BACKGROUND OF THE INVENTION
Field of the Invention
The present invention relates to an external infusion device,
such as a portable insulin pump, and more specifically to an external infusion
device, such as a portable insulin pump, having a casing with multiple
hermetically-sealed housings.
Description of the Related Art
Portable external infusion devices, such as portable insulin
pumps, are well-known. Users, such as diabetics, wear these devices in their
clothing, e.g., on a belt or in a clothing pocket. In order to allow the user to
enjoy a full range of activities, including for example, swimming, and outdoor
activities, it is necessary for the device to resist ingress of water, which could
damage the device's internal electronic components.
The need for such water hermeticity is complicated by an
additional need to ensure pressure equilibrium between the interior of the
device and atmosphere, in order to avoid pressure gradients inside the device
that could adversely impact the delivery of liquid medication, such as insulin. A need for rapid pressure equalization can arise, for example, when the user
flies in an airplane, and pressure in the airplane cabin fluctuates due to ascent
or descent of the airplane. Such a fluctuation in cabin pressure could cause
pressure inside an insulin pump casing to rapidly exceed cabin pressure,
which could result in a sudden unexpected and undesirable infusion of insulin
to the user.
Conventional infusion pumps typically include a casing defining
a single housing. The housing encloses, within a single external wall, a
medicinal reservoir, a driving mechanism, electronic circuitry for controlling
the driving mechanism, a battery, o-nngs sealing a battery door and a
reservoir door, and vents, to allow passage of air, but prevent passage of

liquid. These vents allow pressure within the casing to equalize with
atmospheric pressure.
Notwithstanding these features, the conventional single
housing device has at least one major drawback, namely that ingress of
water, spillage of insulin, or any other ingress of liquid, due to a mechanical
failure, or an operator error, e.g., forgetting to securely shut the reservoir door
or battery door after changing the reservoir or the battery, allows liquid to
reach electric components and the sensitive electronic circuitry, which can
damage the components and circuitry permanently, or at least cause the
device to malfunction.
Moreover, while some known infusion pumps include a casing
with separate compartments, these compartments are not hermetically sealed
from one another, so water leaking into one compartment also can flow into
the other compartment(s), with the same risk to electronic components and
circuitry.
SUMMARY OF THE INVENTION
Accordingly, the present invention is directed to an infusion
device and a multiple-housing casing for an infusion device that mitigates or
substantially obviates one or more problems associated with limitations and
disadvantages of the related art. Additional features and advantages of the
invention will be set forth in the description which follows, and in part will be
apparent from the description, or may be learned by practice of the invention.
The advantages of the invention will be realized and attained by the apparatus
particularly pointed out in the written description, drawings, and claims below.
To achieve these and other advantages, and in accordance with
the purpose of the invention, as embodied and broadly described herein, the
invention comprises an external infusion device, e.g., a portable insulin pump,
having a casing with multiple compartments, each compartment housing
components of the device and being hermetically sealed from the other
compartments to define multiple housings joined together. Surrounded by an

outer wall, the casing includes a first or reservoir housing enclosing a drive
mechanism and a refillable or replaceable liquid reservoir, e.g., an insulin
reservoir or the like. The casing further includes a second or electronics and
mechanical housing, enclosing pump components and electronics for
controlling the pump and the drive mechanism to dispense the liquid from the
liquid reservoir according to a selected pattern. The casing further includes a
third or battery housing, enclosing a battery or batteries.
Preferably, the first, or reservoir housing, is accessible by the
user via a first opening in the casing outer wall, for refilling or replacing the
reservoir. The third, or battery housing is accessible by the user via a second
opening in the casing outer wall for recharging or replacing the battery or
batteries. Preferably, the second or electronics and mechanical housing is
not accessible by the user.
Primary vents are provided in the external wall for venting the
infusion device to atmosphere, each of the primary vents including a
hydrophobic barrier, such as a hydrophobic membrane, which permits
passage of air or gas, and permits pressure equalization, but prevents
passage of liquid.
At least one secondary vent also including a hydrophobic barrier
as described above, is provided between selected housing, for example,
between the electronics and mechanical housing and the reservoir housing,
and/or between the electronics and mechanical housing and the battery
housing, or both.
Preferably, the second or electronics and mechanical housing is
vented, via a secondary vent, to either the reservoir housing or the battery
housing and then via the respective primary vent, to atmosphere.
Preferably, the hydrophobic membranes are selected so that a
water entry pressure exceeds a pressure to which the membrane will be
subjected upon immersion in liquid, and so that an airflow rate is as high as
possible, to permit rapid pressure equalization.

