
is released, the resilient gasket acts to urge the
valve stem upwardly to its initial position.
Although this seal does not involve a sliding
action, after repeated deformation resulting from
operation of the stem the gasket is likely to
deteriorate and become less resilient which would lead
to less efficiency in the sealing of the valve and
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allow migration of products or powders past it.
Furthermore, it could lead to less effective sealing
against the valve stem which would- lead to the same
problems mentioned above in that some products or
5 powders could migrate past the seal and cause leakage
or incorrect dosage.
Theref ore according to the invention, there is
provided a metering valve to be f itted to an aerosol
container ~or dispensing a product, said valve
10 comprising a housing, a metering chamber located
within said housing and a hollow actuator stem
extending into the chamber and axially slidable
relative thereto, the metering chamber and actuator
stem being moveable into and out of positive sealing
15 contact with oppositely facing valve seats provided on
the valve housing and the metering chamber
respectively, and sealing means being provided between
the actuator stem and the housing and f ixed to the
housing such that relative movement between the stem
20 and housing is permitted, characterised in that the
sealing means consist of a flexible web or membrane
f ixed to the actuator stem .
The provision of oppositely facing valve seats
with a f ixed f lexible membrane or web averts the use
25 of sliding or deforming seals resulting in a
considerably improved metering valve.
In each of the metering valves described in US-A-
3301444, a further problem arises in that the metering
chamber which receives aerosol prior to dispensing is
30 refilled with a fresh dose of aerosol immediately
after the previous dose of aerosol has been dispensed
therefrom. The fresh dose then remains in the
metering chamber until the valve is subsequently
operated to dispense the next dose. Such an
35 arrangement is disadvantageous in that the fresh does
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74945
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of aerosol can tend to drain from the metering chamber
at least to some extent over a period of time. When
that happens, the next (licp~onc-~ dose will be
incomplete and can have undesirable consequences for a
5 person suffering, for example, from asthma where the
~us ~ ness of the initial dose is important .
Moreover, where a fresh charge of aerosol remains in
the metering chamber for a long period of time, the
s~l~p~-n~qe-l drug can settle in the chamber and will not
10 be properly discharged from the dispensing chamber
when the next dose is dispensed.
The invention further provides that the metering
chamber receives aerosol for dispensing by the
actuator stem and the sealing contact of the metering
15 chamber against its associated valve seat prevents a
fresh charge of aerosol entering the metering chamber
after a previous charge has been dispensed therefrom,
until the metering chamber and associated seal are
subsequently separated by operating the valve to
20 dispense a further dose.
With such a valve, the metering chamber is not
refilled with a fresh dose of aerosol until the user
of the aerosol next operates the valve to dispense the
aerosol. Therefore, fresh doses will not be left in
25 the metering chamber for periods of time between
dispensings .
21 74945
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A preferred form of the irvention will be described,
by way of eYample, with referer,ce to the ~ nying
drawings, in which:
Fig. ~ is a cross section through a valve ;n
accordance with the invention before beinq fitted to
an aeroso l cont a i n~r;
Fig. 2 is a cross-sectional view of the valve of
Fig. I fitted to an aerosol container and showing a
filling nozzle applied to the outer erd of the
disp~nsing stem,
Fig. 3 is a view simi lar to Fis. 2, showing the
positions of the va}ve members during filling;
Fis;. 4 is a cross-sectional view of the top of
the filled container in inverted position prior to
di spens i ng; and
Figs. 5 to 7 are views similar to Fig. 4,
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illustrating succe5sive stages of the dispensing
process .
.,
Referring to Fig. 1, a valve housing 7 provided with
at least one port 20 in the upper part of its wal 1,
contains a metering member 2 def ining a metering
chamber 2a of a size d~r~nd~nt upon the dose to be
~i.-r--n~.i. The member 2 is normally urged by a spring
4 into a closed position in which its open upper end,
provided with one or more sealing rinqs 2b, makes
sealing contact with the lower face of a valve seat 3
in the form of a gasket to isolate the chamber 2a from
the interior of the housing 7. The chamber 2a
contains a further val ve seat 9, which may be made of
a compatible elastic material such as synthetic
rubber, for sealing contact with the lower end of a
dispensing member stem 6 when the latter is moved into
its closed position to isolate the interior of the
~stem from the chamber 2a. The stem 6, which may
contain a constriction 19 to assist atomization of the
aerosol mixture, is centralised and supported for
linear r ~ L relative to the member 2 by a guide 5
which may be extended, as shown, to limit return
travel of the stem. The inner end of the stem 6 is
secured to or formed integral ly with one end of a
r ~ e or web in the form of a resi 1 ient bel lows 1,
The bellows may have a helical, thread-like form to
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facilitate moulding from plastics. The other end of
the bel lows 1 bears against a shoulder formed on the
quide 5 and i5 provided with an external flange which
is clamped ~etween the top of the housing 7 and the
valve set 3 by a ferrule 11 which may be made of an
aluminium Al loy and also serves to secure the guide 5
and a sealing ring 8 for ~nq~; t with the mouth of
an aerosol container when the ferrule is secured to
the container by crimping, as shown in Fig. 2. The
bel lows 1 prevents leakage of aerosol between the stem
6 and the open end of the housing 7 and in particular
between the external surface of the stem 6 and the
guide 5.
