U.S. patent number 3,602,661 [Application Number 04/882,645] was granted by the patent office on 1971-08-31 for immersion responsive sensor.
This patent grant is currently assigned to Saab-Scania Aktiebolag. Invention is credited to Karl-gosta Liedberg.
United States Patent |
3,602,661 |
Liedberg |
August 31, 1971 |
**Please see images for:
( Certificate of Correction ) ** |
IMMERSION RESPONSIVE SENSOR
Abstract
The immersion responsive sensor of an automatically inflatable
life jacket comprises concentric inner and outer tubular
electrodes, the outer one having water access apertures at zones
spaced axially from the ends of the inner one. The outer one
comprises part of a housing that encloses a battery. Seal means
extend across the outer electrode in axially spaced relation to the
inner one and have frustoconical inner surfaces that drain water
toward the apertures.
Inventors: |
Liedberg; Karl-gosta
(Linkoping, SW) |
Assignee: |
Saab-Scania Aktiebolag
(Linkoping, SW)
|
Family
ID: |
20302728 |
Appl.
No.: |
04/882,645 |
Filed: |
December 5, 1969 |
Foreign Application Priority Data
|
|
|
|
|
Dec 9, 1968 [SW] |
|
|
16776/68 |
|
Current U.S.
Class: |
200/61.05 |
Current CPC
Class: |
B63C
9/24 (20130101); B63B 2209/02 (20130101) |
Current International
Class: |
B63C
9/00 (20060101); B63C 9/18 (20060101); H01H
29/00 (20060101); H01h 029/00 () |
Field of
Search: |
;200/61.04,61.06,61.07,61.05 ;340/235 |
References Cited
[Referenced By]
U.S. Patent Documents
Primary Examiner: Schaefer; Robert K.
Assistant Examiner: Ginsburg; M.
Claims
This invention is defined by the following claims:
1. Means responsive to immersion in water to complete a circuit
through which an electrical device such as a squib igniter is
energized from a battery to effect actuation of emergency
equipment, said immersion responsive means comprising:
A. an elongated substantially tubular outer member
1. having an end portion that comprises a battery chamber in which
the battery is receivable and
2. having an intermediate portion between its ends that has an
electrically conductive inner surface which provides one of a pair
of electrodes for electrical connection by water, said intermediate
portion being apertured in zones near its ends to provide for entry
of water thereinto;
B. sealing means including sealing wall members of electrically
insulating material spanning said tubular member and sealed thereto
all around it at the ends of said intermediate portion, axially
outwardly adjacent to each of said apertured zones, one of said
sealing wall members cooperating with said end portion of the
tubular member in defining the battery chamber; and
C. a rigid inner member, means whereby said rigid member is
supported by one of said sealing wall members in substantially
coaxial radially inwardly spaced relationship to the intermediate
portion of the outer tubular member and which extends through a
substantial portion of the length of said intermediate portion,
said inner member having an electrically conductive outer surface
which provides the other of said pair of electrodes.
2. The immersion responsive means of claim 1, further characterized
by:
each of said sealing wall members having an axially inner surface
which is inclined laterally and axially outwardly from the axis of
the outer tubular member, to encourage any water in said
intermediate portion to drain out of the same through its apertured
end zones.
3. The immersion responsive means of claim 1, further characterized
by:
the opposite end portion of the outer tubular member cooperating
with the other sealing member to define another chamber for housing
electrical instrumentalities for connection with the battery and
with said inner and outer members and the electrical device.
4. The immersion responsive means of claim 3, wherein said inner
member is tubular, further characterized by:
A. said sealing means including a tubular electrical insulating
element extending coaxially through said intermediate portion of
the tubular outer member, within said inner member, from one to the
other of the sealing wall members and in sealing relation with
them; and
B. an elongated electrical conductor extending through said
insulating element and the wall members for connection at one end
with one terminal of the battery and at its other end with said
electrical instrumentalities.
Description
This invention relates to immersion responsive means for
automatically initiating inflation of a life jacket or the like,
and is more particularly concerned with an improved immersion
responsive sensor for completing a circuit that energizes an
electrical actuator when the sensor is immersed in water.
