Note: Descriptions are shown in the official language in which they were submitted.
The present invention relates to gas generatLng systems and in
particular to devices for generating gas to Lnflate a marker balloon,
life jacket, life raft, or like Lnflatable ob~ect when the devlce is
immersed (wholly or partially) in water.
By "gas-generating chemicals" in this Specification is meant
chemicals which will react with water to produce a lighter-than-air
gas. A sui~able chemical for this purpose is sodium borohydride with
a catalyst such as anhydrous cobalt chloride. The g~s generated in
this case would be hydrogen. The speed of the reaction may be
increased with the use of other catalysts.
Thus, in accordance with the present teachings, a device is
provided for generating lighter-than-air gas to inflate an object.
The device comprises chemlcals to react with water to produce a
lighter-than-air gas, a reaction chamber which houses the chemicals
and a water chamber for containing water for the reaction. A valve
means is provided operable when the device is immersed to permit the
entry of ambient water into the water chamber with control means
operable to delay the closing of the valve means and the transfer
of a significant quantity of water from the water chamber to the
reaction chamber until such time as sufficient water to complete
the whole of the desired gas-generating reaction has been accepted
into the water chamber.
Conveniently, closure of the valve means is caused by gas pressure
produced in the water chamber during the gas-generating reaction.
In some embodiments, the control means include a wick, or one or more
narrow bore tubes, at least initially providing substantially
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the only water pcl-th from the water challlber to t,he reaction chamber.
Usually in these~ embodinlents, the device will be designed lnitially
to float with tlle water chamber at a higher level -than the reac-tion
chamber -to enable water to :Elow freely under ~ravi-ty from -the wa-ter
chamber -to the reaction chamber once -the gas genera-ting process is
under way. This mi~ht be achieved :for example by providing the
device with ballast or a floa-t or a region of relatively high
buoyancy.
According to a preferred feature of these embodiments, the
water chamber and at least that part of the reaction chamber
housing the chemicals, are separated by a flexible-walled section
which prior to the generation oE significant quantities of gas
:in the device is held in a collapsed s-tate by the ambient water
pressure acting on -the outer walls of -the sec-tion. This initially
isolates the water chamber from the reaction chamber except for
the water path provided by the wick or tube(s) referred to above.
However, as soon as the gas generated in the device reaches a
sufficient pressure to overcome the collapsing action of the
ambient water pressure, the flexible-walled section will inflate
to provide a passageway be-tween the -two chambers which will allow
water in the water chamber to flow freely into the reaction
chamber under ~ravity,
When a wick is used, it can be made from any suitable flexible
conventional wick material provided it is dense enough to ensure
that initially the ambient water pressure will not collapse it and
prevent -the flow of water along the wick. The density of the wick
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may be varied to suit the dalay required. A suitable wick material
would be non-woven reinforced nylon material of porous nature such
as '3M SCOTCHBRITE' marketed by the ~linnesota Mini,ng and klanufacturing
Company Limited.
In other embodiments, the connection between the water chamber
and the reaction chamber at all times provides an unrastrirted
passageway for a free flow of water between the two chambers but
initially this flow is prevented by having the device so orientated
that the water chamberis at a lower level than the reaction chamber.
In these alternative embodiments, the control means conveniently
comprises a mass which after a certain period of time automatically
moves to change the centre of gravity of the device in such a way
as to cause the device to take up some new oribntation in which the
water chamber is at a higher level than the reaction chamber.
Water in the water chamber is then free to flow unhindered into the
reaction chamber.
