Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
AEROSO~ DISPENSING DEYICE
This invention relates to a dispensing device
which is particularly suited ~or dispensing and
administering metered amounts of fluids. The
principal use for such a device is in di~pensing
metered amounts of a medicament-containing liquid in
aerosol form for inhalation therapy.
In particular the invention i6 concerned with a
dispensins device of that type where the metered dose
of the drug is administered in response to the
inhalation of the patient.
Metered dose inhalers are well known in medicine
for the treatment of, or alleviation of the effects of
respiratory complaints, for example asthma, and
generally comprise a pressurised aerosol dispensing
container, removably mounted within a carrier, and
means for actuating a valve within the container to
cause release of a metered amount of the medicament-
containing liquid to be released towards a chamber
having a mouthpiece for use by the patient. The means
for actuating the valve may be a manually operated
trigger device, or the patient may simply press on the
closed end of the container with a thumb or finger, but
in either case the patient is intended to co-ordinate
the actuation of the valve with inhalation in order to
obtain the maximum benefit from the medicament.
Un~ortunately, many patients needing this type of
treatmant are unable to co-ordinate their breathing
with the manual actuation of the valve.
It is an object of the invention to provide a
metered dose inhaler wherein the release of the aerosol
medicament i~ actuated by the inhalation of the
patient.
In one aspect of the invention there is provided
an inhalation-actuable dispensing device for use with a
pressurised aerosol dispen~ing container comprising:
a receptacle for said container;
means defining a storage chamber arranged to receive a
metered dose from the container, and having an outlet:
a valve means having a closed position in which, in
use, it closes the outlet under pressure from the dose
in the chamber, and an open position in which the
outlet is open to allow the dose to leave the chamber
and enter the outlet spout;
an outlet spout through which a user can inhale; and
a releasing device responsive to inhalation of a user
to move said valve means to its open position.
In a preferred arrangement, response of the`
piston unit to inhalation causes actuation of a valve
to release the stored medicament from the receiving and
storage means into the mouthpiece.
various embodiment~ of the invention will now be
described by way of example only, with reference to the
accompanying drawings, in which:
Figure 1 is a view mainly in section o~ an
inhalation device according to the invention;
Figure 2 is a section vie~ t~ a larger scale of
some parts of Figure l;
Figure 2a is a view similar to Figure 2, but
showing a fragment of a modification thereof; and
Figure 3 is a section view of another embodiment
of the invention.
As seen in Figures 1 and 2, an inhalation device
2 includes a housing 4 having therein a compartment 6
for an aerosol medicament dispenser 8. The dispenser
8 includes a canister 10 and an outlet tube 12, details
of which latter are clearly seen in Figure 2.
The canister 10 contains a medicament suspended
or dissolved in a liquid aerosol propellant, the
medicament being suitable for inhalation therapy. The
interior of the canister 10 communicates with the
outlet tube 12 via an outlet valve (which is of
conventional form and is not shown), the valve
including a metering chamber. The tube 12 has a
transfer port (not visible in the drawings) which when,
and only when, the tube is moved inwardly with respect
to canister 10, provides communication between the
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interior of the metering chamber and the interior o~
the tube.
The housing 4 is formed with a bore 14, coaxial
with the compartment 6 and the outlet tube 12 fits
within that bore, the outer end face of the tube being
in contact with a 6houlder 16 at the ~ottom of the bore
14.
The housing 4 has an outlet spout in the form of
a mouthpiece 18 and a hollow interior portion 20.
Coaxially with the compartment 6 and below the level o~
the mouthpiece 13 is a vertically depending short
cylindrical part 22 formed with a bore 24.
A projection 26 extends into the hollow portion
20 and the bore 14 extends into the upper portion of
that projection. A delivery tube 28 defining a
delivery chamber 29 is located in a bore 30, coaxial
with the bore 14 in the projection 26 and extends
upwardly for a short distance above the shoulder 16 at
the bcttom of the bore 14. An outlet orifice 32
connects the chamber 29 with the interior portion 20
and the mouthpiece 18 of the housing 4.
Within the bore 24 of the housing is located a
piston 34 having a skirt 36 and a top portion 42. A
plurality of holes 38 extend through the skirt around
its periphery.