Aviators, sailors and others whose work or recreation subjects them
to the risk of immersion in a body of water have need for personal
flotation gear, such as a life jacket, which is normally in a
compact and unobtrusive condition so that it does not interfere
with the wearer's activities at times when it is not performing its
emergency function, but which can be inflated very quickly when the
wearer falls into water. To meet this need, inflatable life jackets
have come into widespread use. Such a life jacket comprises a small
bottle of compressed gas and a mechanism for quickly releasing the
gas into the inflatable body of the life jacket.
With many such jackets it is necessary that the wearer manually
actuate a part on the gas release mechanism in order to initiate
inflation of the jacket, but since the wearer may be unconscious or
seriously disabled at the time of his entry into water, increasing
attention is being given to the provision of means for
automatically effecting inflation of a life jacket in response to
its immersion. In general an automatic inflation device comprises a
sensor which cooperates with an amplifier or switching device and
which responds to the presence of water by causing current to flow
from a battery to an electrical igniter for a squib or small
cartridge. When the igniter is thus energized, the squib explodes
and drives a punch through a seal on the compressed gas bottle,
thereby releasing gas from the bottle to permit it to inflate the
life jacket.
The immersion responsive sensor is of course a critical part of the
automatic inflation apparatus. Unless it functions reliably in an
emergency, the jacket may not inflate and the wearer may lose his
life. On the other hand, if the sensor initiates inflation at a
time when it should not do so, as in the presence of rain or salt
water spray, the inflated jacket may so impede the wearer's
activities that its very presence endangers his safety.
In general the sensor comprises a pair of spaced-apart electrodes
that are connected in an electrical circuit comprising the battery
and the switch or amplifier. When the sensor is immersed, water
provides a conductive path between the electrodes, permitting a
small control current to flow in the electric circuit. By means of
the amplifier or switch, a larger energizing current is then caused
to flow in a circuit comprising the battery and the squib igniter
or other electrical actuator, thus triggering off the short
sequence of events that leads to inflation of the life jacket. When
the sensor is not immersed in water, the space between the
electrodes of the sensor is relied upon to afford such a high
resistance in the circuit comprising the battery and the amplifier
that the current flowing therein is at most so small as to be
negligible.
In fact, the sensor for an automatically inflatable life jacket has
a tendency not to afford a clear-cut on-or-off type of response.
When the sensor is immersed, the current through it must be high
enough to initiate ignition of the squib, regardless of whether it
is immersed in salt water, which is a relatively good conductor of
current, or in fresh water which conducts current rather poorly.
When not immersed, the sensor should preferably have an effectively
infinite resistance, so that no drainage of the battery takes place
even over extended periods of time. Furthermore, the sensor should
have such practically infinite resistance even when it is subjected
to conditions of extreme atmospheric humidity, and to rain, fog and
salt spray, for otherwise it can cause an unexpected and undesired
inflation of the life jacket.
Not only must the sensor be able to discriminate between immersion
in fresh water and mere exposure to salt spray, but when the
apparatus produces an output that initiates life jacket inflation,
it must be such an output as will insure ignition of the squib,
irrespective of the response current value of the particular squib.
Squibs commonly used for life jacket inflation devices vary widely
in their ignition current requirements. The minimum current
required for ignition of one squib may be as much as twice as high
as the minimum current needed for ignition of another. Therefore
the only sure way to effect ignition of a particular squib is to
supply its igniter with a current no lower than is adequate to fire
a squib having the highest minimum ignition current
requirement.
In sum, therefore, an automatic inflation initiating device for a
life jacket must be capable of a rather close discrimination with
respect to the conditions of its environment, but it must either
permit no current flow or, when its sensor is immersed, it must
cause enough current to flow to the squib igniter to fire a squib
having the highest expectable ignition temperature.
With these considerations in mind, it is the general object of this
invention to provide an immersion responsive device for initiating
automatic inflation of a life jacket or the like, having a sensor
which allows no current to flow in its electrical circuits at times
when the sensor is not immersed, even under conditions of high
humidity including rain and salt spray, but which, when its sensor
is immersed in either salt water or fresh water, provides a high
enough ignition current flow to fire any acceptable squib.
Another and more specific object of this invention is to provide an
immersion responsive sensor which tends to rid itself of any
accumulation of water that develops from causes other than
immersion, such as rain, fog and spray; and which, moreover,
responds only to the presence of a coherent body of water between
the sensor electrodes, as distinguished from a film of water or
mere drops, but which nevertheless does not require complete and
total immersion in water to cause inflation to be initiated.