Devices according to the present invention preferably include
a transfer chamber between the reaction chamber and the connection
for the object to be inflated. The extra length of path provided
by the transfer chamber gives the wa~te products produced during
the gas generation process a greater opportunity to settle out from ''
the gas during its passage through the device so that the gas ~ ~
should be relatively uncontaminated by the time it reaches the object
to be inflated. It is usually considered desirable,however, to
exclude the transfer chamber from the reaction space available during
at least the initial part of the gas generation procesq, first '
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becauso a smaller reclctioll sl)nce Le.lds to ~ more efficient reac-tion,
and secondly becau~e when the water entry valve i~ pressur0-
responsive, the smallel- the reaction sl)ace the more quiclcly will -the
valve-closing pressure be reached after the desired amount of water
has been taken into -the device. Accordingly, it is preferable
ini-tially to separate the transfer chamber from the other two
chambers by a closure member which opens only in response to a pressure
on the gas-generating side of-the member indicative of the gas
generation process having reached a high enough pressure to close
the water entry valve. The clo~sure member may,for e~ample, tak~
the form of a membrane constructed from a material of appropriate
bursting strength.
Although for some applications the device of the present
invention micJht, for example, include a bellows section which
could be manually expanded to suck water into the device for
commencement of the gas generating process, other means, preferably
of an automatic or semi-automatic nature, are usually more
convenient:and to be preferred.
For example the device might include a flexible part which is
automatically expanded ~e.g. by a spring) on the release of a catch
associated either with the device or with a support or carrying
case for the device. In one such example the catch is only released
when the device is immersed so that the expanding action of the
flexible part will draw in the desired amount of water into the
device. In another example, the catch may be released to expand
the device when it is out of the water but in this case the device
.
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must of COlll'~;e itlClllde some IlleanY (e~ a water-soluble closure
member) by which the device is preven~e(l from openirlg until is
is imalersed.
ln a varialiotl o~ the ~irst of these two examples the catch
could be releclsed autoll1alicaLly by dissolving a water soluble
mernber which in the inoperative condition of the device holds the
ca-tch closed. Alterna-tively this member could in fact comprise
the ca-tch. In a variation of the second of the two examples the
flexible part of the device could be replaced by a rigid par-t but
the device would then have to be evacuated during its manufacture.
As an alternative to these various systems for getting water
into the device, this latter could simply be a rigid or semi-rigid
device 50 construc-ted as to sink under its own weight with the
water entering the inside of the dovice through some convenient
opening. The openin~ could for example be a permanently exposed
opening, or one initially sealed off by a water soluble closure
member, or one exposed by removal of a conventional lid member
either when the device is immersed or prior to or during immersion.
The inven-tion further includes an assembly comprising the
device of -the present invention connected up with the object to be
inflated and according to a further feature the flow of gas from
the device to the object is controLled by a valve.
A preferred valve for this purpose comprises an envelope of
flexible resilient material having a first portion apertured to
allow ingress of gas from the device into the envelope, a second
portion housed inside the object and apertured to permit gas in the
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envelope to escape into the object, ar1d a pair of opposed walL
regions lying between the apertures in the first and second
portions and urgecl towards each other into a valve-closirg
relationship by the pressure of the gas in the obj0c-t.
The princi~l advantage of this particular valve is that
it can be made light in weight to maximise -the lift of the
balloon. It will also have low resistance to 1;he ingress of
gas from the device i.e. the back pressure exerted by the valve
is minimal. This latter characteristic means that the device
itself can readily be construc-ted in such a manner and from such
materials as to be easily packed snugly in a reasonably sized
carrying case when it is desirable that it should be carried
round as part of a ~ser'snormal equipment e.g. when intended
for use in a marker balloorl assembly for a man who has falLen
overboard.
Generally speaking, the valve envelope may be of any rubber
or composition material of a suitably elastic nat~re. The
envelope may be in the form of a tube or of a balloon. The
outline shape of the envelope is not critical but long and
bulbous shapes are preferred. It should preferably lie flat in
its natural state i.e. with the two main faces touching, or
nearly so. The envelope could for example be made with a flat,
or nearly flat, former or from two pieces of identical shape
which are flxed together at their outer edges.
One version of -the valve is made by perforating a balloon-like
envelope (or by cutting the end from it) to form the gas exit. The
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two abutting surfaces oE the envelope are then held together either
by glueing, welding, st~pLing, rivetting, stitchiny, moulding, or any
o-ther convenient means, adjacent to -the gas exit. Partially fixing
the two naturally abut-ting faces of the envelope together in -this
way, results in an inherent stress being crea-ted by the two elastic
surfaces when these are forced apar-t by gas passing through the
envelope into the object to be inflated. When the gas flow is
stopped this inherent stress causes the two surfaces to come
together again and the valve is held in this flattened closed
L0 condition by the back pressure of ga$ in the object in which the
valve is located.