It is to be understood that both the foregoing general description
and the following detailed description are exemplary and explanatory and are
intended to provide further explanation of the invention as claimed.
The accompanying drawings are included to provide a further
understanding of the invention. They are incorporated in and constitute a part
of, the specification, illustrate a presently preferred embodiment of the
invention, and together with the specification, serve to explain the principles of
the invention.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS

Fig. 1 is a schematic depiction of a multiple-housing casing for
an external infusion device in accordance with the present invention;
Fig. 2 is a schematic depiction of a multiple-housing casing in
accordance with the invention, depicting ventilation of the housings via
primary and secondary vents;
Fig. 3 is a schematic depiction of a multiple-housing casing in
accordance with an invention, depicting ventilation in a first abnormal situation
comprising occlusion of the reservoir housing primary vent;
Fig. 4 is a schematic depiction of a multiple-housing casing in
accordance with the invention, depicting ventilation in a second abnormal
situation, comprising occlusion of the battery housing primary vent;
Fig. 5 is a schematic depiction of a multiple-housing casing in
accordance with the invention, depicting ventilation in a third abnormal
situation, comprising occlusion of a reservoir housing secondary vent;
Fig 6 is a schematic depiction of a multiple-housing casing in
accordance with the invention, depicting ventilation in a fourth abnormal
situation, comprising occlusion of a battery housing secondary vent;
Fig. 7 is a top perspective view of an external infusion device
casing in accordance with the invention;
Fig. 8 is a front view of the external infusion device casing of
Fig. 7;

Fig. 9 is a schematic depiction of a conventional single housing
for an external infusion pump.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
Reference will now be made in detail to the present preferred
embodiment of the invention, an example of which is illustrated in the
accompanying drawings.
As embodied herein and referring to Figs. 1 and 7, an external
infusion device 20 includes a multiple-housing casing 22.
In accordance with the invention, an external wall 24 surrounds
a plurality of housings, discussed below, for enclosing various components of
the external infusion device, respectively the housings being separated by a
series of internal walls 26 into separate housings that are hermetically sealed
and substantially isolated from one another, the hermetically-sealed housings
being joined together. As embodied herein, and referring to Figs. 1 and 9, a
first or "reservoir" housing 30 is defined by internal walls 26 within the external
wall 24. Reservoir housing 30 is configured to hold a refillable, or alternatively
replaceable, liquid reservoir 32. Reservoir 32 includes a generally cylindrical
storage portion 33, terminating in a reduced-diameter tip 37, the storage
portion 33 being configured to hold medicinal liquid, e.g., insulin. Reservoir
32 also includes a linear-moving plunger 34. Storage portion 33 and plunger
34 cooperate to define a syringe structure, as is well-known in the art.
Preferably, reservoir housing 30 includes an opening, closed by a screw-on
cap 35, mounted in external wall 24, to give the user of the device access to
reservoir compartment 30 in order to refill or replace the reservoir 32 as
necessary. It is further preferred that a sealing o-ring 36 be provided to form
a seal between the reservoir 32 and the walls of reservoir housing 30. It is
also preferred that screw-on cap 35 can be configured with a port 37, to allow
flow of the liquid, e.g., the insulin, out of the reservoir 32 and, via a cannula
(not shown), to the user.