It is also an object of this invention to provide an automatic
immersion responsive inflation initiating mechanism of the
character described which is very compact and light in weight,
which carries its battery in a sealed compartment protected from
moisture and humidity, even during immersion, and which has a
sensor that is protected from airborne moisture such as rain, fog
and spray, but which water is readily accessible upon actual
immersion.
With these observations and objectives in mind, the manner in which
the invention achieves its purpose will be appreciated from the
following description and the accompanying drawings, which
exemplify the invention, it being understood that such changes in
the precise method of practicing the invention and in the specific
apparatus disclosed herein may be made as come within the scope of
the appended claims.
The accompanying drawings illustrate two complete examples of
embodiments of the invention constructed according to the best
modes so far devised for the practical application of the
principles thereof, and in which:
FIG. 1 is a front view of a life jacket embodying the principles of
this invention, shown being worn and in its normal uninflated
condition;
FIG. 2 is a vertical sectional view of the inflating and inflation
initiating mechanism of the life jacket;
FIG. 3 is a diagram of the electrical circuit of the immersion
responsive inflation initiating mechanism; and
FIG. 4 is an enlarged detail view of a modified embodiment of the
sensor, shown partly in side elevation and partly in section.
Referring now to the accompanying drawings, the numeral 5
designates generally an inflatable life vest or life jacket
embodying the principles of this invention, which is generally
U-shaped to have its bight portion around the back of the wearer's
neck and its leg portions extending downwardly and overlying his
chest. A strap 6 extending transversely to the leg portions of the
jacket and secured to them near their lower free ends is fastened
around the wearer's waist to secure the device to him.
In its normal uninflated condition, shown in FIG. 1, the life
jacket is folded to a substantially flat condition, close to the
wearer's body, and it therefore offers little or no interference to
bodily movements. When inflated, it distends to a condition in
which it can bouyantly support the upper portion of the wearer'body
and keep his head out of water.
As is generally conventional, the jacket comprises an outer
tubelike envelope of fabric which encloses and protects an
inflatable bladder. A zipper 7 on the envelope, extending
lengthwise all around it, can be opened for ready access to the
bladder.
The activating mechanism for the jacket is carried in a pocket 8
formed in the fabric envelope at one side thereof. A manual
inflation control knob 9 hangs down from the mechanism on a short
cord 10 to be accessible beneath the pocket for manual initiation
of inflation by a downward pull on the knob 9. The device is also
capable of effecting automatic inflation of the jacket in
consequence of immersion of the mechanism in a body of water.
The activating mechanism in the pocket 8, which is designated
generally by 12, is best seen in FIG. 2. It comprises, in general,
a body or base casting 14 which supports a pressure gas bottle 15,
a puncturing pin 16, an actuating lever 18, a sensor 19, a battery
20, and electrical circuit means 23 responsive to immersion of the
sensor.
The bottle 15, which contains a charge of gas (e.g., carbon
dioxide) under high pressure, is secured to the base casting 14
with its mouth downward and opening to one end of a generally
U-shaped passage 21 in the base casting. The mouth of the bottle is
normally sealed by a frangible diaphragm that is intended to be
ruptured, for jacket inflation, by the puncturing pin 16, which is
arranged to slide up and down in the upright portion of the
U-shaped passage 21 that is directly beneath the bottle.
The puncturing pin to is pointed at its upper end and has a shoe at
its lower end that engages one arm 25 of the actuating lever 18.
The actuating lever is medially fulcrumed on a pivot 26 secured in
the casting 14, and it has its other arm 28 engaged by a plunger 29
to which the upper end of the cord 10 is secured.
When the plunger 29 is moved downwardly, either by a manual pull on
the cord 10 or by operation of the automatic mechanism described
hereinafter, it swings the arm 28 of the lever 18 downwardly, and
concomitantly swings the arm 25 of said lever upwardly, thereby
driving the pin 16 up into rupturing engagement with the diaphragm
in the mouth of the bottle. The gas thus released from the bottle
flows through the U-shaped passage 21 in the base casting to an
outlet nipple 30 that has a sealed connection with the bladder,
whence it flows into the bladder to inflate the same.
A feature of the activating mechanism of the invention is a
condition indicator that is visible through a small window 31 in
the base casting. The condition indicator comprises a rotor 32
which has an axially wide rim 33 extending part way around it and
which is mounted for rotation on a pin 34 that is fixed in the base
casting. The rotor 32 is biased in one direction of its rotation by
means of a small spring 35.