The object to be inflated by the device is conveniently attached
to it by a water soluble connection and means may be provided so
that this connec-tion is exposed to ambient wa-ter only when the
L5 object has been satisEac-torily inflated. In two such embodiments
for example the connection is initially held clear of the ambient
water by having the device initially in a floating condition. In
one of these two embodiments a moving mass is used to change the
orientation of the device at a suitable instant to immerse -the
connection in the water. In the other of the two embodiments, the
device is vented and gas continuing to leak out through the vent
results in -the device sinlcing to a level at which the connection
is immersed in the ambient water.
Where a movable m~ss is used to immerse the cormection between
the device and the balloon and/or to invert the device in those
embodiments where inversion is required to bring the water chamber
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1~8~
to a higher level than the reaction chamber or vice-versa, -then
-the mass may, for example, be secured to one end of a len~-th
of line that at its other end is perrrlanently secured to a first
region of the device whilst being temporarily attached at an
intermediate portion of the line to a second region of the device.
The temporary attachment conveniently takes the form of a
water soluble connection ~or example which when it dissolves in
the ambient water in which the device is wholly or partially
immersed, releases the mass -to result in the point of application
of the force exerted by the mass moving from the second region
of the device to the ~`irst region. This change causes the device
to take up the desired new orientation. The same method can be
used if desired for other related applications e.g. to trig~er
a flashin~-ligh-t distress signal etc.
As indicated in the preamble to the Specification, the term
"immersed" when applied to the device, should, unless otherwise
specified or implied in the context, be taken to include both the
situation where the device is fully immersed and the situation
where it is only partially immersed. Where immersion of the
device is necessary for ambient water to act on a wa-ter soluble
item associated with, or forming a part of the device, then obviously
in such cases -the device must at least be immersed to the point at
which the item is in contact with the water so that the
desired action can~take~place.
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Embodiments of the invention will now be described, by way of
example only, with reference -to -the partially d:iagrammatic accompanying
drawings in which:-
~ igures 1 and 2 show a longit~dinal section and an elevation of
a first assembly. Although the assembly would not normally assume thecondition shown in these Figures, it has been ~i:Llustrated in this way
so as more clearly to indicate the more important features of -the
assembly;
Figure 3 shows on an enlarged scale that part of the device
connected to the object to be inflated.
Figures 4 to 7 show, on a reduced scales, ~the.asse~bly:of
Figures 1 to 3 as it would actually be at variaus stages of its
operation;
Figures ~ to 13 show longitudinal sections of other e~bodiments
at intermediate stages of -their operation;
Figure 14 shows a vertical section of the last of these
embodiments at a later stage of its operation;
Figure 15 shows a vertical section (on an enlarged scale) of a
water-soluble link system for attaching a ballast weight to the
device; and
Figure 16 shows a part of Figure 1 on an enlnrgad scale ancl
with components illustrated separated for clarity.
The same reference numerals have been used to indicate
corresponding items in the various embodiments.
Thus referring first to Figures 1 and 2, a device 6 according
to the present invention comprises a flexible envelope 8 defining
~7
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a reaction chamber 10, a watar chamber 12, and a transfer chamber 14.
The gas producing chemicals 16 are contained in a water permeable
or water soluble bag 18 in the reaction chamber and this is
connected to the water chamber by a wick 20.
In the illustrated embodiment, envelope 8 is made from 7034
~ ~ , .
gauge "Synthene" co-extruded nylon/polythene film (marketed by
Smith and Nephew Plas~ics Limited) and bag 18 is made from
standard grade water-soluble paper (marketed by ENA~ Limited).
:
The chemicals 16 are those mentioned in the preamble to the
Specification as being suitable for hydrogen generation.