As embodied herein, reservoir housing 30 also includes a
driving mechanism, preferably a lead screw 38 and a drive nut 138, as
broadly shown in Fig. 1, for applying pressure to the plunger 34, and thereby
to the liquid in the storage portion 33 of reservoir 32, to dispense the liquid
therein out through the port 37. Lead screw 38 rotates, and its rotational
motion acts on the drive nut 138, which translates the rotational motion to
linear motion, and pushes in a linear direction against plunger 34. Lead screw
38 passes through an aperture 39 in the internal wall 26 to a pump
mechanism, which will be described below.
In accordance with the invention, and as embodied herein,
referring to Fig. 1, a second or electronics and mechanical housing 40 is
provided within external wall 24. Electronics and mechanical housing 40
encloses a pump mechanism 41, which as broadly embodied herein, includes
a motor 142, preferably a brushless dc motor, a planetary gear box 143, and a
speed-reducing gear train 144, for transmitting power from the motor 142 to
the base of the lead screw 38. A seal 42 is provided in aperture 39, which
with the lead screw 38, seals the aperture 39 from water leakage, while still
allowing passage through the aperture 39 of the lead screw 38. Seal 42
preferably is a rotational ball seal, which opposes passage of water through
the aperture 39, while reducing friction acting on lead screw 38. Electronics
and mechanical housing 40 further encloses an electronics package 43,
including, e.g., a controller, a memory, a transmitter/receiver for transmitting
and receiving wireless data and control signals to and from an external control
source, and associated electronics for interacting with a keypad and a display
(not shown) on external wall 24. The pump mechanism 41, the lead screw 38
and the plunger 34 function together to dispense the liquid from the reservoir
32 to the user according to a selected pattern. For example, in the case
where the external infusion device 20 is an insulin pump, and the reservoir 32
contains liquid insulin, electronics package 43 may be programmed with one
or more basal patterns governing delivery of insulin to the user in accordance

with, e.g., the user's measured blood glucose level, the user's ingestion of
food, the user's level of exercise, and so on, as is well known in the field of
diabetes treatment. These basal patterns can be programmed into the
controller in the electronics package 43 either locally, or from the external
control source. As embodied herein, the electronics and mechanical housing
40 is not accessible by the user.
In accordance with the invention, and as embodied herein,
referring to Fig. 1, a third or "battery" housing 50 is provided inside external
wall 24. Battery housing 50 is configured to enclose a battery 52 or else
multiple batteries 52. The precise type of battery is not essential to the
invention. Preferably battery housing 50 includes an opening, sealed by a
door 54, removably or pivotally mounted in external wall 24, to give the user
access to the battery housing 50 in order to replace or recharge the battery or
batteries 52 as needed, and it is further preferable that door 54 include a
sealing o-ring 56.
In accordance with the invention, a plurality of primary vents are
provided for venting the infusion device to the atmosphere. As embodied
herein, and referring to Figs. 1, 7, and 8, a first primary vent 60 is provided in
external wall 24, with an opening into the reservoir housing 30. First primary
vent 60 vents to atmosphere the reservoir housing 30 in order to ensure there
is no differential pressure between the plunger 34 and atmosphere, which
could result in an inadvertent driving force being applied to the liquid in
reservoir 32 capable of dispensing the liquid. As embodied herein, a second
primary vent 62 is provided, preferably in battery housing door 54, opening
into battery housing 50. Second primary vent 62 vents to atmosphere the
battery housing 50 in order to prevent uncontrolled pressure build-up in the
compartment resulting from gas buildup, e.g., hydrogen gas resulting from a
chemical reaction in the battery.
Preferably both of the first and second primary vents 60 and 62
include an aperture, sealed with a hydrophobic barrier, such as a hydrophobic

membrane 64, such membranes being well known in the art. Hydrophobic
membranes allow air and other gases to pass therethrough, thereby allowing
pressure to equalize across each primary vent, but will prevent passage of
water therethrough.
As embodied herein, no primary vent is provided directly
between the electronics and mechanical housing 40 and the atmosphere;
nevertheless, venting of electronics and pump housing 40 is accomplished in
the manner discussed below.
In accordance with the invention, at least one secondary vent is
provided between selected ones of the compartments. As embodied herein,
each secondary vent also includes a hydrophobic barrier, e.g., a hydrophobic
membrane.
As embodied herein, and as shown in Figs. 1-6, a secondary
vent 66, including a hydrophobic membrane 64, similar to the hydrophobic
membranes used in primary vents 60 and 62 is provided in internal wall 26,
between the electronics and mechanical housing 40 and the reservoir housing
30, between the electronics and mechanical housing 40 and the battery
housing 50, or both. Secondary vent or vents 66 prevent an undesired
buildup of pressure in the electronics and mechanical housing 40, thereby
preventing condensation within the compartment, and ensuring an adequate
back pressure on the keypad (not shown) on external wall 24. Secondary
vent or vents 66 allow the electronics and mechanical housing 40 to vent to
atmosphere via the primary vent 60 or 62, in the respective reservoir housing
30 or battery housing 50, or both.
As embodied herein, redundancy created by the presence of
primary vents 60 and 62 and secondary vent or vents 66, shown in Fig. 2,
ensures venting and pressure equalization of all three housings, even during
abnormal situations, such as, for example, occlusion of the reservoir housing
primary vent 60 (shown, e.g., in Fig. 3), occlusion of the battery housing

