GAS CAPSULE

CAPSULE DE GAZ

English Abstract

A method of filling a capsule with helium comprises making a first crimp in a
neck
portion of the capsule spaced from the free end of the neck and subsequently
making a second crimp at or immediately adjacent the free end of the neck to
effectively form a chamber between the two crimps which inhibits the helium
reaching the free end which is subsequently welded.

Claims

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CLAIMS
1. A method of filling a capsule having a hollow body portion and a hollow
neck
portion extending therefrom with fluid under pressure, comprising the steps:-
a) applying in a fluid tight manner a filling cap to the free end of the neck
portion initially to evacuate the hollow body portion and subsequently
to fill the hollow body portion with the fluid under pressure;
b) with the filling cap still in place and pressure still applied to the
fluid,
crimping the neck portion at a location spaced from the free end of the
neck portion;
c) removing the filling cap thereby revealing the free end of the neck
portion;
d) applying a second crimp at or immediately adjacent the free end of the
neck portion; and
e) welding the free end of the neck portion to seal hermetically the
capsule.
2. A method as claimed in claim 1, in which the fluid is helium at a pressure
of at
least 30 bar.
3. A method as claimed in claim 1 or 2, in which the capsule is made from
aluminium or an aluminium alloy.

6
4. A method as claimed in any one of claims 1 to 3, in which the free end of
the neck portion is laser welded to seal hermetically the capsule.
5. A method as claimed in any one of claims 1 to 4, in which an interim
chamber is formed between a crimp at the location spaced from the free
end of the neck portion and the second crimp.

Description

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GAS CAPSULE
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The present invention relates to capsules for containing a volume of fluid at
high
pressure, that is, between 30 and 80 bar.
Sealed capsules are well known in circumstances where the force of the fluid
under
pressure is employed to dispense a substance such as discharging draught beer
from a beer dispenser or expelling soda water from a soda siphon. They can
also
be used for liquid containers for soft drinks or beer under pressure.
It is also known to employ sealed capsules containing helium at high pressures
in
medical devices using the energy of the pressurised helium to drive a
therapeutic
agent through the skin of a patient.
In PCT published application W094/24263 there is described a needle-less
syringe,
which includes a metal capsule containing helium gas at high pressure which is
used
to force particles of a therapeutic agent through the skin of a patient in a
substantially painless manner. The capsule is detachable from the remainder of
the
syringe and once used, either a new charge of gas can be placed in the capsule
or
more favourably the capsule can be discarded and a new capsule charged with
gas
-' can be attached to the remainder of the syringe.
In the circumstance where the gas capsule is a throw away item it is important
that it
can be manufactured simply and cheaply. In medical applications helium gas is
a
favoured fluid since it is very light which makes it suitable for use as a
propellant for
therapeutic agents in that when it impinges against the skin of a patient it
will bounce
off into the atmosphere and not pass through the skin of the patient. However,
helium because it is light, is difficult to contain since it will leak through
the most
minuscule fault in a container.

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It is an aim of the present invention to provide a method of filling a capsule
with fluid
under high pressure; and in particular a method of filling a gas capsule with
helium
at a pressure of at least 30 bar.
According to the present invention, a method of filling a capsule having a
hollow
body portion from which extends a hollow neck portion with a fluid under
pressure
comprises the steps of:-
a) applying in a fluid tight manner a filling cap to the free end of the neck
portion
initially to evacuate the hollow body portion and subsequently to fill the
hollow
body portion with the fluid under pressure;
b) with the filling cap still in place and pressure still applied to the
fluid, crimping
the neck portion at a location spaced from the free end of the neck portion;
c) removing the filling cap thereby revealing the free end of the neck
portion;
d) applying a second crimp at or immediately adjacent to the free end of the
neck portion; and
e) welding the free end of the neck portion to hermetically seal the capsule.
Preferably the fluid is helium at a pressure of at least 30 bar.
An embodiment of the invention will now be described by way of example,
reference
being made to the Figures of the accompanying diagrammatic drawing in which;
Figure 1 is a plan view of a capsule for containing a fluid under pressure;

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Figure 2 is a view similar to Figure 1 but showing a first crimp applied to a
neck
portion of the capsule; and
Figure 3 is similar to Figures 1 and 2 but showing a second crimp applied to
the
neck portion according to the present invention.
As shown, a capsule 1 comprises a hollow cylindrical body portion 2 made, for
example, from aluminium or an aluminium alloy from which extends an elongate
hollow neck portion 4 of smaller diameter than the body portion 2. Initially
the neck
portion 4 has an open free end 6.
When it is desired to fill the capsule 1 with a fluid such as helium under
pressure, a
filling cap (not shown) is applied in a manner known ep r se to the free end 6
of the
neck portion 4. A vacuum is applied at the filling cap to evacuate the hollow
cylinder
body portion 2 after which the body portion 2 is filled with the fluid under
pressure.
With the filling cap still in place over the free end of the neck portion 4
and pressure
still applied to the fluid within the body portion 2, the neck portion 4 is
crimped at a
location spaced from said free end 6 (see Figure 2). This crimp is made
sufficiently
firm to avoid significant leakage of fluid from the body portion 2.
The filling cap is then removed from the free end 6 of the neck portion 4 to
reveal
said free end 6. Immediately said free end 6 is revealed then a second crimp
is
applied (see Figure 3) at or immediately adjacent said free end and at
substantially
the same time the free end 6 is laser welded to seal hermetically the end of
the neck
portion 4.
The purpose of the first crimp is to prevent fluid under pressure from
reaching the
second crimp and thus the free end 6 so that the laser weld can be made
without
gas permeation holes. Effectively, the two crimps define an interim chamber
which

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prevents or inhibits fluid under pressure reaching the point where the free
end 6 of
the neck portion 4 is to be welded.
The crimps can be effected with either a circular swage type crimp or a simple
flat
crimp.
When the capsule is to be used in connection with a needleless syringe then
the
fluid will be helium at a pressure of at least 30 bar.
Clearly there will be other applications where the capsule will contain a gas
or liquid
under pressure at substantially less than 30 bar.

Representative Drawing