When free to do so the chamber 12 is expanded (as shown for
illustrative purposes in Figure 1) by an expansion spring 22
contained within the chamber. Reference numeral 24 indicates a
one-way valve allowing ambient water to enter chamber 12 during
this expansion.
In Figure 16, the three basic components of valve 24 are
shown separated for greater clarity. These components are an
annular rubber diaphragm 200, a peripherally apertured metal
disc 202, and an apertured part 204 of the envelope engageable
by the disc 202. These components are urged by the spring 22
into a water-tight;relationship in which the apertures 206, 208
in the disc and envelope are covered by the diaphragm 2000 As
will be clear from the description of the operation of the valve,
although spring 22 urges the valve into a valve-closed position~
whether or not it is closed in practice at any given instant will
depend on the pressure differential across the valve at that
instant.
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35~4~1:
Althoug}1 only two nli(~Jr1ecl apertures 206, 20~ are shown, thesc
are conveniently each one ot` two c1inmetricAlly opposed aper-tures
in the compor1ents concerne(1.
Returninc1 now -to ~igures l and 2, it will be seen -that the
water chamber 12 -is initially separa-ted from the -transfer chamber l4
by a membrane 26. An at-tachment nipple 28 allows the object to be
inflated by the device (mar}cer balloon 30) to be connected up with
-the transfer chamber. Balloon 30 may be of any convenient design
e.g. a conventional metereological balloon. The one used in the
illus-trated embodiment is a lO gram~Beritex balloon (marketed by
Philips Patents Limited)0
Numeral 32 indica-tes a one-way low-pressure valve preventing
gas that has entered balloon 30 from leaking back into transfer
chamber L4. This valve will be described in more detail later in
the Specification with reference to ~igure 3. The balloon is
tethered to the device by a length of line 3~ stored in a fixed
reel lO0, also shown in more detail in ~igure 3. In use the
line will be unwound from the inside of the reel. This enables
the line to be freely unwound from any angleO
The assembly is completed by a line 36 from the balloon end
of the device to the user (not shown) and by a line 38 from that
same end to a ballast weight 40 which, at least initially, is
suspended from the other end of the device by two lines 42, 44
connected together by means of a water soluble link 460 The
link 46 etc. which is shown diagrammatically in Figures l ~o 7 and
in some of the other figuresj will be described in greater detail
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later in the Specification with reference to ~igure -l5. With a
typically sized device (say two foot long) the weight 40 might be
of -the order of one pound.
In the inoperative condition of -the device (with spring 22
compressed and envelope 8 and balloon 30 deflated) the envelope
and the balloon will be tightly rolled up and packed snugly in a
carrying case (not shown) which amongst other things will be ;~
effective to maintain the expansion spriny in its compressed state.
If the user falls overboard say and desires to use the marker
balloon 30 to indicate his positlon for rescue purposes, then with
the device immersed in the water he opens the lid of the carrying
case and the weight 40 will fall out dragging the rest of the
device behind it. Spring 22 as soon as it is free from the
restraining action oE the carrier case will expand causing ambient
watcr to be sucked into chamber 12 through valve 2k. ~igure 4
shows the device at this stage. Numeral 48 in Figure 4 indicates
the surface of the sea of course. Line 36, which is affixed inside
the carrying case (itself affixed to the wearer), will ensure that
the device remains attached to its user.
The sea water that has entered water chamber 12 will quickly
percolate through the wick 20 (e.g. in 5 to 7 seconds) into the
reaction chamber 10. While all this i9 happening the opposite walls
of those portions of the envelope defining the reaction chamber 10
will be held tight together by the pressure exerted by the sea on
the outside of the device. However, after the first water has
arrived in the reaction chamber 10 and the gas generating process
12
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has commenced, the gases producecl in chamber 10 will quickly :increase
the internal pressure in this par-t of the device until it excseds
the external pressure exerted by the sea and when this happens -the
walls of the reaction chamber 10 will be forced apart and the rest
of the water in chamber 12 can fali freely into chAmber 10. This is
the si-tuation shown in Figure 5. Typically it m:ight take some
fifteen seconds to inflate the r0action chamber in this way. It
will be seen that the device now has sufficient buoyancy to float
with the balloon ehd of the device clear of the sea.