primary vent 62 (shown, e.g., in Fig. 4), or occlusion of one of the secondary
vents 66 (shown, e.g., in Figs. 5 and 6).
Moreover, as embodied herein, if the battery housing 50, and/or
the reservoir housing 30 were to inadvertently fill with liquid because of (a) the
mechanical failure of one or both o-rings 36 or 56; (b) the user's failure to
secure one or both housing doors 35 or 54; or (c) failure of the hydrophobic
membrane 64 in primary vent 60 or primary vent 62, the hydrophobic
membrane(s) 64 in secondary vent or vents 66 plus the seal 42 in lead screw
aperture 39 will isolate the liquid to the flooded compartment 30 or 50, as Ihe
case may be, and will prevent the liquid from entering the electronics and
mechanical housing 40, thereby protecting the motor of pump 41, and the
sensitive electronics package 43 in the electronics and mechanical housing
40.
Preferably, the hydrophobic membranes 64 in primary vents 60,
and 62, as well as the hydrophobic membrane or membranes 64 in secondary
vent or vents 66, are selected so that a water entry pressure (WEP) of each
membrane significantly exceeds a fluid pressure at a selected depth, i.e., the
depth to which they can reasonably expect to be exposed upon immersion in
water. For example, in the case where a test pressure of 5.2 psi is requested
(i.e., water pressure at a depth of 12 feet below the surface), a selected WEP
of approximately 10 to 15 psi provides a preferable design margin.
it is likewise preferable that once a suitable WEP is selected, the
hydrophobic membrane is selected from among those providing the highest
available air flow rate, in order to achieve, along with the desired water
resistance, the ability to equalize pressure across the membrane as rapidly as
possible.
It will be apparent to those skilled in the art that modifications
and variations may be made to the external infusion device casing of the
present invention without departing from the spirit or scope of the invention.

The present invention covers all such modifications and variations provided
they fall within the scope of the attached claims and their legal equivalents.

WE CLAIM
1. An infusion device (20), comprising:
a casing (22) comprising an external wall (24) and a plurality of internal
housing comprising first housing (30) enclosing a liquid reservoir (32) and a
drive mechanism;
an electronics assembly (43) and a pump assembly (41) provided in a second
housing (40) for controlling the drive mechanism to dispense the liquid from
the reservoir (32) according to a selected pattern;
a battery (52) provided in a third housing (50);
a first primary vent (60) provided between the first housing (30) and the
exterior of the casing (22) for venting the infusion device (20) to
atmosphere,;
a second primary vent (62) provided between the third housing (50) and the
exterior of the casing (22) for venting the infusion device (20) to atmosphere;
at least one secondary vent (66) provided between said first housing (30) and
said second housing (40); and
at least one secondary vent (66) for venting the infusion device to
atmosphere provided between said third housing (50) and said second
housing (40);

each of said primary and secondary vents (60, 62, 66) comprising a
hydrophobic barrier (64) allowing passage of gas therethrough while
preventing passage of liquid therethrough.
2. The infusion device (20) as claimed in claim 1, wherein said liquid reservoir
(32) contains insulin.
3. The infusion device (20) as claimed in claim 1, wherein said liquid reservoir

(32) defines a syringe, comprising a generally tubular liquid storage section
(33) and a movable plunger (34).

4. The infusion device (20) as claimed in claim 1, wherein said drive mechanism
comprises a lead screw (38) and a drive nut (138).
5. The infusion device (20) as claimed in claim 1 wherein said second housing
(40) is vented to atmosphere via at least one of said secondary vents (66)
and at least one of said first and third housings (30,50).
6. The infusion device (20) as claimed in claim 1 wherein said first housing (30)
comprises means for a user to access said first housing (30).
7. The infusion device (20) as claimed in claim 1, wherein said third housing
(50) comprises means for a user to access said third housing (50).
8. The infusion device (20) as claimed in claim 1, wherein said second housing
(40) is inaccessible by a user.