Fixed by adhesive to the bottom of the projection
26 is a low friction sealing disc 39, and a length of
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very thin stif~ wire 40 passes upwardly through the
sealing disc, in frictional contact therewith, and
freely through the hollow delivery tubs 28. The wire
also extends downwardly and passes freely through a
hole 41 in the top portion 42 of the piston 34.
To the topmost end o~ the wire is fixed a valve
head 44 which, when the inhaler is not in use, sits in
sealing contact with the top face of the delivery tube
28 under the weight of the piston 34. Two discs 46
and 48 are fixed on the wire 40, one disc 46 being
positioned around the middle point o~ the length of the
wire, and the other disc 48 being positioned adjacent
the lower end of the wire and below the portion 42 o~
the piston 34.
The canister 10 is slidable up and down in the
compartment 6 and may be thus moved manually by direct
digital pressure on the end of the canister, or a
system of leverage or a scrPw arrangement may be
provided. In the example shown in Figure 1, a lever
50 is hinged about a pivot pin S2 fast in a bifurcated
lug 54 on the housing, and a projection S6 can be
pressed down onto the top of the canister 10 by rocking
the lever manually.
In use, the patient presses the canister
downwardly into the compartment 6 as just described,
thus actuating the outlet valve within the canister.
This causes a metered dose of medicament and propellant
20~ ~ 3~2
to pass via the metering chamber into the hollow
chamber 13 defined within the outlet tube 12 above the
delivery tube 28 which is at that stage sealed by the
valve head 44. Sealing is effected by virtue of the
fact that the propellant in the chamber 13 is at
substantially above atmospheric pressure and thus
forces the valve head 44 against the end of the tube
28. It is to be understood that the whole of the dose
does not at this stage enter the chamber 13. This is
because the chamber 13 is in communication with the
metering chamber via the above mentioned transfer port,
so that the dose is held partly in the chamber 13 and
partly in the metering chamber, depending on the
relative sizes thereof.
While continuing to hold the canister in its
downward position, the patient places his mouth over
the mouthpiece 18 of the housing and inhales through
the mouth. Holding the canister in its downward
position has the effect of preventing the dose held in
the chamber 13 escaping through the transfer port.
Inhalation by the patient generates a decrease in
pressure within the hollow interior portion 20 of the
housing which causes the piston 34 to move upwardly to
the position shown in chain lines in Figure 1 where its
top face engages the disc 46, moving the wire 40
upwardly to disengage the valve head 44 from its
sealing relationship with the top of the delivery tube
.
28. Because the cross-sectional area of the piston 34
is very large compared to the area of the valve head
44, a relatively small pressure di~ference across the
piston is sufficient to overcome a much larger opposing
di~ference across the valve head. The metered dose of
medicament and propellant in the metering chamber of
the dispenser outlet valve and in the chamber 13 passes
into the delivery tube 28 and through the outlet
orifice 32 where it mixes with air entering the hollow
portion 20 of the housing through the holes 38 in the
walls of the elevated piston 34. ~hus, a metered
dose of medicament is inhaled by the patient.
If desired, means (not shown) may be provided for
holding the canister in its downward position during
inhalation without re~uiring the patient to continue to
press down on the lever 50, for example in the form of
a 90 degree coarse helix turn screw.
In the above described embodiment the weight of
the piston is sufficient to return the wire and valve
head to their lowered position and yet sufficiently
light in weight to be raised by the act of inhalation
by the patient~ The friction of the sealing disc 39
on the wire 40 is sufficiently limited to ensure very
little resistance to axial movement of the wire, but
ade~uate to cause effective sealing of the lower end of
the delivery tube 28. It should be noted that it is
not necessary for a high degree of sealing to be
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provided between the sealing disc 39 and the wire 40,
since the metered dose is only in the region
immediately above the sealing disc transiently on its
way to the outlet orifice 32.
Alternatively, a flexible diaphragm may be u~ed,
this being secured e.g. by adhesive, around its
peripheral margi~ to the bottom face of the projection
26, and to the wire 40c Sufficient flexure of the
diaphragm would be obtained to allow the small amount
of elevation necessary to raise the valve head 44 from
its seating on the delivery tube.