The increased internal pressure in the device will also be
effective to close valve 2k thereby preventing further water from
being introduced into the device for the gas-producing reaction.
In one typical embodiment put under test, about 20 seconds
elapsed from when the valve 2k was opened to when sufficient water
has percolated through into -the reaction chamber via wick 20 for
-the gases to expand the envelope into the position illustrated in
Figure 5. This is adequata time:for the chamber 12 to fill by the
required amount.
When the gas generating reaction has progressed to som~thing
near its final stage, the pressure in the device will be
sufficiently high to rupture the membrane 26 and the gas generated
by the reaction will escape through transfer chamber lk to inflate
this part of the device and to commence inflation of the balloon 30.
As already explained the purpose of the membrane 26 is to~contain
the reaction to a reasonably small volume during at least the
major part of the gas generating process.
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Sufficient gas is generated in the process for the balloon to
be in a satisfactorily infla-ted condi-tion by the time the pressures
in the balloon and the device have equalised. At this point the
valve 3~ closes (Figure 6).
rhe water soluble link 46 referred -to earlier has all this
time been exposed to the action of the sea, and is of such a size,
and so designed, that after the balloon has been fully inflated,
link 46 will finally dis~olve completely away allowing the two
lines 42 and 44 to separate. The mass 40 will now be free to fall
under its own weight dragging down the balloDn-end of the device into
the sea as shown in Figure 7. Wlth the balloDn end of the device
immersed as shown, the sea water will quickly dissolve the water
soluble connection 110 and the balloon will rise to the end of its
line 34 to indicate the position of the wearer of the de*ice.
Typically, line 34 would be about 100 feet long. Reference
numeral 50 in Figure 7 indicates the remains of the exhausted
chemical reaction.
Referring now to Figure 8 this shows an embodiment of the
invention in which the essential difference from the previous
embodiment is that the positions of the water chamber and the
reaction chamber have been interchanged. Thus whereas in the
embodiment of Figures 1 to 7, the ambient water enters the water
chamber 12 and percolates downwardly through wick 20 into the
reaction chamber lO(t ïn the embodiment of Figure 8, the wick is
omitted and instead the bag of gas generating chemicals extends
downwardly from the reaction chamber into the top of the water
14
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f ~
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chamber so that when the desired amount of water has been taken into
the water chamber through valve 24, it will come into contact with
the lower end of the bag 18 and gas generation will commencen As
the bag 18 is made of water soluble material, at least that part of
it wetted by water from chamber 12 will very quickly dissolve away
(e.g. in 2 or 3 ~ec~nds~ allowing the chemicals 16 to pour freely
from the bag into the water chamber for completion of the gas
generation process.
In the embodiment of Figure 9, the spring-biassed flexible-walled
water chamber 12 of the earlier embodiments, is replaced by a
rigid-walled chamber 52 and the valve 22 is covered by a water
soluble plug 54 e.g. of an effervesc0nt compound such as Alka-Selzer
(marketed by Miles Laboratories Limited)~ Alternatively a water
soluble film could be used to cover the valve e.g. of the type used
in connection llO.c The devic~ comes with'chamber 52'air free 90 ,that
typically after Z or ~ second~ ~hen plug 54 ha3,d~solved,sea uater will'be
sucked into the water chamber and the device will commence to
operate in an exactly analogous fashion to that already described
with reference to the embodiments of Figures 1 to 8~
Figure 10 shows yet another embodiment. In the device of
Figure 10, the water chamber and the reaction chamber are
provided~by,different portions of a rigid walled part 56 with the '~
chemicals initially housed at the top end section and the water
chamber provided by the lower sections. The ballast weight ill2)
25 is secured in the bottom of part 56 by a bolt 114 . At it3 upper
end, the device has an apertured lug 116 enabling the device to be
attached by a line 118 to a life buoy for example.
r .,~ ~ ,
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i
1~11 35~
Part 56 is in fact only the lower piece of a larger housing 120
in the top piece of which are contained a flexible transfer chamber
envslope 14 and the marker balloon 30 to be inflated. The top and
bottom portions of the housing are internally separated by a plat~l22
but this latter is centrally apertured (at 124) to provide a conneotion
between the interiors of the transfer chamber and the reaction chamber.