9. The infusion device (20) as claimed in claim 1, wherein said hydrophobic
barriers (64) comprise membranes, each said membrane having a pre-
selected minimum water entry pressure greater than or equal to
approximately 68.900 Pa (10 psi).
10. The infusion device (20) as claimed in claim 1, wherein said casing (22)
portable.
11.The infusion device (20) as claimed in claim 1, wherein said liquid reservoir
(32) is refillable.
12.The infusion device (20) as claimed in claim 1, wherein said liquid reservoir
(32) is replaceable.
13.The infusion device (32) as claimed in claim 1, wherein said drive mechanism
extends from said first housing (30) to said second housing (40) via an
opening comprising a seal (42).
H.The infusion device (20) as claimed in claim 1, wherein said first, second, and
third housings (30,40,50) are sealed from one another against passage of
liquid therebetween.
15. A casing (22) for an external infusion pump, comprising:
an outer wall;

a first housing (30) configured to enclose a liquid reservoir (32) and a drive
mechanism;
an internal second housing (40) configured to enclose pump components (41)
and an electronic control assembly (43);
a third housing (50) configured to enclose at least one battery (52);
a first primary vent (60) provided between the first housing (30) and the
exterior of the casing (22) for venting the casing (22) to atmosphere;
a second primary vent (62) provided between the third housing (50) and the
exterior of the casing (22) for venting the casing (22) to atmosphere;
at least one secondary vent (66) for venting the infusion device to
atmosphere provided between said first housing (30) and said second
housing (40); and
at least one secondary vent (66) provided between said third housing (50)
and said second housing (40), wherein
each of said primary and secondary vents (60, 62, 66) contain a hydrophobic
barrier (64) allowing air passage therethrough while preventing passage of
liquid therethrough.

16.The casing (22) as claimed in claim 15, wherein said first housing (30)
comprises a means for a user to access said first housing (30).
17.The casing (22) as claimed in claim 15, wherein said third housing (50)
comprises a means for a user to access said third housing (50).
18.The casing (22) as claimed in claim 15, wherein said second housing is
inaccessible by a user.
19.The casing (22) as claimed in claim 15, wherein said outer wall(24) is
configured to be portable.
20.The casing (22) as claimed in claim 15, wherein said second housing (40) is
vented to atmosphere via said at least one secondary vent (66) and at least
one of said first and third housing (30, 50).
21.The casing (22) as claimed in claim 15, wherein said vents (60,62,66)
comprised a hydrophobic membrane (66) having a pre-selected water entry
pressure between about 68.900 Pa (10 psi) and about 103.000 Pa (15 psi).
22.The casing (22) as claimed in claim 15, wherein said first housing (30) is
defined by an internal wall (26) housing an aperture (39) configured to pass
said drive mechanism therethrough, and sealed by a seal (42).

23.The casing (22) as claimed in claim 15, wherein said first housing (30), said
second housing (40), and said third housing (50) are sealed from one another
against passage of liquid therebetween.

ABSTRACT

TITLE "AN INFUSION DEVICE"
The invention relates to an infusion device (20), comprising a casing (22)
comprising an external wall (24) and a plurality of internal housing comprising
first housing (30) enclosing a liquid reservoir (32) and a drive mechanism; an
electronics assembly (43) and a pump assembly (41) provided in a second
housing (40) for controlling the drive mechanism to dispense the liquid from the
reservoir (32) according to a selected pattern; a battery (52) provided in a third
housing (50); a first primary vent (60) provided between the first housing (30)
and the exterior of the casing (22) for venting the infusion device (20) to
atmosphere; a second primary vent (62) provided between the third housing
(50) and the exterior of the casing (22) for venting the infusion device (20) to
atmosphere; at least one secondary vent (66) provided between said first
housing (30) and said second housing (40); and at least one secondary vent (66)
for venting the infusion device to atmosphere provided between said third
housing (50) and said second housing (40); each of said primary and secondary
vents (60, 62, 66) comprising a hydrophobic barrier (64) allowing passage of gas
therethrough while preventing passage of liquid therethrough.