If it is found necessary, a light compression
spring 150 may be interposed as shown in Figure 2a
between the sealing disc 39 and the disc 46 to bias the
valve head towards its seating on the delivery tube.
This ~nsures that the valve head is always seated on
the delivery tube before the dispenser is actuated by
the patient, thus eliminating ths possibility that the
first part of the dose entering the chamber 13 might
escape past the valve head before the valve head had
time to seal under the pressure in the chamber 13. It
also ensures that the dose cannot leave the chamber 13
merely by the device being inverted after the dispenser
is actuated. Were it not for the spring, this could
occur by the piston falling towards, and striking, the
disc 46.
If so desired, the piston 34 may be retained
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within the bore 24 by providing a grid, wire gauze or
the like over the open end of the bore. This is shown
in Figure 2a, where there is an and cap 152 with air
hole~ 154 therein. Alternatively, the lower face oP
the cylindrical part 22 may be provided with an
inwardly directed annular rim which axtends beneath the
walls 36 of the piston. In either case, the piston 34
does not need to be attached to- the wire 40, and the
lower purtion of the wire and the disc 48 can be
omitted. However, the above mentioned compression
spring is then needed to return the valve head 46 to
its sealing position.
In another alternative arrangement, the
cylindrical part 22 is provided with holes around its
periphery and the piston is inverted, having its
portion 42 at the bottom, but also being provided with
holes 38 spaced around the upturned skirt. The holes
in the cylindrical part are effectively sealed off by
the continuous part of the skirt 36 when the piston is
in its lowermost position. In this arrangement
inhalation by the patient causes the piston to rise and
when the holes in the skirt align with the holes in the
cylindrical part 22, air flows through the aligned
holes to the mouthpiece. In order to ensure alignment
o~ the holes in the skirt with those in the cylindrical
part a suitable spline arrangement may be provided
between piston 34 and bore 24. Alternatively, the
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holes 38 may be interconnected by an annular groove
formed in the outer sur~ace o~ the skirt.
In a ~urther alternatiYe arrangement, shown in
Figure 3, the intermediate chamber is loaded with a
metered dose of medicament which is released into the
mouthpiece by means o~ a magnetically actuated poppet
valve which is activated by the inhalation of the
patient.
As seen in Figure 3, the canister 10 is located
in a housing 104 and its outlet tube 12 extends into a
bore 114 which is connected by a small diameter hole
llS to an intermediate chamber 120. ~he chamber 120
is connected to the mouthpiece 118 by an outlet member
ll9 having an outlet orifice 121 ~urrounded by a valve
seat 122. A poppet valve 124 is biassed towards the
valve s~at 122 by a light spring 1260 The poppet
valve 124 is slidable in a bore 128 formed in the
housing 104 and a further bore 130 ext~nds from a
cavity 132 formed in a cylindrical part 134 of the
housing towards the bore 128. The bores 128 and 130
are separated only by a very thin web. Within the
bore 130 is a cylindrical part 138 of a piston unit
which has a piston head 140 normally in engagement with
a seating 142 and retained there by a light spring 144.
The cavity 132 is connected to the mouthpiece by a
passageway 146.
The poppet valve 124 and the cylindrical part 138
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are made so that they can attract each other
magnetically. For this purpose, the cylindrical part
138 has an element 139 which is a magnet or is o~ a
magnetisable material, and the poppet valve includes a
magnet or, provided the element 139 is a magnet, is of
magnetisable material.
In operation, the canister is depressed as
described earlier, to charge the intermediate chamber
120 with a metered dose o~ medicament and propellant.
The patient then inhales through the mouthpiece 118 and
this causes a drop in pressure within the cavity 132.
The dif~erence in pressures on either eide of the
piston head 140 is suffici~nt to overcome the action of
the spring 144 and to cause the cylindrical part 138
with its element 139 to move further into the bore 130
until it contacts the web 136. The proximity of the
element 139 acts to withdraw the valve 124 from its
sealing position in contact with the valve seat 122 and
the medicament mixes with air flowing past piston head
140 and is inhaled by the patient.