An 0-ring 126 secures tha bottom of envelope 14 to the plate 122~ but other
similar fixings oan be used instead if desired.
The top qnd of the housing 120 is in the form of a removable
lid 128 which is secured by a short line 130 with a carrying `: -
bracket 132 for the device. ~racket 132 might for examPle be secured
to a light craft, boat or ship.
Reference numerals 134, 136 indicate two tube~ leading from
peripheral apertures in the plate 122 to the bottom of the water
chamber 12. The top ends of the tubes are a~sociated with one way
entry valves 138, 140 arranged to permit a downwards flow of water
through the two tubes. Typically valves 138, 140 might be disc or
ball valves.
In operation of this embodiment, the device is removed from its
support bracket and is hurled with its lifebuoy tnot shown) into the
the sea. The line 130 will be put under tension to jerk the lid 128
off the container so that it is open-topped when it hits the water.
The buoyancy of the device is such that it will begin to sink under
its own weight and water will pour in at the top end of the housing.
From there it will drain through tubes 134, 135 into the bottom of -
the water chamber 12. When the water has risen to
~ ` :
the level of the chemictlls 16, gas generation will commence and the
increase in pressure in -the reaction chamber will close valves 138, 1~0
preventin~J further water from entering -the lower part of the device.
The dimensions of the wa-ter chamber are such, of course that by
this stage sufficient water will have been accep1;ed for comple-tion
of -the ~as genera-ting process.
At a predetermined pressure produced a-t or near completion of
the gas generating process, -the membrane 26 will burs-t and the
transfer chamber envelope 14 and the marker balloon 30 will in-~late
in the usual way. The transfer chamber 14 is provided with a vent
hole 61 at some point above -that at which the balloon is attached.
Gas is allowed -to escape through -this hole from the time that the
membrane bursts and gas enters -the transfer chamber but the rate
of escape is small in rela-tion to the input into the balloon.
When the reactlon ceases, the pressure in the transfer chamber
is roughly the same as -that in the balloon but with valve 32 closed,
the residue gas in chamber 14 will continue to vent to atmosphere
through hole 61 until the buoyancy of the device is sufficiently
reduced for the weight 112 to sink it to a Ievel at~which the neck
of the balloon is immersed in the sea. The water soluble
connection 110 will dissolve away soon after.
The essential difference between thq embodiment of Figure 11 and
that of Figure 10 is that whereas in the earlier embodiment the
water enters the top of the devicq and is conveyed from there to the
bottom of the water chamber through appropriate tubes, in the
embodiment of Figure 11, the water enters the bottom of the device
: : :
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directly into the water chamber. As wi-th the previous embodiment
however, the water chamber and the reac-tion chamber are still
provided in different portions of a common rigid walled part 56
with the chemicals initially housed a-t the top end of the section
(at a position indica-ted by numeral 1~2 in Figure 11) so that
sufficient watel to compLete the gas-generating reaction must
have been talcen into the device before the water can contact the
chemicals and the en-try valve (1~) be closed by the gas pressure
generated by the reaction.
In the modification shown in Figure 12, an annular mass 62
is included at the bottom of the water chamber so that even when
-the gas-producing operation has been completed and membrane 26
has ruptured, the net weight of the device is still sufficient to
hold the water soluble connection 110 below sea level. Obviously
as before this connection must be such that it will not free the
balloon until sufficient time has elapsed for this latter to be
fully inflatedO Al-though relatively bulky when compared with the
previous embodiment, the embodiment of Figure 12 offers an
alternative version of the device in which the need to change the
orientation of the device at some stage in i~s operation is done
away with.
Figure 13 shows a rigid-walled version of the device in which
the transfer chamber and the water chamber are one and the same
thing and the reaction chamber (10) is at the opposite end of the
device to the ballast weight 40 and the balloon 30.