When the puncturing pin 16 is in its normal position, it engages a
noncircular peripheral portion of the rotor 32 to confine the rotor
against turning in response to the bias of the spring 35, and at
such times a green colored area on the rim 33 of the rotor is in
register with the window 31 to provide a visible indication that
the mechanism is safely available for use. When the puncturing pin
is raised into rupturing engagement with the diaphragm, it releases
the rotor 32 for spring propelled rotation through a predetermined
fraction of a turn, by which a red colored area on the rotor rim 33
is brought into register with the window 31, to signify that the
bottle has been discharged and should be replaced before the life
jacket is used.
Seated in the base casting just above the plunger 29 is an
explosive squib 37 that is fired for automatic inflation. When the
sensor 19 is immersed in water, current is caused to flow from the
battery 20 to an igniter for the squib. The pressure gases
generated by the squib when it is thus fired drive the plunger 29
downward and thus effect rupturing of the gas bottle diaphragm.
The battery 20 and the electrical circuit means 23 are enclosed in
an elongated cylindrical housing member 40 which also comprises a
part of the sensor 19. The housing member 40 is an upright, axially
elongated shell having a generally cylindrical sidewall 41 and an
end wall 42 at its top. At its bottom the cylindrical sidewall 41
of the housing member surrounds a headset, 39 on the base casting
in which the squib is received, and it has a sealing engagement
with the casting. Just above the squib there is a compartment in
the housing member in which are located the electrical circuit
means 23.
The battery 20 (which can be of the nickel-cadmium type or a
similar type having a long shelf acute is enclosed in the upper end
portion of the housing member with one of its terminals engaging
the end wall 42 to make an electrical connection therewith, said
end wall preferably having a central downwardly depressed dimple,
as at 43, to insure good contact with the terminal.
The medial portion of the housing sidewall 41, between the battery
and the electrical circuit means, comprises an outer electrode 46
of the immersion sensor 19. Cooperating with it is an inner tubular
electrode 47 that is rigidly held in concentric relation to the
outer one by means of generally upright posts 49 that are secured
at their bottoms in one of a pair of electrically insulating seal
members 50 and 51. The seal members extend across the housing
member 40 in axially spaced relation to the inner electrode and
thus define a sensor compartment in the housing. Each of the seal
members is preferably made of a water repellent nonhygroscopic
plastic insulating material, such as nylon or Teflon, and has an
inner frustoconical surface 52 that is inclined radially and
axially outwardly. Axially inwardly adjacent to the junction of
each of these frustoconical surfaces with the outer sensor element
46, the latter has a plurality of holes 53 through which water can
enter the sensor compartment. Note that the frustoconical inner
surfaces 52 of the seal members encourage rapid drainage of water
out of the sensor compartment, through the holes 53, regardless of
the orientation of the housing member 40, thus preventing any
accumulation of condensate water or the like that might bridge the
electrodes. The holes 53 are located in zones spaced axially
outwardly from the ends of the inner electrode so that the latter
does not interfere with such drainage.
The posts 49 that support the inner electrode 47 are disposed
radially inwardly of the inner electrode and extend generally
parallel to its axis. Each post has its lower end rigidly secured
in the lower seal member 51 and has an outwardly curved upper end
portion which is secured to the inner electrode, as by soldering or
welding, to have a good mechanical and electrical connection
therewith. At least one of the posts comprises a conductor which
extends through the lower seal member to provide an electrical
connection between the inner electrode and the resistor 44 and
thyristor 45 that are housed beneath the lower seal member.
Note that the posts 49 are so arranged that any water which might
tend to accumulate on the supporting means for the inner electrode
will not be in bridging relation to the two electrodes. Preferably
the posts 49 are coated with nylon or Teflon to protect them from
corrosion and to discourage accumulations of water in the sensor
chamber.
As already mentioned, one terminal of the battery 20 is grounded
through its engagement with the housing end wall 42. The other
battery terminal 48 is connected with the electrical circuit means
by means of a rigid conductor 54 that extends coaxially through the
sensor compartment. The conductor 54 is insulated from the sensor
compartment by tubular coaxial stem portions 55 on the seal
members, extending axially inwardly from their frustoconical
surfaces and through the bores of which the conductor 54 extends.