The container may be pre-filled before fitting the
valve or filled with the valve in position usinq a
~1 ~ e f i 11 ing machine in thê manner i 1 lustrated in
F i gs . 2 and 3 .
E~eferrinq to Fig. 2, the nozzle of the filling machine
is ~ppl ied to the outer end of the stem 6 which moves
downward into sealing ~ng-,_ t with the valve seat
9. The supply of mixture under p~ e through the
~tem 6 acts on the lower end of the chamber 2 which
moves downward into its open position to permit the
mixture to pas& f rom the stem 6 through the chamber 2
and into the container throuqh the port 20, as
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i l lustrated by the arrows 21 and 22 in Fig. 3 .
Wh~n the container has been filled the valve members
return to the positions shown in Fig. 1 and Fig. 4,
the latter showing the container inverted prior to
d i ,qp-.nq i ng a metered dose of i ts contents .
For dispensing, an actuator (not shown) is affixed to
the outer portion of the stem 6 and the latter is
moved upward in the direction of the arrow 12 in Fig.
5 to bring the base of the stem into seal ing
r _, t with the valve seat 9 to isolate the
metering chamber from at ~F, ' e as indicated at 13 in
Fig. 5. Further movement of the stem 6 in the
direction of the arrow 14 in Fig. 6, moves the open
end of the chamber 2 away from the valve seat (which
is oppositely facing with respect to the valve seat 9)
to allow the aerosol mixture from the container to
fill the chamber 2a as indicated at 15 in Fig. 6 and
provide the metered dose therein. The valve is then
pr i med ready for dispens ing, and by moving the stem 6
in the oppo5ite direction, as indicated by the arrow
16 in Fig. 7, the contents of the chamber 2 are
expel led through the stem, as indicated by the arrows
18 in Fig. 7, and when the actuator is released the
~tem is returned to its original position by the
bellows 1 and the spring 4. Instead of the stem 6
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passing through the centre of the bel lows 1, the
latter may be inverted and the stem affixed to its
upper end.
It will be appreciated that the metering chamber 2a
remains empty after the metered dose therein has been
~; sr~nced by operation of the stem 6 . Only upon
DuL~ u_.~tly operating the stem 6 to disr~n~e a
further dose of aerosol wi 11 ~he metering chamber 2a
ref i 11 to provide another metered dose .
The valve housing 7 is also capable of acting as a dip
cup when the aerosol container is required to be
emptied in an inverted position. For that end the
port 20 in the wall of the valve housing 7 is provided
at the highest point of the main container cavity.
The port 20 i~ thus at the lowest point of the cavity
when the container i~ upside-down for use and so the
entire content of the container can drain through the
port 20 for dispensing.
Also a small tube 30 indicated in broken lines in Fig
2, may be positioned with one end sealingly located in
the port 20 and its opposite end positioned near the
closed lower end of the container. When the user
operates the valve with the container in the Fig 2
position, aerosol will travel up the tube 30 and ir,to
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the chamber 2a.
Instead of providing a resilient bellows 1, a non-
resi 1 ier,t f lexible membrane or web may be provided to
prevent leakage of aerosol between the stem 6 and the
open end of the housing 7. Pressure of the aerosol in
the metering chamber 2a will be sufficient to move the
stem 6 away from the valve seat 9 to dispense the
aerosol but, if llecessary, the stem could be biased
normal ly away from the valve seat 9 by means of a
spring, eg, as i~dicated at 32 in broken lines in Fig
1.
The term "aerosol " as used herein includes a
pressurised dispensing container charged with a liquid
produc t and pressur i sed by a 1 i qu i d prope l 1 en t wh i ch
is volatile at room temperature. The term "aerosol"
as a term of art also refers to the liquid in the
container as required by context.
.
.
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