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In thi~ embodiment the ballast weight l~0 pulls the device down
so that sea water enters the combined transfer/water chamber ~64)
via the one way entry ~alve 18. When sufficient water for the
complete gas-generating reaction has en-tered the chamber 64, the l-
water soluble link 46 will finally dissolve away and the maqs willmove under gravity to pull the device over a~ indicated in Figure 14.
This will cause ths water to be thrown on to the chemicals 16 and
the gas producing reaction will commence. When the balloon has
fully inflated, a water soluble plug (or 3eal) 66, in what i~ now
the lower part of the device, finally dis~olves away allowin~l water
to entertthe device to sink it to a level at which only the
buoyancy of the balloon in the sea will keep it afloat. Thi~
immerses the water soluble connection 110 in the sea and thi~
connection quickly dissolves away to allow the balloon to rise to
the end of its line and the device to sink awayO
Fi~ure 15 shows on an enlarged scale the link 46 referred to
above and shown in the various other Figures of the drawings. '~
It will be seen from Figure 15 that the link comprises a casing 67
apertured at 68:and containing a water soluble tablet 69 which traps
the line 42 in the casing. The tablet might, ~or example, be a
water-soluble 'effervescent~ tablet e.g. an Alka~Selzer tablet of
approximately 1 inch diameter and 3/16 inch thick~e~3' with a'ce'ntral
`of'hole 3/16 inch diame~e~., TypicalIy th~ di'ssol~ing ti~ of
this tablet,might be approximately 11 minutes~
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Line 44 i9 secured to the casing itself. Wherl the tablet has
finally dissolved, line ~2 is free to leave the casing through
aperture 68 and the mas~ 40 can swing away under gravity supported
by the line 38.
Referring now to Figure 3, this shows on an enlarged scale
preferred versions of the valve 32 and reel 100 referred to earlier
in the Specification. As will be seen from this Figure, the
illustrated valve is basically of a flexible balloon-like
construction. In the illustrated embodiment in fact, a standard
Aeriel balloon ~narkebedby the London Rubber Company Limited) was
modified for this purpose by punching a hole 70 through the balloon
and then stapiing its two walls together at 74 to encourage them to
cling together in response to even a very small excess pressure on
the outside faces of the valve. The stem portions of the valve 32
and themarher balloon 30 are secured by 0-rings 71, 72 on to a
connector piece 73 which is held in an abutting relationship with
the nipple 28 by several turns of water soluble material held in
place by 0-rings 72 75~ In the illustrated embodiment, this
~) .
material is a polYvinyl acetate (PVA) film marketed by ENA~ Limited,
three turns of 0.002 inch thickness film being sufficient to give
the desired dissolving time of 30-60 seconds. Of course if other
dissolving times are required, these can be ~btained by changing
the number of turns andjor the grade of the PVA film.
At its lower end, nipple 28 is rigidly mounted in an
attachment plate 76 welded into the wall of that part of the
'. : ' ' '.
4~L
envelope 8 providing the transfer chamber 1l~. Alternatively
plate 76 cou1d be attached to the envelope by an adhesive.
In addition to supportirl~ nipple 28, the attachment plate 76
carries an anrlular disc 77 forming the lower one of two such
discs 77, 78 which together constitute the reel lO0. The assembly
procedure is as folLows. When -the valve 32 and balloon 30 have been
assembled as described (in their deflated states of course), then a
collapsible mandrel is placed on disc 77 and line 31~ is wound around
the outside of the mandrel as a coil 79. The inner end of the coil
is secured to a brass ring 80 carried on the neck of the balloon 30
and too large to pass through 0-ring 71. The outer end of the coil
is secured -to a top corner of the device as shown at 81 in Figure 2.
The -top disc 78 is now secured in place by a number of attachment
' lugs 82 bent up from the lower disc 77 as shown in Figure 3. ~he
mandrel conveniently takes the form of a flat semi-circular spring.
This spring is now compressed to an increased curvature enabling
it to be removed through the aperlure in disc 77. This completes
the assembling of reel lO0.
.
. . . ...