These stem portions are preferably formed integrally with the
respective seal portions 50 and 51 and abut one another with a snug
sealing engagement so that they protect the conductor from contact
with any water that may be in the sensor compartment as well as
electrically insulating it.
To insure a good contact between the conductor 54 and the battery
terminal 48, a U-shaped conductive spring contactor 56 is
preferably secured to the top of the conductor, above the upper
seal member 50, which contactor engages said battery terminal under
bias.
It will be apparent that the upper seal member 50 cooperates with
the upper end of the housing member 40 to provide a sealed,
waterproof compartment in which the battery 20 is protectively
housed, and that the lower seal member 51 cooperates with the lower
portion of the housing member and with the boss 39 on the body
casting to provide another sealed compartment that houses the
electrical circuit means 23. In addition, the lower seal member can
be provided with a downwardly projecting cylindrical sidewall
portion 60 that defines a downwardly opening cavity in which the
resistor 44 and thyristor 45 are housed, and this cavity can be
filled in whole or in part with a plastic encapsulating material to
further protect the electrical circuit means.
Since the sensor responds to the presence of a coherent quantity of
water bridging the annular space between the electrodes 46 and 47,
its opposing surfaces should be of a material that is a good
electrical conductor and is resistant to corrosion. For this reason
the inner surface of the outer electrode and the outer surface of
the inner one are preferably silver plated. The radial distance
between these surfaces should be not less than about 5 millimeters
so that they cannot be bridged by drops of water that form on them
as the result of condensation or are deposited on them by rain or
spray.
The water access holes or ports 53 should not be so large that
spray and rain drops that have passed through the fabric of the
pocket 8 can readily enter them, but they should be big enough so
that water which tries to leave the sensor chamber through them is
not held by surface tension. As illustrated by FIG. 4, the holes 53
can be formed by deforming localized portions of the housing wall
outwardly, to produce corbellings 57 like the teeth of a grater
that deflect downwardly flowing water away from the holes.
Preferably the lower corbellings are made somewhat larger than the
upper ones, in view of the draining action of the holes.
As shown in FIG. 3, the inner electrode 47 of the sensor is
connected with the resistor 44 and with the gate of the thyristor
45, while the anode and cathode of the thyristor are connected in a
series circuit with the battery 20 and the igniter 58 for the
squib.
It is necessary that there be only a small flow of current in the
gate circuit of a thyristor in order to trigger the device and
permit a relatively large current to flow in its anode-cathode
circuit. Once triggered, however, the thyristor remains forwardly
conductive until current is diverted from its circuit or the
current source fails, even though current flow ceases in the gate
circuit. But until the thyristor is triggered by a gate signal, it
blocks current flow through its anode-cathode circuit as
effectively as an open switch.
With these characteristics of the thyristor 45 in mind, it will be
seen that under normal conditions there will be no current drain
whatsoever from the battery 20, and the battery will therefore
require only very infrequent attention, depending upon its shelf
life or any possible emergency activation of the mechanism. This is
because the sensor offers an effectively infinite resistance
relative to the battery voltage, so long as the sensor is not
immersed in water. Should a drop or two of water somehow bridge the
sensor electrodes, the inflation mechanism will not be triggered by
it, inasmuch as the very tiny current flow through such a small
volume of water will not attain the critical gate signal value at
which the thyristor is rendered forwardly conductive.
However, when the sensor is actually immersed in water, water will
quickly enter through the holes 53 and fill the annular space
between the electrodes 46 and 47, soon providing a sufficiently
low-resistance current conducting path between them to provide for
a flow of gate circuit current that is of the critical triggering
value.
Since the opposing surfaces of the inner and outer electrodes have
substantial area, the space between them need not be completely
filled with water for the current flow through such water to reach
the critical value. This fact permits the sensor to respond to
immersion in either salt water or fresh water, inasmuch as fresh
water must attain a somewhat higher level in the sensor chamber
than salt water in order to effect triggering of the thyristor.
From the foregoing description taken with the accompanying drawings
it will be apparent that this invention provides an automatic
inflation mechanism for a life jacket or the like that has a very
reliable sensor, not affected by rain, atmospheric humidity or even
salt water spray, but which initiates inflation of the life jacket
promptly upon being immersed in either fresh water or salt water,
and which causes no drain on the battery that energizes the device
until actual immersion occurs.
Those skilled in the art will appreciate that the invention can be
embodied in forms other than as herein disclosed for purposes of
illustration.
* * * * *